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Versions: (draft-salam-trill-oam-framework) 00 01 02 03 04 RFC 7174

TRILL Working Group                                          Samer Salam
INTERNET-DRAFT                                        Tissa Senevirathne
Intended Status: Informational                                     Cisco

                                                              Sam Aldrin
                                                         Donald Eastlake
                                                                  Huawei

Expires: November 24, 2013                                  May 23, 2013


                          TRILL OAM Framework
                   draft-ietf-trill-oam-framework-02


Abstract

   This document specifies a reference framework for Operations,
   Administration and Maintenance (OAM) in TRILL networks. The focus of
   the document is on the fault and performance management aspects of
   TRILL OAM.


Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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Copyright and License Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the



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   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.2 Relationship to Other OAM Work . . . . . . . . . . . . . . .  5
   2. TRILL OAM Model . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.1 OAM Layering . . . . . . . . . . . . . . . . . . . . . . . .  6
       2.1.1 Relationship to CFM  . . . . . . . . . . . . . . . . . .  7
       2.1.2 Relationship to BFD  . . . . . . . . . . . . . . . . . .  8
       2.1.3 Relationship to Link OAM . . . . . . . . . . . . . . . .  8
     2.2 TRILL OAM in the RBridge Port Model  . . . . . . . . . . . .  8
     2.3 Network, Service and Flow OAM  . . . . . . . . . . . . . . . 10
     2.4 Maintenance Domains  . . . . . . . . . . . . . . . . . . . . 11
     2.5 Maintenance Entity and Maintenance Entity Group  . . . . . . 12
     2.6 MEPs and MIPs  . . . . . . . . . . . . . . . . . . . . . . . 12
     2.7 Maintenance Point Addressing . . . . . . . . . . . . . . . . 14
   3. OAM Frame Format  . . . . . . . . . . . . . . . . . . . . . . . 15
     3.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 15
     3.2 Determination of Flow Entropy  . . . . . . . . . . . . . . . 17
       3.2.1 Address Learning and Flow Entropy  . . . . . . . . . . . 17
     3.3 OAM Message Channel  . . . . . . . . . . . . . . . . . . . . 18
     3.4 Identification of OAM Messages . . . . . . . . . . . . . . . 18
   4. Fault Management  . . . . . . . . . . . . . . . . . . . . . . . 18
     4.1 Proactive Fault Management Functions . . . . . . . . . . . . 18
       4.1.1 Fault Detection (Continuity Check) . . . . . . . . . . . 19
       4.1.2 Defect Indication  . . . . . . . . . . . . . . . . . . . 19
         4.1.2.1 Forward Defect Indication  . . . . . . . . . . . . . 19
         4.1.2.2 Reverse Defect Indication (RDI)  . . . . . . . . . . 20
     4.2 On-Demand Fault Management Functions . . . . . . . . . . . . 20
       4.2.1 Connectivity Verification  . . . . . . . . . . . . . . . 20
         4.2.1.1 Unicast  . . . . . . . . . . . . . . . . . . . . . . 21
         4.2.1.2 Multicast  . . . . . . . . . . . . . . . . . . . . . 21
       4.2.2 Fault Isolation  . . . . . . . . . . . . . . . . . . . . 22
   5. Performance Monitoring  . . . . . . . . . . . . . . . . . . . . 22



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     5.1 Packet Loss  . . . . . . . . . . . . . . . . . . . . . . . . 23
     5.2 Packet Delay . . . . . . . . . . . . . . . . . . . . . . . . 23
   6. Operational and Manageability Considerations  . . . . . . . . . 24
     6.1 TRILL OAM Configuration  . . . . . . . . . . . . . . . . . . 24
       6.1.1 Maintenance Domain Parameters  . . . . . . . . . . . . . 24
       6.1.2 Maintenance Association Parameters . . . . . . . . . . . 24
       6.1.3 Maintenance Endpoint Parameters  . . . . . . . . . . . . 25
       6.1.4 Continuity Check Parameters (applicable per MA)  . . . . 25
       6.1.5 Connectivity Verification Parameters (applicable per
             operation) . . . . . . . . . . . . . . . . . . . . . . . 25
       6.1.6 Fault Isolation Parameters (applicable per operation)  . 26
       6.1.7 Packet Loss Monitoring . . . . . . . . . . . . . . . . . 27
       6.1.8 Packet Delay Monitoring  . . . . . . . . . . . . . . . . 28
     6.2 TRILL OAM Notifications  . . . . . . . . . . . . . . . . . . 28
     6.3 Collecting Performance Monitoring Metrics  . . . . . . . . . 29
   7. Security Considerations . . . . . . . . . . . . . . . . . . . . 30
   8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 30
   9. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 30
   10.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 30
     10.1  Normative References . . . . . . . . . . . . . . . . . . . 30
     10.2  Informative References . . . . . . . . . . . . . . . . . . 31
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32





























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1.  Introduction

   This document specifies a reference framework for Operations,
   Administration and Maintenance (OAM, [RFC6291]) in TRILL (Transparent
   Interconnection of Lots of Links) networks.

   TRILL [RFC6325] specifies a protocol for shortest-path frame routing
   in multi-hop networks with arbitrary topologies and link
   technologies, using the IS-IS routing protocol. TRILL capable devices
   are referred to as TRILL Switches or RBridges (Routing Bridges).
   RBridges provide an optimized and transparent Layer 2 delivery
   service for Ethernet unicast and multicast traffic. Some
   characteristics of a TRILL network that are different from IEEE 802.1
   bridging are the following:

   - TRILL networks support arbitrary link technology between TRILL
   switches. Hence, a TRILL switch port may not have a 48-bit MAC
   Address [802] but might, for example, have an IP address as an
   identifier [TRILL-IP] or no unique identifier (PPP [RFC6361]).

   - TRILL networks do not enforce congruency of unicast and multicast
   paths between a given pair of RBridges.

   - TRILL networks do not impose symmetry of the forward and reverse
   paths between a given pair of RBridges.

   - TRILL switches terminate spanning tree protocols instead of
   propagating them.

   In this document, we refer to the term OAM as defined in [RFC6291].
   The Operations aspect involves finding problems that prevent proper
   functioning of the network.  It also includes monitoring of the
   network to identify potential problems before they occur.
   Administration involves keeping track of network resources.
   Maintenance activities are focused on facilitating repairs and
   upgrades as well as corrective and preventive measures. [ISO/IEC
   7498-4] defines 5 functional areas in the OSI model for network
   management, commonly referred to as FCAPS:

   -Fault Management
   -Configuration Management
   -Accounting Management
   -Performance Management
   -Security Management

   The focus of this document is on the first and fourth functional
   aspects, Fault Management and Performance Management, in TRILL
   networks. These primarily map to the "Operations" and "Maintenance"



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   part of OAM.

   This draft provides a generic framework for a comprehensive solution
   that meets the requirements outlined in [RFC6905]. However, specific
   mechanisms to address these requirements are considered to be outside
   the scope of this document.

1.1  Terminology

   The following acronyms are used in this document:

      BFD - Bidirectional Forwarding Detection [RFC5880]
      CFM - Connectivity Fault Management [802.1Q]
      ECMP - Equal Cost Multi-Pathing
      FGL - Fine Grained Label(ing) [TRILL-FGL]
      IEEE - Institute for Electrical and Electronic Engineers
      IP - Internet Protocol, includes both IPv4 and IPv6
      LAN - Local Area Network
      MAC - Media Access Control [802]
      MA - Maintenance Association
      ME - Maintenance Entity
      MEP - Maintenance End Point
      MIP - Maintenance Intermediate Point
      MP - Maintenance Point (MEP or MIP)
      OAM - Operations, Administration, and Maintenance [RFC6291]
      PPP - Point-to-Point Protocol [RFC1661]
      RBridge - Routing Bridge, a device implementing TRILL [RFC6325]
      RDI - Reverse Defect Indication
      TRILL - Transparent Interconnection of Lots of Links [RFC6325]
      TRILL Switch - an alternate name for an RBridge
      VLAN - Virtual LAN [802.1Q]

1.2 Relationship to Other OAM Work

   OAM is a technology area where a wealth of prior art exists. This
   document leverages concepts and draws upon elements defined and/or
   used in the following documents:

   [RFC6905] defines the requirements for TRILL OAM that serve as the
   basis for this framework. It also defines terminology that is used
   extensively in this document.

   [802.1Q] specifies the Connectivity Fault Management (CFM) protocol,
   which defines the concepts of Maintenance Domains, Maintenance End
   Points, and Maintenance Intermediate Points.

   [Y.1731] extends Connectivity Fault Management in the following
   areas: it defines fault notification and alarm suppression functions



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   for Ethernet.  It also specifies mechanisms for Ethernet performance
   management, including loss, delay, jitter, and throughput
   measurement.

   [TRILL-BFD] defines a TRILL encapsulation for BFD that enables the
   use of the latter for network fast convergence.

2. TRILL OAM Model

2.1 OAM Layering

   In the TRILL architecture, the TRILL layer is independent of the
   underlying Link Layer technology. Therefore, it is possible to run
   TRILL over any transport layer capable of carrying TRILL packets such
   as Ethernet [RFC6325], PPP [RFC6361], or IP [TRILL-IP]. Furthermore,
   TRILL provides a virtual Ethernet connectivity service that is
   transparent to higher layer entities (e.g. Layer 3 and above). This
   strict layering is observed by TRILL OAM.

   Of particular interest is the layering of TRILL OAM with respect to:

   - BFD, which is typically used for fast convergence

   - Ethernet CFM [802.1Q] on paths from an external device, over a
   TRILL campus, to another external device, especially since TRILL
   switches are likely to be deployed where existing 802.1 bridges can
   be such external devices.

   - Link OAM, on links interior to a TRILL campus, which is link
   technology specific.

   Consider the example network depicted in Figure 1 below, where a
   TRILL network is interconnected via Ethernet links:


















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                           LAN                LAN
           +---+   +---+  ======  +---+  =============  +---+
    +--+   |   |   |   | | +--+ | |   | | +--+   +--+ | |   |   +--+
    |B1|---|RB1|---|RB2|---|B2|---|RB3|---|B3|---|B4|---|RB4|---|B5|
    +--+   |   |   |   | | +--+ | |   | | +--+   +--+ | |   |   +--+
           +---+   +---+  ======  +---+  =============  +---+

    a. Ethernet CFM (Client Layer) on path over the TRILL campus
       >---o------------------------------------------------o---<


    b. TRILL OAM (Network Layer)
               >------o-----------o---------------------<


    c. Ethernet CFM (Transport Layer) on interior Ethernet LANs
                      >---o--o---<    >---o--o---o--o---<


    d. BFD (Media Independent Link Layer)
              #---#   #----------#   #-----------------#


    e. Link OAM (Media Dependent Link Layer)
       *---*   *---*   *---*  *---*   *---*  *---*  *---*   *---*


    Legend:  >, < MEP    o MIP    # BFD Endpoint    * Link OAM Endpoint

   Figure 1: OAM Layering in TRILL

   Where Bn and RBn (n= 1,2,3, ...) denote IEEE 802.1Q bridges and TRILL
   RBridges, respectively.

2.1.1 Relationship to CFM

   In the context of a TRILL network, CFM can be used as either a client
   layer OAM or a transport layer OAM mechanism.

   When acting as a client layer OAM (see Figure 1a), CFM provides fault
   management capabilities for the user, on an end-to-end basis over the
   TRILL network. Edge ports of the TRILL network may be visible to CFM
   operations through the optional presence of a CFM Maintenance
   Intermediate Point (MIP) in the TRILL switches edge Ethernet ports.

   When acting as a transport layer OAM (see Figure 1c), CFM provides
   fault management functions for the IEEE 802.1Q bridged LANs that may
   interconnect RBridges. Such bridged LANs can be used as TRILL level



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   links between RBridges. RBridges directly connected to the
   intervening 802.1Q bridges may host CFM Down Maintenance End Points
   (MEPs).

2.1.2 Relationship to BFD

   One-hop BFD (see Figure 1d) runs between adjacent RBridges and
   provides fast link as well as node failure detection capability
   [TRILL-BFD]. Note that TRILL BFD also provides some testing of the
   TRILL protocol stack and thus sits a layer above Link OAM, which is
   media specific. BFD provides fast convergence characteristics to
   TRILL networks. The requirements for BFD are different from those of
   the TRILL OAM mechanisms that are the prime focus of this document.
   Furthermore, BFD does not use the frame format described in section
   3.1.

   TRILL BFD differs from TRILL OAM in two significant ways:

   1. A TRILL BFD transmitter is always bound to a specific TRILL output
   port.

   2. TRILL BFD messages can be transmitted by the originator out a port
   to a neighbor RBridge when the adjacency is in the Detect or Two-Way
   states as well as when the adjacency is in the Report (Up) state
   [RFC6327].

   In contrast, TRILL OAM messages are typically transmitted by
   appearing to have been received on a TRILL input port (refer to
   Section 2.2 for details). In that case, the output ports on which
   TRILL OAM message are sent are determined by the TRILL routing
   function. The TRILL routing function will only send on links that are
   in the Report state and have been incorporated into the local view of
   the campus topology.

2.1.3 Relationship to Link OAM

   Link OAM (see Figure 1e) depends on the nature of the technology used
   in the links interconnecting RBridges. For example, for Ethernet
   links, [802.3] Clause 57 OAM may be used.

2.2 TRILL OAM in the RBridge Port Model

   TRILL OAM processing can be represented as a layer situated between
   the port's TRILL encapsulation/de-capsulation function and the TRILL
   Forwarding Engine function, on any RBridge port. TRILL OAM requires
   services of the RBridge forwarding engine and utilizes information
   from the IS-IS control plane. Figure 2 below depicts TRILL OAM
   processing in the context of the RBridge port model defined in



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   [RFC6325]. In this figure, double lines represent flow of both frames
   and information.

   This figure shows a conceptual model. It is to be understood that
   implementations need not mirror this exact model as long as the
   intended OAM requirements and functionality are preserved.













































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           +-----------------------------------------------+----
           |            (Flow of OAM Messages)       RBridge
           |         +----------------------+
           |         |+-------------------+||  Forwarding Engine,
           |         ||                    ||  IS-IS, Etc.
           |         ||                    ||  Processing of
           |         V                      V  TRILL packets
           +---------------------------------------------+-----
                     ||                     ||          ...other ports
               +------------+             +------------+
   UP MEP   /\ | TRILL OAM  |             | TRILL OAM  | /\ UP MEP
   MIP      () |   Layer    |             |   Layer    | () MIP
   DOWN MEP \/ +------------+             +------------+ \/ DOWN MEP
               |   TRILL    |             |   TRILL    |
               | Encap/Decap|             | Encap/Decap|
               +------------+             +------------+
               |End Station |             |End Station |
               |VLAN &      |             |VLAN &      |
               |Priority    |             |Priority    |
               |Processing  |             |Processing  |
               +------------+             +------------+ <-- ISS
               |802.1/802.3 |             |802.1/802.3 |
               |Low Level   |             |Low Level   |
               |Control     |             |Control     |
               |Frame       |             |Frame       |
               |Processing, |             |Processing, |
               |Port/Link   |             |Port/Link   |
               |Control     |             |Control     |
               |Logic       |             |Logic       |
               +------------+             +------------+
               | 802.3PHY   |             | 802.3PHY   |
               |(Physical   |             |(Physical   |
               | interface) |             | interface) |
               +------------+             +------------+
                 ||                         ||
                Link                       Link



   Figure 2: TRILL OAM in RBridge Port Model

   Note that the terms "MEP" and "MIP" in the above figure are explained
   in detail in section 2.6 below.

2.3 Network, Service and Flow OAM

   OAM functions in a TRILL network can be conducted at different
   granularity. This gives rise to 'Network', 'Service' and 'Flow' OAM,



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   listed in order of finer granularity.

   Network OAM mechanisms provide fault and performance management
   functions in the context of a 'test' VLAN or fine-grained label
   [TRILL-FGL]. The test VLAN can be thought of as a management or
   diagnostics VLAN that extends to all RBridges in a TRILL network. In
   order to account for multipathing, Network OAM functions also make
   use of test flows (both unicast and multicast) to provide coverage of
   the various paths in the network.

   Service OAM mechanisms provide fault and performance management
   functions in the context of the actual VLAN or fine-grained label set
   for which end station service is enabled. Test flows are used here,
   as well, to provide coverage in the case of multipathing.

   Flow OAM mechanisms provide the most fine grained fault and
   performance management capabilities, where OAM functions are
   performed in the context of end station flows within VLANs or fine-
   grained labels. While Flow OAM provides the most granular control, it
   clearly poses scalability challenges if attempted on large numbers of
   flows.

2.4 Maintenance Domains

   The concept of Maintenance Domains, or OAM Domains, is well known in
   the industry. IEEE [802.1Q] defines the notion of a Maintenance
   Domain as a collection of devices (e.g. network elements) that are
   grouped for administrative and/or management purposes. Maintenance
   domains usually delineate trust relationships, varying addressing
   schemes, network infrastructure capabilities, etc.

   When mapped to TRILL, a Maintenance Domain is defined as a collection
   of RBridges in a network for which connectivity faults and
   performance degradation are to be managed by a single operator. All
   RBridges in a given Maintenance Domain are, by definition, managed by
   a single entity (e.g. an enterprise or a data center operator, etc.).
   [RFC6325] defines the operation of TRILL in a single IS-IS area, with
   the assumption that a single operator manages the network. In this
   context, a single (default) Maintenance Domain is sufficient for
   TRILL OAM.

   However, when considering scenarios where different TRILL networks
   need to be interconnected, for example as discussed in [TRILL-ML],
   then the introduction of multiple Maintenance Domains and Maintenance
   Domain hierarchies becomes useful to map and enforce administrative
   boundaries. When considering multi-domain scenarios, the following
   rules must be followed: TRILL OAM domains must not partially
   intersect, but must either be disjoint or nest to form a hierarchy



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   (i.e. a higher Maintenance Domain may completely enclose a lower
   Domain). A Maintenance Domain is typically identified by a Domain
   Name and a Maintenance Level (a numeric identifier). If two domains
   are nested, the encompassing domain must be assigned a higher
   Maintenance Level number than the enclosed domain. For this reason,
   the encompassing domain is commonly referred to as the 'higher'
   domain, and the enclosed domain is referred to as the 'lower' domain.
   OAM functions in the lower domain are completely transparent to the
   higher domain. Furthermore, OAM functions in the higher domain only
   have visibility to the boundary of the lower domain (for example, an
   attempt to trace the path in the higher domain will depict the entire
   lower domain as a single-hop between the RBridges that constitute the
   boundary of that lower domain). By the same token, OAM functions in
   the higher domain are transparent to RBridges that are internal to
   the lower domain. The hierarchical nesting of domains is established
   through operator configuration of the RBridges.

        +-------------------+  +---------------+  +-------------------+
        |                   |  |     TRILL     |  |                   |
        |       Site 1     +----+Interconnect +----+    Site 2        |
        |       TRILL      | RB |  Network    | RB |    TRILL         |
        |      (Level 1)   +----+  (Level 2)  +----+   (Level 1)      |
        |                   |  |               |  |                   |
        +-------------------+  +---------------+  +-------------------+

        <------------------------End-to-End Domain-------------------->

        <----Site Domain----> <--Interconnect --> <----Site Domain---->
                                   Domain

                         Figure 3: TRILL OAM Maintenance Domains

2.5 Maintenance Entity and Maintenance Entity Group

   TRILL OAM functions are performed in the context of logical endpoint
   pairs referred to as Maintenance Entities (ME). A Maintenance Entity
   defines a relationship between two points in a TRILL network where
   OAM functions (e.g. monitoring operations) are applied. The two
   points that define a Maintenance Entity are known as Maintenance End
   Points (MEPs) - see section 2.6 below. The set of Maintenance End
   Points that belong to the same Maintenance Domain are referred to as
   a Maintenance Association (MA). On the network path in between MEPs,
   there can be zero or more intermediate points, called Maintenance
   Intermediate Points (MIPs).  MEPs can be part of more than one ME in
   a given MA.

2.6 MEPs and MIPs




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   OAM capabilities on RBridges can be defined in terms of logical
   groupings of functions that can be categorized into two functional
   objects: Maintenance End Points (MEPs) and Maintenance Intermediate
   Points (MIPs). The two are collectively referred to as Maintenance
   Points (MPs).

   MEPs are the active components of TRILL OAM: MEPs source TRILL OAM
   messages periodically or on-demand based on operator configuration
   actions. Furthermore, MEPs ensure that TRILL OAM messages do not leak
   outside a given Maintenance Domain, e.g. out of the TRILL network and
   into end stations. MIPs, on the other hand, are internal to a
   Maintenance Domain. They are the more passive components of TRILL
   OAM, primarily responsible for forwarding TRILL OAM messages and
   selectively responding to a subset of these messages.

   The following figure shows the MEP and MIP placement for the
   Maintenance Domains depicted in Figure 3 above.


           TRILL Site 1          Interconnect       TRILL Site 2
        +-----------------+ +------------------+ +-----------------+
        |                 | |                  | |                 |
        |  +---+  +---+  +---+  +---+  +---+  +---+  +---+  +---+  |
        |  |RB1|--|RB2|--|RB3|--|RB4|--|RB5|--|RB6|--|RB7|--|RB8|  |
        |  +---+  +---+  +---+  +---+  +---+  +---+  +---+  +---+  |
        |                 | |                  | |                 |
        +-----------------+ +------------------+ +-----------------+

            <E------------I--------------------I-------------E>

            <E------I----E><E----I-------I----E><E-----I-----E>



         Legend E: MEP      I: MIP

                              Figure 4: MEPs and MIPs

   A single RBridge may host multiple MEPs of different technologies,
   e.g. TRILL OAM MEP(s) and [802.1Q] MEP(s). This does not mean that
   the protocol operation is necessarily consolidated into a single
   functional entity on those ports. The protocol functions for each MEP
   remain independent and reside in different shims in the RBridge Port
   model of Figure 2: the TRILL OAM MEP resides in the "TRILL OAM
   Processing" block whereas a CFM MEP resides in the "End Station VLAN
   & Priority Processing" block.

   In the model of Section 2.2, a single MEP and/or MIP per MA can be



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   instantiated per RBridge port. A MEP is further qualified with an
   administratively set direction (UP or DOWN), as follows:

   - An UP MEP sends and receives OAM messages through the RBridge
   Forwarding Engine. This means that an UP MEP effectively communicates
   with MEPs on other RBridges through TRILL interfaces other than the
   one that the MEP is configured on.

   - A DOWN MEP sends and receives OAM messages through the link
   connected to the interface on which the MEP is configured.

   In order to support TRILL OAM functions on sections, as described in
   [RFC6905], while maintaining the simplicity of a single TRILL OAM
   Maintenance Domain, the TRILL OAM Layer may be implemented on a
   virtual port with no physical layer (Null PHY). In this case, the
   Down MEP function is not supported, since the virtual port does not
   attach to a link; as such, a Down MEP on a virtual port would not be
   capable of sending or receiving OAM messages.

   A TRILL OAM solution that conforms to this framework:

   - must support the MIP function on TRILL ports (to
     support fault isolation)
   - must support the UP MEP function on a TRILL virtual port (to
     support OAM functions on Sections, as defined in [RFC6905])
   - may support the UP MEP function on TRILL ports
   - may support the DOWN MEP function on TRILL ports

2.7 Maintenance Point Addressing

   TRILL OAM functions must provide the capability to address a specific
   Maintenance Point or a set of one or more Maintenance Points in a MA.
   To that end, RBridges need to recognize two sets of addresses:

   - Individual MP addresses

   - Group MP Addresses

   TRILL OAM will support the Shared MP address model, where all MPs on
   an RBridge share the same Individual MP address. In other words,
   TRILL OAM messages can be addressed to a specific RBridge but not to
   a specific port on an RBridge.

   One cannot discern, from observing the external behavior of an
   RBridge, whether TRILL OAM messages are actually delivered to a
   certain MP or another entity within the RBridge. The Shared MP
   address model takes advantage of this fact by allowing MPs in
   different RBridge ports to share the same Individual MP address. The



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   MPs may still be implemented as residing on different RBridge ports
   and for the most part, they have distinct identities.

   The Group MP addresses enable the OAM mechanism to reach all the MPs
   in a given MA. Certain OAM functions, e.g. pruned tree verification,
   require addressing a subset of the MPs in a MA. Group MP addresses
   are not defined for such subsets. Rather, the OAM function in
   question must use the Group MP addresses combined with an indication
   of the scope of the MP subset encoded in the OAM Message Channel.
   This prevents an unwieldy set of responses to Group MP addresses.

3. OAM Frame Format

3.1 Motivation

   In order for TRILL OAM messages to accurately test the data-path,
   these messages must be transparent to transit RBridges. That is, a
   TRILL OAM message must be indistinguishable from a TRILL data packet
   through normal transit RBridge processing. Only the target RBridge,
   which needs to process the message, should identify and trap the
   packet as a control message through normal processing. Additionally
   methods must be provided to prevent OAM packets from being
   transmitted out as native frames.

   The TRILL OAM packet format proposed below provides the necessary
   flexibility to exercise the data path as closely as possible to
   actual data packets.
























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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .      Link Header              . Variable
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   +      TRILL Header             + 8 bytes fixed part of TRILL Header
   |                               | _
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  \
   |   DA   /   SA             |   |   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   |
   |   Data Label              |   |    \  Flow Entropy
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    /  Fixed Size
   .                               .   |
   .                               .   |
   |                               | _/
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       OAM EtherType           | 2 bytes
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .   OAM Message Channel         . Variable
   .                               .
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   .    Link Trailer               . Variable
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Figure 5: OAM Frame Format


   The TRILL Header is as specified in [RFC6325] and amended in [TRILL-
   FGL], and the Link Header and Trailer are as specified for the link
   technology. (Link types standardized so far are [RFC6325] for
   Ethernet and [RFC6361] for PPP). These fields need to be as similar
   as practical to the Link Header/Trailer and TRILL Header of the
   normal TRILL data packet corresponding to the traffic that OAM is
   testing.

   The OAM EtherType demarcates the boundary between the Flow Entropy
   and the OAM Message Channel. The OAM EtherType is expected at a
   deterministic offset from the TRILL Header, thereby allowing
   applications to clearly identify the beginning of the OAM Message
   Channel. Additionally, it facilitates the use of the same OAM frame
   structure by different Ethernet technologies.




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   The Link Trailer is usually a checksum, such as the Ethernet Frame
   Check Sequence, which is examined at a low level very early in the
   frame input process and automatically generated as part of the low
   level frame output process. If the checksum fails, the frame is
   normally discarded with no higher level processing.

3.2 Determination of Flow Entropy

   The Flow Entropy is a fixed length field that is populated with
   either real packet data or synthetic data that mimics the intended
   flow. It always start with a destination and source MAC address area
   followed by a Data Label area (either a VLAN or fine grain label).

   For a Layer 2 flow (i.e. non-IP) the Flow Entropy must specify the
   desired Ethernet header, including the MAC destination and source
   addresses as well as a VLAN tag or fine grain label.

   For a Layer 3 flow, the Flow Entropy must specify the desired
   Ethernet header, the IP header and UDP or TCP header fields, although
   the Ethernet layer header fields are also still present.

   Not all fields in the Flow Entropy field need to be identical to the
   data flow that the OAM message is mimicking. The only requirement is
   for the selected flow entropy to follow the same path as the data
   flow that it is mimicking. In other words, the selected flow entropy
   must result in the same ECMP selection or multicast pruning behavior
   or other applicable forwarding paradigm.

   When performing diagnostics on user flows, the OAM mechanisms must
   allow the network operator to configure the flow entropy parameters
   (e.g. Layer 2 and/or 3) on the RBridge from which the diagnostic
   operations are to be triggered.

   When running OAM functions over Test Flows, the TRILL OAM may provide
   a mechanism for discovering the flow entropy parameters by querying
   the RBridges dynamically, or allow the network operator to configure
   the flow entropy parameters.

3.2.1 Address Learning and Flow Entropy

   Edge TRILL switches, like traditional 802.1 bridges, are required to
   learn MAC address associations. Learning is accomplished either by
   snooping data packets or through other methods. The flow entropy
   field of TRILL OAM messages mimics real packets and may impact the
   address learning process of the TRILL data plane. TRILL OAM is
   required to provide methods to prevent any learning of addresses from
   the flow entropy field of OAM messages that would interfere with
   normal TRILL operation. This can be done, for example, by



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   suppressing/preventing MAC address learning from OAM messages.

3.3 OAM Message Channel

   The OAM Message Channel provides methods to communicate OAM specific
   details between RBridges. [802.1Q] CFM and [RFC4379] have implemented
   OAM message channels. It is desirable to select an appropriate
   technology and re-use it, instead of redesigning yet another OAM
   channel. TRILL is a transport layer that carries Ethernet frames, so
   the TRILL OAM model specified earlier is based on the [802.1Q] CFM
   model. The use of [802.1Q] CFM encoding format for the OAM Message
   channel is one possible choice. [TRILL-OAM] presents a proposal on
   the use of [802.1Q] CFM payload as the OAM message channel.

3.4 Identification of OAM Messages

   RBridges must be able to identify OAM messages that are destined to
   them, either individually or as a group, so as to properly process
   those messages.

   TRILL, as defined in [RFC6325], does not specify a method to identify
   OAM messages. The most reliable method to identify these messages,
   without imposing restrictions on the Flow Entropy field, involves
   modifying the definition of the TRILL header to include an "Alert"
   flag. This flag signals that the contents of the TRILL packet is a
   control message as opposed to user data. The use of such a flag would
   not be limited to TRILL OAM, and may be leveraged by any other TRILL
   control protocol that require in-band behavior. The TRILL header
   currently has two reserved bits that are unused. One of those bits
   may be used as the Alert flag. In order to guarantee accurate in-band
   forwarding behavior, RBridges must not use the Alert flag in ECMP
   hashing decisions. Furthermore, to ensure that this flag remains
   protocol agnostic, TRILL OAM mechanisms must not rely solely on the
   Alert flag to identify OAM messages. Rather, these solutions must
   identify OAM messages based on the combination of the Alert flag and
   the OAM EtherType.

   Since the above mechanism requires modification of the TRILL header,
   it is not backward compatible. TRILL OAM solutions should provide
   alternate methods to identify OAM messages that work on existing
   RBridge implementations, thereby providing backwards compatibility.

4. Fault Management

   Section 4.1 below discusses proactive fault management and Section
   4.2 discusses on-demand fault management.

4.1 Proactive Fault Management Functions



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   Proactive fault management functions are configured by the network
   operator to run periodically without a time bound, or are configured
   to trigger certain actions upon the occurrence of specific events.

4.1.1 Fault Detection (Continuity Check)

   Proactive fault detection is performed by periodically monitoring the
   reachability between service endpoints, i.e. MEPs in a given MA,
   through the exchange of Continuity Check messages. The reachability
   between any two arbitrary MEP may be monitored for a specified path,
   all paths or any representative path. The fact that TRILL networks do
   not enforce congruency between unicast and multicast paths means that
   the proactive fault detection mechanism must provide procedures to
   monitor the unicast paths independently of the multicast paths.
   Furthermore, where the network has ECMP, the proactive fault
   detection mechanism must be capable of exercising the equal-cost
   paths individually.

   The set of MEPs exchanging Continuity Check messages in a given
   domain and for a specific monitored entity (flow, network or service)
   must use the same transmission period. As long as the fault detection
   mechanism involves MEPs transmitting periodic heartbeat messages
   independently, then this OAM procedure is not affected by the lack of
   forward/reverse path symmetry in TRILL.

   The proactive fault detection function must detect the following
   types of defects:

   - Loss of continuity to one or more remote MEPs
   - Unexpected connectivity between isolated VLANs or
     fine-grained labels (mismerge)
   - Unexpected connectivity to one or more remote MEPs
   - Mismatch of the Continuity Check transmission period between MEPs

4.1.2 Defect Indication

   TRILL OAM must support event-driven defect indication upon the
   detection of a connectivity defect. Defect indications can be
   categorized into two types:

4.1.2.1 Forward Defect Indication

   This is used to signal a failure that is detected by a lower layer
   OAM mechanism. Forward Defect indication is transmitted away from the
   direction of the failure. For example, consider a simple network
   comprising of four RBridges connected in series: RB1, RB2, RB3 and
   RB4. Both RB1 and RB4 are hosting TRILL OAM MEPs, whereas RB2 and RB3
   have MIPs. If the link between RB2 and RB3 fails, then RB2 can send a



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   forward defect indication towards RB1 while RB3 sends a forward
   defect indication towards RB4.

   Forward defect indication may be used for alarm suppression and/or
   for purpose of inter-working with other layer OAM protocols. Alarm
   suppression is useful when a transport/network level fault translates
   to multiple service or flow level faults. In such a scenario, it is
   enough to alert a network management station (NMS) of the single
   transport/network level fault in lieu of flooding that NMS with a
   multitude of Service or Flow granularity alarms.

4.1.2.2 Reverse Defect Indication (RDI)

   RDI is used to signal that the advertising MEP has detected a loss of
   continuity defect. RDI is transmitted in the direction of the
   failure. For example, consider the same series network of the
   previous section (4.1.2.1). If RB1 detects that is has lost
   connectivity to RB4 because it is no longer receiving Continuity
   Check messages from the MEP on RB4, then RB1 can transmit an RDI
   towards RB4 to inform the latter of the failure. If the failure is
   unidirectional (i.e. it is affecting the direction from RB4 to RB1),
   then the RDI enables RB4 to become aware of the unidirectional
   connectivity anomaly.

   In the presence of equal-cost paths between MEPs, RDI must be able to
   identify on which equal-cost path the failure was detected.

   RDI allows single-sided management, where the network operator can
   examine the state of a single MEP and deduce the overall health of a
   monitored entity (network, flow or service).

4.2 On-Demand Fault Management Functions

   On-demand fault management functions are initiated manually by the
   network operator either as a one-time occurrence or as an action/test
   that continues for a time bound period. These functions enable the
   operator to run diagnostics to investigate a defect condition.

4.2.1 Connectivity Verification

   As specified in [RFC6905], TRILL OAM must support on-demand
   connectivity verification for unicast and multicast. The connectivity
   verification mechanism must provide a means for specifying and
   carrying in the messages:

   - variable length payload/padding to test MTU related connectivity
   problems.




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   - test message formats as defined in [RFC2544].

4.2.1.1 Unicast

   Unicast connectivity verification operation must be initiated from a
   MEP and may target either a MIP or another MEP. For unicast,
   connectivity verification can be performed at either Network or Flow
   granularity.

   Connectivity verification at the Network granularity tests
   connectivity between a MEP on a source RBridge and a MIP or MEP on a
   target RBridge over a test VLAN or fine grain label and for a test
   flow. The operator must supply the source and target RBridges for the
   operation, and the test VLAN/flow information uses pre-set values or
   defaults.

   Connectivity verification at the Flow granularity tests connectivity
   between a MEP on a source RBridge and a MIP or MEP on a target
   RBridge over an operator specified VLAN or fine grain label with
   operator specified flow parameters.

   The above functions must be supported on sections, as defined in
   [RFC6905]. When connectivity verification is triggered over a
   section, and the initiating MEP does not coincide with the edge
   (ingress) RBridge, the MEP must use the edge RBridge nickname instead
   of the local RBridge nickname on the associated connectivity
   verification messages. The operator must supply the edge RBridge
   nickname as part of the operation parameters.

4.2.1.2 Multicast

   For multicast, the connectivity verification function tests all
   branches and leaf nodes of a multi-destination distribution tree for
   reachability. This function should include mechanisms to prevent
   reply storms from overwhelming the initiating RBridge. This may be
   done, for example, by staggering the replies through the introduction
   of a random delay timer, with a preset upper bound, on the responding
   RBridge ([802.1Q] CFM uses similar mechanisms for Linktrace Reply
   messages to mitigate the load on the originating MEP). The upper
   bound on the timer value should be selected by the OAM solution to be
   long enough to accommodate large distribution trees, while allowing
   the connectivity verification operation to conclude within a
   reasonable time. To further prevent reply storms, connectivity
   verification operation is initiated from a MEP and must target MEPs
   only. MIPs are transparent to multicast connectivity verification.

   Per [RFC6905], multicast connectivity verification must provide the
   following granularity of operation:



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   A. Un-pruned Tree

   - Connectivity verification for un-pruned multi-destination
   distribution tree. The operator in this case supplies the tree
   identifier (root nickname) and campus wide diagnostic VLAN or fine
   grain label.

   B. Pruned Tree

   - Connectivity verification for a VLAN or fine-grain label in a given
   multi-destination distribution tree. The operator in this case
   supplies the tree identifier and VLAN or fine grain label.

   - Connectivity verification for an IP multicast group in a given
   multi-destination distribution tree. The operator in this case
   supplies: the tree identifier, VLAN or fine grain label and IP (S,G)
   or (*,G).

4.2.2 Fault Isolation

   TRILL OAM must support an on-demand connectivity fault localization
   function. This is the capability to trace the path of a Flow on a
   hop-by-hop (i.e. RBridge by RBridge) basis to isolate failures. This
   involves the capability to narrow down the locality of a fault to a
   particular port, link or node. The characteristic of forward/reverse
   path asymmetry, in TRILL, renders fault isolation into a direction-
   sensitive operation. That is, given two RBridges A and B,
   localization of connectivity faults between them requires running
   fault isolation procedures from RBridge A to RBridge B as well as
   from RBridge B to RBridge A. Generally speaking, single-sided fault
   isolation is not possible in TRILL OAM.

   Furthermore, TRILL OAM should support fault isolation over
   distribution trees for both un-pruned as well as pruned trees. The
   former allows the tracing of all active branches of a tree, whereas
   the latter allows tracing of the active subset of branches associated
   with a given Flow.

5. Performance Monitoring

   Performance Monitoring functions are optional in TRILL OAM, per
   [RFC6905]. These functions can be performed both proactively and on-
   demand. Proactive management involves a scheduling function, where
   the performance monitoring probes can be triggered on a recurring
   basis. Since the basic performance monitoring functions involved are
   the same, we make no distinction between proactive and on-demand
   functions in this section.




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5.1 Packet Loss

   Given that TRILL provides inherent support for multipoint-to-
   multipoint connectivity, then packet loss cannot be accurately
   measured by means of counting user data packets. This is because user
   packets can be delivered to more RBridges or more ports than are
   necessary (e.g. due to broadcast, un-pruned multicast or unknown
   unicast flooding). As such, a statistical means of approximating
   packet loss rate is required. This can be achieved by sending
   "synthetic" (i.e. TRILL OAM) packets that are counted only by those
   ports (MEPs) that are required to receive them. This provides a
   statistical approximation of the number of data frames lost, even
   with multipoint-to-multipoint connectivity. TRILL OAM mechanisms for
   synthetic packet loss measurement should follow the statistical
   considerations specified in [MEF35], especially with regards to the
   volume/frequency of synthetic traffic generation and associated
   impact on packet loss count accuracy.

   Packet loss probes must be initiated from a MEP and must target a
   MEP. This function should be supported on sections, as defined in
   [RFC6905]. When packet loss is measured over a section, and the
   initiating MEP does not coincide with the edge (ingress) RBridge, the
   MEP must use the edge RBridge nickname instead of the local RBridge
   nickname on the associated loss measurement messages. The user must
   supply the edge RBridge nickname as part of the operation parameters.

   TRILL OAM mechanisms should support one-way and two-way packet loss
   monitoring. In one-way monitoring, a source RBridge triggers packet
   loss monitoring messages to a target RBridge, and the latter is
   responsible for calculating the loss in the direction from the source
   RBridge towards the target RBridge. In two-way monitoring, a source
   RBridge triggers packet loss monitoring messages to a target RBridge,
   and the latter replies to the source with response messages. The
   source RBridge can then monitor packet loss in both directions
   (source to target and target to source).

5.2 Packet Delay

   Packet delay is measured by inserting time-stamps in TRILL OAM
   packets. In order to ensure high accuracy of measurement, TRILL OAM
   must specify the time-stamp location at fixed offsets within the OAM
   packet in order to facilitate hardware-based time-stamping. Hardware
   implementations must implement the time-stamping function as close to
   the wire as practical in order to maintain high accuracy.

   TRILL OAM mechanisms should support one-way and two-way packet delay
   monitoring. In one-way monitoring, a source RBridge triggers packet
   delay-monitoring messages to a target RBridge, and the latter is



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   responsible for calculating the delay in the direction from the
   source RBridge towards the target RBridge. This requires
   synchronization of the clocks between the two RBridges. In two-way
   monitoring, a source RBridge triggers packet delay monitoring
   messages to a target RBridge, and the latter replies to the source
   with response messages. The source RBridge can then monitor packet
   delay in both directions (source to target and target to source) as
   well as the cumulative round-trip delay. In this case as well,
   monitoring the delay in a single direction requires clock
   synchronization between the two RBridges. Whereas monitoring the
   round-trip delay does not require clock synchronization. Mechanisms
   for clock synchronization between RBridges are outside the scope of
   this document.

6. Operational and Manageability Considerations

6.1 TRILL OAM Configuration

   RBridges may be configured to enable TRILL OAM functions via the
   device Command Line Interface (CLI) or through one of the defined
   management protocols, such as SNMP [RFC3410] or NETCONF [RFC6241].

   In order to maintain the plug-and-play characteristics of TRILL, the
   number of parameters that need to be configured on RBridges, in order
   to activate TRILL OAM, should be kept to a minimum. To that end,
   TRILL OAM mechanisms should rely on default values and auto-discovery
   mechanisms (e.g. leveraging IS-IS) where applicable. The following is
   a non-exhaustive list of configuration parameters that apply to TRILL
   OAM.

6.1.1 Maintenance Domain Parameters

   - Maintenance Domain Name
     An alphanumeric name for the Maintenance Domain. The recommended
     default value is the character string "DEFAULT".

   - Maintenance Domain Level
     An integer in the range 0 to 7 indicating the Level at which the
     Maintenance Domain is to be created. Default value is 0.

6.1.2 Maintenance Association Parameters

   - MA Name
     An alphanumeric name that uniquely identifies the Maintenance
     Association. This is an IETF [RFC2579] DisplayString, with the
     exception that character codes 0-31 (decimal) are not used. The
     recommended default value is a character string set to the value of
     the VLAN or fine grain label as "vl" or "fgl" concatenated with the



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     VLAN ID or FGL ID as an unsigned decimal integer.

   - List of MEP Identifiers
     A list of the identifiers of the MEPs that belong to the MA. This
     is optional, and required only if the operator wants to detect
     missing MEPs as part of the Continuity Check function.

6.1.3 Maintenance Endpoint Parameters

   - MEP Identifier
     An integer, unique over a given Maintenance Association,
     identifying a specific MEP. [802.1Q] CFM limits this to the range 1
     to 8191. This document recommends expanding the range from 1 to
     65535 so that the RBridge Nickname can be used as a default value.
     This will help keep TRILL OAM low-touch in terms of configuration
     overhead.

   - Direction
     Indicates whether this is an UP MEP or DOWN MEP.

   - Associated Interface
     Specifies the interface on which the MEP is configured.

   - MA context
     Specifies the Maintenance Association to which the MEP belongs.

6.1.4 Continuity Check Parameters (applicable per MA)

   - Transmission interval
     Indicates the interval at which Continuity Check messages are sent
     by a MEP.

   - Loss threshold
     Indicates the number of consecutive Continuity Check messages that
     a MEP must not receive from any one of the other MEPs in its MA
     before indicating either a MEP failure or a network failure.
     Recommended default value is 3.


   - VLAN / Fine grain label / Flow parameters
     The VLAN or fine grain label and flow parameters to be used in the
     Continuity Check messages.


   - Hop Count
     The Hop Count to be used in the Continuity Check messages.

6.1.5 Connectivity Verification Parameters (applicable per operation)



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   - MA context
     Specifies the Maintenance Association in which the Connectivity
     Verification operation is to be performed.

   - Target RBridge Nickname (unicast), Tree Identifier (Multicast) and
   IP multicast group
     For unicast, the Nickname of the RBridge that is the target of the
     Connectivity Verification operation. For multicast, the target Tree
     Identifier for un-pruned tree verification or the Tree Identifier
     and IP multicast group (S, G) or (*, G) for pruned tree
     verification.

   - VLAN / Fine grain label / Flow parameters
     The VLAN or fine grain label and flow parameters to be used in the
     Connectivity Verification message.

   - Operation timeout value
     The timeout on the initiating MEP before the Connectivity
     Verification operation is declared to have failed. The recommended
     default value is 5 seconds.

   - Repeat Count
     The number of Connectivity Verification messages that must be
     transmitted per operation. The recommended default value is 1.

   - Hop Count
     The Hop Count to be used in the Connectivity Verification messages.

   - Reply Mode
     Indicates whether the response to the Connectivity Verification
     operation should be sent in-band or out-of-band.

   - Scope List (Multicast)
     List of MEP Identifiers that must respond to the message.

6.1.6 Fault Isolation Parameters (applicable per operation)

   - MA context
     Specifies the Maintenance Association in which the Fault Isolation
     operation is to be performed.

   - Target RBridge Nickname (unicast), Tree Identifier (Multicast) and
   IP multicast group
     For unicast, the Nickname of the RBridge that is the target of the
     Fault Isolation operation. For multicast, the target Tree
     Identifier for un-pruned tree tracing or the Tree Identifier and IP
     multicast group (S, G) or (*, G) for pruned tree tracing.




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   - VLAN / Fine grain label / Flow parameters
     The VLAN or fine grain label and flow parameters to be used in the
     Fault Isolation messages.

   - Operation timeout value
     The timeout on the initiating MEP before the Fault Isolation
     operation is declared to have failed. The recommended default value
     is 5 seconds.

   - Hop Count
     The Hop Count to be used in the Fault Isolation messages.

   - Reply Mode
     Indicates whether the response to the Fault Isolation operation
     should be sent in-band or out-of-band.

   - Scope List (Multicast)
     List of MEP Identifiers that must respond to the message.

6.1.7 Packet Loss Monitoring

   - MA context
     Specifies the Maintenance Association in which the Packet Loss
     Monitoring operation is to be performed.

   - Target RBridge Nickname
     The Nickname of the RBridge that is the target of the Packet Loss
     Monitoring operation.

   - VLAN / Fine grain label / Flow parameters
     The VLAN or fine grain label and flow parameters to be used in the
     Packet Loss monitoring messages.

   - Transmission Rate
     The transmission rate at which the Packet Loss monitoring messages
     are to be sent.

   - Monitoring Interval
     The total duration of time for which a single Packet Loss
     monitoring probe is to continue.

   - Repeat Count
     The number of probe operations to be performed. For on-demand
     monitoring, this is typically set to 1. For proactive monitoring
     this may be set to allow for infinite monitoring.

   - Hop Count
     The Hop Count to be used in the Packet Loss monitoring messages.



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   - Mode
     Indicates whether one-way or two-way loss measurement is required.

6.1.8 Packet Delay Monitoring

   - MA context
     Specifies the Maintenance Association in which the Packet Delay
     monitoring operation is to be performed

   - Target RBridge Nickname
     The Nickname of the RBridge that is the target of the Packet Delay
     monitoring operation.

   - VLAN / Fine grain label / Flow parameters
     The VLAN or fine grain label and flow parameters to be used in the
     Packet Delay monitoring messages.

   - Transmission Rate
     The transmission rate at which the Packet Delay monitoring messages
     are to be sent.

   - Monitoring Interval
     The total duration of time for which a single Packet Delay
     monitoring probe is to continue.

   - Repeat Count
     The number of probe operations to be performed. For on-demand
     monitoring, this is typically set to 1. For proactive monitoring
     this may be set to allow for infinite monitoring.

   - Hop Count
     The Hop Count to be used in the Packet Delay monitoring messages.

   - Mode
     Indicates whether one-way or two-way delay measurement is required.

6.2 TRILL OAM Notifications

   TRILL OAM mechanisms should trigger notifications to alert operators
   to certain conditions. Such conditions include but are not limited
   to:

   - Faults detected by proactive mechanisms.
   - Reception of event-driven defect indications.
   - Logged security incidents pertaining to the OAM message channel.
   - Protocol errors (e.g. caused by mis-configuration).

   Notifications generated by TRILL OAM mechanisms may be via SNMP,



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   Syslog messages [RFC5424] or any other standard management protocol
   that supports asynchronous notifications.

6.3 Collecting Performance Monitoring Metrics

   When performing the optional TRILL OAM Performance Monitoring
   functions, two RBridge designations are involved: a source RBridge
   and a target RBridge. The source RBridge is the one from which the
   Performance Monitoring probe is initiated, and the target RBridge is
   the destination of the probe. The goal being to monitor performance
   characteristics between the two RBridges. The RBridge from which the
   network operator can extract the results of the probe (i.e. the
   Performance Monitoring metrics) depends on whether one-way or two-way
   performance monitoring functions are performed:

   In the case of one-way performance monitoring functions, the metrics
   will be available at the target RBridge.

   In the case of two-way performance monitoring functions, all the
   metrics will be available at the source RBridge, and a subset will be
   available at the target RBridge. More specifically, metrics in the
   direction from source to target as well as the direction from target
   to source will be available at the source RBridge. Whereas, metrics
   in the direction from source to target will be available at the
   target RBridge.


























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7. Security Considerations

   TRILL OAM must provide mechanisms for:

   -     Preventing denial of service attacks caused by exploitation of
   the OAM message channel, where a rogue device may overload the
   RBridges and the network with OAM messages. This could lead to
   interruption of the OAM services and in the extreme case disrupt
   network connectivity. Mechanisms such as control-plane policing
   combined with shaping or rate limiting of OAM messaging can be
   employed to mitigate this.

   -     Optionally authenticate at communicating endpoints (MEPs and
   MIPs) that an OAM message has originated at an appropriate
   communicating endpoint.

   -     Preventing TRILL OAM packets from leaking outside of the TRILL
   network or outside their corresponding Maintenance Domain. This can
   be done by having MEPs implement a filtering function based on the
   Maintenance Level associated with received OAM packets.

   For general TRILL Security Considerations, see [RFC6325].

8. IANA Considerations

   This document requires no IANA Actions. RFC Editor: Please delete
   this section before publication.

9. Acknowledgements

   We thank Gayle Noble, Dan Romascanu, Olen Stokes, Susan Hares, Ali
   Karimi and Prabhu Raj for their thorough review of this work and
   their comments.

10.  References

10.1  Normative References


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

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

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for



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              Network Interconnect Devices", RFC 2544, March 1999.


   [RFC2579]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Textual Conventions for SMIv2", STD
              58, RFC 2579, April 1999.

   [RFC6291]  Andersson et al., BCP 161 "Guidelines for the Use of the
              "OAM" Acronym in the IETF", June 2011.

   [RFC6327]  Eastlake 3rd, D., Perlman, R., Ghanwani, A., Dutt, D., and
              V. Manral, "Routing Bridges (RBridges): Adjacency", RFC
              6327, July 2011.

   [TRILL-FGL] D. Eastlake et al., "TRILL Fine-Grained Labeling", draft-
              ietf-trill-fine-labeling, work in progress.

   [802.1Q]   "IEEE Standard for Local and metropolitan area networks -
              Media Access Control (MAC) Bridges and Virtual Bridge
              Local Area Networks", IEEE Std 802.1Q-2011, 31 August
              2011.

   [802]      "IEEE Standard for Local and Metropolitan Area Networks -
              Overview and Architecture", IEEE Std 802-2001, 8 March
              2002.

10.2  Informative References

   [Y.1731]  "ITU-T Recommendation Y.1731 (02/08) - OAM functions and
              mechanisms for Ethernet based networks", February 2008.

   [ISO/IEC 7498-4] "Information processing systems -- Open Systems
              Interconnection -- Basic Reference Model -- Part 4:
              Management framework", ISO/IEC, 1989.

   [TRILL-BFD] V. Manral, et al., "TRILL (Transparent Interconnetion of
              Lots of Links): Bidirectional Forwarding Detection (BFD)
              Support", draft-ietf-trill-rbridge-bfd-07, work in
              progress, July 2012.

   [TRILL-OAM] T. Senevirathne, et al., "TRILL Fault Management", draft-
              tissa-trill-oam-fm-01, work in progress, February 2013.

   [TRILL-IP] M. Wasserman, et al., "Transparent Interconnection of Lots
              of Links (TRILL) over IP", draft-mrw-trill-over-ip-02,
              work in progress, September 2012.

   [RFC1661]  Simpson, W., Ed., "The Point-to-Point Protocol (PPP)", STD



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              51, RFC 1661, July 1994.

   [RFC6361]  Carlson & Eastlake, "PPP Transparent Interconnection of
              Lots of Links (TRILL) Protocol Control Protocol", RFC
              6361, August 2011.

   [RFC5880] Katz & Ward, "Bidirectional Forwarding Detection (BFD)",
              RFC 5880, June 2010.

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

   [TRILL-ML] Perlman, et al., "Alternatives for Multilevel TRILL",
              draft-perlman-trill-rbridge-multilevel-05, work in
              progress, December 2012.

   [RFC3410] Case, et al., "Introduction and Applicability Statements
              for Internet-Standard Management Framework", RFC 3410,
              December 2002.

   [RFC6241] Enns, et al., "Network Configuration Protocol (NETCONF)",
              RFC 6241, June 2011.

   [RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424, March 2009.

   [MEF35] "MEF 35 - Service OAM Performance Monitoring Implementation
              Agreement", Metro Ethernet Forum, April 2012.



Authors' Addresses


   Samer Salam
   Cisco
   595 Burrard Street, Suite 2123
   Vancouver, BC V7X 1J1, Canada
   Email: ssalam@cisco.com


   Tissa Senevirathne
   Cisco
   375 East Tasman Drive
   San Jose, CA 95134, USA
   Email: tsenevir@cisco.com





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   Sam Aldrin
   Huawei Technologies
   2330 Central Expressway
   Santa Clara, CA 95050, USA
   Email: sam.aldrin@gmail.com


   Donald Eastlake
   Huawei Technologies
   155 Beaver Street
   Milford, MA 01757, USA
   Tel: 1-508-333-2270
   Email: d3e3e3@gmail.com






































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