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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: December 14, 2018 Nokia 6 K. Patel 7 Arrcus 8 June 12, 2018 10 Signalling ERLD using BGP-LS 11 draft-ietf-idr-bgp-ls-segment-routing-rld-02 13 Abstract 15 This document defines the attribute encoding to use for BGP-LS to 16 expose ERLD "Entropy capable Readable Label Depth" from a node 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 https://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 December 14, 2018. 42 Copyright Notice 44 Copyright (c) 2018 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 (https://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. Origination of ERLD in BGP-LS . . . . . . . . . . . . . . . . 3 64 5. ERLD support by a node . . . . . . . . . . . . . . . . . . . 4 65 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 66 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 67 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 68 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 9.1. Normative References . . . . . . . . . . . . . . . . . . 5 70 9.2. Informative References . . . . . . . . . . . . . . . . . 5 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 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 will allow a network SDN controller to 84 influence the path used for each tunnel. The SDN controller may for 85 example only create tunnels with a label stack smaller or equal as 86 the ERLD of each node on the path. This will allow the network to 87 behave accordingly (e.g. make use of Entropy Labels to improve ECMP) 88 upon the imposed Segment Routing label stack on each packet. 90 This document describes how to use BGP-LS to expose the ERLD of a 91 node. 93 2. Conventions used in this document 95 2.1. Terminology 97 BGP-LS: Distribution of Link-State and TE Information using Border 98 Gateway Protocol 100 ERLD: Entropy capable Readable Label Depth 102 PCC: Path Computation Client 104 PCE: Path Computation Element 106 PCEP: Path Computation Element Protocol 108 SID: Segment Identifier 110 SR: Segment routing 112 3. Problem Statement 114 In existing technology both ISIS [4] and OSPF [3] have proposed 115 extensions to signal the RLD (Readable Label Depth) and ELC (Entropy 116 Label Capability) of a node. However, if a network SDN controller is 117 connected to the network through a BGP-LS session and not through 118 ISIS or OSPF technology, then both RLD and ELC needs to be signalled 119 using BGP-LS encoding. This document describes the extension BGP-LS 120 requires to transport the combined RLD and ELC into an ERLD (Entropy 121 capable Readable Label Depth) attribute. 123 A network SDN controller having awareness of the ERLD can for example 124 use it as a constraint on path computation to make sure that high 125 bandwidth LSPs are not placed on LAG (Link Aggregation Group), 126 containing links with smaller member bandwidth, if they know the 127 Entropy Label cannot be processed by the node at the ingress to the 128 link. 130 4. Origination of ERLD in BGP-LS 132 Both ISIS [4] and OSPF [3] have proposed extensions to signal the RLD 133 (Readable Label Depth) and ELC (Entropy Label Capability) for a node. 134 A BGP-LS router exporting the IGP LSDB, MUST NOT encode the IGP RLD 135 value in an BGP-LS ERLD attribute, if the associated node ELC is not 136 signalled. 138 5. ERLD support by a node 140 Node ERLD is encoded in a new Node Attribute TLV, as defined in 141 RFC7752 [2]. 143 0 1 2 3 144 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 1 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 146 | Type | Length | 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | ERLD | 149 +-+-+-+-+-+-+-+-+ 151 Figure 1 153 Type : A 2-octet field specifying code-point of the new TLV type. 154 Code-point: TBA from BGP-LS Node Descriptor, Link Descriptor, 155 Prefix Descriptor, and Attribute TLVs registry 157 Length: A 2-octet field that indicates the length of the value 158 portion 160 ERLD: Node ERLD is a number in the range of 0-254. The value of 0 161 represents lack of ability to read a label stack of any depth, any 162 other value represents the readable label depth of the node. 164 6. Security Considerations 166 This document does not introduce security issues beyond those 167 discussed in RFC7752 [2] 169 7. Acknowledgements 171 Thanks to discussions with Acee Lindem, Jeff Tantsura, Stephane 172 Litkowski, Bruno Decraene, Kireeti Kompella, John E. Drake and 173 Carlos Pignataro to bring the concept of combining ELC and RLD into a 174 single ERLD signalled parameter more suitable for SDN controller 175 based networks. 177 8. IANA Considerations 179 This document requests assigning a new code-points from the BGP-LS 180 Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute 181 TLVs registry as specified in section 5. 183 Note: placeholder IANA request 184 Request Node ERLD codepoint 186 BGP-LS TLV Code Point: TBD1 188 ISIS TLV 242/TBD2 190 Note: There is nothing in IANA from draft draft-ietf-isis-mpls-elc 192 Note: Draft talks only about ELC/RLD and that is mismatch with ERLD 194 OSPF RI TLV TBD5 196 OSPF ELC in Non-OSPF functionality Capability Bits (TBD6) 198 9. References 200 9.1. Normative References 202 [1] Bradner, S., "Key words for use in RFCs to Indicate 203 Requirement Levels", BCP 14, RFC 2119, March 1997, 204 . 206 [2] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 207 S. Ray, "North-Bound Distribution of Link-State and 208 Traffic Engineering (TE) Information Using BGP", RFC 7752, 209 DOI 10.17487/RFC7752, March 2016, 210 . 212 9.2. Informative References 214 [3] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 215 Litkowski, "draft-ietf-ospf-mpls-elc", January 2018. 217 [4] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 218 Litkowski, "draft-ietf-isis-mpls-elc", January 2018. 220 Authors' Addresses 222 Gunter Van de Velde (editor) 223 Nokia 224 Antwerp 225 BE 227 Email: gunter.van_de_velde@nokia.com 228 Wim Henderickx 229 Nokia 230 Belgium 232 Email: wim.henderickx@nokia.com 234 Matthew Bocci 235 Nokia 236 Shoppenhangers Road 237 Maidenhead, Berks 238 UK 240 Email: matthew.bocci@nokia.com 242 Keyur Patel 243 Arrcus 244 USA 246 Email: keyur@arrcus.com