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TRILL Working Group                                  Tissa Senevirathne
Internet Draft                                            Dinesh G Dutt
Intended status: Standards Track                                  CISCO
                                                         Vishwas Manral
                                                          HP Networking
                                                             Sam Aldrin
                                                                 HuaWei


                                                           July 6, 2012
Expires: January 2013



                     ICMP based OAM Solution for TRILL
                       draft-tissa-trill-oam-04.txt




Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on December 6, 2012.

Copyright Notice

   Copyright (c) 2012 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 presents a solution suite for TRILL data plane
   monitoring and failure detection. Methods presented herein allow in-
   cooperating IP payloads, exercising multi-paths, verifying multicast
   trees, locating end stations, virtual segments and diagnosing
   connectivity problems. ICMP protocol is proposed as framework for
   error reporting. Document also presents network wide health
   monitoring, distribution and reporting methods that are intended for
   efficient troubleshooting.

Table of Contents


   1. Introduction...................................................4
      1.1. Motivation................................................6
      1.2. Contributors..............................................7
   2. Conventions used in this document..............................7
   3. Protocol Architecture Overview.................................7
      3.1. Overview of Tools.........................................8
      3.2. TRILL Data Plane..........................................9
      3.3. Monitoring...............................................10
      3.4. Traffic Triggered Monitoring (TTM).......................10
      3.5. Distribution.............................................10
      3.6. ISIS.....................................................11
      3.7. Reporting................................................11
   4. Frame Format..................................................11
      4.1. Encoding of Request message..............................12
      4.2. Encoding of Response Message.............................13
      4.3. Encoding of Notification Message.........................13
         4.3.1. Pseudo IP Header....................................15
      4.4. OAM Command Messages.....................................15
   5. 127/8 in-band OAM IP address..................................16
      5.1. IPv6 default in-band address.............................16
   6. Identification of Diagnostic frames...........................17


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      6.1. Identification of Layer 2 Flow...........................17
      6.2. Identification of IP Flows...............................17
      6.3. Identification of Flows using Hop-Count Restrictions.....19
      6.4. Identification of Multicast Flows........................20
         6.4.1. Identification of overall tree verification frames..20
         6.4.2. Identification of Layer 2 Multicast group verification
         frames.....................................................21
         6.4.3. Identification of IP Multicast group verification
         frames.....................................................21
      6.5. Default OAM flow Parameters..............................21
      6.6. Validation of OAM Request and Response frames............22
   7. ISIS Extensions...............................................23
   8. ICMP multi part extensions....................................25
      8.1. ICMP Echo Request and Response message extensions........25
      8.2. C-Type Definitions.......................................26
   9. Details of Diagnostic tools...................................57
      9.1. Loopback Message.........................................57
         9.1.1. Theory of Operation.................................58
            9.1.1.1. Originator RBridge.............................58
            9.1.1.2. Intermediate RBridge...........................59
            9.1.1.3. Destination RBridge............................59
      9.2. Loopback Message Hop-count method........................60
         9.2.1. Identification of OAM frames........................60
         9.2.2. Prevent leaking out from TRILL network..............60
      9.3. Path Trace Message.......................................61
         9.3.1. Theory of Operation.................................61
            9.3.1.1. Originator RBridge.............................61
            9.3.1.2. Intermediate RBridge...........................62
            9.3.1.3. Destination RBridge............................63
      9.4. Multicast Tree Verification (MTV) Message................63
         9.4.1. Theory of Operation.................................64
            9.4.1.1. Originator RBridge.............................64
            9.4.1.2. Intermediate RBridge...........................65
            9.4.1.3. In scope RBridges..............................66
      9.5. MAC address discovery Message............................67
         9.5.1. Theory of Operation.................................68
            9.5.1.1. Originator RBridge.............................68
            9.5.1.2. Receiving RBridges.............................69
      9.6. Address-Binding Verification Message.....................71
         9.6.1. Extension to ARP and invARP.........................72
            9.6.1.1. Encoding ARP-invARP extensions.................74
      9.7. End-Station Attachment Point Discovery...................76
      9.8. DRB and AF Discovery.....................................77
         9.8.1. Theory of Operation.................................78
            9.8.1.1. Originator RBridge.............................78
            9.8.1.2. Receiving RBridge..............................78
      9.9. Diagnostic Payload Discovery for ECMP coverage...........80


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         9.9.1. Theory of Operations................................82
            9.9.1.1. Receiving RBridge..............................83
      9.10. Notification Messages...................................84
   10. Monitoring and Reporting.....................................85
      10.1. Data categories.........................................87
      10.2. Advertising Policy......................................87
         10.2.1. Multi Instance ISIS and Flooding Scope.............89
      10.3. Summary Category........................................89
      10.4. Detail Category.........................................91
      10.5. Vendor Specific Category................................97
   11. Traffic Triggered Monitoring (TTM)...........................98
      11.1. TTM Policy.............................................100
      11.2. TTM Commands...........................................102
      11.3. Reverse Flow Monitoring (RFM)..........................103
   12. Security Considerations.....................................103
   13. IANA Considerations.........................................103
      13.1. IANA considerations....................................103
         13.1.1. ICMP Extensions...................................103
         13.1.2. TRILL-OAM UDP port................................103
         13.1.3. ARP Extensions....................................103
         13.1.4. Well known Multicast MAC..........................104
      13.2. IEEE Registration Authority Consideration..............104
   14. References..................................................104
      14.1. Normative References...................................104
      14.2. Informative References.................................105
   15. Acknowledgments.............................................105
   Appendix A. Reports.............................................106
      A.1. Sample Reports..........................................106
      A.2. Summary Report..........................................106
      A.3. Detail Report...........................................107
      A.4. C-Type usage in messages................................108
   Authors' Addresses..............................................109

1. Introduction

   TRILL protocol has revolutionized how Layer 2 networks are being
   built and used. Legacy Ethernet networks provide single path for
   forwarding traffic and require all of the switches in the network to
   learn end-station MAC addresses. TRILL, on the other hand utilize
   multiple active links for forwarding thereby maximizing the overall
   network bandwidth utilization. TRILL is simple plug-and-play
   solution and does not require intermediate devices to learn MAC
   addresses of end-stations. These powerful characteristics of TRILL
   optimize performance and increase scaling limits. However, with that
   comes increased difficulty in diagnosing connectivity problems and
   locating end stations.



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   Network operators are used to troubleshooting legacy networks with
   single paths. Legacy devices maintain forwarding database of all
   end-station addresses in the Layer 2 network. Network administrators
   can trace the path taken by specific MAC address by examining the
   forwarding databases of devices. TRILL core switches, by design do
   not maintain end-station address database. Hence, administrators may
   not be able to trace a path taken by a specific MAC address by
   tracing the forwarding databases. Additionally, a given device may
   utilize multiple active paths to reach to a destination and may use
   a completely different forwarding topology for multicast traffic
   than it would use for unicast traffic. These challenges mandate the
   presence of an effective tool set to monitor and diagnose data plane
   failures in TRILL networks. These tools and protocols must stay as
   close as possible to the forwarding paths taken by actual data. OAM
   frames should not leak to end stations or out of the TRILL network
   to legacy networks.

   TRILL base protocol specification [RFC6325] does not specify
   algorithm for selecting a path from a set of equal cost paths to
   forward a given flow. The majority of traffic in the networks is IP
   centric and most devices deploy some sort of hashing algorithm to
   identify the forwarding path from set of equal cost paths for a
   given flow. Thus, it is desirable to use IP address and TCP/UDP port
   information as inputs to the ECMP selection hash function. Use of
   such higher level information provides better distribution of flows
   across multiple equal cost paths. This document, propose a framework
   that allow specifying, various combinations of payloads including IP
   payloads and actual payloads.

   As TRILL based networks get deployed, during the transition period,
   it may be required for TRILL RBridges to co-exist with legacy
   networks. It is very helpful for the network operator if TRILL data
   plane failure detection tools allow isolating problem to specific
   legacy device or at least to the interface(s) that the downstream
   legacy device is connected. Solutions presented in this document
   facilitate identifying legacy devices or RBridge interfaces legacy
   devices are connected to.

   ICMP (Internet Control Message Protocol)[RFC 792] has been in use
   for nearly three decades. ICMP multipart extensions [RFC4884],
   propose methods to extend ICMP messages to include additional
   information, without changing or inventing new ICMP message types.
   In this document we utilize ICMP for reporting of errors. ICMP
   multipart extensions will be utilized to define additional
   information that is specific to TRILL. Additionally use of ICMP
   allows sending error reports either in-band or out-of-band. Use of
   out-of-band ICMP allows network operators to diagnose uni-


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   directional path failures easily. Also, the same ICMP infrastructure
   can be utilized to generate unsolicited error notifications for
   TRILL data plane failures, such as Destination unreachable, Time
   Exceed (TTL expiry), Parameter Mismatch (MTU mismatch) etc..

   Availability of Network health information is a valuable starting
   point for any failure detection process. In this document we present
   the concept of network regions, monitoring of network regions and
   distribution of network health.

   Diagnostic tools are also commonly referred to as OAM (Operations,
   Administration and Maintenance). In this document we use words
   diagnostics and OAM interchangeably. Unless explicitly specified
   both the words means the same.

1.1. Motivation

   Currently published TRILL OAM solutions, [TRILLCH] and [TRILLOAM],
   mainly focus on data plane encoding and individual tools. The
   encoding methods presented in [TRILLCH] and [TRILLOAM], require
   defining OAM channel that utilize a special EtherType.
   Implementations that utilize ECMP selection algorithms based on
   higher layer address information may require flexible OAM channel
   that allow specifying different payloads including IP based
   payloads.

   Availability of network health information is important for
   efficient isolation of network connectivity problems. Currently
   there are neither standard sets of such data to be distributed nor
   framework to distribute network health data. Lack of such leads to
   cumbersome and time consuming troubleshooting of network
   connectivity issues, especially in multi-vendor networks.

   Device virtualization is an increasing trend in datacenters and
   large enterprises. Physical servers may host multiple virtual
   servers and these virtual servers may move from physical server to
   physical server based on load balancing policies. As part of network
   connectivity problem isolation, it is important to identify the
   location of the virtual servers and RBridges they are connected to.
   Currently, administrators are required to utilize multiple tools to
   locate these virtual machines and connecting RBridges.

   ICMP has been in use over three decades as the primary OAM tool of
   IP infrastructure.  It is highly desirable to utilize the framework
   of existing infrastructure such as ICMP, thereby leveraging
   knowledge, implementation and time to market.



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   TRILL networks can co-exist with multi access LAN networks at the
   boundary of the TRILL network. TRILL protocol [RFC6325], introduced
   Designated RBridge (DRB) and Appointed Forwarder (AF) concepts to
   ensure loop free forwarding and load splitting at the boundary of
   TRILL and multi access LAN networks. Discovery of DRB,AF and
   associated VLANs are important for effective fault isolation at the
   TRILL and multi access LAN boundary. Currently there are no known
   tools available for the purpose.

   In this document we propose a framework and solution suite that will
   address the above.



1.2. Contributors

   Many people contributed with ideas and comments. Among all,
   following people made notable contributions to all parts of this
   document and spend time reviewing, debating and commenting to ensure
   this specification addressees the problem space.

   Ian Cox, Ronak Desai, Satya Dillikar ,Rohit Watve, Ashok Ganesan and
   Leonard Tracy.

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].

   In this document, these words will appear with that interpretation
   only when in ALL CAPS. Lower case uses of these words are not to be
   interpreted as carrying RFC-2119 significance.

3. Protocol Architecture Overview

   Effective OAM solution is not only a set of tools but a wholesome
   solution that covers all aspects of OAM, such as tools, monitoring,
   reporting etc. Solution presented in this document contains multiple
   subcomponents that cover various elements of the total solution.
   There are six subcomponents in the proposed architecture. These
   subcomponents collectively are called TRILL OAM Protocol. Here we
   present an overview of the architecture of the solution and explain
   the purpose of each of subcomponents and interaction between
   different subcomponents. Subsequent sections cover details of each
   of the subcomponents.



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      +--+
      |  | +-------------+    +----------+
      |  | | Reporting   |    |          |
      |  | +-------------+    |          |
      |  |       ^            | ISIS     |
      |T |       |            |          |
      |R | +-------------+    | (GenApp) |
      |I | |             |<-->|          |
      |L | | Distribution|    |          |
      |L | +-------------+    +----------+
      |  |      ^
      |O |      |
      |A | +-------------+    +----------+
      |M | |             |    |   TTM    |
      |  | | Monitoring  |<-->|          |
      |P | +-------------+    +----------+
      |r |      ^                  ^
      |o |      |                  |
      |t |      v                  V
      |o | +------------+    +------------+
      |c | |            |    | Data Plane |
      |o | |  Tools     |<-->|            |
      |l | +------------+    +------------+
      |  |
      +--+

                      Figure 1 Architecture Overview



3.1. Overview of Tools

   The Tools subcomponent consists of series of utilities to implement
   various data plane monitoring and failure detections methods.
   Individual tools are invoked directly by the user or by the
   monitoring subcomponent. Individual tools allow, where applicable,
   for callers to specify options such as ECMP coverage, destination
   RBridge nickname, pay-load etc. Tools interface with the TRILL data
   plane layer to send and receive OAM frames. At the time of writing
   following tools are included as part of the tool set.

     1. Loopback Message (Ping)

     2. Path Trace Message (Trace route)

     3. Multicast Tree Verification (mtv)


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     4. MAC discovery

     5. Address Binding Verification

     6. IP End-station Locator

     7. DRB-AF discovery

     8. Notification messages

     9. OAM Command messages

   Tools, based on the intended use, can be classified in to 3 broader
   categories as below.

   +--------------------+------------------------------+
   | Category           |  Tools                       |
   +--------------------+------------------------------+
   | Fault Verification |   Loop Back Message          |
   +--------------------+------------------------------+
   | Fault Isolation    | Path Trace Message,          |
   |                    | Multicast Tree Verification  |
   +--------------------+------------------------------+
   | Auxiliary          | MAC discovery                |
   |                    | Address Binding Verification |
   |                    | IP End-station Locator       |
   |                    | DRB-AF Discovery             |
   |                    | Error Notification           |
   |                    | OAM command messages         |
   +--------------------+------------------------------+

3.2. TRILL Data Plane

   The TRILL data plane receives and transmits frames on behalf of the
   tools subcomponent. As far as the encapsulation is concerned, TRILL
   data plane layer treat these frames exactly as it would treat a
   regular data frame. In fact one of the key design goals is to
   maintain TRILL data plane diagnostic (OAM) frames as close as
   possible to actual data frames. Additionally, implementation MUST
   satisfy the following requirements:

     1. OAM frames SHOULD NOT leak in to legacy Ethernet or to end
        stations outside the TRILL cloud




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     2. RBridge MUST have ability to identify OAM (diagnostics) frames
        intended for a destination RBridge.

     3. RBridgeS SHOULD have ability to identify TRILL data OAM frames
        that are not intended for itself and forward such frames
        without assistance from the CPU.

     We explain in Section 6 various methods available to identify
     TRILL OAM (diagnostic) frames intended for the local RBridge and
     satisfy above requirements.

3.3. Monitoring

   The Monitoring subcomponent utilize the tools subcomponent to
   monitor the TRILL data plane and proactively detect connectivity
   faults, configuration errors (cross connect errors) etc. The
   monitoring subcomponent provides options to specify frequency,
   retransmission count, ECMP choice and all other applicable options
   to the specific tool being used to implement the monitoring service.
   Based on the configuration specified by the user, the monitoring
   subcomponent periodically invokes the applicable tools.
   Additionally, based on configuration, monitoring results are
   propagated to the distribution subcomponent. Monitoring results are
   always associated with a monitoring region. The monitoring region is
   an administrative partition of the network such that it: 1. Maximize
   the fault coverage, 2. Optimize network health data summarization.
   More details of regions are discussed in Section 10.

   The Monitoring subcomponent also interfaces with Traffic Triggered
   Monitoring subcomponent.

3.4. Traffic Triggered Monitoring (TTM)

   Traffic Triggered Monitoring facilitates monitoring and diagnose of
   live data traffic. TTM subcomponent interfaces with the Data Plane
   to install required TTM policies. Details of the TTM framework and
   operations are presented in section 11.

3.5. Distribution

   The distribution subcomponent has two primary inputs

     o Data from the Monitoring Layer

     o Data from other RBridges via ISIS GenApp

   The distribution subcomponent performs the following functions:


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     o Advertising locally generated data

     o Applying Advertising policies and re-advertising received data

     o Maintaining the network health Database

     Details of distribution layer and data handling are presented in
     section 10.

3.6. ISIS

   TRILL OAM protocol suite proposed in this document utilize ISIS to
   distribute

   OAM capability of individual RBridge

   In-band OAM IP and MAC address

   Above, OAM capability and In-band OAM address information are
   advertised using ISIS MT-Protocol extensions.[section 7. ]

   Network monitoring data are distributed using ISIS GenApp extension
   methods specified in [GenApp]. Details of encoding and proposed TLV
   definitions are defined in detail in section 7.



3.7. Reporting

   The Reporting subcomponent allows users to define and use various
   reports on network health. The Reporting subcomponent utilize data
   available in the distribution subcomponent to generate requested
   reports. Sample reports are listed in Appendix A.

4. Frame Format

   TRILL data plane diagnostic (OAM) frames can be broadly classified
   in to four types: request, response, notification and command
   messages. Request messages are generated to measure TRILL data plane
   characteristics, such as connectivity. Response messages are
   generated by a RBridge in response to a request. Notifications are
   unsolicited messages generated due to certain failures such as
   unreachable destination. OAM command messages provide a generic
   framework of communication between RBridges for OAM purposes.
   Details of individual messages are covered in later sections. Here
   we present frame encoding format for Request, Response and
   Notification messages.


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4.1. Encoding of Request message




        +-------------------------------+
        | Outer Header                  |
        +-------------------------------+
        | TRILL Header                  |
        +-------------------------------+ ---
        | L2 Header + EthType           |  ^
        +-------------------------------+  | Diagnostic
        | IP Header (including TCP/UDP) |  | payload
        +-------------------------------+  |
        | User defined data or          |  |
        . padded to zero                .  |
        |                               |  v
        +-------------------------------+ ---
        | ICMP Header                   |
        +-------------------------------+
        |  Common ICMP Extension Header |
        +-------------------------------+
        |ICMP extensions (optional)     |
        +-------------------------------+


       Figure 2 Encoding TRILL data plane diagnostic request message

   The above diagram depicts encapsulation of TRILL data plane
   diagnostic request frames. Encoded in the frame is the diagnostic
   payload. The diagnostic payload is a flexible structure that allow
   user to specify different kinds of payloads, including actual
   payloads. Most hardware implementations use
   IPDA:IPSA:DestPor:SrcPort based hash method to select ECMP paths for
   IP frames. For non IP payloads, RBridges normally uses a Layer 2 MAC
   DA and SA based hash for selecting an ECMP path. Flexible diagnostic
   payload allow user to drive end to end ECMP selection based on
   payload without needing additional hardware. Also, in terms of
   forwarding, this keeps diagnostic frame as close as possible to data
   frames. The length of the diagnostic payload must be deterministic.
   We propose a fixed 128 byte size for the diagnostic payload section
   of the OAM frame. This allows including IPv6 frames with multiple
   802.1Q tags in to the diagnostic payload. The remaining bytes are
   set to zero, if the specified frame is smaller than the 128 byte
   fixed size.




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   ICMP header immediately follows the diagnostic payload. The ICMP
   header is constructed as defined in [RFC792] and [PINGEXT].
   [PINGEXT] provide methods to extend ICMP echo request message to
   include ICMP multi part extensions.

   ICMP multi part extensions [RFC 4884] are defined to carry
   additional information and are encoded after the ICMP
   header.[section 8. ]

4.2. Encoding of Response Message

        +-------------------------------+
        | TRILL Header or MAC Header    |
        +-------------------------------+
        | IP Header                     |  ^
        +-------------------------------+  |
        | ICMP Header                   |
        +-------------------------------+  Response Message
        | Common ICMP Extension Header  |  |
        +-------------------------------+  |
        |                               |  |
        |   original frame              |  |
        . (TRILL Header +               .  |
        .  diagnostic payload)          .  |
        |                               |  |
        +-------------------------------+  |
        |ICMP extensions                |  |
        +-------------------------------+  v


                 Figure 3 Encoding of OAM response message

   The above diagram depicts encoding of OAM response messages. If in-
   band delivery is requested, the OAM response message MUST be encoded
   as payload in a TRILL data frame. The ingress RBridge nickname MUST
   be set to the RBridge nickname of the node generating the response.
   Egress RBRidge nickname MUST be set to the ingress RBridge nickname
   of the, original TRILL data frame that triggered this response.

    Normal IP forwarding rules MUST be followed, if an out-of-band
   response is requested.

4.3. Encoding of Notification Message

     Notification messages are generated in response to an error
   condition such as delivery failure due to incompatible MTU or
   destination RBridge not in the forwarding table etc.. Out-of-band


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   responses are generally indicated by explicitly including the
   indication to receive an out-of-band response in the TRILL OAM
   request frame. Since notifications are generated proactively, the
   originator RBridge may not have methods to identify the IP address
   required to deliver an out-of-band response. Hence, in this document
   we propose to deliver Notification messages in-band. Delivery of
   out-of-band messages are outside the scope of this document.

   The RBridge generating the Notification message MUST include up to
   128bytes of the original frame that triggered the notification
   message. If the original frame contains less than 128 bytes, then
   the remaining bytes MUST be padded with zeros.

        +-------------------------------+
        | TRILL Header                  |
        +-------------------------------+
        | IP Header                     |
        +-------------------------------+
        | ICMP Header                   |
        +-------------------------------+
        |  Pseudo IP header             |
        |                               |
        +-------------------------------+
        |                               |
        |   original frame              |
        . (TRILL Header + L2+ Ethtype   .
        .  + data)                      .
        |                               |
        +-------------------------------+
        |ICMP extensions                |
        +-------------------------------+


                 Figure 4 Encoding of Notification message

   The TRILL outer header of the frame that triggered the notification
   message is not included in the notification message. The Next-Hop
   header information in the original frame is of local significance to
   the specific link and may not be of interest to the originator of
   the data frame.

   The Following error messages are currently supported

     o Time Expiry
     o Destination Unreachable
     o Parameter Problem



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   Additional TRILL OAM error codes may be specified as ICMP multipart
   extensions in above notifications messages. These error codes
   indicate the cause of the error. Please see section 8. for error
   code definitions and section 9.10. for theory of operation.

4.3.1. Pseudo IP Header

   RFC 792 requires original payload section of ICMP messages, Time
   Expiry, Destination Unreachable and Parameter Problem to contain a
   valid IP header. RFC 1122 recommends ICMP implementations to
   multiplex incoming error notification messages to the related
   application based on the IP header information. The Pseudo IP header
   defined here intends to serve that purpose.

   In this document we propose, for the purpose of TRILL OAM, to
   construct the pseudo IP header as a UDP header. IP addresses are
   derived based on the in-band IP addresses of the RBridges (section
   5. ). The destination port is the well known UDP destination port in
   the block of assigned "User Ports" (1024-49151). We intend to
   request IANA assignment of a UDP destination port for use in TRILL
   OAM.

4.4. OAM Command Messages

        +-------------------------------+
        | TRILL Header or MAC Header    |
        +-------------------------------+
        | IP Header                     |  ^
        +-------------------------------+  |
        | ICMP Header                   |
        +-------------------------------+  Command Message
        | Common ICMP Extension Header  |  |
        +-------------------------------+  |
        |ICMP extensions                |  |
        +-------------------------------+  v


                 Figure 5 Encoding of OAM Command Message

   OAM command messages are originated by RBridges to indicate other
   RBridges in the network to execute commands on behalf of the
   originating RBridge. OAM command messages are not required to follow
   a specific ECMP path. Hence, OAM messages do not contain a
   diagnostic payload section.

   Destination IP address of the OAM command message is either in-band
   OAM IP address or out-of-band management IP address of the


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   destination RBridge. Incoming OAM command message are delivered to
   the ICMP stack by the IP stack. ICMP stack further identify the
   message as an OAM message due to embedded ICMP extensions. ICMP
   stack delivers OAM command message to the OAM processing module for
   further processing.

   The TTM (Traffic Triggered Monitoring) framework presented in
   section 11.  and the Diagnostic Payload discovery presented in
   section 9.9.  extensively utilizes OAM command messages.



5. 127/8 in-band OAM IP address

   In this document we propose to use same ICMP framework deployed in
   IP infrastructure for communicating OAM information. RBridges are
   not required to have IP interfaces enabled. However, in order to
   receive and process ICMP messages, RBridges are required to have at
   least a pseudo IP address. In this document, we propose to use 127/8
   addressing scheme similar to the MPLS data plane failure detection
   methods [RFC 4379]. It is important that each RBridge have a
   straightforward method of identifying corresponding in-band OAM IP
   address of any given RBridge, without additional processing or
   lookups.

   The 127/8 Address range is allocated for internal loopback addresses
   [RFC 1122] and required not to be routed. RFC 4379 updates RFC 1122
   to utilize 127/8 addressing to communicate between devices in a
   peer-to-peer model that does not require routing. In this document,
   we propose to use 127/8 addressing model to identify in-band IP
   address required for OAM purposes. Additional methods are provided
   as ISIS LSP extension to announce, other addresses, user may desire
   to use for OAM in-band purpose. By default all RBridges MUST support
   the 127/8 addressing model specified here.

   Each RBridge nickname is 16bits wide [RFC6325]. Let's assume RBridge
   nickname RB is divided in RB(msb) and RB(lsb), such that, RB(msb)
   takes the upper 8bits of the RB and RB(lsb) takes the lower 8bits of
   the RB. Corresponding in-band IP address of RB is
   127.RB(msb).RB(lsb).100. Implementation MUST facilitate methods to
   avoid conflicts between in-band OAM address and implementation
   specific 127/8 address allocations.

5.1. IPv6 default in-band address

   IPv6 based systems have two options to derive the in-band IP
   address. The systems may choose, IPv6 native loopback address


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   ::RBid:100 or IPv4 mapped IPv6 addressing format of
   ::FFFF:127.RB(msb).RB(lsb).100.

   RFC 4379, MPLS Data Plane failure detection methods, utilize IPV4
   mapped IPv6 addressing. One of the design objectives of the proposal
   is to re-use as many existing OAM extensions as possible. Hence,
   implementation that support IPv6 MUST utilize the IPv4 mapped IPv6
   addressing fomat for default IPv6 in-band address. Deployments that
   desire to utilize native addressing MAY advertise native IPv6 in-
   band address using OAM extensions in section 7.

6. Identification of Diagnostic frames

   In this document we have proposed to use the TRILL header as defined
   in [RFC6325], without modifications. The standard TRILL header
   currently, does not provide option to identify diagnostic frames.
   Hence, it is important to have circumstantial methods to identify
   diagnostic frames intended for the local RBridge and prevent leaking
   of diagnostic frames outside of TRILL network. In this section we
   explain, various methods to attain the above goals.

6.1. Identification of Layer 2 Flow

   As stated earlier, most RBridges use Destination and Source MAC
   address, combination to determine the next hop ECMP interface to
   forward non IP frames. It is required to provide flexibility for the
   user to specify destination MAC address and source MAC address. We
   propose to use special EthType (TBD) to indentify OAM (diagnostic)
   frames that contain non IP diagnostic payloads.

   Each RBridge, if TRILL data plane OAM enabled, MUST provide
   following processing:

     o Forward frames that have egress RBridge nickname equal to local
        RBridge nickname and EthType equal to Diagnostic Ethtype, to
        the Central Processing Unit (CPU). Such frames SHOULD NOT
        egress out of the RBridge.
     o The RBridge SHOULD not egress frames with Diagnostic Ethtype to
        non TRILL interfaces.

6.2. Identification of IP Flows

   As stated earlier, most RBridges use combination of IP address and
   Layer 4 information such as UDP/TCP Port, to determine the next hop
   ECMP interface to forward IP frames. Hence, it is important to
   provide flexibility for users to specify destination IP addressing
   and payload information.


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   In this section we propose several approaches to identify OAM
   (diagnostic) frames with IP payloads that are addressed to the local
   RBridge for processing

   Method 1:

   Use of Well known Destination MAC address:

   We propose to use a well known diagnostic MAC address (TBD-DMAC-1),
   as the Destination MAC address of the inner Layer 2 header.

   Each RBridge, if TRILL data plane diagnostic is enabled, MUST
   provide the following processing:

     o Forward frames which have egress RBridge nickname equal to the
        local RBridge nickname and Destination MAC address of the inner
        Layer 2 header equal to the Well Known Diagnostic MAC address
        (TBD-DMAC-1) to the Central Processing Unit (CPU). If RBridge
        nickname is not equal to the local RBridge nickname, frame MUST
        be forwarded normally.
     o RBridge SHOULD NOT egress frames with the Diagnostic MAC
        address (TBD-DMAC-1) as destination address to non TRILL
        interfaces.



   Method 2:

   Use of Well known Source MAC address:

   We propose to use a well known source MAC address (TBD-SMAC-1), as
   the source MAC address of the inner Layer 2 header.

   Each RBridge, if TRILL data plane diagnostic is enabled, MUST
   provide following processing:

     o Forward frames that have egress RBridge nickname equal to the
        local RBridge nickname and source MAC address of the inner
        Layer 2 header equal to Well Known source MAC address (TBD-
        SMAC-1), to the Central Processing Unit (CPU). If the egress
        RBridge nickname is not equal to the local RBridge nickname
        then the frame MUST be forwarded normally.
     o Each RBridge SHOULD NOT egress frames with Well known MAC
        address as source address to non TRILL interfaces.
     o RBridge SHOULD NOT dynamically learn the well known Source MAC
        address (TBD-SMAC-1) specified above.



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   Method 3:

   Use of RBridge specific OAM MAC address:

   Each RBridge may advertise, MAC address for the purpose of receiving
   OAM frames with IP payloads. Sending RBridges may use the advertised
   MAC address as the destination MAC address of the inner Layer 2
   header of originating diagnostic request frames.

   Each RBridge, if TRILL OAM is enabled MUST provide following
   processing:

     o Forward frames that has egress RBridge equal to the local
        RBridge nickname AND Destination MAC address of the inner Layer
        2 header equal to the advertised RBridge specific OAM MAC
        address, to the Central Processing Unit (CPU).
     o RBridge SHOULD NOT egress frames with RBridge specific OAM MAC
        address as destination address to non TRILL interfaces.

6.3. Identification of Flows using Hop-Count Restrictions

   Methods presented in Sections 6.1. and 6.2. utilize one or more
   fields in the data frame to identify OAM frames against real data
   frames. As a result, operator does not have complete flexibility of
   specifying all of the fields in the diagnostic payload. This
   restriction while acceptable in most cases may not be acceptable in
   some cases. There may be instances that operator desire to specify
   the exact frame under investigation.

   RFC 6325 section 3.6 explains handling of TRILL Hop-Count field.
   Accordingly, frames received with Hop-Count of zero (0) MUST not be
   forwarded.

   OAM frames that wishes to utilize Hop-Count restriction process MUST
   first discover the Hop-Count from ingress RBridge to the egress
   RBridge. Hop-Count discovery may be accomplished using Path Trace
   message specified in section 9.3.

   Desired OAM frame is then encoded using methods specified in this
   document. Hop-Count field of the TRILL header is updated with the
   above discovered Hop-Count value.

   Additionally, it is recommended, to invalidate the inner diagnostic
   payload IP checksum, if the specified diagnostic payload is an IP
   packet. Invalidation of the inner diagnostic payload IP checksum
   prevent end stations processing of OAM packets, in the unlikely
   event of such OAM packets leaking out to of the TRILL network.


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   Egress RBridge processing routines MUST have methods to identifying
   OAM frames with Hop-Count expiry from actual data frames with Hop-
   Count expiry. OAM frame validation process specified in section 6.6.
   , MUST be followed. A frame MUST be treated as a data frame with
   Hop-Count expiry, if the OAM validation process specified in section
   6.6. failed.

6.4. Identification of Multicast Flows

   Multicast frames are forwarded using one of the available multicast
   trees in the TRILL network [RFC6325]. Selection of a multicast tree
   is done at the ingress RBridge. Multicast frames are directed to a
   selected multicast tree at the ingress. Hence exact payload
   definition is not required for the purpose of ECMP selection.
   However, based on multicast pruning, certain multicast addresses may
   not be required to be forwarded to all members of the tree.
   Intermediate switches perform, (S,G) or (*,G), forwarding based on
   IP addresses for IP frames and MAC address for non IP frames. Hence,
   in order to verify the effect of multicast pruning users may require
   methods to specify Layer 2 and/or IP addressing information, as
   applicable. There are two types of multicast tree verification
   messages:

     o Overall Tree Verification Messages
     o Pruned Tree Verification Messages

6.4.1. Identification of overall tree verification frames

   We propose to utilize a well known multicast diagnostic MAC address
   (TBD-GMAC-1) for this purpose. If TRILL data plane diagnostics are
   enabled, this specific MAC address MUST be installed on every
   RBridge for all tress and MUST NOT be subject to pruning.

   Each RBridge performs (*,G) forwarding of the frames based on the
   well known multicast diagnostic MAC address (TBD-GMAC-1) in the
   inner Layer 2 destination address. Additionally, it sends a copy of
   the frame to the CPU for analysis and generates a response to the
   requester. Please see section 8.3 for details of multicast tree
   verification message processing.

   A RBridge SHOULD NOT egress multicast frames with above diagnostic
   MAC address in to non TRILL interfaces. Also, RBridge MUST discard
   any native frame received on non TRILL interfaces with the above
   diagnostic MAC address as the destination MAC address.





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6.4.2. Identification of Layer 2 Multicast group verification frames

   We propose to utilize the diagnostic EthType (TBD) that was defined
   earlier for identification of Layer 2 group verification frames.
   User SHOULD have the ability specify destination MAC address, source
   MAC Address, VLAN and payload data up to 128 octets.

   Each RBridge, performs standard multicast forwarding. Additionally,
   if EthType of the frame is equal to the well known diagnostic
   Ethtype (TBD), the RBridge sends a copy of the frame to the CPU for
   analysis and generating response to the requester. Please see
   section 9.3 for details of multicast tree verification message
   processing.

   RBridge MUST NOT egress multicast frames with above EthType in to
   non TRILL interfaces. Also, RBridge MUST discard any native frame
   received on non TRILL interfaces with the above EthType.



6.4.3. Identification of IP Multicast group verification frames

   We propose to use the well known MAC address (TBD-SMAC-1) defined in
   section 6.2 as the source MAC address. Users have flexibility to
   define, IP Address, VLAN and other payload data upto 128 octets. The
   Destination MAC address is derived based on the IP Multicast
   destination address.

   RBridges perform (S,G) or (*,G) forwarding using the IP address
   information. Additionally, each RBridge send a copy of the frame to
   the CPU, if the source MAC address matches the well known MAC
   address defined here in.

   RBridge MUST NOT egress multicast frames with above source MAC
   address to non TRILL interfaces. Also, each RBridge MUST discard any
   native frame received on a non TRILL interfaces with the above
   source MAC address.

   RBridge MUST NOT dynamically learn the well known source MAC address
   specified here.

6.5. Default OAM flow Parameters

   Parameters specified herein SHOULD be utilized as default
   parameters. Parameters specified under the Fixed category MUST not
   be changed based on user specification and MUST be followed exactly
   as specified below.


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    +--------------+--------------------------+-----------------+
    | Flow type    |  Default Values          |  Fixed fields   |
    +--------------+--------------------------+-----------------+
    | Layer 2      | DA= Well Known MAC       | EthType=OAM(TBD)|
    |              | SA= RBridge Interface MAC|                 |
    |              | VLAN=native VLAN         |                 |
    |              |                          |                 |
    +--------------+--------------------------+-----------------+
    | IPv4         | IP Address =             | EthType=0x8000  |
    |  OR          | in-band address          |       OR        |
    | IPv6         | IP Dest. Port = 3503     | EthType=0x86DD  |
    |              | IP Src. Port  = TBD      |                 |
    |              | DA = OAM MAC of egress   |                 |
    |              | RBridge                  |                 |
    |              | SA =ingress RBr interface|                 |
    |              | MAC                      |                 |
    |              | VLAN=native VLAN         |                 |
    +--------------+--------------------------+-----------------+
    | Multicast    | SA= RBridge Interface MAC|DA=Well Known    |
    | Tree         | VLAN=native VLAN         |Multicast MAC    |
    | Verification |                          | EthType=OAM(TBD)|
    +--------------+--------------------------+-----------------+
    | Layer 2      | DA= Well Known MAC       | EthType=OAM(TBD)|
    | Multicast    | SA= RBridge Interface MAC|                 |
    |              | VLAN=native VLAN         |                 |
    +--------------+--------------------------+-----------------+
    | IP           | IP Dest Address =        | EthType=0x8000  |
    | Multicast    | Default OAM MCast address|     OR          |
    |              | IP Src. Address =        | EthType=0x86DD  |
    |              | in-band-address          |                 |
    |              | IP Dest. Port = 3503     |                 |
    |              | IP Src. Port  = TBD      |                 |
    |              | DA = OAM MAC of egress   |                 |
    |              | RBridge                  |                 |
    |              | SA =ingress RBr interface|                 |
    |              | MAC                      |                 |
    |              | VLAN=native VLAN         |                 |
    +--------------+--------------------------+-----------------+


          Figure 6 Default Parameters of Diagnostic(OAM) Payloads

6.6. Validation of OAM Request and Response frames

   OAM processing module MUST further validate the received
   request/response messages to ensure their compliance to this
   specification using the methods specified herein.


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   OAM messages are encodeded as specified above and contain an ICMP
   Header and an ICMP Common Header as specified in [PINGEXT].

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Version|        Length         |           Checksum            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Magic-Number (0x54726163)                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 7 ICMP Common Extension Header

   The OAM process MUST offset to the common header and validate the
   Version and Magic-number fields. The Version MUST be one (1) and
   Magic-number MUST be 0x54726163. If the Version or the Magic-number
   does not match, then the frame is not an OAM frame.

   If these fields are matching the specified values, then the checksum
   is calculated over the Version, Length and Magic number fields. The
   calculated checksum is compared against the checksum in the frame.
   If the two values do not match then the frame is not an OAM frame.

   Frames that pass both the tests above are further qualified as
   below.

   The Length field in the common ICMP header specifies the starting
   location of the ICMP Extension. The first ICMP Extension is the
   Version and Flags Extension (C-type 1) (Section 8.1. ).

   Version and Flag fields of c-type 1 MUST be validated to identify
   whether the OAM frame is of a known version. OAM frames of unknown
   versions are discarded.

   Frames that pass all of the above tests are valid OAM frames and
   further processed according to the OAM code specified in the Version
   and Flags Extensions.

7. ISIS Extensions

   A new ISIS subTLV definition is required to announce the following
   OAM related information:

     o OAM capability
     o OAM in-band IP address
     o OAM in-band MAC address



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   We propose to define a single sub TLV structure within ROUTER-
   CAPABILITY ISIS TLV (242), to announce the above OAM information.

    +--------+
    | Type   |
    +--------+
    | Length |
    +--------+--------+
    |ver| Res |v|i|m|o|
    +-----------------+
    | Sender nickname |
    +-----------------+
    |                 |
    | OAM MAC address |
    |                 |
    +-----------------+
    |                 |
    | OAM in-band     |
    . IP address      .
    |                 |
    +-----------------+

                      Figure 8 ISIS extension for OAM

   Type : (1 octet) TBD (one of the sub-TLV definitions under MT-PORT-
   CAP ISIS TLV)

   Length : ( 1 octet) Length of the subTLV, in octets, excluding Type
   and Length fields. Minimum 2.

   Ver : (4 bits) indicate the OAM version. Currently set to zero.

   Res : (1 octet), Reserved for future use. Set to zero on
   transmission and ignored on recipt.

   V   : (1 bit) if set, indicates IP address included in the TLV is
   IPv6. Only one of I or V bit MUST be set. If both are set, it is a
   malformed TLV and must be discarded without further processing.

   I   : (1 bit) if set indicate IP address included in the TLV is
   IPv4. Only one of I or V bits MUST be set. If both are set, it is
   malformed TLV and must be discarded without any further processing.

   M : (1 bit) If set, indicates MAC address is included in the TLV.

   O : (1 bit) If set, indicates announcing RBridge is OAM capable.



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   MAC Address : (6 octets), IEEE MAC address, associated with the in-
   band IP address. If included, the MAC address MUST precede the IP
   address.

   IP Address : (4 or 16 octets), OAM in-band IP address. If present
   MUST follow MAC address.

   Above PDU encoding MUST follow exact order as specified and fields
   are not interchangeable.

   NOTE: Both I and V flags MAY be set to zero to indicate that
   announcing RBRidge desire to use the default OAM address. The
   default OAM address is the 127/8 address derived as specified in
   section 5.

8. ICMP multi part extensions

   We propose to utilize a new Class-Num [RFC4884] to identify TRILL
   OAM related extensions specified in this document and other related
   documents. IANA has established a registry for ICMP extensions and
   we intend to seek a Class-Num assigned for this purpose.

   Within the TRILL OAM Class-Num, C-Types are defined and registered
   in the IANA to identify various different extensions specified
   herein and other related future documents.

8.1. ICMP Echo Request and Response message extensions

   RFC 4884 proposes a framework to extend ICMP message types: Time
   Expiry, Parameter Problem and Destination Unreachable. RFC 4884
   therefore cannot be applied to extend other ICMP messages, such as
   ICMP echo request and response messages. ICMP Echo request and
   response is by far the most widely used OAM tool. Extensibility of
   ICMP Echo request in a backward compatible manner is very important.
   Such a framework provides flexibility to the ICMP message structure
   to carry application specific information.

   [PINGEXT] presents a framework to extend ICMP messages in a backward
   compatible manner and allow encoding specific extensions in RFC 4884
   compliant c-types.

   In this document, we propose to utilize the framework presented in
   [PINGEXT] to extend the ICMP echo request or response structures
   encoded within the TRILL OAM messages.





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8.2. C-Type Definitions

   C-Types defined in this section MUST be embedded in the ICMP
   Extension object format proposed in section 8 of RFC 4884. Figure 9
   presents the format of the ICMP Extension object defined in RFC
   4884. Figure 9 is entirely for reference purposes only and readers
   are referred to RFC 4884 for most up to date information.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Length            |   Class-Num   |   C-Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                   // (Object payload) //                      |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                      Figure 9 ICMP Extension Object



   Section below defines the format of the object payloads, only. ICMP
   Object header MUST precedes object payloads defined in section 8.2.
   Figure 10 below presents an example of encoding C-Type 1, i.e
   Version and Flags object.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Length            |   Class-Num   |   C-Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Version       |    code       | Reserved                |F|c|o|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Figure 10   Example of Encoding Version and Flags object



   Version and Flags: C-Type 1

   Contain Version number, code and associated flags. Currently Out-of
   band Request, Final and Cross Connect Error flags are defined.




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    Bits
        31          24        16             2  1  0
        +------------+---------+-----------+--+--+--+
        | Version    | code    | Reserved  |F |C | o|
        +------------+---------+-----------+--+--+--+


                  Figure 11   C-Type 1, Version and Flags

   Version (8 bits): Currently set to zero

   Code (1 octet) : TRILL OAM Message codes. See below for currently
   available TRILL OAM Message codes.

   Reserved (22 bits): Set to zero on transmission and ignored on
   receipt

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

   C (1 bit ): Cross connect error (VLAN mapping error), if set
   indicates VLAN cross connect error detected. 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.

   TRILL OAM Message codes:

   0  : Loopback Message Request
   1  : Loopback Message Response
   2  : Path Trace Request
   3  : Path Trace Response
   4  : Time Expiry Notification (error)
   5  : Parameter Problem Notification (error)
   6  : Destination Unreachable (error)
   7  : Multicast Tree Verification Request
   8  : Multicast Tree Verification Response
   9  : MAC Address discovery Request
   10 : MAC Address discovery Response
   11 : DRB discovery request
   12 : DRB discovery response
   13 : AF discovery request
   14 : AF discovery response
   15 : AF-VLAN discovery request
   16 : AF-VLAN discovery response
   17 : TTM Set Message


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   18 : TTM Get Message
   19 : TTM Remove Message
   20 : TTM Response Message
   21 : TTM Indication Message
   22 : Payload Generation request Message
   23 : Payload Generation response Message
   24 : Loopback Message request with Hop-count
   25 : Loopback Message response for message code 24.
   26 - 255 : Reserved

   Originator IP Address: (C-type 2)

   Length of the ICMP extension header indicates whether the address is
   IPv4 or IPv6. Please refer to RFC 4884 for ICMP extension encoding
   and ICMP header structure.

   Bits
         31                                0
         +---------------------------------+
         |                                 |
         . IP Address                      .
         |                                 |
         +------------+--------------------+

                Figure 12   C-Type 2 Originator IP address





   Upstream Identification: (C-type 3)

   The Upstream Identification C-type structure encodes upstream path
   information such as upstream neighbor nickname, ingress interface
   index (ifindex) and name of the ingress port.














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    Bits
        31                                 0
        +------------------+---------------+
        |  nickname        | Reserved      |
        +------------------+---------------.
        |            ifindex               |
        +------------+---------------------+
        |   Slot           |    Port       |
        +------------------+---------------|
        |    Speed         |    State      |
        +------------------+---------------+

               Figure 13   C-Type 3 Upstream Identification

   Nickname (2 octets): TRILL 16 bit nickname of the upstream RBRdige.
   [RFCtrill]

   Reserved (2 octetc)       : Reserved, set to zero on transmission
   and ignored on receipt.

   Ifindex  (2 octets) : unsigned integer of local significance

   Slot     (2 octets) : Slot number

   Port     (2 octets) : Port number

   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.

   0: Down - no errors
   1: Disable
   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   6: Link Monitoring disable
   All other values reserved.

   Monitored VLAN(diagnostic VLAN ) : (C-type 4)

   Monitored VLAN c-type include in the ICMP extensions allows for
   testing the integrity of the inner payload VLAN and the expected
   VLAN. The expected VLAN is encoded in the Monitored VLAN c-type. The
   destination RBRidge, compare the VLAN of the inner payload with the
   VLAN value encoded in the Monitored VLAN c-type. If these two VLAN


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   values mismatch, RBRidge SHOULD set the cross connect flag in the
   response. A RBridge MUST NOT set the cross connect error flag for
   other than the above specified VLAN mismatch scenario.

    Bits
        16                                0
        +---------------------------------+
        | Reserved   |  VLAN              |
        +------------+--------------------+

             Figure 14   C-Type 4 Monitored (Diagnostic) VLAN

   Downstream Identification: (C-Type 5)

   The Downstream Identification C-type carries multiple sets of data,
   each corresponding to individual downstream neighbor among
   collection of equal cost paths.

    Bits
        31                                0
        +------------------+---------------+
        | ecmp count       | Reserved      |
        +------------------+---------------+ ----
        | Reserved         | nickname      | ^
        +------------------+---------------+ |
        |            ifindex               | | Next hop
        +------------+---------------------+ | neighbor
        |   Slot           |    Port       | | information
        +------------------+---------------| |
        |    Speed         |    State      | v
        +------------------+---------------+ ----
        |                                  |
        |  Repeat next hop neighbor        |
        .  identification for each         .
        |  neighbor                        |
        |                                  |
        +----------------------------------+

              Figure 15   C-Type 5 Downstream Identification

   Ecmp count (2 octets): Number of equal cost paths to the given
   destination from this RBridge.

   Reserved (4 octets): Reserved, set to zero on transmission and
   ignored on receipt.

   Next-hop neighbor information:


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   Nickname (16 bits): TRILL 16 bit nickname [RFCtrill]

   Ifindex  (2 octets) : unsigned integer of local significance

   Slot     (2 octets) : Slot number

   Port     (2 octets) : Port number

   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.

   0: Down - no errors
   1: Disable
   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   6: Link monitoring disable
   All other values reserved.

   NOTE: Repeat Next-hope neighbor identification entry per each ECMP.
   Total number of neighbor entries MUST equal to ecmp count.
   Individual neighbor entry MAY have variable length.



   Path for this payload: (c-Type 6)

   Path for this payload indicates the next hop neighbor that this
   frame could have been forwarded on based on the payload hashing.

















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   Bits
        31                                 0
        +------------------+---------------+
        |  nickname        | Reserved      |
        +------------------+---------------.
        |            ifindex               |
        +------------+---------------------+
        |   Slot           |    Port       |
        +------------------+---------------|
        |    Speed         |    State      |
        +------------------+---------------+


                Figure 16   C-Type 6 Path for this payload

   Nickname (16 bits): TRILL 16 bit nickname [RFCtrill]

   Ifindex  (2 octets) : unsigned integer of local significance. 0xFFFF
   indicate CPU.

   Slot     (2 octets) : Slot number

   Port     (2 octets) : Port number

   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.

   0: Down - no errors
   1: Disable
   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   6: Link monitoring disable
   All other values reserved.

   DRB Information (c-Type 7)

       31             16       8     0
       +---------------+--------+--+-+
       | nickname      | state  | R|P|
       +---------------+--------+--+-+

                      Figure 17   Nickname of the DRB


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   Nickname (2 octets) : TRILL nickname of the DRB

   State    (1 octets) : DRB state

   R        ( 7 bits ) : set to zero on Transmission and ignored on
   receipt

   P        (1 bits )  : Set when pseudo node bypass is indicated by
   the DRB for the link

   AF Information (C-Type 7)

   Follow the same encoding as C-Type 6, above.

   Nickname and state are of the AF.

   Enable VLAN List (c-Type 8)

       31  27        16  12         0
       +--+-----------+--+----------+
       |R | St-VLAN   |R | End-VLAN |
       +--+-----------+--+----------+


                       Figure 18   Enabled VLAN List

   R (4 bits) : Reserved, set to zero on transmission and ignored on
   receipt.

   St-VLAN (12 bits) : Start VLAN

   End-VLAN (12 bits) : End VLAN

   Start VLAN and End VLAN represent the range of enabled VLANS. If the
   VLAN range is non contiguous, then multiple Enabled VLAN lists MUST
   be included, each representing a contiguous VLAN set.

   Announcing VLAN set (c-Type 9)

   Announcing VLAN list uses the same format as the Enable VLAN List
   (c-Type 8)








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       31  27        16  12         0
       +--+-----------+--+----------+
       |R | St-VLAN   |R | End-VLAN |
       +--+-----------+--+----------+


                     Figure 19   Announcing VLAN List

   R (4 bits) : Reserved, set to zero on transmission and ignored on
   receipt.

   St-VLAN (12 bits) : Start VLAN

   End-VLAN (12 bits) : End VLAN

   Start VLAN and End VLAN represent the range of announcing VLANS. If
   the VLAN range is non contiguous, then multiple of announcing VLAN
   list MUST be included, each representing a contiguous VLAN set.



   AF List (c-Type 10)

   This c-Type lists the VLANs for which responding RBridge is a the
   appointed forwarder.

       31  27        16  12         0
       +--------------+-------------+
       | Reserved     | nickname    |
       +--+-----------+--+----------+
       |R | St-VLAN   |R | End-VLAN |
       +--+-----------+--+----------+


                            Figure 20   AF List

   Reserved (2 octets) : set to zero on transmission and ignored on
   receipt.

   Nickname (2 octets) : TRILL 16 bit nickname of the RBridge

   R (4 bits) : Reserved, set to zero on transmission and ignored on
   receipt.

   St-VLAN (12 bits) : Start VLAN

   End-VLAN (12 bits) : End VLAN


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   AF List MUST be repeated for each of the contiguous VLAN ranges that
   the responding RBridge function as Appointed Forwarder.

   DRB Life Time (c-Type 11)

   DRB Life time indicates the Life time, of the DRB operational role,
   of the RBridge.

      31                                     0
      +--------------------------------------+
      |                                      |0
      +   Life Time                          +
      |                                      |1
      +--------------------------------------+

                         Figure 21   DRB Life Time

   Life Time ( 8 octets): Indicates the Life time of the operational
   role in seconds.

   AF Lifetime (C-Type 12)

   AF Life time indicates the Life time, of the AF operational role, of
   the RBridge for the specified VLAN.

   Encoding follow the same format specified in C-Type 11.

   Designated VLAN changes (C-Type 13)

   Indicates number of times a given RBridge has observed Designated
   VLAN changes. Each change may potentially lead to traffic
   disruptions.

       15            0
       +-------------+
       | Change count|
       +-------------+

            Figure 22   Number of times Designated VLAN changes



   Change count (2 octets): Indicates number of times a given RBridge
   has observed Designated VLAN changes

   RBridge scope List (c-Type 14)



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    15           0
     +-----------+
     |  R  |  Nu |
     +-----------+
     | nickname 1|
     +-----------+
     .           .
     .           .
     | nickname n|
     +-----------+

                     Figure 23   Scope List c-Type 14

   R (1 octet ) : Reserved, zero on transmission and ignored on recipt.

   Nu (1 octet) : number of nicknames listed

   Nickname 1 .. n (2 octets) each: List TRILL RBridge nickname of in
   scope RBridges.

   Nicknames MUST be numerically sorted. With nickname1 the lowest to
   nickname n the highest. This facilitate easy processing the
   receiving RBridge.

   Nu = 0 indicate no embedded nicknames in the message and response
   required from all RBridges, where applicable.

   Multicast Tree downstream List (c-Type 15)





















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   Multicast Tree downstream list provides information on downstream
   leaf Rbridges on the specified tree.

   Bits
        31                                0
        +------------------+---------------+
        | leaf count       | Reserved      |
        +------------------+---------------+ ----
        | Reserved         | nickname      | ^
        +------------------+---------------+ |
        |            ifindex               | | Downstream
        +------------+---------------------+ | leaf
        |   Slot           |    Port       | | information
        +------------------+---------------| |
        |    Speed         |    State      | v
        +------------------+---------------+ ----
        |                                  |
        |  Repeat downstream               |
        .  leaf information for each       .
        |  downstream RBridge              |
        |                                  |
        +----------------------------------+


           Figure 24   C-Type 15 Multicast Tree Downstream List



   Leaf count (16 bits): Number of RBridges downstream to this RBridge.

   Downstream leaf information:

      Nickname (16 bits): TRILL 16 bit nickname [RFCtrill]

      Ifindex (32 bits) : Unsigned 32 bit integer that has only a local
   significance to the sending RBridge. Value 0xFFFF indicates CPU
   interface.

   Slot     (2 octets) : Slot number

   Port     (2 octets) : Port number

   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.



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   0: Down - no errors
   1: Disable
   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   All other values reserved.



   NOTE: Repeat downstream RBridges reachability information per each
   leaf node. Total number of neighbor entries MUST equal to leaf
   count. Individual neighbor entry MAY have variable length.

   MAC-discovery Address List (c-Type 16)

    15           0
    +------------+
    | count      |
    +------------+
    | MAC        |
    + Address 1  +
    |            |
    +            +
    |            |
    +------------+
    |            |
    .            .
    .            .
    .MAC         .
    |Address n   |
    +------------+


                  Figure 25   MAC-discovery Address List

   Count (2 octets) : Number of MAC addresses embedded in the response

   MAC Address ( 6 octets) : 6 octet MAC address

   MAC-discovery response Address List (c-Type 17)








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     15             0
     +--------------+
     | count        |
     +--------------+
     | T | VLAN     |
     +---+----------+
     | L | Reserved |
     +---+----------+
     |              |
     + Service Tag  +
     |              |
     +--------------+
     |              |
     + MAC          +
     | Address      |
     +              +
     |              |
     +--------------+
     | Age          |
     +              +
     |              |
     +              +
     |              |
     +              +
     |              |
     +--------------+
     | Ifindex      |
     +              +
     |              |
     +--------------+
     | vNTAG        |
     +--------------+
     | Slot         |
     +--------------+
     | Port         |
     +--------------+
     | State        |
     +--------------+
     | Speed        |
     +--------------+

                    Figure 26   MAC-discovery response

   Count (2 octets) : Number of MAC addresses embedded in the response

   T      (4 bits ) : Type of MAC address 0 - Dynamic, 1 Static, 2-15
   Reserved


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   VLAN   (12 bits) : VLAN identifier associated with the MAC address

   L      (8 bits)  : Length of Service Tag in bits.

   Service Tag (4 octes): Service Tag is right aligned. For 24 bit
   Length, left most 8 bits of Service Tag MUST be set to zero.

   MAC Address ( 6 octets) : 6 octet MAC address

   Age (8 octets ): Age of the MAC address in seconds. For a static MAC
   address, this field is ignored.

   Ifindex ( 4 octets) : Interface index on which MAC address is learnt

   Slot (2 octets) : Slot number of the interface on which this MAC
   address is learnt

   Port (2 octets): Port number of the interface on which this MAC
   address is learnt.

   vNTAG (2 octets): virtual TAG identifier associated with the MAC
   address. Value 0 indicate no vNTAG association with the MAC address.

   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.

   0: Down - no errors
   1: Disable
   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   6: Un-monitored
   All other values reserved.



   Error code (c-Type 18)

   Error code c-Type allows an RBridge to specify various error codes
   within high-level notification messages such as Time Expiry,
   Parameter Problem and Destination unreachable. The sub-error codes
   within each of the error code allow specifying further details of
   the error.



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     Bits
        31                                0
        +------------------+--------------+
        | Error Code       | sub-code     |
        +------------------+--------------+

                     Figure 27   C-Type 18 Error code

   Error Code (2 octets) : Identify the error. Currently following
   errors are defined

   0 - VLAN non existent
   1 - VLAN in suspended state
   2 - Cross connect error
   3 - Unknwon RBridge nickname
   4 - Not AF
   5 - MTU mismatch
   6 - Interface not in forwarding state
   7 - Service Tag non existent
   8 - Service Tag in suspended state
   9 - 0xFFFF - Reserved for future use and MUST not be used in
   transmission.

   Sub-code (2 octets) : identify the sub-error code.
   0 - 0xFFFF - Reserved for future use and MUST not be used in
   transmission.


   Warning code (c-Type 19)

   Warning code c-Type allow a RBridge to specify various error codes
   within high-level notification messages such as Time Expiry,
   Parameter Problem and Destination unreachable. The sub-warning codes
   within each of the warning codes allow to specify further details of
   the warning.

     Bits
        31                                0
        +------------------+--------------+
        | Warning Code     | sub-code     |
        +------------------+--------------+

                    Figure 28   C-Type 19 Warning code

   Warning Code (2 octets) : Identify the Warning. Currently following
   Warnings are defined



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   0 - Inavlid RBridge nickname (RBridge nickname in the range 0xffco
   to 0xffff)
   1 - Invalid VLAN (Reserved VLAN)
   2 - AF VLAN list Mismatch
   3 - 0xFFFF - Reserved for future use and MUST not be used in
   transmission.

   Sub-code (2 octets) : identify the sub-error code.

   0 - 0xFFFF - Reserved for future use and MUST not be used in
   transmission.



   Information code (c-Type 20)

   Information code c-Type allow a RBridge to specify various
   information codes within the high-level notification messages such
   as Time Expiry, Parameter Problem and Destination unreachable. The
   sub-info codes within each of the code allow specifying further
   details of the information.

     Bits
        31                                0
        +------------------+--------------+
        | Information Code | sub-code     |
        +------------------+--------------+

                  Figure 29   C-Type 20 Information code

   Information Code (2 octets) : Identify the Information. Currently
   following Information are defined

   0 - 0xFFFF - Reserved for future use and MUST not be used in
   transmission.

   Sub-code (2 octets) : identify the sub-error code.

   0 - 0xFFFF - Reserved for future use and MUST not be used in
   transmission.

   Diagnostic-Payload (c-Type 21)

   The Disagnostic-Payload c-Type encodes Trill-header and diagnostic
   payload for response messages or original frame for notification
   messages. The length of the embedded diagnostic-payload is indicated
   by the Length in the C-type header ([RFC4884]).


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     Bits
        31                                0
        +------------------+--------------+
        |                                 |
        .      Diagnostic-Payload         .
        |                                 |
        +------------------+--------------+

                  Figure 30   C-Type 21 Information code

   Diagnostic-Payload : 0 or more 32bit words.

   This c-type MUST only be included in Response or notification
   messages only. It MUST only occur exactly once within the message.



   Data (c-Type 22)

   The Data c-Type facilitates encoding of any arbitrary set of data in
   to the OAM messages. Such Opaque data may be utilized to generate
   TRILL OAM frames with different lengths. It may also be utilized for
   other purposes, such usage methods are outside the scope of this
   document.

     Bits
        31                                0
        +------------------+--------------+
        |                                 |
        .      Data-Payload               .
        |                                 |
        +------------------+--------------+

                  Figure 31   C-Type 21 Information code

   Data-Payload : 0 or more 32bit words.

   This c-type may occur zero or more times within a given OAM message

   Service Tag (c-Type 23)

   Overlay Technologies such as[FNGRAIN], utilize Identification Tags
   that are wider than the 12bit VLAN Tag used in IEEE 802.1Q.
   Objective of these tags, regardless of the width, is to identify
   virtual service instance within the overlay network. Hence, in this
   document the tag is referred to as Service Tag.



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    0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Service Tag                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 32   C-Type 23 Service Tag

   Service Tag: 4-octets wide opaque value.

   Applications that requires 24bit service Tags MUST set upper 8bits
   to zero in transmission and discards requests received with non zero
   value in upper 8bits.

   Control Plane Forwarding Verification Request(c-Type 24)

   Downstream Identification (c-Type 5) presented earlier facilitate
   users to discover forwarding paths available on the dataplane to
   reach the specified destination. It is often desirable to discover
   control and data plane inconsistencies. Control Plane Forwarding
   Verification c-Type facilitate the users to optionally obtain
   Forwarding information available on the control plane.

   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Ecmp Identifier              |   egress nickname             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 33   C-Type 24 control Plane Forwarding Verification Request

   Ecmp Count : (2 octets) : Ecmp Identifier indicates the ECMP to
   verified. Value 0xFF indicate all of the ECMP needed to be verified.

   Egress nickname : (2 octets), nickname of the destination RBridge.

   Control Plane Forwarding Verification Response(c-Type 25)

   Control Plane Forwarding Verification Response is generated in
   response to c-Type 24 above.








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   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  ECMP count              |   Reserved                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  ECMP Identifier         |  nickname                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               ifindex                                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Slot                |       Port                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Speed               |       State                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   . Repeat next hop neighbor information for each neighbor        .
   | ECMP Identifier to State represent next hop information       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Figure 34   C-Type 25 control Plane Forwarding Verification Response

   Ecmp count (2 octets): Number of equal cost paths to the given
   destination from this RBridge.

   Reserved (2 octets): Reserved, set to zero on transmission and
   ignored on receipt.

   Next-hop neighbor information:

   ECMP Identifier: ECMP Identifier for this record.

   Nickname (2 octets): TRILL 2 octet nickname [RFCtrill]. Value 0xFFFF
   indicates requested ECMP Identifier is invalid.

   Ifindex  (2 octets) : unsigned integer of local significance

   Slot     (2 octets) : Slot number

   Port     (2 octets) : Port number

   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.

   0: Down - no errors
   1: Disable


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   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   6: Link monitoring disable
   All other values reserved.

   NOTE: Repeat Next-hope neighbor identification entry per each ECMP.
   Total number of neighbor entries MUST equal to ecmp count.
   Individual neighbor entry MAY have variable length.

   Reverse Path Forwarding Verification Request(c-Type 26)

   Downstream Identification (c-Type 5) presented earlier facilitate
   users to discover forwarding paths available on the data plane to
   reach the specified destination. It is often desirable to discover
   the reachability and ECMP information along the reverse path. C-Type
   presented here allows users to discover Reverse Path to a specified
   RBRidge from the receiver. This is an optional parameter and can be
   included in Loopback messages, Path Trace messages and OAM Command
   messages.

   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Ecmp Identifier              |          nickname             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 35   C-Type 26 Reverse Path Forwarding Verification Request

   Ecmp Count : (2 octets) : Ecmp Identifier indicates the interested
   Reverse Path ECMP. Value 0xFF indicate all of the ECMP.

   nickname : (2 octets), nickname of the destination RBridge.

   Reverse Path Forwarding Verification Response(c-Type 27)

   Reverse Path Forwarding Verification Response is generated in
   response to c-Type 26 above.










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   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Ecmp count              |   Reserved                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  ECMP Identifier         |  nickname                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               ifindex                                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Slot                |       Port                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Speed               |       State                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   . Repeat next hop neighbor information for each neighbor        .
   | ECMP Identifier to State represent next hop information       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


    Figure 36   C-Type 27 Reverse Path Forwarding Verification Response

   Ecmp count (2 octets): Number of equal cost paths to the given
   destination from this RBridge.

   Reserved (2 octets): Reserved, set to zero on transmission and
   ignored on receipt.

   Next-hop neighbor information:

   ECMP Identifier: ECMP Identifier for this record.

   Nickname (2 octets): TRILL 2 octet nickname [RFCtrill]. Value 0xFFFF
   indicates requested ECMP Identifier is invalid.

   Ifindex  (2 octets) : unsigned integer of local significance

   Slot     (2 octets) : Slot number

   Port     (2 octets) : Port number

   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.

   0: Down - no errors
   1: Disable


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   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   6: Link monitoring disable
   All other values reserved.

   NOTE: Repeat Next-hope neighbor identification entry per each ECMP.
   Total number of neighbor entries MUST equal to ecmp count.
   Individual neighbor entry MAY have variable length.

   Traffic Triggered Monitoring (TTM) Profile (c-Type 28)

   Details of Traffic Triggered Monitoring are presented in section 11.
   TTM profile defines the container c-Type for the TTM profile. With
   the TTM profile c-type, other related c-types are included. Included
   c-types are linked through next c-type field. Value zero in next c-
   type field indicate end of included c-types.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Priority                     |         Identifier            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | C |  F  |            Frequency                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Count                                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Reserved                |      Next c-type              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 37   C-Type 28 TTM Profile

   C Indicate the Class

   TTM Profile action (c-Type 29)

   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Action       | Reserved    |         Next c-type             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 38   C-Type 29 TTM action

   Action (2 octets):


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      0: count RX packets

     1:  Count TX packets
     2:  Count RX bytes
     3:  Count TX bytes
     4:  Log
     5:  Capture
     6: - 0xFF reserved



   NOTE: Given TTM Profile may contain multiple actions. E.g. count TX,
   count RX and Log.

   TTM Test Point (TP) (c-type 30)

   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Slot                         |         Port                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Reserved                    |  Next c-type                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   Figure 39   C-Type 30 TTM Test Point

   NOTE: Given TTM Profile may contain multiple Test Points.

   TTM Ingress End Point (c-type 31)

   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T   |  Reserved               |    next c-type                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    End Point Address                                          .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                Figure 40   C-Type 31 TTM Ingress End Point

   T 3 bits:

     1: TRILL RBridge nickname (Length of End Point is 2 octets)


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     2: IPv4 End Point (Length of the End Point is 4 octets)
     3: IPv6 End Point (Length of the End Point is 16 octets)
     4: 7 Reserved.


   End Point Address: Address of the End Point as defined by the T
   value.

   Next c-type is the c-type of the next information. Value zero
   indicates this as the last c-type.

   TTM Egress End Point (c-type 32)

   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T   |  Reserved               |    next c-type                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    End Point Address                                          .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                Figure 41   C-Type 32 TTM Egress End Point

   T 3 bits:

     5: TRILL RBridge nickname (Length of End Point is 2 octets)
     6: IPv4 End Point (Length of the End Point is 4 octets)
     7: IPv6 End Point (Length of the End Point is 16 octets)
     8: 7 Reserved.


   End Point Address: Address of the End Point as defined by the T
   value.

   Next c-type is the c-type of the next information. Value zero
   indicates this as the last c-type.



   TTM Pattern (c-type 33)






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   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T     |  Reserved             |    next c-type                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    TTM Pattern                                                .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    TTM Pattern mask                                           .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 42   C-Type 33 TTM Pattern

   T 4 bits:

     0: TRILL ingress RBridge nickname (Length of the pattern is 2
        octets)
     1: TRILL egress RBridge nickname (Length of the pattern is 2
        octets)
     2: IPv4 Source End Point (Length of the pattern is 4 octets)
     3: IPv4 Destination End Point (Length of the pattern is 4 octets)
     4: IPv6 Source End Point (Length of the pattern is 16 octets)
     5: IPv6 Destination End Point (Length of the pattern is 16 octets)
     6: Source MAC address (Length of the pattern is 6 octets)
     7: Destination MAC address  (Length of the pattern is 6 octets)
     8: EthType (Length of the pattern is 2 octets)
     9: VLAN (Length of the pattern is 2 octets) Right justified, upper
        4 bits are do not care.
     10: Service Tag 24 bits. Right aligned with upper octet do not
        care.
     11: Service Tag 32 bits
        All other values Reserved.



   TTM Pattern Mask defines the mask of the specified pattern. Length
   of the pattern mask is identical to the length of the addres.

   Next c-type is the c-type of the next information. Value zero
   indicates this as the last c-type.

   TTM Opaque Pattern (c-Type 34)



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   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Length          |  Offset     |    next c-type                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    TTM Pattern                                                .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    TTM Pattern mask                                           .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                 Figure 43   C-Type 34 TTM Opaque pattern

   Length: (1 octets) define the length of the TTM pattern in octets.

   Offset: (1 octets) defines the offset from the pre-amble of the
   frame the specified pattern MUST be applied.

   TTM Pattern is the pattern to be matched. Length of the pattern is
   specified by the Length field.

   TTM Pattern mask is the mask for the specified pattern. Length of
   the pattern is specified by the Length field.

   NOTE: Only one TTM Opaque pattern MUST be included in a given TTM
   profile. TTM profiles with more than one Opaque Pattern MUST be
   rejected.

   End Point (c-type 35)

   End Point c-type (35) indicate the address on the device that is
   generating the message. For TRILL this represent the 16 bit nickname
   of the RBridge.












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   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T   |  Reserved                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    End Point Address                                          .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                      Figure 44   C-Type 35 End Point

   T 3 bits:

     9: TRILL RBridge nickname (Length of End Point is 2 octets)
     10: IPv4 End Point (Length of the End Point is 4 octets)
     11: IPv6 End Point (Length of the End Point is 16 octets)
     12: 7 Reserved.


   End Point Address: Address of the End Point as defined by the T
   value.

   TTM Test Payload (c-type 36)

   TTM Profile allow users to inject test frames from an intermediate
   device. C-type 35 End Point allows specifying egress end point of
   the tunnel or RBridge. C-type 36 presented here provide methods of
   specifying the required frame.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Length of frame        |    next c-type                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .    Test Frame                                                 .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 45   C-Type 36 TTM Test Payload

   Length (2 octets) specify the length of the Test Frame

   Next c-type is the next c-type within the TTM profile.


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   Test frame is the payload of the frame, excluding pre-amble and FCS.

   Seed Destination MAC address (c-type 37)

   Seed Destination MAC address is used when discovering diagnostic
   payloads combinations that span certain ECMP path combination. A
   given payload discovery request may contain multiple Seed MAC
   addresses. The identification field within the seed MAC address
   uniquely identifies a specific seed. MAC address field within the
   seed is divided in to 6 fields. Each of these fields is named MA-1
   to MA-6 and one octet wide.  MA-x can take any legal value specified
   by IEEE MAC address specification. Non zero value in MA-x indicates
   that specific octets cannot be changed by the downstream RBridge
   when generating the diagnostic payload. MA-x fields with zero
   indicates either it is a fixed field or field that is available for
   downstream Rbridges to derive appropriate payload value. Each of the
   Max with zero value has corresponding C-type 39, MAC-Octet bit
   vector. Each bit in the MAC-Octets Mask indicates a valid value for
   that MA-x field. MAC-Octet Mask of zero length indicates the
   corresponding MA-x field has fixed value zero.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Identifier      |Reserve|    MAC-0      |  MAC-1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | MAC-2         |    MAC-3      |    MAC-4      |  MAC-5        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


            Figure 46   C-Type 37 Seed Destination MAC address

   Identifier (12 bits) Uniquely identify a MAC address seed within a
   diagnostic payload discovery message

   MAC-0 to MAC-5 Represent an octet in the IEEE MAC address and may
   take any legal value specified in IEEE 802.1. Any MAC-x field of
   value zero MUST have a corresponding C-type 39, MAC-Octet bit
   vector.

   Seed Source MAC address (c-type 38)

   Seed Source MAC address, c-type 38, has same format as c-type 37.

   MAC-Octet bit vector (c-type 39)




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   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Identifier      |MAC-x  | bit-offset    | Length        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .                  bit-vector                                   .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 47   C-Type 39 MAC-Octet bit vector

   Identifier (12 bits), uniquely identifies a MAC address seed within
   a diagnostic payload discovery message.

   MAC-x : Value 0-5 indicates the MAC address octet represented by
   this bit-vector.

   Bit-offset (octet) indicates the starting value of the bit-0 of bit
   vector. E.g. when bit-offset is 40, starting value of bit-0 is 40,
   bit-1 is 41 and so on.

   Length (octet) indicates the length of the bit vector in bits.

   A value 1 in a bit vector position indicates the value represented
   by that bit is an applicable value to be considered for the MAC-x
   field.

   Payload generation request (c-Type 40)

   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ECMP start    |  ECMP end     |   egress nickname             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 48   C-Type 40 Payload generation request

   ECMP start, ECMP end : (1 octet each) : ECMP start and ECMP end
   indicate the ECMP to verified. Value 0xFF in ECMP start and ECMP end
   indicate all of the available ECMP needed to be verified.

   Egress nickname : (2 octets), nickname of the destination RBridge.

   Payload generation response (c-Type 41)




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   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |ECMP identifier|Res      |   S |   egress nickname             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 49   C-Type 41 Payload generation response

   ECMP Identifier: (1 octet) :

   Egress nickname : (2 octets), nickname of the destination RBridge.

   Res : (6 bits), set to zero on transmission and ignored on recipt.

   S : (3 bits) indicates the status.

     0. Success
     1. ECMP does not exist
     2. Unable to generate payload using the proposed seed
     3. System overloaded try later
     4. - 7 Reserved MUST not be used.

   TTM command Response sub-codes (c-Type 42)

   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Sub-code       |    Reserved                           |status |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 50   C-Type 42 TTM command Response sub-code

   Sub-codes (1 octet):

         0 :  Set response
         1 :  Get Response
         2 :  Remove Response
         3-                  255 : are reserved and must not be used.

   Reserved (1 octet): set to zero on transmission and ignored on
   recipt.

   Status (1 octet):

              0 :                        Success
              1 :                        TTM profile does not exist
              2 :                        Remove failed


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              3 :                        Get failed
              4 :                        Set failed - resource exceeded
              5 :                        Set failed - other reasons

              6-255 : Reserved and MUST not be used

   EthType (c-Type 43)

   0                  1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Reserved         |  Eth Type                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 51   C-Type 43 Eth Type

   Eth Type (2 octets): Represent IEEE Ether Type

   Reserved (2 octets): Set to zero on transmission and ignored on
   receipt.



9. Details of Diagnostic tools

   In this section we present details of various diagnostic tools that
   are identified as part of the solution. We assume, readers are
   familiar with frame encoding methods, diagnostic frame
   identification methods, and ISIS and ICMP extensions presented
   earlier in the document. In this section we will only make reference
   to the extensions and methods, please refer to prior section for
   details.

9.1. Loopback Message

   Loopback message is utilized for fault verification. It verifies
   connectivity between two RBridges, for a specified flow. Monitoring
   subsystem may use Loopback Message for connectivity monitoring and
   proactive fault detection. Users may specify exact flow, part of it
   or not at all. Additionally, users may also specify, ECMP choice at
   the ingress. ECMP choice can be a specific index, set of index, all
   of the index or non. If no ECMP index specified, payload is used to
   determine the ECMP choice. Method of deriving the ECMP choice using
   payload is implementation dependent and is outside the scope of this
   document. However, CPU generating the Loopback message SHOULD use
   the same ECMP selection algorithm as the data plane. Additionally
   some implementation may allow users to specify the ingress interface


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   that actual flow may ingress to the RBridge. Although ability to
   inject the data plane diagnostic frames from the ingress interface
   is optional feature, it is highly desirable, as it allows verifying
   end-end connectivity from an ingress port to an egress RBridge.

   Egress RBridge can send its response either in-band or out-of-band.
   In-band-response, additionally allow to measure round trip delay.
   In-band responses are tagged with the same VLAN as the request
   frame. ICMP multi part extensions in the request message allow user
   to specify whether out-of-band response required. If out-of-band
   request required, IP address it desire to receive the response MUST
   be specified.

   Additionally, diagnostic VLAN, may be specified as part of the ICMP
   multi part extensions. Receiver RBridge may compare inner VLAN in
   the payload and the specified diagnostic VLAN. If the two specified
   VLAN values do not match, C flag in Version C-type SHOULD be set to
   indicate cross connect error..

9.1.1. Theory of Operation

9.1.1.1. Originator RBridge

   Identify the destination RBridge based on user specification or
   based on location of the specified address (see below sections for
   MAC discovery and address locator).

   Construct the diagnostic payload based on user specified parameters.
   Default parameters MUST be utilized for unspecified payload
   parameters. See Figure 6 for default parameters.

   Construct the ICMP Echo request header. Assign applicable
   identification number and sequence number for the request.

   ICMP multi part extension Version MUST be included and set
   appropriate flags. Specify the code as Loopback Message Request(0).

   Construct following ICMP multipart extensions, where applicable

     o Out-of-band response request

     o Out-of-band IP address

     o Diagnostic VLAN





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   Specify the Hop count of the TRILL data frame per user
   specification. Or utilize the applicable Hop count value, if TRILL
   TTL is not being specified.

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

   RBridge may continue to retransmit, the request at periodic
   interval, until a response received or re-transmission count
   expires. At each new re-transmission sequence number may be
   incremented.

9.1.1.2. Intermediate RBridge

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

9.1.1.3. Destination RBridge

   Destination RBridge performs, frame identification methods specified
   in above section 5. If the Loopback message is addressed to the
   local RBridge, then the RBridge forward the Loopback messages to the
   CPU for processing. CPU performs frame validation and constructs the
   response as stated below.

   Construct the IP header for the ICMP echo response. If no out-of-
   band response requested, IP address in the IP header MUST be in-band
   IP address. If out-of-band response requested destination IP address
   is the IP address specified in the request message. Source IP
   address is derived based on the outgoing IP interface address.

   Construct the ICMP echo reply header using the received ICMP echo
   request.

   Include the received TRILL header and diagnostic payload in to the
   data field of the ICMP echo request frame [section 4.2. ].

   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.

   Error handling:




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   If VLAN cross connect error detected or inner.VLAN does not exsist
   in the RBridge then generate Destination Unreachable message and
   specify the cause using error codes.

9.2. Loopback Message Hop-count method

   The Loopback message procedures presented in section 9.1. utilize
   customers specified payload to derive the diagnostic payload
   embedded in the OAM message. Encoding methods presented in section
   6. , require that certain fields of the diagnostic payload to
   contain some fixed well-known values. Time to time operators may
   desire to include identical payload fields with no modifications.
   Hop-count method presented in this section facilitates inclusion of
   un-modified payload. When unmodified payloads are included as the
   diagnostic payload, there MUST be methods to identify such OAM
   frames from regular data frames and there MUST be methods to prevent
   such OAM frames leaking out of TRILL network.

9.2.1. Identification of OAM frames

   Egress RBridge receives loopback messages employing hop-count method
   as hop-count expired frames. There MUST be methods to identify OAM
   frames employing hop-count expiry method from other frames that
   experience hop count expiry.

   Firstly, procedures specified in section 6.6. MUST be utilized by
   the egress RBridge to differentiate receiving hop-count expired OAM
   frames from data frames.

   Secondly, the egress RBridge identifies the hop-count expired OAM
   messages from loopback messages utilizing hop-count expiry method by
   examining OAM Message code. OAM messages utilizing hop-count expiry
   method MUST specify TRILL OAM Message code as "Loopback Message
   request with Hop-count" (24).

9.2.2. Prevent leaking out from TRILL network

   First, the ingress RBRidge that is generating the loopback message
   MUST discover the TRILL hop count to the egress RBridge. Hop count
   to the egress RBRidge MAY be discovered either using the Path Trace
   Message specified in section 9.3. or some other method. The
   discovered Hop count MUST be used as the hop count included in the
   TRILL header.

   Further, if the specified payload is IP, the IP header checksum
   SHOULD BE invalidated. The invalidation of IP checksum, prevents end



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   stations further processing the OAM frames, in the unlike event it
   reached the end station.

   All other operations are similar to Loopback Message processing
   presented in section 9.1.

9.3. Path Trace Message

   Primary use of Path Trace Message, commonly known in the IP world as
   "traceroute", is fault isolation. It may also be used for plotting
   path taken from a given RBridge to another RBridge. 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 expect a Time Expiry message from the next hop or a
   successful response. If a Time Expiry message is received as the
   response, the originator RBridge record the information received
   from intermediate node that generated the Time Expiry message and
   resend 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
   reach a configured maximum value.

9.3.1. Theory of Operation

9.3.1.1. Originator RBridge

   Identify the destination RBridge based on user specification or
   based on location of the specified address (see below sections for
   MAC discovery and address locator).

   Construct the diagnostic payload based on user specified parameters.
   Default parameters MUST be utilized for unspecified payload
   parameters. See Figure 4 for default parameters.

   Construct the ICMP Echo request header. Assign applicable
   identification number and sequence number for the request.

   ICMP multi part extension Version MUST be included and set
   appropriate flags. Set the code to Path Trace Request (2)

   Construct following ICMP multipart extensions, where applicable

     o Out-of-band response request

     o Out-of-band IP address

     o Diagnostic VLAN


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   Specify the Hope Count of the TRILL data frame as 1 for the first
   frame. Or use Hope Count value incremented by 1 if this is a
   retransmission generated in response to received Time Expiry
   message.

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

   RBridge may continue to retransmit, the request at periodic
   interval, until a response received or re-transmission count
   expires. At each new re-transmission sequence number may be
   incremented.



9.3.1.2. Intermediate RBridge

   Intermediate RBridge receive the diagnostic frame as Hope count
   expired frame. Based on flow encoding methods explained in above
   section 5, RBridge identify TRILL data plane diagnostic frames from
   actual data frames with Hope count expiry. Hop count time expiry
   messages may be generated for actual data frames as well. However,
   Hop count expiry message for actual data frames are always sent in-
   band, as actual payload does not have methods to specify the
   response delivery method.

   CPU of intermediate RBridge that receives OAM frame with Hope count
   expiry performs following:

   Identify wheather in-band or out of band response requested.
   Construct the IP header accordingly.

   Construct the ICMP Time Expiry message as specified in RFC 792 and
   RFC 4884. RFC 4884 specifies format of ICMP header when including
   ICMP multipart messages.

   Include original TRILL header and diagnostic payload of the original
   frame as data for ICMP Time Expiry message. Update the length field
   to reflect the size of the TRILL header and diagnostic payload.

   Include following ICMP multipart extensions

   Version

   Set the code to Path Trace Response (3)

   Nickname of the RBridge


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   Information of the ingress interface (speed,state,slot,port)

   Index of the interface where frame was received

   nickname of the upstream RBridge the frame was received

   Downstream ecmp count

   List of Downstream RBridges {nickname, interface index and interface
   information}

   Downstream path this specific payload take { RBridge nickname,
   interface index and interface information}

   Optionally include following ICMP multipart extensions

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

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

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

9.3.1.3. Destination RBridge

   Processing is identical to section 8.1.1.3

9.4. Multicast Tree Verification (MTV) Message

   Multicast Tree Verification messages allow verifying multicast tree
   integrity and Multicast address pruning. IGMP snooping is widely
   deployed in Layer 2 networks for restricting forwarding of multicast
   traffic to unwanted destinations. This is accomplished by pruning
   the multicast tree such that for specified (S,G,VLAN) or (*,G,VLAN),
   only required destinations are included in the outgoing interface
   list. It is possible due to timing or implementation defects,
   inaccurate pruning of multicast tree, may occur. Such events lead to
   incorrect multicast connectivity. Multicast tree verification and
   Multicast group verification messages are design to detect such
   multicast connectivity defects. Additionally, these tools can be
   used for plotting a given multicast tree within the TRILL network.

   Multicast tree verification OAM frames are copied to the CPU of
   every intermediate RBridge that are part of the Multicast tree being


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   verified. Originator of the Multicast Tree verification message,
   specify the scope of RBridges that a response is required. Only, the
   RBridges listed in the scope field response to the request. Other
   RBridges silently discard the request. Definition of scope parameter
   is required to prevent receiving large number of responses. Typical
   scenario of multicast 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,
   facilitate narrowing down the focus only to the interested RBridges.

   Implementations MAY choose to rate limit CPU bound multicast
   traffic. As result of rate limiting or due to other congestion
   conditions, time to time, MTV messages may be discarded by the
   intermediate RBRidges and requester may be required to retransmit
   the request. Implementations SHOULD narrow the embedded scope of
   retransmission request only to RBRidges that has failed to respond.

9.4.1. Theory of Operation

9.4.1.1. Originator RBridge

   User is required at minimum to specify either the multicast trees
   that needed to be verified or Multicast MAC address and VLAN or VLAN
   and Multicast destination IP address. Alternatively, for more
   specific multicast flow verification, user MAY specify more
   information e.g. source MAC address, VLAN, Destination and Source IP
   addresses. Implementation, at minimum, must allow user to specify,
   choice of multicast trees, Destination Multicast MAC address and
   VLAN that needed to be verified. Although, it is not mandatory, it
   is highly desired to provide option to specify the scope.

   Default parameters MUST be used for unspecified parameters. Please
   refer to Figure 6 for default payload parameters for MTV message.

   Based on user specified parameters, originating RBridge identify the
   nickname that represent the multicast tree.

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

   Construct the diagnostic payload based on user specified parameters.
   For overall multicast tree verification message only multicast tree
   is specified as input. For generic multicast group verification,
   additional information such as group address is specified. Based on
   user provided parameters, implementation SHOULD identify whether the
   request is for overall multicast tree verification or for specific
   group verification.


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   For overall multicast tree verification, use well known multicast
   destination MAC address (TBD_GMAC-1) defined in above section 6.4.1.
   as the inner destination MAC address of the TRILL frame. Remaining
   parameters are derived based on default values specified in Figure 6

   Construct ICMP echo request message header and include sequence
   number and identifier. Identifier and sequence number facilitate the
   originator to map the response to the correct request.

   Version ICMP multipart extension MUST be included.

   Code MUST be specified as Multicast Tree Verification Request (7)

   Optionally, include following ICMP multipart extensions, where
   applicable

     o Out-of-band response request

     o Out-of-band IP address

     o Diagnostic VLAN

     o In scope RBridge list.

          o  NOTE: "Nu" field in ICMP extension RBridge scope (section
             8.2. ) MUST be set to zero, if response required from all
             RBridges.

   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 diagnostic frame to the TRILL data plane for
   transmission.

   RBridge may continue to retransmit, the request at a periodic
   interval, until a response received or re-transmission count
   expires. At each new re-transmission sequence number may be
   incremented. At each re-transmission, RBRidge may further reduce the
   scope to the RBRidges it has not received a response.



9.4.1.2. Intermediate RBridge

   Intermediate RBridges identify multicast verification frames per the
   procedure explained in section 6.4. .


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   CPU of the RBridge validate the frame and analyze the scope RBridge
   list. If 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, RBridge proceed to section 9.3.1.3
   for further processing.

9.4.1.3.  In scope RBridges

   RBridge go through following processing, upon identifying that it's
   nickname is specified in the scope RBridge list.

   Identify wheather in-band or out of band response requested.
   Construct the IP header accordingly.

   Construct the ICMP echo response message as specified in RFC 792.



   Include TRILL header and diagnostic payload of the received OAM
   message as data of the ICMP response message.

   Include following ICMP multipart extensions

   Version, update the code as Multicast Tree Verification Response (8)

   Nickname of the RBridge

   Name of the ingress interface frame was received

   Interface index where frame was received

   Nickname of the upstream RBRidge the frame was received

   Downstream leaf node count

   Leaf RBridge list {RBridge nickname, interface index and interface
   name}

   Optionally, if VLAN cross connect error detected, then set C flag
   (cross connect error) in the versions extension.

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

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


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   Error Handling:

   RBridge MUST generate applicable notification messages if any error
   such as inner VLAN not available, detected against the OAM message.

9.5. MAC address discovery Message

   MAC address discovery message is defined to discover following
   information

     o RBridge nickname where the MAC address is learnt

     o Interface Index and Name on which the MAC address is learnt

     o Type (i.e. Static, Dynamic, Secure etc.)

     o Age of the MAC address

     o Virtual Interface Tag (vNTAG)

     o Interface Type (Legacy or TRILL Shared)

     o DRB on the VLAN (If Applicable)

     o AF for the VLAN (If Applicable)

     o Time AF operational (If Applicable)

   Optionally, an implementation may include the following information

     o System MAC address of the device connected to the port with
        which the MAC address is associated.

     o System information, such as name, IP address and location of
        the device connected to the port with which the MAC address is
        associated.

     o Information related to this MAC address from the remote
        device..

   The method of obtaining the above optional information is outside
   the scope of this document. However, implementation may consider
   link level control protocols such as LLDP for the purpose.






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9.5.1. Theory of Operation

   There are two possible options to implement MAC address discovery.
   Either we may define a new MAC-discovery ISIS sub-TLV and use ESADI
   to propagate the request (similar to the MAC-Reachability TLV
   [RFC6165]) OR we may use multicast tree verification message and
   include a ICMP multipart extension to indicate that the message is a
   MAC discovery message.

   Using the ISIS based method has disadvantage of being non real time
   and subjected to protocol delays. The second method above is
   independent of any control plane protocol implementation and can be
   exercised in real-time. Hence, in this document, we propose to
   utilize second method.

9.5.1.1. Originator RBridge

   Use the well known Multicast MAC address described in section 6.4.1.
   , above as the inner destination MAC address of the diagnostic
   payload. Use the applicable source MAC address and VLAN. Use the
   diagnostic EthType defined earlier as the EthtType. Pad the
   remainder of the diagnostic payload with zero.

   Construct ICMP echo request message and include sequence number and
   identifier. The sequence number and identifier facilitate the
   originator to map the response to the correct request.

   Construct following ICMP multipart extensions

     o Version

     o Set the OAM code to the MAC address discovery request (9)

     o Indicate that this is a MAC discovery message

     o One or more MAC address to be discovered

     o VLAN ID of  MAC addresses (optional)

     o Service Tag that represent the overlay network (optional)

     o Out-of-band response request (optional)

     o Out-of-band IP address (optional)

     o In scope RBridge list. If response required from all RBridges,
        then the Nu count in RBridge scope list MUST be set to zero.


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   Specify the TTL value of the TRILL data frame to the applicable
   value.

   Set the egress RBridge nickname to the nickname of the multicast
   tree used for broadcast and unknown unciast.

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

   An RBridge may continue to retransmit the request at periodic
   interval until re-transmission count expires. At each new re-
   transmission sequence number may be incremented. The RBridge scope
   list of re-transmission messages MUST be pruned to include only the
   response pending RBridges. It is possible that more than one RBridge
   has learnt the requested MAC address. Hence the implementation MUST
   wait until the total wait time expires and SHOULD NOT abort the
   discovery process on receiving a single response.



9.5.1.2. Receiving RBridges

   CPU of Intermediate RBridges receives a copy of the MAC discovery
   frame through methods explained in section 6.4.2. and 6.4.1.

   Receiving in scope RBridges analyze the embedded ICMP multipart
   extensions to identify whether the request is for MAC discovery.

   If the request is for MAC discovery, then the receiving RBridge
   queries its forwarding database to identify, whether requested MAC
   address is present with specified VLAN information.

   The receiving RBridge generate responses only for identified MAC
   entries. If there are no matching MAC entries, the receiving RBridge
   silently discards the MAC discovery request.

   If a matching MAC address is found, the receiving RBridge generates
   a Destination unreachable ICMP message (Type = 3) and code = 12,
   "Destination host unreachable for type of service". This essentially
   indicates, it has found the MAC address but has reached the end of
   the TRILL network where the MAC address is located.

   RFC 4884 allow extension of ICMP messages. Only ICMP messages
   Destination Unreachable, Time Expired and Parameter Problem are
   currently extensible in RFC 4884 compliant manner. Other messages
   are only extensible for known payload size and considered non
   compliant to RFC 4884. For MAC discovery messages there is no


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   requirement to include original data payload. Also response to MAC
   discovery can contain large amount of MAC address information.
   Hence, we conclude to utilize Destination unreachable message as
   opposed to using an ICMP echo response with fixed pay load size.

   The receiving RBridge constructs the response as follows:

   Construct the IP header based on the requested response type, in-
   band or out-of-band. For an in-band response, use RBridge in-band IP
   address. For an out-of-band response, use the provided egress
   RBridge out-of-band address.

   Construct the ICMP Destination Unreachable message per section 4.1
   of RFC 4884. Specify, ICMP type=3 and code = 12. Specify the length
   as zero. (i.e, no data included and ICMP extensions directly
   follow).

   Construct the pseudo IP header per section 4.3.1.

   Include the following ICMP multi part extensions;

      nickname of this RBridge. (This is required in the event of out -
   of band response to identify the originating RBridge nickname)

      Version

      Code, set to MAC address discovery response (10)

   Additionally, include the following ICMP multipart extensions, for
   each MAC address that was specified in the request and is present in
   the RBridge forwarding DB:

     o Interface Index and Interface Information
        (Speed,Slot,Port,State) on which MAC address learnt

     o Type (i.e. static, Dynamic, Secure etc.)

     o Age of the MAC address

     o Virtual Interface Identification (vNTAG)

     o Interface Type (Legacy or Trill Shared)

     o DRB on the VLAN (If Applicable)

     o AF for the VLAN (If Applicable)



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     o Time AF operational (If Applicable)



   Optionally an implementation may include the following information:

     o The system MAC address of the device connected to the port with
        which the MAC address is associated.

     o System information, such as name, IP address and location of
        the device connected to the port on which MAC address is
        associated.

     o Information related to this MAC address from the remote device.



    If the response size is greater than the maximum MTU size of the
   outgoing interface, then multiple responses MAY be generated. The
   final response frame MUST contain ICMP multipart extension Version
   (C-Type 1) with F (final response)flag set.

   The response frame is delivered to the TRILL data plane for in-band-
   response.

   If out of band response was requested, the response frame is
   delivered to the IP protocol stack.



9.6. Address-Binding Verification Message

   Virtual machine provisioning is a very common practice in data
   centers and enterprises. It is normal for virtual machines to move
   from one physical machine to another physical machine. As a result
   ARP tables on gateways can be stale and network operators may need
   to resort to multiple tools to identify the location of a given IP
   address that is being diagnosed for connectivity. Even if the
   location of the server that host the given IP address is identified
   using other tools, additional steps may be required to further
   identify the RBridge that interface with the physical server.

   It is important to have set of tools that allow an operator to
   quickly and easily identify the physical MAC address associated with
   a given IP address, or IP addresses associated with a given physical
   MAC address. Additionally, it may be required to identify the
   RBridge that connects to the given IP address. In this section, we


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   present methods to identify MAC address to IP addresses or IP
   address to MAC address bindings.

   Address binding tools presented here need to be exercised from
   either a router or an RBridge that has IP services enabled on a
   given VLAN.

   There are two different address binding resolutions required

     1. MAC address to IP addresses binding

     2. IP address to MAC address binding.

   We propose to use invARP [RFC 2390] to resolve MAC address to IP
   address(es) binding and ARP [RFC 826] to resolve IP address to MAC
   binding information. It is possible a given physical server to host
   multiple virtual machines (i.e. IP Addresses). Hence, it is expected
   to receive one or more responses, to an invARP request. However,
   invARP in its current form is incapable of identifying whether a
   single multi-homed host or multiple virtual hosts. At the time of
   RFC 2390 and original ARP standard RFC 892 were written, virtual
   machine concept did not exist. Hence, these protocols in its current
   form do not include virtual machine identifiers such as vNTAGs. This
   lapse of identification of virtual machines, make troubleshooting of
   large virtual machine networks, with dynamic server allocation, very
   difficult. Hence, we propose to extend, ARP [RFC 892] and invARP
   [RFC 2390], protocol to carry, virtual machine identification tags.

   Upon discovery of MAC address or identification that a given MAC
   address is associated with a valid IP addresses, user may employ the
   locator utilities listed in section 9.7. to identify the
   corresponding RBridge and associated interface information.
   Alternatively, implementation may support ARP response snooping with
   extension explained in 9.5.1 to encode RBridge and location
   information into ARP or invARP responses.

9.6.1. Extension to ARP and invARP

   RFC 2390 presents methods to discover protocol address associated
   with a given hardware address. In this section we propose methods to
   extend RFC 2390 and RFC 892 to encode additional virtual interface
   tag information and device information that may facilitate
   identifying physical machine locations.

   It is important the extensions proposed in the standard are
   transparent to current implementations.



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   Figure 53, below, depicts the format of an ARP/invARP frame with the
   proposed extensions embedded.

   ARP frame as defined in RFC 892 and RFC 2390 has a fixed structure
   and include only the length fields for addresses. Implementations
   index in to these fix address fields and do not check the total
   length of the response frame as part of validation. Hence, we
   propose to include the extensions at the end after the target
   protocol address. Implementations that do not support the new
   extensions will safely ignore these values.

   We expect additional identification information carried in ARP and
   invARP to be limited. Furthermore, these, identification information
   have compact and deterministic size. Hence, we propose not to use
   explicit, length identification field, instead derive the length of
   the value field implicitly, based on the class and class types
   defined below. ARP and invARP follow identical encoding structures.
































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     31                      0
     +-----------+-----------+
     | Hw Addr   | Protocol  |
     +-----+-----+-----------+
     | HL  | AL  | Op Code   |
     +-----+-----+-----------+
     |                       |
     . Source Hw Address     .
     |                       |
     +-----------------------+
     |                       |
     . Source Proto Address  .
     |                       |
     +-----------------------+
     |                       |
     . Target Hw Address     .
     |                       |
     +-----------------------+
     |                       |
     . Target Proto Address  .
     |                       |
     +-----------------------+
     | Extensions            |
     .                       .
     |                       |
     +-----------------------+

                  Figure 52   Encoding of ARP and invARP

9.6.1.1. Encoding ARP-invARP extensions

   ARP Extension encoding structure and proposed extensions are
   presented in this section. We propose a compact structure for ARP
   encoding. In Figure 53 "Class" identifies the Object Class and the
   "Class Type" (c-Type) within the class identify specific data
   element within the object class. C-Type implicitly indicates the
   size of the object. The encoded object size MUST NOT exceed the
   implied size of the corresponding Class and c-Type.











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    +-------+------+--------------+
    |Class  |C-Type|              |
    +-------+------+              +
    |                             |
    .     Object                  .
    |                             |
    +-----------------------------+

                  Figure 53   Encoding of ARP Extensions

   Class : (1 octet). Define to identify the Object Class.

   C-Type : (1 octet). Define Object type within Object class.

   Object : (Variable octet, depends on the Class and C-Types)


    +--------+--------+-------+---------------------------------+
    |Class   |C-Type  |Name   | Description                     |
    +--------+--------+-------+---------------------------------+
    |  1     | 1      |vNTAG  |vNTAG of the interface           |
    +--------+--------+-------+---------------------------------+
    |  2     | 1      |RBridge|TRILL RBridge nickname           |
    +--------+--------+-------+---------------------------------+
    |        | 2      |ifindex|ifindex of RBridge interface ARP |
    |        |        |       |response arrived                 |
    +--------+--------+-------+---------------------------------|
    |        | 3      |Slot   |Slot id of RBridge interface ARP |
    |        |        |       |response arrived                 |
    +-----------------------------------------------------------+
    |        | 4      |Port   |Port id of RBridge interface ARP|
    |        |        |       |response arrived                 |
    +--------+--------+-------+---------------------------------+

               Figure 54   Table of Class, C-Type and usage

Figure 54, above, presents Class, c-Type and application definitions.
vNTAG, rBridge, Slot and Port are each 2 octets in length. The length
of ifindex is 4 octets. All of the above extensions are optional. vNTAG
is inserted by the end station that is responding to the ARP request.
All other fields are inserted by the TRILL RBridge that interface with
the end-station and implement ARP response snooping. ARP response
snooping is similar to Dynamic ARP inspections, implemented by many
major vendors. Dynamic ARP inspection validates the Source IP address
of ARP response against known IP addresses to prevent ARP cache
poisoning by rogue stations. ARP response snooping, on the other hand,
intercepts ARP response frames and inserts required fields as defined


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in this standard. Implementations may extend the dynamic ARP inspection
framework to implement ARP response snooping.

In the interim, most end stations and servers may not insert the
proposed vNTAG information. Hence, optionally, ARP response snooping,
process on TRILL RBridge, MAY insert vNTAG information on behalf of the
end station or server.

9.7. End-Station Attachment Point Discovery

   In traditional deployments, end stations and servers were relatively
   static in their locations. As a result localizing a fault was
   relatively easier.

   The virtual machine concept is an increasing trend in Datacenter and
   large enterprises. Dynamic load balancing policies of Virtual
   infrastructure, based on various load balancing policies, move
   virtual machines between different physical servers. This dynamic
   motion of virtual machines causes difficulty in associating a given
   virtual server to a RBridge. As a result, localizing a fault is a
   difficult task and requires use of multiple applications. Some
   virtual machine deployments utilize a single MAC address to
   represent all the virtual servers in a single physical server.
   Hence, it is important, to identify both the physical attachment
   point and the virtual segment information, such as VLAN and Virtual
   Tags.

   ARP/invARP extensions presented above facilitate discovery of the
   attachment information, however, some implementation may face
   scaling issues due to the large number of ARP requests. An
   alternative method is presented below.

   The End-Station attachment Point Discovery methods presented here,
   allow discovering, RBridge, interface information, VLAN, virtual
   Tags, etc, associated with a given IP Address.

   The End-Station attachment Point Discovery is a two step process.
   However implementations may present a single user interface that
   combines both the steps.

   Step 1: Utilize ARP to discover the MAC address associated with the
   specified IP address. Identify the ingress RBridge nickname by
   analyzing the TRILL header and identify the VLAN information based
   on the inner VLAN.

   Step 2: Utilize MAC discovery methods explained above to discover,
   interface and virtual Tag information associated with the MAC


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   address discovered in above Step 1. Implementation SHOULD narrow the
   scope of the MAC discovery to include only the RBridge and VLAN
   discovered in step 1.

9.8. DRB and AF Discovery

   The TRILL Base Protocol standard [RFC 6325] specifies support for
   multi-access legacy network and shared segments between TRILL and
   legacy devices. Legacy networks ensure loop free forwarding via the
   IEEE 802.1D (Spanning Tree) protocol. RFC 6325 and RFC 6327 specify
   loop prevention methods in mixed environments where the TRILL
   network borders with a legacy multi-access network. RFC 6325 also
   provide methods for load splitting of native traffic in to the TRILL
   network. These are accomplished by having a single Designated
   RBridge (DRB) for a given LAN segment which designates an Appointed
   Forwarder (AF) for each VLAN on the segment to ingress and egress
   traffic originating and destined to and from the legacy network.

   Based on network dynamics, configurations, and failures, DRB and/or
   AF designation may change from time to time. Hence, discovery of DRB
   and AF is very important to effectively troubleshoot network
   connectivity problems that involve TRILL and legacy networks
   connected via non P2P TRILL interfaces.

   DRB-AF discovery message has three variations.

     1. All DRB discovery

     2. All AF discovery

     3. VLAN,AF discovery

   Above messages are identified with a unique TRILL OAM message code
   (section 8. ).

   DRB-AF discovery messages allow for identifying the following
   parameters:

     o Nickname of the DRB

     o STP Root Bridge identifier

     o Up time of AF (if responder is the AF)

     o Up time of DRB (if Responder is DRB)

     o Enabled VLAN List


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     o Announcing VLAN List

     o DRB State (If Responder is the DRB)

     o AF State (If Responder is AF)

     o Pseudo Node bypass (If the Responder is the DRB)

     o Number of times the Designated VLAN has changed

     o AF List (nickname,start VLAN,end VLAN)(If the Responder is DRB)

   The above parameters are encoded in to the response message via ICMP
   multipart extensions (section 8. )

9.8.1. Theory of Operation

   DRB-AF discovery message utilize same addressing and format as the
   MAC discovery message (Section 9.5. )

9.8.1.1. Originator RBridge

   Follow the steps specified in section 9.5.1.1. , with the following
   exceptions

   Specify the message as one of the DRB-AF messages.

   If the message is VLAN,AF discovery message, then include the
   interest VLAN list.

9.8.1.2. Receiving RBridge

   Follow the processing steps specified in section 9.5.1.2.  with the
   following exceptions:

   If RBridge is in the scope list or All-RBridge scope is specified,
   then the RBridge processes the message as follows:

   If the message is DRB discovery message then the receiving RBridge
   include the following information:

     o Response code set to DRB discovery response (12)

     o Nickname of the DRB

     o Nickname of AF of the specified VLAN



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     o STP Root Bridge identifier

     o DRB Life time

     o Enabled VLAN List

     o Announcing VLAN List

     o DRB State

     o Pseudo Node bypass

     o Number of times Designated VLAN change

     o AF List (nickname,start VLAN,end VLAN)



   If the message is an AF discovery or VLAN, AF discovery message,
   then the receiving RBridge first validate whether the RBbridge is
   the AF for the specified VLAN list and include following
   information:

     o Response code set AF discover response (14) or AF-VLAN discover
        response (16)

     o Nickname of the DRB

     o Nickname of AF of the specified VLAN or AF VLAN-List if VLAN is
        not specified.

     o STP Root Bridge identifier

     o AF Life time (i.e. How long has been AF)

     o Enabled VLAN List

     o Announcing VLAN List

     o AF State

     o Number of times Designated VLAN change

   If RBridge is not the AF for specified VLAN then include ERROR code
   Not AF (4) (see Figure 27).




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   If RBridge is AF for only a subset of VLANs specified in the request
   then include WARINING "AF VLAN list Mismatch" (3) and include the
   VLAN list that the RBridge is functioning as AF. (Figure 28)

9.9. Diagnostic Payload Discovery for ECMP coverage

   This document specifies that a 128 byte Diagnostic Payload to be
   embedded in the OAM frame. The Diagnostic Payload embedded in the
   OAM frame determines the ECMP path taken by the OAM frame. Hence, It
   is important to have methods that allow operators to discover
   diagnostic payload constructs that direct OAM frames through desired
   ECMP paths. RFC 4379 proposes a method to discover payload
   combinations in MPLS networks. We propose to use a similar approach,
   with some modifications.

   RBridge MUST derive diagnostic payload combination such that when
   applicable hashing methods are applied to the diagnostic payload,
   the OAM frames that contain the diagnostic payload follow the
   requested path. The diagnostic payload contain Destination and
   Source MAC addresses, VLAN Tag, Ethertype, Layer 3 and Layer 4
   addressing information and packet data. TRILL RBridges operate as
   Layer 2 devices and learn source MAC addresses against ingress
   RBridge nickname. Use of any arbitrary MAC address as source MAC
   address may affect RBridge learning. Hence we suggest using either a
   well-known OAM MAC address or operator specified MAC address as the
   source MAC address of the generated diagnostic payload. TRILL, Layer
   2 forwarding happens in the context of a VLAN. Specification of a
   random VLAN in the generated diagnostic payload may lead to
   different forwarding behavior of OAM frames than the actual data
   frames that operator desire to diagnose. Hence, operator is required
   to specify the desired VLAN in the payload generation request.

   Operator generates Payload discovery command from RBridge RB(a), in
   the message operator MUST specify the seed Destination MAC address,
   desired VLAN and required ECMP coverage and final egress RBRidge
   RB(x). Receiving RBrdige (RBi) using the provided information in the
   request and using local hashing algorithm, generates series of
   proposed payloads. The generated payloads are returned to the
   requester. Requester may use the received proposal as a seed and
   request the next RBridge (RBj) downstream from RBi to generate
   diagnostic payloads that would cover the desired ECMP path
   downstream from RB(j). RB(a) may continue this process until
   specific set of payloads are derived such that it covers desired
   paths from ingress RBridge RB(i) to egress RBRidge RB(x). These
   derived payload allows RB(a) to test end-end coverage from RB(a) to
   RB(x) over a specific path.



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   Encoding of proposed MAC address seed require further clarification
   and some illustration to ensure clearer understanding.

   Seed MAC address is encoded in c-type 37 as 6 octet value. A given
   request can contain multiple seeds. Each of the seeds are
   indentified with a unique 12 bit identifier.

   Each zero valued octet in a MAC address seed has a corresponding bit
   value vector (c-type 39). Non-zero octets of the MAC address seed
   are considered fixed valued and are not considered for payload
   proposal generation.

   Bit value vector is 256 bits long. Each bit in the bit vector value
   represents a value for the corresponding octet of the MAC address
   seed. Values that are included in the proposal are represented by
   setting the corresponding bit vector values to 1.

   As an Example let's consider requester desire to use destination MAC
   address 0x00:0A:0B:00:00:00 to 0x00:0A:0B:0F:0F:0F to generate the
   payload proposals.

   Requester encode the destination MAC address seed using c-type 37
   (Seed Destination MAC address) as follows

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 1 1 0 1 0 1 0 0|0 0 0 0|0 0 0 0 0 0 0 0|0 0 0-0 1 0 1 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 1 0 1 1|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Corresponding desired range for each of the octets that contain 0
   (zero) are encoded as follows, using c-type 39 (MAC octet bit
   vector).

   Example encoding of MAC-0:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 1 1 0 1 0 1 0 0|0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Octet zero (MAC-0) of MAC address seed is represented in the above
   c-type 39. Value zero in MAC-0 field of the above c-type 39


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   indicates that other values may be considered for the proposal.
   However, in this example, for MAC-0 user requires maintaining value
   zero and does not desire for the responder to consider other options
   for MAC-0 field. Hence bit vector length is set to zero to indicate
   that.

   Example encoding of MAC-3:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 1 1 0 1 0 1 0 0|0 0 1 1|0 0 0 0 0 0 0 0|0 0 0 1 0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   In the above example MAC-3 bit vector is represented using c-type
   39. Bit vector offset has been set to zero to represent, propose
   value range start from 0. Bit vector length has been set to 16 to
   indicate 16 values from the bit vector offset to be considered for
   the proposal. In this example, the available range for the proposal
   is 0x0 to 0xF.

9.9.1. Theory of Operations

   The ingress RBridge sends an Payload discovery OAM Command Message
   to the intermediate RBridge from which it desires to discover the
   diagnostic payloads for the specified ECMP choices. Also specified
   in the Command Message is the egress RBridge nickname, desired VLAN,
   EthType and ECMP choices.

   As an example consider the topology in Figure 55. RB1 desires to
   identify diagnostic payloads required to cover all of the ECMP
   choices RB2 has towards egress RBridge RB7 for a specific VLANx.

   RB1 generates an ECMP discovery OAM command message to RB2. In the
   ECMP discovery message, RB1 includes egress RBridge nickname (RB7),
   ECMP choices to be covered, interested VLAN (VLANx), Destination MAC
   address seed, and EthType.










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                              +-----+
                      --------| RB3 |---------
                     |        |     |         |
                     |        +-----+         |
     +-----+      +-----+                  +-----+     +-----+
     | RB1 |------| RB2 |     +-----+      | RB6 |     |  RB7|
     |     |      |     |-----| RB4 |------|     |-----|     |
     +-----+      +-----+     |     |      +-----+     +-----+
                     |        +-----+         |
                     |                        |
                     |        +-----+         |
                     |        | RB5 |         |
                      --------|     |---------
                              +-----+

                        Figure 55   Sample Topology



9.9.1.1. Receiving RBridge

   The receiving RBridge (RB2), first, MUST perform the required pre-
   processing and OAM message validation as specified in section 6.6.

   Upon validation of the message, the receiving RBridge, using the
   ECMP selection algorithm of the local RBridge and the payload seed
   received from the requester, derives the required payload proposals
   for the requested ECMP choices such that OAM frames containing the
   proposed diagnostic payloads follow the requested ECMP path. If the
   received payload seed contain multiple seed values, the local
   RBridge is required to consider all of the seed values. Bit vector
   positions of the c-type 39 that do not generate the required ECMP
   choice or local RBridge did not consider for payload generation MUST
   be set to zero.

   If the requested ECMP choice is not available at the Receiving
   RBridge, an ECMP selection error is generated. (e.g.Ingres RBridge
   requested to generate payload for path 10, and local RBridge has
   only 5 paths to the egress RBridge, then ECMP paths 6-10 are at
   error)

   The resulting payload proposals are returned to the requester via
   Payload generation response OAM message. Payload generation response
   OAM message may be delivered either in-band or out of band to the
   requesting RBridge.




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   Following TLVs are required to specify the requested operations and
   results.

   TLVs in the Command Request Message

     o Payload Generation Request (c-type 40)
          o Egress RBridge nickname (c-type 40)
          o ECMP choices (c-type 40)
     o Interested VLAN (c-type 4)
     o Interested EthType (c-type 43)
     o Seed Destination MAC Address (c-type 37)
     o Seed Source MAC Address (c-type 38) (optional)
     o MAC Octet bit-vector (c-type 39)
     o Service Tag (c-type 23) (optional)
   TLVS in the Command Response Message

     o Payload generation response (c-type 41) (for each ECMP choice)
          o ECMP choice status (for each of the requested ECMP)
     o Interested VLAN (c-type 4)
     o Interested EthType (c-type 43)
     o Seed Destination MAC Address (c-type 37)
     o Seed Source MAC Address (c-type 38) (optional, included only if
        present in the request)
     o MAC Octet bit-vector (c-type 39) (bit values appropriately set)
     o Service Tag (c-type 23) (optional)
   Please see section 8.2. for encoding format of the applicable TLVs.

   The request originator may utilize the above payload proposals
   received from an intermediate RBridge to iteratively discover
   payload proposals along the path from ingress RBridge to the desired
   RBridge. At each of the iteration requester may utilize received
   proposals as seeds to the next hop downstream RBridge.

9.10. Notification Messages

   Notification messages are generated either due to regular TRILL data
   frames or TRILL OAM frames. Implementation MUST not generate
   notification messages on notification messages.




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   There are 3 types of Notification messages:

     o Time Expiry
     o Destination Unreachable
     o Parameter Problem

   Within these Notification messages, error, warning and information
   ICMP extensions may be included to identify the details of the
   notification message. Section 4.3. above covers details of encoding
   Notification messages, section 8.2. covers ICMP extensions.

   Time expiry messages are generated when TRILL hope-count field reach
   to zero. If applicable, It may contain additional error, warning or
   information extensions.

   Destination unreachable notification may be generated for following
   scenarios; additional scenarios may be added later.

     o Egress RBridge nickname unknown
     o Inner VLAN does not exist or suspended
     o Not the AF for inner VLAN

   Parameter Problem notification may be generated for following
   scenarios; additional scenarios may be added later.

     o Invalid RBridge nickname (RBridge nickname is one of the
        reserved 0xFFC0 - 0xFFFF)
     o MTU mismatch
     o Invalid VLAN (Reserved VLANs)
     o Interface state is not forwarding



10. Monitoring and Reporting

   Proactive identification of data plane failures are important part
   of maintaining Service Level Agreements (SLA). In traditional Layer
   2, networks, there is only a single active path to monitor and both
   multicast and unicast traffic follow identical paths. With TRILL,
   there are multiple active paths and unicast and multicast traffic
   take potentially different paths, depending on the flow parameters.

   TRILL deployment in a typical data center may have 10's of 1000 of
   links and 100's of RBridges. In such an enviorement, there may be
   large number of active paths between two end points. As an example,
   assume a topology with 4 RBridges connected serially with 32 ECMP
   links at each hop. In the stated example topology, there are


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   32x32x32=32768 possible paths. Monitoring all of the possible path
   combinations is not scalable. However, skipping some combination of
   paths leads to reduce coverage and hence reduced effectiveness of
   monitoring data. Even if one was brave enough to monitor all of the
   links, analyzing and diagnosing a problem is quite cumbersome due to
   the large amount of data. In other words, there must be methods to
   scale the problem and present information in a more concise manner
   that is still effective.

   In this document we propose to use the "region" concept to partition
   the network in to logical sections. Regions are monitored
   independently. Detailed sets of monitoring data are distributed
   throughout the region. A summary set of monitoring data is
   distributed throughout the network. Network operators can obtain a
   network health snapshot of the entire network from any RBridge in
   the network. Detailed health report of a given region can be
   obtained from any RBridge in the region.

   An RBridge associate itself with a region through its interfaces. A
   given interface can belong to one and only one region. An RBridge
   can have multiple interfaces belonging to different regions. Each
   RBridge is responsible for collecting monitoring data, organizing
   the data in to regions and advertising the data to its peers. Please
   see section 10.2, Advertising Policy for details.

   In theory a network topology can be any arbitrary graph. In
   practices, however, it is some set of sub-graphs repeating to
   construct the overall topology. Each sub-graphs or set of sub-graphs
   can be considered a region for monitoring purpose. The manner in
   which regions are partitioned is an administrative choice such that;

      1. Maximize the fault coverage.

      2. Optimize network health data summarization.

   As an example consider a typical datacenter topology depicted in
   Figure 10. Typical datacenter may have multiple Points of
   Demarcation (POD)s connected with an aggregation layer. A POD can be
   considered as a region and may be individually monitored.










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                 +o--o+        +o---o+      +o--o+
    +~~~~~~~~~~~~|    |~~~~~~~~|     |~~~~~~|    |~~~~~~~~~~~~~~~+
    |            | RB |        | RB  |      | RB |               |
    |            +o--o+        +o---o+      +o--o+               |
    |             |  |          |   |        |  |                |
    |                                                            |
    |               Region Rm                                    |
    |                                                            |
    |    |  |    |  |                       |  |    |  |         |
    |   +o--o+  +o--o+                     +o--o+  +o--o+        |
    +~~~| RB |~~| RB |~~~~~~~~~~~~~~~~~~~~~| RB |~~| RB |~~~~~~~~+
      +~|    |~~|    |~~+                +~|    |~~|    |~~+
      | +o--o+  +o--o+  |                | +o--o+  +o--o+  |
      |  |  |    |  |   |                |  |  |    |  |   |
      |                 |                |                 |
      |                 |                |                 |
      |   Region R1     |    . .  .      |   Region Rn     |
      |                 |                |                 |
      |                 |                |                 |
      |  |  |    |  |   |                |  |  |    |  |   |
      | +o--o+  +o--o+  |                | +o--o+  +o--o+  |
      +~|    |~~|    |~~+                +~|    |~~|    |~~+
        | RB |  | RB |                     | RB |  |RB  |
        +-o--+  +o.o.+                     +-o--+  +o.o.+

                     Figure 56   Example of "regions"

10.1. Data categories

   There are 3 categories of monitoring data. They are, Summary
   Category, Detail Category and Vendor Specific Category. The Summary
   and Detail categories are mandatory. That is, every RBridge that is
   compliant to this standard and support Monitoring, MUST support all
   the elements defined under the Summary and Detail categories. The
   Vendor specific Category is optional. Vendor specific data elements
   are only available within the region. An RBridge that does not
   understand the Vendor specific data elements forward them to
   neighboring RBridges per Advertising Policies define in section
   10.2.  Individual data elements and structure of encoding Summary,
   Detail and Vendor specific categories are presented in sections
   10.3. - 10.5. .

10.2. Advertising Policy

   Each RBridge is responsible for advertising monitoring data to the
   OAM capable neighbors.



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   Different interfaces on an RBridge can belong to different regions.
   However a given interface can belong to one and only one region. As
   a result a given RBridge may receive data from multiple regions.
   Each RBridge is responsible for advertising proper data categories
   over a given interface to the neighbor.

   Rule 1: No monitoring data are distributed:

         o On legacy interfaces

         o To neighbors not OAM capable

         o When ISIS state is not 2-way

         o When monitoring data advertisement is disabled

   Rule 2: Distribution of Summary category data:

         o Distribute on all OAM capable interfaces

         o Do not distribute summary data element of a region back to
            the originating region. (i.e. do not distribute on to
            interfaces that have the same region name as the data
            element)

         o Summary data for local region is derived from Detail data.
            (local summary data is never advertised into the local
            region per the above rule. However, it is advertised out to
            other regions the RBridge has interfaces in to)

   Rule 3: Distribution of Detail category

         o Distributed on OAM capable interfaces

         o Region of the data element and region of the interface must
            match for propagating a data element over an interface
            (i.e. Do not advertise to other regions)

         o Do not advertise data element back in to the originator
            RBridge.

   Each RBridge distribute data at periodic intervals. Each RBridge
   collects data it has received, analyzes them and redistribute
   according to the rules specified above. The distribution interval
   should be appropriately adjusted to not overload ISIS routing
   operations.



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   Then Monitoring application is responsible for maintaining the
   Application specific LSP. We propose to use Generic Application
   Encoding methods explained in [GenAPP] for distributing Monitoring
   data. TRILL operates in ISIS Level-1 layer, hence S,D flags defined
   in [GenAPP] MUST be set to zero.

   We propose to obtain specific Application ID [GenAPP][RFC5226] from
   IANA for the purpose of registering TRILL Monitoring data
   distribution.

   Within the Application ID context, a series of sub-TLV are defined
   to carry specified information.

10.2.1. Multi Instance ISIS and Flooding Scope

   As presented above, Summary data has a flooding scope of the entire
   ISIS domain and Detail and Vendor data have a flooding scope of the
   applicable monitoring region.

   [ISISMI] provides a frame work to define multiple instances of ISIS
   and multiple instances of ISIS topologies within a given ISIS
   instance. These topologies may have different flooding scopes. The
   flooding scope of a topology limits the extent of the distribution
   of an LSP associated with that topology. Topologies defined within
   the ISIS TRILL-OAM instance are independent of the TRILL data plane
   multi-topology definitions within the TRILL ISIS protocol instance.

   It is recommended to have a separate ISIS instance for the purpose
   of TRILL-OAM. Within the TRILL-OAM ISIS instance, the following
   topologies MUST be defined with the specified flooding scope.

   The Global Topology is created within the TRILL-OAM ISIS instance to
   include all of the RBridges in the OAM domain. Summary category
   GenAPP data LSPs are flooded within the scope of the Global
   Topology.

   Regional Topologies are created within the TRILL-OAM ISIS instance
   per each region for regions a given RBridge is associated with. A
   Regional Topology includes RBridges and interfaces within the
   applicable region. LSPs carrying Detail and Vendor category data are
   flooded within the applicable Regional Topology.

10.3. Summary Category

   Then following individual data elements are defined within the
   summary category.



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     o Name of the region

     o Total number of RBridges in the regions

     o Total number of TRILL enabled ports in the region

     o Percentage of TRILL enabled ports down

     o Percentage of TRILL enabled ports oversubscribed

     o Maximum number of paths in the largest ECMP in the region



   Then following structure encodes each of the data elements within
   the summary category.

       +----------+
       | subTlv   |            2 octets
       +----------+----------+
       | Region-ID           | 4 octets
       +---------------------+
       |L |                  |
       .--+                  .
       .                     .
       |                     |
       +----------+----------+
       | #Rbrdidge|            2 octets
       +----------+
       | #Ports   |            2 octets
       +----------+
       | #UpPorts |            2 octets
       +----------+
       | #OsubPort|            2 octets
       +----------+
       | #ErrPorts|            2 octets
       +----------+
       | #ECMP    |            2 octets
       +----------+
       | #DwnPorts|            2 octets
       +----------+

                Figure 57   Encoding Summary Category Data

   subType : (2 octets) is always 1 for summary category




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   Regiond-ID : (4 octets) is unsigned 32 bit integer identifier of the
   region

   L     : ( 1 octet), length of the subsequent field

   Region Name : '\0' terminated ASCII string of region name of
   variable size to maximum of 255 octets.

   #Rbridge: (2 octets), number of RBridges in the region

   #Ports: (2 octets) Total number of TRILL enabled ports available on
   this RBridge

   #Up Ports: (2 octets) Total number of TRILL enabled ports that are
   operationally up.

   #OSPorts : (2 octets) Total number of TRILL enabled ports that are
   oversubscribed.

   #ErrPorts : (2 octets) Total number of TRILL enabled ports that are
   indicating errors.

   #DwnPorts : (2 octets) Total number of TRILL enabled ports that are
   operationally down.

   #ECMP : (2 octets) Maximum number of ECMP as seen by this region
   ISIS routing table.



10.4. Detail Category

   Following data elements MUST be present within the detail category.

     o Name of the region

     o Name of the RBridge

     o RBridge up time

     o Total number of neighbors

     o Total number of TRILL enabled ports in the RBridge

     o Total number of TRILL enabled ports Up

     o Total number of TRILL enabled ports oversubscribed


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     o Total number of TRILL enabled ports observing errors

     o Maximum number of links in the largest ECMP of the switch

     o Port data: Name of each TRILL enabled Port and Port state (Up,
        oversubscribed, error) and interface index.

     o Adjacency Matrix

          o List of {neighbor RBridge nickname and interface index of
             ports connecting to the neighbor RBridge}.

          o NOTE: Interface index in the Adjacency matrix is used as
             key in to port data to obtain Port name and state.



































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       +----------+
       | subType  |            2 octets
       +----------+
       | RBridge  |
       +----------+----------+
       | Region-ID           | 4 octets
       +---------------------+
       | L|                  |
       .--+                  .
       .   Region Name       .
       |                     |
       +----------+----------+
       |  UpTime             |
       |                     | 8 octets
       +---------------------+
       | #Ports   |            2 octets
       +----------+
       | #Up Ports|            2 octets
       +----------+
       | #OsubPort|            2 octets
       +----------+
       | #ErrPorts|            2 octets
       +----------+
       | #ECMP    |            2 octets
       +----------+
       | #DwnPorts|            2 octets
       +----------+
       | subtype-2|            2 octets
       +----------+----------+
       |                     |
       .   Port Data         .
       .                     .
       |                     |
       +----------+----------+
       | subtype-3|             2 octets
       +----------+----------+
       |                     |
       .  Adjacency Matrix   .
       .                     .
       |                     |
       +---------------------+

                 Figure 58   Encoding Detail Category Data

   subType : (2 octets) always 2 for Detail category

   RBridge: (2 octets) TRILL RBridge nickname [RFCtrill]


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   Regiond-ID : (4 octets) unsigned 32 bit integer identifier of the
   region

   L     : ( 1 octet), length of the subsequent field

   Region Name : '\0' terminated ASCII string of region name of
   variable size to maximum of 255 octets.

   Up Time: (8 octets), number of seconds RBridge has been operational.
   If an RBridge reaches maximum count, it MUST NOT rollover.

   #Ports: (2 octets) Total number of TRILL enabled ports available on
   this RBridge

   #Up Ports: (2 octets) Total number of TRILL enabled ports that are
   operationally up.

   #OSPorts : (2 octets) Total number of TRILL enabled ports that are
   oversubscribed.

   #ErrPorts : (2 octets) Total number of TRILL enabled ports that are
   indicating errors.

   #DwnPorts : (2 octets) Total number of TRILL enabled ports that are
   operationally down.

   #ECMP : (2 octets) Maximum number of ECMP as seen by this RBridge
   ISIS routing table.

   subtype-2: (2 octets): Set to 3. Following this sub type is the
   variable length Port Data. See below for details

   sutype-3: (2 octets): Set to 4. Following this sub type is the
   variable length Adjacency Matrix. See below for details















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       +----------+
       | subType  |            2 octets
       +----------+
       | RBridge  |
       +----------+----------+
       | F |                   1 octets
       +----------+
       | subtype-p|            2 octets
       +----------+----------+
       | ifindex             | 4 octets
       +----------+----------+
       | Slot     | Port     |
       .----------+----------+
       | Speed    | State    |
       +---------------------+

                      Figure 59   Encoding Port data

   subType : (2 octets) Set to3 for Port Data

   RBridge: (2 octets) TRILL RBridge nickname [RFCtrill]

   Regiond-ID : (4 octets) unsigned 32 bit integer identifier of the
   region

   L     : ( 1 octet), length of the subsequent field in octets.

   Region Name : '\0' terminated ASCII string of region name of
   variable size to maximum of 255 octets.

   F : (1 octet) Flag. When set, indicates this is the last Port data
   set from this node. It is possible Port data encoding to exceed MTU
   size due to large number of interfaces. The F flag allows to for
   advertising the information in multiple LSP packets.

   subtype-p: (2 octets) set to 5 to indicate that this is a single
   Port entry within subtype 3. SubType 5 MUST always be embedded with
   subtype 3. Within subtype 3 there can be multiple subtype 5, one for
   each port entry.

   Ifindex : (4 octets) 32 bit unsigned integer, used as key to port
   data advertised.

   Slot     (2 octets) : Slot number

   Port     (2 octets) : Port number



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   Speed    (2 octets) : Speed in 100Mbps. Zero (0) indicates port
   speeds less than 100Mbps.

   State    (2 octets) : Represent the state of the port.

   0: Down - no errors
   1: Disable
   2: Forwarding-no errors
   3: Down - errors
   4: Forwarding - errors
   5: Forwarding - oversubscribed
   6: Link Monitoring disable
   All other values reserved.




       +----------+
       | subType  |            2 octets
       +----------+
       | RBridge  |
       +----+-----+
       | F  |                  1 octets
       +----+-----+
       | subtype-a|            2 octets
       +----------+
       | nrBridge |            2 octets
       +----------+
       | #ports   |            2 octets
       +----------+----------+
       | ifindex             | 4 octets
       +---------------------+
       .                     .
       +---------------------+

                   Figure 60   Encoding Adjacency Matrix

   subType : (2 octets) set to 4 for Adjacency Matrix

   RBridge: (2 octets) TRILL RBridge nickname [RFCtrill]

   Regiond-ID : (4 octets) unsigned 32 bit integer identifier of the
   region

   L     : ( 1 octet), length of the region name in octets




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   Region Name : '\0' terminated ASCII string of region name of
   variable size to a maximum of 255 octets.

   F : (1 octet) Flag.  When set, indicates this is the last Port data
   set from this node. It is possible Port data encoding to exceed MTU
   size due to large number of interfaces. The F flag allows to for
   advertising the information in multiple LSP packets.

   subtype-a: (2 octets) set to 6 to indicates a single adjacency entry
   within subtype 4. SubType 6 MUST always be embedded with subtype 4.
   Within subtype 4, there can be multiple subtype 6, one for each
   adjacency.

   nrBRIDGE : (2 octets), nickname of the next hop RBridge

   #ports : (2 octets), total number of parallel links from RBridge to
   nrBRIDGE

   Ifindex : (4 octets) 32 bit unsigned integer, used as key to port
   data advertised.

10.5. Vendor Specific Category

   Vendors may specify additional data elements to be distributed as
   part of the monitoring data suite. All vendor specific data elements
   MUST contain the regions name and follow the structure defined
   below.






















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       +----------+
       | subType  |            2 octets
       +----------+
       | RBridge  |            2 octets
       +----------+----------+
       | Region-ID           | 4 octets
       +---+-----------------+
       | L |                 |
       .---+                 .
       .  Region Name        .
       |                     |
       +----------+----------+
       | Vendor OUI          | 4 octets
       +---------------------+
       |                     |
       . Vendor specific     .
       .  Information        .
       |                     |
       +---------------------+


            Figure 61   Encoding Vendor specific category Data

   subType : (2 octets) set to250 for Vendor specific category

   RBridge: (2 octets) TRILL RBridge nickname [RFCtrill]

   Regiond-ID : (4 octets) unsigned 32 bit integer identifier of the
   region

   L     : ( 1 octet), length of the region name in octets

   Region Name : '\0' terminated ASCII string of region name of
   variable size to maximum of 255 octets.

   Vendor OUI : 3 octets of IEEE vendor OUI. Right justified. Most
   significant octet in network byte order is set to zero and ignored
   on recipt.

   Vendor specific information : variable size and vendor dependent.

11. Traffic Triggered Monitoring (TTM)

   Identification and verification of faults as well as fault
   monitoring methods using simplified payload structures were
   presented in previous sections of this document. In practice some
   faults may be due to more complex relationship between several


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   flows. The Traffic Triggered Monitoring methods presented in this
   section proposes methods to monitor and analyze traffic passing
   through different Test Points (TP) in the network. Additionally,
   some of the methods presented earlier require having one or more
   fields of the payload to be fixed to some known pattern. Use of
   known patterns in payloads, while adequate in many occasions, may
   not be adequate in other occasions. TTM allows operators to monitor
   and/or diagnose a network using actual live traffic, with minimum or
   no impact on actual data flow. The TTM Framework has the following
   components.

   TTM Profile: Is bound to a TTM Test Point (interface). Specify the
   structure of the data stream (i.e. MAC, IP address, VLAN etc) that
   need to be monitored and associated actions, frequency and duration.

   TTM Initiator: An RBridge or external station that initiates a TTM
   profile.

   TTM Receptor: An RBridge that installs and monitors TTM Profiles on
   a TP on behalf of a TTM Initiator.

   TTM Test Point (TP): An interface on a specified RBridge.

   TTM Messages: TTM Messages provides a messaging framework for TTM
   related inter RBridge communications. The TTM messaging framework is
   an extension to the OAM command messages.

   TTM ingress End Point: The TTM ingress End Point is the ingress
   RBridge of the specified flow.

   TTM egress End Point: The TTM egress End Point is the egress RBridge
   of the specified flow.

















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       <-- --------------------->
           TTM Messages
                           TTM Receptor-1
                              +-----+
                      --------| RB3 |---------
                     |      TP|     |         |
     TTM Initiator   |        +-----+         |
     +-----+      +-----+   TTM Receptro-2 +-----+     +-----+
     | RB1 |------| RB2 |     +-----+      | RB6 |     |  RB7|
     |     |      |     |-----| RB4 |------|     |-----|     |
     +-----+      +-----+   TP|     |TP    +-----+     +-----+
    TTM ingress EP   |        +-----+         |
                     |     TTM Receptor-3     |       TTM egress EP
                     |        +-----+         |
                     |      TP| RB5 |         |
                      --------|     |---------
                              +-----+

                 Figure 62   Traffic Triggered Monitoring



11.1. TTM Policy

   The TTM policy is a high level container that defines rules and
   actions. The TTM policy contains several sections.

     o TTM pattern
     o TTM mask
     o TTM Class
     o TTM frequency
     o TTM count
     o TTM actions
     o TTM Test Point
     o TTM Ingress Point
     o TTM Egress Point

   TTM pattern: The TTM pattern can be either 128byte opaque data or
   set of fixed fields. The 128byte opaque data section allows users to
   define a required pattern.  The TTM fixed fields are Dest MAC, Src
   MAC, VLAN, EthType, Src IP, Dest IP, TTL, Protocol Type, or Src/Dest
   UDP ports.

   TTM mask: The TTM mask allows users to further refine the pattern
   matching criteria.




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   TTM Class: The TTM Class defines whether the TTM policy is Forward
   Flow Monitoring (FFM) or Reverse Flow Monitoring (RFM). Please see
   below for details.

   TTM frequency: TTM frequency defines the frequency of actions
   specified.

   TTM Count: TTM Count defines number of times the given TTM actions
   such as Capturing, Logging, Sampling and Injecting must be applied.
   Count is a 32bit unsigned integer. 1 indicates single instance.
   0xFFFF indicates continued application until the TTM is removed by
   user actions.

   TTM actions: TTM actions are

     o count RX frames
     o count TX frames
     o count RX bytes
     o count TX bytes
     o count errors,
     o log,
     o Capture etc.

   NOTE: TTM action counters are 64bits wide. Counter values may be
   distributed using the distribution framework, specified in section
   10. Distribution of counter values allows user to monitor statistics
   from any remote RBridge.

     Logging indicates logging a copy of the received frame in to a
     locally defined space.

     Capture indicates forwarding a copy of the frame matching the TTM
     policy to a remote destination.

     Implementation of logging and capture are outside the scope of the
     document.

   TTM Test Point: TTM Test Point is an interface on an RBridge where
   the specified TTM profile is applied. User may either specify one or
   more interfaces or specify automatic. The automatic scope indicates
   the Receptor RBridge will derive the Test Points using ingress and
   egress End Point specifications.

   TTM ingress End Point: TTM ingress End Point is the nickname of the
   ingress RBridge.




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   TTM egress End Point: TTM egress End Point is the nickname of the
   egress RBridge.

11.2. TTM Commands

   TTM commands:

     o TTM Set
     o TTM Get
     o TTM Remove
     o TTM Response
     o TTM Indications

   TTM Set message is OAM Message type 17. This message is originated
   by the Initiator to install a TTM profile.

   TTM Get message is OAM Message type 18. This message is originated
   by the Initiator to Get a TTM profile or sub component of a profile
   such as a counter.

   TTM Remove message is OAM Message type 19. This message is
   originated by the Initiator to Remove a TTM profile.

   TTM Response message is OAM Message type 20. This message is
   originated by the Receptor in response to one of the Set, Get or
   Remove messages. The Response message contains a message sub-code to
   indicate whether it is a response to a Set, Get or Remove message.
   It also contains the status code of the original request.

   TTM Indications are generated by the receptors in response to
   asynchronous events such as packet capture.

   TTM policies are encoded in to the OAM command messages using
   structures defined in section 8.2.

   Forward Flow Monitoring (FFM)

   The exact path taken by a given frame depends on the pattern of the
   payload. Forward Flow monitoring allows users to specify TTM
   profiles that match a specified policy in the direction of the
   normal traffic flow. i.e. Traffic ingress from the TTM ingress End
   Point and egress from the TTM egress End Point.







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11.3. Reverse Flow Monitoring (RFM)

   Traffic is bi-directional in nature. Any effective OAM solution
   should have methods to detect and monitor traffic flows in both
   forward and reverse directions. RFM allows users to:

   1. Monitor frames traversing in the reverse direction. That is
   frames traversing from TTM egress End Point to TTM ingress End
   Point.

   2. Inject a given data frame from a specified RBridge (RBe) to
   (RBi). The TTM policy contains additional user data field that
   specify the frame that is to be injected from RBe to RBi.

12. Security Considerations

   Security considerations are under investigation.

13. IANA Considerations

13.1. IANA considerations

   Following IANA considerations are required

13.1.1. ICMP Extensions

   Request IANA to assign new Class-Num for TRILL OAM ICMP extensions.

   Request to form a sub-registry under ICMP extensions to include c-
   types defined in this document and allocate future requests.
   Currently c-types 1-20 are defined in section 8.2.

13.1.2. TRILL-OAM UDP port

   Request IANA to assign a well-known UDP port for the purpose of
   TRILL-OAM. Details of usage of well-known UDP port are presented in
   section 4.3.1.

13.1.3. ARP Extensions

   Request IANA to form a new registry to allocate ARP extensions
   defined in section 9.6.1. . Class-Num allocated within ARP
   extensions are allocated by IANA on first come first serve basis. C-
   type within a given Class-Num are defined by owners of the Class-Num
   and sub-registry MUST be established within ARP extensions.




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13.1.4. Well known Multicast MAC

   Request IETF authority to allocate one of the TRILL allocated
   Multicast MAC address (01-80-C2-00-00-43 to 01-80-C2-00-00-4F)for
   the purpose.

13.2. IEEE Registration Authority Consideration

   Well known unicast MAC address for the purpose of identifying OAM
   frames.

   Well known unciast MAC address for the purpose of identifying
   certain OAM frames.

   EthType <TBD> for the purpose of identifying OAM frames.



14. References

14.1. Normative References

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

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

   [RFC6326] Eastlake, Donald. et.al. "Transparent Interconnection of
             Lots of Links (TRILL) Use of IS-IS", RFC 6326, July 2011.

   [RFC6327] Eastlake, Donald. et.al. "Routing Bridges (RBridges):
             Adjacency", RFC 6327, July 2011.

   [RFC6165] Barnajee, A. and Ward, D." Extensions to IS-IS for Layer-2
             Systems", RFC 6165, April 2011.

   [GenApp]  Ginsberg, L. et.al. "Advertising Generic Information in
             IS-IS", draft-ietf-isis-genapp-04.txt, November,2010.

   [RFC4884] Bonica, R. et.al "Extended ICMP to support Multi-Part
             messages",RFC 4884, April, 2007.

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



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   [TRILLCH] Eastlake, Donald. et.al. "RBridges: TRILL RBridge Channel
             Support", draft-ietf-trill-channel-02.txt, Work in
             Progress, July, 2011.

   [TRILLOAM] Bond, D. and Manral, V. "RBridges: Operations,
             Administration and Maintenance (OAM) Support", draft-ietf-
             trill-rbridge-oam-00.txt, Work in Progress, July, 2011.

   [PINGEXT] Shen, N. et.al. "Traceroute and Ping Message Extensions",
             draft-shen-traceroute-ping-msg-ext-03.txt, Work in
             Progress, October, 2011.

   [ISISMI] Previdi, S. et.al. "IS-IS Multi-Instance", draft-ietf-isis-
             mi-05.txt, Work in Progress, October, 2011.



14.2. Informative References

   [RFC792]  Postel, J. "Internet Control Message Proctocol (ICMP)",
             RFC 792, September, 1981.

   [RFC826]  Plummer, D. "Address Resolution Protocol", RFC 826,
             November, 1982.

   [RFC2390] Bradley, T. et.al. "Inverse Address Resolution Protocol",
             September, RFC 2390, 1988.

   [RFC5226] Narten, T. and Alverstand, H. "Guidelines for writing an
             IANA sections in RFCs", RFC 5226, May 2008.

15. Acknowledgments

   Authors wish to thank people who volunteered to review this document
   and provided comments. Les Ginsberg provided guidance, comments and
   support in defining usage of GenApp and ISIS-MI. Carlos Pignataro
   and Naiming Shen provided valuable comments related to ICMP
   extensions.

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









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Appendix A.                 Reports

A.1. Sample Reports

   In this section we present sample reports of summary data and sample
   output of detail data.

A.2. Summary Report

Region  Number         Max ECMP   Total#     % of Up   %of Ports       Err
        of switches               Of Ports   Ports    Oversubscribed   Ports
xxx        40              16        400        100              10      1
yyy         8               2        25          75               6      0




































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A.3. Detail Report

    Region Name : <xx>

   Total Number of Switches in the region   : 10
   Total Number of Core Ports in the region : 16
   Number of Operationally up Core Ports    : 14
   Number of Oversubscribed Core Ports      : 2
   Number of Error Core Ports               : 0

   Maximum Switch Up Time  : 15days:8Hr:10M:0S
   Minimum Switch Up Time  : 0days:0Hr:1M:0S

   Switch Adjacency Matrix:

   (*) oversubscribed Links
   (x) down Links
   (?) error Links

   Switch        Next Hop switch                Interfaces
    S1                S2                        eth81,eth8/2(*),eth81
                                                 eth 10/2(x)

                      S3                        eth5/1 (?)

                      S4                        eth5/2,eth7/1

    S2                S1                        eth4/1,eth4/2,eth3/1
                                                eth3/2(x)



















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A.4. C-Type usage in messages

   The Table below lists various OAM messages and applicable mandatory
   and optional c-types.

   +------------------+---------------------+------------------+
   | Message          | Mandatory Parameters|OptionalParameters|
   +------------------+---------------------+------------------+
   |Loopback Request  | Version (1)         | VLAN (4)         |
   |                  |                     | Service Tag (23) |
   |                  |                     | Out-of-band      |
   |                  |                     | request Flag (1) |
   |                  |                     | Reverse Path (26)|
   |                  |                     | Control Plane    |
   |                  |                     | Verification (24)|
   |                  |                     | Originator       |
   |                  |                     | IP address    (2)|
   +------------------+---------------------+------------------+
   |Loopback Response |Version (1)          |Reverse Path      |
   |                  |Cross Connect Error  |Response      (27)|
   |                  |Flag (1)             |Control Plane     |
   |                  |Final Flag (1)       |Response      (25)|
   +------------------+---------------------+------------------+
   |Path Trace        | Version (1)         |VLAN          (4) |
   |Request           |                     |Service Tag   (23)|
   |                  |                     |Out-of-band       |
   |                  |                     |request flag  (1) |
   |                  |                     |Reverse Path  (26)|
   |                  |                     |Control Plane     |
   |                  |                     |Verification  (24)|
   |                  |                     |Originator        |
   |                  |                     |IP address    (2) |
   +------------------+---------------------+------------------+
   |Path Trace        |Version (1)          |Reverse Path      |
   |Response          |Cross Connect Error  |Response      (27)|
   |                  |Flag (1)             |Control Plane     |
   |                  |Final Flag (1)       |Response      (25)|
   |                  |Upstream             |                  |
   |                  |Identification    (2)|                  |
   |                  |Downstream           |                  |
   |                  |Identification    (5)|                  |
   |                  |Path of this         |                  |
   |                  |Payload           (6)|                  |
   +------------------+---------------------+------------------+


                Figure 63   Optional and Mandatory c-types


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   +------------------+---------------------+------------------+
   |Message           |Mandatory Parameters |OptionalParameters|
   +------------------+---------------------+------------------+
   |Multicast Tree    |Version           (1)|VLAN          (4) |
   |Verification      |                     |Service Tag   (23)|
   |Request           |                     |In Scope      (14)|
   |                  |                     |Control Plane     |
   |                  |                     |Verification  (24)|
   |                  |                     |Originator        |
   |                  |                     |IP address    (2) |
   +------------------+---------------------+------------------+
   |Multicast Tree    |Version    (1)       |Control Plane     |
   |Verification      |Cross Connect Error  |Response      (25)|
   |Response          |Flag       (1)       |                  |
   |                  |Final Flag (1)       |                  |
   |                  |Upstream             |                  |
   |                  |Identification (2)   |                  |
   |                  |Multicast Tree       |                  |
   |                  |Downstream List (15) |                  |
   |                  |RBridge nickname(35) |                  |
   +------------------+---------------------+------------------+

                Figure 64   Optional and Mandatory c-types


Authors' Addresses

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

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










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   Dinesh G Dutt
   CISCO Systems
   3800 Zankar Road
   San Jose, CA 95134

   Email: ddutt@cisco.com


   Vishwas Manral
   Hewlett-Packard Co.
   19111 Pruneridge Ave.
   Cupertino, CA  95014


   Phone: 408-447-0000
   EMail: vishwas.manral@hp.com


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

   Email: aldrin.ietf@gmail.com

























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