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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: January 10, 2012 D. Lewis 6 cisco Systems 7 July 9, 2011 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-15 12 Abstract 14 This draft describes a network-based protocol that enables separation 15 of IP addresses into two new numbering spaces: Endpoint Identifiers 16 (EIDs) and Routing Locators (RLOCs). No changes are required to 17 either host protocol stacks or to the "core" of the Internet 18 infrastructure. LISP can be incrementally deployed, without a "flag 19 day", and offers traffic engineering, multi-homing, and mobility 20 benefits even to early adopters, when there are relatively few LISP- 21 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 January 10, 2012. 44 Copyright Notice 46 Copyright (c) 2011 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 . . . . . . . . . . . . . . . . . . . . 4 62 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 7 64 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 12 65 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 14 66 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . . 16 67 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 17 68 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 17 69 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . . 19 70 5.4. Dealing with Large Encapsulated Packets . . . . . . . . . 22 71 5.4.1. A Stateless Solution to MTU Handling . . . . . . . . . 23 72 5.4.2. A Stateful Solution to MTU Handling . . . . . . . . . 24 73 5.5. Using Virtualization and Segmentation with LISP . . . . . 24 74 6. EID-to-RLOC Mapping . . . . . . . . . . . . . . . . . . . . . 26 75 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats . . . . . 26 76 6.1.1. LISP Packet Type Allocations . . . . . . . . . . . . . 28 77 6.1.2. Map-Request Message Format . . . . . . . . . . . . . . 28 78 6.1.3. EID-to-RLOC UDP Map-Request Message . . . . . . . . . 31 79 6.1.4. Map-Reply Message Format . . . . . . . . . . . . . . . 32 80 6.1.5. EID-to-RLOC UDP Map-Reply Message . . . . . . . . . . 36 81 6.1.6. Map-Register Message Format . . . . . . . . . . . . . 38 82 6.1.7. Map-Notify Message Format . . . . . . . . . . . . . . 40 83 6.1.8. Encapsulated Control Message Format . . . . . . . . . 41 84 6.2. Routing Locator Selection . . . . . . . . . . . . . . . . 43 85 6.3. Routing Locator Reachability . . . . . . . . . . . . . . . 45 86 6.3.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 47 87 6.3.2. RLOC Probing Algorithm . . . . . . . . . . . . . . . . 48 88 6.4. EID Reachability within a LISP Site . . . . . . . . . . . 49 89 6.5. Routing Locator Hashing . . . . . . . . . . . . . . . . . 50 90 6.6. Changing the Contents of EID-to-RLOC Mappings . . . . . . 50 91 6.6.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . 51 92 6.6.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . 52 93 6.6.3. Database Map Versioning . . . . . . . . . . . . . . . 54 94 7. Router Performance Considerations . . . . . . . . . . . . . . 55 95 8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 56 96 8.1. First-hop/Last-hop Tunnel Routers . . . . . . . . . . . . 57 97 8.2. Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 57 98 8.3. ISP Provider-Edge (PE) Tunnel Routers . . . . . . . . . . 58 99 8.4. LISP Functionality with Conventional NATs . . . . . . . . 58 100 8.5. Packets Egressing a LISP Site . . . . . . . . . . . . . . 59 101 9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 60 102 9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 61 103 9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 61 104 9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 61 105 10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 63 106 10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 63 107 10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 63 108 10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 63 109 10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 65 110 10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 65 111 11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 67 112 12. Security Considerations . . . . . . . . . . . . . . . . . . . 68 113 13. Network Management Considerations . . . . . . . . . . . . . . 70 114 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 71 115 14.1. LISP Address Type Codes . . . . . . . . . . . . . . . . . 71 116 14.2. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 71 117 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 72 118 15.1. Normative References . . . . . . . . . . . . . . . . . . . 72 119 15.2. Informative References . . . . . . . . . . . . . . . . . . 73 120 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 76 121 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 77 122 B.1. Changes to draft-ietf-lisp-15.txt . . . . . . . . . . . . 77 123 B.2. Changes to draft-ietf-lisp-14.txt . . . . . . . . . . . . 77 124 B.3. Changes to draft-ietf-lisp-13.txt . . . . . . . . . . . . 77 125 B.4. Changes to draft-ietf-lisp-12.txt . . . . . . . . . . . . 78 126 B.5. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 79 127 B.6. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 80 128 B.7. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 81 129 B.8. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 81 130 B.9. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 83 131 B.10. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 84 132 B.11. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 85 133 B.12. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 86 134 B.13. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 88 135 B.14. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 88 136 B.15. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 89 137 B.16. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 89 138 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 90 140 1. Requirements Notation 142 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 143 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 144 document are to be interpreted as described in [RFC2119]. 146 2. Introduction 148 This document describes the Locator/Identifier Separation Protocol 149 (LISP), which provides a set of functions for routers to exchange 150 information used to map from non-routeable Endpoint Identifiers 151 (EIDs) to routeable Routing Locators (RLOCs). It also defines a 152 mechanism for these LISP routers to encapsulate IP packets addressed 153 with EIDs for transmission across an Internet that uses RLOCs for 154 routing and forwarding. 156 Creation of LISP was initially motivated by discussions during the 157 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 158 October, 2006 (see [RFC4984]). A key conclusion of the workshop was 159 that the Internet routing and addressing system was not scaling well 160 in the face of the explosive growth of new sites; one reason for this 161 poor scaling is the increasing number of multi-homed and other sites 162 that cannot be addressed as part of topologically- or provider-based 163 aggregated prefixes. Additional work that more completely described 164 the problem statement may be found in [RADIR]. 166 A basic observation, made many years ago in early networking research 167 such as that documented in [CHIAPPA] and [RFC4984], is that using a 168 single address field for both identifying a device and for 169 determining where it is topologically located in the network requires 170 optimization along two conflicting axes: for routing to be efficient, 171 the address must be assigned topologically; for collections of 172 devices to be easily and effectively managed, without the need for 173 renumbering in response to topological change (such as that caused by 174 adding or removing attachment points to the network or by mobility 175 events), the address must explicitly not be tied to the topology. 177 The approach that LISP takes to solving the routing scalability 178 problem is to replace IP addresses with two new types of numbers: 179 Routing Locators (RLOCs), which are topologically assigned to network 180 attachment points (and are therefore amenable to aggregation) and 181 used for routing and forwarding of packets through the network; and 182 Endpoint Identifiers (EIDs), which are assigned independently from 183 the network topology, are used for numbering devices, and are 184 aggregated along administrative boundaries. LISP then defines 185 functions for mapping between the two numbering spaces and for 186 encapsulating traffic originated by devices using non-routeable EIDs 187 for transport across a network infrastructure that routes and 188 forwards using RLOCs. Both RLOCs and EIDs are syntactically- 189 identical to IP addresses; it is the semantics of how they are used 190 that differs. 192 This document describes the protocol that implements these functions. 193 The database which stores the mappings between EIDs and RLOCs is 194 explicitly a separate "module" to facilitate experimentation with a 195 variety of approaches. One database design that is being developed 196 and prototyped as part of the LISP working group work is [ALT]. 197 Others that have been described but not implemented include [CONS], 198 [EMACS], [RPMD], [NERD]. Finally, [LISP-MS], documents a general- 199 purpose service interface for accessing a mapping database; this 200 interface is intended to make the mapping database modular so that 201 different approaches can be tried without the need to modify 202 installed xTRs. 204 This experimental specification does not address automated key 205 management. Addressing automated key management is necessary for 206 Internet standards. See Section 12 for further security details. 208 3. Definition of Terms 210 Provider Independent (PI) Addresses: PI addresses are an address 211 block assigned from a pool where blocks are not associated with 212 any particular location in the network (e.g. from a particular 213 service provider), and is therefore not topologically aggregatable 214 in the routing system. 216 Provider Assigned (PA) Addresses: PA addresses are an a address 217 block assigned to a site by each service provider to which a site 218 connects. Typically, each block is sub-block of a service 219 provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and 220 is aggregated into the larger block before being advertised into 221 the global Internet. Traditionally, IP multihoming has been 222 implemented by each multi-homed site acquiring its own, globally- 223 visible prefix. LISP uses only topologically-assigned and 224 aggregatable address blocks for RLOCs, eliminating this 225 demonstrably non-scalable practice. 227 Routing Locator (RLOC): A RLOC is an IPv4 or IPv6 address of an 228 egress tunnel router (ETR). A RLOC is the output of a EID-to-RLOC 229 mapping lookup. An EID maps to one or more RLOCs. Typically, 230 RLOCs are numbered from topologically-aggregatable blocks that are 231 assigned to a site at each point to which it attaches to the 232 global Internet; where the topology is defined by the connectivity 233 of provider networks, RLOCs can be thought of as PA addresses. 234 Multiple RLOCs can be assigned to the same ETR device or to 235 multiple ETR devices at a site. 237 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 238 IPv6) value used in the source and destination address fields of 239 the first (most inner) LISP header of a packet. The host obtains 240 a destination EID the same way it obtains an destination address 241 today, for example through a Domain Name System (DNS) [RFC1034] 242 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 243 The source EID is obtained via existing mechanisms used to set a 244 host's "local" IP address. An EID is allocated to a host from an 245 EID-prefix block associated with the site where the host is 246 located. An EID can be used by a host to refer to other hosts. 247 EIDs MUST NOT be used as LISP RLOCs. Note that EID blocks may be 248 assigned in a hierarchical manner, independent of the network 249 topology, to facilitate scaling of the mapping database. In 250 addition, an EID block assigned to a site may have site-local 251 structure (subnetting) for routing within the site; this structure 252 is not visible to the global routing system. In theory, the bit 253 string that represents an EID for one device can represent an RLOC 254 for a different device. As the architecture is realized, if a 255 given bit string is both an RLOC and an EID, it must refer to the 256 same entity in both cases. When used in discussions with other 257 Locator/ID separation proposals, a LISP EID will be called a 258 "LEID". Throughout this document, any references to "EID" refers 259 to an LEID. 261 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are 262 allocated to a site by an address allocation authority. EID- 263 prefixes are associated with a set of RLOC addresses which make up 264 a "database mapping". EID-prefix allocations can be broken up 265 into smaller blocks when an RLOC set is to be associated with the 266 smaller EID-prefix. A globally routed address block (whether PI 267 or PA) is not inherently an EID-prefix. A globally routed address 268 block may be used by its assignee as an EID block. The converse 269 is not supported. That is, a site which receives an explicitly 270 allocated EID-prefix may not use that EID-prefix as a globally 271 prefix. This would require coordination and cooperation with the 272 entities managing the mapping infrastructure. Once this has been 273 done, that block could be removed from the globally routed IP 274 system, if other suitable transition and access mechanisms are in 275 place. Discussion of such transition and access mechanisms can be 276 found in [INTERWORK] and [LISP-DEPLOY]. 278 End-system: An end-system is an IPv4 or IPv6 device that originates 279 packets with a single IPv4 or IPv6 header. The end-system 280 supplies an EID value for the destination address field of the IP 281 header when communicating globally (i.e. outside of its routing 282 domain). An end-system can be a host computer, a switch or router 283 device, or any network appliance. 285 Ingress Tunnel Router (ITR): An ITR is a router which accepts an IP 286 packet with a single IP header (more precisely, an IP packet that 287 does not contain a LISP header). The router treats this "inner" 288 IP destination address as an EID and performs an EID-to-RLOC 289 mapping lookup. The router then prepends an "outer" IP header 290 with one of its globally-routable RLOCs in the source address 291 field and the result of the mapping lookup in the destination 292 address field. Note that this destination RLOC may be an 293 intermediate, proxy device that has better knowledge of the EID- 294 to-RLOC mapping closer to the destination EID. In general, an ITR 295 receives IP packets from site end-systems on one side and sends 296 LISP-encapsulated IP packets toward the Internet on the other 297 side. 299 Specifically, when a service provider prepends a LISP header for 300 Traffic Engineering purposes, the router that does this is also 301 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 302 on the outer destination address (the originating ITR's supplied 303 RLOC) or the inner destination address (the originating hosts 304 supplied EID). 306 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 307 network that prepends an additional LISP header for Traffic 308 Engineering purposes. 310 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 311 packet where the destination address in the "outer" IP header is 312 one of its own RLOCs. The router strips the "outer" header and 313 forwards the packet based on the next IP header found. In 314 general, an ETR receives LISP-encapsulated IP packets from the 315 Internet on one side and sends decapsulated IP packets to site 316 end-systems on the other side. ETR functionality does not have to 317 be limited to a router device. A server host can be the endpoint 318 of a LISP tunnel as well. 320 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 321 network that strips an outer LISP header for Traffic Engineering 322 purposes. 324 xTR: A xTR is a reference to an ITR or ETR when direction of data 325 flow is not part of the context description. xTR refers to the 326 router that is the tunnel endpoint. Used synonymously with the 327 term "Tunnel Router". For example, "An xTR can be located at the 328 Customer Edge (CE) router", meaning both ITR and ETR functionality 329 is at the CE router. 331 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 332 demand table in an ITR that stores, tracks, and is responsible for 333 timing-out and otherwise validating EID-to-RLOC mappings. This 334 cache is distinct from the full "database" of EID-to-RLOC 335 mappings, it is dynamic, local to the ITR(s), and relatively small 336 while the database is distributed, relatively static, and much 337 more global in scope. 339 EID-to-RLOC Database: The EID-to-RLOC database is a global 340 distributed database that contains all known EID-prefix to RLOC 341 mappings. Each potential ETR typically contains a small piece of 342 the database: the EID-to-RLOC mappings for the EID prefixes 343 "behind" the router. These map to one of the router's own, 344 globally-visible, IP addresses. The same database mapping entries 345 MUST be configured on all ETRs for a given site. In a steady 346 state the EID-prefixes for the site and the locator-set for each 347 EID-prefix MUST be the same on all ETRs. Procedures to enforce 348 and/or verify this are outside the scope of this document. Note 349 that there may be transient conditions when the EID-prefix for the 350 site and locator-set for each EID-prefix may not be the same on 351 all ETRs. This has no negative implications. 353 Recursive Tunneling: Recursive tunneling occurs when a packet has 354 more than one LISP IP header. Additional layers of tunneling may 355 be employed to implement traffic engineering or other re-routing 356 as needed. When this is done, an additional "outer" LISP header 357 is added and the original RLOCs are preserved in the "inner" 358 header. Any references to tunnels in this specification refers to 359 dynamic encapsulating tunnels and never are they statically 360 configured. 362 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 363 ETR removes a LISP header, then acts as an ITR to prepend another 364 LISP header. Doing this allows a packet to be re-routed by the 365 re-encapsulating router without adding the overhead of additional 366 tunnel headers. Any references to tunnels in this specification 367 refers to dynamic encapsulating tunnels and never are they 368 statically configured. When using multiple mapping database 369 systems, care must be taken to not create reencapsulation loops. 371 LISP Header: a term used in this document to refer to the outer 372 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-byte 373 header that follows the UDP header, an ITR prepends or an ETR 374 strips. 376 Address Family Identifier (AFI): a term used to describe an address 377 encoding in a packet. An address family currently pertains to an 378 IPv4 or IPv6 address. See [AFI]/[AFI-REGISTRY] and [RFC3232] for 379 details. An AFI value of 0 used in this specification indicates 380 an unspecified encoded address where the length of the address is 381 0 bytes following the 16-bit AFI value of 0. 383 Negative Mapping Entry: A negative mapping entry, also known as a 384 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 385 is advertised or stored with no RLOCs. That is, the locator-set 386 for the EID-to-RLOC entry is empty or has an encoded locator count 387 of 0. This type of entry could be used to describe a prefix from 388 a non-LISP site, which is explicitly not in the mapping database. 389 There are a set of well defined actions that are encoded in a 390 Negative Map-Reply. 392 Data Probe: A data-probe is a LISP-encapsulated data packet where 393 the inner header destination address equals the outer header 394 destination address used to trigger a Map-Reply by a decapsulating 395 ETR. In addition, the original packet is decapsulated and 396 delivered to the destination host if the destination EID is in the 397 EID-prefix range configured on the ETR. Otherwise, the packet is 398 discarded. A Data Probe is used in some of the mapping database 399 designs to "probe" or request a Map-Reply from an ETR; in other 400 cases, Map-Requests are used. See each mapping database design 401 for details. 403 Proxy ITR (PITR): A PITR is also known as a PTR is defined and 404 described in [INTERWORK], a PITR acts like an ITR but does so on 405 behalf of non-LISP sites which send packets to destinations at 406 LISP sites. 408 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 409 PETR acts like an ETR but does so on behalf of LISP sites which 410 send packets to destinations at non-LISP sites. 412 Route-returnability: is an assumption that the underlying routing 413 system will deliver packets to the destination. When combined 414 with a nonce that is provided by a sender and returned by a 415 receiver limits off-path data insertion. 417 LISP site: is a set of routers in an edge network that are under a 418 single technical administration. LISP routers which reside in the 419 edge network are the demarcation points to separate the edge 420 network from the core network. 422 Client-side: a term used in this document to indicate a connection 423 initiation attempt by an EID. The ITR(s) at the LISP site are the 424 first to get involved in obtaining database map cache entries by 425 sending Map-Request messages. 427 Server-side: a term used in this document to indicate a connection 428 initiation attempt is being accepted for a destination EID. The 429 ETR(s) at the destination LISP site are the first to send Map- 430 Replies to the source site initiating the connection. The ETR(s) 431 at this destination site can obtain mappings by gleaning 432 information from Map-Requests, Data-Probes, or encapsulated 433 packets. 435 Locator-Status-Bits (LSBs): Locator status bits are present in the 436 LISP header. They are used by ITRs to inform ETRs about the up/ 437 down status of all ETRs at the local site. These bits are used as 438 a hint to convey up/down router status and not path reachability 439 status. The LSBs can be verified by use of one of the Locator 440 Reachability Algoriths described in Section 6.3. 442 4. Basic Overview 444 One key concept of LISP is that end-systems (hosts) operate the same 445 way they do today. The IP addresses that hosts use for tracking 446 sockets, connections, and for sending and receiving packets do not 447 change. In LISP terminology, these IP addresses are called Endpoint 448 Identifiers (EIDs). 450 Routers continue to forward packets based on IP destination 451 addresses. When a packet is LISP encapsulated, these addresses are 452 referred to as Routing Locators (RLOCs). Most routers along a path 453 between two hosts will not change; they continue to perform routing/ 454 forwarding lookups on the destination addresses. For routers between 455 the source host and the ITR as well as routers from the ETR to the 456 destination host, the destination address is an EID. For the routers 457 between the ITR and the ETR, the destination address is an RLOC. 459 Another key LISP concept is the "Tunnel Router". A tunnel router 460 prepends LISP headers on host-originated packets and strip them prior 461 to final delivery to their destination. The IP addresses in this 462 "outer header" are RLOCs. During end-to-end packet exchange between 463 two Internet hosts, an ITR prepends a new LISP header to each packet 464 and an egress tunnel router strips the new header. The ITR performs 465 EID-to-RLOC lookups to determine the routing path to the ETR, which 466 has the RLOC as one of its IP addresses. 468 Some basic rules governing LISP are: 470 o End-systems (hosts) only send to addresses which are EIDs. They 471 don't know addresses are EIDs versus RLOCs but assume packets get 472 to LISP routers, which in turn, deliver packets to the destination 473 the end-system has specified. 475 o EIDs are always IP addresses assigned to hosts. 477 o LISP routers mostly deal with Routing Locator addresses. See 478 details later in Section 4.1 to clarify what is meant by "mostly". 480 o RLOCs are always IP addresses assigned to routers; preferably, 481 topologically-oriented addresses from provider CIDR blocks. 483 o When a router originates packets it may use as a source address 484 either an EID or RLOC. When acting as a host (e.g. when 485 terminating a transport session such as SSH, TELNET, or SNMP), it 486 may use an EID that is explicitly assigned for that purpose. An 487 EID that identifies the router as a host MUST NOT be used as an 488 RLOC; an EID is only routable within the scope of a site. A 489 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 490 usage where a router could use its "host-like" EID to terminate 491 iBGP sessions to other routers in a site while at the same time 492 using RLOCs to terminate eBGP sessions to routers outside the 493 site. 495 o EIDs are not expected to be usable for global end-to-end 496 communication in the absence of an EID-to-RLOC mapping operation. 497 They are expected to be used locally for intra-site communication. 499 o EID prefixes are likely to be hierarchically assigned in a manner 500 which is optimized for administrative convenience and to 501 facilitate scaling of the EID-to-RLOC mapping database. The 502 hierarchy is based on a address allocation hierarchy which is 503 independent of the network topology. 505 o EIDs may also be structured (subnetted) in a manner suitable for 506 local routing within an autonomous system. 508 An additional LISP header may be prepended to packets by a TE-ITR 509 when re-routing of the path for a packet is desired. A potential 510 use-case for this would be an ISP router that needs to perform 511 traffic engineering for packets flowing through its network. In such 512 a situation, termed Recursive Tunneling, an ISP transit acts as an 513 additional ingress tunnel router and the RLOC it uses for the new 514 prepended header would be either a TE-ETR within the ISP (along 515 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 516 inter-ISP traffic engineered path, where an agreement to build such a 517 path exists). 519 In order to avoid excessive packet overhead as well as possible 520 encapsulation loops, this document mandates that a maximum of two 521 LISP headers can be prepended to a packet. For initial LISP 522 deployments, it is assumed two headers is sufficient, where the first 523 prepended header is used at a site for Location/Identity separation 524 and second prepended header is used inside a service provider for 525 Traffic Engineering purposes. 527 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 528 For example, the ITR for a particular end-to-end packet exchange 529 might be the first-hop or default router within a site for the source 530 host. Similarly, the egress tunnel router might be the last-hop 531 router directly-connected to the destination host. Another example, 532 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 533 could be the site's border router at the service provider attachment 534 point. Mixing and matching of site-operated, ISP-operated, and other 535 tunnel routers is allowed for maximum flexibility. See Section 8 for 536 more details. 538 4.1. Packet Flow Sequence 540 This section provides an example of the unicast packet flow with the 541 following conditions: 543 o Source host "host1.example.abc.com" is sending a packet to 544 "host2.example.xyz.com", exactly what host1 would do if the site 545 was not using LISP. 547 o Each site is multi-homed, so each tunnel router has an address 548 (RLOC) assigned from the service provider address block for each 549 provider to which that particular tunnel router is attached. 551 o The ITR(s) and ETR(s) are directly connected to the source and 552 destination, respectively, but the source and destination can be 553 located anywhere in LISP site. 555 o Map-Requests can be sent on the underlying routing system topology 556 or over an alternative topology [ALT]. 558 o Map-Replies are sent on the underlying routing system topology. 560 Client host1.example.abc.com wants to communicate with server 561 host2.example.xyz.com: 563 1. host1.example.abc.com wants to open a TCP connection to 564 host2.example.xyz.com. It does a DNS lookup on 565 host2.example.xyz.com. An A/AAAA record is returned. This 566 address is the destination EID. The locally-assigned address of 567 host1.example.abc.com is used as the source EID. An IPv4 or IPv6 568 packet is built and forwarded through the LISP site as a normal 569 IP packet until it reaches a LISP ITR. 571 2. The LISP ITR must be able to map the EID destination to an RLOC 572 of one of the ETRs at the destination site. The specific method 573 used to do this is not described in this example. See [ALT] or 574 [CONS] for possible solutions. 576 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 577 rate-limited. 579 4. When an alternate mapping system is not in use, the Map-Request 580 packet is routed through the underlying routing system. 581 Otherwise, the Map-Request packet is routed on an alternate 582 logical topology. In either case, when the Map-Request arrives 583 at one of the ETRs at the destination site, it will process the 584 packet as a control message. 586 5. The ETR looks at the destination EID of the Map-Request and 587 matches it against the prefixes in the ETR's configured EID-to- 588 RLOC mapping database. This is the list of EID-prefixes the ETR 589 is supporting for the site it resides in. If there is no match, 590 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 591 returned to the ITR. 593 6. The ITR receives the Map-Reply message, parses the message (to 594 check for format validity) and stores the mapping information 595 from the packet. This information is stored in the ITR's EID-to- 596 RLOC mapping cache. Note that the map cache is an on-demand 597 cache. An ITR will manage its map cache in such a way that 598 optimizes for its resource constraints. 600 7. Subsequent packets from host1.example.abc.com to 601 host2.example.xyz.com will have a LISP header prepended by the 602 ITR using the appropriate RLOC as the LISP header destination 603 address learned from the ETR. Note the packet may be sent to a 604 different ETR than the one which returned the Map-Reply due to 605 the source site's hashing policy or the destination site's 606 locator-set policy. 608 8. The ETR receives these packets directly (since the destination 609 address is one of its assigned IP addresses), strips the LISP 610 header and forwards the packets to the attached destination host. 612 In order to defer the need for a mapping lookup in the reverse 613 direction, an ETR MAY create a cache entry that maps the source EID 614 (inner header source IP address) to the source RLOC (outer header 615 source IP address) in a received LISP packet. Such a cache entry is 616 termed a "gleaned" mapping and only contains a single RLOC for the 617 EID in question. More complete information about additional RLOCs 618 SHOULD be verified by sending a LISP Map-Request for that EID. Both 619 ITR and the ETR may also influence the decision the other makes in 620 selecting an RLOC. See Section 6 for more details. 622 5. LISP Encapsulation Details 624 Since additional tunnel headers are prepended, the packet becomes 625 larger and can exceed the MTU of any link traversed from the ITR to 626 the ETR. It is recommended in IPv4 that packets do not get 627 fragmented as they are encapsulated by the ITR. Instead, the packet 628 is dropped and an ICMP Too Big message is returned to the source. 630 This specification recommends that implementations support for one of 631 the proposed fragmentation and reassembly schemes. These two 632 existing schemes are detailed in Section 5.4. 634 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 635 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 636 header is in IPv4 packet format and the other header is in IPv6 637 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 638 is in IPv6 packet format and the other header is in IPv4 packet 639 format). The next sub-sections illustrate packet formats for the 640 homogenous case (IPv4-in-IPv4 and IPv6-in-IPv6) but all 4 641 combinations SHOULD be supported. 643 5.1. LISP IPv4-in-IPv4 Header Format 645 0 1 2 3 646 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 1 647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 648 / |Version| IHL |Type of Service| Total Length | 649 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 650 | | Identification |Flags| Fragment Offset | 651 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 652 OH | Time to Live | Protocol = 17 | Header Checksum | 653 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 654 | | Source Routing Locator | 655 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 656 \ | Destination Routing Locator | 657 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 658 / | Source Port = xxxx | Dest Port = 4341 | 659 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 660 \ | UDP Length | UDP Checksum | 661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 662 L |N|L|E|V|I|flags| Nonce/Map-Version | 663 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 664 S / | Instance ID/Locator Status Bits | 665 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 666 / |Version| IHL |Type of Service| Total Length | 667 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 668 | | Identification |Flags| Fragment Offset | 669 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 670 IH | Time to Live | Protocol | Header Checksum | 671 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 672 | | Source EID | 673 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 674 \ | Destination EID | 675 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 677 5.2. LISP IPv6-in-IPv6 Header Format 679 0 1 2 3 680 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 1 681 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 682 / |Version| Traffic Class | Flow Label | 683 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 685 | | Payload Length | Next Header=17| Hop Limit | 686 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 | | 688 O + + 689 u | | 690 t + Source Routing Locator + 691 e | | 692 r + + 693 | | 694 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 695 d | | 696 r + + 697 | | 698 ^ + Destination Routing Locator + 699 | | | 700 \ + + 701 \ | | 702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 703 / | Source Port = xxxx | Dest Port = 4341 | 704 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 705 \ | UDP Length | UDP Checksum | 706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 707 L |N|L|E|V|I|flags| Nonce/Map-Version | 708 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 709 S / | Instance ID/Locator Status Bits | 710 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 711 / |Version| Traffic Class | Flow Label | 712 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 713 / | Payload Length | Next Header | Hop Limit | 714 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 715 | | 716 I + + 717 n | | 718 n + Source EID + 719 e | | 720 r + + 721 | | 722 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 723 d | | 724 r + + 725 | | 726 ^ + Destination EID + 727 \ | | 728 \ + + 729 \ | | 730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 732 5.3. Tunnel Header Field Descriptions 734 Inner Header: The inner header is the header on the datagram 735 received from the originating host. The source and destination IP 736 addresses are EIDs. 738 Outer Header: The outer header is a new header prepended by an ITR. 739 The address fields contain RLOCs obtained from the ingress 740 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 741 from [RFC0768]. The DF bit of the Flags field is set to 0 when 742 the method in Section 5.4.1 is used and set to 1 when the method 743 in Section 5.4.2 is used. 745 UDP Header: The UDP header contains a ITR selected source port when 746 encapsulating a packet. See Section 6.5 for details on the hash 747 algorithm used to select a source port based on the 5-tuple of the 748 inner header. The destination port MUST be set to the well-known 749 IANA assigned port value 4341. 751 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 752 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 753 [UDP-TUNNELS]. When a packet with a zero UDP checksum is received 754 by an ETR, the ETR MUST accept the packet for decapsulation. When 755 an ITR transmits a non-zero value for the UDP checksum, it MUST 756 send a correctly computed value in this field. When an ETR 757 receives a packet with a non-zero UDP checksum, it MAY choose to 758 verify the checksum value. If it chooses to perform such 759 verification, and the verification fails, the packet MUST be 760 silently dropped. If the ETR chooses not to perform the 761 verification, or performs the verification successfully, the 762 packet MUST be accepted for decapsulation. The handling of UDP 763 checksums for all tunneling protocols, including LISP, is under 764 active discussion within the IETF. When that discussion 765 concludes, any necessary changes will be made to align LISP with 766 the outcome of the broader discussion. 768 UDP Length: The UDP length field is for an IPv4 encapsulated packet, 769 the inner header Total Length plus the UDP and LISP header lengths 770 are used. For an IPv6 encapsulated packet, the inner header 771 Payload Length plus the size of the IPv6 header (40 bytes) plus 772 the size of the UDP and LISP headers are used. The UDP header 773 length is 8 bytes. 775 N: The N bit is the nonce-present bit. When this bit is set to 1, 776 the low-order 24-bits of the first 32-bits of the LISP header 777 contains a Nonce. See Section 6.3.1 for details. Both N and V 778 bits MUST NOT be set in the same packet. If they are, a 779 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 780 having a Nonce value present. 782 L: The L bit is the Locator-Status-Bits field enabled bit. When this 783 bit is set to 1, the Locator-Status-Bits in the second 32-bits of 784 the LISP header are in use. 786 x 1 x x 0 x x x 787 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 788 |N|L|E|V|I|flags| Nonce/Map-Version | 789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 790 | Locator Status Bits | 791 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 793 E: The E bit is the echo-nonce-request bit. When this bit is set to 794 1, the N bit MUST be 1. This bit SHOULD be ignored and has no 795 meaning when the N bit is set to 0. See Section 6.3.1 for 796 details. 798 V: The V bit is the Map-Version present bit. When this bit is set to 799 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 800 This bit indicates that the first 4 bytes of the LISP header is 801 encoded as: 803 0 x 0 1 x x x x 804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 805 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 807 | Instance ID/Locator Status Bits | 808 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 810 I: The I bit is the Instance ID bit. See Section 5.5 for more 811 details. When this bit is set to 1, the Locator Status Bits field 812 is reduced to 8-bits and the high-order 24-bits are used as an 813 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 814 are transmitted as zero and ignored on receipt. The format of the 815 last 4 bytes of the LISP header would look like: 817 x x x x 1 x x x 818 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 819 |N|L|E|V|I|flags| Nonce/Map-Version | 820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 821 | Instance ID | LSBs | 822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 824 flags: The flags field is a 3-bit field is reserved for future flag 825 use. It MUST be set to 0 on transmit and MUST be ignored on 826 receipt. 828 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 829 generated by an ITR when the N-bit is set to 1. The nonce is also 830 used when the E-bit is set to request the nonce value to be echoed 831 by the other side when packets are returned. When the E-bit is 832 clear but the N-bit is set, a remote ITR is either echoing a 833 previously requested echo-nonce or providing a random nonce. See 834 Section 6.3.1 for more details. 836 LISP Locator Status Bits: The locator status bits field in the LISP 837 header is set by an ITR to indicate to an ETR the up/down status 838 of the Locators in the source site. Each RLOC in a Map-Reply is 839 assigned an ordinal value from 0 to n-1 (when there are n RLOCs in 840 a mapping entry). The Locator Status Bits are numbered from 0 to 841 n-1 from the least significant bit of field. The field is 32-bits 842 when the I-bit is set to 0 and is 8 bits when the I-bit is set to 843 1. When a Locator Status Bit is set to 1, the ITR is indicating 844 to the ETR the RLOC associated with the bit ordinal has up status. 845 See Section 6.3 for details on how an ITR can determine the status 846 of the ETRs at the same site. When a site has multiple EID- 847 prefixes which result in multiple mappings (where each could have 848 a different locator-set), the Locator Status Bits setting in an 849 encapsulated packet MUST reflect the mapping for the EID-prefix 850 that the inner-header source EID address matches. If the LSB for 851 an anycast locator is set to 1, then there is at least one RLOC 852 with that address the ETR is considered 'up'. 854 When doing ITR/PITR encapsulation: 856 o The outer header Time to Live field (or Hop Limit field, in case 857 of IPv6) SHOULD be copied from the inner header Time to Live 858 field. 860 o The outer header Type of Service field (or the Traffic Class 861 field, in the case of IPv6) SHOULD be copied from the inner header 862 Type of Service field (with one caveat, see below). 864 When doing ETR/PETR decapsulation: 866 o The inner header Time to Live field (or Hop Limit field, in case 867 of IPv6) SHOULD be copied from the outer header Time to Live 868 field, when the Time to Live field of the outer header is less 869 than the Time to Live of the inner header. Failing to perform 870 this check can cause the Time to Live of the inner header to 871 increment across encapsulation/decapsulation cycle. This check is 872 also performed when doing initial encapsulation when a packet 873 comes to an ITR or PITR destined for a LISP site. 875 o The inner header Type of Service field (or the Traffic Class 876 field, in the case of IPv6) SHOULD be copied from the outer header 877 Type of Service field (with one caveat, see below). 879 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 880 after decapsulating, the net effect of this is that the new outer 881 header will carry the same Time to Live as the old outer header. 883 Copying the TTL serves two purposes: first, it preserves the distance 884 the host intended the packet to travel; second, and more importantly, 885 it provides for suppression of looping packets in the event there is 886 a loop of concatenated tunnels due to misconfiguration. See 887 Section 9.3 for TTL exception handling for traceroute packets. 889 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 890 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 891 requires special treatment in order to avoid discarding indications 892 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 893 field from the inner header to the outer header. Re-encapsulation 894 MUST copy the 2-bit ECN field from the stripped outer header to the 895 new outer header. If the ECN field contains a congestion indication 896 codepoint (the value is '11', the Congestion Experienced (CE) 897 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 898 the stripped outer header to the surviving inner header that is used 899 to forward the packet beyond the ETR. These requirements preserve 900 Congestion Experienced (CE) indications when a packet that uses ECN 901 traverses a LISP tunnel and becomes marked with a CE indication due 902 to congestion between the tunnel endpoints. 904 5.4. Dealing with Large Encapsulated Packets 906 This section proposes two mechanisms to deal with packets that exceed 907 the path MTU between the ITR and ETR. 909 It is left to the implementor to decide if the stateless or stateful 910 mechanism should be implemented. Both or neither can be used since 911 it is a local decision in the ITR regarding how to deal with MTU 912 issues, and sites can interoperate with differing mechanisms. 914 Both stateless and stateful mechanisms also apply to Reencapsulating 915 and Recursive Tunneling. So any actions below referring to an ITR 916 also apply to an TE-ITR. 918 5.4.1. A Stateless Solution to MTU Handling 920 An ITR stateless solution to handle MTU issues is described as 921 follows: 923 1. Define an architectural constant S for the maximum size of a 924 packet, in bytes, an ITR would like to receive from a source 925 inside of its site. 927 2. Define L to be the maximum size, in bytes, a packet of size S 928 would be after the ITR prepends the LISP header, UDP header, and 929 outer network layer header of size H. 931 3. Calculate: S + H = L. 933 When an ITR receives a packet from a site-facing interface and adds H 934 bytes worth of encapsulation to yield a packet size greater than L 935 bytes, it resolves the MTU issue by first splitting the original 936 packet into 2 equal-sized fragments. A LISP header is then prepended 937 to each fragment. The size of the encapsulated fragments is then 938 (S/2 + H), which is less than the ITR's estimate of the path MTU 939 between the ITR and its correspondent ETR. 941 When an ETR receives encapsulated fragments, it treats them as two 942 individually encapsulated packets. It strips the LISP headers then 943 forwards each fragment to the destination host of the destination 944 site. The two fragments are reassembled at the destination host into 945 the single IP datagram that was originated by the source host. 947 This behavior is performed by the ITR when the source host originates 948 a packet with the DF field of the IP header is set to 0. When the DF 949 field of the IP header is set to 1, or the packet is an IPv6 packet 950 originated by the source host, the ITR will drop the packet when the 951 size is greater than L, and sends an ICMP Too Big message to the 952 source with a value of S, where S is (L - H). 954 When the outer header encapsulation uses an IPv4 header, an 955 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 956 can be avoided. An implementation MAY set the DF bit in such headers 957 to 0 if it has good reason to believe there are unresolvable path MTU 958 issues between the sending ITR and the receiving ETR. 960 This specification recommends that L be defined as 1500. 962 5.4.2. A Stateful Solution to MTU Handling 964 An ITR stateful solution to handle MTU issues is described as follows 965 and was first introduced in [OPENLISP]: 967 1. The ITR will keep state of the effective MTU for each locator per 968 mapping cache entry. The effective MTU is what the core network 969 can deliver along the path between ITR and ETR. 971 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 972 with DF bit set to 1, exceeds what the core network can deliver, 973 one of the intermediate routers on the path will send an ICMP Too 974 Big message to the ITR. The ITR will parse the ICMP message to 975 determine which locator is affected by the effective MTU change 976 and then record the new effective MTU value in the mapping cache 977 entry. 979 3. When a packet is received by the ITR from a source inside of the 980 site and the size of the packet is greater than the effective MTU 981 stored with the mapping cache entry associated with the 982 destination EID the packet is for, the ITR will send an ICMP Too 983 Big message back to the source. The packet size advertised by 984 the ITR in the ICMP Too Big message is the effective MTU minus 985 the LISP encapsulation length. 987 Even though this mechanism is stateful, it has advantages over the 988 stateless IP fragmentation mechanism, by not involving the 989 destination host with reassembly of ITR fragmented packets. 991 5.5. Using Virtualization and Segmentation with LISP 993 When multiple organizations inside of a LISP site are using private 994 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 995 segregated due to possible address duplication. An Instance ID in 996 the address encoding can aid in making the entire AFI based address 997 unique. See IANA Considerations Section 14.1 for details for 998 possible address encodings. 1000 An Instance ID can be carried in a LISP encapsulated packet. An ITR 1001 that prepends a LISP header, will copy a 24-bit value, used by the 1002 LISP router to uniquely identify the address space. The value is 1003 copied to the Instance ID field of the LISP header and the I-bit is 1004 set to 1. 1006 When an ETR decapsulates a packet, the Instance ID from the LISP 1007 header is used as a table identifier to locate the forwarding table 1008 to use for the inner destination EID lookup. 1010 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 1011 24-bit Instance ID. 1013 6. EID-to-RLOC Mapping 1015 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 1017 The following UDP packet formats are used by the LISP control-plane. 1019 0 1 2 3 1020 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 1021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1022 |Version| IHL |Type of Service| Total Length | 1023 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1024 | Identification |Flags| Fragment Offset | 1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1026 | Time to Live | Protocol = 17 | Header Checksum | 1027 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1028 | Source Routing Locator | 1029 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1030 | Destination Routing Locator | 1031 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1032 / | Source Port | Dest Port | 1033 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1034 \ | UDP Length | UDP Checksum | 1035 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1036 | | 1037 | LISP Message | 1038 | | 1039 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1041 0 1 2 3 1042 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 1043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1044 |Version| Traffic Class | Flow Label | 1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1046 | Payload Length | Next Header=17| Hop Limit | 1047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1048 | | 1049 + + 1050 | | 1051 + Source Routing Locator + 1052 | | 1053 + + 1054 | | 1055 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1056 | | 1057 + + 1058 | | 1059 + Destination Routing Locator + 1060 | | 1061 + + 1062 | | 1063 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1064 / | Source Port | Dest Port | 1065 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1066 \ | UDP Length | UDP Checksum | 1067 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1068 | | 1069 | LISP Message | 1070 | | 1071 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1073 The LISP UDP-based messages are the Map-Request and Map-Reply 1074 messages. When a UDP Map-Request is sent, the UDP source port is 1075 chosen by the sender and the destination UDP port number is set to 1076 4342. When a UDP Map-Reply is sent, the source UDP port number is 1077 set to 4342 and the destination UDP port number is copied from the 1078 source port of either the Map-Request or the invoking data packet. 1079 Implementations MUST be prepared to accept packets when either the 1080 source port or destination UDP port is set to 4342 due to NATs 1081 changing port number values. 1083 The UDP Length field will reflect the length of the UDP header and 1084 the LISP Message payload. 1086 The UDP Checksum is computed and set to non-zero for Map-Request, 1087 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1088 on receipt and if the checksum fails, the packet MUST be dropped. 1090 LISP-CONS [CONS] uses TCP to send LISP control messages. The format 1091 of control messages includes the UDP header so the checksum and 1092 length fields can be used to protect and delimit message boundaries. 1094 This main LISP specification is the authoritative source for message 1095 format definitions for the Map-Request and Map-Reply messages. 1097 6.1.1. LISP Packet Type Allocations 1099 This section will be the authoritative source for allocating LISP 1100 Type values. Current allocations are: 1102 Reserved: 0 b'0000' 1103 LISP Map-Request: 1 b'0001' 1104 LISP Map-Reply: 2 b'0010' 1105 LISP Map-Register: 3 b'0011' 1106 LISP Map-Notify: 4 b'0100' 1107 LISP Encapsulated Control Message: 8 b'1000' 1109 6.1.2. Map-Request Message Format 1111 0 1 2 3 1112 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 1113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1114 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1116 | Nonce . . . | 1117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1118 | . . . Nonce | 1119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1120 | Source-EID-AFI | Source EID Address ... | 1121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1122 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1124 | ... | 1125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1126 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1128 / | Reserved | EID mask-len | EID-prefix-AFI | 1129 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1130 \ | EID-prefix ... | 1131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1132 | Map-Reply Record ... | 1133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1134 | Mapping Protocol Data | 1135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1137 Packet field descriptions: 1139 Type: 1 (Map-Request) 1141 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1142 Requests sent by an ITR. 1144 M: When set, it indicates a Map-Reply Record segment is included in 1145 the Map-Request. 1147 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1148 treated as a locator reachability probe. The receiver SHOULD 1149 respond with a Map-Reply with the probe-bit set, indicating the 1150 Map-Reply is a locator reachability probe reply, with the nonce 1151 copied from the Map-Request. See Section 6.3.2 for more details. 1153 S: This is the SMR bit. See Section 6.6.2 for details. 1155 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1156 Map-Request. 1158 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1159 sending a Map-Request in response to a received SMR-based Map- 1160 Request. 1162 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1163 receipt. 1165 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1166 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1167 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1168 Address) pair must always be encoded. Multiple ITR-RLOC Address 1169 fields are used so a Map-Replier can select which destination 1170 address to use for a Map-Reply. The IRC value ranges from 0 to 1171 31, and for a value of 1, there are 2 ITR-RLOC addresses encoded 1172 and so on up to 31 which encodes a total of 32 ITR-RLOC addresses. 1174 Record Count: The number of records in this Map-Request message. A 1175 record is comprised of the portion of the packet that is labeled 1176 'Rec' above and occurs the number of times equal to Record Count. 1177 For this version of the protocol, a receiver MUST accept and 1178 process Map-Requests that contain one or more records, but a 1179 sender MUST only send Map-Requests containing one record. Support 1180 for requesting multiple EIDs in a single Map-Request message will 1181 be specified in a future version of the protocol. 1183 Nonce: An 8-byte random value created by the sender of the Map- 1184 Request. This nonce will be returned in the Map-Reply. The 1185 security of the LISP mapping protocol depends critically on the 1186 strength of the nonce in the Map-Request message. The nonce 1187 SHOULD be generated by a properly seeded pseudo-random (or strong 1188 random) source. See [RFC4086] for advice on generating security- 1189 sensitive random data. 1191 Source-EID-AFI: Address family of the "Source EID Address" field. 1193 Source EID Address: This is the EID of the source host which 1194 originated the packet which is invoking this Map-Request. When 1195 Map-Requests are used for refreshing a map-cache entry or for 1196 RLOC-probing, an AFI value 0 is used and this field is of zero 1197 length. 1199 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1200 follows this field. 1202 ITR-RLOC Address: Used to give the ETR the option of selecting the 1203 destination address from any address family for the Map-Reply 1204 message. This address MUST be a routable RLOC address of the 1205 sender of the Map-Request message. 1207 EID mask-len: Mask length for EID prefix. 1209 EID-prefix-AFI: Address family of EID-prefix according to [AFI] 1211 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1212 address-family. When a Map-Request is sent by an ITR because a 1213 data packet is received for a destination where there is no 1214 mapping entry, the EID-prefix is set to the destination IP address 1215 of the data packet. And the 'EID mask-len' is set to 32 or 128 1216 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1217 about the status of a mapping it already has cached, the EID- 1218 prefix used in the Map-Request has the same mask-length as the 1219 EID-prefix returned from the site when it sent a Map-Reply 1220 message. 1222 Map-Reply Record: When the M bit is set, this field is the size of a 1223 single "Record" in the Map-Reply format. This Map-Reply record 1224 contains the EID-to-RLOC mapping entry associated with the Source 1225 EID. This allows the ETR which will receive this Map-Request to 1226 cache the data if it chooses to do so. 1228 Mapping Protocol Data: See [CONS] for details. This field is 1229 optional and present when the UDP length indicates there is enough 1230 space in the packet to include it. 1232 6.1.3. EID-to-RLOC UDP Map-Request Message 1234 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1235 wants to test an RLOC for reachability, or wants to refresh a mapping 1236 before TTL expiration. For the initial case, the destination IP 1237 address used for the Map-Request is the destination-EID from the 1238 packet which had a mapping cache lookup failure. For the latter 2 1239 cases, the destination IP address used for the Map-Request is one of 1240 the RLOC addresses from the locator-set of the map cache entry. The 1241 source address is either an IPv4 or IPv6 RLOC address depending if 1242 the Map-Request is using an IPv4 versus IPv6 header, respectively. 1243 In all cases, the UDP source port number for the Map-Request message 1244 is an ITR/PITR selected 16-bit value and the UDP destination port 1245 number is set to the well-known destination port number 4342. A 1246 successful Map-Reply updates the cached set of RLOCs associated with 1247 the EID prefix range. 1249 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1250 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1251 be placed in the IRC field. The ITR MAY include all locally 1252 configured locators in this list or just provide one locator address 1253 from each address family it supports. If the ITR erroneously 1254 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1255 Request. 1257 Map-Requests can also be LISP encapsulated using UDP destination port 1258 4342 with a LISP type value set to "Encapsulated Control Message", 1259 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1260 LISP encapsulated the same way from a Map-Server to an ETR. Details 1261 on encapsulated Map-Requests and Map-Resolvers can be found in 1262 [LISP-MS]. 1264 Map-Requests MUST be rate-limited. It is recommended that a Map- 1265 Request for the same EID-prefix be sent no more than once per second. 1267 An ITR that is configured with mapping database information (i.e. it 1268 is also an ETR) may optionally include those mappings in a Map- 1269 Request. When an ETR configured to accept and verify such 1270 "piggybacked" mapping data receives such a Map-Request and it does 1271 not have this mapping in the map-cache, it may originate a "verifying 1272 Map-Request", addressed to the map-requesting ITR. If the ETR has a 1273 map-cache entry that matches the "piggybacked" EID and the RLOC is in 1274 the locator-set for the entry, then it may send the "verifying Map- 1275 Request" directly to the originating Map-Request source. If the RLOC 1276 is not in the locator-set, then the ETR MUST send the "verifying Map- 1277 Request" to the "piggybacked" EID. Doing this forces the "verifying 1278 Map-Request" to go through the mapping database system to reach the 1279 authoritative source of information about that EID, guarding against 1280 RLOC-spoofing in in the "piggybacked" mapping data. 1282 6.1.4. Map-Reply Message Format 1284 0 1 2 3 1285 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 1286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1287 |Type=2 |P|E|S| Reserved | Record Count | 1288 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1289 | Nonce . . . | 1290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1291 | . . . Nonce | 1292 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1293 | | Record TTL | 1294 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1295 R | Locator Count | EID mask-len | ACT |A| Reserved | 1296 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1297 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1298 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1299 r | EID-prefix | 1300 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1301 | /| Priority | Weight | M Priority | M Weight | 1302 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1303 | o | Unused Flags |L|p|R| Loc-AFI | 1304 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1305 | \| Locator | 1306 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1307 | Mapping Protocol Data | 1308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1310 Packet field descriptions: 1312 Type: 2 (Map-Reply) 1314 P: This is the probe-bit which indicates that the Map-Reply is in 1315 response to a locator reachability probe Map-Request. The nonce 1316 field MUST contain a copy of the nonce value from the original 1317 Map-Request. See Section 6.3.2 for more details. 1319 E: Indicates that the ETR which sends this Map-Reply message is 1320 advertising that the site is enabled for the Echo-Nonce locator 1321 reachability algorithm. See Section 6.3.1 for more details. 1323 S: This is the Security bit. When set to 1 the field following the 1324 Mapping Protocol Data field will have the following format. The 1325 detailed format of the Authentication Data Content is for further 1326 study. 1328 0 1 2 3 1329 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 1330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1331 | AD Type | Authentication Data Content . . . | 1332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1334 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1335 receipt. 1337 Record Count: The number of records in this reply message. A record 1338 is comprised of that portion of the packet labeled 'Record' above 1339 and occurs the number of times equal to Record count. 1341 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1342 from the Map-Request is echoed in this Nonce field of the Map- 1343 Reply. 1345 Record TTL: The time in minutes the recipient of the Map-Reply will 1346 store the mapping. If the TTL is 0, the entry SHOULD be removed 1347 from the cache immediately. If the value is 0xffffffff, the 1348 recipient can decide locally how long to store the mapping. 1350 Locator Count: The number of Locator entries. A locator entry 1351 comprises what is labeled above as 'Loc'. The locator count can 1352 be 0 indicating there are no locators for the EID-prefix. 1354 EID mask-len: Mask length for EID prefix. 1356 ACT: This 3-bit field describes negative Map-Reply actions. These 1357 bits are used only when the 'Locator Count' field is set to 0. 1358 The action bits are encoded only in Map-Reply messages. The 1359 actions defined are used by an ITR or PTR when a destination EID 1360 matches a negative mapping cache entry. Unassigned values should 1361 cause a map-cache entry to be created and, when packets match this 1362 negative cache entry, they will be dropped. The current assigned 1363 values are: 1365 (0) No-Action: The map-cache is kept alive and no packet 1366 encapsulation occurs. 1368 (1) Natively-Forward: The packet is not encapsulated or dropped 1369 but natively forwarded. 1371 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1373 (3) Drop: A packet that matches this map-cache entry is dropped. 1374 An ICMP Unreachable message SHOULD be sent. 1376 A: The Authoritative bit, when sent by a UDP-based message is always 1377 set to 1 by an ETR. See [CONS] for TCP-based Map-Replies. When a 1378 Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, the 1379 Authoritative bit is set to 0. This indicates to requesting ITRs 1380 that the Map-Reply was not originated by a LISP node managed at 1381 the site that owns the EID-prefix. 1383 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1384 sender is informing the ITR what the version number is for the 1385 EID-record contained in the Map-Reply. The ETR can allocate this 1386 number internally but MUST coordinate this value with other ETRs 1387 for the site. When this value is 0, there is no versioning 1388 information conveyed. The Map-Version Number can be included in 1389 Map-Request and Map-Register messages. See Section 6.6.3 for more 1390 details. 1392 EID-prefix-AFI: Address family of EID-prefix according to [AFI]. 1394 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1395 address-family. 1397 Priority: each RLOC is assigned a unicast priority. Lower values 1398 are more preferable. When multiple RLOCs have the same priority, 1399 they may be used in a load-split fashion. A value of 255 means 1400 the RLOC MUST NOT be used for unicast forwarding. 1402 Weight: when priorities are the same for multiple RLOCs, the weight 1403 indicates how to balance unicast traffic between them. Weight is 1404 encoded as a relative weight of total unicast packets that match 1405 the mapping entry. For example if there are 4 locators in a 1406 locator set, where the weights assigned are 30, 20, 20, and 10, 1407 the first locator will get 37.5% of the traffic, the 2nd and 3rd 1408 locators will get 25% of traffic and the 4th locator will get 1409 12.5% of the traffic. If all weights for a locator-set are equal, 1410 receiver of the Map-Reply will decide how to load-split traffic. 1411 See Section 6.5 for a suggested hash algorithm to distribute load 1412 across locators with same priority and equal weight values. 1414 M Priority: each RLOC is assigned a multicast priority used by an 1415 ETR in a receiver multicast site to select an ITR in a source 1416 multicast site for building multicast distribution trees. A value 1417 of 255 means the RLOC MUST NOT be used for joining a multicast 1418 distribution tree. 1420 M Weight: when priorities are the same for multiple RLOCs, the 1421 weight indicates how to balance building multicast distribution 1422 trees across multiple ITRs. The weight is encoded as a relative 1423 weight (similar to the unicast Weights) of total number of trees 1424 built to the source site identified by the EID-prefix. If all 1425 weights for a locator-set are equal, the receiver of the Map-Reply 1426 will decide how to distribute multicast state across ITRs. 1428 Unused Flags: set to 0 when sending and ignored on receipt. 1430 L: when this bit is set, the locator is flagged as a local locator to 1431 the ETR that is sending the Map-Reply. When a Map-Server is doing 1432 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1433 0 for all locators in this locator-set. 1435 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1436 locator address, for which this bit is set, is the one being RLOC- 1437 probed and may be different from the source address of the Map- 1438 Reply. An ITR that RLOC-probes a particular locator, MUST use 1439 this locator for retrieving the data structure used to store the 1440 fact that the locator is reachable. The "p" bit is set for a 1441 single locator in the same locator set. If an implementation sets 1442 more than one "p" bit erroneously, the receiver of the Map-Reply 1443 MUST select the first locator. The "p" bit MUST NOT be set for 1444 locator-set records sent in Map-Request and Map-Register messages. 1446 R: set when the sender of a Map-Reply has a route to the locator in 1447 the locator data record. This receiver may find this useful to 1448 know if the locator is up but not necessarily reachable from the 1449 receiver's point of view. See also Section 6.4 for another way 1450 the R-bit may be used. 1452 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1453 assigned to an ETR. Note that the destination RLOC address MAY be 1454 an anycast address. A source RLOC can be an anycast address as 1455 well. The source or destination RLOC MUST NOT be the broadcast 1456 address (255.255.255.255 or any subnet broadcast address known to 1457 the router), and MUST NOT be a link-local multicast address. The 1458 source RLOC MUST NOT be a multicast address. The destination RLOC 1459 SHOULD be a multicast address if it is being mapped from a 1460 multicast destination EID. 1462 Mapping Protocol Data: See [CONS] for details. This field is 1463 optional and present when the UDP length indicates there is enough 1464 space in the packet to include it. The Mapping Protocol Data is 1465 used when needed by the particular mapping system. 1467 6.1.5. EID-to-RLOC UDP Map-Reply Message 1469 A Map-Reply returns an EID-prefix with a prefix length that is less 1470 than or equal to the EID being requested. The EID being requested is 1471 either from the destination field of an IP header of a Data-Probe or 1472 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1473 globally-routable IP addresses of all ETRs for the LISP site. Each 1474 RLOC conveys status reachability but does not convey path 1475 reachability from a requesters perspective. Separate testing of path 1476 reachability is required, See Section 6.3 for details. 1478 Note that a Map-Reply may contain different EID-prefix granularity 1479 (prefix + length) than the Map-Request which triggers it. This might 1480 occur if a Map-Request were for a prefix that had been returned by an 1481 earlier Map-Reply. In such a case, the requester updates its cache 1482 with the new prefix information and granularity. For example, a 1483 requester with two cached EID-prefixes that are covered by a Map- 1484 Reply containing one, less-specific prefix, replaces the entry with 1485 the less-specific EID-prefix. Note that the reverse, replacement of 1486 one less-specific prefix with multiple more-specific prefixes, can 1487 also occur but not by removing the less-specific prefix rather by 1488 adding the more-specific prefixes which during a lookup will override 1489 the less-specific prefix. 1491 When an ETR is configured with overlapping EID-prefixes, a Map- 1492 Request with an EID that longest matches any EID-prefix MUST be 1493 returned in a single Map-Reply message. For instance, if an ETR had 1494 database mapping entries for EID-prefixes: 1496 10.0.0.0/8 1497 10.1.0.0/16 1498 10.1.1.0/24 1499 10.1.2.0/24 1501 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1502 count of 1 to be returned with a mapping record EID-prefix of 1503 10.1.1.0/24. 1505 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1506 count of 3 to be returned with mapping records for EID-prefixes 1507 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1509 Note that not all overlapping EID-prefixes need to be returned, only 1510 the more specifics (note in the second example above 10.0.0.0/8 was 1511 not returned for requesting EID 10.1.5.5) entries for the matching 1512 EID-prefix of the requesting EID. When more than one EID-prefix is 1513 returned, all SHOULD use the same Time-to-Live value so they can all 1514 time out at the same time. When a more specific EID-prefix is 1515 received later, its Time-to-Live value in the Map-Reply record can be 1516 stored even when other less specifics exist. When a less specific 1517 EID-prefix is received later, its map-cache expiration time SHOULD be 1518 set to the minimum expiration time of any more specific EID-prefix in 1519 the map-cache. This is done so the integrity of the EID-prefix set 1520 is wholly maintained so no more-specific entries are removed from the 1521 map-cache while keeping less-specific entries. 1523 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1524 per second to the same requesting router. For scalability, it is 1525 expected that aggregation of EID addresses into EID-prefixes will 1526 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1527 prefix range thereby reducing the number of Map-Request messages. 1529 Map-Reply records can have an empty locator-set. A negative Map- 1530 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1531 convey special actions by the sender to the ITR or PTR which have 1532 solicited the Map-Reply. There are two primary applications for 1533 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1534 ITR or PTR when a destination is for a LISP site versus a non-LISP 1535 site. And the other is to source quench Map-Requests which are sent 1536 for non-allocated EIDs. 1538 For each Map-Reply record, the list of locators in a locator-set MUST 1539 appear in the same order for each ETR that originates a Map-Reply 1540 message. The locator-set MUST be sorted in order of ascending IP 1541 address where an IPv4 locator address is considered numerically 'less 1542 than' an IPv6 locator address. 1544 When sending a Map-Reply message, the destination address is copied 1545 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1546 can choose a locator address from one of the address families it 1547 supports. For Data-Probes, the destination address of the Map-Reply 1548 is copied from the source address of the Data-Probe message which is 1549 invoking the reply. The source address of the Map-Reply is one of 1550 the local IP addresses chosen to allow uRPF checks to succeed in the 1551 upstream service provider. The destination port of a Map-Reply 1552 message is copied from the source port of the Map-Request or Data- 1553 Probe and the source port of the Map-Reply message is set to the 1554 well-known UDP port 4342. 1556 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1558 When an ETR is misconfigured or compromised, it could return coarse 1559 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1560 cover EID-prefixes which are allocated to other sites redirecting 1561 their traffic to the locators of the compromised site. 1563 To solve this problem, there are two basic solutions that could be 1564 used. The first is to have Map-Servers proxy-map-reply on behalf of 1565 ETRs so their registered EID-prefixes are the ones returned in Map- 1566 Replies. Since the interaction between an ETR and Map-Server is 1567 secured with shared-keys, it is more difficult for an ETR to 1568 misbehave. The second solution is to have ITRs and PTRs cache EID- 1569 prefixes with mask-lengths that are greater than or equal to a 1570 configured prefix length. This limits the damage to a specific width 1571 of any EID-prefix advertised, but needs to be coordinated with the 1572 allocation of site prefixes. These solutions can be used 1573 independently or at the same time. 1575 At the time of this writing, other approaches are being considered 1576 and researched. 1578 6.1.6. Map-Register Message Format 1580 The usage details of the Map-Register message can be found in 1581 specification [LISP-MS]. This section solely defines the message 1582 format. 1584 The message is sent in UDP with a destination UDP port of 4342 and a 1585 randomly selected UDP source port number. 1587 The Map-Register message format is: 1589 0 1 2 3 1590 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 1591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1592 |Type=3 |P| Reserved |M| Record Count | 1593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1594 | Nonce . . . | 1595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1596 | . . . Nonce | 1597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1598 | Key ID | Authentication Data Length | 1599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1600 ~ Authentication Data ~ 1601 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1602 | | Record TTL | 1603 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1604 R | Locator Count | EID mask-len | ACT |A| Reserved | 1605 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1606 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1607 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1608 r | EID-prefix | 1609 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1610 | /| Priority | Weight | M Priority | M Weight | 1611 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1612 | o | Unused Flags |L|p|R| Loc-AFI | 1613 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1614 | \| Locator | 1615 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1617 Packet field descriptions: 1619 Type: 3 (Map-Register) 1621 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1622 Register message requesting for the Map-Server to proxy Map-Reply. 1623 The Map-Server will send non-authoritative Map-Replies on behalf 1624 of the ETR. Details on this usage will be provided in a future 1625 version of this draft. 1627 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1628 receipt. 1630 M: This is the want-map-notify bit, when set to 1 an ETR is 1631 requesting for a Map-Notify message to be returned in response to 1632 sending a Map-Register message. The Map-Notify message sent by a 1633 Map-Server is used to an acknowledge receipt of a Map-Register 1634 message. 1636 Record Count: The number of records in this Map-Register message. A 1637 record is comprised of that portion of the packet labeled 'Record' 1638 above and occurs the number of times equal to Record count. 1640 Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages. 1642 Key ID: A configured ID to find the configured Message 1643 Authentication Code (MAC) algorithm and key value used for the 1644 authentication function. 1646 Authentication Data Length: The length in bytes of the 1647 Authentication Data field that follows this field. The length of 1648 the Authentication Data field is dependent on the Message 1649 Authentication Code (MAC) algorithm used. The length field allows 1650 a device that doesn't know the MAC algorithm to correctly parse 1651 the packet. 1653 Authentication Data: The message digest used from the output of the 1654 Message Authentication Code (MAC) algorithm. The entire Map- 1655 Register payload is authenticated with this field preset to 0. 1656 After the MAC is computed, it is placed in this field. 1657 Implementations of this specification MUST include support for 1658 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-128-256 [RFC6234] 1659 is recommended. 1661 The definition of the rest of the Map-Register can be found in the 1662 Map-Reply section. 1664 6.1.7. Map-Notify Message Format 1666 The usage details of the Map-Notify message can be found in 1667 specification [LISP-MS]. This section solely defines the message 1668 format. 1670 The message is sent inside a UDP packet with a source UDP port equal 1671 to 4342 and a destination port equal to the source port from the Map- 1672 Register message this Map-Notify message is responding to. 1674 The Map-Notify message format is: 1676 0 1 2 3 1677 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 1678 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1679 |Type=4 | Reserved | Record Count | 1680 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1681 | Nonce . . . | 1682 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1683 | . . . Nonce | 1684 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1685 | Key ID | Authentication Data Length | 1686 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1687 ~ Authentication Data ~ 1688 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1689 | | Record TTL | 1690 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1691 R | Locator Count | EID mask-len | ACT |A| Reserved | 1692 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1693 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1694 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1695 r | EID-prefix | 1696 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1697 | /| Priority | Weight | M Priority | M Weight | 1698 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1699 | o | Unused Flags |L|p|R| Loc-AFI | 1700 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1701 | \| Locator | 1702 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1704 Packet field descriptions: 1706 Type: 4 (Map-Notify) 1708 The Map-Notify message has the same contents as a Map-Register 1709 message. See Map-Register section for field descriptions. 1711 6.1.8. Encapsulated Control Message Format 1713 An Encapsulated Control Message is used to encapsulate control 1714 packets sent between xTRs and the mapping database system described 1715 in [LISP-MS]. 1717 0 1 2 3 1718 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 1719 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1720 / | IPv4 or IPv6 Header | 1721 OH | (uses RLOC addresses) | 1722 \ | | 1723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1724 / | Source Port = xxxx | Dest Port = 4342 | 1725 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1726 \ | UDP Length | UDP Checksum | 1727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1728 LH |Type=8 |S| Reserved | 1729 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1730 / | IPv4 or IPv6 Header | 1731 IH | (uses RLOC or EID addresses) | 1732 \ | | 1733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1734 / | Source Port = xxxx | Dest Port = yyyy | 1735 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1736 \ | UDP Length | UDP Checksum | 1737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1738 LCM | LISP Control Message | 1739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1741 Packet header descriptions: 1743 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1744 source and destination header address fields. 1746 UDP: The outer UDP header with destination port 4342. The source 1747 port is randomly allocated. The checksum field MUST be non-zero. 1749 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1750 and what follows is either an IPv4 or IPv6 header as encoded by 1751 the first 4 bits after the reserved field. 1753 S: This is the Security bit. When set to 1 the field following the 1754 Reserved field will have the following format. The detailed 1755 format of the Authentication Data Content is for further study. 1757 0 1 2 3 1758 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 1759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1760 | AD Type | Authentication Data Content . . . | 1761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1763 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1764 addresses in the header address fields. When a Map-Request is 1765 encapsulated in this packet format the destination address in this 1766 header is an EID. 1768 UDP: The inner UDP header where the port assignments depends on the 1769 control packet being encapsulated. When the control packet is a 1770 Map-Request or Map-Register, the source port is ITR/PITR selected 1771 and the destination port is 4342. When the control packet is a 1772 Map-Reply, the source port is 4342 and the destination port is 1773 assigned from the source port of the invoking Map-Request. Port 1774 number 4341 MUST NOT be assigned to either port. The checksum 1775 field MUST be non-zero. 1777 LCM: The format is one of the control message formats described in 1778 this section. At this time, only Map-Request messages and PIM 1779 Join-Prune messages [MLISP] are allowed to be encapsulated. 1780 Encapsulating other types of LISP control messages are for further 1781 study. When Map-Requests are sent for RLOC-probing purposes (i.e 1782 the probe-bit is set), they MUST NOT be sent inside Encapsulated 1783 Control Messages. 1785 6.2. Routing Locator Selection 1787 Both client-side and server-side may need control over the selection 1788 of RLOCs for conversations between them. This control is achieved by 1789 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1790 messages. Alternatively, RLOC information may be gleaned from 1791 received tunneled packets or EID-to-RLOC Map-Request messages. 1793 The following enumerates different scenarios for choosing RLOCs and 1794 the controls that are available: 1796 o Server-side returns one RLOC. Client-side can only use one RLOC. 1797 Server-side has complete control of the selection. 1799 o Server-side returns a list of RLOC where a subset of the list has 1800 the same best priority. Client can only use the subset list 1801 according to the weighting assigned by the server-side. In this 1802 case, the server-side controls both the subset list and load- 1803 splitting across its members. The client-side can use RLOCs 1804 outside of the subset list if it determines that the subset list 1805 is unreachable (unless RLOCs are set to a Priority of 255). Some 1806 sharing of control exists: the server-side determines the 1807 destination RLOC list and load distribution while the client-side 1808 has the option of using alternatives to this list if RLOCs in the 1809 list are unreachable. 1811 o Server-side sets weight of 0 for the RLOC subset list. In this 1812 case, the client-side can choose how the traffic load is spread 1813 across the subset list. Control is shared by the server-side 1814 determining the list and the client determining load distribution. 1815 Again, the client can use alternative RLOCs if the server-provided 1816 list of RLOCs are unreachable. 1818 o Either side (more likely on the server-side ETR) decides not to 1819 send a Map-Request. For example, if the server-side ETR does not 1820 send Map-Requests, it gleans RLOCs from the client-side ITR, 1821 giving the client-side ITR responsibility for bidirectional RLOC 1822 reachability and preferability. Server-side ETR gleaning of the 1823 client-side ITR RLOC is done by caching the inner header source 1824 EID and the outer header source RLOC of received packets. The 1825 client-side ITR controls how traffic is returned and can alternate 1826 using an outer header source RLOC, which then can be added to the 1827 list the server-side ETR uses to return traffic. Since no 1828 Priority or Weights are provided using this method, the server- 1829 side ETR MUST assume each client-side ITR RLOC uses the same best 1830 Priority with a Weight of zero. In addition, since EID-prefix 1831 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1832 on tunnel routers can grow to be very large. 1834 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1835 received encapsulated packet, is only stored and used for a few 1836 seconds, pending verification. Verification is performed by 1837 sending a Map-Request to the source EID (the inner header IP 1838 source address) of the received encapsulated packet. A reply to 1839 this "verifying Map-Request" is used to fully populate the map- 1840 cache entry for the "gleaned" EID and is stored and used for the 1841 time indicated from the TTL field of a received Map-Reply. When a 1842 verified map-cache entry is stored, data gleaning no longer occurs 1843 for subsequent packets which have a source EID that matches the 1844 EID-prefix of the verified entry. 1846 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1847 reachable when the R-bit for the locator record is set to 1. When 1848 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1849 RLOC. Neither the information contained in a Map-Reply or that 1850 stored in the mapping database system provides reachability 1851 information for RLOCs. Note that reachability is not part of the 1852 mapping system and is determined using one or more of the Routing 1853 Locator Reachability Algorithms described in the next section. 1855 6.3. Routing Locator Reachability 1857 Several mechanisms for determining RLOC reachability are currently 1858 defined: 1860 1. An ETR may examine the Loc-Status-Bits in the LISP header of an 1861 encapsulated data packet received from an ITR. If the ETR is 1862 also acting as an ITR and has traffic to return to the original 1863 ITR site, it can use this status information to help select an 1864 RLOC. 1866 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1867 message for an RLOC it is using. This indicates that the RLOC is 1868 likely down. 1870 3. An ITR which participates in the global routing system can 1871 determine that an RLOC is down if no BGP RIB route exists that 1872 matches the RLOC IP address. 1874 4. An ITR may receive an ICMP Port Unreachable message from a 1875 destination host. This occurs if an ITR attempts to use 1876 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1877 non-LISP-capable site. 1879 5. An ITR may receive a Map-Reply from a ETR in response to a 1880 previously sent Map-Request. The RLOC source of the Map-Reply is 1881 likely up since the ETR was able to send the Map-Reply to the 1882 ITR. 1884 6. When an ETR receives an encapsulated packet from an ITR, the 1885 source RLOC from the outer header of the packet is likely up. 1887 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1888 described in this section, namely Echo-Noncing or RLOC-Probing. 1890 When determining Locator up/down reachability by examining the Loc- 1891 Status-Bits from the LISP encapsulated data packet, an ETR will 1892 receive up to date status from an encapsulating ITR about 1893 reachability for all ETRs at the site. CE-based ITRs at the source 1894 site can determine reachability relative to each other using the site 1895 IGP as follows: 1897 o Under normal circumstances, each ITR will advertise a default 1898 route into the site IGP. 1900 o If an ITR fails or if the upstream link to its PE fails, its 1901 default route will either time-out or be withdrawn. 1903 Each ITR can thus observe the presence or lack of a default route 1904 originated by the others to determine the Locator Status Bits it sets 1905 for them. 1907 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1908 Loc-Status-Bits in a LISP encapsulated packet are numbered from 0 to 1909 n-1 starting with the least significant bit. For example, if an RLOC 1910 listed in the 3rd position of the Map-Reply goes down (ordinal value 1911 2), then all ITRs at the site will clear the 3rd least significant 1912 bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they 1913 encapsulate. 1915 When an ETR decapsulates a packet, it will check for any change in 1916 the Loc-Status-Bits field. When a bit goes from 1 to 0, the ETR will 1917 refrain from encapsulating packets to an RLOC that is indicated as 1918 down. It will only resume using that RLOC if the corresponding Loc- 1919 Status-Bit returns to a value of 1. Loc-Status-Bits are associated 1920 with a locator-set per EID-prefix. Therefore, when a locator becomes 1921 unreachable, the Loc-Status-Bit that corresponds to that locator's 1922 position in the list returned by the last Map-Reply will be set to 1923 zero for that particular EID-prefix. 1925 When ITRs at the site are not deployed in CE routers, the IGP can 1926 still be used to determine the reachability of Locators provided they 1927 are injected into the IGP. This is typically done when a /32 address 1928 is configured on a loopback interface. 1930 When ITRs receive ICMP Network or Host Unreachable messages as a 1931 method to determine unreachability, they will refrain from using 1932 Locators which are described in Locator lists of Map-Replies. 1933 However, using this approach is unreliable because many network 1934 operators turn off generation of ICMP Unreachable messages. 1936 If an ITR does receive an ICMP Network or Host Unreachable message, 1937 it MAY originate its own ICMP Unreachable message destined for the 1938 host that originated the data packet the ITR encapsulated. 1940 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 1941 locator address from a locator-set in a mapping entry matches a 1942 prefix. If it does not find one and BGP is running in the Default 1943 Free Zone (DFZ), it can decide to not use the locator even though the 1944 Loc-Status-Bits indicate the locator is up. In this case, the path 1945 from the ITR to the ETR that is assigned the locator is not 1946 available. More details are in [LOC-ID-ARCH]. 1948 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 1949 Reply is returned, reachability of the Locator has been determined. 1950 Obviously, sending such probes increases the number of control 1951 messages originated by tunnel routers for active flows, so Locators 1952 are assumed to be reachable when they are advertised. 1954 This assumption does create a dependency: Locator unreachability is 1955 detected by the receipt of ICMP Host Unreachable messages. When an 1956 Locator has been determined to be unreachable, it is not used for 1957 active traffic; this is the same as if it were listed in a Map-Reply 1958 with priority 255. 1960 The ITR can test the reachability of the unreachable Locator by 1961 sending periodic Requests. Both Requests and Replies MUST be rate- 1962 limited. Locator reachability testing is never done with data 1963 packets since that increases the risk of packet loss for end-to-end 1964 sessions. 1966 When an ETR decapsulates a packet, it knows that it is reachable from 1967 the encapsulating ITR because that is how the packet arrived. In 1968 most cases, the ETR can also reach the ITR but cannot assume this to 1969 be true due to the possibility of path asymmetry. In the presence of 1970 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 1971 use the lack of return traffic as an indication that the ETR is 1972 unreachable. Instead, it MUST use an alternate mechanisms to 1973 determine reachability. 1975 6.3.1. Echo Nonce Algorithm 1977 When data flows bidirectionally between locators from different 1978 sites, a data-plane mechanism called "nonce echoing" can be used to 1979 determine reachability between an ITR and ETR. When an ITR wants to 1980 solicit a nonce echo, it sets the N and E bits and places a 24-bit 1981 nonce in the LISP header of the next encapsulated data packet. 1983 When this packet is received by the ETR, the encapsulated packet is 1984 forwarded as normal. When the ETR next sends a data packet to the 1985 ITR, it includes the nonce received earlier with the N bit set and E 1986 bit cleared. The ITR sees this "echoed nonce" and knows the path to 1987 and from the ETR is up. 1989 The ITR will set the E-bit and N-bit for every packet it sends while 1990 in echo-nonce-request state. The time the ITR waits to process the 1991 echoed nonce before it determines the path is unreachable is variable 1992 and a choice left for the implementation. 1994 If the ITR is receiving packets from the ETR but does not see the 1995 nonce echoed while being in echo-nonce-request state, then the path 1996 to the ETR is unreachable. This decision may be overridden by other 1997 locator reachability algorithms. Once the ITR determines the path to 1998 the ETR is down it can switch to another locator for that EID-prefix. 2000 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 2001 be implementing both ITR and ETR functionality for the echo nonce 2002 mechanism to operate. 2004 The ITR and ETR may both go into echo-nonce-request state at the same 2005 time. The number of packets sent or the time during which echo nonce 2006 requests are sent is an implementation specific setting. However, 2007 when an ITR is in echo-nonce-request state, it can echo the ETR's 2008 nonce in the next set of packets that it encapsulates and then 2009 subsequently, continue sending echo-nonce-request packets. 2011 This mechanism does not completely solve the forward path 2012 reachability problem as traffic may be unidirectional. That is, the 2013 ETR receiving traffic at a site may not be the same device as an ITR 2014 which transmits traffic from that site or the site to site traffic is 2015 unidirectional so there is no ITR returning traffic. 2017 The echo-nonce algorithm is bilateral. That is, if one side sets the 2018 E-bit and the other side is not enabled for echo-noncing, then the 2019 echoing of the nonce does not occur and the requesting side may 2020 regard the locator unreachable erroneously. An ITR SHOULD only set 2021 the E-bit in a encapsulated data packet when it knows the ETR is 2022 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 2023 Reply message. 2025 Note that other locator reachability mechanisms are being researched 2026 and can be used to compliment or even override the Echo Nonce 2027 Algorithm. See next section for an example of control-plane probing. 2029 6.3.2. RLOC Probing Algorithm 2031 RLOC Probing is a method that an ITR or PTR can use to determine the 2032 reachability status of one or more locators that it has cached in a 2033 map-cache entry. The probe-bit of the Map-Request and Map-Reply 2034 messages are used for RLOC Probing. 2036 RLOC probing is done in the control-plane on a timer basis where an 2037 ITR or PTR will originate a Map-Request destined to a locator address 2038 from one of its own locator addresses. A Map-Request used as an 2039 RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the 2040 ALT like one would when soliciting mapping data. The EID record 2041 encoded in the Map-Request is the EID-prefix of the map-cache entry 2042 cached by the ITR or PTR. The ITR may include a mapping data record 2043 for its own database mapping information which contains the local 2044 EID-prefixes and RLOCs for its site. 2046 When an ETR receives a Map-Request message with the probe-bit set, it 2047 returns a Map-Reply with the probe-bit set. The source address of 2048 the Map-Reply is set according to the procedure described in 2049 Section 6.1.5. The Map-Reply SHOULD contain mapping data for the 2050 EID-prefix contained in the Map-Request. This provides the 2051 opportunity for the ITR or PTR, which sent the RLOC-probe to get 2052 mapping updates if there were changes to the ETR's database mapping 2053 entries. 2055 There are advantages and disadvantages of RLOC Probing. The greatest 2056 benefit of RLOC Probing is that it can handle many failure scenarios 2057 allowing the ITR to determine when the path to a specific locator is 2058 reachable or has become unreachable, thus providing a robust 2059 mechanism for switching to using another locator from the cached 2060 locator. RLOC Probing can also provide rough RTT estimates between a 2061 pair of locators which can be useful for network management purposes 2062 as well as for selecting low delay paths. The major disadvantage of 2063 RLOC Probing is in the number of control messages required and the 2064 amount of bandwidth used to obtain those benefits, especially if the 2065 requirement for failure detection times are very small. 2067 Continued research and testing will attempt to characterize the 2068 tradeoffs of failure detection times versus message overhead. 2070 6.4. EID Reachability within a LISP Site 2072 A site may be multihomed using two or more ETRs. The hosts and 2073 infrastructure within a site will be addressed using one or more EID 2074 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2075 mapping system. One possible failure mode is for an ETR to lose 2076 reachability to one or more of the EID prefixes within its own site. 2077 When this occurs when the ETR sends Map-Replies, it can clear the 2078 R-bit associated with its own locator. And when the ETR is also an 2079 ITR, it can clear its locator-status-bit in the encapsulation data 2080 header. 2082 It is recognized there are no simple solutions to the site 2083 partitioning problem because it is hard to know which part of the 2084 EID-prefix range is partitioned. And which locators can reach any 2085 sub-ranges of the EID-prefixes. This problem is under investigation 2086 with the expectation that experiments will tell us more. Note, this 2087 is not a new problem introduced by the LISP architecture. The 2088 problem exists today when a multi-homed site uses BGP to advertise 2089 its reachability upstream. 2091 6.5. Routing Locator Hashing 2093 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2094 a requesting ITR, the locator-set for the EID-prefix may contain 2095 different priority values for each locator address. When more than 2096 one best priority locator exists, the ITR can decide how to load 2097 share traffic against the corresponding locators. 2099 The following hash algorithm may be used by an ITR to select a 2100 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2102 1. Either a source and destination address hash can be used or the 2103 traditional 5-tuple hash which includes the source and 2104 destination addresses, source and destination TCP, UDP, or SCTP 2105 port numbers and the IP protocol number field or IPv6 next- 2106 protocol fields of a packet a host originates from within a LISP 2107 site. When a packet is not a TCP, UDP, or SCTP packet, the 2108 source and destination addresses only from the header are used to 2109 compute the hash. 2111 2. Take the hash value and divide it by the number of locators 2112 stored in the locator-set for the EID-to-RLOC mapping. 2114 3. The remainder will be yield a value of 0 to "number of locators 2115 minus 1". Use the remainder to select the locator in the 2116 locator-set. 2118 Note that when a packet is LISP encapsulated, the source port number 2119 in the outer UDP header needs to be set. Selecting a hashed value 2120 allows core routers which are attached to Link Aggregation Groups 2121 (LAGs) to load-split the encapsulated packets across member links of 2122 such LAGs. Otherwise, core routers would see a single flow, since 2123 packets have a source address of the ITR, for packets which are 2124 originated by different EIDs at the source site. A suggested setting 2125 for the source port number computed by an ITR is a 5-tuple hash 2126 function on the inner header, as described above. 2128 Many core router implementations use a 5-tuple hash to decide how to 2129 balance packet load across members of a LAG. The 5-tuple hash 2130 includes the source and destination addresses of the packet and the 2131 source and destination ports when the protocol number in the packet 2132 is TCP or UDP. For this reason, UDP encoding is used for LISP 2133 encapsulation. 2135 6.6. Changing the Contents of EID-to-RLOC Mappings 2137 Since the LISP architecture uses a caching scheme to retrieve and 2138 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2139 date mapping is to re-request the mapping. However, the ITRs do not 2140 know when the mappings change and the ETRs do not keep track of which 2141 ITRs requested its mappings. For scalability reasons, we want to 2142 maintain this approach but need to provide a way for ETRs change 2143 their mappings and inform the sites that are currently communicating 2144 with the ETR site using such mappings. 2146 When adding a new locator record in lexicographic order to the end of 2147 a locator-set, it is easy to update mappings. We assume new mappings 2148 will maintain the same locator ordering as the old mapping but just 2149 have new locators appended to the end of the list. So some ITRs can 2150 have a new mapping while other ITRs have only an old mapping that is 2151 used until they time out. When an ITR has only an old mapping but 2152 detects bits set in the loc-status-bits that correspond to locators 2153 beyond the list it has cached, it simply ignores them. However, this 2154 can only happen for locator addresses that are lexicographically 2155 greater than the locator addresses in the existing locator-set. 2157 When a locator record is inserted in the middle of a locator-set, to 2158 maintain lexicographic order, the SMR procedure in Section 6.6.2 is 2159 used to inform ITRs and PTRs of the new locator-status-bit mappings. 2161 When a locator record is removed from a locator-set, ITRs that have 2162 the mapping cached will not use the removed locator because the xTRs 2163 will set the loc-status-bit to 0. So even if the locator is in the 2164 list, it will not be used. For new mapping requests, the xTRs can 2165 set the locator AFI to 0 (indicating an unspecified address), as well 2166 as setting the corresponding loc-status-bit to 0. This forces ITRs 2167 with old or new mappings to avoid using the removed locator. 2169 If many changes occur to a mapping over a long period of time, one 2170 will find empty record slots in the middle of the locator-set and new 2171 records appended to the locator-set. At some point, it would be 2172 useful to compact the locator-set so the loc-status-bit settings can 2173 be efficiently packed. 2175 We propose here three approaches for locator-set compaction, one 2176 operational and two protocol mechanisms. The operational approach 2177 uses a clock sweep method. The protocol approaches use the concept 2178 of Solicit-Map-Requests and Map-Versioning. 2180 6.6.1. Clock Sweep 2182 The clock sweep approach uses planning in advance and the use of 2183 count-down TTLs to time out mappings that have already been cached. 2184 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2185 there is a 24 hour window to time out old mappings. The following 2186 clock sweep procedure is used: 2188 1. 24 hours before a mapping change is to take effect, a network 2189 administrator configures the ETRs at a site to start the clock 2190 sweep window. 2192 2. During the clock sweep window, ETRs continue to send Map-Reply 2193 messages with the current (unchanged) mapping records. The TTL 2194 for these mappings is set to 1 hour. 2196 3. 24 hours later, all previous cache entries will have timed out, 2197 and any active cache entries will time out within 1 hour. During 2198 this 1 hour window the ETRs continue to send Map-Reply messages 2199 with the current (unchanged) mapping records with the TTL set to 2200 1 minute. 2202 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2203 messages with the new (changed) mapping records. So any active 2204 caches can get the new mapping contents right away if not cached, 2205 or in 1 minute if they had the mapping cached. The new mappings 2206 are cached with a time to live equal to the TTL in the Map-Reply. 2208 6.6.2. Solicit-Map-Request (SMR) 2210 Soliciting a Map-Request is a selective way for ETRs, at the site 2211 where mappings change, to control the rate they receive requests for 2212 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2213 the mappings they have cached. 2215 Since the ETRs don't keep track of remote ITRs that have cached their 2216 mappings, they do not know which ITRs need to have their mappings 2217 updated. As a result, an ETR will solicit Map-Requests (called an 2218 SMR message) from those sites to which it has been sending 2219 encapsulated data to for the last minute. In particular, an ETR will 2220 send an SMR an ITR to which it has recently sent encapsulated data. 2222 An SMR message is simply a bit set in a Map-Request message. An ITR 2223 or PTR will send a Map-Request when they receive an SMR message. 2224 Both the SMR sender and the Map-Request responder MUST rate-limited 2225 these messages. Rate-limiting can be implemented as a global rate- 2226 limiter or one rate-limiter per SMR destination. 2228 The following procedure shows how a SMR exchange occurs when a site 2229 is doing locator-set compaction for an EID-to-RLOC mapping: 2231 1. When the database mappings in an ETR change, the ETRs at the site 2232 begin to send Map-Requests with the SMR bit set for each locator 2233 in each map-cache entry the ETR caches. 2235 2. A remote ITR which receives the SMR message will schedule sending 2236 a Map-Request message to the source locator address of the SMR 2237 message or to the mapping database system. A newly allocated 2238 random nonce is selected and the EID-prefix used is the one 2239 copied from the SMR message. If the source locator is the only 2240 locator in the cached locator-set, the remote ITR SHOULD send a 2241 Map-Request to the database mapping system just in case the 2242 single locator has changed and may no longer be reachable to 2243 accept the Map-Request. 2245 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2246 Map-Reply while continuing to use the cached mapping. When Map 2247 Versioning is used, described in Section 6.6.3, an SMR sender can 2248 detect if an ITR is using the most up to date database mapping. 2250 4. The ETRs at the site with the changed mapping will reply to the 2251 Map-Request with a Map-Reply message that has a nonce from the 2252 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2253 limited. This is important to avoid Map-Reply implosion. 2255 5. The ETRs, at the site with the changed mapping, record the fact 2256 that the site that sent the Map-Request has received the new 2257 mapping data in the mapping cache entry for the remote site so 2258 the loc-status-bits are reflective of the new mapping for packets 2259 going to the remote site. The ETR then stops sending SMR 2260 messages. 2262 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2263 To avoid map-cache entry corruption by a third-party, a sender of an 2264 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2265 based Map-Request and the source is not in the locator-set for the 2266 stored map-cache entry, then the responding Map-Request MUST be sent 2267 with an EID destination to the mapping database system. Since the 2268 mapping database system is more secure to reach an authoritative ETR, 2269 it will deliver the Map-Request to the authoritative source of the 2270 mapping data. 2272 When an ITR receives an SMR-based Map-Request for which it does not 2273 have a cached mapping for the EID in the SMR message, it MAY not send 2274 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2275 SMR messages to all locators in the locator-set it has stored in its 2276 map-cache but the remote ITRs that receive the SMR may not be sending 2277 packets to the site. There is no point in updating the ITRs until 2278 they need to send, in which case, they will send Map-Requests to 2279 obtain a map-cache entry. 2281 6.6.3. Database Map Versioning 2283 When there is unidirectional packet flow between an ITR and ETR, and 2284 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2285 ITR so encapsulation can stop to a removed locator and start to a new 2286 locator in the locator-set. 2288 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2289 number. This is known as the Destination Map-Version Number. ITRs 2290 include the Destination Map-Version Number in packets they 2291 encapsulate to the site. When an ETR decapsulates a packet and 2292 detects the Destination Map-Version Number is less than the current 2293 version for its mapping, the SMR procedure described in Section 6.6.2 2294 occurs. 2296 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2297 Version number. This is known as the Source Map-Version Number. 2298 When an ETR decapsulates a packet and detects the Source Map-Version 2299 Number is greater than the last Map-Version Number sent in a Map- 2300 Reply from the ITR's site, the ETR will send a Map-Request to one of 2301 the ETRs for the source site. 2303 A Map-Version Number is used as a sequence number per EID-prefix. So 2304 values that are greater, are considered to be more recent. A value 2305 of 0 for the Source Map-Version Number or the Destination Map-Version 2306 Number conveys no versioning information and an ITR does no 2307 comparison with previously received Map-Version Numbers. 2309 A Map-Version Number can be included in Map-Register messages as 2310 well. This is a good way for the Map-Server can assure that all ETRs 2311 for a site registering to it will be Map-Version number synchronized. 2313 See [VERSIONING] for a more detailed analysis and description of 2314 Database Map Versioning. 2316 7. Router Performance Considerations 2318 LISP is designed to be very hardware-based forwarding friendly. A 2319 few implementation techniques can be used to incrementally implement 2320 LISP: 2322 o When a tunnel encapsulated packet is received by an ETR, the outer 2323 destination address may not be the address of the router. This 2324 makes it challenging for the control plane to get packets from the 2325 hardware. This may be mitigated by creating special FIB entries 2326 for the EID-prefixes of EIDs served by the ETR (those for which 2327 the router provides an RLOC translation). These FIB entries are 2328 marked with a flag indicating that control plane processing should 2329 be performed. The forwarding logic of testing for particular IP 2330 protocol number value is not necessary. There are a few proven 2331 cases where no changes to existing deployed hardware were needed 2332 to support the LISP data-plane. 2334 o On an ITR, prepending a new IP header consists of adding more 2335 bytes to a MAC rewrite string and prepending the string as part of 2336 the outgoing encapsulation procedure. Routers that support GRE 2337 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2338 support this action. 2340 o A packet's source address or interface the packet was received on 2341 can be used to select a VRF (Virtual Routing/Forwarding). The 2342 VRF's routing table can be used to find EID-to-RLOC mappings. 2344 8. Deployment Scenarios 2346 This section will explore how and where ITRs and ETRs can be deployed 2347 and will discuss the pros and cons of each deployment scenario. For 2348 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2350 There are two basic deployment trade-offs to consider: centralized 2351 versus distributed caches and flat, recursive, or re-encapsulating 2352 tunneling. When deciding on centralized versus distributed caching, 2353 the following issues should be considered: 2355 o Are the tunnel routers spread out so that the caches are spread 2356 across all the memories of each router? 2358 o Should management "touch points" be minimized by choosing few 2359 tunnel routers, just enough for redundancy? 2361 o In general, using more ITRs doesn't increase management load, 2362 since caches are built and stored dynamically. On the other hand, 2363 more ETRs does require more management since EID-prefix-to-RLOC 2364 mappings need to be explicitly configured. 2366 When deciding on flat, recursive, or re-encapsulation tunneling, the 2367 following issues should be considered: 2369 o Flat tunneling implements a single tunnel between source site and 2370 destination site. This generally offers better paths between 2371 sources and destinations with a single tunnel path. 2373 o Recursive tunneling is when tunneled traffic is again further 2374 encapsulated in another tunnel, either to implement VPNs or to 2375 perform Traffic Engineering. When doing VPN-based tunneling, the 2376 site has some control since the site is prepending a new tunnel 2377 header. In the case of TE-based tunneling, the site may have 2378 control if it is prepending a new tunnel header, but if the site's 2379 ISP is doing the TE, then the site has no control. Recursive 2380 tunneling generally will result in suboptimal paths but at the 2381 benefit of steering traffic to resource available parts of the 2382 network. 2384 o The technique of re-encapsulation ensures that packets only 2385 require one tunnel header. So if a packet needs to be rerouted, 2386 it is first decapsulated by the ETR and then re-encapsulated with 2387 a new tunnel header using a new RLOC. 2389 The next sub-sections will survey where tunnel routers can reside in 2390 the network. 2392 8.1. First-hop/Last-hop Tunnel Routers 2394 By locating tunnel routers close to hosts, the EID-prefix set is at 2395 the granularity of an IP subnet. So at the expense of more EID- 2396 prefix-to-RLOC sets for the site, the caches in each tunnel router 2397 can remain relatively small. But caches always depend on the number 2398 of non-aggregated EID destination flows active through these tunnel 2399 routers. 2401 With more tunnel routers doing encapsulation, the increase in control 2402 traffic grows as well: since the EID-granularity is greater, more 2403 Map-Requests and Map-Replies are traveling between more routers. 2405 The advantage of placing the caches and databases at these stub 2406 routers is that the products deployed in this part of the network 2407 have better price-memory ratios then their core router counterparts. 2408 Memory is typically less expensive in these devices and fewer routes 2409 are stored (only IGP routes). These devices tend to have excess 2410 capacity, both for forwarding and routing state. 2412 LISP functionality can also be deployed in edge switches. These 2413 devices generally have layer-2 ports facing hosts and layer-3 ports 2414 facing the Internet. Spare capacity is also often available in these 2415 devices as well. 2417 8.2. Border/Edge Tunnel Routers 2419 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2420 space associated with a site to be reachable via a small set of RLOCs 2421 assigned to the CE routers for that site. This is the default 2422 behavior envisioned in the rest of this specification. 2424 This offers the opposite benefit of the first-hop/last-hop tunnel 2425 router scenario: the number of mapping entries and network management 2426 touch points are reduced, allowing better scaling. 2428 One disadvantage is that less of the network's resources are used to 2429 reach host endpoints thereby centralizing the point-of-failure domain 2430 and creating network choke points at the CE router. 2432 Note that more than one CE router at a site can be configured with 2433 the same IP address. In this case an RLOC is an anycast address. 2434 This allows resilience between the CE routers. That is, if a CE 2435 router fails, traffic is automatically routed to the other routers 2436 using the same anycast address. However, this comes with the 2437 disadvantage where the site cannot control the entrance point when 2438 the anycast route is advertised out from all border routers. Another 2439 disadvantage of using anycast locators is the limited advertisement 2440 scope of /32 (or /128 for IPv6) routes. 2442 8.3. ISP Provider-Edge (PE) Tunnel Routers 2444 Use of ISP PE routers as tunnel endpoint routers is not the typical 2445 deployment scenario envisioned in the specification. This section 2446 attempts to capture some of reasoning behind this preference of 2447 implementing LISP on CE routers. 2449 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2450 than a site, control over the location of the egress tunnel 2451 endpoints. That is, the ISP can decide if the tunnel endpoints are 2452 in the destination site (in either CE routers or last-hop routers 2453 within a site) or at other PE edges. The advantage of this case is 2454 that two tunnel headers can be avoided. By having the PE be the 2455 first router on the path to encapsulate, it can choose a TE path 2456 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2457 the destination end site. 2459 An obvious disadvantage is that the end site has no control over 2460 where its packets flow or the RLOCs used. Other disadvantages 2461 include the difficulty in synchronizing path liveness updates between 2462 CE and PE routers. 2464 As mentioned in earlier sections a combination of these scenarios is 2465 possible at the expense of extra packet header overhead, if both site 2466 and provider want control, then recursive or re-encapsulating tunnels 2467 are used. 2469 8.4. LISP Functionality with Conventional NATs 2471 LISP routers can be deployed behind Network Address Translator (NAT) 2472 devices to provide the same set of packet services hosts have today 2473 when they are addressed out of private address space. 2475 It is important to note that a locator address in any LISP control 2476 message MUST be a globally routable address and therefore SHOULD NOT 2477 contain [RFC1918] addresses. If a LISP router is configured with 2478 private addresses, they MUST be used only in the outer IP header so 2479 the NAT device can translate properly. Otherwise, EID addresses MUST 2480 be translated before encapsulation is performed. Both NAT 2481 translation and LISP encapsulation functions could be co-located in 2482 the same device. 2484 More details on LISP address translation can be found in [INTERWORK]. 2486 8.5. Packets Egressing a LISP Site 2488 When a LISP site is using two ITRs for redundancy, the failure of one 2489 ITR will likely shift outbound traffic to the second. This second 2490 ITR's cache may not not be populated with the same EID-to-RLOC 2491 mapping entries as the first. If this second ITR does not have these 2492 mappings, traffic will be dropped while the mappings are retrieved 2493 from the mapping system. The retrieval of these messages may 2494 increase the load of requests being sent into the mapping system. 2495 Deployment and experimentation will determine whether this issue 2496 requires more attention. 2498 9. Traceroute Considerations 2500 When a source host in a LISP site initiates a traceroute to a 2501 destination host in another LISP site, it is highly desirable for it 2502 to see the entire path. Since packets are encapsulated from ITR to 2503 ETR, the hop across the tunnel could be viewed as a single hop. 2504 However, LISP traceroute will provide the entire path so the user can 2505 see 3 distinct segments of the path from a source LISP host to a 2506 destination LISP host: 2508 Segment 1 (in source LISP site based on EIDs): 2510 source-host ---> first-hop ... next-hop ---> ITR 2512 Segment 2 (in the core network based on RLOCs): 2514 ITR ---> next-hop ... next-hop ---> ETR 2516 Segment 3 (in the destination LISP site based on EIDs): 2518 ETR ---> next-hop ... last-hop ---> destination-host 2520 For segment 1 of the path, ICMP Time Exceeded messages are returned 2521 in the normal matter as they are today. The ITR performs a TTL 2522 decrement and test for 0 before encapsulating. So the ITR hop is 2523 seen by the traceroute source has an EID address (the address of 2524 site-facing interface). 2526 For segment 2 of the path, ICMP Time Exceeded messages are returned 2527 to the ITR because the TTL decrement to 0 is done on the outer 2528 header, so the destination of the ICMP messages are to the ITR RLOC 2529 address, the source RLOC address of the encapsulated traceroute 2530 packet. The ITR looks inside of the ICMP payload to inspect the 2531 traceroute source so it can return the ICMP message to the address of 2532 the traceroute client as well as retaining the core router IP address 2533 in the ICMP message. This is so the traceroute client can display 2534 the core router address (the RLOC address) in the traceroute output. 2535 The ETR returns its RLOC address and responds to the TTL decrement to 2536 0 like the previous core routers did. 2538 For segment 3, the next-hop router downstream from the ETR will be 2539 decrementing the TTL for the packet that was encapsulated, sent into 2540 the core, decapsulated by the ETR, and forwarded because it isn't the 2541 final destination. If the TTL is decremented to 0, any router on the 2542 path to the destination of the traceroute, including the next-hop 2543 router or destination, will send an ICMP Time Exceeded message to the 2544 source EID of the traceroute client. The ICMP message will be 2545 encapsulated by the local ITR and sent back to the ETR in the 2546 originated traceroute source site, where the packet will be delivered 2547 to the host. 2549 9.1. IPv6 Traceroute 2551 IPv6 traceroute follows the procedure described above since the 2552 entire traceroute data packet is included in ICMP Time Exceeded 2553 message payload. Therefore, only the ITR needs to pay special 2554 attention for forwarding ICMP messages back to the traceroute source. 2556 9.2. IPv4 Traceroute 2558 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2559 ICMP Time Exceeded messages only include the invoking IP header and 8 2560 bytes that follow the IP header. Therefore, when a core router sends 2561 an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP 2562 payload is the encapsulated header it prepended followed by a UDP 2563 header. The original invoking IP header, and therefore the identity 2564 of the traceroute source is lost. 2566 The solution we propose to solve this problem is to cache traceroute 2567 IPv4 headers in the ITR and to match them up with corresponding IPv4 2568 Time Exceeded messages received from core routers and the ETR. The 2569 ITR will use a circular buffer for caching the IPv4 and UDP headers 2570 of traceroute packets. It will select a 16-bit number as a key to 2571 find them later when the IPv4 Time Exceeded messages are received. 2572 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2573 16-bit number as the UDP source port in the encapsulating header. 2574 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2575 header of the encapsulating header is present in the ICMP payload 2576 thereby allowing the ITR to find the cached headers for the 2577 traceroute source. The ITR puts the cached headers in the payload 2578 and sends the ICMP Time Exceeded message to the traceroute source 2579 retaining the source address of the original ICMP Time Exceeded 2580 message (a core router or the ETR of the site of the traceroute 2581 destination). 2583 The signature of a traceroute packet comes in two forms. The first 2584 form is encoded as a UDP message where the destination port is 2585 inspected for a range of values. The second form is encoded as an 2586 ICMP message where the IP identification field is inspected for a 2587 well-known value. 2589 9.3. Traceroute using Mixed Locators 2591 When either an IPv4 traceroute or IPv6 traceroute is originated and 2592 the ITR encapsulates it in the other address family header, you 2593 cannot get all 3 segments of the traceroute. Segment 2 of the 2594 traceroute can not be conveyed to the traceroute source since it is 2595 expecting addresses from intermediate hops in the same address format 2596 for the type of traceroute it originated. Therefore, in this case, 2597 segment 2 will make the tunnel look like one hop. All the ITR has to 2598 do to make this work is to not copy the inner TTL to the outer, 2599 encapsulating header's TTL when a traceroute packet is encapsulated 2600 using an RLOC from a different address family. This will cause no 2601 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2603 10. Mobility Considerations 2605 There are several kinds of mobility of which only some might be of 2606 concern to LISP. Essentially they are as follows. 2608 10.1. Site Mobility 2610 A site wishes to change its attachment points to the Internet, and 2611 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2612 providers. Changes in EID-RLOC mappings for sites are expected to be 2613 handled by configuration, outside of the LISP protocol. 2615 10.2. Slow Endpoint Mobility 2617 An individual endpoint wishes to move, but is not concerned about 2618 maintaining session continuity. Renumbering is involved. LISP can 2619 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2620 decoupling the address space used by a site from the address spaces 2621 used by its ISPs. [RFC4984] 2623 10.3. Fast Endpoint Mobility 2625 Fast endpoint mobility occurs when an endpoint moves relatively 2626 rapidly, changing its IP layer network attachment point. Maintenance 2627 of session continuity is a goal. This is where the Mobile IPv4 2628 [RFC5944] and Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used, 2629 and primarily where interactions with LISP need to be explored. 2631 The problem is that as an endpoint moves, it may require changes to 2632 the mapping between its EID and a set of RLOCs for its new network 2633 location. When this is added to the overhead of mobile IP binding 2634 updates, some packets might be delayed or dropped. 2636 In IPv4 mobility, when an endpoint is away from home, packets to it 2637 are encapsulated and forwarded via a home agent which resides in the 2638 home area the endpoint's address belongs to. The home agent will 2639 encapsulate and forward packets either directly to the endpoint or to 2640 a foreign agent which resides where the endpoint has moved to. 2641 Packets from the endpoint may be sent directly to the correspondent 2642 node, may be sent via the foreign agent, or may be reverse-tunneled 2643 back to the home agent for delivery to the mobile node. As the 2644 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2645 mappings are required for communication between the mobile node and 2646 the home agent, whether via foreign agent or not. As a mobile 2647 endpoint changes networks, up to three LISP mapping changes may be 2648 required: 2650 o The mobile node moves from an old location to a new visited 2651 network location and notifies its home agent that it has done so. 2652 The Mobile IPv4 control packets the mobile node sends pass through 2653 one of the new visited network's ITRs, which needs a EID-RLOC 2654 mapping for the home agent. 2656 o The home agent might not have the EID-RLOC mappings for the mobile 2657 node's "care-of" address or its foreign agent in the new visited 2658 network, in which case it will need to acquire them. 2660 o When packets are sent directly to the correspondent node, it may 2661 be that no traffic has been sent from the new visited network to 2662 the correspondent node's network, and the new visited network's 2663 ITR will need to obtain an EID-RLOC mapping for the correspondent 2664 node's site. 2666 In addition, if the IPv4 endpoint is sending packets from the new 2667 visited network using its original EID, then LISP will need to 2668 perform a route-returnability check on the new EID-RLOC mapping for 2669 that EID. 2671 In IPv6 mobility, packets can flow directly between the mobile node 2672 and the correspondent node in either direction. The mobile node uses 2673 its "care-of" address (EID). In this case, the route-returnability 2674 check would not be needed but one more LISP mapping lookup may be 2675 required instead: 2677 o As above, three mapping changes may be needed for the mobile node 2678 to communicate with its home agent and to send packets to the 2679 correspondent node. 2681 o In addition, another mapping will be needed in the correspondent 2682 node's ITR, in order for the correspondent node to send packets to 2683 the mobile node's "care-of" address (EID) at the new network 2684 location. 2686 When both endpoints are mobile the number of potential mapping 2687 lookups increases accordingly. 2689 As a mobile node moves there are not only mobility state changes in 2690 the mobile node, correspondent node, and home agent, but also state 2691 changes in the ITRs and ETRs for at least some EID-prefixes. 2693 The goal is to support rapid adaptation, with little delay or packet 2694 loss for the entire system. Also IP mobility can be modified to 2695 require fewer mapping changes. In order to increase overall system 2696 performance, there may be a need to reduce the optimization of one 2697 area in order to place fewer demands on another. 2699 In LISP, one possibility is to "glean" information. When a packet 2700 arrives, the ETR could examine the EID-RLOC mapping and use that 2701 mapping for all outgoing traffic to that EID. It can do this after 2702 performing a route-returnability check, to ensure that the new 2703 network location does have a internal route to that endpoint. 2704 However, this does not cover the case where an ITR (the node assigned 2705 the RLOC) at the mobile-node location has been compromised. 2707 Mobile IP packet exchange is designed for an environment in which all 2708 routing information is disseminated before packets can be forwarded. 2709 In order to allow the Internet to grow to support expected future 2710 use, we are moving to an environment where some information may have 2711 to be obtained after packets are in flight. Modifications to IP 2712 mobility should be considered in order to optimize the behavior of 2713 the overall system. Anything which decreases the number of new EID- 2714 RLOC mappings needed when a node moves, or maintains the validity of 2715 an EID-RLOC mapping for a longer time, is useful. 2717 10.4. Fast Network Mobility 2719 In addition to endpoints, a network can be mobile, possibly changing 2720 xTRs. A "network" can be as small as a single router and as large as 2721 a whole site. This is different from site mobility in that it is 2722 fast and possibly short-lived, but different from endpoint mobility 2723 in that a whole prefix is changing RLOCs. However, the mechanisms 2724 are the same and there is no new overhead in LISP. A map request for 2725 any endpoint will return a binding for the entire mobile prefix. 2727 If mobile networks become a more common occurrence, it may be useful 2728 to revisit the design of the mapping service and allow for dynamic 2729 updates of the database. 2731 The issue of interactions between mobility and LISP needs to be 2732 explored further. Specific improvements to the entire system will 2733 depend on the details of mapping mechanisms. Mapping mechanisms 2734 should be evaluated on how well they support session continuity for 2735 mobile nodes. 2737 10.5. LISP Mobile Node Mobility 2739 A mobile device can use the LISP infrastructure to achieve mobility 2740 by implementing the LISP encapsulation and decapsulation functions 2741 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2742 node" can use topologically-independent EID IP addresses that are not 2743 advertised into and do not impose a cost on the global routing 2744 system. These EIDs are maintained at the edges of the mapping system 2745 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2746 only the correspondents of the LISP mobile node. 2748 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2749 more details. 2751 11. Multicast Considerations 2753 A multicast group address, as defined in the original Internet 2754 architecture is an identifier of a grouping of topologically 2755 independent receiver host locations. The address encoding itself 2756 does not determine the location of the receiver(s). The multicast 2757 routing protocol, and the network-based state the protocol creates, 2758 determines where the receivers are located. 2760 In the context of LISP, a multicast group address is both an EID and 2761 a Routing Locator. Therefore, no specific semantic or action needs 2762 to be taken for a destination address, as it would appear in an IP 2763 header. Therefore, a group address that appears in an inner IP 2764 header built by a source host will be used as the destination EID. 2765 The outer IP header (the destination Routing Locator address), 2766 prepended by a LISP router, will use the same group address as the 2767 destination Routing Locator. 2769 Having said that, only the source EID and source Routing Locator 2770 needs to be dealt with. Therefore, an ITR merely needs to put its 2771 own IP address in the source Routing Locator field when prepending 2772 the outer IP header. This source Routing Locator address, like any 2773 other Routing Locator address MUST be globally routable. 2775 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2776 ITR when a received data packet is a multicast data packet or when 2777 processing a source-specific Join (either by IGMPv3 or PIM). But the 2778 source Routing Locator is decided by the multicast routing protocol 2779 in a receiver site. That is, an EID to Routing Locator translation 2780 is done at control-time. 2782 Another approach is to have the ITR not encapsulate a multicast 2783 packet and allow the host built packet to flow into the core even if 2784 the source address is allocated out of the EID namespace. If the 2785 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2786 routers can RPF to the ITR (the Locator address which is injected 2787 into core routing) rather than the host source address (the EID 2788 address which is not injected into core routing). 2790 To avoid any EID-based multicast state in the network core, the first 2791 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2792 and Interworking with non-LISP sites is described in specification 2793 [MLISP]. 2795 12. Security Considerations 2797 It is believed that most of the security mechanisms will be part of 2798 the mapping database service when using control plane procedures for 2799 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2800 as described in this specification, protection is provided against 2801 ETR spoofing by using Return- Routability mechanisms evidenced by the 2802 use of a 24-bit Nonce field in the LISP encapsulation header and a 2803 64-bit Nonce field in the LISP control message. The nonce, coupled 2804 with the ITR accepting only solicited Map-Replies goes a long way 2805 toward providing decent authentication. 2807 LISP does not rely on a PKI infrastructure or a more heavy weight 2808 authentication system. These systems challenge the scalability of 2809 LISP which was a primary design goal. 2811 DoS attack prevention will depend on implementations rate-limiting 2812 Map-Requests and Map-Replies to the control plane as well as rate- 2813 limiting the number of data-triggered Map-Replies. 2815 An incorrectly implemented or malicious ITR might choose to ignore 2816 the priority and weights provided by the ETR in its Map-Reply. This 2817 traffic steering would be limited to the traffic that is sent by this 2818 ITR's site, and no more severe than if the site initiated a bandwidth 2819 DoS attack on (one of) the ETR's ingress links. The ITR's site would 2820 typically gain no benefit from not respecting the weights, and would 2821 likely to receive better service by abiding by them. 2823 To deal with map-cache exhaustion attempts in an ITR/PTR, the 2824 implementation should consider putting a maximum cap on the number of 2825 entries stored with a reserve list for special or frequently accessed 2826 sites. This should be a configuration policy control set by the 2827 network administrator who manages ITRs and PTRs. When overlapping 2828 EID-prefixes occur across multiple map-cache entries, the integrity 2829 of the set must be wholly maintained. So if a more-specific entry 2830 cannot be added due to reaching the maximum cap, then none of the 2831 less specifics should be stored in the map-cache. 2833 Given that the ITR/PTR maintains a cache of EID-to-RLOC mappings, 2834 cache sizing and maintenance is an issue to be kept in mind during 2835 implementation. It is a good idea to have instrumentation in place 2836 to detect thrashing of the cache. Implementation experimentation 2837 will be used to determine which cache management strategies work 2838 best. It should be noted that an undersized cache in an ITR/PTR not 2839 only causes adverse affect on the site or region they support, but 2840 may also cause increased Map-Request load on the mapping system. 2842 There is a security risk implicit in the fact that ETRs generate the 2843 EID prefix to which they are responding. An ETR can claim a shorter 2844 prefix than it is actually responsible for. Various mechanisms to 2845 ameliorate or resolve this issue will be examined in the future, 2846 [LISP-SEC]. 2848 Spoofing of inner header addresses of LISP encapsulated packets is 2849 possible like with any tunneling mechanism. ITRs MUST verify the 2850 source address of a packet to be an EID that belongs to the site's 2851 EID-prefix range prior to encapsulation. An ETR must only 2852 decapsulate and forward datagrams with an inner header destination 2853 that matches one of its EID-prefix ranges. If, upon receipt and 2854 decapsulation, the destination EID of a datagram does not match one 2855 of the ETR's configured EID-prefixes, the ETR MUST drop the 2856 datragram. If a LISP encapsulated packet arrives at an ETR, it MAY 2857 compare the inner header source EID address and the outer header 2858 source RLOC address with the mapping that exists in the mapping 2859 database. Then when spoofing attacks occur, the outer header source 2860 RLOC address can be used to trace back the attack to the source site, 2861 using existing operational tools. 2863 This experimental specification does not address automated key 2864 management (AKM). BCP 107 provides guidance in this area. In 2865 addition, at the time of this writing, substantial work is being 2866 undertaken to improve security of the routing system [KARP], [RPKI], 2867 [BGP-SEC], [LISP-SEC], Future work on LISP should address BCP-107 as 2868 well as other open security considerations, which may require changes 2869 to this specification. 2871 13. Network Management Considerations 2873 Considerations for Network Management tools exist so the LISP 2874 protocol suite can be operationally managed. The mechanisms can be 2875 found in [LISP-MIB] and [LISP-LIG]. 2877 14. IANA Considerations 2879 This section provides guidance to the Internet Assigned Numbers 2880 Authority (IANA) regarding registration of values related to the LISP 2881 specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. 2883 There are two name spaces in LISP that require registration: 2885 o LISP IANA registry allocations should not be made for purposes 2886 unrelated to LISP routing or transport protocols. 2888 o The following policies are used here with the meanings defined in 2889 BCP 26: "Specification Required", "IETF Consensus", "Experimental 2890 Use", "First Come First Served". 2892 14.1. LISP Address Type Codes 2894 Instance ID type codes have a range from 0 to 15, of which 0 and 1 2895 have been allocated [LCAF]. New Type Codes MUST be allocated 2896 starting at 2. Type Codes 2 - 10 are to be assigned by IETF Review. 2897 Type Codes 11 - 15 are available on a First Come First Served policy. 2899 The following codes have been allocated: 2901 Type 0: Null Body Type 2903 Type 1: AFI List Type 2905 See [LCAF] for details for other possible unapproved address 2906 encodings. The unapproved LCAF encodings are an area for further 2907 study and experimentation. 2909 14.2. LISP UDP Port Numbers 2911 The IANA registry has allocated UDP port numbers 4341 and 4342 for 2912 LISP data-plane and control-plane operation, respectively. 2914 15. References 2916 15.1. Normative References 2918 [BGP-SEC] Lepinski, M., "An Overview of BGPSEC", 2919 draft-lepinski-bgpsec-overview-00.txt (work in progress), 2920 March 2011. 2922 [KARP] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 2923 Routing Protocols (KARP)Design Guidelines", 2924 draft-ietf-karp-design-guide-02.txt (work in progress), 2925 March 2011. 2927 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 2928 August 1980. 2930 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 2931 STD 13, RFC 1034, November 1987. 2933 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 2934 E. Lear, "Address Allocation for Private Internets", 2935 BCP 5, RFC 1918, February 1996. 2937 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2938 Requirement Levels", BCP 14, RFC 2119, March 1997. 2940 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 2941 ESP and AH", RFC 2404, November 1998. 2943 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 2944 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 2945 March 2000. 2947 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 2948 via IPv4 Clouds", RFC 3056, February 2001. 2950 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 2951 of Explicit Congestion Notification (ECN) to IP", 2952 RFC 3168, September 2001. 2954 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 2955 an On-line Database", RFC 3232, January 2002. 2957 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 2958 A., Peterson, J., Sparks, R., Handley, M., and E. 2959 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 2960 June 2002. 2962 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 2963 in IPv6", RFC 3775, June 2004. 2965 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 2966 Requirements for Security", BCP 106, RFC 4086, June 2005. 2968 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 2969 (CIDR): The Internet Address Assignment and Aggregation 2970 Plan", BCP 122, RFC 4632, August 2006. 2972 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 2973 Optimization for Mobile IPv6", RFC 4866, May 2007. 2975 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 2976 Workshop on Routing and Addressing", RFC 4984, 2977 September 2007. 2979 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2980 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2981 May 2008. 2983 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 2984 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 2986 [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", 2987 RFC 5944, November 2010. 2989 [RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 2990 (SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011. 2992 [RPKI] Lepinski, M., "An Infrastructure to Support Secure 2993 Internet Routing", draft-ietf-sidr-arch-13.txt (work in 2994 progress), February 2011. 2996 [UDP-TUNNELS] 2997 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 2998 Packets", draft-eubanks-chimento-6man-01.txt (work in 2999 progress), October 2010. 3001 15.2. Informative References 3003 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3004 NUMBERS 3005 http://www.iana.org/assignments/address-family-numbers. 3007 [AFI-REGISTRY] 3008 IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3009 NUMBER registry http://www.iana.org/assignments/ 3010 address-family-numbers/ 3011 address-family-numbers.xml#address-family-numbers-1. 3013 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 3014 Alternative Topology (LISP-ALT)", 3015 draft-ietf-lisp-alt-07.txt (work in progress). 3017 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 3018 Enhancement to the Internet Architecture", Internet- 3019 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt. 3021 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 3022 Content distribution Overlay Network Service for LISP", 3023 draft-meyer-lisp-cons-04.txt (work in progress). 3025 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 3026 Mappings Multicast Across Cooperating Systems for LISP", 3027 draft-curran-lisp-emacs-00.txt (work in progress). 3029 [INTERWORK] 3030 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 3031 "Interworking LISP with IPv4 and IPv6", 3032 draft-ietf-lisp-interworking-02.txt (work in progress). 3034 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 3035 Address Format", draft-farinacci-lisp-lcaf-05.txt (work in 3036 progress). 3038 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 3039 "Renumbering: Threat or Menace?", Usenix . 3041 [LISP-DEPLOY] 3042 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 3043 "LISP Network Element Deployment Considerations", 3044 draft-jakab-lisp-deployment-03.txt (work in progress). 3046 [LISP-LIG] 3047 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 3048 draft-ietf-lisp-lig-02.txt (work in progress). 3050 [LISP-MAIN] 3051 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 3052 "Locator/ID Separation Protocol (LISP)", 3053 draft-farinacci-lisp-12.txt (work in progress). 3055 [LISP-MIB] 3056 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 3057 draft-ietf-lisp-mib-02.txt (work in progress). 3059 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 3060 Mobility Architecture", draft-meyer-lisp-mn-05.txt (work 3061 in progress). 3063 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 3064 draft-ietf-lisp-ms-09.txt (work in progress). 3066 [LISP-SEC] 3067 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 3068 Bonaventure, "LISP-Security (LISP-SEC)", 3069 draft-ietf-lisp-sec-00.txt (work in progress). 3071 [LOC-ID-ARCH] 3072 Meyer, D. and D. Lewis, "Architectural Implications of 3073 Locator/ID Separation", 3074 draft-meyer-loc-id-implications-01.txt (work in progress). 3076 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 3077 "LISP for Multicast Environments", 3078 draft-ietf-lisp-multicast-06.txt (work in progress). 3080 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 3081 draft-lear-lisp-nerd-08.txt (work in progress). 3083 [OPENLISP] 3084 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 3085 Report", draft-iannone-openlisp-implementation-02.txt 3086 (work in progress). 3088 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 3089 draft-narten-radir-problem-statement-05.txt (work in 3090 progress). 3092 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 3093 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 3094 September 2005. 3096 [RPMD] Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol 3097 for Routing Protocol Meta-data Dissemination", 3098 draft-handley-p2ppush-unpublished-2007726.txt (work in 3099 progress). 3101 [VERSIONING] 3102 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3103 Versioning", draft-ietf-lisp-map-versioning-01.txt (work 3104 in progress). 3106 Appendix A. Acknowledgments 3108 An initial thank you goes to Dave Oran for planting the seeds for the 3109 initial ideas for LISP. His consultation continues to provide value 3110 to the LISP authors. 3112 A special and appreciative thank you goes to Noel Chiappa for 3113 providing architectural impetus over the past decades on separation 3114 of location and identity, as well as detailed review of the LISP 3115 architecture and documents, coupled with enthusiasm for making LISP a 3116 practical and incremental transition for the Internet. 3118 The authors would like to gratefully acknowledge many people who have 3119 contributed discussion and ideas to the making of this proposal. 3120 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3121 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3122 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3123 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3124 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3125 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3126 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3127 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3128 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3129 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3130 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3131 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3132 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3133 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3134 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3135 Clarence Filsfils, and Alia Atlas. 3137 This work originated in the Routing Research Group (RRG) of the IRTF. 3138 The individual submission [LISP-MAIN] was converted into this IETF 3139 LISP working group draft. 3141 Appendix B. Document Change Log 3143 B.1. Changes to draft-ietf-lisp-15.txt 3145 o Posted July 2011. Fixing IDnits errors. 3147 o Change description on how to select a source address for RLOC- 3148 probe Map-Replies to refer to the "EID-to-RLOC Map-Reply Message" 3149 section. 3151 B.2. Changes to draft-ietf-lisp-14.txt 3153 o Post working group last call and pre-IESG last call review. 3155 o Indicate that an ICMP Unreachable message should be sent when a 3156 packet matches a drop-based negative map-cache entry. 3158 o Indicate how a map-cache set of overlapping EID-prefixes must 3159 maintian integrity when the map-cache maximum cap is reached. 3161 o Add Joel's description for the definition of an EID, that the bit 3162 string value can be an RLOC for another device in abstract but the 3163 architecture allows it to be an EID of one device and the same 3164 value as an RLOC for another device. 3166 o In the "Tunnel Encapsulation Details" section, indicate that 4 3167 combinations of encapsulation are supported. 3169 o Add what ETR should do for a Data-Probe when received for a 3170 destination EID outside of its EID-prefix range. This was added 3171 in the Data Probe definition section. 3173 o Added text indicating that more-specific EID-prefixes must not be 3174 removed when less-specific entries stay in the map-cache. This is 3175 to preserve the integrity of the EID-prefix set. 3177 o Add clarifying text in the Security Considerations section about 3178 how an ETR must not decapsulate and forward a packet that is not 3179 for its configured EID-prefix range. 3181 B.3. Changes to draft-ietf-lisp-13.txt 3183 o Posted June 2011 to complete working group last call. 3185 o Tracker item 87. Put Yakov suggested wording in the EID-prefix 3186 definition section to reference [INTERWORK] and [LISP-DEPLOY] 3187 about discussion on transition and access mechanisms. 3189 o Change "ITRs" to "ETRs" in the Locator Status Bit definition 3190 section and data packet description section per Damien's comment. 3192 o Remove the normative reference to [LISP-SEC] when describing the 3193 S-bit in the ECM and Map-Reply headers. 3195 o Tracker item 54. Added text from John Scudder in the "Packets 3196 Egressing a LISP Site" section. 3198 o Add sentence to the "Reencapsulating Tunnel" definition about how 3199 reencapsulation loops can occur when not coordinating among 3200 multiple mapping database systems. 3202 o Remove "In theory" from a sentence in the Security Considerations 3203 section. 3205 o Remove Security Area Statement title and reword section with 3206 Eliot's provided text. The text was agreed upon by LISP-WG chairs 3207 and Security ADs. 3209 o Remove word "potential" from the over-claiming paragraph of the 3210 Security Considerations section per Stephen's request. 3212 o Wordsmithing and other editorial comments from Alia. 3214 B.4. Changes to draft-ietf-lisp-12.txt 3216 o Posted April 2011. 3218 o Tracker item 87. Provided rewording how an EID-prefix can be 3219 resued in the definition section of "EID-prefix". 3221 o Tracker item 95. Change "eliminate" to "defer" in section 4.1. 3223 o Tracker item 110. Added that the Mapping Protocol Data field in 3224 the Map-Reply message is only used when needed by the particular 3225 Mapping Database System. 3227 o Tracker item 111. Indicate that if an LSB that is assocaited with 3228 an anycast address, that there is at least one RLOC that is up. 3230 o Tracker item 108. Make clear the R-bit does not define RLOC path 3231 reachability. 3233 o Tracker item 107. Indicate that weights are relative to each 3234 other versus requiring an addition of up to 100%. 3236 o Tracker item 46. Add a sentence how LISP products should be sized 3237 for the appropriate demand so cache thrashing is avoided. 3239 o Change some references of RFC 5226 to [AFI] per Luigi. 3241 o Per Luigi, make reference to "EID-AFI" consistent to "EID-prefix- 3242 AFI". 3244 o Tracker item 66. Indicate that appending locators to a locator- 3245 set is done when the added locators are lexicographically greater 3246 than the previous ones in the set. 3248 o Tracker item 87. Once again reword the definition of the EID- 3249 prefix to reflect recent comments. 3251 o Tracker item 70. Added text to security section on what the 3252 implications could be if an ITR does not obey priority and weights 3253 from a Map-Reply message. 3255 o Tracker item 54. Added text to the new section titled "Packets 3256 Egressing a LISP Site" to describe the implications when two or 3257 more ITRs exist at a site where only one ITR is used for egress 3258 traffic and when there is a shift of traffic to the others, how 3259 the map-cache will need to be populated in those new egress ITRs. 3261 o Tracker item 33. Make more clear in the Routing Locator Selection 3262 section what an ITR should do when it sees an R-bit of 0 in a 3263 locator-record of a Map-Reply. 3265 o Tracker item 33. Add paragraph to the EID Reachability section 3266 indicating that site parittioning is under investigation. 3268 o Tracker item 58. Added last paragraph of Security Considerations 3269 section about how to protect inner header EID address spoofing 3270 attacks. 3272 o Add suggested Sam text to indicate that all security concerns need 3273 not be addressed for moving document to Experimental RFC status. 3274 Put this in a subsection of the Secuirty Considerations section. 3276 B.5. Changes to draft-ietf-lisp-11.txt 3278 o Posted March 30, 2011. 3280 o Change IANA URL. The URL we had pointed to a general protocol 3281 numbers page. 3283 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3284 Requests to be sent to a MN ETR via the map-server. 3286 o Generalize text for the defintion of Reencapsuatling tunnels. 3288 o Add pargraph suggested by Joel to explain how implementation 3289 experimentation will be used to determine the proper cache 3290 management techniques. 3292 o Add Yakov provided text for the definition of "EID-to-RLOC 3293 "Database". 3295 o Add reference in Section 8, Deployment Scenarios, to the 3296 draft-jakab-lisp-deploy-02.txt draft. 3298 o Clarify sentence about no hardware changes needed to support LISP 3299 encapsulation. 3301 o Add paragraph about what is the procedure when a locator is 3302 inserted in the middle of a locator-set. 3304 o Add a definition for Locator-Status-Bits so we can emphasize they 3305 are used as a hint for router up/down status and not path 3306 reachability. 3308 o Change "BGP RIB" to "RIB" per Clarence's comment. 3310 o Fixed complaints by IDnits. 3312 o Add subsection to Security Considerations section indicating how 3313 EID-prefix overclaiming in Map-Replies is for further study and 3314 add a reference to LISP-SEC. 3316 B.6. Changes to draft-ietf-lisp-10.txt 3318 o Posted March 2011. 3320 o Add p-bit to Map-Request so there is documentary reasons to know 3321 when a PITR has sent a Map-Request to an ETR. 3323 o Add Map-Notify message which is used to acknowledge a Map-Register 3324 message sent to a Map-Server. 3326 o Add M-bit to the Map-Register message so an ETR that wants an 3327 acknowledgment for the Map-Register can request one. 3329 o Add S-bit to the ECM and Map-Reply messages to describe security 3330 data that can be present in each message. Then refer to 3332 [LISP-SEC] for expansive details. 3334 o Add Network Management Considerations section and point to the MIB 3335 and LIG drafts. 3337 o Remove the word "simple" per Yakov's comments. 3339 B.7. Changes to draft-ietf-lisp-09.txt 3341 o Posted October 2010. 3343 o Add to IANA Consideration section about the use of LCAF Type 3344 values that accepted and maintained by the IANA registry and not 3345 the LCAF specification. 3347 o Indicate that implementations should be able to receive LISP 3348 control messages when either UDP port is 4342, so they can be 3349 robust in the face of intervening NAT boxes. 3351 o Add paragraph to SMR section to indicate that an ITR does not need 3352 to respond to an SMR-based Map-Request when it has no map-cache 3353 entry for the SMR source's EID-prefix. 3355 B.8. Changes to draft-ietf-lisp-08.txt 3357 o Posted August 2010. 3359 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3360 Register messages. 3362 o Clarify language in section 6.1.5 about Map-Replying to Data- 3363 Probes or Map-Requests. 3365 o Indicate that outer TTL should only be copied to inner TTL when it 3366 is less than inner TTL. 3368 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3369 value of 0. 3371 o Indicate that SMRs can have a global or per SMR destination rate- 3372 limiter. 3374 o Add clarifications to the SMR procedures. 3376 o Add definitions for "client-side" and 'server-side" terms used in 3377 this specification. 3379 o Clear up language in section 6.4, last paragraph. 3381 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3382 probe a PETR and have it return a Map-Reply with a locator-set of 3383 size 0. The way it is spec'ed the map-cache entry has action 3384 "dropped". Drop-action is set to 3. 3386 o Add statement about normalizing locator weights. 3388 o Clarify R-bit definition in the Map-Reply locator record. 3390 o Add section on EID Reachability within a LISP site. 3392 o Clarify another disadvantage of using anycast locators. 3394 o Reworded Abstract. 3396 o Change section 2.0 Introduction to remove obsolete information 3397 such as the LISP variant definitions. 3399 o Change section 5 title from "Tunneling Details" to "LISP 3400 Encapsulation Details". 3402 o Changes to section 5 to include results of network deployment 3403 experience with MTU. Recommend that implementations use either 3404 the stateful or stateless handling. 3406 o Make clarification wordsmithing to Section 7 and 8. 3408 o Identify that if there is one locator in the locator-set of a map- 3409 cache entry, that an SMR from that locator should be responded to 3410 by sending the the SMR-invoked Map-Request to the database mapping 3411 system rather than to the RLOC itself (which may be unreachable). 3413 o When describing Unicast and Multicast Weights indicate the the 3414 values are relative weights rather than percentages. So it 3415 doesn't imply the sum of all locator weights in the locator-set 3416 need to be 100. 3418 o Do some wordsmithing on copying TTL and TOS fields. 3420 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3421 combed the spec. 3423 o Removed Section 14 "Prototype Plans and Status". We felt this 3424 type of section is no longer appropriate for a protocol 3425 specification. 3427 o Add clarification text for the IRC description per Damien's 3428 commentary. 3430 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3431 per Vina's comment about a possible DoS vector. 3433 o Clarify (S/2 + H) in the stateless MTU section. 3435 o Add text to reflect Damien's comment about the description of the 3436 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3437 addresses are local addresses of the Map-Requester. 3439 B.9. Changes to draft-ietf-lisp-07.txt 3441 o Posted April 2010. 3443 o Added I-bit to data header so LSB field can also be used as an 3444 Instance ID field. When this occurs, the LSB field is reduced to 3445 8-bits (from 32-bits). 3447 o Added V-bit to the data header so the 24-bit nonce field can also 3448 be used for source and destination version numbers. 3450 o Added Map-Version 12-bit value to the EID-record to be used in all 3451 of Map-Request, Map-Reply, and Map-Register messages. 3453 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3454 can decide what address to select for the destination of a Map- 3455 Reply. 3457 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3458 the Locator-Set record of an EID-record for a Map-Reply message. 3459 The L-bit indicates which RLOCs in the locator-set are local to 3460 the sender of the message. The P-bit indicates which RLOC is the 3461 source of a RLOC-probe Reply (Map-Reply) message. 3463 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3465 o Made editorial and clarification changes based on comments from 3466 Dhirendra Trivedi. 3468 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3470 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3471 6.3.1. 3473 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3474 for Map-Register messages. 3476 o Add NAT section per Ron Bonica comments. 3478 o Fix IDnits issues per Ron Bonica. 3480 o Added section on Virtualization and Segmentation to explain the 3481 use if the Instance ID field in the data header. 3483 o There are too many P-bits, keep their scope to the packet format 3484 description and refer to them by name every where else in the 3485 spec. 3487 o Scanned all occurrences of "should", "should not", "must" and 3488 "must not" and uppercased them. 3490 o John Zwiebel offered text for section 4.1 to modernize the 3491 example. Thanks Z! 3493 o Make it more clear in the definition of "EID-to-RLOC Database" 3494 that all ETRs need to have the same database mapping. This 3495 reflects a comment from John Scudder. 3497 o Add a definition "Route-returnability" to the Definition of Terms 3498 section. 3500 o In section 9.2, add text to describe what the signature of 3501 traceroute packets can look like. 3503 o Removed references to Data Probe for introductory example. Data- 3504 probes are still part of the LISP design but not encouraged. 3506 o Added the definition for "LISP site" to the Definition of Terms" 3507 section. 3509 B.10. Changes to draft-ietf-lisp-06.txt 3511 Editorial based changes: 3513 o Posted December 2009. 3515 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3517 o Add text to indicate that Map-Register messages must contain a 3518 computed UDP checksum. 3520 o Add definitions for PITR and PETR. 3522 o Indicate an AFI value of 0 is an unspecified address. 3524 o Indicate that the TTL field of a Map-Register is not used and set 3525 to 0 by the sender. This change makes this spec consistent with 3526 [LISP-MS]. 3528 o Change "... yield a packet size of L bytes" to "... yield a packet 3529 size greater than L bytes". 3531 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3532 Reply messages. 3534 o Clarify that LSBs that go beyond the number of locators do not to 3535 be SMRed when the locator addresses are greater lexicographically 3536 than the locator in the existing locator-set. 3538 o Add Gregg, Srini, and Amit to acknowledgment section. 3540 o Clarify in the definition of a LISP header what is following the 3541 UDP header. 3543 o Clarify "verifying Map-Request" text in section 6.1.3. 3545 o Add Xu Xiaohu to the acknowledgment section for introducing the 3546 problem of overlapping EID-prefixes among multiple sites in an RRG 3547 email message. 3549 Design based changes: 3551 o Use stronger language to have the outer IPv4 header set DF=1 so we 3552 can avoid fragment reassembly in an ETR or PETR. This will also 3553 make IPv4 and IPv6 encapsulation have consistent behavior. 3555 o Map-Requests should not be sent in ECM with the Probe bit is set. 3556 These type of Map-Requests are used as RLOC-probes and are sent 3557 directly to locator addresses in the underlying network. 3559 o Add text in section 6.1.5 about returning all EID-prefixes in a 3560 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3561 configure. 3563 o Add text in a new subsection of section 6.1.5 about dealing with 3564 Map-Replies with coarse EID-prefixes. 3566 B.11. Changes to draft-ietf-lisp-05.txt 3568 o Posted September 2009. 3570 o Added this Document Change Log appendix. 3572 o Added section indicating that encapsulated Map-Requests must use 3573 destination UDP port 4342. 3575 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3576 data in Map-Register payload. 3578 o Added Jari to acknowledgment section. 3580 o State the source-EID is set to 0 when using Map-Requests to 3581 refresh or RLOC-probe. 3583 o Make more clear what source-RLOC should be for a Map-Request. 3585 o The LISP-CONS authors thought that the Type definitions for CONS 3586 should be removed from this specification. 3588 o Removed nonce from Map-Register message, it wasn't used so no need 3589 for it. 3591 o Clarify what to do for unspecified Action bits for negative Map- 3592 Replies. Since No Action is a drop, make value 0 Drop. 3594 B.12. Changes to draft-ietf-lisp-04.txt 3596 o Posted September 2009. 3598 o How do deal with record count greater than 1 for a Map-Request. 3599 Damien and Joel comment. Joel suggests: 1) Specify that senders 3600 compliant with the current document will always set the count to 3601 1, and note that the count is included for future extensibility. 3602 2) Specify what a receiver compliant with the draft should do if 3603 it receives a request with a count greater than 1. Presumably, it 3604 should send some error back? 3606 o Add Fred Templin in acknowledgment section. 3608 o Add Margaret and Sam to the acknowledgment section for their great 3609 comments. 3611 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3613 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3614 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3615 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3616 ignore the checksum completely. And of course we'd need to 3617 confirm that can actually be implemented. In particular, hardware 3618 that verifies UDP checksums on receive needs to be checked to make 3619 sure it permits 0 checksums." 3621 o Margaret wants a reference to 3622 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3624 o Fix description in Map-Request section. Where we describe Map- 3625 Reply Record, change "R-bit" to "M-bit". 3627 o Add the mobility bit to Map-Replies. So PTRs don't probe so often 3628 for MNs but often enough to get mapping updates. 3630 o Indicate SHA1 can be used as well for Map-Registers. 3632 o More Fred comments on MTU handling. 3634 o Isidor comment about spec'ing better periodic Map-Registers. Will 3635 be fixed in draft-ietf-lisp-ms-02.txt. 3637 o Margaret's comment on gleaning: "The current specification does 3638 not make it clear how long gleaned map entries should be retained 3639 in the cache, nor does it make it clear how/ when they will be 3640 validated. The LISP spec should, at the very least, include a 3641 (short) default lifetime for gleaned entries, require that they be 3642 validated within a short period of time, and state that a new 3643 gleaned entry should never overwrite an entry that was obtained 3644 from the mapping system. The security implications of storing 3645 "gleaned" entries should also be explored in detail." 3647 o Add section on RLOC-probing per working group feedback. 3649 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3650 Noel. 3652 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3653 control plane only. 3655 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3656 fields can be turned off and used for another future purpose. For 3657 Luigi et al versioning convergence. 3659 o Add a N-bit to the data header suggested by Noel. Then the nonce 3660 field could be used when N is not 1. 3662 o Clarify that when E-bit is 0, the nonce field can be an echoed 3663 nonce or a random nonce. Comment from Jesper. 3665 o Indicate when doing data-gleaning that a verifying Map-Request is 3666 sent to the source-EID of the gleaned data packet so we can avoid 3667 map-cache corruption by a 3rd party. Comment from Pedro. 3669 o Indicate that a verifying Map-Request, for accepting mapping data, 3670 should be sent over the ALT (or to the EID). 3672 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3674 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3675 noncing. Comment by Pedro and Dino. 3677 o Jesper made a comment to loosen the language about requiring the 3678 copy of inner TTL to outer TTL since the text to get mixed-AF 3679 traceroute to work would violate the "MUST" clause. Changed from 3680 MUST to SHOULD in section 5.3. 3682 B.13. Changes to draft-ietf-lisp-03.txt 3684 o Posted July 2009. 3686 o Removed loc-reach-bits longword from control packets per Damien 3687 comment. 3689 o Clarifications in MTU text from Roque. 3691 o Added text to indicate that the locator-set be sorted by locator 3692 address from Isidor. 3694 o Clarification text from John Zwiebel in Echo-Nonce section. 3696 B.14. Changes to draft-ietf-lisp-02.txt 3698 o Posted July 2009. 3700 o Encapsulation packet format change to add E-bit and make loc- 3701 reach-bits 32-bits in length. 3703 o Added Echo-Nonce Algorithm section. 3705 o Clarification how ECN bits are copied. 3707 o Moved S-bit in Map-Request. 3709 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3710 RLOC-Probe Algorithm. 3712 o Added to Mobility section to reference [LISP-MN]. 3714 B.15. Changes to draft-ietf-lisp-01.txt 3716 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3718 o Defined LEID to be a "LISP EID". 3720 o Indicate encapsulation use IPv4 DF=0. 3722 o Added negative Map-Reply messages with drop, native-forward, and 3723 send-map-request actions. 3725 o Added Proxy-Map-Reply bit to Map-Register. 3727 B.16. Changes to draft-ietf-lisp-00.txt 3729 o Posted May 2009. 3731 o Rename of draft-farinacci-lisp-12.txt. 3733 o Acknowledgment to RRG. 3735 Authors' Addresses 3737 Dino Farinacci 3738 cisco Systems 3739 Tasman Drive 3740 San Jose, CA 95134 3741 USA 3743 Email: dino@cisco.com 3745 Vince Fuller 3746 cisco Systems 3747 Tasman Drive 3748 San Jose, CA 95134 3749 USA 3751 Email: vaf@cisco.com 3753 Dave Meyer 3754 cisco Systems 3755 170 Tasman Drive 3756 San Jose, CA 3757 USA 3759 Email: dmm@cisco.com 3761 Darrel Lewis 3762 cisco Systems 3763 170 Tasman Drive 3764 San Jose, CA 3765 USA 3767 Email: darlewis@cisco.com