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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-24) exists of draft-ietf-lisp-15 == Outdated reference: A later version (-10) exists of draft-ietf-lisp-alt-09 == Outdated reference: A later version (-06) exists of draft-ietf-lisp-interworking-02 == Outdated reference: A later version (-16) exists of draft-ietf-lisp-ms-11 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-threats-00 Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group L. Iannone 3 Internet-Draft TU Berlin - Deutsche Telekom 4 Intended status: Experimental Laboratories AG 5 Expires: April 15, 2012 D. Saucez 6 O. Bonaventure 7 Universite catholique de Louvain 8 October 13, 2011 10 LISP Map-Versioning 11 draft-ietf-lisp-map-versioning-05.txt 13 Abstract 15 This document describes the LISP (Locator/ID Separation Protocol) 16 Map-Versioning mechanism, which provides in-packet information about 17 Endpoint-ID to Routing Locator (EID-to-RLOC) mappings used to 18 encapsulate LISP data packets. The proposed approach is based on 19 associating a version number to EID-to-RLOC mappings and transport 20 such a version number in the LISP specific header of LISP- 21 encapsulated packets. LISP Map-Versioning is particularly useful to 22 inform communicating Ingress Tunnel Routers (ITRs) and Egress Tunnel 23 Routers (ETRs) about modifications of the mappings used to 24 encapsulate packets. The mechanism is transparent to legacy 25 implementations, since in the LISP-specific header and in the Map 26 Records, bits used for Map-Versioning can be safely ignored by ITRs 27 and ETRs that do not support the mechanism. 29 Status of this Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on April 15, 2012. 46 Copyright Notice 48 Copyright (c) 2011 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 65 3. Definitions of Terms . . . . . . . . . . . . . . . . . . . . . 4 66 4. EID-to-RLOC Map-Version number . . . . . . . . . . . . . . . . 4 67 4.1. The Null Map-Version . . . . . . . . . . . . . . . . . . . 5 68 5. Dealing with Map-Version numbers . . . . . . . . . . . . . . . 6 69 5.1. Handling Destination Map-Version number . . . . . . . . . 7 70 5.2. Handling Source Map-Version number . . . . . . . . . . . . 9 71 6. LISP header and Map-Version numbers . . . . . . . . . . . . . 9 72 7. Map Record and Map-Version . . . . . . . . . . . . . . . . . . 10 73 8. Benefits and case studies for Map-Versioning . . . . . . . . . 11 74 8.1. Synchronization of different xTRs . . . . . . . . . . . . 11 75 8.2. Map-Versioning and unidirectional traffic . . . . . . . . 12 76 8.3. Map-Versioning and interworking . . . . . . . . . . . . . 13 77 8.3.1. Map-Versioning and Proxy-ITRs . . . . . . . . . . . . 13 78 8.3.2. Map-Versioning and LISP-NAT . . . . . . . . . . . . . 14 79 8.3.3. Map-Versioning and Proxy-ETRs . . . . . . . . . . . . 14 80 8.4. RLOC shutdown/withdraw . . . . . . . . . . . . . . . . . . 15 81 8.5. Map-Version for lightweight LISP implementation . . . . . 15 82 9. Incremental deployment and implementation status . . . . . . . 16 83 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16 84 10.1. Map-Versioning against traffic disruption . . . . . . . . 16 85 10.2. Map-Versioning against reachability information DoS . . . 17 86 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 87 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 88 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 89 13.1. Normative References . . . . . . . . . . . . . . . . . . . 18 90 13.2. Informative References . . . . . . . . . . . . . . . . . . 18 91 Appendix A. Estimation of time before Map-Version wrap-around . . 18 92 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 19 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 95 1. Introduction 97 This document describes the Map-Versioning mechanism used to provide 98 information on changes in the EID-to-RLOC mappings used in the LISP 99 ([I-D.ietf-lisp]) context to perform packet encapsulation. The 100 mechanism is totally transparent to xTRs not supporting such 101 functionality. It is not meant to replace any existing LISP 102 mechanism, but rather to extend them providing new functionalities. 103 If for any unforseen reason a normative conflict between the present 104 document and the LISP main specifications is found, the latter 105 ([I-D.ietf-lisp]) has precedence on the present document. 107 The basic mechanism is to associate a Map-Version number to each LISP 108 EID-to-RLOC mapping and transport such a version number in the LISP- 109 specific header. When a mapping changes, a new version number is 110 assigned to the updated mapping. A change in an EID-to-RLOC mapping 111 can be a change in the RLOCs set, by adding or removing one or more 112 RLOCs, but it can also be a change in the priority or weight of one 113 or more RLOCs. 115 When Map-Versioning is used, LISP-encapsulated data packets contain 116 the version number of the two mappings used to select the RLOCs in 117 the outer header (i.e., both source and destination). These version 118 numbers are encoded in the 24 low-order bits of the first longword of 119 the LISP header and indicated by a specific bit in the flags (first 8 120 high-order bits of the first longword of the LISP header). Note that 121 not all packets need to carry version numbers. 123 When an ITR encapsulates a data packet, with a LISP header containing 124 the Map-Version numbers, it puts in the LISP-specific header two 125 version numbers: 127 1. The version number assigned to the mapping (contained in the EID- 128 to-RLOC Database) used to select the source RLOC. 130 2. The version number assigned to the mapping (contained in the EID- 131 to-RLOC Cache) used to select the destination RLOC. 133 This operation is two-fold. On the one hand, it enables the ETR 134 receiving the packet to know if the ITR has the latest version number 135 that any ETR at the destination EID site has provided to the ITR in a 136 Map-Reply. If it is not the case the ETR can send to the ITR a Map- 137 Request containing the updated mapping or soliciting a Map-Request 138 from the ITR (both cases are already defined in [I-D.ietf-lisp]). In 139 this way the ITR can update its cache. On the other hand, it enables 140 an ETR receiving such a packet to know if it has in its EID-to-RLOC 141 Cache the latest mapping for the source EID (in case of bidirectional 142 traffic). If it is not the case a Map-Request can be sent. 144 2. Requirements Notation 146 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 147 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 148 document are to be interpreted as described in [RFC2119]. 150 3. Definitions of Terms 152 The present document uses terms already defined in main LISP 153 specification [I-D.ietf-lisp]. Hereafter are defined only the terms 154 that are specific to the Map-Versioning mechanism. Throughout the 155 whole document Big Endian bit ordering is used. 157 Map-Version number: An unsigned 12-bits assigned to an EID-to-RLOC 158 mapping, not including the value 0 (0x000). 160 Null Map-Version: The 12-bits null value of 0 (0x000) is not used as 161 Map-Version number. It is used to signal that no Map-Version 162 number is assigned to the EID-to-RLOC mapping. 164 Source Map-Version number: Map-Version number of the EID-to-RLOC 165 mapping used to select the source address (RLOC) of the outer IP 166 header of LISP-encapsulated packets. 168 Destination Map-Version number: Map-Version number of the EID-to- 169 RLOC mapping used to select the destination address (RLOC) of the 170 outer IP header of LISP-encapsulated packets. 172 4. EID-to-RLOC Map-Version number 174 The EID-to-RLOC Map-Version number consists in an unsigned 12-bits 175 integer. The version number is assigned on a per-mapping basis, 176 meaning that different mappings have a different version number, 177 which is also updated independently. An update in the version number 178 (i.e., a newer version) consists in incrementing by one the older 179 version number. Appendix A contains a rough estimation of the wrap- 180 around time for the Map-Version number. 182 The space of version numbers has a circular order where half of the 183 version numbers is greater(i.e., newer) than the current Map-Version 184 number and the other half is smaller (i.e., older) than current Map- 185 Version number. In a more formal way, assuming we have two version 186 numbers V1 and V2 and that the numbers are expressed on N bits, the 187 following steps MUST be performed (in the same order as hereafter) to 188 strictly define their order: 190 1. V1 = V2 : The map-version number are the same. 192 2. V2 > V1 : if and only if 194 V2 > V1 AND (V2 - V1) <= 2**(N-1) 196 OR 198 V1 > V2 AND (V1 - V2) > 2**(N-1) 200 3. V1 > V2 : otherwise. 202 Using 12 bits, as defined in this document, and assuming a Map- 203 Version value of 69, Map-Version numbers in the range [70; 69 + 2048] 204 are greater than 69, while Map-Version numbers in the range [69 + 205 2049; (69 + 4096) mod 4096] are smaller than 69. 207 Map-version number are assigned to mappings by configuration. The 208 initial Map-Version number of a new EID-to-RLOC mapping SHOULD be 209 assigned randomly, but it MUST NOT be set to the Null Map-Version 210 value (0x000), because it has a special meaning (see Section 4.1). 212 Upon reboot, an ETR will use mappings configured in its EID-to-RLOC 213 Database. If those mappings have a Map-Version number, it will be 214 used according to the mechnisms described in this document. ETRs 215 MUST NOT automatically generate and assign Map-Version numbers to 216 mappings in the EID-to-RLOC Database. 218 4.1. The Null Map-Version 220 The value 0x000 (zero) is not a valid Map-Version number indicating 221 the version of the EID-to-RLOC mapping. Such a value is used for 222 special purposes and is named the Null Map-Version number. 224 The Null Map-Version MAY appear in the LISP specific header as either 225 Source Map-Version number (cf. Section 5.2) or Destination Map- 226 Version number (cf. Section 5.1). When the Source Map-Version number 227 is set to the Null Map-version value it means that no map version 228 information is conveyed for the source site. This means that if a 229 mapping exists for the source EID in the EID-to-RLOC Cache, then the 230 ETR MUST NOT compare the received Null Map-Version with the content 231 of the EID-to-RLOC cache. When the Destination Map-version number is 232 set to the Null Map-version value it means that no map version 233 information is conveyed for the destination site. This means that 234 the ETR MUST NOT compare the value with the Map-Version number of the 235 mapping for the destination EID present in the EID-to-RLOC Database. 237 The other use of the Null Map-Version number is in the Map Records, 238 which are part of the Map-Request, Map-Reply and Map-Register 239 messages (defined in [I-D.ietf-lisp]). Map Records that have a Null 240 Map-Version number indicate that there is no Map-Version number 241 associated with the mapping. This means that LISP encapsulated 242 packets, destined to the EID-Prefix the Map Record refers to, MUST 243 either not contain any Map-Version numbers (V bit set to 0), or if it 244 contains Map-Version numbers (V bit set to 1) then the destination 245 Map-Version number MUST be set to the Null Map-Version number. Any 246 value different from zero means that Map-Versioning is supported and 247 MAY be used. 249 The fact that the 0 value has a special meaning for the Map-Version 250 number implies that, when updating a Map-Version number because of a 251 change in the mapping, if the next value is 0 then Map-Version number 252 MUST be incremented by 2 (i.e., set to 1, which is the next valid 253 value). 255 5. Dealing with Map-Version numbers 257 The main idea of using Map-Version numbers is that whenever there is 258 a change in the mapping (e.g., adding/removing RLOCs, a change in the 259 weights due to TE policies, or a change in the priorities) or a LISP 260 site realizes that one or more of its own RLOCs are not reachable 261 anymore from a local perspective (e.g., through IGP, or policy 262 changes) the LISP site updates the mapping also assigning a new Map- 263 Version number. 265 To each mapping, a version number is associated and changes each time 266 the mapping is changed. Note that map-versioning does not introduce 267 new problems concerning the coordination of different ETRs of a 268 domain. Indeed, ETRs belonging to the same LISP site must return for 269 a specific EID-prefix the same mapping, including the same Map- 270 Version number. In principle this is orthogonal to whether or not 271 map-versioning is used. The synchronization problem and its 272 implication on the traffic is out of the scope of this document. 274 In order to announce in a data-driven fashion that the mapping has 275 been updated, Map-Version numbers used to create the outer IP header 276 of the LISP-encapsulated packet are embedded in the LISP-specific 277 header. This means that the header needs to contain two Map-Version 278 numbers: 280 o The Source Map-Version number of the EID-to-RLOC mapping in the 281 EID-to-RLOC Database used to select the source RLOC. 283 o The Destination Map-Version number of the EID-to-RLOC mapping in 284 the EID-to-RLOC Cache used to select the destination RLOC. 286 By embedding both Source Map-Version number and Destination Map- 287 Version number an ETR receiving a LISP packet with Map-Version 288 numbers, can perform the following checks: 290 1. The ITR that has sent the packet has an up-to-date mapping in its 291 cache for the destination EID and is performing encapsulation 292 correctly. 294 2. In case of bidirectional traffic, the mapping in the local ETR 295 EID-to-RLOC cache for the source EID is up-to-date. 297 If one or both of the above conditions do not hold, the ETR can send 298 a Map-Request either to make the ITR aware that a new mapping is 299 available (see Section 5.1) or to update the mapping in the local 300 cache (see Section 5.2). 302 5.1. Handling Destination Map-Version number 304 When an ETR receives a packet, the Destination Map-Version number 305 relates to the mapping for the destination EID for which the ETR is a 306 RLOC. This mapping is part of the ETR EID-to-RLOC Database. Since 307 the ETR is authoritative for the mapping, it has the correct and up- 308 to-date Destination Map-Version number. A check on this version 309 number can be done, where the following cases can arise: 311 1. The packets arrive with the same Destination Map-Version number 312 stored in the EID-to-RLOC Database. This is the regular case. 313 The ITR sending the packet has in its EID-to-RLOC Cache an up-to- 314 date mapping. No further actions are needed. 316 2. The packet arrives with a Destination Map-Version number greater 317 (i.e., newer) than the one stored in the EID-to-RLOC Database. 318 Since the ETR is authoritative on the mapping, meaning that the 319 Map-Version number of its mapping is the correct one, this 320 implies that someone is not behaving correctly with respect to 321 the specifications. In this case the packet carries a version 322 number that is not valid, otherwise the ETR would have the same, 323 and SHOULD be silently dropped. 325 3. The packets arrive with a Destination Map-Version number smaller 326 (i.e., older) than the one stored in the EID-to-RLOC Database. 327 This means that the ITR sending the packet has an old mapping in 328 its EID-to-RLOC Cache containing stale information. The ITR 329 sending the packet has to be informed that a newer mapping is 330 available. This is done with a Map-Request message sent back to 331 the ITR. The Map-Request will either trigger a Map-Request back 332 using the Solicit-Map-Request (SMR) bit or it will piggyback the 333 newer mapping. These are not new mechanisms; how to SMR or 334 piggyback mappings in Map-Request messages is already described 335 in [I-D.ietf-lisp], while their security is discussed in 336 [I-D.ietf-lisp-threats]. These Map-Request messages should be 337 rate limited (rate limitation policies are also described in 338 [I-D.ietf-lisp]). The feature introduced by Map-Version numbers 339 is the possibility of blocking traffic not using the latest 340 mapping. Indeed, after a certain number of retries, if the 341 Destination Map-Version number in the packets is not updated, the 342 ETR MAY drop packets with a stale Map-Version number while 343 strongly reducing the rate of Map-Request messages. This because 344 either the ITR is refusing to use the mapping for which the ETR 345 is authoritative or (worse) it might be some form of attack. 346 Another case might be that the control-plane is experiencing 347 transient failures so the Map-Requests cannot reach that ITR. By 348 keeping sending Map-Requests at very low rate it is possible to 349 recover from this situation. 351 The rule in the third case MAY be more restrictive. If the mapping 352 has been the same for a period of time as long as the TTL (defined in 353 [I-D.ietf-lisp]) of the previous version of the mapping, all packets 354 arriving with an old Map-Version SHOULD be silently dropped right 355 away without issuing any Map-Request. The reason that allows such 356 action is the fact that if the new mapping with the updated version 357 number has been unchanged for at least the same time as the TTL of 358 the older mapping, all the entries in the caches of ITRs must have 359 expired. Hence, all ITRs sending traffic should have refreshed the 360 mapping according to [I-D.ietf-lisp]. If packets with old Map- 361 Version number are still received, then either someone has not 362 respected the TTL, or it is a form of spoof/attack. In both cases 363 this is not valid behavior with respect to the specifications and the 364 packet SHOULD be silently dropped. 366 LISP-encapsulated packets with the V-bit set, when the original 367 mapping in the EID-to-RLOC Database has version number set to the 368 Null Map-Version value, MAY be silently dropped. As explained in 369 Section 4.1, if an EID-to-RLOC mapping has a Null Map-Version, it 370 means that ITRs, using the mapping for encapsulation, MUST NOT use 371 Map-Version number in the LISP-specific header. 373 For LISP-encapsulated packets with the V-bit set, when the original 374 mapping in the EID-to-RLOC Database has version number set to a value 375 different from the Null Map-Version value, a Destination Map-Version 376 number equal to the Null Map-Version value means that the Destination 377 Map-Version number MUST be ignored. 379 5.2. Handling Source Map-Version number 381 When an ETR receives a packet, the Source Map-Version number relates 382 to the mapping for the source EID for which the ITR that sent the 383 packet is authoritative. If the ETR has an entry in its EID-to-RLOC 384 Cache for the source EID, then a check can be performed and the 385 following cases can arise: 387 1. The packet arrives with the same Source Map-Version number stored 388 in the EID-to-RLOC Cache. This is the correct regular case. The 389 ITR has in its cache an up-to-date copy of the mapping. No 390 further actions are needed. 392 2. The packet arrives with a Source Map-Version number greater 393 (i.e., newer) than the one stored in the local EID-to-RLOC Cache. 394 This means that ETR has in its cache a mapping that is stale and 395 needs to be updated. A Map-Request SHOULD be sent to get the new 396 mapping for the source EID. This is a normal Map-Request message 397 sent through the mapping system and MUST respect the 398 specifications in [I-D.ietf-lisp], including rate limitation 399 policies. 401 3. The packet arrives with a Source Map-Version number smaller 402 (i.e., older) than the one stored in the local EID-to-RLOC Cache. 403 Such a case is not valid with respect to the specifications. 404 Indeed, if the mapping is already present in the EID-to-RLOC 405 Cache, this means that an explicit Map-Request has been sent and 406 a Map-Reply has been received from an authoritative source. 407 Assuming that the mapping system is not corrupted anyhow, the 408 Map-Version in the EID-to-RLOC Cache is the correct one, while 409 the one carried by the packet is stale. In this situation the 410 packet MAY be silently dropped. 412 If the ETR does not have an entry in the EID-to-RLOC Cache for the 413 source EID (e.g., in case of unidirectional traffic) then the Source 414 Map-Version number can be safely ignored. 416 For LISP-encapsulated packets with the V-bit set, if the Source Map- 417 Version number is the Null Map-Version value, it means that the 418 Source Map-Version number MUST be ignored. 420 6. LISP header and Map-Version numbers 422 In order for the versioning approach to work, the LISP specific 423 header has to carry both Source Map-Version number and Destination 424 Map-Version number. This is done by setting the V-bit in the LISP 425 specific header as defined in [I-D.ietf-lisp] Section 5.3. When the 426 V-bit is set the low-order 24-bits of the first longword are used to 427 transport both source and destination Map-Version numbers. In 428 particular the first 12 bits are used for Source Map-Version number 429 and the second 12 bits for the Destination Map-Version number. 431 Hereafter is the example of LISP header carrying version numbers in 432 the case of IPv4-in-IPv4 encapsulation. The same setting can be used 433 for any other case (IPv4-in-IPv6, IPv6-in-IPv4, and IPv6-in-IPv6). 435 0 1 2 3 436 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 1 437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 438 / |N|L|E|V|I|flags| Source Map-Version |Destination Map-Version| 439 LISP+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 \ | Instance ID/Locator Status Bits | 441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 443 Source Map-Version number (12 bits): Map-Version of the mapping used 444 by the ITR to select the RLOC present in the "Source Routing 445 Locator" field. How to set on transmission and handle on 446 reception this value is described in Section 5.2. 448 Destination Map-Version number (12 bits): Map-Version of the mapping 449 used by the ITR to select the RLOC present in the "Destination 450 Routing Locator" field. How to set on transmission and handle on 451 reception this value is described in Section 5.1. 453 The present document just specifies how to use the low-order 24-bits 454 of the first longword of the LISP-specific header when the V-bit is 455 set to 1. All other cases, including the bit fields of the rest of 456 the LISP-specific header and the whole LISP packet format are 457 specified in [I-D.ietf-lisp]. Not all of the LISP encapsulated 458 packets need to carry version numbers. When Map-Version numbers are 459 carried the V-bit MUST be set to 1. All legal combinations of the 460 flags, when the V-bit is set to 1, are described in [I-D.ietf-lisp]. 462 7. Map Record and Map-Version 464 To accommodate the proposed mechanism, the Map Records that are 465 transported on Map-Request/Map-Reply/Map-Register messages need to 466 carry the Map-Version number as well. For this purpose the 12-bits 467 before the EID-AFI field in the Record that describe a mapping is 468 used. This is defined in Section 6.1.4 of [I-D.ietf-lisp] and 469 reported here as example. 471 0 1 2 3 472 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 1 473 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 474 | | Record TTL | 475 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 476 R | Locator Count | EID mask-len | ACT |A| Reserved | 477 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 478 c | Rsvd | Map-Version Number | EID-prefix-AFI | 479 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 480 r | EID-prefix | 481 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 482 | /| Priority | Weight | M Priority | M Weight | 483 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 484 | o | Unused Flags |L|p|R| Loc-AFI | 485 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 486 | \| Locator | 487 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 Map-Version Number: Map-Version of the mapping contained in the 490 Record. As explained in Section 4.1 this field can be zero (0), 491 meaning that no Map-Version is associated to the mapping, hence 492 packets that are LISP-encapsulated using this mapping MUST NOT 493 contain Map-Version numbers in the LISP specific header and the 494 V-bit MUST be set to 0. 496 This packet format works perfectly with xTRs that do not support Map- 497 Versioning, since they can simply ignore those bits. 499 8. Benefits and case studies for Map-Versioning 501 In the following sections we provide more discussion on various 502 aspects and use of the Map-Versioning. Security observations are 503 instead grouped in Section 10. 505 8.1. Synchronization of different xTRs 507 Map-Versioning does not require additional synchronization mechanism 508 compared to the normal functioning of LISP without Map-Versioning. 509 Clearly all the ETRs have to reply with the same Map-Version number, 510 otherwise there can be an inconsistency that creates additional 511 control traffic, instabilities, traffic disruptions. It is the same 512 without Map-Versioning, with ETRs that have to reply with the same 513 mapping, otherwise the same problems can arise. 515 As an example, let's consider the topology of Figure 1 where ITR A.1 516 of domain A is sending unidirectional traffic to the domain B, while 517 A.2 of domain A exchange bidirectional traffic with domain B. In 518 particular, ITR A.2 send traffic to ETR B and ETR A.2 receives 519 traffic from ITR B. 521 +-----------------+ +-----------------+ 522 | Domain A | | Domain B | 523 | +---------+ | | 524 | | ITR A.1 |--- | | 525 | +---------+ \ +---------+ | 526 | | ------->| ETR B | | 527 | | ------->| | | 528 | +---------+ / | | | 529 | | ITR A.2 |--- -----| ITR B | | 530 | | | / +---------+ | 531 | | ETR A.2 |<----- | | 532 | +---------+ | | 533 | | | | 534 +-----------------+ +-----------------+ 536 Figure 1 538 Obviously in the case of Map-Versioning both ITR A.1 and ITR A.2 of 539 domain A must use the same value otherwise the ETR of domain B will 540 start to send Map-Requests. 542 The same problem can, however, arise without Map-Versioning. For 543 instance, if the two ITRs of domain A send different Loc Status Bits. 544 In this case either the traffic is disrupted, if the ETR B trusts the 545 Locator Status Bits, or if ETR B does not trusts the Locator Status 546 Bits it will start sending Map-Requests to confirm the each change in 547 the reachability. 549 So far, LISP does not provide any specific synchronization mechanism, 550 but assumes that synchronization is provided by configuring the 551 different xTRs consistently. The same applies for Map-Versioning. 552 If in the future any synchronization mechanism is provided, Map- 553 Versioning will take advantage of it automatically since it is 554 included in the Record format, as described in Section 7. 556 8.2. Map-Versioning and unidirectional traffic 558 When using Map-Versioning the LISP specific header carries two Map- 559 Version numbers, for both source and destination mappings. This can 560 raise the question on what will happen in the case of unidirectional 561 flows, like for instance in the case presented in Figure 2, since 562 LISP specification do not mandate for ETR to have a mapping for the 563 source EID. 565 +-----------------+ +-----------------+ 566 | Domain A | | Domain B | 567 | +---------+ +---------+ | 568 | | ITR A |----------->| ETR B | | 569 | +---------+ +---------+ | 570 | | | | 571 +-----------------+ +-----------------+ 573 Figure 2 575 For what concerns the ITR, it is able to put both source and 576 destination version number in the LISP header since the Source Map- 577 Version number is in ITR's database, while the Destination Map- 578 Version number is in ITR's cache. 580 For what concerns the ETR, it simply checks only the Destination Map- 581 Version number in the same way as described in Section 5, ignoring 582 the Source Map-Version number. 584 8.3. Map-Versioning and interworking 586 Map-Versioning is compatible with the LISP interworking between LISP 587 and non-LISP sites as defined in [I-D.ietf-lisp-interworking]. LISP 588 interworking defines three techniques to make LISP sites and non-LISP 589 sites, namely Proxy-ITR, LISP-NAT, and Proxy-ETR. Hereafter it is 590 described how Map-Versioning relates to these three mechanisms. 592 8.3.1. Map-Versioning and Proxy-ITRs 594 The purpose of the Proxy-ITR (PITR) is to encapsulate traffic 595 originating in a non-LISP site in order to deliver the packet to one 596 of the ETRs of the LISP site (cf. Figure 3). This case is very 597 similar to the unidirectional traffic case described in Section 8.2, 598 hence similar rules apply. 600 +----------+ +-------------+ 601 | LISP | | non-LISP | 602 | Domain A | | Domain B | 603 | +-------+ +-----------+ | | 604 | | ETR A |<-------| Proxy ITR |<-------| | 605 | +-------+ +-----------+ | | 606 | | | | 607 +----------+ +-------------+ 609 Figure 3 611 The main difference is that a Proxy-ITR does not have any mapping, 612 since it just encapsulate packets arriving from non-LISP site, thus 613 cannot provide a Source Map-Version. In this case, the proxy-ITR 614 will just put the Null Map-Version value as Source Map-Version 615 number, while the receiving ETR will ignore the field. 617 With this setup the LISP Domain A is able to check whether or not the 618 PITR is using the latest mapping. If this is not the case the 619 mapping for LISP Domain A on the PITR can be updated using one of the 620 mechanisms defined in [I-D.ietf-lisp] and 621 [I-D.ietf-lisp-interworking]. 623 8.3.2. Map-Versioning and LISP-NAT 625 The LISP-NAT mechanism is based on address translation from non- 626 routable EIDs to routable EIDs and does not involve any form of 627 encapsulation. As such Map-Versioning does not apply in this case. 629 8.3.3. Map-Versioning and Proxy-ETRs 631 The purpose of the Proxy-ETR (PETR) is to decapsulate traffic 632 originating in a LISP site in order to deliver the packet to the non- 633 LISP site (cf. Figure 4). One of the main reasons of deploy PETRs is 634 to bypass uRPF (Unicast Reverse Path Forwarding) checks on the 635 provider edge. 637 +----------+ +-------------+ 638 | LISP | | non-LISP | 639 | Domain A | | Domain B | 640 | +-------+ +-----------+ | | 641 | | ITR A |------->| Proxy ETR |------->| | 642 | +-------+ +-----------+ | | 643 | | | | 644 +----------+ +-------------+ 646 Figure 4 648 A Proxy-ETR does not have any mapping, since it just decapsulates 649 packets arriving from LISP site. In this case, the ITR will just put 650 the Null Map-Version value as Destination Map-Version number, while 651 the receiving Proxy-ETR will ignore the field. 653 With this setup the Proxy-ETR is able to check whether or not the 654 mapping has changed. If this is the case the mapping for LISP Domain 655 A on the PETR can be updated using one of the mechanisms defined in 656 [I-D.ietf-lisp] and [I-D.ietf-lisp-interworking]. 658 8.4. RLOC shutdown/withdraw 660 Map-Versioning can be even used to perform a graceful shutdown or 661 withdraw of a specific RLOC. This is achieved by simply issuing a 662 new mapping, with an updated Map-Version number, where the specific 663 RLOC to be shut down is withdrawn or announced as unreachable (R bit 664 in the Map Record, see [I-D.ietf-lisp]), but without actually turning 665 it off. 667 Once no more traffic is received by the RLOC, it can be shut down 668 gracefully, because at least all sites actively using the mapping 669 have updated it. 671 It should be pointed out that for frequent up/down changes such a 672 mechanism should not be used since this can generate excessive load 673 on the Mapping System. 675 8.5. Map-Version for lightweight LISP implementation 677 The use of Map-Versioning can help in developing a lightweight 678 implementation of LISP. This comes with the price of not supporting 679 Loc-Status-Bit, which are useful in some contexts. 681 In the current LISP specifications the set of RLOCs must always be 682 maintained ordered and consistent with the content of the Loc Status 683 Bits (see section 6.5 of [I-D.ietf-lisp]). With Map-Versioning such 684 type of mechanisms can be avoided. When a new RLOC is added to a 685 mapping, it is not necessary to "append" new locators to the existing 686 ones as explained in Section 6.5 of [I-D.ietf-lisp]. A new mapping 687 with a new Map-Version number will be issued, and since the old 688 locators are still valid the transition will be with no disruptions. 689 The same applies for the case a RLOC is withdrawn. There is no need 690 to maintain holes in the list of locators, as is the case when using 691 Locator Status Bits, for sites that are not using the RLOC that has 692 been withdrawn the transition will be with no disruptions. 694 All of these operations, as already stated, do not need to maintain 695 any consistency among Locator Status Bits, and the way RLOC are 696 stored in the cache. 698 Further, Map-Version can be used to substitute the "clock sweep" 699 operation described in Section 6.5.1 of [I-D.ietf-lisp]. Indeed, 700 every LISP site communicating to a specific LISP site that has 701 updated the mapping will be informed of the available new mapping in 702 a data-driven manner. 704 Note that what is proposed in the present section is just an example 705 and MUST NOT be considered as specifications for a lightweight LISP 706 implementation. In case the IETF decides to undertake such a work, 707 it will be documented elsewhere. 709 9. Incremental deployment and implementation status 711 Map-Versioning can be incrementally deployed without any negative 712 impact on existing LISP elements (e.g., xTRs, Map-Servers, Proxy- 713 ITRs, etc). Any LISP element that does not support Map-Versioning 714 can safely ignore them. Further, there is no need of any specific 715 mechanism to discover if an xTR supports or not Map-Versioning. This 716 information is already included in the Map Record. 718 Map-Versioning is currently implemented in OpenLISP 719 [I-D.iannone-openlisp-implementation]. 721 Note that the reference document for LISP implementation and 722 interoperability tests remains [I-D.ietf-lisp]. 724 10. Security Considerations 726 Map-Versioning does not introduce any security issue concerning both 727 the data-plane and the control-plane. On the contrary, as described 728 in the following, if Map-Versioning may be used also to update 729 mappings in case of change in the reachability information (i.e., 730 instead of the Locator Status Bits) it is possible to reduce the 731 effects of some DoS or spoofing attacks that can happen in an 732 untrusted environment. 734 Robustness of the Map-Versioning mechanism leverages on a trusted 735 Mapping Distribution System. A thorough security analysis of LISP is 736 documented in [I-D.ietf-lisp-threats]. 738 10.1. Map-Versioning against traffic disruption 740 An attacker can try to disrupt ongoing communications by creating 741 LISP encapsulated packets with wrong Locator Status Bits. If the xTR 742 blindly trusts the Locator Status Bits it will change the 743 encapsulation accordingly, which can result in traffic disruption. 745 This does not happen in the case of Map-Versioning. As described in 746 Section 5, upon a version number change the xTR first issues a Map- 747 Request. The assumption is that the mapping distribution system is 748 sufficiently secure that Map-Request and Map-Reply messages and their 749 content can be trusted. Security issues concerning specific mapping 750 distribution system are out of the scope of this document. In the 751 case of Map-Versioning the attacker should "guess" a valid version 752 number that triggers a Map-Request, as described in Section 5, 753 otherwise the packet is simply dropped. Nevertheless, guessing a 754 version number that generates a Map-Request is easy, hence it is 755 important to follow the rate limitations policies described in 756 [I-D.ietf-lisp] in order to avoid DoS attacks. 758 Note that a similar level of security can be obtained with Loc Status 759 Bits, by simply making mandatory to verify any change through a Map- 760 Request. However, in this case Locator Status Bits loose their 761 meaning, because, it does not matter anymore which specific bits has 762 changed, the xTR will query the mapping system and trust the content 763 of the received Map-Reply. Furthermore there is no way to perform 764 filtering as in the Map-Versioning in order to drop packets that do 765 not carry a valid Map-Version number. In the case of Locator Status 766 Bits, any random change can trigger a Map-Request (unless rate 767 limitation is enabled which raise another type of attack discussed in 768 Section 10.2). 770 10.2. Map-Versioning against reachability information DoS 772 Attackers can try to trigger a large amount of Map-Request by simply 773 forging packets with random Map-Version or random Locator Status 774 Bits. In both cases the Map-Requests are rate limited as described 775 in [I-D.ietf-lisp]. However, differently from Locator Status Bit 776 where there is no filtering possible, in the case of Map-Versioning 777 is possible to filter not valid version numbers before triggering a 778 Map-Request, thus helping in reducing the effects of DoS attacks. In 779 other words the use of Map-Versioning enables a fine control on when 780 to update a mapping or when to notify that a mapping has been 781 updated. 783 It is clear, that Map-Versioning does not protect against DoS and 784 DDoS attacks, where an xTR looses processing power doing checks on 785 the LISP header of packets sent by attackers. This is independent 786 from Map-Versioning and is the same for Loc Status Bits. 788 11. IANA Considerations 790 This document has no actions for IANA. 792 12. Acknowledgements 794 The authors would like to thank Alia Atlas, Jesper Skriver, Pierre 795 Francois, Noel Chiappa, Dino Farinacci for their comments and review. 797 This work has been partially supported by the INFSO-ICT-216372 798 TRILOGY Project (www.trilogy-project.org). 800 13. References 802 13.1. Normative References 804 [I-D.ietf-lisp] 805 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 806 "Locator/ID Separation Protocol (LISP)", 807 draft-ietf-lisp-15 (work in progress), July 2011. 809 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 810 Requirement Levels", BCP 14, RFC 2119, March 1997. 812 13.2. Informative References 814 [I-D.iannone-openlisp-implementation] 815 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 816 Implementation Report", 817 draft-iannone-openlisp-implementation-01 (work in 818 progress), July 2008. 820 [I-D.ietf-lisp-alt] 821 Fuller, V., Farinacci, D., Meyer, D., and D. Lewis, "LISP 822 Alternative Topology (LISP+ALT)", draft-ietf-lisp-alt-09 823 (work in progress), September 2011. 825 [I-D.ietf-lisp-interworking] 826 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 827 "Interworking LISP with IPv4 and IPv6", 828 draft-ietf-lisp-interworking-02 (work in progress), 829 June 2011. 831 [I-D.ietf-lisp-ms] 832 Fuller, V. and D. Farinacci, "LISP Map Server", 833 draft-ietf-lisp-ms-11 (work in progress), August 2011. 835 [I-D.ietf-lisp-threats] 836 Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats 837 Analysis", draft-ietf-lisp-threats-00 (work in progress), 838 July 2011. 840 Appendix A. Estimation of time before Map-Version wrap-around 842 The present section proposes an estimation of the wrap-around time 843 for the proposed 12 bits size for the Map-Version number. Using a 844 granularity of seconds and assuming as worst-case that a new version 845 is issued each second, it takes slightly more than 1 hour before the 846 version wraps around. Note that the granularity of seconds is in 847 line with the rate limitation policy for Map-Request messages, as 848 proposed in the LISP main specifications ([I-D.ietf-lisp]). 849 Alternatively a granularity of minutes can also be used, as for the 850 TTL of the Map-Reply ([I-D.ietf-lisp]). In this case the worst 851 scenario is when a new version is issued every minute, leading to a 852 much longer time before wrap-around. In particular, when using 12 853 bits, the wrap-around time is almost 3 days. 855 For general information, hereafter there is a table with a rough 856 estimation of the time before wrap-around in the worst-case scenario, 857 considering different sizes (bits length) of the Map-Version number 858 and different time granularity. 860 +---------------+--------------------------------------------+ 861 |Version Number | Time before wrap around | 862 | Size (bits) +---------------------+----------------------+ 863 | |Granularity: Minutes | Granularity: Seconds | 864 | | (mapping changes | (mapping changes | 865 | | every 1 minute) | every 1 second) | 866 +-------------------------------------+----------------------+ 867 | 32 | 8171 Years | 136 Years | 868 | 30 | 2042 Years | 34 Years | 869 | 24 | 31 Years | 194 Days | 870 | 16 | 45 Days | 18 Hours | 871 | 15 | 22 Days | 9 Hours | 872 | 14 | 11 Days | 4 Hours | 873 | 13 | 5.6 Days | 2.2 Hours | 874 | 12 | 2.8 Days | 1.1 Hours | 875 +---------------+---------------------+----------------------+ 877 Figure 5: Estimation of time before wrap-around 879 Appendix B. Document Change Log 881 o Version 05 Posted October 2011. 883 * Added sentence in Section 3 on the use of Big Endian, as for 884 comment of P. Resnick. 886 * Extended the end of Section 4 in order to clarify that Map- 887 Version numbers are assigned to mappings by configuration and 888 not automatically generated by ETRs, as for comments of R. 889 Sparks 891 * Changed formal definition of Map-Version order (greater vs. 892 smaller) in Section 4 as for comments from R. Housley and R. 893 Sparks. 895 * Added disclaimer in Section 1 stating that in case of unforseen 896 conflict with the main spec the base document has precedence on 897 the present one, as for comment from Sthephen Farrell. 899 o Version 04 Posted September 2011. 901 * Added clarifications in Section 1, Section 4, Section 5.2, and 902 Section 5.1 to address Stephen Farrell's comments. 904 * Used the term LISP Site instead of ISP in Section 5 as 905 suggested by Stephen Farrell. 907 * Deleted "(usually contains the nonce)" from Section 6 because 908 confusing, as suggested by Stephen Farrell. 910 * Fixed several typos pointed out by Stephen Farrell. 912 o Version 03 Posted September 2011. 914 * Added reference in Section 7 toward the main lisp documents 915 specifying the section, as requested by Jari Arkko. 917 * Fixed all typos and editorial issues pointed out by Jari Arkko. 919 * Added clarification in Section 8.4 as requested by Jari Arkko. 921 * Extentend all acronyms in the abstract as requested by Jari 922 Arkko. 924 * Clarified silent drop polocy in Section 5.2 as requested by 925 both Richard Barnes and Jari Arkko. 927 * Fixed typos pointed out by Richard Barnes. 929 o Version 02 Posted July 2011. 931 * Added text in Section 5 about ETR synchronization, as suggested 932 by Alia Atlas. 934 * Modified text in Section 8.5 concerning lightweight LISP 935 implementation, as suggested by Alia Atlas. 937 * Deleted text concerning old versions of [I-D.ietf-lisp-ms] and 938 [I-D.ietf-lisp-alt] in Section 7, as pointed out by Alia Atlas. 940 * Fixed section 4.1 to be less restrictive, as suggested by 941 Jesper Skriver. 943 o Version 01 Posted March 2011. 945 * Changed the wording from "Map-Version number 0" to "Null Map- 946 Version. 948 * Clarification of the use of the Null Map-Version value as 949 Source Map-Version Number and Destination Map-Version Number. 951 * Extended the section describing Map-Versioning and LISP 952 Interworking co-existence. 954 * Reduce packet format description to avoid double definitions 955 with the main specs. 957 o Version 00 Posted September 2010. 959 * Added Section "Definitions of Terms". 961 * Editorial polishing of all sections. 963 * Added clarifications in section "Dealing with Map-Version 964 numbers" for the case of the special Map-Version number 0. 966 * Rename of draft-iannone-mapping-versioning-02.txt. 968 Authors' Addresses 970 Luigi Iannone 971 TU Berlin - Deutsche Telekom Laboratories AG 972 Ernst-Reuter Platz 7 973 Berlin 974 Germany 976 Email: luigi@net.t-labs.tu-berlin.de 978 Damien Saucez 979 Universite catholique de Louvain 980 Place St. Barbe 2 981 Louvain-la-Neuve 982 Belgium 984 Email: damien.saucez@uclouvain.be 985 Olivier Bonaventure 986 Universite catholique de Louvain 987 Place St. Barbe 2 988 Louvain-la-Neuve 989 Belgium 991 Email: olivier.bonaventure@uclouvain.be