Internet DRAFT - draft-vandevelde-idr-bgp-ls-segment-routing-rld
draft-vandevelde-idr-bgp-ls-segment-routing-rld
IDR Working Group G. Van de Velde, Ed.
Internet-Draft W. Henderickx
Intended status: Standards Track M. Bocci
Expires: October 26, 2017 Nokia
K. Patel
Arrcus
April 24, 2017
Signalling ERLD using BGP-LS
draft-vandevelde-idr-bgp-ls-segment-routing-rld-03
Abstract
This document defines the attributes to use for BGP-LS to expose a
node or link ERLD "Entropy capable 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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 26, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Van de Velde, et al. Expires October 26, 2017 [Page 1]
Internet-Draft Signalling ERLD using BGP-LS April 2017
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
4. ERLD support by a node . . . . . . . . . . . . . . . . . . . 3
5. ERLD support by a link . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
When Segment Routing tunnels are computed by a centralised
controller, it is beneficial that the controller knows the ERLD
(Entropy capable Readable Label Depth) of each node or link a tunnel
traverses. A network node signalling an ERLD MUST support the
ability to read the signalled number of labels before any action is
done upon the packet and SHOULD support entropy awareness found
within the signalled ERLD depth.
ERLD awareness of each node and link will allow a 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 ERLD of each node and link 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 ERLD of a
node.
Van de Velde, et al. Expires October 26, 2017 [Page 2]
Internet-Draft Signalling ERLD using BGP-LS April 2017
2. Conventions used in this document
2.1. Terminology
BGP-LS: Distribution of Link-State and TE Information using Border
Gateway Protocol
ERLD: Entropy capable Readable Label Depth
PCC: Path Computation Client
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 RLD (Readable Label Depth) and ELC (Entropy
Label Capability) of a node or link. However, if a network SDN
controller is connected to the network through a BGP-LS session and
not through ISIS or OSPF technology, then both RLD and ELC needs to
be signaled in BGP-LS accordingly. This document describes the
extension BGP-LS requires to transport the combination of RLD and ELC
into ERLD node and link attributes.
A network SDN controller having awareness of the ERLD Entropy capable
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. ERLD support by a node
Node ERLD is encoded in a new Node Attribute TLV, as defined in
RFC7752 [2].
Van de Velde, et al. Expires October 26, 2017 [Page 3]
Internet-Draft Signalling ERLD using BGP-LS April 2017
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ERLD |
+-+-+-+-+-+-+-+-+
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
ERLD: Node ERLD 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. ERLD support by a link
Link ERLD is encoded in a new Link 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ERLD |
+-+-+-+-+-+-+-+-+
Figure 2
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
Van de Velde, et al. Expires October 26, 2017 [Page 4]
Internet-Draft Signalling ERLD using BGP-LS April 2017
ERLD: Link ERLD 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 link.
6. Security Considerations
This document does not introduce security issues beyond those
discussed in RFC7752 [2]
7. Acknowledgements
Thanks to discussions with Acee Lindem, Jeff Tantsura, Stephane
Litkowski, Bruno Decraene, Kireeti Kompella, John E. Drake and
Carlos Pignataro to bring the concept of combining ELC and RLD into a
single ERLD signalled parameter more suitable for SDN controller
based networks.
8. IANA Considerations
This document requests assigning 2 new code-points from the BGP-LS
Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
TLVs registry as specified in sections 4 and 5.
9. References
9.1. 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>.
9.2. 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-isis-mpls-elc", October 2016.
Van de Velde, et al. Expires October 26, 2017 [Page 5]
Internet-Draft Signalling ERLD using BGP-LS April 2017
Authors' Addresses
Gunter Van de Velde (editor)
Nokia
Antwerp
BE
Email: gunter.van_de_velde@nokia.com
Wim Henderickx
Nokia
Belgium
Email: wim.henderickx@nokia.com
Matthew Bocci
Nokia
Shoppenhangers Road
Maidenhead, Berks
UK
Email: matthew.bocci@nokia.com
Keyur Patel
Arrcus
USA
Email: keyur@arrcus.com
Van de Velde, et al. Expires October 26, 2017 [Page 6]
