PCE Working Group D. Dhody
Internet-Draft Huawei Technologies
Intended status: Standards Track Q. Wu
Expires: January 2, 2015 Huawei
July 2014

Path Computation Element communication Protocol extension for relationship between LSPs and Attributes


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 defines a mechanism to create associations between a set of LSPs and a set of attributes (such as configuration parameters or behaviors).

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Table of Contents

1. Introduction

[RFC5440] describes the Path Computation Element communication Protocol (PCEP) which enables the communication between a Path Computation Client (PCC) and a Path Control Element (PCE), or between two PCEs based on the PCE architecture [RFC4655].

[I-D.minei-pce-association-group] introduces a generic mechanism to create a grouping of LSPs which can then be used to define associations between a set of LSPs and a set of attributes (such as configuration parameters or behaviours).

This document specifies a PCEP extension to associate one or more LSPs with a set of attributes, which includes, but not limited to -

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.

Association Group ID.
Label Switch Router.
Multiprotocol Label Switching.
Path Computation Client. Any client application requesting a path computation to be performed by a Path Computation Element.
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.
Path Computation Element Communication Protocol.

3. Motivation

This section discusses in more detail the motivation and use cases for such a assosiation.

3.1. Policy based Constraints

In the context of policy-enabled path computation [RFC5394], path computation policies may be applied at both a PCC and a PCE. Consider an Label Switch Router (LSR) with a policy enabled PCC, it receives a service request via signaling, including over a Network-Network Interface (NNI) or User Network Interface (UNI) reference point, or receives a configuration request over a management interface to establish a service. The PCC may also apply user- or service-specific policies to decide how the path selection process should be constrained, that is, which constraints, diversities, optimization criterion, and constraint relaxation strategies should be applied in order for the service LSP(s) to have a likelihood to be successfully established and provide necessary QoS and resilience against network failures. The user- or service-specific policies applied to PCC and are then passed to the PCE along with the Path computation request, in the form of constraints [RFC5394].

PCEP speaker can use the generic mechanism as per [I-D.minei-pce-association-group] to assosiate a set of LSPs with policy and its resulting path computation constraints. This way simplifying the path computation message exchanges.

3.2. Bundled requests

In some scenarios(e.g.,the topology example described in Section 4.6 of [RFC6805]), there is a need to send multiple requests with the same constraints and attributes to the PCE. Currently these requests are either sent in a separate path computation request (PCReq) messages or bundled together in one (or more) PCReq messages. In either case, the constraints and attributes need to be encoded separately for each request even though they are exactly identical.

If a assosiation is used to identify these constraints and attributes shared by multiple requests, thus simplifying the path computation message exchanges.

4. Overview

As per [I-D.minei-pce-association-group], LSPs are associated with other LSPs with which they interact by adding them to a common association group. This document use the same association for attributes and called Attribute Association Group (AAG) based on the generic Association object. This document defines a new association type called "Attribute Association Type" of value TBD. An AAG can have one or more LSPs and its assosiated attributes. The scope and handling of AAG identifier is similar to the generic association identifier defined in [I-D.minei-pce-association-group].

5. Attribute Association Group

The format of the Association object used for AAG is shown in Figure 1:

 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   |  Generic flags    |R| Type-specific flags             |
|             Association group id                              |
//            Optional TLVs                                    //

Figure 1: The Association Object format

Type - TBD for the Path Protection Associaiton Type

6. Security Considerations


7. IANA Considerations


8. Acknowledgments

A special thanks to author of [I-D.minei-pce-association-group], this document borrow some of the text from it.

9. References

9.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC4655] Farrel, A., Vasseur, J. and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009.
[I-D.minei-pce-association-group] Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H., Zhang, X. and Y. Tanaka, "PCEP Extensions for Establishing Relationships Between Sets of LSPs", Internet-Draft draft-minei-pce-association-group-04, November 2015.

9.2. Informative References

[RFC5394] Bryskin, I., Papadimitriou, D., Berger, L. and J. Ash, "Policy-Enabled Path Computation Framework", RFC 5394, DOI 10.17487/RFC5394, December 2008.
[RFC6805] King, D. and A. Farrel, "The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS", RFC 6805, DOI 10.17487/RFC6805, November 2012.

Appendix A. Contributor Addresses

Xian Zhang
Huawei Technologies
Bantian, Longgang District
Shenzhen  518129

EMail: zhang.xian@huawei.com
Udayasree Palle
Huawei Technologies
Leela Palace
Bangalore, Karnataka  560008

EMail: udayasree.palle@huawei.com


Authors' Addresses

Dhruv Dhody Huawei Technologies Leela Palace Bangalore, Karnataka 560008 INDIA EMail: dhruv.ietf@gmail.com
Qin Wu Huawei Technologies 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China EMail: sunseawq@huawei.com