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Versions: 00 01 02 draft-ietf-trill-oam-fm

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


                                                      February 17, 2013
Expires: August 2013



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


Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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Copyright Notice

   Copyright (c) 2013 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

   TRILL OAM Fault Management solution is presented in this document.
   Methods proposed 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
   different set of information is required 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 "A" Flag...............8
      3.3. Backwards Compatibility Method............................8
      3.4. OAM Capability Announcement...............................9
   4. TRILL OAM Layering vs. IEEE Layering..........................10
      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. TRLL 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............12
         4.3.4. Transmit Processing of Multicast packets............13
      4.4. TRILL OAM Layer Processing...............................14
   5. Maintenance Associations (MA) in TRILL........................15
   6. MEP Addressing................................................16
      6.1. Use of MIP in TRILL......................................19
   7. Approach for Backwards Compatibility..........................21
   8. Continuity Check Message (CCM)................................22
   9. TRILL OAM Message Channel.....................................24
      9.1. TRILL OAM Message header.................................24
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      9.2. TRILL OAM Opcodes........................................25
      9.3. Format of TRILL OAM TLV..................................25
      9.4. TRILL OAM TLVs...........................................26
         9.4.1. Common TLVs between 802.1ag and TRILL...............26
         9.4.2. TRILL OAM Specific TLVs.............................26
            9.4.2.1. TRILL OAM Application Identifier TLV...........27
         9.4.3. Out Of Band Reply Address TLV.......................28
            9.4.3.1. Diagnostics Label TLV..........................29
            9.4.3.2. Original Data Payload TLV......................30
            9.4.3.3. RBridge scope TLV..............................30
            9.4.3.4. Previous RBridge nickname TLV..................31
            9.4.3.5. Next Hop RBridge List TLV......................31
            9.4.3.6. Multicast Receiver Port count TLV..............32
         9.4.4. Flow Identifier (flow-id) TLV.......................33
   10. Loopback Message.............................................34
         10.1.1. Loopback OAM Message format........................34
         10.1.2. Theory of Operation................................34
            10.1.2.1. Originator RBridge............................34
            10.1.2.2. Intermediate RBridge..........................35
            10.1.2.3. Destination RBridge...........................35
   11. Path Trace Message...........................................36
         11.1.1. Theory of Operation................................36
            11.1.1.1. Originator RBridge............................36
            11.1.1.2. Intermediate RBridge..........................37
            11.1.1.3. Destination RBridge...........................38
   12. Multi-Destination Tree Verification (MTV) Message............38
      12.1. Multi-Destination Tree Verification (MTV) OAM Message
      Format........................................................39
      12.2. Theory of Operation.....................................39
         12.2.1. Originator RBridge.................................39
         12.2.2. Receiving RBridge..................................40
         12.2.3. In scope RBridges..................................40
   13. Application of Continuity Check Message (CCM) in TRILL.......41
      13.1. CCM Error notification - Method-1.......................42
      13.2. CCM Error Notification Method-2.........................43
      13.3. Theory of Operation.....................................44
         13.3.1. Originator RBridge.................................44
         13.3.2. Intermediate RBridge...............................45
         13.3.3. Destination RBridge................................45
   14. Multiple Fragment Reply......................................45
   15. Security Considerations......................................46
   16. Allocation Considerations....................................46
      16.1. IEEE Allocation Considerations..........................46
      16.2. IANA Considerations.....................................46
   17. References...................................................47
      17.1. Normative References....................................47
      17.2. Informative References..................................47
   18. Acknowledgments..............................................48

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1. Introduction

   The general structure of TRILL OAM messages is presented in
   [TRILLOAMFM]. According to [TRILLOAMFM], 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.

   The OAM message channel, if defined properly, can be shared between
   different technologies. A common OAM channel allows a uniform user
   experience for the customers, savings on operator training, re-use
   of software code base and faster time to market.

   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 standard utilizes the same messaging format as
   [8021Q] and OAM messages where applicable. In this document, we take
   a similar stance and propose reusing [8021Q] in TRILL OAM. We assume
   readers are familiar with [8021Q] and Y1731. Readers who are not
   familiar with these documents are encouraged to review [8021Q] and
   Y1731.

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 [TRILLOAMFM]

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

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

      MA - Maintenance Association [8021Q] [TRILLOAMFM]

      CCM - Continuity Check Message [8021Q]

      LBM - Loop Back Message [8021Q]

      PTM - Path Trace Message

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      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]



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 packet. Selection
   of the path of choice is implementation dependent. 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.
   [TRILLOAMFM] proposes a 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 bytes
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .   Flow Entropy                . 128 bytes
   .                               .
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   OAM Ether Type              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .   OAM Message Channel         . Variable
   .                               .
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Link Trailer              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                   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: Minimum of 8 bytes when the Extended Header is not
   included [RFC6325]

   Flow Entropy: This is a 128-byte fixed size opaque field. The least
   significant bits of the field MUST be padded with zeros, up to 128
   bytes, when the flow entropy is less than 128 bytes. Flow entropy
   enables emulation of the forwarding behavior of the desired data
   packets.

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

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   OAM Message Channel: This is a variable size section that carries
   OAM related information. We propose reusing the message format
   defined in [8021Q] for this purpose.

   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. However, it
   is important, for backwards compatibility reasons, to define methods
   of identifying TRILL OAM frames without using these extensions.
   Section 3.3. presents a set of possible methods for identifying OAM
   frames without using the proposed extensions of section 3.2. The
   methods defined in section 3.3. impose limitations on the
   construction of the flow entropy field of the OAM frames and SHOULD
   be used for backwards compatibility scenarios only.



 3.2. Use of TRILL OAM Flag

   The TRILL Header, as defined in [RFC6325], has two reserved bits
   that are currently unused. RBridges are currently required to ignore
   these fields. 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. (TISSA: Move to A)


   Implementations that follow the extension of using the "A" flag to
   identify frames MUST exclusively use that flag and methods specified
   in section 3.2.1. The "A" flag MUST NOT be utilized for forwarding
   decisions such as the selection of ECMP paths, etc.

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


                           Figure 2 TRILL Header
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   A (1 bit) - Indicates this is a possible OAM frame and is subject to
   specific handling as specified in this document.

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

    3.2.1. Handling of TRILL frames with "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.

    3.3. Backwards Compatibility Method

   For unicast frames, TRILL OAM packets are identified by its TRILL
   egress nickname and the presence of either Reserved Inner.MacSA
   (TBD) or OAM Ether Type 0x8902 [8021Q].

   For multicast frames, TRILL OAM packets are identified by either OAM
   EtherType 0x8902 [8021Q] or Reserved Inner.MacSA (TBD) .

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



   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Flow Entropy   |Inner    |OAM Ether|Egress   |
   |               |MacSA    |Type     |nickname |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |unicast L2     | N/A     |Match    |Match    |
   |               |         |         |         |
   |Multicast L2   | N/A     |Match    |N/A      |
   |               |         |         |         |
   |Unicast IP     | Match   |N/A      |Match    |
   |               |         |         |         |
   |Multicast IP   | Match   |N/A      |N/A      |
   |               |         |         |         |
   |Notification   | N/A     |Match    |Match    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 3 Identification of TRILL OAM Frames





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    3.4. OAM Capability Announcement

   Any given TRILL RBridge can be one of: OAM incapable OR OAM capable
   with new extensions OR 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.

   We propose to utilize the capability flags defined in TRILL version
   sub-TLV (TRILL-VER) [rfc6326bis]. The following 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 section 3.3. 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 B flag is ignored on the receiving side.

      +-+-+-+-+-+-+-+-+
      | 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 4 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.





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4. TRILL OAM Layering vs. IEEE Layering

   In this section we present the placement of the TRILL OAM shim
   within the IEEE 802.1 layers. The processing of both the Transmit
   and Receive directions is explained.




                       +-+-+-+-+-+-+-+-+-+-+
                       |   RBridge Layer   |
                       |   Processing      |
                       +-+-+-+-+-+-+-+-+-+-+
                                |
                                |
                            +-+-+-+-+-+-+
                            | TRILL OAM | UP MEP
                            | Layer     |   MIP
                            +-+-+-+-+-+-+ Down MEP
                                 |
                                 |
                            +-+-+-+-+-+-+
      (3)-------->          | TRILL     |
                            | Encap/Decap
                            +-+-+-+-+-+-+
                                |
                            +-+-+-+-+-+-+
      (2)-------->          |End station|
                            | VLAN & priority Processing
                            +-+-+-+-+-+-+
                                |
                            +-+-+-+-+-+-+
      (1)-------->          |ISS        |
                            |Processing |
                            +-+-+-+-+-+-+
                                |
                |             |
                            |             |



             Figure 5 Placement of TRILL MP within IEEE 802.1



   [RFC6325] Section 4.6 provides a detail explanation of frame
   processing. Please refer to [RFC6325] for processing scenarios not
   covered herein.

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 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 frames, this is Outer DA and Outer SA. M1 is the remainder
   of the packet from the VLAN EtherType onwards.

    4.1.2. Transmit Processing.

   ISS layer receives 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
   from the M1 part of the received indication and construct
   (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, M2 to from M1. Pass down (DA,SA,M1) to
   the ISS processing Layer.

 4.3. TRLL 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 Local DA and Frame is of TRILL EtherType

        . 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

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

     o If DA matches local DA and EtherType is not TRILL type

        .               Discard frame

     o If DA does not match and port is Appointed Forwarder and
   EtherType is not TRILL

        . Insert TRILL-Hdr and send (TRILL-HDR, iDA,iSA,i-VL, M3)
          indication to RBridge Layer <- This is the edge 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 and (TRILL Alert Flag set
             and OAM EtherType present) then

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

          o  Else

               . Set discard flag

     o If egress TRILL nickname is not local

          o Insert Outer DA, Outer SA, Outer VLAN, TRILL EtherType and
             construct (DA,SA,VLAN,M2). Where M2 is (TRILL-HDR, iDA,
             iSA, iVL, M)

     o Else set the discard flag

     o If discard flag is false forward (DA,SA,V,M2) to the VLAN End
        Station processing Layer. Otherwise, discard the packet.

 4.3.3. Receive Processing for Multicast packets

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

     o If the DA matches the Well-known TRILL multicast MAC address
        and Ethertype of the frame is TRILL

          o Strip DA,SA and V. From M2, construct (TRILL-HDR, iDA, iSA,
             iVL and M3).
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          o If TRILL OAM Flag is set and Ether Type OAM 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 matches the well-known TRILL multicast MAC address
        but Ethertype is not TRILL

          o Discard the packet

     o If the DA does not match the well-known TRILL multicast MAC
        address and Ether Type is not TRILL type

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

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

     o Else

          o Discard the packet

 4.3.4. Transmit Processing of Multicast 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 ODA, OSA, O-VL and TRILL
             ether type. 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 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 ODA,
             OSA, O-VL and TRILL ether type. M2 here is (Ethertype
             TRILL, TRILL-HDR, iDA, iSA, iVL, M)

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     o Else unicast packets as defined in section 4.3.2.

     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 and De-capsulation layer and RBridge Layer. It
   performs 1. Identification of OAM frames that need local processing
   2. Perform 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 does 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 the 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. 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 on the technology dependent portion of
   the packet. Hence we propose to utilize the MAID as defined in
   [8021Q]. 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.ag MIB
   definitions, each MEP's MIB contains one or more flow entropy
   definitions corresponding to the set of flows that the MEP monitors.

   We propose to augment the [8021Q] MIB to add the TRILL specific
   information. Figure 6, 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 6 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, for qualifying OAM
   packets, we propose to use a combination of the egress RBridge
   nickname and Inner VLAN/FGL to address the MEP.

   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 7 below for a visual depiction of these
   different de-multiplexers.

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

        a. Identify the MEP that is associated with the Inner VLAN.
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   2. MEP first validate 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, then the configured MD-LEVEL
          of the MEP discard the packet

        c. If the packer MD-LEVEL is greater, then the configured MD-
          LEVEL of the MEP 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 7 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 pass through. Additionally, Merge component ensure, as
        explained earlier, 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 MEP 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 11. , we propose to use a hop-count expiry
   approach 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 a interface.
   As such, a mechanism is required to identify which MIP should
   respond or to an incoming OAM message.

   We propose to use the same approach as presented above for MEPs with
   some variations. It is important to note that "M", merge block of
   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 8 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 (PTM) or Multi-destination Tree
   Verification (MTV) OpCode are passed on to the respective
   processors.

   Packets with unknown OpCodes are counted and discarded.






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7. Approach for Backwards Compatibility

   Methodology presented in this document is in-line with the [8021Q]
   framework or provide fault management coverage. However, in
   practice, some platforms may not have the required capabilities to
   support some of the proposed techniques. In this section, we present
   a method that allows RBridges, which do not have the required
   hardware capabilities, to participate in the proposed OAM solution.

   For backwards compatibility, we propose to locate MEPs and MIPs 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 [TRILLOAMREQ] and in the
   Transmission processing in Figure 9.



   Receiver Processing:

   If (M==1 && F==1) then
      Copy to CPU and Forward normally as defined in RFC 6325
   Else if (M==0 && F==1 && egress nickname is the processing RBridge)
   then
      Forward to CPU BUT DO NOT forward along the data plane

   Else
      Forward as defined in [RFC6325]
   End;

   Transmit Processing:

   If (F==1) then
     Forward as defined in [RFC6325] BUT Do not de-capsulate and
   forward as a native frame
   Else
     Forward as defined in [RFC6325]


          Figure 9 Pseudo code for Backward compatible Processing



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    [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 in
   to a TRILL domain with different MD-Level.

   This leaking may not cause any functionality loss. 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, TRILL campuses are managed by a single operator, 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 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.

8. Continuity Check Message (CCM)

   CCM 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. Within the MA, we propose to define the entropy values of the
   monitored flows. CCM transmit logic will utilize these flow entropy
   values when constructing the CCM packets. Please see section 13.
   later in the document for the theory of operation of CCM.

   We propose to augment the MIB of [8021Q] with definition of flow-
   entropy. Please see [TRILLOAMMIB] for definition of these and other
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   TRILL related OAM MIB definitions. Below Figure depicts the
   correlation between MA, CCM and proposed flow-entropy.




             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 10   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 to be
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   used in the response. CCMs are unidirectional and have no explicit
   reply; as such, the issue of the response flow entropy does not
   arise. In the transmitted CCM, each MEP reports local status using
   the Remote Defect Indication (RDI) flag. Additionally, a MEP may
   raise SNMP TRAPs [TRLLOAMMIB] as Alarms when a connectivity failure
   occurs.

9. 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.

 9.1. TRILL OAM Message header

   As discussed earlier, we propose to use the message format defined
   in IEEE 802.1ag. We believe 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 11   OAM Message Format



     o MD-L: Maintenance Domain Level (3 bits). Identifies the
        maintenance domain level. For TRILL, this MAY be always set to
        zero. However, in multilevel TRILL, backbone MAY be of a
        different MD-LEVEL. (Please refer to [8021Q] for the definition
        of MD-Level)

     o Version: Indicates the version (5 bits). As specified 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.

 9.2. TRILL OAM Opcodes

   The following Opcodes are defined for TRILL. Each of the Opcodes
   defines a separate 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 : Notification Message
    TBD-67 : Multicast Tree Verification Reply
    TBD-68 : Multicast Tree Verification Message


    9.3. Format of TRILL OAM TLV

   We propose to use the same TLV format as defined in section 21.5.1
   of [8021Q]. The following figure depicts the general format of a
   TRILL OAM TLV:



   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type       |        Length                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                               |
   .            Value(variable)                    .
   |                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 12   TRILL OAM TLV
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   Type (1 octet) : Specifies the Type of the TLV (see sections 9.4.
   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.

    9.4. TRILL OAM TLVs

   In this section we define TRILL related TLVs. We propose to re-use
   [8021Q] defined TLVs where applicable. Types 32-63 are reserved for
   ITU-T Y.1731. We propose to reserve Types 64-95 for TRILL OAM TLVs.

    9.4.1. 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]. NOTE: Presented within brackets is the
   corresponding Type defined in [8021Q].

   1. End TLV  (0)
   2. Sender ID TLV (1)
   3. Port Status TLV (2)
   4. Data TLV (3)
   5. Interface Status TLV (4)
   6. Reply Ingress TLV (5)
   7. Reply Egress TLV (6)
   8. LTM Egress Identifier TLV (7)
   9. LTR Egress Identifier TLV (8)
   10.   Reserved (9-30)
   11.   Organization specific TLV (31)

    9.4.2. 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.

   1. TRILL OAM Application Identifier  (TBD-TLV-64)
   2. Out of Band IP Address (TBD_TLV-65)
   3. Diagnostic VLAN (TBD-TLV-66)
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   4. RBridge Scope (TBD-TLV-67)
   5. Original Payload (TBD-TLV-68)
   6. Previous RBridge Nickname(TBD-TLV-69)
   7. TRILL Next Hop RBridge List (ECMP) (TBD-TLV-70)
   8. Multicast Receiver Availability (TBD-TLV-71)
   9. Flow Identifier (TBD-TLV-72)
   10.   Reserved (TBD-TLV-72 to TBD-TLV-95)

9.4.2.1. 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 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 13   TRILL OAM Message TLV

   Type (1 octet) = 64 indicate that this is the TRILL OAM Version

   Length (2 octets) = 6

   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 or notification 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.

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   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.



    9.4.3. 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.

                        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 14   Out of Band IP Address TLV

   Type (1 octet) = 64

   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.

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9.4.3.1. 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.




                        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 15   Diagnostic VLAN TLV

   Type (1 octet) = 65 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 deployment intermediate
   devices may perform label (VLAN) translation. In such scenarios,
   originator should not include the diagnostic Label TLV in OAM
   messages. Inclusion of diagnostic TLV will generated unwanted label
   error notifications.








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 9.4.3.2. 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 16   Out of Band IP Address TLV

   Length (2 octets) =  variable

 9.4.3.3. RBridge scope TLV

   RBridge scope TLV identifies nicknames of RBridges from which a
   response is required. 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 12. for details.

                        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   RBridge Scope TLV

   Type (1 octet) = 67 indicates that this is the "RBridge scope TLV"
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   Length (2 octets) = variable. Minimum value is 2.

   Nickname (2 octets) = 16 bit RBridge nickname.

 9.4.3.4. 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 18   Upstream RBridge nickname TLV

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

   Length (2 octets) = 4.

   Nickname (2 octets) = 16 bit RBridge nickname.

    9.4.3.5. 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.







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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 19   Next Hop RBridge List TLV

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

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

   Nickname (2 octets) = 16 bit RBridge nickname.

 9.4.3.6. 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 VLAN specified by the Diagnostic VLAN TLV.

   Multicast Receiver Port countis an Optional TLV.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type       | Length                        | Reserved      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              number of Receivers                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


              Figure 20   Multicast Receiver Availability TLV

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

   Length (2 octets) = 5.

   Number if Receivers (4 octets) = Indicates the number of Multicast
   receivers available on the responding RBridge on the VLAN specified
   by the diagnostic VLAN.


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    9.4.4. Flow Identifier (flow-id) TLV

   Flow Identifier (flow-id) uniquely identifies a specific flow. The
   flow-id value is unique per MEP and needed 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 21   Out of Band IP Address TLV

   Type (1 octet) = 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].

   Flow-id (2 octets) = uniquely identifies the flow per MEP. Different
   MEP 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 does not contain MEP-ID in OAM header.
   Applications may use MEP-ID information for different purposes of
   troubleshooting.















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10. Loopback Message

10.1.1. 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 22   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. Session Identification Number is a 32-bit integer that allows
   the requesting RBridge to uniquely identify the corresponding
   session. Responding RBridges, MUST echo the received "Loopback
   Transaction Identifier" number without modification.

10.1.2. Theory of Operation

10.1.2.1. Originator RBridge

   Originator RBridge Identifies the destination RBridge nickname based
   on user specification or based on location of the specified
   destination inner MAC address.

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

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

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

   Include following OAM TLVs, where applicable

     o Out-of-band Reply address TLV
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     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.

   RBridge 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.

 10.1.2.2. Intermediate RBridge

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

 10.1.2.3. 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.

   TRILL OAM application layer further validates the received OAM frame
   by examining 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)

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

11. 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, we propose TRILL OAM to
   utilize 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 Path Trace message is identical to Loopback message
   except, that it is first transmitted with a TRILL Hop count field
   value of 1. 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.

11.1.1. Theory of Operation

11.1.1.1. 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 applicable Session Identification number
   for the request. Return-code and sub-code MUST be set to zero.

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

   Include following OAM TLVs, where applicable

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     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.



 11.1.1.2. 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-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

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   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.

    11.1.1.3. Destination RBridge

   Processing is identical to section 11.1.1.2. With the exception that
   TRILL OAM Opcode is set to Path Trace Reply (64).

12. 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 scope parameter is required to prevent receiving a
   large number of responses. Typical scenario of distribution tree
   verification or group verification involves verifying multicast
   connectivity to selected set of end-nodes as opposed to the entire
   network. Availability of the scope facilitates narrowing down the
   focus to only the interested RBridges.
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   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.

 12.1. 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 10. with the exception that the
   Loopback Transaction Identifier, in section 10.1.1. , is replaced
   with the Session Identifier.

 12.2. Theory of Operation

 12.2.1. Originator RBridge

   User is required at minimum to specify either the distriubiton trees
   that need to be verified, or 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 section 3.2 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 represent 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.

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   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)

   Specify the Hop count of the TRILL data frame per user
   specification. Or 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.

   RBridge may continue to retransmit the request at a periodic
   interval, until 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.

 12.2.2. 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 12.2.3.

 12.2.3.  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 include in the OAM message.

   Set the Return Code to (0) and Return sub code to zero (0). Update
   the TRILL OAM opcode to 67 (Multicast Tree Verification Reply).

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   Include following TLVs

   Upstream RBridge nickname TLV (69)

   Reply Ingress TLV (5)

   Interface Status TLV (4)

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

   Sender ID TLV (1)

   Multicast Receiver Availability TLV (71)

   If VLAN 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.



13. Application of Continuity Check Message (CCM) in TRILL

   Section 8. provides an overview of CCM Messages defined in [8021Q]
   and how they can be used within the TRILL OAM. In this section, we
   present 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. [TRILLOAMREQ] 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 proposed solution accomplishes the
   requirements specified in [TRILLOAMREQ] within the framework of
   [8021Q] in a straightforward manner and with minimum changes.
   Section 8, above proposed to define multiple flows within the CCM
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   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.

   Obvious question arises is, how does the originating RBridge knows
   which flow or flows are at fault?

    13.1. CCM Error notification - Method-1

   This is accomplished with a combination of RDI flag in the CCM
   header and SNMP Notifications (Traps).

   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.

   When an MEP notice a CCM timeout from a remote MEP ( MEP-A), it sets
   the RDI flag on next CCM message it generates. Additionally, it logs
   and sends SNMP notification that contain the remote MEP
   Identification, Sequence Number of the last CCM message it received
   and if available the Sequence Number of the first CCM message it
   received after the failure. CCM Messages generated by MEP-A has
   monotonically increasing Sequence Numbers; hence operator can easily
   identify flows that correspond to specific Sequence Numbers.

   Following example illustrate the above.

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

   Assume there are 3 flows between MEP-A and MEP-B.

   Lets assume MEP-A allocates sequence numbers as follows

   Flow-1 {1,2,3,4,13,14,15,16,.. }

   Flow-2 {5,6,7,8,17,18,19,20,.. }

   Flow-3 {9,10,12,11,21,22,23,24,.. }

   Lets 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 8'th CCM message. At this
   time the sequence number of the last good CCM message MEP-B has
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   received from MEP-A is 4. Hence MEP-B will generate an CCM error
   SNMP notification with MEP-A and Last good sequence number 4.

   When MEP-A switch to flow-3 after transmitting flow-2, MEP-B will
   start receiving CCM messages, in this example it will be CCM message
   with Sequence Numbers 9,21 and so on. When receipt of a new CCM
   message from a specific MEP, after a CCM timeout, TRILL OAM will
   generate SNMP Notification of CCM resume witn remote MEP-ID and the
   first valid Sequence number after the CCM timeout. In the foregoing
   example, it is MEP-A and Sequence Number 9.

   We propose to augment remote MEP list under CCM MIB Object to
   contain "Last Sequence Number" and "CCM Timeout" variables. Last
   Sequence Number is updated every time a CCM is received from remote
   MEP. CCM Timeout variable is set when a CCM timeout has occurred and
   cleared when a CCM is received. Combination of the two new MIB
   variables and use of monotonically increasing sequence numbers allow
   TRILL OAM to clearly identify specific flow or flows at fault.

 13.2. CCM Error Notification Method-2

   This is accomplished with a combination of RDI flag in the CCM
   header, flow-id TLV and SNMP Notifications (Traps).

   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 notice a CCM timeout from a remote MEP ( MEP-A), it sets
   the RDI flag on 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 maintain a unique flow-id per each flow, hence operator can
   easily identify flows that correspond to the specific flow-id.

   Following example illustrate the above.

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

   Assume there are 3 flows between MEP-A and MEP-B.

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

   Lets 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 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 notification with
   MEP-A and Last good flow-id (1) and sequence number 4.

   When MEP-A switch to flow-3 after transmitting flow-2, MEP-B will
   start receiving CCM messages, in this example it will be CCM message
   with Sequence Numbers 9,10,11,12,21 and so on. When receipt of a new
   CCM message from a specific MEP, after a CCM timeout, TRILL OAM will
   generate 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.

   We propose to augment remote MEP list under CCM MIB Object 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 CCM
   timeout is occurred and cleared when CCM is received.

13.3. Theory of Operation

13.3.1. 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 TLV specified in [8021Q]

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

   At the 5  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.

    13.3.2. Intermediate RBridge

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

    13.3.3. 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.

   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. Opcode de-multiplexer delivers CCM packets to the CCM
   process.

   CCM Process performs processing specified in [8021Q].

   Additionally CCM process updates the CCM Management Object with the
   sequence number of the received CCM packet. Note: Last received CCM
   sequence number and CCM timeout is tracked per each remote MEP.

   If CCM timeout is true for the sending remote MEP, then clear the
   CCM timeout in the CCM Management object and generate SNMP
   notification as specified above.



14. Multiple Fragment Reply

   Response Message as described in 4.4.2.1 allows Multiple Fragment
   Reply with use of Final Flag. In case of Multiple Fragment Reply,
   due to response exceeding MTU size, all messages MUST follow the
   procedure defined in this section.

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

   Same session Identification Number MUST be included in all related
   fragments of the same message.

   TRILL OAM Application Identifier TLV MUST BE included with the
   appropriate Final Flag field. Final Flag, MUST, only be set on the
   final fragment of the reply.

15. 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.

16. Allocation Considerations

16.1. 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.

16.2. IANA Considerations

   - IANA is requested to allocate a multicast MAC address from the
   block assigned to TRILL

   - Set up sub-registry within the TRILL Parameters registry for block
   of TRILL OAM OpCodes -

   - Set up sub-registry within the TRILL Parameters registry for TRILL
   OAM TLV Types -

   - Set up sub-registry within the TRILL Parameters registry for TRILL
   OAM return code and return sub codes -

   - Request a unicast MAC addressed, reserved for identification of
   OAM packets discussed in backward compatibility method (section 3.3.
   )










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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.

    [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", BCP 26, RFC 5226,
             May 2008.

   [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.

    17.2. Informative References

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

   [TRILLOAMMIB] "TRILL OAM MIB", To be published.

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

   [TRILLOAMREQ] Senevirathne, T., et.al., "Requirements for
             Operations, Administration and Maintenance (OAM) in
             TRILL", draft-ietf-trill-oam-req, Work in Progress,
             November, 2012.

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



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

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



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18. Acknowledgments

   Work in this document was largely inspired by the directions
   provided by Stewart Bryant in finding a common OAM solution between
   SDO.

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










































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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

   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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