idnits 2.17.1 draft-ietf-isis-segment-routing-msd-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 1, 2017) is 2606 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC5305' is defined on line 270, but no explicit reference was found in the text == Unused Reference: 'RFC1195' is defined on line 295, but no explicit reference was found in the text == Unused Reference: 'RFC5120' is defined on line 299, but no explicit reference was found in the text ** Obsolete normative reference: RFC 4971 (Obsoleted by RFC 7981) == Outdated reference: A later version (-13) exists of draft-ietf-isis-mpls-elc-02 == Outdated reference: A later version (-16) exists of draft-ietf-pce-segment-routing-08 == Outdated reference: A later version (-05) exists of draft-tantsura-idr-bgp-ls-segment-routing-msd-02 -- Obsolete informational reference (is this intentional?): RFC 7752 (Obsoleted by RFC 9552) Summary: 1 error (**), 0 flaws (~~), 7 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IS-IS Working Group J. Tantsura 3 Internet-Draft Individual 4 Intended status: Standards Track U. Chunduri 5 Expires: September 2, 2017 Huawei 6 S. Aldrin 7 Google, Inc 8 L. Ginsberg 9 Cisco Systems 10 March 1, 2017 12 Signaling MSD (Maximum SID Depth) using IS-IS 13 draft-ietf-isis-segment-routing-msd-01 15 Abstract 17 This document proposes a way to signal Maximum SID Depth (MSD) 18 supported by a node at node and/or link granularity by an ISIS 19 Router. In a Segment Routing (SR) enabled network a centralized 20 controller that programs SR tunnels needs to know the MSD supported 21 by the head-end at node and/or link granularity to push the SID stack 22 of an appropriate depth. MSD is relevent to the head-end of a SR 23 tunnel or Binding-SID anchor node where Binding-SID expansions migth 24 result in creation of a new SID stack. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on September 2, 2017. 43 Copyright Notice 45 Copyright (c) 2017 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 1.1. Conventions used in this document . . . . . . . . . . . . 3 62 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 63 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 3. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 66 4. LINK MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 67 5. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 5 68 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 69 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 70 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6 71 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 72 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 73 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 74 10.2. Informative References . . . . . . . . . . . . . . . . . 7 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 77 1. Introduction 79 When Segment Routing tunnels are computed by a centralized 80 controller, it is critical that the controller learns the MSD 81 "Maximum SID Depth" of the node or link SR tunnel exits over, so the 82 SID stack depth of a path computed doesn't exceed that the node is 83 capable of imposing. This document describes how to use IS-IS to 84 signal the MSD of a node or link to a centralized controller. 86 PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD 87 in SR PCE Capability TLV and METRIC Object. However, if PCEP is not 88 supported/configured on the head-end of a SR tunnel or a Binding-SID 89 anchor node and controller does not participate in IGP routing, it 90 has no way to learn the MSD of nodes and links MSD has been 91 configured. BGP-LS [RFC7752] defines a way to expose topology and 92 associated attributes and capabilities of the nodes in that topology 93 to a centralized controller. MSD signaling by BGP-LS has been 94 defined in [I-D.tantsura-idr-bgp-ls-segment-routing-msd]. Tipicaly, 95 BGP-LS is configured on a small number of nodes, that do not 96 necessarily act as head-ends. In order, for BGP-LS to signal MSD for 97 the all nodes and links in the network MSD is relevant, MSD 98 capabilites should be distributed to every IS-IS router in the 99 network. 101 [I-D.ietf-isis-mpls-elc] defines Readable Label Deepth Capability 102 (RLDC) that is used by a head-end to insert Entropy Label (EL) at 103 appropriate depth, so it coud be read by transit nodes. MSD in 104 contrary signals ability to push SID's stack of a particular depth. 106 MSD of type 1 (IANA Registry) is used to signal number of SID a node 107 is capable of imposing, to be used by a path computation element/ 108 controller and is only relevant to the part of the stack created as 109 the result of the computation. In case, there are additional labels 110 (e.g. service) that are to be pushed to the stack - MSD SHOULD be 111 adjusted to reflect that. In the future, new MSD types could be 112 defined to signal additional capabilities: entropy labels, labels 113 that can be pushed thru recirculation, etc. 115 1.1. Conventions used in this document 117 1.1.1. Terminology 119 BGP-LS:Distribution of Link-State and TE Information using Border 120 Gateway Protocol 122 ISIS: Intermediate System to Intermediate System 124 MSD: Maximum SID Depth 126 PCC: Path Computation Client 128 PCE: Path Computation Element 130 PCEP: Path Computation Element Protocol 132 SID: Segment Identifier 134 SR: Segment Routing 136 1.2. Requirements Language 138 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 139 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 140 document are to be interpreted as described in RFC 2119 [RFC2119]. 142 2. Terminology 144 This memo makes use of the terms defined in [RFC4971]. 146 3. Node MSD Advertisement 148 A new sub-TLV within the body of IS-IS Router Capability TLV 149 [RFC4971], Node MSD sub-TLV is defined to carry the provisioned MSD 150 of the router originating the Router Capability TLV. Node MSD is the 151 lowest MSD supported by the node and can be provisioned in IS-IS 152 instance. 154 0 1 2 3 155 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 1 157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 158 | Type | Length | Sub-Type and Value | 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 Figure 1: Node MSD Sub-TLV 163 The Type (1 byte) of this sub-TLV is TBD (IANA). 165 Length is variable (minimum of 2, multiple of 2 octets) and 166 represents the total length of value field. 168 Value field consists of a 1 octet sub-type (IANA Registry) and 1 169 octet value. 171 Sub-Type 1 (IANA Section), MSD and the Value field contains maximum 172 MSD of the router originating the Router Capability TLV. Node 173 Maximum MSD is a number in the range of 0-254. 0 represents lack of 174 the ability to push MSD of any depth; any other value represents that 175 of the node. This value SHOULD represent the lowest value supported 176 by node. 178 Other Sub-types other than defined above are reserved for future 179 extensions. This TLV is optional. The scope of the advertisement is 180 specific to the deployment. 182 4. LINK MSD Advertisement 184 A new sub-TLV - Link MSD sub-TLV is defined to carry the provisioned 185 MSD of the interface associated with the link. 187 0 1 2 3 188 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 1 190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 191 | Type | Length | Sub-Type and Value | 192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 194 Figure 2: Link MSD Sub-TLV 196 The Type (1 byte) of this sub-TLV is TBD (IANA). 198 Length is variable and similar to what is defined in Section 3. 200 Value field consists of a 1 octet sub-type (IANA Registry) and 1 201 octet value. 203 Sub-Type 1 (IANA Section), MSD and the Value field contains Link MSD 204 of the router originating the corresponding TLV's 22, 23, 141, 222, 205 and 223. Link MSD is a number in the range of 0-254. 0 represents 206 lack of the ability to push MSD of any depth; any other value 207 represents that of the particular link MSD value. 209 5. Node MSD vs Link MSD conflict resolution 211 When both Node MSD and Link MSD are present, the value in the Link 212 MSD MUST be used. 214 6. IANA Considerations 216 This document includes a request to IANA to allocate sub-TLV type 217 codes for the new sub TLV proposed in Section 3 of this document from 218 IS-IS Router Capability TLV Registry as defined by [RFC4971]. Also 219 for link MSD, we request IANA to allocate new sub-TLV codes as 220 defined in Section 4 from Sub-TLVs for TLVs 22, 23, 141, 222 and 223 221 registry. 223 This document also request IANA to create a new Sub-type registry as 224 proposed in Section 3, Section 4. 226 Value Name Reference 227 ----- --------------------- ------------- 228 0 Reserved This document 229 1 MSD This document 230 2-250 Unassigned This document 231 251-254 Experimental This document 232 255 Reserved This document 234 Figure 3: MSD Sub-type Codepoints Registry 236 7. Security Considerations 238 This document describes a mechanism to signal Segment Routing MSD 239 supported at node and/or link granularity through IS-IS LSPs and does 240 not introduce any new security issues. 242 8. Contributors 244 The following people contributed to this document: 246 Peter Psenak 248 Email: ppsenak@cisco.com 250 9. Acknowledgements 252 The authors would like to thank Stephane Litkowski and Bruno Decraene 253 for their reviews and valuable comments. 255 10. References 257 10.1. Normative References 259 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 260 Requirement Levels", BCP 14, RFC 2119, 261 DOI 10.17487/RFC2119, March 1997, 262 . 264 [RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., 265 "Intermediate System to Intermediate System (IS-IS) 266 Extensions for Advertising Router Information", RFC 4971, 267 DOI 10.17487/RFC4971, July 2007, 268 . 270 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 271 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 272 2008, . 274 10.2. Informative References 276 [I-D.ietf-isis-mpls-elc] 277 Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 278 Litkowski, "Signaling Entropy Label Capability Using IS- 279 IS", draft-ietf-isis-mpls-elc-02 (work in progress), 280 October 2016. 282 [I-D.ietf-pce-segment-routing] 283 Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., 284 Raszuk, R., Lopez, V., Tantsura, J., Henderickx, W., and 285 J. Hardwick, "PCEP Extensions for Segment Routing", draft- 286 ietf-pce-segment-routing-08 (work in progress), October 287 2016. 289 [I-D.tantsura-idr-bgp-ls-segment-routing-msd] 290 Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan, 291 "Signaling Maximum SID Depth using Border Gateway Protocol 292 Link-State", draft-tantsura-idr-bgp-ls-segment-routing- 293 msd-02 (work in progress), January 2017. 295 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 296 dual environments", RFC 1195, DOI 10.17487/RFC1195, 297 December 1990, . 299 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 300 Topology (MT) Routing in Intermediate System to 301 Intermediate Systems (IS-ISs)", RFC 5120, 302 DOI 10.17487/RFC5120, February 2008, 303 . 305 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 306 S. Ray, "North-Bound Distribution of Link-State and 307 Traffic Engineering (TE) Information Using BGP", RFC 7752, 308 DOI 10.17487/RFC7752, March 2016, 309 . 311 Authors' Addresses 313 Jeff Tantsura 314 Individual 316 Email: jefftant.ietf@gmail.com 317 Uma Chunduri 318 Huawei 320 Email: uma.chunduri@huawei.com 322 Sam Aldrin 323 Google, Inc 325 Email: aldrin.ietf@gmail.com 327 Les Ginsberg 328 Cisco Systems 330 Email: ginsberg@cisco.com