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Versions: 00 draft-dhody-pce-recv-srlg

PCE Working Group                                               D. Dhody
Internet-Draft                                                  F. Zhang
Intended status: Standards Track                                X. Zhang
Expires: April 11, 2014                              Huawei Technologies
                                                        October 08, 2013


             PCEP Extensions for Receiving SRLG Information
                   draft-dhody-pce-srlg-collection-00

Abstract

   The Path Computation Element (PCE) provides functions of path
   computation in support of traffic engineering in networks controlled
   by Multi-Protocol Label Switching (MPLS) and Generalized MPLS
   (GMPLS).

   This document provides extensions for the Path Computation Element
   Protocol (PCEP) to support collection of Shared Risk Link Group
   (SRLG) information during path computation and encoding this
   information in the reply message.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on April 11, 2014.

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



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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  PCEP Requirements . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Extension to PCEP . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  The Extension of the RP Object  . . . . . . . . . . . . .   4
     4.2.  SRLG Subobject in ERO . . . . . . . . . . . . . . . . . .   4
   5.  Other Considerations  . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Backward Compatibility  . . . . . . . . . . . . . . . . .   5
     5.2.  Confidentiality via PathKey . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Manageability Considerations  . . . . . . . . . . . . . . . .   5
     7.1.  Control of Function and Policy  . . . . . . . . . . . . .   5
     7.2.  Information and Data Models . . . . . . . . . . . . . . .   5
     7.3.  Liveness Detection and Monitoring . . . . . . . . . . . .   5
     7.4.  Verify Correct Operations . . . . . . . . . . . . . . . .   6
     7.5.  Requirements On Other Protocols . . . . . . . . . . . . .   6
     7.6.  Impact On Network Operations  . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  New Subobjects for the ERO Object . . . . . . . . . . . .   6
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   6
   Appendix A.  Contributor Addresses  . . . . . . . . . . . . . . .   8

1.  Introduction

   As per [RFC4655], PCE based path computation model is deployed in
   large, multi-domain, multi-region, or multi-layer networks.  In such
   case PCEs may cooperate with each other to provide end to end optimal
   path.

   It is important to understand which TE links in the network might be
   at risk from the same failures.  In this sense, a set of links may
   constitute a 'shared risk link group' (SRLG) if they share a resource
   whose failure may affect all links in the set [RFC4202].  H-LSP
   (Hierarchical LSP) or S-LSP (Stitched LSP) can be used for carrying
   one or more other LSPs as described in [RFC4206] and [RFC6107].
   H-LSP and S-LSP may be computed by PCE(s) and further form as a TE



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   link.  The SRLG information of such LSPs can be collected during path
   computation itself and encoded in the PCEP Path Computation Reply
   (PCRep) message.  [I-D.zhang-ccamp-gmpls-uni-app] describes the use
   of PCE for end to end User-Network Interface (UNI) path computation.

   [I-D.farrel-interconnected-te-info-exchange] describes a scaling
   problem with SRLGs in multi-layer environment and introduce a concept
   of Macro SRLG.  Lower layer SRLG collection at the time of path
   computation can be used to generate such a Macro SRLG at the PCE.

   Note that [I-D.ietf-ccamp-rsvp-te-srlg-collect] specifies a similar
   extension to Resource ReserVation Protocol-Traffic Engineering (RSVP-
   TE) where SRLG information is collected at the time of signaling.

1.1.  Requirements Language

   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.  Terminology

   The following terminology is used in this document.

   CPS:  Confidential Path Segment.  A segment of a path that contains
      nodes and links that the policy requires not to be disclosed
      outside the domain.

   PCE:  Path Computation Element.  An entity (component, application,
      or network node) that is capable of computing a network path or
      route based on a network graph and applying computational
      constraints.

   SRLG:  Shared Risk Link Group.

   UNI:  User-Network Interface.

3.  PCEP Requirements

   Following key requirements are identified for PCEP to enable SRLG
   information collection during path computation:

   SRLG Collection Indication:  The PCEP speaker must be capable of
      indicating whether the SRLG information of the LSP should be
      collected during the path computation procedure.






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   SRLG Collection:  If requested, the SRLG information should be
      collected during the path computation and encoded in the PCRep
      message.

4.  Extension to PCEP

   This document extends the existing RP (Request Parameters) object
   [RFC5440] so that a PCEP speaker can request SRLG information
   collection during path computation.  The SRLG subobject maybe carried
   inside the Explicit Route Object (ERO) in the PCRep message.

4.1.  The Extension of the RP Object

   This document adds the following flags to the RP Object:

   S (SRLG - 1 bit):  when set, in a PCReq message, this indicates that
      the SRLG information of the Label switched path (LSP) should be
      collected during the path computation procedure.  Otherwise, when
      cleared, this indicates that the SRLG information should not be
      collected.  In a PCRep message, when the S bit is set this
      indicates that the returned path in ERO also carry the SRLG
      information; otherwise (when the S bit is cleared), the returned
      path does not carry SRLG information.

4.2.  SRLG Subobject in ERO

   As per [RFC5440], ERO is used to encode the path of a TE LSP and is
   carried within a PCRep message to provide the computed path when
   computation was successful.

   The SRLG of a path is the union of the SRLGs of the links in the LSP
   [RFC4202].  The SRLG subobject is defined in
   [I-D.ietf-ccamp-rsvp-te-srlg-collect], as shown below:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |     Length    |  Reserved     |    Flags      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 SRLG ID 1 (4 bytes)                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                           ......                              ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 SRLG ID n (4 bytes)                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






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   The meaning and description of Type, Length and SRLG ID can be found
   in [I-D.ietf-ccamp-rsvp-te-srlg-collect].  Bits in the Flags field is
   ignored.

   The SRLG subobject should be encoded inside the ERO object in the
   PCRep message when the S-Bit (SRLG) is set in the PCReq message.

5.  Other Considerations

5.1.  Backward Compatibility

   If a PCE receives a request and the PCE does not understand the new
   SRLG flag in the RP object, then the PCE SHOULD reject the request.

   If PCEP speaker receives a PCRep message with SRLG subobject that it
   does not support or recognize, it must act according to the existing
   processing rules.

5.2.  Confidentiality via PathKey

   [RFC5520] defines a mechanism to hide the contents of a segment of a
   path, called the Confidential Path Segment (CPS).  The CPS may be
   replaced by a path-key that can be conveyed in the PCEP and signaled
   within in a RSVP-TE ERO.

   When path-key confidentiality is used, collection of SRLG information
   and encoding this information in PCRep along with the path-key could
   be useful to compute a SRLG disjoint backup path at the later
   instance.

6.  Security Considerations

   TBD.

7.  Manageability Considerations

7.1.  Control of Function and Policy

   TBD.

7.2.  Information and Data Models

   TBD.

7.3.  Liveness Detection and Monitoring

   TBD.




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7.4.  Verify Correct Operations

   TBD.

7.5.  Requirements On Other Protocols

   TBD.

7.6.  Impact On Network Operations

   TBD.

8.  IANA Considerations

   IANA assigns values to PCEP parameters in registries defined in
   [RFC5440].  IANA is requested to make the following additional
   assignments.

8.1.  New Subobjects for the ERO Object

   IANA has previously assigned an Object-Class and Object-Type to the
   ERO carried in PCEP messages [RFC5440].  IANA also maintains a list
   of subobject types valid for inclusion in the ERO.

   IANA is requested to assign one new subobject types for inclusion in
   the ERO as follows:

                  Subobject Meaning         Reference
                   34 (TBD) SRLG sub-object This document


9.  Acknowledgments

   TBD.

10.  References

10.1.  Normative References

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

10.2.  Informative References

   [RFC4202]  Kompella, K. and Y. Rekhter, "Routing Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4202, October 2005.




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   [RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
              Hierarchy with Generalized Multi-Protocol Label Switching
              (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [RFC4874]  Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
              Extension to Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE)", RFC 4874, April 2007.

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440, March
              2009.

   [RFC5520]  Bradford, R., Vasseur, JP., and A. Farrel, "Preserving
              Topology Confidentiality in Inter-Domain Path Computation
              Using a Path-Key-Based Mechanism", RFC 5520, April 2009.

   [RFC6107]  Shiomoto, K. and A. Farrel, "Procedures for Dynamically
              Signaled Hierarchical Label Switched Paths", RFC 6107,
              February 2011.

   [I-D.ietf-ccamp-rsvp-te-srlg-collect]
              Zhang, F., Li, D., Dios, O., Margaria, C., and M. Hartley,
              "RSVP-TE Extensions for Collecting SRLG Information",
              draft-ietf-ccamp-rsvp-te-srlg-collect-03 (work in
              progress), September 2013.

   [I-D.farrel-interconnected-te-info-exchange]
              Farrel, A., Drake, J., Bitar, N., Swallow, G., and D.
              Ceccarelli, "Problem Statement and Architecture for
              Information Exchange Between Interconnected Traffic
              Engineered Networks", draft-farrel-interconnected-te-info-
              exchange-01 (work in progress), July 2013.

   [I-D.zhang-ccamp-gmpls-uni-app]
              Zhang, F., Dios, O., Farrel, A., Zhang, X., and D.
              Ceccarelli, "Applicability of Generalized Multiprotocol
              Label Switching (GMPLS) User-Network Interface (UNI)",
              draft-zhang-ccamp-gmpls-uni-app-04 (work in progress),
              July 2013.









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Appendix A.  Contributor Addresses

   Udayasree Palle
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: udayasree.palle@huawei.com

   Avantika
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: avantika.sushilkumar@huawei.com


Authors' Addresses

   Dhruv Dhody
   Huawei Technologies
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: dhruv.ietf@gmail.com


   Fatai Zhang
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen, Guangdong  518129
   P.R.China

   EMail: zhangfatai@huawei.com


   Xian Zhang
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen, Guangdong  518129
   P.R.China

   EMail: zhang.xian@huawei.com





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