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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group D. Farinacci 3 Internet-Draft V. Fuller 4 Intended status: Experimental D. Meyer 5 Expires: July 25, 2012 D. Lewis 6 cisco Systems 7 January 22, 2012 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-20 12 Abstract 14 This draft describes a network layer based protocol that enables 15 separation of IP addresses into two new numbering spaces: Endpoint 16 Identifiers (EIDs) and Routing Locators (RLOCs). No changes are 17 required to either host protocol stacks or to the "core" of the 18 Internet infrastructure. LISP can be incrementally deployed, without 19 a "flag day", and offers traffic engineering, multi-homing, and 20 mobility benefits to early adopters, even when there are relatively 21 few LISP-capable sites. 23 Design and development of LISP was largely motivated by the problem 24 statement produced by the October 2006 IAB Routing and Addressing 25 Workshop. 27 Status of this Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on July 25, 2012. 44 Copyright Notice 46 Copyright (c) 2012 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 5 62 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 63 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 8 64 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 14 65 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 16 66 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . . 18 67 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 19 68 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 19 69 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . . 21 70 5.4. Dealing with Large Encapsulated Packets . . . . . . . . . 25 71 5.4.1. A Stateless Solution to MTU Handling . . . . . . . . . 25 72 5.4.2. A Stateful Solution to MTU Handling . . . . . . . . . 26 73 5.5. Using Virtualization and Segmentation with LISP . . . . . 26 74 6. EID-to-RLOC Mapping . . . . . . . . . . . . . . . . . . . . . 28 75 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats . . . . . 28 76 6.1.1. LISP Packet Type Allocations . . . . . . . . . . . . . 30 77 6.1.2. Map-Request Message Format . . . . . . . . . . . . . . 30 78 6.1.3. EID-to-RLOC UDP Map-Request Message . . . . . . . . . 33 79 6.1.4. Map-Reply Message Format . . . . . . . . . . . . . . . 34 80 6.1.5. EID-to-RLOC UDP Map-Reply Message . . . . . . . . . . 38 81 6.1.6. Map-Register Message Format . . . . . . . . . . . . . 40 82 6.1.7. Map-Notify Message Format . . . . . . . . . . . . . . 42 83 6.1.8. Encapsulated Control Message Format . . . . . . . . . 43 84 6.2. Routing Locator Selection . . . . . . . . . . . . . . . . 45 85 6.3. Routing Locator Reachability . . . . . . . . . . . . . . . 47 86 6.3.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 49 87 6.3.2. RLOC Probing Algorithm . . . . . . . . . . . . . . . . 50 88 6.4. EID Reachability within a LISP Site . . . . . . . . . . . 51 89 6.5. Routing Locator Hashing . . . . . . . . . . . . . . . . . 52 90 6.6. Changing the Contents of EID-to-RLOC Mappings . . . . . . 53 91 6.6.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . 54 92 6.6.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . 54 93 6.6.3. Database Map Versioning . . . . . . . . . . . . . . . 56 94 7. Router Performance Considerations . . . . . . . . . . . . . . 57 95 8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 58 96 8.1. First-hop/Last-hop Tunnel Routers . . . . . . . . . . . . 59 97 8.2. Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 59 98 8.3. ISP Provider-Edge (PE) Tunnel Routers . . . . . . . . . . 60 99 8.4. LISP Functionality with Conventional NATs . . . . . . . . 60 100 8.5. Packets Egressing a LISP Site . . . . . . . . . . . . . . 61 101 9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 62 102 9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 63 103 9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 63 104 9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 63 105 10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 65 106 10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 65 107 10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 65 108 10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 65 109 10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 67 110 10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 67 111 11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 69 112 12. Security Considerations . . . . . . . . . . . . . . . . . . . 70 113 13. Network Management Considerations . . . . . . . . . . . . . . 72 114 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 73 115 14.1. LISP ACT and Flag Fields . . . . . . . . . . . . . . . . . 73 116 14.2. LISP Address Type Codes . . . . . . . . . . . . . . . . . 73 117 14.3. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 73 118 14.4. LISP Key ID Numbers . . . . . . . . . . . . . . . . . . . 74 119 15. Known Open Issues and Areas of Future Work . . . . . . . . . . 75 120 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 77 121 16.1. Normative References . . . . . . . . . . . . . . . . . . . 77 122 16.2. Informative References . . . . . . . . . . . . . . . . . . 78 123 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 82 124 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 83 125 B.1. Changes to draft-ietf-lisp-20.txt . . . . . . . . . . . . 83 126 B.2. Changes to draft-ietf-lisp-19.txt . . . . . . . . . . . . 83 127 B.3. Changes to draft-ietf-lisp-18.txt . . . . . . . . . . . . 83 128 B.4. Changes to draft-ietf-lisp-17.txt . . . . . . . . . . . . 83 129 B.5. Changes to draft-ietf-lisp-16.txt . . . . . . . . . . . . 83 130 B.6. Changes to draft-ietf-lisp-15.txt . . . . . . . . . . . . 83 131 B.7. Changes to draft-ietf-lisp-14.txt . . . . . . . . . . . . 83 132 B.8. Changes to draft-ietf-lisp-13.txt . . . . . . . . . . . . 84 133 B.9. Changes to draft-ietf-lisp-12.txt . . . . . . . . . . . . 85 134 B.10. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 86 135 B.11. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 87 136 B.12. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 87 137 B.13. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 88 138 B.14. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 90 139 B.15. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 91 140 B.16. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 92 141 B.17. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 93 142 B.18. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 95 143 B.19. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 95 144 B.20. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 95 145 B.21. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 96 146 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 97 148 1. Requirements Notation 150 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 151 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 152 document are to be interpreted as described in [RFC2119]. 154 2. Introduction 156 This document describes the Locator/Identifier Separation Protocol 157 (LISP), which provides a set of functions for routers to exchange 158 information used to map from non globally routeable Endpoint 159 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 160 defines a mechanism for these LISP routers to encapsulate IP packets 161 addressed with EIDs for transmission across the< Internet that uses 162 RLOCs for routing and forwarding. 164 Creation of LISP was initially motivated by discussions during the 165 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 166 October, 2006 (see [RFC4984]). A key conclusion of the workshop was 167 that the Internet routing and addressing system was not scaling well 168 in the face of the explosive growth of new sites; one reason for this 169 poor scaling is the increasing number of multi-homed and other sites 170 that cannot be addressed as part of topologically- or provider-based 171 aggregated prefixes. Additional work that more completely described 172 the problem statement may be found in [RADIR]. 174 A basic observation, made many years ago in early networking research 175 such as that documented in [CHIAPPA] and [RFC4984], is that using a 176 single address field for both identifying a device and for 177 determining where it is topologically located in the network requires 178 optimization along two conflicting axes: for routing to be efficient, 179 the address must be assigned topologically; for collections of 180 devices to be easily and effectively managed, without the need for 181 renumbering in response to topological change (such as that caused by 182 adding or removing attachment points to the network or by mobility 183 events), the address must explicitly not be tied to the topology. 185 The approach that LISP takes to solving the routing scalability 186 problem is to replace IP addresses with two new types of numbers: 187 Routing Locators (RLOCs), which are topologically assigned to network 188 attachment points (and are therefore amenable to aggregation) and 189 used for routing and forwarding of packets through the network; and 190 Endpoint Identifiers (EIDs), which are assigned independently from 191 the network topology, are used for numbering devices, and are 192 aggregated along administrative boundaries. LISP then defines 193 functions for mapping between the two numbering spaces and for 194 encapsulating traffic originated by devices using non-routeable EIDs 195 for transport across a network infrastructure that routes and 196 forwards using RLOCs. Both RLOCs and EIDs are syntactically- 197 identical to IP addresses; it is the semantics of how they are used 198 that differs. 200 This document describes the protocol that implements these functions. 201 The database which stores the mappings between EIDs and RLOCs is 202 explicitly a separate "module" to facilitate experimentation with a 203 variety of approaches. One database design that is being developed 204 and prototyped as part of the LISP working group work is [ALT]. 205 Others that have been described but not implemented include [CONS], 206 [EMACS], [NERD]. Finally, [LISP-MS], documents a general-purpose 207 service interface for accessing a mapping database; this interface is 208 intended to make the mapping database modular so that different 209 approaches can be tried without the need to modify installed LISP 210 capable devices in LISP sites. 212 This experimental specification has areas that require additional 213 experience and measurement. It is NOT RECOMMENDED for deployment 214 beyond experimental situations. Results of experimentation may lead 215 to modifications and enhancements of protocol mechanisms defined in 216 this document. See Section 15 for specific, known issues that are in 217 need of further work during development, implementation, and 218 experimentation. 220 An examination of the implications of LISP on Internet traffic, 221 applications, routers, and security is for future study. This 222 analysis will explain what role LISP can play in scalable routing and 223 will also look at scalability and levels of state required for 224 encapsulation, decapsulation, liveness, and so on. 226 3. Definition of Terms 228 Provider Independent (PI) Addresses: PI addresses are an address 229 block assigned from a pool where blocks are not associated with 230 any particular location in the network (e.g. from a particular 231 service provider), and is therefore not topologically aggregatable 232 in the routing system. 234 Provider Assigned (PA) Addresses: PA addresses are an address block 235 assigned to a site by each service provider to which a site 236 connects. Typically, each block is sub-block of a service 237 provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and 238 is aggregated into the larger block before being advertised into 239 the global Internet. Traditionally, IP multihoming has been 240 implemented by each multi-homed site acquiring its own, globally- 241 visible prefix. LISP uses only topologically-assigned and 242 aggregatable address blocks for RLOCs, eliminating this 243 demonstrably non-scalable practice. 245 Routing Locator (RLOC): A RLOC is an IPv4 [RFC0791] or IPv6 246 [RFC2460] address of an egress tunnel router (ETR). A RLOC is the 247 output of an EID-to-RLOC mapping lookup. An EID maps to one or 248 more RLOCs. Typically, RLOCs are numbered from topologically- 249 aggregatable blocks that are assigned to a site at each point to 250 which it attaches to the global Internet; where the topology is 251 defined by the connectivity of provider networks, RLOCs can be 252 thought of as PA addresses. Multiple RLOCs can be assigned to the 253 same ETR device or to multiple ETR devices at a site. 255 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 256 IPv6) value used in the source and destination address fields of 257 the first (most inner) LISP header of a packet. The host obtains 258 a destination EID the same way it obtains an destination address 259 today, for example through a Domain Name System (DNS) [RFC1034] 260 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 261 The source EID is obtained via existing mechanisms used to set a 262 host's "local" IP address. An EID used on the public Internet 263 must have the same properties as any other IP address used in that 264 manner; this means, among other things, that it must be globally 265 unique. An EID is allocated to a host from an EID-prefix block 266 associated with the site where the host is located. An EID can be 267 used by a host to refer to other hosts. EIDs MUST NOT be used as 268 LISP RLOCs. Note that EID blocks MAY be assigned in a 269 hierarchical manner, independent of the network topology, to 270 facilitate scaling of the mapping database. In addition, an EID 271 block assigned to a site may have site-local structure 272 (subnetting) for routing within the site; this structure is not 273 visible to the global routing system. In theory, the bit string 274 that represents an EID for one device can represent an RLOC for a 275 different device. As the architecture is realized, if a given bit 276 string is both an RLOC and an EID, it must refer to the same 277 entity in both cases. When used in discussions with other 278 Locator/ID separation proposals, a LISP EID will be called a 279 "LEID". Throughout this document, any references to "EID" refers 280 to an LEID. 282 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are 283 allocated to a site by an address allocation authority. EID- 284 prefixes are associated with a set of RLOC addresses which make up 285 a "database mapping". EID-prefix allocations can be broken up 286 into smaller blocks when an RLOC set is to be associated with the 287 larger EID-prefix block. A globally routed address block (whether 288 PI or PA) is not inherently an EID-prefix. A globally routed 289 address block MAY be used by its assignee as an EID block. The 290 converse is not supported. That is, a site which receives an 291 explicitly allocated EID-prefix may not use that EID-prefix as a 292 globally routed prefix. This would require coordination and 293 cooperation with the entities managing the mapping infrastructure. 294 Once this has been done, that block could be removed from the 295 globally routed IP system, if other suitable transition and access 296 mechanisms are in place. Discussion of such transition and access 297 mechanisms can be found in [INTERWORK] and [LISP-DEPLOY]. 299 End-system: An end-system is an IPv4 or IPv6 device that originates 300 packets with a single IPv4 or IPv6 header. The end-system 301 supplies an EID value for the destination address field of the IP 302 header when communicating globally (i.e. outside of its routing 303 domain). An end-system can be a host computer, a switch or router 304 device, or any network appliance. 306 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 307 LISP site. Packets sent by sources inside of the LISP site to 308 destinations outside of the site are candidates for encapsulation 309 by the ITR. The ITR treats the IP destination address as an EID 310 and performs an EID-to-RLOC mapping lookup. The router then 311 prepends an "outer" IP header with one of its globally-routable 312 RLOCs in the source address field and the result of the mapping 313 lookup in the destination address field. Note that this 314 destination RLOC MAY be an intermediate, proxy device that has 315 better knowledge of the EID-to-RLOC mapping closer to the 316 destination EID. In general, an ITR receives IP packets from site 317 end-systems on one side and sends LISP-encapsulated IP packets 318 toward the Internet on the other side. 320 Specifically, when a service provider prepends a LISP header for 321 Traffic Engineering purposes, the router that does this is also 322 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 323 on the outer destination address (the originating ITR's supplied 324 RLOC) or the inner destination address (the originating hosts 325 supplied EID). 327 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 328 network that prepends an additional LISP header for Traffic 329 Engineering purposes. 331 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 332 packet where the destination address in the "outer" IP header is 333 one of its own RLOCs. The router strips the "outer" header and 334 forwards the packet based on the next IP header found. In 335 general, an ETR receives LISP-encapsulated IP packets from the 336 Internet on one side and sends decapsulated IP packets to site 337 end-systems on the other side. ETR functionality does not have to 338 be limited to a router device. A server host can be the endpoint 339 of a LISP tunnel as well. 341 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 342 network that strips an outer LISP header for Traffic Engineering 343 purposes. 345 xTR: A xTR is a reference to an ITR or ETR when direction of data 346 flow is not part of the context description. xTR refers to the 347 router that is the tunnel endpoint. Used synonymously with the 348 term "Tunnel Router". For example, "An xTR can be located at the 349 Customer Edge (CE) router", meaning both ITR and ETR functionality 350 is at the CE router. 352 LISP Router: A LISP router is a router that performs the functions 353 of any or all of ITR, ETR, PITR, or PETR. 355 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 356 demand table in an ITR that stores, tracks, and is responsible for 357 timing-out and otherwise validating EID-to-RLOC mappings. This 358 cache is distinct from the full "database" of EID-to-RLOC 359 mappings, it is dynamic, local to the ITR(s), and relatively small 360 while the database is distributed, relatively static, and much 361 more global in scope. 363 EID-to-RLOC Database: The EID-to-RLOC database is a global 364 distributed database that contains all known EID-prefix to RLOC 365 mappings. Each potential ETR typically contains a small piece of 366 the database: the EID-to-RLOC mappings for the EID prefixes 367 "behind" the router. These map to one of the router's own, 368 globally-visible, IP addresses. The same database mapping entries 369 MUST be configured on all ETRs for a given site. In a steady 370 state the EID-prefixes for the site and the locator-set for each 371 EID-prefix MUST be the same on all ETRs. Procedures to enforce 372 and/or verify this are outside the scope of this document. Note 373 that there MAY be transient conditions when the EID-prefix for the 374 site and locator-set for each EID-prefix may not be the same on 375 all ETRs. This has no negative implications since a partial set 376 of locators can be used. 378 Recursive Tunneling: Recursive tunneling occurs when a packet has 379 more than one LISP IP header. Additional layers of tunneling MAY 380 be employed to implement traffic engineering or other re-routing 381 as needed. When this is done, an additional "outer" LISP header 382 is added and the original RLOCs are preserved in the "inner" 383 header. Any references to tunnels in this specification refers to 384 dynamic encapsulating tunnels and they are never statically 385 configured. 387 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 388 ETR removes a LISP header, then acts as an ITR to prepend another 389 LISP header. Doing this allows a packet to be re-routed by the 390 re-encapsulating router without adding the overhead of additional 391 tunnel headers. Any references to tunnels in this specification 392 refers to dynamic encapsulating tunnels and they are never 393 statically configured. When using multiple mapping database 394 systems, care must be taken to not create reencapsulation loops. 396 LISP Header: a term used in this document to refer to the outer 397 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-octet 398 header that follows the UDP header, an ITR prepends or an ETR 399 strips. 401 Address Family Identifier (AFI): a term used to describe an address 402 encoding in a packet. An address family currently pertains to an 403 IPv4 or IPv6 address. See [AFI]/[AFI-REGISTRY] and [RFC3232] for 404 details. An AFI value of 0 used in this specification indicates 405 an unspecified encoded address where the length of the address is 406 0 octets following the 16-bit AFI value of 0. 408 Negative Mapping Entry: A negative mapping entry, also known as a 409 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 410 is advertised or stored with no RLOCs. That is, the locator-set 411 for the EID-to-RLOC entry is empty or has an encoded locator count 412 of 0. This type of entry could be used to describe a prefix from 413 a non-LISP site, which is explicitly not in the mapping database. 414 There are a set of well defined actions that are encoded in a 415 Negative Map-Reply (Section 6.1.5). 417 Data Probe: A data-probe is a LISP-encapsulated data packet where 418 the inner header destination address equals the outer header 419 destination address used to trigger a Map-Reply by a decapsulating 420 ETR. In addition, the original packet is decapsulated and 421 delivered to the destination host if the destination EID is in the 422 EID-prefix range configured on the ETR. Otherwise, the packet is 423 discarded. A Data Probe is used in some of the mapping database 424 designs to "probe" or request a Map-Reply from an ETR; in other 425 cases, Map-Requests are used. See each mapping database design 426 for details. When using Data Probes, by sending Map-Requests on 427 the underlying routing system, EID-prefixes must be advertised. 428 However, this is discouraged if the core is to scale by having 429 less EID-prefixes stored in the core router's routing tables. 431 Proxy ITR (PITR): A PITR is defined and described in [INTERWORK], a 432 PITR acts like an ITR but does so on behalf of non-LISP sites 433 which send packets to destinations at LISP sites. 435 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 436 PETR acts like an ETR but does so on behalf of LISP sites which 437 send packets to destinations at non-LISP sites. 439 Route-returnability: is an assumption that the underlying routing 440 system will deliver packets to the destination. When combined 441 with a nonce that is provided by a sender and returned by a 442 receiver, this limits off-path data insertion. A route- 443 returnability check is verified when a message is sent with a 444 nonce, another message is returned with the same nonce, and the 445 destination of the original message appears as the source of the 446 returned message. 448 LISP site: is a set of routers in an edge network that are under a 449 single technical administration. LISP routers which reside in the 450 edge network are the demarcation points to separate the edge 451 network from the core network. 453 Client-side: a term used in this document to indicate a connection 454 initiation attempt by an EID. The ITR(s) at the LISP site are the 455 first to get involved in obtaining database map cache entries by 456 sending Map-Request messages. 458 Server-side: a term used in this document to indicate a connection 459 initiation attempt is being accepted for a destination EID. The 460 ETR(s) at the destination LISP site are the first to send Map- 461 Replies to the source site initiating the connection. The ETR(s) 462 at this destination site can obtain mappings by gleaning 463 information from Map-Requests, Data-Probes, or encapsulated 464 packets. 466 Locator Status Bits (LSBs): Locator status bits are present in the 467 LISP header. They are used by ITRs to inform ETRs about the up/ 468 down status of all ETRs at the local site. These bits are used as 469 a hint to convey up/down router status and not path reachability 470 status. The LSBs can be verified by use of one of the Locator 471 Reachability Algorithms described in Section 6.3. 473 Anycast Address: a term used in this document to refer to the same 474 IPv4 or IPv6 address configured and used on multiple systems at 475 the same time. An EID or RLOC can be an anycast address in each 476 of their own address spaces. 478 4. Basic Overview 480 One key concept of LISP is that end-systems (hosts) operate the same 481 way they do today. The IP addresses that hosts use for tracking 482 sockets, connections, and for sending and receiving packets do not 483 change. In LISP terminology, these IP addresses are called Endpoint 484 Identifiers (EIDs). 486 Routers continue to forward packets based on IP destination 487 addresses. When a packet is LISP encapsulated, these addresses are 488 referred to as Routing Locators (RLOCs). Most routers along a path 489 between two hosts will not change; they continue to perform routing/ 490 forwarding lookups on the destination addresses. For routers between 491 the source host and the ITR as well as routers from the ETR to the 492 destination host, the destination address is an EID. For the routers 493 between the ITR and the ETR, the destination address is an RLOC. 495 Another key LISP concept is the "Tunnel Router". A tunnel router 496 prepends LISP headers on host-originated packets and strips them 497 prior to final delivery to their destination. The IP addresses in 498 this "outer header" are RLOCs. During end-to-end packet exchange 499 between two Internet hosts, an ITR prepends a new LISP header to each 500 packet and an egress tunnel router strips the new header. The ITR 501 performs EID-to-RLOC lookups to determine the routing path to the 502 ETR, which has the RLOC as one of its IP addresses. 504 Some basic rules governing LISP are: 506 o End-systems (hosts) only send to addresses which are EIDs. They 507 don't know addresses are EIDs versus RLOCs but assume packets get 508 to their intended destinations. In a system where LISP is 509 deployed, LISP routers intercept EID addressed packets and assist 510 in delivering them across the network core where EIDs cannot be 511 routed. The procedure a host uses to send IP packets does not 512 change. 514 o EIDs are always IP addresses assigned to hosts. 516 o LISP routers mostly deal with Routing Locator addresses. See 517 details later in Section 4.1 to clarify what is meant by "mostly". 519 o RLOCs are always IP addresses assigned to routers; preferably, 520 topologically-oriented addresses from provider CIDR (Classless 521 Inter-Domain Routing) blocks. 523 o When a router originates packets it may use as a source address 524 either an EID or RLOC. When acting as a host (e.g. when 525 terminating a transport session such as SSH, TELNET, or SNMP), it 526 may use an EID that is explicitly assigned for that purpose. An 527 EID that identifies the router as a host MUST NOT be used as an 528 RLOC; an EID is only routable within the scope of a site. A 529 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 530 usage where a router could use its "host-like" EID to terminate 531 iBGP sessions to other routers in a site while at the same time 532 using RLOCs to terminate eBGP sessions to routers outside the 533 site. 535 o Packets with EIDs in them are not expected to be delivered end-to- 536 end in the absence of an EID-to-RLOC mapping operation. They are 537 expected to be used locally for intra-site communication or to be 538 encapsulated for inter-site communication. 540 o EID prefixes are likely to be hierarchically assigned in a manner 541 which is optimized for administrative convenience and to 542 facilitate scaling of the EID-to-RLOC mapping database. The 543 hierarchy is based on a address allocation hierarchy which is 544 independent of the network topology. 546 o EIDs may also be structured (subnetted) in a manner suitable for 547 local routing within an autonomous system. 549 An additional LISP header MAY be prepended to packets by a TE-ITR 550 when re-routing of the path for a packet is desired. A potential 551 use-case for this would be an ISP router that needs to perform 552 traffic engineering for packets flowing through its network. In such 553 a situation, termed Recursive Tunneling, an ISP transit acts as an 554 additional ingress tunnel router and the RLOC it uses for the new 555 prepended header would be either a TE-ETR within the ISP (along 556 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 557 inter-ISP traffic engineered path, where an agreement to build such a 558 path exists). 560 In order to avoid excessive packet overhead as well as possible 561 encapsulation loops, this document mandates that a maximum of two 562 LISP headers can be prepended to a packet. For initial LISP 563 deployments, it is assumed two headers is sufficient, where the first 564 prepended header is used at a site for Location/Identity separation 565 and second prepended header is used inside a service provider for 566 Traffic Engineering purposes. 568 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 569 For example, the ITR for a particular end-to-end packet exchange 570 might be the first-hop or default router within a site for the source 571 host. Similarly, the egress tunnel router might be the last-hop 572 router directly-connected to the destination host. Another example, 573 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 574 could be the site's border router at the service provider attachment 575 point. Mixing and matching of site-operated, ISP-operated, and other 576 tunnel routers is allowed for maximum flexibility. See Section 8 for 577 more details. 579 4.1. Packet Flow Sequence 581 This section provides an example of the unicast packet flow with the 582 following conditions: 584 o Source host "host1.abc.example.com" is sending a packet to 585 "host2.xyz.example.com", exactly what host1 would do if the site 586 was not using LISP. 588 o Each site is multi-homed, so each tunnel router has an address 589 (RLOC) assigned from the service provider address block for each 590 provider to which that particular tunnel router is attached. 592 o The ITR(s) and ETR(s) are directly connected to the source and 593 destination, respectively, but the source and destination can be 594 located anywhere in LISP site. 596 o Map-Requests can be sent on the underlying routing system 597 topology, to a mapping database system, or directly over an 598 alternative topology [ALT]. A Map-Request is sent for an external 599 destination when the destination is not found in the forwarding 600 table or matches a default route. 602 o Map-Replies are sent on the underlying routing system topology. 604 Client host1.abc.example.com wants to communicate with server 605 host2.xyz.example.com: 607 1. host1.abc.example.com wants to open a TCP connection to 608 host2.xyz.example.com. It does a DNS lookup on 609 host2.xyz.example.com. An A/AAAA record is returned. This 610 address is the destination EID. The locally-assigned address of 611 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 612 packet is built and forwarded through the LISP site as a normal 613 IP packet until it reaches a LISP ITR. 615 2. The LISP ITR must be able to map the destination EID to an RLOC 616 of one of the ETRs at the destination site. The specific method 617 used to do this is not described in this example. See [ALT] or 618 [CONS] for possible solutions. 620 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 621 rate-limited. 623 4. When an alternate mapping system is not in use, the Map-Request 624 packet is routed through the underlying routing system. 625 Otherwise, the Map-Request packet is routed on an alternate 626 logical topology, for example the [ALT] database mapping system. 627 In either case, when the Map-Request arrives at one of the ETRs 628 at the destination site, it will process the packet as a control 629 message. 631 5. The ETR looks at the destination EID of the Map-Request and 632 matches it against the prefixes in the ETR's configured EID-to- 633 RLOC mapping database. This is the list of EID-prefixes the ETR 634 is supporting for the site it resides in. If there is no match, 635 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 636 returned to the ITR. 638 6. The ITR receives the Map-Reply message, parses the message (to 639 check for format validity) and stores the mapping information 640 from the packet. This information is stored in the ITR's EID-to- 641 RLOC mapping cache. Note that the map cache is an on-demand 642 cache. An ITR will manage its map cache in such a way that 643 optimizes for its resource constraints. 645 7. Subsequent packets from host1.abc.example.com to 646 host2.xyz.example.com will have a LISP header prepended by the 647 ITR using the appropriate RLOC as the LISP header destination 648 address learned from the ETR. Note the packet MAY be sent to a 649 different ETR than the one which returned the Map-Reply due to 650 the source site's hashing policy or the destination site's 651 locator-set policy. 653 8. The ETR receives these packets directly (since the destination 654 address is one of its assigned IP addresses), checks the validity 655 of the addresses, strips the LISP header, and forwards packets to 656 the attached destination host. 658 In order to defer the need for a mapping lookup in the reverse 659 direction, an ETR MAY create a cache entry that maps the source EID 660 (inner header source IP address) to the source RLOC (outer header 661 source IP address) in a received LISP packet. Such a cache entry is 662 termed a "gleaned" mapping and only contains a single RLOC for the 663 EID in question. More complete information about additional RLOCs 664 SHOULD be verified by sending a LISP Map-Request for that EID. Both 665 ITR and the ETR may also influence the decision the other makes in 666 selecting an RLOC. See Section 6 for more details. 668 5. LISP Encapsulation Details 670 Since additional tunnel headers are prepended, the packet becomes 671 larger and can exceed the MTU of any link traversed from the ITR to 672 the ETR. It is RECOMMENDED in IPv4 that packets do not get 673 fragmented as they are encapsulated by the ITR. Instead, the packet 674 is dropped and an ICMP Too Big message is returned to the source. 676 This specification RECOMMENDS that implementations provide support 677 for one of the proposed fragmentation and reassembly schemes. Two 678 existing schemes are detailed in Section 5.4. 680 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 681 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 682 header is in IPv4 packet format and the other header is in IPv6 683 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 684 is in IPv6 packet format and the other header is in IPv4 packet 685 format). The next sub-sections illustrate packet formats for the 686 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6) but all 4 687 combinations MUST be supported. 689 5.1. LISP IPv4-in-IPv4 Header Format 691 0 1 2 3 692 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 1 693 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 694 / |Version| IHL |Type of Service| Total Length | 695 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 696 | | Identification |Flags| Fragment Offset | 697 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 698 OH | Time to Live | Protocol = 17 | Header Checksum | 699 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 700 | | Source Routing Locator | 701 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 702 \ | Destination Routing Locator | 703 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 704 / | Source Port = xxxx | Dest Port = 4341 | 705 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 706 \ | UDP Length | UDP Checksum | 707 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 708 L |N|L|E|V|I|flags| Nonce/Map-Version | 709 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 710 S / | Instance ID/Locator Status Bits | 711 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 / |Version| IHL |Type of Service| Total Length | 713 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 714 | | Identification |Flags| Fragment Offset | 715 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 716 IH | Time to Live | Protocol | Header Checksum | 717 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 718 | | Source EID | 719 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 720 \ | Destination EID | 721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 723 5.2. LISP IPv6-in-IPv6 Header Format 725 0 1 2 3 726 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 1 727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 728 / |Version| Traffic Class | Flow Label | 729 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 731 | | Payload Length | Next Header=17| Hop Limit | 732 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 733 | | 734 O + + 735 u | | 736 t + Source Routing Locator + 737 e | | 738 r + + 739 | | 740 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 741 d | | 742 r + + 743 | | 744 ^ + Destination Routing Locator + 745 | | | 746 \ + + 747 \ | | 748 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 749 / | Source Port = xxxx | Dest Port = 4341 | 750 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 751 \ | UDP Length | UDP Checksum | 752 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 753 L |N|L|E|V|I|flags| Nonce/Map-Version | 754 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 755 S / | Instance ID/Locator Status Bits | 756 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 757 / |Version| Traffic Class | Flow Label | 758 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 759 / | Payload Length | Next Header | Hop Limit | 760 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 761 | | 762 I + + 763 n | | 764 n + Source EID + 765 e | | 766 r + + 767 | | 768 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 769 d | | 770 r + + 771 | | 772 ^ + Destination EID + 773 \ | | 774 \ + + 775 \ | | 776 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 778 5.3. Tunnel Header Field Descriptions 780 Inner Header (IH): The inner header is the header on the datagram 781 received from the originating host. The source and destination IP 782 addresses are EIDs, [RFC0791], [RFC2460]. 784 Outer Header: (OH) The outer header is a new header prepended by an 785 ITR. The address fields contain RLOCs obtained from the ingress 786 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 787 from [RFC0768]. The setting of the DF bit Flags field is 788 according to rules in Section 5.4.1 and Section 5.4.2. 790 UDP Header: The UDP header contains an ITR selected source port when 791 encapsulating a packet. See Section 6.5 for details on the hash 792 algorithm used to select a source port based on the 5-tuple of the 793 inner header. The destination port MUST be set to the well-known 794 IANA assigned port value 4341. 796 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 797 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 798 [UDP-TUNNELS] [UDP-ZERO]. When a packet with a zero UDP checksum 799 is received by an ETR, the ETR MUST accept the packet for 800 decapsulation. When an ITR transmits a non-zero value for the UDP 801 checksum, it MUST send a correctly computed value in this field. 802 When an ETR receives a packet with a non-zero UDP checksum, it MAY 803 choose to verify the checksum value. If it chooses to perform 804 such verification, and the verification fails, the packet MUST be 805 silently dropped. If the ETR chooses not to perform the 806 verification, or performs the verification successfully, the 807 packet MUST be accepted for decapsulation. The handling of UDP 808 checksums for all tunneling protocols, including LISP, is under 809 active discussion within the IETF. When that discussion 810 concludes, any necessary changes will be made to align LISP with 811 the outcome of the broader discussion. 813 UDP Length: The UDP length field is set for an IPv4 encapsulated 814 packet to be the sum of the inner header IPv4 Total Length plus 815 the UDP and LISP header lengths. For an IPv6 encapsulated packet, 816 the UDP length field is the sum of the inner header IPv6 Payload 817 Length, the size of the IPv6 header (40 octets), and the size of 818 the UDP and LISP headers. 820 N: The N bit is the nonce-present bit. When this bit is set to 1, 821 the low-order 24-bits of the first 32-bits of the LISP header 822 contains a Nonce. See Section 6.3.1 for details. Both N and V 823 bits MUST NOT be set in the same packet. If they are, a 824 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 825 having a Nonce value present. 827 L: The L bit is the Locator Status Bits field enabled bit. When this 828 bit is set to 1, the Locator Status Bits in the second 32-bits of 829 the LISP header are in use. 831 x 1 x x 0 x x x 832 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 833 |N|L|E|V|I|flags| Nonce/Map-Version | 834 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 835 | Locator Status Bits | 836 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 838 E: The E bit is the echo-nonce-request bit. This bit MUST be ignored 839 and has no meaning when the N bit is set to 0. When the N bit is 840 set to 1 and this bit is set to 1, means an ITR is requesting for 841 the nonce value in the Nonce field to be echoed back in LISP 842 encapsulated packets when the ITR is also an ETR. See 843 Section 6.3.1 for details. 845 V: The V bit is the Map-Version present bit. When this bit is set to 846 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 847 This bit indicates that the LISP header is encoded in this case 848 as: 850 0 x 0 1 x x x x 851 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 852 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 853 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 854 | Instance ID/Locator Status Bits | 855 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 857 I: The I bit is the Instance ID bit. See Section 5.5 for more 858 details. When this bit is set to 1, the Locator Status Bits field 859 is reduced to 8-bits and the high-order 24-bits are used as an 860 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 861 are transmitted as zero and ignored on receipt. The format of the 862 LISP header would look like in this case: 864 x x x x 1 x x x 865 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 866 |N|L|E|V|I|flags| Nonce/Map-Version | 867 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 868 | Instance ID | LSBs | 869 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 871 flags: The flags field is a 3-bit field is reserved for future flag 872 use. It MUST be set to 0 on transmit and MUST be ignored on 873 receipt. 875 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 876 generated by an ITR when the N-bit is set to 1. Nonce generation 877 algorithms are an implementation matter but are required to 878 generate different nonces when sending to different destinations. 879 However, the same nonce can be used for a period of time to the 880 same destination. The nonce is also used when the E-bit is set to 881 request the nonce value to be echoed by the other side when 882 packets are returned. When the E-bit is clear but the N-bit is 883 set, a remote ITR is either echoing a previously requested echo- 884 nonce or providing a random nonce. See Section 6.3.1 for more 885 details. 887 LISP Locator Status Bits (LSBs): When the L-bit is also set, the 888 locator status bits field in the LISP header is set by an ITR to 889 indicate to an ETR the up/down status of the Locators in the 890 source site. Each RLOC in a Map-Reply is assigned an ordinal 891 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 892 The Locator Status Bits are numbered from 0 to n-1 from the least 893 significant bit of field. The field is 32-bits when the I-bit is 894 set to 0 and is 8 bits when the I-bit is set to 1. When a Locator 895 Status Bit is set to 1, the ITR is indicating to the ETR the RLOC 896 associated with the bit ordinal has up status. See Section 6.3 897 for details on how an ITR can determine the status of the ETRs at 898 the same site. When a site has multiple EID-prefixes which result 899 in multiple mappings (where each could have a different locator- 900 set), the Locator Status Bits setting in an encapsulated packet 901 MUST reflect the mapping for the EID-prefix that the inner-header 902 source EID address matches. If the LSB for an anycast locator is 903 set to 1, then there is at least one RLOC with that address the 904 ETR is considered 'up'. 906 When doing ITR/PITR encapsulation: 908 o The outer header Time to Live field (or Hop Limit field, in case 909 of IPv6) SHOULD be copied from the inner header Time to Live 910 field. 912 o The outer header Type of Service field (or the Traffic Class 913 field, in the case of IPv6) SHOULD be copied from the inner header 914 Type of Service field (with one exception, see below). 916 When doing ETR/PETR decapsulation: 918 o The inner header Time to Live field (or Hop Limit field, in case 919 of IPv6) SHOULD be copied from the outer header Time to Live 920 field, when the Time to Live field of the outer header is less 921 than the Time to Live of the inner header. Failing to perform 922 this check can cause the Time to Live of the inner header to 923 increment across encapsulation/decapsulation cycle. This check is 924 also performed when doing initial encapsulation when a packet 925 comes to an ITR or PITR destined for a LISP site. 927 o The inner header Type of Service field (or the Traffic Class 928 field, in the case of IPv6) SHOULD be copied from the outer header 929 Type of Service field (with one exception, see below). 931 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 932 after decapsulating, the net effect of this is that the new outer 933 header will carry the same Time to Live as the old outer header minus 934 1. 936 Copying the TTL serves two purposes: first, it preserves the distance 937 the host intended the packet to travel; second, and more importantly, 938 it provides for suppression of looping packets in the event there is 939 a loop of concatenated tunnels due to misconfiguration. See 940 Section 9.3 for TTL exception handling for traceroute packets. 942 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 943 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 944 requires special treatment in order to avoid discarding indications 945 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 946 field from the inner header to the outer header. Re-encapsulation 947 MUST copy the 2-bit ECN field from the stripped outer header to the 948 new outer header. If the ECN field contains a congestion indication 949 codepoint (the value is '11', the Congestion Experienced (CE) 950 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 951 the stripped outer header to the surviving inner header that is used 952 to forward the packet beyond the ETR. These requirements preserve 953 Congestion Experienced (CE) indications when a packet that uses ECN 954 traverses a LISP tunnel and becomes marked with a CE indication due 955 to congestion between the tunnel endpoints. 957 5.4. Dealing with Large Encapsulated Packets 959 This section proposes two mechanisms to deal with packets that exceed 960 the path MTU between the ITR and ETR. 962 It is left to the implementor to decide if the stateless or stateful 963 mechanism should be implemented. Both or neither can be used since 964 it is a local decision in the ITR regarding how to deal with MTU 965 issues, and sites can interoperate with differing mechanisms. 967 Both stateless and stateful mechanisms also apply to Reencapsulating 968 and Recursive Tunneling. So any actions below referring to an ITR 969 also apply to an TE-ITR. 971 5.4.1. A Stateless Solution to MTU Handling 973 An ITR stateless solution to handle MTU issues is described as 974 follows: 976 1. Define an architectural constant S for the maximum size of a 977 packet, in octets, an ITR would like to receive from a source 978 inside of its site. 980 2. Define L to be the maximum size, in octets, a packet of size S 981 would be after the ITR prepends the LISP header, UDP header, and 982 outer network layer header of size H. Therefore, S + H = L. 984 When an ITR receives a packet from a site-facing interface and adds H 985 octets worth of encapsulation to yield a packet size greater than L 986 octets, it resolves the MTU issue by first splitting the original 987 packet into 2 equal-sized fragments. A LISP header is then prepended 988 to each fragment. The size of the encapsulated fragments is then 989 (S/2 + H), which is less than the ITR's estimate of the path MTU 990 between the ITR and its correspondent ETR. 992 When an ETR receives encapsulated fragments, it treats them as two 993 individually encapsulated packets. It strips the LISP headers then 994 forwards each fragment to the destination host of the destination 995 site. The two fragments are reassembled at the destination host into 996 the single IP datagram that was originated by the source host. Note 997 that reassembly can happen at the ETR if the encapsulated packet was 998 fragmented at or after the ITR. 1000 This behavior is performed by the ITR when the source host originates 1001 a packet with the DF field of the IP header is set to 0. When the DF 1002 field of the IP header is set to 1, or the packet is an IPv6 packet 1003 originated by the source host, the ITR will drop the packet when the 1004 size is greater than L, and sends an ICMP Too Big message to the 1005 source with a value of S, where S is (L - H). 1007 When the outer header encapsulation uses an IPv4 header, an 1008 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 1009 can be avoided. An implementation MAY set the DF bit in such headers 1010 to 0 if it has good reason to believe there are unresolvable path MTU 1011 issues between the sending ITR and the receiving ETR. 1013 This specification RECOMMENDS that L be defined as 1500. 1015 5.4.2. A Stateful Solution to MTU Handling 1017 An ITR stateful solution to handle MTU issues is described as follows 1018 and was first introduced in [OPENLISP]: 1020 1. The ITR will keep state of the effective MTU for each locator per 1021 mapping cache entry. The effective MTU is what the core network 1022 can deliver along the path between ITR and ETR. 1024 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 1025 with DF bit set to 1, exceeds what the core network can deliver, 1026 one of the intermediate routers on the path will send an ICMP Too 1027 Big message to the ITR. The ITR will parse the ICMP message to 1028 determine which locator is affected by the effective MTU change 1029 and then record the new effective MTU value in the mapping cache 1030 entry. 1032 3. When a packet is received by the ITR from a source inside of the 1033 site and the size of the packet is greater than the effective MTU 1034 stored with the mapping cache entry associated with the 1035 destination EID the packet is for, the ITR will send an ICMP Too 1036 Big message back to the source. The packet size advertised by 1037 the ITR in the ICMP Too Big message is the effective MTU minus 1038 the LISP encapsulation length. 1040 Even though this mechanism is stateful, it has advantages over the 1041 stateless IP fragmentation mechanism, by not involving the 1042 destination host with reassembly of ITR fragmented packets. 1044 5.5. Using Virtualization and Segmentation with LISP 1046 When multiple organizations inside of a LISP site are using private 1047 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 1048 segregated due to possible address duplication. An Instance ID in 1049 the address encoding can aid in making the entire AFI based address 1050 unique. See IANA Considerations Section 14.2 for details for 1051 possible address encodings. 1053 An Instance ID can be carried in a LISP encapsulated packet. An ITR 1054 that prepends a LISP header, will copy a 24-bit value, used by the 1055 LISP router to uniquely identify the address space. The value is 1056 copied to the Instance ID field of the LISP header and the I-bit is 1057 set to 1. 1059 When an ETR decapsulates a packet, the Instance ID from the LISP 1060 header is used as a table identifier to locate the forwarding table 1061 to use for the inner destination EID lookup. 1063 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 1064 24-bit Instance ID. 1066 6. EID-to-RLOC Mapping 1068 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 1070 The following UDP packet formats are used by the LISP control-plane. 1072 0 1 2 3 1073 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 1074 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1075 |Version| IHL |Type of Service| Total Length | 1076 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1077 | Identification |Flags| Fragment Offset | 1078 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1079 | Time to Live | Protocol = 17 | Header Checksum | 1080 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1081 | Source Routing Locator | 1082 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1083 | Destination Routing Locator | 1084 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1085 / | Source Port | Dest Port | 1086 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1087 \ | UDP Length | UDP Checksum | 1088 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1089 | | 1090 | LISP Message | 1091 | | 1092 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1094 0 1 2 3 1095 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 1096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1097 |Version| Traffic Class | Flow Label | 1098 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1099 | Payload Length | Next Header=17| Hop Limit | 1100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1101 | | 1102 + + 1103 | | 1104 + Source Routing Locator + 1105 | | 1106 + + 1107 | | 1108 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1109 | | 1110 + + 1111 | | 1112 + Destination Routing Locator + 1113 | | 1114 + + 1115 | | 1116 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1117 / | Source Port | Dest Port | 1118 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1119 \ | UDP Length | UDP Checksum | 1120 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1121 | | 1122 | LISP Message | 1123 | | 1124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1126 The LISP UDP-based messages are the Map-Request and Map-Reply 1127 messages. When a UDP Map-Request is sent, the UDP source port is 1128 chosen by the sender and the destination UDP port number is set to 1129 4342. When a UDP Map-Reply is sent, the source UDP port number is 1130 set to 4342 and the destination UDP port number is copied from the 1131 source port of either the Map-Request or the invoking data packet. 1132 Implementations MUST be prepared to accept packets when either the 1133 source port or destination UDP port is set to 4342 due to NATs 1134 changing port number values. 1136 The UDP Length field will reflect the length of the UDP header and 1137 the LISP Message payload. 1139 The UDP Checksum is computed and set to non-zero for Map-Request, 1140 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1141 on receipt and if the checksum fails, the packet MUST be dropped. 1143 The format of control messages includes the UDP header so the 1144 checksum and length fields can be used to protect and delimit message 1145 boundaries. 1147 6.1.1. LISP Packet Type Allocations 1149 This section will be the authoritative source for allocating LISP 1150 Type values and for defining LISP control message formats. Current 1151 allocations are: 1153 Reserved: 0 b'0000' 1154 LISP Map-Request: 1 b'0001' 1155 LISP Map-Reply: 2 b'0010' 1156 LISP Map-Register: 3 b'0011' 1157 LISP Map-Notify: 4 b'0100' 1158 LISP Encapsulated Control Message: 8 b'1000' 1160 6.1.2. Map-Request Message Format 1162 0 1 2 3 1163 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 1164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1165 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1167 | Nonce . . . | 1168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1169 | . . . Nonce | 1170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1171 | Source-EID-AFI | Source EID Address ... | 1172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1173 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1175 | ... | 1176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1177 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1179 / | Reserved | EID mask-len | EID-prefix-AFI | 1180 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1181 \ | EID-prefix ... | 1182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1183 | Map-Reply Record ... | 1184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1186 Packet field descriptions: 1188 Type: 1 (Map-Request) 1190 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1191 Requests sent by an ITR. Set to 1 when an ITR wants the 1192 destination site to return the Map-Reply rather than the mapping 1193 database system. 1195 M: This is the map-data-present bit, when set, it indicates a Map- 1196 Reply Record segment is included in the Map-Request. 1198 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1199 treated as a locator reachability probe. The receiver SHOULD 1200 respond with a Map-Reply with the probe-bit set, indicating the 1201 Map-Reply is a locator reachability probe reply, with the nonce 1202 copied from the Map-Request. See Section 6.3.2 for more details. 1204 S: This is the Solicit-Map-Request (SMR) bit. See Section 6.6.2 for 1205 details. 1207 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1208 Map-Request. 1210 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1211 sending a Map-Request in response to a received SMR-based Map- 1212 Request. 1214 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1215 receipt. 1217 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1218 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1219 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1220 Address) pair MUST be encoded. Multiple ITR-RLOC Address fields 1221 are used so a Map-Replier can select which destination address to 1222 use for a Map-Reply. The IRC value ranges from 0 to 31. For a 1223 value of 0, there is 1 ITR-RLOC address encoded, and for a value 1224 of 1, there are 2 ITR-RLOC addresses encoded and so on up to 31 1225 which encodes a total of 32 ITR-RLOC addresses. 1227 Record Count: The number of records in this Map-Request message. A 1228 record is comprised of the portion of the packet that is labeled 1229 'Rec' above and occurs the number of times equal to Record Count. 1230 For this version of the protocol, a receiver MUST accept and 1231 process Map-Requests that contain one or more records, but a 1232 sender MUST only send Map-Requests containing one record. Support 1233 for requesting multiple EIDs in a single Map-Request message will 1234 be specified in a future version of the protocol. 1236 Nonce: An 8-octet random value created by the sender of the Map- 1237 Request. This nonce will be returned in the Map-Reply. The 1238 security of the LISP mapping protocol depends critically on the 1239 strength of the nonce in the Map-Request message. The nonce 1240 SHOULD be generated by a properly seeded pseudo-random (or strong 1241 random) source. See [RFC4086] for advice on generating security- 1242 sensitive random data. 1244 Source-EID-AFI: Address family of the "Source EID Address" field. 1246 Source EID Address: This is the EID of the source host which 1247 originated the packet which is caused the Map-Request. When Map- 1248 Requests are used for refreshing a map-cache entry or for RLOC- 1249 probing, an AFI value 0 is used and this field is of zero length. 1251 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1252 follows this field. 1254 ITR-RLOC Address: Used to give the ETR the option of selecting the 1255 destination address from any address family for the Map-Reply 1256 message. This address MUST be a routable RLOC address of the 1257 sender of the Map-Request message. 1259 EID mask-len: Mask length for EID prefix. 1261 EID-prefix-AFI: Address family of EID-prefix according to [AFI] 1263 EID-prefix: 4 octets if an IPv4 address-family, 16 octets if an IPv6 1264 address-family. When a Map-Request is sent by an ITR because a 1265 data packet is received for a destination where there is no 1266 mapping entry, the EID-prefix is set to the destination IP address 1267 of the data packet. And the 'EID mask-len' is set to 32 or 128 1268 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1269 about the status of a mapping it already has cached, the EID- 1270 prefix used in the Map-Request has the same mask-length as the 1271 EID-prefix returned from the site when it sent a Map-Reply 1272 message. 1274 Map-Reply Record: When the M bit is set, this field is the size of a 1275 single "Record" in the Map-Reply format. This Map-Reply record 1276 contains the EID-to-RLOC mapping entry associated with the Source 1277 EID. This allows the ETR which will receive this Map-Request to 1278 cache the data if it chooses to do so. 1280 6.1.3. EID-to-RLOC UDP Map-Request Message 1282 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1283 wants to test an RLOC for reachability, or wants to refresh a mapping 1284 before TTL expiration. For the initial case, the destination IP 1285 address used for the Map-Request is the data packet's destination 1286 address (i.e. the destination-EID) which had a mapping cache lookup 1287 failure. For the latter two cases, the destination IP address used 1288 for the Map-Request is one of the RLOC addresses from the locator-set 1289 of the map cache entry. The source address is either an IPv4 or IPv6 1290 RLOC address depending if the Map-Request is using an IPv4 versus 1291 IPv6 header, respectively. In all cases, the UDP source port number 1292 for the Map-Request message is an ITR/PITR selected 16-bit value and 1293 the UDP destination port number is set to the well-known destination 1294 port number 4342. A successful Map-Reply, which is one that has a 1295 nonce that matches an outstanding Map-Request nonce, will update the 1296 cached set of RLOCs associated with the EID prefix range. 1298 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1299 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1300 be placed in the IRC field. The ITR MAY include all locally 1301 configured locators in this list or just provide one locator address 1302 from each address family it supports. If the ITR erroneously 1303 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1304 Request. 1306 Map-Requests can also be LISP encapsulated using UDP destination port 1307 4342 with a LISP type value set to "Encapsulated Control Message", 1308 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1309 LISP encapsulated the same way from a Map-Server to an ETR. Details 1310 on encapsulated Map-Requests and Map-Resolvers can be found in 1311 [LISP-MS]. 1313 Map-Requests MUST be rate-limited. It is RECOMMENDED that a Map- 1314 Request for the same EID-prefix be sent no more than once per second. 1316 An ITR that is configured with mapping database information (i.e. it 1317 is also an ETR) MAY optionally include those mappings in a Map- 1318 Request. When an ETR configured to accept and verify such 1319 "piggybacked" mapping data receives such a Map-Request and it does 1320 not have this mapping in the map-cache, it MAY originate a "verifying 1321 Map-Request", addressed to the map-requesting ITR and the ETR MAY add 1322 a map-cache entry. If the ETR has a map-cache entry that matches the 1323 "piggybacked" EID and the RLOC is in the locator-set for the entry, 1324 then it may send the "verifying Map-Request" directly to the 1325 originating Map-Request source. If the RLOC is not in the locator- 1326 set, then the ETR MUST send the "verifying Map-Request" to the 1327 "piggybacked" EID. Doing this forces the "verifying Map-Request" to 1328 go through the mapping database system to reach the authoritative 1329 source of information about that EID, guarding against RLOC-spoofing 1330 in in the "piggybacked" mapping data. 1332 6.1.4. Map-Reply Message Format 1334 0 1 2 3 1335 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 1336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1337 |Type=2 |P|E|S| Reserved | Record Count | 1338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1339 | Nonce . . . | 1340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1341 | . . . Nonce | 1342 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1343 | | Record TTL | 1344 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1345 R | Locator Count | EID mask-len | ACT |A| Reserved | 1346 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1347 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1348 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1349 r | EID-prefix | 1350 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1351 | /| Priority | Weight | M Priority | M Weight | 1352 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1353 | o | Unused Flags |L|p|R| Loc-AFI | 1354 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1355 | \| Locator | 1356 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1358 Packet field descriptions: 1360 Type: 2 (Map-Reply) 1362 P: This is the probe-bit which indicates that the Map-Reply is in 1363 response to a locator reachability probe Map-Request. The nonce 1364 field MUST contain a copy of the nonce value from the original 1365 Map-Request. See Section 6.3.2 for more details. 1367 E: Indicates that the ETR which sends this Map-Reply message is 1368 advertising that the site is enabled for the Echo-Nonce locator 1369 reachability algorithm. See Section 6.3.1 for more details. 1371 S: This is the Security bit. When set to 1 the following 1372 authentication information will be appended to the end of the Map- 1373 Reply. The detailed format of the Authentication Data Content is 1374 for further study. 1376 0 1 2 3 1377 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 1378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1379 | AD Type | Authentication Data Content . . . | 1380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1382 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1383 receipt. 1385 Record Count: The number of records in this reply message. A record 1386 is comprised of that portion of the packet labeled 'Record' above 1387 and occurs the number of times equal to Record count. 1389 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1390 from the Map-Request is echoed in this Nonce field of the Map- 1391 Reply. When a 24-bit value is supplied, it resides in the low- 1392 order 64 bits of the nonce field. 1394 Record TTL: The time in minutes the recipient of the Map-Reply will 1395 store the mapping. If the TTL is 0, the entry SHOULD be removed 1396 from the cache immediately. If the value is 0xffffffff, the 1397 recipient can decide locally how long to store the mapping. 1399 Locator Count: The number of Locator entries. A locator entry 1400 comprises what is labeled above as 'Loc'. The locator count can 1401 be 0 indicating there are no locators for the EID-prefix. 1403 EID mask-len: Mask length for EID prefix. 1405 ACT: This 3-bit field describes negative Map-Reply actions. In any 1406 other message type, these bits are set to 0 and ignored on 1407 receipt. These bits are used only when the 'Locator Count' field 1408 is set to 0. The action bits are encoded only in Map-Reply 1409 messages. The actions defined are used by an ITR or PITR when a 1410 destination EID matches a negative mapping cache entry. 1411 Unassigned values should cause a map-cache entry to be created 1412 and, when packets match this negative cache entry, they will be 1413 dropped. The current assigned values are: 1415 (0) No-Action: The map-cache is kept alive and no packet 1416 encapsulation occurs. 1418 (1) Natively-Forward: The packet is not encapsulated or dropped 1419 but natively forwarded. 1421 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1423 (3) Drop: A packet that matches this map-cache entry is dropped. 1424 An ICMP Unreachable message SHOULD be sent. 1426 A: The Authoritative bit, when sent is always set to 1 by an ETR. 1427 When a Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, 1428 the Authoritative bit is set to 0. This indicates to requesting 1429 ITRs that the Map-Reply was not originated by a LISP node managed 1430 at the site that owns the EID-prefix. 1432 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1433 sender is informing the ITR what the version number is for the 1434 EID-record contained in the Map-Reply. The ETR can allocate this 1435 number internally but MUST coordinate this value with other ETRs 1436 for the site. When this value is 0, there is no versioning 1437 information conveyed. The Map-Version Number can be included in 1438 Map-Request and Map-Register messages. See Section 6.6.3 for more 1439 details. 1441 EID-prefix-AFI: Address family of EID-prefix according to [AFI]. 1443 EID-prefix: 4 octets if an IPv4 address-family, 16 octets if an IPv6 1444 address-family. 1446 Priority: each RLOC is assigned a unicast priority. Lower values 1447 are more preferable. When multiple RLOCs have the same priority, 1448 they MAY be used in a load-split fashion. A value of 255 means 1449 the RLOC MUST NOT be used for unicast forwarding. 1451 Weight: when priorities are the same for multiple RLOCs, the weight 1452 indicates how to balance unicast traffic between them. Weight is 1453 encoded as a relative weight of total unicast packets that match 1454 the mapping entry. For example if there are 4 locators in a 1455 locator set, where the weights assigned are 30, 20, 20, and 10, 1456 the first locator will get 37.5% of the traffic, the 2nd and 3rd 1457 locators will get 25% of traffic and the 4th locator will get 1458 12.5% of the traffic. If all weights for a locator-set are equal, 1459 receiver of the Map-Reply will decide how to load-split traffic. 1460 See Section 6.5 for a suggested hash algorithm to distribute load 1461 across locators with same priority and equal weight values. 1463 M Priority: each RLOC is assigned a multicast priority used by an 1464 ETR in a receiver multicast site to select an ITR in a source 1465 multicast site for building multicast distribution trees. A value 1466 of 255 means the RLOC MUST NOT be used for joining a multicast 1467 distribution tree. For more details, see [MLISP]. 1469 M Weight: when priorities are the same for multiple RLOCs, the 1470 weight indicates how to balance building multicast distribution 1471 trees across multiple ITRs. The weight is encoded as a relative 1472 weight (similar to the unicast Weights) of total number of trees 1473 built to the source site identified by the EID-prefix. If all 1474 weights for a locator-set are equal, the receiver of the Map-Reply 1475 will decide how to distribute multicast state across ITRs. For 1476 more details, see [MLISP]. 1478 Unused Flags: set to 0 when sending and ignored on receipt. 1480 L: when this bit is set, the locator is flagged as a local locator to 1481 the ETR that is sending the Map-Reply. When a Map-Server is doing 1482 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1483 0 for all locators in this locator-set. 1485 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1486 locator address, for which this bit is set, is the one being RLOC- 1487 probed and MAY be different from the source address of the Map- 1488 Reply. An ITR that RLOC-probes a particular locator, MUST use 1489 this locator for retrieving the data structure used to store the 1490 fact that the locator is reachable. The "p" bit is set for a 1491 single locator in the same locator set. If an implementation sets 1492 more than one "p" bit erroneously, the receiver of the Map-Reply 1493 MUST select the first locator. The "p" bit MUST NOT be set for 1494 locator-set records sent in Map-Request and Map-Register messages. 1496 R: set when the sender of a Map-Reply has a route to the locator in 1497 the locator data record. This receiver may find this useful to 1498 know if the locator is up but not necessarily reachable from the 1499 receiver's point of view. See also Section 6.4 for another way 1500 the R-bit may be used. 1502 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1503 assigned to an ETR. Note that the destination RLOC address MAY be 1504 an anycast address. A source RLOC can be an anycast address as 1505 well. The source or destination RLOC MUST NOT be the broadcast 1506 address (255.255.255.255 or any subnet broadcast address known to 1507 the router), and MUST NOT be a link-local multicast address. The 1508 source RLOC MUST NOT be a multicast address. The destination RLOC 1509 SHOULD be a multicast address if it is being mapped from a 1510 multicast destination EID. 1512 6.1.5. EID-to-RLOC UDP Map-Reply Message 1514 A Map-Reply returns an EID-prefix with a prefix length that is less 1515 than or equal to the EID being requested. The EID being requested is 1516 either from the destination field of an IP header of a Data-Probe or 1517 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1518 globally-routable IP addresses of all ETRs for the LISP site. Each 1519 RLOC conveys status reachability but does not convey path 1520 reachability from a requesters perspective. Separate testing of path 1521 reachability is required, See Section 6.3 for details. 1523 Note that a Map-Reply may contain different EID-prefix granularity 1524 (prefix + length) than the Map-Request which triggers it. This might 1525 occur if a Map-Request were for a prefix that had been returned by an 1526 earlier Map-Reply. In such a case, the requester updates its cache 1527 with the new prefix information and granularity. For example, a 1528 requester with two cached EID-prefixes that are covered by a Map- 1529 Reply containing one, less-specific prefix, replaces the entry with 1530 the less-specific EID-prefix. Note that the reverse, replacement of 1531 one less-specific prefix with multiple more-specific prefixes, can 1532 also occur but not by removing the less-specific prefix rather by 1533 adding the more-specific prefixes which during a lookup will override 1534 the less-specific prefix. 1536 When an ETR is configured with overlapping EID-prefixes, a Map- 1537 Request with an EID that longest matches any EID-prefix MUST be 1538 returned in a single Map-Reply message. For instance, if an ETR had 1539 database mapping entries for EID-prefixes: 1541 10.0.0.0/8 1542 10.1.0.0/16 1543 10.1.1.0/24 1544 10.1.2.0/24 1546 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1547 count of 1 to be returned with a mapping record EID-prefix of 1548 10.1.1.0/24. 1550 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1551 count of 3 to be returned with mapping records for EID-prefixes 1552 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1554 Note that not all overlapping EID-prefixes need to be returned, only 1555 the more specifics (note in the second example above 10.0.0.0/8 was 1556 not returned for requesting EID 10.1.5.5) entries for the matching 1557 EID-prefix of the requesting EID. When more than one EID-prefix is 1558 returned, all SHOULD use the same Time-to-Live value so they can all 1559 time out at the same time. When a more specific EID-prefix is 1560 received later, its Time-to-Live value in the Map-Reply record can be 1561 stored even when other less specifics exist. When a less specific 1562 EID-prefix is received later, its map-cache expiration time SHOULD be 1563 set to the minimum expiration time of any more specific EID-prefix in 1564 the map-cache. This is done so the integrity of the EID-prefix set 1565 is wholly maintained so no more-specific entries are removed from the 1566 map-cache while keeping less-specific entries. 1568 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1569 per second to the same requesting router. For scalability, it is 1570 expected that aggregation of EID addresses into EID-prefixes will 1571 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1572 prefix range thereby reducing the number of Map-Request messages. 1574 Map-Reply records can have an empty locator-set. A negative Map- 1575 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1576 convey special actions by the sender to the ITR or PITR which have 1577 solicited the Map-Reply. There are two primary applications for 1578 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1579 ITR or PITR when a destination is for a LISP site versus a non-LISP 1580 site. And the other is to source quench Map-Requests which are sent 1581 for non-allocated EIDs. 1583 For each Map-Reply record, the list of locators in a locator-set MUST 1584 appear in the same order for each ETR that originates a Map-Reply 1585 message. The locator-set MUST be sorted in order of ascending IP 1586 address where an IPv4 locator address is considered numerically 'less 1587 than' an IPv6 locator address. 1589 When sending a Map-Reply message, the destination address is copied 1590 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1591 can choose a locator address from one of the address families it 1592 supports. For Data-Probes, the destination address of the Map-Reply 1593 is copied from the source address of the Data-Probe message which is 1594 invoking the reply. The source address of the Map-Reply is one of 1595 the local IP addresses chosen to allow uRPF checks to succeed in the 1596 upstream service provider. The destination port of a Map-Reply 1597 message is copied from the source port of the Map-Request or Data- 1598 Probe and the source port of the Map-Reply message is set to the 1599 well-known UDP port 4342. 1601 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1603 When an ETR is misconfigured or compromised, it could return coarse 1604 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1605 cover EID-prefixes which are allocated to other sites redirecting 1606 their traffic to the locators of the compromised site. 1608 To solve this problem, there are two basic solutions that could be 1609 used. The first is to have Map-Servers proxy-map-reply on behalf of 1610 ETRs so their registered EID-prefixes are the ones returned in Map- 1611 Replies. Since the interaction between an ETR and Map-Server is 1612 secured with shared-keys, it is easier for an ETR to detect 1613 misbehavior. The second solution is to have ITRs and PITRs cache 1614 EID-prefixes with mask-lengths that are greater than or equal to a 1615 configured prefix length. This limits the damage to a specific width 1616 of any EID-prefix advertised, but needs to be coordinated with the 1617 allocation of site prefixes. These solutions can be used 1618 independently or at the same time. 1620 At the time of this writing, other approaches are being considered 1621 and researched. 1623 6.1.6. Map-Register Message Format 1625 The usage details of the Map-Register message can be found in 1626 specification [LISP-MS]. This section solely defines the message 1627 format. 1629 The message is sent in UDP with a destination UDP port of 4342 and a 1630 randomly selected UDP source port number. 1632 The Map-Register message format is: 1634 0 1 2 3 1635 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 1636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1637 |Type=3 |P| Reserved |M| Record Count | 1638 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1639 | Nonce . . . | 1640 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1641 | . . . Nonce | 1642 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1643 | Key ID | Authentication Data Length | 1644 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1645 ~ Authentication Data ~ 1646 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1647 | | Record TTL | 1648 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1649 R | Locator Count | EID mask-len | ACT |A| Reserved | 1650 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1651 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1652 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1653 r | EID-prefix | 1654 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1655 | /| Priority | Weight | M Priority | M Weight | 1656 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1657 | o | Unused Flags |L|p|R| Loc-AFI | 1658 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1659 | \| Locator | 1660 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1662 Packet field descriptions: 1664 Type: 3 (Map-Register) 1666 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1667 Register message requesting for the Map-Server to proxy Map-Reply. 1668 The Map-Server will send non-authoritative Map-Replies on behalf 1669 of the ETR. Details on this usage can be found in [LISP-MS]. 1671 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1672 receipt. 1674 M: This is the want-map-notify bit, when set to 1 an ETR is 1675 requesting for a Map-Notify message to be returned in response to 1676 sending a Map-Register message. The Map-Notify message sent by a 1677 Map-Server is used to an acknowledge receipt of a Map-Register 1678 message. 1680 Record Count: The number of records in this Map-Register message. A 1681 record is comprised of that portion of the packet labeled 'Record' 1682 above and occurs the number of times equal to Record count. 1684 Nonce: This 8-octet Nonce field is set to 0 in Map-Register 1685 messages. Since the Map-Register message is authenticated, the 1686 nonce field is not currently used for any security function but 1687 may be in the future as part of an anti-replay solution. 1689 Key ID: A configured ID to find the configured Message 1690 Authentication Code (MAC) algorithm and key value used for the 1691 authentication function. See Section 14.4 for codepoint 1692 assignments. 1694 Authentication Data Length: The length in octets of the 1695 Authentication Data field that follows this field. The length of 1696 the Authentication Data field is dependent on the Message 1697 Authentication Code (MAC) algorithm used. The length field allows 1698 a device that doesn't know the MAC algorithm to correctly parse 1699 the packet. 1701 Authentication Data: The message digest used from the output of the 1702 Message Authentication Code (MAC) algorithm. The entire Map- 1703 Register payload is authenticated with this field preset to 0. 1704 After the MAC is computed, it is placed in this field. 1705 Implementations of this specification MUST include support for 1706 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-256-128 [RFC6234] 1707 is RECOMMENDED. 1709 The definition of the rest of the Map-Register can be found in the 1710 Map-Reply section. 1712 6.1.7. Map-Notify Message Format 1714 The usage details of the Map-Notify message can be found in 1715 specification [LISP-MS]. This section solely defines the message 1716 format. 1718 The message is sent inside a UDP packet with source and destination 1719 UDP ports equal to 4342. 1721 The Map-Notify message format is: 1723 0 1 2 3 1724 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 1725 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1726 |Type=4 | Reserved | Record Count | 1727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1728 | Nonce . . . | 1729 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1730 | . . . Nonce | 1731 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1732 | Key ID | Authentication Data Length | 1733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1734 ~ Authentication Data ~ 1735 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1736 | | Record TTL | 1737 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1738 R | Locator Count | EID mask-len | ACT |A| Reserved | 1739 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1740 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1741 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1742 r | EID-prefix | 1743 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1744 | /| Priority | Weight | M Priority | M Weight | 1745 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1746 | o | Unused Flags |L|p|R| Loc-AFI | 1747 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1748 | \| Locator | 1749 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1751 Packet field descriptions: 1753 Type: 4 (Map-Notify) 1755 The Map-Notify message has the same contents as a Map-Register 1756 message. See Map-Register section for field descriptions. 1758 6.1.8. Encapsulated Control Message Format 1760 An Encapsulated Control Message (ECM) is used to encapsulate control 1761 packets sent between xTRs and the mapping database system described 1762 in [LISP-MS]. 1764 0 1 2 3 1765 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 1766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1767 / | IPv4 or IPv6 Header | 1768 OH | (uses RLOC addresses) | 1769 \ | | 1770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1771 / | Source Port = xxxx | Dest Port = 4342 | 1772 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1773 \ | UDP Length | UDP Checksum | 1774 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1775 LH |Type=8 |S| Reserved | 1776 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1777 / | IPv4 or IPv6 Header | 1778 IH | (uses RLOC or EID addresses) | 1779 \ | | 1780 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1781 / | Source Port = xxxx | Dest Port = yyyy | 1782 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1783 \ | UDP Length | UDP Checksum | 1784 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1785 LCM | LISP Control Message | 1786 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1788 Packet header descriptions: 1790 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1791 source and destination header address fields. 1793 UDP: The outer UDP header with destination port 4342. The source 1794 port is randomly allocated. The checksum field MUST be non-zero. 1796 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1797 and what follows is either an IPv4 or IPv6 header as encoded by 1798 the first 4 bits after the reserved field. 1800 S: This is the Security bit. When set to 1 the field following the 1801 Reserved field will have the following format. The detailed 1802 format of the Authentication Data Content is for further study. 1804 0 1 2 3 1805 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 1806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1807 | AD Type | Authentication Data Content . . . | 1808 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1810 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1811 addresses in the header address fields. When a Map-Request is 1812 encapsulated in this packet format the destination address in this 1813 header is an EID. 1815 UDP: The inner UDP header where the port assignments depends on the 1816 control packet being encapsulated. When the control packet is a 1817 Map-Request or Map-Register, the source port is ITR/PITR selected 1818 and the destination port is 4342. When the control packet is a 1819 Map-Reply, the source port is 4342 and the destination port is 1820 assigned from the source port of the invoking Map-Request. Port 1821 number 4341 MUST NOT be assigned to either port. The checksum 1822 field MUST be non-zero. 1824 LCM: The format is one of the control message formats described in 1825 this section. At this time, only Map-Request messages are allowed 1826 to be encapsulated. And in the future, PIM Join-Prune messages 1827 [MLISP] might be allowed. Encapsulating other types of LISP 1828 control messages are for further study. When Map-Requests are 1829 sent for RLOC-probing purposes (i.e the probe-bit is set), they 1830 MUST NOT be sent inside Encapsulated Control Messages. 1832 6.2. Routing Locator Selection 1834 Both client-side and server-side may need control over the selection 1835 of RLOCs for conversations between them. This control is achieved by 1836 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1837 messages. Alternatively, RLOC information MAY be gleaned from 1838 received tunneled packets or EID-to-RLOC Map-Request messages. 1840 The following enumerates different scenarios for choosing RLOCs and 1841 the controls that are available: 1843 o Server-side returns one RLOC. Client-side can only use one RLOC. 1844 Server-side has complete control of the selection. 1846 o Server-side returns a list of RLOC where a subset of the list has 1847 the same best priority. Client can only use the subset list 1848 according to the weighting assigned by the server-side. In this 1849 case, the server-side controls both the subset list and load- 1850 splitting across its members. The client-side can use RLOCs 1851 outside of the subset list if it determines that the subset list 1852 is unreachable (unless RLOCs are set to a Priority of 255). Some 1853 sharing of control exists: the server-side determines the 1854 destination RLOC list and load distribution while the client-side 1855 has the option of using alternatives to this list if RLOCs in the 1856 list are unreachable. 1858 o Server-side sets weight of 0 for the RLOC subset list. In this 1859 case, the client-side can choose how the traffic load is spread 1860 across the subset list. Control is shared by the server-side 1861 determining the list and the client determining load distribution. 1862 Again, the client can use alternative RLOCs if the server-provided 1863 list of RLOCs are unreachable. 1865 o Either side (more likely on the server-side ETR) decides not to 1866 send a Map-Request. For example, if the server-side ETR does not 1867 send Map-Requests, it gleans RLOCs from the client-side ITR, 1868 giving the client-side ITR responsibility for bidirectional RLOC 1869 reachability and preferability. Server-side ETR gleaning of the 1870 client-side ITR RLOC is done by caching the inner header source 1871 EID and the outer header source RLOC of received packets. The 1872 client-side ITR controls how traffic is returned and can alternate 1873 using an outer header source RLOC, which then can be added to the 1874 list the server-side ETR uses to return traffic. Since no 1875 Priority or Weights are provided using this method, the server- 1876 side ETR MUST assume each client-side ITR RLOC uses the same best 1877 Priority with a Weight of zero. In addition, since EID-prefix 1878 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1879 on tunnel routers can grow to be very large. 1881 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1882 received encapsulated packet, is only stored and used for a few 1883 seconds, pending verification. Verification is performed by 1884 sending a Map-Request to the source EID (the inner header IP 1885 source address) of the received encapsulated packet. A reply to 1886 this "verifying Map-Request" is used to fully populate the map- 1887 cache entry for the "gleaned" EID and is stored and used for the 1888 time indicated from the TTL field of a received Map-Reply. When a 1889 verified map-cache entry is stored, data gleaning no longer occurs 1890 for subsequent packets which have a source EID that matches the 1891 EID-prefix of the verified entry. 1893 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1894 reachable when the R-bit for the locator record is set to 1. When 1895 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1896 RLOC. Neither the information contained in a Map-Reply or that 1897 stored in the mapping database system provides reachability 1898 information for RLOCs. Note that reachability is not part of the 1899 mapping system and is determined using one or more of the Routing 1900 Locator Reachability Algorithms described in the next section. 1902 6.3. Routing Locator Reachability 1904 Several mechanisms for determining RLOC reachability are currently 1905 defined: 1907 1. An ETR may examine the Locator Status Bits in the LISP header of 1908 an encapsulated data packet received from an ITR. If the ETR is 1909 also acting as an ITR and has traffic to return to the original 1910 ITR site, it can use this status information to help select an 1911 RLOC. 1913 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1914 message for an RLOC it is using. This indicates that the RLOC is 1915 likely down. Note, trusting ICMP messages may not be desirable 1916 but neither is ignoring them completely. Implementations are 1917 encouraged to follow current best practices in treating these 1918 conditions. 1920 3. An ITR which participates in the global routing system can 1921 determine that an RLOC is down if no BGP RIB route exists that 1922 matches the RLOC IP address. 1924 4. An ITR may receive an ICMP Port Unreachable message from a 1925 destination host. This occurs if an ITR attempts to use 1926 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1927 non-LISP-capable site. 1929 5. An ITR may receive a Map-Reply from an ETR in response to a 1930 previously sent Map-Request. The RLOC source of the Map-Reply is 1931 likely up since the ETR was able to send the Map-Reply to the 1932 ITR. 1934 6. When an ETR receives an encapsulated packet from an ITR, the 1935 source RLOC from the outer header of the packet is likely up. 1937 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1938 described in this section, namely Echo-Noncing or RLOC-Probing. 1940 When determining Locator up/down reachability by examining the 1941 Locator Status Bits from the LISP encapsulated data packet, an ETR 1942 will receive up to date status from an encapsulating ITR about 1943 reachability for all ETRs at the site. CE-based ITRs at the source 1944 site can determine reachability relative to each other using the site 1945 IGP as follows: 1947 o Under normal circumstances, each ITR will advertise a default 1948 route into the site IGP. 1950 o If an ITR fails or if the upstream link to its PE fails, its 1951 default route will either time-out or be withdrawn. 1953 Each ITR can thus observe the presence or lack of a default route 1954 originated by the others to determine the Locator Status Bits it sets 1955 for them. 1957 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1958 Locator Status Bits in a LISP encapsulated packet are numbered from 0 1959 to n-1 starting with the least significant bit. For example, if an 1960 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1961 value 2), then all ITRs at the site will clear the 3rd least 1962 significant bit (xxxx x0xx) of the Locator Status Bits field for the 1963 packets they encapsulate. 1965 When an ETR decapsulates a packet, it will check for any change in 1966 the Locator Status Bits field. When a bit goes from 1 to 0, the ETR 1967 if acting also as an ITR, will refrain from encapsulating packets to 1968 an RLOC that is indicated as down. It will only resume using that 1969 RLOC if the corresponding Locator Status Bit returns to a value of 1. 1970 Locator Status Bits are associated with a locator-set per EID-prefix. 1971 Therefore, when a locator becomes unreachable, the Locator Status Bit 1972 that corresponds to that locator's position in the list returned by 1973 the last Map-Reply will be set to zero for that particular EID- 1974 prefix. 1976 When ITRs at the site are not deployed in CE routers, the IGP can 1977 still be used to determine the reachability of Locators provided they 1978 are injected into the IGP. This is typically done when a /32 address 1979 is configured on a loopback interface. 1981 When ITRs receive ICMP Network or Host Unreachable messages as a 1982 method to determine unreachability, they will refrain from using 1983 Locators which are described in Locator lists of Map-Replies. 1984 However, using this approach is unreliable because many network 1985 operators turn off generation of ICMP Unreachable messages. 1987 If an ITR does receive an ICMP Network or Host Unreachable message, 1988 it MAY originate its own ICMP Unreachable message destined for the 1989 host that originated the data packet the ITR encapsulated. 1991 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 1992 locator address from a locator-set in a mapping entry matches a 1993 prefix. If it does not find one and BGP is running in the Default 1994 Free Zone (DFZ), it can decide to not use the locator even though the 1995 Locator Status Bits indicate the locator is up. In this case, the 1996 path from the ITR to the ETR that is assigned the locator is not 1997 available. More details are in [LOC-ID-ARCH]. 1999 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 2000 Reply is returned, reachability of the Locator has been determined. 2001 Obviously, sending such probes increases the number of control 2002 messages originated by tunnel routers for active flows, so Locators 2003 are assumed to be reachable when they are advertised. 2005 This assumption does create a dependency: Locator unreachability is 2006 detected by the receipt of ICMP Host Unreachable messages. When an 2007 Locator has been determined to be unreachable, it is not used for 2008 active traffic; this is the same as if it were listed in a Map-Reply 2009 with priority 255. 2011 The ITR can test the reachability of the unreachable Locator by 2012 sending periodic Requests. Both Requests and Replies MUST be rate- 2013 limited. Locator reachability testing is never done with data 2014 packets since that increases the risk of packet loss for end-to-end 2015 sessions. 2017 When an ETR decapsulates a packet, it knows that it is reachable from 2018 the encapsulating ITR because that is how the packet arrived. In 2019 most cases, the ETR can also reach the ITR but cannot assume this to 2020 be true due to the possibility of path asymmetry. In the presence of 2021 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 2022 use the lack of return traffic as an indication that the ETR is 2023 unreachable. Instead, it MUST use an alternate mechanisms to 2024 determine reachability. 2026 6.3.1. Echo Nonce Algorithm 2028 When data flows bidirectionally between locators from different 2029 sites, a data-plane mechanism called "nonce echoing" can be used to 2030 determine reachability between an ITR and ETR. When an ITR wants to 2031 solicit a nonce echo, it sets the N and E bits and places a 24-bit 2032 nonce [RFC4086] in the LISP header of the next encapsulated data 2033 packet. 2035 When this packet is received by the ETR, the encapsulated packet is 2036 forwarded as normal. When the ETR next sends a data packet to the 2037 ITR, it includes the nonce received earlier with the N bit set and E 2038 bit cleared. The ITR sees this "echoed nonce" and knows the path to 2039 and from the ETR is up. 2041 The ITR will set the E-bit and N-bit for every packet it sends while 2042 in echo-nonce-request state. The time the ITR waits to process the 2043 echoed nonce before it determines the path is unreachable is variable 2044 and a choice left for the implementation. 2046 If the ITR is receiving packets from the ETR but does not see the 2047 nonce echoed while being in echo-nonce-request state, then the path 2048 to the ETR is unreachable. This decision may be overridden by other 2049 locator reachability algorithms. Once the ITR determines the path to 2050 the ETR is down it can switch to another locator for that EID-prefix. 2052 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 2053 be implementing both ITR and ETR functionality for the echo nonce 2054 mechanism to operate. 2056 The ITR and ETR may both go into echo-nonce-request state at the same 2057 time. The number of packets sent or the time during which echo nonce 2058 requests are sent is an implementation specific setting. However, 2059 when an ITR is in echo-nonce-request state, it can echo the ETR's 2060 nonce in the next set of packets that it encapsulates and then 2061 subsequently, continue sending echo-nonce-request packets. 2063 This mechanism does not completely solve the forward path 2064 reachability problem as traffic may be unidirectional. That is, the 2065 ETR receiving traffic at a site may not be the same device as an ITR 2066 which transmits traffic from that site or the site to site traffic is 2067 unidirectional so there is no ITR returning traffic. 2069 The echo-nonce algorithm is bilateral. That is, if one side sets the 2070 E-bit and the other side is not enabled for echo-noncing, then the 2071 echoing of the nonce does not occur and the requesting side may 2072 regard the locator unreachable erroneously. An ITR SHOULD only set 2073 the E-bit in a encapsulated data packet when it knows the ETR is 2074 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 2075 Reply message. 2077 Note that other locator reachability mechanisms are being researched 2078 and can be used to compliment or even override the Echo Nonce 2079 Algorithm. See next section for an example of control-plane probing. 2081 6.3.2. RLOC Probing Algorithm 2083 RLOC Probing is a method that an ITR or PITR can use to determine the 2084 reachability status of one or more locators that it has cached in a 2085 map-cache entry. The probe-bit of the Map-Request and Map-Reply 2086 messages are used for RLOC Probing. 2088 RLOC probing is done in the control-plane on a timer basis where an 2089 ITR or PITR will originate a Map-Request destined to a locator 2090 address from one of its own locator addresses. A Map-Request used as 2091 an RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on 2092 the ALT like one would when soliciting mapping data. The EID record 2093 encoded in the Map-Request is the EID-prefix of the map-cache entry 2094 cached by the ITR or PITR. The ITR may include a mapping data record 2095 for its own database mapping information which contains the local 2096 EID-prefixes and RLOCs for its site. 2098 When an ETR receives a Map-Request message with the probe-bit set, it 2099 returns a Map-Reply with the probe-bit set. The source address of 2100 the Map-Reply is set according to the procedure described in 2101 Section 6.1.5. The Map-Reply SHOULD contain mapping data for the 2102 EID-prefix contained in the Map-Request. This provides the 2103 opportunity for the ITR or PITR, which sent the RLOC-probe to get 2104 mapping updates if there were changes to the ETR's database mapping 2105 entries. 2107 There are advantages and disadvantages of RLOC Probing. The greatest 2108 benefit of RLOC Probing is that it can handle many failure scenarios 2109 allowing the ITR to determine when the path to a specific locator is 2110 reachable or has become unreachable, thus providing a robust 2111 mechanism for switching to using another locator from the cached 2112 locator. RLOC Probing can also provide rough RTT estimates between a 2113 pair of locators which can be useful for network management purposes 2114 as well as for selecting low delay paths. The major disadvantage of 2115 RLOC Probing is in the number of control messages required and the 2116 amount of bandwidth used to obtain those benefits, especially if the 2117 requirement for failure detection times are very small. 2119 Continued research and testing will attempt to characterize the 2120 tradeoffs of failure detection times versus message overhead. 2122 6.4. EID Reachability within a LISP Site 2124 A site may be multihomed using two or more ETRs. The hosts and 2125 infrastructure within a site will be addressed using one or more EID 2126 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2127 mapping system. One possible failure mode is for an ETR to lose 2128 reachability to one or more of the EID prefixes within its own site. 2129 When this occurs when the ETR sends Map-Replies, it can clear the 2130 R-bit associated with its own locator. And when the ETR is also an 2131 ITR, it can clear its locator-status-bit in the encapsulation data 2132 header. 2134 It is recognized there are no simple solutions to the site 2135 partitioning problem because it is hard to know which part of the 2136 EID-prefix range is partitioned. And which locators can reach any 2137 sub-ranges of the EID-prefixes. This problem is under investigation 2138 with the expectation that experiments will tell us more. Note, this 2139 is not a new problem introduced by the LISP architecture. The 2140 problem exists today when a multi-homed site uses BGP to advertise 2141 its reachability upstream. 2143 6.5. Routing Locator Hashing 2145 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2146 a requesting ITR, the locator-set for the EID-prefix may contain 2147 different priority values for each locator address. When more than 2148 one best priority locator exists, the ITR can decide how to load 2149 share traffic against the corresponding locators. 2151 The following hash algorithm may be used by an ITR to select a 2152 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2154 1. Either a source and destination address hash can be used or the 2155 traditional 5-tuple hash which includes the source and 2156 destination addresses, source and destination TCP, UDP, or SCTP 2157 port numbers and the IP protocol number field or IPv6 next- 2158 protocol fields of a packet a host originates from within a LISP 2159 site. When a packet is not a TCP, UDP, or SCTP packet, the 2160 source and destination addresses only from the header are used to 2161 compute the hash. 2163 2. Take the hash value and divide it by the number of locators 2164 stored in the locator-set for the EID-to-RLOC mapping. 2166 3. The remainder will yield a value of 0 to "number of locators 2167 minus 1". Use the remainder to select the locator in the 2168 locator-set. 2170 Note that when a packet is LISP encapsulated, the source port number 2171 in the outer UDP header needs to be set. Selecting a hashed value 2172 allows core routers which are attached to Link Aggregation Groups 2173 (LAGs) to load-split the encapsulated packets across member links of 2174 such LAGs. Otherwise, core routers would see a single flow, since 2175 packets have a source address of the ITR, for packets which are 2176 originated by different EIDs at the source site. A suggested setting 2177 for the source port number computed by an ITR is a 5-tuple hash 2178 function on the inner header, as described above. 2180 Many core router implementations use a 5-tuple hash to decide how to 2181 balance packet load across members of a LAG. The 5-tuple hash 2182 includes the source and destination addresses of the packet and the 2183 source and destination ports when the protocol number in the packet 2184 is TCP or UDP. For this reason, UDP encoding is used for LISP 2185 encapsulation. 2187 6.6. Changing the Contents of EID-to-RLOC Mappings 2189 Since the LISP architecture uses a caching scheme to retrieve and 2190 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2191 date mapping is to re-request the mapping. However, the ITRs do not 2192 know when the mappings change and the ETRs do not keep track of which 2193 ITRs requested its mappings. For scalability reasons, we want to 2194 maintain this approach but need to provide a way for ETRs change 2195 their mappings and inform the sites that are currently communicating 2196 with the ETR site using such mappings. 2198 When adding a new locator record in lexicographic order to the end of 2199 a locator-set, it is easy to update mappings. We assume new mappings 2200 will maintain the same locator ordering as the old mapping but just 2201 have new locators appended to the end of the list. So some ITRs can 2202 have a new mapping while other ITRs have only an old mapping that is 2203 used until they time out. When an ITR has only an old mapping but 2204 detects bits set in the loc-status-bits that correspond to locators 2205 beyond the list it has cached, it simply ignores them. However, this 2206 can only happen for locator addresses that are lexicographically 2207 greater than the locator addresses in the existing locator-set. 2209 When a locator record is inserted in the middle of a locator-set, to 2210 maintain lexicographic order, the SMR procedure in Section 6.6.2 is 2211 used to inform ITRs and PITRs of the new locator-status-bit mappings. 2213 When a locator record is removed from a locator-set, ITRs that have 2214 the mapping cached will not use the removed locator because the xTRs 2215 will set the loc-status-bit to 0. So even if the locator is in the 2216 list, it will not be used. For new mapping requests, the xTRs can 2217 set the locator AFI to 0 (indicating an unspecified address), as well 2218 as setting the corresponding loc-status-bit to 0. This forces ITRs 2219 with old or new mappings to avoid using the removed locator. 2221 If many changes occur to a mapping over a long period of time, one 2222 will find empty record slots in the middle of the locator-set and new 2223 records appended to the locator-set. At some point, it would be 2224 useful to compact the locator-set so the loc-status-bit settings can 2225 be efficiently packed. 2227 We propose here three approaches for locator-set compaction, one 2228 operational and two protocol mechanisms. The operational approach 2229 uses a clock sweep method. The protocol approaches use the concept 2230 of Solicit-Map-Requests and Map-Versioning. 2232 6.6.1. Clock Sweep 2234 The clock sweep approach uses planning in advance and the use of 2235 count-down TTLs to time out mappings that have already been cached. 2236 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2237 there is a 24 hour window to time out old mappings. The following 2238 clock sweep procedure is used: 2240 1. 24 hours before a mapping change is to take effect, a network 2241 administrator configures the ETRs at a site to start the clock 2242 sweep window. 2244 2. During the clock sweep window, ETRs continue to send Map-Reply 2245 messages with the current (unchanged) mapping records. The TTL 2246 for these mappings is set to 1 hour. 2248 3. 24 hours later, all previous cache entries will have timed out, 2249 and any active cache entries will time out within 1 hour. During 2250 this 1 hour window the ETRs continue to send Map-Reply messages 2251 with the current (unchanged) mapping records with the TTL set to 2252 1 minute. 2254 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2255 messages with the new (changed) mapping records. So any active 2256 caches can get the new mapping contents right away if not cached, 2257 or in 1 minute if they had the mapping cached. The new mappings 2258 are cached with a time to live equal to the TTL in the Map-Reply. 2260 6.6.2. Solicit-Map-Request (SMR) 2262 Soliciting a Map-Request is a selective way for ETRs, at the site 2263 where mappings change, to control the rate they receive requests for 2264 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2265 the mappings they have cached. 2267 Since the ETRs don't keep track of remote ITRs that have cached their 2268 mappings, they do not know which ITRs need to have their mappings 2269 updated. As a result, an ETR will solicit Map-Requests (called an 2270 SMR message) from those sites to which it has been sending 2271 encapsulated data to for the last minute. In particular, an ETR will 2272 send an SMR an ITR to which it has recently sent encapsulated data. 2274 An SMR message is simply a bit set in a Map-Request message. An ITR 2275 or PITR will send a Map-Request when they receive an SMR message. 2276 Both the SMR sender and the Map-Request responder MUST rate-limited 2277 these messages. Rate-limiting can be implemented as a global rate- 2278 limiter or one rate-limiter per SMR destination. 2280 The following procedure shows how a SMR exchange occurs when a site 2281 is doing locator-set compaction for an EID-to-RLOC mapping: 2283 1. When the database mappings in an ETR change, the ETRs at the site 2284 begin to send Map-Requests with the SMR bit set for each locator 2285 in each map-cache entry the ETR caches. 2287 2. A remote ITR which receives the SMR message will schedule sending 2288 a Map-Request message to the source locator address of the SMR 2289 message or to the mapping database system. A newly allocated 2290 random nonce is selected and the EID-prefix used is the one 2291 copied from the SMR message. If the source locator is the only 2292 locator in the cached locator-set, the remote ITR SHOULD send a 2293 Map-Request to the database mapping system just in case the 2294 single locator has changed and may no longer be reachable to 2295 accept the Map-Request. 2297 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2298 Map-Reply while continuing to use the cached mapping. When Map 2299 Versioning is used, described in Section 6.6.3, an SMR sender can 2300 detect if an ITR is using the most up to date database mapping. 2302 4. The ETRs at the site with the changed mapping will reply to the 2303 Map-Request with a Map-Reply message that has a nonce from the 2304 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2305 limited. This is important to avoid Map-Reply implosion. 2307 5. The ETRs, at the site with the changed mapping, record the fact 2308 that the site that sent the Map-Request has received the new 2309 mapping data in the mapping cache entry for the remote site so 2310 the loc-status-bits are reflective of the new mapping for packets 2311 going to the remote site. The ETR then stops sending SMR 2312 messages. 2314 Experimentation is in progress to determine the appropriate rate- 2315 limit parameters. 2317 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2318 To avoid map-cache entry corruption by a third-party, a sender of an 2319 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2320 based Map-Request and the source is not in the locator-set for the 2321 stored map-cache entry, then the responding Map-Request MUST be sent 2322 with an EID destination to the mapping database system. Since the 2323 mapping database system is more secure to reach an authoritative ETR, 2324 it will deliver the Map-Request to the authoritative source of the 2325 mapping data. 2327 When an ITR receives an SMR-based Map-Request for which it does not 2328 have a cached mapping for the EID in the SMR message, it MAY not send 2329 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2330 SMR messages to all locators in the locator-set it has stored in its 2331 map-cache but the remote ITRs that receive the SMR may not be sending 2332 packets to the site. There is no point in updating the ITRs until 2333 they need to send, in which case, they will send Map-Requests to 2334 obtain a map-cache entry. 2336 6.6.3. Database Map Versioning 2338 When there is unidirectional packet flow between an ITR and ETR, and 2339 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2340 ITR so encapsulation can stop to a removed locator and start to a new 2341 locator in the locator-set. 2343 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2344 number. This is known as the Destination Map-Version Number. ITRs 2345 include the Destination Map-Version Number in packets they 2346 encapsulate to the site. When an ETR decapsulates a packet and 2347 detects the Destination Map-Version Number is less than the current 2348 version for its mapping, the SMR procedure described in Section 6.6.2 2349 occurs. 2351 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2352 Version number. This is known as the Source Map-Version Number. 2353 When an ETR decapsulates a packet and detects the Source Map-Version 2354 Number is greater than the last Map-Version Number sent in a Map- 2355 Reply from the ITR's site, the ETR will send a Map-Request to one of 2356 the ETRs for the source site. 2358 A Map-Version Number is used as a sequence number per EID-prefix. So 2359 values that are greater, are considered to be more recent. A value 2360 of 0 for the Source Map-Version Number or the Destination Map-Version 2361 Number conveys no versioning information and an ITR does no 2362 comparison with previously received Map-Version Numbers. 2364 A Map-Version Number can be included in Map-Register messages as 2365 well. This is a good way for the Map-Server can assure that all ETRs 2366 for a site registering to it will be Map-Version number synchronized. 2368 See [VERSIONING] for a more detailed analysis and description of 2369 Database Map Versioning. 2371 7. Router Performance Considerations 2373 LISP is designed to be very hardware-based forwarding friendly. A 2374 few implementation techniques can be used to incrementally implement 2375 LISP: 2377 o When a tunnel encapsulated packet is received by an ETR, the outer 2378 destination address may not be the address of the router. This 2379 makes it challenging for the control plane to get packets from the 2380 hardware. This may be mitigated by creating special FIB entries 2381 for the EID-prefixes of EIDs served by the ETR (those for which 2382 the router provides an RLOC translation). These FIB entries are 2383 marked with a flag indicating that control plane processing should 2384 be performed. The forwarding logic of testing for particular IP 2385 protocol number value is not necessary. There are a few proven 2386 cases where no changes to existing deployed hardware were needed 2387 to support the LISP data-plane. 2389 o On an ITR, prepending a new IP header consists of adding more 2390 octets to a MAC rewrite string and prepending the string as part 2391 of the outgoing encapsulation procedure. Routers that support GRE 2392 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2393 support this action. 2395 o A packet's source address or interface the packet was received on 2396 can be used to select a VRF (Virtual Routing/Forwarding). The 2397 VRF's routing table can be used to find EID-to-RLOC mappings. 2399 For performance issues related to map-cache management, see section 2400 Section 12. 2402 8. Deployment Scenarios 2404 This section will explore how and where ITRs and ETRs can be deployed 2405 and will discuss the pros and cons of each deployment scenario. For 2406 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2408 There are two basic deployment trade-offs to consider: centralized 2409 versus distributed caches and flat, recursive, or re-encapsulating 2410 tunneling. When deciding on centralized versus distributed caching, 2411 the following issues should be considered: 2413 o Are the tunnel routers spread out so that the caches are spread 2414 across all the memories of each router? A centralized cache is 2415 when an ITR keeps a cache for all the EIDs it is encapsulating to. 2416 The packet takes a direct path to the destination locator. A 2417 distributed cache is when an ITR needs help from other re- 2418 encapsulating routers because it does not store all the cache 2419 entries for the EIDs is it encapsulating to. So the packet takes 2420 a path through re-encapsulating routers that have a different set 2421 of cache entries. 2423 o Should management "touch points" be minimized by choosing few 2424 tunnel routers, just enough for redundancy? 2426 o In general, using more ITRs doesn't increase management load, 2427 since caches are built and stored dynamically. On the other hand, 2428 more ETRs does require more management since EID-prefix-to-RLOC 2429 mappings need to be explicitly configured. 2431 When deciding on flat, recursive, or re-encapsulation tunneling, the 2432 following issues should be considered: 2434 o Flat tunneling implements a single tunnel between source site and 2435 destination site. This generally offers better paths between 2436 sources and destinations with a single tunnel path. 2438 o Recursive tunneling is when tunneled traffic is again further 2439 encapsulated in another tunnel, either to implement VPNs or to 2440 perform Traffic Engineering. When doing VPN-based tunneling, the 2441 site has some control since the site is prepending a new tunnel 2442 header. In the case of TE-based tunneling, the site may have 2443 control if it is prepending a new tunnel header, but if the site's 2444 ISP is doing the TE, then the site has no control. Recursive 2445 tunneling generally will result in suboptimal paths but at the 2446 benefit of steering traffic to resource available parts of the 2447 network. 2449 o The technique of re-encapsulation ensures that packets only 2450 require one tunnel header. So if a packet needs to be rerouted, 2451 it is first decapsulated by the ETR and then re-encapsulated with 2452 a new tunnel header using a new RLOC. 2454 The next sub-sections will survey where tunnel routers can reside in 2455 the network. 2457 8.1. First-hop/Last-hop Tunnel Routers 2459 By locating tunnel routers close to hosts, the EID-prefix set is at 2460 the granularity of an IP subnet. So at the expense of more EID- 2461 prefix-to-RLOC sets for the site, the caches in each tunnel router 2462 can remain relatively small. But caches always depend on the number 2463 of non-aggregated EID destination flows active through these tunnel 2464 routers. 2466 With more tunnel routers doing encapsulation, the increase in control 2467 traffic grows as well: since the EID-granularity is greater, more 2468 Map-Requests and Map-Replies are traveling between more routers. 2470 The advantage of placing the caches and databases at these stub 2471 routers is that the products deployed in this part of the network 2472 have better price-memory ratios then their core router counterparts. 2473 Memory is typically less expensive in these devices and fewer routes 2474 are stored (only IGP routes). These devices tend to have excess 2475 capacity, both for forwarding and routing state. 2477 LISP functionality can also be deployed in edge switches. These 2478 devices generally have layer-2 ports facing hosts and layer-3 ports 2479 facing the Internet. Spare capacity is also often available in these 2480 devices as well. 2482 8.2. Border/Edge Tunnel Routers 2484 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2485 space associated with a site to be reachable via a small set of RLOCs 2486 assigned to the CE routers for that site. This is the default 2487 behavior envisioned in the rest of this specification. 2489 This offers the opposite benefit of the first-hop/last-hop tunnel 2490 router scenario: the number of mapping entries and network management 2491 touch points are reduced, allowing better scaling. 2493 One disadvantage is that less of the network's resources are used to 2494 reach host endpoints thereby centralizing the point-of-failure domain 2495 and creating network choke points at the CE router. 2497 Note that more than one CE router at a site can be configured with 2498 the same IP address. In this case an RLOC is an anycast address. 2499 This allows resilience between the CE routers. That is, if a CE 2500 router fails, traffic is automatically routed to the other routers 2501 using the same anycast address. However, this comes with the 2502 disadvantage where the site cannot control the entrance point when 2503 the anycast route is advertised out from all border routers. Another 2504 disadvantage of using anycast locators is the limited advertisement 2505 scope of /32 (or /128 for IPv6) routes. 2507 8.3. ISP Provider-Edge (PE) Tunnel Routers 2509 Use of ISP PE routers as tunnel endpoint routers is not the typical 2510 deployment scenario envisioned in the specification. This section 2511 attempts to capture some of reasoning behind this preference of 2512 implementing LISP on CE routers. 2514 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2515 than a site, control over the location of the egress tunnel 2516 endpoints. That is, the ISP can decide if the tunnel endpoints are 2517 in the destination site (in either CE routers or last-hop routers 2518 within a site) or at other PE edges. The advantage of this case is 2519 that two tunnel headers can be avoided. By having the PE be the 2520 first router on the path to encapsulate, it can choose a TE path 2521 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2522 the destination end site. 2524 An obvious disadvantage is that the end site has no control over 2525 where its packets flow or the RLOCs used. Other disadvantages 2526 include the difficulty in synchronizing path liveness updates between 2527 CE and PE routers. 2529 As mentioned in earlier sections a combination of these scenarios is 2530 possible at the expense of extra packet header overhead, if both site 2531 and provider want control, then recursive or re-encapsulating tunnels 2532 are used. 2534 8.4. LISP Functionality with Conventional NATs 2536 LISP routers can be deployed behind Network Address Translator (NAT) 2537 devices to provide the same set of packet services hosts have today 2538 when they are addressed out of private address space. 2540 It is important to note that a locator address in any LISP control 2541 message MUST be a globally routable address and therefore SHOULD NOT 2542 contain [RFC1918] addresses. If a LISP router is configured with 2543 private addresses, they MUST be used only in the outer IP header so 2544 the NAT device can translate properly. Otherwise, EID addresses MUST 2545 be translated before encapsulation is performed. Both NAT 2546 translation and LISP encapsulation functions could be co-located in 2547 the same device. 2549 More details on LISP address translation can be found in [INTERWORK]. 2551 8.5. Packets Egressing a LISP Site 2553 When a LISP site is using two ITRs for redundancy, the failure of one 2554 ITR will likely shift outbound traffic to the second. This second 2555 ITR's cache may not not be populated with the same EID-to-RLOC 2556 mapping entries as the first. If this second ITR does not have these 2557 mappings, traffic will be dropped while the mappings are retrieved 2558 from the mapping system. The retrieval of these messages may 2559 increase the load of requests being sent into the mapping system. 2560 Deployment and experimentation will determine whether this issue 2561 requires more attention. 2563 9. Traceroute Considerations 2565 When a source host in a LISP site initiates a traceroute to a 2566 destination host in another LISP site, it is highly desirable for it 2567 to see the entire path. Since packets are encapsulated from ITR to 2568 ETR, the hop across the tunnel could be viewed as a single hop. 2569 However, LISP traceroute will provide the entire path so the user can 2570 see 3 distinct segments of the path from a source LISP host to a 2571 destination LISP host: 2573 Segment 1 (in source LISP site based on EIDs): 2575 source-host ---> first-hop ... next-hop ---> ITR 2577 Segment 2 (in the core network based on RLOCs): 2579 ITR ---> next-hop ... next-hop ---> ETR 2581 Segment 3 (in the destination LISP site based on EIDs): 2583 ETR ---> next-hop ... last-hop ---> destination-host 2585 For segment 1 of the path, ICMP Time Exceeded messages are returned 2586 in the normal manner as they are today. The ITR performs a TTL 2587 decrement and test for 0 before encapsulating. So the ITR hop is 2588 seen by the traceroute source has an EID address (the address of 2589 site-facing interface). 2591 For segment 2 of the path, ICMP Time Exceeded messages are returned 2592 to the ITR because the TTL decrement to 0 is done on the outer 2593 header, so the destination of the ICMP messages are to the ITR RLOC 2594 address, the source RLOC address of the encapsulated traceroute 2595 packet. The ITR looks inside of the ICMP payload to inspect the 2596 traceroute source so it can return the ICMP message to the address of 2597 the traceroute client as well as retaining the core router IP address 2598 in the ICMP message. This is so the traceroute client can display 2599 the core router address (the RLOC address) in the traceroute output. 2600 The ETR returns its RLOC address and responds to the TTL decrement to 2601 0 like the previous core routers did. 2603 For segment 3, the next-hop router downstream from the ETR will be 2604 decrementing the TTL for the packet that was encapsulated, sent into 2605 the core, decapsulated by the ETR, and forwarded because it isn't the 2606 final destination. If the TTL is decremented to 0, any router on the 2607 path to the destination of the traceroute, including the next-hop 2608 router or destination, will send an ICMP Time Exceeded message to the 2609 source EID of the traceroute client. The ICMP message will be 2610 encapsulated by the local ITR and sent back to the ETR in the 2611 originated traceroute source site, where the packet will be delivered 2612 to the host. 2614 9.1. IPv6 Traceroute 2616 IPv6 traceroute follows the procedure described above since the 2617 entire traceroute data packet is included in ICMP Time Exceeded 2618 message payload. Therefore, only the ITR needs to pay special 2619 attention for forwarding ICMP messages back to the traceroute source. 2621 9.2. IPv4 Traceroute 2623 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2624 ICMP Time Exceeded messages only include the invoking IP header and 8 2625 octets that follow the IP header. Therefore, when a core router 2626 sends an IPv4 Time Exceeded message to an ITR, all the ITR has in the 2627 ICMP payload is the encapsulated header it prepended followed by a 2628 UDP header. The original invoking IP header, and therefore the 2629 identity of the traceroute source is lost. 2631 The solution we propose to solve this problem is to cache traceroute 2632 IPv4 headers in the ITR and to match them up with corresponding IPv4 2633 Time Exceeded messages received from core routers and the ETR. The 2634 ITR will use a circular buffer for caching the IPv4 and UDP headers 2635 of traceroute packets. It will select a 16-bit number as a key to 2636 find them later when the IPv4 Time Exceeded messages are received. 2637 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2638 16-bit number as the UDP source port in the encapsulating header. 2639 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2640 header of the encapsulating header is present in the ICMP payload 2641 thereby allowing the ITR to find the cached headers for the 2642 traceroute source. The ITR puts the cached headers in the payload 2643 and sends the ICMP Time Exceeded message to the traceroute source 2644 retaining the source address of the original ICMP Time Exceeded 2645 message (a core router or the ETR of the site of the traceroute 2646 destination). 2648 The signature of a traceroute packet comes in two forms. The first 2649 form is encoded as a UDP message where the destination port is 2650 inspected for a range of values. The second form is encoded as an 2651 ICMP message where the IP identification field is inspected for a 2652 well-known value. 2654 9.3. Traceroute using Mixed Locators 2656 When either an IPv4 traceroute or IPv6 traceroute is originated and 2657 the ITR encapsulates it in the other address family header, you 2658 cannot get all 3 segments of the traceroute. Segment 2 of the 2659 traceroute can not be conveyed to the traceroute source since it is 2660 expecting addresses from intermediate hops in the same address format 2661 for the type of traceroute it originated. Therefore, in this case, 2662 segment 2 will make the tunnel look like one hop. All the ITR has to 2663 do to make this work is to not copy the inner TTL to the outer, 2664 encapsulating header's TTL when a traceroute packet is encapsulated 2665 using an RLOC from a different address family. This will cause no 2666 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2668 10. Mobility Considerations 2670 There are several kinds of mobility of which only some might be of 2671 concern to LISP. Essentially they are as follows. 2673 10.1. Site Mobility 2675 A site wishes to change its attachment points to the Internet, and 2676 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2677 providers. Changes in EID-RLOC mappings for sites are expected to be 2678 handled by configuration, outside of the LISP protocol. 2680 10.2. Slow Endpoint Mobility 2682 An individual endpoint wishes to move, but is not concerned about 2683 maintaining session continuity. Renumbering is involved. LISP can 2684 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2685 decoupling the address space used by a site from the address spaces 2686 used by its ISPs. [RFC4984] 2688 10.3. Fast Endpoint Mobility 2690 Fast endpoint mobility occurs when an endpoint moves relatively 2691 rapidly, changing its IP layer network attachment point. Maintenance 2692 of session continuity is a goal. This is where the Mobile IPv4 2693 [RFC5944] and Mobile IPv6 [RFC6275] [RFC4866] mechanisms are used, 2694 and primarily where interactions with LISP need to be explored. 2696 The problem is that as an endpoint moves, it may require changes to 2697 the mapping between its EID and a set of RLOCs for its new network 2698 location. When this is added to the overhead of mobile IP binding 2699 updates, some packets might be delayed or dropped. 2701 In IPv4 mobility, when an endpoint is away from home, packets to it 2702 are encapsulated and forwarded via a home agent which resides in the 2703 home area the endpoint's address belongs to. The home agent will 2704 encapsulate and forward packets either directly to the endpoint or to 2705 a foreign agent which resides where the endpoint has moved to. 2706 Packets from the endpoint may be sent directly to the correspondent 2707 node, may be sent via the foreign agent, or may be reverse-tunneled 2708 back to the home agent for delivery to the mobile node. As the 2709 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2710 mappings are required for communication between the mobile node and 2711 the home agent, whether via foreign agent or not. As a mobile 2712 endpoint changes networks, up to three LISP mapping changes may be 2713 required: 2715 o The mobile node moves from an old location to a new visited 2716 network location and notifies its home agent that it has done so. 2717 The Mobile IPv4 control packets the mobile node sends pass through 2718 one of the new visited network's ITRs, which needs an EID-RLOC 2719 mapping for the home agent. 2721 o The home agent might not have the EID-RLOC mappings for the mobile 2722 node's "care-of" address or its foreign agent in the new visited 2723 network, in which case it will need to acquire them. 2725 o When packets are sent directly to the correspondent node, it may 2726 be that no traffic has been sent from the new visited network to 2727 the correspondent node's network, and the new visited network's 2728 ITR will need to obtain an EID-RLOC mapping for the correspondent 2729 node's site. 2731 In addition, if the IPv4 endpoint is sending packets from the new 2732 visited network using its original EID, then LISP will need to 2733 perform a route-returnability check on the new EID-RLOC mapping for 2734 that EID. 2736 In IPv6 mobility, packets can flow directly between the mobile node 2737 and the correspondent node in either direction. The mobile node uses 2738 its "care-of" address (EID). In this case, the route-returnability 2739 check would not be needed but one more LISP mapping lookup may be 2740 required instead: 2742 o As above, three mapping changes may be needed for the mobile node 2743 to communicate with its home agent and to send packets to the 2744 correspondent node. 2746 o In addition, another mapping will be needed in the correspondent 2747 node's ITR, in order for the correspondent node to send packets to 2748 the mobile node's "care-of" address (EID) at the new network 2749 location. 2751 When both endpoints are mobile the number of potential mapping 2752 lookups increases accordingly. 2754 As a mobile node moves there are not only mobility state changes in 2755 the mobile node, correspondent node, and home agent, but also state 2756 changes in the ITRs and ETRs for at least some EID-prefixes. 2758 The goal is to support rapid adaptation, with little delay or packet 2759 loss for the entire system. Also IP mobility can be modified to 2760 require fewer mapping changes. In order to increase overall system 2761 performance, there may be a need to reduce the optimization of one 2762 area in order to place fewer demands on another. 2764 In LISP, one possibility is to "glean" information. When a packet 2765 arrives, the ETR could examine the EID-RLOC mapping and use that 2766 mapping for all outgoing traffic to that EID. It can do this after 2767 performing a route-returnability check, to ensure that the new 2768 network location does have a internal route to that endpoint. 2769 However, this does not cover the case where an ITR (the node assigned 2770 the RLOC) at the mobile-node location has been compromised. 2772 Mobile IP packet exchange is designed for an environment in which all 2773 routing information is disseminated before packets can be forwarded. 2774 In order to allow the Internet to grow to support expected future 2775 use, we are moving to an environment where some information may have 2776 to be obtained after packets are in flight. Modifications to IP 2777 mobility should be considered in order to optimize the behavior of 2778 the overall system. Anything which decreases the number of new EID- 2779 RLOC mappings needed when a node moves, or maintains the validity of 2780 an EID-RLOC mapping for a longer time, is useful. 2782 10.4. Fast Network Mobility 2784 In addition to endpoints, a network can be mobile, possibly changing 2785 xTRs. A "network" can be as small as a single router and as large as 2786 a whole site. This is different from site mobility in that it is 2787 fast and possibly short-lived, but different from endpoint mobility 2788 in that a whole prefix is changing RLOCs. However, the mechanisms 2789 are the same and there is no new overhead in LISP. A map request for 2790 any endpoint will return a binding for the entire mobile prefix. 2792 If mobile networks become a more common occurrence, it may be useful 2793 to revisit the design of the mapping service and allow for dynamic 2794 updates of the database. 2796 The issue of interactions between mobility and LISP needs to be 2797 explored further. Specific improvements to the entire system will 2798 depend on the details of mapping mechanisms. Mapping mechanisms 2799 should be evaluated on how well they support session continuity for 2800 mobile nodes. 2802 10.5. LISP Mobile Node Mobility 2804 A mobile device can use the LISP infrastructure to achieve mobility 2805 by implementing the LISP encapsulation and decapsulation functions 2806 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2807 node" can use topologically-independent EID IP addresses that are not 2808 advertised into and do not impose a cost on the global routing 2809 system. These EIDs are maintained at the edges of the mapping system 2810 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2811 only the correspondents of the LISP mobile node. 2813 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2814 more details. 2816 11. Multicast Considerations 2818 A multicast group address, as defined in the original Internet 2819 architecture is an identifier of a grouping of topologically 2820 independent receiver host locations. The address encoding itself 2821 does not determine the location of the receiver(s). The multicast 2822 routing protocol, and the network-based state the protocol creates, 2823 determines where the receivers are located. 2825 In the context of LISP, a multicast group address is both an EID and 2826 a Routing Locator. Therefore, no specific semantic or action needs 2827 to be taken for a destination address, as it would appear in an IP 2828 header. Therefore, a group address that appears in an inner IP 2829 header built by a source host will be used as the destination EID. 2830 The outer IP header (the destination Routing Locator address), 2831 prepended by a LISP router, will use the same group address as the 2832 destination Routing Locator. 2834 Having said that, only the source EID and source Routing Locator 2835 needs to be dealt with. Therefore, an ITR merely needs to put its 2836 own IP address in the source Routing Locator field when prepending 2837 the outer IP header. This source Routing Locator address, like any 2838 other Routing Locator address MUST be globally routable. 2840 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2841 ITR when a received data packet is a multicast data packet or when 2842 processing a source-specific Join (either by IGMPv3 or PIM). But the 2843 source Routing Locator is decided by the multicast routing protocol 2844 in a receiver site. That is, an EID to Routing Locator translation 2845 is done at control-time. 2847 Another approach is to have the ITR not encapsulate a multicast 2848 packet and allow the host built packet to flow into the core even if 2849 the source address is allocated out of the EID namespace. If the 2850 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2851 routers can RPF to the ITR (the Locator address which is injected 2852 into core routing) rather than the host source address (the EID 2853 address which is not injected into core routing). 2855 To avoid any EID-based multicast state in the network core, the first 2856 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2857 and Interworking with non-LISP sites is described in specification 2858 [MLISP]. 2860 12. Security Considerations 2862 It is believed that most of the security mechanisms will be part of 2863 the mapping database service when using control plane procedures for 2864 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2865 as described in this specification, protection is provided against 2866 ETR spoofing by using Return-Routability (see Section 3) mechanisms 2867 evidenced by the use of a 24-bit Nonce field in the LISP 2868 encapsulation header and a 64-bit Nonce field in the LISP control 2869 message. 2871 The nonce, coupled with the ITR accepting only solicited Map-Replies 2872 provides a basic level of security, in many ways similar to the 2873 security experienced in the current Internet routing system. It is 2874 hard for off-path attackers to launch attacks against these LISP 2875 mechanisms, as they do not have the nonce values. Sending a large 2876 number of packets to accidentally find the right nonce value is 2877 possible, but would already by itself be a denial-of-service attack. 2878 On-path attackers can perform far more serious attacks, but on-path 2879 attackers can launch serious attacks in the current Internet as well, 2880 including eavesdropping, blocking or redirecting traffic. See more 2881 discussion on this topic in Section 6.1.5.1. 2883 LISP does not rely on a PKI or a more heavy weight authentication 2884 system. These systems challenge the scalability of LISP which was a 2885 primary design goal. 2887 DoS attack prevention will depend on implementations rate-limiting 2888 Map-Requests and Map-Replies to the control plane as well as rate- 2889 limiting the number of data-triggered Map-Replies. 2891 An incorrectly implemented or malicious ITR might choose to ignore 2892 the priority and weights provided by the ETR in its Map-Reply. This 2893 traffic steering would be limited to the traffic that is sent by this 2894 ITR's site, and no more severe than if the site initiated a bandwidth 2895 DoS attack on (one of) the ETR's ingress links. The ITR's site would 2896 typically gain no benefit from not respecting the weights, and would 2897 likely to receive better service by abiding by them. 2899 To deal with map-cache exhaustion attempts in an ITR/PITR, the 2900 implementation should consider putting a maximum cap on the number of 2901 entries stored with a reserve list for special or frequently accessed 2902 sites. This should be a configuration policy control set by the 2903 network administrator who manages ITRs and PITRs. When overlapping 2904 EID-prefixes occur across multiple map-cache entries, the integrity 2905 of the set must be wholly maintained. So if a more-specific entry 2906 cannot be added due to reaching the maximum cap, then none of the 2907 less specifics should be stored in the map-cache. 2909 Given that the ITR/PITR maintains a cache of EID-to-RLOC mappings, 2910 cache sizing and maintenance is an issue to be kept in mind during 2911 implementation. It is a good idea to have instrumentation in place 2912 to detect thrashing of the cache. Implementation experimentation 2913 will be used to determine which cache management strategies work 2914 best. In general, it is difficult to defend against cache trashing 2915 attacks. It should be noted that an undersized cache in an ITR/PITR 2916 not only causes adverse affect on the site or region they support, 2917 but may also cause increased Map-Request load on the mapping system. 2919 "Piggybacked" mapping data discussed in Section 6.1.3 specifies how 2920 to handle such mappings and includes the possibility for an ETR to 2921 temporarily accept such a mapping before verification when running in 2922 "trusted" environments. In such cases, there is a potential threat 2923 that a fake mapping could be inserted (even if only for a short 2924 period) into a map-cache. As noted in Section 6.1.3, an ETR MUST be 2925 specifically configured to run in such a mode and might usefully only 2926 consider some specific ITRs as also running in that same trusted 2927 environment. 2929 There is a security risk implicit in the fact that ETRs generate the 2930 EID prefix to which they are responding. An ETR can claim a shorter 2931 prefix than it is actually responsible for. Various mechanisms to 2932 ameliorate or resolve this issue will be examined in the future, 2933 [LISP-SEC]. 2935 Spoofing of inner header addresses of LISP encapsulated packets is 2936 possible like with any tunneling mechanism. ITRs MUST verify the 2937 source address of a packet to be an EID that belongs to the site's 2938 EID-prefix range prior to encapsulation. An ETR must only 2939 decapsulate and forward datagrams with an inner header destination 2940 that matches one of its EID-prefix ranges. If, upon receipt and 2941 decapsulation, the destination EID of a datagram does not match one 2942 of the ETR's configured EID-prefixes, the ETR MUST drop the datagram. 2943 If a LISP encapsulated packet arrives at an ETR, it SHOULD compare 2944 the inner header source EID address and the outer header source RLOC 2945 address with the mapping that exists in the mapping database. Then 2946 when spoofing attacks occur, the outer header source RLOC address can 2947 be used to trace back the attack to the source site, using existing 2948 operational tools. 2950 This experimental specification does not address automated key 2951 management (AKM). BCP 107 provides guidance in this area. In 2952 addition, at the time of this writing, substantial work is being 2953 undertaken to improve security of the routing system [KARP], [RPKI], 2954 [BGP-SEC], [LISP-SEC]. Future work on LISP should address BCP-107 as 2955 well as other open security considerations, which may require changes 2956 to this specification. 2958 13. Network Management Considerations 2960 Considerations for Network Management tools exist so the LISP 2961 protocol suite can be operationally managed. The mechanisms can be 2962 found in [LISP-MIB] and [LISP-LIG]. 2964 14. IANA Considerations 2966 This section provides guidance to the Internet Assigned Numbers 2967 Authority (IANA) regarding registration of values related to the LISP 2968 specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. 2970 There are four name spaces in LISP that require registration: 2972 o LISP IANA registry allocations should not be made for purposes 2973 unrelated to LISP routing or transport protocols. 2975 o The following policies are used here with the meanings defined in 2976 BCP 26: "Specification Required", "IETF Review", "Experimental 2977 Use", "First Come First Served". 2979 14.1. LISP ACT and Flag Fields 2981 New ACT values (Section 6.1.4) can be allocated through IETF review 2982 or IESG approval. Four values have already been allocated by this 2983 specification (Section 6.1.4). 2985 In addition, the LISP protocol has a number of flag and reserved 2986 fields, such as the LISP header flags field (Section 5.3). New bits 2987 for flags can be taken into use from these fields through IETF review 2988 or IESG approval, but these need not be managed by IANA. 2990 14.2. LISP Address Type Codes 2992 LISP Address [LCAF] type codes have a range from 0 to 255. New type 2993 codes MUST be allocated consecutively starting at 0. Type Codes 0 - 2994 127 are to be assigned by IETF review or IESG approval. 2996 Type Codes 128 - 255 are available on a First Come First Served 2997 policy. 2999 This registry, initially empty, is constructed for future-use 3000 experimental work of LCAF values. See [LCAF] for details for other 3001 possible unapproved address encodings. The unapproved LCAF encodings 3002 are an area for further study and experimentation. 3004 14.3. LISP UDP Port Numbers 3006 The IANA registry has allocated UDP port numbers 4341 and 4342 for 3007 LISP data-plane and control-plane operation, respectively. 3009 14.4. LISP Key ID Numbers 3011 The following Key ID values are defined by this specification as used 3012 in any packet type that references a Key ID field: 3014 Name Number Defined in 3015 ----------------------------------------------- 3016 None 0 n/a 3017 HMAC-SHA-1-96 1 [RFC2404] 3018 HMAC-SHA-256-128 2 [RFC6234] 3020 15. Known Open Issues and Areas of Future Work 3022 As an experimental specification, this work is, by definition, 3023 incomplete. Specific areas where additional experience and work are 3024 needed include: 3026 o At present, only [ALT] is defined for implementing a database of 3027 EID-to-RLOC mapping information. Additional research on other 3028 mapping database systems is strongly encouraged. 3030 o Failure and recovery of LISP site partitioning (see Section 6.4), 3031 in the presence of redundant configuration (see Section 8.5) needs 3032 further research and experimentation. 3034 o The characteristics of map-cache management under exceptional 3035 conditions, such as denial-of-service attacks are not fully 3036 understood. Further experience is needed to determine whether 3037 current caching methods are practical or in need of further 3038 development. In particular, the performance, scaling and security 3039 characteristics of the map-cache will be discovered as part of 3040 this experiment. Performance metrics to be observed are packet 3041 reordering associated with the LISP data probe and loss of the 3042 first packet in a flow associated with map-caching. The impact of 3043 these upon TCP will be observed. See Section 12 for additional 3044 thoughts and considerations. 3046 o Preliminary work has been done to ensure that sites employing LISP 3047 can interconnect with the rest of the Internet. This work is 3048 documented in [INTERWORK], but further experimentation and 3049 experience is needed. 3051 o At present, no mechanism for automated key management for message 3052 authentication is defined. Addressing automated key management is 3053 necessary before this specification could be developed into a 3054 standards track RFC. See Section 12 for further details regarding 3055 security considerations. 3057 o In order to maintain security and stability, Internet Protocols 3058 typically isolate the control and data planes. Therefore, user 3059 activity cannot cause control plane state to be created or 3060 destroyed. LISP does not maintain this separation. The degree to 3061 which the loss of separation impacts security and stability is a 3062 topic for experimental observation. 3064 o LISP allows for different mapping database systems to be used. 3065 While only one [ALT] is currently well-defined, each mapping 3066 database will likely have some impact on the security of the EID- 3067 to-RLOC mappings. How each mapping database system's security 3068 properties impact on LISP overall is for further study. 3070 o An examination of the implications of LISP on Internet traffic, 3071 applications, routers, and security is needed. This will help to 3072 understand the consequences for network stability, routing 3073 protocol function, routing scalability, migration and backward 3074 compatibility, and implementation scalability (as influenced by 3075 additional protocol components, additional state, and additional 3076 processing for encapsulation, decapsulation, liveness). 3078 Other LISP documents may also include open issues and areas for 3079 future work. 3081 16. References 3083 16.1. Normative References 3085 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 3086 Alternative Topology (LISP-ALT)", 3087 draft-ietf-lisp-alt-09.txt (work in progress). 3089 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 3090 draft-ietf-lisp-ms-12.txt (work in progress). 3092 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 3093 August 1980. 3095 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 3096 September 1981. 3098 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 3099 E. Lear, "Address Allocation for Private Internets", 3100 BCP 5, RFC 1918, February 1996. 3102 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3103 Requirement Levels", BCP 14, RFC 2119, March 1997. 3105 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 3106 ESP and AH", RFC 2404, November 1998. 3108 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3109 (IPv6) Specification", RFC 2460, December 1998. 3111 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 3112 of Explicit Congestion Notification (ECN) to IP", 3113 RFC 3168, September 2001. 3115 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 3116 an On-line Database", RFC 3232, January 2002. 3118 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 3119 Requirements for Security", BCP 106, RFC 4086, June 2005. 3121 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 3122 (CIDR): The Internet Address Assignment and Aggregation 3123 Plan", BCP 122, RFC 4632, August 2006. 3125 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3126 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 3127 May 2008. 3129 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 3130 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 3132 [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", 3133 RFC 5944, November 2010. 3135 [RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 3136 (SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011. 3138 [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support 3139 in IPv6", RFC 6275, July 2011. 3141 [UDP-TUNNELS] 3142 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 3143 Packets", draft-eubanks-chimento-6man-01.txt (work in 3144 progress), October 2010. 3146 [UDP-ZERO] 3147 Fairhurst, G. and M. Westerland, "IPv6 UDP Checksum 3148 Considerations", draft-ietf-6man-udpzero-04.txt (work in 3149 progress), October 2011. 3151 [VERSIONING] 3152 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3153 Versioning", draft-ietf-lisp-map-versioning-05.txt (work 3154 in progress). 3156 16.2. Informative References 3158 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3159 NUMBERS 3160 http://www.iana.org/assignments/address-family-numbers. 3162 [AFI-REGISTRY] 3163 IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3164 NUMBER registry http://www.iana.org/assignments/ 3165 address-family-numbers/ 3166 address-family-numbers.xml#address-family-numbers-1. 3168 [BGP-SEC] Lepinski, M., "An Overview of BGPSEC", 3169 draft-lepinski-bgpsec-overview-00.txt (work in progress), 3170 March 2011. 3172 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 3173 Enhancement to the Internet Architecture", Internet- 3174 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt. 3176 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 3177 Content distribution Overlay Network Service for LISP", 3178 draft-meyer-lisp-cons-04.txt (work in progress). 3180 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 3181 Mappings Multicast Across Cooperating Systems for LISP", 3182 draft-curran-lisp-emacs-00.txt (work in progress). 3184 [INTERWORK] 3185 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 3186 "Interworking LISP with IPv4 and IPv6", 3187 draft-ietf-lisp-interworking-02.txt (work in progress). 3189 [KARP] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 3190 Routing Protocols (KARP)Design Guidelines", 3191 draft-ietf-karp-design-guide-06.txt (work in progress), 3192 October 2011. 3194 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 3195 Address Format", draft-farinacci-lisp-lcaf-06.txt (work in 3196 progress). 3198 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 3199 "Renumbering: Threat or Menace?", Usenix . 3201 [LISP-DEPLOY] 3202 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 3203 "LISP Network Element Deployment Considerations", 3204 draft-ietf-lisp-deployment-02.txt (work in progress). 3206 [LISP-LIG] 3207 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 3208 draft-ietf-lisp-lig-06.txt (work in progress). 3210 [LISP-MAIN] 3211 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 3212 "Locator/ID Separation Protocol (LISP)", 3213 draft-farinacci-lisp-12.txt (work in progress). 3215 [LISP-MIB] 3216 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 3217 draft-ietf-lisp-mib-02.txt (work in progress). 3219 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 3220 Mobility Architecture", draft-meyer-lisp-mn-06.txt (work 3221 in progress). 3223 [LISP-SEC] 3224 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 3226 Bonaventure, "LISP-Security (LISP-SEC)", 3227 draft-ietf-lisp-sec-00.txt (work in progress). 3229 [LOC-ID-ARCH] 3230 Meyer, D. and D. Lewis, "Architectural Implications of 3231 Locator/ID Separation", 3232 draft-meyer-loc-id-implications-02.txt (work in progress). 3234 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 3235 "LISP for Multicast Environments", 3236 draft-ietf-lisp-multicast-10.txt (work in progress). 3238 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 3239 draft-lear-lisp-nerd-08.txt (work in progress). 3241 [OPENLISP] 3242 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 3243 Report", draft-iannone-openlisp-implementation-01.txt 3244 (work in progress). 3246 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 3247 draft-narten-radir-problem-statement-05.txt (work in 3248 progress). 3250 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 3251 STD 13, RFC 1034, November 1987. 3253 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 3254 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 3255 March 2000. 3257 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 3258 via IPv4 Clouds", RFC 3056, February 2001. 3260 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 3261 A., Peterson, J., Sparks, R., Handley, M., and E. 3262 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 3263 June 2002. 3265 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 3266 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 3267 September 2005. 3269 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 3270 Optimization for Mobile IPv6", RFC 4866, May 2007. 3272 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 3273 Workshop on Routing and Addressing", RFC 4984, 3274 September 2007. 3276 [RPKI] Lepinski, M., "An Infrastructure to Support Secure 3277 Internet Routing", draft-ietf-sidr-arch-13.txt (work in 3278 progress), February 2011. 3280 Appendix A. Acknowledgments 3282 An initial thank you goes to Dave Oran for planting the seeds for the 3283 initial ideas for LISP. His consultation continues to provide value 3284 to the LISP authors. 3286 A special and appreciative thank you goes to Noel Chiappa for 3287 providing architectural impetus over the past decades on separation 3288 of location and identity, as well as detailed review of the LISP 3289 architecture and documents, coupled with enthusiasm for making LISP a 3290 practical and incremental transition for the Internet. 3292 The authors would like to gratefully acknowledge many people who have 3293 contributed discussion and ideas to the making of this proposal. 3294 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3295 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3296 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3297 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3298 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3299 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3300 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3301 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3302 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3303 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3304 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3305 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3306 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3307 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3308 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3309 Clarence Filsfils, and Alia Atlas. 3311 This work originated in the Routing Research Group (RRG) of the IRTF. 3312 The individual submission [LISP-MAIN] was converted into this IETF 3313 LISP working group draft. 3315 The LISP working group would like to give a special thanks to Jari 3316 Arkko, the Internet Area AD at the time the set of LISP documents 3317 were being prepared for IESG last call, for his meticulous review and 3318 detail commentary on the 7 working group last call drafts progressing 3319 toward experimental RFCs. 3321 Appendix B. Document Change Log 3323 B.1. Changes to draft-ietf-lisp-20.txt 3325 o Posted January 2012 for resolution to Adrian Farrel's security 3326 comments as well as additions to the end of section 2, Elwyn 3327 Davies Gen-Art comments, and Ralph Droms' IANA and EID definition 3328 comments. 3330 B.2. Changes to draft-ietf-lisp-19.txt 3332 o Posted January 2012 for Stephen Farrell's comment resolution. 3334 B.3. Changes to draft-ietf-lisp-18.txt 3336 o Posted December 2011 after reflecting comments from IANA. 3338 o Create reference to sections 5.4.1 and 5.4.2 about DF bit setting 3339 from section 5.3. 3341 o Inserted two references for Route-Returnability and on-path 3342 attacks in Security Considerations section. 3344 B.4. Changes to draft-ietf-lisp-17.txt 3346 o Posted December 2011 after IETF last call comments. 3348 o Make Map-Notify port assignment be 4342 in both source and 3349 destination ports. This change was agreed on and put in [LISP-MS] 3350 but was not updated in this spec. 3352 B.5. Changes to draft-ietf-lisp-16.txt 3354 o Posted October 2011 after AD review by Jari. 3356 B.6. Changes to draft-ietf-lisp-15.txt 3358 o Posted July 2011. Fixing IDnits errors. 3360 o Change description on how to select a source address for RLOC- 3361 probe Map-Replies to refer to the "EID-to-RLOC Map-Reply Message" 3362 section. 3364 B.7. Changes to draft-ietf-lisp-14.txt 3366 o Post working group last call and pre-IESG last call review. 3368 o Indicate that an ICMP Unreachable message should be sent when a 3369 packet matches a drop-based negative map-cache entry. 3371 o Indicate how a map-cache set of overlapping EID-prefixes must 3372 maintain integrity when the map-cache maximum cap is reached. 3374 o Add Joel's description for the definition of an EID, that the bit 3375 string value can be an RLOC for another device in abstract but the 3376 architecture allows it to be an EID of one device and the same 3377 value as an RLOC for another device. 3379 o In the "Tunnel Encapsulation Details" section, indicate that 4 3380 combinations of encapsulation are supported. 3382 o Add what ETR should do for a Data-Probe when received for a 3383 destination EID outside of its EID-prefix range. This was added 3384 in the Data Probe definition section. 3386 o Added text indicating that more-specific EID-prefixes must not be 3387 removed when less-specific entries stay in the map-cache. This is 3388 to preserve the integrity of the EID-prefix set. 3390 o Add clarifying text in the Security Considerations section about 3391 how an ETR must not decapsulate and forward a packet that is not 3392 for its configured EID-prefix range. 3394 B.8. Changes to draft-ietf-lisp-13.txt 3396 o Posted June 2011 to complete working group last call. 3398 o Tracker item 87. Put Yakov suggested wording in the EID-prefix 3399 definition section to reference [INTERWORK] and [LISP-DEPLOY] 3400 about discussion on transition and access mechanisms. 3402 o Change "ITRs" to "ETRs" in the Locator Status Bit definition 3403 section and data packet description section per Damien's comment. 3405 o Remove the normative reference to [LISP-SEC] when describing the 3406 S-bit in the ECM and Map-Reply headers. 3408 o Tracker item 54. Added text from John Scudder in the "Packets 3409 Egressing a LISP Site" section. 3411 o Add sentence to the "Reencapsulating Tunnel" definition about how 3412 reencapsulation loops can occur when not coordinating among 3413 multiple mapping database systems. 3415 o Remove "In theory" from a sentence in the Security Considerations 3416 section. 3418 o Remove Security Area Statement title and reword section with 3419 Eliot's provided text. The text was agreed upon by LISP-WG chairs 3420 and Security ADs. 3422 o Remove word "potential" from the over-claiming paragraph of the 3423 Security Considerations section per Stephen's request. 3425 o Wordsmithing and other editorial comments from Alia. 3427 B.9. Changes to draft-ietf-lisp-12.txt 3429 o Posted April 2011. 3431 o Tracker item 87. Provided rewording how an EID-prefix can be 3432 reused in the definition section of "EID-prefix". 3434 o Tracker item 95. Change "eliminate" to "defer" in section 4.1. 3436 o Tracker item 110. Added that the Mapping Protocol Data field in 3437 the Map-Reply message is only used when needed by the particular 3438 Mapping Database System. 3440 o Tracker item 111. Indicate that if an LSB that is associated with 3441 an anycast address, that there is at least one RLOC that is up. 3443 o Tracker item 108. Make clear the R-bit does not define RLOC path 3444 reachability. 3446 o Tracker item 107. Indicate that weights are relative to each 3447 other versus requiring an addition of up to 100%. 3449 o Tracker item 46. Add a sentence how LISP products should be sized 3450 for the appropriate demand so cache thrashing is avoided. 3452 o Change some references of RFC 5226 to [AFI] per Luigi. 3454 o Per Luigi, make reference to "EID-AFI" consistent to "EID-prefix- 3455 AFI". 3457 o Tracker item 66. Indicate that appending locators to a locator- 3458 set is done when the added locators are lexicographically greater 3459 than the previous ones in the set. 3461 o Tracker item 87. Once again reword the definition of the EID- 3462 prefix to reflect recent comments. 3464 o Tracker item 70. Added text to security section on what the 3465 implications could be if an ITR does not obey priority and weights 3466 from a Map-Reply message. 3468 o Tracker item 54. Added text to the new section titled "Packets 3469 Egressing a LISP Site" to describe the implications when two or 3470 more ITRs exist at a site where only one ITR is used for egress 3471 traffic and when there is a shift of traffic to the others, how 3472 the map-cache will need to be populated in those new egress ITRs. 3474 o Tracker item 33. Make more clear in the Routing Locator Selection 3475 section what an ITR should do when it sees an R-bit of 0 in a 3476 locator-record of a Map-Reply. 3478 o Tracker item 33. Add paragraph to the EID Reachability section 3479 indicating that site partitioning is under investigation. 3481 o Tracker item 58. Added last paragraph of Security Considerations 3482 section about how to protect inner header EID address spoofing 3483 attacks. 3485 o Add suggested Sam text to indicate that all security concerns need 3486 not be addressed for moving document to Experimental RFC status. 3487 Put this in a subsection of the Security Considerations section. 3489 B.10. Changes to draft-ietf-lisp-11.txt 3491 o Posted March 30, 2011. 3493 o Change IANA URL. The URL we had pointed to a general protocol 3494 numbers page. 3496 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3497 Requests to be sent to a MN ETR via the map-server. 3499 o Generalize text for the definition of Reencapsuatling tunnels. 3501 o Add paragraph suggested by Joel to explain how implementation 3502 experimentation will be used to determine the proper cache 3503 management techniques. 3505 o Add Yakov provided text for the definition of "EID-to-RLOC 3506 "Database". 3508 o Add reference in Section 8, Deployment Scenarios, to the 3509 draft-jakab-lisp-deploy-02.txt draft. 3511 o Clarify sentence about no hardware changes needed to support LISP 3512 encapsulation. 3514 o Add paragraph about what is the procedure when a locator is 3515 inserted in the middle of a locator-set. 3517 o Add a definition for Locator Status Bits so we can emphasize they 3518 are used as a hint for router up/down status and not path 3519 reachability. 3521 o Change "BGP RIB" to "RIB" per Clarence's comment. 3523 o Fixed complaints by IDnits. 3525 o Add subsection to Security Considerations section indicating how 3526 EID-prefix overclaiming in Map-Replies is for further study and 3527 add a reference to LISP-SEC. 3529 B.11. Changes to draft-ietf-lisp-10.txt 3531 o Posted March 2011. 3533 o Add p-bit to Map-Request so there is documentary reasons to know 3534 when a PITR has sent a Map-Request to an ETR. 3536 o Add Map-Notify message which is used to acknowledge a Map-Register 3537 message sent to a Map-Server. 3539 o Add M-bit to the Map-Register message so an ETR that wants an 3540 acknowledgment for the Map-Register can request one. 3542 o Add S-bit to the ECM and Map-Reply messages to describe security 3543 data that can be present in each message. Then refer to 3544 [LISP-SEC] for expansive details. 3546 o Add Network Management Considerations section and point to the MIB 3547 and LIG drafts. 3549 o Remove the word "simple" per Yakov's comments. 3551 B.12. Changes to draft-ietf-lisp-09.txt 3553 o Posted October 2010. 3555 o Add to IANA Consideration section about the use of LCAF Type 3556 values that accepted and maintained by the IANA registry and not 3557 the LCAF specification. 3559 o Indicate that implementations should be able to receive LISP 3560 control messages when either UDP port is 4342, so they can be 3561 robust in the face of intervening NAT boxes. 3563 o Add paragraph to SMR section to indicate that an ITR does not need 3564 to respond to an SMR-based Map-Request when it has no map-cache 3565 entry for the SMR source's EID-prefix. 3567 B.13. Changes to draft-ietf-lisp-08.txt 3569 o Posted August 2010. 3571 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3572 Register messages. 3574 o Clarify language in section 6.1.5 about Map-Replying to Data- 3575 Probes or Map-Requests. 3577 o Indicate that outer TTL should only be copied to inner TTL when it 3578 is less than inner TTL. 3580 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3581 value of 0. 3583 o Indicate that SMRs can have a global or per SMR destination rate- 3584 limiter. 3586 o Add clarifications to the SMR procedures. 3588 o Add definitions for "client-side" and 'server-side" terms used in 3589 this specification. 3591 o Clear up language in section 6.4, last paragraph. 3593 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3594 probe a PETR and have it return a Map-Reply with a locator-set of 3595 size 0. The way it is spec'ed the map-cache entry has action 3596 "dropped". Drop-action is set to 3. 3598 o Add statement about normalizing locator weights. 3600 o Clarify R-bit definition in the Map-Reply locator record. 3602 o Add section on EID Reachability within a LISP site. 3604 o Clarify another disadvantage of using anycast locators. 3606 o Reworded Abstract. 3608 o Change section 2.0 Introduction to remove obsolete information 3609 such as the LISP variant definitions. 3611 o Change section 5 title from "Tunneling Details" to "LISP 3612 Encapsulation Details". 3614 o Changes to section 5 to include results of network deployment 3615 experience with MTU. Recommend that implementations use either 3616 the stateful or stateless handling. 3618 o Make clarification wordsmithing to Section 7 and 8. 3620 o Identify that if there is one locator in the locator-set of a map- 3621 cache entry, that an SMR from that locator should be responded to 3622 by sending the the SMR-invoked Map-Request to the database mapping 3623 system rather than to the RLOC itself (which may be unreachable). 3625 o When describing Unicast and Multicast Weights indicate the the 3626 values are relative weights rather than percentages. So it 3627 doesn't imply the sum of all locator weights in the locator-set 3628 need to be 100. 3630 o Do some wordsmithing on copying TTL and TOS fields. 3632 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3633 combed the spec. 3635 o Removed Section 14 "Prototype Plans and Status". We felt this 3636 type of section is no longer appropriate for a protocol 3637 specification. 3639 o Add clarification text for the IRC description per Damien's 3640 commentary. 3642 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3643 per Vina's comment about a possible DoS vector. 3645 o Clarify (S/2 + H) in the stateless MTU section. 3647 o Add text to reflect Damien's comment about the description of the 3648 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3649 addresses are local addresses of the Map-Requester. 3651 B.14. Changes to draft-ietf-lisp-07.txt 3653 o Posted April 2010. 3655 o Added I-bit to data header so LSB field can also be used as an 3656 Instance ID field. When this occurs, the LSB field is reduced to 3657 8-bits (from 32-bits). 3659 o Added V-bit to the data header so the 24-bit nonce field can also 3660 be used for source and destination version numbers. 3662 o Added Map-Version 12-bit value to the EID-record to be used in all 3663 of Map-Request, Map-Reply, and Map-Register messages. 3665 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3666 can decide what address to select for the destination of a Map- 3667 Reply. 3669 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3670 the Locator-Set record of an EID-record for a Map-Reply message. 3671 The L-bit indicates which RLOCs in the locator-set are local to 3672 the sender of the message. The P-bit indicates which RLOC is the 3673 source of a RLOC-probe Reply (Map-Reply) message. 3675 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3677 o Made editorial and clarification changes based on comments from 3678 Dhirendra Trivedi. 3680 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3682 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3683 6.3.1. 3685 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3686 for Map-Register messages. 3688 o Add NAT section per Ron Bonica comments. 3690 o Fix IDnits issues per Ron Bonica. 3692 o Added section on Virtualization and Segmentation to explain the 3693 use if the Instance ID field in the data header. 3695 o There are too many P-bits, keep their scope to the packet format 3696 description and refer to them by name every where else in the 3697 spec. 3699 o Scanned all occurrences of "should", "should not", "must" and 3700 "must not" and uppercased them. 3702 o John Zwiebel offered text for section 4.1 to modernize the 3703 example. Thanks Z! 3705 o Make it more clear in the definition of "EID-to-RLOC Database" 3706 that all ETRs need to have the same database mapping. This 3707 reflects a comment from John Scudder. 3709 o Add a definition "Route-returnability" to the Definition of Terms 3710 section. 3712 o In section 9.2, add text to describe what the signature of 3713 traceroute packets can look like. 3715 o Removed references to Data Probe for introductory example. Data- 3716 probes are still part of the LISP design but not encouraged. 3718 o Added the definition for "LISP site" to the Definition of Terms" 3719 section. 3721 B.15. Changes to draft-ietf-lisp-06.txt 3723 Editorial based changes: 3725 o Posted December 2009. 3727 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3729 o Add text to indicate that Map-Register messages must contain a 3730 computed UDP checksum. 3732 o Add definitions for PITR and PETR. 3734 o Indicate an AFI value of 0 is an unspecified address. 3736 o Indicate that the TTL field of a Map-Register is not used and set 3737 to 0 by the sender. This change makes this spec consistent with 3738 [LISP-MS]. 3740 o Change "... yield a packet size of L octets" to "... yield a 3741 packet size greater than L octets". 3743 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3744 Reply messages. 3746 o Clarify that LSBs that go beyond the number of locators do not to 3747 be SMRed when the locator addresses are greater lexicographically 3748 than the locator in the existing locator-set. 3750 o Add Gregg, Srini, and Amit to acknowledgment section. 3752 o Clarify in the definition of a LISP header what is following the 3753 UDP header. 3755 o Clarify "verifying Map-Request" text in section 6.1.3. 3757 o Add Xu Xiaohu to the acknowledgment section for introducing the 3758 problem of overlapping EID-prefixes among multiple sites in an RRG 3759 email message. 3761 Design based changes: 3763 o Use stronger language to have the outer IPv4 header set DF=1 so we 3764 can avoid fragment reassembly in an ETR or PETR. This will also 3765 make IPv4 and IPv6 encapsulation have consistent behavior. 3767 o Map-Requests should not be sent in ECM with the Probe bit is set. 3768 These type of Map-Requests are used as RLOC-probes and are sent 3769 directly to locator addresses in the underlying network. 3771 o Add text in section 6.1.5 about returning all EID-prefixes in a 3772 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3773 configure. 3775 o Add text in a new subsection of section 6.1.5 about dealing with 3776 Map-Replies with coarse EID-prefixes. 3778 B.16. Changes to draft-ietf-lisp-05.txt 3780 o Posted September 2009. 3782 o Added this Document Change Log appendix. 3784 o Added section indicating that encapsulated Map-Requests must use 3785 destination UDP port 4342. 3787 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3788 data in Map-Register payload. 3790 o Added Jari to acknowledgment section. 3792 o State the source-EID is set to 0 when using Map-Requests to 3793 refresh or RLOC-probe. 3795 o Make more clear what source-RLOC should be for a Map-Request. 3797 o The LISP-CONS authors thought that the Type definitions for CONS 3798 should be removed from this specification. 3800 o Removed nonce from Map-Register message, it wasn't used so no need 3801 for it. 3803 o Clarify what to do for unspecified Action bits for negative Map- 3804 Replies. Since No Action is a drop, make value 0 Drop. 3806 B.17. Changes to draft-ietf-lisp-04.txt 3808 o Posted September 2009. 3810 o How do deal with record count greater than 1 for a Map-Request. 3811 Damien and Joel comment. Joel suggests: 1) Specify that senders 3812 compliant with the current document will always set the count to 3813 1, and note that the count is included for future extensibility. 3814 2) Specify what a receiver compliant with the draft should do if 3815 it receives a request with a count greater than 1. Presumably, it 3816 should send some error back? 3818 o Add Fred Templin in acknowledgment section. 3820 o Add Margaret and Sam to the acknowledgment section for their great 3821 comments. 3823 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3825 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3826 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3827 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3828 ignore the checksum completely. And of course we'd need to 3829 confirm that can actually be implemented. In particular, hardware 3830 that verifies UDP checksums on receive needs to be checked to make 3831 sure it permits 0 checksums." 3833 o Margaret wants a reference to 3834 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3836 o Fix description in Map-Request section. Where we describe Map- 3837 Reply Record, change "R-bit" to "M-bit". 3839 o Add the mobility bit to Map-Replies. So PITRs don't probe so 3840 often for MNs but often enough to get mapping updates. 3842 o Indicate SHA1 can be used as well for Map-Registers. 3844 o More Fred comments on MTU handling. 3846 o Isidor comment about spec'ing better periodic Map-Registers. Will 3847 be fixed in draft-ietf-lisp-ms-02.txt. 3849 o Margaret's comment on gleaning: "The current specification does 3850 not make it clear how long gleaned map entries should be retained 3851 in the cache, nor does it make it clear how/ when they will be 3852 validated. The LISP spec should, at the very least, include a 3853 (short) default lifetime for gleaned entries, require that they be 3854 validated within a short period of time, and state that a new 3855 gleaned entry should never overwrite an entry that was obtained 3856 from the mapping system. The security implications of storing 3857 "gleaned" entries should also be explored in detail." 3859 o Add section on RLOC-probing per working group feedback. 3861 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3862 Noel. 3864 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3865 control plane only. 3867 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3868 fields can be turned off and used for another future purpose. For 3869 Luigi et al versioning convergence. 3871 o Add a N-bit to the data header suggested by Noel. Then the nonce 3872 field could be used when N is not 1. 3874 o Clarify that when E-bit is 0, the nonce field can be an echoed 3875 nonce or a random nonce. Comment from Jesper. 3877 o Indicate when doing data-gleaning that a verifying Map-Request is 3878 sent to the source-EID of the gleaned data packet so we can avoid 3879 map-cache corruption by a 3rd party. Comment from Pedro. 3881 o Indicate that a verifying Map-Request, for accepting mapping data, 3882 should be sent over the ALT (or to the EID). 3884 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3886 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3887 noncing. Comment by Pedro and Dino. 3889 o Jesper made a comment to loosen the language about requiring the 3890 copy of inner TTL to outer TTL since the text to get mixed-AF 3891 traceroute to work would violate the "MUST" clause. Changed from 3892 MUST to SHOULD in section 5.3. 3894 B.18. Changes to draft-ietf-lisp-03.txt 3896 o Posted July 2009. 3898 o Removed loc-reach-bits longword from control packets per Damien 3899 comment. 3901 o Clarifications in MTU text from Roque. 3903 o Added text to indicate that the locator-set be sorted by locator 3904 address from Isidor. 3906 o Clarification text from John Zwiebel in Echo-Nonce section. 3908 B.19. Changes to draft-ietf-lisp-02.txt 3910 o Posted July 2009. 3912 o Encapsulation packet format change to add E-bit and make loc- 3913 reach-bits 32-bits in length. 3915 o Added Echo-Nonce Algorithm section. 3917 o Clarification how ECN bits are copied. 3919 o Moved S-bit in Map-Request. 3921 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3922 RLOC-Probe Algorithm. 3924 o Added to Mobility section to reference [LISP-MN]. 3926 B.20. Changes to draft-ietf-lisp-01.txt 3928 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3930 o Defined LEID to be a "LISP EID". 3932 o Indicate encapsulation use IPv4 DF=0. 3934 o Added negative Map-Reply messages with drop, native-forward, and 3935 send-map-request actions. 3937 o Added Proxy-Map-Reply bit to Map-Register. 3939 B.21. Changes to draft-ietf-lisp-00.txt 3941 o Posted May 2009. 3943 o Rename of draft-farinacci-lisp-12.txt. 3945 o Acknowledgment to RRG. 3947 Authors' Addresses 3949 Dino Farinacci 3950 cisco Systems 3951 Tasman Drive 3952 San Jose, CA 95134 3953 USA 3955 Email: dino@cisco.com 3957 Vince Fuller 3958 cisco Systems 3959 Tasman Drive 3960 San Jose, CA 95134 3961 USA 3963 Email: vaf@cisco.com 3965 Dave Meyer 3966 cisco Systems 3967 170 Tasman Drive 3968 San Jose, CA 3969 USA 3971 Email: dmm@cisco.com 3973 Darrel Lewis 3974 cisco Systems 3975 170 Tasman Drive 3976 San Jose, CA 3977 USA 3979 Email: darlewis@cisco.com