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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7752 (ref. '2') (Obsoleted by RFC 9552) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR Working Group G. Van de Velde, Ed. 3 Internet-Draft W. Henderickx 4 Intended status: Standards Track M. Bocci 5 Expires: January 28, 2018 Nokia 6 K. Patel 7 Arrcus 8 July 27, 2017 10 Signalling ERLD using BGP-LS 11 draft-ietf-idr-bgp-ls-segment-routing-rld-00 13 Abstract 15 This document defines the attributes to use for BGP-LS to expose a 16 node or link ERLD "Entropy capable Readable Label Depth" to a 17 centralised controller (PCE/SDN). 19 Requirements Language 21 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 22 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 23 document are to be interpreted as described in RFC 2119 [1]. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on January 28, 2018. 42 Copyright Notice 44 Copyright (c) 2017 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Conventions used in this document . . . . . . . . . . . . . . 3 61 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 62 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 63 4. ERLD support by a node . . . . . . . . . . . . . . . . . . . 3 64 5. ERLD support by a link . . . . . . . . . . . . . . . . . . . 4 65 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 66 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 67 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 68 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 9.1. Normative References . . . . . . . . . . . . . . . . . . 5 70 9.2. Informative References . . . . . . . . . . . . . . . . . 5 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 73 1. Introduction 75 When Segment Routing tunnels are computed by a centralised 76 controller, it is beneficial that the controller knows the ERLD 77 (Entropy capable Readable Label Depth) of each node or link a tunnel 78 traverses. A network node signalling an ERLD MUST support the 79 ability to read the signalled number of labels before any action is 80 done upon the packet and SHOULD support entropy awareness found 81 within the signalled ERLD depth. 83 ERLD awareness of each node and link will allow a network SDN 84 controller to influence the path used for each tunnel. The SDN 85 controller may for example only create tunnels with a label stack 86 smaller or equal as the ERLD of each node and link on the path. This 87 will allow the network to behave accordingly (e.g. make use of 88 Entropy Labels to improve ECMP) upon the imposed Segment Routing 89 labels on each packet. 91 This document describes how to use BGP-LS to expose the ERLD of a 92 node. 94 2. Conventions used in this document 96 2.1. Terminology 98 BGP-LS: Distribution of Link-State and TE Information using Border 99 Gateway Protocol 101 ERLD: Entropy capable Readable Label Depth 103 PCC: Path Computation Client 105 PCE: Path Computation Element 107 PCEP: Path Computation Element Protocol 109 SID: Segment Identifier 111 SR: Segment routing 113 3. Problem Statement 115 In existing technology both ISIS [4] and OSPF [3] have proposed 116 extensions to signal the RLD (Readable Label Depth) and ELC (Entropy 117 Label Capability) of a node or link. However, if a network SDN 118 controller is connected to the network through a BGP-LS session and 119 not through ISIS or OSPF technology, then both RLD and ELC needs to 120 be signaled in BGP-LS accordingly. This document describes the 121 extension BGP-LS requires to transport the combination of RLD and ELC 122 into ERLD node and link attributes. 124 A network SDN controller having awareness of the ERLD Entropy capable 125 Readable Label Depth can for example use it as a constraint on path 126 computation so that it can make sure that high bandwidth LSPs are not 127 placed on LAG links with smaller member bandwidths if they know the 128 Entropy Label cannot be processed by the node at the ingress to the 129 link. 131 4. ERLD support by a node 133 Node ERLD is encoded in a new Node Attribute TLV, as defined in 134 RFC7752 [2]. 136 0 1 2 3 137 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 1 138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 | Type | Length | 140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 141 | ERLD | 142 +-+-+-+-+-+-+-+-+ 144 Figure 1 146 Type : A 2-octet field specifying code-point of the new TLV type. 147 Code-point: TBA from BGP-LS Node Descriptor, Link Descriptor, 148 Prefix Descriptor, and Attribute TLVs registry 150 Length: A 2-octet field that indicates the length of the value 151 portion 153 ERLD: Node ERLD is a number in the range of 0-254. The value of 0 154 represents lack of ability to read a label stack of any depth, any 155 other value represents the readable label depth of the node. 157 5. ERLD support by a link 159 Link ERLD is encoded in a new Link Attribute TLV, as defined in 160 RFC7752 [2]. 162 0 1 2 3 163 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 1 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | Type | Length | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 | ERLD | 168 +-+-+-+-+-+-+-+-+ 170 Figure 2 172 Type : A 2-octet field specifying code-point of the new TLV type. 173 Code-point: TBA from BGP-LS Node Descriptor, Link Descriptor, 174 Prefix Descriptor, and Attribute TLVs registry 176 Length: A 2-octet field that indicates the length of the value 177 portion 178 ERLD: Link ERLD is a number in the range of 0-254. The value of 0 179 represents lack of ability to read a label stack of any depth, any 180 other value represents the readable label depth of the link. 182 6. Security Considerations 184 This document does not introduce security issues beyond those 185 discussed in RFC7752 [2] 187 7. Acknowledgements 189 Thanks to discussions with Acee Lindem, Jeff Tantsura, Stephane 190 Litkowski, Bruno Decraene, Kireeti Kompella, John E. Drake and 191 Carlos Pignataro to bring the concept of combining ELC and RLD into a 192 single ERLD signalled parameter more suitable for SDN controller 193 based networks. 195 8. IANA Considerations 197 This document requests assigning 2 new code-points from the BGP-LS 198 Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute 199 TLVs registry as specified in sections 4 and 5. 201 9. References 203 9.1. Normative References 205 [1] Bradner, S., "Key words for use in RFCs to Indicate 206 Requirement Levels", BCP 14, RFC 2119, March 1997, 207 . 209 [2] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 210 S. Ray, "North-Bound Distribution of Link-State and 211 Traffic Engineering (TE) Information Using BGP", RFC 7752, 212 DOI 10.17487/RFC7752, March 2016, 213 . 215 9.2. Informative References 217 [3] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 218 Litkowski, "draft-ietf-ospf-mpls-elc", October 2016. 220 [4] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 221 Litkowski, "draft-ietf-isis-mpls-elc", October 2016. 223 Authors' Addresses 225 Gunter Van de Velde (editor) 226 Nokia 227 Antwerp 228 BE 230 Email: gunter.van_de_velde@nokia.com 232 Wim Henderickx 233 Nokia 234 Belgium 236 Email: wim.henderickx@nokia.com 238 Matthew Bocci 239 Nokia 240 Shoppenhangers Road 241 Maidenhead, Berks 242 UK 244 Email: matthew.bocci@nokia.com 246 Keyur Patel 247 Arrcus 248 USA 250 Email: keyur@arrcus.com