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

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 . 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 - Configured Parameters Policies Behaviour

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 .

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.

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

In the context of policy-enabled path computation , 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 . PCEP speaker can use the generic mechanism as per to assosiate a set of LSPs with policy and its resulting path computation constraints. This way simplifying the path computation message exchanges.

In some scenarios(e.g.,the topology example described in Section 4.6 of ), 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.

As per , 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 .

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

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 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type - TBD for the Path Protection Associaiton Type

TBD

A special thanks to author of , this document borrow some of the text from it.