Network Working Group                                             L. Jin
Internet-Draft                                                   R. Chen
Intended status: Standards Track                                     ZTE
Expires: September 5, 2012                                 March 4, 2012


   Static pseudowire configuration checking using Generic Associated
                 Channel (G-ACh) Advertisement Protocol
              draft-jc-pwe3-mpls-tp-static-checking-00.txt

Abstract

   This draft introduces a way to do static pseudowire configuration
   checking, so as to easy the trouble shooting of static PW in MPLS-TP.
   The idea is to use Generic Associated Channel (G-ACh) Advertisement
   Protocol (GAP) [I-D.ietf-mpls-gach-adv] in underlying PSN Tunnel to
   transfer PW configuration parameters, to achieve static PW
   configuration checking.

Status of this Memo

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   This Internet-Draft will expire on September 5, 2012.

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  GAP Extensions  . . . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  Message Encoding  . . . . . . . . . . . . . . . . . . . . . 3
     3.2.  PE Procedure  . . . . . . . . . . . . . . . . . . . . . . . 5
       3.2.1.  PE message processing . . . . . . . . . . . . . . . . . 5
       3.2.2.  PW Configuration Check Process  . . . . . . . . . . . . 6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     7.1.  Normative references  . . . . . . . . . . . . . . . . . . . 7
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8































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1.  Introduction

   This draft introduces a way to do static pseudowire configuration
   checking, so as to easy the trouble shooting of static PW in MPLS-TP.
   The idea is to use Generic Associated Channel (G-ACh) Advertisement
   Protocol (GAP) [I-D.ietf-mpls-gach-adv] in underlying PSN Tunnel to
   transfer PW configuration parameters, to achieve static PW
   configuration checking.  A precondition of this functionality is that
   the underlying PSN Tunnel is already operational, and with GAP
   enabled.


2.  Motivation

   The manual configuration of static PW in MPLS-TP requires configuring
   many parameters at two PE sides, and these parameters should be
   aligned, so as to make PW be operational.  If one of the parameters
   on the two PE mis-matching, the PW would not operate correctly.  For
   the dynamic PW, the parameters would be negotiated by signaling
   session, and easy to find out the configuration error if PW is not
   operational UP.  But for static PW, there is no such kind of
   signaling session, it is difficult for operators to do trouble
   shooting, to figure out which parameters mis-match at two PE sides.

   In order to ease the trouble shooting of static PW, this draft relies
   on GAP running on underlying PSN Tunnel to transfer PW configuration
   parameters, so as to check PW configuration parameters automatically
   on each PE to figure out parameter mis-matching.


3.  GAP Extensions

3.1.  Message Encoding

   A new GAP application "static PW checking" is defined in this draft.
   The default lifetime would be 120 seconds.  Two new TLV objects
   "local static PW element" and "remote static PW element" are defined
   for this application, see the format below.













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        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   PW Element  |    Reserved   |            Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                        Generalized ID FEC                     +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Interface Parameters                    |
       |                              "                                |
       |                              "                                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |0|0| Incoming Label (0x0200)   |      Length                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Label                                                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |0|0| Outgoing Label (0x0200)   |      Length                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Label                                                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

   Local static PW element type: to be assigned by IANA.
   Remote static PW element type: to be assigned by IANA.

   The value of "local&remote static PW element" TLV should carry local
   static PW configuration and remote static PW configuration
   separately.  Multiple "local&remote static PW element" TLVs could be
   included in "static PW configuration" application data block.

   The value of "local&remote static PW element" TLV object would
   include:
   1.  Generalized PWid FEC (type 129) [RFC4447] along with AII Type 2
   [RFC5003];
   2.  Interface parameters TLV for Generalized PWid FEC defined in
   [RFC4447];
   3.  Incoming and outgoing generic label as defined in [RFC5036];

   The Generalized PWid FEC and incoming generic label MUST be included
   in static PW element.  The Incoming and outgoing will use same
   generic label type, and the first label should be the incoming label,
   and second label should be outgoing label.

   The remote static PW element SHOULD be sent only along with local
   static PW element, where the two PW elements belong to the same PW
   Path.  That means remote static PW element should not be sent



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   independently.

   The GAP Suppress message defined in [I-D.ietf-mpls-gach-adv] is only
   applied for one application.  We implement one particular static PW
   element suppressing by defining a new TLV, called PW Suppress TLV, to
   indicate suppressing special PW information transmission.  Multiple
   Generalized ID FEC elements could be included in this TLV.  The
   format would be as follows:


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |PW Suppress TLV|    Reserved   |            Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                        Generalized ID FEC                     +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 Multiple Generalized ID FEC!                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2

   The type of PW suppress TLV is to be assigned by IANA.  The format of
   Generalized ID FEC is defined in [RFC4447].  The C-bit, PW type in
   Generalized ID FEC should be zero.

   A GAP message could contain both local&remote static PW element TLV
   and PW Suppress TLV.

3.2.  PE Procedure

3.2.1.  PE message processing

   The GAP message of static PW checking application should be sent at
   least three times within lifetime.

   For the static PW, the parameters of one pseudowire needed would
   include: PW Path Identifier [RFC6370], PW type, Control Work, In&Out
   PW Label, interface parameters and etc.  When constructing "static PW
   element" TLV, all the PW parameters should be carried.

   When a PW is configured on the PE, and corresponding PSN Tunnel is
   operational UP, PE SHOULD send its local PW configuration information
   through GAP with local static PW element TLV.  If PE has already
   received remote PW configuration information belong to the same PW
   Path through "local static PW element" TLV from remote PE, the GAP



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   message SHOULD additionally include exactly the same received TLV in
   "remote static PW element" TLV.

   When the remote PE receives GAP message with static PW element TLV,
   it SHOULD save the PW parameters in "local static PW element" TLV as
   remote PW information for a period of "lifetime" which is specified
   in the GAP message.

   If the receiving GAP message also has "remote static PW element" TLV,
   PE should check local PW parameters with that in "remote static PW
   element" TLV.  If the same, PE should send GAP message with PW
   suppress TLV contained the specified PW information to peer PE.  If
   not, PE send GAP message with local PW configuration information
   carried in "local static PW element" TLV, and the received remote PW
   configuration information carried in "remote static PW element" TLV.

   Whenever PE receives the GAP message with PW suppress TLV, it SHOULD
   stop sending GAP message with specified PW information.  Whenever the
   PE updates locally PW configuration information, PE could send GAP
   message with static PW element to update information in remote PE.

3.2.2.  PW Configuration Check Process

   The PE would associate a PW with Generalized PWid FEC of:
       AGI = AGI
       SAII = A1-{Global_ID::Node_ID::AC_ID}
       TAII = Z9-{Global_ID::Node_ID::AC_ID}
   and a PW with Generalized PWid FEC of:
       AGI = AGI
       SAII = Z9-{Global_ID::Node_ID::AC_ID}
       TAII = A1-{Global_ID::Node_ID::AC_ID}
   as one PW Path.  When the PE has both local and remote PW parameters
   for one PW, it should do parameter checking as follows:
   1.  Check control word, if both sides have same capability.  If not,
   an error would report.
   2.  Check PW type, if both sides have the same.  If not, an error
   would report.
   3.  Check and negotiate interface parameters as defined in [RFC4447].
   4.  Check In&Out PW label, if local in_label equals remote out_label,
   and local out_label equals remote in_label.  If not, an error would
   report.

   The mechanism described in this draft could also be used as label
   advertisement, so as to avoid out_label negotiation manually between
   two PE, and to avoid mis-configuration.  Then the static PW is
   allowed to configure only in_label instead of both in&out label.
   Then if the remote PE does not send the out_label, PE will not check
   local in_label and remote out_label.  If PE does not have local



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   out_label, it should use remote in_label as local out_label.


4.  Security Considerations

   No new security threat is introduced by the mechanism in this draft.


5.  IANA Considerations

   IANA is requested to allocate a new Application ID in the "G-Ach
   Advertisement Protocol Applications and Data Types" registry.

   A new TLV Object "Local Static PW Element" type is requested to be
   allocated, suggested value would be 1.

   A new TLV Object "Remote Static PW Element" type is requested to be
   allocated, suggested value would be 2.

   A new TLV Object "PW Suppress TLV" type is requested to be allocated,
   suggested value would be 3.


6.  Acknowledgements

   The authors would like to thank Stewart Bryant for the his review and
   contributions.


7.  References

7.1.  Normative references

   [I-D.ietf-mpls-gach-adv]
              Frost, D., Bocci, M., and S. Bryant, "MPLS Generic
              Associated Channel (G-ACh) Advertisement Protocol",
              draft-ietf-mpls-gach-adv-00 (work in progress),
              January 2012.

7.2.  Informative References

   [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.

   [RFC5003]  Metz, C., Martini, L., Balus, F., and J. Sugimoto,
              "Attachment Individual Identifier (AII) Types for
              Aggregation", RFC 5003, September 2007.



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

   [RFC6370]  Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
              Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.


Authors' Addresses

   Lizhong Jin
   ZTE Corporation
   889, Bibo Road
   Shanghai, 201203, China

   Email: lizhong.jin@zte.com.cn


   Ran Chen
   ZTE Corporation
   No.19 East Huayuan Road
   Beijing, 100191, China

   Email: chen.ran@zte.com.cn




























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