PCE Working Group S. Sivabalan
Internet-Draft J. Medved
Intended status: Standards Track Cisco Systems, Inc.
Expires: July 13, 2014 X. Zhang
Huawei Technologies
January 13, 2014
IGP Extensions for Stateful PCE Discovery
draft-sivabalan-pce-disco-stateful-03
Abstract
When a PCE is a Label Switching Router (LSR) participating in the
Interior Gateway Protocol (IGP), or even a server participating in
IGP, its presence and path computation capabilities can be advertised
using IGP flooding. Such IGP extensions exist for OSPF and ISIS.
This document specifies two new PCE capabilities advertised by IGP.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IGP Extensions for Stateful PCE Capabilities . . . . . . . . . 4
4. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 5
5. Management Considerations . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP),
which defines the communication between a Path Computation Client
(PCC) and a Path Control Element (PCE), or between PCE and PCE,
enabling computation of Multiprotocol Label Switching (MPLS) for
Traffic Engineering Label Switched Path (TE LSP) characteristics.
Stateful PCE [I-D.ietf-pce-stateful-pce] specifies a set of
extensions to PCEP to enable stateful control of TE LSPs between and
across PCEP sessions in compliance with [RFC4657]. It includes
mechanisms to effect LSP state synchronization between PCCs and PCEs,
delegation of control of LSPs to PCEs, and PCE control of timing and
sequence of path computations within and across PCEP sessions. It
focuses on a model where LSPs are configured on the PCC and the LSP's
path routing and the timing of its setup is delegated to the PCE.
When PCCs are LSRs participating in the IGP (OSPF or IS-IS), and PCEs
are either LSRs or servers also participating in the IGP, an
effective mechanism for PCE discovery within an IGP routing domain
consists of utilizing IGP advertisements. Such extension to OSPF to
IS-IS exists in [RFC5088] and [RFC5089], respectively. Currently,
the IGP PCE capability does not indicate whether the advertised PCE
is stateful. Advertising active and passive stateful PCE
capabilities would facilitate a PCC to learn about available stateful
PCEs, as well as about a PCE's capability to modify LSP parameters.
A PCC could listen to IGP updates, or use other mechanisms that carry
IGP information to interested clients, such as BGP-LS
([I-D.ietf-idr-ls-distribution]) where IGP PCE capability
advertisements can be carried in the Opaque Prefix Attribute defined
in Section 3.3.3.6. This document extends the IGP PCE capability
advertisement mechanism to include active and passive stateful PCEs.
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 RFC 2119 [RFC2119]
2. Terminology
The following terminology is used in this document:
IGP: Interior Gateway Protocol
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IS-IS: Intermediate System to Intermediate System
LSR: Label Switching Router
OSPF: Open Shortest Path First
PCC: Path Computation Client
PCE: Path Computation Client
PCEP: Path Computation Client
3. IGP Extensions for Stateful PCE Capabilities
The PCE-CAP-FLAGS sub-TLV is an optional sub-TLV used to advertise
PCE capabilities. It MAY be present within the PCED sub-TLV carried
by OSPF or IS-IS. [RFC5088] and [RFC5089] provide the description
and processing rules for this sub-TLV when carried within OSPF and
IS-IS, respectively.
The PCE-CAP-FLAGS sub-TLV has the following format:
o TYPE: 5
o LENGTH: Multiple of 4
o VALUE: This contains an array of units of 32 bit flags with the
most significant bit as 0. Each bit represents one PCE capability
PCE capability bits are defined in [RFC5088]. This document defines
new capability bits for the stateful PCE as follows:
Bit Capability
11 Active Stateful PCE capability
12 Passive Stateful PCE capability
Note that while active and passive stateful PCE capabilities may be
advertised during discovery, PCEP Speakers that wish to use stateful
PCEP MUST negotiate stateful PCEP capabilities during PCEP session
setup, as specified in Section 7.1.1 in [I-D.ietf-pce-stateful-pce].
A PCC MAY initiate stateful PCEP capability negotiation at PCEP
session setup even if it did not receive any IGP PCE capability
advertisements.
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4. Backward Compatibility
An LSR that does not support the new IGP PCE capability bits
specified in this document silently ignores those bits.
IGP extensions defined in this document do not introduce any new
interoperability issues.
5. Management Considerations
A configuration option may be provided for advertising and
withdrawing Stateful PCE IGP capability on a PCE.
6. Security Considerations
Security considerations described in [RFC5088] are applicable to
stateful PCE capabilities. No additional security measures are
required.
7. IANA Considerations
IANA is requested to allocate new bits in "PCE Capability Flags"
registry for stateful PCE capability as follows:
Bit Meaning Reference
11 Active stateful PCE capability This document
12 Passive stateful PCE capability This document
8. References
8.1. Normative References
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-04
(work in progress), November 2013.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE",
draft-ietf-pce-stateful-pce-07 (work in progress),
December 2013.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"IS-IS Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5089, January 2008.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
8.2. Informative References
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
Authors' Addresses
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
Jan Medved
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134
USA
Email: jmedved@cisco.com
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Xian Zhang
Huawei Technologies
F3-5-B R&D Center, Huawei Base Bantian, Longgang District
Shenzhen, Guangdong 518129
P.R.China
Email: zhang.xian@huawei.com
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