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Versions: 00                                                            
Network Working Group                                        Yuanlin Bao
Internet-Draft                                                  Xihua Fu
Intended status: Informational                                 Fei Zhang
Expires: September 1, 2010                               ZTE Corporation
                                                       February 28, 2010


    LDP Signaling Extension For Management Plane To Control Plane PW
                Ownership Transfer In A MPLS-TP Network
               draft-bao-pwe3-pw-transfer-ldp-ext-00.txt

Abstract

   This memo describes an extension to LDP signaling that enables the PW
   ownership transfer between the Management Plane and the Control
   Plane.  This document defines all PW transfer related procedures.
   This includes the handling of failure conditions and subsequent
   reversion to original state.  A basic premise of the extension is
   that the transfer procedures must never impact an already established
   Data plane connection.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 1, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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 BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Conventions used in this document . . . . . . . . . . . . . 3
   2.  LDP Extension . . . . . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  PW Ownership Transfer TLV . . . . . . . . . . . . . . . . . 4
   3.  PW Transfer Procedure . . . . . . . . . . . . . . . . . . . . . 4
     3.1.  PW Ownership Transfer from MP to CP . . . . . . . . . . . . 4
       3.1.1.  MS-PW specification . . . . . . . . . . . . . . . . . . 5
       3.1.2.  Failure Handling  . . . . . . . . . . . . . . . . . . . 5
     3.2.  PW Ownership Transfer from CP to MP . . . . . . . . . . . . 5
       3.2.1.  Failure Handling  . . . . . . . . . . . . . . . . . . . 5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7





















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1.  Introduction

   As defined in [RFC3985] PWE3 is a mechanism that emulates the
   essential attributes of a telecommunications service (such as a T1
   leased line or Frame Relay) over a PSN.  Traditionally, pseudowir
   (PW) are controlled by means of a Network Management System (NMS)
   operating within the Management Plane (MP).  NMS/MP is the owner of
   PW, being responsible of it's set up, tear down and maintenance.

   The adoption of a PW Control Plane ([RFC4447] and [DYNAMIC-MS-PW]) in
   a network that is already in service - controlled by NMS at MP level
   - introduces the need for a procedure able to coordinate a control
   transfer of PW from MP to CP.

   In addition, the control transfer in the opposite direction, from CP
   to MP should be possible as well.  The procedures described in this
   memo can be applied to a PW in any DP switching technology and any
   network architecture.

   This memo describes an extension to LDP Protocol [RFC4447], [RFC5036]
   signaling that enables the transfer of PW ownership between the
   Management and the Control Planes.  All transfer related procedures
   are defined below.  This includes the handling of failure conditions
   and subsequent reversion to original state.  A basic premise of the
   extension is that the transfer procedures must never impact the
   exchange of user data on PWs that are already established in the data
   plane.

1.1.  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 [RFC2119].


2.  LDP Extension

   To ensure the PW ownership transfer between MP and CP automatically,
   T-PE/S-PE SHOULD has the knowledge that it is the PW transfer
   signaling message.  Furthermore, for MS-PW transfer T-PE/S-PE SHOULD
   know the next hop, so, the PW path MUST be carried in the LDP Label
   Mapping message.  Since [SEG-PW] has defined PW switching point TLV
   (S-PE TLV) and Sub-TLV to the switching points that the PW traverses,
   so S-PE TLV and Sub-TLV can be used to carry the PW path.  Therefore,
   this section only defines a new LDP TLV - Transfer TLV - which can be
   used to indicate a PW transfer signaling procedure.





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2.1.  PW Ownership Transfer TLV

   The PW Ownership Transfer TLV (PW-OH TLV) is defined as following:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0|0| PW Transfer  (0x0xxxx)     |        Length                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |POT|
     +-+-+

                    Figure 1: PW Ownership Transfer TLV

      POT (2 bits): PW Ownership Transfer.  This TLV is optional and
      carried in Optional Parameters of LDP Label Mapping and Label
      Withdraw message defined in [RFC5036].

      01 - PW ownership transfer from management plane to control plane

      11 - PW ownership transfer from control plane to management plane


3.  PW Transfer Procedure

3.1.  PW Ownership Transfer from MP to CP

   The MP to CP PW transfer procedure MUST create a LDP session along
   the path of the PW to be transfer from MP to CP, associat the LDP
   session to the existing FEC-Label mapping owned by the MP and at the
   same time transfer PW ownership to the CP.

   The operator instructs the source/destinational T-PE to transfer
   control of the PW from the MP to the CP.  For MS-PW operator MUST
   also supply the exact path of the MS-PW and FEC-Label mapping
   information.

   The source/destinational T-PE MUST check that no corresponding LDP
   state exists and that corresponding Data Plane state does exist.  If
   there is an error, this MUST be reported to the operator and further
   protocol action MUST NOT be taken.

   The source/destination T-PE completes the LDP initialization as the
   procedure described in [RFC5036] and [RFC4447].  After the LDP
   initialization, the source T-PE SHOULD sends a Label Mapping message
   with PW Ownership Transfer TLV in Optional Parameters to it's LDP
   peer the destination T-PE, and vis versa.  When destination/source
   T-PE receives this PW transfer Label Mapping message, it only creates



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   the LDP signaling state on the control plane, and any action for data
   plane MUST not be triggered.

3.1.1.  MS-PW specification

   o  The behaviour of T-PE

      The source/destination T-PE of PW transfering from MP to CP,
      SHOULD encond the PW path into S-PE TLV and Sub-TLV and set the Ho
      of PW-OH TLV to 01, then encond these TLVs into Label Mapping
      message.  After source/destination T-PE completes the Label
      Message enconding, it sends the message to the downstream node,
      i.e.  S-PE.

   o  The behaviour of S-PE

      When S-PE receives the PW transfer Label Mapping message, it
      SHOULD create the PW signaling state in the control plane, and get
      the next hop from the S-PE TLV and Sub-TLV.  After S-PE creates
      the PW signaling state in the control plane, it sends the PW
      transfer LDP Label Mapping message to the next hop.

3.1.2.  Failure Handling

   This section is to be studied in the next version.

3.2.  PW Ownership Transfer from CP to MP

   The CP to MP transfer procedure MUST delete the existing LDP session
   information and MUST NOT affect the cross-connected resources, but
   just move their ownership to the MP.  That is, after PW ownership
   transfer from CP to MP, the PW is no longer under control of LDP.

   The source/destination T-PE node MUST send a Label Withdraw message
   in the downstream direction with the Ho of PW-OH TLV set to 11
   carried in Optional Parameters.  No action is taken over the DP.  For
   MS-PW, S-PE must forward such message towards the source or
   destination node for forward and reverse direction respectively.
   Downstream nodes processing a Label Withdraw message MUST NOT remove
   any associated data plane state.

3.2.1.  Failure Handling

   This section is to be studied in the next version.







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4.  Security Considerations

   TBD.


5.  IANA Considerations

   TBD.


6.  Acknowledgements

   The RFC text was produced using Marshall Rose's xml2rfc tool.


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.

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

   [RFC4447]  Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
              Heron, "Pseudowire Setup and Maintenance Using the Label
              Distribution Protocol (LDP)", RFC 4447, April 2006.

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.

   [RFC5659]  Bocci, M. and S. Bryant, "An Architecture for Multi-
              Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
              October 2009.

7.2.  Informative References

   [DYNAMIC-MS-PW]
              Luca Martini, Matthew Bocci, and Florin Balus, "Dynamic
              Placement of Multi Segment Pseudo Wires",
              draft-ietf-pwe3-dynamic-ms-pw-10.txt Working in progress.

   [MPLS-TP-CP]
              Loa Andersson, Lou Berger, and Luyuan Fang, "MPLS-TP
              Control Plane Framework",
              draft-abfb-mpls-tp-control-plane-framework-01.txt Working
              in progress.



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   [SEG-PW]   Luca Martini and Chris Metz, "Segmented Pseudowire",
              draft-ietf-pwe3-segmented-pw-13.txt Working in progress.


Authors' Addresses

   Yuanlin Bao
   ZTE Corporation
   5F, R&D Building 3, ZTE Industrial Park, XiLi LiuXian Road
   Nanshan District, Shenzhen  518055
   P.R.China

   Phone: +86 755 26773731
   Email: bao.yuanlin@zte.com.cn
   URI:   http://www.zte.com.cn/


   Xihua Fu
   ZTE Corporation
   West District,ZTE Plaza,No.10,Tangyan South Road,Gaoxin District
   Xi An  710065
   P.R.China

   Phone: +86 13798412242
   Email: fu.xihua@zte.com.cn
   URI:   http://www.zte.com.cn/


   Fei Zhang
   ZTE Corporation
   NO.68, Zijinhua Road, Yuhuatai District
   Nanjing  210000
   P.R.China

   Phone: +86 25 52877612
   Email: zhang.fei3@zte.com.cn















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