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IETF RFC 6006
Extensions to the Path Computation Element Communication Protocol (PCEP) for Point-to-Multipoint Traffic Engineering Label Switched Paths
Last modified on Tuesday, September 21st, 2010
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Internet Engineering Task Force (IETF) Q. Zhao, Ed.
Request for Comments: 6006 Huawei Technology
Category: Standards Track D. King, Ed.
ISSN: 2070-1721 Old Dog Consulting
F. Verhaeghe
Thales Communication France
T. Takeda
NTT Corporation
Z. Ali
Cisco Systems, Inc.
J. Meuric
France Telecom
September 2010
Extensions to
the Path Computation Element Communication Protocol (PCEP)
for Point-to-Multipoint Traffic Engineering Label Switched Paths
 Abstract
Point-to-point Multiprotocol Label Switching (MPLS) and Generalized
MPLS (GMPLS) Traffic Engineering Label Switched Paths (TE LSPs) may
be established using signaling techniques, but their paths may first
need to be determined. The Path Computation Element (PCE) has been
identified as an appropriate technology for the determination of the
paths of point-to-multipoint (P2MP) TE LSPs.
This document describes extensions to the PCE communication Protocol
(PCEP) to handle requests and responses for the computation of paths
for P2MP TE LSPs.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 6006.
Zhao, et al. Standards Track PAGE 1 
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction ....................................................3
1.1. Terminology ................................................4
1.2. Requirements Language ......................................5
2. PCC-PCE Communication Requirements ..............................5
3. Protocol Procedures and Extensions ..............................6
3.1. P2MP Capability Advertisement ..............................6
3.1.1. P2MP Computation TLV in the Existing PCE
Discovery Protocol ..................................6
3.1.2. Open Message Extension ..............................7
3.2. Efficient Presentation of P2MP LSPs ........................7
3.3. P2MP Path Computation Request/Reply Message Extensions .....8
3.3.1. The Extension of the RP Object ......................8
3.3.2. The New P2MP END-POINTS Object ......................9
3.4. Request Message Format ....................................12
3.5. Reply Message Format ......................................12
3.6. P2MP Objective Functions and Metric Types .................13
3.6.1. New Objective Functions ............................13
3.6.2. New Metric Object Types ............................14
3.7. Non-Support of P2MP Path Computation ......................14
Zhao, et al. Standards Track PAGE 2
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
3.8. Non-Support by Back-Level PCE Implementations .............15
3.9. P2MP TE Path Reoptimization Request .......................15
3.10. Adding and Pruning Leaves to/from the P2MP Tree ..........16
3.11. Discovering Branch Nodes .................................19
3.11.1. Branch Node Object ................................19
3.12. Synchronization of P2MP TE Path Computation Requests .....19
3.13. Request and Response Fragmentation .......................20
3.13.1. Request Fragmentation Procedure ...................21
3.13.2. Response Fragmentation Procedure ..................21
3.13.3. Fragmentation Examples ............................21
3.14. UNREACH-DESTINATION Object ...............................22
3.15. P2MP PCEP-ERROR Objects and Types ........................23
3.16. PCEP NO-PATH Indicator ...................................24
4. Manageability Considerations ...................................25
4.1. Control of Function and Policy ............................25
4.2. Information and Data Models ...............................25
4.3. Liveness Detection and Monitoring .........................25
4.4. Verifying Correct Operation ...............................25
4.5. Requirements for Other Protocols and Functional
Components ................................................26
4.6. Impact on Network Operation ...............................26
5. Security Considerations ........................................26
6. IANA Considerations ............................................27
6.1. PCEP TLV Type Indicators ..................................27
6.2. Request Parameter Bit Flags ...............................27
6.3. Objective Functions .......................................27
6.4. Metric Object Types .......................................27
6.5. PCEP Objects ..............................................28
6.6. PCEP-ERROR Objects and Types ..............................29
6.7. PCEP NO-PATH Indicator ....................................30
6.8. SVEC Object Flag ..........................................30
6.9. OSPF PCE Capability Flag ..................................30
7. Acknowledgements ...............................................30
8. References .....................................................30
8.1. Normative References ......................................30
8.2. Informative References ....................................32
1. Introduction
The Path Computation Element (PCE) defined in [RFC 4655] is an entity
that is capable of computing a network path or route based on a
network graph, and applying computational constraints. A Path
Computation Client (PCC) may make requests to a PCE for paths to be
computed.
[RFC 4875] describes how to set up point-to-multipoint (P2MP) Traffic
Engineering Label Switched Paths (TE LSPs) for use in Multiprotocol
Label Switching (MPLS) and Generalized MPLS (GMPLS) networks.
Zhao, et al. Standards Track PAGE 3
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
The PCE has been identified as a suitable application for the
computation of paths for P2MP TE LSPs [RFC 5671].
The PCE communication Protocol (PCEP) is designed as a communication
protocol between PCCs and PCEs for point-to-point (P2P) path
computations and is defined in [RFC 5440]. However, that
specification does not provide a mechanism to request path
computation of P2MP TE LSPs.
A P2MP LSP is comprised of multiple source-to-leaf (S2L) sub-LSPs.
These S2L sub-LSPs are set up between ingress and egress Label
Switching Routers (LSRs) and are appropriately overlaid to construct
a P2MP TE LSP. During path computation, the P2MP TE LSP may be
determined as a set of S2L sub-LSPs that are computed separately and
combined to give the path of the P2MP LSP, or the entire P2MP TE LSP
may be determined as a P2MP tree in a single computation.
This document relies on the mechanisms of PCEP to request path
computation for P2MP TE LSPs. One path computation request message
from a PCC may request the computation of the whole P2MP TE LSP, or
the request may be limited to a sub-set of the S2L sub-LSPs. In the
extreme case, the PCC may request the S2L sub-LSPs to be computed
individually with it being the PCC's responsibility to decide whether
to signal individual S2L sub-LSPs or combine the computation results
to signal the entire P2MP TE LSP. Hence the PCC may use one path
computation request message or may split the request across multiple
path computation messages.
1.1. Terminology
Terminology used in this document:
TE LSP: Traffic Engineering Label Switched Path.
LSR: Label Switching Router.
OF: Objective Function: A set of one or more optimization criteria
used for the computation of a single path (e.g., path cost
minimization), or for the synchronized computation of a set of
paths (e.g., aggregate bandwidth consumption minimization).
P2MP: Point-to-Multipoint.
P2P: Point-to-Point.
This document also uses the terminology defined in [RFC 4655],
[RFC 4875], and [RFC 5440].
Zhao, et al. Standards Track PAGE 4
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
1.2. Requirements Language
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 [RFC 2119].
2. PCC-PCE Communication Requirements
This section summarizes the PCC-PCE communication requirements for
P2MP MPLS-TE LSPs described in [RFC 5862]. The numbering system
corresponds to the requirement numbers used in [RFC 5862].
1. The PCC MUST be able to specify that the request is a P2MP path
computation request.
2. The PCC MUST be able to specify that objective functions are to
be applied to the P2MP path computation request.
3. The PCE MUST have the capability to reject a P2MP path request
and indicate non-support of P2MP path computation.
4. The PCE MUST provide an indication of non-support of P2MP path
computation by back-level PCE implementations.
5. A P2MP path computation request MUST be able to list multiple
destinations.
6. A P2MP path computation response MUST be able to carry the path
of a P2MP LSP.
7. By default, the path returned by the PCE SHOULD use the
compressed format.
8. It MUST be possible for a single P2MP path computation request or
response to be conveyed by a sequence of messages.
9. It MUST NOT be possible for a single P2MP path computation
request to specify a set of different constraints, traffic
parameters, or quality-of-service requirements for different
destinations of a P2MP LSP.
10. P2MP path modification and P2MP path diversity MUST be supported.
11. It MUST be possible to reoptimize existing P2MP TE LSPs.
12. It MUST be possible to add and remove P2MP destinations from
existing paths.
Zhao, et al. Standards Track PAGE 5
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
13. It MUST be possible to specify a list of applicable branch nodes
to use when computing the P2MP path.
14. It MUST be possible for a PCC to discover P2MP path computation
capability.
15. The PCC MUST be able to request diverse paths when requesting a
P2MP path.
3. Protocol Procedures and Extensions
The following section describes the protocol extensions required to
satisfy the requirements specified in Section 2 ("PCC-PCE
Communication Requirements") of this document.
3.1. P2MP Capability Advertisement
3.1.1. P2MP Computation TLV in the Existing PCE Discovery Protocol
[RFC 5088] defines a PCE Discovery (PCED) TLV carried in an OSPF
Router Information Link State Advertisement (LSA) defined in
[RFC 4970] to facilitate PCE discovery using OSPF. [RFC 5088]
specifies that no new sub-TLVs may be added to the PCED TLV. This
document defines a new flag in the OSPF PCE Capability Flags to
indicate the capability of P2MP computation.
Similarly, [RFC 5089] defines the PCED sub-TLV for use in PCE
Discovery using IS-IS. This document will use the same flag
requested for the OSPF PCE Capability Flags sub-TLV to allow IS-IS to
indicate the capability of P2MP computation.
The IANA assignment for a shared OSPF and IS-IS P2MP Capability Flag
is documented in Section 6.9 ("OSPF PCE Capability Flag") of this
document.
PCEs wishing to advertise that they support P2MP path computation
would set the bit (10) accordingly. PCCs that do not understand this
bit will ignore it (per [RFC 5088] and [RFC 5089]). PCEs that do not
support P2MP will leave the bit clear (per the default behavior
defined in [RFC 5088] and [RFC 5089]).
PCEs that set the bit to indicate support of P2MP path computation
MUST follow the procedures in Section 3.3.2 ("The New P2MP END-POINTS
Object") to further qualify the level of support.
Zhao, et al. Standards Track PAGE 6
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
3.1.2. Open Message Extension
Based on the Capabilities Exchange requirement described in
[RFC 5862], if a PCE does not advertise its P2MP capability during
discovery, PCEP should be used to allow a PCC to discover, during the
Open Message Exchange, which PCEs are capable of supporting P2MP path
computation.
To satisfy this requirement, we extend the PCEP OPEN object by
defining a new optional TLV to indicate the PCE's capability to
perform P2MP path computations.
IANA has allocated value 6 from the "PCEP TLV Type Indicators" sub-
registry, as documented in Section 6.1 ("PCEP TLV Type Indicators").
The description is "P2MP capable", and the length value is 2 bytes.
The value field is set to default value 0.
The inclusion of this TLV in an OPEN object indicates that the sender
can perform P2MP path computations.
The capability TLV is meaningful only for a PCE, so it will typically
appear only in one of the two Open messages during PCE session
establishment. However, in case of PCE cooperation (e.g.,
inter-domain), when a PCE behaving as a PCC initiates a PCE session
it SHOULD also indicate its path computation capabilities.
3.2. Efficient Presentation of P2MP LSPs
When specifying additional leaves, or optimizing existing P2MP TE
LSPs as specified in [RFC 5862], it may be necessary to pass existing
P2MP LSP route information between the PCC and PCE in the request and
reply messages. In each of these scenarios, we need new path objects
for efficiently passing the existing P2MP LSP between the PCE and
PCC.
We specify the use of the Resource Reservation Protocol Traffic
Engineering (RSVP-TE) extensions Explicit Route Object (ERO) to
encode the explicit route of a TE LSP through the network. PCEP ERO
sub-object types correspond to RSVP-TE ERO sub-object types. The
format and content of the ERO object are defined in [RFC 3209] and
[RFC 3473].
The Secondary Explicit Route Object (SERO) is used to specify the
explicit route of a S2L sub-LSP. The path of each subsequent S2L
sub-LSP is encoded in a P2MP_SECONDARY_EXPLICIT_ROUTE object SERO.
The format of the SERO is the same as an ERO defined in [RFC 3209] and
[RFC 3473].
Zhao, et al. Standards Track PAGE 7
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
The Secondary Record Route Object (SRRO) is used to record the
explicit route of the S2L sub-LSP. The class of the P2MP SRRO is the
same as the SRRO defined in [RFC 4873].
The SERO and SRRO are used to report the route of an existing TE LSP
for which a reoptimization is desired. The format and content of the
SERO and SRRO are defined in [RFC 4875].
A new PCEP object class and type are requested for SERO and SRRO.
Object-Class Value 29
Name SERO
Object-Type 1: SERO
2-15: Unassigned
Reference RFC 6006
Object-Class Value 30
Name SRRO
Object-Type 1: SRRO
2-15: Unassigned
Reference RFC 6006
The IANA assignment is documented in Section 6.5 ("PCEP Objects").
Since the explicit path is available for immediate signaling by the
MPLS or GMPLS control plane, the meanings of all of the sub-objects
and fields in this object are identical to those defined for the ERO.
3.3. P2MP Path Computation Request/Reply Message Extensions
This document extends the existing P2P RP (Request Parameters) object
so that a PCC can signal a P2MP path computation request to the PCE
receiving the PCEP request. The END-POINTS object is also extended
to improve the efficiency of the message exchange between PCC and PCE
in the case of P2MP path computation.
3.3.1. The Extension of the RP Object
The PCE path computation request and reply messages will need the
following additional parameters to indicate to the receiving PCE that
the request and reply messages have been fragmented across multiple
messages, that they have been requested for a P2MP path, and whether
the route is represented in the compressed or uncompressed format.
This document adds the following flags to the RP Object:
Zhao, et al. Standards Track PAGE 8
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
The F-bit is added to the flag bits of the RP object to indicate to
the receiver that the request is part of a fragmented request, or is
not a fragmented request.
o F (RP fragmentation bit - 1 bit):
0: This indicates that the RP is not fragmented or it is the last
piece of the fragmented RP.
1: This indicates that the RP is fragmented and this is not the
last piece of the fragmented RP. The receiver needs to wait
for additional fragments until it receives an RP with the same
RP-ID and with the F-bit set to 0.
The N-bit is added in the flag bits field of the RP object to signal
the receiver of the message that the request/reply is for P2MP or is
not for P2MP.
o N (P2MP bit - 1 bit):
0: This indicates that this is not a PCReq or PCRep message for
P2MP.
1: This indicates that this is a PCReq or PCRep message for P2MP.
The E-bit is added in the flag bits field of the RP object to signal
the receiver of the message that the route is in the compressed
format or is not in the compressed format. By default, the path
returned by the PCE SHOULD use the compressed format.
o E (ERO-compression bit - 1 bit):
0: This indicates that the route is not in the compressed format.
1: This indicates that the route is in the compressed format.
The IANA assignment is documented in Section 6.2 ("Request Parameter
Bit Flags") of this document.
3.3.2. The New P2MP END-POINTS Object
The END-POINTS object is used in a PCReq message to specify the
source IP address and the destination IP address of the path for
which a path computation is requested. To represent the end points
for a P2MP path efficiently, we define two new types of END-POINTS
objects for the P2MP path:
Zhao, et al. Standards Track PAGE 9
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
o Old leaves whose path can be modified/reoptimized;
o Old leaves whose path must be left unchanged.
With the new END-POINTS object, the PCE path computation request
message is expanded in a way that allows a single request message to
list multiple destinations.
In total, there are now 4 possible types of leaves in a P2MP request:
o New leaves to add (leaf type = 1)
o Old leaves to remove (leaf type = 2)
o Old leaves whose path can be modified/reoptimized (leaf type = 3)
o Old leaves whose path must be left unchanged (leaf type = 4)
A given END-POINTS object gathers the leaves of a given type. The
type of leaf in a given END-POINTS object is identified by the END-
POINTS object leaf type field.
Using the new END-POINTS object, the END-POINTS portion of a request
message for the multiple destinations can be reduced by up to 50% for
a P2MP path where a single source address has a very large number of
destinations.
Note that a P2MP path computation request can mix the different types
of leaves by including several END-POINTS objects per RP object as
shown in the PCReq Routing Backus-Naur Form (RBNF) [RFC 5511] format
in Section 3.4 ("Request Message Format").
Zhao, et al. Standards Track PAGE 10
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
The format of the new END-POINTS object body for IPv4 (Object-Type 3)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Leaf type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. The New P2MP END-POINTS Object Body Format for IPv4
The format of the END-POINTS object body for IPv6 (Object-Type 4) 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Leaf type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Source IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. The New P2MP END-POINTS Object Body Format for IPv6
The END-POINTS object body has a variable length. These are
multiples of 4 bytes for IPv4, and multiples of 16 bytes, plus 4
bytes, for IPv6.
Zhao, et al. Standards Track PAGE 11
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
3.4. Request Message Format
The PCReq message is encoded as follows using RBNF as defined in
[RFC 5511].
Below is the message format for the request message:
<PCReq Message>::= <Common Header>
<request>
where:
<request>::= <RP>
<end-point-rro-pair-list>
[<OF>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]
[<LOAD-BALANCING>]
where:
<end-point-rro-pair-list>::=
<END-POINTS>[<RRO-List>][<BANDWIDTH>]
[<end-point-rro-pair-list>]
<RRO-List>::=<RRO>[<BANDWIDTH>][<RRO-List>]
<metric-list>::=<METRIC>[<metric-list>]
Figure 3. The Message Format for the Request Message
Note that we preserve compatibility with the [RFC 5440] definition of
<request>. At least one instance of <endpoints> MUST be present in
this message.
We have documented the IANA assignment of additional END-POINTS
Object-Types in Section 6.5 ("PCEP Objects") of this document.
3.5. Reply Message Format
The PCRep message is encoded as follows using RBNF as defined in
[RFC 5511].
Zhao, et al. Standards Track PAGE 12
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Below is the message format for the reply message:
<PCRep Message>::= <Common Header>
<response>
<response>::=<RP>
[<end-point-path-pair-list>]
[<NO-PATH>]
[<attribute-list>]
where:
<end-point-path-pair-list>::=
[<END-POINTS>]<path>[<end-point-path-pair-list>]
<path> ::= (<ERO>|<SERO>) [<path>]
<attribute-list>::=[<OF>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]
Figure 4. The Message Format for the Reply Message
The optional END-POINTS object in the reply message is used to
specify which paths are removed, changed, not changed, or added for
the request. The path is only needed for the end points that are
added or changed.
If the E-bit (ERO-Compress bit) was set to 1 in the request, then the
path will be formed by an ERO followed by a list of SEROs.
Note that we preserve compatibility with the [RFC 5440] definition of
<response> and the optional <end-point-path-pair-list> and <path>.
3.6. P2MP Objective Functions and Metric Types
3.6.1. New Objective Functions
Six objective functions have been defined in [RFC 5541] for P2P path
computation.
This document defines two additional objective functions -- namely,
SPT (Shortest Path Tree) and MCT (Minimum Cost Tree) that apply to
P2MP path computation. Hence two new objective function codes have
to be defined.
The description of the two new objective functions is as follows.
Zhao, et al. Standards Track PAGE 13
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Objective Function Code: 7
Name: Shortest Path Tree (SPT)
Description: Minimize the maximum source-to-leaf cost with respect
to a specific metric or to the TE metric used as the default
metric when the metric is not specified (e.g., TE or IGP metric).
Objective Function Code: 8
Name: Minimum Cost Tree (MCT)
Description: Minimize the total cost of the tree, that is the sum
of the costs of tree links, with respect to a specific metric or
to the TE metric used as the default metric when the metric is not
specified.
Processing these two new objective functions is subject to the rules
defined in [RFC 5541].
3.6.2. New Metric Object Types
There are three types defined for the <METRIC> object in [RFC 5440] --
namely, the IGP metric, the TE metric, and the hop count metric.
This document defines three additional types for the <METRIC> object:
the P2MP IGP metric, the P2MP TE metric, and the P2MP hop count
metric. They encode the sum of the metrics of all links of the tree.
We propose the following values for these new metric types:
o P2MP IGP metric: T=8
o P2MP TE metric: T=9
o P2MP hop count metric: T=10
3.7. Non-Support of P2MP Path Computation
o If a PCE receives a P2MP path request and it understands the P2MP
flag in the RP object, but the PCE is not capable of P2MP
computation, the PCE MUST send a PCErr message with a PCEP-ERROR
object and corresponding Error-Value. The request MUST then be
cancelled at the PCC. New Error-Types and Error-Values are
requested in Section 6 ("IANA Considerations") of this document.
o If the PCE does not understand the P2MP flag in the RP object,
then the PCE MUST send a PCErr message with Error-value=2
(capability not supported).
Zhao, et al. Standards Track PAGE 14
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
3.8. Non-Support by Back-Level PCE Implementations
If a PCE receives a P2MP request and the PCE does not understand the
P2MP flag in the RP object, and therefore the PCEP P2MP extensions,
then the PCE SHOULD reject the request.
3.9. P2MP TE Path Reoptimization Request
A reoptimization request for a P2MP TE path is specified by the use
of the R-bit within the RP object as defined in [RFC 5440] and is
similar to the reoptimization request for a P2P TE path. The only
difference is that the user MUST insert the list of RROs and SRROs
after each type of END-POINTS in the PCReq message, as described in
the "Request Message Format" section (Section 3.4) of this document.
An example of a reoptimization request and subsequent PCReq message
is described below:
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 3
RRO list
OF (optional)
Figure 5. PCReq Message Example 1 for Optimization
In this example, we request reoptimization of the path to all leaves
without adding or pruning leaves. The reoptimization request would
use an END-POINT type 3. The RRO list would represent the P2MP LSP
before the optimization, and the modifiable path leaves would be
indicated in the END-POINTS object.
It is also possible to specify distinct leaves whose path cannot be
modified. An example of the PCReq message in this scenario would be:
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Figure 6. PCReq Message Example 2 for Optimization
Zhao, et al. Standards Track PAGE 15
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
3.10. Adding and Pruning Leaves to/from the P2MP Tree
When adding new leaves to or removing old leaves from the existing
P2MP tree, by supplying a list of existing leaves, it SHOULD be
possible to optimize the existing P2MP tree. This section explains
the methods for adding new leaves to or removing old leaves from the
existing P2MP tree.
To add new leaves, the user MUST build a P2MP request using END-
POINTS with leaf type 1.
To remove old leaves, the user must build a P2MP request using END-
POINTS with leaf type 2. If no type-2 END-POINTS exist, then the PCE
MUST send an error type 17, value=1: The PCE is not capable of
satisfying the request due to no END-POINTS with leaf type 2.
When adding new leaves to or removing old leaves from the existing
P2MP tree, the PCC must also provide the list of old leaves, if any,
including END-POINTS with leaf type 3, leaf type 4, or both. New
PCEP-ERROR objects and types are necessary for reporting when certain
conditions are not satisfied (i.e., when there are no END-POINTS with
leaf type 3 or 4, or in the presence of END-POINTS with leaf type 1
or 2). A generic "Inconsistent END-POINT" error will be used if a
PCC receives a request that has an inconsistent END-POINT (i.e., if a
leaf specified as type 1 already exists). These IANA assignments are
documented in Section 6.6 ("PCEP-ERROR Objects and Types") of this
document.
For old leaves, the user MUST provide the old path as a list of RROs
that immediately follows each END-POINTS object. This document
specifies error values when specific conditions are not satisfied.
The following examples demonstrate full and partial reoptimization of
existing P2MP LSPs:
Case 1: Adding leaves with full reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
RRO list
END-POINTS for leaf type 3
RRO list
OF (optional)
Zhao, et al. Standards Track PAGE 16
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Case 2: Adding leaves with partial reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Case 3: Adding leaves without reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Case 4: Pruning Leaves with full reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
OF (optional)
Case 5: Pruning leaves with partial reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Zhao, et al. Standards Track PAGE 17
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Case 6: Pruning leaves without reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Case 7: Adding and pruning leaves with full reoptimization of
existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
OF (optional)
Case 8: Adding and pruning leaves with partial reoptimization of
existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Case 9: Adding and pruning leaves without reoptimization of existing
paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Zhao, et al. Standards Track PAGE 18
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
3.11. Discovering Branch Nodes
Before computing the P2MP path, a PCE may need to be provided means
to know which nodes in the network are capable of acting as branch
LSRs. A PCE can discover such capabilities by using the mechanisms
defined in [RFC 5073].
3.11.1. Branch Node Object
The PCC can specify a list of nodes that can be used as branch nodes
or a list of nodes that cannot be used as branch nodes by using the
Branch Node Capability (BNC) Object. The BNC Object has the same
format as the Include Route Object (IRO) defined in [RFC 5440], except
that it only supports IPv4 and IPv6 prefix sub-objects. Two Object-
types are also defined:
o Branch node list: List of nodes that can be used as branch nodes.
o Non-branch node list: List of nodes that cannot be used as branch
nodes.
The object can only be carried in a PCReq message. A Path Request
may carry at most one Branch Node Object.
The Object-Class and Object-types have been allocated by IANA. The
IANA assignment is documented in Section 6.5 ("PCEP Objects").
3.12. Synchronization of P2MP TE Path Computation Requests
There are cases when multiple P2MP LSPs' computations need to be
synchronized. For example, one P2MP LSP is the designated backup of
another P2MP LSP. In this case, path diversity for these dependent
LSPs may need to be considered during the path computation.
The synchronization can be done by using the existing Synchronization
VECtor (SVEC) functionality defined in [RFC 5440].
Zhao, et al. Standards Track PAGE 19
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
An example of synchronizing two P2MP LSPs, each having two leaves for
Path Computation Request Messages, is illustrated below:
Common Header
SVEC for sync of LSP1 and LSP2
OF (optional)
END-POINTS1 for P2MP
RRO1 list
END-POINTS2 for P2MP
RRO2 list
Figure 7. PCReq Message Example for Synchronization
This specification also defines two new flags to the SVEC Object Flag
Field for P2MP path dependent computation requests. The first new
flag is to allow the PCC to request that the PCE should compute a
secondary P2MP path tree with partial path diversity for specific
leaves or a specific S2L sub-path to the primary P2MP path tree. The
second flag, would allow the PCC to request that partial paths should
be link direction diverse.
The following flags are added to the SVEC object body in this
document:
o P (Partial Path Diverse bit - 1 bit):
When set, this would indicate a request for path diversity for a
specific leaf, a set of leaves, or all leaves.
o D (Link Direction Diverse bit - 1 bit):
When set, this would indicate a request that a partial path or
paths should be link direction diverse.
The IANA assignment is referenced in Section 6.8 of this document.
3.13. Request and Response Fragmentation
The total PCEP message length, including the common header, is
16 bytes. In certain scenarios the P2MP computation request may not
fit into a single request or response message. For example, if a
tree has many hundreds or thousands of leaves, then the request or
response may need to be fragmented into multiple messages.
Zhao, et al. Standards Track PAGE 20
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
The F-bit has been outlined in "The Extension of the RP Object"
(Section 3.3.1) of this document. The F-bit is used in the RP object
header to signal that the initial request or response was too large
to fit into a single message and will be fragmented into multiple
messages. In order to identify the single request or response, each
message will use the same request ID.
3.13.1. Request Fragmentation Procedure
If the initial request is too large to fit into a single request
message, the PCC will split the request over multiple messages. Each
message sent to the PCE, except the last one, will have the F-bit set
in the RP object to signify that the request has been fragmented into
multiple messages. In order to identify that a series of request
messages represents a single request, each message will use the same
request ID.
The assumption is that request messages are reliably delivered and in
sequence, since PCEP relies on TCP.
3.13.2. Response Fragmentation Procedure
Once the PCE computes a path based on the initial request, a response
is sent back to the PCC. If the response is too large to fit into a
single response message, the PCE will split the response over
multiple messages. Each message sent to the PCE, except the last
one, will have the F-bit set in the RP object to signify that the
response has been fragmented into multiple messages. In order to
identify that a series of response messages represents a single
response, each message will use the same response ID.
Again, the assumption is that response messages are reliably
delivered and in sequence, since PCEP relies on TCP.
3.13.3. Fragmentation Examples
The following example illustrates the PCC sending a request message
with Req-ID1 to the PCE, in order to add one leaf to an existing tree
with 1200 leaves. The assumption used for this example is that one
request message can hold up to 800 leaves. In this scenario, the
original single message needs to be fragmented and sent using two
smaller messages, which have the Req-ID1 specified in the RP object,
and with the F-bit set on the first message, and cleared on the
second message.
Zhao, et al. Standards Track PAGE 21
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Common Header
RP1 with Req-ID1 and P2MP=1 and F-bit=1
OF (optional)
END-POINTS1 for P2MP
RRO1 list
Common Header
RP2 with Req-ID1 and P2MP=1 and F-bit=0
OF (optional)
END-POINTS1 for P2MP
RRO1 list
Figure 8. PCReq Message Fragmentation Example
To handle a scenario where the last fragmented message piece is lost,
the receiver side of the fragmented message may start a timer once it
receives the first piece of the fragmented message. When the timer
expires and it has not received the last piece of the fragmented
message, it should send an error message to the sender to signal that
it has received an incomplete message. The relevant error message is
documented in Section 3.15 ("P2MP PCEP-ERROR Objects and Types").
3.14. UNREACH-DESTINATION Object
The PCE path computation request may fail because all or a subset of
the destinations are unreachable.
In such a case, the UNREACH-DESTINATION object allows the PCE to
optionally specify the list of unreachable destinations.
This object can be present in PCRep messages. There can be up to one
such object per RP.
The following UNREACH-DESTINATION objects will be required:
UNREACH-DESTINATION Object-Class is 28.
UNREACH-DESTINATION Object-Type for IPv4 is 1.
UNREACH-DESTINATION Object-Type for IPv6 is 2.
Zhao, et al. Standards Track PAGE 22
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The format of the UNREACH-DESTINATION object body for IPv4 (Object-
Type=1) 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9. UNREACH-DESTINATION Object Body for IPv4
The format of the UNREACH-DESTINATION object body for IPv6 (Object-
Type=2) 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10. UNREACH-DESTINATION Object Body for IPv6
3.15. P2MP PCEP-ERROR Objects and Types
To indicate an error associated with policy violation, a new error
value "P2MP Path computation not allowed" should be added to the
existing error code for policy violation (Error-Type=5) as defined in
[RFC 5440]:
Zhao, et al. Standards Track PAGE 23
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Error-Type=5; Error-Value=7: if a PCE receives a P2MP path
computation request that is not compliant with administrative
privileges (i.e., "The PCE policy does not support P2MP path
computation"), the PCE MUST send a PCErr message with a PCEP-ERROR
object (Error-Type=5) and an Error-Value (Error-Value=7). The
corresponding P2MP path computation request MUST also be cancelled.
To indicate capability errors associated with the P2MP path request,
a new Error-Type (16) and subsequent error-values are defined as
follows for inclusion in the PCEP-ERROR object:
Error-Type=16; Error-Value=1: if a PCE receives a P2MP path request
and the PCE is not capable of satisfying the request due to
insufficient memory, the PCE MUST send a PCErr message with a PCEP-
ERROR object (Error-Type=16) and an Error-Value (Error-Value=1). The
corresponding P2MP path computation request MUST also be cancelled.
Error-Type=16; Error-Value=2: if a PCE receives a P2MP path request
and the PCE is not capable of P2MP computation, the PCE MUST send a
PCErr message with a PCEP-ERROR object (Error-Type=16) and an Error-
Value (Error-Value=2). The corresponding P2MP path computation
request MUST also be cancelled.
To indicate P2MP message fragmentation errors associated with a P2MP
path request, a new Error-Type (17) and subsequent error-values are
defined as follows for inclusion in the PCEP-ERROR object:
Error-Type=18; Error-Value=1: if a PCE has not received the last
piece of the fragmented message, it should send an error message to
the sender to signal that it has received an incomplete message
(i.e., "Fragmented request failure"). The PCE MUST send a PCErr
message with a PCEP-ERROR object (Error-Type=18) and an Error-Value
(Error-Value=1).
3.16. PCEP NO-PATH Indicator
To communicate the reasons for not being able to find P2MP path
computation, the NO-PATH object can be used in the PCRep message.
One new bit is defined in the NO-PATH-VECTOR TLV carried in the
NO-PATH Object:
bit 24: when set, the PCE indicates that there is a reachability
problem with all or a subset of the P2MP destinations. Optionally,
the PCE can specify the destination or list of destinations that are
not reachable using the new UNREACH-DESTINATION object defined in
Section 3.14.
Zhao, et al. Standards Track PAGE 24
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
4. Manageability Considerations
[RFC 5862] describes various manageability requirements in support of
P2MP path computation when applying PCEP. This section describes how
manageability requirements mentioned in [RFC 5862] are supported in
the context of PCEP extensions specified in this document.
Note that [RFC 5440] describes various manageability considerations in
PCEP, and most of the manageability requirements mentioned in
[RFC 5862] are already covered there.
4.1. Control of Function and Policy
In addition to PCE configuration parameters listed in [RFC 5440], the
following additional parameters might be required:
o The ability to enable or disable P2MP path computations on the
PCE.
o The PCE may be configured to enable or disable the advertisement
of its P2MP path computation capability. A PCE can advertise its
P2MP capability via the IGP discovery mechanism discussed in
Section 3.1.1 ("P2MP Computation TLV in the Existing PCE Discovery
Protocol"), or during the Open Message Exchange discussed in
Section 3.1.2 ("Open Message Extension").
4.2. Information and Data Models
A number of MIB objects have been defined for general PCEP control
and monitoring of P2P computations in [PCEP-MIB]. [RFC 5862]
specifies that MIB objects will be required to support the control
and monitoring of the protocol extensions defined in this document.
A new document will be required to define MIB objects for PCEP
control and monitoring of P2MP computations.
4.3. Liveness Detection and Monitoring
There are no additional considerations beyond those expressed in
[RFC 5440], since [RFC 5862] does not address any additional
requirements.
4.4. Verifying Correct Operation
There are no additional requirements beyond those expressed in
[RFC 4657] for verifying the correct operation of the PCEP sessions.
It is expected that future MIB objects will facilitate verification
of correct operation and reporting of P2MP PCEP requests, responses,
and errors.
Zhao, et al. Standards Track PAGE 25
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
4.5. Requirements for Other Protocols and Functional Components
The method for the PCE to obtain information about a PCE capable of
P2MP path computations via OSPF and IS-IS is discussed in
Section 3.1.1 ("P2MP Computation TLV in the Existing PCE Discovery
Protocol") of this document.
The subsequent IANA assignments are documented in Section 6.9 ("OSPF
PCE Capability Flag") of this document.
4.6. Impact on Network Operation
It is expected that the use of PCEP extensions specified in this
document will not significantly increase the level of operational
traffic. However, computing a P2MP tree may require more PCE state
compared to a P2P computation. In the event of a major network
failure and multiple recovery P2MP tree computation requests being
sent to the PCE, the load on the PCE may also be significantly
increased.
5. Security Considerations
As described in [RFC 5862], P2MP path computation requests are more
CPU-intensive and also utilize more link bandwidth. In the event of
an unauthorized P2MP path computation request, or a denial of service
attack, the subsequent PCEP requests and processing may be disruptive
to the network. Consequently, it is important that implementations
conform to the relevant security requirements of [RFC 5440] that
specifically help to minimize or negate unauthorized P2MP path
computation requests and denial of service attacks. These mechanisms
include:
o Securing the PCEP session requests and responses using TCP
security techniques (Section 10.2 of [RFC 5440]).
o Authenticating the PCEP requests and responses to ensure the
message is intact and sent from an authorized node (Section 10.3
of [RFC 5440]).
o Providing policy control by explicitly defining which PCCs, via IP
access-lists, are allowed to send P2MP path requests to the PCE
(Section 10.6 of [RFC 5440]).
PCEP operates over TCP, so it is also important to secure the PCE and
PCC against TCP denial of service attacks. Section 10.7.1 of
[RFC 5440] outlines a number of mechanisms for minimizing the risk of
TCP based denial of service attacks against PCEs and PCCs.
Zhao, et al. Standards Track PAGE 26
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
PCEP implementations SHOULD consider the additional security provided
by the TCP Authentication Option (TCP-AO) [RFC 5925].
6. IANA Considerations
IANA maintains a registry of PCEP parameters. A number of IANA
considerations have been highlighted in previous sections of this
document. IANA has made the following allocations.
6.1. PCEP TLV Type Indicators
As described in Section 3.1.2., the newly defined P2MP capability TLV
allows the PCE to advertise its P2MP path computation capability.
IANA has made the following allocation from the "PCEP TLV Type
Indicators" sub-registry.
Value Description Reference
6 P2MP capable RFC 6006
6.2. Request Parameter Bit Flags
As described in Section 3.3.1, three new RP Object Flags have been
defined. IANA has made the following allocations from the PCEP "RP
Object Flag Field" sub-registry:
Bit Description Reference
18 Fragmentation (F-bit) RFC 6006
19 P2MP (N-bit) RFC 6006
20 ERO-compression (E-bit) RFC 6006
6.3. Objective Functions
As described in Section 3.6.1, two new Objective Functions have been
defined. IANA has made the following allocations from the PCEP
"Objective Function" sub-registry:
Code Point Name Reference
7 SPT RFC 6006
8 MCT RFC 6006
6.4. Metric Object Types
As described in Section 3.6.2, three new metric object T fields have
been defined. IANA has made the following allocations from the PCEP
"METRIC Object T Field" sub-registry:
Zhao, et al. Standards Track PAGE 27
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Value Description Reference
8 P2MP IGP metric RFC 6006
9 P2MP TE metric RFC 6006
10 P2MP hop count metric RFC 6006
6.5. PCEP Objects
As discussed in Section 3.3.2, two new END-POINTS Object-Types are
defined. IANA has made the following Object-Type allocations from
the "PCEP Objects" sub-registry:
Object-Class Value 4
Name END-POINTS
Object-Type 3: IPv4
4: IPv6
5-15: Unassigned
Reference RFC 6006
As described in Section 3.2, Section 3.11.1, and Section 3.14, four
PCEP Object-Classes and six PCEP Object-Types have been defined.
IANA has made the following allocations from the "PCEP Objects" sub-
registry:
Object-Class Value 28
Name UNREACH-DESTINATION
Object-Type 1: IPv4
2: IPv6
3-15: Unassigned
Reference RFC 6006
Object-Class Value 29
Name SERO
Object-Type 1: SERO
2-15: Unassigned
Reference RFC 6006
Object-Class Value 30
Name SRRO
Object-Type 1: SRRO
2-15: Unassigned
Reference RFC 6006
Zhao, et al. Standards Track PAGE 28
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Object-Class Value 31
Name Branch Node Capability Object
Object-Type 1: Branch node list
2: Non-branch node list
3-15: Unassigned
Reference RFC 6006
6.6. PCEP-ERROR Objects and Types
As described in Section 3.15, a number of new PCEP-ERROR Object Error
Types and Values have been defined. IANA has made the following
allocations from the PCEP "PCEP-ERROR Object Error Types and Values"
sub-registry:
Error
Type Meaning Reference
5 Policy violation
Error-value=7: RFC 6006
P2MP Path computation is not allowed
16 P2MP Capability Error
Error-Value=0: Unassigned RFC 6006
Error-Value=1: RFC 6006
The PCE is not capable to satisfy the request
due to insufficient memory
Error-Value=2: RFC 6006
The PCE is not capable of P2MP computation
17 P2MP END-POINTS Error
Error-Value=0: Unassigned RFC 6006
Error-Value=1: RFC 6006
The PCE is not capable to satisfy the request
due to no END-POINTS with leaf type 2
Error-Value=2: RFC 6006
The PCE is not capable to satisfy the request
due to no END-POINTS with leaf type 3
Error-Value=3: RFC 6006
The PCE is not capable to satisfy the request
due to no END-POINTS with leaf type 4
Error-Value=4: RFC 6006
The PCE is not capable to satisfy the request
due to inconsistent END-POINTS
18 P2MP Fragmentation Error
Error-Value=0: Unassigned RFC 6006
Error-Value=1: RFC 6006
Fragmented request failure
Zhao, et al. Standards Track PAGE 29
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
6.7. PCEP NO-PATH Indicator
As discussed in Section 3.16, a new NO-PATH-VECTOR TLV Flag Field has
been defined. IANA has made the following allocation from the PCEP
"NO-PATH-VECTOR TLV Flag Field" sub-registry:
Bit Description Reference
24 P2MP Reachability Problem RFC 6006
6.8. SVEC Object Flag
As discussed in Section 3.12, two new SVEC Object Flags are defined.
IANA has made the following allocation from the PCEP "SVEC Object
Flag Field" sub-registry:
Bit Description Reference
19 Partial Path Diverse RFC 6006
20 Link Direction Diverse RFC 6006
6.9. OSPF PCE Capability Flag
As discussed in Section 3.1.1, a new OSPF Capability Flag is defined
to indicate P2MP path computation capability. IANA has made the
following assignment from the OSPF Parameters "Path Computation
Element (PCE) Capability Flags" registry:
Bit Description Reference
10 P2MP path computation RFC 6006
7. Acknowledgements
The authors would like to thank Adrian Farrel, Young Lee, Dan Tappan,
Autumn Liu, Huaimo Chen, Eiji Okim, Nick Neate, Suresh Babu K, Dhruv
Dhody, Udayasree Palle, Gaurav Agrawal, Vishwas Manral, Dan
Romascanu, Tim Polk, Stewart Bryant, David Harrington, and Sean
Turner for their valuable comments and input on this document.
8. References
8.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Zhao, et al. Standards Track PAGE 30
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
[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.
[RFC 3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, January 2003.
[RFC 4873] Berger, L., Bryskin, I., Papadimitriou, D., and A.
Farrel, "GMPLS Segment Recovery", RFC 4873, May 2007.
[RFC 4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for Point-to-
Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May
2007.
[RFC 4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R.,
and S. Shaffer, "Extensions to OSPF for Advertising
Optional Router Capabilities", RFC 4970, July 2007.
[RFC 5073] Vasseur, J., Ed., and J. Le Roux, Ed., "IGP Routing
Protocol Extensions for Discovery of Traffic Engineering
Node Capabilities", RFC 5073, December 2007.
[RFC 5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "OSPF Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5088, January 2008.
[RFC 5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "IS-IS Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5089, January 2008.
[RFC 5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
[RFC 5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
Computation Element (PCE) Communication Protocol (PCEP)",
RFC 5440, March 2009.
[RFC 5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541, June 2009.
Zhao, et al. Standards Track PAGE 31
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
8.2. Informative References
[RFC 4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
August 2006.
[RFC 4657] Ash, J., Ed., and J. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol Generic
Requirements", RFC 4657, September 2006.
[RFC 5671] Yasukawa, S. and A. Farrel, Ed., "Applicability of the
Path Computation Element (PCE) to Point-to-Multipoint
(P2MP) MPLS and GMPLS Traffic Engineering (TE)",
RFC 5671, October 2009.
[RFC 5862] Yasukawa, S. and A. Farrel, "Path Computation Clients
(PCC) - Path Computation Element (PCE) Requirements for
Point-to-Multipoint MPLS-TE", RFC 5862, June 2010.
[RFC 5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010.
[PCEP-MIB] Koushik, K., Stephan, E., Zhao, Q., and D. King, "PCE
communication protocol (PCEP) Management Information
Base", Work in Progress, July 2010.
Contributors
Jean-Louis Le Roux
France Telecom
2, Avenue Pierre-Marzin
22307 Lannion Cedex
France
EMail: jeanlouis.leroux@orange-ftgroup.com
Mohamad Chaitou
France
EMail: mohamad.chaitou@gmail.com
Zhao, et al. Standards Track PAGE 32
RFC 6006 Extensions to PCEP for P2MP TE LSPs September 2010
Authors' Addresses
Quintin Zhao (editor)
Huawei Technology
125 Nagog Technology Park
Acton, MA 01719
US
EMail: qzhao@huawei.com
Daniel King (editor)
Old Dog Consulting
UK
EMail: daniel@olddog.co.uk
Fabien Verhaeghe
Thales Communication France
160 Bd Valmy 92700 Colombes
France
EMail: fabien.verhaeghe@gmail.com
Tomonori Takeda
NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585
Japan
EMail: takeda.tomonori@lab.ntt.co.jp
Zafar Ali
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
EMail: zali@cisco.com
Julien Meuric
France Telecom
2, Avenue Pierre-Marzin
22307 Lannion Cedex
France
EMail: julien.meuric@orange-ftgroup.com
Zhao, et al. Standards Track PAGE 33
Extensions to the Path Computation Element Communication Protocol (PCEP) for Point-to-Multipoint Traffic Engineering Label Switched Paths
RFC TOTAL SIZE: 68107 bytes
PUBLICATION DATE: Tuesday, September 21st, 2010
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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