One document matched: draft-sajassi-mohan-l2vpn-vpls-fm-00.txt


   Internet Draft Document                                Ali Sajassi 
   Layer-2 VPN Working Group                            Cisco Systems 
   draft-sajassi-mohan-l2vpn-vpls-fm-00.txt              Dinesh Mohan 
                                                      Nortel Networks 
                                                                      
   Norm Finn                                           Shahram Davari 
   Thomas Nadeau                                           PMC Sierra 
   Monique Morrow                                                     
   Cisco Systems                                       Vasile Radoaca 
                                                       Nortel Networks 
                                                                      
   Expires: November 2004                                  March 2004 
                                                                         
    
             Fault Management for Virtual Private LAN Services  
                 draft-sajassi-mohan-l2vpn-vpls-fm-00.txt 
    
   1.  Status of this Memo 
    
   This document is an Internet-Draft and is in full conformance 
   with all provisions of Section 10 of RFC2026. 
    
   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups.  Note that      
   other groups may also distribute working documents as Internet-
   Drafts. 
    
   Internet-Drafts are draft documents valid for a maximum of six 
   months and may be updated, replaced, or obsoleted by other documents 
   at any time.  It is inappropriate to use Internet-Drafts as 
   reference material or to cite them other than as "work in progress." 
    
   The list of current Internet-Drafts can be accessed at 
        http://www.ietf.org/ietf/1id-abstracts.txt 
   The list of Internet-Draft Shadow Directories can be accessed at 
        http://www.ietf.org/shadow.html. 
    
   2.  Abstract 
    
    
   3.  Conventions 
    
   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 
    
   Placement of this Memo in Internet Area 
    
   RELATED DOCUMENTS 
    
    
    
     
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   http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-vpls-
   requirements-00.txt 
   http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-l2-framework-
   03.txt 
   http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-vpls-ldp-01.txt 
    
    
   WHERE DOES THIS FIT IN THE PICTURE OF THE Internet WORK 
    
   L2VPN 
    
   WHY IS IT TARGETED AT THIS WG 
    
   This draft describes Fault Management mechanisms/procedures for VPLS 
   which is a Layer-2 VPN. 
    
   JUSTIFICATION 
    
   This draft describes Fault Management mechanisms/procedures for VPLS 
   which is a Layer-2 VPN. 
    
    
 
   Table of Contents 
    
   1. Status of this Memo.............................................1 
   2. Abstract........................................................1 
   3. Conventions.....................................................1 
   4. Overview........................................................3 
   5. Layering........................................................4 
   5.1. OAM Domains...................................................5 
   5.2. Maintenance & Intermediate Points.............................6 
   5.2.1. Maintenance and Intermediate Points IDs.....................8 
   6. Fault Management Mechanisms.....................................8 
   6.1. Fault Detection...............................................8 
   6.2. Fault Verification...........................................10 
   6.3. Fault Isolation..............................................10 
   7. Fault Management Messages......................................11 
   7.1. Generic Ethernet OAM Frame - Header Information..............11 
   7.2. Generic Ethernet OAM Frame û OAM Body Information............12 
   7.3. Continuity Check.............................................12 
   7.4. Loopback.....................................................13 
   7.5. TraceRoute...................................................13 
   7.5.1. TraceRoute Request Format..................................13 
   7.5.2. TraceRoute Reply Format....................................13 
   8. Acknowledgments................................................14 
   9. Security Considerations........................................14 
    
     
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   10. Intellectual Property Considerations..........................14 
   11. Full Copyright Statement......................................14 
   12. References....................................................15 
   13. Authors' Addresses............................................15 
    
    
   4.  Overview 
    
   The Scope of network management functionality (aka OAM&P: Operation, 
   Administration, Maintenance, and Provisioning) for any network 
   technology is very broad in nature  
    
   OSI has defined the following five generic functional areas for 
   network management, commonly abbreviated as ôFCAPSö [NM-Standards]: 
   Fault Management (FM), Performance Management, Configuration 
   Management, Accounting Management, and Security Management. This 
   draft only deals with Fault Management aspects of OAM&P for VPLS and 
   defines mechanisms and procedures for it. Performance management 
   aspects of OAM&P for VPLS are addressed in a companion draft [PM- 
   MOHAN-SAJASSI].  
    
   Fault Management can further be sub-divided into the following 
   categories: 
            
     - Fault Detection 
     - Fault Verification 
     - Fault Isolation 
     - Fault Notification 
     - Fault Recovery 
    
   Fault Detection deals with mechanism(s) that can detect both hard 
   failures, such as link and node failures, and soft failures, such as 
   software failure, memory corruption, mis-configuration, etc. 
   Typically a lightweight protocol is desirable to detect the fault 
   and thus it would be prudent to verify the fault via Fault 
   Verification mechanism before taking additional steps in isolating 
   the fault. After verifying that a fault has occurred along the data 
   path, it is important to be able to isolate the fault to a given 
   node or link (e.g., diagnose the fault). Therefore, a Fault 
   Isolation mechanism is needed in Fault Management. Fault 
   Notification mechanism can be used in conjunction with Fault 
   Detection mechanism to notify the upstream and downstream nodes of a 
   fault. Finally, Fault Recovery deals with recovering from the 
   detected failure by switching to an alternate available node or link 
   (e.g., node redundancy or link redundancy). 
    
   The scope of this draft is limited to the first three aspects of the 
   Fault Management, i.e. Fault Detection, Fault Verification and Fault 
   Isolation, in the context of provider networks.  
    
     
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   This document first starts off with a description and a reference 
   model for OAM layering and furthermore emphasizes the importance of 
   proper independent layering in design and development of OAM 
   functionality. Next it describes mechanisms and procedures for fault 
   detection, verification, and isolation for VPLS. 
    
    
    
   This proposal is aligned with the current discussions in other 
   standard bodies such as ITU-T Q3/13, IEEE 802.1, and MEF which are 
   addressing OAM for both Ethernet-based services and Ethernet-based 
   networks.  
 
    
    
   5.  Layering 
    
   As defined in [L2-FRWK], Virtual Private LAN Service is a bridged 
   LAN service provided to a set of CEs that are members of a VPN. The 
   CEs that are member of the same VPN (e.g., the same VPLS instance) 
   communicate with each other as if they are connected via a bridged 
   LAN. The bridged LAN functionality is emulated by a network of PEs 
   to which the CEs are connected. This network of PEs can belong to a 
   single network operator or can span across multiple network 
   operators. Furthermore, it can belong to a single service provider 
   or can span across multiple service providers. A service provider is 
   responsible for providing VPLS services to its customers; whereas, a 
   network operator (aka facility provider) provides the necessary 
   facilities to the service provider(s) in support of their services.  
   A network operator and a service provider can be the same entity or 
   they can be different administrative organizations.  
    
    
   When discussing the fault management mechanisms for VPLS, it is 
   important to consider that the end-to-end service can span across 
   different types of VPLS networks. As an example, in case of [VPLS-
   LDP], the access network on one side can be bridged network e.g. 
   [IEEE 802.1ad], as described in section 11 of [VPLS-LDP]; whereas, 
   the access network on other side can be MPLS based as described in 
   section 10 of [VPLS-LDP]; and the core network connecting them can 
   be IP, MPLS, ATM, or SONET. Similarly, the VPLS service instance can 
   span across distributed VPLS as described in [VPLS-ROSEN]. 
   Therefore, it is important that the fault management mechanisms can 
   be applied to all these network types. Each such network may be 
   associated with a separate administrative domain and also multiple 
   such networks may be associated with a single administrative domain. 
   Different types of pseudo wires may be in use to support end-to-end 
   VPLS. Therefore, for VPLS fault management, it is important to 
   ensure that the fault management mechanisms for VPLS are independent 
    
     
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   of the underlying transport mechanisms (e.g., 802.3, MPLS, IP, ATM, 
   SONET, etc.) and solely rely on Ethernet MAC layer.  
    
   As shown in Figure 1, an example of VPLS service is shown across a 
   service provider network marked by UPE and NPE devices. The customer 
   A is represented by CE devices across its different sites. The 
   service provider network is segmented into core network and two 
   types of access network. Figure 1(A) shows the bridged access 
   network represented by its bridge components marked ôBö, and the 
   MPLS access and core network represented by MPLS components marked 
   ôPö. Figure 1(B) shows the service/network view at the Ethernet MAC 
   layer marked by ôEö. 
                                                         
           ---                                                   --- 
          /   \         ------      -------      ----           /   \ 
          | A CE--     /      \    /       \    /    \       --CE A | 
          \   /   \   /        \  /         \  /      \     /   \   / 
           ---     --UPE       NPE          NPE        UPE--     --- 
                      \        /  \         /  \      / 
                       \      /    \       /    \    /      
                        ------      -------      ---- 
    
       (A)    CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE 
    
       (B)    E------E---E--E---E------------E----------E-----E 
    
    
                        Figure 1 
    
   As shown in Figure 1(B), only the nodes with Ethernet functionality 
   are visible to Fault Management mechanisms operating at Ethernet MAC 
   layer and the P nodes are invisible. Therefore, the fault management 
   along the path of P nodes (e.g., between two PEs) is covered by 
   transport layer FM (e.g., MPLS FM) and it is outside the scope of 
   this document. 
    
    
   5.1.  OAM Domains 
    
   As described in the previous section, a VPLS instance for a given 
   customer can span across one or more service providers and network 
   operators. Therefore, when discussing OAM tools for VPLS, e.g. fault 
   management, it is important to provide OAM capabilities and 
   functionality over each domain that a service provider or a network 
   operator is responsible for. For these reasons, it is also important 
   that OAM messages are not allowed to enter/exit other domains. We 
   define an OAM domain as a network region over which OAM messages 
   operate unobstructed as explained below.  
    
   At the edge of an OAM domain, filtering constructs should prevent 
   OAM messages from exiting and entering that domain. FM domains can 
    
     
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   be nested but not overlapped. In other words, if there is a 
   hierarchy of the FM domains, the FM messages of a higher-level 
   domain pass transparently through the lower-level domains but the FM 
   messages of a lower-level domain get blocked/filtered at the edge of 
   that domain.  
    
   In order to facilitate the processing of FM messages, we associate 
   each domain with a one-octet level at which it operates. Domains 
   with larger level numbers can contain domain with smaller level 
   numbers but the converse is not true. 
    
   A PE can be part of several domains with each interface belonging to 
   same or different domains. A PE shall block outgoing FM messages and 
   filter out incoming messages whose domain level is lower or equal to 
   the one configured on that interface and pass through the messages 
   whose domain level is greater than the one configured on that 
   interface.  
    
   Figure 2 depicts three domains: (A) customer domain which is among 
   the CEs of a given customer, (B) service provider domain which is 
   among the edge PEs of the given service provider, and (C) network 
   operator domain which is among the PEs of a given operator. 
    
           ---                                                   --- 
          /   \         ------      -------      ----           /   \ 
          |   CE--     /      \    /       \    /    \       --CE   | 
          \   /   \   /        \  /         \  /      \     /   \   / 
           ---     --UPE       NPE          NPE        UPE--     --- 
                      \        /  \         /  \      / 
                       \      /    \       /    \    /      
                        ------      -------      ---- 
    
      (A)     |<----------------------------------------------->| 
                                    customer 
    
      (B)            |<---------------------------------->| 
                                    provider  
    
      (C)            |<--------->|<----------->|<-------->| 
                       operator     operator     operator 
    
                                     Figure 2 
    
    
 
   5.2.  Maintenance & Intermediate Points 
    
   Maintenance points are responsible for origination and termination 
   of OAM/FM messages. Maintenance points are located at the edge of 
   their corresponding domains. Intermediate points are located within 
   their corresponding domains and they can process and respond to OAM 
    
     
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   messages but they never initiate them. Since Maintenance points are 
   located at the edge of their domains, they are responsible for 
   filtering outbound OAM messages from leaving the domain or inbound 
   OAM messages from entering the domain. Maintenance and intermediate 
   points correspond to a PE or more specifically to an interface of a 
   PE. For example, an OAM/FM message can be said to originate from an 
   ingress PE or more specifically an ingress interface of that PE.  
    
   Since domains are hierarchical as described above, the maintenance 
   and intermediate points that are associated with the domains become 
   hierarchical as well. A maintenance point of a higher-level domain 
   is always a maintenance point of a lower-level domain but the 
   converse is not always true since the maintenance point of lower-
   level domain can either be intermediate point or a maintenance point 
   of a higher-level domain. Furthermore, the intermediate points of a 
   lower-level domain are always transparent to the higher-level domain 
   (e.g., OAM/FM messages of a higher-level domain are not seen by 
   intermediate points of a lower-level domain and get passed through 
   them transparently). 
    
           ---                                                   --- 
          /   \         ------      -------      ----           /   \ 
          | A CE--     /      \    /       \    /    \       --CE A | 
          \   /   \   /        \  /         \  /      \     /   \   / 
           ---     --UPE       NPE          NPE        UPE--     --- 
                      \        /  \         /  \      / 
                       \      /    \       /    \    /      
                        ------      -------      ---- 
    
       (A)    CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE 
    
       (B)    E------E---E--E---E------------E----------E-----E 
                                                                
       (C)    MP----IP----------------------------------IP---MP 
                                 Customer Domain 
    
       (D)           MP---------IP-----------IP-------MP 
                                 Provider domain 
    
       (E)           MP--IP--IP--MP----------MP-------MP 
                       operator     operator    operator 
                        domain       domain      domain 
    
       (F)                       MP--IP--IP--MP--IP---MP 
                                      MPLS        MPLS 
                                     domain      domain 
    
    
    
                                        Figure 3 
    
    
     
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   As shown in Figure 3, (C) represents that maintenance points and 
   intermediate points that are visible within the customer domain. (D) 
   represents the maintenance points and intermediate points visible 
   within the service provider domain, while (E) represents the 
   maintenance points and intermediate points visible within each 
   operator domain. Further, (F) represents the maintenance points and 
   intermediate points corresponding to the MPLS layer and may apply 
   MPLS based mechanisms like [LSP-PING], [VCCV] etc. The MPLS layer 
   shown in this Figure, is just an example and is outside the scope of 
   this document. 
 
 
    
   5.2.1.  Maintenance and Intermediate Points IDs 
    
   As mentioned previously, VPLS OAM/FM should be independent of 
   underlying transport layer and should dependent on Ethernet MAC 
   layer. Therefore, at Ethernet MAC layer, the Maintenance points and 
   Intermediate points should be identified with their Ethernet MAC 
   addresses. As described in [VPLS-LDP], VPLS instance is identified 
   in an Ethernet domain (e.g., 8021.d domain) using VLAN tag (service 
   tag) while in an MPLS/IP network, PW-ids are used. Both PW-ids and 
   VLAN tags for a given VPLS instance are associated with a globally 
   unique service instance identifier (e.g., VPN identifier). 
   Maintenance and Intermediate Points ID shall be unique within their 
   corresponding domain.  
    
   Ethernet frames are used for OAM/FM messages and the source MAC 
   address of the OAM/FM frames represent the source maintenance or 
   intermediate point in that domain. For Unicast OAM/FM frames, the 
   destination MAC address represents the destination maintenance or 
   intermediate point in that domain. For multicast OAM/FM frames, the 
   destination MAC addresses correspond to all maintenance and 
   optionally to all intermediate points in that domain. 
    
    
   6.  Fault Management Mechanisms 
    
    
   6.1.  Fault Detection 
    
   Ethernet Continuity Check (CC) provides a means to detect both hard 
   failures and soft failures such as software failure, memory 
   corruption, or mis-configuration. The failure detection is achieved 
   by each maintenance point (e.g., each edge PE) transmitting a 
   heartbeat message periodically for each VPLS (service) instance. 
   Therefore, each edge PE receives a set of heartbeat messages 
   periodically from other edge PEs of that service instance. Once the 
   local PE stops receiving the periodic heartbeats from the remote PE, 
   it assumes that either the remote PE has failed or an unrecoverable 
   failure on the path has happened. The PE can subsequently notify the 
    
     
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   operator of the failure, using mechanisms that are out of scope of 
   this draft, and initiate the failure verification and isolation 
   steps either automatically or through operator command. 
    
   If a PE is put out of commission, then in order to avoid triggering 
   false failure detection, the out-of-commissioned PE shall indicate 
   its soon to be out-of-state status to other member PEs for each 
   service instance that it participates through a flag in the CC 
   message. The other member PEs of the service instance, upon 
   receiving this indication, would deactivate the corresponding timer 
   for the heartbeat of that PE. Once PE devices have received and 
   processed the CC messages, each PE will have a view of all active 
   PEs for a given VPLS instance (service instance).  
    
 
   Upon receiving CC messages, at the receiving maintenance point, a CC 
   validity timer is started which is used to determine the loss of CC 
   messages. A CC loss is assumed when the next CC message is not 
   received within the timeout of this validity timer. If n consecutive 
   CC messages are lost, a fault for that remote maintenance point is 
   detected. Subsequent fault verification and isolation procedures can 
   be exercised. Fault notification mechanisms, which may also follow 
   the fault detection, are out of scope for this document. 
    
   The fault may correspond to a hard failure or a soft failure within 
   the network. Also a hard failure may result in network isolation 
   which leads to loss of CC messages for many service instances. If 
   the hard failure can be detected and reported to the Management 
   entity, additional notifications by each maintenance point may not 
   be needed û e.g., it is desirable to have an alarm suppression 
   mechanism for notifications that get generated as the result of CC 
   timeouts.  
    
   Since this message is sent periodically, in order to facilitate the 
   processing and filtering of this message, both the message type and 
   domain level is embedded in the multicast MAC address. It may be 
   noted, that the associated Multicast MAC address will be specified 
   in IEEE 802.1. 
    
   A CC messages does not require a response and requires only O (n) 
   message transmission within its member group. In other words, if a 
   service instance has N member PEs, only N CC messages need to be 
   transmitted periodically û one from each PE. However, if this was to 
   be done by point-to-point Ping messages, then O (N**2) messages 
   would have been required.  
    
   The maintenance points shall allow the filtering of CC messages from 
   either entering or exiting its OAM domain. 
 
    
    
     
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   6.2.  Fault Verification 
    
   This non-intrusive unicast loopback is a mechanism similar to IP 
   Ping function that sends a request message from a source bridge to 
   another bridge and expects a response from that bridge.  
     
   To verify the connectivity between maintenance/intermediate points, 
   the request message is initiated by a maintenance point with a DA 
   MAC address set to the MAC address of either a intermediate point or 
   the peer maintenance point.   
    
   The maintenance points shall allow the filtering of fault 
   verification messages from either entering or exiting its OAM 
   domain. 
 
    
   6.3.  Fault Isolation 
    
   TraceRoute function is used to isolate faults visible at Ethernet 
   MAC layer. TraceRoute can be used to isolate a fault associated with 
   a given VPLS service instance. It should be noted that fault 
   isolation in a connection-less (multi-point) environment is more 
   challenging than a connection-oriented (point-to-point) environment. 
   In case of Ethernet, fault isolation can be even more challenging 
   since the MAC address of a target node can age out in several 
   minutes (e.g. typically 5 min) when the fault results in isolating 
   the target node. As a result of this age-out, the occurrence of a 
   network-isolating fault results in erasure of information leading to 
   the location of the fault!  
    
    
   The TraceRoute function uses OAM message with a well-defined 
   multicast MAC address. The TraceRoute Request gets initiated by a 
   maintenance point and traverses hop-by-hop and each intermediate 
   point along the path intercepts the TraceRoute Request and forwards 
   it onto the next hop only after processing it. The processing 
   includes looking at the target MAC address contained in the 
   TraceRoute message. The originating maintenance point expects a 
   response to its TraceRoute request. It should be noted that the 
   source maintenance point sends a single request message to the next 
   hop along the trace path; however, it can receive many responses 
   from different intermediate points (and the peer maintenance point) 
   along the trace path as the result of the message traversing hop by 
   hop. 
    
   Similar to CC messages, TraceRoute multicast MAC address will be 
   specified by IEEE 802.1. 
    
   Given that an end-to-end TraceRoute flow is different from that of a 
   user data flow (TraceRoute goes through the control plane of each 
   hop; whereas, user data flow doesnÆt), there can exist rare 
    
     
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   situation in which the fault can not be detected by the TraceRoute 
   flow. Given that the TraceRoute flow can identify all the points 
   along the traced path (based on responses received at the source 
   maintenance point) one can run multiple Loopback messages between 
   the source maintenance point and different intermediate points (and 
   the peer maintenance point) to further isolate the data-plane 
   fault/corruption in such rare situations. 
    
   As mentioned previously, the age-out of MAC address entries can lead 
   to erasure of information at intermediate nodes, which is used for 
   the TraceRoute mechanism. Possible ways to address this behavior 
   include: 
    
     - Launching TraceRoute mechanism following fault 
        detection/isolation such that it gets exercised within the 
        window of age-out. 
     - Maintaining information about the destination maintenance point 
        at the intermediate points along the path (Note: this can be 
        facilitated by the CC messages.) 
     - Maintaining visibility of path at the source maintenance points 
        through periodic TraceRoute messages (Note: this periodicity 
        should be larger than the CC periodicity) 
      
 
   7.  Fault Management Messages 
    
   Since OAM/FM mechanisms for VPLS solely dependent on Ethernet MAC 
   layer, the corresponding messages are based on Ethernet frames. A 
   generic format can be defined for all Ethernet OAM messages.  
   The information carried in the Ethernet OAM messages is described 
   next for the purpose of discussion. Since these discussions are 
   still on-going in ITU-T Q3/13, IEEE 802.1 and MEF, a specific frame 
   format is not presented here. 
    
    
   7.1.  Generic Ethernet OAM Frame - Header Information 
 
     - OAM Destination MAC Address: This MAC address can either be the 
        unicast address of a maintenance/intermediate point, or it can 
        be a well-defined multicast address. 
    
     - OAM Source MAC Address: This MAC address corresponds to the 
        maintenance or intermediate point. 
    
     - VLAN Ether Type and Tag: This optional VLAN tag represents the 
        service instance within an Ethernet Access domain. 
        Note: Different Ethernet Access domains can use different VLAN 
        tags corresponding to the same service instance. However, each 
    
     
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        S-VLAN tag is unique within an access domain and corresponds to 
        a single service instance.  
    
     - OAM Ethernet Type: It identifies that message is of type OAM. 
    
     - OAM Version: The Version field identifies the OAM version 
        number. 
 
     - Opcode: The Opcode identifies the type of OAM frame.  The OAM 
        frame types that may be defined are: 
            . Continuty Check (0x00) 
            . TraceRoute Request (0x02) 
            . TraceRoute Reply (0x03) 
            . Loopback Request (0x04) 
            . Loopback Reply (0x05)  
            . Vendor Specific (0xFF).  The vendor specific op-code is 
               provided to allow vendors or other organizations to 
               extend OAM functions in proprietary ways.   
            . Other op-codes may be defined in the future. 
      
     - Domain Level: This identifies the hierarchy of OAM domain 
        associated with the OAM message.  
    
   7.2.  Generic Ethernet OAM Frame û OAM Body Information 
 
     - Service ID TLV: Identifies the VPLS/Service instance across the 
        entire VPLS network and relates to the VPLS Service identifiers 
        within each sub-network (e.g. VLAN tags within bridged access 
        domains etc). 
      
     - Transaction ID: Supplied by the originator of the FM message 
        and returned in the reply message (Loopback or TraceRoute). 
 
     - OAM Data: This is a data field associated with the 
        corresponding OAM opcode and information contained is dependent 
        on the type of OAM message. The OAM frame including OAM data 
        portion should result in an Ethernet frame with valid length. 
        Therefore, if necessary the OAM frame may be padded with zeros 
        for a minimum size frame.  
    
    
   7.3.  Continuity Check 
 
   OAM data field for CC Messages may include the following TLVs: 
    
    
     
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     - Lifetime TLV: Specifies the number of seconds, after the 
        receipt of CC message, that the information related to CC 
        message may be discarded by the recipient.  
    
     - Maintenance Point State TLV: Identifies the state of the 
        maintenance point and/or ports associated with it. 
    
     - Device Management Address TLV: May identify the Layer 3 address 
        required to access the source Maintenance PointÆs control MIB. 
 
    
   7.4.  Loopback 
    
   Specific OAM data field information is FFS. 
    
    
   7.5.  TraceRoute 
    
   7.5.1.  TraceRoute Request Format 
    
   The OAM data field of a TraceRoute Request may contain the following 
   TLVs: 
    
     - Source Maintenance Point MAC TLV: Specifies the MAC address of 
        the maintenance point that originated the TraceRoute request. 
        It may be different from the source MAC address of a TraceRoute 
        request, because each bridge along the path puts its own MAC 
        address in the source MAC address field, while retaining the 
        Source Maintenance Point MAC TLV. 
     - Target Maintenance Point MAC TLV: Specifies the MAC address of 
        the peer maintenance point. This TLV is passed on to the next 
        hop. 
     - Hop Count TLV: Hop Count TLV is the hop count of the 
        intermediate/maintenance point(s) from where the response is 
        expected by source maintenance point.  
 
 
   7.5.2.  TraceRoute Reply Format 
    
   The OAM data field of a TraceRoute Reply contains the following 
   TLVs: 
    
     - Hop Count TLV: It is the number of hops between the responding 
        intermediate/maintenance point and the source maintenance 
        point. 
     - Ingress Device Management Address TLV: The TLV specifies the 
        Layer 3 address required to access the control MIB for the 
    
     
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        Maintenance Point or Intermediate Point on which the TraceRoute 
        Request was received.  
    
   8.  Acknowledgments 
    
   We wish to thank Marc Holness, Tim Mancour, and Paul Bottorff for 
   their valuable feedback. 
 
    
   9.  Security Considerations 
    
   Security issues resulting from this draft will be discussed in 
   greater depth at a later point.  It is recommended in [RFC3036] that 
   LDP security (authentication) methods be applied.  This would 
   prevent unauthorized participation by a PE in a VPLS.  Traffic 
   separation for a VPLS is effected by using VC labels.  However, for 
   additional levels of security, the customer MAY deploy end-to-end 
   security, which is out of the scope of this draft.  In addition, the 
   L2FRAME] document describes security issues in greater depth. 
    
    
   10.  Intellectual Property Considerations 
    
   This document is being submitted for use in IETF standards 
   discussions. 
    
    
   11.  Full Copyright Statement 
    
   Copyright (C) The Internet Society (2001).  All Rights Reserved.  
   This document and translations of it may be copied and furnished to 
   others, and derivative works that comment on or otherwise explain it 
   or assist in its implementation may be prepared, copied, published 
   and distributed, in whole or in part, without restriction of any 
   kind, provided that the above copyright notice and this paragraph 
   are included on all such copies and derivative works.  However, this 
   document itself may not be modified in any way, such as by removing 
   the copyright notice or references to the Internet Society or other 
   Internet organizations, except as needed for the purpose of 
   developing Internet standards in which case the procedures for 
   copyrights defined in the Internet Standards process must be 
   followed, or as required to translate it into languages other than 
   English. 
    
   The limited permissions granted above are perpetual and will not be 
   revoked by the Internet Society or its successors or assigns. 
    
   This document and the information contained herein is provided on an 
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 
    
     
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   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 
    
   12.  References 
    
   [PWE3-ETHERNET] "Encapsulation Methods for Transport of Ethernet 
   Frames Over IP/MPLS Networks", draft-ietf-pwe3-ethernet-encap-
   01.txt, Work in progress, November 2002. 
    
   [802.1D-ORIG] Original 802.1D - ISO/IEC 10038, ANSI/IEEE Std 802.1D-
   1993 "MAC Bridges". 
    
   [802.1D-REV] 802.1D - "Information technology - Telecommunications 
   and information exchange between systems - Local and metropolitan 
   area networks - Common specifications - Part 3: Media Access Control 
   (MAC) Bridges: Revision. This is a revision of ISO/IEC 10038: 1993, 
   802.1j-1992 and 802.6k-1992. It incorporates P802.11c, P802.1p and 
   P802.12e." ISO/IEC 15802-3: 1998. 
    
   [802.1Q] 802.1Q - ANSI/IEEE Draft Standard P802.1Q/D11, "IEEE 
   Standards for Local and Metropolitan Area Networks: Virtual Bridged 
   Local Area Networks", July 1998. 
    
   [VPLS-REQ] "Requirements for Virtual Private LAN Services (VPLS)", 
   draft-ietf-ppvpn-vpls-requirements-01.txt, Work in progress, October 
   2002. 
    
   [L2FRAME] "L2VPN Framework", draft-ietf-ppvpn-l2-framework-03, Work 
   in Progress, February 2003. 
    
   [802.1ad] ôIEEE standard for Provider Bridges, Work in Progress, 
   December 2002ö 
    
   <To be updated in the next Rev.> 
 
   13.  Authors' Addresses 
    
   Ali Sajassi                        Dinesh Mohan 
   Cisco Systems, Inc.                Nortel Networks 
   170 West Tasman Drive              3500 Carling Ave. 
   San Jose, CA  95134                Ottawa, ON  K2H 8E9 
   Email: sajassi@cisco.com           Email: mohand@nortelnetworks.com 
    
   Norm Finn                          Vasile Radoaca 
   Cisco Systems, Inc.                Nortel Networks 
   170 West Tasman Drive              600 Technology Park 
   San Jose, CA  95134                Billerica, MA 01821 
   Email: nfinn@cisco.com             Email: vasile@nortelnetworks.com
         
   Thomas D. Nadeau                   Shahram Davari  
    
     
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   Cisco Systems, Inc.                PMC Sierra  
   300 Beaver Brook Road              411 Legget Drive  
   Boxborough, MA 01719               Ottawa, ON K2K 3C9  
   Email: tnadeau@cisco.com           Email: shahram_davari@pmc-
   sierra.com    
    
   Monique Morrow  
   Cisco Systems, Inc.  
   Glatt-com  
   CH-8301 Glattzentrum  
   Switzerland  
   Email: mmorrow@cisco.com      
    
    
     
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