idnits 2.17.1 draft-ietf-isis-segment-routing-msd-07.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 (December 04, 2017) is 2328 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 294, but no explicit reference was found in the text == Unused Reference: 'RFC1195' is defined on line 323, but no explicit reference was found in the text == Unused Reference: 'RFC5120' is defined on line 327, but no explicit reference was found in the text == Outdated reference: A later version (-18) exists of draft-ietf-idr-bgp-ls-segment-routing-msd-01 == Outdated reference: A later version (-13) exists of draft-ietf-isis-mpls-elc-02 == Outdated reference: A later version (-16) exists of draft-ietf-pce-segment-routing-11 -- Obsolete informational reference (is this intentional?): RFC 7752 (Obsoleted by RFC 9552) Summary: 0 errors (**), 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: June 7, 2018 Huawei Technologies 6 S. Aldrin 7 Google, Inc 8 L. Ginsberg 9 Cisco Systems 10 December 04, 2017 12 Signaling MSD (Maximum SID Depth) using IS-IS 13 draft-ietf-isis-segment-routing-msd-07 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 IS-IS 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 impose the SID 22 stack of an appropriate depth. MSD is relevant to the head-end of a 23 SR tunnel or Binding-SID anchor node where Binding-SID expansions 24 might 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 https://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 June 7, 2018. 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 (https://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 . . . . . . . . . . . . . . . . . . . . . . 7 72 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 73 10.1. Normative References . . . . . . . . . . . . . . . . . . 7 74 10.2. Informative References . . . . . . . . . . . . . . . . . 7 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 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 the number of SIDs 83 the node is capable of imposing. This document describes how to use 84 IS-IS to signal the MSD of a node or link to a centralized 85 controller. 87 PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD 88 in SR PCE Capability TLV and METRIC Object. However, if PCEP is not 89 supported/configured on the head-end of a SR tunnel or a Binding-SID 90 anchor node and controller does not participate in IGP routing, it 91 has no way to learn the MSD of nodes and links which has been 92 configured. BGP-LS [RFC7752] defines a way to expose topology and 93 associated attributes and capabilities of the nodes in that topology 94 to a centralized controller. MSD signaling by BGP-LS has been 95 defined in [I-D.ietf-idr-bgp-ls-segment-routing-msd]. Typically, 96 BGP-LS is configured on a small number of nodes, that do not 97 necessarily act as head-ends. In order, for BGP-LS to signal MSD for 98 the all nodes and links in the network MSD is relevant, MSD 99 capabilites SHOULD be distributed to every IS-IS router in the 100 network. 102 [I-D.ietf-isis-mpls-elc] defines Readable Label Depth Capability 103 (RLDC) that is used by a head-end to insert Entropy Label (EL) at 104 appropriate depth, so it could be read by transit nodes. MSD in 105 contrary signals ability to impose SID's stack of a particular depth. 107 MSD of type 1 (IANA Registry), called Base MSD, is used to signal the 108 total number of SIDs a node is capable of imposing, to be used by a 109 path computation element/controller. In case, there are additional 110 SIDs (e.g. service) that are to be imposed to the stack - this would 111 be signaled with an another MSD type (TBD), no adjustment to the Base 112 MSD should be made. In the future, new MSD types could be defined to 113 signal additional capabilities: entropy labels, SIDs that can be 114 imposed thru recirculation, or another dataplane e.g IPv6. 116 1.1. Conventions used in this document 118 1.1.1. Terminology 120 BGP-LS: Distribution of Link-State and TE Information using Border 121 Gateway Protocol 123 IS-IS: Intermediate System to Intermediate System 125 MSD: Maximum SID Depth 127 PCC: Path Computation Client 129 PCE: Path Computation Element 131 PCEP: Path Computation Element Protocol 133 SID: Segment Identifier 135 SR: Segment Routing 137 1.2. Requirements Language 139 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 140 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 141 document are to be interpreted as described in RFC 2119 [RFC2119]. 143 2. Terminology 145 This memo makes use of the terms defined in [RFC7981]. 147 3. Node MSD Advertisement 149 A new sub-TLV within the body of IS-IS Router Capability TLV 150 [RFC7981], Node MSD sub-TLV is defined to carry the provisioned MSD 151 of the router originating the Router Capability TLV. Node MSD is the 152 lowest MSD supported by the node of any interface and can be 153 provisioned in IS-IS instance. 155 0 1 2 3 156 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 1 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 159 | Type | Length | Sub-Type and Value | 160 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 162 Figure 1: Node MSD Sub-TLV 164 The Type (1 byte) of this sub-TLV has value of 23. 166 Length is variable (minimum of 2, multiple of 2 octets) and 167 represents the total length of value field. 169 Value field consists of a 1 octet sub-type (IANA Registry) and 1 170 octet value. 172 Sub-Type 1 (IANA Section), MSD and the Value field contains maximum 173 MSD of the router originating the Router Capability TLV. Node 174 Maximum MSD is a number in the range of 0-254. 0 represents lack of 175 the ability to impose MSD stack of any depth; any other value 176 represents that of the node. This value SHOULD represent the lowest 177 value supported by node. 179 Other Sub-types other than defined above are reserved for future 180 extensions. This sub-TLV is optional. The scope of the 181 advertisement is specific to the deployment. 183 4. Link MSD Advertisement 185 A new sub-TLV - Link MSD sub-TLV is defined for TLVs 22, 23, 141, 186 222, and 223 to carry the provisioned MSD of the interface associated 187 with the link. 189 0 1 2 3 190 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 1 192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 193 | Type | Length | Sub-Type and Value | 194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 196 Figure 2: Link MSD Sub-TLV 198 The Type (1 byte) of this sub-TLV has value of 15. 200 Length is variable and similar to what is defined in Section 3. 202 Value field consists of a 1 octet sub-type (IANA Registry) and 1 203 octet value. 205 Sub-Type 1 (IANA Section), MSD and the Value field contains Link MSD 206 of the router originating the corresponding TLV's 22, 23, 141, 222, 207 and 223. Link MSD is a number in the range of 0-254. 0 represents 208 lack of the ability to impose MSD stack of any depth; any other value 209 represents that of the particular link MSD value. 211 5. Node MSD vs Link MSD conflict resolution 213 When both Node MSD and Link MSD are present, the value in the Link 214 MSD MUST be used. 216 6. IANA Considerations 218 This document includes a request to IANA to allocate sub-TLV type 219 codes for the new sub TLV proposed in Section 3 of this document from 220 IS-IS Router Capability TLV Registry as defined by [RFC7981]. 222 Following values have been allocated by IANA: 224 Value Description Reference 225 ----- --------------- ------------- 226 23 Node MSD This document 228 Figure 3: Node MSD 230 For the Link MSD, we request IANA to allocate new sub-TLV codes as 231 defined in Section 4 from Sub-TLVs for TLVs 22, 23, 141, 222 and 223 232 registry. 234 Value Description Reference 235 ----- --------------- ------------- 236 15 Link MSD This document 238 Figure 4: Link MSD 240 Per TLV information where Link MSD sub-TLV can be part of: 242 TLV 22 23 25 141 222 223 243 --- -------------------- 244 y y y y y y 246 Figure 5: TLVs where LINK MSD Sub-TLV can be present 248 This document requests creation of a new IANA managed registry under 249 a new category of "Interior Gateway Protocol (IGP) Parameters" IANA 250 registries to identify MSD types as proposed in Section 3, Section 4. 251 The registration procedure is "Expert Review" as defined in 252 [RFC8126]. Suggested registry name is "MSD Sub-types". Types are an 253 unsigned 8 bit number. The following values are defined by this 254 document 256 Value Name Reference 257 ----- --------------------- ------------- 258 0 Reserved This document 259 1 Base MSD This document 260 2-250 Unassigned This document 261 251-254 Experimental This document 262 255 Reserved This document 264 Figure 6: MSD Sub-type Codepoints Registry 266 7. Security Considerations 268 This document describes a mechanism to signal Segment Routing MSD 269 supported at node and/or link granularity through IS-IS LSPs and does 270 not introduce any new security issues. 272 8. Contributors 274 The following people contributed to this document: 276 Peter Psenak 278 Email: ppsenak@cisco.com 280 9. Acknowledgements 282 The authors would like to thank Stephane Litkowski and Bruno Decraene 283 for their reviews and valuable comments. 285 10. References 287 10.1. Normative References 289 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 290 Requirement Levels", BCP 14, RFC 2119, 291 DOI 10.17487/RFC2119, March 1997, 292 . 294 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 295 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 296 2008, . 298 [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions 299 for Advertising Router Information", RFC 7981, 300 DOI 10.17487/RFC7981, October 2016, 301 . 303 10.2. Informative References 305 [I-D.ietf-idr-bgp-ls-segment-routing-msd] 306 Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan, 307 "Signaling Maximum SID Depth using Border Gateway Protocol 308 Link-State", draft-ietf-idr-bgp-ls-segment-routing-msd-01 309 (work in progress), October 2017. 311 [I-D.ietf-isis-mpls-elc] 312 Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. 313 Litkowski, "Signaling Entropy Label Capability Using IS- 314 IS", draft-ietf-isis-mpls-elc-02 (work in progress), 315 October 2016. 317 [I-D.ietf-pce-segment-routing] 318 Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 319 and J. Hardwick, "PCEP Extensions for Segment Routing", 320 draft-ietf-pce-segment-routing-11 (work in progress), 321 November 2017. 323 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 324 dual environments", RFC 1195, DOI 10.17487/RFC1195, 325 December 1990, . 327 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 328 Topology (MT) Routing in Intermediate System to 329 Intermediate Systems (IS-ISs)", RFC 5120, 330 DOI 10.17487/RFC5120, February 2008, 331 . 333 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 334 S. Ray, "North-Bound Distribution of Link-State and 335 Traffic Engineering (TE) Information Using BGP", RFC 7752, 336 DOI 10.17487/RFC7752, March 2016, 337 . 339 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 340 Writing an IANA Considerations Section in RFCs", BCP 26, 341 RFC 8126, DOI 10.17487/RFC8126, June 2017, 342 . 344 Authors' Addresses 346 Jeff Tantsura 347 Individual 349 Email: jefftant.ietf@gmail.com 351 Uma Chunduri 352 Huawei Technologies 354 Email: uma.chunduri@huawei.com 356 Sam Aldrin 357 Google, Inc 359 Email: aldrin.ietf@gmail.com 361 Les Ginsberg 362 Cisco Systems 364 Email: ginsberg@cisco.com