Path Computation Element communication
Protocol extension for associating Policies and LSPsHuawei TechnologiesDivyashree Techno Park, WhitefieldBangaloreKarnataka560066Indiadhruv.ietf@gmail.comCisco Systems, Inc.2000 Innovation DriveKanataOntarioK2K 3E8Canadamsiva@cisco.comOrangestephane.litkowski@orange.comIndividualjefftant.ietf@gmail.comMetaswitch Networks100 Church StreetEnfieldMiddlesexUKJonathan.Hardwick@metaswitch.com
Routing
PCE Working Group
This document introduces a simple mechanism to associate policies to
a group of Label Switched Paths (LSPs) via an extension to the Path Computation
Element (PCE) Communication Protocol (PCEP). 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
.PCEP Extensions
for Stateful PCE Model
describes a set of extensions to PCEP to
enable active control of MPLS-TE and GMPLS tunnels.
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. Currently, the LSPs can either be signaled via RSVP-TE or can be
segment routed as specified in . 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 behaviors) and is equally applicable
to the active and passive modes of a stateful PCE or a stateless PCE.This document specifies a PCEP extension to associate one or
more LSPs with policies using the generic association mechanism.A PCEP speaker may want to influence the PCEP peer with respect
to path selection and other policies. This document describes a
PCEP extension to associate policies by creating Policy Association
Group (PAG) and encoding this association in PCEP messages. The
specification is applicable to both stateful and stateless
PCEP sessions.
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.Label Switch Router.Multiprotocol Label Switching.Policy Association Group.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.Paths computed using PCE MAY be subjected to various policies on
both PCE and PCC. For example, in a centralized traffic engineering
scenario, network operators may instantiate LSPs and specifies
policies for traffic steering, path monitoring, etc., for some LSPs
via the stateful PCE. Similarly, a PCC may request a user- or
service-specific policy to be applied at the PCE, such as constraints relaxation to
meet optimal QoS and resiliency. PCEP speaker can use the generic mechanism as per
to associate a set
of LSPs with policy, without the need to know the
details of such policies, which simplifies network operations, avoids
frequent software upgrades, as well provides an ability to introduce
new policy faster.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 associate a set
of LSPs with policy and its resulting path computation constraints.
This simplified 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. Grouping can also be used to
define association between LSPs
and policies associated to them.
One new Association Type is defined in this document,
based on the generic Association object -
Association type = TBD1 ("Policy
Association Type") for Policy Association Group (PAG) A PAG can have one or more LSPs and its associated policy(s).
The Association ID defined in
is used to identify the PAG.Association groups
and their memberships are defined using the ASSOCIATION object defined in
. Two object types for IPv4 and IPv6
are defined. The ASSOCIATION object includes "Association type" indicating
the type of the association group. This document add a new Association type - Association type = TBD1 ("Policy
Association Type") for PAG.PAG may carry optional TLVs including but not limited to -VENDOR-INFORMATION-TLV: Used to communicate arbitrary vendor specific behavioral
information, described in .This document defines one new type for association, which do not add any new
security concerns beyond those discussed in ,
and in itself. Some deployments may find policy associations and their implications
as extra sensitive
and thus should employ suitable PCEP security mechanisms like TCP-AO
or .This document defines the following new association type originally
defined in .
An operator MUST BE allowed to configure the policy associations at PCEP peers
and associate it with the LSPs. describes the PCEP MIB, there are no new MIB Objects
for this document.Mechanisms defined in this document do not imply any new liveness detection
and monitoring requirements in addition to those already listed in
.Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
.Mechanisms defined in this document do not imply any new requirements
on other protocols.Mechanisms defined in this document do not have any impact on
network operations in addition to those already listed in
.A special thanks to author of
, this document borrow
some of the text from it.