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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-18) exists of draft-ietf-idr-bgp-ls-segment-routing-ext-16 == Outdated reference: A later version (-13) exists of draft-ietf-isis-mpls-elc-12 ** Obsolete normative reference: RFC 7752 (Obsoleted by RFC 9552) Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSR Working Group X. Xu 3 Internet-Draft Alibaba Inc 4 Intended status: Standards Track S. Kini 5 Expires: November 29, 2020 6 P. Psenak 7 C. Filsfils 8 S. Litkowski 9 Cisco Systems, Inc. 10 M. Bocci 11 Nokia 12 May 28, 2020 14 Signaling Entropy Label Capability and Entropy Readable Label Depth 15 Using OSPF 16 draft-ietf-ospf-mpls-elc-14 18 Abstract 20 Multiprotocol Label Switching (MPLS) has defined a mechanism to load- 21 balance traffic flows using Entropy Labels (EL). An ingress Label 22 Switching Router (LSR) cannot insert ELs for packets going into a 23 given Label Switched Path (LSP) unless an egress LSR has indicated 24 via signaling that it has the capability to process ELs, referred to 25 as the Entropy Label Capability (ELC), on that LSP. In addition, it 26 would be useful for ingress LSRs to know each LSR's capability for 27 reading the maximum label stack depth and performing EL-based load- 28 balancing, referred to as Entropy Readable Label Depth (ERLD). This 29 document defines a mechanism to signal these two capabilities using 30 OSPFv2 and OSPFv3 and BGP-LS. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on November 29, 2020. 49 Copyright Notice 51 Copyright (c) 2020 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 67 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 3. Advertising ELC Using OSPF . . . . . . . . . . . . . . . . . 3 69 3.1. Advertising ELC Using OSPFv2 . . . . . . . . . . . . . . 4 70 3.2. Advertising ELC Using OSPFv3 . . . . . . . . . . . . . . 4 71 4. Advertising ERLD Using OSPF . . . . . . . . . . . . . . . . . 4 72 5. Signaling ELC and ERLD in BGP-LS . . . . . . . . . . . . . . 5 73 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 74 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 75 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6 76 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 77 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 78 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 79 10.2. Informative References . . . . . . . . . . . . . . . . . 8 80 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 82 1. Introduction 84 [RFC6790] describes a method to load-balance Multiprotocol Label 85 Switching (MPLS) traffic flows using Entropy Labels (EL). It also 86 introduces the concept of Entropy Label Capability (ELC) and defines 87 the signaling of this capability via MPLS signaling protocols. 88 Recently, mechanisms have been defined to signal labels via link- 89 state Interior Gateway Protocols (IGP) such as OSPFv2 [RFC8665] and 90 OSPFv3 [RFC8666]. This draft defines a mechanism to signal the ELC 91 using OSPFv2 and OSPFv3. 93 In cases where Segment Routing (SR) is used with the MPLS Data Plane 94 (e.g., SR-MPLS [RFC8660]), it would be useful for ingress LSRs to 95 know each intermediate LSR's capability of reading the maximum label 96 stack depth and performing EL-based load-balancing. This capability, 97 referred to as Entropy Readable Label Depth (ERLD) as defined in 98 [RFC8662], may be used by ingress LSRs to determine the position of 99 the EL label in the stack, and whether it is necessary to insert 100 multiple ELs at different positions in the label stack. This 101 document defines a mechanism to signal the ERLD using OSPFv2 and 102 OSPFv3. 104 2. Terminology 106 This memo makes use of the terms defined in [RFC6790], and [RFC8662]. 108 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 109 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 110 "OPTIONAL" in this document are to be interpreted as described in BCP 111 14 [RFC2119] [RFC8174] when, and only when, they appear in all 112 capitals, as shown here. 114 The key word OSPF is used throughout the document to refer to both 115 OSPFv2 and OSPFv3. 117 3. Advertising ELC Using OSPF 119 Even though ELC is a property of the node, in some cases it is 120 advantageous to associate and advertise the ELC with a prefix. In 121 multi-area networks, routers may not know the identity of the prefix 122 originator in a remote area, or may not know the capabilities of such 123 originator. Similarly, in a multi domain network, the identity of 124 the prefix originator and its capabilities may not be known to the 125 ingress LSR. 127 If a router has multiple interfaces, the router MUST NOT announce ELC 128 unless all of its interfaces are capable of processing ELs. 130 If the router supports ELs on all of its interfaces, it SHOULD 131 advertise the ELC with every local host prefix it advertises in OSPF. 133 The ELC signaling MUST be preserved when an OSPF Area Border Router 134 (ABR) distributes information between areas. To do so, an ABR MUST 135 originate an OSPFv2 Extended Prefix Opaque LSA [RFC7684] including 136 the received ELC setting. 138 When an OSPF Autonomous System Boundary Router (ASBR) redistributes a 139 prefix from another instance of OSPF or from some other protocol, it 140 SHOULD preserve the ELC signaling for the prefix if it exists. To do 141 so, an ASBR SHOULD originate an Extended Prefix Opaque LSA [RFC7684] 142 including the ELC setting of the redistributed prefix. The flooding 143 scope of the Extended Prefix Opaque LSA MUST match the flooding scope 144 of the LSA that an ASBR originates as a result of the redistribution. 146 The exact mechanism used to exchange ELC between protocol instances 147 on an ASBR is outside of the scope of this document. 149 3.1. Advertising ELC Using OSPFv2 151 [RFC7684] defines the OSPFv2 Extended Prefix TLV to advertise 152 additional attributes associated with a prefix. The OSPFv2 Extended 153 Prefix TLV includes a one-octet Flags field. A new flag in the Flags 154 field is used to signal the ELC for the prefix: 156 0x20 - E-Flag (ELC Flag): Set by the advertising router to 157 indicate that the prefix originator is capable of processing ELs. 159 3.2. Advertising ELC Using OSPFv3 161 [RFC5340] defines the OSPFv3 PrefixOptions field to indicate 162 capabilities associated with a prefix. A new bit in the OSPFv3 163 PrefixOptions is used to signal the ELC for the prefix: 165 0x40 - E-Flag (ELC Flag): Set by the advertising router to 166 indicate that the prefix originator is capable of processing ELs. 168 The ELC signaling MUST be preserved when an OSPFv3 Area Border 169 Router (ABR) distributes information between areas. The setting 170 of the ELC Flag in the Inter-Area-Prefix-LSA [RFC5340] or in the 171 Inter-Area-Prefix TLV [RFC8362], generated by an ABR, MUST be the 172 same as the value the ELC Flag associated with the prefix in the 173 source area. 175 When an OSPFv3 Autonomous System Boundary Router (ASBR) 176 redistributes a prefix from another instance of OSPFv3 or from 177 some other protocol, it SHOULD preserve the ELC signaling for the 178 prefix if it exists. The setting of the ELC Flag in the AS- 179 External-LSA, NSSA-LSA [RFC5340] or in the External-Prefix TLV 180 [RFC8362], generated by an ASBR, MUST be the same as the value of 181 the ELC Flag associated with the prefix in the source domain. The 182 exact mechanism used to exchange ELC between protocol instances on 183 the ASBR is outside of the scope of this document. 185 4. Advertising ERLD Using OSPF 187 The ERLD is advertised in a Node MSD TLV [RFC8476] using the ERLD-MSD 188 type defined in [I-D.ietf-isis-mpls-elc]. 190 If a router has multiple interfaces with different capabilities of 191 reading the maximum label stack depth, the router MUST advertise the 192 smallest value found across all of its interfaces. 194 The absence of ERLD-MSD advertisements indicates only that the 195 advertising node does not support advertisement of this capability. 197 When the ERLD-MSD type is received in the OSPFv2 or OSPFv3 Link MSD 198 Sub-TLV [RFC8476], it MUST be ignored. 200 The considerations for advertising the ERLD are specified in 201 [RFC8662]. 203 5. Signaling ELC and ERLD in BGP-LS 205 The OSPF extensions defined in this document can be advertised via 206 BGP-LS (Distribution of Link-State and TE Information Using BGP) 207 [RFC7752] using existing BGP-LS TLVs. 209 The ELC is advertised using the Prefix Attribute Flags TLV as defined 210 in [I-D.ietf-idr-bgp-ls-segment-routing-ext]. 212 The ERLD-MSD is advertised using the Node MSD TLV as defined in 213 [I-D.ietf-idr-bgp-ls-segment-routing-msd]. 215 6. IANA Considerations 217 Early allocation has been done by IANA for this document as follows: 219 - Flag 0x20 in the OSPFv2 Extended Prefix TLV Flags registry has 220 been allocated by IANA to the E-Flag (ELC Flag). 222 - Bit 0x40 in the "OSPFv3 Prefix Options (8 bits)" registry has 223 been allocated by IANA to the E-Flag (ELC Flag). 225 7. Security Considerations 227 This document specifies the ability to advertise additional node 228 capabilities using OSPF and BGP-LS. As such, the security 229 considerations as described in [RFC5340], [RFC7770], [RFC7752], 230 [RFC7684], [RFC8476], [RFC8662], 231 [I-D.ietf-idr-bgp-ls-segment-routing-ext] and 232 [I-D.ietf-idr-bgp-ls-segment-routing-msd] are applicable to this 233 document. 235 Incorrectly setting the E flag during origination, propagation or 236 redistribution may lead to poor or no load-balancing of the MPLS 237 traffic or black-holing of the MPLS traffic on the egress node. 239 Incorrectly setting of the ERLD value may lead to poor or no load- 240 balancing of the MPLS traffic. 242 8. Contributors 244 The following people contributed to the content of this document and 245 should be considered as co-authors: 247 Gunter Van de Velde (editor) 248 Nokia 249 Antwerp 250 BE 252 Email: gunter.van_de_velde@nokia.com 254 Wim Henderickx 255 Nokia 256 Belgium 258 Email: wim.henderickx@nokia.com 260 Keyur Patel 261 Arrcus 262 USA 264 Email: keyur@arrcus.com 266 9. Acknowledgements 268 The authors would like to thank Yimin Shen, George Swallow, Acee 269 Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura , Bruno 270 Decraene and Carlos Pignataro for their valuable comments. 272 10. References 274 10.1. Normative References 276 [I-D.ietf-idr-bgp-ls-segment-routing-ext] 277 Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., 278 and M. Chen, "BGP Link-State extensions for Segment 279 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16 280 (work in progress), June 2019. 282 [I-D.ietf-idr-bgp-ls-segment-routing-msd] 283 Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G., 284 and N. Triantafillis, "Signaling MSD (Maximum SID Depth) 285 using Border Gateway Protocol - Link State", draft-ietf- 286 idr-bgp-ls-segment-routing-msd-18 (work in progress), May 287 2020. 289 [I-D.ietf-isis-mpls-elc] 290 Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S., 291 and M. Bocci, "Signaling Entropy Label Capability and 292 Entropy Readable Label Depth Using IS-IS", draft-ietf- 293 isis-mpls-elc-12 (work in progress), April 2020. 295 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 296 Requirement Levels", BCP 14, RFC 2119, 297 DOI 10.17487/RFC2119, March 1997, 298 . 300 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF 301 for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, 302 . 304 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and 305 L. Yong, "The Use of Entropy Labels in MPLS Forwarding", 306 RFC 6790, DOI 10.17487/RFC6790, November 2012, 307 . 309 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., 310 Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute 311 Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 312 2015, . 314 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and 315 S. Ray, "North-Bound Distribution of Link-State and 316 Traffic Engineering (TE) Information Using BGP", RFC 7752, 317 DOI 10.17487/RFC7752, March 2016, 318 . 320 [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and 321 S. Shaffer, "Extensions to OSPF for Advertising Optional 322 Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, 323 February 2016, . 325 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 326 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 327 May 2017, . 329 [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and 330 F. Baker, "OSPFv3 Link State Advertisement (LSA) 331 Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 332 2018, . 334 [RFC8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, 335 "Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476, 336 DOI 10.17487/RFC8476, December 2018, 337 . 339 [RFC8662] Kini, S., Kompella, K., Sivabalan, S., Litkowski, S., 340 Shakir, R., and J. Tantsura, "Entropy Label for Source 341 Packet Routing in Networking (SPRING) Tunnels", RFC 8662, 342 DOI 10.17487/RFC8662, December 2019, 343 . 345 10.2. Informative References 347 [RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S., 348 Decraene, B., Litkowski, S., and R. Shakir, "Segment 349 Routing with the MPLS Data Plane", RFC 8660, 350 DOI 10.17487/RFC8660, December 2019, 351 . 353 [RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler, 354 H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 355 Extensions for Segment Routing", RFC 8665, 356 DOI 10.17487/RFC8665, December 2019, 357 . 359 [RFC8666] Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions 360 for Segment Routing", RFC 8666, DOI 10.17487/RFC8666, 361 December 2019, . 363 Authors' Addresses 365 Xiaohu Xu 366 Alibaba Inc 368 Email: xiaohu.xxh@alibaba-inc.com 370 Sriganesh Kini 372 Email: sriganeshkini@gmail.com 373 Peter Psenak 374 Cisco Systems, Inc. 375 Eurovea Centre, Central 3 376 Pribinova Street 10 377 Bratislava 81109 378 Slovakia 380 Email: ppsenak@cisco.com 382 Clarence Filsfils 383 Cisco Systems, Inc. 384 Brussels 385 Belgium 387 Email: cfilsfil@cisco.com 389 Stephane Litkowski 390 Cisco Systems, Inc. 391 La Rigourdiere 392 Cesson Sevigne 393 France 395 Email: slitkows@cisco.com 397 Matthew Bocci 398 Nokia 399 Shoppenhangers Road 400 Maidenhead, Berks 401 UK 403 Email: matthew.bocci@nokia.com