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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) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 isis B. Liu, Ed. 3 Internet-Draft Huawei Technologies 4 Intended status: Standards Track L. Ginsberg 5 Expires: November 10, 2017 Cisco Systems 6 B. Decraene 7 Orange 8 I. Farrer 9 Deutsche Telekom AG 10 M. Abrahamsson 11 T-Systems 12 May 9, 2017 14 ISIS Auto-Configuration 15 draft-ietf-isis-auto-conf-05 17 Abstract 19 This document specifies IS-IS auto-configuration mechanisms. The key 20 components are IS-IS System ID self-generation, duplication detection 21 and duplication resolution. These mechanisms provide limited IS-IS 22 functions, and so are suitable for networks where plug-and-play 23 configuration is expected. 25 Requirements Language 27 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 28 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 29 "OPTIONAL" in this document are to be interpreted as described in 30 [RFC2119] when they appear in ALL CAPS. When these words are not in 31 ALL CAPS (such as "should" or "Should"), they have their usual 32 English meanings, and are not to be interpreted as [RFC2119] key 33 words. 35 Status of This Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF). Note that other groups may also distribute 42 working documents as Internet-Drafts. The list of current Internet- 43 Drafts is at http://datatracker.ietf.org/drafts/current/. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 49 This Internet-Draft will expire on November 10, 2017. 51 Copyright Notice 53 Copyright (c) 2017 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (http://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 69 2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 70 3. Protocol Specification . . . . . . . . . . . . . . . . . . . 3 71 3.1. IS-IS Default Configuration . . . . . . . . . . . . . . . 3 72 3.2. IS-IS NET Generation . . . . . . . . . . . . . . . . . . 4 73 3.3. Router-Fingerprint TLV . . . . . . . . . . . . . . . . . 5 74 3.4. Protocol Operation . . . . . . . . . . . . . . . . . . . 6 75 3.4.1. Start-Up mode . . . . . . . . . . . . . . . . . . . . 6 76 3.4.2. Adjacency Formation . . . . . . . . . . . . . . . . . 7 77 3.4.3. IS-IS System ID Duplication Detection . . . . . . . . 7 78 3.4.4. Duplicate System ID Resolution Procedures . . . . . . 7 79 3.4.5. System ID and Router-Fingerprint Generation 80 Considerations . . . . . . . . . . . . . . . . . . . 8 81 3.4.6. Duplication of both System ID and Router-Fingerprint 9 82 3.5. Additional IS-IS TLVs Usage Guidelines . . . . . . . . . 10 83 3.5.1. Authentication TLV . . . . . . . . . . . . . . . . . 11 84 3.5.2. Metric Used in Reachability TLVs . . . . . . . . . . 11 85 3.5.3. Dynamic Host Name TLV . . . . . . . . . . . . . . . . 11 86 4. Security Considerations . . . . . . . . . . . . . . . . . . . 11 87 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 88 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 89 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 90 7.1. Normative References . . . . . . . . . . . . . . . . . . 12 91 7.2. Informative References . . . . . . . . . . . . . . . . . 13 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 94 1. Introduction 96 This document specifies mechanisms for IS-IS [RFC1195] 97 [ISO_IEC10589][RFC5308] to be auto-configuring. Such mechanisms 98 could reduce the management burden for configuring a network, 99 especially where plug-and-play device configuration is required. 101 IS-IS auto-configuration is comprised of the following functions: 103 1. IS-IS default configuration. 105 2. IS-IS System ID self-generation. 107 3. System ID duplication detection and resolution. 109 4. ISIS TLV utilization (Authentication TLV, metrics in reachability 110 advertisements, and Dynamic Host Name TLV). 112 This document also defines mechanisms to prevent the unintentional 113 interoperation of auto-configured routers with non-autoconfigured 114 routers. See Section 3.3. 116 2. Scope 118 The auto-configuration mechanisms support both IPv4 and IPv6 119 deployments. 121 These auto-configuration mechanisms aim to cover simple deployment 122 cases. The following important features are not supported: 124 o Multiple IS-IS instances. 126 o Multi-area and level-2 routing. 128 o Interworking with other routing protocols. 130 IS-IS auto-configuration is primarily intended for use in small (i.e. 131 10s of devices) and unmanaged deployments. It allows IS-IS to be 132 used without the need for any configuration by the user. It is not 133 recommended for larger deployments. 135 3. Protocol Specification 137 3.1. IS-IS Default Configuration 139 o IS-IS interfaces MUST be auto-configured to an interface type 140 corresponding to their layer-2 capability. For example, Ethernet 141 interfaces will be auto-configured as broadcast networks and 142 Point-to-Point Protocol (PPP) interfaces will be auto-configured 143 as Point-to-Point interfaces. 145 o IS-IS auto-configuration instances MUST be configured as level-1, 146 so that the interfaces operate as level-1 only. 148 o originatingLSPBufferSize is set to 512. 150 o MaxAreaAddresses is set to 3 152 o Extended IS Reachability and IP Reachability TLVs [RFC5305] MUST 153 be used i.e. a router operating in auto configuration mode MUST 154 NOT use any of the following TLVs: 156 * IS Neighbors (2) 158 * IP Internal Reachability (128) 160 * IP External Reachability (130) 162 TLVs listed above MUST be ignored on receipt. 164 3.2. IS-IS NET Generation 166 In IS-IS, a router (known as an Intermediate System) is identified by 167 a Network Entity Title (NET) which is a type of Network Service 168 Access Point (NSAP). The NET is the address of an instance of the 169 IS-IS protocol running on an Intermediate System (IS). 171 The auto-configuration mechanism generates the IS-IS NET as the 172 following: 174 o Area address 176 In IS-IS auto-configuration, this field MUST be 13 octets long 177 and set to all 0. 179 o System ID 181 This field follows the area address field, and is 6 octets in 182 length. There are two basic requirements for the System ID 183 generation: 185 - As specified by the IS-IS protocol, this field must be 186 unique among all routers in the same area. 188 - After its initial generation, the System ID SHOULD remain 189 stable. Changes such as interface enable/disable, interface 190 connect/disconnect, device reboot, firmware update, or 191 configuration changes SHOULD NOT cause the system ID to 192 change. System ID change as part of the System ID collision 193 resolution process MUST be supported. Implementations 194 SHOULD allow the System ID to be cleared by a user initiated 195 system reset. 197 More specific considerations for System ID generation are 198 described in Section 3.4.5. 200 3.3. Router-Fingerprint TLV 202 The Router-Fingerprint TLV is similar to the Router-Hardware- 203 Fingerprint TLV defined in [RFC7503]. However, the TLV defined here 204 includes a flags field to support indicating that the router is in 205 Start-up mode and is operating in auto-configuration mode. 207 0 1 2 3 208 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 1 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | Type | Length | 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | Flags Field | | 213 +-+-+-+-+-+-+-+-+ Router Fingerprint (Variable) . 214 . . 215 . . 216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 Type: to be assigned by IANA. 219 Length: the length of the value field. Must be >= 33. 220 Flags field (1 octet) 222 0 1 2 3 4 5 6 7 223 +-+-+-+-+-+-+-+-+ 224 |S|A| Reserved | 225 +-+-+-+-+-+-+-+-+ 227 S flag: when set, indicates the router is in "start-up" mode. 228 A flag: when set, indicates that the router is operating in 229 auto-configuration mode. The purpose of the flag is so that 230 two routers can identify if they are both using auto-configuration. 231 If the A flag setting does not match in hellos then no adjacency 232 should be formed. 233 Reserved: these bits MUST be set to zero and MUST be ignored by 234 the receiver. 236 Router Fingerprint: 32 or more octets. 238 More specific considerations for Router-Fingerprint are described in 239 Section 3.4.5. 241 Router Fingerprint TLV MUST be included in Intermediate System to 242 Intermediate System Hellos (IIHs) originated by a router operating in 243 auto-configuration mode. An auto-configuration mode router MUST 244 ignore IIHs that don't contain the Router Fingerprint TLV. 246 Router Fingerprint TLV MUST be included in Link State PDU (LSP) #0 247 originated by a router operating in auto-configuration mode. If an 248 LSP #0 which does NOT contain a Router Fingerprint TLV is received by 249 a Router operating in auto-configuration mode the LSP is flooded as 250 normal, but the entire LSP set originated by the sending router MUST 251 be ignored when running the Decision process. 253 The router fingerprint TLV MUST NOT be included in an LSP with a non- 254 zero number and when received MUST be ignored. 256 3.4. Protocol Operation 258 This section describes the operation of a router supporting auto- 259 configuration mode. 261 3.4.1. Start-Up mode 263 When a router starts operation in auto-configuration mode, both the S 264 and A bits MUST be set in the Router Fingerprint TLV included in both 265 hellos and LSP #0. During this mode only LSP #0 is generated and IS 266 or IP/IPv6 reachability TLVs MUST NOT be included in LSP #0. A 267 router remains in Start-up mode for a minimum period of time 268 (recommended to be 1 minute). This time should be sufficient to 269 bring up adjacencies to all expected neighbors. A router leaves 270 Start-up mode once the minimum time has elapsed and full LSP database 271 synchronization is achieved with all neighbors in the UP state. 273 When a router exits startup-mode it clears the S bit in Router 274 Fingerprint TLVs it sends in hellos and LSP#0. The router MAY now 275 advertise IS neighbor and IP/IPv6 prefix reachability in its LSPs and 276 MAY generate LSPs with a non-zero number. 278 The purpose of Start-up Mode is to minimize the occurrence of System 279 ID changes for a router once it has become fully operational. Any 280 System ID change during Start-up mode will have minimal impact on a 281 running network because while in Start-up mode the router is not yet 282 being used for forwarding traffic. 284 3.4.2. Adjacency Formation 286 Routers operating in auto-configuration mode MUST NOT form 287 adjacencies with routers which are NOT operating in auto- 288 configuration mode. The presence of the Router Fingerprint TLV with 289 the A bit set indicates the router is operating in auto-configuration 290 mode. 292 NOTE: The use of the special area address of all 0's makes it 293 unlikely that a router which is not operating in auto-configuration 294 mode will be in the same area as a router operating in auto- 295 configuration mode. However, the check for the Router Fingerprint 296 TLV with A bit set provides additional protection. 298 3.4.3. IS-IS System ID Duplication Detection 300 The System ID of each node MUST be unique. As described in 301 Section 3.4.5, the System ID is generated based on entropies (e.g. 302 MAC address) which are generally expected to be unique. However, 303 since there may be limitations to the available entropies, there is 304 still the possibility of System ID duplication. This section defines 305 how IS-IS detects and resolves System ID duplication. Duplicate 306 System ID may occur between neighbors or between routers in the same 307 area which are not neighbors. 309 Duplicate System ID with a neighbor is detected when the System ID 310 received in an IIH is identical to the local System ID and the 311 Router-Fingerprint in the received Router-Fingerprint TLV does NOT 312 match the locally generated Router-Fingerprint. 314 Duplicate System ID with a non-neighbor is detected when an LSP #0 is 315 received, the System ID of the originator is identical to the local 316 System ID, and the Router-Fingerprint in the Router-Fingerprint TLV 317 does NOT match the locally generated Router-Fingerprint. 319 3.4.4. Duplicate System ID Resolution Procedures 321 When duplicate System ID is detected one of the systems MUST assign 322 itself a different System ID and perform a protocol restart. The 323 resolution procedure attempts to minimize disruption to a running 324 network by choosing a router which is in Start-up mode to be 325 restarted whenever possible. 327 The contents of the Router-Fingerprint TLVs for the two routers with 328 duplicate System IDs are compared. 330 If one TLV has the S bit set (router is in Start-up mode) and one TLV 331 has the S bit clear (router is NOT in Start-up mode) the router in 332 Start-up mode MUST generate a new System ID and restart the protocol. 334 If both TLVs have the S bit set (both routers are in Start-up mode) 335 or both TLVs have the S bit clear (neither router is in Start-up 336 mode) then the router with numerically smaller Router-Fingerprint 337 MUST generate a new System ID and restart the protocol. 339 Fingerprint comparison is performed octet by octet starting from the 340 first received octet until a difference is detected. If the 341 fingerprints have different lengths and all octets up to the shortest 342 length are identical then the fingerprint with smaller length is 343 considered smaller. 345 If the fingerprints are identical in both content and length (and 346 state of the S bit is identical) and the duplication is detected in 347 hellos then the both routers MUST generate a new System ID and 348 restart the protocol. 350 If fingerprints are identical in both content and length and the 351 duplication is detected in LSP #0 then the procedures defined in 352 Section 3.4.6 MUST be followed. 354 3.4.5. System ID and Router-Fingerprint Generation Considerations 356 As specified in this document, there are two distinguishing items 357 that need to be self-generated: the System ID and Router-Fingerprint. 358 In a network device, normally there are some resources which can 359 provide an extremely high probability of uniqueness (some examples 360 listed below). These resources can be used as seeds to derive 361 identifiers. 363 o MAC address(es) 365 o Configured IP address(es) 367 o Hardware IDs (e.g. CPU ID) 369 o Device serial number(s) 371 o System clock at a certain specific time 373 o Arbitrary received packet(s) on an interface(s) 375 This document recommends the use of an IEEE 802 48-bit MAC address 376 associated with the router as the initial System ID. This document 377 does not specify a specific method to re-generate the System ID when 378 duplication happens. 380 This document also does not specify a specific method to generate the 381 Router-Fingerprint. 383 There is an important concern that the seeds listed above (except MAC 384 address) might not be available in some small devices such as home 385 routers. This is because of hardware/software limitations and the 386 lack of sufficient communication packets at the initial stage in home 387 routers when doing ISIS auto-configuration. In this case, this 388 document suggests using the MAC address as System ID and generating a 389 pseudo-random number based on another seed (such as the memory 390 address of a certain variable in the program) as the Router- 391 Fingerprint. The pseudo-random number might not have a very high 392 probability of uniqueness in this solution, but should be sufficient 393 in home networks scenarios. 395 The considerations surrounding System ID stability described in 396 section Section 3.2 also need to be applied. 398 3.4.6. Duplication of both System ID and Router-Fingerprint 400 As described above, the resources for generating System ID/ 401 Fingerprint might be very constrained during the initial stages. 402 Hence, the duplication of both System ID and Router-Fingerprint needs 403 to be considered. In such a case it is possible that a router will 404 receive an LSP with System ID and Router-Fingerprint identical to the 405 local values but the LSP is NOT identical to the locally generated 406 copy i.e. sequence number is newer or sequence number is the same but 407 the LSP has a valid checksum which does not match. The term DD-LSP 408 is used to describe such an LSP. 410 In a benign case, this will occur if a router restarts and it 411 receives copies of its own LSPs from its previous incarnation. This 412 benign case needs to be distinguished from the pathological case 413 where there are two different routers with the same System ID and the 414 same Router-Fingerprint. 416 In the benign case, the restarting router will generate a new version 417 of its own LSP with higher sequence number and flood the new LSP 418 version. This will cause other routers in the network to update 419 their LSPDB and synchronization will be achieved. 421 In the pathological case the generation of a new version of an LSP by 422 one of the "twins" will cause the other twin to generate the same LSP 423 with a higher sequence number - and oscillation will continue without 424 achieving LSPDB synchronization. 426 Note that comparison of S bit in the Router-Fingerprint TLV cannot be 427 performed as in the benign case it is expected that the S bit will be 428 clear. Also note that the conditions for detecting duplicate System 429 ID will NOT be satisfied because both the System ID and the Router- 430 Fingerprint will be identical. 432 The following procedure is defined: 434 DD-state is a boolean which indicates if a 435 DD-LSP #0 has been received 436 DD-count is the count of the number of occurences 437 of reception of a DD-LSP 438 DD-timer is a timer associated with reception of 439 DD-LSPs. Recommended value is 60 seconds. 440 DD-max is the maximum number of DD-LSPs allowed 441 to be received in DD-timer interval. 442 Recommended value is 3. 444 When a DD-LSP is received: 446 If DD-state is FALSE: 447 DD-state is set to TRUE 448 DD-timer is started 449 DD-count is initialized to 1. 451 If DD-state is TRUE: 452 DD-count is incremented 453 If DD-count is >= DD-max: 454 Local system MUST generate a new System ID 455 and Router-Fingerprint and restart the protocol 456 DD-state is (re)initialized to FALSE and 457 DD-timer cancelled. 459 If DD-timer expires: 460 DD-state is set to FALSE. 462 Note that to minimze the likelihood of duplication of both System ID 463 and Router-fingerprint reoccuring, routers SHOULD have more entropies 464 available. One simple way to achieve this is to add the LSP sequence 465 number of the next LSP it will send to the Router-Fingerprint. 467 3.5. Additional IS-IS TLVs Usage Guidelines 469 This section describes the behavior of selected TLVs when used by a 470 router supporting IS-IS auto-configuration. 472 3.5.1. Authentication TLV 474 It is RECOMMENDED that IS-IS routers supporting this specification 475 offer an option to explicitly configure a single password for HMAC- 476 MD5 authentication as specified in[RFC5304]. 478 3.5.2. Metric Used in Reachability TLVs 480 It is RECOMMENDED that IS-IS auto-configuration routers use a high 481 metric value (e.g. 100000) as default in order to allow manually 482 configured adjacencies to be preferred over auto-configured. 484 3.5.3. Dynamic Host Name TLV 486 IS-IS auto-configuration routers MAY advertise their Dynamic Host 487 Name TLV (TLV 137, [RFC5301]). The host name could be provisioned by 488 an IT system, or just use the name of vendor, device type or serial 489 number, etc. 491 To guarantee the uniqueness of the host name, the System ID SHOULD be 492 appended as a suffix in the names. 494 4. Security Considerations 496 In the absence of cryptographic authentication it is possible for an 497 attacker to inject a PDU falsely indicating there is a duplicate 498 system-id. This may trigger automatic restart of the protocol using 499 the duplicate-id resolution procedures defined in this document. 501 Note that the use of authentication is incompatible with auto- 502 configuration as it requires some manual configuration. 504 For wired deployment, the wired connection itself could be considered 505 as an implicit authentication in that unwanted routers are usually 506 not able to connect (i.e. there is some kind of physical security in 507 place preventing the connection of rogue devices); for wireless 508 deployment, the authentication could be achieved at the lower 509 wireless link layer. 511 5. IANA Considerations 513 This document requires the definition of a new IS-IS TLV to be 514 reflected in the "IS-IS TLV Codepoints" registry: 516 Type Description IIH LSP SNP Purge 517 ---- ------------ --- --- --- ----- 518 TBA Router-Fingerprint Y Y N Y 520 6. Acknowledgements 522 This document was heavily inspired by [RFC7503]. 524 Martin Winter, Christian Franke and David Lamparter gave essential 525 feedback to improve the technical design based on their 526 implementation experience. 528 Many useful comments were made by Acee Lindem, Karsten Thomann, 529 Hannes Gredler, Peter Lothberg, Uma Chundury, Qin Wu, Sheng Jiang and 530 Nan Wu, etc. 532 This document was produced using the xml2rfc tool [RFC7991]. 533 (initially prepared using 2-Word-v2.0.template.dot. ) 535 7. References 537 7.1. Normative References 539 [ISO_IEC10589] 540 "Intermediate system to Intermediate system intra-domain 541 routeing information exchange protocol for use in 542 conjunction with the protocol for providing the 543 connectionless-mode Network Service (ISO 8473), ISO/IEC 544 10589:2002, Second Edition.", Nov 2002. 546 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 547 dual environments", RFC 1195, DOI 10.17487/RFC1195, 548 December 1990, . 550 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 551 Requirement Levels", BCP 14, RFC 2119, 552 DOI 10.17487/RFC2119, March 1997, 553 . 555 [RFC5301] McPherson, D. and N. Shen, "Dynamic Hostname Exchange 556 Mechanism for IS-IS", RFC 5301, DOI 10.17487/RFC5301, 557 October 2008, . 559 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 560 Authentication", RFC 5304, DOI 10.17487/RFC5304, October 561 2008, . 563 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 564 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 565 2008, . 567 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 568 DOI 10.17487/RFC5308, October 2008, 569 . 571 7.2. Informative References 573 [RFC7503] Lindem, A. and J. Arkko, "OSPFv3 Autoconfiguration", 574 RFC 7503, DOI 10.17487/RFC7503, April 2015, 575 . 577 [RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary", 578 RFC 7991, DOI 10.17487/RFC7991, December 2016, 579 . 581 Authors' Addresses 583 Bing Liu (editor) 584 Huawei Technologies 585 Q10, Huawei Campus, No.156 Beiqing Road 586 Hai-Dian District, Beijing, 100095 587 P.R. China 589 Email: leo.liubing@huawei.com 591 Les Ginsberg 592 Cisco Systems 593 821 Alder Drive 594 Milpitas CA 95035 595 USA 597 Email: ginsberg@cisco.com 599 Bruno Decraene 600 Orange 601 France 603 Email: bruno.decraene@orange.com 605 Ian Farrer 606 Deutsche Telekom AG 607 Bonn 608 Germany 610 Email: ian.farrer@telekom.de 611 Mikael Abrahamsson 612 T-Systems 613 Stockholm 614 Sweden 616 Email: mikael.abrahamsson@t-systems.se