Path Computation Element communication Protocol extension for relationship between LSPs and Attributes or Policies
draft-dhody-pce-association-attr-05

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

Status of This Memo

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This Internet-Draft will expire on April 27, 2017.

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Table of Contents

• 1. Introduction
• 1.1. Requirements Language
• 2. Terminology
• 3. Motivation
• 3.1. Opaque Identifier
• 3.2. Bundled requests
• 4. Overview
• 5. Attribute Association Group
• 5.1. ATTRIBUTE-OBJECT-TLV
• 6. Security Considerations
• 7. IANA Considerations
• 7.1. Association object Type Indicators
• 7.2. PCEP TLV Type Indicators
• 8. Manageability Considerations
• 8.1. Control of Function and Policy
• 8.2. Information and Data Models
• 8.3. Liveness Detection and Monitoring
• 8.4. Verify Correct Operations
• 8.5. Requirements On Other Protocols
• 8.6. Impact On Network Operations
• 9. Acknowledgments
• 10. References
• 10.1. Normative References
• 10.2. Informative References
• Appendix A. Policy
• Appendix B. Contributor Addresses
• Authors' Addresses

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.ietf-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) and is equally applicable to the active and passive modes of a stateful PCE and a stateless PCE.

This document specifies a PCEP extension to associate one or more LSPs with a set of attributes.

PCEP Extensions for Stateful PCE Model [I-D.ietf-pce-stateful-pce] describes a set of extensions to PCEP to enable active control of MPLS-TE and GMPLS tunnels. [I-D.ietf-pce-pce-initiated-lsp] describes the setup and teardown of PCE-initiated LSPs under the active stateful PCE model, without the need for local configuration on the PCC, thus allowing for a dynamic network. The mechanims described in this document is equally applicable to these deployment models.

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.

AAG:

Attribute Association Group.

LSR:

Label Switch Router.

MPLS:

Multiprotocol Label Switching.

PAG:

Policy Association Group.

PCC:

Path Computation Client. Any client application requesting a path computation to be performed by a Path Computation Element.

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.

PCEP:

Path Computation Element Communication Protocol.

3. Motivation

This section discusses in more detail the motivation and use cases for such an association including but not limited to -

3.1. Opaque Identifier

An opaque identifier may represent attributes such as configured parameters or constraints that a PCEP speaker may invoke on a peer. Thus a PCEP speaker may only need an opaque identifier to invoke these attributes (parameters or constraints) rather than encoding them explicitly in each PCEP message.

This can also be used for tagging bunch of LSP to a particular customer or for creation of virtual network like in case of Abstraction and Control of TE Networks (ACTN) [I-D.ietf-teas-actn-requirements]. (See [I-D.leedhody-pce-vn-association])

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 association is used to identify these constraints and attributes shared by multiple requests and grouped together via association mechanism, thus simplifying the path computation message exchanges.

4. Overview

As per [I-D.ietf-pce-association-group], LSPs are associated with other LSPs with which they interact by adding them to a common association group. This grouping can then be used to define associations between sets of LSPs or between a set of LSPs and a set of attributes (such as configuration parameters). A new optional Association Object-type is defined based on the generic Association object -

• Attribute Association Group (AAG)

Thus this document defines a new association type called "Attribute Association Type" of value TBD1. An AAG can have one or more LSPs and its associated attributes. The scope and handling of AAG identifier is similar to the generic association identifier defined in [I-D.ietf-pce-association-group].

One or more LSP are grouped via a single group identifier as defined in [I-D.ietf-pce-association-group]. The attributes that may be associated with this set of LSPs may either are -

• known to the PCEP peers via some external means like configuration, policy enforcement etc (can be considered as 'out-of-band'). PCEP speaker simply use the AAG identifier in the PCEP message and the peer is supposed to be aware of the associated attributes. This is suitable for stateless PCE where the PCEP peers should be aware of the association and its significance outside of the protocol.
• or communicated to the PCEP peer via PCEP itself on first use (can be considered as 'in-band'). PCEP speaker creates a new AAG by using a new identifier and the associated attributes are communicated via TLVs in association object. This is applicable for stateful PCE only.

Error handling would be taken up in future revision.

5. Attribute Association Group

The format of the generic 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |         Reserved              |            Flags            |R|
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      Association type (TBD1)  |      Association ID           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              IPv4 Association Source                          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //                   Optional TLVs                             //
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |         Reserved              |            Flags            |R|
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      Association type (TBD1)  |      Association ID           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 |                    IPv6 Association Source                    |
 |                                                               |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //                   Optional TLVs                             //
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     

 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 (TBD2)         |           Length              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object-Class  |   OT  |Res|P|I|   Object Length (bytes)       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
//                        (Object body)                        //
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    

Value     Name                        Reference
TBD1      Attribute Association Type  [This I.D.]

Value     Name                        Reference
TBD2      ATTRIBUTE-OBJECT-TLV        [This I.D.]

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

EMail: zhang.xian@huawei.com

Udayasree Palle
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka  560066
India

EMail: udayasree.palle@huawei.com