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IETF RFC 4204
Link Management Protocol (LMP)
Last modified on Monday, October 10th, 2005
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Network Working Group J. Lang, Ed.
Request for Comments: 4204 Sonos, Inc.
Category: Standards Track October 2005
Link Management Protocol (LMP)
 Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright © The Internet Society (2005).
Abstract
For scalability purposes, multiple data links can be combined to form
a single traffic engineering (TE) link. Furthermore, the management
of TE links is not restricted to in-band messaging, but instead can
be done using out-of-band techniques. This document specifies a link
management protocol (LMP) that runs between a pair of nodes and is
used to manage TE links. Specifically, LMP will be used to maintain
control channel connectivity, verify the physical connectivity of the
data links, correlate the link property information, suppress
downstream alarms, and localize link failures for
protection/restoration purposes in multiple kinds of networks.
Table of Contents
1. Introduction ....................................................3
1.1. Terminology ................................................5
2. LMP Overview ....................................................6
3. Control Channel Management ......................................8
3.1. Parameter Negotiation ......................................9
3.2. Hello Protocol ............................................10
4. Link Property Correlation ......................................13
5. Verifying Link Connectivity ....................................15
5.1. Example of Link Connectivity Verification .................18
6. Fault Management ...............................................19
6.1. Fault Detection ...........................................20
6.2. Fault Localization Procedure ..............................20
6.3. Examples of Fault Localization ............................21
Lang Standards Track PAGE 1 
RFC 4204 Link Management Protocol (LMP) October 2005
6.4. Channel Activation Indication .............................22
6.5. Channel Deactivation Indication ...........................23
7. Message_Id Usage ...............................................23
8. Graceful Restart ...............................................24
9. Addressing .....................................................25
10. Exponential Back-off Procedures ...............................26
10.1. Operation ...............................................26
10.2. Retransmission Algorithm ................................27
11. LMP Finite State Machines .....................................28
11.1. Control Channel FSM .....................................28
11.2. TE Link FSM .............................................32
11.3. Data Link FSM ...........................................34
12. LMP Message Formats ...........................................38
12.1. Common Header ...........................................39
12.2. LMP Object Format .......................................41
12.3. Parameter Negotiation Messages ..........................42
12.4. Hello Message (Msg Type = 4) ............................43
12.5. Link Verification Messages ..............................43
12.6. Link Summary Messages ...................................47
12.7. Fault Management Messages ...............................49
13. LMP Object Definitions ........................................50
13.1. CCID (Control Channel ID) Class .........................50
13.2. NODE_ID Class ...........................................51
13.3. LINK_ID Class ...........................................52
13.4. INTERFACE_ID Class ......................................53
13.5. MESSAGE_ID Class ........................................54
13.6. CONFIG Class ............................................55
13.7. HELLO Class .............................................56
13.8. BEGIN_VERIFY Class ......................................56
13.9. BEGIN_VERIFY_ACK Class ..................................58
13.10. VERIFY_ID Class ........................................59
13.11. TE_LINK Class ..........................................59
13.12. DATA_LINK Class ........................................61
13.13. CHANNEL_STATUS Class ...................................65
13.14. CHANNEL_STATUS_REQUEST Class ...........................68
13.15. ERROR_CODE Class .......................................70
14. References ....................................................71
14.1. Normative References ....................................71
14.2. Informative References ..................................72
15. Security Considerations .......................................73
15.1. Security Requirements ...................................73
15.2. Security Mechanisms .....................................74
16. IANA Considerations ...........................................76
17. Acknowledgements ..............................................83
18. Contributors ..................................................83
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RFC 4204 Link Management Protocol (LMP) October 2005
1. Introduction
Networks are being developed with routers, switches, crossconnects,
dense wavelength division multiplexed (DWDM) systems, and add-drop
multiplexors (ADMs) that use a common control plane, e.g.,
Generalized MPLS (GMPLS), to dynamically allocate resources and to
provide network survivability using protection and restoration
techniques. A pair of nodes may have thousands of interconnects,
where each interconnect may consist of multiple data links when
multiplexing (e.g., Frame Relay DLCIs at Layer 2, time division
multiplexed (TDM) slots or wavelength division multiplexed (WDM)
wavelengths at Layer 1) is used. For scalability purposes, multiple
data links may be combined into a single traffic-engineering (TE)
link.
To enable communication between nodes for routing, signaling, and
link management, there must be a pair of IP interfaces that are
mutually reachable. We call such a pair of interfaces a control
channel. Note that "mutually reachable" does not imply that these
two interfaces are (directly) connected by an IP link; there may be
an IP network between the two. Furthermore, the interface over which
the control messages are sent/received may not be the same interface
over which the data flows. This document specifies a link management
protocol (LMP) that runs between a pair of nodes and is used to
manage TE links and verify reachability of the control channel. For
the purposes of this document, such nodes are considered "LMP
neighbors" or simply "neighboring nodes".
In GMPLS, the control channels between two adjacent nodes are no
longer required to use the same physical medium as the data links
between those nodes. For example, a control channel could use a
separate virtual circuit, wavelength, fiber, Ethernet link, an IP
tunnel routed over a separate management network, or a multi-hop IP
network. A consequence of allowing the control channel(s) between
two nodes to be logically or physically diverse from the associated
data links is that the health of a control channel does not
necessarily correlate to the health of the data links, and vice-
versa. Therefore, a clean separation between the fate of the control
channel and data links must be made. New mechanisms must be
developed to manage the data links, both in terms of link
provisioning and fault management.
Among the tasks that LMP accomplishes is checking that the grouping
of links into TE links, as well as the properties of those links, are
the same at both end points of the links -- this is called "link
property correlation". Also, LMP can communicate these link
properties to the IGP module, which can then announce them to other
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RFC 4204 Link Management Protocol (LMP) October 2005
nodes in the network. LMP can also tell the signaling module the
mapping between TE links and control channels. Thus, LMP performs a
valuable "glue" function in the control plane.
Note that while the existence of the control network (single or
multi-hop) is necessary for enabling communication, it is by no means
sufficient. For example, if the two interfaces are separated by an
IP network, faults in the IP network may result in the lack of an IP
path from one interface to another, and therefore an interruption of
communication between the two interfaces. On the other hand, not
every failure in the control network affects a given control channel,
hence the need for establishing and managing control channels.
For the purposes of this document, a data link may be considered by
each node that it terminates on as either a 'port' or a 'component
link', depending on the multiplexing capability of the endpoint on
that link; component links are multiplex capable, whereas ports are
not multiplex capable. This distinction is important since the
management of such links (including, for example, resource
allocation, label assignment, and their physical verification) is
different based on their multiplexing capability. For example, a
Frame Relay switch is able to demultiplex an interface into virtual
circuits based on DLCIs; similarly, a SONET crossconnect with OC-192
interfaces may be able to demultiplex the OC-192 stream into four
OC-48 streams. If multiple interfaces are grouped together into a
single TE link using link bundling [RFC 4201], then the link resources
must be identified using three levels: Link_Id, component interface
Id, and label identifying virtual circuit, timeslot, etc. Resource
allocation happens at the lowest level (labels), but physical
connectivity happens at the component link level. As another
example, consider the case where an optical switch (e.g., PXC)
transparently switches OC-192 lightpaths. If multiple interfaces are
once again grouped together into a single TE link, then link bundling
[RFC 4201] is not required and only two levels of identification are
required: Link_Id and Port_Id. In this case, both resource
allocation and physical connectivity happen at the lowest level
(i.e., port level).
To ensure interworking between data links with different multiplexing
capabilities, LMP-capable devices SHOULD allow sub-channels of a
component link to be locally configured as (logical) data links. For
example, if a Router with 4 OC-48 interfaces is connected through a
4:1 MUX to a cross-connect with OC-192 interfaces, the cross-connect
should be able to configure each sub-channel (e.g., STS-48c SPE if
the 4:1 MUX is a SONET MUX) as a data link.
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RFC 4204 Link Management Protocol (LMP) October 2005
LMP is designed to support aggregation of one or more data links into
a TE link (either ports into TE links, or component links into TE
links). The purpose of forming a TE link is to group/map the
information about certain physical resources (and their properties)
into the information that is used by Constrained SPF for the purpose
of path computation, and by GMPLS signaling.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119].
The reader is assumed to be familiar with the terminology in
[RFC 3471], [RFC 4202], and [RFC 4201].
Bundled Link:
As defined in [RFC 4201], a bundled link is a TE link such that,
for the purpose of GMPLS signaling, a combination of <link
identifier, label> is not sufficient to unambiguously identify the
appropriate resources used by an LSP. A bundled link is composed
of two or more component links.
Control Channel:
A control channel is a pair of mutually reachable interfaces that
are used to enable communication between nodes for routing,
signaling, and link management.
Component Link:
As defined in [RFC 4201], a component link is a subset of resources
of a TE Link such that (a) the partition is minimal, and (b)
within each subset a label is sufficient to unambiguously identify
the appropriate resources used by an LSP.
Data Link:
A data link is a pair of interfaces that are used to transfer user
data. Note that in GMPLS, the control channel(s) between two
adjacent nodes are no longer required to use the same physical
medium as the data links between those nodes.
Link Property Correlation:
This is a procedure to correlate the local and remote properties
of a TE link.
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RFC 4204 Link Management Protocol (LMP) October 2005
Multiplex Capability:
The ability to multiplex/demultiplex a data stream into sub-rate
streams for switching purposes.
Node_Id:
For a node running OSPF, the LMP Node_Id is the same as the
address contained in the OSPF Router Address TLV. For a node
running IS-IS and advertising the TE Router ID TLV, the Node_Id is
the same as the advertised Router ID.
Port:
An interface that terminates a data link.
TE Link:
As defined in [RFC 4202], a TE link is a logical construct that
represents a way to group/map the information about certain
physical resources (and their properties) that interconnect LSRs
into the information that is used by Constrained SPF for the
purpose of path computation, and by GMPLS signaling.
Transparent:
A device is called X-transparent if it forwards incoming signals
from input to output without examining or modifying the X aspect
of the signal. For example, a Frame Relay switch is network-layer
transparent; an all-optical switch is electrically transparent.
2. LMP Overview
The two core procedures of LMP are control channel management and
link property correlation. Control channel management is used to
establish and maintain control channels between adjacent nodes. This
is done using a Config message exchange and a fast keep-alive
mechanism between the nodes. The latter is required if lower-level
mechanisms are not available to detect control channel failures.
Link property correlation is used to synchronize the TE link
properties and verify the TE link configuration.
LMP requires that a pair of nodes have at least one active bi-
directional control channel between them. Each direction of the
control channel is identified by a Control Channel Id (CC_Id), and
the two directions are coupled together using the LMP Config message
exchange. Except for Test messages, which may be limited by the
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RFC 4204 Link Management Protocol (LMP) October 2005
transport mechanism for in-band messaging, all LMP packets are run
over UDP with an LMP port number. The link level encoding of the
control channel is outside the scope of this document.
An "LMP adjacency" is formed between two nodes when at least one bi-
directional control channel is established between them. Multiple
control channels may be active simultaneously for each adjacency;
control channel parameters, however, MUST be individually negotiated
for each control channel. If the LMP fast keep-alive is used over a
control channel, LMP Hello messages MUST be exchanged over the
control channel. Other LMP messages MAY be transmitted over any of
the active control channels between a pair of adjacent nodes. One or
more active control channels may be grouped into a logical control
channel for signaling, routing, and link property correlation
purposes.
The link property correlation function of LMP is designed to
aggregate multiple data links (ports or component links) into a TE
link and to synchronize the properties of the TE link. As part of
the link property correlation function, a LinkSummary message
exchange is defined. The LinkSummary message includes the local and
remote Link_Ids, a list of all data links that comprise the TE link,
and various link properties. A LinkSummaryAck or LinkSummaryNack
message MUST be sent in response to the receipt of a LinkSummary
message indicating agreement or disagreement on the link properties.
LMP messages are transmitted reliably using Message_Ids and
retransmissions. Message_Ids are carried in MESSAGE_ID objects. No
more than one MESSAGE_ID object may be included in an LMP message.
For control-channel-specific messages, the Message_Id is within the
scope of the control channel over which the message is sent. For
TE-link-specific messages, the Message_Id is within the scope of the
LMP adjacency. The value of the Message_Id is monotonically
increasing and wraps when the maximum value is reached.
In this document, two additional LMP procedures are defined: link
connectivity verification and fault management. These procedures are
particularly useful when the control channels are physically diverse
from the data links. Link connectivity verification is used for data
plane discovery, Interface_Id exchange (Interface_Ids are used in
GMPLS signaling, either as port labels or component link identifiers,
depending on the configuration), and physical connectivity
verification. This is done by sending Test messages over the data
links and TestStatus messages back over the control channel. Note
that the Test message is the only LMP message that must be
transmitted over the data link. The ChannelStatus message exchange
is used between adjacent nodes for both the suppression of downstream
alarms and the localization of faults for protection and restoration.
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RFC 4204 Link Management Protocol (LMP) October 2005
For LMP link connectivity verification, the Test message is
transmitted over the data links. For X-transparent devices, this
requires examining and modifying the X aspect of the signal. The LMP
link connectivity verification procedure is coordinated using a
BeginVerify message exchange over a control channel. To support
various aspects of transparency, a Verify Transport Mechanism is
included in the BeginVerify and BeginVerifyAck messages. Note that
there is no requirement that all data links must lose their
transparency simultaneously; but, at a minimum, it must be possible
to terminate them one at a time. There is also no requirement that
the control channel and TE link use the same physical medium;
however, the control channel MUST be terminated by the same two
control elements that control the TE link. Since the BeginVerify
message exchange coordinates the Test procedure, it also naturally
coordinates the transition of the data links in and out of the
transparent mode.
The LMP fault management procedure is based on a ChannelStatus
message exchange that uses the following messages: ChannelStatus,
ChannelStatusAck, ChannelStatusRequest, and ChannelStatusResponse.
The ChannelStatus message is sent unsolicited and is used to notify
an LMP neighbor about the status of one or more data channels of a TE
link. The ChannelStatusAck message is used to acknowledge receipt of
the ChannelStatus message. The ChannelStatusRequest message is used
to query an LMP neighbor for the status of one or more data channels
of a TE Link. The ChannelStatusResponse message is used to
acknowledge receipt of the ChannelStatusRequest message and indicate
the states of the queried data links.
3. Control Channel Management
To initiate an LMP adjacency between two nodes, one or more bi-
directional control channels MUST be activated. The control channels
can be used to exchange control-plane information such as link
provisioning and fault management information (implemented using a
messaging protocol such as LMP, proposed in this document), path
management and label distribution information (implemented using a
signaling protocol such as RSVP-TE [RFC 3209]), and network topology
and state distribution information (implemented using traffic
engineering extensions of protocols such as OSPF [RFC 3630] and IS-IS
[RFC 3784]).
For the purposes of LMP, the exact implementation of the control
channel is not specified; it could be, for example, a separate
wavelength or fiber, an Ethernet link, an IP tunnel through a
separate management network, or the overhead bytes of a data link.
Each node assigns a node-wide, unique, 32-bit, non-zero integer
control channel identifier (CC_Id). This identifier comes from the
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RFC 4204 Link Management Protocol (LMP) October 2005
same space as the unnumbered interface Id. Furthermore, LMP packets
are run over UDP with an LMP port number. Thus, the link level
encoding of the control channel is not part of the LMP specification.
To establish a control channel, the destination IP address on the far
end of the control channel must be known. This knowledge may be
manually configured or automatically discovered. Note that for in-
band signaling, a control channel could be explicitly configured on a
particular data link. In this case, the Config message exchange can
be used to dynamically learn the IP address on the far end of the
control channel. This is done by sending the Config message with the
unicast IP source address and the multicast IP destination address
(224.0.0.1 or ff02::1). The ConfigAck and ConfigNack messages MUST
be sent to the source IP address found in the IP header of the
received Config message.
Control channels exist independently of TE links and multiple control
channels may be active simultaneously between a pair of nodes.
Individual control channels can be realized in different ways; one
might be implemented in-fiber while another one may be implemented
out-of-fiber. As such, control channel parameters MUST be negotiated
over each individual control channel, and LMP Hello packets MUST be
exchanged over each control channel to maintain LMP connectivity if
other mechanisms are not available. Since control channels are
electrically terminated at each node, it may be possible to detect
control channel failures using lower layers (e.g., SONET/SDH).
There are four LMP messages that are used to manage individual
control channels. They are the Config, ConfigAck, ConfigNack, and
Hello messages. These messages MUST be transmitted on the channel to
which they refer. All other LMP messages may be transmitted over any
of the active control channels between a pair of LMP adjacent nodes.
In order to maintain an LMP adjacency, it is necessary to have at
least one active control channel between a pair of adjacent nodes
(recall that multiple control channels can be active simultaneously
between a pair of nodes). In the event of a control channel failure,
alternate active control channels can be used and it may be possible
to activate additional control channels as described below.
3.1. Parameter Negotiation
Control channel activation begins with a parameter negotiation
exchange using Config, ConfigAck, and ConfigNack messages. The
contents of these messages are built using LMP objects, which can be
either negotiable or non-negotiable (identified by the N bit in the
object header). Negotiable objects can be used to let LMP peers
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RFC 4204 Link Management Protocol (LMP) October 2005
agree on certain values. Non-negotiable objects are used for the
announcement of specific values that do not need, or do not allow,
negotiation.
To activate a control channel, a Config message MUST be transmitted
to the remote node, and in response, a ConfigAck message MUST be
received at the local node. The Config message contains the Local
Control Channel Id (CC_Id), the sender's Node_Id, a Message_Id for
reliable messaging, and a CONFIG object. It is possible that both
the local and remote nodes initiate the configuration procedure at
the same time. To avoid ambiguities, the node with the higher
Node_Id wins the contention; the node with the lower Node_Id MUST
stop transmitting the Config message and respond to the Config
message it received. If the Node_Ids are equal, then one (or both)
nodes have been misconfigured. The nodes MAY continue to retransmit
Config messages in hopes that the misconfiguration is corrected.
Note that the problem may be solved by an operator changing the
Node_Ids on one or both nodes.
The ConfigAck message is used to acknowledge receipt of the Config
message and express agreement on ALL of the configured parameters
(both negotiable and non-negotiable).
The ConfigNack message is used to acknowledge receipt of the Config
message, indicate which (if any) non-negotiable CONFIG objects are
unacceptable, and to propose alternate values for the negotiable
parameters.
If a node receives a ConfigNack message with acceptable alternate
values for negotiable parameters, the node SHOULD transmit a Config
message using these values for those parameters.
If a node receives a ConfigNack message with unacceptable alternate
values, the node MAY continue to retransmit Config messages in hopes
that the misconfiguration is corrected. Note that the problem may be
solved by an operator changing parameters on one or both nodes.
In the case where multiple control channels use the same physical
interface, the parameter negotiation exchange is performed for each
control channel. The various LMP parameter negotiation messages are
associated with their corresponding control channels by their node-
wide unique identifiers (CC_Ids).
3.2. Hello Protocol
Once a control channel is activated between two adjacent nodes, the
LMP Hello protocol can be used to maintain control channel
connectivity between the nodes and to detect control channel
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RFC 4204 Link Management Protocol (LMP) October 2005
failures. The LMP Hello protocol is intended to be a lightweight
keep-alive mechanism that will react to control channel failures
rapidly so that IGP Hellos are not lost and the associated link-state
adjacencies are not removed unnecessarily.
3.2.1. Hello Parameter Negotiation
Before sending Hello messages, the HelloInterval and
HelloDeadInterval parameters MUST be agreed upon by the local and
remote nodes. These parameters are exchanged in the Config message.
The HelloInterval indicates how frequently LMP Hello messages will be
sent, and is measured in milliseconds (ms). For example, if the
value were 150, then the transmitting node would send the Hello
message at least every 150 ms. The HelloDeadInterval indicates how
long a device should wait to receive a Hello message before declaring
a control channel dead, and is measured in milliseconds (ms).
The HelloDeadInterval MUST be greater than the HelloInterval, and
SHOULD be at least 3 times the value of HelloInterval. If the fast
keep-alive mechanism of LMP is not used, the HelloInterval and
HelloDeadInterval parameters MUST be set to zero.
The values for the HelloInterval and HelloDeadInterval should be
selected carefully to provide rapid response time to control channel
failures without causing congestion. As such, different values will
likely be configured for different control channel implementations.
When the control channel is implemented over a directly connected
link, the suggested default values for the HelloInterval is 150 ms
and for the HelloDeadInterval is 500 ms.
When a node has either sent or received a ConfigAck message, it may
begin sending Hello messages. Once it has sent a Hello message and
received a valid Hello message (i.e., with expected sequence numbers;
see Section 3.2.2), the control channel moves to the up state. (It
is also possible to move to the up state without sending Hellos if
other methods are used to indicate bi-directional control-channel
connectivity. For example, indication of bi-directional connectivity
may be learned from the transport layer.) If, however, a node
receives a ConfigNack message instead of a ConfigAck message, the
node MUST not send Hello messages and the control channel SHOULD NOT
move to the up state. See Section 11.1 for the complete control
channel FSM.
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RFC 4204 Link Management Protocol (LMP) October 2005
3.2.2. Fast Keep-alive
Each Hello message contains two sequence numbers: the first sequence
number (TxSeqNum) is the sequence number for the Hello message being
sent and the second sequence number (RcvSeqNum) is the sequence
number of the last Hello message received from the adjacent node over
this control channel.
There are two special sequence numbers. TxSeqNum MUST NOT ever be 0.
TxSeqNum = 1 is used to indicate that the sender has just started or
has restarted and has no recollection of the last TxSeqNum that was
sent. Thus, the first Hello sent has a TxSeqNum of 1 and an RxSeqNum
of 0. When TxSeqNum reaches (2^32)-1, the next sequence number used
is 2, not 0 or 1, as these have special meanings.
Under normal operation, the difference between the RcvSeqNum in a
Hello message that is received and the local TxSeqNum that is
generated will be at most 1. This difference can be more than one
only when a control channel restarts or when the values wrap.
Since the 32-bit sequence numbers may wrap, the following expression
may be used to test if a newly received TxSeqNum value is less than a
previously received value:
If ((int) old_id - (int) new_id > 0) {
New value is less than old value;
}
Having sequence numbers in the Hello messages allows each node to
verify that its peer is receiving its Hello messages. By including
the RcvSeqNum in Hello packets, the local node will know which Hello
packets the remote node has received.
The following example illustrates how the sequence numbers operate.
Note that only the operation at one node is shown, and alternative
scenarios are possible:
1) After completing the configuration stage, Node A sends Hello
messages to Node B with {TxSeqNum=1;RcvSeqNum=0}.
2) Node A receives a Hello from Node B with {TxSeqNum=1;RcvSeqNum=1}.
When the HelloInterval expires on Node A, it sends Hellos to Node
B with {TxSeqNum=2;RcvSeqNum=1}.
3) Node A receives a Hello from Node B with {TxSeqNum=2;RcvSeqNum=2}.
When the HelloInterval expires on Node A, it sends Hellos to Node
B with {TxSeqNum=3;RcvSeqNum=2}.
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RFC 4204 Link Management Protocol (LMP) October 2005
3.2.3. Control Channel Down
To allow bringing a control channel down gracefully for
administration purposes, a ControlChannelDown flag is available in
the Common Header of LMP packets. When data links are still in use
between a pair of nodes, a control channel SHOULD only be taken down
administratively when there are other active control channels that
can be used to manage the data links.
When bringing a control channel down administratively, a node MUST
set the ControlChannelDown flag in all LMP messages sent over the
control channel. The node that initiated the control channel down
procedure may stop sending Hello messages after HelloDeadInterval
seconds have passed, or if it receives an LMP message over the same
control channel with the ControlChannelDown flag set.
When a node receives an LMP packet with the ControlChannelDown flag
set, it SHOULD send a Hello message with the ControlChannelDown flag
set and move the control channel to the down state.
3.2.4. Degraded State
A consequence of allowing the control channels to be physically
diverse from the associated data links is that there may not be any
active control channels available while the data links are still in
use. For many applications, it is unacceptable to tear down a link
that is carrying user traffic simply because the control channel is
no longer available; however, the traffic that is using the data
links may no longer be guaranteed the same level of service. Hence,
the TE link is in a Degraded state.
When a TE link is in the Degraded state, routing and signaling SHOULD
be notified so that new connections are not accepted and the TE link
is advertised with no unreserved resources.
4. Link Property Correlation
As part of LMP, a link property correlation exchange is defined for
TE links using the LinkSummary, LinkSummaryAck, and LinkSummaryNack
messages. The contents of these messages are built using LMP
objects, which can be either negotiable or non-negotiable (identified
by the N flag in the object header). Negotiable objects can be used
to let both sides agree on certain link parameters. Non-negotiable
objects are used for announcement of specific values that do not
need, or do not allow, negotiation.
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RFC 4204 Link Management Protocol (LMP) October 2005
Each TE link has an identifier (Link_Id) that is assigned at each end
of the link. These identifiers MUST be the same type (i.e, IPv4,
IPv6, unnumbered) at both ends. If a LinkSummary message is received
with different local and remote TE link types, then a LinkSummaryNack
message MUST be sent with Error Code "Bad TE Link Object".
Similarly, each data link is assigned an identifier (Interface_Id) at
each end. These identifiers MUST also be the same type at both ends.
If a LinkSummary message is received with different local and remote
Interface_Id types, then a LinkSummaryNack message MUST be sent with
Error Code "Bad Data Link Object".
Link property correlation SHOULD be done before the link is brought
up and MAY be done any time a link is up and not in the Verification
process.
The LinkSummary message is used to verify for consistency the TE and
data link information on both sides. Link Summary messages are also
used (1) to aggregate multiple data links (either ports or component
links) into a TE link; (2) to exchange, correlate (to determine
inconsistencies), or change TE link parameters; and (3) to exchange,
correlate (to determine inconsistencies), or change Interface_Ids
(either Port_Ids or component link identifiers).
The LinkSummary message includes a TE_LINK object followed by one or
more DATA_LINK objects. The TE_LINK object identifies the TE link's
local and remote Link_Id and indicates support for fault management
and link verification procedures for that TE link. The DATA_LINK
objects are used to characterize the data links that comprise the TE
link. These objects include the local and remote Interface_Ids, and
may include one or more sub-objects further describing the properties
of the data links.
If the LinkSummary message is received from a remote node, and the
Interface_Id mappings match those that are stored locally, then the
two nodes have agreement on the Verification procedure (see Section
5) and data link identification configuration. If the verification
procedure is not used, the LinkSummary message can be used to verify
agreement on manual configuration.
The LinkSummaryAck message is used to signal agreement on the
Interface_Id mappings and link property definitions. Otherwise, a
LinkSummaryNack message MUST be transmitted, indicating which
Interface mappings are not correct and/or which link properties are
not accepted. If a LinkSummaryNack message indicates that the
Interface_Id mappings are not correct and the link verification
procedure is enabled, the link verification process SHOULD be
repeated for all mismatched, free data links; if an allocated data
link has a mapping mismatch, it SHOULD be flagged and verified when
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RFC 4204 Link Management Protocol (LMP) October 2005
it becomes free. If a LinkSummaryNack message includes negotiable
parameters, then acceptable values for those parameters MUST be
included. If a LinkSummaryNack message is received and includes
negotiable parameters, then the initiator of the LinkSummary message
SHOULD send a new LinkSummary message. The new LinkSummary message
SHOULD include new values for the negotiable parameters. These
values SHOULD take into account the acceptable values received in the
LinkSummaryNack message.
It is possible that the LinkSummary message could grow quite large
due to the number of DATA LINK objects. An LMP implementation SHOULD
be able to fragment when transmitting LMP messages, and MUST be able
to re-assemble IP fragments when receiving LMP messages.
5. Verifying Link Connectivity
In this section, an optional procedure is described that may be used
to verify the physical connectivity of the data links and dynamically
learn (i.e., discover) the TE link and Interface_Id associations.
The procedure SHOULD be done when establishing a TE link, and
subsequently, on a periodic basis for all unallocated (free) data
links of the TE link.
Support for this procedure is indicated by setting the "Link
Verification Supported" flag in the TE_LINK object of the LinkSummary
message.
If a BeginVerify message is received and link verification is not
supported for the TE link, then a BeginVerifyNack message MUST be
transmitted with Error Code indicating, "Link Verification Procedure
not supported for this TE Link."
A unique characteristic of transparent devices is that the data is
not modified or examined during normal operation. This
characteristic poses a challenge for validating the connectivity of
the data links and establishing the label mappings. Therefore, to
ensure proper verification of data link connectivity, it is required
that, until the data links are allocated for user traffic, they must
be opaque (i.e., lose their transparency). To support various
degrees of opaqueness (e.g., examining overhead bytes, terminating
the IP payload, etc.) and, hence, different mechanisms to transport
the Test messages, a Verify Transport Mechanism field is included in
the BeginVerify and BeginVerifyAck messages.
There is no requirement that all data links be terminated
simultaneously; but, at a minimum, the data links MUST be able to be
terminated one at a time. Furthermore, for the link verification
procedure it is assumed that the nodal architecture is designed so
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RFC 4204 Link Management Protocol (LMP) October 2005
that messages can be sent and received over any data link. Note that
this requirement is trivial for opaque devices since each data link
is electrically terminated and processed before being forwarded to
the next opaque device; but that in transparent devices this is an
additional requirement.
To interconnect two nodes, a TE link is defined between them, and at
a minimum, there MUST be at least one active control channel between
the nodes. For link verification, a TE link MUST include at least
one data link.
Once a control channel has been established between the two nodes,
data link connectivity can be verified by exchanging Test messages
over each of the data links specified in the TE link. It should be
noted that all LMP messages except the Test message are exchanged
over the control channels and that Hello messages continue to be
exchanged over each control channel during the data link verification
process. The Test message is sent over the data link that is being
verified. Data links are tested in the transmit direction because
they are unidirectional; therefore, it may be possible for both nodes
to (independently) exchange the Test messages simultaneously.
To initiate the link verification procedure, the local node MUST send
a BeginVerify message over a control channel. To limit the scope of
Link Verification to a particular TE Link, the local Link_Id MUST be
non-zero. If this field is zero, the data links can span multiple TE
links and/or they may comprise a TE link that is yet to be
configured. For the case where the local Link_Id field is zero, the
"Verify all Links" flag of the BEGIN_VERIFY object is used to
distinguish between data links that span multiple TE links and those
that have not yet been assigned to a TE link. Specifically,
verification of data links that span multiple TE links is indicated
by setting the local Link_Id field to zero and setting the "Verify
all Links" flag. Verification of data links that have not yet been
assigned to a TE link is indicated by setting the local Link_Id field
to zero and clearing the "Verify all Links" flag.
The BeginVerify message also contains the number of data links that
are to be verified; the interval (called VerifyInterval) at which the
Test messages will be sent; the encoding scheme and transport
mechanisms that are supported; the data rate for Test messages; and,
when the data links correspond to fibers, the wavelength identifier
over which the Test messages will be transmitted.
If the remote node receives a BeginVerify message and it is ready to
process Test messages, it MUST send a BeginVerifyAck message back to
the local node specifying the desired transport mechanism for the
TEST messages. The remote node includes a 32-bit, node-unique
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RFC 4204 Link Management Protocol (LMP) October 2005
Verify_Id in the BeginVerifyAck message. The Verify_Id MAY be
randomly selected; however, it MUST NOT overlap any other Verify_Id
currently being used by the node selecting it. The Verify_Id is then
used in all corresponding verification messages to differentiate them
from different LMP peers and/or parallel Test procedures. When the
local node receives a BeginVerifyAck message from the remote node, it
may begin testing the data links by transmitting periodic Test
messages over each data link. The Test message includes the
Verify_Id and the local Interface_Id for the associated data link.
The remote node MUST send either a TestStatusSuccess or a
TestStatusFailure message in response for each data link. A
TestStatusAck message MUST be sent to confirm receipt of the
TestStatusSuccess and TestStatusFailure messages. Unacknowledged
TestStatusSuccess and TestStatusFailure messages SHOULD be
retransmitted until the message is acknowledged or until a retry
limit is reached (see also Section 10).
It is also permissible for the sender to terminate the Test procedure
anytime after sending the BeginVerify message. An EndVerify message
SHOULD be sent for this purpose.
Message correlation is done using message identifiers and the
Verify_Id; this enables verification of data links, belonging to
different link bundles or LMP sessions, in parallel.
When the Test message is received, the received Interface_Id (used in
GMPLS as either a Port label or component link identifier, depending
on the configuration) is recorded and mapped to the local
Interface_Id for that data link, and a TestStatusSuccess message MUST
be sent. The TestStatusSuccess message includes the local
Interface_Id along with the Interface_Id and Verify_Id received in
the Test message. The receipt of a TestStatusSuccess message
indicates that the Test message was detected at the remote node and
the physical connectivity of the data link has been verified. When
the TestStatusSuccess message is received, the local node SHOULD mark
the data link as up and send a TestStatusAck message to the remote
node. If, however, the Test message is not detected at the remote
node within an observation period (specified by the
VerifyDeadInterval), the remote node MUST send a TestStatusFailure
message over the control channel, which indicates that the
verification of the physical connectivity of the data link has
failed. When the local node receives a TestStatusFailure message, it
SHOULD mark the data link as FAILED and send a TestStatusAck message
to the remote node. When all the data links on the list have been
tested, the local node SHOULD send an EndVerify message to indicate
that testing is complete on this link.
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RFC 4204 Link Management Protocol (LMP) October 2005
If the local/remote data link mappings are known, then the link
verification procedure can be optimized by testing the data links in
a defined order known to both nodes. The suggested criterion for
this ordering is by increasing the value of the remote Interface_Id.
Both the local and remote nodes SHOULD maintain the complete list of
Interface_Id mappings for correlation purposes.
5.1. Example of Link Connectivity Verification
Figure 1 shows an example of the link verification scenario that is
executed when a link between Node A and Node B is added. In this
example, the TE link consists of three free ports (each transmitted
along a separate fiber) and is associated with a bi-directional
control channel (indicated by a "c"). The verification process is as
follows:
o A sends a BeginVerify message over the control channel to B,
indicating it will begin verifying the ports that form the TE
link. The LOCAL_LINK_ID object carried in the BeginVerify message
carries the identifier (IP address or interface index) that A
assigns to the link.
o Upon receipt of the BeginVerify message, B creates a Verify_Id and
binds it to the TE Link from A. This binding is used later when B
receives the Test messages from A, and these messages carry the
Verify_Id. B discovers the identifier (IP address or interface
index) that A assigns to the TE link by examining the
LOCAL_LINK_ID object carried in the received BeginVerify message.
(If the data ports are not yet assigned to the TE Link, the
binding is limited to the Node_Id of A.) In response to the
BeginVerify message, B sends the BeginVerifyAck message to A. The
LOCAL_LINK_ID object carried in the BeginVerifyAck message is used
to carry the identifier (IP address or interface index) that B
assigns to the TE link. The REMOTE_LINK_ID object carried in the
BeginVerifyAck message is used to bind the Link_Ids assigned by
both A and B. The Verify_Id is returned to A in the
BeginVerifyAck message over the control channel.
o When A receives the BeginVerifyAck message, it begins transmitting
periodic Test messages over the first port (Interface Id=1). The
Test message includes the Interface_Id for the port and the
Verify_Id that was assigned by B.
o When B receives the Test messages, it maps the received
Interface_Id to its own local Interface_Id = 10 and transmits a
TestStatusSuccess message over the control channel back to Node A.
The TestStatusSuccess message includes both the local and received
Interface_Ids for the port as well as the Verify_Id. The
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RFC 4204 Link Management Protocol (LMP) October 2005
Verify_Id is used to determine the local/remote TE link
identifiers (IP addresses or interface indices) to which the data
links belong.
o A will send a TestStatusAck message over the control channel back
to B, indicating it received the TestStatusSuccess message.
o The process is repeated until all of the ports are verified.
o At this point, A will send an EndVerify message over the control
channel to B, indicating that testing is complete.
o B will respond by sending an EndVerifyAck message over the control
channel back to A.
Note that this procedure can be used to "discover" the
connectivity of the data ports.
+---------------------+ +---------------------+
+ + + +
+ Node A +<-------- c --------->+ Node B +
+ + + +
+ + + +
+ 1 +--------------------->+ 10 +
+ + + +
+ + + +
+ 2 + /---->+ 11 +
+ + /----/ + +
+ + /---/ + +
+ 3 +----/ + 12 +
+ + + +
+ + + +
+ 4 +--------------------->+ 14 +
+ + + +
+---------------------+ +---------------------+
Figure 1: Example of link connectivity between Node A and Node B.
6. Fault Management
In this section, an optional LMP procedure is described that is used
to manage failures by rapid notification of the status of one or more
data channels of a TE Link. The scope of this procedure is within a
TE link, and as such, the use of this procedure is negotiated as part
of the LinkSummary exchange. The procedure can be used to rapidly
isolate data link and TE link failures, and is designed to work for
both unidirectional and bi-directional LSPs.
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RFC 4204 Link Management Protocol (LMP) October 2005
An important implication of using transparent devices is that
traditional methods that are used to monitor the health of allocated
data links may no longer be appropriate. Instead of fault detection
being in layer 2 or layer 3, it is delegated to the physical layer
(i.e., loss of light or optical monitoring of the data).
Recall that a TE link connecting two nodes may consist of a number of
data links. If one or more data links fail between two nodes, a
mechanism must be used for rapid failure notification so that
appropriate protection/restoration mechanisms can be initiated. If
the failure is subsequently cleared, then a mechanism must be used to
notify that the failure is clear and the channel status is OK.
6.1. Fault Detection
Fault detection should be handled at the layer closest to the
failure; for optical networks, this is the physical (optical) layer.
One measure of fault detection at the physical layer is detecting
loss of light (LOL). Other techniques for monitoring optical signals
are still being developed and will not be further considered in this
document. However, it should be clear that the mechanism used for
fault notification in LMP is independent of the mechanism used to
detect the failure, and simply relies on the fact that a failure is
detected.
6.2. Fault Localization Procedure
In some situations, a data link failure between two nodes is
propagated downstream such that all the downstream nodes detect the
failure without localizing the failure. To avoid multiple alarms
stemming from the same failure, LMP provides failure notification
through the ChannelStatus message. This message may be used to
indicate that a single data channel has failed, multiple data
channels have failed, or an entire TE link has failed. Failure
correlation is done locally at each node upon receipt of the failure
notification.
To localize a fault to a particular link between adjacent nodes, a
downstream node (downstream in terms of data flow) that detects data
link failures will send a ChannelStatus message to its upstream
neighbor indicating that a failure has been detected (bundling
together the notification of all the failed data links). An upstream
node that receives the ChannelStatus message MUST send a
ChannelStatusAck message to the downstream node indicating it has
received the ChannelStatus message. The upstream node should
correlate the failure to see if the failure is also detected locally
for the corresponding LSP(s). If, for example, the failure is clear
on the input of the upstream node or internally, then the upstream
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RFC 4204 Link Management Protocol (LMP) October 2005
node will have localized the failure. Once the failure is
correlated, the upstream node SHOULD send a ChannelStatus message to
the downstream node indicating that the channel is failed or is OK.
If a ChannelStatus message is not received by the downstream node, it
SHOULD send a ChannelStatusRequest message for the channel in
question. Once the failure has been localized, the signaling
protocols may be used to initiate span or path protection and
restoration procedures.
If all of the data links of a TE link have failed, then the upstream
node MAY be notified of the TE link failure without specifying each
data link of the failed TE link. This is done by sending failure
notification in a ChannelStatus message identifying the TE Link
without including the Interface_Ids in the CHANNEL_STATUS object.
6.3. Examples of Fault Localization
In Figure 2, a sample network is shown where four nodes are connected
in a linear array configuration. The control channels are bi-
directional and are labeled with a "c". All LSPs are also bi-
directional.
In the first example [see Fig. 2(a)], there is a failure on one
direction of the bi-directional LSP. Node 4 will detect the failure
and will send a ChannelStatus message to Node 3 indicating the
failure (e.g., LOL) to the corresponding upstream node. When Node 3
receives the ChannelStatus message from Node 4, it returns a
ChannelStatusAck message back to Node 4 and correlates the failure
locally. When Node 3 correlates the failure and verifies that the
failure is clear, it has localized the failure to the data link
between Node 3 and Node 4. At that time, Node 3 should send a
ChannelStatus message to Node 4 indicating that the failure has been
localized.
In the second example [see Fig. 2(b)], a single failure (e.g., fiber
cut) affects both directions of the bi-directional LSP. Node 2 (Node
3) will detect the failure of the upstream (downstream) direction and
send a ChannelStatus message to the upstream (in terms of data flow)
node indicating the failure (e.g., LOL). Simultaneously (ignoring
propagation delays), Node 1 (Node 4) will detect the failure on the
upstream (downstream) direction, and will send a ChannelStatus
message to the corresponding upstream (in terms of data flow) node
indicating the failure. Node 2 and Node 3 will have localized the
two directions of the failure.
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RFC 4204 Link Management Protocol (LMP) October 2005
+-------+ +-------+ +-------+ +-------+
+ Node1 + + Node2 + + Node3 + + Node4 +
+ +-- c ---+ +-- c ---+ +-- c ---+ +
----+---\ + + + + + + +
<---+---\\--+--------+-------+---\ + + + /--+--->
+ \--+--------+-------+---\\---+-------+---##---+---//--+----
+ + + + \---+-------+--------+---/ +
+ + + + + + (a) + +
----+-------+--------+---\ + + + + +
<---+-------+--------+---\\--+---##---+--\ + + +
+ + + \--+---##---+--\\ + + +
+ + + + (b) + \\--+--------+-------+--->
+ + + + + \--+--------+-------+----
+ + + + + + + +
+-------+ +-------+ +-------+ +-------+
Figure 2: Two types of data link failures are shown (indicated
by ## in the figure):
(A) a data link corresponding to the downstream direction of a
bi-directional LSP fails,
(B) two data links corresponding to both directions of a bi-
directional LSP fail. The control channel connecting two
nodes is indicated with a "c".
6.4. Channel Activation Indication
The ChannelStatus message may also be used to notify an LMP neighbor
that the data link should be actively monitored. This is called
Channel Activation Indication. This is particularly useful in
networks with transparent nodes where the status of data links may
need to be triggered using control channel messages. For example, if
a data link is pre-provisioned and the physical link fails after
verification and before inserting user traffic, a mechanism is needed
to indicate the data link should be active, otherwise the failure may
not be detectable.
The ChannelStatus message is used to indicate that a channel or group
of channels are now active. The ChannelStatusAck message MUST be
transmitted upon receipt of a ChannelStatus message. When a
ChannelStatus message is received, the corresponding data link(s)
MUST be put into the Active state. If upon putting them into the
Active state, a failure is detected, the ChannelStatus message SHOULD
be transmitted as described in Section 6.2.
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RFC 4204 Link Management Protocol (LMP) October 2005
6.5. Channel Deactivation Indication
The ChannelStatus message may also be used to notify an LMP neighbor
that the data link no longer needs to be actively monitored. This is
the counterpart to the Channel Active Indication.
When a ChannelStatus message is received with Channel Deactive
Indication, the corresponding data link(s) MUST be taken out of the
Active state.
7. Message_Id Usage
The MESSAGE_ID and MESSAGE_ID_ACK objects are included in LMP
messages to support reliable message delivery. This section
describes the usage of these objects. The MESSAGE_ID and
MESSAGE_ID_ACK objects contain a Message_Id field.
Only one MESSAGE_ID/MESSAGE_ID_ACK object may be included in any LMP
message.
For control-channel-specific messages, the Message_Id field is within
the scope of the CC_Id. For TE link specific messages, the
Message_Id field is within the scope of the LMP adjacency.
The Message_Id field of the MESSAGE_ID object contains a generator-
selected value. This value MUST be monotonically increasing. A
value is considered to be previously used when it has been sent in an
LMP message with the same CC_Id (for control channel specific
messages) or LMP adjacency (for TE Link specific messages). The
Message_Id field of the MESSAGE_ID_ACK object contains the Message_Id
field of the message being acknowledged.
Unacknowledged messages sent with the MESSAGE_ID object SHOULD be
retransmitted until the message is acknowledged or until a retry
limit is reached (see also Section 10).
Note that the 32-bit Message_Id value may wrap. The following
expression may be used to test if a newly received Message_Id value
is less than a previously received value:
If ((int) old_id - (int) new_id > 0) {
New value is less than old value;
}
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RFC 4204 Link Management Protocol (LMP) October 2005
Nodes processing incoming messages SHOULD check to see if a newly
received message is out of order and can be ignored. Out-of-order
messages can be identified by examining the value in the Message_Id
field. If a message is determined to be out-of-order, that message
should be silently dropped.
If the message is a Config message, and the Message_Id value is less
than the largest Message_Id value previously received from the sender
for the CC_Id, then the message SHOULD be treated as being out-of-
order.
If the message is a LinkSummary message and the Message_Id value is
less than the largest Message_Id value previously received from the
sender for the TE Link, then the message SHOULD be treated as being
out-of-order.
If the message is a ChannelStatus message and the Message_Id value is
less than the largest Message_Id value previously received from the
sender for the specified TE link, then the receiver SHOULD check the
Message_Id value previously received for the state of each data
channel included in the ChannelStatus message. If the Message_Id
value is greater than the most recently received Message_Id value
associated with at least one of the data channels included in the
message, the message MUST NOT be treated as out of order; otherwise,
the message SHOULD be treated as being out of order. However, the
state of any data channel MUST NOT be updated if the Message_Id value
is less than the most recently received Message_Id value associated
with the data channel.
All other messages MUST NOT be treated as out-of-order.
8. Graceful Restart
This section describes the mechanism to resynchronize the LMP state
after a control plane restart. A control plane restart may occur
when bringing up the first control channel after a control
communications failure. A control communications failure may be the
result of an LMP adjacency failure or a nodal failure wherein the LMP
control state is lost, but the data plane is unaffected. The latter
is detected by setting the "LMP Restart" bit in the Common Header of
the LMP messages. When the control plane fails due to the loss of
the control channel, the LMP link information should be retained. It
is possible that a node may be capable of retaining the LMP link
information across a nodal failure. However, in both cases the
status of the data channels MUST be synchronized.
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RFC 4204 Link Management Protocol (LMP) October 2005
It is assumed the Node_Id and Local Interface_Ids remain stable
across a control plane restart.
After the control plane of a node restarts, the control channel(s)
must be re-established using the procedures of Section 3.1. When
re-establishing control channels, the Config message SHOULD be sent
using the unicast IP source and destination addresses.
If the control plane failure was the result of a nodal failure where
the LMP control state is lost, then the "LMP Restart" flag MUST be
set in LMP messages until a Hello message is received with the
RcvSeqNum equal to the local TxSeqNum. This indicates that the
control channel is up and the LMP neighbor has detected the restart.
The following assumes that the LMP component restart only occurred on
one end of the TE Link. If the LMP component restart occurred on
both ends of the TE Link, the normal procedures for LinkSummary
should be used, as described in Section 4.
Once a control channel is up, the LMP neighbor MUST send a
LinkSummary message for each TE Link across the adjacency. All the
objects of the LinkSummary message MUST have the N-bit set to 0,
indicating that the parameters are non-negotiable. This provides the
local/remote Link_Id and Interface_Id mappings, the associated data
link parameters, and indication of which data links are currently
allocated to user traffic. When a node receives the LinkSummary
message, it checks its local configuration. If the node is capable
of retaining the LMP link information across a restart, it must
process the LinkSummary message as described in Section 4 with the
exception that the allocated/de-allocated flag of the DATA_LINK
object received in the LinkSummary message MUST take precedence over
any local value. If, however, the node was not capable of retaining
the LMP link information across a restart, the node MUST accept the
data link parameters of the received LinkSummary message and respond
with a LinkSummaryAck message.
Upon completion of the LinkSummary exchange, the node that has
restarted the control plane SHOULD send a ChannelStatusRequest
message for that TE link. The node SHOULD also verify the
connectivity of all unallocated data channels.
9. Addressing
All LMP messages are run over UDP with an LMP port number (except, in
some cases, the Test messages, which may be limited by the transport
mechanism for in-band messaging). The destination address of the IP
packet MAY be either the address learned in the Configuration
procedure (i.e., the Source IP address found in the IP header of the
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RFC 4204 Link Management Protocol (LMP) October 2005
received Config message), an IP address configured on the remote
node, or the Node_Id. The Config message is an exception as
described below.
The manner in which a Config message is addressed may depend on the
signaling transport mechanism. When the transport mechanism is a
point-to-point link, Config messages SHOULD be sent to the Multicast
address (224.0.0.1 or ff02::1). Otherwise, Config messages MUST be
sent to an IP address on the neighboring node. This may be
configured at both ends of the control channel or may be
automatically discovered.
10. Exponential Back-off Procedures
This section is based on [RFC 2961] and provides exponential back-off
procedures for message retransmission. Implementations MUST use the
described procedures or their equivalent.
10.1. Operation
The following operation is one possible mechanism for exponential
back-off retransmission of unacknowledged LMP messages. The sending
node retransmits the message until an acknowledgement message is
received or until a retry limit is reached. When the sending node
receives the acknowledgement, retransmission of the message is
stopped. The interval between message retransmission is governed by
a rapid retransmission timer. The rapid retransmission timer starts
at a small interval and increases exponentially until it reaches a
threshold.
The following time parameters are useful to characterize the
procedures:
Rapid retransmission interval Ri:
Ri is the initial retransmission interval for unacknowledged
messages. After sending the message for the first time, the
sending node will schedule a retransmission after Ri milliseconds.
Rapid retry limit Rl:
Rl is the maximum number of times a message will be transmitted
without being acknowledged.
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RFC 4204 Link Management Protocol (LMP) October 2005
Increment value Delta:
Delta governs the speed with which the sender increases the
retransmission interval. The ratio of two successive
retransmission intervals is (1 + Delta).
Suggested default values for an initial retransmission interval (Ri)
of 500 ms are a power of 2 exponential back-off (Delta = 1) and a
retry limit of 3.
10.2. Retransmission Algorithm
After a node transmits a message requiring acknowledgement, it should
immediately schedule a retransmission after Ri seconds. If a
corresponding acknowledgement message is received before Ri seconds,
then message retransmission SHOULD be canceled. Otherwise, it will
retransmit the message after (1+Delta)*Ri seconds. The
retransmission will continue until either an appropriate
acknowledgement message is received or the rapid retry limit, Rl, has
been reached.
A sending node can use the following algorithm when transmitting a
message that requires acknowledgement:
Prior to initial transmission, initialize Rk = Ri and Rn = 0.
while (Rn++ < Rl) {
transmit the message;
wake up after Rk milliseconds;
Rk = Rk * (1 + Delta);
}
/* acknowledged message or no reply from receiver and Rl
reached*/
do any needed clean up;
exit;
Asynchronously, when a sending node receives a corresponding
acknowledgment message, it will change the retry count, Rn, to Rl.
Note that the transmitting node does not advertise or negotiate the
use of the described exponential back-off procedures in the Config or
LinkSummary messages.
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RFC 4204 Link Management Protocol (LMP) October 2005
11. LMP Finite State Machines
11.1. Control Channel FSM
The control channel FSM defines the states and logics of operation of
an LMP control channel.
11.1.1. Control Channel States
A control channel can be in one of the states described below. Every
state corresponds to a certain condition of the control channel and
is usually associated with a specific type of LMP message that is
periodically transmitted to the far end.
Down: This is the initial control channel state. In this
state, no attempt is being made to bring the control
channel up and no LMP messages are sent. The control
channel parameters should be set to the initial values.
ConfSnd: The control channel is in the parameter negotiation
state. In this state the node periodically sends a
Config message, and is expecting the other side to reply
with either a ConfigAck or ConfigNack message. The FSM
does not transition into the Active state until the
remote side positively acknowledges the parameters.
ConfRcv: The control channel is in the parameter negotiation
state. In this state, the node is waiting for acceptable
configuration parameters from the remote side. Once such
parameters are received and acknowledged, the FSM can
transition to the Active state.
Active: In this state the node periodically sends a Hello message
and is waiting to receive a valid Hello message. Once a
valid Hello message is received, it can transition to the
up state.
Up: The CC is in an operational state. The node receives
valid Hello messages and sends Hello messages.
GoingDown: A CC may go into this state because of administrative
action. While a CC is in this state, the node sets the
ControlChannelDown bit in all the messages it sends.
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RFC 4204 Link Management Protocol (LMP) October 2005
11.1.2. Control Channel Events
Operation of the LMP control channel is described in terms of FSM
states and events. Control channel events are generated by the
underlying protocols and software modules, as well as by the packet
processing routines and FSMs of associated TE links. Every event has
its number and a symbolic name. Description of possible control
channel events is given below.
1 : evBringUp: This is an externally triggered event indicating
that the control channel negotiation should begin.
This event, for example, may be triggered by an
operator command, by the successful completion of a
control channel bootstrap procedure, or by
configuration. Depending on the configuration,
this will trigger either
1a) the sending of a Config message,
1b) a period of waiting to receive a Config
message from the remote node.
2 : evCCDn: This event is generated when there is indication
that the control channel is no longer available.
3 : evConfDone: This event indicates a ConfigAck message has been
received, acknowledging the Config parameters.
4 : evConfErr: This event indicates a ConfigNack message has been
received, rejecting the Config parameters.
5 : evNewConfOK: New Config message was received from neighbor and
positively acknowledged.
6 : evNewConfErr: New Config message was received from neighbor and
rejected with a ConfigNack message.
7 : evContenWin: New Config message was received from neighbor at
the same time a Config message was sent to the
neighbor. The local node wins the contention. As
a result, the received Config message is ignored.
8 : evContenLost: New Config message was received from neighbor at
the same time a Config message was sent to the
neighbor. The local node loses the contention.
8a) The Config message is positively
acknowledged.
8b) The Config message is negatively
acknowledged.
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RFC 4204 Link Management Protocol (LMP) October 2005
9 : evAdminDown: The administrator has requested that the control
channel is brought down administratively.
10: evNbrGoesDn: A packet with ControlChannelDown flag is received
from the neighbor.
11: evHelloRcvd: A Hello packet with expected SeqNum has been
received.
12: evHoldTimer: The HelloDeadInterval timer has expired indicating
that no Hello packet has been received. This moves
the control channel back into the Negotiation
state, and depending on the local configuration,
this will trigger either
12a) the sending of periodic Config messages,
12b) a period of waiting to receive Config
messages from the remote node.
13: evSeqNumErr: A Hello with unexpected SeqNum received and
discarded.
14: evReconfig: Control channel parameters have been reconfigured
and require renegotiation.
15: evConfRet: A retransmission timer has expired and a Config
message is resent.
16: evHelloRet: The HelloInterval timer has expired and a Hello
packet is sent.
17: evDownTimer: A timer has expired and no messages have been
received with the ControlChannelDown flag set.
11.1.3. Control Channel FSM Description
Figure 3 illustrates operation of the control channel FSM in a form
of FSM state transition diagram.
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RFC 4204 Link Management Protocol (LMP) October 2005
+--------+
+----------------->| |<--------------+
| +--------->| Down |<----------+ |
| |+---------| |<-------+ | |
| || +--------+ | | |
| || | ^ 2,9| 2| 2|
| ||1b 1a| | | | |
| || v |2,9 | | |
| || +--------+ | | |
| || +->| |<------+| | |
| || 4,7,| |ConfSnd | || | |
| || 14,15+--| |<----+ || | |
| || +--------+ | || | |
| || 3,8a| | | || | |
| || +---------+ |8b 14,12a| || | |
| || | v | || | |
| |+-|------>+--------+ | || | |
| | | +->| |-----|-|+ | |
| | |6,14| |ConfRcv | | | | |
| | | +--| |<--+ | | | |
| | | +--------+ | | | | |
| | | 5| ^ | | | | |
| | +---------+ | | | | | | |
| | | | | | | | | |
| | v v |6,12b | | | | |
| |10 +--------+ | | | | |
| +----------| | | | | | |
| | +--| Active |---|-+ | | |
10,17| | 5,16| | |-------|---+ |
+-------+ 9 | 13 +->| | | | |
| Going |<--|----------+--------+ | | |
| Down | | 11| ^ | | |
+-------+ | | |5 | | |
^ | v | 6,12b| | |
|9 |10 +--------+ | |12a,14 |
| +----------| |---+ | |
| | Up |-------+ |
+------------------| |---------------+
+--------+
| ^
| |
+---+
11,13,16
Figure 3: Control Channel FSM
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RFC 4204 Link Management Protocol (LMP) October 2005
Event evCCDn always forces the FSM to the down state. Events
evHoldTimer and evReconfig always force the FSM to the Negotiation
state (either ConfSnd or ConfRcv).
11.2. TE Link FSM
The TE Link FSM defines the states and logics of operation of the LMP
TE Link.
11.2.1. TE Link States
An LMP TE link can be in one of the states described below. Every
state corresponds to a certain condition of the TE link and is
usually associated with a specific type of LMP message that is
periodically transmitted to the far end via the associated control
channel or in-band via the data links.
Down: There are no data links allocated to the TE link.
Init: Data links have been allocated to the TE link, but the
configuration has not yet been synchronized with the LMP
neighbor. The LinkSummary message is periodically
transmitted to the LMP neighbor.
Up: This is the normal operational state of the TE link. At
least one LMP control channel is required to be
operational between the nodes sharing the TE link. As
part of normal operation, the LinkSummary message may be
periodically transmitted to the LMP neighbor or generated
by an external request.
Degraded: In this state, all LMP control channels are down, but the
TE link still includes some data links that are allocated
to user traffic.
11.2.2. TE Link Events
Operation of the LMP TE link is described in terms of FSM states and
events. TE Link events are generated by the packet processing
routines and by the FSMs of the associated control channel(s) and the
data links. Every event has its number and a symbolic name.
Descriptions of possible events are given below.
1 : evDCUp: One or more data channels have been enabled and
assigned to the TE Link.
2 : evSumAck: LinkSummary message received and positively
acknowledged.
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RFC 4204 Link Management Protocol (LMP) October 2005
3 : evSumNack: LinkSummary message received and negatively
acknowledged.
4 : evRcvAck: LinkSummaryAck message received acknowledging the
TE Link Configuration.
5 : evRcvNack: LinkSummaryNack message received.
6 : evSumRet: Retransmission timer has expired and LinkSummary
message is resent.
7 : evCCUp: First active control channel goes up.
8 : evCCDown: Last active control channel goes down.
9 : evDCDown: Last data channel of TE Link has been removed.
11.2.3. TE Link FSM Description
Figure 4 illustrates operation of the LMP TE Link FSM in a form of
FSM state transition diagram.
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RFC 4204 Link Management Protocol (LMP) October 2005
3,7,8
+--+
| |
| v
+--------+
| |
+------------>| Down |<---------+
| | | |
| +--------+ |
| | ^ |
| 1| |9 |
| v | |
| +--------+ |
| | |<-+ |
| | Init | |3,5,6 |9
| | |--+ 7,8 |
9| +--------+ |
| | |
| 2,4| |
| v |
+--------+ 7 +--------+ |
| |------>| |----------+
| Deg | | Up |
| |<------| |
+--------+ 8 +--------+
| ^
| |
+--+
2,3,4,5,6
Figure 4: LMP TE Link FSM
In the above FSM, the sub-states that may be implemented when the
link verification procedure is used have been omitted.
11.3. Data Link FSM
The data link FSM defines the states and logics of operation of a
data link within an LMP TE link. Operation of a data link is
described in terms of FSM states and events. Data links can either
be in the active (transmitting) mode, where Test messages are
transmitted from them, or the passive (receiving) mode, where Test
messages are received through them. For clarity, separate FSMs are
defined for the active/passive data links; however, a single set of
data link states and events are defined.
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RFC 4204 Link Management Protocol (LMP) October 2005
11.3.1. Data Link States
Any data link can be in one of the states described below. Every
state corresponds to a certain condition of the data link.
Down: The data link has not been put in the resource pool
(i.e., the link is not 'in service')
Test: The data link is being tested. An LMP Test message is
periodically sent through the link.
PasvTest: The data link is being checked for incoming test
messages.
Up/Free: The link has been successfully tested and is now put
in the pool of resources (in-service). The link has
not yet been allocated to data traffic.
Up/Alloc: The link is up and has been allocated for data
traffic.
11.3.2. Data Link Events
Data link events are generated by the packet processing routines and
by the FSMs of the associated control channel and the TE link.
Every event has its number and a symbolic name. Description of
possible data link events is given below:
1 :evCCUp: First active control channel goes up.
2 :evCCDown: LMP neighbor connectivity is lost. This indicates
the last LMP control channel has failed between
neighboring nodes.
3 :evStartTst: This is an external event that triggers the
sending of Test messages over the data link.
4 :evStartPsv: This is an external event that triggers the
listening for Test messages over the data link.
5 :evTestOK: Link verification was successful and the link can
be used for path establishment.
(a) This event indicates the Link Verification
procedure (see Section 5) was successful
for this data link and a TestStatusSuccess
message was received over the control
channel.
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RFC 4204 Link Management Protocol (LMP) October 2005
(b) This event indicates the link is ready for
path establishment, but the Link
Verification procedure was not used. For
in-band signaling of the control channel,
the control channel establishment may be
sufficient to verify the link.
6 :evTestRcv: Test message was received over the data port and a
TestStatusSuccess message is transmitted over the
control channel.
7 :evTestFail: Link verification returned negative results. This
could be because (a) a TestStatusFailure message
was received, or (b) the Verification procedure
has ended without receiving a TestStatusSuccess or
TestStatusFailure message for the data link.
8 :evPsvTestFail: Link verification returned negative results. This
indicates that a Test message was not detected and
either (a) the VerifyDeadInterval has expired or
(b) the Verification procedure has ended and the
VerifyDeadInterval has not yet expired.
9 :evLnkAlloc: The data link has been allocated.
10:evLnkDealloc: The data link has been de-allocated.
11:evTestRet: A retransmission timer has expired and the Test
message is resent.
12:evSummaryFail: The LinkSummary did not match for this data port.
13:evLocalizeFail: A Failure has been localized to this data link.
14:evdcDown: The data channel is no longer available.
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RFC 4204 Link Management Protocol (LMP) October 2005
11.3.3. Active Data Link FSM Description
Figure 5 illustrates operation of the LMP active data link FSM in a
form of FSM state transition diagram.
+------+
| |<-------+
+--------->| Down | |
| +----| |<-----+ |
| | +------+ | |
| |5b 3| ^ | |
| | | |7 | |
| | v | | |
| | +------+ | |
| | | |<-+ | |
| | | Test | |11 | |
| | | |--+ | |
| | +------+ | |
| | 5a| 3^ | |
| | | | | |
| | v | | |
|12 | +---------+ | |
| +-->| |14 | |
| | Up/Free |----+ |
+---------| | |
+---------+ |
9| ^ |
| | |
v |10 |
+---------+ |
| |13 |
|Up/Alloc |------+
| |
+---------+
Figure 5: Active LMP Data Link FSM
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RFC 4204 Link Management Protocol (LMP) October 2005
11.3.4. Passive Data Link FSM Description
Figure 6 illustrates operation of the LMP passive data link FSM in a
form of FSM state transition diagram.
+------+
| |<------+
+---------->| Down | |
| +-----| |<----+ |
| | +------+ | |
| |5b 4| ^ | |
| | | |8 | |
| | v | | |
| | +----------+ | |
| | | PasvTest | | |
| | +----------+ | |
| | 6| 4^ | |
| | | | | |
| | v | | |
|12 | +---------+ | |
| +--->| Up/Free |14 | |
| | |---+ |
+----------| | |
+---------+ |
9| ^ |
| | |
v |10 |
+---------+ |
| |13 |
|Up/Alloc |-----+
| |
+---------+
Figure 6: Passive LMP Data Link FSM
12. LMP Message Formats
All LMP messages (except, in some cases, the Test messages, which are
limited by the transport mechanism for in-band messaging) are run
over UDP with an LMP port number (701).
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RFC 4204 Link Management Protocol (LMP) October 2005
12.1. Common Header
In addition to the UDP header and standard IP header, all LMP
messages (except, in some cases, the Test messages which may be
limited by the transport mechanism for in-band messaging) have the
following common header:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vers | (Reserved) | Flags | Msg Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LMP Length | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Reserved field should be sent as zero and ignored on receipt.
All values are defined in network byte order (i.e., big-endian byte
order).
Vers: 4 bits
Protocol version number. This is version 1.
Flags: 8 bits
The following bit-values are defined. All other bits are reserved
and should be sent as zero and ignored on receipt.
0x01: ControlChannelDown
0x02: LMP Restart
This bit is set to indicate that a nodal failure has occurred
and the LMP control state has been lost. This flag may be
reset to 0 when a Hello message is received with RcvSeqNum
equal to the local TxSeqNum.
Msg Type: 8 bits
The following values are defined. All other values are reserved
1 = Config
2 = ConfigAck
3 = ConfigNack
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RFC 4204 Link Management Protocol (LMP) October 2005
4 = Hello
5 = BeginVerify
6 = BeginVerifyAck
7 = BeginVerifyNack
8 = EndVerify
9 = EndVerifyAck
10 = Test
11 = TestStatusSuccess
12 = TestStatusFailure
13 = TestStatusAck
14 = LinkSummary
15 = LinkSummaryAck
16 = LinkSummaryNack
17 = ChannelStatus
18 = ChannelStatusAck
19 = ChannelStatusRequest
20 = ChannelStatusResponse
All of the messages are sent over the control channel EXCEPT the
Test message, which is sent over the data link that is being
tested.
LMP Length: 16 bits
The total length of this LMP message in bytes, including the
common header and any variable-length objects that follow.
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RFC 4204 Link Management Protocol (LMP) October 2005
12.2. LMP Object Format
LMP messages are built using objects. Each object is identified by
its Object Class and Class-type. Each object has a name, which is
always capitalized in this document. LMP objects can be either
negotiable or non-negotiable (identified by the N bit in the object
header). Negotiable objects can be used to let the devices agree on
certain values. Non-negotiable objects are used for announcement of
specific values that do not need or do not allow negotiation.
All values are defined in network byte order (i.e., big-endian byte
order).
The format of the LMP object is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N| C-Type | Class | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// (object contents) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
N: 1 bit
The N flag indicates if the object is negotiable (N=1) or non-
negotiable (N=0).
C-Type: 7 bits
Class-type, unique within an Object Class. Values are defined in
Section 13.
Class: 8 bits
The Class indicates the object type. Each object has a name,
which is always capitalized in this document.
Length: 16 bits
The Length field indicates the length of the object in bytes,
including the N, C-Type, Class, and Length fields.
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RFC 4204 Link Management Protocol (LMP) October 2005
12.3. Parameter Negotiation Messages
12.3.1. Config Message (Msg Type = 1)
The Config message is used in the control channel negotiation phase
of LMP. The contents of the Config message are built using LMP
objects. The format of the Config message is as follows:
<Config Message> ::= <Common Header> <LOCAL_CCID> <MESSAGE_ID>
<LOCAL_NODE_ID> <CONFIG>
The above transmission order SHOULD be followed.
The MESSAGE_ID object is within the scope of the LOCAL_CCID object.
The Config message MUST be periodically transmitted until (1) it
receives a ConfigAck or ConfigNack message, (2) a retry limit has
been reached and no ConfigAck or ConfigNack message has been
received, or (3) it receives a Config message from the remote node
and has lost the contention (e.g., the Node_Id of the remote node is
higher than the Node_Id of the local node). Both the retransmission
interval and the retry limit are local configuration parameters.
12.3.2. ConfigAck Message (Msg Type = 2)
The ConfigAck message is used to acknowledge receipt of the Config
message and indicate agreement on all parameters.
<ConfigAck Message> ::= <Common Header> <LOCAL_CCID> <LOCAL_NODE_ID>
<REMOTE_CCID> <MESSAGE_ID_ACK>
<REMOTE_NODE_ID>
The above transmission order SHOULD be followed.
The contents of the REMOTE_CCID, MESSAGE_ID_ACK, and REMOTE_NODE_ID
objects MUST be obtained from the Config message being acknowledged.
12.3.3. ConfigNack Message (Msg Type = 3)
The ConfigNack message is used to acknowledge receipt of the Config
message and indicate disagreement on non-negotiable parameters or
propose other values for negotiable parameters. Parameters where
agreement was reached MUST NOT be included in the ConfigNack Message.
The format of the ConfigNack message is as follows:
<ConfigNack Message> ::= <Common Header> <LOCAL_CCID>
<LOCAL_NODE_ID> <REMOTE_CCID>
<MESSAGE_ID_ACK> <REMOTE_NODE_ID> <CONFIG>
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RFC 4204 Link Management Protocol (LMP) October 2005
The above transmission order SHOULD be followed.
The contents of the REMOTE_CCID, MESSAGE_ID_ACK, and REMOTE_NODE_ID
objects MUST be obtained from the Config message being negatively
acknowledged.
It is possible that multiple parameters may be invalid in the Config
message.
If a negotiable CONFIG object is included in the ConfigNack message,
it MUST include acceptable values for the parameters.
If the ConfigNack message includes CONFIG objects for non-negotiable
parameters, they MUST be copied from the CONFIG objects received in
the Config message.
If the ConfigNack message is received and only includes CONFIG
objects that are negotiable, then a new Config message SHOULD be
sent. The values in the CONFIG object of the new Config message
SHOULD take into account the acceptable values included in the
ConfigNack message.
If a node receives a Config message and recognizes the CONFIG object,
but does not recognize the C-Type, a ConfigNack message including the
unknown CONFIG object MUST be sent.
12.4. Hello Message (Msg Type = 4)
The format of the Hello message is as follows:
<Hello Message> ::= <Common Header> <LOCAL_CCID> <HELLO>
The above transmission order SHOULD be followed.
The Hello message MUST be periodically transmitted at least once
every HelloInterval msec. If no Hello message is received within the
HelloDeadInterval, the control channel is assumed to have failed.
12.5. Link Verification Messages
12.5.1. BeginVerify Message (Msg Type = 5)
The BeginVerify message is sent over the control channel and is used
to initiate the link verification process. The format is as follows:
<BeginVerify Message> ::= <Common Header> <LOCAL_LINK_ID>
<MESSAGE_ID> [<REMOTE_LINK_ID>]
<BEGIN_VERIFY>
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RFC 4204 Link Management Protocol (LMP) October 2005
The above transmission order SHOULD be followed.
To limit the scope of Link Verification to a particular TE Link, the
Link_Id field of the LOCAL_LINK_ID object MUST be non-zero. If this
field is zero, the data links can span multiple TE links and/or they
may comprise a TE link that is yet to be configured. In the special
case where the local Link_Id field is zero, the "Verify all Links"
flag of the BEGIN_VERIFY object is used to distinguish between data
links that span multiple TE links and those that have not yet been
assigned to a TE link (see Section 5).
The REMOTE_LINK_ID object may be included if the local/remote Link_Id
mapping is known.
The Link_Id field of the REMOTE_LINK_ID object MUST be non-zero if
included.
The BeginVerify message MUST be periodically transmitted until (1)
the node receives either a BeginVerifyAck or BeginVerifyNack message
to accept or reject the verify process or (2) a retry limit has been
reached and no BeginVerifyAck or BeginVerifyNack message has been
received. Both the retransmission interval and the retry limit are
local configuration parameters.
12.5.2. BeginVerifyAck Message (Msg Type = 6)
When a BeginVerify message is received and Test messages are ready to
be processed, a BeginVerifyAck message MUST be transmitted.
<BeginVerifyAck Message> ::= <Common Header> [<LOCAL_LINK_ID>]
<MESSAGE_ID_ACK> <BEGIN_VERIFY_ACK>
<VERIFY_ID>
The above transmission order SHOULD be followed.
The LOCAL_LINK_ID object may be included if the local/remote Link_Id
mapping is known or learned through the BeginVerify message.
The Link_Id field of the LOCAL_LINK_ID MUST be non-zero if included.
The contents of the MESSAGE_ID_ACK object MUST be obtained from the
BeginVerify message being acknowledged.
The VERIFY_ID object contains a node-unique value that is assigned by
the generator of the BeginVerifyAck message. This value is used to
uniquely identify the Verification process from multiple LMP
neighbors and/or parallel Test procedures between the same LMP
neighbors.
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RFC 4204 Link Management Protocol (LMP) October 2005
12.5.3. BeginVerifyNack Message (Msg Type = 7)
If a BeginVerify message is received and a node is unwilling or
unable to begin the Verification procedure, a BeginVerifyNack message
MUST be transmitted.
<BeginVerifyNack Message> ::= <Common Header> [<LOCAL_LINK_ID>]
<MESSAGE_ID_ACK> <ERROR_CODE>
The above transmission order SHOULD be followed.
The contents of the MESSAGE_ID_ACK object MUST be obtained from the
BeginVerify message being negatively acknowledged.
If the Verification process is not supported, the ERROR_CODE MUST
indicate "Link Verification Procedure not supported".
If Verification is supported, but the node is unable to begin the
procedure, the ERROR_CODE MUST indicate "Unwilling to verify". If a
BeginVerifyNack message is received with such an ERROR_CODE, the node
that originated the BeginVerify SHOULD schedule a BeginVerify
retransmission after Rf seconds, where Rf is a locally defined
parameter.
If the Verification Transport mechanism is not supported, the
ERROR_CODE MUST indicate "Unsupported verification transport
mechanism".
If remote configuration of the Link_Id is not supported and the
content of the REMOTE_LINK_ID object (included in the BeginVerify
message) does not match any configured values, the ERROR_CODE MUST
indicate "Link_Id configuration error".
If a node receives a BeginVerify message and recognizes the
BEGIN_VERIFY object but does not recognize the C-Type, the ERROR_CODE
MUST indicate "Unknown object C-Type".
12.5.4. EndVerify Message (Msg Type = 8)
The EndVerify message is sent over the control channel and is used to
terminate the link verification process. The EndVerify message may
be sent any time the initiating node desires to end the Verify
procedure. The format is as follows:
<EndVerify Message> ::=<Common Header> <MESSAGE_ID> <VERIFY_ID>
The above transmission order SHOULD be followed.
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RFC 4204 Link Management Protocol (LMP) October 2005
The EndVerify message will be periodically transmitted until (1) an
EndVerifyAck message has been received or (2) a retry limit has been
reached and no EndVerifyAck message has been received. Both the
retransmission interval and the retry limit are local configuration
parameters.
12.5.5. EndVerifyAck Message (Msg Type =9)
The EndVerifyAck message is sent over the control channel and is used
to acknowledge the termination of the link verification process. The
format is as follows:
<EndVerifyAck Message> ::= <Common Header> <MESSAGE_ID_ACK>
<VERIFY_ID>
The above transmission order SHOULD be followed.
The contents of the MESSAGE_ID_ACK object MUST be obtained from the
EndVerify message being acknowledged.
12.5.6. Test Message (Msg Type = 10)
The Test message is transmitted over the data link and is used to
verify its physical connectivity. Unless explicitly stated, these
messages MUST be transmitted over UDP like all other LMP messages.
The format of the Test messages is as follows:
<Test Message> ::= <Common Header> <LOCAL_INTERFACE_ID> <VERIFY_ID>
The above transmission order SHOULD be followed.
Note that this message is sent over a data link and NOT over the
control channel. The transport mechanism for the Test message is
negotiated using the Verify Transport Mechanism field of the
BEGIN_VERIFY object and the Verify Transport Response field of the
BEGIN_VERIFY_ACK object (see Sections 13.8 and 13.9).
The local (transmitting) node sends a given Test message periodically
(at least once every VerifyInterval ms) on the corresponding data
link until (1) it receives a correlating TestStatusSuccess or
TestStatusFailure message on the control channel from the remote
(receiving) node or (2) all active control channels between the two
nodes have failed. The remote node will send a given TestStatus
message periodically over the control channel until it receives
either a correlating TestStatusAck message or an EndVerify message.
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RFC 4204 Link Management Protocol (LMP) October 2005
12.5.7. TestStatusSuccess Message (Msg Type = 11)
The TestStatusSuccess message is transmitted over the control channel
and is used to transmit the mapping between the local Interface_Id
and the Interface_Id that was received in the Test message.
<TestStatusSuccess Message> ::= <Common Header> <LOCAL_LINK_ID>
<MESSAGE_ID> <LOCAL_INTERFACE_ID>
<REMOTE_INTERFACE_ID> <VERIFY_ID>
The above transmission order SHOULD be followed.
The contents of the REMOTE_INTERFACE_ID object MUST be obtained from
the corresponding Test message being positively acknowledged.
12.5.8. TestStatusFailure Message (Msg Type = 12)
The TestStatusFailure message is transmitted over the control channel
and is used to indicate that the Test message was not received.
<TestStatusFailure Message> ::= <Common Header> <MESSAGE_ID>
<VERIFY_ID>
The above transmission order SHOULD be followed.
12.5.9. TestStatusAck Message (Msg Type = 13)
The TestStatusAck message is used to acknowledge receipt of the
TestStatusSuccess or TestStatusFailure messages.
<TestStatusAck Message> ::= <Common Header> <MESSAGE_ID_ACK>
<VERIFY_ID>
The above transmission order SHOULD be followed.
The contents of the MESSAGE_ID_ACK object MUST be obtained from the
TestStatusSuccess or TestStatusFailure message being acknowledged.
12.6. Link Summary Messages
12.6.1. LinkSummary Message (Msg Type = 14)
The LinkSummary message is used to synchronize the Interface_Ids and
correlate the properties of the TE link. The format of the
LinkSummary message is as follows:
<LinkSummary Message> ::= <Common Header> <MESSAGE_ID> <TE_LINK>
<DATA_LINK> [<DATA_LINK>...]
Lang Standards Track PAGE 47
RFC 4204 Link Management Protocol (LMP) October 2005
The above transmission order SHOULD be followed.
The LinkSummary message can be exchanged any time a link is not in
the Verification process. The LinkSummary message MUST be
periodically transmitted until (1) the node receives a LinkSummaryAck
or LinkSummaryNack message or (2) a retry limit has been reached and
no LinkSummaryAck or LinkSummaryNack message has been received. Both
the retransmission interval and the retry limit are local
configuration parameters.
12.6.2. LinkSummaryAck Message (Msg Type = 15)
The LinkSummaryAck message is used to indicate agreement on the
Interface_Id synchronization and acceptance/agreement on all the link
parameters. It is on the reception of this message that the local
node makes the Link_Id associations.
<LinkSummaryAck Message> ::= <Common Header> <MESSAGE_ID_ACK>
The above transmission order SHOULD be followed.
12.6.3. LinkSummaryNack Message (Msg Type = 16)
The LinkSummaryNack message is used to indicate disagreement on non-
negotiated parameters or propose other values for negotiable
parameters. Parameters on which agreement was reached MUST NOT be
included in the LinkSummaryNack message.
<LinkSummaryNack Message> ::= <Common Header> <MESSAGE_ID_ACK>
<ERROR_CODE> [<DATA_LINK>...]
The above transmission order SHOULD be followed.
The DATA_LINK objects MUST include acceptable values for all
negotiable parameters. If the LinkSummaryNack includes DATA_LINK
objects for non-negotiable parameters, they MUST be copied from the
DATA_LINK objects received in the LinkSummary message.
If the LinkSummaryNack message is received and only includes
negotiable parameters, then a new LinkSummary message SHOULD be sent.
The values received in the new LinkSummary message SHOULD take into
account the acceptable parameters included in the LinkSummaryNack
message.
If the LinkSummary message is received with unacceptable, non-
negotiable parameters, the ERROR_CODE MUST indicate "Unacceptable
non-negotiable LINK_SUMMARY parameters."
Lang Standards Track PAGE 48
RFC 4204 Link Management Protocol (LMP) October 2005
If the LinkSummary message is received with unacceptable negotiable
parameters, the ERROR_CODE MUST indicate "Renegotiate LINK_SUMMARY
parameters."
If the LinkSummary message is received with an invalid TE_LINK
object, the ERROR_CODE MUST indicate "Invalid TE_LINK object."
If the LinkSummary message is received with an invalid DATA_LINK
object, the ERROR_CODE MUST indicate "Invalid DATA_LINK object."
If the LinkSummary message is received with a TE_LINK object but the
C-Type is unknown, the ERROR_CODE MUST indicate, "Unknown TE_LINK
object C-Type."
If the LinkSummary message is received with a DATA_LINK object but
the C-Type is unknown, the ERROR_CODE MUST indicate, "Unknown
DATA_LINK object C-Type."
12.7. Fault Management Messages
12.7.1. ChannelStatus Message (Msg Type = 17)
The ChannelStatus message is sent over the control channel and is
used to notify an LMP neighbor of the status of a data link. A node
that receives a ChannelStatus message MUST respond with a
ChannelStatusAck message. The format is as follows:
<ChannelStatus Message> ::= <Common Header> <LOCAL_LINK_ID>
<MESSAGE_ID> <CHANNEL_STATUS>
The above transmission order SHOULD be followed.
If the CHANNEL_STATUS object does not include any Interface_Ids, then
this indicates the entire TE Link has failed.
12.7.2. ChannelStatusAck Message (Msg Type = 18)
The ChannelStatusAck message is used to acknowledge receipt of the
ChannelStatus Message. The format is as follows:
<ChannelStatusAck Message> ::= <Common Header> <MESSAGE_ID_ACK>
The above transmission order SHOULD be followed.
The contents of the MESSAGE_ID_ACK object MUST be obtained from the
ChannelStatus message being acknowledged.
Lang Standards Track PAGE 49
RFC 4204 Link Management Protocol (LMP) October 2005
12.7.3. ChannelStatusRequest Message (Msg Type = 19)
The ChannelStatusRequest message is sent over the control channel and
is used to request the status of one or more data link(s). A node
that receives a ChannelStatusRequest message MUST respond with a
ChannelStatusResponse message. The format is as follows:
<ChannelStatusRequest Message> ::= <Common Header> <LOCAL_LINK_ID>
<MESSAGE_ID>
[<CHANNEL_STATUS_REQUEST>]
The above transmission order SHOULD be followed.
If the CHANNEL_STATUS_REQUEST object is not included, then the
ChannelStatusRequest is being used to request the status of ALL of
the data link(s) of the TE Link.
12.7.4. ChannelStatusResponse Message (Msg Type = 20)
The ChannelStatusResponse message is used to acknowledge receipt of
the ChannelStatusRequest Message and notify the LMP neighbor of the
status of the data channel(s). The format is as follows:
<ChannelStatusResponse Message> ::= <Common Header> <MESSAGE_ID_ACK>
<CHANNEL_STATUS>
The above transmission order SHOULD be followed.
The contents of the MESSAGE_ID_ACK objects MUST be obtained from the
ChannelStatusRequest message being acknowledged.
13. LMP Object Definitions
13.1. CCID (Control Channel ID) Class
Class = 1
o C-Type = 1, LOCAL_CCID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CC_Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 50
RFC 4204 Link Management Protocol (LMP) October 2005
CC_Id: 32 bits
This MUST be node-wide unique and non-zero. The CC_Id identifies
the control channel of the sender associated with the message.
This object is non-negotiable.
o C-Type = 2, REMOTE_CCID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CC_Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
CC_Id: 32 bits
This identifies the remote node's CC_Id and MUST be non-zero.
This object is non-negotiable.
13.2. NODE_ID Class
Class = 2
o C-Type = 1, LOCAL_NODE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Node_Id:
This identities the node that originated the LMP packet.
This object is non-negotiable.
o C-Type = 2, REMOTE_NODE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 51
RFC 4204 Link Management Protocol (LMP) October 2005
Node_Id:
This identities the remote node.
This object is non-negotiable.
13.3. LINK_ID Class
Class = 3
o C-Type = 1, IPv4 LOCAL_LINK_ID
o C-Type = 2, IPv4 REMOTE_LINK_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 3, IPv6 LOCAL_LINK_ID
o C-Type = 4, IPv6 REMOTE_LINK_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Link_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 5, Unnumbered LOCAL_LINK_ID
o C-Type = 6, Unnumbered REMOTE_LINK_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 52
RFC 4204 Link Management Protocol (LMP) October 2005
Link_Id:
For LOCAL_LINK_ID, this identifies the sender's Link associated
with the message. This value MUST be non-zero.
For REMOTE_LINK_ID, this identifies the remote node's Link_Id and
MUST be non-zero.
This object is non-negotiable.
13.4. INTERFACE_ID Class
Class = 4
o C-Type = 1, IPv4 LOCAL_INTERFACE_ID
o C-Type = 2, IPv4 REMOTE_INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 3, IPv6 LOCAL_INTERFACE_ID
o C-Type = 4, IPv6 REMOTE_INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Interface_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 5, Unnumbered LOCAL_INTERFACE_ID
o C-Type = 6, Unnumbered REMOTE_INTERFACE_ID
Lang Standards Track PAGE 53
RFC 4204 Link Management Protocol (LMP) October 2005
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Interface_Id:
For the LOCAL_INTERFACE_ID, this identifies the data link. This
value MUST be node-wide unique and non-zero.
For the REMOTE_INTERFACE_ID, this identifies the remote node's
data link. The Interface_Id MUST be non-zero.
This object is non-negotiable.
13.5. MESSAGE_ID Class
Class = 5
o C-Type=1, MessageId
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message_Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Message_Id:
The Message_Id field is used to identify a message. This value is
incremented and only decreases when the value wraps. This is used
for message acknowledgment.
This object is non-negotiable.
o C-Type = 2, MessageIdAck
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message_Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 54
RFC 4204 Link Management Protocol (LMP) October 2005
Message_Id:
The Message_Id field is used to identify the message being
acknowledged. This value is copied from the MESSAGE_ID object of
the message being acknowledged.
This object is non-negotiable.
13.6. CONFIG Class
Class = 6.
o C-Type = 1, HelloConfig
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HelloInterval | HelloDeadInterval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
HelloInterval: 16 bits.
Indicates how frequently the Hello packets will be sent and is
measured in milliseconds (ms).
HelloDeadInterval: 16 bits.
If no Hello packets are received within the HelloDeadInterval, the
control channel is assumed to have failed. The HelloDeadInterval
is measured in milliseconds (ms). The HelloDeadInterval MUST be
greater than the HelloInterval, and SHOULD be at least 3 times the
value of HelloInterval.
If the fast keep-alive mechanism of LMP is not used, the
HelloInterval and HelloDeadInterval MUST be set to zero.
Lang Standards Track PAGE 55
RFC 4204 Link Management Protocol (LMP) October 2005
13.7. HELLO Class
Class = 7
o C-Type = 1, Hello
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TxSeqNum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RcvSeqNum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TxSeqNum: 32 bits
This is the current sequence number for this Hello message. This
sequence number will be incremented when the sequence number is
reflected in the RcvSeqNum of a Hello packet that is received over
the control channel.
TxSeqNum=0 is not allowed. TxSeqNum=1 is used to indicate that
this is the first Hello message sent over the control channel.
RcvSeqNum: 32 bits
This is the sequence number of the last Hello message received
over the control channel. RcvSeqNum=0 is used to indicate that a
Hello message has not yet been received.
This object is non-negotiable.
13.8. BEGIN_VERIFY Class
Class = 8
o C-Type = 1
Lang Standards Track PAGE 56
RFC 4204 Link Management Protocol (LMP) October 2005
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | VerifyInterval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Data Links |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EncType | (Reserved) | Verify Transport Mechanism |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TransmissionRate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Reserved field should be sent as zero and ignored on receipt.
Flags: 16 bits
The following flags are defined:
0x0001 Verify all Links
If this bit is set, the verification process checks all
unallocated links; else it only verifies new ports or
component links that are to be added to this TE link.
0x0002 Data Link Type
If set, the data links to be verified are ports, otherwise
they are component links
VerifyInterval: 16 bits
This is the interval between successive Test messages and is
measured in milliseconds (ms).
Number of Data Links: 32 bits
This is the number of data links that will be verified.
EncType: 8 bits
This is the encoding type of the data link. The defined EncType
values are consistent with the LSP Encoding Type values of
[RFC 3471].
Lang Standards Track PAGE 57
RFC 4204 Link Management Protocol (LMP) October 2005
Verify Transport Mechanism: 16 bits
This defines the transport mechanism for the Test Messages. The
scope of this bit mask is restricted to each encoding type. The
local node will set the bits corresponding to the various
mechanisms it can support for transmitting LMP test messages. The
receiver chooses the appropriate mechanism in the BeginVerifyAck
message.
The following flag is defined across all Encoding Types. All
other flags are dependent on the Encoding Type.
0x8000 Payload:Test Message transmitted in the payload
Capable of transmitting Test messages in the payload.
The Test message is sent as an IP packet as defined
above.
TransmissionRate: 32 bits
This is the transmission rate of the data link over which the Test
messages will be transmitted. This is expressed in bytes per
second and represented in IEEE floating-point format.
Wavelength: 32 bits
When a data link is assigned to a port or component link that is
capable of transmitting multiple wavelengths (e.g., a fiber or
waveband-capable port), it is essential to know which wavelength
the test messages will be transmitted over. This value
corresponds to the wavelength at which the Test messages will be
transmitted over and has local significance. If there is no
ambiguity as to the wavelength over which the message will be
sent, then this value SHOULD be set to 0.
13.9. BEGIN_VERIFY_ACK Class
Class = 9
o C-Type = 1
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VerifyDeadInterval | Verify_Transport_Response |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 58
RFC 4204 Link Management Protocol (LMP) October 2005
VerifyDeadInterval: 16 bits
If a Test message is not detected within the
VerifyDeadInterval, then a node will send the TestStatusFailure
message for that data link.
Verify_Transport_Response: 16 bits
The recipient of the BeginVerify message (and the future
recipient of the TEST messages) chooses the transport mechanism
from the various types that are offered by the transmitter of
the Test messages. One and only one bit MUST be set in the
verification transport response.
This object is non-negotiable.
13.10. VERIFY_ID Class
Class = 10
o C-Type = 1
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Verify_Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Verify_Id: 32 bits
This is used to differentiate Test messages from different TE
links and/or LMP peers. This is a node-unique value that is
assigned by the recipient of the BeginVerify message.
This object is non-negotiable.
13.11. TE_LINK Class
Class = 11
o C-Type = 1, IPv4 TE_LINK
Lang Standards Track PAGE 59
RFC 4204 Link Management Protocol (LMP) October 2005
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local_Link_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote_Link_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 2, IPv6 TE_LINK
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Local_Link_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Remote_Link_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 3, Unnumbered TE_LINK
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local_Link_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote_Link_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Reserved field should be sent as zero and ignored on receipt.
Lang Standards Track PAGE 60
RFC 4204 Link Management Protocol (LMP) October 2005
Flags: 8 bits
The following flags are defined. All other bit-values are
reserved and should be sent as zero and ignored on receipt.
0x01 Fault Management Supported.
0x02 Link Verification Supported.
Local_Link_Id:
This identifies the node's local Link_Id and MUST be non-zero.
Remote_Link_Id:
This identifies the remote node's Link_Id and MUST be non-zero.
13.12. DATA_LINK Class
Class = 12
o C-Type = 1, IPv4 DATA_LINK
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local_Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote_Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// (Subobjects) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 61
RFC 4204 Link Management Protocol (LMP) October 2005
o C-Type = 2, IPv6 DATA_LINK
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Local_Interface_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Remote_Interface_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// (Subobjects) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 3, Unnumbered DATA_LINK
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local_Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote_Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// (Subobjects) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 62
RFC 4204 Link Management Protocol (LMP) October 2005
The Reserved field should be sent as zero and ignored on receipt.
Flags: 8 bits
The following flags are defined. All other bit-values are
reserved and should be sent as zero and ignored on receipt.
0x01 Interface Type: If set, the data link is a port, otherwise it
is a component link.
0x02 Allocated Link: If set, the data link is currently allocated
for user traffic. If a single Interface_Id
is used for both the transmit and receive
data links, then this bit only applies to the
transmit interface.
0x04 Failed Link: If set, the data link is failed and not
suitable for user traffic.
Local_Interface_Id:
This is the local identifier of the data link. This MUST be
node-wide unique and non-zero.
Remote_Interface_Id:
This is the remote identifier of the data link. This MUST be
non-zero.
Subobjects
The contents of the DATA_LINK object consist of a series of
variable-length data items called subobjects. The subobjects are
defined in Section 13.12.1 below.
A DATA_LINK object may contain more than one subobject. More than
one subobject of the same Type may appear if multiple capabilities
are supported over the data link.
Lang Standards Track PAGE 63
RFC 4204 Link Management Protocol (LMP) October 2005
13.12.1. Data Link Subobjects
The contents of the DATA_LINK object include a series of variable-
length data items called subobjects. Each subobject has the form:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------//--------------+
| Type | Length | (Subobject contents) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--------------//---------------+
Type: 8 bits
The Type indicates the type of contents of the subobject.
Currently defined values are:
Type = 1, Interface Switching Type
Type = 2, Wavelength
Length: 8 bits
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. The Length MUST be at
least 4, and MUST be a multiple of 4.
13.12.1.1. Subobject Type 1: Interface Switching Type
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Switching Type| EncType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Reservable Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Reservable Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Switching Type: 8 bits
This is used to identify the local Interface Switching Type of the
TE link as defined in [RFC 3471].
EncType: 8 bits
This is the encoding type of the data link. The defined EncType
values are consistent with the LSP Encoding Type values of
[RFC 3471].
Lang Standards Track PAGE 64
RFC 4204 Link Management Protocol (LMP) October 2005
Minimum Reservable Bandwidth: 32 bits
This is measured in bytes per second and represented in IEEE
floating point format.
Maximum Reservable Bandwidth: 32 bits
This is measured in bytes per second and represented in IEEE
floating point format.
If the interface only supports a fixed rate, the minimum and maximum
bandwidth fields are set to the same value.
13.12.1.2. Subobject Type 2: Wavelength
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | (Reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Reserved field should be sent as zero and ignored on receipt.
Wavelength: 32 bits
This value indicates the wavelength carried over the port. Values
used in this field only have significance between two neighbors.
13.13. CHANNEL_STATUS Class
Class = 13
Lang Standards Track PAGE 65
RFC 4204 Link Management Protocol (LMP) October 2005
o C-Type = 1, IPv4 INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|D| Channel Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|D| Channel Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o C-Type = 2, IPv6 INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Interface_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|D| Channel Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Interface_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|D| Channel Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 66
RFC 4204 Link Management Protocol (LMP) October 2005
o C-Type = 3, Unnumbered INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|D| Channel Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|D| Channel_Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Active bit: 1 bit
This indicates that the Channel is allocated to user traffic and
the data link should be actively monitored.
Direction bit: 1 bit
This indicates the direction (transmit/receive) of the data
channel referred to in the CHANNEL_STATUS object. If set, this
indicates the data channel is in the transmit direction.
Channel_Status: 30 bits
This indicates the status condition of a data channel. The
following values are defined. All other values are reserved.
1 Signal Okay (OK): Channel is operational
2 Signal Degrade (SD): A soft failure caused by a BER exceeding
a preselected threshold. The specific
BER used to define the threshold is
configured.
3 Signal Fail (SF): A hard signal failure including (but not
limited to) loss of signal (LOS), loss of
frame (LOF), or Line AIS.
This object contains one or more Interface_Ids followed by a
Channel_Status field.
To indicate the status of the entire TE Link, there MUST be only one
Interface_Id, and it MUST be zero.
Lang Standards Track PAGE 67
RFC 4204 Link Management Protocol (LMP) October 2005
This object is non-negotiable.
13.14. CHANNEL_STATUS_REQUEST Class
Class = 14
o C-Type = 1, IPv4 INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This object contains one or more Interface_Ids.
The Length of this object is 4 + 4N in bytes, where N is the number
of Interface_Ids.
Lang Standards Track PAGE 68
RFC 4204 Link Management Protocol (LMP) October 2005
o C-Type = 2, IPv6 INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Interface_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Interface_Id (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This object contains one or more Interface_Ids.
The Length of this object is 4 + 16N in bytes, where N is the number
of Interface_Ids.
o C-Type = 3, Unnumbered INTERFACE_ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface_Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 69
RFC 4204 Link Management Protocol (LMP) October 2005
This object contains one or more Interface_Ids.
The Length of this object is 4 + 4N in bytes, where N is the number
of Interface_Ids.
This object is non-negotiable.
13.15. ERROR_CODE Class
Class = 20
o C-Type = 1, BEGIN_VERIFY_ERROR
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ERROR CODE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following bit-values are defined in network byte order (i.e.,
big-endian byte order):
0x01 = Link Verification Procedure not supported.
0x02 = Unwilling to verify.
0x04 = Unsupported verification transport mechanism.
0x08 = Link_Id configuration error.
0x10 = Unknown object C-Type.
All other bit-values are reserved and should be sent as zero and
ignored on receipt.
Multiple bits may be set to indicate multiple errors.
This object is non-negotiable.
If a BeginVerifyNack message is received with Error Code 2, the node
that originated the BeginVerify SHOULD schedule a BeginVerify
retransmission after Rf seconds, where Rf is a locally defined
parameter.
o C-Type = 2, LINK_SUMMARY_ERROR
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ERROR CODE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang Standards Track PAGE 70
RFC 4204 Link Management Protocol (LMP) October 2005
The following bit-values are defined in network byte order (i.e.,
big-endian byte order):
0x01 = Unacceptable non-negotiable LINK_SUMMARY parameters.
0x02 = Renegotiate LINK_SUMMARY parameters.
0x04 = Invalid TE_LINK Object.
0x08 = Invalid DATA_LINK Object.
0x10 = Unknown TE_LINK object C-Type.
0x20 = Unknown DATA_LINK object C-Type.
All other bit-values are reserved and should be sent as zero and
ignored on receipt.
Multiple bits may be set to indicate multiple errors.
This object is non-negotiable.
14. References
14.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling
in MPLS Traffic Engineering (TE)", RFC 4201, October
2005.
[RFC 4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing
Extensions in Support of Generalized Multi-Protocol Label
Switching (GMPLS)", RFC 4202, October 2005.
[RFC 2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
and S. Molendini, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, April 2001.
[RFC 2402] Kent, S. and R. Atkinson, "IP Authentication Header", RFC
2402, November 1998.
[RFC 2406] Kent, S. and R. Atkinson, "IP Encapsulating Security
Payload (ESP)", RFC 2406, November 1998.
[RFC 2407] Piper, D., "The Internet IP Security Domain of
Interpretation for ISAKMP", RFC 2407, November 1998.
[RFC 2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
Lang Standards Track PAGE 71
RFC 4204 Link Management Protocol (LMP) October 2005
[RFC 3471] Berger, L., Ed., "Generalized MPLS - Signaling
Functional Description", RFC 3471, January 2003.
14.2. Informative References
[RFC 3630] Katz, D., Kompella, K., and D. Yeung, "Traffic
Engineering (TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[RFC 3784] Smit, H. and T. Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE)",
RFC 3784, June 2004.
[RFC 2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[RFC 2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC 3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
Lang Standards Track PAGE 72
RFC 4204 Link Management Protocol (LMP) October 2005
15. Security Considerations
There are number of attacks that an LMP protocol session can
potentially experience. Some examples include:
o an adversary may spoof control packets;
o an adversary may modify the control packets in transit;
o an adversary may replay control packets;
o an adversary may study a number of control packets and try to
break the key using cryptographic tools. If the
hash/encryption algorithm used has known weaknesses, then it
becomes easy for the adversary to discover the key using simple
tools.
This section specifies an IPsec-based security mechanism for LMP.
15.1. Security Requirements
The following requirements are applied to the mechanism described in
this section.
o LMP security MUST be able to provide authentication, integrity,
and replay protection.
o For LMP traffic, confidentiality is not needed. Only
authentication is needed to ensure that the control packets
(packets sent along the LMP Control Channel) are originating
from the right place and have not been modified in transit.
LMP Test packets exchanged through the data links do not need
to be protected.
o For LMP traffic, protecting the identity of LMP end-points is
not commonly required.
o The security mechanism should provide for well defined key
management schemes. The key management schemes should be well
analyzed to be cryptographically secure. The key management
schemes should be scalable. In addition, the key management
system should be automatic.
o The algorithms used for authentication MUST be
cryptographically sound. Also, the security protocol MUST
allow for negotiating and using different authentication
algorithms.
Lang Standards Track PAGE 73
RFC 4204 Link Management Protocol (LMP) October 2005
15.2. Security Mechanisms
IPsec is a protocol suite that is used to secure communication at the
network layer between two peers. This protocol is comprised of IP
Security architecture document [RFC 2401], IKE [RFC 2409], IPsec AH
[RFC 2402], and IPsec ESP [RFC 2406]. IKE is the key management
protocol for IP networks, while AH and ESP are used to protect IP
traffic. IKE is defined specific to IP domain of interpretation.
Considering the requirements described in Section 15.1, it is
recommended that, where security is needed for LMP, implementations
use IPsec as described below:
1. Implementations of LMP over IPsec protocol SHOULD support manual
keying mode.
Manual keying mode provides an easy way to set up and diagnose
IPsec functionality.
However, note that manual keying mode cannot effectively support
features such as replay protection and automatic re-keying. An
implementer using manual keys must be aware of these limits.
It is recommended that an implementer use manual keying only for
diagnostic purposes and use dynamic keying protocol to make use of
features such as replay protection and automatic re-keying.
2. IPsec ESP with trailer authentication in tunnel mode MUST be
supported.
3. Implementations MUST support authenticated key exchange protocols.
IKE [RFC 2409] MUST be used as the key exchange protocol if keys
are dynamically negotiated between peers.
4. Implementation MUST use the IPsec DOI [RFC 2407].
5. For IKE protocol, the identities of the SAs negotiated in Quick
Mode represent the traffic that the peers agree to protect and are
comprised of address space, protocol, and port information.
For LMP over IPsec, it is recommended that the identity payload
for Quick mode contain the following information:
The identities MUST be of type IP addresses and the value of the
identities SHOULD be the IP addresses of the communicating peers.
Lang Standards Track PAGE 74
RFC 4204 Link Management Protocol (LMP) October 2005
The protocol field MUST be UDP. The port field SHOULD be set to
zero to indicate port fields should be ignored. This implies all
UDP traffic between the peers must be sent through the IPsec
tunnel. If an implementation supports port-based selectors, it
can opt for a more finely grained selector by specifying the port
field to the LMP port. If, however, the peer does not use port-
based selectors, the implementation MUST fall back to using a port
selector value of 0.
6. Aggressive mode of IKE negotiation MUST be supported.
When IPsec is configured to be used with a peer, all LMP messages
are expected to be sent over the IPsec tunnel (crypto channel).
Similarly, an LMP receiver configured to use Ipsec with a peer
should reject any LMP traffic that does not come through the
crypto channel.
The crypto channel can be pre-setup with the LMP neighbor, or the
first LMP message sent to the peer can trigger the creation of the
IPsec tunnel.
A set of control channels can share the same crypto channel. When
LMP Hellos are used to monitor the status of the control channel,
it is important to keep in mind that the keep-alive failure in a
control channel may also be due to a failure in the crypto
channel. The following method is recommended to ensure that an
LMP communication path between two peers is working properly.
o If LMP Hellos detect a failure on a control channel, switch to
an alternate control channel and/or try to establish a new
control channel.
o Ensure the health of the control channels using LMP Hellos. If
all control channels indicate a failure and it is not possible
to bring up a new control channel, tear down all existing
control channels. Also, tear down the crypto channel (both the
IKE SA and IPsec SAs).
o Reestablish the crypto channel. Failure to establish a crypto
channel indicates a fatal failure for LMP communication.
o Bring up the control channel. Failure to bring up the control
channel indicates a fatal failure for LMP communication.
Lang Standards Track PAGE 75
RFC 4204 Link Management Protocol (LMP) October 2005
When LMP peers are dynamically discovered (particularly the
initiator), the following points should be noted:
When using pre-shared key authentication in identity protection
mode (main mode), the pre-shared key is required to compute the
value of SKEYID (used for deriving keys to encrypt messages
during key exchange). In main mode of IKE, the pre-shared key
to be used has to be identified before receiving the peer's
identity payload. The pre-shared key is required for
calculating SKEYID. The only information available about the
peer at this point is its IP address from which the negotiation
came from. Keying off the IP address of a peer to get the
pre-shared key is not possible since the addresses are dynamic
and not known beforehand.
Aggressive mode key exchange can be used since identification
payloads are sent in the first message.
Note, however, that aggressive mode is prone to passive denial
of service attacks. Using a shared secret (group shared
secret) among a number of peers is strongly discouraged because
this opens up the solution to man-in-the-middle attacks.
Digital-signature-based authentication is not prone to such
problems. It is RECOMMENDED that a digital-signature-based
authentication mechanism be used where possible.
If pre-shared-key-based authentication is required, then
aggressive mode SHOULD be used. IKE pre-shared authentication
key values SHOULD be protected in a manner similar to the
user's account password.
16. IANA Considerations
The IANA has assigned port number 701 to LMP.
In the following, guidelines are given for IANA assignment for each
LMP name space. Ranges are specified for Private Use, to be assigned
by Expert Review, and to be assigned by Standards Action (as defined
in [RFC 2434].
Assignments made from LMP number spaces set aside for Private Use
(i.e., for proprietary extensions) need not be documented.
Independent LMP implementations using the same Private Use code
points will in general not interoperate, so care should be exercised
in using these code points in a multi-vendor network.
Lang Standards Track PAGE 76
RFC 4204 Link Management Protocol (LMP) October 2005
Assignments made from LMP number spaces to be assigned by Expert
Review are to be reviewed by an Expert designated by the IESG. The
intent in this document is that code points from these ranges are
used for Experimental extensions; as such, assignments MUST be
accompanied by Experimental RFCs. If deployment suggests that these
extensions are useful, then they should be described in Standards
Track RFCs, and new code points from the Standards Action ranges MUST
be assigned.
Assignments from LMP number spaces to be assigned by Standards Action
MUST be documented by a Standards Track RFC, typically submitted to
an IETF Working Group, but in any case following the usual IETF
procedures for Proposed Standards.
The Reserved bits of the LMP Common Header should be allocated by
Standards Action, pursuant to the policies outlined in [RFC 2434].
LMP defines the following name spaces that require management:
- LMP Message Type.
- LMP Object Class.
- LMP Object Class type (C-Type). These are unique within the
Object Class.
- LMP Sub-object Class type (Type). These are unique within the
Object Class.
The LMP Message Type name space should be allocated as follows:
pursuant to the policies outlined in [RFC 2434], the numbers in the
range 0-127 are allocated by Standards Action, 128-240 are allocated
through an Expert Review, and 241-255 are reserved for Private Use.
The LMP Object Class name space should be allocated as follows:
pursuant to the policies outlined in [RFC 2434], the numbers in the
range of 0-127 are allocated by Standards Action, 128-247 are
allocated through an Expert Review, and 248-255 are reserved for
Private Use.
The policy for allocating values out of the LMP Object Class name
space is part of the definition of the specific Class instance. When
a Class is defined, its definition must also include a description of
the policy under which the Object Class names are allocated.
The policy for allocating values out of the LMP Sub-object Class name
space is part of the definition of the specific Class instance. When
a Class is defined, its definition must also include a description of
the policy under which sub-objects are allocated.
Lang Standards Track PAGE 77
RFC 4204 Link Management Protocol (LMP) October 2005
The following name spaces have been assigned by IANA:
------------------------------------------------------------------
LMP Message Type name space
o Config message (Message type = 1)
o ConfigAck message (Message type = 2)
o ConfigNack message (Message type = 3)
o Hello message (Message type = 4)
o BeginVerify message (Message type = 5)
o BeginVerifyAck message (Message type = 6)
o BeginVerifyNack message (Message type = 7)
o EndVerify message (Message type = 8)
o EndVerifyAck message (Message type = 9)
o Test message (Message type = 10)
o TestStatusSuccess message (Message type = 11)
o TestStatusFailure message (Message type = 12)
o TestStatusAck message (Message type = 13)
o LinkSummary message (Message type = 14)
o LinkSummaryAck message (Message type = 15)
o LinkSummaryNack message (Message type = 16)
o ChannelStatus message (Message type = 17)
o ChannelStatusAck message (Message type = 18)
o ChannelStatusRequest message (Message type = 19)
o ChannelStatusResponse message (Message type = 20)
------------------------------------------------------------------
Lang Standards Track PAGE 78
RFC 4204 Link Management Protocol (LMP) October 2005
LMP Object Class name space and Class type (C-Type)
o CCID Class name (1)
The CCID Object Class type name space should be allocated as follows:
pursuant to the policies outlined in [RFC 2434], the numbers in the
range 0-111 are allocated by Standards Action, 112-119 are allocated
through an Expert Review, and 120-127 are reserved for Private Use.
- LOCAL_CCID (C-Type = 1)
- REMOTE_CCID (C-Type = 2)
o NODE_ID Class name (2)
The NODE ID Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- LOCAL_NODE_ID (C-Type = 1)
- REMOTE_NODE_ID (C-Type = 2)
o LINK_ID Class name (3)
The LINK_ID Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- IPv4 LOCAL_LINK_ID (C-Type = 1)
- IPv4 REMOTE_LINK_ID (C-Type = 2)
- IPv6 LOCAL_LINK_ID (C-Type = 3)
- IPv6 REMOTE_LINK_ID (C-Type = 4)
- Unnumbered LOCAL_LINK_ID (C-Type = 5)
- Unnumbered REMOTE_LINK_ID (C-Type = 6)
o INTERFACE_ID Class name (4)
The INTERFACE_ID Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
Lang Standards Track PAGE 79
RFC 4204 Link Management Protocol (LMP) October 2005
- IPv4 LOCAL_INTERFACE_ID (C-Type = 1)
- IPv4 REMOTE_INTERFACE_ID (C-Type = 2)
- IPv6 LOCAL_INTERFACE_ID (C-Type = 3)
- IPv6 REMOTE_INTERFACE_ID (C-Type = 4)
- Unnumbered LOCAL_INTERFACE_ID (C-Type = 5)
- Unnumbered REMOTE_INTERFACE_ID (C-Type = 6)
o MESSAGE_ID Class name (5)
The MESSAGE_ID Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- MESSAGE_ID (C-Type = 1)
- MESSAGE_ID_ACK (C-Type = 2)
o CONFIG Class name (6)
The CONFIG Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- HELLO_CONFIG (C-Type = 1)
o HELLO Class name (7)
The HELLO Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- HELLO (C-Type = 1)
o BEGIN_VERIFY Class name (8)
The BEGIN_VERIFY Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- Type 1 (C-Type = 1)
Lang Standards Track PAGE 80
RFC 4204 Link Management Protocol (LMP) October 2005
o BEGIN_VERIFY_ACK Class name (9)
The BEGIN_VERIFY_ACK Object Class type name space should be allocated
as follows: pursuant to the policies outlined in [RFC 2434], the
numbers in the range 0-111 are allocated by Standards Action, 112-119
are allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- Type 1 (C-Type = 1)
o VERIFY_ID Class name (10)
The VERIFY_ID Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- Type 1 (C-Type = 1)
o TE_LINK Class name (11)
The TE_LINK Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- IPv4 TE_LINK (C-Type = 1)
- IPv6 TE_LINK (C-Type = 2)
- Unnumbered TE_LINK (C-Type = 3)
o DATA_LINK Class name (12)
The DATA_LINK Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
private Use.
- IPv4 DATA_LINK (C-Type = 1)
- IPv6 DATA_LINK (C-Type = 2)
- Unnumbered DATA_LINK (C-Type = 3)
Lang Standards Track PAGE 81
RFC 4204 Link Management Protocol (LMP) October 2005
The DATA_LINK Sub-object Class name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range of 0-127 are allocated by Standards Action, 128-247 are
allocated through an Expert Review, and 248-255 are reserved for
private Use.
- Interface Switching Type (sub-object Type = 1)
- Wavelength (sub-object Type = 2)
o CHANNEL_STATUS Class name (13)
The CHANNEL_STATUS Object Class type name space should be allocated
as follows: pursuant to the policies outlined in [RFC 2434], the
numbers in the range 0-111 are allocated by Standards Action, 112-119
are allocated through an Expert Review, and 120-127 are reserved for
Private Use.
- IPv4 INTERFACE_ID (C-Type = 1)
- IPv6 INTERFACE_ID (C-Type = 2)
- Unnumbered INTERFACE_ID (C-Type = 3)
o CHANNEL_STATUS_REQUESTClass name (14)
The CHANNEL_STATUS_REQUEST Object Class type name space should be
allocated as follows: pursuant to the policies outlined in [RFC 2434],
the numbers in the range 0-111 are allocated by Standards Action,
112-119 are allocated through an Expert Review, and 120-127 are
reserved for Private Use.
- IPv4 INTERFACE_ID (C-Type = 1)
- IPv6 INTERFACE_ID (C-Type = 2)
- Unnumbered INTERFACE_ID (C-Type = 3)
o ERROR_CODE Class name (20)
The ERROR_CODE Object Class type name space should be allocated as
follows: pursuant to the policies outlined in [RFC 2434], the numbers
in the range 0-111 are allocated by Standards Action, 112-119 are
allocated through an Expert Review, and 120-127 are reserved for
private Use.
- BEGIN_VERIFY_ERROR (C-Type = 1)
- LINK_SUMMARY_ERROR (C-Type = 2)
Lang Standards Track PAGE 82
RFC 4204 Link Management Protocol (LMP) October 2005
17. Acknowledgements
The authors would like to thank Andre Fredette for his many
contributions to this document. We would also like to thank Ayan
Banerjee, George Swallow, Adrian Farrel, Dimitri Papadimitriou, Vinay
Ravuri, and David Drysdale for their insightful comments and
suggestions. We would also like to thank John Yu, Suresh Katukam,
and Greg Bernstein for their helpful suggestions for the in-band
control channel applicability.
18. Contributors
Jonathan P. Lang
Sonos, Inc.
223 E. De La Guerra St.
Santa Barbara, CA 93101
EMail: jplang@ieee.org
Krishna Mitra
Independent Consultant
EMail: kmitra@earthlink.net
John Drake
Calient Networks
5853 Rue Ferrari
San Jose, CA 95138
EMail: jdrake@calient.net
Kireeti Kompella
Juniper Networks, Inc.
1194 North Mathilda Avenue
Sunnyvale, CA 94089
EMail: kireeti@juniper.net
Yakov Rekhter
Juniper Networks, Inc.
1194 North Mathilda Avenue
Sunnyvale, CA 94089
EMail: yakov@juniper.net
Lang Standards Track PAGE 83
RFC 4204 Link Management Protocol (LMP) October 2005
Lou Berger
Movaz Networks
EMail: lberger@movaz.com
Debanjan Saha
IBM Watson Research Center
EMail: dsaha@us.ibm.com
Debashis Basak
Accelight Networks
70 Abele Road, Suite 1201
Bridgeville, PA 15017-3470
EMail: dbasak@accelight.com
Hal Sandick
Shepard M.S.
2401 Dakota Street
Durham, NC 27705
EMail: sandick@nc.rr.com
Alex Zinin
Alcatel
EMail: alex.zinin@alcatel.com
Bala Rajagopalan
Intel Corp.
2111 NE 25th Ave
Hillsboro, OR 97123
EMail: bala.rajagopalan@intel.com
Sankar Ramamoorthi
Juniper Networks, Inc.
1194 North Mathilda Avenue
Sunnyvale, CA 94089
EMail: sankarr@juniper.net
Lang Standards Track PAGE 84
RFC 4204 Link Management Protocol (LMP) October 2005
Contact Address
Jonathan P. Lang
Sonos, Inc.
829 De La Vina, Suite 220
Santa Barbara, CA 93101
EMail: jplang@ieee.org
Lang Standards Track PAGE 85
RFC 4204 Link Management Protocol (LMP) October 2005
Full Copyright Statement
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Link Management Protocol (LMP)
RFC TOTAL SIZE: 186515 bytes
PUBLICATION DATE: Monday, October 10th, 2005
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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