Internet DRAFT - draft-tantsura-bgp-ls-segment-routing-msd
draft-tantsura-bgp-ls-segment-routing-msd
IDR Working Group J. Tantsura
Internet-Draft G. Mirsky
Intended status: Standards Track Ericsson
Expires: July 11, 2016 S. Sivabalan
Cisco
U. Chunduri
Ericsson
January 8, 2016
Signaling Maximum SID Depth using Border Gateway Protocol Link-State
draft-tantsura-bgp-ls-segment-routing-msd-02
Abstract
This document discusses use of BGP-LS to expose node and/or link on a
node MSD "Maximum SID Depth" to a centralized controller (PCE/SDN).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 2
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 2
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 3
4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
When Segment Routing tunnels are computed by a centralized
controller, it is crucial that the controller knows MSD "Maximum SID
Depth" of the node or link SR tunnel exits over, so it doesn't
download a path with SID (label stack) of a depth more than the node
or link configured is capable of imposing.This document describes how
to use BGP-LS to expose the MSD of the node or link configured to a
centralized controller.
1.1. Conventions used in this document
1.1.1. Terminology
BGP-LS: Distribution of Link-State and TE Information using Border
Gateway Protocol
MSD: Maximum SID Depth
PCC: Path Computation Client
PCE: Path Computation Element
PCEP: Path Computation Element Protocol
SID: Segment Identifier
SR: Segment routing
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1.1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
2. Problem Statement
In existing technology only PCEP has extension to signal the MSD (SR
PCE Capability TLV/ METRIC Object as defined in
[I-D.ietf-pce-segment-routing],If PCEP is not supported by the node
(head-end of the SR tunnel) controller has no way to learn the MSD of
the node/link configured.
3. MSD supported by a node
Node MSD is a number in the range of 0-254. The vaule of 0
represents lack of ability to push MSD of any depth, any other value
represents that of the node.
Node MSD is encoded in the Opaque Node Attribute TLV, as defined in
[I-D.ietf-idr-ls-distribution]
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Opaque node attributes (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Opaque Node attribute format
4. MSD supported on a link
Link MSD is a number in the range of 0-254.The value of 0 represents
lack of ability to push MSD of any depth, any other value represents
that of the link.
Link MSD is encoded in the Opaque Link Attribute TLV, as defined in
[I-D.ietf-idr-ls-distribution]
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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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Opaque link attributes (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Opaque link attribute format
5. IANA Considerations
TBA
6. Security Considerations
This document does not introduce security issues beyond those
discussed in [I-D.ietf-idr-ls-distribution]
7. Acknowledgements
We like to thank Nikos Triantafillis for the valuable comments.
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-13
(work in progress), October 2015.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick,
"PCEP Extensions for Segment Routing", draft-ietf-pce-
segment-routing-06 (work in progress), August 2015.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., rjs@rob.sh, r., Tantsura,
J., and E. Crabbe, "Segment Routing with MPLS data plane",
draft-ietf-spring-segment-routing-mpls-02 (work in
progress), October 2015.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
8.2. Informative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing", draft-ietf-isis-segment-
routing-extensions-06 (work in progress), December 2015.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-06 (work in progress), December 2015.
Authors' Addresses
Jeff Tantsura
Ericsson
Email: jeff.tantsura@ericsson.com
Greg Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
Siva Sivabalan
Cisco
Email: msiva@cisco.com
Uma Chunduri
Ericsson
Email: uma.chunduri@ericsson.com
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