draft-ietf-pce-inter-layer-req-09.txt   draft-ietf-pce-inter-layer-req-10.txt 
Network Working Group T. Takeda (Ed.) Network Working Group T. Takeda (Ed.)
Internet Draft NTT Internet Draft NTT
Category: Informational A. Farrel (Ed.) Category: Informational A. Farrel
Created: December 2008 Old Dog Consulting Created: August 21, 2009 Old Dog Consulting
Expires: February 21, 2010
PCC-PCE Communication and PCE Discovery Requirements for PCC-PCE Communication and PCE Discovery Requirements for
Inter-Layer Traffic Engineering Inter-Layer Traffic Engineering
draft-ietf-pce-inter-layer-req-09.txt draft-ietf-pce-inter-layer-req-10.txt
Status of this Memo Status of this Memo
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http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
The Path Computation Element (PCE) provides functions of path The Path Computation Element (PCE) provides functions of path
computation in support of traffic engineering in Multi-Protocol Label computation in support of traffic engineering in Multi-Protocol Label
Switching (MPLS) and Generalized MPLS (GMPLS) networks. Switching (MPLS) and Generalized MPLS (GMPLS) networks.
MPLS and GMPLS networks may be constructed from layered client/server MPLS and GMPLS networks may be constructed from layered client/server
networks. It is advantageous for overall network efficiency to networks. It is advantageous for overall network efficiency to
provide end-to-end traffic engineering across multiple network layers. provide end-to-end traffic engineering across multiple network
PCE is a candidate solution for such requirements. layers. PCE is a candidate solution for such requirements.
Generic requirements for a communication protocol between Path Generic requirements for a communication protocol between Path
Computation Clients (PCCs) and PCEs are presented in "PCE Computation Clients (PCCs) and PCEs are presented in "PCE
Communication Protocol Generic Requirements". Generic requirements Communication Protocol Generic Requirements". Generic requirements
for PCE discovery protocol are presented in "Requirements for Path for PCE discovery protocol are presented in "Requirements for Path
Computation Element (PCE) Discovery". Computation Element (PCE) Discovery".
This document complements the generic requirements and presents This document complements the generic requirements and presents
detailed sets of PCC-PCE communication protocol requirements and PCE detailed sets of PCC-PCE communication protocol requirements and PCE
discovery protocol requirements for inter-layer traffic engineering. discovery protocol requirements for inter-layer traffic engineering.
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................3
1.1. Terminology..................................................3 1.1. Terminology..................................................3
2. Motivation for PCE-Based Inter-Layer Path Computation..........4 2. Motivation for PCE-Based Inter-Layer Path Computation..........4
3. PCC-PCE Communication and Discovery Requirements for Inter-Layer 3. PCC-PCE Communication and Discovery Requirements for
Traffic Engineering...............................................5 Inter-Layer Traffic Engineering................................5
3.1. PCC-PCE Communication........................................5 3.1. PCC-PCE Communication........................................5
3.1.1. Control of Inter-Layer Path Computation....................5 3.1.1. Control of Inter-Layer Path Computation....................5
3.1.2. Control of The Type of Path to be Computed.................5 3.1.2. Control of The Type of Path to be Computed.................5
3.1.3. Communication of Inter-Layer Constraints...................6 3.1.3. Communication of Inter-Layer Constraints...................7
3.1.4. Adaptation Capability......................................7 3.1.4. Adaptation Capability......................................7
3.1.5. Cooperation Between PCEs...................................7 3.1.5. Cooperation Between PCEs...................................7
3.1.6. Inter-Layer Diverse paths..................................7 3.1.6. Inter-Layer Diverse paths..................................7
3.2. Capabilities Advertisements for PCE Discovery................7 3.2. Capabilities Advertisements for PCE Discovery................8
3.3. Supported Network Models.....................................8 3.3. Supported Network Models.....................................8
4. Manageability considerations...................................8 4. Manageability considerations...................................8
4.1. Control of Function and Policy...............................8 4.1. Control of Function and Policy...............................8
4.2. Information and Data Models..................................8 4.2. Information and Data Models..................................9
4.3. Liveness Detection and Monitoring............................9 4.3. Liveness Detection and Monitoring............................9
4.4. Verifying Correct Operation..................................9 4.4. Verifying Correct Operation..................................9
4.5. Requirements on Other Protocols and Functional Components....9 4.5. Requirements on Other Protocols and Functional Components....9
4.6. Impact on Network Operation.................................10 4.6. Impact on Network Operation.................................10
5. Security Considerations.......................................10 5. Security Considerations.......................................10
6. IANA Considerations...........................................10 6. IANA Considerations...........................................10
7. Acknowledgments...............................................10 7. Acknowledgments...............................................10
8. References....................................................10 8. References....................................................11
8.1. Normative References........................................10 8.1. Normative References........................................11
8.2. Informative References......................................11 8.2. Informative References......................................11
9. Authors' Addresses............................................12 9. Authors' Addresses............................................12
1. Introduction 1. Introduction
The Path Computation Element (PCE) defined in [RFC4655] is an entity The Path Computation Element (PCE) defined in [RFC4655] is an entity
that is capable of computing a network path or route based on a that is capable of computing a network path or route based on a
network graph, and applying computational constraints. network graph, and applying computational constraints.
A network may comprise multiple layers. These layers may represent A network may comprise multiple layers. These layers may represent
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"REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in RFC 2119 [RFC2119] for clarity of interpreted as described in RFC 2119 [RFC2119] for clarity of
requirement specification. requirement specification.
2. Motivation for PCE-Based Inter-Layer Path Computation 2. Motivation for PCE-Based Inter-Layer Path Computation
[RFC4206] defines a way to signal an MPLS or a GMPLS LSP with an [RFC4206] defines a way to signal an MPLS or a GMPLS LSP with an
explicit route in a higher layer of a network that includes hops explicit route in a higher layer of a network that includes hops
traversed by LSPs in lower layers of the network. The computation of traversed by LSPs in lower layers of the network. The computation of
end-to-end paths across layers is called Inter-Layer Path Computation. end-to-end paths across layers is called Inter-Layer Path
Computation.
An LSR in the higher layer might not have information on the topology An LSR in the higher layer might not have information on the topology
of lower layers, particularly in an overlay or augmented model, and of lower layers, particularly in an overlay or augmented model, and
hence might not be able to compute an end-to-end path across layers. hence might not be able to compute an end-to-end path across layers.
PCE-based inter-layer path computation, consists of relying on one or PCE-based inter-layer path computation, consists of relying on one or
more PCEs to compute an end-to-end path across layers. This could more PCEs to compute an end-to-end path across layers. This could
rely on a single PCE path computation where the PCE has topology rely on a single PCE path computation where the PCE has topology
information about multiple layers and can directly compute an end-to- information about multiple layers and can directly compute an end-to-
end path across layers considering the topology of all of the layers. end path across layers considering the topology of all of the layers.
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hops) of one or more lower-layer LSPs not yet established. hops) of one or more lower-layer LSPs not yet established.
The path computation response from a PCE to a PCC MUST report the The path computation response from a PCE to a PCC MUST report the
type of path computed, and where a multi-layer path is returned, PCEP type of path computed, and where a multi-layer path is returned, PCEP
MUST support the inclusion, as part of end-to-end path, of the path MUST support the inclusion, as part of end-to-end path, of the path
of the lower-layer LSPs to be established. of the lower-layer LSPs to be established.
If a response message from a PCE to PCC carries a mono-layer path If a response message from a PCE to PCC carries a mono-layer path
that is specified by strict hops but includes virtual TE link(s), or that is specified by strict hops but includes virtual TE link(s), or
includes loose hop(s), or carries a multi-layer path that can include includes loose hop(s), or carries a multi-layer path that can include
the complete path of one or more lower-layer LSPs not yet established, the complete path of one or more lower-layer LSPs not yet
the signaling of the higher-layer LSP may trigger the establishment established, the signaling of the higher-layer LSP may trigger the
of the lower-layer LSPs (triggered signaling). The triggered establishment of the lower-layer LSPs (triggered signaling). The
signaling may increase the higher-layer connection setup latency. An triggered signaling may increase the higher-layer connection setup
ingress LSR for the higher-layer LSP, or a PCC, needs to know whether latency. An ingress LSR for the higher-layer LSP, or a PCC, needs to
triggered signaling is required or not. know whether triggered signaling is required or not.
A request from a PCC to a PCE MUST allow indicating whether triggered A request from a PCC to a PCE MUST allow indicating whether triggered
signaling is acceptable or not. signaling is acceptable or not.
A response from a PCE to a PCC MUST allow indicating whether the A response from a PCE to a PCC MUST allow indicating whether the
computed path requires triggered signaling or not. computed path requires triggered signaling or not.
Note that a PCE may not be able to distinguish virtual TE links from Note that a PCE may not be able to distinguish virtual TE links from
regular TE links. In such cases, even if a request from a PCC to a regular TE links. In such cases, even if a request from a PCC to a
PCE indicates that triggered signaling is not acceptable, a PCE may PCE indicates that triggered signaling is not acceptable, a PCE may
choose virtual TE links in path computation. Therefore, when a choose virtual TE links in path computation. Therefore, when a
network uses virtual TE links and a PCE is not able to distinguish network uses virtual TE links and a PCE is not able to distinguish
virtual TE links from regular TE links, it MUST be understood that a virtual TE links from regular TE links, it MUST be understood that a
PCE may choose virtual TE links even if a request from a PCC to a PCE PCE may choose virtual TE links even if a request from a PCC to a PCE
indicates triggered signaling is not acceptable. indicates triggered signaling is not acceptable.
Also note that an ingress LSR may be present in multiple layers. Thus, Also note that an ingress LSR may be present in multiple layers.
when a mono-layer path is requested or supplied, PCEP MUST be able to Thus, when a mono-layer path is requested or supplied, PCEP MUST be
indicate the required/provided path layer. able to indicate the required/provided path layer.
3.1.3. Communication of Inter-Layer Constraints 3.1.3. Communication of Inter-Layer Constraints
A request from a PCC to a PCE MUST support the inclusion of A request from a PCC to a PCE MUST support the inclusion of
constraints for a multi-layer path. This includes control over which constraints for a multi-layer path. This includes control over which
network layers may, must, or must not be included in the computed network layers may, must, or must not be included in the computed
path. Such control may be expressed in terms of the switching types path. Such control may be expressed in terms of the switching types
of the layer networks. of the layer networks.
Furthermore, it may be desirable to constrain the number of layer Furthermore, it may be desirable to constrain the number of layer
boundaries crossed (i.e., the number of adaptations performed on the boundaries crossed (i.e., the number of adaptations performed on the
end-to-end path), so PCEP SHOULD include a constraint or objective end-to-end path), so PCEP SHOULD include a constraint or objective
function to minimize or cap the number of adaptations on a path, and function to minimize or cap the number of adaptations on a path, and
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the behavior of an individual PCECP request to the originating PCC. the behavior of an individual PCECP request to the originating PCC.
In particular, where a request is forwarded between multiple PCEs In particular, where a request is forwarded between multiple PCEs
neither the PCC nor the first PCE can monitor the liveness of all neither the PCC nor the first PCE can monitor the liveness of all
inter-PCE-PCE connections or of the PCEs themselves. In this case, inter-PCE-PCE connections or of the PCEs themselves. In this case,
suitable performance of the original PCEP request relies on each PCE suitable performance of the original PCEP request relies on each PCE
operating correct monitoring procedures and correlating any failures operating correct monitoring procedures and correlating any failures
back to the PCEP requests that are outstanding. These requirements back to the PCEP requests that are outstanding. These requirements
are no different from those for any cooperative PCE usage, and are are no different from those for any cooperative PCE usage, and are
expected to be already covered by general, and by inter-AS and inter- expected to be already covered by general, and by inter-AS and inter-
area implementations. Such a procedure is specified in [BRPC]. area implementations. Such a procedure is specified in [RFC5441].
In addition, [PCEP-MON] specifies mechanisms to gather various state In addition, [PCEP-MON] specifies mechanisms to gather various state
metrics along the path computation chain. metrics along the path computation chain.
4.4. Verifying Correct Operation 4.4. Verifying Correct Operation
There are no additional requirements beyond those expressed in There are no additional requirements beyond those expressed in
[RFC4657] for verifying the correct operation of the PCEP. Note that [RFC4657] for verifying the correct operation of the PCEP. Note that
verification of the correct operation of the PCE and its algorithms verification of the correct operation of the PCE and its algorithms
is out of scope for the protocol requirements, but a PCC MAY send the is out of scope for the protocol requirements, but a PCC MAY send the
same request to more than one PCE and compare the results. same request to more than one PCE and compare the results.
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Element (PCE)-Based Architecture", RFC 4655, September Element (PCE)-Based Architecture", RFC 4655, September
2006. 2006.
[RFC4657] J. Ash, J.L Le Roux et al., " Path Computation Element [RFC4657] J. Ash, J.L Le Roux et al., " Path Computation Element
(PCE) Communication Protocol Generic Requirements", RFC (PCE) Communication Protocol Generic Requirements", RFC
4657, September 2006. 4657, September 2006.
[RFC4674] JL Le Roux et al., "Requirements for Path Computation [RFC4674] JL Le Roux et al., "Requirements for Path Computation
Element (PCE) Discovery", RFC 4674, September 2006. Element (PCE) Discovery", RFC 4674, September 2006.
[RFC5145] K. Shiomoto, "Framework for MPLS-TE to GMPLS Migration",
RFC 5145, March 2008.
[RFC5146] K. Kumaki et al., "Interworking Requirements to Support
Operation of MPLS-TE over GMPLS Networks", RFC 5146, March
2008.
[RFC5212] K. Shiomoto et al., "Requirements for GMPLS-Based Multi- [RFC5212] K. Shiomoto et al., "Requirements for GMPLS-Based Multi-
Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July
2008. 2008.
[PCE-INTER-LAYER-FRWK] E. Oki et al., "Framework for PCE-Based [PCE-INTER-LAYER-FRWK] E. Oki et al., "Framework for PCE-Based
Inter-Layer MPLS and GMPLS Traffic Engineering", draft- Inter-Layer MPLS and GMPLS Traffic Engineering", draft-
ietf-pce-inter-layer-frwk (work in progress). ietf-pce-inter-layer-frwk (work in progress).
[PCEP-MIB] A. Koushik, and E. Stephan, "PCE communication protocol [PCEP-MIB] A. Koushik, and E. Stephan, "PCE communication protocol
(PCEP) Management Information Base", draft-kkoushik-pce- (PCEP) Management Information Base", draft-ietf-pce-pcep-
pcep-mib (work in progress). mib (work in progress).
[RFC5145] K. Shiomoto, "Framework for MPLS-TE to GMPLS Migration",
RFC 5145, March 2008.
[RFC5146] K. Kumaki et al., "Interworking Requirements to Support
Operation of MPLS-TE over GMPLS Networks", RFC 5146, March
2008.
[BRPC] JP. Vasseur (Ed.), "A Backward Recursive PCE-based [RFC5441] JP. Vasseur (Ed.), "A Backward-Recursive PCE-Based
Computation (BRPC) Procedure To Compute Shortest Computation (BRPC) Procedure to Compute Shortest
Constrained Inter-domain Traffic Engineering Label Switched Constrained Inter-Domain Traffic Engineering Label Switched
Paths", draft-ietf-pce-brpc (work in progress). Paths", RFC 5441, April 2009.
[PCEP-MON] JP. Vasseur (Ed.), "A set of monitoring tools for Path [PCEP-MON] JP. Vasseur (Ed.), "A set of monitoring tools for Path
Computation Element based Architecture", draft-ietf-pce- Computation Element based Architecture", draft-ietf-pce-
Monitoring (work in progress). Monitoring (work in progress).
9. Authors' Addresses 9. Authors' Addresses
Eiji Oki Eiji Oki
University of Electro-Communications University of Electro-Communications
Tokyo Tokyo, Japan
Japan
Email: oki@ice.uec.ac.jp Email: oki@ice.uec.ac.jp
Jean-Louis Le Roux Jean-Louis Le Roux
France Telecom R&D, France Telecom R&D,
Av Pierre Marzin, Av Pierre Marzin,
22300 Lannion, France 22300 Lannion, France
Email: jeanlouis.leroux@orange-ftgroup.com Email: jeanlouis.leroux@orange-ftgroup.com
Kenji Kumaki Kenji Kumaki
KDDI Corporation KDDI Corporation
Garden Air Tower Garden Air Tower
Iidabashi, Chiyoda-ku, Iidabashi, Chiyoda-ku,
Tokyo 102-8460, JAPAN Tokyo 102-8460, JAPAN
Phone: +81-3-6678-3103
Email: ke-kumaki@kddi.com Email: ke-kumaki@kddi.com
Adrian Farrel Adrian Farrel
Old Dog Consulting Old Dog Consulting
Email: adrian@olddog.co.uk Email: adrian@olddog.co.uk
Tomonori Takeda Tomonori Takeda
NTT NTT
3-9-11 Midori-cho, 3-9-11 Midori-cho,
Musashino-shi, Tokyo 180-8585, Japan Musashino-shi, Tokyo 180-8585, Japan
Email: takeda.tomonori@lab.ntt.co.jp Email: takeda.tomonori@lab.ntt.co.jp
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