PCE Working Group D. Dhody
Internet-Draft Q. Wu
Intended status: Standards Track Huawei Technologies
Expires: January 6, 2016 July 5, 2015
Path Computation Element communication Protocol extension for
relationship between LSPs and Attributes
draft-dhody-pce-association-attr-02
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 behaviours).
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 . . . . . . . . . . . . . . . . 4
3.3. Bundled requests . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Attribute Association Group . . . . . . . . . . . . . . . . . 5
5.1. ATTRIBUTE-OBJECT-TLV . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7.1. Association object Type Indicators . . . . . . . . . . . 7
7.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 7
8. Manageability Considerations . . . . . . . . . . . . . . . . 8
8.1. Control of Function and Policy . . . . . . . . . . . . . 8
8.2. Information and Data Models . . . . . . . . . . . . . . . 8
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 8
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 8
8.5. Requirements On Other Protocols . . . . . . . . . . . . . 8
8.6. Impact On Network Operations . . . . . . . . . . . . . . 8
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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) and is equally applicable to
the active and passive modes of a stateful PCE and a stateless PCE.
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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
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.
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.
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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
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
simplified 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 and grouped together via association
mechanism, 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 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 or behaviors). A new
optional Association Object is defined. 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.
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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 single group identifier as defined
in [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. This is suitable for stateless PCE where the PCEP
peers should be aware of the association and its significance
outside of the protocol.
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. 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:
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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 | Flags |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Flags |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Association Source |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The Association Object formats
Type - TBD for the Attribute Association Type.
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 behavioural
information, described in [RFC7150].
5.1. ATTRIBUTE-OBJECT-TLV
The ATTRIBUTE-OBJECT-TLV(s) 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 body) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: ATTRIBUTE-OBJECT-TLV format
The type of the TLV is [TBD] and it has a variable length. The value
part consist of a PCEP object (including common header [RFC5440]
identifying the object) that is associated with this AAG. This TLV
identifies the attributes associated with this group. For each
attribute a separate TLV is used. Future PCEP message exchanges may
only carry the AAG.
6. Security Considerations
This document defines a new type for association and a new ATTRIBUTE-
OBJECT-TLV which do not add any new security concerns beyond those
discussed in [RFC5440], [I-D.ietf-pce-stateful-pce] and
[I-D.minei-pce-association-group] in itself.
Some deployments may find these associations and their implications
as extra sensitive and thus should employ suitable PCEP security
mechanisms like TCP-AO or [I-D.ietf-pce-pceps].
7. IANA Considerations
7.1. Association object Type Indicators
This document defines the following new association type originally
defined in [I-D.minei-pce-association-group].
Value Name Reference
TBD Attribute Association Type [This I.D.]
7.2. PCEP TLV Type Indicators
This document defines the following new PCEP TLV; IANA is requested
to make the following allocations from this registry.
http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators
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Value Name Reference
TBD ATTRIBUTE-OBJECT-TLV [This I.D.]
8. Manageability Considerations
8.1. Control of Function and Policy
An operator MUST BE allowed to configure the attribute associations
at PCEP peers and associate it with the LSPs.
8.2. Information and Data Models
[RFC7420] describes the PCEP MIB, there are no new MIB Objects for
this document.
8.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
8.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440].
8.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
8.6. Impact On Network Operations
Mechanisms defined in this document do not have any impact on network
operations in addition to those already listed in [RFC5440].
9. Acknowledgments
A special thanks to author of [I-D.minei-pce-association-group], this
document borrow some of the text from it.
10. References
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10.1. 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.
[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-01 (work in progress), July
2015.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-11 (work in progress), April 2015.
10.2. 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.
[RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module", RFC
7420, December 2014.
[I-D.ietf-pce-pceps]
Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure
Transport for PCEP", draft-ietf-pce-pceps-04 (work in
progress), May 2015.
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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
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560037
INDIA
EMail: udayasree.palle@huawei.com
Authors' Addresses
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560037
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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