Using the Generic Associated Channel Label for Pseudowire in the MPLS Transport Profile (MPLS-TP)
draft-ietf-pwe3-mpls-tp-gal-in-pw-01

Network Working Group                                            Han Li 
Internet Draft                                             China Mobile 
Updates (if published): RFC5586 
Intended status: Standards Track                           Luca Martini 
                                                           Cisco System 
                                                                       
                                                                 Jia He 
                                                                 Huawei 
                                                                       
                                                             Feng Huang 
                                                         Alcatel-Lucent 
                                                                       
                                                                       
Expires: November 2011                                     May 11, 2011 
                                      

    Using the Generic Associated Channel Label for Pseudowire in MPLS-TP 
                 draft-ietf-pwe3-mpls-tp-gal-in-pw-01.txt 

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Abstract 

   This document describes the requirements for using the Generic 
   Associated Channel Label (GAL) in Pseudowires (PWs) in MPLS-TP 
   networks, and provides an update to the description of GAL usage in 
   [RFC5586] by removing the restriction that is imposed on using GAL 
   for PWs especially in MPLS-TP environments. 

   . 

Table of Contents 

    
   1. Introduction ................................................ 2 
   2. Conventions used in this document ........................... 3 
      2.1. Terminology ............................................ 3 
   3. GAL Usage for MPLS-TP PW .................................... 3 
   4. Security Considerations ..................................... 4 
   5. IANA Considerations ......................................... 4 
   6. Acknowledgments ............................................. 5 
   7. References .................................................. 5 
      7.1. Normative References ................................... 5 
      7.2. Informative References ................................. 5 
   8. Authors' Addresses .......................................... 5 
    
1. Introduction 

   [RFC5586] generalizes the associated control channel mechanism of 
   [RFC5085] to be used for Sections, Label Switched Paths (LSPs), and 
   Pseudowires (PWs) in MPLS networks. [RFC5085] defines the Associated 
   Channel Header (ACH), and [RFC5586] generalizes this for use in the 
   Generic Associated Channel (G-ACh).  

   [RFC5586] defines a generalized label-based exception mechanism using 
   the Generic Associated Channel Label (GAL) to work together with the 
   ACH for use with LSPs but places restrictions on GAL usage with PWs.  

   This document removes the restriction imposed by [RFC5586]. 

    

 
 
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2. Conventions used in this document 

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 
   document are to be interpreted as described in [RFC 2119]. 

2.1. Terminology 

   ACH      Associated Channel Header 

   CW       Control Word 

   G-ACh    Generic Associated Channel 

   GAL      G-ACh Label 

   MPLS-TP  MPLS Transport Profile 

   OAM      Operation, Administration, and Maintenance 

3. GAL Usage for MPLS-TP PW  

   According to the MPLS-TP requirement document [RFC5654], it is 
   necessary that MPLS-TP mechanisms and capabilities be able to 
   interoperate with the existing IETF MPLS [RFC3031] and IETF PWE3 
   [RFC3985] architectures appropriate. [RFC5586] differentiates between 
   the usage of the GAL with PWs in MPLS and MPLS-TP environments in 
   section 4.2 as follows:  

       In MPLS-TP, the GAL MUST be used with packets on a G-ACh on LSPs, 
       Concatenated Segments of LSPs, and with Sections, and MUST NOT be 
       used with PWs. 

   This indicates that the GAL can be used for MPLS-TP LSPs and Sections, 
   but not for PWs using an MPLS-TP PSN. 

   However, there is no restriction imposed on the usage of the GAL in 
   MPLS PWs, which is described immediately afterwards in the same 
   section of [RFC5586] (Section 4.2): 

       However, in other MPLS environments, this document places no 
       restrictions on where the GAL may appear within the label stack 
       or its use with PWs. 

   The inconsistency between the usage of the GAL with MPLS PWs and 
   MPLS-TP PWs may cause unnecessary implementation differences and is 
   in disagreement with the MPLS-TP requirements. 
 
 
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   Therefore, this document specifies that the GAL can be used with 
   packets on a G-ACh on LSPs, Concatenated Segments of LSPs, Sections, 
   and PWs in both MPLS and MPLS-TP environments without discrimination.  

   [RFC5586] is updated by removing the restrictions on using GAL for PW 
   as follows: 

   -  Section 1 (Introduction) in [RFC5586], the original text: 

          The GAL mechanism is defined to work together with the ACH for 
          LSPs and MPLS Sections. 

      is replaced by: 

          The GAL mechanism is defined to work together with the ACH for 
          LSPs and MPLS Sections, and for PWs. 

   -  Section 4.2. (GAL Applicability and Usage) in [RFC5586], the 
      original text: 

          In MPLS-TP, the GAL MUST be used with packets on a G-ACh on 
          LSPs, Concatenated Segments of LSPs, and with Sections, and 
          MUST NOT be used with PWs. It MUST always be at the bottom of 
          the label stack (i.e., S bit set to 1). However, in other MPLS 
          environments, this document places no restrictions on where 
          the GAL may appear within the label stack or its use with PWs. 

      is replaced by: 

          In MPLS-TP, the GAL MUST be used with packets on a G-ACh on 
          LSPs, Concatenated Segments of LSPs, and with Sections, and 
          MAY be used with PWs. It MUST always be at the bottom of the 
          label stack (i.e., S bit set to 1). However, in other MPLS 
          environments, this document places no restrictions on where 
          the GAL may appear within the label stack. 

4. Security Considerations 

   No further security considerations than [RFC5586]. 

5. IANA Considerations 

   There are no IANA actions required. 

 
 
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6. Acknowledgments 

   The authors would like to thank Luyuan Fang, Adrian Farrel, Haiyan 
   Zhang, Guanghui Sun, Italo Busi, Matthew Bocci for their 
   contributions to this work. 

   The authors would also like to thank the authors of [RFC5586] and 
   people who were involved in the development of [RFC5586]. 

7. References 

7.1. Normative References 

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

   [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 
             Label Switching Architecture", RFC 3031, January 2001. 

   [RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge 
             (PWE3) Architecture", RFC 3985, March 2005. 

   [RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic 
             Associated Channel", RFC5586, June 2009 

7.2. Informative References 

   [RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit 
             Connectivity Verification (VCCV): A Control Channel for 
             Pseudowires", RFC 5085, December 2007. 

   [RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., 
             and S. Ueno, "Requirements of an MPLS Transport Profile", 
             RFC 5654, September 2009. 

    

8. Authors' Addresses 

   Han Li
   China Mobile Communications Corporation
   Email: lihan@chinamobile.com

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   Luca Martini
   Cisco Systems, Inc.
   Email: lmartini@cisco.com

   Jia He
   Huawei Technologies Co., Ltd.
   Email: hejia@huawei.com

   Feng Huang
   Alcatel-Lucent shanghai Bell
   Email: feng.f.huang@alcatel-sbell.com.cn

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   Copyright (c) 2010 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 
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