IDR Working Group G. Van de Velde, Ed.
Internet-Draft W. Henderickx
Intended status: Standards Track M. Bocci
Expires: September 4, 2017 Nokia
March 3, 2017
Signalling RLD using BGP-LS
draft-vandevelde-idr-bgp-ls-segment-routing-rld-01
Abstract
This document defines the attribute to use for BGP-LS to expose a
node RLD "Readable Label Depth" to a centralised controller (PCE/
SDN).
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 [1].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
4. RLD support by a node . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
When Segment Routing tunnels are computed by a centralised
controller, it is beneficial that the controller knows the RLD
"Readable Label Depth" of each node the computed tunnel traverses.
RLD awareness of each node will allow the network SDN controller to
influence the path used for each tunnel. The SDN controller may for
example only create tunnels with a label stack smaller or equal as
the RLD of each node on the path. This will allow the network to
behave accordingly (e.g. make use of Entropy Labels to improve ECMP)
upon the imposed Segment Routing labels on each packet.
This document describes how to use BGP-LS to expose the RLD of a
node.
2. Conventions used in this document
2.1. Terminology
BGP-LS: Distribution of Link-State and TE Information using Border
Gateway Protocol
RLD: Readable Label Depth
PCC: Path Computation Client
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PCE: Path Computation Element
PCEP: Path Computation Element Protocol
SID: Segment Identifier
SR: Segment routing
3. Problem Statement
In existing technology both ISIS [4] and OSPF [3] have proposed
extensions to signal the Readable Label Depth of a node. However, if
a network SDN controller is connected to the network through a BGP-LS
session and not through ISIS or OSPF technology, then the RLD needs
to be conveyed in BGP-LS accordingly. This document describes the
extension BGP-LS requires to transport the RLD.
A network SDN controller having awareness of the Readable Label Depth
can for example use it as a constraint on path computation so that it
can make sure that high bandwidth LSPs are not placed on LAG links
with smaller member bandwidths if they know the Entropy Label cannot
be processed by the node at the ingress to the link.
4. RLD support by a node
Node RLD is encoded in a new Node Attribute TLV, as defined in
RFC7752 [2].
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RLD |
+-+-+-+-+-+-+-+-+
Figure 1
Type : A 2-octet field specifying code-point of the new TLV type.
Code-point: TBA from BGP-LS Node Descriptor, Link Descriptor,
Prefix Descriptor, and Attribute TLVs registry
Length: A 2-octet field that indicates the length of the value
portion
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RLD: Node RLD is a number in the range of 0-254. The value of 0
represents lack of ability to read a label stack of any depth, any
other value represents the readable label depth of the node.
5. Security Considerations
This document does not introduce security issues beyond those
discussed in RFC7752 [2]
6. Acknowledgements
7. IANA Considerations
This document requests assigning 1 new code-points from the BGP-LS
Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
TLVs registry as specified in sections 4.
8. References
8.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://xml.resource.org/public/rfc/html/rfc2119.html>.
[2] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<http://www.rfc-editor.org/info/rfc7752>.
8.2. Informative References
[3] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "draft-ietf-ospf-mpls-elc", October 2016.
[4] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "draft-ietf-ospf-mpls-elc", October 2016.
Authors' Addresses
Gunter Van de Velde (editor)
Nokia
Antwerp
BE
Email: gunter.van_de_velde@nokia.com
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Wim Henderickx
Nokia
Belgium
Email: wim.henderickx@nokia.com
Matthew Bocci
Nokia
Shoppenhangers Road
Maidenhead, Berks
UK
Email: matthew.bocci@nokia.com
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