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RFC 7079

The Pseudowire (PW) and Virtual Circuit Connectivity Verification (VCCV) Implementation Survey Results

Pages: 41
Informational
Part 1 of 2 – Pages 1 to 19
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Internet Engineering Task Force (IETF)                 N. Del Regno, Ed.
Request for Comments: 7079                  Verizon Communications, Inc.
Category: Informational                                    A. Malis, Ed.
ISSN: 2070-1721                                               Consultant
                                                           November 2013


The Pseudowire (PW) and Virtual Circuit Connectivity Verification (VCCV)
                     Implementation Survey Results

Abstract

The IETF Pseudowire Emulation Edge-to-Edge (PWE3) working group has defined many encapsulations of various layer 1 and layer 2 service- specific PDUs and circuit data. In most of these encapsulations, use of the Pseudowire (PW) Control Word is required. However, there are several encapsulations for which the Control Word is optional, and this optionality has been seen in practice to possibly introduce interoperability concerns between multiple implementations of those encapsulations. This survey of the Pseudowire / Virtual Circuit Connectivity Verification (VCCV) user community was conducted to determine implementation trends and the possibility of always mandating the Control Word. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7079.
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Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   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.
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Table of Contents

1. Introduction ....................................................4 1.1. PW/VCCV Survey Overview ....................................5 1.2. PW/VCCV Survey Form ........................................5 1.3. PW/VCCV Survey Highlights ..................................7 2. Survey Results ..................................................8 2.1. Summary of Results .........................................8 2.2. Respondents ................................................8 2.3. Pseudowire Encapsulations Implemented ......................9 2.4. Number of Pseudowires Deployed ............................10 2.5. VCCV Control Channel in Use ...............................11 2.6. VCCV Connectivity Verification Types in Use ...............14 2.7. Control Word Support for Encapsulations for Which CW Is Optional ............................................16 2.8. Open-Ended Question .......................................17 3. Security Considerations ........................................18 4. Acknowledgements ...............................................18 5. Informative References .........................................19 Appendix A. Survey Responses ......................................20 A.1. Respondent 1 ...............................................20 A.2. Respondent 2 ...............................................21 A.3. Respondent 3 ...............................................22 A.4. Respondent 4 ...............................................23 A.5. Respondent 5 ...............................................24 A.6. Respondent 6 ...............................................25 A.7. Respondent 7 ...............................................27 A.8. Respondent 8 ...............................................28 A.9. Respondent 9 ...............................................29 A.10. Respondent 10 .............................................30 A.11. Respondent 11 .............................................31 A.12. Respondent 12 .............................................32 A.13. Respondent 13 .............................................33 A.14. Respondent 14 .............................................35 A.15. Respondent 15 .............................................36 A.16. Respondent 16 .............................................38 A.17. Respondent 17 .............................................39
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1. Introduction

Most Pseudowire Emulation Edge-to-Edge (PWE3) encapsulations mandate the use of the Control Word (CW) to carry information essential to the emulation, to inhibit Equal-Cost Multipath (ECMP) behavior, and to discriminate Operations, Administration, and Maintenance (OAM) from Pseudowire (PW) packets. However, some encapsulations treat the Control Word as optional. As a result, implementations of the CW, for encapsulations for which it is optional, vary by equipment manufacturer, equipment model, and service provider network. Similarly, Virtual Circuit Connectivity Verification (VCCV) supports three Control Channel (CC) types and multiple Connectivity Verification (CV) types. This flexibility has led to reports of interoperability issues within deployed networks and associated documents to attempt to remedy the situation. The encapsulations and modes for which the Control Word is currently optional are: o Ethernet Tagged Mode [RFC4448] o Ethernet Raw Mode [RFC4448] o Point-to-Point Protocol (PPP) [RFC4618] o High-Level Data Link Control (HDLC) [RFC4618] o Frame Relay Port Mode [RFC4618] o ATM (N:1 Cell Mode) [RFC4717] Virtual Circuit Connectivity Verification (VCCV) [RFC5085] defines three Control Channel types for MPLS PWs: Type 1, using the PW Control Word; Type 2, using the Router Alert (RA) Label; and Type 3, using Time to Live (TTL) Expiration (e.g., MPLS PW Label with TTL == 1). While Type 2 (RA Label) is indicated as being "the preferred mode of VCCV operation when the Control Word is not present", RFC 5085 does not indicate a mandatory Control Channel to ensure interoperable implementations. The closest it comes to mandating a control channel is the requirement to support Type 1 (Control Word) whenever the CW is present. As such, the three options yield seven implementation permutations (assuming you have to support at least one Control Channel type to provide VCCV). Due to these permutations, interoperability challenges have been identified by several VCCV users.
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   In order to assess the best approach to address the observed
   interoperability issues, the PWE3 working group decided to solicit
   feedback from the PW and VCCV user community regarding
   implementation.  This document presents the survey questionnaire and
   the information returned by those in the user community who
   participated.

1.1. PW/VCCV Survey Overview

Per the direction of the PWE3 working group chairs, a survey was created to sample the nature of implementations of PWs, with specific emphasis on Control Word usage, and VCCV, with emphasis on Control Channel and Control Type usage. The survey consisted of a series of questions based on direction of the WG chairs and the survey opened to the public on November 4, 2010. The survey was conducted using the SurveyMonkey tool, http://www.surveymonkey.com. The survey ran from November 4, 2010 until February 25, 2011 and was repeatedly publicized on the PWE3 email list over that period. The editors took precautions to ensure the validity of the sample and the data. Specifically, only responses with recognizable non-vendor company-affiliated email addresses were accepted. Unrecognizable or personal email addresses would have been contacted to determine their validity, but none were received. Only one response was received from each responding company. If multiple responses from a company had been received, they would have been contacted to determine whether the responses were duplicative or additive. This, however, did not occur.

1.2. PW/VCCV Survey Form

The PW/VCCV Implementation Survey requested the following information about user implementations (the lists of implementation choices were taken verbatim from the survey): - Responding Organization. No provisions were made for anonymous responses, as all responses required a valid email address in order to validate the survey response. However, the results herein are reported anonymously, except for an alphabetic list of participating organizations in Section 2.2.
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   -  Of the various encapsulations (and options therein) known at the
      time, including the WG document, "Encapsulation Methods for
      Transport of Fibre Channel" (now [RFC6307]), which were
      implemented by the respondent.  These included:

      o  Ethernet Tagged Mode - RFC 4448

      o  Ethernet Raw Mode - RFC 4448

      o  Structure-Agnostic Time Division Multiplexing (TDM) over Packet
         (SAToP) - RFC 4553

      o  PPP - RFC 4618

      o  HDLC - RFC 4618

      o  Frame Relay (Port Mode) - RFC 4619

      o  Frame Relay (1:1 Mode) - RFC 4619

      o  ATM (N:1 Mode) - RFC 4717

      o  ATM (1:1 Mode) - RFC 4717

      o  ATM (AAL5 Service Data Unit (SDU) Mode) - RFC 4717

      o  ATM (AAL5 PDU Mode) - RFC 4717

      o  Circuit Emulation over Packet (CEP) - RFC 4842

      o  Circuit Emulation Service over Packet Switched Network
         (CESoPSN) - RFC 5086

      o  Time Division Multiplexing over IP (TDMoIP) - RFC 5087

      o  Fiber Channel (Port Mode) - "Encapsulation Methods for
         Transport of Fibre Channel" (now RFC 6307)

   -  Approximately how many PWs of each type were deployed.
      Respondents could list a number, or for the sake of privacy, could
      just respond "In-Use" instead.
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   -  For each encapsulation listed above, the respondent could indicate
      which Control Channel [RFC5085] was in use.  (See Section 1 for a
      discussion of these Control Channels.)  The options listed were:

      o  Control Word (Type 1)

      o  Router Alert Label (Type 2)

      o  TTL Expiry (Type 3)

   -  For each encapsulation listed above, the respondent could indicate
      which Connectivity Verification types [RFC5085] were in use.  The
      options were:

      o  Internet Control Message Protocol (ICMP) Ping

      o  Label Switched Path (LSP) Ping

   -  For each encapsulation type for which the Control Word is
      optional, the respondents could indicate the encapsulation(s) for
      which Control Word was supported by the equipment vendor, and
      whether the CW was also in use in the network.  The encapsulations
      listed were:

      o  Ethernet (Tagged Mode)

      o  Ethernet (Raw Mode)

      o  PPP

      o  HDLC

      o  Frame Relay (Port Mode)

      o  ATM (N:1 Cell Mode)

   -  Finally, a free-form entry was provided for the respondent to
      provide feedback regarding PW and VCCV deployments, VCCV
      interoperability challenges, or the survey or any other network/
      vendor details they wished to share.

1.3. PW/VCCV Survey Highlights

There were seventeen responses to the survey that met the validity requirements in Section 1.1. The responding companies are listed below in Section 2.2.
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2. Survey Results

2.1. Summary of Results

Prior to this survey, there was considerable speculation about whether the Control Word could always be mandated, with several proposals to do so. However, the survey showed that there was considerable deployment of PWs that did not use the CW. The publication of this survey serves as a reminder of the extent of PWs without the CW in use, and hence a reminder that the CW-less modes cannot be deprecated in the near future.

2.2. Respondents

The following companies, listed here alphabetically as received in the survey responses, participated in the PW/VCCV Implementation Survey. Responses were only solicited from non-vendors (users and service providers), and no vendors responded (although if they had, their response would not have been included). The data provided has been aggregated. No specific company's response will be detailed herein. o AboveNet o AMS-IX o Bright House Networks o Cox Communications o Deutsche Telekom AG o Easynet Global Services o France Telecom Orange o Internet Solution o MTN South Africa o OJSC MegaFon o Superonline o Telecom New Zealand o Telstra Corporation
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   o  Time Warner Cable

   o  Tinet

   o  Verizon

   o  Wipro Technologies

2.3. Pseudowire Encapsulations Implemented

The following request was made: "In your network in general, across all products, please indicate which pseudowire encapsulations your company has implemented." Of all responses, the following list shows the percentage of responses for each encapsulation: o Ethernet Tagged Mode - RFC 4448 = 76.5% o Ethernet Raw Mode - RFC 4448 = 82.4% o SAToP - RFC 4553 = 11.8% o PPP - RFC 4618 = 11.8% o HDLC - RFC 4618 = 5.9% o Frame Relay (Port Mode) - RFC 4619 = 17.6% o Frame Relay (1:1 Mode) - RFC 4619 = 41.2% o ATM (N:1 Mode) - RFC 4717 = 5.9% o ATM (1:1 Mode) - RFC 4717 = 17.6% o ATM (AAL5 SDU Mode) - RFC 4717 = 5.9% o ATM (AAL5 PDU Mode) - RFC 4717 = 0.0% o CEP - RFC 4842 = 0.0% o CESoPSN - RFC 5086 = 11.8% o TDMoIP - RFC 5087 = 11.8% o Fiber Channel (Port Mode) - "Encapsulation Methods for Transport of Fibre Channel" (now RFC 6307) = 5.9%
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2.4. Number of Pseudowires Deployed

The following question was asked: "Approximately how many pseudowires are deployed of each encapsulation type. Note, this should be the number of pseudowires in service, carrying traffic, or pre-positioned to do so." The following list shows the number of pseudowires in use for each encapsulation: o Ethernet Tagged Mode = 93,861 o Ethernet Raw Mode = 94,231 o SAToP - RFC 4553 = 20,050 o PPP - RFC 4618 = 500 o HDLC - RFC 4618 = 0 o Frame Relay (Port Mode) - RFC 4619 = 5,002 o Frame Relay (1:1 Mode) - RFC 4619 = 50,959 o ATM (N:1 Mode) - RFC 4717 = 50,000 o ATM (1:1 Mode) - RFC 4717 = 70,103 o ATM (AAL5 SDU Mode) - RFC 4717 = 0 o ATM (AAL5 PDU Mode) - RFC 4717 = 0 o CEP - RFC 4842 = 0 o CESoPSN - RFC 5086 = 21,600 o TDMoIP - RFC 5087 = 20,000 o Fiber Channel (Port Mode) - "Encapsulation Methods for Transport of Fibre Channel" (now RFC 6307) = 0 In the above responses (on several occasions), the response was in the form of "> XXXXX" where the response indicated a number greater than the one provided. Where applicable, the number itself was used in the sums above. For example, ">20K" and "20K+" yielded 20K.
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   Additionally, the following encapsulations were listed as "In-Use"
   with no quantity provided:

   o  Ethernet Raw Mode: 2 Responses

   o  ATM (AAL5 SDU Mode): 1 Response

   o  TDMoIP: 1 Response

2.5. VCCV Control Channel in Use

The following instructions were given: "Please indicate which VCCV Control Channel is used for each encapsulation type. Understanding that users may have different networks with varying implementations, for your network in general, please select all which apply." The numbers below indicate the number of responses. The responses were: o Ethernet Tagged Mode - RFC 4448 * Control Word (Type 1) = 7 * Router Alert Label (Type 2) = 3 * TTL Expiry (Type 3) = 3 o Ethernet Raw Mode - RFC 4448 * Control Word (Type 1) = 8 * Router Alert Label (Type 2) = 4 * TTL Expiry (Type 3) = 4 o SAToP - RFC 4553 * Control Word (Type 1) = 1 * Router Alert Label (Type 2) = 0 * TTL Expiry (Type 3) = 0 o PPP - RFC 4618 * Control Word (Type 1) = 0 * Router Alert Label (Type 2) = 0 * TTL Expiry (Type 3) = 0
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   o  HDLC - RFC 4618

      *  Control Word (Type 1) = 0

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 0

   o  Frame Relay (Port Mode) - RFC 4619

      *  Control Word (Type 1) = 1

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 0

   o  Frame Relay (1:1 Mode) - RFC 4619

      *  Control Word (Type 1) = 3

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 2

   o  ATM (N:1 Mode) - RFC 4717

      *  Control Word (Type 1) = 1

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 0

   o  ATM (1:1 Mode) - RFC 4717

      *  Control Word (Type 1) = 1

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 1

   o  ATM (AAL5 SDU Mode) - RFC 4717

      *  Control Word (Type 1) = 0

      *  Router Alert Label (Type 2) = 1

      *  TTL Expiry (Type 3) = 0
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   o  ATM (AAL5 PDU Mode) - RFC 4717

      *  Control Word (Type 1) = 0

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 0

   o  CEP - RFC 4842

      *  Control Word (Type 1) = 0

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 0

   o  CESoPSN - RFC 5086

      *  Control Word (Type 1) = 0

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 1

   o  TDMoIP - RFC 5087

      *  Control Word (Type 1) = 0

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 0

   o  Fiber Channel (Port Mode) - "Encapsulation Methods for Transport
      of Fibre Channel" (now RFC 6307)

      *  Control Word (Type 1) = 0

      *  Router Alert Label (Type 2) = 0

      *  TTL Expiry (Type 3) = 0
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2.6. VCCV Connectivity Verification Types in Use

The following instructions were given: "Please indicate which VCCV Connectivity Verification types are used in your networks for each encapsulation type." Note that Bidirectional Forwarding Detection (BFD) was not one of the choices. The responses were as follows: o Ethernet Tagged Mode - RFC 4448 * ICMP Ping = 5 * LSP Ping = 11 o Ethernet Raw Mode - RFC 4448 * ICMP Ping = 6 * LSP Ping = 11 o SAToP - RFC 4553 * ICMP Ping = 0 * LSP Ping = 2 o PPP - RFC 4618 * ICMP Ping = 0 * LSP Ping = 0 o HDLC - RFC 4618 * ICMP Ping = 0 * LSP Ping = 0 o Frame Relay (Port Mode) - RFC 4619 * ICMP Ping = 0 * LSP Ping = 1 o Frame Relay (1:1 Mode) - RFC 4619 * ICMP Ping = 2 * LSP Ping = 5
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   o  ATM (N:1 Mode) - RFC 4717

      *  ICMP Ping = 0

      *  LSP Ping = 1

   o  ATM (1:1 Mode) - RFC 4717

      *  ICMP Ping = 0

      *  LSP Ping = 3

   o  ATM (AAL5 SDU Mode) - RFC 4717

      *  ICMP Ping = 0

      *  LSP Ping = 1

   o  ATM (AAL5 PDU Mode) - RFC 4717

      *  ICMP Ping = 0

      *  LSP Ping = 0

   o  CEP - RFC 4842

      *  ICMP Ping = 0

      *  LSP Ping = 0

   o  CESoPSN - RFC 5086

      *  ICMP Ping = 0

      *  LSP Ping = 1

   o  TDMoIP - RFC 5087

      *  ICMP Ping = 0

      *  LSP Ping = 1

   o  Fiber Channel (Port Mode) - "Encapsulation Methods for Transport
      of Fibre Channel" (now RFC 6307)

      *  ICMP Ping = 0

      *  LSP Ping = 0
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2.7. Control Word Support for Encapsulations for Which CW Is Optional

The following instructions were given: "Please indicate your network's support of and use of the Control Word for encapsulations for which the Control Word is optional." The responses were: o Ethernet (Tagged Mode) * Supported by Network/Equipment = 13 * Used in Network = 6 o Ethernet (Raw Mode) * Supported by Network/Equipment = 14 * Used in Network = 7 o PPP * Supported by Network/Equipment = 5 * Used in Network = 0 o HDLC * Supported by Network/Equipment = 4 * Used in Network = 0 o Frame Relay (Port Mode) * Supported by Network/Equipment = 3 * Used in Network = 1 o ATM (N:1 Cell Mode) * Supported by Network/Equipment = 5 * Used in Network = 1
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2.8. Open-Ended Question

Space was provided for user feedback. The following instructions were given: "Please use this space to provide any feedback regarding PW and VCCV deployments, VCCV interoperability challenges, this survey or any network/vendor details you wish to share." Below are the responses, made anonymous. The responses are otherwise provided here verbatim. 1. BFD VCCV Control Channel is not indicated in the survey (may be required for PW redundancy purpose) 2. Using CV is not required at the moment 3. COMPANY has deployed several MPLS network elements, from multiple vendors. COMPANY is seeking a uniform implementation of VCCV Control Channel (CC) capabilities across its various vendor platforms. This will provide COMPANY with significant advantages in reduced operational overheads when handling cross-domain faults. Having a uniform VCCV feature implementation in COMPANY multi-vendor network leads to: o Reduced operational cost and complexity o Reduced OSS development to coordinate incompatible VCCV implementations. o Increased end-end service availability when handing faults. In addition, currently some of COMPANY deployed VCCV traffic flows (on some vendor platforms) are not guaranteed to follow those of the customer's application traffic (a key operational requirement). As a result, the response from the circuit ping cannot faithfully reflect the status of the circuit. This leads to ambiguity regarding the operational status of our networks. An in-band method is highly preferred, with COMPANY having a clear preference for VCCV Circuit Ping using PWE Control Word. This preference is being pursued with each of COMPANY vendors. 4. PW VCCV is very useful tool for finding faults in each PW channel. Without this we can not find fault on a PW channel. PW VCCV using BFD is another better option. Interoperability challenges are with Ethernet OAM mechanism.
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   5.  We are using L2PVPN AToM like-to-like models - ATMoMPLS - EoMPLS
       ATMoMPLS : This service offered for transporting ATM cells over
       IP/MPLS core with Edge ATM CE devices including BPX, Ericsson
       Media Gateway etc.  This is purely a Port mode with cell-packing
       configuration on it to have best performance.  QoS marking is
       done for getting LLQ treatment in the core for these MPLS
       encapsulated ATM packets.  EoMPLS: This service offered for
       transporting 2G/3G traffic from network such as Node-B to RNC's
       over IP/MPLS backbone core network.  QoS marking is done for
       getting guaranteed bandwidth treatment in the core for these MPLS
       encapsulated ATM packets.  In addition to basic L2VPN service
       configuration, these traffic are routed via MPLS TE tunnels with
       dedicated path and bandwidth defined to avoid bandwidth related
       congestion.

   6.  EQUIPMENT MANUFACTURER does not provide options to configure VCCV
       control-channel and its sub options for LDP based L2Circuits.
       How can we achieve end-to-end management and fault detection of
       PW without VCCV in such cases?

   7.  I'm very interested in this work as we continue to experience
       interop challenges particularly with newer vendors to the space
       who are only implementing VCCV via control word.  Vendors who
       have tailed their MPLS OAM set specifically to the cell backhaul
       space and mandatory CW have been known to fall into this space.
       That's all I've got.

3. Security Considerations

As this document is an informational report of the PW/VCCV User Implementation Survey results, no protocol security considerations are introduced.

4. Acknowledgements

We would like to thank the chairs of the PWE3 working group for their guidance and review of the survey questions. We would also like to sincerely thank those listed in Section 2.2. who took the time and effort to participate.
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5. Informative References

[RFC4448] Martini, L., Rosen, E., El-Aawar, N., and G. Heron, "Encapsulation Methods for Transport of Ethernet over MPLS Networks", RFC 4448, April 2006. [RFC4618] Martini, L., Rosen, E., Heron, G., and A. Malis, "Encapsulation Methods for Transport of PPP/High-Level Data Link Control (HDLC) over MPLS Networks", RFC 4618, September 2006. [RFC4717] Martini, L., Jayakumar, J., Bocci, M., El-Aawar, N., Brayley, J., and G. Koleyni, "Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks", RFC 4717, December 2006. [RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", December 2007. [RFC6307] Black, D., Dunbar, L., Roth, M., and R. Solomon, "Encapsulation Methods for Transport of Fibre Channel Traffic over MPLS Networks", RFC 6307, April 2012.


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