Internet Engineering Task Force S. Sivabalan
Internet-Draft J. Medved
Intended status: Informational Cisco Systems, Inc.
Expires: July 30, 2013 January 28, 2013
IGP Extensions for Stateful PCE Discovery
draft-sivabalan-pce-disco-stateful-00
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 . . . . . . . . . . . . . . . . . . . . . . . . . 2
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1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Overview of Protocol Extensions . . . . . . . . . . . . . . . 3
4. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 3
5. Management Considerations . . . . . . . . . . . . . . . . . . 3
6. Security Considerations . . . . . . . . . . . . . . . . . . . 3
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 4
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. A
mechanism for instantiating LSPs on a PCC using stateful PCE is
specified in [I-D.crabbe-pce-pce-initiated-lsp]. Such mechanism is
considered useful in applications such as Software Defined Networks
(SDN), demand engineering, etc.
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 or capable to actively instantiate LSPs on a PCC.
Advertising such capabilities would facilitate a PCC to learn about
available stateful PCEs, as well as about a PCE's capability to
instantiate LSPs. 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]). This document extends the
IGP capability advertisement mechanism to include stateful PCE and
PCE-based LSP instantiation capabilities.
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
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The following terminology is used in this document:
IGP: Interior Gateway Protocol
IS-IS: Intermediate System to Intermediate System
LSR: Label Switching Router
OSPF: Open Shortest Path First
PCC: Path Computation Client
PCE: Path Computation Element
PCEP: Path Computation Element Protocol
3. Overview of Protocol Extensions
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 value field of the PCE-CAP-FLAGS sub-TLV is made up of an array
of units of 32-bit flags numbered from the most significant as bit 0,
where each bit represents one PCE capability.
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
9 Support stateful PCE capability
10 Support PCE-based tunnel instantiation capability
4. Backward Compatibility
An LSR that does not support the new IGP PCE capability bits
specified in this document silently ignores those bits.
5. Management Considerations
TBD.
6. Security Considerations
Security considerations described in [RFC5088] are applicable to
stateful PCE capabilities. No additional security measures are
required.
7. IANA Considerations
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IANA is requested to allocate a new bit in "PCE Capability Flags"
registry for stateful PCE capability as follows:
Bit Meaning Reference
9 Stateful PCE capability This document
10 PCE-based tunnel instantiation capability This document
Table 1
8. References
8.1. Normative References
[I-D.crabbe-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", Internet-Draft draft-crabbe-pce-pce-initiated-
lsp-00, October 2012.
[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", Internet-Draft draft-ietf-idr-ls-
distribution-01, October 2012.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE", Internet-Draft draft-ietf-
pce-stateful-pce-02, October 2012.
[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.L. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
Authors' Addresses
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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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