draft-ietf-idr-bgp-ls-segment-routing-rld-04.txt   draft-ietf-idr-bgp-ls-segment-routing-rld-05.txt 
IDR Working Group G. Van de Velde, Ed. IDR Working Group G. Van de Velde, Ed.
Internet-Draft W. Henderickx Internet-Draft W. Henderickx
Intended status: Standards Track M. Bocci Intended status: Standards Track M. Bocci
Expires: December 20, 2019 Nokia Expires: February 21, 2020 Nokia
K. Patel K. Patel
Arrcus Arrcus
June 18, 2019 August 20, 2019
Signalling ERLD using BGP-LS Signalling ERLD using BGP-LS
draft-ietf-idr-bgp-ls-segment-routing-rld-04 draft-ietf-idr-bgp-ls-segment-routing-rld-05
Abstract Abstract
This document defines the attribute encoding to use for BGP-LS to This document defines the attribute encoding to use for BGP-LS to
expose ERLD "Entropy capable Readable Label Depth" from a node to a expose ERLD "Entropy capable Readable Label Depth" from a node to a
centralised controller (PCE/SDN). centralised controller (PCE/SDN).
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 2
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
4. Origination of ERLD in BGP-LS . . . . . . . . . . . . . . . . 3 4. Advertising of ERLD in BGP-LS . . . . . . . . . . . . . . . . 3
5. ERLD support by a node . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . 4
9.1. Normative References . . . . . . . . . . . . . . . . . . 5 8.2. Informative References . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
When Segment Routing tunnels are computed by a centralised When Segment Routing tunnels are computed by a centralised
controller, it is beneficial that the controller knows the ERLD controller, it is beneficial that the controller knows the ERLD
(Entropy capable Readable Label Depth) of each node or link a tunnel (Entropy Readable Label Depth) of each node or link a tunnel
traverses. A network node signalling an ERLD MUST support the traverses. A network node signalling an ERLD MUST support the
ability to read the signalled number of labels before any action is ability to read the signalled number of labels before any action is
done upon the packet and SHOULD support entropy awareness found done upon the packet and SHOULD support entropy awareness found
within the signalled ERLD depth. within the signalled ERLD depth.
ERLD awareness of each node will allow a network SDN controller to ERLD awareness of each node will allow a network SDN controller to
influence the path used for each tunnel. The SDN controller may for influence the path used for each tunnel. The SDN controller may for
example only create tunnels with a label stack smaller or equal as example only create tunnels with a label stack smaller or equal as
the ERLD of each node on the path. This will allow the network to the ERLD of each node on the path. This will allow the network to
behave accordingly (e.g. make use of Entropy Labels to improve ECMP) behave accordingly (e.g. make use of Entropy Labels to improve ECMP)
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influence the path used for each tunnel. The SDN controller may for influence the path used for each tunnel. The SDN controller may for
example only create tunnels with a label stack smaller or equal as example only create tunnels with a label stack smaller or equal as
the ERLD of each node on the path. This will allow the network to the ERLD of each node on the path. This will allow the network to
behave accordingly (e.g. make use of Entropy Labels to improve ECMP) behave accordingly (e.g. make use of Entropy Labels to improve ECMP)
upon the imposed Segment Routing label stack on each packet. upon the imposed Segment Routing label stack on each packet.
This document describes how to use BGP-LS to expose the ERLD of a This document describes how to use BGP-LS to expose the ERLD of a
node. node.
2. Conventions used in this document 2. Conventions used in this document
2.1. Terminology 2.1. Terminology
BGP-LS: Distribution of Link-State and TE Information using Border BGP-LS: Distribution of Link-State and TE Information using Border
Gateway Protocol Gateway Protocol
ERLD: Entropy capable Readable Label Depth ERLD: Entropy capable Readable Label Depth
PCC: Path Computation Client ELC: Entropy Label Capability
PCE: Path Computation Element
PCEP: Path Computation Element Protocol MSD: Maximum SID Depth
SID: Segment Identifier SID: Segment Identifier
SR: Segment routing
3. Problem Statement 3. Problem Statement
In existing technology both ISIS [4] and OSPF [3] have proposed For Segment Routing technology both ISIS [7] and OSPF [6] have
extensions to signal the RLD (Readable Label Depth) and ELC (Entropy proposed extensions to signal the ERLD (Entropy Readable Label Depth)
Label Capability) of a node. However, if a network SDN controller is and ELC (Entropy Label Capability) of a node. However, if a network
connected to the network through a BGP-LS session and not through SDN controller is connected to the network through a BGP-LS session
ISIS or OSPF technology, then both RLD and ELC needs to be signalled and not through either ISIS or OSPF technology, then both ERLD and
using BGP-LS encoding. This document describes the extension BGP-LS ELC needs to be signalled using BGP-LS encoding. This document
requires to transport the combined RLD and ELC into an ERLD (Entropy describes the extension BGP-LS requires to signal ERLD.
capable Readable Label Depth) attribute.
A network SDN controller having awareness of the ERLD can for example A network SDN controller having awareness of the ERLD can for example
use it as a constraint on path computation to make sure that high use it as a constraint on path computation to make sure that high
bandwidth LSPs are not placed on LAG (Link Aggregation Group), bandwidth LSPs are not placed on LAG (Link Aggregation Group),
containing links with smaller member bandwidth, if they know the containing links with smaller member bandwidth, if they know the
Entropy Label cannot be processed by the node at the ingress to the entropy label cannot be processed by the node at the ingress to the
link. link.
4. Origination of ERLD in BGP-LS 4. Advertising of ERLD in BGP-LS
Both ISIS [4] and OSPF [3] have proposed extensions to signal the RLD Both ISIS [7] and OSPF [6] have proposed extensions to signal the
(Readable Label Depth) and ELC (Entropy Label Capability) for a node. ERLD (Entropy Readable Label Depth) and ELC (Entropy Label
A BGP-LS router exporting the IGP LSDB, MUST NOT encode the IGP RLD Capability) using new MSD-type of the Node MSD sub-Type TLV RFC8491
value in an BGP-LS ERLD attribute, if the associated node ELC is not [4] or RFC8476 [3].
signalled.
5. ERLD support by a node This document defines a new node BGP MSD sub-type TLV from draft-
ietf-idr-bgp-ls-segment-routing-msd [5] to signal the ERLD.
Node ERLD is encoded in a new Node Attribute TLV, as defined in A BGP-LS router exporting the IGP LSDB, MUST NOT encode the IGP ERLD
RFC7752 [2]. value in an BGP-LS ERLD attribute, if the associated ELC is not
signalled.
0 1 2 3 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 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 | | MSD-Type=TBD | ERLD-Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ERLD |
+-+-+-+-+-+-+-+-+
Figure 1 Figure 1
Type : A 2-octet field specifying code-point of the new TLV type. The BGP-LS ERLD is encoded as a node MSD sub-type defined in the IANA
Code-point: TBA from BGP-LS Node Descriptor, Link Descriptor, registry titled "IGP MSD-Types" under the "Interior Gateway Protocol
Prefix Descriptor, and Attribute TLVs registry (IGP) Parameters" registry created by RFC8491 [4].
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 The ERLD-Value field in the range between 0 to 255 is set to the BGP-
represents lack of ability to read a label stack of any depth, any LS imported IGP ERLD. The value of 0 represents lack of ability to
other value represents the readable label depth of the node. read a label stack of any depth, any other value represents the
readable label depth of the node.
6. Security Considerations 5. Security Considerations
This document does not introduce security issues beyond those This document does not introduce security issues beyond those
discussed in RFC7752 [2] discussed in RFC7752 [2]
7. Acknowledgements 6. Acknowledgements
Thanks to discussions with Acee Lindem, Jeff Tantsura, Stephane Thanks to discussions with Acee Lindem, Jeff Tantsura, Stephane
Litkowski, Bruno Decraene, Kireeti Kompella, John E. Drake and Litkowski, Bruno Decraene, Kireeti Kompella, John E. Drake and
Carlos Pignataro to bring the concept of combining ELC and RLD into a Carlos Pignataro to bring the concept of combining ELC and RLD into a
single ERLD signalled parameter more suitable for SDN controller single ERLD signalled parameter more suitable for SDN controller
based networks. based networks.
8. IANA Considerations 7. IANA Considerations
This document requests assigning a new code-points from the BGP-LS This document requests assigning new BGP MSD sub-TLV code-points as
Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute described in section 4.
TLVs registry as specified in section 5.
Note: placeholder IANA request Note: placeholder IANA request
Request Node ERLD codepoint
BGP-LS TLV Code Point: TBD1
ISIS TLV 242/TBD2
Note: There is nothing in IANA from draft draft-ietf-isis-mpls-elc 8. References
Note: Draft talks only about ELC/RLD and that is mismatch with ERLD
OSPF RI TLV TBD5
OSPF ELC in Non-OSPF functionality Capability Bits (TBD6)
9. References
9.1. Normative References 8.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate [1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997, Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://xml.resource.org/public/rfc/html/rfc2119.html>. <http://xml.resource.org/public/rfc/html/rfc2119.html>.
[2] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [2] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>. <https://www.rfc-editor.org/info/rfc7752>.
9.2. Informative References [3] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
"Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476,
DOI 10.17487/RFC8476, December 2018,
<https://www.rfc-editor.org/info/rfc8476>.
[3] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. [4] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
Litkowski, "draft-ietf-ospf-mpls-elc", January 2018. "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.
[4] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. [5] Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G.,
Litkowski, "draft-ietf-isis-mpls-elc", January 2018. and N. Triantafillis, "draft-ietf-idr-bgp-ls-segment-
routing-msd", June 2019.
8.2. Informative References
[6] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "draft-ietf-ospf-mpls-elc", May 2019.
[7] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "draft-ietf-isis-mpls-elc", May 2019.
Authors' Addresses Authors' Addresses
Gunter Van de Velde (editor) Gunter Van de Velde (editor)
Nokia Nokia
Antwerp Antwerp
BE BE
Email: gunter.van_de_velde@nokia.com Email: gunter.van_de_velde@nokia.com
Wim Henderickx Wim Henderickx
Nokia Nokia
Belgium Belgium
Email: wim.henderickx@nokia.com Email: wim.henderickx@nokia.com
Matthew Bocci Matthew Bocci
Nokia Nokia
Shoppenhangers Road Shoppenhangers Road
Maidenhead, Berks Maidenhead, Berks
UK UK
Email: matthew.bocci@nokia.com Email: matthew.bocci@nokia.com
Keyur Patel Keyur Patel
Arrcus Arrcus
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