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IETF RFC 7455
Last modified on Wednesday, March 11th, 2015
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Internet Engineering Task Force (IETF) T. Senevirathne
Request for Comments: 7455 N. Finn
Updates: 6325 S. Salam
Category: Standards Track D. Kumar
ISSN: 2070-1721 Cisco
D. Eastlake 3rd
S. Aldrin
Y. Li
Huawei
March 2015
Transparent Interconnection of Lots of Links (TRILL): Fault Management
 Abstract
This document specifies Transparent Interconnection of Lots of Links
(TRILL) Operations, Administration, and Maintenance (OAM) fault
management. Methods in this document follow the CFM (Connectivity
Fault Management) framework defined in IEEE 802.1 and reuse OAM tools
where possible. Additional messages and TLVs are defined for TRILL-
specific applications or for cases where a different set of
information is required other than CFM as defined in IEEE 802.1.
This document updates RFC 6325.
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 7455.
Senevirathne, et al. Standards Track PAGE 1 
RFC 7455 TRILL Fault Management March 2015
Copyright Notice
Copyright (c) 2015 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
carefully, as they describe your rights and restrictions with respect
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.
Senevirathne, et al. Standards Track PAGE 2
RFC 7455 TRILL Fault Management March 2015
Table of Contents
1. Introduction ....................................................5
2. Conventions Used in This Document ...............................5
3. General Format of TRILL OAM Packets .............................6
3.1. Identification of TRILL OAM Frames .........................8
3.2. Use of TRILL OAM Alert Flag ................................8
3.2.1. Handling of TRILL Frames with the "A" Flag ..........9
3.3. OAM Capability Announcement ................................9
3.4. Identification of the OAM Message .........................10
4. TRILL OAM Layering vs. IEEE Layering ...........................11
4.1. Processing at the ISS Layer ...............................12
4.1.1. Receive Processing .................................12
4.1.2. Transmit Processing ................................12
4.2. End-Station VLAN and Priority Processing ..................12
4.2.1. Receive Processing .................................12
4.2.2. Transmit Processing ................................12
4.3. TRILL Encapsulation and Decapsulation Layer ...............12
4.3.1. Receive Processing for Unicast Packets .............12
4.3.2. Transmit Processing for Unicast Packets ............13
4.3.3. Receive Processing for Multicast Packets ...........14
4.3.4. Transmit Processing of Multicast Packets ...........15
4.4. TRILL OAM Layer Processing ................................16
5. Maintenance Associations (MAs) in TRILL ........................17
6. MEP Addressing .................................................18
6.1. Use of MIP in TRILL .......................................21
7. Continuity Check Message (CCM) .................................22
8. TRILL OAM Message Channel ......................................25
8.1. TRILL OAM Message Header ..................................25
8.2. TRILL-Specific OAM OpCodes ................................26
8.3. Format of TRILL OAM TLV ...................................26
8.4. TRILL OAM TLVs ............................................27
8.4.1. Common TLVs between CFM and TRILL ..................27
8.4.2. TRILL OAM-Specific TLVs ............................27
8.4.3. TRILL OAM Application Identifier TLV ...............28
8.4.4. Out-of-Band Reply Address TLV ......................30
8.4.5. Diagnostic Label TLV ...............................31
8.4.6. Original Data Payload TLV ..........................32
8.4.7. RBridge Scope TLV ..................................32
8.4.8. Previous RBridge Nickname TLV ......................33
8.4.9. Next-Hop RBridge List TLV ..........................34
8.4.10. Multicast Receiver Port Count TLV .................34
8.4.11. Flow Identifier TLV ...............................35
8.4.12. Reflector Entropy TLV .............................36
8.4.13. Authentication TLV ................................37
Senevirathne, et al. Standards Track PAGE 3
RFC 7455 TRILL Fault Management March 2015
9. Loopback Message ...............................................38
9.1. Loopback Message Format ...................................38
9.2. Theory of Operation .......................................39
9.2.1. Actions by Originator RBridge ......................39
9.2.2. Intermediate RBridge ...............................39
9.2.3. Destination RBridge ................................40
10. Path Trace Message ............................................40
10.1. Theory of Operation ......................................41
10.1.1. Actions by Originator RBridge .....................41
10.1.2. Intermediate RBridge ..............................42
10.1.3. Destination RBridge ...............................43
11. Multi-Destination Tree Verification Message (MTVM) ............43
11.1. MTVM Format ..............................................44
11.2. Theory of Operation ......................................44
11.2.1. Actions by Originator RBridge .....................44
11.2.2. Receiving RBridge .................................45
11.2.3. In-Scope RBridges .................................45
12. Application of Continuity Check Message (CCM) in TRILL ........46
12.1. CCM Error Notification ...................................47
12.2. Theory of Operation ......................................48
12.2.1. Actions by Originator RBridge .....................48
12.2.2. Intermediate RBridge ..............................49
12.2.3. Destination RBridge ...............................49
13. Fragmented Reply ..............................................50
14. Security Considerations .......................................50
15. IANA Considerations ...........................................52
15.1. OAM Capability Flags .....................................52
15.2. CFM Code Points ..........................................52
15.3. MAC Addresses ............................................53
15.4. Return Codes and Sub-codes ...............................53
15.5. TRILL Nickname Address Family ............................54
16. References ....................................................54
16.1. Normative References .....................................54
16.2. Informative References ...................................55
Appendix A. Backwards Compatibility ...............................57
A.1. Maintenance Point (MEP/MIP) Model ........................57
A.2. Data-Plane Encoding and Frame Identification .............57
Appendix B. Base Mode for TRILL OAM ...............................59
Appendix C. MAC Addresses Request .................................61
Acknowledgments ...................................................62
Authors' Addresses ................................................62
Senevirathne, et al. Standards Track PAGE 4
RFC 7455 TRILL Fault Management March 2015
1. Introduction
The general structure of TRILL OAM messages is presented in
[RFC 7174]. TRILL OAM messages consist of six parts: Link Header,
TRILL Header, Flow Entropy, OAM Ethertype, OAM Message Channel, and
Link Trailer.
The OAM Message Channel carries various control information and OAM-
related data between TRILL switches, also known as RBridges or
Routing Bridges.
A common OAM Message Channel representation can be shared between
different technologies. This consistency between different OAM
technologies promotes nested fault monitoring and isolation between
technologies that share the same OAM framework.
The TRILL OAM Message Channel is formatted as specified in IEEE
Connectivity Fault Management (CFM) [8021Q].
The ITU-T Y.1731 [Y1731] standard utilizes the same messaging format
as [8021Q] OAM messages where applicable. This document takes a
similar stance and reuses [8021Q] in TRILL OAM. It is assumed that
readers are familiar with [8021Q] and [Y1731]. Readers who are not
familiar with these documents are encouraged to review them.
This document specifies TRILL OAM fault management. It updates
[RFC 6325] as specified in Section 3.1. TRILL performance monitoring
is specified in [RFC 7456].
2. Conventions Used in This Document
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].
Capitalized IANA Considerations terms such as "Standards Action" are
to be interpreted as described in [RFC 5226].
Acronyms used in the document include the following:
CCM - Continuity Check Message [8021Q]
DA - Destination Address
ECMP - Equal-Cost Multipath
FGL - Fine-Grained Label
Senevirathne, et al. Standards Track PAGE 5
RFC 7455 TRILL Fault Management March 2015
ISS - Internal Sub-Layer Service [8021Q]
LBM - Loopback Message [8021Q]
LBR - Loopback Reply [8021Q]
MA - Maintenance Association [8021Q] [RFC 7174]
MAC - Media Access Control (MAC)
MD - Maintenance Domain [8021Q]
MEP - Maintenance End Point [RFC 7174] [8021Q]
MIP - Maintenance Intermediate Point [RFC 7174] [8021Q]
MP - Maintenance Point [RFC 7174]
MTVM - Multi-destination Tree Verification Message
MTVR - Multi-destination Tree Verification Reply
OAM - Operations, Administration, and Maintenance [RFC 6291]
PRI - Priority of Ethernet Frames [8021Q]
PTM - Path Trace Message
PTR - Path Trace Reply
SA - Source Address
SAP - Service Access Point [8021Q]
TRILL - Transparent Interconnection of Lots of Links [RFC 6325]
3. General Format of TRILL OAM Packets
The TRILL forwarding paradigm allows an implementation to select a
path from a set of equal-cost paths to forward a unicast TRILL Data
packet. For multi-destination TRILL Data packets, a distribution
tree is chosen by the TRILL switch that ingresses or creates the
packet. Selection of the path of choice is implementation dependent
at each hop for unicast and at the ingress for multi-destination.
However, it is a common practice to utilize Layer 2 through Layer 4
information in the frame payload for path selection.
Senevirathne, et al. Standards Track PAGE 6
RFC 7455 TRILL Fault Management March 2015
For accurate monitoring and/or diagnostics, OAM messages are required
to follow the same path as corresponding data packets. [RFC 7174]
presents the high-level format of OAM messages. The details of the
TRILL OAM frame format are defined in this document.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Link Header . Variable
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ TRILL Header + 6 or more bytes
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Flow Entropy . 96 bytes
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OAM Ethertype |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. OAM Message Channel . Variable
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Trailer | Variable
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Format of TRILL OAM Messages
o Link Header: Media-dependent header. For Ethernet, this includes
the Destination MAC, Source MAC, VLAN (optional), and Ethertype
fields.
o TRILL Header: Fixed size of 6 bytes when the Extended Header is
not included [RFC 6325].
o Flow Entropy: A 96-byte, fixed-size field. The rightmost bits of
the field MUST be padded with zeros, up to 96 bytes, when the
flow-entropy information is less than 96 bytes. Flow Entropy
enables emulation of the forwarding behavior of the desired data
packets. The Flow Entropy field starts with the Inner.MacDA. The
offset of the Inner.MacDA depends on whether extensions are
included or not as specified in [RFC 7179] and [RFC 6325]. Such
extensions are not commonly supported in current TRILL
implementations.
Senevirathne, et al. Standards Track PAGE 7
RFC 7455 TRILL Fault Management March 2015
o OAM Ethertype: A 16-bit Ethertype that identifies the OAM Message
Channel that follows. This document specifies using the Ethertype
0x8902 allocated for CFM [8021Q].
o OAM Message Channel: A variable-size section that carries OAM-
related information. The message format is as specified in
[8021Q].
o Link Trailer: Media-dependent trailer. For Ethernet, this is the
FCS (Frame Check Sequence).
3.1. Identification of TRILL OAM Frames
TRILL, as originally specified in [RFC 6325], did not have a specific
flag or method to identify OAM frames. This document updates
[RFC 6325] to include specific methods to identify TRILL OAM frames.
Section 3.2 explains the details of the method.
3.2. Use of TRILL OAM Alert Flag
The TRILL Header, as defined in [RFC 6325], has two reserved bits.
This document specifies use of the reserved bit next to the Version
field in the TRILL Header as the Alert flag. The Alert flag will be
denoted by "A". RBridges MUST NOT use the "A" flag for forwarding
decisions such as the selection of which ECMP path or multi-
destination tree to select.
Implementations that comply with this document MUST utilize the "A"
flag and CFM Ethertype to identify TRILL OAM frames.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| V |A|R|M|Op-Length| Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Egress RBridge Nickname | Ingress RBridge Nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options...
+-+-+-+-+-+-+-+-+-+-+-+-
Figure 2: TRILL Header with the "A" Flag
o A (1 bit): Indicates this is a possible OAM frame and is subject
to specific handling as specified in this document.
All other TRILL Header fields carry the same meaning as defined in
[RFC 6325].
Senevirathne, et al. Standards Track PAGE 8
RFC 7455 TRILL Fault Management March 2015
3.2.1. Handling of TRILL Frames with the "A" Flag
The value "1" in the "A" flag indicates TRILL frames that may qualify
as OAM frames. Implementations are further REQUIRED to validate such
frames by comparing the value at the OAM Ethertype (Figure 1)
location with the CFM Ethertype "0x8902" [8021Q]. If the value
matches, such frames are identified as TRILL OAM frames and SHOULD be
processed as discussed in Section 4.
Frames with the "A" flag set that do not contain a CFM Ethertype are
not considered OAM frames. Such frames MUST be silently discarded.
OAM-capable RBridges MUST NOT generate OAM frames to an RBridge that
is not OAM capable.
Intermediate RBridges that are not OAM capable (i.e., do not
understand the "A" flag) follow the process defined in Section 3.3 of
[RFC 6325] and forward OAM frames with the "A" flag unaltered.
3.3. OAM Capability Announcement
Any given RBridge can be (1) OAM incapable, (2) OAM capable with new
extensions, or (3) OAM capable with the backwards-compatibility
method. The OAM request originator, prior to origination of the
request, is required to identify the OAM capability of the target and
generate the appropriate OAM message.
The capability flags defined in the TRILL Version sub-TLV (TRILL-VER)
[RFC 7176] will be utilized for announcing OAM capabilities. The
following OAM-related capability flags are defined:
O - OAM capable
B - Backwards-compatible OAM
A capability announcement with the "O" flag set to 1 and the "B" flag
set to 1 indicates that the originating RBridge is OAM capable but
utilizes the backwards-compatibility method defined in Appendix A. A
capability announcement with the "O" flag set to 1 and the "B" flag
set to 0 indicates that the originating RBridge is OAM capable and
utilizes the method specified in Section 3.2.
When the "O" flag is set to 0, the announcing implementation is
considered not capable of OAM, and the "B" flag is ignored.
Senevirathne, et al. Standards Track PAGE 9
RFC 7455 TRILL Fault Management March 2015
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+
| Max-version | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+
|A|F|O|B|Other Capabilities and Header Flags| (4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+
0 1 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 0 1
Figure 3: TRILL-VER Sub-TLV [RFC 7176] with "O" and "B" Flags
In Figure 3, "A" is the Affinity sub-TLV support flag as indicated in
[RFC 7176], and "F" is the FGL-safe flag as indicated in [RFC 7172] and
[RFC 7176]. The "O" and "B" flags are located after the "F" flag in
the Capability and Header Flags field of the TRILL-VER sub-TLV, as
depicted in Figure 3 above. Usage of the "O" and "B" flags is
discussed above.
Absence of the TRILL-VER sub-TLV means the announcing RBridge is not
OAM capable.
3.4. Identification of the OAM Message
The ingress RBridge nickname allows recipients to identify the origin
of the message in most cases. However, when an out-of-band reply is
generated, the responding RBridge nickname is not easy to identify.
The [8021Q] Sender ID TLV (1) provides methods to identify the device
by including the Chassis ID. The Chassis ID allows different
addressing formats such as IANA Address Family enumerations. IANA
has allocated Address Family Number 16396 for TRILL nickname. In
TRILL OAM, the Chassis ID sub-type of the Sender ID TLV is set to
16396, and the Chassis ID field contains the corresponding TRILL
nickname.
When the Sender ID TLV is present and the Chassis ID sub-type is set
to 16396, the sender RBridge TRILL nickname SHOULD be derived from
the nickname embedded in the Chassis ID. Otherwise, the sender
RBridge TRILL nickname SHOULD be derived from the ingress RBridge
nickname.
Senevirathne, et al. Standards Track PAGE 10
RFC 7455 TRILL Fault Management March 2015
4. TRILL OAM Layering vs. IEEE Layering
This section presents the placement of the TRILL OAM shim within the
IEEE 802.1 layers. The transmit and receive processing are
explained.
+-+-+-+-+-+-+-+-+-+-+
| RBridge Layer |
| Processing |
+-+-+-+-+-+-+-+-+-+-+
|
|
+-+-+-+-+-+-+
| TRILL OAM | UP MEP
| Layer | MIP
+-+-+-+-+-+-+ Down MEP
|
|
+-+-+-+-+-+-+
(3)--------> | TRILL |
| Encap/Decap
+-+-+-+-+-+-+
|
+-+-+-+-+-+-+
(2)--------> |End-station|
| VLAN & Priority Processing
+-+-+-+-+-+-+
|
+-+-+-+-+-+-+
(1)--------> |ISS |
|Processing |
+-+-+-+-+-+-+
|
|
|
Figure 4: Placement of TRILL MP within IEEE 802.1
[RFC 6325], Section 4.6 as updated by [RFC 7180] provides a detailed
explanation of frame processing. Please refer to those documents for
additional details and for processing scenarios not covered herein.
Sections 4.1 and 4.2 apply to links using a broadcast LAN technology
such as Ethernet.
Senevirathne, et al. Standards Track PAGE 11
RFC 7455 TRILL Fault Management March 2015
On links using an inherently point-to-point technology, such as PPP
[RFC 6361], there is no Outer.MacDA, Outer.MacSA, or Outer.VLAN
because these are part of the Link Header for Ethernet. Point-to-
point links typically have Link Headers without these fields.
4.1. Processing at the ISS Layer
4.1.1. Receive Processing
The ISS layer receives an indication from the port. It extracts DA
and SA, and it marks the remainder of the payload as M1. The ISS
layer passes on (DA, SA, M1) as an indication to the higher layer.
For TRILL Ethernet frames, this is Outer.MacDA and Outer.MacSA. M1
is the remainder of the packet.
4.1.2. Transmit Processing
The ISS layer receives an indication from the higher layer that
contains (DA, SA, M1). It constructs an Ethernet frame and passes
down to the port.
4.2. End-Station VLAN and Priority Processing
4.2.1. Receive Processing
Receive (DA, SA, M1) indication from the ISS layer. Extract the VLAN
ID and priority from the M1 part of the received indication (or
derive them from the port defaults or other default parameters) and
construct (DA, SA, VLAN, PRI, M2). VLAN+PRI+M2 maps to M1 in the
received indication. Pass (DA, SA, VLAN, PRI, M2) to the TRILL
Encapsulation/Decapsulation layer.
4.2.2. Transmit Processing
Receive (DA, SA, VLAN, PRI, M2) indication from the TRILL
Encapsulation/Decapsulation layer. Merge VLAN, PRI, M2 to form M1.
Pass down (DA, SA, M1) to the ISS layer.
4.3. TRILL Encapsulation and Decapsulation Layer
4.3.1. Receive Processing for Unicast Packets
o Receive indication (DA, SA, VLAN, PRI, M2) from the End-Station
VLAN and Priority Processing layer.
o If the DA matches the port Local DA and the frame is of TRILL
Ethertype:
Senevirathne, et al. Standards Track PAGE 12
RFC 7455 TRILL Fault Management March 2015
- Discard DA, SA, VLAN, and PRI. From M2, derive (TRILL-HDR,
iDA, iSA, i-VL, M3).
- If TRILL nickname is Local and TRILL Header Alert flag is set:
* Pass on to OAM processing.
- Else, pass on (TRILL-HDR, iDA, iSA, i-VL, M3) to the RBridge
layer.
o If the DA matches the port Local DA and the Ethertype is RBridge-
Channel [RFC 7178]:
- Process as a possible unicast native RBridge Channel packet.
o If the DA matches the port Local DA and the Ethertype is neither
TRILL nor RBridge-Channel:
- Discard packet.
o If the DA does not match, the port is Appointed Forwarder for
VLAN, and the Ethertype is not TRILL or RBridge-Channel:
- Insert TRILL-HDR and send (TRILL-HDR, iDA, iSA,i-VL, M3)
indication to the RBridge layer (this is the TRILL Ingress
Function).
4.3.2. Transmit Processing for Unicast Packets
o Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from the RBridge
layer.
o If the egress TRILL nickname is local:
- If the port is Appointed Forwarder for iVL, the port is not
configured as a trunk or point-to-point (P2P) port, the TRILL
Alert flag is set, and the OAM Ethertype is present, then:
* Strip TRILL-HDR and construct (DA, SA, VLAN, M2) (this is
the TRILL Egress Function).
- Else:
* Discard packet.
Senevirathne, et al. Standards Track PAGE 13
RFC 7455 TRILL Fault Management March 2015
o If the egress TRILL nickname is not local:
- Insert Outer.MacDA, Outer.MacSA, Outer.VLAN, and TRILL
Ethertype, and construct (DA, SA, VLAN, M2) where M2 is (TRILL-
HDR, iDA, iSA, iVL, M).
o Forward (DA, SA, V, M2) to the End-Station VLAN and Priority
Processing layer.
4.3.3. Receive Processing for Multicast Packets
o Receive (DA, SA, V, M2) from the End-Station VLAN and Priority
Processing layer.
o If the DA is All-RBridges and the Ethertype is TRILL:
- Strip DA, SA, and V. From M2, extract (TRILL-HDR, iDA, iSA,
iVL, and M3).
- If the TRILL Alert flag is set and the OAM Ethertype is present
at the end of Flow Entropy:
* Perform OAM processing.
- Else, extract the TRILL Header, inner MAC addresses, and
Inner.VLAN, and pass indication (TRILL-HDR, iDA, iSA, iVL and
M3) to the TRILL RBridge layer.
o If the DA is All-IS-IS-RBridges and the Ethertype is L2-IS-IS,
then pass frame up to TRILL IS-IS processing.
o If the DA is All-RBridges or All-IS-IS-RBridges but the Ethertype
is not TRILL or L2-IS-IS respectively:
- Discard the packet.
o If the Ethertype is TRILL but the multicast DA is not All-RBridges
or if the Ethertype is L2-IS-IS but the multicast DA is not All-
IS-IS-RBridges:
- Discard the packet.
o If the DA is All-Edge-RBridges and the Ethertype is RBridge-
Channel [RFC 7178]:
- Process as a possible multicast native RBridge Channel packet.
Senevirathne, et al. Standards Track PAGE 14
RFC 7455 TRILL Fault Management March 2015
o If the DA is in the initial bridging/link protocols block
(01-80-C2-00-00-00 to 01-80-C2-00-00-0F) or is in the TRILL block
and not assigned for Outer.MacDA use (01-80-C2-00-00-42 to
01-80-C2-00-00-4F), then:
- The frame is not propagated through an RBridge although some
special processing may be done at the port as specified in
[RFC 6325], and the frame may be dispatched to Layer 2
processing at the port if certain protocols are supported by
that port (examples include the Link Aggregation Protocol and
the Link-Layer Discovery Protocol).
o If the DA is some other multicast value:
- Insert TRILL-HDR and construct (TRILL-HDR, iDA, iSA, IVL, M3).
- Pass the (TRILL-HDR, iDA, iSA, IVL, M3) to the RBridge layer.
4.3.4. Transmit Processing of Multicast Packets
The following ignores the case of transmitting TRILL IS-IS packets.
o Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from the RBridge
layer.
o If the TRILL Header multicast ("M") flag is set, the TRILL-HDR
Alert flag is set, and the OAM Ethertype is present, then:
- Construct (DA, SA, V, M2) by inserting TRILL Outer.MacDA of
All-RBridges, Outer.MacSA, Outer.VLAN, and TRILL Ethertype. M2
here is (Ethertype TRILL, TRILL-HDR, iDA, iSA, iVL, M).
Note: A second copy of native format is not made.
o Else, if the TRILL Header multicast ("M") flag is set and the
Alert flag not set:
- If the port is Appointed Forwarder for iVL and the port is not
configured as a trunk port or a P2P port, strip TRILL-HDR, iSA,
iDA, and iVL and construct (DA, SA, V, M2) for native format.
- Make a second copy (DA, SA, V, M2) by inserting TRILL
Outer.MacDA, Outer.MacSA, Outer.VLAN, and TRILL Ethertype. M2
here is (Ethertype TRILL, TRILL-HDR, iDA, iSA, iVL, M).
o Pass the indication (DA, SA, V, M2) to the End-Station VLAN and
Priority Processing layer.
Senevirathne, et al. Standards Track PAGE 15
RFC 7455 TRILL Fault Management March 2015
4.4. TRILL OAM Layer Processing
The TRILL OAM layer is located between the TRILL
Encapsulation/Decapsulation layer and the RBridge layer. It performs
the following: 1) identifies OAM frames that need local processing
and 2) performs OAM processing or redirects to the CPU for OAM
processing.
o Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from the RBridge
layer. M3 is the payload after Inner.VLAN iVL.
o If the TRILL Header multicast ("M") flag is set, the TRILL Alert
flag is set, and TRILL OAM Ethertype is present, then:
- If MEP or MIP is configured on the Inner.VLAN/FGL of the
packet, then:
* Discard packets that have MD-Level less than that of the MEP
or packets that do not have MD-Level present (e.g., due to
packet truncation).
* If MD-Level matches MD-Level of the MEP, then:
+ Redirect to OAM processing (Do not forward further).
* If MD-Level matches MD-Level of MIP, then:
+ Make a copy for OAM processing and continue.
* If MD-Level matches MD-Level of MEP, then:
+ Redirect the OAM packet to OAM processing and do not
forward along or forward as a native packet.
o Else, if the TRILL Alert flag is set and the TRILL OAM Ethertype
is present, then:
- If MEP or MIP is configured on the Inner.VLAN/FGL of the
packet, then:
* Discard packets that have MD-Level not present or where MD-
Level is less than that of the MEP.
* If MD-Level matches MD-Level of the MEP, then:
+ Redirect to OAM processing (do not forward further).
Senevirathne, et al. Standards Track PAGE 16
RFC 7455 TRILL Fault Management March 2015
* If MD-Level matches MD-Level of MIP, then:
+ Make a copy for OAM processing and continue.
o Else, for a non-OAM packet:
- Continue.
o Pass the indication (DA, SA, V, M2) to the End-Station VLAN and
Priority Processing layer.
Note: In the receive path, the processing above compares with the
Down MEP and MIP Half functions. In the transmit processing, it
compares with Up MEP and MIP Half functions.
Appointed Forwarder is a function that the TRILL
Encapsulation/Decapsulation layer performs. The TRILL
Encapsulation/Decapsulation layer is responsible for prevention of
leaking of OAM packets as native frames.
5. Maintenance Associations (MAs) in TRILL
[8021Q] defines a Maintenance Association as a logical relationship
between a group of nodes. Each Maintenance Association (MA) is
identified with a unique MAID of 48 bytes [8021Q]. CCM and other
related OAM functions operate within the scope of an MA. The
definition of MA is technology independent. Similarly, it is encoded
within the OAM message, not in the technology-dependent portion of
the packet. Hence, the MAID as defined in [8021Q] can be utilized
for TRILL OAM without modifications. This also allows us to utilize
CCM and LBM messages defined in [8021Q] as is.
In TRILL, an MA may contain two or more RBridges (MEPs). For
unicast, it is likely that the MA contains exactly two MEPs that are
the two end points of the flow. For multicast, the MA may contain
two or more MEPs.
For TRILL, in addition to all of the standard [8021Q] CFM MIB
definitions, each MEP's MIB contains one or more Flow Entropy
definitions corresponding to the set of flows that the MEP monitors.
[8021Q] CFM MIB is augmented to add the TRILL-specific information.
Figure 5 depicts the augmentation of the CFM MIB to add the TRILL-
specific Flow Entropy.
Senevirathne, et al. Standards Track PAGE 17
RFC 7455 TRILL Fault Management March 2015
MA---
|
--- MEP
|
. - Remote MEP List
.
|
--- MEP-A
|
--- MEP-B
.
|
. - Flow Entropy List { Augments IEEE8021-CFM-MIB}
|
--- (Flow Entropy-1)
|
--- (Flow Entropy-2)
|
. --- (Flow Entropy-n)
|
Other MIB entries
Figure 5: Correlation of TRILL-Augmented MIB
The detailed TRILL OAM MIB will be specified in a separate document
[TRILLOAMMIB].
6. MEP Addressing
In IEEE CFM [8021Q], OAM messages address the target MEP by utilizing
a unique MAC address. In TRILL, a MEP is addressed by a combination
of the egress RBridge nickname and the Inner.VLAN/FGL.
Additionally, MEPs are represented by a 2-octet MEP-ID that is
independent of the underlying technology. In CFM [8021Q], the value
of MEP-ID is restricted to the range of 1 to 8191. However, on a CFM
[8021Q] packet, MEP-IDs are encoded as a 2-octet field. In the TRILL
Base Mode operation presented in Appendix B, MEP-IDs are mapped
1-to-1 with the RBridge nicknames. Hence, in TRILL, a MEP-ID MUST be
a number in the range from 1 to 65535.
At the MEP, OAM packets go through a hierarchy of OpCode
demultiplexers. The OpCode demultiplexers channel the incoming OAM
packets to the appropriate message processor (e.g., LBM). Refer to
Figure 6 for a visual depiction of these different demultiplexers.
Senevirathne, et al. Standards Track PAGE 18
RFC 7455 TRILL Fault Management March 2015
The demultiplexing sequence is as follows:
1. Identify the packets that need OAM processing at the local
RBridge as specified in Section 4.
a. Identify the MEP that is associated with the Inner.VLAN/FGL.
2. The MEP first validates the MD-Level and then:
a. Redirects to the MD-Level demultiplexer.
3. The MD-Level demultiplexer compares the MD-Level of the packet
against the MD-Level of the local MEPs of a given MD-Level on the
port. (Note: there can be more than one MEP at the same MD-Level
but they belong to different MAs.)
a. If the packet MD-Level is equal to the configured MD-Level of
the MEP, then pass to the OpCode demultiplexer.
b. If the packet MD-Level is less than the configured MD-Level
of the MEP, discard the packet.
c. If the packet MD-Level is greater than the configured
MD-Level of the MEP, then pass on to the next-higher MD-Level
demultiplexer, if available. Otherwise, if no such higher
MD-Level demultiplexer exists, then forward the packet as
normal data.
4. The OpCode demultiplexer compares the OpCode in the packet with
supported OpCodes.
a. If the OpCode is CCM, LBM, LBR, PTM, PTR, MTVM, or MTVR, then
pass on to the correct processor.
b. If the OpCode is unknown, then discard.
Senevirathne, et al. Standards Track PAGE 19
RFC 7455 TRILL Fault Management March 2015
|
.CCM LBM PTM MTVM . .
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+
| OP Code DE-Mux |--- Unknown
+-+-+-+-+-+-+-+-+-+-+-+-+
^ ^ ^
MD==Li | | |
+-+-+ +-+-+ +-+-+
| L |-->|L2 |-.- |Ln |---- >
+-+-+ +-+-+ +-+-+ |
| ^ | | |
MD<LI Drop | Drop Drop |
| |
MD not --- |TRILL OAM need local |
Present | Processing |
| |
TRILL Data ---- TRILL Data ----
------->| T |----------------- >| M |--- >
+ TRILL OAM ---- + pass through OAM ----
Figure 6: OAM Demultiplexers at MEP for Active SAP
o T: Denotes Tap. Identifies OAM frames that need local processing.
These are the packets with the Alert flag set and OAM Ethertype
present after the Flow Entropy of the packet.
o M: The post-processing merge that merges data and OAM messages
that are passed through. Additionally, the merge component
ensures, as explained earlier, that OAM packets are not forwarded
out as native frames.
o L: Denotes MD-Level processing. Packets whose MD-Level is less
than the MD-Level of the current processing step will be dropped.
Packets with equal MD-Levels are passed on to the OpCode
demultiplexer. Others are passed on to the next-level MD
processors or eventually to the merge point (M).
NOTE: LBM, LBR, MTVM, MTVR, PTM, and PTR are not subject to MA
demultiplexers. These packets do not have an MA encoded in the
packet. Adequate response can be generated to these packets, without
loss of functionality, by any of the MEPs present on that interface
or an entity within the RBridge.
Senevirathne, et al. Standards Track PAGE 20
RFC 7455 TRILL Fault Management March 2015
6.1. Use of MIP in TRILL
Maintenance Intermediate Points (MIPs) are mainly used for fault
isolation. Link Trace Messages in [8021Q] utilize a well-known
multicast MAC address, and MIPs generate responses to Link Trace
Messages. Response to Link Trace Messages or lack thereof can be
used for fault isolation in TRILL.
As explained in Section 10, a Hop Count expiry approach will be
utilized for fault isolation and path tracing. The approach is very
similar to the well-known IP trace-route approach. Hence, explicit
addressing of MIPs is not required for the purpose of fault
isolation.
Any given RBridge can have multiple MIPs located within an interface.
As such, a mechanism is required to identify which MIP should respond
to an incoming OAM message. Any MIP residing within the ingress
interface may reply to the incoming Path Trace Message without loss
of functionality or information. As specified in Section 3.4, the
address of the responding RBridge can be identified by means of the
Sender ID TLV (1). The Reply Ingress TLV (5) identifies the
interface id. The combination of these allows the recipient of the
response to uniquely identify the responder.
A similar approach to that presented above for MEPs can be used for
MIP processing. It is important to note that "M", the merge block of
a MIP, does not prevent OAM packets leaking out as native frames. On
edge interfaces, MEPs MUST be configured to prevent the leaking of
TRILL OAM packets out of the TRILL campus.
Senevirathne, et al. Standards Track PAGE 21
RFC 7455 TRILL Fault Management March 2015
PTM PTR MTVM MTVR
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP Code De-Mux |-> Unknown
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
^ ^ ^
MD==Li | | |
+-+-+ +-+-+ +-+-+
| L |- >|L2 |-.- |Ln |------+
+-+-+ +-+-+ +-+-+ |
^ |
| |
Drop | |
MD not --- |TRILL OAM |
Present | |
| v
TRILL Data ---- TRILL Data -----
------- >| T |------------------ >| M |---->
+ TRILL OAM ---- ----
Figure 7: OAM Demultiplexers at MIP for Active SAP
o T: Tap processing for MIP. All packets with the TRILL Header
Alert flag set are captured.
o L: MD-Level Processing. Packets with matching MD-Levels are
"copied" to the OpCode demultiplexer, and the original packet is
passed on to the next MD-Level processor. Other packets are
simply passed on to the next MD-Level processor without copying to
the OpCode demultiplexer.
o M: The intermediate point processing merge that merges data and
OAM messages that are passed through.
Packets that carry Path Trace Message (PTM) or Multi-destination Tree
Verification Message (MTVM) OpCodes are passed on to the respective
processors.
Packets with unknown OpCodes are counted and discarded.
7. Continuity Check Message (CCM)
CCMs are used to monitor connectivity and configuration errors.
[8021Q] monitors connectivity by listening to periodic CCM messages
received from its remote MEP partners in the MA. An [8021Q] MEP
identifies cross-connect errors by comparing the MAID in the received
CCM message with the MEP's local MAID. The MAID [8021Q] is a 48-byte
field that is technology independent. Similarly, the MEP-ID is a
Senevirathne, et al. Standards Track PAGE 22
RFC 7455 TRILL Fault Management March 2015
2-byte field that is independent of the technology. Given this
generic definition of CCM fields, CCM as defined in [8021Q] can be
utilized in TRILL with no changes. TRILL-specific information may be
carried in CCMs when encoded using TRILL-specific TLVs or sub-TLVs.
This is possible since CCMs may carry optional TLVs.
Unlike classical Ethernet environments, TRILL contains multipath
forwarding. The path taken by a packet depends on the payload of the
packet. The Maintenance Association (MA) identifies the interested
Maintenance End Points (MEPs) of a given monitored path. For
unicast, there are only two MEPs per MA. For multicast, there can be
two or more MEPs in the MA. The entropy values of the monitored
flows are defined within the MA. CCM transmit logic will utilize
these Flow Entropy values when constructing the CCM packets. Please
see Section 12 for the theory of operation of CCM.
The MIB in [8021Q] is augmented with the definition of Flow Entropy.
Please see [TRILLOAMMIB] for this and other TRILL-related OAM MIB
definitions. Figure 8 depicts the correlation between MA, CCM, and
the Flow Entropy.
Senevirathne, et al. Standards Track PAGE 23
RFC 7455 TRILL Fault Management March 2015
MA---
|
--- MEP
|
. - Remote MEP List
.
|
--- MEP-A
|
--- MEP-B
.
|
. - Flow Entropy List {Augments IEEE8021-CFM-MIB}
|
--- (Flow Entropy-1)
|
--- (Flow Entropy-2)
|
. ---(Flow Entropy-n)
|
. - CCM
|
--- (standard 8021ag entries)
|
--- (Hop Count) { Augments IEEE8021-CFM-MIB}
|
--- (Any other TRILL OAM-specific entries)
{Augmented}
|
.
|
- Other MIB entries
Figure 8: Augmentation of CCM MIB in TRILL
In a multi-pathing environment, a flow, by definition, is
unidirectional. A question may arise as to what Flow Entropy should
be used in the response. CCMs are unidirectional and have no
explicit reply; as such, the issue of the response Flow Entropy does
not arise. In the transmitted CCM, each MEP reports local status
using the Remote Defect Indication (RDI) flag. Additionally, a MEP
may raise SNMP TRAPs [TRILLOAMMIB] as alarms when a connectivity
failure occurs.
Senevirathne, et al. Standards Track PAGE 24
RFC 7455 TRILL Fault Management March 2015
8. TRILL OAM Message Channel
The TRILL OAM Message Channel can be divided into two parts: TRILL
OAM message header and TRILL OAM TLVs. Every OAM message MUST
contain a single TRILL OAM message header and a set of one or more
specified OAM message TLVs.
8.1. TRILL OAM Message Header
As discussed earlier, a common messaging framework between [8021Q],
TRILL, and other similar standards such as Y.1731 is accomplished by
reusing the OAM message header defined in [8021Q].
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MD-L | Version | OpCode | Flags |FirstTLVOffset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. OpCode-Specific Information .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. TLVs .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: OAM Message Format
o MD-L: Maintenance Domain Level (3 bits). For TRILL, in general,
this field is set to a single value across the TRILL campus. When
using the TRILL Base Mode as specified in Appendix B, MD-L is set
to 3. However, extension of TRILL (for example, to support
multilevel) may create different MD-Levels, and the MD-L field
must be appropriately set in those scenarios. (Please refer to
[8021Q] for the definition of MD-Level).
o Version: Indicates the version (5 bits) as specified in [8021Q].
This document does not require changing the Version defined in
[8021Q].
o OpCode: Operation Code (8 bits). Specifies the operation
performed by the message. See Section 8.2.
o Flags: Includes operational flags (1 byte). The definition of
flags is OpCode-specific and is covered in the applicable
sections.
Senevirathne, et al. Standards Track PAGE 25
RFC 7455 TRILL Fault Management March 2015
o FirstTLVOffset: Defines the location of the first TLV, in bytes,
starting from the end of the FirstTLVOffset field (1 byte).
(Refer to [8021Q] for the definition of the FirstTLVOffset.)
o OpCode-Specific Information: May contain Session Identification
Number, timestamp, etc.
The MD-L, Version, OpCode, Flags, and FirstTLVOffset fields
collectively are referred to as the OAM message header.
8.2. TRILL-Specific OAM OpCodes
The following TRILL-specific CFM OpCodes are defined. Each of the
OpCodes indicates a separate type of TRILL OAM message. Details of
the messages are presented in Sections 10 and 11.
TRILL OAM message OpCodes:
64: Path Trace Reply
65: Path Trace Message
66: Multi-destination Tree Verification Reply
67: Multi-destination Tree Verification Message
Loopback and CCM Messages reuse the OpCodes defined by [8021Q].
8.3. Format of TRILL OAM TLV
The same CFM TLV format as defined in [8021Q] is used for TRILL OAM.
The following figure depicts the general format of a TRILL OAM TLV:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Value (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: TRILL OAM TLV
o Type (1 octet): Specifies the type of the TLV (see Section 8.4 for
TLV types).
o Length (2 octets): Specifies the length of the Value field in
octets. Length of the Value field can be zero or more octets.
Senevirathne, et al. Standards Track PAGE 26
RFC 7455 TRILL Fault Management March 2015
o Value (variable): The length and the content of this field depend
on the type of TLV. Please refer to applicable TLV definitions
for details.
Semantics and usage of Type values allocated for TRILL OAM purpose
are defined by this document and other future related documents.
8.4. TRILL OAM TLVs
TRILL-related TLVs are defined in this section. TLVS defined in
[8021Q] are reused, where applicable.
8.4.1. Common TLVs between CFM and TRILL
The following TLVs are defined in [8021Q]. We reuse them where
applicable. The format and semantics of the TLVs are as defined in
[8021Q].
Type Name of TLV in [8021Q]
---- ----------------------
0 End TLV
1 Sender ID TLV
2 Port Status TLV
3 Data TLV
4 Interface Status TLV
5 Reply Ingress TLV
6 Reply Egress TLV
7 LTM Egress Identifier TLV
8 LTR Egress Identifier TLV
9-30 Reserved
31 Organization Specific TLV
8.4.2. TRILL OAM-Specific TLVs
Listed below is a summary of TRILL OAM TLVs and their corresponding
codes. Format and semantics of TRILL OAM TLVs are defined in
subsequent sections.
Senevirathne, et al. Standards Track PAGE 27
RFC 7455 TRILL Fault Management March 2015
Type TLV Name
---- ------------------------------------
64 TRILL OAM Application Identifier TLV
65 Out-of-Band Reply Address TLV
66 Diagnostic Label TLV
67 Original Data Payload TLV
68 RBridge Scope TLV
69 Previous RBridge Nickname TLV
70 Next-Hop RBridge List TLV
71 Multicast Receiver Port Count TLV
72 Flow Identifier TLV
73 Reflector Entropy TLV
74 Authentication TLV
The TRILL OAM Application Identifier TLV (64) MUST be the first TLV.
An End TLV (0) MUST be included as the last TLV. All other TLVs can
be included in any order.
8.4.3. TRILL OAM Application Identifier TLV
The TRILL OAM Application Identifier TLV carries information specific
to TRILL OAM applications. The TRILL OAM Application Identifier TLV
MUST always be present and MUST be the first TLV in TRILL OAM
messages. Messages that do not include the TRILL OAM Application
Identifier TLV as the first TLV MUST be discarded by a TRILL MP.
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 | Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved1 | Fragment-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code |Return Sub-code| Reserved2 |F|C|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: TRILL OAM Application Identifier TLV
o Type (1 octet): 64, TRILL OAM Application Identifier TLV
o Length (2 octets): 9
o Version (1 octet): Currently set to zero. Indicates the TRILL OAM
version. The TRILL OAM version can be different than the [8021Q]
version.
o Reserved1 (3 octets): Set to zero on transmission and ignored on
reception.
Senevirathne, et al. Standards Track PAGE 28
RFC 7455 TRILL Fault Management March 2015
o Fragment-ID (1 octet): Indicates the fragment number of the
current message. This applies only to reply messages; in request
messages, it must be set to zero on transmission and ignored on
receipt. The "F" flag defined below MUST be set with the final
message, whether it is the last fragment of the fragmented message
or the only message of the reply. Section 13 provides more
details on OAM message fragmentation.
o Return Code (1 octet): Set to zero on requests. Set to an
appropriate value in response messages.
o Return Sub-code (1 octet): Set to zero on transmission of request
message. The Return Sub-code identifies categories within a
specific Return Code and MUST be interpreted within a Return Code.
o Reserved2 (12 bits): Set to zero on transmission and ignored on
reception.
o F (1 bit): Final flag. When set, indicates this is the last
response.
o C (1 bit): Cross-Connect Error flag (VLAN/FGL mapping error). If
set, indicates that the label (VLAN/FGL) in the Flow Entropy is
different than the label included in the Diagnostic Label TLV.
This field is ignored in request messages and MUST only be
interpreted in response messages.
o O (1 bit): If set, indicates OAM out-of-band response requested.
o I (1 bit): If set, indicates OAM in-band response requested.
NOTE: When both O and I bits are set to zero, this indicates that no
response is required (silent mode). Users MAY specify both O and I,
one of them, or none. When both O and I bits are set, the response
is sent both in-band and out-of-band.
Senevirathne, et al. Standards Track PAGE 29
RFC 7455 TRILL Fault Management March 2015
8.4.4. Out-of-Band Reply Address TLV
The Out-of-Band Reply Address TLV specifies the address to which an
out-of-band OAM reply message MUST be sent. When the O bit in the
TRILL Version sub-TLV (Section 3.3) is not set, the Out-of-Band Reply
Address TLV is ignored.
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 | Address Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Addr Length | |
+-+-+-+-+-+-+-+-+ |
| |
. Reply Address .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Out-of-Band Reply Address TLV
o Type (1 octet): 65, Out-of-Band Reply Address TLV
o Length (2 octets): Variable. Minimum length is 2 + the length (in
octets) of the shortest address. Currently, the minimum value of
this field is 4, but this could change in the future if a new
address shorter than the TRILL nickname is defined.
o Address Type (1 octet):
0 - IPv4
1 - IPv6
2 - TRILL nickname
All other values reserved.
o Addr Length (1 octet): Depends on the Address Type. Currently,
defined values are:
4 - IPv4
16 - IPv6
2 - TRILL nickname
Other lengths may be acceptable for future Address Types.
Senevirathne, et al. Standards Track PAGE 30
RFC 7455 TRILL Fault Management March 2015
o Reply Address (variable): Address where the reply needs to be
sent. Length depends on the address specification.
8.4.5. Diagnostic Label TLV
The Diagnostic Label TLV specifies the data label (VLAN or FGL) in
which the OAM messages are generated. Receiving RBridge MUST compare
the data label of the Flow Entropy to the data label specified in the
Diagnostic Label TLV. The "C" flag (Cross Connect Error) in the
response (TRILL OAM Application Identifier TLV; Section 8.4.3) MUST
be set when the two VLANs do not match.
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 | L-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Diagnostic Label TLV
o Type (1 octet): 66, Diagnostic Label TLV
o Length (2 octets): 5
o L-Type (1 octet): Label type
0 - Indicates a right-justified 802.1Q 12-bit VLAN padded on the
left with bits that must be sent as zero and ignored on
receipt
1 - Indicates a TRILL 24-bit fine-grained label
o Reserved (1 octet): Set to zero on transmission and ignored on
reception.
o Label (24 bits): Either 12-bit VLAN or 24 bit fine-grained label.
RBridges do not perform label error checking when the Diagnostic
Label TLV is not included in the OAM message. In certain
deployments, intermediate devices may perform label translation. In
such scenarios, the originator should not include the Diagnostic
Label TLV in OAM messages. Inclusion of Diagnostic Label TLV will
generate unwanted label error notifications.
Senevirathne, et al. Standards Track PAGE 31
RFC 7455 TRILL Fault Management March 2015
8.4.6. Original Data Payload TLV
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 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
. Original Payload .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Original Data Payload TLV
o Type (1 octet): 67, Original Data Payload TLV
o Length (2 octets): variable
o Original Payload: The original TRILL Header and Flow Entropy.
Used in constructing replies to the Loopback Message (see
Section 9) and the Path Trace Message (see Section 10).
8.4.7. RBridge Scope TLV
The RBridge Scope TLV identifies nicknames of RBridges from which a
response is required. The RBridge Scope TLV is only applicable to
Multi-destination Tree Verification Messages. This TLV SHOULD NOT be
included in other messages. Receiving RBridges MUST ignore this TLV
on messages other than Multi-destination Tree Verification Messages.
Each TLV can contain up to 255 nicknames of in-scope RBridges. A
Multi-destination Tree Verification Message may contain multiple
RBridge scope TLVs, in the event that more than 255 in-scope RBridges
need to be specified.
Absence of the RBridge Scope TLV indicates that a response is needed
from all the RBridges. Please see Section 11 for details.
Senevirathne, et al. Standards Track PAGE 32
RFC 7455 TRILL Fault Management March 2015
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 | nOfnicknames |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname-1 | Nickname-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Nickname-n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: RBridge Scope TLV
o Type (1 octet): 68, RBridge Scope TLV
o Length (2 octets): Variable. Minimum value is 1.
o nOfnicknames (1 octet): Indicates the number of nicknames included
in this TLV. Zero (0) indicates no nicknames are included in the
TLV. When this field is set to zero (0), the Length field MUST be
set to 1.
o Nickname (2 octets): 16-bit RBridge nickname
8.4.8. Previous RBridge Nickname TLV
The Previous RBridge Nickname TLV identifies the nickname or
nicknames of the previous RBridge. [RFC 6325] allows a given RBridge
to hold multiple nicknames.
The Previous RBridge Nickname TLV is an optional TLV. Multiple
instances of this TLV MAY be included when an upstream RBridge is
represented by more than 255 nicknames (highly unlikely).
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (continued) | Nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: Previous RBridge Nickname TLV
o Type (1 octet): 69, Previous RBridge Nickname TLV
o Length (2 octets): 5
Senevirathne, et al. Standards Track PAGE 33
RFC 7455 TRILL Fault Management March 2015
o Reserved (3 octet): Set to zero on transmission and ignored on
reception.
o Nickname (2 octets): RBridge nickname
8.4.9. Next-Hop RBridge List TLV
The Next-Hop RBridge List TLV identifies the nickname or nicknames of
the downstream next-hop RBridges. [RFC 6325] allows a given RBridge
to have multiple equal-cost paths to a specified destination. Each
next-hop RBridge is represented by one of its nicknames.
The Next-Hop RBridge List TLV is an optional TLV. Multiple instances
of this TLV MAY be included when there are more than 255 equal-cost
paths to the destination.
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 | nOfnicknames |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname-1 | Nickname-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Nickname-n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: Next-Hop RBridge List TLV
o Type (1 octet): 70, Next-Hop RBridge List TLV
o Length (2 octets): Variable. Minimum value is 1.
o nOfnicknames (1 octet): Indicates the number of nicknames included
in this TLV. Zero (0) indicates no nicknames are included in the
TLV. When this field is set to zero (0), the Length field MUST be
set to 1.
o Nickname (2 octets): 16-bit RBridge nickname
8.4.10. Multicast Receiver Port Count TLV
The Multicast Receiver Port Count TLV identifies the number of ports
interested in receiving the specified multicast stream within the
responding RBridge on the label (VLAN or FGL) specified by the
Diagnostic Label TLV.
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RFC 7455 TRILL Fault Management March 2015
The Multicast Receiver Port Count TLV is an optional TLV.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Receivers |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: Multicast Receiver Port Count TLV
o Type (1 octet): 71, Multicast Receiver Port Count TLV
o Length (2 octets): 5
o Reserved (1 octet): Set to zero on transmission and ignored on
reception.
o Number of Receivers (4 octets): Indicates the number of multicast
receivers available on the responding RBridge on the label
specified by the diagnostic label.
8.4.11. Flow Identifier TLV
The Flow Identifier TLV uniquely identifies a specific flow. The
flow-identifier value is unique per MEP and needs to be interpreted
as such.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MEP-ID | flow-identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 19: Flow Identifier TLV
o Type (1 octet): 72, Flow Identifier TLV
o Length (2 octets): 5
o Reserved (1 octet): Set to 0 on transmission and ignored on
reception.
o MEP-ID (2 octets): MEP-ID of the originator [8021Q]. In TRILL,
MEP-ID can take a value from 1 to 65535.
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o flow-identifier (2 octets): Uniquely identifies the flow per MEP.
Different MEPs may allocate the same flow-identifier value. The
{MEP-ID, flow-identifier} pair is globally unique.
Inclusion of the MEP-ID in the Flow Identifier TLV allows the
inclusion of a MEP-ID for messages that do not contain a MEP-ID in
their OAM header. Applications may use MEP-ID information for
different types of troubleshooting.
8.4.12. Reflector Entropy TLV
The Reflector Entropy TLV is an optional TLV. This TLV, when
present, tells the responder to utilize the Reflector Entropy
specified within the TLV as the flow-entropy of the response message.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Reflector Entropy .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 20: Reflector Entropy TLV
o Type (1 octet): 73, Reflector Entropy TLV
o Length (2 octets): 97
o Reserved (1 octet): Set to zero on transmission and ignored by the
recipient.
o Reflector Entropy (96 octets): Flow Entropy to be used by the
responder. May be padded with zeros if the desired flow-entropy
information is less than 96 octets.
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8.4.13. Authentication TLV
The Authentication TLV is an optional TLV that can appear in any OAM
message or reply in TRILL.
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 | Auth Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Authentication Value .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 21: Authentication TLV
o Type (1 octet): 74, Authentication TLV
o Length (2 octets): Variable
o The Auth Type and following Authentication Value are the same as
the Auth Type and following value for the [IS-IS] Authentication
TLV. It is RECOMMENDED that Auth Type 3 be used. Auth Types 0,
1, 2, and 54 MUST NOT be used. With Auth Type 3, the
Authentication TLV is as follows:
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 | Auth Type = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. Authentication Data (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 22: Authentication TLV with Auth Type 3
With Auth Type 3, the process is generally as specified in [RFC 5310]
using the same Key ID space as TRILL [IS-IS]. The area covered by
the Authentication TLV is from the beginning of the TRILL Header to
the end of the TRILL OAM Message Channel; the Link Header and Trailer
are not included. The TRILL Header Alert, Reserved bit, and Hop
Count are treated as zero for the purposes of computing and verifying
the Authentication Data.
Senevirathne, et al. Standards Track PAGE 37
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Key distribution is out of the scope of this document as the keying
distributed for IS-IS is used.
An RBridge supporting OAM authentication can be configured to either
(1) ignore received OAM Authentication TLVs and not send them, (2)
ignore received OAM Authentication TLVs but include them in all OAM
packets sent, or (3) to include Authentication TLVs in all OAM
messages sent and enforce authentication of OAM messages received.
When an RBridge is enforcing authentication, it discards any OAM
message subject to OAM processing that does not contain an
Authentication TLV or an Authentication TLV does not verify.
9. Loopback Message
9.1. Loopback Message Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MD-L | Version | OpCode | Flags |FirstTLVOffset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loopback Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. TLVs .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 23: Loopback Message Format
The figure above depicts the format of the Loopback Request and
Response messages as defined in [8021Q]. The OpCode for the Loopback
Message is set to 3, and the OpCode for the reply message is set to 2
[8021Q]. The Loopback Transaction Identifier (commonly called the
Session Identification Number or Session ID in this document) is a
32-bit integer that allows the requesting RBridge to uniquely
identify the corresponding session. Responding RBridges, without
modification, MUST echo the received "Loopback Transaction
Identifier" number.
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9.2. Theory of Operation
9.2.1. Actions by Originator RBridge
The originator RBridge takes the following actions:
o Identifies the destination RBridge nickname based on user
specification or based on the specified destination MAC or IP
address.
o Constructs the Flow Entropy based on user-specified parameters or
implementation-specific default parameters.
o Constructs the TRILL OAM header: sets the OpCode to Loopback
Message type (3) [8021Q]. Assigns applicable Loopback Transaction
Identifier number for the request.
o The TRILL OAM Application Identifier TLV MUST be included with the
flags set to applicable values.
o Includes following OAM TLVs, where applicable:
- Out-of-Band Reply Address TLV
- Diagnostic Label TLV
- Sender ID TLV
o Specifies the Hop Count of the TRILL Data frame per user
specification or utilize an applicable Hop Count value.
o Dispatches the OAM frame for transmission.
RBridges may continue to retransmit the request at periodic intervals
until a response is received or the retransmission count expires. At
each transmission, the Session Identification Number MUST be
incremented.
9.2.2. Intermediate RBridge
Intermediate RBridges forward the frame as a normal data frame; no
special handling is required.
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9.2.3. Destination RBridge
If the Loopback Message is addressed to the local RBridge and
satisfies the OAM identification criteria specified in Section 3.1,
then the RBridge data plane forwards the message to the CPU for
further processing.
The TRILL OAM application layer further validates the received OAM
frame by checking for the presence of OAM Ethertype at the end of the
Flow Entropy. Frames that do not contain OAM Ethertype at the end of
the Flow Entropy MUST be discarded.
Construction of the TRILL OAM response:
o The TRILL OAM application encodes the received TRILL Header and
Flow Entropy in the Original Data Payload TLV and includes it in
the OAM message.
o Set the Return Code to (1) "Reply" and Return Sub-code to zero (0)
"Valid Response". Update the TRILL OAM OpCode to 2 (Loopback
Message Reply).
o Optionally, if the VLAN/FGL identifier value of the received Flow
Entropy differs from the value specified in the Diagnostic Label
TLV, set the "C" flag (Cross Connect Error) in the TRILL OAM
Application Identifier TLV.
o Include the Sender ID TLV (1).
o If in-band response was requested, dispatch the frame to the TRILL
data plane with request-originator RBridge nickname as the egress
RBridge nickname.
o If out-of-band response was requested, dispatch the frame to the
IP forwarding process.
10. Path Trace Message
The primary use of the Path Trace Message is for fault isolation. It
may also be used for plotting the path taken from a given RBridge to
another RBridge.
[8021Q] accomplishes the objectives of the TRILL Path Trace Message
using Link Trace Messages. Link Trace Messages utilize a well-known
multicast MAC address. This works for [8021Q] because both the
unicast and multicast paths are congruent. However, in TRILL,
multicast and unicast are not congruent. Hence, TRILL OAM uses a new
message format: the Path Trace Message.
Senevirathne, et al. Standards Track PAGE 40
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The Path Trace Message has the same format as the Loopback Message.
The OpCode for Path Trace Reply is 64, and the OpCode for the Path
Trace Message is 65.
Operation of the Path Trace Message is identical to the Loopback
Message except that it is first transmitted with a TRILL Header Hop
Count field value of 1. The sending RBridge expects an "Intermediate
RBridge" Return Sub-code from the next hop or a "Valid response"
Return Sub-code response from the destination RBridge. If an
"Intermediate RBridge" Return Sub-code is received in the response,
the originator RBridge records the information received from the
intermediate node that generated the message and resends the message
by incrementing the previous Hop Count value by 1. This process is
continued until, a response is received from the destination RBridge,
a Path Trace process timeout occurs, or the Hop Count reaches a
configured maximum value.
10.1. Theory of Operation
10.1.1. Actions by Originator RBridge
The originator RBridge takes the following actions:
o Identifies the destination RBridge based on user specification or
based on location of the specified MAC address.
o Constructs the Flow Entropy based on user-specified parameters or
implementation-specific default parameters.
o Constructs the TRILL OAM header: set the OpCode to Path Trace
Message type (65). Assign an applicable Session Identification
number for the request. Return Code and Return Sub-code MUST be
set to zero.
o The TRILL OAM Application Identifier TLV MUST be included with the
flags set to applicable values.
o Includes the following OAM TLVs, where applicable:
- Out-of-Band Reply Address TLV
- Diagnostic Label TLV
- Sender ID TLV
o Specifies the Hop Count of the TRILL Data frame as 1 for the first
request.
Senevirathne, et al. Standards Track PAGE 41
RFC 7455 TRILL Fault Management March 2015
o Dispatches the OAM frame to the TRILL data plane for transmission.
An RBridge may continue to retransmit the request at periodic
intervals until a response is received or the retransmission count
expires. At each new retransmission, the Session Identification
number MUST be incremented. Additionally, for responses received
from intermediate RBridges, the RBridge nickname and interface
information MUST be recorded.
10.1.2. Intermediate RBridge
Path Trace Messages transit through Intermediate RBridges
transparently, unless the Hop Count has expired.
The TRILL OAM application layer further validates the received OAM
frame by examining the presence of the TRILL Alert flag and OAM
Ethertype at the end of the Flow Entropy and by examining the
MD-Level. Frames that do not contain OAM Ethertype at the end of the
Flow Entropy MUST be discarded.
Construction of the TRILL OAM response:
o The TRILL OAM application encodes the received TRILL Header and
Flow Entropy in the Original Data Payload TLV and includes it in
the OAM message.
o Set the Return Code to (1) "Reply" and Return Sub-code to two (2)
"Intermediate RBridge". Update the TRILL OAM OpCode to 64 (Path
Trace Reply).
o If the VLAN/FGL identifier value of the received Flow Entropy
differs from the value specified in the diagnostic label, set the
"C" flag (Cross Connect Error) in the TRILL OAM Application
Identifier TLV.
o Include the following TLVs:
- Previous RBridge Nickname TLV (69)
- Reply Ingress TLV (5)
- Reply Egress TLV (6)
- Interface Status TLV (4)
- Next-Hop RBridge List TLV (70) (Repeat for each ECMP)
- Sender ID TLV (1)
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RFC 7455 TRILL Fault Management March 2015
o If a cross-connect error is detected, set the "C" flag (Cross-
Connect Error) in the reply's TRILL OAM Application Identifier
TLV.
o If in-band response was requested, dispatch the frame to the TRILL
data plane with request-originator RBridge nickname as the egress
RBridge nickname.
o If out-of-band response was requested, dispatch the frame to the
standard IP forwarding process.
10.1.3. Destination RBridge
Processing is identical to that in Section 10.1.2 with the exception
that the TRILL OAM OpCode is set to Path Trace Reply (64).
11. Multi-Destination Tree Verification Message (MTVM)
Multi-destination Tree Verification Messages allow verifying TRILL
distribution tree integrity and pruning. TRILL VLAN/FGL and
multicast pruning are described in [RFC 6325], [RFC 7180], and
[RFC 7172]. Multi-destination Tree Verification and Multicast Group
Verification Messages are designed to detect pruning defects.
Additionally, these tools can be used for plotting a given multicast
tree within the TRILL campus.
Multi-destination Tree Verification OAM frames are copied to the CPU
of every intermediate RBridge that is part of the distribution tree
being verified. The originator of the Multi-destination Tree
Verification Message specifies the scope of RBridges from which a
response is required. Only the RBridges listed in the scope field
respond to the request. Other RBridges silently discard the request.
Inclusion of the scope field is required to prevent receiving an
excessive number of responses. The typical scenario of distribution
tree verification or group verification involves verifying multicast
connectivity to a selected set of end nodes as opposed to the entire
network. Availability of the scope facilitates narrowing down the
focus to only the RBridges of interest.
Implementations MAY choose to rate-limit CPU-bound multicast traffic.
As a result of rate-limiting or due to other congestion conditions,
MTVM messages may be discarded from time to time by the intermediate
RBridges, and the requester may be required to retransmit the
request. Implementations SHOULD narrow the embedded scope of
retransmission requests only to RBridges that have failed to respond.
Senevirathne, et al. Standards Track PAGE 43
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11.1. MTVM Format
The format of MTVM is identical to the Loopback Message format
defined in Section 9 with the exception that the OpCode used is 67.
11.2. Theory of Operation
11.2.1. Actions by Originator RBridge
The user is required, at a minimum, to specify either the
distribution trees that need to be verified, the Multicast MAC
address and VLAN/FGL, or the VLAN/FGL and Multicast Destination IP
address. Alternatively, for more specific multicast flow
verification, the user MAY specify more information, e.g., source MAC
address, VLAN/FGL, and Destination and Source IP addresses.
Implementations, at a minimum, must allow the user to specify a
choice of distribution trees, Destination Multicast MAC address, and
VLAN/FGL that needs to be verified. Although it is not mandatory, it
is highly desired to provide an option to specify the scope. It
should be noted that the source MAC address and some other parameters
may not be specified if the backwards-compatibility method in
Appendix A is used to identify the OAM frames.
Default parameters MUST be used for unspecified parameters. Flow
Entropy is constructed based on user-specified parameters and/or
default parameters.
Based on user specified parameters, the originating RBridge does the
following:
o Identifies the nickname that represents the multicast tree.
o Obtains the applicable Hop Count value for the selected multicast
tree.
o Constructs TRILL OAM message header and includes the Session
Identification number. The Session Identification Number
facilitates the originator mapping the response to the correct
request.
o Includes the TRILL OAM Application Identifier TLV, which MUST be
included.
o Includes the OpCode Multicast Tree Verification Message (67).
o Includes RBridge Scope TLV (68).
Senevirathne, et al. Standards Track PAGE 44
RFC 7455 TRILL Fault Management March 2015
o Optionally, includes the following TLVs, where applicable:
- Out-of-Band IP Address TLV (65)
- Diagnostic Label TLV (66)
- Sender ID TLV (1)
o Specifies the Hop Count of the TRILL Data frame per user
specification or alternatively utilizes the applicable Hop Count
value if the TRILL Hop Count is not being specified by the user.
o Dispatches the OAM frame to the TRILL data plane to be ingressed
for transmission.
The RBridge may continue to retransmit the request at a periodic
interval until either a response is received or the retransmission
count expires. At each new retransmission, the Session
Identification Number MUST be incremented. At each retransmission,
the RBridge may further reduce the scope to the RBridges that it has
not received a response from.
11.2.2. Receiving RBridge
Receiving RBridges identify multicast verification frames per the
procedure explained in Section 3.2.
The RBridge validates the frame and analyzes the scope RBridge list.
If the RBridge Scope TLV is present and the local RBridge nickname is
not specified in the scope list, it will silently discard the frame.
If the local RBridge is specified in the scope list OR the RBridge
Scope TLV is absent, the receiving RBridge proceeds with further
processing as defined in Section 11.2.3.
11.2.3. In-Scope RBridges
Construction of the TRILL OAM response:
o The TRILL OAM application encodes the received TRILL Header and
Flow Entropy in the Original Data Payload TLV and includes them in
the OAM message.
o Set the Return Code to zero (0) and Return Sub-code to zero (0).
Update the TRILL OAM OpCode to 66 (Multi-destination Tree
Verification Reply).
Senevirathne, et al. Standards Track PAGE 45
RFC 7455 TRILL Fault Management March 2015
o Include following TLVs:
- Previous RBridge Nickname TLV (69)
- Reply Ingress TLV (5)
- Interface Status TLV (4)
- Next-Hop RBridge List TLV (70)
- Sender ID TLV (1)
- Multicast Receiver Port Count TLV (71)
o If a VLAN/FGL cross-connect error is detected, set the "C" flag
(Cross-Connect Error) in the TRILL OAM Application Identifier TLV.
o If in-band response was requested, dispatch the frame to the TRILL
data plane with request-originator RBridge nickname as the egress
RBridge nickname.
o If out-of-band response was requested, dispatch the frame to the
standard IP forwarding process.
12. Application of Continuity Check Message (CCM) in TRILL
Section 7 provides an overview of CCM Messages defined in [8021Q] and
how they can be used within TRILL OAM. This section presents the
application and theory of operations of CCM within the TRILL OAM
framework. Readers are referred to [8021Q] for CCM message format
and applicable TLV definitions and usages. Only the TRILL-specific
aspects are explained below.
In TRILL, between any two given MEPs, there can be multiple potential
paths. Whereas in [8021Q], there is always a single path between any
two MEPs at any given time. [RFC 6905] requires solutions to have the
ability to monitor continuity over one or more paths.
CCM Messages are uni-directional, such that there is no explicit
response to a received CCM message. Connectivity status is indicated
by setting the applicable flags (e.g., RDI) of the CCM messages
transmitted by a MEP.
It is important that the solution presented in this document
accomplishes the requirements specified in [RFC 6905] within the
framework of [8021Q] in a straightforward manner and with minimum
changes. Section 8 defines multiple flows within the CCM object,
Senevirathne, et al. Standards Track PAGE 46
RFC 7455 TRILL Fault Management March 2015
each corresponding to a flow that a given MEP wishes to monitor.
Hence, CCM, in multipath environments like TRILL, monitors per-flow
connectivity and cross-connect errors.
Receiving MEPs do not cross-check whether a received CCM belongs to a
specific flow from the originating RBridge. Any attempt to track
status of individual flows may explode the amount of state
information that any given RBridge has to maintain.
The obvious question arises: how does the originating RBridge know
which flow or flows are at fault?
This is accomplished with a combination of the RDI flag in the CCM
header, Flow Identifier TLV, and SNMP Notifications (Traps).
Section 12.1 discusses the procedure.
12.1. CCM Error Notification
Each MEP transmits four CCM messages per each flow. ([8021Q] detects
CCM fault when three consecutive CCM messages are lost). Each CCM
message has a unique sequence number (Session ID) and unique flow-
identifier. The flow-identifier is included in the OAM message via
the Flow Identifier TLV.
When a MEP notices a CCM timeout from a remote MEP (MEP-A), it sets
the RDI flag on the next CCM message it generates. Additionally, it
logs and sends an SNMP notification that contains the remote MEP
Identification, flow-identifier, and the sequence number of the last
CCM message it received, and, if available, the flow-identifier and
the sequence number of the first CCM message it received after the
failure. Each MEP maintains a unique flow-identifier per each flow;
hence, the operator can easily identify flows that correspond to the
specific flow-identifier.
The following example illustrates the above.
Assume there are two MEPs: MEP-A and MEP-B.
Assume there are three flows between MEP-A and MEP-B.
Let's assume MEP-A allocates sequence numbers as follows:
Flow-1 Sequence={1,2,3,4,13,14,15,16,.. } flow-identifier=(1)
Flow-2 Sequence={5,6,7,8,17,18,19,20,.. } flow-identifier=(2)
Flow-3 Sequence={9,10,12,11,21,22,23,24,.. } flow-identifier=(3)
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Let's assume Flow-2 is at fault.
MEP-B receives CCM from MEP-A with sequence numbers 1, 2, 3, and 4
but did not receive 5, 6, 7, and 8. CCM timeout is set to three CCM
intervals in [8021Q]. Hence, MEP-B detects the error at the 8th CCM
message. At this time, the sequence number of the last good CCM
message MEP-B has received from MEP-A is 4, and the flow-identifier
of the last good CCM Message is (1). Hence, MEP-B will generate a
CCM error SNMP notification with MEP-A, last good flow-identifier
(1), and sequence number 4.
When MEP-A switches to Flow-3 after transmitting Flow-2, MEP-B will
start receiving CCM messages. In the foregoing example, it will be a
CCM message with sequence numbers 9, 10, 11, 12, and 21 and so on.
When in receipt of a new CCM message from a specific MEP, after a CCM
timeout, the TRILL OAM will generate an SNMP Notification of CCM
resume with remote MEP-ID, the first valid flow-identifier, and the
sequence number after the CCM timeout. In the foregoing example, it
is MEP-A, flow-identifier (3), and sequence number 9.
The remote MEP list under the CCM MIB Object is augmented to contain
"Last Sequence Number", flow-identifier, and "CCM Timeout" variables.
"Last Sequence Number" and flow-identifier are updated every time a
CCM is received from a remote MEP. The CCM Timeout variable is set
when the CCM timeout occurs and is cleared when a CCM is received.
12.2. Theory of Operation
12.2.1. Actions by Originator RBridge
The originator RBridge takes the following actions:
o Derives the Flow Entropy field based on flow-entropy information
specified in the CCM Management object.
o Constructs the TRILL CCM OAM header as specified in [8021Q].
o The TRILL OAM Application Identifier TLV MUST be included as the
first TLV with the flags set to applicable values.
o Includes other TLVs specified in [8021Q].
o Includes the following optional TLV, where applicable:
- Sender ID TLV (1)
o Specifies the Hop Count of the TRILL Data frame per user
specification or utilize an applicable Hop Count value.
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RFC 7455 TRILL Fault Management March 2015
o Dispatches the OAM frame to the TRILL data plane for transmission.
An RBridge transmits a total of four requests, each at CCM
retransmission interval. At each transmission, the Session
Identification number MUST be incremented by one.
At the 5th retransmission interval, the Flow Entropy of the CCM
packet is updated to the next flow-entropy information specified in
the CCM Management object. If the current Flow Entropy is the last
Flow Entropy specified, move to the first Flow Entropy specified and
continue the process.
12.2.2. Intermediate RBridge
Intermediate RBridges forward the frame as a normal data frame; no
special handling is required.
12.2.3. Destination RBridge
If the CCM Message is addressed to the local RBridge or multicast and
satisfies the OAM identification methods specified in Section 3.2,
then the RBridge data plane forwards the message to the CPU for
further processing.
The TRILL OAM application layer further validates the received OAM
frame by examining the presence of OAM Ethertype at the end of the
Flow Entropy. Frames that do not contain OAM Ethertype at the end of
the Flow Entropy MUST be discarded.
The TRILL OAM application layer then validates the MD-Level and pass
the packet to the OpCode demultiplexer. The OpCode demultiplexer
delivers CCM packets to the CCM process.
The CCM process performs the processing specified in [8021Q].
Additionally, the CCM process updates the CCM Management object with
the sequence number of the received CCM packet. Note: The last
received CCM sequence number and CCM timeout are tracked per each
remote MEP.
If the CCM timeout is true for the sending remote MEP, then clear the
CCM timeout in the CCM Management object and generate the SNMP
notification as specified above.
Senevirathne, et al. Standards Track PAGE 49
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13. Fragmented Reply
TRILL OAM allows fragmented reply messages. In case of fragmented
replies, all parts of the reply MUST follow the procedure defined in
this section.
The same Session Identification Number MUST be included in all
related fragments of the same message.
The TRILL OAM Application Identifier TLV MUST be included, with the
Fragment-ID field monotonically increasing with each fragment
transmitted with the appropriate Final flag field. The Final flag
MUST only be equal to one on the final fragment of the reply.
On the receiver, the process MUST order the fragments based on the
Fragment-ID. Any fragments received after the final fragment MUST be
discarded. Messages with incomplete fragments (i.e., messages with
one or missing fragments after the receipt of the fragment with the
final flag set) MUST be discarded as well.
If the number of fragments exceeds the maximum supported fragments
(255), then the Return Code of the reply message MUST be set to 1
(Reply message), and the Return Sub-code MUST be set to 1 (Fragment
limit exceeded).
14. Security Considerations
Forged OAM packets could cause false error or failure indications,
mask actual errors or failures, or be used for denial of service.
Source addresses for messages can be forged and the out-of-band reply
facility (see Section 8.4.4) provides for explicitly supplying the
address for replies. For protection against forged OAM packets, the
Authentication TLV (see Section 8.4.13) can be used in an OAM message
in TRILL. This TLV is virtually identical to the IS-IS
Authentication TLV specified in [IS-IS] and depends on IS-IS keying
material and the current state of IS-IS keying as discussed in
[KARPISIS] and [RFC 5310]. In particular, there is currently no
standardized IS-IS automated key management.
Of course, authentication is ineffective unless verified and
ineffective against senders who have the keying material needed to
produce OAM messages that will pass authentication checks.
Implementations MUST implement rate-limiting functionality to protect
against exploitation of OAM messages as a means of denial-of-service
attacks. Aggressive rate-limiting may trigger false positive errors
against CCM and LBM-based session monitoring.
Senevirathne, et al. Standards Track PAGE 50
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Even with authentication, replay of authenticated messages may be
possible. There are four types of messages: Continuity Check (CCM),
Loopback, Path Trace, and Multi-destination Tree Verification (MTVM).
In the case of CCM messages, sequence numbers are required (see
Section 12.1) that can protect against replay. In the case of
Loopback Messages (see Section 9.1), a Loopback Transaction
Identifier is included that, as required by [8021Q], is incremented
with each transmission and can detect replays. PTMs (see Section 10)
and MTVMs (see Section 11.1) are specified to have the same format as
Loopback Messages (although with different OpCodes), so they also
have an identifier incremented with each transmission that can detect
replays. Thus, all TRILL OAM messages have a field that can be used
for replay protection.
For general TRILL-related security considerations, please refer to
[RFC 6325].
[8021Q] requires that the MEP filters or passes through OAM messages
based on the MD-Level. The MD-Level is embedded deep in the OAM
message. Hence, conventional methods of frame filtering may not be
able to filter frames based on the MD-Level. As a result, OAM
messages that must be dropped due to MD-Level mismatch may leak into
a TRILL domain with a different MD-Level.
This leaking may not cause any functionality loss. The receiving
MEP/MIP is required to validate the MD-level prior to acting on the
message. Any frames received with an incorrect MD-Level need to be
dropped.
Generally, a single operator manages each TRILL campus; hence, there
is no risk of security exposure. However, in the event of multi-
operator deployments, operators should be aware of possible exposure
of device-specific information, and appropriate measures must be
taken.
It is also important to note that the MPLS OAM framework [RFC 4379]
does not include the concept of domains and OAM filtering based on
operators. It is our opinion that the lack of OAM frame filtering
based on domains does not introduce significant functional deficiency
or security risk.
It is possible to mandate requiring different credentials to use
different OAM functions or capabilities within a specific OAM
function. Implementations may consider grouping users to different
security clearance levels and restricting functions and capabilities
to different clearance levels. However, exact implementation details
of such a framework are outside the scope of this document.
Senevirathne, et al. Standards Track PAGE 51
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15. IANA Considerations
IANA has made the assignments described below.
15.1. OAM Capability Flags
Two TRILL-VER sub-TLV Capability Flags (see Section 3.3) have been
assigned as follows:
Bit Description Reference
--- ----------- ---------
2 OAM capable RFC 7455
3 Backwards-compatible OAM RFC 7455
15.2. CFM Code Points
Four OpCodes have been assigned from the "CFM OAM IETF OpCodes" sub-
registry as follows:
Value Assignment Reference
----- ---------- ---------
64 Path Trace Reply RFC 7455
65 Path Trace Message RFC 7455
66 Multi-destination Tree Verification Reply RFC 7455
67 Multi-destination Tree Verification Message RFC 7455
Eleven TLV Types have been assigned from the "CFM OAM IETF TLV Types"
sub-registry as follows:
Value Assignment Reference
----- ---------- ---------
64 TRILL OAM Application Identifier TLV RFC 7455
65 Out-of-Band Reply Address TLV RFC 7455
66 Diagnostic Label TLV RFC 7455
67 Original Data Payload TLV RFC 7455
68 RBridge Scope TLV RFC 7455
69 Previous RBridge Nickname TLV RFC 7455
70 Next-Hop RBridge List TLV RFC 7455
71 Multicast Receiver Port Count TLV RFC 7455
72 Flow Identifier TLV RFC 7455
73 Reflector Entropy TLV RFC 7455
74 Authentication TLV RFC 7455
Senevirathne, et al. Standards Track PAGE 52
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15.3. MAC Addresses
IANA has assigned a unicast and a multicast MAC address under the
IANA Organizationally Unique Identifier (OUI) for identification of
OAM packets as discussed for the backwards-compatibility method
(Appendix A.2) and based on the request template in Appendix C. The
assigned addresses are 00-00-5E-90-01-00 (unicast) and
01-00-5E-90-01-00 (multicast).
15.4. Return Codes and Sub-codes
IANA has created the "TRILL OAM Return Codes" registry within the
"Transparent Interconnection of Lots of Links (TRILL) Parameters"
registry and a separate sub-code sub-registry for each Return Code as
shown below:
Registry: TRILL OAM Return Codes
Registration Procedure: Standards Action
Return Code Assignment References
----------- ---------- ----------
0 Request message RFC 7455
1 Reply message RFC 7455
2-255 Unassigned RFC 7455
Sub-Registry: Sub-codes for TRILL OAM Return Code 0
Registration Procedure: Standards Action
Sub-code Assignment References
-------- ---------- ----------
0 Valid request RFC 7455
1-255 Unassigned RFC 7455
Sub-Registry: Sub-codes for TRILL OAM Return Code 1
Registration Procedure: Standards Action
Sub-code Assignment References
-------- ---------- ----------
0 Valid response RFC 7455
1 Fragment limit exceeded RFC 7455
2 Intermediate RBridge RFC 7455
3-255 Unassigned RFC 7455
Senevirathne, et al. Standards Track PAGE 53
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15.5. TRILL Nickname Address Family
IANA has allocated 16396 as the Address Family Number for TRILL
nickname.
16. References
16.1. Normative References
[8021Q] IEEE, "IEEE Standard for Local and metropolitan area
networks -- Bridges and Bridged Networks", IEEE Std
802.1Q, December 2014.
[IS-IS] ISO/IEC, "Information technology -- Telecommunications and
information exchange between systems -- Intermediate
System to Intermediate System intra-domain routeing
information exchange protocol for use in conjunction with
the protocol for providing the connectionless-mode network
service (ISO 8473)", ISO/IEC 10589:2002, Second Edition,
2002.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/RFC 2119>.
[RFC 5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008, <http://www.rfc-editor.org/info/RFC 5226>.
[RFC 5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, February 2009,
<http://www.rfc-editor.org/info/RFC 5310>.
[RFC 6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011,
<http://www.rfc-editor.org/info/RFC 6325>.
[RFC 7172] Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., and
D. Dutt, "Transparent Interconnection of Lots of Links
(TRILL): Fine-Grained Labeling", RFC 7172, May 2014,
<http://www.rfc-editor.org/info/RFC 7172>.
Senevirathne, et al. Standards Track PAGE 54
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16.2. Informative References
[KARPISIS] Chunduri, U., Tian, A., and W. Lu, "KARP IS-IS security
analysis", Work in Progress, draft-ietf-karp-isis-
analysis-04, March 2015.
[RFC 4379] Eronen, P., Ed., and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", RFC
4279, December 2005,
<http://www.rfc-editor.org/info/RFC 4279>.
[RFC 6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291, June 2011,
<http://www.rfc-editor.org/info/RFC 6291>.
[RFC 6361] Carlson, J. and D. Eastlake 3rd, "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol Control
Protocol", RFC 6361, August 2011,
<http://www.rfc-editor.org/info/RFC 6361>.
[RFC 6905] Senevirathne, T., Bond, D., Aldrin, S., Li, Y., and R.
Watve, "Requirements for Operations, Administration, and
Maintenance (OAM) in Transparent Interconnection of Lots
of Links (TRILL)", RFC 6905, March 2013,
<http://www.rfc-editor.org/info/RFC 6905>.
[RFC 7174] Salam, S., Senevirathne, T., Aldrin, S., and D. Eastlake
3rd, "Transparent Interconnection of Lots of Links (TRILL)
Operations, Administration, and Maintenance (OAM)
Framework", RFC 7174, May 2014,
<http://www.rfc-editor.org/info/RFC 7174>.
[RFC 7176] Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt,
D., and A. Banerjee, "Transparent Interconnection of Lots
of Links (TRILL) Use of IS-IS", RFC 7176, May 2014,
<http://www.rfc-editor.org/info/RFC 7176>.
[RFC 7178] Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.
Ward, "Transparent Interconnection of Lots of Links
(TRILL): RBridge Channel Support", RFC 7178, May 2014,
<http://www.rfc-editor.org/info/RFC 7178>.
[RFC 7179] Eastlake 3rd, D., Ghanwani, A., Manral, V., Li, Y., and C.
Bestler, "Transparent Interconnection of Lots of Links
(TRILL): Header Extension", RFC 7179, May 2014,
<http://www.rfc-editor.org/info/RFC 7179>.
Senevirathne, et al. Standards Track PAGE 55
RFC 7455 TRILL Fault Management March 2015
[RFC 7180] Eastlake 3rd, D., Zhang, M., Ghanwani, A., Manral, V., and
A. Banerjee, "Transparent Interconnection of Lots of Links
(TRILL): Clarifications, Corrections, and Updates", RFC
7180, May 2014, <http://www.rfc-editor.org/info/RFC 7180>.
[RFC 7456] Mizrahi, T., Senevirathne, T., Salam, S., Kumar, D., and
D. Eastlake 3rd, "Loss and Delay Measurement in
Transparent Interconnection of Lots of Links (TRILL)", RFC
7456, March 2015,
<http://www.rfc-editor.org/info/RFC 7456>.
[TRILLOAMMIB]
Kumar, D., Salam, S., and T. Senevirathne, "TRILL OAM
MIB", Work in Progress, draft-deepak-trill-oam-mib-01,
October 2013.
[Y1731] ITU-T, "OAM functions and mechanisms for Ethernet based
networks", ITU-T Recommendation G.8013/Y.1731, November
2013.
Senevirathne, et al. Standards Track PAGE 56
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Appendix A. Backwards Compatibility
The methodology presented in this document is in-line with the
framework defined in [8021Q] for providing fault management coverage.
However, in practice, some TRILL platforms may not have the
capabilities to support some of the required techniques. In this
appendix, we present a method that allows RBridges, which do not have
the required hardware capabilities, to participate in the TRILL OAM
solution.
There are two broad areas to be considered: 1) the Maintenance Point
(MEP/MIP) Model and 2) data-plane encoding and frame identification.
A.1. Maintenance Point (MEP/MIP) Model
For backwards compatibility, MEPs and MIPs are located in the CPU.
This will be referred to as the "central brain" model as opposed to
"port brain" model.
In the "central brain" model, an RBridge using either Access Control
Lists (ACLs) or some other method forwards qualifying OAM messages to
the CPU. The CPU then performs the required processing and
multiplexing to the correct MP (Maintenance Point).
Additionally, RBridges MUST have the capability to prevent the
leaking of OAM packets, as specified in [RFC 6905].
A.2. Data-Plane Encoding and Frame Identification
The backwards-compatibility method presented in this section defines
methods to identify OAM frames when implementations do not have
capabilities to utilize the TRILL OAM Alert flag presented earlier in
this document to identify OAM frames in the hardware.
It is assumed that ECMP path selection of non-IP flows utilizes MAC
DA, MAC SA, and VLAN; IP flows utilize IP DA, IP SA, TCP/UDP port
numbers, and other Layer 3 and Layer 4 information. The well-known
fields to identify OAM flows are chosen such that they mimic the ECMP
selection of the actual data along the path. However, it is
important to note that there may be implementations that would
utilize these well-known fields for ECMP selections. Hence,
implementations that support OAM SHOULD move to utilizing the TRILL
Alert flag, as soon as possible, and methods presented here SHOULD be
used only as an interim solution.
Senevirathne, et al. Standards Track PAGE 57
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Identification methods are divided in to four broader groups:
1. Identification of Unicast non-IP OAM Flows,
2. Identification of Multicast non-IP OAM Flows,
3. Identification of Unicast IP OAM Flows, and
4. Identification of Multicast IP OAM Flows.
As presented in Figure 24, based on the flow type (as defined above),
implementations are required to use a well-known value in either the
Inner.MacSA field or OAM Ethertype field to identify OAM flows.
A receiving RBridge identifies OAM flows based on the presence of the
well-known values in the specified fields. Additionally, for unicast
flows, the egress RBridge nickname of the packet MUST match that of
the local RBridge, or for multicast flows, the TRILL Header multicast
("M") flag MUST be set.
Unicast OAM flows that qualify for local processing MUST be
redirected to the OAM process and MUST NOT be forwarded (to prevent
leaking of the packet out of the TRILL campus).
A copy of multicast OAM flows that qualify for local processing MUST
be sent to the OAM process, and the packets MUST be forwarded along
the normal path. Additionally, methods MUST be in place to prevent
multicast packets from leaking out of the TRILL campus.
Figure 24 summarizes the identification of different OAM frames from
data frames.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flow Entropy |Inner.MacSA |OAM Ethertype |Egress |
| | | |nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Unicast no IP | N/A |Match |Match |
| | | | |
|Multicast no IP| N/A |Match |N/A |
| | | | |
|Unicast IP | Match |N/A |Match |
| | | | |
|Multicast IP | Match |N/A |N/A |
| | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 24: Identification of TRILL OAM Frames
Senevirathne, et al. Standards Track PAGE 58
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The unicast and multicast Inner.MacSAs used for the unicast and
multicast IP cases, respectively, are 00-00-5E-90-01-00 and
01-00-5E-90-01-00. These have been assigned per the request in
Appendix C.
It is important to note that all RBridges MUST generate OAM flows
with the "A" flag set and CFM Ethertype "0x8902" at the Flow Entropy
off-set. However, well-known values MUST be utilized as part of the
flow-entropy when generating OAM messages destined for older RBridges
that are compliant to the backwards-compatibility method defined in
this appendix.
Appendix B. Base Mode for TRILL OAM
CFM, as defined in [8021Q], requires configuration of several
parameters before the protocol can be used. These parameters include
MAID, Maintenance Domain Level (MD-Level), and MEP-IDs. The Base
Mode for TRILL OAM defined here facilitates ease of use and provides
out-of-the-box plug-and-play capabilities, supporting the operational
and manageability considerations described in Section 6 of [RFC 7174].
All RBridges that support TRILL OAM MUST support the Base Mode
operation.
All RBridges MUST create a default MA with MAID as specified herein.
MAID [8021Q] has a flexible format and includes two parts:
Maintenance Domain Name and Short MA Name. In the Base Mode
operation, the value of the Maintenance Domain Name must be the
character string "TrillBaseMode" (excluding the quotes). In the Base
Mode operation, the Short MA Name format is set to a 2-octet integer
format (value 3 in Short MA Format field) and Short MA Name set to
65532 (0xFFFC).
The default MA belongs to MD-Level 3.
In the Base Mode of operation, each RBridge creates a single UP MEP
associated with a virtual OAM port with no physical layer (NULL PHY).
The MEP-ID associated with this MEP is the 2-octet RBridge nickname.
By default, all RBridges operating in Base Mode for TRILL OAM are
able to initiate LBM, PTM, and other OAM tools with no configuration.
Implementations MAY provide default flow-entropy to be included in
OAM messages. Content of the default flow-entropy is outside the
scope of this document.
Senevirathne, et al. Standards Track PAGE 59
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Figure 25 depicts encoding of MAID within CCM messages.
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Field Name |Size |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Maintenance | 1 |
|Domain Format | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Maintenance | 2 |
|Domain Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Maintenance | variable|
|Domain Name | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Short MA | 1 |
|Name Format | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Short MA | 2 |
|Name Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Short MA | variable|
|Name | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Padding | Variable|
+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 25: MAID Structure as Defined in [8021Q]
Maintenance Domain Name Format: set to value 4
Maintenance Domain Name Length: set to value 13
Maintenance Domain Name: set to TrillBaseMode
Short MA Name Format: set to value 3
Short MA Name Length: set to value 2
Short MA Name: set to FFFC
Padding: set of zero up to 48 octets of total length of the MAID
Please refer to [8021Q] for details.
Senevirathne, et al. Standards Track PAGE 60
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Appendix C. MAC Addresses Request
Applicant Name: IETF TRILL Working Group
Applicant Email: tsenevir@cisco.com
Applicant Telephone: +1-408-853-2291
Use Name: TRILL OAM
Document: RFC 7455
Specify whether this is an application for EUI-48 or EUI-64
identifiers: EUI-48
Size of Block requested: 1
Specify multicast, unicast, or both: Both
Senevirathne, et al. Standards Track PAGE 61
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Acknowledgments
Work on this document was largely inspired by the directions provided
by Stewart Bryant in finding a common OAM solution between SDOs.
Acknowledgments are due for many who volunteered to review this
document, notably, Jari Arkko, Adrian Farrel, Pete Resnick, Stephen
Farrell, Dan Romascanu, Gayle Nobel, and Tal Mizrahi.
Special appreciation is due to Dinesh Dutt for his support and
encouragement, especially during the initial discussion phase of
TRILL OAM.
Authors' Addresses
Tissa Senevirathne
Cisco Systems
375 East Tasman Drive
San Jose, CA 95134
United States
Phone: +1 408-853-2291
EMail: tsenevir@cisco.com
Norman Finn
Cisco Systems
510 McCarthy Blvd
Milpitas, CA 95035
United States
EMail: nfinn@cisco.com
Samer Salam
Cisco Systems
595 Burrard St., Suite 2123
Vancouver, BC V7X 1J1
Canada
EMail: ssalam@cisco.com
Senevirathne, et al. Standards Track PAGE 62
RFC 7455 TRILL Fault Management March 2015
Deepak Kumar
Cisco Systems
510 McCarthy Blvd
Milpitas, CA 95035
United States
Phone: +1 408-853-9760
EMail: dekumar@cisco.com
Donald Eastlake 3rd
Huawei Technologies
155 Beaver Street
Milford, MA 01757
United States
Phone: +1-508-333-2270
EMail: d3e3e3@gmail.com
Sam Aldrin
Huawei Technologies
2330 Central Express Way
Santa Clara, CA 95951
United States
EMail: aldrin.ietf@gmail.com
Yizhou Li
Huawei Technologies
101 Software Avenue
Nanjing 210012
China
Phone: +86-25-56625375
EMail: liyizhou@huawei.com
Senevirathne, et al. Standards Track PAGE 63
RFC TOTAL SIZE: 126153 bytes
PUBLICATION DATE: Wednesday, March 11th, 2015
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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