One document matched: draft-mohan-sajassi-l2vpn-oam-req-frmk-00.txt


   Internet Draft Document                               Dinesh Mohan 
   Layer-2 VPN Working Group                          Nortel Networks 
   draft-mohan-sajassi-l2vpn-oam-req-frmk-00.txt          Ali Sajassi 
                                                        Cisco Systems 
                                                                      
                                                       Shahram Davari 
                                                           PMC Sierra 
                                                                      
                                                             Norm Finn 
                                                         Cisco Systems 
                                                                      
                                                       Vasile Radoaca 
                                                      Nortel Networks 
                                                                      
   Expires: January 2005                                    July 2004 
                                                                         
    
                    VPLS OAM Requirements and Framework  
               draft-mohan-sajassi-l2vpn-oam-req-frmk-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 
    
     
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   Placement of this Memo in Routing Area 
    
   RELATED DOCUMENTS 
    
    
   http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-l2-framework-
   03.txt 
   http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-requirements-
   01.txt 
   http://www.ietf.org/internet-drafts/draft-ietf-l3vpn-mgt-fwk-01.txt 
   http://www.ietf.org/internet-drafts/draft-sajassi-mohan-l2vpn-vpls-
   fm-00.txt 
   http://www.ietf.org/internet-drafts/draft-mohan-sajassi-l2vpn-vpls-
   pm-00.txt 
   http://www.ietf.org/internet-drafts/draft-nadeau-pwe3-oam-msg-map-
   04.txt 
    
   WHERE DOES THIS FIT IN THE PICTURE OF THE ROUTING WORK 
    
   L2VPN 
    
   WHY IS IT TARGETED AT THIS WG 
    
   This draft describes requirements and framework for VPLS OAM. 
    
   JUSTIFICATION 
    
   The charter of L2VPN WG includes L2VPN specific OAM extensions, 
   where the extensions apply to existing OAM solutions for VPLS, VPWS, 
   and IP-only L2VPNs. 
 
 
   Table of Contents 
    
   1. Status of this Memo.............................................1 
   2. Abstract........................................................1 
   3. Conventions.....................................................1 
   4. Overview........................................................3 
   5. L2VPN Services & Networks.......................................4 
   6. OAM Layering....................................................6 
   6.1. OAM Domains...................................................6 
   6.2. Maintenance Entity Points & Maintenance Intermediate Points...7 
   6.2.1. MEP and MIP Identifiers.....................................9 
   7. VPLS OAM Requirements...........................................9 
   7.1. Discovery.....................................................9 
   7.2. Connectivity Fault Management.................................9 
   7.2.1. Connectivity Fault Detection...............................10 
   7.2.2. Connectivity Fault Verification............................10 
   7.2.3. Connectivity Fault Localization............................10 
    
     
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   7.2.4. Connectivity Fault Alarm...................................10 
   7.3. Frame Loss...................................................10 
   7.4. Frame Delay..................................................11 
   7.5. Frame Delay Variation........................................11 
   7.6. Data Path Execution..........................................12 
   7.7. Scalability..................................................12 
   7.8. Extensibility................................................12 
   7.9. Security.....................................................12 
   7.10. Transport Independence......................................13 
   7.11. Application Independence....................................13 
   7.12. Backward Compatibility......................................13 
   7.13. Availability................................................14 
   8. Acknowledgments................................................14 
   9. Security Considerations........................................14 
   10. Intellectual Property Considerations..........................14 
   11. Full Copyright Statement......................................14 
   12. References....................................................15 
   13. Authors' Addresses............................................16 
    
    
   4. Overview 
    
   This draft provides framework and requirements for Virtual Private 
   LAN Service (VPLS) Operation, Administration and Maintenance (OAM).  
    
   The scope of OAM for any service and/or transport/network 
   infrastructure technologies can be very broad in nature. OSI has 
   defined the following five generic functional areas for network 
   management, commonly abbreviated as ôFCAPSö [NM-Standards]: a) Fault 
   Management, b) Performance Management, c) Configuration Management, 
   d) Accounting Management, and e) Security Management.  
    
   This draft focuses on the Fault and Performance Management aspects. 
   Other functional aspects of FCAPS are for further study. 
    
   [L2VPN-FRWK] specified three different types of Layer 2 VPN (i.e. 
   services). These are VPWS, VPLS and IPLS. The framework and 
   requirements presented in this draft applies to VPLS. 
    
   Fault Management can typically be viewed in terms of the following 
   categories: 
    
     - Fault Detection 
     - Fault Verification 
     - Fault Isolation 
     - Fault Notification 
     - Fault Recovery 
    
     
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   Fault Detection deals with mechanism(s) that can detect both hard 
   failures, such as link and device 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 
   device or link. 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 devices of a fault. Finally, Fault Recovery deals 
   with recovering from the detected failure by switching to an 
   alternate available device or link (e.g., device redundancy or link 
   redundancy). 
 
    
   Performance Management deals with mechanism(s) that allow 
   determining and measuring the performance of network/services under 
   consideration and notification of them. Performance Management can 
   be used to verify the compliance to both the service and network 
   level specifications. Performance Management typically consists of 
   measurement of Performance Parameters e.g. Frame Loss, Frame Delay, 
   Frame Delay Variation aka Jitter etc. This draft introduces some of 
   these performance parameters.  
    
   This document provides 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.  
    
   This proposal is aligned with the current discussions in other 
   standard bodies and groups such as ITU-T Q.3/13, IEEE 802.1, and MEF 
   which are addressing Ethernet network and service OAM.  
 
    
   5. L2VPN Services & Networks 
    
   As described in [L2VPN-REQ], following Figure 1 shows a L2VPN 
   reference model. L2VPN A represents a point-to-point service while 
   L2VPN B represents a bridged service. 
     
    
       +-----+                                   +-----+ 
       + CE1 +--+                             +--| CE2 | 
       +-----+  |    .....................    |  +-----+ 
       L2VPN A  |  +----+             +----+  |  L2VPN A 
                +--| PE |-- Service --| PE |--+ 
                   +----+   Provider  +----+ 
                  /  .      Backbone     .  \    --------_ 
       +-----+   /   .         |         .   \  /        \   +-----+ 
       + CE4 +--+    .         |         .    +-\ Access  \--| CE5 | 
    
     
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       +-----+       .       +----+      .      | Network |  +-----+ 
       L2VPN B       ........| PE |.......       \       /   L2VPN B 
                             +----+   ^           ------- 
                               |      | logical 
                               |      | switching 
                            +-----+   | instance 
                            | CE3 |    
                            +-----+ 
                            L2VPN B 
    
                  Figure 1: L2VPN Reference Model 
    
    
   [L2VPN-FRWK] specifies VPWS, VPLS and IPLS services. VPWS is a 
   point-to-point service where CEs are presented with point-to-point 
   virtual circuits. VPLS is a bridged LAN service provided to a set of 
   CEs that are members of a VPN. CEs that are member of the same 
   service instance communicate with each other as if they are 
   connected via a bridged LAN. IPLS is a special VPLS which is used to 
   carry only IP service packets. 
    
   The point-to-point or 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 L2VPN 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.  
    
   [L2VPN-REQ] assumes the availability of runtime monitoring protocols 
   while defining requirements for management interfaces. This draft 
   specifies the requirements and framework for operations, 
   administration and maintenance (OAM) protocols between network 
   devices. 
    
   When discussing the OAM mechanisms for VPLS, it is important to 
   consider that the end-to-end service can span across different types 
   of L2VPN 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]. 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 [ROSEN-SIG].  
    
   Therefore, it is important that the OAM 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 
    
     
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   be associated with a single administrative domain. Different types 
   of pseudo wires may be in use to support end-to-end L2VPNs. 
   Therefore, for L2VPN OAM, it is important to ensure that the OAM 
   mechanisms are independent of the underlying transport mechanisms 
   and solely rely on layer 2 services, e.g. for VPLS service, the 
   transparency of OAM mechanisms must be ensured over underlying 
   transport technologies such as MPLS, IP, etc. 
    
    
   6. OAM Layering 
    
   Figure 2 shows an example of a VPLS service (with two CE belonging 
   to customer A) across a service provider network marked by UPE and 
   NPE devices. More CE devices belonging to the same Customer A can be 
   connected across customerÆs different sites. Service provider 
   network is segmented into core network and two types of access 
   network. Figure 2(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 2(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 2: Service specific device view  
    
   As shown in Figure 2(B), only the devices with Ethernet 
   functionality are visible to OAM mechanisms operating at Ethernet 
   MAC layer and the P devices are invisible. Therefore, the OAM along 
   the path of P devices (e.g., between two PEs) is covered by 
   transport layer and it is outside the scope of this document. 
    
    
   6.1. OAM Domains 
    
   As described in the previous section, a VPLS service for a given 
   customer can span across one or more service providers and network 
   operators. Therefore, when discussing OAM tools for VPLS 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 frames are not 
    
     
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   allowed to enter/exit other domains. We define an OAM domain as a 
   network region over which OAM frames operate unobstructed as 
   explained below.  
    
   At the edge of an OAM domain, filtering constructs should prevent 
   OAM frames from exiting and entering that domain. OAM domains can be 
   nested but not overlapped. In other words, if there is a hierarchy 
   of the OAM domains, the OAM messages of a higher-level domain pass 
   transparently through the lower-level domains but the OAM messages 
   of a lower-level domain get blocked/filtered at the edge of that 
   domain.  
    
   In order to facilitate the processing of OAM messages, each domain 
   can be associated with a 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 OAM 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 3 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 3: OAM Domains 
    
 
   6.2. Maintenance Entity Points & Maintenance Intermediate Points 
    
    
     
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   Maintenance Entity Points (MEPs) are responsible for origination and 
   termination of OAM messages. MEPs are located at the edge of their 
   corresponding OAM domains. Maintenance Intermediate Points (MIPs) 
   are located within their corresponding domains and they normally 
   pass OAM messages but never initiate them. Since MEPs are located at 
   the edge of their domains, they are responsible for filtering 
   outbound OAM frames from leaving the domain or inbound OAM frames 
   from entering the domain. MEPs and MIPs correspond to a PE or more 
   specifically to an interface of a PE. For example, an OAM message 
   can be said to originate from an ingress PE or more specifically an 
   ingress interface of that PE.  
    
   Since OAM domains are hierarchical as described above, the MEPs and 
   MIPs associated with the OAM domains become hierarchical as well. A 
   MEP of a higher-level domain is always a MEP of a lower-level domain 
   but the converse is not always true since the MEP of lower-level 
   domain can either be MIP or a MEP of a higher-level domain. 
   Furthermore, the MIPs of a lower-level domain are always transparent 
   to the higher-level domain (e.g., OAM messages of a higher-level 
   domain are not seen by MIPs 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)    MEP---MIP--------------------------------MIP---MEP 
                                 Customer Domain 
    
       (D)          MEP--------MIP-----------MIP-------MEP 
                                 Provider domain 
    
       (E)          MEP-MIP-MIP-MEP----------MEP-------MEP 
                       Operator     Operator    Operator 
                        domain       domain      domain 
    
       (F)                      MEP--MIP-MIP-MEP--MIP--MEP 
                                      MPLS        MPLS 
                                     domain      domain 
 
                  Figure 4: OAM Domains, MEPs & MIPs  
    
    
    
     
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   As shown in Figure 4, (C) represents those MEPs and MIPs that are 
   visible within the customer domain. (D) represents the MEPs and MIPs 
   visible within the service provider domain, while (E) represents the 
   MEPs and MIPs visible within each operator domain. Further, (F) 
   represents the MEPs and MIPs corresponding to the MPLS layer and may 
   apply MPLS based mechanisms. The MPLS layer shown in Figure 4 is 
   just an example and specific OAM mechanisms are outside the scope of 
   this document. 
 
    
   6.2.1. MEP and MIP Identifiers 
    
   As mentioned previously, L2VPN OAM should be independent of 
   underlying transport layer and only be dependent on service layer, 
   e.g. Ethernet MAC layer in case of VPLS service. As an example, for 
   Ethernet MAC layer, the MEPs and MIPs should be identified with 
   their Ethernet MAC addresses. As described in [VPLS-LDP], VPLS 
   instance can be 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 Service Identifier (e.g., VPN identifier). 
   MEPs and MIPs Identifiers, i.e. MEP Ids and MIP Ids must be unique 
   within their corresponding Service Identifiers within the OAM 
   domains.  
    
   For Ethernet services e.g. VPLS, Ethernet frames are used for OAM 
   messages and the source MAC address of the OAM frames represent the 
   source MEP in that domain. For unicast Ethernet OAM frames, the 
   destination MAC address represents the destination MEP in that 
   domain. For multicast Ethernet OAM frames, the destination MAC 
   addresses corresponds to all MEPs in that domain. 
    
 
   7. VPLS OAM Requirements 
    
   7.1. Discovery 
    
   Discovery allows a service aware device to learn about other devices 
   that support the same service instance within a given domain.  
    
   Discovery also allows a service aware device to learn sufficient 
   information (e.g. IP addresses, MAC addressed etc.) from other 
   service aware devices such that OAM messages can be exchanged among 
   the service aware devices. 
    
   (R1) OAM MUST allow a service aware device to discover other devices 
   that share the same service instance(s) within a given OAM domain. 
    
    
   7.2. Connectivity Fault Management 
    
    
     
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   Service is realized by exchanging service frames/packets between 
   devices that support the service instance. To allow the exchange of 
   service frames, connectivity between these service aware devices is 
   required.  
    
   7.2.1. Connectivity Fault Detection 
   
   To ensure service, pro-active connectivity monitoring is required. 
   Connectivity monitoring facilitates connectivity fault detection. 
    
   (R2a) OAM MUST allow pro-active connectivity monitoring between two 
   service aware devices that support the same service instance within 
   a given OAM domain. 
    
   7.2.2. Connectivity Fault Verification 
   
   Once a connectivity fault is detected, connectivity fault 
   verification may be performed.  
    
   (R2b) OAM MUST allow connectivity fault verification between two 
   service aware devices that support the same service instance within 
   a given OAM domain. 
    
   7.2.3. Connectivity Fault Localization 
   
   Further, localization of connectivity fault may be carried out.  
    
   (R2c) OAM MUST allow connectivity fault localization between two 
   service aware devices that support the same service instance within 
   a given OAM domain. 
    
   7.2.4. Connectivity Fault Alarm 
   
   Typically, when connectivity fault is detected and optionally 
   verified, service device may notify the EMS/NMS (Element Management 
   System/Network Management System).  
    
   However, a single transport/network fault may cause multiple 
   services to fail causing multiple connectivity faults. Though 
   independence with transport/network OAM mechanisms is desirable, it 
   may be useful to suppress service connectivity fault notification 
   when the fault causing condition is detected at the 
   transport/network. Therefore, OAM must allow alarm notification to 
   allow suppression of service connectivity fault notifications. 
    
   (R2d) OAM MUST allow forwarding of transport/network fault 
   indications to those service aware devices that support service 
   instance affected by the fault. 
    
    
   7.3. Frame Loss 
    
      
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   A service may be considered degraded if it is sensitive to service 
   frames/packets loss during transit between the service aware 
   devices. To determine if a service is degraded due to frame/packet 
   loss, measurement of frame/packet loss is required. 
    
   (R3) OAM MUST support measurement of per-service frame/packet loss 
   between two service aware devices that support the same service 
   instance within a given OAM domain. 
    
    
   7.4. Frame Delay 
    
   A service may be sensitive to delay experienced by the service 
   frames/packets during transit between the service aware devices. To 
   determine if a service is degraded due to frame/packet delay, 
   measurement of frame/packet delay is required. 
    
   Frame/packet delay measurement can be of two types: 
    
   One-way delay 
   One-way delay is used to characterize certain applications like 
   multicast and broadcast applications. The measurement for one-way 
   delay usually requires clock synchronization between two devices in 
   question. 
    
   Two-way delay 
   Two-way delay or round-trip delay does not require clock 
   synchronization between two devices involved in measurement and is 
   usually sufficient to determine the frame/packet delay being 
   experienced.  
 
   (R4a) OAM MUST support measurement of per-service two-way 
   frame/packet delay between two service aware devices that support 
   the same service instance within a given OAM domain. 
    
   (R4b) OAM SHOULD support measurement of per-service one-way 
   frame/packet delay between two service aware devices that support 
   the same service instance within a given OAM domain. 
    
    
   7.5. Frame Delay Variation 
    
   A service may be sensitive to delay variation experienced by the 
   service frames/packets during transit between the service aware 
   devices. To determine if a service is degraded due to frame/packet 
   delay variation, measurement of frame/packet delay variation is 
   required. For frame/packet delay variation measurements, one-way 
   mechanisms are considered to be sufficient. 
    
   (R5) OAM MUST support measurement of per-service frame/packet delay 
   variation between two service aware devices that support the same 
   service instance within a given OAM domain. 
    
     
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   7.6. Data Path Execution 
    
   If the OAM frames flow across a different path than the one used by 
   service frames/packets, accurate measurement and/or determination of 
   service state may not be made. Therefore data path, i.e. the one 
   being taken by service frames/packets, must be used for the service 
   OAM. 
    
   (R6) OAM frames MUST be forwarded along the same path as the 
   service/data frames. 
    
    
   7.7. Scalability 
    
   Mechanisms developed for OAM need to be such that per-service OAM 
   can be supported even though the OAM may only be used for limited 
   services e.g. premium services and may not be used for best effort 
   services. 
    
   Note: The specific numbers or range of services should align with 
   the [L2VPN-FRWK] 
    
   (R7) OAM MUST be scalable such that a service device can support OAM 
   for each service that is supported by the device. 
    
    
   7.8. Extensibility 
    
   Extensibility is intended to allow introduction of additional 
   functionality in future such that backward compatibility can be 
   maintained i.e. when working with older version devices, service OAM 
   with reduced functionality is still possible. 
    
   (R8) OAM MUST be extensible such that new functionality and 
   information elements related to this functionality can be introduced 
   in future. 
    
    
   7.9. Security 
    
   OAM frames belonging to an OAM domain originate and terminate within 
   that OAM domain. Security implies that an OAM domain must be capable 
   of filtering OAM frames. The filtering is such that the OAM frames 
   are prevented from leaking outside their domain. Also, OAM frames 
   from outside the OAM domains should be either discarded (when such 
   OAM frames belong to same or lower-level OAM domain) or 
   transparently passed (when such OAM frames belong to a higher-level 
   OAM domain).  
    
    
     
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   (R9a) OAM frames MUST be prevented from leaking outside their OAM 
   domain. 
    
   (R9b) OAM frames from outside an OAM domain MUST be prevented from 
   entering the OAM domain when such OAM frames belong to the same 
   level or lower-level OAM domain. 
    
   (R9c) OAM frames from outside an OAM domain MUST be transported 
   transparently inside the OAM domain when such OAM frames belong to 
   the higher-level OAM domain. 
    
    
   7.10. Transport Independence 
    
   Service frame/packets delivery is carried out across transport 
   infrastructure, also called as network infrastructure. Though 
   specific transport/network technologies may provider own OAM 
   capabilities, Service OAM must be independently supported as many 
   different transport/network technologies can be used to carry 
   service frame/packets. 
    
   (R10a) OAM MUST be independent of the underlying transport/network 
   technologies and specific transport/network OAM capabilities. 
    
   (R10b) OAM MAY allow interworking with specific transport/network 
   OAM to utilize transport/network OAM capabilities. 
    
    
   7.11. Application Independence 
    
   Service itself may be used to carry application frame/packets. The 
   application may use its own OAM; service OAM must not be dependent 
   on application OAM. As an example, a VPLS service may be used to 
   carry IP traffic; however, VPLS OAM should not assume IP or rely on 
   the use of IP level OAM functions. 
    
   (R11a) OAM MUST be independent of the application technologies and 
   specific application OAM capabilities. 
    
   (R11b) OAM MAY allow interworking with specific application OAM to 
   allow applications to utilize service OAM capabilities. 
    
    
   7.12. Backward Compatibility 
    
   Service OAM should be such that non-service aware and/or OAM 
   incapable devices in the middle of the OAM domain should be able to 
   forward the OAM frames similar to the regular service/data 
   frames/packets. 
    
    
     
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   (R12) OAM MUST be defined such that devices not supporting the OAM 
   are able to forward the OAM frames in a similar fashion as the 
   regular service/data frames/packets. 
    
    
   7.13. Availability 
    
   A service may be considered unavailable if the service 
   frames/packets do not reach their intended destination (e.g. 
   connectivity is down or frame/packet loss is occurring) or the 
   service is degraded (e.g. frame/packet delay and/or delay variation 
   threshold is exceeded).  
    
   Entry and exit conditions may be defined for unavailable state. 
   Availability itself may be defined in context of service type.  
    
   Since availability measurement may be associated with connectivity, 
   frame/packet loss, frame/packet delay and frame/packet delay 
   variation measurements, no additional requirements are specified 
   currently. 
    
    
   8. Acknowledgments 
    
   We wish to thank Yoav Cohen, Marc Holness, Malcolm Betts, Paul 
   Bottorff, Norm Finn, and Monique Morrow 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 
    
     
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   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 
   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. 
    
   [L2VPN-FRWK] "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.> 
    
     
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   13. Authors' Addresses 
    
   Dinesh Mohan                       Ali Sajassi 
   Nortel Networks                    Cisco Systems, Inc. 
   3500 Carling Ave.                  170 West Tasman Drive 
   Ottawa, ON  K2H 8E9                San Jose, CA 95134 
   Email: mohand@nortelnetworks.com   Email: sajassi@cisco.com 
 
   Vasile Radoaca                     Norm Finn 
   Nortel Networks                    Cisco Systems, Inc. 
   600 Technology Park                170 West Tasman Drive 
   Billerica, MA 01821                San Jose, CA 95134 
   Email: vasile@nortelnetworks.com   Email: nfinn@cisco.com 
                 
   Shahram Davari                      
   PMC Sierra                          
   411 Legget Drive  
   Ottawa, ON K2K 3C9  
   Email: shahram_davari@pmc-sierra.com 
   


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