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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) == Outdated reference: A later version (-10) exists of draft-ietf-karp-design-guide-06 == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-00 == Outdated reference: A later version (-12) exists of draft-ietf-lisp-deployment-05 == Outdated reference: A later version (-13) exists of draft-ietf-lisp-mib-07 == Outdated reference: A later version (-16) exists of draft-meyer-lisp-mn-08 == Outdated reference: A later version (-29) exists of draft-ietf-lisp-sec-04 -- Unexpected draft version: The latest known version of draft-meyer-loc-id-implications is -01, but you're referring to -02. == Outdated reference: A later version (-09) exists of draft-lear-lisp-nerd-08 == Outdated reference: A later version (-08) exists of draft-ietf-6man-udpchecksums-05 == Outdated reference: A later version (-12) exists of draft-ietf-6man-udpzero-07 Summary: 2 errors (**), 0 flaws (~~), 12 warnings (==), 2 comments (--). 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: May 17, 2013 D. Lewis 6 cisco Systems 7 November 13, 2012 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-24 12 Abstract 14 This draft describes a network layer based protocol that enables 15 separation of IP addresses into two new numbering spaces: Endpoint 16 Identifiers (EIDs) and Routing Locators (RLOCs). No changes are 17 required to either host protocol stacks or to the "core" of the 18 Internet infrastructure. LISP can be incrementally deployed, without 19 a "flag day", and offers traffic engineering, multi-homing, and 20 mobility benefits to early adopters, even when there are relatively 21 few LISP-capable sites. 23 Design and development of LISP was largely motivated by the problem 24 statement produced by the October 2006 IAB Routing and Addressing 25 Workshop. 27 Status of this Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on May 17, 2013. 44 Copyright Notice 46 Copyright (c) 2012 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 5 62 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 63 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 8 64 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 14 65 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 16 66 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . . 18 67 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 19 68 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 19 69 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . . 21 70 5.4. Dealing with Large Encapsulated Packets . . . . . . . . . 25 71 5.4.1. A Stateless Solution to MTU Handling . . . . . . . . . 25 72 5.4.2. A Stateful Solution to MTU Handling . . . . . . . . . 26 73 5.5. Using Virtualization and Segmentation with LISP . . . . . 26 74 6. EID-to-RLOC Mapping . . . . . . . . . . . . . . . . . . . . . 28 75 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats . . . . . 28 76 6.1.1. LISP Packet Type Allocations . . . . . . . . . . . . . 30 77 6.1.2. Map-Request Message Format . . . . . . . . . . . . . . 30 78 6.1.3. EID-to-RLOC UDP Map-Request Message . . . . . . . . . 33 79 6.1.4. Map-Reply Message Format . . . . . . . . . . . . . . . 34 80 6.1.5. EID-to-RLOC UDP Map-Reply Message . . . . . . . . . . 38 81 6.1.6. Map-Register Message Format . . . . . . . . . . . . . 40 82 6.1.7. Map-Notify Message Format . . . . . . . . . . . . . . 42 83 6.1.8. Encapsulated Control Message Format . . . . . . . . . 43 84 6.2. Routing Locator Selection . . . . . . . . . . . . . . . . 45 85 6.3. Routing Locator Reachability . . . . . . . . . . . . . . . 47 86 6.3.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 49 87 6.3.2. RLOC Probing Algorithm . . . . . . . . . . . . . . . . 50 88 6.4. EID Reachability within a LISP Site . . . . . . . . . . . 51 89 6.5. Routing Locator Hashing . . . . . . . . . . . . . . . . . 52 90 6.6. Changing the Contents of EID-to-RLOC Mappings . . . . . . 53 91 6.6.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . 54 92 6.6.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . 54 93 6.6.3. Database Map Versioning . . . . . . . . . . . . . . . 56 94 7. Router Performance Considerations . . . . . . . . . . . . . . 57 95 8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 58 96 8.1. First-hop/Last-hop Tunnel Routers . . . . . . . . . . . . 59 97 8.2. Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 59 98 8.3. ISP Provider-Edge (PE) Tunnel Routers . . . . . . . . . . 60 99 8.4. LISP Functionality with Conventional NATs . . . . . . . . 60 100 8.5. Packets Egressing a LISP Site . . . . . . . . . . . . . . 61 101 9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 62 102 9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 63 103 9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 63 104 9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 63 105 10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 65 106 10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 65 107 10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 65 108 10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 65 109 10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 67 110 10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 67 111 11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 69 112 12. Security Considerations . . . . . . . . . . . . . . . . . . . 70 113 13. Network Management Considerations . . . . . . . . . . . . . . 72 114 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 73 115 14.1. LISP ACT and Flag Fields . . . . . . . . . . . . . . . . . 73 116 14.2. LISP Address Type Codes . . . . . . . . . . . . . . . . . 73 117 14.3. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 74 118 14.4. LISP Key ID Numbers . . . . . . . . . . . . . . . . . . . 74 119 15. Known Open Issues and Areas of Future Work . . . . . . . . . . 75 120 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 77 121 16.1. Normative References . . . . . . . . . . . . . . . . . . . 77 122 16.2. Informative References . . . . . . . . . . . . . . . . . . 78 123 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 82 124 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 83 125 B.1. Changes to draft-ietf-lisp-24.txt . . . . . . . . . . . . 83 126 B.2. Changes to draft-ietf-lisp-23.txt . . . . . . . . . . . . 83 127 B.3. Changes to draft-ietf-lisp-22.txt . . . . . . . . . . . . 83 128 B.4. Changes to draft-ietf-lisp-21.txt . . . . . . . . . . . . 83 129 B.5. Changes to draft-ietf-lisp-20.txt . . . . . . . . . . . . 83 130 B.6. Changes to draft-ietf-lisp-19.txt . . . . . . . . . . . . 83 131 B.7. Changes to draft-ietf-lisp-18.txt . . . . . . . . . . . . 83 132 B.8. Changes to draft-ietf-lisp-17.txt . . . . . . . . . . . . 84 133 B.9. Changes to draft-ietf-lisp-16.txt . . . . . . . . . . . . 84 134 B.10. Changes to draft-ietf-lisp-15.txt . . . . . . . . . . . . 84 135 B.11. Changes to draft-ietf-lisp-14.txt . . . . . . . . . . . . 84 136 B.12. Changes to draft-ietf-lisp-13.txt . . . . . . . . . . . . 85 137 B.13. Changes to draft-ietf-lisp-12.txt . . . . . . . . . . . . 85 138 B.14. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 87 139 B.15. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 88 140 B.16. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 88 141 B.17. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 88 142 B.18. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 90 143 B.19. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 92 144 B.20. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 93 145 B.21. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 93 146 B.22. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 95 147 B.23. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 95 148 B.24. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 96 149 B.25. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 96 150 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 97 152 1. Requirements Notation 154 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 155 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 156 document are to be interpreted as described in [RFC2119]. 158 2. Introduction 160 This document describes the Locator/Identifier Separation Protocol 161 (LISP), which provides a set of functions for routers to exchange 162 information used to map from non globally routeable Endpoint 163 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 164 defines a mechanism for these LISP routers to encapsulate IP packets 165 addressed with EIDs for transmission across the< Internet that uses 166 RLOCs for routing and forwarding. 168 Creation of LISP was initially motivated by discussions during the 169 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 170 October, 2006 (see [RFC4984]). A key conclusion of the workshop was 171 that the Internet routing and addressing system was not scaling well 172 in the face of the explosive growth of new sites; one reason for this 173 poor scaling is the increasing number of multi-homed and other sites 174 that cannot be addressed as part of topologically- or provider-based 175 aggregated prefixes. Additional work that more completely described 176 the problem statement may be found in [RADIR]. 178 A basic observation, made many years ago in early networking research 179 such as that documented in [CHIAPPA] and [RFC4984], is that using a 180 single address field for both identifying a device and for 181 determining where it is topologically located in the network requires 182 optimization along two conflicting axes: for routing to be efficient, 183 the address must be assigned topologically; for collections of 184 devices to be easily and effectively managed, without the need for 185 renumbering in response to topological change (such as that caused by 186 adding or removing attachment points to the network or by mobility 187 events), the address must explicitly not be tied to the topology. 189 The approach that LISP takes to solving the routing scalability 190 problem is to replace IP addresses with two new types of numbers: 191 Routing Locators (RLOCs), which are topologically assigned to network 192 attachment points (and are therefore amenable to aggregation) and 193 used for routing and forwarding of packets through the network; and 194 Endpoint Identifiers (EIDs), which are assigned independently from 195 the network topology, are used for numbering devices, and are 196 aggregated along administrative boundaries. LISP then defines 197 functions for mapping between the two numbering spaces and for 198 encapsulating traffic originated by devices using non-routeable EIDs 199 for transport across a network infrastructure that routes and 200 forwards using RLOCs. Both RLOCs and EIDs are syntactically- 201 identical to IP addresses; it is the semantics of how they are used 202 that differs. 204 This document describes the protocol that implements these functions. 205 The database which stores the mappings between EIDs and RLOCs is 206 explicitly a separate "module" to facilitate experimentation with a 207 variety of approaches. One database design that is being developed 208 for experimentation as part of the LISP working group work is [ALT]. 209 Others that have been described include [CONS], [EMACS], [NERD]. 210 Finally, [LISP-MS], documents a general-purpose service interface for 211 accessing a mapping database; this interface is intended to make the 212 mapping database modular so that different approaches can be tried 213 without the need to modify installed LISP capable devices in LISP 214 sites. 216 This experimental specification has areas that require additional 217 experience and measurement. It is NOT RECOMMENDED for deployment 218 beyond experimental situations. Results of experimentation may lead 219 to modifications and enhancements of protocol mechanisms defined in 220 this document. See Section 15 for specific, known issues that are in 221 need of further work during development, implementation, and 222 experimentation. 224 An examination of the implications of LISP on Internet traffic, 225 applications, routers, and security is for future study. This 226 analysis will explain what role LISP can play in scalable routing and 227 will also look at scalability and levels of state required for 228 encapsulation, decapsulation, liveness, and so on. 230 3. Definition of Terms 232 Provider Independent (PI) Addresses: PI addresses are an address 233 block assigned from a pool where blocks are not associated with 234 any particular location in the network (e.g. from a particular 235 service provider), and is therefore not topologically aggregatable 236 in the routing system. 238 Provider Assigned (PA) Addresses: PA addresses are an address block 239 assigned to a site by each service provider to which a site 240 connects. Typically, each block is sub-block of a service 241 provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and 242 is aggregated into the larger block before being advertised into 243 the global Internet. Traditionally, IP multihoming has been 244 implemented by each multi-homed site acquiring its own, globally- 245 visible prefix. LISP uses only topologically-assigned and 246 aggregatable address blocks for RLOCs, eliminating this 247 demonstrably non-scalable practice. 249 Routing Locator (RLOC): A RLOC is an IPv4 [RFC0791] or IPv6 250 [RFC2460] address of an egress tunnel router (ETR). A RLOC is the 251 output of an EID-to-RLOC mapping lookup. An EID maps to one or 252 more RLOCs. Typically, RLOCs are numbered from topologically- 253 aggregatable blocks that are assigned to a site at each point to 254 which it attaches to the global Internet; where the topology is 255 defined by the connectivity of provider networks, RLOCs can be 256 thought of as PA addresses. Multiple RLOCs can be assigned to the 257 same ETR device or to multiple ETR devices at a site. 259 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 260 IPv6) value used in the source and destination address fields of 261 the first (most inner) LISP header of a packet. The host obtains 262 a destination EID the same way it obtains an destination address 263 today, for example through a Domain Name System (DNS) [RFC1034] 264 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 265 The source EID is obtained via existing mechanisms used to set a 266 host's "local" IP address. An EID used on the public Internet 267 must have the same properties as any other IP address used in that 268 manner; this means, among other things, that it must be globally 269 unique. An EID is allocated to a host from an EID-prefix block 270 associated with the site where the host is located. An EID can be 271 used by a host to refer to other hosts. EIDs MUST NOT be used as 272 LISP RLOCs. Note that EID blocks MAY be assigned in a 273 hierarchical manner, independent of the network topology, to 274 facilitate scaling of the mapping database. In addition, an EID 275 block assigned to a site may have site-local structure 276 (subnetting) for routing within the site; this structure is not 277 visible to the global routing system. In theory, the bit string 278 that represents an EID for one device can represent an RLOC for a 279 different device. As the architecture is realized, if a given bit 280 string is both an RLOC and an EID, it must refer to the same 281 entity in both cases. When used in discussions with other 282 Locator/ID separation proposals, a LISP EID will be called a 283 "LEID". Throughout this document, any references to "EID" refers 284 to an LEID. 286 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are 287 allocated to a site by an address allocation authority. EID- 288 prefixes are associated with a set of RLOC addresses which make up 289 a "database mapping". EID-prefix allocations can be broken up 290 into smaller blocks when an RLOC set is to be associated with the 291 larger EID-prefix block. A globally routed address block (whether 292 PI or PA) is not inherently an EID-prefix. A globally routed 293 address block MAY be used by its assignee as an EID block. The 294 converse is not supported. That is, a site which receives an 295 explicitly allocated EID-prefix may not use that EID-prefix as a 296 globally routed prefix. This would require coordination and 297 cooperation with the entities managing the mapping infrastructure. 298 Once this has been done, that block could be removed from the 299 globally routed IP system, if other suitable transition and access 300 mechanisms are in place. Discussion of such transition and access 301 mechanisms can be found in [INTERWORK] and [LISP-DEPLOY]. 303 End-system: An end-system is an IPv4 or IPv6 device that originates 304 packets with a single IPv4 or IPv6 header. The end-system 305 supplies an EID value for the destination address field of the IP 306 header when communicating globally (i.e. outside of its routing 307 domain). An end-system can be a host computer, a switch or router 308 device, or any network appliance. 310 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 311 LISP site. Packets sent by sources inside of the LISP site to 312 destinations outside of the site are candidates for encapsulation 313 by the ITR. The ITR treats the IP destination address as an EID 314 and performs an EID-to-RLOC mapping lookup. The router then 315 prepends an "outer" IP header with one of its globally-routable 316 RLOCs in the source address field and the result of the mapping 317 lookup in the destination address field. Note that this 318 destination RLOC MAY be an intermediate, proxy device that has 319 better knowledge of the EID-to-RLOC mapping closer to the 320 destination EID. In general, an ITR receives IP packets from site 321 end-systems on one side and sends LISP-encapsulated IP packets 322 toward the Internet on the other side. 324 Specifically, when a service provider prepends a LISP header for 325 Traffic Engineering purposes, the router that does this is also 326 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 327 on the outer destination address (the originating ITR's supplied 328 RLOC) or the inner destination address (the originating hosts 329 supplied EID). 331 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 332 network that prepends an additional LISP header for Traffic 333 Engineering purposes. 335 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 336 packet where the destination address in the "outer" IP header is 337 one of its own RLOCs. The router strips the "outer" header and 338 forwards the packet based on the next IP header found. In 339 general, an ETR receives LISP-encapsulated IP packets from the 340 Internet on one side and sends decapsulated IP packets to site 341 end-systems on the other side. ETR functionality does not have to 342 be limited to a router device. A server host can be the endpoint 343 of a LISP tunnel as well. 345 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 346 network that strips an outer LISP header for Traffic Engineering 347 purposes. 349 xTR: A xTR is a reference to an ITR or ETR when direction of data 350 flow is not part of the context description. xTR refers to the 351 router that is the tunnel endpoint. Used synonymously with the 352 term "Tunnel Router". For example, "An xTR can be located at the 353 Customer Edge (CE) router", meaning both ITR and ETR functionality 354 is at the CE router. 356 LISP Router: A LISP router is a router that performs the functions 357 of any or all of ITR, ETR, PITR, or PETR. 359 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 360 demand table in an ITR that stores, tracks, and is responsible for 361 timing-out and otherwise validating EID-to-RLOC mappings. This 362 cache is distinct from the full "database" of EID-to-RLOC 363 mappings, it is dynamic, local to the ITR(s), and relatively small 364 while the database is distributed, relatively static, and much 365 more global in scope. 367 EID-to-RLOC Database: The EID-to-RLOC database is a global 368 distributed database that contains all known EID-prefix to RLOC 369 mappings. Each potential ETR typically contains a small piece of 370 the database: the EID-to-RLOC mappings for the EID prefixes 371 "behind" the router. These map to one of the router's own, 372 globally-visible, IP addresses. The same database mapping entries 373 MUST be configured on all ETRs for a given site. In a steady 374 state the EID-prefixes for the site and the locator-set for each 375 EID-prefix MUST be the same on all ETRs. Procedures to enforce 376 and/or verify this are outside the scope of this document. Note 377 that there MAY be transient conditions when the EID-prefix for the 378 site and locator-set for each EID-prefix may not be the same on 379 all ETRs. This has no negative implications since a partial set 380 of locators can be used. 382 Recursive Tunneling: Recursive tunneling occurs when a packet has 383 more than one LISP IP header. Additional layers of tunneling MAY 384 be employed to implement traffic engineering or other re-routing 385 as needed. When this is done, an additional "outer" LISP header 386 is added and the original RLOCs are preserved in the "inner" 387 header. Any references to tunnels in this specification refers to 388 dynamic encapsulating tunnels and they are never statically 389 configured. 391 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 392 ETR removes a LISP header, then acts as an ITR to prepend another 393 LISP header. Doing this allows a packet to be re-routed by the 394 re-encapsulating router without adding the overhead of additional 395 tunnel headers. Any references to tunnels in this specification 396 refers to dynamic encapsulating tunnels and they are never 397 statically configured. When using multiple mapping database 398 systems, care must be taken to not create reencapsulation loops 399 through misconfiguration. 401 LISP Header: a term used in this document to refer to the outer 402 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-octet 403 header that follows the UDP header, an ITR prepends or an ETR 404 strips. 406 Address Family Identifier (AFI): a term used to describe an address 407 encoding in a packet. An address family currently pertains to an 408 IPv4 or IPv6 address. See [AFI]/[AFI-REGISTRY] and [RFC3232] for 409 details. An AFI value of 0 used in this specification indicates 410 an unspecified encoded address where the length of the address is 411 0 octets following the 16-bit AFI value of 0. 413 Negative Mapping Entry: A negative mapping entry, also known as a 414 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 415 is advertised or stored with no RLOCs. That is, the locator-set 416 for the EID-to-RLOC entry is empty or has an encoded locator count 417 of 0. This type of entry could be used to describe a prefix from 418 a non-LISP site, which is explicitly not in the mapping database. 419 There are a set of well defined actions that are encoded in a 420 Negative Map-Reply (Section 6.1.5). 422 Data Probe: A data-probe is a LISP-encapsulated data packet where 423 the inner header destination address equals the outer header 424 destination address used to trigger a Map-Reply by a decapsulating 425 ETR. In addition, the original packet is decapsulated and 426 delivered to the destination host if the destination EID is in the 427 EID-prefix range configured on the ETR. Otherwise, the packet is 428 discarded. A Data Probe is used in some of the mapping database 429 designs to "probe" or request a Map-Reply from an ETR; in other 430 cases, Map-Requests are used. See each mapping database design 431 for details. When using Data Probes, by sending Map-Requests on 432 the underlying routing system, EID-prefixes must be advertised. 433 However, this is discouraged if the core is to scale by having 434 less EID-prefixes stored in the core router's routing tables. 436 Proxy ITR (PITR): A PITR is defined and described in [INTERWORK], a 437 PITR acts like an ITR but does so on behalf of non-LISP sites 438 which send packets to destinations at LISP sites. 440 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 441 PETR acts like an ETR but does so on behalf of LISP sites which 442 send packets to destinations at non-LISP sites. 444 Route-returnability: is an assumption that the underlying routing 445 system will deliver packets to the destination. When combined 446 with a nonce that is provided by a sender and returned by a 447 receiver, this limits off-path data insertion. A route- 448 returnability check is verified when a message is sent with a 449 nonce, another message is returned with the same nonce, and the 450 destination of the original message appears as the source of the 451 returned message. 453 LISP site: is a set of routers in an edge network that are under a 454 single technical administration. LISP routers which reside in the 455 edge network are the demarcation points to separate the edge 456 network from the core network. 458 Client-side: a term used in this document to indicate a connection 459 initiation attempt by an EID. The ITR(s) at the LISP site are the 460 first to get involved in obtaining database map cache entries by 461 sending Map-Request messages. 463 Server-side: a term used in this document to indicate a connection 464 initiation attempt is being accepted for a destination EID. The 465 ETR(s) at the destination LISP site are the first to send Map- 466 Replies to the source site initiating the connection. The ETR(s) 467 at this destination site can obtain mappings by gleaning 468 information from Map-Requests, Data-Probes, or encapsulated 469 packets. 471 Locator Status Bits (LSBs): Locator status bits are present in the 472 LISP header. They are used by ITRs to inform ETRs about the up/ 473 down status of all ETRs at the local site. These bits are used as 474 a hint to convey up/down router status and not path reachability 475 status. The LSBs can be verified by use of one of the Locator 476 Reachability Algorithms described in Section 6.3. 478 Anycast Address: a term used in this document to refer to the same 479 IPv4 or IPv6 address configured and used on multiple systems at 480 the same time. An EID or RLOC can be an anycast address in each 481 of their own address spaces. 483 4. Basic Overview 485 One key concept of LISP is that end-systems (hosts) operate the same 486 way they do today. The IP addresses that hosts use for tracking 487 sockets, connections, and for sending and receiving packets do not 488 change. In LISP terminology, these IP addresses are called Endpoint 489 Identifiers (EIDs). 491 Routers continue to forward packets based on IP destination 492 addresses. When a packet is LISP encapsulated, these addresses are 493 referred to as Routing Locators (RLOCs). Most routers along a path 494 between two hosts will not change; they continue to perform routing/ 495 forwarding lookups on the destination addresses. For routers between 496 the source host and the ITR as well as routers from the ETR to the 497 destination host, the destination address is an EID. For the routers 498 between the ITR and the ETR, the destination address is an RLOC. 500 Another key LISP concept is the "Tunnel Router". A tunnel router 501 prepends LISP headers on host-originated packets and strips them 502 prior to final delivery to their destination. The IP addresses in 503 this "outer header" are RLOCs. During end-to-end packet exchange 504 between two Internet hosts, an ITR prepends a new LISP header to each 505 packet and an egress tunnel router strips the new header. The ITR 506 performs EID-to-RLOC lookups to determine the routing path to the 507 ETR, which has the RLOC as one of its IP addresses. 509 Some basic rules governing LISP are: 511 o End-systems (hosts) only send to addresses which are EIDs. They 512 don't know addresses are EIDs versus RLOCs but assume packets get 513 to their intended destinations. In a system where LISP is 514 deployed, LISP routers intercept EID addressed packets and assist 515 in delivering them across the network core where EIDs cannot be 516 routed. The procedure a host uses to send IP packets does not 517 change. 519 o EIDs are always IP addresses assigned to hosts. 521 o LISP routers mostly deal with Routing Locator addresses. See 522 details later in Section 4.1 to clarify what is meant by "mostly". 524 o RLOCs are always IP addresses assigned to routers; preferably, 525 topologically-oriented addresses from provider CIDR (Classless 526 Inter-Domain Routing) blocks. 528 o When a router originates packets it may use as a source address 529 either an EID or RLOC. When acting as a host (e.g. when 530 terminating a transport session such as SSH, TELNET, or SNMP), it 531 may use an EID that is explicitly assigned for that purpose. An 532 EID that identifies the router as a host MUST NOT be used as an 533 RLOC; an EID is only routable within the scope of a site. A 534 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 535 usage where a router could use its "host-like" EID to terminate 536 iBGP sessions to other routers in a site while at the same time 537 using RLOCs to terminate eBGP sessions to routers outside the 538 site. 540 o Packets with EIDs in them are not expected to be delivered end-to- 541 end in the absence of an EID-to-RLOC mapping operation. They are 542 expected to be used locally for intra-site communication or to be 543 encapsulated for inter-site communication. 545 o EID prefixes are likely to be hierarchically assigned in a manner 546 which is optimized for administrative convenience and to 547 facilitate scaling of the EID-to-RLOC mapping database. The 548 hierarchy is based on a address allocation hierarchy which is 549 independent of the network topology. 551 o EIDs may also be structured (subnetted) in a manner suitable for 552 local routing within an autonomous system. 554 An additional LISP header MAY be prepended to packets by a TE-ITR 555 when re-routing of the path for a packet is desired. A potential 556 use-case for this would be an ISP router that needs to perform 557 traffic engineering for packets flowing through its network. In such 558 a situation, termed Recursive Tunneling, an ISP transit acts as an 559 additional ingress tunnel router and the RLOC it uses for the new 560 prepended header would be either a TE-ETR within the ISP (along 561 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 562 inter-ISP traffic engineered path, where an agreement to build such a 563 path exists). 565 In order to avoid excessive packet overhead as well as possible 566 encapsulation loops, this document mandates that a maximum of two 567 LISP headers can be prepended to a packet. For initial LISP 568 deployments, it is assumed two headers is sufficient, where the first 569 prepended header is used at a site for Location/Identity separation 570 and second prepended header is used inside a service provider for 571 Traffic Engineering purposes. 573 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 574 For example, the ITR for a particular end-to-end packet exchange 575 might be the first-hop or default router within a site for the source 576 host. Similarly, the egress tunnel router might be the last-hop 577 router directly-connected to the destination host. Another example, 578 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 579 could be the site's border router at the service provider attachment 580 point. Mixing and matching of site-operated, ISP-operated, and other 581 tunnel routers is allowed for maximum flexibility. See Section 8 for 582 more details. 584 4.1. Packet Flow Sequence 586 This section provides an example of the unicast packet flow with the 587 following conditions: 589 o Source host "host1.abc.example.com" is sending a packet to 590 "host2.xyz.example.com", exactly what host1 would do if the site 591 was not using LISP. 593 o Each site is multi-homed, so each tunnel router has an address 594 (RLOC) assigned from the service provider address block for each 595 provider to which that particular tunnel router is attached. 597 o The ITR(s) and ETR(s) are directly connected to the source and 598 destination, respectively, but the source and destination can be 599 located anywhere in LISP site. 601 o Map-Requests can be sent on the underlying routing system 602 topology, to a mapping database system, or directly over an 603 alternative topology [ALT]. A Map-Request is sent for an external 604 destination when the destination is not found in the forwarding 605 table or matches a default route. 607 o Map-Replies are sent on the underlying routing system topology. 609 Client host1.abc.example.com wants to communicate with server 610 host2.xyz.example.com: 612 1. host1.abc.example.com wants to open a TCP connection to 613 host2.xyz.example.com. It does a DNS lookup on 614 host2.xyz.example.com. An A/AAAA record is returned. This 615 address is the destination EID. The locally-assigned address of 616 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 617 packet is built and forwarded through the LISP site as a normal 618 IP packet until it reaches a LISP ITR. 620 2. The LISP ITR must be able to map the destination EID to an RLOC 621 of one of the ETRs at the destination site. The specific method 622 used to do this is not described in this example. See [ALT] or 623 [CONS] for possible solutions. 625 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 626 rate-limited. 628 4. When an alternate mapping system is not in use, the Map-Request 629 packet is routed through the underlying routing system. 630 Otherwise, the Map-Request packet is routed on an alternate 631 logical topology, for example the [ALT] database mapping system. 632 In either case, when the Map-Request arrives at one of the ETRs 633 at the destination site, it will process the packet as a control 634 message. 636 5. The ETR looks at the destination EID of the Map-Request and 637 matches it against the prefixes in the ETR's configured EID-to- 638 RLOC mapping database. This is the list of EID-prefixes the ETR 639 is supporting for the site it resides in. If there is no match, 640 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 641 returned to the ITR. 643 6. The ITR receives the Map-Reply message, parses the message (to 644 check for format validity) and stores the mapping information 645 from the packet. This information is stored in the ITR's EID-to- 646 RLOC mapping cache. Note that the map cache is an on-demand 647 cache. An ITR will manage its map cache in such a way that 648 optimizes for its resource constraints. 650 7. Subsequent packets from host1.abc.example.com to 651 host2.xyz.example.com will have a LISP header prepended by the 652 ITR using the appropriate RLOC as the LISP header destination 653 address learned from the ETR. Note the packet MAY be sent to a 654 different ETR than the one which returned the Map-Reply due to 655 the source site's hashing policy or the destination site's 656 locator-set policy. 658 8. The ETR receives these packets directly (since the destination 659 address is one of its assigned IP addresses), checks the validity 660 of the addresses, strips the LISP header, and forwards packets to 661 the attached destination host. 663 In order to defer the need for a mapping lookup in the reverse 664 direction, an ETR MAY create a cache entry that maps the source EID 665 (inner header source IP address) to the source RLOC (outer header 666 source IP address) in a received LISP packet. Such a cache entry is 667 termed a "gleaned" mapping and only contains a single RLOC for the 668 EID in question. More complete information about additional RLOCs 669 SHOULD be verified by sending a LISP Map-Request for that EID. Both 670 ITR and the ETR may also influence the decision the other makes in 671 selecting an RLOC. See Section 6 for more details. 673 5. LISP Encapsulation Details 675 Since additional tunnel headers are prepended, the packet becomes 676 larger and can exceed the MTU of any link traversed from the ITR to 677 the ETR. It is RECOMMENDED in IPv4 that packets do not get 678 fragmented as they are encapsulated by the ITR. Instead, the packet 679 is dropped and an ICMP Too Big message is returned to the source. 681 This specification RECOMMENDS that implementations provide support 682 for one of the proposed fragmentation and reassembly schemes. Two 683 existing schemes are detailed in Section 5.4. 685 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 686 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 687 header is in IPv4 packet format and the other header is in IPv6 688 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 689 is in IPv6 packet format and the other header is in IPv4 packet 690 format). The next sub-sections illustrate packet formats for the 691 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6) but all 4 692 combinations MUST be supported. 694 5.1. LISP IPv4-in-IPv4 Header Format 696 0 1 2 3 697 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 1 698 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 699 / |Version| IHL |Type of Service| Total Length | 700 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 701 | | Identification |Flags| Fragment Offset | 702 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 703 OH | Time to Live | Protocol = 17 | Header Checksum | 704 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 705 | | Source Routing Locator | 706 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 707 \ | Destination Routing Locator | 708 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 709 / | Source Port = xxxx | Dest Port = 4341 | 710 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 711 \ | UDP Length | UDP Checksum | 712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 713 L |N|L|E|V|I|flags| Nonce/Map-Version | 714 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 715 S / | Instance ID/Locator Status Bits | 716 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 / |Version| IHL |Type of Service| Total Length | 718 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 719 | | Identification |Flags| Fragment Offset | 720 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 721 IH | Time to Live | Protocol | Header Checksum | 722 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 723 | | Source EID | 724 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 725 \ | Destination EID | 726 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 728 5.2. LISP IPv6-in-IPv6 Header Format 730 0 1 2 3 731 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 1 732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 733 / |Version| Traffic Class | Flow Label | 734 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 736 | | Payload Length | Next Header=17| Hop Limit | 737 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 738 | | 739 O + + 740 u | | 741 t + Source Routing Locator + 742 e | | 743 r + + 744 | | 745 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 746 d | | 747 r + + 748 | | 749 ^ + Destination Routing Locator + 750 | | | 751 \ + + 752 \ | | 753 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 754 / | Source Port = xxxx | Dest Port = 4341 | 755 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 756 \ | UDP Length | UDP Checksum | 757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 L |N|L|E|V|I|flags| Nonce/Map-Version | 759 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 760 S / | Instance ID/Locator Status Bits | 761 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 762 / |Version| Traffic Class | Flow Label | 763 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 764 / | Payload Length | Next Header | Hop Limit | 765 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 766 | | 767 I + + 768 n | | 769 n + Source EID + 770 e | | 771 r + + 772 | | 773 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 774 d | | 775 r + + 776 | | 777 ^ + Destination EID + 778 \ | | 779 \ + + 780 \ | | 781 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 783 5.3. Tunnel Header Field Descriptions 785 Inner Header (IH): The inner header is the header on the datagram 786 received from the originating host. The source and destination IP 787 addresses are EIDs, [RFC0791], [RFC2460]. 789 Outer Header: (OH) The outer header is a new header prepended by an 790 ITR. The address fields contain RLOCs obtained from the ingress 791 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 792 from [RFC0768]. The setting of the DF bit Flags field is 793 according to rules in Section 5.4.1 and Section 5.4.2. 795 UDP Header: The UDP header contains an ITR selected source port when 796 encapsulating a packet. See Section 6.5 for details on the hash 797 algorithm used to select a source port based on the 5-tuple of the 798 inner header. The destination port MUST be set to the well-known 799 IANA assigned port value 4341. 801 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 802 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 803 [UDP-TUNNELS] [UDP-ZERO]. When a packet with a zero UDP checksum 804 is received by an ETR, the ETR MUST accept the packet for 805 decapsulation. When an ITR transmits a non-zero value for the UDP 806 checksum, it MUST send a correctly computed value in this field. 807 When an ETR receives a packet with a non-zero UDP checksum, it MAY 808 choose to verify the checksum value. If it chooses to perform 809 such verification, and the verification fails, the packet MUST be 810 silently dropped. If the ETR chooses not to perform the 811 verification, or performs the verification successfully, the 812 packet MUST be accepted for decapsulation. The handling of UDP 813 checksums for all tunneling protocols, including LISP, is under 814 active discussion within the IETF. When that discussion 815 concludes, any necessary changes will be made to align LISP with 816 the outcome of the broader discussion. 818 UDP Length: The UDP length field is set for an IPv4 encapsulated 819 packet to be the sum of the inner header IPv4 Total Length plus 820 the UDP and LISP header lengths. For an IPv6 encapsulated packet, 821 the UDP length field is the sum of the inner header IPv6 Payload 822 Length, the size of the IPv6 header (40 octets), and the size of 823 the UDP and LISP headers. 825 N: The N bit is the nonce-present bit. When this bit is set to 1, 826 the low-order 24-bits of the first 32-bits of the LISP header 827 contains a Nonce. See Section 6.3.1 for details. Both N and V 828 bits MUST NOT be set in the same packet. If they are, a 829 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 830 having a Nonce value present. 832 L: The L bit is the Locator Status Bits field enabled bit. When this 833 bit is set to 1, the Locator Status Bits in the second 32-bits of 834 the LISP header are in use. 836 x 1 x x 0 x x x 837 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 838 |N|L|E|V|I|flags| Nonce/Map-Version | 839 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 840 | Locator Status Bits | 841 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 843 E: The E bit is the echo-nonce-request bit. This bit MUST be ignored 844 and has no meaning when the N bit is set to 0. When the N bit is 845 set to 1 and this bit is set to 1, means an ITR is requesting for 846 the nonce value in the Nonce field to be echoed back in LISP 847 encapsulated packets when the ITR is also an ETR. See 848 Section 6.3.1 for details. 850 V: The V bit is the Map-Version present bit. When this bit is set to 851 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 852 This bit indicates that the LISP header is encoded in this case 853 as: 855 0 x 0 1 x x x x 856 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 857 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 858 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 859 | Instance ID/Locator Status Bits | 860 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 862 I: The I bit is the Instance ID bit. See Section 5.5 for more 863 details. When this bit is set to 1, the Locator Status Bits field 864 is reduced to 8-bits and the high-order 24-bits are used as an 865 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 866 are transmitted as zero and ignored on receipt. The format of the 867 LISP header would look like in this case: 869 x x x x 1 x x x 870 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 871 |N|L|E|V|I|flags| Nonce/Map-Version | 872 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 873 | Instance ID | LSBs | 874 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 876 flags: The flags field is a 3-bit field is reserved for future flag 877 use. It MUST be set to 0 on transmit and MUST be ignored on 878 receipt. 880 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 881 generated by an ITR when the N-bit is set to 1. Nonce generation 882 algorithms are an implementation matter but are required to 883 generate different nonces when sending to different destinations. 884 However, the same nonce can be used for a period of time to the 885 same destination. The nonce is also used when the E-bit is set to 886 request the nonce value to be echoed by the other side when 887 packets are returned. When the E-bit is clear but the N-bit is 888 set, a remote ITR is either echoing a previously requested echo- 889 nonce or providing a random nonce. See Section 6.3.1 for more 890 details. 892 LISP Locator Status Bits (LSBs): When the L-bit is also set, the 893 locator status bits field in the LISP header is set by an ITR to 894 indicate to an ETR the up/down status of the Locators in the 895 source site. Each RLOC in a Map-Reply is assigned an ordinal 896 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 897 The Locator Status Bits are numbered from 0 to n-1 from the least 898 significant bit of field. The field is 32-bits when the I-bit is 899 set to 0 and is 8 bits when the I-bit is set to 1. When a Locator 900 Status Bit is set to 1, the ITR is indicating to the ETR the RLOC 901 associated with the bit ordinal has up status. See Section 6.3 902 for details on how an ITR can determine the status of the ETRs at 903 the same site. When a site has multiple EID-prefixes which result 904 in multiple mappings (where each could have a different locator- 905 set), the Locator Status Bits setting in an encapsulated packet 906 MUST reflect the mapping for the EID-prefix that the inner-header 907 source EID address matches. If the LSB for an anycast locator is 908 set to 1, then there is at least one RLOC with that address the 909 ETR is considered 'up'. 911 When doing ITR/PITR encapsulation: 913 o The outer header Time to Live field (or Hop Limit field, in case 914 of IPv6) SHOULD be copied from the inner header Time to Live 915 field. 917 o The outer header Type of Service field (or the Traffic Class 918 field, in the case of IPv6) SHOULD be copied from the inner header 919 Type of Service field (with one exception, see below). 921 When doing ETR/PETR decapsulation: 923 o The inner header Time to Live field (or Hop Limit field, in case 924 of IPv6) SHOULD be copied from the outer header Time to Live 925 field, when the Time to Live field of the outer header is less 926 than the Time to Live of the inner header. Failing to perform 927 this check can cause the Time to Live of the inner header to 928 increment across encapsulation/decapsulation cycle. This check is 929 also performed when doing initial encapsulation when a packet 930 comes to an ITR or PITR destined for a LISP site. 932 o The inner header Type of Service field (or the Traffic Class 933 field, in the case of IPv6) SHOULD be copied from the outer header 934 Type of Service field (with one exception, see below). 936 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 937 after decapsulating, the net effect of this is that the new outer 938 header will carry the same Time to Live as the old outer header minus 939 1. 941 Copying the TTL serves two purposes: first, it preserves the distance 942 the host intended the packet to travel; second, and more importantly, 943 it provides for suppression of looping packets in the event there is 944 a loop of concatenated tunnels due to misconfiguration. See 945 Section 9.3 for TTL exception handling for traceroute packets. 947 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 948 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 949 requires special treatment in order to avoid discarding indications 950 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 951 field from the inner header to the outer header. Re-encapsulation 952 MUST copy the 2-bit ECN field from the stripped outer header to the 953 new outer header. If the ECN field contains a congestion indication 954 codepoint (the value is '11', the Congestion Experienced (CE) 955 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 956 the stripped outer header to the surviving inner header that is used 957 to forward the packet beyond the ETR. These requirements preserve 958 Congestion Experienced (CE) indications when a packet that uses ECN 959 traverses a LISP tunnel and becomes marked with a CE indication due 960 to congestion between the tunnel endpoints. 962 5.4. Dealing with Large Encapsulated Packets 964 This section proposes two mechanisms to deal with packets that exceed 965 the path MTU between the ITR and ETR. 967 It is left to the implementor to decide if the stateless or stateful 968 mechanism should be implemented. Both or neither can be used since 969 it is a local decision in the ITR regarding how to deal with MTU 970 issues, and sites can interoperate with differing mechanisms. 972 Both stateless and stateful mechanisms also apply to Reencapsulating 973 and Recursive Tunneling. So any actions below referring to an ITR 974 also apply to an TE-ITR. 976 5.4.1. A Stateless Solution to MTU Handling 978 An ITR stateless solution to handle MTU issues is described as 979 follows: 981 1. Define H to be the size, in octets, of the outer header an ITR 982 prepends to a packet. This includes the UDP and LISP header 983 lengths. 985 2. Define L to be the size, in octets, of the maximum sized packet 986 an ITR can send to an ETR without the need for the ITR or any 987 intermediate routers to fragment the packet. 989 3. Define an architectural constant S for the maximum size of a 990 packet, in octets, an ITR must receive so the effective MTU can 991 be met. That is, S = L - H. 993 When an ITR receives a packet from a site-facing interface and adds H 994 octets worth of encapsulation to yield a packet size greater than L 995 octets, it resolves the MTU issue by first splitting the original 996 packet into 2 equal-sized fragments. A LISP header is then prepended 997 to each fragment. The size of the encapsulated fragments is then 998 (S/2 + H), which is less than the ITR's estimate of the path MTU 999 between the ITR and its correspondent ETR. 1001 When an ETR receives encapsulated fragments, it treats them as two 1002 individually encapsulated packets. It strips the LISP headers then 1003 forwards each fragment to the destination host of the destination 1004 site. The two fragments are reassembled at the destination host into 1005 the single IP datagram that was originated by the source host. Note 1006 that reassembly can happen at the ETR if the encapsulated packet was 1007 fragmented at or after the ITR. 1009 This behavior is performed by the ITR when the source host originates 1010 a packet with the DF field of the IP header is set to 0. When the DF 1011 field of the IP header is set to 1, or the packet is an IPv6 packet 1012 originated by the source host, the ITR will drop the packet when the 1013 size is greater than L, and sends an ICMP Too Big message to the 1014 source with a value of S, where S is (L - H). 1016 When the outer header encapsulation uses an IPv4 header, an 1017 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 1018 can be avoided. An implementation MAY set the DF bit in such headers 1019 to 0 if it has good reason to believe there are unresolvable path MTU 1020 issues between the sending ITR and the receiving ETR. 1022 This specification RECOMMENDS that L be defined as 1500. 1024 5.4.2. A Stateful Solution to MTU Handling 1026 An ITR stateful solution to handle MTU issues is described as follows 1027 and was first introduced in [OPENLISP]: 1029 1. The ITR will keep state of the effective MTU for each locator per 1030 mapping cache entry. The effective MTU is what the core network 1031 can deliver along the path between ITR and ETR. 1033 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 1034 with DF bit set to 1, exceeds what the core network can deliver, 1035 one of the intermediate routers on the path will send an ICMP Too 1036 Big message to the ITR. The ITR will parse the ICMP message to 1037 determine which locator is affected by the effective MTU change 1038 and then record the new effective MTU value in the mapping cache 1039 entry. 1041 3. When a packet is received by the ITR from a source inside of the 1042 site and the size of the packet is greater than the effective MTU 1043 stored with the mapping cache entry associated with the 1044 destination EID the packet is for, the ITR will send an ICMP Too 1045 Big message back to the source. The packet size advertised by 1046 the ITR in the ICMP Too Big message is the effective MTU minus 1047 the LISP encapsulation length. 1049 Even though this mechanism is stateful, it has advantages over the 1050 stateless IP fragmentation mechanism, by not involving the 1051 destination host with reassembly of ITR fragmented packets. 1053 5.5. Using Virtualization and Segmentation with LISP 1055 When multiple organizations inside of a LISP site are using private 1056 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 1057 segregated due to possible address duplication. An Instance ID in 1058 the address encoding can aid in making the entire AFI based address 1059 unique. See IANA Considerations Section 14.2 for details for 1060 possible address encodings. 1062 An Instance ID can be carried in a LISP encapsulated packet. An ITR 1063 that prepends a LISP header, will copy a 24-bit value, used by the 1064 LISP router to uniquely identify the address space. The value is 1065 copied to the Instance ID field of the LISP header and the I-bit is 1066 set to 1. 1068 When an ETR decapsulates a packet, the Instance ID from the LISP 1069 header is used as a table identifier to locate the forwarding table 1070 to use for the inner destination EID lookup. 1072 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 1073 24-bit Instance ID. 1075 6. EID-to-RLOC Mapping 1077 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 1079 The following UDP packet formats are used by the LISP control-plane. 1081 0 1 2 3 1082 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 1083 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1084 |Version| IHL |Type of Service| Total Length | 1085 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1086 | Identification |Flags| Fragment Offset | 1087 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1088 | Time to Live | Protocol = 17 | Header Checksum | 1089 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1090 | Source Routing Locator | 1091 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1092 | Destination Routing Locator | 1093 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1094 / | Source Port | Dest Port | 1095 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1096 \ | UDP Length | UDP Checksum | 1097 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1098 | | 1099 | LISP Message | 1100 | | 1101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1103 0 1 2 3 1104 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 1105 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1106 |Version| Traffic Class | Flow Label | 1107 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1108 | Payload Length | Next Header=17| Hop Limit | 1109 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1110 | | 1111 + + 1112 | | 1113 + Source Routing Locator + 1114 | | 1115 + + 1116 | | 1117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1118 | | 1119 + + 1120 | | 1121 + Destination Routing Locator + 1122 | | 1123 + + 1124 | | 1125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1126 / | Source Port | Dest Port | 1127 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1128 \ | UDP Length | UDP Checksum | 1129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1130 | | 1131 | LISP Message | 1132 | | 1133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1135 The LISP UDP-based messages are the Map-Request and Map-Reply 1136 messages. When a UDP Map-Request is sent, the UDP source port is 1137 chosen by the sender and the destination UDP port number is set to 1138 4342. When a UDP Map-Reply is sent, the source UDP port number is 1139 set to 4342 and the destination UDP port number is copied from the 1140 source port of either the Map-Request or the invoking data packet. 1141 Implementations MUST be prepared to accept packets when either the 1142 source port or destination UDP port is set to 4342 due to NATs 1143 changing port number values. 1145 The UDP Length field will reflect the length of the UDP header and 1146 the LISP Message payload. 1148 The UDP Checksum is computed and set to non-zero for Map-Request, 1149 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1150 on receipt and if the checksum fails, the packet MUST be dropped. 1152 The format of control messages includes the UDP header so the 1153 checksum and length fields can be used to protect and delimit message 1154 boundaries. 1156 6.1.1. LISP Packet Type Allocations 1158 This section will be the authoritative source for allocating LISP 1159 Type values and for defining LISP control message formats. Current 1160 allocations are: 1162 Reserved: 0 b'0000' 1163 LISP Map-Request: 1 b'0001' 1164 LISP Map-Reply: 2 b'0010' 1165 LISP Map-Register: 3 b'0011' 1166 LISP Map-Notify: 4 b'0100' 1167 LISP Encapsulated Control Message: 8 b'1000' 1169 6.1.2. Map-Request Message Format 1171 0 1 2 3 1172 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 1173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1174 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1176 | Nonce . . . | 1177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1178 | . . . Nonce | 1179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1180 | Source-EID-AFI | Source EID Address ... | 1181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1182 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1184 | ... | 1185 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1186 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1188 / | Reserved | EID mask-len | EID-prefix-AFI | 1189 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1190 \ | EID-prefix ... | 1191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1192 | Map-Reply Record ... | 1193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1195 Packet field descriptions: 1197 Type: 1 (Map-Request) 1199 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1200 Requests sent by an ITR. Set to 1 when an ITR wants the 1201 destination site to return the Map-Reply rather than the mapping 1202 database system. 1204 M: This is the map-data-present bit, when set, it indicates a Map- 1205 Reply Record segment is included in the Map-Request. 1207 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1208 treated as a locator reachability probe. The receiver SHOULD 1209 respond with a Map-Reply with the probe-bit set, indicating the 1210 Map-Reply is a locator reachability probe reply, with the nonce 1211 copied from the Map-Request. See Section 6.3.2 for more details. 1213 S: This is the Solicit-Map-Request (SMR) bit. See Section 6.6.2 for 1214 details. 1216 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1217 Map-Request. 1219 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1220 sending a Map-Request in response to a received SMR-based Map- 1221 Request. 1223 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1224 receipt. 1226 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1227 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1228 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1229 Address) pair MUST be encoded. Multiple ITR-RLOC Address fields 1230 are used so a Map-Replier can select which destination address to 1231 use for a Map-Reply. The IRC value ranges from 0 to 31. For a 1232 value of 0, there is 1 ITR-RLOC address encoded, and for a value 1233 of 1, there are 2 ITR-RLOC addresses encoded and so on up to 31 1234 which encodes a total of 32 ITR-RLOC addresses. 1236 Record Count: The number of records in this Map-Request message. A 1237 record is comprised of the portion of the packet that is labeled 1238 'Rec' above and occurs the number of times equal to Record Count. 1239 For this version of the protocol, a receiver MUST accept and 1240 process Map-Requests that contain one or more records, but a 1241 sender MUST only send Map-Requests containing one record. Support 1242 for requesting multiple EIDs in a single Map-Request message will 1243 be specified in a future version of the protocol. 1245 Nonce: An 8-octet random value created by the sender of the Map- 1246 Request. This nonce will be returned in the Map-Reply. The 1247 security of the LISP mapping protocol depends critically on the 1248 strength of the nonce in the Map-Request message. The nonce 1249 SHOULD be generated by a properly seeded pseudo-random (or strong 1250 random) source. See [RFC4086] for advice on generating security- 1251 sensitive random data. 1253 Source-EID-AFI: Address family of the "Source EID Address" field. 1255 Source EID Address: This is the EID of the source host which 1256 originated the packet which is caused the Map-Request. When Map- 1257 Requests are used for refreshing a map-cache entry or for RLOC- 1258 probing, an AFI value 0 is used and this field is of zero length. 1260 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1261 follows this field. 1263 ITR-RLOC Address: Used to give the ETR the option of selecting the 1264 destination address from any address family for the Map-Reply 1265 message. This address MUST be a routable RLOC address of the 1266 sender of the Map-Request message. 1268 EID mask-len: Mask length for EID prefix. 1270 EID-prefix-AFI: Address family of EID-prefix according to [AFI] 1272 EID-prefix: 4 octets if an IPv4 address-family, 16 octets if an IPv6 1273 address-family. When a Map-Request is sent by an ITR because a 1274 data packet is received for a destination where there is no 1275 mapping entry, the EID-prefix is set to the destination IP address 1276 of the data packet. And the 'EID mask-len' is set to 32 or 128 1277 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1278 about the status of a mapping it already has cached, the EID- 1279 prefix used in the Map-Request has the same mask-length as the 1280 EID-prefix returned from the site when it sent a Map-Reply 1281 message. 1283 Map-Reply Record: When the M bit is set, this field is the size of a 1284 single "Record" in the Map-Reply format. This Map-Reply record 1285 contains the EID-to-RLOC mapping entry associated with the Source 1286 EID. This allows the ETR which will receive this Map-Request to 1287 cache the data if it chooses to do so. 1289 6.1.3. EID-to-RLOC UDP Map-Request Message 1291 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1292 wants to test an RLOC for reachability, or wants to refresh a mapping 1293 before TTL expiration. For the initial case, the destination IP 1294 address used for the Map-Request is the data packet's destination 1295 address (i.e. the destination-EID) which had a mapping cache lookup 1296 failure. For the latter two cases, the destination IP address used 1297 for the Map-Request is one of the RLOC addresses from the locator-set 1298 of the map cache entry. The source address is either an IPv4 or IPv6 1299 RLOC address depending if the Map-Request is using an IPv4 versus 1300 IPv6 header, respectively. In all cases, the UDP source port number 1301 for the Map-Request message is an ITR/PITR selected 16-bit value and 1302 the UDP destination port number is set to the well-known destination 1303 port number 4342. A successful Map-Reply, which is one that has a 1304 nonce that matches an outstanding Map-Request nonce, will update the 1305 cached set of RLOCs associated with the EID prefix range. 1307 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1308 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1309 be placed in the IRC field. The ITR MAY include all locally 1310 configured locators in this list or just provide one locator address 1311 from each address family it supports. If the ITR erroneously 1312 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1313 Request. 1315 Map-Requests can also be LISP encapsulated using UDP destination port 1316 4342 with a LISP type value set to "Encapsulated Control Message", 1317 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1318 LISP encapsulated the same way from a Map-Server to an ETR. Details 1319 on encapsulated Map-Requests and Map-Resolvers can be found in 1320 [LISP-MS]. 1322 Map-Requests MUST be rate-limited. It is RECOMMENDED that a Map- 1323 Request for the same EID-prefix be sent no more than once per second. 1325 An ITR that is configured with mapping database information (i.e. it 1326 is also an ETR) MAY optionally include those mappings in a Map- 1327 Request. When an ETR configured to accept and verify such 1328 "piggybacked" mapping data receives such a Map-Request and it does 1329 not have this mapping in the map-cache, it MAY originate a "verifying 1330 Map-Request", addressed to the map-requesting ITR and the ETR MAY add 1331 a map-cache entry. If the ETR has a map-cache entry that matches the 1332 "piggybacked" EID and the RLOC is in the locator-set for the entry, 1333 then it may send the "verifying Map-Request" directly to the 1334 originating Map-Request source. If the RLOC is not in the locator- 1335 set, then the ETR MUST send the "verifying Map-Request" to the 1336 "piggybacked" EID. Doing this forces the "verifying Map-Request" to 1337 go through the mapping database system to reach the authoritative 1338 source of information about that EID, guarding against RLOC-spoofing 1339 in in the "piggybacked" mapping data. 1341 6.1.4. Map-Reply Message Format 1343 0 1 2 3 1344 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 1345 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1346 |Type=2 |P|E|S| Reserved | Record Count | 1347 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1348 | Nonce . . . | 1349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1350 | . . . Nonce | 1351 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1352 | | Record TTL | 1353 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1354 R | Locator Count | EID mask-len | ACT |A| Reserved | 1355 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1356 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1357 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1358 r | EID-prefix | 1359 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1360 | /| Priority | Weight | M Priority | M Weight | 1361 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1362 | o | Unused Flags |L|p|R| Loc-AFI | 1363 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1364 | \| Locator | 1365 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1367 Packet field descriptions: 1369 Type: 2 (Map-Reply) 1371 P: This is the probe-bit which indicates that the Map-Reply is in 1372 response to a locator reachability probe Map-Request. The nonce 1373 field MUST contain a copy of the nonce value from the original 1374 Map-Request. See Section 6.3.2 for more details. 1376 E: Indicates that the ETR which sends this Map-Reply message is 1377 advertising that the site is enabled for the Echo-Nonce locator 1378 reachability algorithm. See Section 6.3.1 for more details. 1380 S: This is the Security bit. When set to 1 the following 1381 authentication information will be appended to the end of the Map- 1382 Reply. The detailed format of the Authentication Data Content is 1383 for further study. 1385 0 1 2 3 1386 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 1387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1388 | AD Type | Authentication Data Content . . . | 1389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1391 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1392 receipt. 1394 Record Count: The number of records in this reply message. A record 1395 is comprised of that portion of the packet labeled 'Record' above 1396 and occurs the number of times equal to Record count. 1398 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1399 from the Map-Request is echoed in this Nonce field of the Map- 1400 Reply. When a 24-bit value is supplied, it resides in the low- 1401 order 64 bits of the nonce field. 1403 Record TTL: The time in minutes the recipient of the Map-Reply will 1404 store the mapping. If the TTL is 0, the entry SHOULD be removed 1405 from the cache immediately. If the value is 0xffffffff, the 1406 recipient can decide locally how long to store the mapping. 1408 Locator Count: The number of Locator entries. A locator entry 1409 comprises what is labeled above as 'Loc'. The locator count can 1410 be 0 indicating there are no locators for the EID-prefix. 1412 EID mask-len: Mask length for EID prefix. 1414 ACT: This 3-bit field describes negative Map-Reply actions. In any 1415 other message type, these bits are set to 0 and ignored on 1416 receipt. These bits are used only when the 'Locator Count' field 1417 is set to 0. The action bits are encoded only in Map-Reply 1418 messages. The actions defined are used by an ITR or PITR when a 1419 destination EID matches a negative mapping cache entry. 1420 Unassigned values should cause a map-cache entry to be created 1421 and, when packets match this negative cache entry, they will be 1422 dropped. The current assigned values are: 1424 (0) No-Action: The map-cache is kept alive and no packet 1425 encapsulation occurs. 1427 (1) Natively-Forward: The packet is not encapsulated or dropped 1428 but natively forwarded. 1430 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1432 (3) Drop: A packet that matches this map-cache entry is dropped. 1433 An ICMP Unreachable message SHOULD be sent. 1435 A: The Authoritative bit, when sent is always set to 1 by an ETR. 1436 When a Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, 1437 the Authoritative bit is set to 0. This indicates to requesting 1438 ITRs that the Map-Reply was not originated by a LISP node managed 1439 at the site that owns the EID-prefix. 1441 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1442 sender is informing the ITR what the version number is for the 1443 EID-record contained in the Map-Reply. The ETR can allocate this 1444 number internally but MUST coordinate this value with other ETRs 1445 for the site. When this value is 0, there is no versioning 1446 information conveyed. The Map-Version Number can be included in 1447 Map-Request and Map-Register messages. See Section 6.6.3 for more 1448 details. 1450 EID-prefix-AFI: Address family of EID-prefix according to [AFI]. 1452 EID-prefix: 4 octets if an IPv4 address-family, 16 octets if an IPv6 1453 address-family. 1455 Priority: each RLOC is assigned a unicast priority. Lower values 1456 are more preferable. When multiple RLOCs have the same priority, 1457 they MAY be used in a load-split fashion. A value of 255 means 1458 the RLOC MUST NOT be used for unicast forwarding. 1460 Weight: when priorities are the same for multiple RLOCs, the weight 1461 indicates how to balance unicast traffic between them. Weight is 1462 encoded as a relative weight of total unicast packets that match 1463 the mapping entry. For example if there are 4 locators in a 1464 locator set, where the weights assigned are 30, 20, 20, and 10, 1465 the first locator will get 37.5% of the traffic, the 2nd and 3rd 1466 locators will get 25% of traffic and the 4th locator will get 1467 12.5% of the traffic. If all weights for a locator-set are equal, 1468 receiver of the Map-Reply will decide how to load-split traffic. 1469 See Section 6.5 for a suggested hash algorithm to distribute load 1470 across locators with same priority and equal weight values. 1472 M Priority: each RLOC is assigned a multicast priority used by an 1473 ETR in a receiver multicast site to select an ITR in a source 1474 multicast site for building multicast distribution trees. A value 1475 of 255 means the RLOC MUST NOT be used for joining a multicast 1476 distribution tree. For more details, see [MLISP]. 1478 M Weight: when priorities are the same for multiple RLOCs, the 1479 weight indicates how to balance building multicast distribution 1480 trees across multiple ITRs. The weight is encoded as a relative 1481 weight (similar to the unicast Weights) of total number of trees 1482 built to the source site identified by the EID-prefix. If all 1483 weights for a locator-set are equal, the receiver of the Map-Reply 1484 will decide how to distribute multicast state across ITRs. For 1485 more details, see [MLISP]. 1487 Unused Flags: set to 0 when sending and ignored on receipt. 1489 L: when this bit is set, the locator is flagged as a local locator to 1490 the ETR that is sending the Map-Reply. When a Map-Server is doing 1491 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1492 0 for all locators in this locator-set. 1494 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1495 locator address, for which this bit is set, is the one being RLOC- 1496 probed and MAY be different from the source address of the Map- 1497 Reply. An ITR that RLOC-probes a particular locator, MUST use 1498 this locator for retrieving the data structure used to store the 1499 fact that the locator is reachable. The "p" bit is set for a 1500 single locator in the same locator set. If an implementation sets 1501 more than one "p" bit erroneously, the receiver of the Map-Reply 1502 MUST select the first locator. The "p" bit MUST NOT be set for 1503 locator-set records sent in Map-Request and Map-Register messages. 1505 R: set when the sender of a Map-Reply has a route to the locator in 1506 the locator data record. This receiver may find this useful to 1507 know if the locator is up but not necessarily reachable from the 1508 receiver's point of view. See also Section 6.4 for another way 1509 the R-bit may be used. 1511 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1512 assigned to an ETR. Note that the destination RLOC address MAY be 1513 an anycast address. A source RLOC can be an anycast address as 1514 well. The source or destination RLOC MUST NOT be the broadcast 1515 address (255.255.255.255 or any subnet broadcast address known to 1516 the router), and MUST NOT be a link-local multicast address. The 1517 source RLOC MUST NOT be a multicast address. The destination RLOC 1518 SHOULD be a multicast address if it is being mapped from a 1519 multicast destination EID. 1521 6.1.5. EID-to-RLOC UDP Map-Reply Message 1523 A Map-Reply returns an EID-prefix with a prefix length that is less 1524 than or equal to the EID being requested. The EID being requested is 1525 either from the destination field of an IP header of a Data-Probe or 1526 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1527 globally-routable IP addresses of all ETRs for the LISP site. Each 1528 RLOC conveys status reachability but does not convey path 1529 reachability from a requesters perspective. Separate testing of path 1530 reachability is required, See Section 6.3 for details. 1532 Note that a Map-Reply may contain different EID-prefix granularity 1533 (prefix + length) than the Map-Request which triggers it. This might 1534 occur if a Map-Request were for a prefix that had been returned by an 1535 earlier Map-Reply. In such a case, the requester updates its cache 1536 with the new prefix information and granularity. For example, a 1537 requester with two cached EID-prefixes that are covered by a Map- 1538 Reply containing one, less-specific prefix, replaces the entry with 1539 the less-specific EID-prefix. Note that the reverse, replacement of 1540 one less-specific prefix with multiple more-specific prefixes, can 1541 also occur but not by removing the less-specific prefix rather by 1542 adding the more-specific prefixes which during a lookup will override 1543 the less-specific prefix. 1545 When an ETR is configured with overlapping EID-prefixes, a Map- 1546 Request with an EID that longest matches any EID-prefix MUST be 1547 returned in a single Map-Reply message. For instance, if an ETR had 1548 database mapping entries for EID-prefixes: 1550 10.0.0.0/8 1551 10.1.0.0/16 1552 10.1.1.0/24 1553 10.1.2.0/24 1555 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1556 count of 1 to be returned with a mapping record EID-prefix of 1557 10.1.1.0/24. 1559 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1560 count of 3 to be returned with mapping records for EID-prefixes 1561 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1563 Note that not all overlapping EID-prefixes need to be returned, only 1564 the more specifics (note in the second example above 10.0.0.0/8 was 1565 not returned for requesting EID 10.1.5.5) entries for the matching 1566 EID-prefix of the requesting EID. When more than one EID-prefix is 1567 returned, all SHOULD use the same Time-to-Live value so they can all 1568 time out at the same time. When a more specific EID-prefix is 1569 received later, its Time-to-Live value in the Map-Reply record can be 1570 stored even when other less specifics exist. When a less specific 1571 EID-prefix is received later, its map-cache expiration time SHOULD be 1572 set to the minimum expiration time of any more specific EID-prefix in 1573 the map-cache. This is done so the integrity of the EID-prefix set 1574 is wholly maintained so no more-specific entries are removed from the 1575 map-cache while keeping less-specific entries. 1577 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1578 per second to the same requesting router. For scalability, it is 1579 expected that aggregation of EID addresses into EID-prefixes will 1580 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1581 prefix range thereby reducing the number of Map-Request messages. 1583 Map-Reply records can have an empty locator-set. A negative Map- 1584 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1585 convey special actions by the sender to the ITR or PITR which have 1586 solicited the Map-Reply. There are two primary applications for 1587 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1588 ITR or PITR when a destination is for a LISP site versus a non-LISP 1589 site. And the other is to source quench Map-Requests which are sent 1590 for non-allocated EIDs. 1592 For each Map-Reply record, the list of locators in a locator-set MUST 1593 appear in the same order for each ETR that originates a Map-Reply 1594 message. The locator-set MUST be sorted in order of ascending IP 1595 address where an IPv4 locator address is considered numerically 'less 1596 than' an IPv6 locator address. 1598 When sending a Map-Reply message, the destination address is copied 1599 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1600 can choose a locator address from one of the address families it 1601 supports. For Data-Probes, the destination address of the Map-Reply 1602 is copied from the source address of the Data-Probe message which is 1603 invoking the reply. The source address of the Map-Reply is one of 1604 the local IP addresses chosen to allow uRPF checks to succeed in the 1605 upstream service provider. The destination port of a Map-Reply 1606 message is copied from the source port of the Map-Request or Data- 1607 Probe and the source port of the Map-Reply message is set to the 1608 well-known UDP port 4342. 1610 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1612 When an ETR is misconfigured or compromised, it could return coarse 1613 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1614 cover EID-prefixes which are allocated to other sites redirecting 1615 their traffic to the locators of the compromised site. 1617 To solve this problem, there are two basic solutions that could be 1618 used. The first is to have Map-Servers proxy-map-reply on behalf of 1619 ETRs so their registered EID-prefixes are the ones returned in Map- 1620 Replies. Since the interaction between an ETR and Map-Server is 1621 secured with shared-keys, it is easier for an ETR to detect 1622 misbehavior. The second solution is to have ITRs and PITRs cache 1623 EID-prefixes with mask-lengths that are greater than or equal to a 1624 configured prefix length. This limits the damage to a specific width 1625 of any EID-prefix advertised, but needs to be coordinated with the 1626 allocation of site prefixes. These solutions can be used 1627 independently or at the same time. 1629 At the time of this writing, other approaches are being considered 1630 and researched. 1632 6.1.6. Map-Register Message Format 1634 The usage details of the Map-Register message can be found in 1635 specification [LISP-MS]. This section solely defines the message 1636 format. 1638 The message is sent in UDP with a destination UDP port of 4342 and a 1639 randomly selected UDP source port number. 1641 The Map-Register message format is: 1643 0 1 2 3 1644 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 1645 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1646 |Type=3 |P| Reserved |M| Record Count | 1647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1648 | Nonce . . . | 1649 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1650 | . . . Nonce | 1651 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1652 | Key ID | Authentication Data Length | 1653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1654 ~ Authentication Data ~ 1655 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1656 | | Record TTL | 1657 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1658 R | Locator Count | EID mask-len | ACT |A| Reserved | 1659 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1660 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1661 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1662 r | EID-prefix | 1663 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1664 | /| Priority | Weight | M Priority | M Weight | 1665 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1666 | o | Unused Flags |L|p|R| Loc-AFI | 1667 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1668 | \| Locator | 1669 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1671 Packet field descriptions: 1673 Type: 3 (Map-Register) 1675 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1676 Register message requesting for the Map-Server to proxy Map-Reply. 1677 The Map-Server will send non-authoritative Map-Replies on behalf 1678 of the ETR. Details on this usage can be found in [LISP-MS]. 1680 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1681 receipt. 1683 M: This is the want-map-notify bit, when set to 1 an ETR is 1684 requesting for a Map-Notify message to be returned in response to 1685 sending a Map-Register message. The Map-Notify message sent by a 1686 Map-Server is used to an acknowledge receipt of a Map-Register 1687 message. 1689 Record Count: The number of records in this Map-Register message. A 1690 record is comprised of that portion of the packet labeled 'Record' 1691 above and occurs the number of times equal to Record count. 1693 Nonce: This 8-octet Nonce field is set to 0 in Map-Register 1694 messages. Since the Map-Register message is authenticated, the 1695 nonce field is not currently used for any security function but 1696 may be in the future as part of an anti-replay solution. 1698 Key ID: A configured ID to find the configured Message 1699 Authentication Code (MAC) algorithm and key value used for the 1700 authentication function. See Section 14.4 for codepoint 1701 assignments. 1703 Authentication Data Length: The length in octets of the 1704 Authentication Data field that follows this field. The length of 1705 the Authentication Data field is dependent on the Message 1706 Authentication Code (MAC) algorithm used. The length field allows 1707 a device that doesn't know the MAC algorithm to correctly parse 1708 the packet. 1710 Authentication Data: The message digest used from the output of the 1711 Message Authentication Code (MAC) algorithm. The entire Map- 1712 Register payload is authenticated with this field preset to 0. 1713 After the MAC is computed, it is placed in this field. 1714 Implementations of this specification MUST include support for 1715 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-256-128 [RFC6234] 1716 is RECOMMENDED. 1718 The definition of the rest of the Map-Register can be found in the 1719 Map-Reply section. 1721 6.1.7. Map-Notify Message Format 1723 The usage details of the Map-Notify message can be found in 1724 specification [LISP-MS]. This section solely defines the message 1725 format. 1727 The message is sent inside a UDP packet with source and destination 1728 UDP ports equal to 4342. 1730 The Map-Notify message format is: 1732 0 1 2 3 1733 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 1734 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1735 |Type=4 | Reserved | Record Count | 1736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1737 | Nonce . . . | 1738 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1739 | . . . Nonce | 1740 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1741 | Key ID | Authentication Data Length | 1742 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1743 ~ Authentication Data ~ 1744 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1745 | | Record TTL | 1746 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1747 R | Locator Count | EID mask-len | ACT |A| Reserved | 1748 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1749 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1750 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1751 r | EID-prefix | 1752 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1753 | /| Priority | Weight | M Priority | M Weight | 1754 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1755 | o | Unused Flags |L|p|R| Loc-AFI | 1756 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1757 | \| Locator | 1758 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1760 Packet field descriptions: 1762 Type: 4 (Map-Notify) 1764 The Map-Notify message has the same contents as a Map-Register 1765 message. See Map-Register section for field descriptions. 1767 6.1.8. Encapsulated Control Message Format 1769 An Encapsulated Control Message (ECM) is used to encapsulate control 1770 packets sent between xTRs and the mapping database system described 1771 in [LISP-MS]. 1773 0 1 2 3 1774 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 1775 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1776 / | IPv4 or IPv6 Header | 1777 OH | (uses RLOC addresses) | 1778 \ | | 1779 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1780 / | Source Port = xxxx | Dest Port = 4342 | 1781 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1782 \ | UDP Length | UDP Checksum | 1783 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1784 LH |Type=8 |S| Reserved | 1785 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1786 / | IPv4 or IPv6 Header | 1787 IH | (uses RLOC or EID addresses) | 1788 \ | | 1789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1790 / | Source Port = xxxx | Dest Port = yyyy | 1791 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1792 \ | UDP Length | UDP Checksum | 1793 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1794 LCM | LISP Control Message | 1795 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1797 Packet header descriptions: 1799 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1800 source and destination header address fields. 1802 UDP: The outer UDP header with destination port 4342. The source 1803 port is randomly allocated. The checksum field MUST be non-zero. 1805 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1806 and what follows is either an IPv4 or IPv6 header as encoded by 1807 the first 4 bits after the reserved field. 1809 S: This is the Security bit. When set to 1 the field following the 1810 Reserved field will have the following format. The detailed 1811 format of the Authentication Data Content is for further study. 1813 0 1 2 3 1814 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 1815 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1816 | AD Type | Authentication Data Content . . . | 1817 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1819 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1820 addresses in the header address fields. When a Map-Request is 1821 encapsulated in this packet format the destination address in this 1822 header is an EID. 1824 UDP: The inner UDP header where the port assignments depends on the 1825 control packet being encapsulated. When the control packet is a 1826 Map-Request or Map-Register, the source port is ITR/PITR selected 1827 and the destination port is 4342. When the control packet is a 1828 Map-Reply, the source port is 4342 and the destination port is 1829 assigned from the source port of the invoking Map-Request. Port 1830 number 4341 MUST NOT be assigned to either port. The checksum 1831 field MUST be non-zero. 1833 LCM: The format is one of the control message formats described in 1834 this section. At this time, only Map-Request messages are allowed 1835 to be encapsulated. And in the future, PIM Join-Prune messages 1836 [MLISP] might be allowed. Encapsulating other types of LISP 1837 control messages are for further study. When Map-Requests are 1838 sent for RLOC-probing purposes (i.e the probe-bit is set), they 1839 MUST NOT be sent inside Encapsulated Control Messages. 1841 6.2. Routing Locator Selection 1843 Both client-side and server-side may need control over the selection 1844 of RLOCs for conversations between them. This control is achieved by 1845 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1846 messages. Alternatively, RLOC information MAY be gleaned from 1847 received tunneled packets or EID-to-RLOC Map-Request messages. 1849 The following enumerates different scenarios for choosing RLOCs and 1850 the controls that are available: 1852 o Server-side returns one RLOC. Client-side can only use one RLOC. 1853 Server-side has complete control of the selection. 1855 o Server-side returns a list of RLOC where a subset of the list has 1856 the same best priority. Client can only use the subset list 1857 according to the weighting assigned by the server-side. In this 1858 case, the server-side controls both the subset list and load- 1859 splitting across its members. The client-side can use RLOCs 1860 outside of the subset list if it determines that the subset list 1861 is unreachable (unless RLOCs are set to a Priority of 255). Some 1862 sharing of control exists: the server-side determines the 1863 destination RLOC list and load distribution while the client-side 1864 has the option of using alternatives to this list if RLOCs in the 1865 list are unreachable. 1867 o Server-side sets weight of 0 for the RLOC subset list. In this 1868 case, the client-side can choose how the traffic load is spread 1869 across the subset list. Control is shared by the server-side 1870 determining the list and the client determining load distribution. 1871 Again, the client can use alternative RLOCs if the server-provided 1872 list of RLOCs are unreachable. 1874 o Either side (more likely on the server-side ETR) decides not to 1875 send a Map-Request. For example, if the server-side ETR does not 1876 send Map-Requests, it gleans RLOCs from the client-side ITR, 1877 giving the client-side ITR responsibility for bidirectional RLOC 1878 reachability and preferability. Server-side ETR gleaning of the 1879 client-side ITR RLOC is done by caching the inner header source 1880 EID and the outer header source RLOC of received packets. The 1881 client-side ITR controls how traffic is returned and can alternate 1882 using an outer header source RLOC, which then can be added to the 1883 list the server-side ETR uses to return traffic. Since no 1884 Priority or Weights are provided using this method, the server- 1885 side ETR MUST assume each client-side ITR RLOC uses the same best 1886 Priority with a Weight of zero. In addition, since EID-prefix 1887 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1888 on tunnel routers can grow to be very large. 1890 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1891 received encapsulated packet, is only stored and used for a few 1892 seconds, pending verification. Verification is performed by 1893 sending a Map-Request to the source EID (the inner header IP 1894 source address) of the received encapsulated packet. A reply to 1895 this "verifying Map-Request" is used to fully populate the map- 1896 cache entry for the "gleaned" EID and is stored and used for the 1897 time indicated from the TTL field of a received Map-Reply. When a 1898 verified map-cache entry is stored, data gleaning no longer occurs 1899 for subsequent packets which have a source EID that matches the 1900 EID-prefix of the verified entry. 1902 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1903 reachable when the R-bit for the locator record is set to 1. When 1904 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1905 RLOC. Neither the information contained in a Map-Reply or that 1906 stored in the mapping database system provides reachability 1907 information for RLOCs. Note that reachability is not part of the 1908 mapping system and is determined using one or more of the Routing 1909 Locator Reachability Algorithms described in the next section. 1911 6.3. Routing Locator Reachability 1913 Several mechanisms for determining RLOC reachability are currently 1914 defined: 1916 1. An ETR may examine the Locator Status Bits in the LISP header of 1917 an encapsulated data packet received from an ITR. If the ETR is 1918 also acting as an ITR and has traffic to return to the original 1919 ITR site, it can use this status information to help select an 1920 RLOC. 1922 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1923 message for an RLOC it is using. This indicates that the RLOC is 1924 likely down. Note, trusting ICMP messages may not be desirable 1925 but neither is ignoring them completely. Implementations are 1926 encouraged to follow current best practices in treating these 1927 conditions. 1929 3. An ITR which participates in the global routing system can 1930 determine that an RLOC is down if no BGP RIB route exists that 1931 matches the RLOC IP address. 1933 4. An ITR may receive an ICMP Port Unreachable message from a 1934 destination host. This occurs if an ITR attempts to use 1935 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1936 non-LISP-capable site. 1938 5. An ITR may receive a Map-Reply from an ETR in response to a 1939 previously sent Map-Request. The RLOC source of the Map-Reply is 1940 likely up since the ETR was able to send the Map-Reply to the 1941 ITR. 1943 6. When an ETR receives an encapsulated packet from an ITR, the 1944 source RLOC from the outer header of the packet is likely up. 1946 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1947 described in this section, namely Echo-Noncing or RLOC-Probing. 1949 When determining Locator up/down reachability by examining the 1950 Locator Status Bits from the LISP encapsulated data packet, an ETR 1951 will receive up to date status from an encapsulating ITR about 1952 reachability for all ETRs at the site. CE-based ITRs at the source 1953 site can determine reachability relative to each other using the site 1954 IGP as follows: 1956 o Under normal circumstances, each ITR will advertise a default 1957 route into the site IGP. 1959 o If an ITR fails or if the upstream link to its PE fails, its 1960 default route will either time-out or be withdrawn. 1962 Each ITR can thus observe the presence or lack of a default route 1963 originated by the others to determine the Locator Status Bits it sets 1964 for them. 1966 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1967 Locator Status Bits in a LISP encapsulated packet are numbered from 0 1968 to n-1 starting with the least significant bit. For example, if an 1969 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1970 value 2), then all ITRs at the site will clear the 3rd least 1971 significant bit (xxxx x0xx) of the Locator Status Bits field for the 1972 packets they encapsulate. 1974 When an ETR decapsulates a packet, it will check for any change in 1975 the Locator Status Bits field. When a bit goes from 1 to 0, the ETR 1976 if acting also as an ITR, will refrain from encapsulating packets to 1977 an RLOC that is indicated as down. It will only resume using that 1978 RLOC if the corresponding Locator Status Bit returns to a value of 1. 1979 Locator Status Bits are associated with a locator-set per EID-prefix. 1980 Therefore, when a locator becomes unreachable, the Locator Status Bit 1981 that corresponds to that locator's position in the list returned by 1982 the last Map-Reply will be set to zero for that particular EID- 1983 prefix. 1985 When ITRs at the site are not deployed in CE routers, the IGP can 1986 still be used to determine the reachability of Locators provided they 1987 are injected into the IGP. This is typically done when a /32 address 1988 is configured on a loopback interface. 1990 When ITRs receive ICMP Network or Host Unreachable messages as a 1991 method to determine unreachability, they will refrain from using 1992 Locators which are described in Locator lists of Map-Replies. 1993 However, using this approach is unreliable because many network 1994 operators turn off generation of ICMP Unreachable messages. 1996 If an ITR does receive an ICMP Network or Host Unreachable message, 1997 it MAY originate its own ICMP Unreachable message destined for the 1998 host that originated the data packet the ITR encapsulated. 2000 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 2001 locator address from a locator-set in a mapping entry matches a 2002 prefix. If it does not find one and BGP is running in the Default 2003 Free Zone (DFZ), it can decide to not use the locator even though the 2004 Locator Status Bits indicate the locator is up. In this case, the 2005 path from the ITR to the ETR that is assigned the locator is not 2006 available. More details are in [LOC-ID-ARCH]. 2008 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 2009 Reply is returned, reachability of the Locator has been determined. 2010 Obviously, sending such probes increases the number of control 2011 messages originated by tunnel routers for active flows, so Locators 2012 are assumed to be reachable when they are advertised. 2014 This assumption does create a dependency: Locator unreachability is 2015 detected by the receipt of ICMP Host Unreachable messages. When an 2016 Locator has been determined to be unreachable, it is not used for 2017 active traffic; this is the same as if it were listed in a Map-Reply 2018 with priority 255. 2020 The ITR can test the reachability of the unreachable Locator by 2021 sending periodic Requests. Both Requests and Replies MUST be rate- 2022 limited. Locator reachability testing is never done with data 2023 packets since that increases the risk of packet loss for end-to-end 2024 sessions. 2026 When an ETR decapsulates a packet, it knows that it is reachable from 2027 the encapsulating ITR because that is how the packet arrived. In 2028 most cases, the ETR can also reach the ITR but cannot assume this to 2029 be true due to the possibility of path asymmetry. In the presence of 2030 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 2031 use the lack of return traffic as an indication that the ETR is 2032 unreachable. Instead, it MUST use an alternate mechanisms to 2033 determine reachability. 2035 6.3.1. Echo Nonce Algorithm 2037 When data flows bidirectionally between locators from different 2038 sites, a data-plane mechanism called "nonce echoing" can be used to 2039 determine reachability between an ITR and ETR. When an ITR wants to 2040 solicit a nonce echo, it sets the N and E bits and places a 24-bit 2041 nonce [RFC4086] in the LISP header of the next encapsulated data 2042 packet. 2044 When this packet is received by the ETR, the encapsulated packet is 2045 forwarded as normal. When the ETR next sends a data packet to the 2046 ITR, it includes the nonce received earlier with the N bit set and E 2047 bit cleared. The ITR sees this "echoed nonce" and knows the path to 2048 and from the ETR is up. 2050 The ITR will set the E-bit and N-bit for every packet it sends while 2051 in echo-nonce-request state. The time the ITR waits to process the 2052 echoed nonce before it determines the path is unreachable is variable 2053 and a choice left for the implementation. 2055 If the ITR is receiving packets from the ETR but does not see the 2056 nonce echoed while being in echo-nonce-request state, then the path 2057 to the ETR is unreachable. This decision may be overridden by other 2058 locator reachability algorithms. Once the ITR determines the path to 2059 the ETR is down it can switch to another locator for that EID-prefix. 2061 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 2062 be implementing both ITR and ETR functionality for the echo nonce 2063 mechanism to operate. 2065 The ITR and ETR may both go into echo-nonce-request state at the same 2066 time. The number of packets sent or the time during which echo nonce 2067 requests are sent is an implementation specific setting. However, 2068 when an ITR is in echo-nonce-request state, it can echo the ETR's 2069 nonce in the next set of packets that it encapsulates and then 2070 subsequently, continue sending echo-nonce-request packets. 2072 This mechanism does not completely solve the forward path 2073 reachability problem as traffic may be unidirectional. That is, the 2074 ETR receiving traffic at a site may not be the same device as an ITR 2075 which transmits traffic from that site or the site to site traffic is 2076 unidirectional so there is no ITR returning traffic. 2078 The echo-nonce algorithm is bilateral. That is, if one side sets the 2079 E-bit and the other side is not enabled for echo-noncing, then the 2080 echoing of the nonce does not occur and the requesting side may 2081 regard the locator unreachable erroneously. An ITR SHOULD only set 2082 the E-bit in a encapsulated data packet when it knows the ETR is 2083 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 2084 Reply message. 2086 Note that other locator reachability mechanisms are being researched 2087 and can be used to compliment or even override the Echo Nonce 2088 Algorithm. See next section for an example of control-plane probing. 2090 6.3.2. RLOC Probing Algorithm 2092 RLOC Probing is a method that an ITR or PITR can use to determine the 2093 reachability status of one or more locators that it has cached in a 2094 map-cache entry. The probe-bit of the Map-Request and Map-Reply 2095 messages are used for RLOC Probing. 2097 RLOC probing is done in the control-plane on a timer basis where an 2098 ITR or PITR will originate a Map-Request destined to a locator 2099 address from one of its own locator addresses. A Map-Request used as 2100 an RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on 2101 the ALT like one would when soliciting mapping data. The EID record 2102 encoded in the Map-Request is the EID-prefix of the map-cache entry 2103 cached by the ITR or PITR. The ITR may include a mapping data record 2104 for its own database mapping information which contains the local 2105 EID-prefixes and RLOCs for its site. RLOC-probes are sent 2106 periodically using a jittered timer interval. 2108 When an ETR receives a Map-Request message with the probe-bit set, it 2109 returns a Map-Reply with the probe-bit set. The source address of 2110 the Map-Reply is set according to the procedure described in 2111 Section 6.1.5. The Map-Reply SHOULD contain mapping data for the 2112 EID-prefix contained in the Map-Request. This provides the 2113 opportunity for the ITR or PITR, which sent the RLOC-probe to get 2114 mapping updates if there were changes to the ETR's database mapping 2115 entries. 2117 There are advantages and disadvantages of RLOC Probing. The greatest 2118 benefit of RLOC Probing is that it can handle many failure scenarios 2119 allowing the ITR to determine when the path to a specific locator is 2120 reachable or has become unreachable, thus providing a robust 2121 mechanism for switching to using another locator from the cached 2122 locator. RLOC Probing can also provide rough RTT estimates between a 2123 pair of locators which can be useful for network management purposes 2124 as well as for selecting low delay paths. The major disadvantage of 2125 RLOC Probing is in the number of control messages required and the 2126 amount of bandwidth used to obtain those benefits, especially if the 2127 requirement for failure detection times are very small. 2129 Continued research and testing will attempt to characterize the 2130 tradeoffs of failure detection times versus message overhead. 2132 6.4. EID Reachability within a LISP Site 2134 A site may be multihomed using two or more ETRs. The hosts and 2135 infrastructure within a site will be addressed using one or more EID 2136 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2137 mapping system. One possible failure mode is for an ETR to lose 2138 reachability to one or more of the EID prefixes within its own site. 2139 When this occurs when the ETR sends Map-Replies, it can clear the 2140 R-bit associated with its own locator. And when the ETR is also an 2141 ITR, it can clear its locator-status-bit in the encapsulation data 2142 header. 2144 It is recognized there are no simple solutions to the site 2145 partitioning problem because it is hard to know which part of the 2146 EID-prefix range is partitioned. And which locators can reach any 2147 sub-ranges of the EID-prefixes. This problem is under investigation 2148 with the expectation that experiments will tell us more. Note, this 2149 is not a new problem introduced by the LISP architecture. The 2150 problem exists today when a multi-homed site uses BGP to advertise 2151 its reachability upstream. 2153 6.5. Routing Locator Hashing 2155 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2156 a requesting ITR, the locator-set for the EID-prefix may contain 2157 different priority values for each locator address. When more than 2158 one best priority locator exists, the ITR can decide how to load 2159 share traffic against the corresponding locators. 2161 The following hash algorithm may be used by an ITR to select a 2162 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2164 1. Either a source and destination address hash can be used or the 2165 traditional 5-tuple hash which includes the source and 2166 destination addresses, source and destination TCP, UDP, or SCTP 2167 port numbers and the IP protocol number field or IPv6 next- 2168 protocol fields of a packet a host originates from within a LISP 2169 site. When a packet is not a TCP, UDP, or SCTP packet, the 2170 source and destination addresses only from the header are used to 2171 compute the hash. 2173 2. Take the hash value and divide it by the number of locators 2174 stored in the locator-set for the EID-to-RLOC mapping. 2176 3. The remainder will yield a value of 0 to "number of locators 2177 minus 1". Use the remainder to select the locator in the 2178 locator-set. 2180 Note that when a packet is LISP encapsulated, the source port number 2181 in the outer UDP header needs to be set. Selecting a hashed value 2182 allows core routers which are attached to Link Aggregation Groups 2183 (LAGs) to load-split the encapsulated packets across member links of 2184 such LAGs. Otherwise, core routers would see a single flow, since 2185 packets have a source address of the ITR, for packets which are 2186 originated by different EIDs at the source site. A suggested setting 2187 for the source port number computed by an ITR is a 5-tuple hash 2188 function on the inner header, as described above. 2190 Many core router implementations use a 5-tuple hash to decide how to 2191 balance packet load across members of a LAG. The 5-tuple hash 2192 includes the source and destination addresses of the packet and the 2193 source and destination ports when the protocol number in the packet 2194 is TCP or UDP. For this reason, UDP encoding is used for LISP 2195 encapsulation. 2197 6.6. Changing the Contents of EID-to-RLOC Mappings 2199 Since the LISP architecture uses a caching scheme to retrieve and 2200 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2201 date mapping is to re-request the mapping. However, the ITRs do not 2202 know when the mappings change and the ETRs do not keep track of which 2203 ITRs requested its mappings. For scalability reasons, we want to 2204 maintain this approach but need to provide a way for ETRs change 2205 their mappings and inform the sites that are currently communicating 2206 with the ETR site using such mappings. 2208 When adding a new locator record in lexicographic order to the end of 2209 a locator-set, it is easy to update mappings. We assume new mappings 2210 will maintain the same locator ordering as the old mapping but just 2211 have new locators appended to the end of the list. So some ITRs can 2212 have a new mapping while other ITRs have only an old mapping that is 2213 used until they time out. When an ITR has only an old mapping but 2214 detects bits set in the loc-status-bits that correspond to locators 2215 beyond the list it has cached, it simply ignores them. However, this 2216 can only happen for locator addresses that are lexicographically 2217 greater than the locator addresses in the existing locator-set. 2219 When a locator record is inserted in the middle of a locator-set, to 2220 maintain lexicographic order, the SMR procedure in Section 6.6.2 is 2221 used to inform ITRs and PITRs of the new locator-status-bit mappings. 2223 When a locator record is removed from a locator-set, ITRs that have 2224 the mapping cached will not use the removed locator because the xTRs 2225 will set the loc-status-bit to 0. So even if the locator is in the 2226 list, it will not be used. For new mapping requests, the xTRs can 2227 set the locator AFI to 0 (indicating an unspecified address), as well 2228 as setting the corresponding loc-status-bit to 0. This forces ITRs 2229 with old or new mappings to avoid using the removed locator. 2231 If many changes occur to a mapping over a long period of time, one 2232 will find empty record slots in the middle of the locator-set and new 2233 records appended to the locator-set. At some point, it would be 2234 useful to compact the locator-set so the loc-status-bit settings can 2235 be efficiently packed. 2237 We propose here three approaches for locator-set compaction, one 2238 operational and two protocol mechanisms. The operational approach 2239 uses a clock sweep method. The protocol approaches use the concept 2240 of Solicit-Map-Requests and Map-Versioning. 2242 6.6.1. Clock Sweep 2244 The clock sweep approach uses planning in advance and the use of 2245 count-down TTLs to time out mappings that have already been cached. 2246 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2247 there is a 24 hour window to time out old mappings. The following 2248 clock sweep procedure is used: 2250 1. 24 hours before a mapping change is to take effect, a network 2251 administrator configures the ETRs at a site to start the clock 2252 sweep window. 2254 2. During the clock sweep window, ETRs continue to send Map-Reply 2255 messages with the current (unchanged) mapping records. The TTL 2256 for these mappings is set to 1 hour. 2258 3. 24 hours later, all previous cache entries will have timed out, 2259 and any active cache entries will time out within 1 hour. During 2260 this 1 hour window the ETRs continue to send Map-Reply messages 2261 with the current (unchanged) mapping records with the TTL set to 2262 1 minute. 2264 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2265 messages with the new (changed) mapping records. So any active 2266 caches can get the new mapping contents right away if not cached, 2267 or in 1 minute if they had the mapping cached. The new mappings 2268 are cached with a time to live equal to the TTL in the Map-Reply. 2270 6.6.2. Solicit-Map-Request (SMR) 2272 Soliciting a Map-Request is a selective way for ETRs, at the site 2273 where mappings change, to control the rate they receive requests for 2274 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2275 the mappings they have cached. 2277 Since the ETRs don't keep track of remote ITRs that have cached their 2278 mappings, they do not know which ITRs need to have their mappings 2279 updated. As a result, an ETR will solicit Map-Requests (called an 2280 SMR message) from those sites to which it has been sending 2281 encapsulated data to for the last minute. In particular, an ETR will 2282 send an SMR an ITR to which it has recently sent encapsulated data. 2284 An SMR message is simply a bit set in a Map-Request message. An ITR 2285 or PITR will send a Map-Request when they receive an SMR message. 2286 Both the SMR sender and the Map-Request responder MUST rate-limited 2287 these messages. Rate-limiting can be implemented as a global rate- 2288 limiter or one rate-limiter per SMR destination. 2290 The following procedure shows how a SMR exchange occurs when a site 2291 is doing locator-set compaction for an EID-to-RLOC mapping: 2293 1. When the database mappings in an ETR change, the ETRs at the site 2294 begin to send Map-Requests with the SMR bit set for each locator 2295 in each map-cache entry the ETR caches. 2297 2. A remote ITR which receives the SMR message will schedule sending 2298 a Map-Request message to the source locator address of the SMR 2299 message or to the mapping database system. A newly allocated 2300 random nonce is selected and the EID-prefix used is the one 2301 copied from the SMR message. If the source locator is the only 2302 locator in the cached locator-set, the remote ITR SHOULD send a 2303 Map-Request to the database mapping system just in case the 2304 single locator has changed and may no longer be reachable to 2305 accept the Map-Request. 2307 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2308 Map-Reply while continuing to use the cached mapping. When Map 2309 Versioning is used, described in Section 6.6.3, an SMR sender can 2310 detect if an ITR is using the most up to date database mapping. 2312 4. The ETRs at the site with the changed mapping will reply to the 2313 Map-Request with a Map-Reply message that has a nonce from the 2314 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2315 limited. This is important to avoid Map-Reply implosion. 2317 5. The ETRs, at the site with the changed mapping, record the fact 2318 that the site that sent the Map-Request has received the new 2319 mapping data in the mapping cache entry for the remote site so 2320 the loc-status-bits are reflective of the new mapping for packets 2321 going to the remote site. The ETR then stops sending SMR 2322 messages. 2324 Experimentation is in progress to determine the appropriate rate- 2325 limit parameters. 2327 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2328 To avoid map-cache entry corruption by a third-party, a sender of an 2329 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2330 based Map-Request and the source is not in the locator-set for the 2331 stored map-cache entry, then the responding Map-Request MUST be sent 2332 with an EID destination to the mapping database system. Since the 2333 mapping database system is more secure to reach an authoritative ETR, 2334 it will deliver the Map-Request to the authoritative source of the 2335 mapping data. 2337 When an ITR receives an SMR-based Map-Request for which it does not 2338 have a cached mapping for the EID in the SMR message, it MAY not send 2339 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2340 SMR messages to all locators in the locator-set it has stored in its 2341 map-cache but the remote ITRs that receive the SMR may not be sending 2342 packets to the site. There is no point in updating the ITRs until 2343 they need to send, in which case, they will send Map-Requests to 2344 obtain a map-cache entry. 2346 6.6.3. Database Map Versioning 2348 When there is unidirectional packet flow between an ITR and ETR, and 2349 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2350 ITR so encapsulation can stop to a removed locator and start to a new 2351 locator in the locator-set. 2353 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2354 number. This is known as the Destination Map-Version Number. ITRs 2355 include the Destination Map-Version Number in packets they 2356 encapsulate to the site. When an ETR decapsulates a packet and 2357 detects the Destination Map-Version Number is less than the current 2358 version for its mapping, the SMR procedure described in Section 6.6.2 2359 occurs. 2361 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2362 Version number. This is known as the Source Map-Version Number. 2363 When an ETR decapsulates a packet and detects the Source Map-Version 2364 Number is greater than the last Map-Version Number sent in a Map- 2365 Reply from the ITR's site, the ETR will send a Map-Request to one of 2366 the ETRs for the source site. 2368 A Map-Version Number is used as a sequence number per EID-prefix. So 2369 values that are greater, are considered to be more recent. A value 2370 of 0 for the Source Map-Version Number or the Destination Map-Version 2371 Number conveys no versioning information and an ITR does no 2372 comparison with previously received Map-Version Numbers. 2374 A Map-Version Number can be included in Map-Register messages as 2375 well. This is a good way for the Map-Server can assure that all ETRs 2376 for a site registering to it will be Map-Version number synchronized. 2378 See [VERSIONING] for a more detailed analysis and description of 2379 Database Map Versioning. 2381 7. Router Performance Considerations 2383 LISP is designed to be very hardware-based forwarding friendly. A 2384 few implementation techniques can be used to incrementally implement 2385 LISP: 2387 o When a tunnel encapsulated packet is received by an ETR, the outer 2388 destination address may not be the address of the router. This 2389 makes it challenging for the control plane to get packets from the 2390 hardware. This may be mitigated by creating special FIB entries 2391 for the EID-prefixes of EIDs served by the ETR (those for which 2392 the router provides an RLOC translation). These FIB entries are 2393 marked with a flag indicating that control plane processing should 2394 be performed. The forwarding logic of testing for particular IP 2395 protocol number value is not necessary. There are a few proven 2396 cases where no changes to existing deployed hardware were needed 2397 to support the LISP data-plane. 2399 o On an ITR, prepending a new IP header consists of adding more 2400 octets to a MAC rewrite string and prepending the string as part 2401 of the outgoing encapsulation procedure. Routers that support GRE 2402 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2403 support this action. 2405 o A packet's source address or interface the packet was received on 2406 can be used to select a VRF (Virtual Routing/Forwarding). The 2407 VRF's routing table can be used to find EID-to-RLOC mappings. 2409 For performance issues related to map-cache management, see section 2410 Section 12. 2412 8. Deployment Scenarios 2414 This section will explore how and where ITRs and ETRs can be deployed 2415 and will discuss the pros and cons of each deployment scenario. For 2416 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2418 There are two basic deployment trade-offs to consider: centralized 2419 versus distributed caches and flat, recursive, or re-encapsulating 2420 tunneling. When deciding on centralized versus distributed caching, 2421 the following issues should be considered: 2423 o Are the tunnel routers spread out so that the caches are spread 2424 across all the memories of each router? A centralized cache is 2425 when an ITR keeps a cache for all the EIDs it is encapsulating to. 2426 The packet takes a direct path to the destination locator. A 2427 distributed cache is when an ITR needs help from other re- 2428 encapsulating routers because it does not store all the cache 2429 entries for the EIDs is it encapsulating to. So the packet takes 2430 a path through re-encapsulating routers that have a different set 2431 of cache entries. 2433 o Should management "touch points" be minimized by choosing few 2434 tunnel routers, just enough for redundancy? 2436 o In general, using more ITRs doesn't increase management load, 2437 since caches are built and stored dynamically. On the other hand, 2438 more ETRs does require more management since EID-prefix-to-RLOC 2439 mappings need to be explicitly configured. 2441 When deciding on flat, recursive, or re-encapsulation tunneling, the 2442 following issues should be considered: 2444 o Flat tunneling implements a single tunnel between source site and 2445 destination site. This generally offers better paths between 2446 sources and destinations with a single tunnel path. 2448 o Recursive tunneling is when tunneled traffic is again further 2449 encapsulated in another tunnel, either to implement VPNs or to 2450 perform Traffic Engineering. When doing VPN-based tunneling, the 2451 site has some control since the site is prepending a new tunnel 2452 header. In the case of TE-based tunneling, the site may have 2453 control if it is prepending a new tunnel header, but if the site's 2454 ISP is doing the TE, then the site has no control. Recursive 2455 tunneling generally will result in suboptimal paths but at the 2456 benefit of steering traffic to resource available parts of the 2457 network. 2459 o The technique of re-encapsulation ensures that packets only 2460 require one tunnel header. So if a packet needs to be rerouted, 2461 it is first decapsulated by the ETR and then re-encapsulated with 2462 a new tunnel header using a new RLOC. 2464 The next sub-sections will survey where tunnel routers can reside in 2465 the network. 2467 8.1. First-hop/Last-hop Tunnel Routers 2469 By locating tunnel routers close to hosts, the EID-prefix set is at 2470 the granularity of an IP subnet. So at the expense of more EID- 2471 prefix-to-RLOC sets for the site, the caches in each tunnel router 2472 can remain relatively small. But caches always depend on the number 2473 of non-aggregated EID destination flows active through these tunnel 2474 routers. 2476 With more tunnel routers doing encapsulation, the increase in control 2477 traffic grows as well: since the EID-granularity is greater, more 2478 Map-Requests and Map-Replies are traveling between more routers. 2480 The advantage of placing the caches and databases at these stub 2481 routers is that the products deployed in this part of the network 2482 have better price-memory ratios then their core router counterparts. 2483 Memory is typically less expensive in these devices and fewer routes 2484 are stored (only IGP routes). These devices tend to have excess 2485 capacity, both for forwarding and routing state. 2487 LISP functionality can also be deployed in edge switches. These 2488 devices generally have layer-2 ports facing hosts and layer-3 ports 2489 facing the Internet. Spare capacity is also often available in these 2490 devices as well. 2492 8.2. Border/Edge Tunnel Routers 2494 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2495 space associated with a site to be reachable via a small set of RLOCs 2496 assigned to the CE routers for that site. This is the default 2497 behavior envisioned in the rest of this specification. 2499 This offers the opposite benefit of the first-hop/last-hop tunnel 2500 router scenario: the number of mapping entries and network management 2501 touch points are reduced, allowing better scaling. 2503 One disadvantage is that less of the network's resources are used to 2504 reach host endpoints thereby centralizing the point-of-failure domain 2505 and creating network choke points at the CE router. 2507 Note that more than one CE router at a site can be configured with 2508 the same IP address. In this case an RLOC is an anycast address. 2509 This allows resilience between the CE routers. That is, if a CE 2510 router fails, traffic is automatically routed to the other routers 2511 using the same anycast address. However, this comes with the 2512 disadvantage where the site cannot control the entrance point when 2513 the anycast route is advertised out from all border routers. Another 2514 disadvantage of using anycast locators is the limited advertisement 2515 scope of /32 (or /128 for IPv6) routes. 2517 8.3. ISP Provider-Edge (PE) Tunnel Routers 2519 Use of ISP PE routers as tunnel endpoint routers is not the typical 2520 deployment scenario envisioned in the specification. This section 2521 attempts to capture some of reasoning behind this preference of 2522 implementing LISP on CE routers. 2524 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2525 than a site, control over the location of the egress tunnel 2526 endpoints. That is, the ISP can decide if the tunnel endpoints are 2527 in the destination site (in either CE routers or last-hop routers 2528 within a site) or at other PE edges. The advantage of this case is 2529 that two tunnel headers can be avoided. By having the PE be the 2530 first router on the path to encapsulate, it can choose a TE path 2531 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2532 the destination end site. 2534 An obvious disadvantage is that the end site has no control over 2535 where its packets flow or the RLOCs used. Other disadvantages 2536 include the difficulty in synchronizing path liveness updates between 2537 CE and PE routers. 2539 As mentioned in earlier sections a combination of these scenarios is 2540 possible at the expense of extra packet header overhead, if both site 2541 and provider want control, then recursive or re-encapsulating tunnels 2542 are used. 2544 8.4. LISP Functionality with Conventional NATs 2546 LISP routers can be deployed behind Network Address Translator (NAT) 2547 devices to provide the same set of packet services hosts have today 2548 when they are addressed out of private address space. 2550 It is important to note that a locator address in any LISP control 2551 message MUST be a globally routable address and therefore SHOULD NOT 2552 contain [RFC1918] addresses. If a LISP router is configured with 2553 private addresses, they MUST be used only in the outer IP header so 2554 the NAT device can translate properly. Otherwise, EID addresses MUST 2555 be translated before encapsulation is performed. Both NAT 2556 translation and LISP encapsulation functions could be co-located in 2557 the same device. 2559 More details on LISP address translation can be found in [INTERWORK]. 2561 8.5. Packets Egressing a LISP Site 2563 When a LISP site is using two ITRs for redundancy, the failure of one 2564 ITR will likely shift outbound traffic to the second. This second 2565 ITR's cache may not not be populated with the same EID-to-RLOC 2566 mapping entries as the first. If this second ITR does not have these 2567 mappings, traffic will be dropped while the mappings are retrieved 2568 from the mapping system. The retrieval of these messages may 2569 increase the load of requests being sent into the mapping system. 2570 Deployment and experimentation will determine whether this issue 2571 requires more attention. 2573 9. Traceroute Considerations 2575 When a source host in a LISP site initiates a traceroute to a 2576 destination host in another LISP site, it is highly desirable for it 2577 to see the entire path. Since packets are encapsulated from ITR to 2578 ETR, the hop across the tunnel could be viewed as a single hop. 2579 However, LISP traceroute will provide the entire path so the user can 2580 see 3 distinct segments of the path from a source LISP host to a 2581 destination LISP host: 2583 Segment 1 (in source LISP site based on EIDs): 2585 source-host ---> first-hop ... next-hop ---> ITR 2587 Segment 2 (in the core network based on RLOCs): 2589 ITR ---> next-hop ... next-hop ---> ETR 2591 Segment 3 (in the destination LISP site based on EIDs): 2593 ETR ---> next-hop ... last-hop ---> destination-host 2595 For segment 1 of the path, ICMP Time Exceeded messages are returned 2596 in the normal manner as they are today. The ITR performs a TTL 2597 decrement and test for 0 before encapsulating. So the ITR hop is 2598 seen by the traceroute source has an EID address (the address of 2599 site-facing interface). 2601 For segment 2 of the path, ICMP Time Exceeded messages are returned 2602 to the ITR because the TTL decrement to 0 is done on the outer 2603 header, so the destination of the ICMP messages are to the ITR RLOC 2604 address, the source RLOC address of the encapsulated traceroute 2605 packet. The ITR looks inside of the ICMP payload to inspect the 2606 traceroute source so it can return the ICMP message to the address of 2607 the traceroute client as well as retaining the core router IP address 2608 in the ICMP message. This is so the traceroute client can display 2609 the core router address (the RLOC address) in the traceroute output. 2610 The ETR returns its RLOC address and responds to the TTL decrement to 2611 0 like the previous core routers did. 2613 For segment 3, the next-hop router downstream from the ETR will be 2614 decrementing the TTL for the packet that was encapsulated, sent into 2615 the core, decapsulated by the ETR, and forwarded because it isn't the 2616 final destination. If the TTL is decremented to 0, any router on the 2617 path to the destination of the traceroute, including the next-hop 2618 router or destination, will send an ICMP Time Exceeded message to the 2619 source EID of the traceroute client. The ICMP message will be 2620 encapsulated by the local ITR and sent back to the ETR in the 2621 originated traceroute source site, where the packet will be delivered 2622 to the host. 2624 9.1. IPv6 Traceroute 2626 IPv6 traceroute follows the procedure described above since the 2627 entire traceroute data packet is included in ICMP Time Exceeded 2628 message payload. Therefore, only the ITR needs to pay special 2629 attention for forwarding ICMP messages back to the traceroute source. 2631 9.2. IPv4 Traceroute 2633 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2634 ICMP Time Exceeded messages only include the invoking IP header and 8 2635 octets that follow the IP header. Therefore, when a core router 2636 sends an IPv4 Time Exceeded message to an ITR, all the ITR has in the 2637 ICMP payload is the encapsulated header it prepended followed by a 2638 UDP header. The original invoking IP header, and therefore the 2639 identity of the traceroute source is lost. 2641 The solution we propose to solve this problem is to cache traceroute 2642 IPv4 headers in the ITR and to match them up with corresponding IPv4 2643 Time Exceeded messages received from core routers and the ETR. The 2644 ITR will use a circular buffer for caching the IPv4 and UDP headers 2645 of traceroute packets. It will select a 16-bit number as a key to 2646 find them later when the IPv4 Time Exceeded messages are received. 2647 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2648 16-bit number as the UDP source port in the encapsulating header. 2649 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2650 header of the encapsulating header is present in the ICMP payload 2651 thereby allowing the ITR to find the cached headers for the 2652 traceroute source. The ITR puts the cached headers in the payload 2653 and sends the ICMP Time Exceeded message to the traceroute source 2654 retaining the source address of the original ICMP Time Exceeded 2655 message (a core router or the ETR of the site of the traceroute 2656 destination). 2658 The signature of a traceroute packet comes in two forms. The first 2659 form is encoded as a UDP message where the destination port is 2660 inspected for a range of values. The second form is encoded as an 2661 ICMP message where the IP identification field is inspected for a 2662 well-known value. 2664 9.3. Traceroute using Mixed Locators 2666 When either an IPv4 traceroute or IPv6 traceroute is originated and 2667 the ITR encapsulates it in the other address family header, you 2668 cannot get all 3 segments of the traceroute. Segment 2 of the 2669 traceroute can not be conveyed to the traceroute source since it is 2670 expecting addresses from intermediate hops in the same address format 2671 for the type of traceroute it originated. Therefore, in this case, 2672 segment 2 will make the tunnel look like one hop. All the ITR has to 2673 do to make this work is to not copy the inner TTL to the outer, 2674 encapsulating header's TTL when a traceroute packet is encapsulated 2675 using an RLOC from a different address family. This will cause no 2676 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2678 10. Mobility Considerations 2680 There are several kinds of mobility of which only some might be of 2681 concern to LISP. Essentially they are as follows. 2683 10.1. Site Mobility 2685 A site wishes to change its attachment points to the Internet, and 2686 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2687 providers. Changes in EID-RLOC mappings for sites are expected to be 2688 handled by configuration, outside of the LISP protocol. 2690 10.2. Slow Endpoint Mobility 2692 An individual endpoint wishes to move, but is not concerned about 2693 maintaining session continuity. Renumbering is involved. LISP can 2694 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2695 decoupling the address space used by a site from the address spaces 2696 used by its ISPs. [RFC4984] 2698 10.3. Fast Endpoint Mobility 2700 Fast endpoint mobility occurs when an endpoint moves relatively 2701 rapidly, changing its IP layer network attachment point. Maintenance 2702 of session continuity is a goal. This is where the Mobile IPv4 2703 [RFC5944] and Mobile IPv6 [RFC6275] [RFC4866] mechanisms are used, 2704 and primarily where interactions with LISP need to be explored. 2706 The problem is that as an endpoint moves, it may require changes to 2707 the mapping between its EID and a set of RLOCs for its new network 2708 location. When this is added to the overhead of mobile IP binding 2709 updates, some packets might be delayed or dropped. 2711 In IPv4 mobility, when an endpoint is away from home, packets to it 2712 are encapsulated and forwarded via a home agent which resides in the 2713 home area the endpoint's address belongs to. The home agent will 2714 encapsulate and forward packets either directly to the endpoint or to 2715 a foreign agent which resides where the endpoint has moved to. 2716 Packets from the endpoint may be sent directly to the correspondent 2717 node, may be sent via the foreign agent, or may be reverse-tunneled 2718 back to the home agent for delivery to the mobile node. As the 2719 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2720 mappings are required for communication between the mobile node and 2721 the home agent, whether via foreign agent or not. As a mobile 2722 endpoint changes networks, up to three LISP mapping changes may be 2723 required: 2725 o The mobile node moves from an old location to a new visited 2726 network location and notifies its home agent that it has done so. 2727 The Mobile IPv4 control packets the mobile node sends pass through 2728 one of the new visited network's ITRs, which needs an EID-RLOC 2729 mapping for the home agent. 2731 o The home agent might not have the EID-RLOC mappings for the mobile 2732 node's "care-of" address or its foreign agent in the new visited 2733 network, in which case it will need to acquire them. 2735 o When packets are sent directly to the correspondent node, it may 2736 be that no traffic has been sent from the new visited network to 2737 the correspondent node's network, and the new visited network's 2738 ITR will need to obtain an EID-RLOC mapping for the correspondent 2739 node's site. 2741 In addition, if the IPv4 endpoint is sending packets from the new 2742 visited network using its original EID, then LISP will need to 2743 perform a route-returnability check on the new EID-RLOC mapping for 2744 that EID. 2746 In IPv6 mobility, packets can flow directly between the mobile node 2747 and the correspondent node in either direction. The mobile node uses 2748 its "care-of" address (EID). In this case, the route-returnability 2749 check would not be needed but one more LISP mapping lookup may be 2750 required instead: 2752 o As above, three mapping changes may be needed for the mobile node 2753 to communicate with its home agent and to send packets to the 2754 correspondent node. 2756 o In addition, another mapping will be needed in the correspondent 2757 node's ITR, in order for the correspondent node to send packets to 2758 the mobile node's "care-of" address (EID) at the new network 2759 location. 2761 When both endpoints are mobile the number of potential mapping 2762 lookups increases accordingly. 2764 As a mobile node moves there are not only mobility state changes in 2765 the mobile node, correspondent node, and home agent, but also state 2766 changes in the ITRs and ETRs for at least some EID-prefixes. 2768 The goal is to support rapid adaptation, with little delay or packet 2769 loss for the entire system. Also IP mobility can be modified to 2770 require fewer mapping changes. In order to increase overall system 2771 performance, there may be a need to reduce the optimization of one 2772 area in order to place fewer demands on another. 2774 In LISP, one possibility is to "glean" information. When a packet 2775 arrives, the ETR could examine the EID-RLOC mapping and use that 2776 mapping for all outgoing traffic to that EID. It can do this after 2777 performing a route-returnability check, to ensure that the new 2778 network location does have a internal route to that endpoint. 2779 However, this does not cover the case where an ITR (the node assigned 2780 the RLOC) at the mobile-node location has been compromised. 2782 Mobile IP packet exchange is designed for an environment in which all 2783 routing information is disseminated before packets can be forwarded. 2784 In order to allow the Internet to grow to support expected future 2785 use, we are moving to an environment where some information may have 2786 to be obtained after packets are in flight. Modifications to IP 2787 mobility should be considered in order to optimize the behavior of 2788 the overall system. Anything which decreases the number of new EID- 2789 RLOC mappings needed when a node moves, or maintains the validity of 2790 an EID-RLOC mapping for a longer time, is useful. 2792 10.4. Fast Network Mobility 2794 In addition to endpoints, a network can be mobile, possibly changing 2795 xTRs. A "network" can be as small as a single router and as large as 2796 a whole site. This is different from site mobility in that it is 2797 fast and possibly short-lived, but different from endpoint mobility 2798 in that a whole prefix is changing RLOCs. However, the mechanisms 2799 are the same and there is no new overhead in LISP. A map request for 2800 any endpoint will return a binding for the entire mobile prefix. 2802 If mobile networks become a more common occurrence, it may be useful 2803 to revisit the design of the mapping service and allow for dynamic 2804 updates of the database. 2806 The issue of interactions between mobility and LISP needs to be 2807 explored further. Specific improvements to the entire system will 2808 depend on the details of mapping mechanisms. Mapping mechanisms 2809 should be evaluated on how well they support session continuity for 2810 mobile nodes. 2812 10.5. LISP Mobile Node Mobility 2814 A mobile device can use the LISP infrastructure to achieve mobility 2815 by implementing the LISP encapsulation and decapsulation functions 2816 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2817 node" can use topologically-independent EID IP addresses that are not 2818 advertised into and do not impose a cost on the global routing 2819 system. These EIDs are maintained at the edges of the mapping system 2820 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2821 only the correspondents of the LISP mobile node. 2823 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2824 more details. 2826 11. Multicast Considerations 2828 A multicast group address, as defined in the original Internet 2829 architecture is an identifier of a grouping of topologically 2830 independent receiver host locations. The address encoding itself 2831 does not determine the location of the receiver(s). The multicast 2832 routing protocol, and the network-based state the protocol creates, 2833 determines where the receivers are located. 2835 In the context of LISP, a multicast group address is both an EID and 2836 a Routing Locator. Therefore, no specific semantic or action needs 2837 to be taken for a destination address, as it would appear in an IP 2838 header. Therefore, a group address that appears in an inner IP 2839 header built by a source host will be used as the destination EID. 2840 The outer IP header (the destination Routing Locator address), 2841 prepended by a LISP router, will use the same group address as the 2842 destination Routing Locator. 2844 Having said that, only the source EID and source Routing Locator 2845 needs to be dealt with. Therefore, an ITR merely needs to put its 2846 own IP address in the source Routing Locator field when prepending 2847 the outer IP header. This source Routing Locator address, like any 2848 other Routing Locator address MUST be globally routable. 2850 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2851 ITR when a received data packet is a multicast data packet or when 2852 processing a source-specific Join (either by IGMPv3 or PIM). But the 2853 source Routing Locator is decided by the multicast routing protocol 2854 in a receiver site. That is, an EID to Routing Locator translation 2855 is done at control-time. 2857 Another approach is to have the ITR not encapsulate a multicast 2858 packet and allow the host built packet to flow into the core even if 2859 the source address is allocated out of the EID namespace. If the 2860 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2861 routers can RPF to the ITR (the Locator address which is injected 2862 into core routing) rather than the host source address (the EID 2863 address which is not injected into core routing). 2865 To avoid any EID-based multicast state in the network core, the first 2866 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2867 and Interworking with non-LISP sites is described in specification 2868 [MLISP]. 2870 12. Security Considerations 2872 It is believed that most of the security mechanisms will be part of 2873 the mapping database service when using control plane procedures for 2874 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2875 as described in this specification, protection is provided against 2876 ETR spoofing by using Return-Routability (see Section 3) mechanisms 2877 evidenced by the use of a 24-bit Nonce field in the LISP 2878 encapsulation header and a 64-bit Nonce field in the LISP control 2879 message. 2881 The nonce, coupled with the ITR accepting only solicited Map-Replies 2882 provides a basic level of security, in many ways similar to the 2883 security experienced in the current Internet routing system. It is 2884 hard for off-path attackers to launch attacks against these LISP 2885 mechanisms, as they do not have the nonce values. Sending a large 2886 number of packets to accidentally find the right nonce value is 2887 possible, but would already by itself be a denial-of-service attack. 2888 On-path attackers can perform far more serious attacks, but on-path 2889 attackers can launch serious attacks in the current Internet as well, 2890 including eavesdropping, blocking or redirecting traffic. See more 2891 discussion on this topic in Section 6.1.5.1. 2893 LISP does not rely on a PKI or a more heavy weight authentication 2894 system. These systems challenge the scalability of LISP which was a 2895 primary design goal. 2897 DoS attack prevention will depend on implementations rate-limiting 2898 Map-Requests and Map-Replies to the control plane as well as rate- 2899 limiting the number of data-triggered Map-Replies. 2901 An incorrectly implemented or malicious ITR might choose to ignore 2902 the priority and weights provided by the ETR in its Map-Reply. This 2903 traffic steering would be limited to the traffic that is sent by this 2904 ITR's site, and no more severe than if the site initiated a bandwidth 2905 DoS attack on (one of) the ETR's ingress links. The ITR's site would 2906 typically gain no benefit from not respecting the weights, and would 2907 likely to receive better service by abiding by them. 2909 To deal with map-cache exhaustion attempts in an ITR/PITR, the 2910 implementation should consider putting a maximum cap on the number of 2911 entries stored with a reserve list for special or frequently accessed 2912 sites. This should be a configuration policy control set by the 2913 network administrator who manages ITRs and PITRs. When overlapping 2914 EID-prefixes occur across multiple map-cache entries, the integrity 2915 of the set must be wholly maintained. So if a more-specific entry 2916 cannot be added due to reaching the maximum cap, then none of the 2917 less specifics should be stored in the map-cache. 2919 Given that the ITR/PITR maintains a cache of EID-to-RLOC mappings, 2920 cache sizing and maintenance is an issue to be kept in mind during 2921 implementation. It is a good idea to have instrumentation in place 2922 to detect thrashing of the cache. Implementation experimentation 2923 will be used to determine which cache management strategies work 2924 best. In general, it is difficult to defend against cache trashing 2925 attacks. It should be noted that an undersized cache in an ITR/PITR 2926 not only causes adverse affect on the site or region they support, 2927 but may also cause increased Map-Request load on the mapping system. 2929 "Piggybacked" mapping data discussed in Section 6.1.3 specifies how 2930 to handle such mappings and includes the possibility for an ETR to 2931 temporarily accept such a mapping before verification when running in 2932 "trusted" environments. In such cases, there is a potential threat 2933 that a fake mapping could be inserted (even if only for a short 2934 period) into a map-cache. As noted in Section 6.1.3, an ETR MUST be 2935 specifically configured to run in such a mode and might usefully only 2936 consider some specific ITRs as also running in that same trusted 2937 environment. 2939 There is a security risk implicit in the fact that ETRs generate the 2940 EID prefix to which they are responding. An ETR can claim a shorter 2941 prefix than it is actually responsible for. Various mechanisms to 2942 ameliorate or resolve this issue will be examined in the future, 2943 [LISP-SEC]. 2945 Spoofing of inner header addresses of LISP encapsulated packets is 2946 possible like with any tunneling mechanism. ITRs MUST verify the 2947 source address of a packet to be an EID that belongs to the site's 2948 EID-prefix range prior to encapsulation. An ETR must only 2949 decapsulate and forward datagrams with an inner header destination 2950 that matches one of its EID-prefix ranges. If, upon receipt and 2951 decapsulation, the destination EID of a datagram does not match one 2952 of the ETR's configured EID-prefixes, the ETR MUST drop the datagram. 2953 If a LISP encapsulated packet arrives at an ETR, it SHOULD compare 2954 the inner header source EID address and the outer header source RLOC 2955 address with the mapping that exists in the mapping database. Then 2956 when spoofing attacks occur, the outer header source RLOC address can 2957 be used to trace back the attack to the source site, using existing 2958 operational tools. 2960 This experimental specification does not address automated key 2961 management (AKM). BCP 107 provides guidance in this area. In 2962 addition, at the time of this writing, substantial work is being 2963 undertaken to improve security of the routing system [KARP], [RPKI], 2964 [BGP-SEC], [LISP-SEC]. Future work on LISP should address BCP-107 as 2965 well as other open security considerations, which may require changes 2966 to this specification. 2968 13. Network Management Considerations 2970 Considerations for Network Management tools exist so the LISP 2971 protocol suite can be operationally managed. The mechanisms can be 2972 found in [LISP-MIB] and [LISP-LIG]. 2974 14. IANA Considerations 2976 This section provides guidance to the Internet Assigned Numbers 2977 Authority (IANA) regarding registration of values related to the LISP 2978 specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. 2980 There are four name spaces in LISP that require registration: 2982 o LISP IANA registry allocations should not be made for purposes 2983 unrelated to LISP routing or transport protocols. 2985 o The following policies are used here with the meanings defined in 2986 BCP 26: "Specification Required", "IETF Review", "Experimental 2987 Use", "First Come First Served". 2989 14.1. LISP ACT and Flag Fields 2991 New ACT values (Section 6.1.4) can be allocated through IETF review 2992 or IESG approval. Four values have already been allocated by this 2993 specification (Section 6.1.4). 2995 In addition, the LISP protocol has a number of flag and reserved 2996 fields, such as the LISP header flags field (Section 5.3). New bits 2997 for flags can be taken into use from these fields through IETF review 2998 or IESG approval, but these need not be managed by IANA. 3000 14.2. LISP Address Type Codes 3002 LISP Address [LCAF] type codes have a range from 0 to 255. New type 3003 codes MUST be allocated consecutively starting at 0. Type Codes 0 - 3004 127 are to be assigned by IETF review or IESG approval. 3006 Type Codes 128 - 255 are available on a First Come First Served 3007 policy. 3009 This registry, initially empty, is constructed for future-use 3010 experimental work of LCAF values. See [LCAF] for details for other 3011 possible unapproved address encodings. The unapproved LCAF encodings 3012 are an area for further study and experimentation. 3014 14.3. LISP UDP Port Numbers 3016 The IANA registry has allocated UDP port numbers 4341 and 4342 for 3017 lisp-data and lisp-control operation, respectively. IANA is 3018 requested to update the description for udp ports 4341 and 4342 as 3019 follows: 3021 lisp-data 4341 udp LISP Data Packets 3022 lisp-control 4342 udp LISP Control Packets 3024 14.4. LISP Key ID Numbers 3026 The following Key ID values are defined by this specification as used 3027 in any packet type that references a Key ID field: 3029 Name Number Defined in 3030 ----------------------------------------------- 3031 None 0 n/a 3032 HMAC-SHA-1-96 1 [RFC2404] 3033 HMAC-SHA-256-128 2 [RFC6234] 3035 Number values are in the range of 0 to 65355. The allocation of 3036 values is on a first come first serve basis. 3038 15. Known Open Issues and Areas of Future Work 3040 As an experimental specification, this work is, by definition, 3041 incomplete. Specific areas where additional experience and work are 3042 needed include: 3044 o At present, only [ALT] is defined for implementing a database of 3045 EID-to-RLOC mapping information. Additional research on other 3046 mapping database systems is strongly encouraged. 3048 o Failure and recovery of LISP site partitioning (see Section 6.4), 3049 in the presence of redundant configuration (see Section 8.5) needs 3050 further research and experimentation. 3052 o The characteristics of map-cache management under exceptional 3053 conditions, such as denial-of-service attacks are not fully 3054 understood. Further experience is needed to determine whether 3055 current caching methods are practical or in need of further 3056 development. In particular, the performance, scaling and security 3057 characteristics of the map-cache will be discovered as part of 3058 this experiment. Performance metrics to be observed are packet 3059 reordering associated with the LISP data probe and loss of the 3060 first packet in a flow associated with map-caching. The impact of 3061 these upon TCP will be observed. See Section 12 for additional 3062 thoughts and considerations. 3064 o Preliminary work has been done to ensure that sites employing LISP 3065 can interconnect with the rest of the Internet. This work is 3066 documented in [INTERWORK], but further experimentation and 3067 experience is needed. 3069 o At present, no mechanism for automated key management for message 3070 authentication is defined. Addressing automated key management is 3071 necessary before this specification could be developed into a 3072 standards track RFC. See Section 12 for further details regarding 3073 security considerations. 3075 o In order to maintain security and stability, Internet Protocols 3076 typically isolate the control and data planes. Therefore, user 3077 activity cannot cause control plane state to be created or 3078 destroyed. LISP does not maintain this separation. The degree to 3079 which the loss of separation impacts security and stability is a 3080 topic for experimental observation. 3082 o LISP allows for different mapping database systems to be used. 3083 While only one [ALT] is currently well-defined, each mapping 3084 database will likely have some impact on the security of the EID- 3085 to-RLOC mappings. How each mapping database system's security 3086 properties impact on LISP overall is for further study. 3088 o An examination of the implications of LISP on Internet traffic, 3089 applications, routers, and security is needed. This will help to 3090 understand the consequences for network stability, routing 3091 protocol function, routing scalability, migration and backward 3092 compatibility, and implementation scalability (as influenced by 3093 additional protocol components, additional state, and additional 3094 processing for encapsulation, decapsulation, liveness). 3096 o Experiments need to verify that LISP produces no significant 3097 change in the behavior of protocols run between end-systems over a 3098 LISP infrastructure versus being run directly between those same 3099 end-systems. 3101 o Experiments need to verify that the issues raised in the Critique 3102 section of [RFC6115] are either insignificant or have been 3103 addressed by updates to the LISP protocol. 3105 Other LISP documents may also include open issues and areas for 3106 future work. 3108 16. References 3110 16.1. Normative References 3112 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 3113 Alternative Topology (LISP-ALT)", 3114 draft-ietf-lisp-alt-10.txt (work in progress). 3116 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 3117 draft-ietf-lisp-ms-16.txt (work in progress). 3119 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 3120 August 1980. 3122 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 3123 September 1981. 3125 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 3126 E. Lear, "Address Allocation for Private Internets", 3127 BCP 5, RFC 1918, February 1996. 3129 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3130 Requirement Levels", BCP 14, RFC 2119, March 1997. 3132 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 3133 ESP and AH", RFC 2404, November 1998. 3135 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3136 (IPv6) Specification", RFC 2460, December 1998. 3138 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 3139 of Explicit Congestion Notification (ECN) to IP", 3140 RFC 3168, September 2001. 3142 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 3143 an On-line Database", RFC 3232, January 2002. 3145 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 3146 Requirements for Security", BCP 106, RFC 4086, June 2005. 3148 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 3149 (CIDR): The Internet Address Assignment and Aggregation 3150 Plan", BCP 122, RFC 4632, August 2006. 3152 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3153 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 3154 May 2008. 3156 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 3157 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 3159 [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", 3160 RFC 5944, November 2010. 3162 [RFC6115] Li, T., "Recommendation for a Routing Architecture", 3163 RFC 6115, February 2011. 3165 [RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 3166 (SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011. 3168 [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support 3169 in IPv6", RFC 6275, July 2011. 3171 [VERSIONING] 3172 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3173 Versioning", draft-ietf-lisp-map-versioning-09.txt (work 3174 in progress). 3176 16.2. Informative References 3178 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3179 NUMBERS 3180 http://www.iana.org/assignments/address-family-numbers. 3182 [AFI-REGISTRY] 3183 IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3184 NUMBER registry http://www.iana.org/assignments/ 3185 address-family-numbers/ 3186 address-family-numbers.xml#address-family-numbers-1. 3188 [BGP-SEC] Lepinski, M., "An Overview of BGPSEC", 3189 draft-lepinski-bgpsec-overview-00.txt (work in progress), 3190 March 2011. 3192 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 3193 Enhancement to the Internet Architecture", Internet- 3194 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt. 3196 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 3197 Content distribution Overlay Network Service for LISP", 3198 draft-meyer-lisp-cons-04.txt (work in progress). 3200 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 3201 Mappings Multicast Across Cooperating Systems for LISP", 3202 draft-curran-lisp-emacs-00.txt (work in progress). 3204 [INTERWORK] 3205 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 3206 "Interworking LISP with IPv4 and IPv6", 3207 draft-ietf-lisp-interworking-06.txt (work in progress). 3209 [KARP] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 3210 Routing Protocols (KARP)Design Guidelines", 3211 draft-ietf-karp-design-guide-06.txt (work in progress), 3212 October 2011. 3214 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 3215 Address Format", draft-ietf-lisp-lcaf-00.txt (work in 3216 progress). 3218 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 3219 "Renumbering: Threat or Menace?", Usenix . 3221 [LISP-DEPLOY] 3222 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 3223 "LISP Network Element Deployment Considerations", 3224 draft-ietf-lisp-deployment-05.txt (work in progress). 3226 [LISP-LIG] 3227 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 3228 draft-ietf-lisp-lig-06.txt (work in progress). 3230 [LISP-MAIN] 3231 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 3232 "Locator/ID Separation Protocol (LISP)", 3233 draft-farinacci-lisp-12.txt (work in progress). 3235 [LISP-MIB] 3236 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 3237 draft-ietf-lisp-mib-07.txt (work in progress). 3239 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 3240 Mobility Architecture", draft-meyer-lisp-mn-08.txt (work 3241 in progress). 3243 [LISP-SEC] 3244 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 3245 Bonaventure, "LISP-Security (LISP-SEC)", 3246 draft-ietf-lisp-sec-04.txt (work in progress). 3248 [LOC-ID-ARCH] 3249 Meyer, D. and D. Lewis, "Architectural Implications of 3250 Locator/ID Separation", 3251 draft-meyer-loc-id-implications-02.txt (work in progress). 3253 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 3254 "LISP for Multicast Environments", 3255 draft-ietf-lisp-multicast-14.txt (work in progress). 3257 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 3258 draft-lear-lisp-nerd-08.txt (work in progress). 3260 [OPENLISP] 3261 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 3262 Report", draft-iannone-openlisp-implementation-01.txt 3263 (work in progress). 3265 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 3266 draft-narten-radir-problem-statement-05.txt (work in 3267 progress). 3269 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 3270 STD 13, RFC 1034, November 1987. 3272 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 3273 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 3274 March 2000. 3276 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 3277 via IPv4 Clouds", RFC 3056, February 2001. 3279 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 3280 A., Peterson, J., Sparks, R., Handley, M., and E. 3281 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 3282 June 2002. 3284 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 3285 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 3286 September 2005. 3288 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 3289 Optimization for Mobile IPv6", RFC 4866, May 2007. 3291 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 3292 Workshop on Routing and Addressing", RFC 4984, 3293 September 2007. 3295 [RPKI] Lepinski, M., "An Infrastructure to Support Secure 3296 Internet Routing", draft-ietf-sidr-arch-13.txt (work in 3297 progress), February 2011. 3299 [UDP-TUNNELS] 3300 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 3301 Packets", draft-ietf-6man-udpchecksums-05.txt (work in 3302 progress), October 2012. 3304 [UDP-ZERO] 3305 Fairhurst, G. and M. Westerland, "IPv6 UDP Checksum 3306 Considerations", draft-ietf-6man-udpzero-07.txt (work in 3307 progress), October 2012. 3309 Appendix A. Acknowledgments 3311 An initial thank you goes to Dave Oran for planting the seeds for the 3312 initial ideas for LISP. His consultation continues to provide value 3313 to the LISP authors. 3315 A special and appreciative thank you goes to Noel Chiappa for 3316 providing architectural impetus over the past decades on separation 3317 of location and identity, as well as detailed review of the LISP 3318 architecture and documents, coupled with enthusiasm for making LISP a 3319 practical and incremental transition for the Internet. 3321 The authors would like to gratefully acknowledge many people who have 3322 contributed discussion and ideas to the making of this proposal. 3323 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3324 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3325 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3326 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3327 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3328 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3329 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3330 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3331 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3332 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3333 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3334 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3335 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3336 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3337 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3338 Clarence Filsfils, and Alia Atlas. 3340 This work originated in the Routing Research Group (RRG) of the IRTF. 3341 The individual submission [LISP-MAIN] was converted into this IETF 3342 LISP working group draft. 3344 The LISP working group would like to give a special thanks to Jari 3345 Arkko, the Internet Area AD at the time the set of LISP documents 3346 were being prepared for IESG last call, for his meticulous review and 3347 detail commentary on the 7 working group last call drafts progressing 3348 toward experimental RFCs. 3350 Appendix B. Document Change Log 3352 B.1. Changes to draft-ietf-lisp-24.txt 3354 o Posted November 2012 for final pre-RFC version. 3356 o Move draft-ietf-6man-udpchecksums reference back to Informative 3357 References section. 3359 B.2. Changes to draft-ietf-lisp-23.txt 3361 o Posted May 2012 for final pre-RFC version. 3363 o Move only the reference draft-ietf-6man-udpzero to the Informative 3364 References section. Leave the draft-ietf-6man-udpchecksums 3365 reference in the Normative References section. After talking to 3366 many people involved with this issue at Paris IETF, all thought 3367 this would be an acceptable change. 3369 o Added text to IANA Considerations section 14.4 to reflect IANA 3370 comments about allocating Key-ID numbers. 3372 B.3. Changes to draft-ietf-lisp-22.txt 3374 o Posted February 2012 to reflect final DISCUSS comments from Adrian 3375 Farrel. 3377 B.4. Changes to draft-ietf-lisp-21.txt 3379 o Posted February 2012 to reflect DISCUSS comments from Adrian 3380 Farrel, Stewart Bryant, and Wesley Eddy. 3382 B.5. Changes to draft-ietf-lisp-20.txt 3384 o Posted January 2012 for resolution to Adrian Farrel's security 3385 comments as well as additions to the end of section 2, Elwyn 3386 Davies Gen-Art comments, and Ralph Droms' IANA and EID definition 3387 comments. 3389 B.6. Changes to draft-ietf-lisp-19.txt 3391 o Posted January 2012 for Stephen Farrell's comment resolution. 3393 B.7. Changes to draft-ietf-lisp-18.txt 3395 o Posted December 2011 after reflecting comments from IANA. 3397 o Create reference to sections 5.4.1 and 5.4.2 about DF bit setting 3398 from section 5.3. 3400 o Inserted two references for Route-Returnability and on-path 3401 attacks in Security Considerations section. 3403 B.8. Changes to draft-ietf-lisp-17.txt 3405 o Posted December 2011 after IETF last call comments. 3407 o Make Map-Notify port assignment be 4342 in both source and 3408 destination ports. This change was agreed on and put in [LISP-MS] 3409 but was not updated in this spec. 3411 B.9. Changes to draft-ietf-lisp-16.txt 3413 o Posted October 2011 after AD review by Jari. 3415 B.10. Changes to draft-ietf-lisp-15.txt 3417 o Posted July 2011. Fixing IDnits errors. 3419 o Change description on how to select a source address for RLOC- 3420 probe Map-Replies to refer to the "EID-to-RLOC Map-Reply Message" 3421 section. 3423 B.11. Changes to draft-ietf-lisp-14.txt 3425 o Post working group last call and pre-IESG last call review. 3427 o Indicate that an ICMP Unreachable message should be sent when a 3428 packet matches a drop-based negative map-cache entry. 3430 o Indicate how a map-cache set of overlapping EID-prefixes must 3431 maintain integrity when the map-cache maximum cap is reached. 3433 o Add Joel's description for the definition of an EID, that the bit 3434 string value can be an RLOC for another device in abstract but the 3435 architecture allows it to be an EID of one device and the same 3436 value as an RLOC for another device. 3438 o In the "Tunnel Encapsulation Details" section, indicate that 4 3439 combinations of encapsulation are supported. 3441 o Add what ETR should do for a Data-Probe when received for a 3442 destination EID outside of its EID-prefix range. This was added 3443 in the Data Probe definition section. 3445 o Added text indicating that more-specific EID-prefixes must not be 3446 removed when less-specific entries stay in the map-cache. This is 3447 to preserve the integrity of the EID-prefix set. 3449 o Add clarifying text in the Security Considerations section about 3450 how an ETR must not decapsulate and forward a packet that is not 3451 for its configured EID-prefix range. 3453 B.12. Changes to draft-ietf-lisp-13.txt 3455 o Posted June 2011 to complete working group last call. 3457 o Tracker item 87. Put Yakov suggested wording in the EID-prefix 3458 definition section to reference [INTERWORK] and [LISP-DEPLOY] 3459 about discussion on transition and access mechanisms. 3461 o Change "ITRs" to "ETRs" in the Locator Status Bit definition 3462 section and data packet description section per Damien's comment. 3464 o Remove the normative reference to [LISP-SEC] when describing the 3465 S-bit in the ECM and Map-Reply headers. 3467 o Tracker item 54. Added text from John Scudder in the "Packets 3468 Egressing a LISP Site" section. 3470 o Add sentence to the "Reencapsulating Tunnel" definition about how 3471 reencapsulation loops can occur when not coordinating among 3472 multiple mapping database systems. 3474 o Remove "In theory" from a sentence in the Security Considerations 3475 section. 3477 o Remove Security Area Statement title and reword section with 3478 Eliot's provided text. The text was agreed upon by LISP-WG chairs 3479 and Security ADs. 3481 o Remove word "potential" from the over-claiming paragraph of the 3482 Security Considerations section per Stephen's request. 3484 o Wordsmithing and other editorial comments from Alia. 3486 B.13. Changes to draft-ietf-lisp-12.txt 3488 o Posted April 2011. 3490 o Tracker item 87. Provided rewording how an EID-prefix can be 3491 reused in the definition section of "EID-prefix". 3493 o Tracker item 95. Change "eliminate" to "defer" in section 4.1. 3495 o Tracker item 110. Added that the Mapping Protocol Data field in 3496 the Map-Reply message is only used when needed by the particular 3497 Mapping Database System. 3499 o Tracker item 111. Indicate that if an LSB that is associated with 3500 an anycast address, that there is at least one RLOC that is up. 3502 o Tracker item 108. Make clear the R-bit does not define RLOC path 3503 reachability. 3505 o Tracker item 107. Indicate that weights are relative to each 3506 other versus requiring an addition of up to 100%. 3508 o Tracker item 46. Add a sentence how LISP products should be sized 3509 for the appropriate demand so cache thrashing is avoided. 3511 o Change some references of RFC 5226 to [AFI] per Luigi. 3513 o Per Luigi, make reference to "EID-AFI" consistent to "EID-prefix- 3514 AFI". 3516 o Tracker item 66. Indicate that appending locators to a locator- 3517 set is done when the added locators are lexicographically greater 3518 than the previous ones in the set. 3520 o Tracker item 87. Once again reword the definition of the EID- 3521 prefix to reflect recent comments. 3523 o Tracker item 70. Added text to security section on what the 3524 implications could be if an ITR does not obey priority and weights 3525 from a Map-Reply message. 3527 o Tracker item 54. Added text to the new section titled "Packets 3528 Egressing a LISP Site" to describe the implications when two or 3529 more ITRs exist at a site where only one ITR is used for egress 3530 traffic and when there is a shift of traffic to the others, how 3531 the map-cache will need to be populated in those new egress ITRs. 3533 o Tracker item 33. Make more clear in the Routing Locator Selection 3534 section what an ITR should do when it sees an R-bit of 0 in a 3535 locator-record of a Map-Reply. 3537 o Tracker item 33. Add paragraph to the EID Reachability section 3538 indicating that site partitioning is under investigation. 3540 o Tracker item 58. Added last paragraph of Security Considerations 3541 section about how to protect inner header EID address spoofing 3542 attacks. 3544 o Add suggested Sam text to indicate that all security concerns need 3545 not be addressed for moving document to Experimental RFC status. 3546 Put this in a subsection of the Security Considerations section. 3548 B.14. Changes to draft-ietf-lisp-11.txt 3550 o Posted March 30, 2011. 3552 o Change IANA URL. The URL we had pointed to a general protocol 3553 numbers page. 3555 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3556 Requests to be sent to a MN ETR via the map-server. 3558 o Generalize text for the definition of Reencapsuatling tunnels. 3560 o Add paragraph suggested by Joel to explain how implementation 3561 experimentation will be used to determine the proper cache 3562 management techniques. 3564 o Add Yakov provided text for the definition of "EID-to-RLOC 3565 "Database". 3567 o Add reference in Section 8, Deployment Scenarios, to the 3568 draft-jakab-lisp-deploy-02.txt draft. 3570 o Clarify sentence about no hardware changes needed to support LISP 3571 encapsulation. 3573 o Add paragraph about what is the procedure when a locator is 3574 inserted in the middle of a locator-set. 3576 o Add a definition for Locator Status Bits so we can emphasize they 3577 are used as a hint for router up/down status and not path 3578 reachability. 3580 o Change "BGP RIB" to "RIB" per Clarence's comment. 3582 o Fixed complaints by IDnits. 3584 o Add subsection to Security Considerations section indicating how 3585 EID-prefix overclaiming in Map-Replies is for further study and 3586 add a reference to LISP-SEC. 3588 B.15. Changes to draft-ietf-lisp-10.txt 3590 o Posted March 2011. 3592 o Add p-bit to Map-Request so there is documentary reasons to know 3593 when a PITR has sent a Map-Request to an ETR. 3595 o Add Map-Notify message which is used to acknowledge a Map-Register 3596 message sent to a Map-Server. 3598 o Add M-bit to the Map-Register message so an ETR that wants an 3599 acknowledgment for the Map-Register can request one. 3601 o Add S-bit to the ECM and Map-Reply messages to describe security 3602 data that can be present in each message. Then refer to 3603 [LISP-SEC] for expansive details. 3605 o Add Network Management Considerations section and point to the MIB 3606 and LIG drafts. 3608 o Remove the word "simple" per Yakov's comments. 3610 B.16. Changes to draft-ietf-lisp-09.txt 3612 o Posted October 2010. 3614 o Add to IANA Consideration section about the use of LCAF Type 3615 values that accepted and maintained by the IANA registry and not 3616 the LCAF specification. 3618 o Indicate that implementations should be able to receive LISP 3619 control messages when either UDP port is 4342, so they can be 3620 robust in the face of intervening NAT boxes. 3622 o Add paragraph to SMR section to indicate that an ITR does not need 3623 to respond to an SMR-based Map-Request when it has no map-cache 3624 entry for the SMR source's EID-prefix. 3626 B.17. Changes to draft-ietf-lisp-08.txt 3628 o Posted August 2010. 3630 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3631 Register messages. 3633 o Clarify language in section 6.1.5 about Map-Replying to Data- 3634 Probes or Map-Requests. 3636 o Indicate that outer TTL should only be copied to inner TTL when it 3637 is less than inner TTL. 3639 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3640 value of 0. 3642 o Indicate that SMRs can have a global or per SMR destination rate- 3643 limiter. 3645 o Add clarifications to the SMR procedures. 3647 o Add definitions for "client-side" and 'server-side" terms used in 3648 this specification. 3650 o Clear up language in section 6.4, last paragraph. 3652 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3653 probe a PETR and have it return a Map-Reply with a locator-set of 3654 size 0. The way it is spec'ed the map-cache entry has action 3655 "dropped". Drop-action is set to 3. 3657 o Add statement about normalizing locator weights. 3659 o Clarify R-bit definition in the Map-Reply locator record. 3661 o Add section on EID Reachability within a LISP site. 3663 o Clarify another disadvantage of using anycast locators. 3665 o Reworded Abstract. 3667 o Change section 2.0 Introduction to remove obsolete information 3668 such as the LISP variant definitions. 3670 o Change section 5 title from "Tunneling Details" to "LISP 3671 Encapsulation Details". 3673 o Changes to section 5 to include results of network deployment 3674 experience with MTU. Recommend that implementations use either 3675 the stateful or stateless handling. 3677 o Make clarification wordsmithing to Section 7 and 8. 3679 o Identify that if there is one locator in the locator-set of a map- 3680 cache entry, that an SMR from that locator should be responded to 3681 by sending the the SMR-invoked Map-Request to the database mapping 3682 system rather than to the RLOC itself (which may be unreachable). 3684 o When describing Unicast and Multicast Weights indicate the the 3685 values are relative weights rather than percentages. So it 3686 doesn't imply the sum of all locator weights in the locator-set 3687 need to be 100. 3689 o Do some wordsmithing on copying TTL and TOS fields. 3691 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3692 combed the spec. 3694 o Removed Section 14 "Prototype Plans and Status". We felt this 3695 type of section is no longer appropriate for a protocol 3696 specification. 3698 o Add clarification text for the IRC description per Damien's 3699 commentary. 3701 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3702 per Vina's comment about a possible DoS vector. 3704 o Clarify (S/2 + H) in the stateless MTU section. 3706 o Add text to reflect Damien's comment about the description of the 3707 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3708 addresses are local addresses of the Map-Requester. 3710 B.18. Changes to draft-ietf-lisp-07.txt 3712 o Posted April 2010. 3714 o Added I-bit to data header so LSB field can also be used as an 3715 Instance ID field. When this occurs, the LSB field is reduced to 3716 8-bits (from 32-bits). 3718 o Added V-bit to the data header so the 24-bit nonce field can also 3719 be used for source and destination version numbers. 3721 o Added Map-Version 12-bit value to the EID-record to be used in all 3722 of Map-Request, Map-Reply, and Map-Register messages. 3724 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3725 can decide what address to select for the destination of a Map- 3726 Reply. 3728 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3729 the Locator-Set record of an EID-record for a Map-Reply message. 3730 The L-bit indicates which RLOCs in the locator-set are local to 3731 the sender of the message. The P-bit indicates which RLOC is the 3732 source of a RLOC-probe Reply (Map-Reply) message. 3734 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3736 o Made editorial and clarification changes based on comments from 3737 Dhirendra Trivedi. 3739 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3741 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3742 6.3.1. 3744 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3745 for Map-Register messages. 3747 o Add NAT section per Ron Bonica comments. 3749 o Fix IDnits issues per Ron Bonica. 3751 o Added section on Virtualization and Segmentation to explain the 3752 use if the Instance ID field in the data header. 3754 o There are too many P-bits, keep their scope to the packet format 3755 description and refer to them by name every where else in the 3756 spec. 3758 o Scanned all occurrences of "should", "should not", "must" and 3759 "must not" and uppercased them. 3761 o John Zwiebel offered text for section 4.1 to modernize the 3762 example. Thanks Z! 3764 o Make it more clear in the definition of "EID-to-RLOC Database" 3765 that all ETRs need to have the same database mapping. This 3766 reflects a comment from John Scudder. 3768 o Add a definition "Route-returnability" to the Definition of Terms 3769 section. 3771 o In section 9.2, add text to describe what the signature of 3772 traceroute packets can look like. 3774 o Removed references to Data Probe for introductory example. Data- 3775 probes are still part of the LISP design but not encouraged. 3777 o Added the definition for "LISP site" to the Definition of Terms" 3778 section. 3780 B.19. Changes to draft-ietf-lisp-06.txt 3782 Editorial based changes: 3784 o Posted December 2009. 3786 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3788 o Add text to indicate that Map-Register messages must contain a 3789 computed UDP checksum. 3791 o Add definitions for PITR and PETR. 3793 o Indicate an AFI value of 0 is an unspecified address. 3795 o Indicate that the TTL field of a Map-Register is not used and set 3796 to 0 by the sender. This change makes this spec consistent with 3797 [LISP-MS]. 3799 o Change "... yield a packet size of L octets" to "... yield a 3800 packet size greater than L octets". 3802 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3803 Reply messages. 3805 o Clarify that LSBs that go beyond the number of locators do not to 3806 be SMRed when the locator addresses are greater lexicographically 3807 than the locator in the existing locator-set. 3809 o Add Gregg, Srini, and Amit to acknowledgment section. 3811 o Clarify in the definition of a LISP header what is following the 3812 UDP header. 3814 o Clarify "verifying Map-Request" text in section 6.1.3. 3816 o Add Xu Xiaohu to the acknowledgment section for introducing the 3817 problem of overlapping EID-prefixes among multiple sites in an RRG 3818 email message. 3820 Design based changes: 3822 o Use stronger language to have the outer IPv4 header set DF=1 so we 3823 can avoid fragment reassembly in an ETR or PETR. This will also 3824 make IPv4 and IPv6 encapsulation have consistent behavior. 3826 o Map-Requests should not be sent in ECM with the Probe bit is set. 3827 These type of Map-Requests are used as RLOC-probes and are sent 3828 directly to locator addresses in the underlying network. 3830 o Add text in section 6.1.5 about returning all EID-prefixes in a 3831 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3832 configure. 3834 o Add text in a new subsection of section 6.1.5 about dealing with 3835 Map-Replies with coarse EID-prefixes. 3837 B.20. Changes to draft-ietf-lisp-05.txt 3839 o Posted September 2009. 3841 o Added this Document Change Log appendix. 3843 o Added section indicating that encapsulated Map-Requests must use 3844 destination UDP port 4342. 3846 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3847 data in Map-Register payload. 3849 o Added Jari to acknowledgment section. 3851 o State the source-EID is set to 0 when using Map-Requests to 3852 refresh or RLOC-probe. 3854 o Make more clear what source-RLOC should be for a Map-Request. 3856 o The LISP-CONS authors thought that the Type definitions for CONS 3857 should be removed from this specification. 3859 o Removed nonce from Map-Register message, it wasn't used so no need 3860 for it. 3862 o Clarify what to do for unspecified Action bits for negative Map- 3863 Replies. Since No Action is a drop, make value 0 Drop. 3865 B.21. Changes to draft-ietf-lisp-04.txt 3867 o Posted September 2009. 3869 o How do deal with record count greater than 1 for a Map-Request. 3870 Damien and Joel comment. Joel suggests: 1) Specify that senders 3871 compliant with the current document will always set the count to 3872 1, and note that the count is included for future extensibility. 3873 2) Specify what a receiver compliant with the draft should do if 3874 it receives a request with a count greater than 1. Presumably, it 3875 should send some error back? 3877 o Add Fred Templin in acknowledgment section. 3879 o Add Margaret and Sam to the acknowledgment section for their great 3880 comments. 3882 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3884 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3885 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3886 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3887 ignore the checksum completely. And of course we'd need to 3888 confirm that can actually be implemented. In particular, hardware 3889 that verifies UDP checksums on receive needs to be checked to make 3890 sure it permits 0 checksums." 3892 o Margaret wants a reference to 3893 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3895 o Fix description in Map-Request section. Where we describe Map- 3896 Reply Record, change "R-bit" to "M-bit". 3898 o Add the mobility bit to Map-Replies. So PITRs don't probe so 3899 often for MNs but often enough to get mapping updates. 3901 o Indicate SHA1 can be used as well for Map-Registers. 3903 o More Fred comments on MTU handling. 3905 o Isidor comment about spec'ing better periodic Map-Registers. Will 3906 be fixed in draft-ietf-lisp-ms-02.txt. 3908 o Margaret's comment on gleaning: "The current specification does 3909 not make it clear how long gleaned map entries should be retained 3910 in the cache, nor does it make it clear how/ when they will be 3911 validated. The LISP spec should, at the very least, include a 3912 (short) default lifetime for gleaned entries, require that they be 3913 validated within a short period of time, and state that a new 3914 gleaned entry should never overwrite an entry that was obtained 3915 from the mapping system. The security implications of storing 3916 "gleaned" entries should also be explored in detail." 3918 o Add section on RLOC-probing per working group feedback. 3920 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3921 Noel. 3923 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3924 control plane only. 3926 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3927 fields can be turned off and used for another future purpose. For 3928 Luigi et al versioning convergence. 3930 o Add a N-bit to the data header suggested by Noel. Then the nonce 3931 field could be used when N is not 1. 3933 o Clarify that when E-bit is 0, the nonce field can be an echoed 3934 nonce or a random nonce. Comment from Jesper. 3936 o Indicate when doing data-gleaning that a verifying Map-Request is 3937 sent to the source-EID of the gleaned data packet so we can avoid 3938 map-cache corruption by a 3rd party. Comment from Pedro. 3940 o Indicate that a verifying Map-Request, for accepting mapping data, 3941 should be sent over the ALT (or to the EID). 3943 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3945 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3946 noncing. Comment by Pedro and Dino. 3948 o Jesper made a comment to loosen the language about requiring the 3949 copy of inner TTL to outer TTL since the text to get mixed-AF 3950 traceroute to work would violate the "MUST" clause. Changed from 3951 MUST to SHOULD in section 5.3. 3953 B.22. Changes to draft-ietf-lisp-03.txt 3955 o Posted July 2009. 3957 o Removed loc-reach-bits longword from control packets per Damien 3958 comment. 3960 o Clarifications in MTU text from Roque. 3962 o Added text to indicate that the locator-set be sorted by locator 3963 address from Isidor. 3965 o Clarification text from John Zwiebel in Echo-Nonce section. 3967 B.23. Changes to draft-ietf-lisp-02.txt 3969 o Posted July 2009. 3971 o Encapsulation packet format change to add E-bit and make loc- 3972 reach-bits 32-bits in length. 3974 o Added Echo-Nonce Algorithm section. 3976 o Clarification how ECN bits are copied. 3978 o Moved S-bit in Map-Request. 3980 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3981 RLOC-Probe Algorithm. 3983 o Added to Mobility section to reference [LISP-MN]. 3985 B.24. Changes to draft-ietf-lisp-01.txt 3987 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3989 o Defined LEID to be a "LISP EID". 3991 o Indicate encapsulation use IPv4 DF=0. 3993 o Added negative Map-Reply messages with drop, native-forward, and 3994 send-map-request actions. 3996 o Added Proxy-Map-Reply bit to Map-Register. 3998 B.25. Changes to draft-ietf-lisp-00.txt 4000 o Posted May 2009. 4002 o Rename of draft-farinacci-lisp-12.txt. 4004 o Acknowledgment to RRG. 4006 Authors' Addresses 4008 Dino Farinacci 4009 cisco Systems 4010 Tasman Drive 4011 San Jose, CA 95134 4012 USA 4014 Email: dino@cisco.com 4016 Vince Fuller 4017 cisco Systems 4018 Tasman Drive 4019 San Jose, CA 95134 4020 USA 4022 Email: vaf@cisco.com 4024 Dave Meyer 4025 cisco Systems 4026 170 Tasman Drive 4027 San Jose, CA 4028 USA 4030 Email: dmm@cisco.com 4032 Darrel Lewis 4033 cisco Systems 4034 170 Tasman Drive 4035 San Jose, CA 4036 USA 4038 Email: darlewis@cisco.com