PCE Working Group D. Dhody
Internet-Draft Q. Wu
Intended status: Standards Track Huawei Technologies
Expires: January 22, 2015 July 21, 2014
Path Computation Element communication Protocol extension for
relationship between LSPs and Attributes
draft-dhody-pce-association-attr-01
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, policy or behaviors).
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Opaque Identifier . . . . . . . . . . . . . . . . . . . . 3
3.2. Policy based Constraints . . . . . . . . . . . . . . . . 3
3.3. Bundled requests . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Attribute Association Group . . . . . . . . . . . . . . . . . 5
5.1. ATTRIBUTE-OBJECT-TLV . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 8
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 behaviors).
This document specifies a PCEP extension to associate one or more
LSPs with a set of attributes, which includes, but not limited to -
o Configured Parameters
o Policies
o Behaviour
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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.
AGID: Association Group ID.
LSR: Label Switch Router.
MPLS: Multiprotocol Label Switching.
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).
3.2. 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
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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 associate a set of LSPs with
policy and its resulting path computation constraints. This way
simplifying the path computation message exchanges.
3.3. 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, 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 uses the same association for
attributes, 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 associated attributes. The scope and
handling of AAG identifier is similar to the generic association
identifier defined in [I-D.minei-pce-association-group].
One or more LSP are grouped via a common group identifier in the same
way as [I-D.minei-pce-association-group]. The attributes that may be
associated with this set of LSPs may either are -
o 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.
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o 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.
Error handling would be taken up in future revision.
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 Attribute Association Type.
This document does not have any new type-specific flags.
AAG may carry optional TLVs including but not limited to -
o ATTRIBUTE-OBJECT-TLV: Used to communicate associated attributes in
form of PCEP objects, described in this document.
o VENDOR-INFORMATION-TLV: Used to communicate arbitrary behavioral
information, described in [RFC7150].
5.1. ATTRIBUTE-OBJECT-TLV
The ATTRIBUTE-OBJECT-TLV maybe included in AAG object to associate
attributes encoded in PCEP objects.
The format of the ATTRIBUTE-OBJECT-TLV is shown in the following
figure:
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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=[TBD] | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object-Class | OT |Res|P|I| Object Length (bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object-Class | OT |Res|P|I| Object Length (bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object-Class | OT |Res|P|I| Object Length (bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: ATTRIBUTE-OBJECT-TLV format
The type of the TLV is [TBD] and it has a variable length. The value
part consist of the PCEP object header [RFC5440] identifying the
objects that are associated with this AAG. Thus this TLV identify
the attributes present in the PCEP message that are associated with
this group. Future PCEP messages may only carry the AAG.
6. Security Considerations
TBD
7. IANA Considerations
TBD
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, March 1997.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
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[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", draft-
minei-pce-association-group-00 (work in progress), June
2014.
9.2. Informative References
[RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
"Policy-Enabled Path Computation Framework", RFC 5394,
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, November
2012.
[RFC7150] Zhang, F. and A. Farrel, "Conveying Vendor-Specific
Constraints in the Path Computation Element Communication
Protocol", RFC 7150, March 2014.
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Appendix A. Contributor Addresses
Xian Zhang
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R.China
EMail: zhang.xian@huawei.com
Udayasree Palle
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
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
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