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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) -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10589' ** Obsolete normative reference: RFC 4971 (Obsoleted by RFC 7981) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IS-IS for IP Internets P. Sarkar, Ed. 3 Internet-Draft H. Gredler 4 Intended status: Standards Track S. Hegde 5 Expires: May 30, 2016 Juniper Networks, Inc. 6 S. Litkowski 7 B. Decraene 8 Orange 9 Z. Li 10 Huawei Technologies 11 E. Aries 12 R. Rodriguez 13 Facebook 14 H. Raghuveer 15 November 27, 2015 17 Advertising Per-node Admin Tags in IS-IS 18 draft-ietf-isis-node-admin-tag-06 20 Abstract 22 This document describes an extension to the IS-IS routing protocol to 23 add an optional operational capability, that allows tagging and 24 grouping of the nodes in an IS-IS domain. This allows simple 25 management and easy control over route and path selection, based on 26 local configured policies. 28 This document describes the protocol extensions to disseminate per- 29 node administrative tags in IS-IS protocols. 31 Requirements Language 33 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 34 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 35 document are to be interpreted as described in RFC 2119 [RFC2119]. 37 Status of This Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at http://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on May 30, 2016. 54 Copyright Notice 56 Copyright (c) 2015 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (http://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 72 2. Administrative Tag . . . . . . . . . . . . . . . . . . . . . 3 73 3. TLV format . . . . . . . . . . . . . . . . . . . . . . . . . 4 74 3.1. Per-node Admin Tag sub-TLV . . . . . . . . . . . . . . . 4 75 4. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 5 76 5. Applications . . . . . . . . . . . . . . . . . . . . . . . . 6 77 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 78 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 79 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 80 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 81 9.1. Normative References . . . . . . . . . . . . . . . . . . 12 82 9.2. Informative References . . . . . . . . . . . . . . . . . 12 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 85 1. Introduction 87 This document provides mechanisms to advertise per-node 88 administrative tags in the IS-IS Link State PDU [RFC1195]. In 89 certain path-selection applications like for example in traffic- 90 engineering or LFA [RFC5286] selection there is a need to tag the 91 nodes based on their roles in the network and have policies to prefer 92 or prune a certain group of nodes. 94 2. Administrative Tag 96 For the purpose of advertising per-node administrative tags within 97 IS-IS, a new sub-TLV to the IS-IS Router Capability TLV-242 that is 98 defined in [RFC4971] is proposed. Path selection is a functional set 99 which applies both to TE and non-TE applications. Per-node 100 administrative tags are used to advertise an attribute of the node. 101 As such they are independent of the routing protocol used to 102 advertise them. Because per-node administrative tags may be used to 103 advertise many different attributes, associating the advertisement to 104 TLVs specific to a particular use case (e.g. TE extensions to IS- 105 Neighbors TLVs [RFC5305] in the case of TE path selection) is not 106 appropriate. 108 An administrative Tag is a 32-bit integer value that can be used to 109 identify a group of nodes in the IS-IS domain. The new sub-TLV 110 specifies one or more administrative tag values. An IS-IS router 111 advertises the set of groups it is part of in the specific IS-IS 112 level. As an example, all PE-nodes may be configured with certain 113 tag value, whereas all P-nodes are configured with a different tag 114 value. 116 The new sub-TLV defined will be carried inside the IS-IS Router 117 Capability TLV-242 [RFC4971]) in the Link State PDUs originated by 118 the router. TLV 242 can be either specified to be flooded within the 119 specific level in which the same has been originated, or they can be 120 specfied to be relayed from originating level to the other as well. 121 Per-node administrative tags that are included in a 'level-specific' 122 TLV 242 have a 'level-wide' flooding scope associated. On the other 123 hand, per-node administrative tags included in a 'domain-wide' TLV 124 242 have 'domain-wide' flooding scope associated. For details on how 125 TLV 242 are flooded and relayed in the entire network please, refer 126 to [RFC4971]. 128 Choosing the flooding scope to be associated with group tags, is 129 defined by the needs of the operator's usage and is a matter of local 130 policy or configuration. Operator may choose to advertise a set of 131 per-node administrative tags across levels and another set of per- 132 node administrative tags within the specific level. But evidently 133 the same set of per-node administrative tags cannot be advertised 134 both across levels and within a specific level. A receiving IS-IS 135 router will not be able to distinguish between the significance of a 136 per-node administrative tag advertised with 'domain-wide' scope, from 137 that of an administrative tag advertised with 'level-wide' scope, if 138 they have the same value associated but different significance across 139 different scopes. 141 Implementations SHOULD allow configuring one or more per-node 142 administrative tags to be advertised from a given device along with 143 the flooding scope associated with the same. It SHOULD allow 144 provisioning a set of per-node administrative tags having a 'domain- 145 wide' flooding scope, as well as, a set of per-node administrative 146 tags with 'level-wide' flooding scope only. A given per-node 147 administrative tag MAY be advertised with level-specific scope 148 (Level-1 and/or Level-2) or with domain-wide scope, but MUST NOT be 149 advertised in both scopes. Hence implementations MUST NOT allow 150 configuring the same per-node administrative tag values in both 151 'domain-wide' and 'level-wide' scopes. However the same 152 administrative tag value MAY be allowed under multiple levels with 153 'level-wide' scope. 155 The format of per-node Administrative Tag sub-TLV (see Section 3.1) 156 does not include a topology identifier. Therefore it is not possible 157 to indicate a topology specific context when advertising per-node 158 admin tags. Hence, in deployments using multi-topology routing 159 [RFC5120], advertising a separate set of per-node administrative tags 160 for each topology SHOULD NOT be supported. 162 3. TLV format 164 3.1. Per-node Admin Tag sub-TLV 166 The new Per-node Administrative Tag sub-TLV, like other ISIS 167 Capability sub-TLVs, is formatted as Type/Length/Value (TLV)triplets. 168 Figure 1 below shows the format of the new sub-TLV. 170 0 1 2 3 171 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 1 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 | Type | Length | 174 +- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 | Administrative Tag #1 | 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 | Administrative Tag #2 | 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 // // 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | Administrative Tag #N | 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 Type : TBA 186 Length: A 8-bit field that indicates the length of the value 187 portion in octets and will be a multiple of 4 octets 188 dependent on the number of tags advertised. 190 Value: A sequence of multiple 4 octets defining the 191 administrative tags. 193 Figure 1: IS-IS Per-node Administrative Tag sub-TLV 195 The 'Per-node Admin Tag' sub-TLV may be generated more than once by 196 an originating router. This MAY happen if a node carries more than 197 63 per-node administrative groups and a single sub-TLV does not 198 provide sufficient space. As such occurrence of the 'Per-node Admin 199 Tag' sub-TLV does not cancel previous announcements, but rather is 200 cumulative. 202 4. Elements of Procedure 204 Meaning of the Per-node administrative tags is generally opaque to 205 IS-IS. Router advertising the per-node administrative tag (or tags) 206 may be configured to do so without knowing (or even explicitly 207 supporting) functionality implied by the tag. 209 Interpretation of tag values is specific to the administrative domain 210 of a particular network operator. The meaning of a per-node 211 administrative tag is defined by the network local policy and is 212 controlled via the configuration. If a receiving node does not 213 understand the tag value, it ignores the specific tag and floods the 214 Router Capability TLV without any change as defined in [RFC4971]. 216 The semantics of the tag order has no meaning. There is no implied 217 meaning to the ordering of the tags that indicates a certain 218 operation or set of operations that need to be performed based on the 219 ordering. 221 Each tag SHOULD be treated as an independent identifier that MAY be 222 used in policy to perform a policy action. Tags carried by the 223 administrative tag TLV SHOULD be used to indicate independent 224 characteristics of a node. The TLV SHOULD be considered as an 225 unordered list. Whilst policies may be implemented based on the 226 presence of multiple tags (e.g., if tag A AND tag B are present), 227 they MUST NOT be reliant upon the order of the tags (i.e., all 228 policies should be considered commutative operations, such that tag A 229 preceding or following tag B does not change their outcome). 231 As mentioned earlier, to avoid incomplete or inconsistent 232 interpretations of the per-node administrative tags the same tag 233 value MUST NOT be advertised by a router in Router Capabilities of 234 different scopes. Implementations MUST NOT allow configuring the 235 same tag value across domain-wide and 'level-wide' scopes. The same 236 tag value MAY be allowed to be configured and advertised under 237 'level-wide' scope for all levels. A IS-IS Area Border Router (ABR) 238 participating in both levels 1 and 2 MAY advertise the same tag value 239 in the level-specific Router Capability TLVs with 'level-wide' scope 240 generated by it. But the same tag value MUST NOT be advertised in 241 any of level 1 or level 2 Router-Capability TLV with 'domain-wide' 242 flooding scope (refer to [RFC4971] for more details). 244 Future IS-IS protocol extensions MUST NOT require use of per-node 245 administrative tags or define well-known tag values to advertise 246 well-known capabilities. Per-node administrative tags are for 247 generic use and do not require IANA registry. 249 Being part of the Router Capability TLV, the per-node administrative 250 tag sub-TLV MUST be reasonably small and stable. In particular, but 251 not limited to, implementations supporting the per-node 252 administrative tags MUST NOT associate advertised tags to changes in 253 the network topology (both within and outside the IS-IS domain) or 254 reachability of routes. 256 5. Applications 258 This section lists several examples of how implementations might use 259 the Per-node administrative tags. These examples are given only to 260 demonstrate generic usefulness of the router tagging mechanism. 261 Implementation supporting this specification is not required to 262 implement any of the use cases. It is also worth noting that in some 263 described use cases routers configured to advertise tags help other 264 routers in their calculations but do not themselves implement the 265 same functionality. 267 1. Auto-discovery of Services 269 Router tagging may be used to automatically discover group of 270 routers sharing a particular service. 272 For example, service provider might desire to establish full mesh 273 of MPLS TE tunnels between all PE routers in the area of MPLS VPN 274 network. Marking all PE routers with a tag and configuring 275 devices with a policy to create MPLS TE tunnels to all other 276 devices advertising this tag will automate maintenance of the 277 full mesh. When new PE router is added to the area, all other PE 278 devices will open TE tunnels to it without the need of 279 reconfiguring them. 281 2. Policy-based Fast-Reroute 283 Increased deployment of Loop Free Alternates (LFA) as defined in 284 [RFC5286] poses operation and management challenges. 285 [I-D.ietf-rtgwg-lfa-manageability] proposes policies which, when 286 implemented, will ease LFA operation concerns. 288 One of the proposed refinements is to be able to group the nodes 289 in IGP domain with administrative tags and engineer the LFA based 290 on configured policies. 292 (a) Administrative limitation of LFA scope 294 Service provider access infrastructure is frequently designed 295 in layered approach with each layer of devices serving 296 different purposes and thus having different hardware 297 capabilities and configured software features. When LFA 298 repair paths are being computed, it may be desirable to 299 exclude devices from being considered as LFA candidates based 300 on their layer. 302 For example, if the access infrastructure is divided into the 303 Access, Distribution and Core layers it may be desirable for 304 a Distribution device to compute LFA only via Distribution or 305 Core devices but not via Access devices. This may be due to 306 features enabled on Access routers; due to capacity 307 limitations or due to the security requirements. Managing 308 such a policy via configuration of the router computing LFA 309 is cumbersome and error prone. 311 With the Per-node administrative tags it is possible to 312 assign a tag to each layer and implement LFA policy of 313 computing LFA repair paths only via neighbors which advertise 314 the Core or Distribution tag. This requires minimal per-node 315 configuration and network automatically adapts when new links 316 or routers are added. 318 (b) Optimizing LFA calculations 320 Calculation of LFA paths may require significant resources of 321 the router. One execution of Dijkstra algorithm is required 322 for each neighbor eligible to become next hop of repair 323 paths. Thus a router with a few hundreds of neighbors may 324 need to execute the algorithm hundreds of times before the 325 best (or even valid) repair path is found. Manually 326 excluding from the calculation neighbors which are known to 327 provide no valid LFA (such as single-connected routers) may 328 significantly reduce number of Dijkstra algorithm runs. 330 LFA calculation policy may be configured so that routers 331 advertising certain tag value are excluded from LFA 332 calculation even if they are otherwise suitable. 334 3. Controlling Remote LFA tunnel termination 336 [RFC7490] proposed method of tunneling traffic after connected 337 link failure to extend the basic LFA coverage and algorithm to 338 find tunnel tail-end routers fitting LFA requirement. In most 339 cases proposed algorithm finds more than one candidate tail-end 340 router. In real life network it may be desirable to exclude some 341 nodes from the list of candidates based on the local policy. 342 This may be either due to known limitations of the per-node (the 343 router does accept targeted LDP sessions required to implement 344 Remote LFA tunneling) or due to administrative requirements (for 345 example, it may be desirable to choose tail-end router among co- 346 located devices). 348 The Per-node administrative tag delivers simple and scalable 349 solution. Remote LFA can be configured with a policy to accept 350 during the tail-end router calculation as candidates only routers 351 advertising certain tag. Tagging routers allows to both exclude 352 nodes not capable of serving as Remote LFA tunnel tail-ends and 353 to define a region from which tail-end router must be selected. 355 4. Mobile backhaul network service deployment 357 The topology of mobile backhaul network usually adopts ring 358 topology to save fiber resource and it is divided into the 359 aggregate network and the access network. Cell Site 360 Gateways(CSGs) connects the eNodeBs and RNC(Radio Network 361 Controller) Site Gateways(RSGs)connects the RNCs. The mobile 362 traffic is transported from CSGs to RSGs. The network takes a 363 typical aggregate traffic model that more than one access rings 364 will attach to one pair of aggregate site gateways(ASGs) and more 365 than one aggregate rings will attach to one pair of RSGs. 367 ---------------- 368 / \ 369 / \ 370 / \ 371 +------+ +----+ Access +----+ 372 |eNodeB|---|CSG1| Ring 1 |ASG1|------------- 373 +------+ +----+ +----+ \ 374 \ / \ 375 \ / +----+ +---+ 376 \ +----+ |RSG1|----|RNC| 377 -------------| | Aggregate +----+ +---+ 378 |ASG2| Ring | 379 -------------| | +----+ +---+ 380 / +----+ |RSG2|----|RNC| 381 / \ +----+ +---+ 382 / \ / 383 +------+ +----+ Access +----+ / 384 |eNodeB|---|CSG2| Ring 2 |ASG3|------------ 385 +------+ +----+ +----+ 386 \ / 387 \ / 388 \ / 389 ----------------- 391 Figure 2: Mobile Backhaul Network 393 A typical mobile backhaul network with access rings and aggregate 394 links is shown in figure above. The mobile backhaul networks 395 deploy traffic engineering due to the strict Service Level 396 Agreements(SLA). The TE paths may have additional constraints to 397 avoid passing via different access rings or to get completely 398 disjoint backup TE paths. The mobile backhaul networks towards 399 the access side change frequently due to the growing mobile 400 traffic and addition of new eNodeBs. It's complex to satisfy the 401 requirements using cost, link color or explicit path 402 configurations. The per-node administrative tag defined in this 403 document can be effectively used to solve the problem for mobile 404 backhaul networks. The nodes in different rings can be assigned 405 with specific tags. TE path computation can be enhanced to 406 consider additional constraints based on per-node administrative 407 tags. 409 5. Policy-based Explicit Routing 411 Partially meshed network provides multiple paths between any two 412 nodes in the network. In a data center environment, the topology 413 is usually highly symmetric with many/all paths having equal 414 cost. In a long distance network, this is usually less the case 415 for a variety of reasons (e.g. historic, fiber availability 416 constraints, different distances between transit nodes, different 417 roles ...). Hence between a given source and destination, a path 418 is typically preferred over the others, while between the same 419 source and another destination, a different path may be 420 preferred. 422 +--------------------+ 423 | | 424 | +----------+ | 425 | | | | 426 T-10-T | | 427 /| /| | | 428 / | / | | | 429 --+ | | | | | 430 / +--+-+ 100 | | 431 / / | | | | 432 / / R-18-R | | 433 / / /\ /\ | | 434 / | / \ / \ | | 435 / | / x \ | | 436 A-25-A 10 10 \ \ | | 437 / / 10 10 | | 438 / / \ \ | | 439 A-25-A A-25-A | | 440 \ \ / / | | 441 201 201 201 201 | | 442 \ \ / / | | 443 \ x / | | 444 \ / \ / | | 445 \/ \/ | | 446 I-24-I 100 100 447 | | | | 448 | +-----------+ | 449 | | 450 +---------------------+ 452 Figure 3: Explicit Routing topology 454 In the above topology, operator may want to enforce the following 455 high level explicitly routed policies: - Traffic from A nodes to 456 A nodes must not go through I nodes - Traffic from A nodes to I 457 nodes must not go through R and T nodes with per-node 458 administrative tag, tag A can be configured on all A nodes, 459 (similarly I, R, T), and then configure this single CSPF policy 460 on all A nodes to avoid I nodes for path calculation. 462 6. Security Considerations 464 This document does not introduce any further security issues other 465 than those discussed in [ISO10589] and [RFC1195]. 467 7. IANA Considerations 469 IANA maintains the registry for the Router Capability sub-TLVs. IS- 470 IS Administrative Tags will require new type code for the following 471 new sub-TLV defined in this document. 473 i) Per-Node-Admin-Tag Sub-TLV, Type: TBD 475 8. Acknowledgments 477 Many thanks to Les Ginsberg, Dhruv Dhody, Uma Chunduri and Chris 478 Bowers for providing useful inputs. 480 9. References 482 9.1. Normative References 484 [ISO10589] 485 "Intermediate system to Intermediate system intra-domain 486 routeing information exchange protocol for use in 487 conjunction with the protocol for providing the 488 connectionless-mode Network Service (ISO 8473), ISO/IEC 489 10589:2002, Second Edition.", Nov 2002. 491 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 492 Requirement Levels", BCP 14, RFC 2119, 493 DOI 10.17487/RFC2119, March 1997, 494 . 496 [RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., 497 "Intermediate System to Intermediate System (IS-IS) 498 Extensions for Advertising Router Information", RFC 4971, 499 DOI 10.17487/RFC4971, July 2007, 500 . 502 9.2. Informative References 504 [I-D.ietf-rtgwg-lfa-manageability] 505 Litkowski, S., Decraene, B., Filsfils, C., Raza, K., 506 Horneffer, M., and P. Sarkar, "Operational management of 507 Loop Free Alternates", draft-ietf-rtgwg-lfa- 508 manageability-11 (work in progress), June 2015. 510 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 511 dual environments", RFC 1195, DOI 10.17487/RFC1195, 512 December 1990, . 514 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 515 Topology (MT) Routing in Intermediate System to 516 Intermediate Systems (IS-ISs)", RFC 5120, 517 DOI 10.17487/RFC5120, February 2008, 518 . 520 [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for 521 IP Fast Reroute: Loop-Free Alternates", RFC 5286, 522 DOI 10.17487/RFC5286, September 2008, 523 . 525 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 526 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 527 2008, . 529 [RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. 530 So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", 531 RFC 7490, DOI 10.17487/RFC7490, April 2015, 532 . 534 Authors' Addresses 536 Pushpasis Sarkar (editor) 537 Juniper Networks, Inc. 538 Electra, Exora Business Park 539 Bangalore, KA 560103 540 India 542 Email: psarkar@juniper.net 544 Hannes Gredler 545 Juniper Networks, Inc. 546 1194 N. Mathilda Ave. 547 Sunnyvale, CA 94089 548 US 550 Email: hannes@gredler.at 552 Shraddha Hegde 553 Juniper Networks, Inc. 554 Electra, Exora Business Park 555 Bangalore, KA 560103 556 India 558 Email: shraddha@juniper.net 559 Stephane Litkowski 560 Orange 562 Email: stephane.litkowski@orange.com 564 Bruno Decraene 565 Orange 567 Email: bruno.decraene@orange.com 569 Li Zhenbin 570 Huawei Technologies 571 Huawei Bld. No.156 Beiqing Rd 572 Beijing, KA 100095 573 China 575 Email: lizhenbin@huawei.com 577 Ebben Aries 578 Facebook 579 1 Hacker Way 580 Menlo Park, CA 94025 581 US 583 Email: exa@dscp.org 585 Rafael Rodriguez 586 Facebook 587 1 Hacker Way 588 Menlo Park, CA 94025 589 US 591 Email: rafael@fb.com 593 Harish Raghuveer 595 Email: harish.r.prabhu@gmail.com