IDR Working Group G. Van de Velde, Ed. Internet-Draft W. Henderickx Intended status: Standards Track M. Bocci Expires: January 28, 2018 Nokia K. Patel Arrcus July 27, 2017 Signalling ERLD using BGP-LS draft-ietf-idr-bgp-ls-segment-routing-rld-00 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 January 28, 2018. 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 January 28, 2018 [Page 1] Internet-Draft Signalling ERLD using BGP-LS July 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 January 28, 2018 [Page 2] Internet-Draft Signalling ERLD using BGP-LS July 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 January 28, 2018 [Page 3] Internet-Draft Signalling ERLD using BGP-LS July 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 January 28, 2018 [Page 4] Internet-Draft Signalling ERLD using BGP-LS July 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, . [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, . 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 January 28, 2018 [Page 5] Internet-Draft Signalling ERLD using BGP-LS July 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 January 28, 2018 [Page 6]