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Versions: (draft-tissa-trill-oam-fm) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 7455

TRILL Working group                                  Tissa Senevirathne
Internet Draft                                              Norman Finn
Intended status: Standard Track                             Samer Salam
                                                           Deepak Kumar
                                                                  CISCO

                                                        Donald Eastlake
                                                             Sam Aldrin
                                                              Yizhou Li
                                                                 Huawei

                                                       January 12, 2014
Expires: July 2014



                        TRILL Fault Management
                    draft-ietf-trill-oam-fm-01.txt


Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on July 13, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors. All rights reserved.



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   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.

Abstract

   This document specifies TRILL OAM Fault Management. Methods in
   this document follow the IEEE 802.1 CFM framework and reuse OAM
   tools where possible. Additional messages and TLVs are defined
   for TRILL specific applications or where a different set of
   information is required other than IEEE 802.1 CFM.

Table of Contents


   1. Introduction ............................................... 4
   2. Conventions used in this document .......................... 4
   3. General Format of TRILL OAM frames ......................... 5
   3.1. Identification of TRILL OAM frames ....................... 7
   3.2. Use of TRILL OAM Flag .................................... 7
   3.2.1. Handling of TRILL frames with the "A" Flag ............. 8
   3.3. OAM Capability Announcement .............................. 8
   4. TRILL OAM Layering vs. IEEE Layering ....................... 9
   4.1. Processing at ISS Layer ................................. 11
   4.1.1. Receive Processing .................................... 11
   4.1.2. Transmit Processing ................................... 11
   4.2. End Station VLAN and Priority Processing ................ 11
   4.2.1. Receive Processing .................................... 11
   4.2.2. Transmit Procession ................................... 11
   4.3. TRILL Encapsulation and De-capsulation Layer ............ 11
   4.3.1. Receive Processing for Unicast packets ................ 11
   4.3.2. Transmit Processing for unicast packets ............... 12
   4.3.3. Receive Processing for Multicast packets .............. 13
   4.3.4. Transmit Processing of Multicast packets .............. 14
   4.4. TRILL OAM Layer Processing .............................. 15
   5. Maintenance Associations (MA) in TRILL .................... 16
   6. MEP Addressing ............................................ 17
   6.1. Use of MIP in TRILL ..................................... 20
   7. Continuity Check Message (CCM) ............................ 22
   8. TRILL OAM Message Channel ................................. 24
   8.1. TRILL OAM Message header ................................ 24


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   8.2. TRILL OAM Opcodes ....................................... 25
   8.3. Format of TRILL OAM TLV ................................. 25
   8.4. TRILL OAM TLVs .......................................... 26
   8.4.1. Common TLVs between 802.1ag and TRILL ................. 26
   8.4.2. TRILL OAM Specific TLVs ............................... 27
   8.4.3. TRILL OAM Application Identifier TLV .................. 27
   8.4.4. Out Of Band Reply Address TLV ......................... 28
   8.4.5. Diagnostics Label TLV ................................. 29
   8.4.6. Original Data Payload TLV ............................. 31
   8.4.7. RBridge scope TLV ..................................... 31
   8.4.8. Previous RBridge nickname TLV ......................... 32
   8.4.9. Next Hop RBridge List TLV ............................. 33
   8.4.10. Multicast Receiver Port count TLV .................... 33
   8.4.11. Flow Identifier (flow-id) TLV ........................ 34
   8.4.12. Reflector Entropy TLV ................................ 35
   9. Loopback Message .......................................... 36
   9.1. Loopback OAM Message format ............................. 36
   9.2. Theory of Operation ..................................... 36
   9.2.1. Actions by Originator RBridge ......................... 36
   9.2.2. Intermediate RBridge .................................. 37
   9.2.3. Destination RBridge ................................... 37
   10. Path Trace Message ....................................... 38
   10.1. Theory of Operation .................................... 39
   10.1.1. Action by Originator RBridge ......................... 39
   10.1.2. Intermediate RBridge ................................. 39
   10.1.3. Destination RBridge .................................. 41
   11. Multi-Destination Tree Verification (MTV) Message ........ 41
   11.1. Multi-Destination Tree Verification (MTV) OAM Message
   Format ....................................................... 41
   11.2. Theory of Operation .................................... 42
   11.2.1. Actions by Originator RBridge ........................ 42
   11.2.2. Receiving RBridge .................................... 43
   11.2.3. In scope RBridges .................................... 43
   12. Application of Continuity Check Message (CCM) in TRILL ... 44
   12.1. CCM Error Notification ................................. 45
   12.2. Theory of Operation .................................... 46
   12.2.1. Actions by Originator RBridge ........................ 46
   12.2.2. Intermediate RBridge ................................. 47
   12.2.3. Destination RBridge .................................. 47
   13. Fragmented Reply ......................................... 47
   14. Security Considerations .................................. 48
   15. IEEE Allocation Considerations ........................... 48
   16. IANA Considerations ...................................... 48
   17. References ............................................... 48
   17.1. Normative References ................................... 48
   17.2. Informative References ................................. 49
   18. Acknowledgments .......................................... 50


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   Appendix A. Backwards Compatibility .......................... 51
   Appendix B. Base Mode for TRILL OAM .......................... 54
   Appendix C. Unicast MAC Request .............................. 56

 1. Introduction

   The general structure of TRILL OAM messages is presented in
   [TRLOAMFRM]. According to [TRLOAMFRM], TRILL OAM messages consist
   of five parts: link header, TRILL header, flow entropy, OAM
   message channel, and link trailer.

   The OAM message channel allows defining various control
   information and carrying 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.

   This document uses the message format defined in IEEE 802.1ag
   Connectivity Fault Management (CFM) [8021Q] as the basis for the
   TRILL OAM message channel.

   The ITU-T Y.1731 [Y1731] standard utilizes the same messaging
   format as [8021Q] and OAM messages where applicable. This
   document takes a similar stance and reuse [8021Q] in TRILL OAM.
   It is assumed readers are familiar with [8021Q] and [Y1731].
   Readers who are not familiar with these documents are encouraged
   to review them.

 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 [RFC2119].

   Acronyms used in the document include the following:

      MP - Maintenance Point [TRLOAMFRM]

      MEP - Maintenance End Point [TRLOAMFRM] [8021Q]

      MIP - Maintenance Intermediate Point [TRLOAMFRM] [8021Q]

      MA - Maintenance Association [8021Q] [TRLOAMFRM]


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      MD - Maintenance Domain [8021Q]

      CCM - Continuity Check Message [8021Q]

      LBM - Loop Back Message [8021Q]

      PTM - Path Trace Message

      MTV - Multi-destination Tree Verification Message

      OAM - Operations, Administration, and Maintenance [RFC6291]

      TRILL - Transparent Interconnection of Lots of Links [RFC6325]

      FGL  - Fine Grained Label [RFCfgl]

      ECMP - Equal Cost Multipath

      ISS  - Internal Sub Layer Service [8021Q]



3. General Format of TRILL OAM frames

   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.

   For accurate monitoring and/or diagnostics, OAM Messages are
   required to follow the same path as corresponding data packets.
   [TRLOAMFRM] presents the high-level format of the OAM messages.
   The details of the TRILL OAM frame format are defined in this
   document.










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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .    Link  Header               . (variable)
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   +    TRILL Header               + 8 or more bytes
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .   Flow Entropy                . 96 bytes
   .                               .
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   OAM Ether Type              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .   OAM Message Channel         . Variable
   .                               .
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Link Trailer              | Variable
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                 Figure 1 Format of TRILL OAM Messages



   Link Header: Media-dependent header. For Ethernet, this includes
   Destination MAC, Source MAC, VLAN (optional) and EtherType
   fields.

   TRILL Header: Fixed size of 8 bytes when the Extended Header is
   not included [RFC6325]

   Flow Entropy: This is a 96-byte fixed size field. The least
   significant bits of the field MUST be padded with zeros, up to 96
   bytes, when the flow entropy 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 [TRILLEXT] and [RFC6325].

   OAM Ether Type: OAM Ether Type is 16-bit EtherType that
   identifies the OAM Message channel that follows. This document


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   specifies using the EtherType allocated for 802.1ag for this
   purpose. Identifying the OAM Message Channel with a dedicated
   EtherType allows the easy identification of the beginning of the
   OAM message channel across multiple standards.

   OAM Message Channel: This is a variable size section that carries
   OAM related information. The message format defined in [8021Q]
   will be reused for TRILL OAM.

   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 [RFC6325], did not have a
   specific flag or a method to identify OAM frames. This document
   updates [RFC6325] to include specific methods to identify TRILL
   OAM frames. Section 3.2. below explains the details of the
   method.


3.2. Use of TRILL OAM Flag

   The TRILL Header, as defined in [RFC6325], has two reserved bits.
   This document specifies use of the reserved bit next to Version
   field in the TRILL header as the Alert flag. Alert flag will be
   denoted by "A".


   Implementations that comply with this document MUST utilize "A"
   flag and CFM etherType to identify TRILL OAM frames. The "A" flag
   MUST NOT BE utilized for forwarding decisions such as the
   selection of which ECMP path or multi-destination tree to use.

                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   | V |A|R|M|Op-Length| Hop Count |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Egress RBridge Nickname     |  Ingress RBridge Nickname     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Options...
   +-+-+-+-+-+-+-+-+-+-+-+-


                Figure 2 TRILL Header with the "A" Flag

   A (1 bit) - Indicates this is a possible OAM frame and is subject
   to specific handling as specified in this document.


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   All other fields carry the same meaning as defined in RFC6325.

3.2.1. Handling of TRILL frames with the "A" Flag

   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 Ether Type (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 CFM EtherType
   are not considered as OAM frames. Such frames MUST be discarded.

3.3. OAM Capability Announcement

   Any given TRILL RBridge can be (1) OAM incapable or (2) OAM
   capable with new extensions or (3) OAM capable with backwards-
   compatible 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.

   Capability flags defined in TRILL version sub-TLV (TRILL-VER)
   [rfc6326bis] will be utilized for announcing OAM capabilities.
   The following OAM related Flags are defined:

   O - OAM Capable

   B - Backwards Compatible.

   A capability announcement, with O Flag set to 1 and B flag set to
   1, indicates that the implementation is OAM capable but utilize
   backwards compatible method defined in Appendix A. A capability
   announcement, with O Flag set to 1 and B flag set to 0, indicates
   that the implementation is OAM capable and utilizes the method
   specified in section 3.2.

   When O Flag is set to 0, the announcing implementation is
   considered not capable of OAM and in this case the B flag is
   ignored.








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      +-+-+-+-+-+-+-+-+
      | Type          |              (1 byte)
      +-+-+-+-+-+-+-+-+
      | Length        |              (1 byte)
      +-+-+-+-+-+-+-+-+
      | Max-version   |              (1 byte)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
      |A|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 [rfc6326bis] with O and B flags


   NOTE: Bit position of O and B flags in the TRILL-VER sub-TLV are
   presented above as an example. Actual positions of the flags will
   be determined by TRILL WG and IANA and future revision of this
   document will be updated to include the allocations.


4. TRILL OAM Layering vs. IEEE Layering

   This section presents the placement of the TRILL OAM shim within
   the IEEE 802.1 layers. The processing of both the Transmit and
   Receive directions is explained.






















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                       +-+-+-+-+-+-+-+-+-+-+
                       |   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



   [RFC6325] Section 4.6 as updated by [RFCclcorrect] provides a
   detailed explanation of frame processing. Please refer to
   [RFC6325] for processing scenarios not covered herein.

   Sections 4.1 and 4.2 below apply to links using a broadcast LAN
   technology such as Ethernet.

   On links using an inherently point-to-point technology, such as
   PPP [RFC6361], there is no Outer.MacDA, Outer.MacSA, our
   Outer.VLAN because these are part of the link header for
   Ethernet. Point-to-point links typically have link headers


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   without these fields. These fields are primarily significant for
   native frames from and/or to end stations.

4.1. Processing at ISS Layer

4.1.1. Receive Processing

   The ISS Layer receives an indication from the port. It extracts
   DA, SA and marks the remainder of the payload as M1. 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

   Receives (DA, SA, M1) indication from ISS Layer. Extracts the
   VLAN ID an priority from the M1 part of the received indication
   (or derive them from the port defaults or the like) and
   constructs (DA, SA, VLAN, PRI, M2). VLAN+PRI+M2 map to M1 in the
   received indication. Pass (DA, SA, VLAN, PRI, M2) to the TRILL
   encap/decap procession layer.

4.2.2. Transmit Procession

   Receive (DA, SA, VLAN, PRI, M2) indication from TRILL encap/decap
   processing layer. Merge VLAN, PRI, M2 to form M1. Pass down (DA,
   SA, M1) to the ISS processing Layer.

4.3. TRILL Encapsulation and De-capsulation Layer

4.3.1. Receive Processing for Unicast packets

   Receive indication (DA, SA, VLAN, PRI, M2) from End Station VLAN
   and Priority Processing Layer.

      o If DA matches port Local DA and Frame is of TRILL EtherType




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        . Discard DA, SA, VLAN, PRI. From M2, derive (TRILL-HDR, iDA,
          iSA, i-VL, M3)

        . If TRILL nickname is Local and TRILL-OAM Flag is set

            Pass on to OAM processing

        . Else pass on (TRILL-HDR, iDA, iSA, i-VL, M3) to RBridge
          Layer

     o If DA matches port Local DA and EtherType is RBridge-Channel
   [Channel]

        . Process as a possible unicast native RBridge Channel packet

     o If DA matches port Local DA and EtherType is neither TRILL
     nor RBridge-Channel

         . Discard packet

     o If DA does not match and port is Appointed Forwarder for VLAN
   and EtherType is not TRILL or RBridge-Channel

        .  Insert TRILL-Hdr and send (TRILL-HDR, iDA, iSA,i-VL, M3)
          indication to RBridge Layer <- This is the ingress
          function

4.3.2. Transmit Processing for unicast packets

     o  Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from
        RBridge Layer

     o  If egress TRILL nickname is local

          o If port is Appointed Forwarder for iVL and the port is
             not configured as a trunk or p2p port and (TRILL Alert
             Flag set and OAM EtherType present) then

               . Strip TRILL-HDR and construct (DA, SA, VLAN, M2)

          o Else

               . Discard packet

     o  If egress TRILL nickname is not local




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          o Insert Outer.MacDA, Outer.MacSA, Outer.VLAN, 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 VLAN End Station processing
        Layer.

4.3.3. Receive Processing for Multicast packets

     o  Receive (DA, SA, V, M2) from VLAN aware end station
        processing layer

     o  If the DA is All-RBridges and the EtherType is TRILL

          o Strip DA, SA and V. From M2, extract (TRILL-HDR, iDA,
             iSA, iVL and M3).

          o If TRILL OAM Flag is set and OAM EtherType is present at
             the end of Flow entropy

               . Perform OAM Processing

          o Else extract the TRILL header, inner MAC addresses and
             inner VLAN and pass indication (TRILL-HDR, iDA, iSA,
             iVL and M3) to 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
        Ethertype is not TRILL or L2-IS-IS respectively

          o Discard the packet

     o  If the EtherType is TRILL but the multicast DA is not All-
        RBridge or if the EtherType is L2-IS-IS but the multicast Da
        is not All-IS-IS-RBridges

          o Discard the packet

     o  If DA is All-Edge-RBridges and EtherType is RBridge-Channel
        [Channel]

          o   Process as a possible multicast native RBridge
             Channel packet




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     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

          o The frame is not propagated through an RBridge although
             some special processing may be done at the port as
             specified in [RFC6325] and the frame may be dispatched
             to Layer 2 processing at the port if certain protocols
             are supported by that port (examples: Link Aggregation
             Protocol, Link Layer Discovery Protocol).

     o  If the DA is some other multicast value

          o Insert TRILL-HDR and construct (TRILL-HDR, iDA, iSA,
             IVL, M3)

          o Pass the (TRILL-HDR, iDA, iSA, IVL, M3) to 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
        RBridge layer.

     o  If TRILL-HDR multicast flag set and TRILL-HDR Alert flag
        set and OAM EtherType present then:

          o  (DA, SA, V, M2) by inserting TRILL Outer.MacDA of All-
             RBridges, Outer.MacSA, Outer.VL and TRILL EtherType. M2
             here is (Ethertype TRILL, TRILL-HDR, iDA, iSA, iVL, M)

             NOTE: Second copy of native format is not made.

     o  Else If TRILL-HDR multicast flag set and Alert flag not set

          o 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, iVL and construct (DA, SA, V, M2)
             for native format.

          o Make a second copy (DA, SA, V, M2) by inserting TRILL
             Outer.MacDA, Outer.MacSA, Outer.VL and TRILL EtherType.
             M2 here is (EtherType TRILL, TRILL-HDR, iDA, iSA, iVL,
             M)


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     o  Pass the indication (DA, SA, V, M2) to End Station VLAN
        processing layer.

4.4. TRILL OAM Layer Processing

   TRILL OAM Processing Layer is located between the TRILL
   Encapsulation / De-capsulation layer and RBridge Layer. It
   performs 1. Identification of OAM frames that need local
   processing and 2. performs OAM processing or redirect to the CPU
   for OAM processing.

     o  Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from
        RBridge layer.

     o  If the TRILL Multicast Flag is set and TRILL Alert Flag is
        set and TRILL OAM EtherType is present then
          o If MEP or MIP is configured on the Inner.VLAN 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
                    .  Re-direct to OAM Processing (Do not forward
                       further)
               . If MD-LEVEL matches MD-LEVEL of MIP then
                    .  Make a Copy for OAM processing and continue


     o  Else if TRILL Alert Flag is set and TRILL OAM EtherType is
        present then
          o If MEP or MIP is configured on the Inner.VLAN of the
             packet then
               . discard packets that have MD-LEVEL not present or
                  MD-LEVEL is Less than that of the MEP.
               . If MD-LEVEL matches MD-LEVEL of the MEP then
                    .  Re-direct to OAM Processing (Do not forward
                       further)
               . If MD-LEVEL matches MD-LEVEL of MIP then
               . Make a Copy for OAM processing and continue

     o  Else // Non OAM l Packet
          o  Continue

     o  Pass the indication (DA, SA, V, M2) to End Station VLAN
        processing layer.




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   NOTE: In the Received path, processing above compares against
   Down MEP and MIP Half functions. In the transmit processing it
   compares against Up MEP and MIP Half functions.

   Appointed Forwarder is a Functionality that TRILL Encap/De-Cap
   layer performs. The TRILL Encap/De-cap Layer is responsible for
   prevention of leaking of OAM packets as native frames.


5. Maintenance Associations (MA) 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 802.1ag MIB
   definitions, each MEP's MIB contains one or more flow entropy
   definitions corresponding to the set of flows that the MEP
   monitors.

   [8021Q] MIB is augmented to add the TRILL specific information.
   Figure 5, below depicts the augmentation of the CFM MIB to add
   the TRILL specific Flow Entropy.













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             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




6. MEP Addressing

   In IEEE 802.1ag [8021Q], OAM messages address the target MEP by
   utilizing a unique MAC address.  In TRILL a MEP is addressed by
   combination of the egress RBridge nickname and the Inner
   VLAN/FGL.

   At the MEP, OAM packets go through a hierarchy of op-code de-
   multiplexers. The op-code de-multiplexers channel the incoming
   OAM packets to the appropriate message processor (e.g. LBM) The
   reader may refer to Figure 6 below for a visual depiction of
   these different de-multiplexers.

   1. Identify the packets that need OAM processing at the Local
     RBridge as specified in Section 4.


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        a.  Identify the MEP that is associated with the Inner.VLAN.

   2. The MEP first validates the MD-LEVEL and then

        a.  Redirect to MD-LEVEL De-multiplexer

   3. MD-LEVEL de-multiplexer 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 belonging to different MAs)

        a.  If the packet MD-LEVEL is equal to the configured MD-
          LEVEL of the MEP, then pass to the Opcode de-multiplexer

        b.  If the packet MD-LEVEL is less than the configured MD-
          LEVEL of the MEP, discard the packet

        c.  If the packer MD-LEVEL is greater than the configured
          MD-LEVEL of the MEP, then pass on to the next higher MD-
          LEVEL de-multiplexer, if available. Otherwise, if no such
          higher MD-LEVEL de-multiplexer exists, then forward the
          packet as normal data.

   4. Opcode De-multiplexer compares the opcode in the packet with
     supported opcodes

        a.  If Op-code is CCM, LBM, LBR, PTM, PTR, MTVM, MTVR, then
          pass on to the correct Processor

        b.  If Op-code is Unknown, then discard.



















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                               |
                               .CCM   LBM   PTM    MTV
                               |      |    |      |
                             +-+-+-+-+-+-+-+-+-+-+-+-+
                             |        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 De-Multiplexers at MEP for active SAP

        T : Denotes Tap, that identifies OAM frames that need local
        processing. These are the packets with OAM flag set AND OAM
        Ether type is present after the flow entropy of the packet

        M : Is the post processing merge, 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.

        L : Denotes MD-Level processing. Packets with MD-Level less
        than the Level will be dropped. Packets with equal MD-Level
        are passed on to the opcode de-multiplexer. Others are
        passed on to the next level MD processors or eventually to
        the merge point (M).

        NOTE: LBM, MTV and PT are not subject to MA de-multiplexers.
        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.



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6.1. Use of MIP in TRILL

   Maintenance Intermediate Points (MIP) 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.

   Similar approach as 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.






















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                                             PT     MTV
                                              |      |
                             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                             |             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 De-Multiplexers at MIP for active SAP

   T: TAP processing for MIP. All packets with OAM flag set are
   captured.

   L : MD Level Processing, Packet with matching MD Level are
   "copied" to the Opcode de-multiplexer and 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 OP code de-multiplexer.

   M : Merge processor, merge OAM packets to be forwarded along with
   the data flow.

   Packets that carry Path Trace Message (PTM) or Multi-destination
   Tree Verification (MTV) OpCodes are passed on to the respective
   processors.

   Packets with unknown OpCodes are counted and discarded.




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 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 MEPID is a 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 identifies the interested
   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.  below for the theory of operation of CCM.

   The MIB of [8021Q] is augmented with the definition of flow-
   entropy. Please see [TRILLOAMMIB] for definition of these and
   other TRILL related OAM MIB definitions. The below Figure depicts
   the correlation between MA, CCM and the flow-entropy.


















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             MA---
            |
             --- MEP
            |
            . - Remote MEP List
                   .
                   |
                    --- MEP-A
                   |
                    --- MEP-B
                   .

            |
            . - Flow Entropy List {Augments IEEE8021-CFM-MIB}

                   |
                    --- (Flow Entropy-1) {note we have to define
                   |                      destination nickname with
                    --- (Flow-entropy-2)  the flow entropy discuss}
                   |
                   . ---(Flow Entropy n)
           |
           . - CCM
                  |
                   --- (standard 8021ag entries)
                  |
                   --- (hop-count) { Augments IEEE8021-CFM-MIB}
                  |
                   --- (Other TBD 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.


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   Additionally, a MEP may raise SNMP TRAPs [TRILLOAMMIB] as Alarms
   when a connectivity failure occurs.

     8. TRILL OAM Message Channel

   The TRILL OAM Message Channel can be divided into two parts:
   TRILL OAM Message header and TRILL OAM Message 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 can be
   accomplished by re-using 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). Identifies the
        maintenance domain level. For TRILL, in general, this field
        is set to zero. However, extension of TRILL, for example to
        support multilevel, may create different MD-LEVELs and 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].





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     o  Flags: Includes operational flags (1 byte). The definition
        of flags is Opcode-specific and is covered in the applicable
        sections.

     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.)

   MD-L, Version, Opcode, Flags and FirstTLVOffset fields
   collectively are referred to as the OAM Message Header.

   The Opcode specific information section of the OAM Message may
   contain Session Identification number, time-stamp, etc.

8.2. TRILL OAM Opcodes

   The following Opcodes are defined for TRILL. Each of the Opcodes
   indicates a separate type of TRILL OAM message. Details of the
   messages are presented in the related sections.

   TRILL OAM Message Opcodes:

    TBD-64 : Path Trace Reply
    TBD-65 : Path Trace Message
    TBD-66 : Multicast Tree Verification Reply
    TBD-67 : Multicast Tree Verification Message


8.3. Format of TRILL OAM TLV

   The same TLV format as defined in section 21.5.1 of [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



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   Type (1 octet): Specifies the Type of the TLV (see sections 8.4.
   for TLV types).

   Length (2 octets): Specifies the length of the 'Value' field in
   octets. Length of the 'Value' field can be either zero or more
   octets.

   Value (variable): The length and the content of this field depend
   on the type of the TLV. Please refer to applicable TLV
   definitions for the 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. [8021Q] defined
   TLVs are reused, where applicable. Types 32-63 are reserved for
   ITU-T Y.1731. We propose to reserve Types 64-95 for TRILL OAM
   TLVs.

     8.4.1. Common TLVs between 802.1ag and TRILL

   The following TLVs are defined in [8021Q]. We propose to re-use
   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





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 8.4.2. TRILL OAM Specific TLVs

   As indicated above, Types 64-95 will be requested to be reserved
   for TRILL OAM purposes. 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.

     Type           TLV Name
   -----------    ----------------------
    TBD-TLV-64     TRILL OAM Application Identifier
    TBD-TLV-65     Out of Band IP Address
    TBD-TLV-66     Original Payload
    TBD-TLV-67     Diagnostic VLAN
    TBD-TLV-68     RBridge scope
    TBD-TLV-69     Previous RBridge Nickname
    TBD-TLV-70     TRILL Next Hop RBridge List (ECMP)
    TBD-TLV-71     Multicast Receiver Availability
    TBD-TLV-72     Flow Identifier
    TBD-TLV-73     Reflector Entropy
    TBD-TLV-74 to TBD-TLV-95  Reserved


8.4.3. TRILL OAM Application Identifier TLV

   TRILL OAM Application Identifier TLV carries TRILL OAM
   application specific information. 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
   an RBridge, unless that RBridge is also running Ethernet CFM.

                        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       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Return Code  |Return sub-code|      Reserved         |F|C|O|I|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


            Figure 11 TRILL OAM Application Identifier TLV

   Type (1 octet) = TBD-TLV-64 indicate that this is the TRILL OAM
   Application Identifier TLV

   Length (2 octets) = 6



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   TRILL OAM Version (1 Octet), currently set to zero. Indicates the
   TRILL OAM version. TRILL OAM version can be different than the
   [8021Q] version.

   Return Code (1 Octet): Set to zero on requests. Set to an
   appropriate value in response messages.

   Return sub-code (1 Octet): Return sub-code is set to zero on
   transmission of request message. Return sub-code identifies
   categories within a specific Return code. Return sub-code MUST be
   interpreted within a Return code.

   Reserved: set to zero on transmission and ignored on reception.

   F (1 bit): Final flag, when set, indicates this is the last
   response.

   C (1 bit): Label error (VLAN/Label mapping error), if set
   indicates that the label (VLAN/FGL) in the flow entropy is
   different than the label included in the diagnostic TLV.  This
   field is ignored in request messages and MUST only be interpreted
   in response messages.

   O (1 bit): If set, indicates, OAM out-of-band response requested.

   I (1 bit): If set, indicates, OAM in-band response requested.

   NOTE: When both O and I bits are set to zero, indicates that no
   response is required (silent mode). User MAY specify both O and I
   or one of them or none. When both O and I bits are set response
   is sent both in-band and out-of-band.



 8.4.4. Out Of Band Reply Address TLV

   Out of Band Reply Address TLV specifies the address to which an
   out of band OAM reply message MUST be sent. When O bit in the
   TRILL Version TLV is not set, Out of Band Reply Address TLV is
   ignored.









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                        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 IP Address TLV

   Type (1 octet) = TBD-TLV-65

   Length (2 octets) = Variable. Minimum length is 2.

   Address Type (1 Octet): 0 - IPv4. 1 - IPv6. 2 - TRILL RBridge
   nickname. All other values reserved.

   Addr Length (1 Octet). 4 - IPv4. 16 - IPv6, 2 - TRILL RBRidge
   nickname.

   Reply Address (variable): Address where the reply needed to be
   sent. Length depends on the address specification.

 8.4.5. Diagnostics Label TLV

   Diagnostic label 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. Label Error Flag in the response (TRILL
   OAM Message Version TLV) MUST be set when the two VLANs do not
   match.













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                        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(VLAN)
|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
+


                     Figure 13 Diagnostic VLAN TLV

   Type (1 octet) = TBD-TLV-66 indicates that this is the TRILL
   Diagnostic VLAN TLV

   Length (2 octets) = 5

   L-Type (Label type, 1 octet)

      0- indicate 802.1Q 12 bit VLAN.

      1 - indicate TRILL 24 bit fine grain label

   Label (24 bits): Either 12 bit VLAN or 24 bit fine grain label.

   RBridges do not perform Label error checking when Label TLV is
   not included in the OAM message. In certain deployments
   intermediate devices may perform label translation. In such
   scenarios, originator should not include the diagnostic Label TLV
   in OAM messages. Inclusion of diagnostic TLV will generate
   unwanted label error notifications.













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 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

   Type (1 Octet) = TBD-TLV-67

   Length (2 octets) =  variable

 8.4.7. RBridge scope TLV

   RBridge scope TLV identifies nicknames of RBridges from which a
   response is required. The RBridge scope TLV is only applicable to
   Multicast Tree Verification messages. This TLV SHOULD NOT be
   included in other messages. Receiving RBridges MUST ignore this
   TLV on messages other than Multicast Verification Message.

   Each TLV can contain up to 255 nicknames of in scope RBridges. A
   Multicast 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.















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                        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

   Type (1 octet) = TBD-TLV-68 indicates that this is the "RBridge
   scope TLV"

   Length (2 octets) = variable. Minimum value is 2.

   Nickname (2 octets) = 16 bit RBridge nickname.

 8.4.8. Previous RBridge nickname TLV

   "Previous RBridge nickname TLV" identifies the nickname or
   nicknames of the upstream RBridge. [RFC6325] allows a given
   RBridge to hold multiple nicknames.

    "Upstream 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                     |   nickname                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                Figure 16 Previous RBridge nickname TLV

   Type (1 octet) = TBD-TLV-69 indicates that this is the "Upstream
   RBridge nickname"

   Length (2 octets) = 4.


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   Nickname (2 octets) = 16 bit RBridge nickname.

 8.4.9. Next Hop RBridge List TLV

   "Next Hop RBridge List TLV" identifies the nickname or nicknames
   of the downstream next hop RBridges. [RFC6325] 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.

   "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

   Type (1 octet) = TBD-TLV-70 indicates that this is the "Next
   nickname"

   Length (2 octets) = variable. Minimum value is 2.

   Nickname (2 octets) = 16 bit RBridge nickname.

 8.4.10. Multicast Receiver Port count TLV

   "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.

   Multicast Receiver Port count is an Optional TLV.






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                        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 Availability TLV

   Type (1 octet) = TBD-TLV-71 indicates that this is the "Multicast
   Availability TLV"

   Length (2 octets) = 5.

   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 (flow-id) TLV

   Flow Identifier (flow-id) uniquely identifies a specific flow.
   The flow-id 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-id                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                    Figure 19 Flow Identifier  TLV

   Type (1 octet) = TBD-TLV-72

   Length (2 octets) = 5.

   Reserved (1 octet) set to 0 on transmission and ignored on
   reception.

   MEP-ID (2 octets) = MEP-ID of the originator [8021Q].




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   Flow-id (2 octets) = uniquely identifies the flow per MEP.
   Different MEPs may allocate the same flow-id value. The {MEP-ID,
   flow-id} pair is globally unique.

   Inclusion of the MEP-ID in the flow-id TLV allows inclusion of
   MEP-ID for messages that do not contain MEP-ID in OAM header.
   Applications may use MEP-ID information for different types of
   troubleshooting.

 8.4.12. Reflector Entropy TLV

   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



   Type (1 octet) =TBD-TLV-73 Reflector Entropy TLV.

    Length (1 octet) =97.

    Reserved (1 octet) = set to zero on transmission and ignored by
   the recipient.

    Reflector Entropy (96-octet) = Flow Entropy to be used by the
   responder. May be padded with zero if the desired flow entropy is
   less than 96 octets.









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 9. Loopback Message

 9.1. Loopback OAM 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 21 Loopback OAM Message Format

   The above figure depicts the format of the Loopback Request and
   response messages as defined in [8021Q]. The Opcode for Loopback
   Message is set to 65 and the Opcode for the Reply Message is set
   to 64. The Session Identification Number 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..

  9.2. Theory of Operation

9.2.1. Actions by Originator RBridge



   Identifies the destination RBridge nickname based on user
   specification or based on the specified destination MAC or IP
   address.

   Constructs the flow entropy based on user specified parameters or
   implementation specific default parameters.

   Constructs the TRILL OAM header: sets the opcode to Loopback
   message type (3). Assign applicable Loopback Transaction
   Identifier number for the request.

   The TRILL OAM Version TLV MUST be included and with the flags set
   to applicable values.


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   Include following OAM TLVs, where applicable

     o  Out-of-band Reply address TLV

     o  Diagnostic Label TLV

     o  Sender ID TLV

   Specify the Hop count of the TRILL data frame per user
   specification or utilize an applicable Hop count value.

   Dispatch the OAM frame for transmission.

   RBridges may continue to retransmit the request at periodic
   intervals, until a response is received or the re-transmission
   count expires. At each transmission Session Identification number
   MUST be incremented.

9.2.2. Intermediate RBridge

   Intermediate RBridges forward the frame as a normal data frame
   and no special handling is required.

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 and 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:

   TRILL OAM application encodes the received TRILL header and flow
   entropy in the Original payload TLV and includes it in the OAM
   message.

   Set the Return Code and Return sub code to applicable values.
   Update the TRILL OAM opcode to 2 (Loopback Message Reply)





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   Optionally, if the VLAN/FGL identifier value of the received flow
   entropy differs from the value specified in the diagnostic Label,
   set the Label Error Flag on TRILL OAM Application Identifier TLV.

   Include the sender ID TLV (1)

   If in-band response was requested, dispatch the frame to the
   TRILL data plane with request-originator RBridge nickname as the
   egress RBridge nickname.

   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
   for 802.1 both the unicast and multicast paths are congruent.
   However, TRILL is multicast and unicast incongruent. Hence, TRILL
   OAM uses a new message format: the Path Trace message.

   The Path Trace Message has the same format as Loopback Message.
   Opcode for Path Trace Reply Message is 65 and Request 64

   Operation of the Path Trace message is identical to the Loopback
   message except that it is first transmitted with a TRILL Hop
   count field value of 1. The sending RBridge expects a Time Expiry
   Return-Code from the next hop or a successful response. If a Time
   Expiry Return-code is received as the response, the originator
   RBridge records the information received from intermediate node
   that generated the Time Expiry 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 or Path Trace process timeout occur or Hop count reaches
   a configured maximum value.







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 10.1. Theory of Operation

 10.1.1. Action by Originator RBridge

   Identify the destination RBridge based on user specification or
   based on location of the specified MAC address.

   Construct the flow entropy based on user specified parameters or
   implementation specific default parameters.

   Construct the TRILL OAM header: Set the opcode to Path Trace
   Request message type (65). Assign an applicable Session
   Identification number for the request. Return-code and sub-code
   MUST be set to zero.

   The TRILL OAM Application Identifier TLV MUST be included and set
   the flags to applicable values.

   Include following OAM TLVs, where applicable

     o  Out-of-band IP address TLV

     o  Diagnostic Label TLV

     o  Include the Sender ID TLV

   Specify the Hop count of the TRILL data frame as 1 for the first
   request.

   Dispatch 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 re-transmission
   count expires. At each new re-transmission, 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 Hop-count has expired.

   TRILL OAM application layer further validates the received OAM
   frame by examining the presence of TRILL OAM Flag and OAM-


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   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:

   TRILL OAM application encodes the received TRILL header and flow
   entropy in the Original payload TLV and include it in the OAM
   message.

   Set the Return Code to (2) "Time Expired" and Return sub code to
   zero (0). Update the TRILL OAM opcode to 64 (Path Trace Message
   Reply).

   If the VLAN/FGL identifier value of the received flow entropy
   differs from the value specified in the diagnostic Label, set the
   Label Error Flag on TRILL OAM Application Identifier TLV.



   Include following TLVs

   Upstream RBridge nickname TLV (69)

   Reply Ingress TLV (5)

   Reply Egress TLV (6)

   Interface Status TLV (4)

   TRILL Next Hop RBridge (Repeat for each ECMP) (70)

   Sender ID TLV (1)

   If Label error detected, set C flag (Label error detected) in the
   version.

   If in-band response was requested, dispatch the frame to the
   TRILL data plane with request-originator RBRidge nickname as the
   egress RBridge nickname.

   If out-of-band response was requested, dispatch the frame to the
   standard IP forwarding process.






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10.1.3. Destination RBridge

   Processing is identical to section 10.1.2. With the exception
   that TRILL OAM Opcode is set to Path Trace Reply (64).

11. Multi-Destination Tree Verification (MTV) Message

   Multi-Destination Tree Verification messages allow verifying
   TRILL distribution tree integrity and pruning. TRILL VLAN/FGL and
   multicast pruning are described in [RFC6325] [RFCclcorrect] and
   [RFCfgl]. 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 parameter 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, MTV 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 request only to RBRidges that
   have failed to respond.

 11.1. Multi-Destination Tree Verification (MTV) OAM Message Format

   Format of MTV OAM Message format is identical to that of Loopback
   Message format defined in section 9. with the exception that the
   Loopback Transaction Identifier, in section 9.1. , is replaced
   with the Session Identifier.






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 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, or the Multicast MAC
   address and VLAN/FGL, or 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, 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 needed 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 of 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
   identifies the nickname that represents the multicast tree.

   Obtain the applicable Hop count value for the selected multicast
   tree.

   Construct TRILL OAM message header and include Session
   Identification number. Session Identification number facilitate
   the originator to map the response to the correct request.

   TRILL OAM Application Identifier TLV MUST be included.

   Op-Code MUST be specified as Multicast Tree Verification Message
   (70)

   Include RBridge scope TLV (67)

   Optionally, include following TLV, where applicable

     o  Out-of-band IP address

     o  Diagnostic Label

     o  Sender ID TLV (1)


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   Specify the Hop count of the TRILL data frame per user
   specification or alternatively utilize the applicable Hop count
   value if TRILL Hop count is not being specified by the user.

   Dispatch 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 re-
   transmission count expires. At each new re-transmission, the
   Session Identification number MUST be incremented. At each re-
   transmission, 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 sections 3.2.

   CPU of 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 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:

   TRILL OAM application encodes the received TRILL header and flow
   entropy in the Original payload TLV and includes them in the OAM
   message.

   Set the Return Code to (0) and Return sub code to zero (0).
   Update the TRILL OAM opcode to 66 (Multicast Tree Verification
   Reply).

   Include following TLVs:

   Upstream RBridge nickname TLV (69)

   Reply Ingress TLV (5)

   Interface Status TLV (4)



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   TRILL Next Hop RBridge (Repeat for each downstream RBridge) (70)

   Sender ID TLV (1)

   Multicast Receiver Availability TLV (71)

   If Label (VLAN or FGL) cross connect error detected, set C flag
   (Cross connect error detected) in the version.

   If in-band response was requested, dispatch the frame to the
   TRILL data plane with request-originator RBridge nickname as the
   egress RBridge nickname.

   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 the 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. [RFC6905] 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 an MEP.

   It is important that the solution presented in this document
   accomplishes the requirements specified in [RFC6905] within the
   framework of [8021Q] in a straightforward manner and with minimum
   changes. Section 8 above defines multiple flows within the CCM
   object, each corresponding to a flow that a given MEP wishes to
   monitor.

   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.


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   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-id TLV, and SNMP Notifications (Traps). Section
   12.1. 12.1.  below discuss the procedure.

  12.1. CCM Error Notification

   Each MEP transmits 4 CCM messages per each flow. ([8021Q] detects
   CCM fault when 3 consecutive CCM messages are lost). Each CCM
   Message has a unique sequence number and unique flow-identifier.
   The flow identifier is included in the OAM message via flow-id
   TLV.

   When an 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 SNMP notification that contain
   the remote MEP Identification, flow-id and the Sequence Number of
   the last CCM message it received and if available, the flow-id
   and the Sequence Number of the first CCM message it received
   after the failure. Each MEP maintains a unique flow-id per each
   flow, hence the operator can easily identify flows that
   correspond to the specific flow-id.

   The following example illustrates the above.

   Assume there are two MEPs, MEP-A and MEP-B.

   Assume there are 3 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-id=(1)

   Flow-2 Sequence={5,6,7,8,17,18,19,20,.. } flow-id=(2)

   Flow-3 Sequence={9,10,12,11,21,22,23,24,.. } flow-id=(3)

   Let's Assume Flow-2 is at fault.

   MEP-B, receives CCM from MEP-A with sequence numbers 1,2,3,4, but
   did not receive 5,6,7,8. CCM timeout is set to 3 CCM intervals in
   [8021Q]. Hence MEP-B detects the error at the 8'th CCM message.
   At this time the sequence number of the last good CCM message
   MEP-B has received from MEP-A is 4 and flow-id of the last good
   CCM Message is (1). Hence MEP-B will generate a CCM error SNMP


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   notification with MEP-A and Last good flow-id (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 CCM message with Sequence Numbers 9,10,11,12,21 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 and the first valid
   flow-id and the Sequence number after the CCM timeout. In the
   foregoing example, it is MEP-A, flow-id (1) and Sequence Number
   9.

   The remote MEP list under the CCM MIB Object is augmented to
   contain "Last Sequence Number", flow-id and "CCM Timeout"
   variables. Last Sequence Number and flow-id are updated every
   time a CCM is received from a remote MEP. 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

   Derive the flow entropy based on flow entropy specified in the
   CCM Management object.

   Construct the TRILL CCM OAM header as specified in [8021Q].

   TRILL OAM Version TLV MUST be included as the first TLV and set
   the flags to applicable values.

   Include other TLVs specified in [8021Q]

   Include the following optional TRILL OAM TLVs, where applicable

     o  Sender ID TLV

   Specify the Hop count of the TRILL data frame per user
   specification or utilize an applicable Hop count value.

   Dispatch the OAM frame to the TRILL data plane for transmission.

   An RBridge transmits a total of 4 requests, each at CCM
   retransmission interval. At each transmission the Session
   Identification number MUST be incremented by one.



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   At the 5'th retransmission interval, flow entropy of the CCM
   packet is updated to the next flow entropy specified in the CCM
   Management Object. If 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
   and no special handling is required.

12.2.3. Destination RBridge

   If the CCM Message is addressed to the local RBridge or multicast
   and satisfies OAM identification methods specified in sections
   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.

   Validate the MD-LEVEL and pass the packet to the Opcode de-
   multiplexer. The Opcode de-multiplexer delivers CCM packets to
   the CCM process.

   The CCM Process performs 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.



 13. Fragmented Reply

   The response Message allows Fragmented Replies. In case of
   Fragmented Replies, all messages MUST follow the procedure
   defined in this section.

   All Reply Messages MUST be encoded as described in this document.


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   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 appropriate Final Flag field. The Final Flag, MUST, only be
   set on the final fragment of the reply.

 14. Security Considerations

   For general TRILL related security considerations, please refer
   to [RFC6325]. Specific security considerations related methods
   presented in this document are currently under investigation.

 15. IEEE Allocation Considerations

   The IEEE 802.1 Working Group is requested to allocate a separate
   opcode and TLV space within 802.1QCFM messages for TRILL purpose.

 16. IANA Considerations

   IANA is requested to do the following:

   - Assign a multicast MAC address from the block assigned to TRILL
   [RFC6325]

   - Set up sub-registry within the TRILL Parameters registry for
   block of TRILL "OAM OpCodes" (Section 8.2. )

   - Set up sub-registry within the TRILL Parameters registry for
   TRILL "OAM TLV Types" (Section 8.4. )

   - Assign a unicast MAC addressed under the IANA OUI, reserved for
   identification of OAM packets discussed in backward compatibility
   method (Appendix A) See Appendix C.





 17. References

 17.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.




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   [RFC6325] Perlman, R., et.al., "Routing Bridges (RBridges): Base
             Protocol Specification", RFC 6325, July 2011.

   [RFCfgl] D. Eastlake, M. Zhang, P. Agarwal, R. Perlman, D. Dutt,
             "TRILL: Fine-Grained Labeling", draft-ietf-trill-fine-
             labeling, work in progress.

   [8021Q] IEEE, "Media Access Control (MAC) Bridges and Virtual
             Bridged Local Area Networks", IEEE Std 802.1Q-2011,
             August, 2011.



  17.2. Informative References

    [RFC4379] Kompella, K. et.al, "Detecting Multi-Protocol Label
             Switched (MPLS) Data Plane Failures", RFC 4379,
             February 2006.

   [RFC6291] Andersson, L., et.al., "Guidelines f<or the use of the
             "OAM" Acronym in the IETF" RFC 6291, June 2011.

   [RFC6361] Carlson, J. and Eastlake, D. "PPP Transparent
             Interconnection of Lots of Links (TRILL) Protocol
             Control Protocol", RFC 6361, August 201.

   [RFC6905] Senevirathne, T. et.al"Requirements for Operations,
             Administration, and Maintenance (OAM) in Transparent
             Interconnection of Lots of Links (TRILL)", RFC 6905,
             March 2013.



   [RFCclcorrect] Eastlake, Donald, et.al. "TRILL: Clarifications,
             Corrections, and Updates, draft-ietf-trill-clear-
             correct, July 2012, in RFC Editor's queue.

   [TRLOAMFRM] Salam, S., et.al., "TRILL OAM Framework", draft-ietf-
             trill-oam-framework, Work in Progress, November, 2012.

   [TRILLEXT] Eastlake, Donald, et.al. "TRILL: Header Extension",
             draft-ietf-trill-rbridge-extension, June, 2012.

   [Y1731] ITU, "OAM functions and mechanisms for Ethernet based
             networks", ITU-T G.8013/Y.1731, July, 2011.




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   [Channel] D. Eastlake, et.al. , "TRILL: RBridge Channel Support",
             draft-ietf-trill-rbridge-channel-08.txt, in RFC
             Edtior's queue.

   [TRILLOAMMIB] Deepak Kumar et.al, "TRILL OAM MIB", draft-deepak-
             trill-oam-mib, May 2013.



 18. Acknowledgments

   Work in 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, Dan Romascanu, Gayle Nobel and Tal Mizrahi.

   Special appreciations are due for Dinesh Dutt for his support and
   encouragement, especially during the initial discussion phase of
   TRILL OAM.

   This document was prepared using 2-Word-v2.0.template.dot.


























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Appendix A.                  Backwards Compatibility

   Methodology presented above in this document is in-line with the
   [8021Q] framework 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
   section, 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. Maintenance Point
   (MEP/MIP) Model 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 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 [RFC6905].

   [8021Q] requires that the MEP filters or pass 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 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 will
   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 [RFC4379]
   framework does not include the concept of domains and OAM


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   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.

    A.2 Data plane encoding and frame identification

   Backwards compatibility method presented in this section defines
   methods to identify OAM frames when implementations do not have
   capabilities to utilize TRILL OAM Alert flag presented earlier to
   identify OAM frames, in the hardware.

   It is assumed ECMP path selection of non-IP flows utilize MAC DA,
   MAC SA and VLAN, IP Flows utilize IP DA, IP SA and 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 TRILL
   OAM Flag, as soon as possible and methods presented here SHOULD
   be used only as an interim solution.



   Identification methods are divided in to 4 broader groups.

   Identification of Unicast non-IP OAM Flows,

   Identification of Multicast non-IP OAM Flows,

   Identification of Unicast IP OAM Flows and

   Identification of Multicast IP OAM Flows



   As presented in the table below, based on the flow type (as
   defined above), implementations are required to use a well-known
   value in either the source MAC field or Ethertype field to
   identify OAM flows.

   Receiving RBridge identifies OAM flows based on the presence of
   the well-known values in the specified fields, AND additionally,
   for unicast flows, egress RBRdige nickname of the packet MUST
   match that of the local RBRidge or for multicast flows, TRILL
   header mutlicast flag MUST be set.



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   Unicast OAM flows that qualify for local processing MUST be
   redirected to the OAM process and MUST NOT be forwarded (that 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 packet MUST be forwarded
   along the normal path. Additionally, methods MUST be in place to
   prevent multicast packets leaking out of the TRILL campus.

   The following table summarizes the identification of different
   OAM frames from data frames.



   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Flow Entropy   |Inner    |OAM Ether|Egress   |
   |               |MacSA    |Type     |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 22 Identification of TRILL OAM Frames

   It is important to note that all RBridges MUST generate OAM flows
   with "A" flag set and CFM EttherType "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
   RBRdiges that are compliant to the backwards compatibility method
   defined in this document.













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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 MEPIDs. The
   Base Mode for TRILL OAM defined here facilitates ease of use and
   provides out of the box plug-and-play capabilities, per the
   Operational and Manageability considerations described in Section
   6 of [TRLOAMFRM].

   All RBrdiges that support TRILL OAM MUST support 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 Based Mode of
   operation, the value of the Maintenance Domain Name must be the
   character string "TrillBaseMode" (excluding the quotes "). In
   Base Mode operation Short MA Name format is set to 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 RBrdige creates a single UP
   MEP associated with a virtual OAM port with no physical layer
   (NULL PHY). The MEPID associated with this MEP is the 2-octet
   RBridge Nickname.

   By default, all RBridges operating in the Base Mode for TRILL OAM
   are able to initiate LBM, PT and other OAM tools with no
   configuration.

   Implementation MAY provide default flow-entropy to be included in
   OAM messages. Content of the default flow-entropy is outside the
   scope of this document.

   Figure 23, below depicts encoding of MAID within CCM messages.







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   +-+-+-+-+-+-+-+-+-+-+-+-+-+
   |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 23 MAID structure as defined in [8021Q]

   Maintenance Domain Name Format is set to Value: 4

   Maintenance Domain Name Length is set to value: 13

   Maintenance Domain Name is set to: TrillBaseMode

   Short MA Name Format is set to value: 3

   Short MA Name Length is set to value: 2

   Shirt MA Name is set to : FFFC

   Padding : set of zero up to 48 octets of total length of the
   MAID.

   Please refer to [8021Q] for details.




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Appendix C.                  Unicast MAC Request

      Applicant Name: IETF TRILL Working Group

      Applicant Email:  tsenevir@cisco.com

      Applicant Telephone: 408-853-2291

      Use Name: TRILL OAM

      Document: draft-tissa-trill-oam-fm

      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: Unicast






























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Authors' Addresses


   Tissa Senevirathne
   CISCO Systems
   375 East Tasman Drive.
   San Jose, CA 95134
   USA.

   Phone: +1 408-853-2291
   Email: tsenevir@cisco.com


   Norman Finn
   CISCO Systems
   510 McCarthy Blvd
   Milpitas, CA 95035
   USA

   Email: nfinn@cisco.com


   Samer Salam
   CISCO Systems
   595 Burrard St. Suite 2123
   Vancouver, BC V7X 1J1, Canada

   Email: ssalam@cisco.com


   Deepak Kumar
   CISCO Systems
   510 McCarthy Blvd,
   Milpitas, CA 95035, USA

   Phone : +1 408-853-9760
   Email: dekumar@cisco.com


   Donald Eastlake
   Huawei Technologies
   155 Beaver Street
   Milford, MA 01757

   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com



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   Sam Aldrin
   Huawei Technologies
   2330 Central Express Way
   Santa Clara, CA 95951
   USA

   Email: aldrin.ietf@gmail.com


   Yizhou Li
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China

   Phone: +86-25-56625375
   Email: liyizhou@huawei.com
































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