idnits 2.17.1 draft-ietf-lisp-17.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 10 instances of lines with private range IPv4 addresses in the document. If these are generic example addresses, they should be changed to use any of the ranges defined in RFC 6890 (or successor): 192.0.2.x, 198.51.100.x or 203.0.113.x. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (December 6, 2011) is 4518 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-lisp-alt-09 == Outdated reference: A later version (-16) exists of draft-ietf-lisp-ms-12 ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) == Outdated reference: A later version (-12) exists of draft-ietf-6man-udpzero-04 == Outdated reference: A later version (-09) exists of draft-ietf-lisp-map-versioning-05 == Outdated reference: A later version (-06) exists of draft-ietf-lisp-interworking-02 == Outdated reference: A later version (-10) exists of draft-ietf-karp-design-guide-06 == Outdated reference: A later version (-10) exists of draft-farinacci-lisp-lcaf-06 == Outdated reference: A later version (-12) exists of draft-ietf-lisp-deployment-02 == Outdated reference: A later version (-13) exists of draft-ietf-lisp-mib-02 == Outdated reference: A later version (-16) exists of draft-meyer-lisp-mn-06 -- Unexpected draft version: The latest known version of draft-meyer-loc-id-implications is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 == Outdated reference: A later version (-14) exists of draft-ietf-lisp-multicast-10 == Outdated reference: A later version (-09) exists of draft-lear-lisp-nerd-08 Summary: 2 errors (**), 0 flaws (~~), 14 warnings (==), 2 comments (--).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: June 8, 2012 D. Lewis 6 cisco Systems 7 December 6, 2011 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-17 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 June 8, 2012. 44 Copyright Notice 46 Copyright (c) 2011 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 62 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 7 64 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 12 65 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 14 66 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . . 16 67 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 17 68 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 17 69 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . . 19 70 5.4. Dealing with Large Encapsulated Packets . . . . . . . . . 23 71 5.4.1. A Stateless Solution to MTU Handling . . . . . . . . . 23 72 5.4.2. A Stateful Solution to MTU Handling . . . . . . . . . 24 73 5.5. Using Virtualization and Segmentation with LISP . . . . . 24 74 6. EID-to-RLOC Mapping . . . . . . . . . . . . . . . . . . . . . 26 75 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats . . . . . 26 76 6.1.1. LISP Packet Type Allocations . . . . . . . . . . . . . 28 77 6.1.2. Map-Request Message Format . . . . . . . . . . . . . . 28 78 6.1.3. EID-to-RLOC UDP Map-Request Message . . . . . . . . . 31 79 6.1.4. Map-Reply Message Format . . . . . . . . . . . . . . . 32 80 6.1.5. EID-to-RLOC UDP Map-Reply Message . . . . . . . . . . 36 81 6.1.6. Map-Register Message Format . . . . . . . . . . . . . 38 82 6.1.7. Map-Notify Message Format . . . . . . . . . . . . . . 40 83 6.1.8. Encapsulated Control Message Format . . . . . . . . . 41 84 6.2. Routing Locator Selection . . . . . . . . . . . . . . . . 43 85 6.3. Routing Locator Reachability . . . . . . . . . . . . . . . 45 86 6.3.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 47 87 6.3.2. RLOC Probing Algorithm . . . . . . . . . . . . . . . . 48 88 6.4. EID Reachability within a LISP Site . . . . . . . . . . . 49 89 6.5. Routing Locator Hashing . . . . . . . . . . . . . . . . . 50 90 6.6. Changing the Contents of EID-to-RLOC Mappings . . . . . . 51 91 6.6.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . 52 92 6.6.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . 52 93 6.6.3. Database Map Versioning . . . . . . . . . . . . . . . 54 94 7. Router Performance Considerations . . . . . . . . . . . . . . 55 95 8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 56 96 8.1. First-hop/Last-hop Tunnel Routers . . . . . . . . . . . . 57 97 8.2. Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 57 98 8.3. ISP Provider-Edge (PE) Tunnel Routers . . . . . . . . . . 58 99 8.4. LISP Functionality with Conventional NATs . . . . . . . . 58 100 8.5. Packets Egressing a LISP Site . . . . . . . . . . . . . . 59 101 9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 60 102 9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 61 103 9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 61 104 9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 61 105 10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 63 106 10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 63 107 10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 63 108 10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 63 109 10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 65 110 10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 65 111 11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 67 112 12. Security Considerations . . . . . . . . . . . . . . . . . . . 68 113 13. Network Management Considerations . . . . . . . . . . . . . . 70 114 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 71 115 14.1. LISP ACT and Flag Fields . . . . . . . . . . . . . . . . . 71 116 14.2. LISP Address Type Codes . . . . . . . . . . . . . . . . . 71 117 14.3. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 71 118 14.4. LISP Key ID Numbers . . . . . . . . . . . . . . . . . . . 72 119 15. Known Open Issues and Areas of Future Work . . . . . . . . . . 73 120 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 75 121 16.1. Normative References . . . . . . . . . . . . . . . . . . . 75 122 16.2. Informative References . . . . . . . . . . . . . . . . . . 76 123 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 80 124 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 81 125 B.1. Changes to draft-ietf-lisp-17.txt . . . . . . . . . . . . 81 126 B.2. Changes to draft-ietf-lisp-16.txt . . . . . . . . . . . . 81 127 B.3. Changes to draft-ietf-lisp-15.txt . . . . . . . . . . . . 81 128 B.4. Changes to draft-ietf-lisp-14.txt . . . . . . . . . . . . 81 129 B.5. Changes to draft-ietf-lisp-13.txt . . . . . . . . . . . . 82 130 B.6. Changes to draft-ietf-lisp-12.txt . . . . . . . . . . . . 82 131 B.7. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 84 132 B.8. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 85 133 B.9. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 85 134 B.10. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 85 135 B.11. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 87 136 B.12. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 89 137 B.13. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 90 138 B.14. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 90 139 B.15. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 92 140 B.16. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 92 141 B.17. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 93 142 B.18. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 93 143 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 94 145 1. Requirements Notation 147 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 148 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 149 document are to be interpreted as described in [RFC2119]. 151 2. Introduction 153 This document describes the Locator/Identifier Separation Protocol 154 (LISP), which provides a set of functions for routers to exchange 155 information used to map from non globally routeable Endpoint 156 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 157 defines a mechanism for these LISP routers to encapsulate IP packets 158 addressed with EIDs for transmission across the< Internet that uses 159 RLOCs for routing and forwarding. 161 Creation of LISP was initially motivated by discussions during the 162 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 163 October, 2006 (see [RFC4984]). A key conclusion of the workshop was 164 that the Internet routing and addressing system was not scaling well 165 in the face of the explosive growth of new sites; one reason for this 166 poor scaling is the increasing number of multi-homed and other sites 167 that cannot be addressed as part of topologically- or provider-based 168 aggregated prefixes. Additional work that more completely described 169 the problem statement may be found in [RADIR]. 171 A basic observation, made many years ago in early networking research 172 such as that documented in [CHIAPPA] and [RFC4984], is that using a 173 single address field for both identifying a device and for 174 determining where it is topologically located in the network requires 175 optimization along two conflicting axes: for routing to be efficient, 176 the address must be assigned topologically; for collections of 177 devices to be easily and effectively managed, without the need for 178 renumbering in response to topological change (such as that caused by 179 adding or removing attachment points to the network or by mobility 180 events), the address must explicitly not be tied to the topology. 182 The approach that LISP takes to solving the routing scalability 183 problem is to replace IP addresses with two new types of numbers: 184 Routing Locators (RLOCs), which are topologically assigned to network 185 attachment points (and are therefore amenable to aggregation) and 186 used for routing and forwarding of packets through the network; and 187 Endpoint Identifiers (EIDs), which are assigned independently from 188 the network topology, are used for numbering devices, and are 189 aggregated along administrative boundaries. LISP then defines 190 functions for mapping between the two numbering spaces and for 191 encapsulating traffic originated by devices using non-routeable EIDs 192 for transport across a network infrastructure that routes and 193 forwards using RLOCs. Both RLOCs and EIDs are syntactically- 194 identical to IP addresses; it is the semantics of how they are used 195 that differs. 197 This document describes the protocol that implements these functions. 198 The database which stores the mappings between EIDs and RLOCs is 199 explicitly a separate "module" to facilitate experimentation with a 200 variety of approaches. One database design that is being developed 201 and prototyped as part of the LISP working group work is [ALT]. 202 Others that have been described but not implemented include [CONS], 203 [EMACS], [NERD]. Finally, [LISP-MS], documents a general-purpose 204 service interface for accessing a mapping database; this interface is 205 intended to make the mapping database modular so that different 206 approaches can be tried without the need to modify installed LISP 207 capable devices in LISP sites. 209 This experimental specification has areas that require additional 210 experience and measurement. Results of such work may lead to 211 modifications and enhancements of protocol mechanisms defined in this 212 document. See Section 15 for specific, known issues that are in need 213 of further work during development, implementation, and prototype 214 deployment. 216 3. Definition of Terms 218 Provider Independent (PI) Addresses: PI addresses are an address 219 block assigned from a pool where blocks are not associated with 220 any particular location in the network (e.g. from a particular 221 service provider), and is therefore not topologically aggregatable 222 in the routing system. 224 Provider Assigned (PA) Addresses: PA addresses are an an address 225 block assigned to a site by each service provider to which a site 226 connects. Typically, each block is sub-block of a service 227 provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and 228 is aggregated into the larger block before being advertised into 229 the global Internet. Traditionally, IP multihoming has been 230 implemented by each multi-homed site acquiring its own, globally- 231 visible prefix. LISP uses only topologically-assigned and 232 aggregatable address blocks for RLOCs, eliminating this 233 demonstrably non-scalable practice. 235 Routing Locator (RLOC): A RLOC is an IPv4 or IPv6 address of an 236 egress tunnel router (ETR). A RLOC is the output of an EID-to- 237 RLOC mapping lookup. An EID maps to one or more RLOCs. 238 Typically, RLOCs are numbered from topologically-aggregatable 239 blocks that are assigned to a site at each point to which it 240 attaches to the global Internet; where the topology is defined by 241 the connectivity of provider networks, RLOCs can be thought of as 242 PA addresses. Multiple RLOCs can be assigned to the same ETR 243 device or to multiple ETR devices at a site. 245 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 246 IPv6) value used in the source and destination address fields of 247 the first (most inner) LISP header of a packet. The host obtains 248 a destination EID the same way it obtains an destination address 249 today, for example through a Domain Name System (DNS) [RFC1034] 250 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 251 The source EID is obtained via existing mechanisms used to set a 252 host's "local" IP address. An EID is allocated to a host from an 253 EID-prefix block associated with the site where the host is 254 located. An EID can be used by a host to refer to other hosts. 255 EIDs MUST NOT be used as LISP RLOCs. Note that EID blocks MAY be 256 assigned in a hierarchical manner, independent of the network 257 topology, to facilitate scaling of the mapping database. In 258 addition, an EID block assigned to a site may have site-local 259 structure (subnetting) for routing within the site; this structure 260 is not visible to the global routing system. In theory, the bit 261 string that represents an EID for one device can represent an RLOC 262 for a different device. As the architecture is realized, if a 263 given bit string is both an RLOC and an EID, it must refer to the 264 same entity in both cases. When used in discussions with other 265 Locator/ID separation proposals, a LISP EID will be called a 266 "LEID". Throughout this document, any references to "EID" refers 267 to an LEID. 269 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are 270 allocated to a site by an address allocation authority. EID- 271 prefixes are associated with a set of RLOC addresses which make up 272 a "database mapping". EID-prefix allocations can be broken up 273 into smaller blocks when an RLOC set is to be associated with the 274 larger EID-prefix block. A globally routed address block (whether 275 PI or PA) is not inherently an EID-prefix. A globally routed 276 address block MAY be used by its assignee as an EID block. The 277 converse is not supported. That is, a site which receives an 278 explicitly allocated EID-prefix may not use that EID-prefix as a 279 globally routed prefix. This would require coordination and 280 cooperation with the entities managing the mapping infrastructure. 281 Once this has been done, that block could be removed from the 282 globally routed IP system, if other suitable transition and access 283 mechanisms are in place. Discussion of such transition and access 284 mechanisms can be found in [INTERWORK] and [LISP-DEPLOY]. 286 End-system: An end-system is an IPv4 or IPv6 device that originates 287 packets with a single IPv4 or IPv6 header. The end-system 288 supplies an EID value for the destination address field of the IP 289 header when communicating globally (i.e. outside of its routing 290 domain). An end-system can be a host computer, a switch or router 291 device, or any network appliance. 293 Ingress Tunnel Router (ITR): An ITR is a router which accepts an IP 294 packet with a single IP header (more precisely, an IP packet that 295 does not contain a LISP header). The router treats this "inner" 296 IP destination address as an EID and performs an EID-to-RLOC 297 mapping lookup. The router then prepends an "outer" IP header 298 with one of its globally-routable RLOCs in the source address 299 field and the result of the mapping lookup in the destination 300 address field. Note that this destination RLOC MAY be an 301 intermediate, proxy device that has better knowledge of the EID- 302 to-RLOC mapping closer to the destination EID. In general, an ITR 303 receives IP packets from site end-systems on one side and sends 304 LISP-encapsulated IP packets toward the Internet on the other 305 side. 307 Specifically, when a service provider prepends a LISP header for 308 Traffic Engineering purposes, the router that does this is also 309 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 310 on the outer destination address (the originating ITR's supplied 311 RLOC) or the inner destination address (the originating hosts 312 supplied EID). 314 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 315 network that prepends an additional LISP header for Traffic 316 Engineering purposes. 318 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 319 packet where the destination address in the "outer" IP header is 320 one of its own RLOCs. The router strips the "outer" header and 321 forwards the packet based on the next IP header found. In 322 general, an ETR receives LISP-encapsulated IP packets from the 323 Internet on one side and sends decapsulated IP packets to site 324 end-systems on the other side. ETR functionality does not have to 325 be limited to a router device. A server host can be the endpoint 326 of a LISP tunnel as well. 328 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 329 network that strips an outer LISP header for Traffic Engineering 330 purposes. 332 xTR: A xTR is a reference to an ITR or ETR when direction of data 333 flow is not part of the context description. xTR refers to the 334 router that is the tunnel endpoint. Used synonymously with the 335 term "Tunnel Router". For example, "An xTR can be located at the 336 Customer Edge (CE) router", meaning both ITR and ETR functionality 337 is at the CE router. 339 LISP Router: A LISP router is a router that performs the functions 340 of any or all of ITR, ETR, PITR, or PETR. 342 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 343 demand table in an ITR that stores, tracks, and is responsible for 344 timing-out and otherwise validating EID-to-RLOC mappings. This 345 cache is distinct from the full "database" of EID-to-RLOC 346 mappings, it is dynamic, local to the ITR(s), and relatively small 347 while the database is distributed, relatively static, and much 348 more global in scope. 350 EID-to-RLOC Database: The EID-to-RLOC database is a global 351 distributed database that contains all known EID-prefix to RLOC 352 mappings. Each potential ETR typically contains a small piece of 353 the database: the EID-to-RLOC mappings for the EID prefixes 354 "behind" the router. These map to one of the router's own, 355 globally-visible, IP addresses. The same database mapping entries 356 MUST be configured on all ETRs for a given site. In a steady 357 state the EID-prefixes for the site and the locator-set for each 358 EID-prefix MUST be the same on all ETRs. Procedures to enforce 359 and/or verify this are outside the scope of this document. Note 360 that there MAY be transient conditions when the EID-prefix for the 361 site and locator-set for each EID-prefix may not be the same on 362 all ETRs. This has no negative implications. 364 Recursive Tunneling: Recursive tunneling occurs when a packet has 365 more than one LISP IP header. Additional layers of tunneling MAY 366 be employed to implement traffic engineering or other re-routing 367 as needed. When this is done, an additional "outer" LISP header 368 is added and the original RLOCs are preserved in the "inner" 369 header. Any references to tunnels in this specification refers to 370 dynamic encapsulating tunnels and they are never statically 371 configured. 373 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 374 ETR removes a LISP header, then acts as an ITR to prepend another 375 LISP header. Doing this allows a packet to be re-routed by the 376 re-encapsulating router without adding the overhead of additional 377 tunnel headers. Any references to tunnels in this specification 378 refers to dynamic encapsulating tunnels and they are never 379 statically configured. When using multiple mapping database 380 systems, care must be taken to not create reencapsulation loops. 382 LISP Header: a term used in this document to refer to the outer 383 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-byte 384 header that follows the UDP header, an ITR prepends or an ETR 385 strips. 387 Address Family Identifier (AFI): a term used to describe an address 388 encoding in a packet. An address family currently pertains to an 389 IPv4 or IPv6 address. See [AFI]/[AFI-REGISTRY] and [RFC3232] for 390 details. An AFI value of 0 used in this specification indicates 391 an unspecified encoded address where the length of the address is 392 0 bytes following the 16-bit AFI value of 0. 394 Negative Mapping Entry: A negative mapping entry, also known as a 395 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 396 is advertised or stored with no RLOCs. That is, the locator-set 397 for the EID-to-RLOC entry is empty or has an encoded locator count 398 of 0. This type of entry could be used to describe a prefix from 399 a non-LISP site, which is explicitly not in the mapping database. 400 There are a set of well defined actions that are encoded in a 401 Negative Map-Reply. 403 Data Probe: A data-probe is a LISP-encapsulated data packet where 404 the inner header destination address equals the outer header 405 destination address used to trigger a Map-Reply by a decapsulating 406 ETR. In addition, the original packet is decapsulated and 407 delivered to the destination host if the destination EID is in the 408 EID-prefix range configured on the ETR. Otherwise, the packet is 409 discarded. A Data Probe is used in some of the mapping database 410 designs to "probe" or request a Map-Reply from an ETR; in other 411 cases, Map-Requests are used. See each mapping database design 412 for details. 414 Proxy ITR (PITR): A PITR is also known as a PTR is defined and 415 described in [INTERWORK], a PITR acts like an ITR but does so on 416 behalf of non-LISP sites which send packets to destinations at 417 LISP sites. 419 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 420 PETR acts like an ETR but does so on behalf of LISP sites which 421 send packets to destinations at non-LISP sites. 423 Route-returnability: is an assumption that the underlying routing 424 system will deliver packets to the destination. When combined 425 with a nonce that is provided by a sender and returned by a 426 receiver, this limits off-path data insertion. 428 LISP site: is a set of routers in an edge network that are under a 429 single technical administration. LISP routers which reside in the 430 edge network are the demarcation points to separate the edge 431 network from the core network. 433 Client-side: a term used in this document to indicate a connection 434 initiation attempt by an EID. The ITR(s) at the LISP site are the 435 first to get involved in obtaining database map cache entries by 436 sending Map-Request messages. 438 Server-side: a term used in this document to indicate a connection 439 initiation attempt is being accepted for a destination EID. The 440 ETR(s) at the destination LISP site are the first to send Map- 441 Replies to the source site initiating the connection. The ETR(s) 442 at this destination site can obtain mappings by gleaning 443 information from Map-Requests, Data-Probes, or encapsulated 444 packets. 446 Locator Status Bits (LSBs): Locator status bits are present in the 447 LISP header. They are used by ITRs to inform ETRs about the up/ 448 down status of all ETRs at the local site. These bits are used as 449 a hint to convey up/down router status and not path reachability 450 status. The LSBs can be verified by use of one of the Locator 451 Reachability Algorithms described in Section 6.3. 453 4. Basic Overview 455 One key concept of LISP is that end-systems (hosts) operate the same 456 way they do today. The IP addresses that hosts use for tracking 457 sockets, connections, and for sending and receiving packets do not 458 change. In LISP terminology, these IP addresses are called Endpoint 459 Identifiers (EIDs). 461 Routers continue to forward packets based on IP destination 462 addresses. When a packet is LISP encapsulated, these addresses are 463 referred to as Routing Locators (RLOCs). Most routers along a path 464 between two hosts will not change; they continue to perform routing/ 465 forwarding lookups on the destination addresses. For routers between 466 the source host and the ITR as well as routers from the ETR to the 467 destination host, the destination address is an EID. For the routers 468 between the ITR and the ETR, the destination address is an RLOC. 470 Another key LISP concept is the "Tunnel Router". A tunnel router 471 prepends LISP headers on host-originated packets and strips them 472 prior to final delivery to their destination. The IP addresses in 473 this "outer header" are RLOCs. During end-to-end packet exchange 474 between two Internet hosts, an ITR prepends a new LISP header to each 475 packet and an egress tunnel router strips the new header. The ITR 476 performs EID-to-RLOC lookups to determine the routing path to the 477 ETR, which has the RLOC as one of its IP addresses. 479 Some basic rules governing LISP are: 481 o End-systems (hosts) only send to addresses which are EIDs. They 482 don't know addresses are EIDs versus RLOCs but assume packets get 483 to destinations, which in turn, LISP routers deliver packets to 484 the destination the end-system has specified. The procedure a 485 host uses to send IP packets does not change. 487 o EIDs are always IP addresses assigned to hosts. 489 o LISP routers mostly deal with Routing Locator addresses. See 490 details later in Section 4.1 to clarify what is meant by "mostly". 492 o RLOCs are always IP addresses assigned to routers; preferably, 493 topologically-oriented addresses from provider CIDR (Classless 494 Inter-Domain Routing) blocks. 496 o When a router originates packets it may use as a source address 497 either an EID or RLOC. When acting as a host (e.g. when 498 terminating a transport session such as SSH, TELNET, or SNMP), it 499 may use an EID that is explicitly assigned for that purpose. An 500 EID that identifies the router as a host MUST NOT be used as an 501 RLOC; an EID is only routable within the scope of a site. A 502 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 503 usage where a router could use its "host-like" EID to terminate 504 iBGP sessions to other routers in a site while at the same time 505 using RLOCs to terminate eBGP sessions to routers outside the 506 site. 508 o Packets with EIDs in them are not expected to be delivered end-to- 509 end in the absence of an EID-to-RLOC mapping operation. They are 510 expected to be used locally for intra-site communication or to be 511 encapsulated for inter-site communication. 513 o EID prefixes are likely to be hierarchically assigned in a manner 514 which is optimized for administrative convenience and to 515 facilitate scaling of the EID-to-RLOC mapping database. The 516 hierarchy is based on a address allocation hierarchy which is 517 independent of the network topology. 519 o EIDs may also be structured (subnetted) in a manner suitable for 520 local routing within an autonomous system. 522 An additional LISP header MAY be prepended to packets by a TE-ITR 523 when re-routing of the path for a packet is desired. A potential 524 use-case for this would be an ISP router that needs to perform 525 traffic engineering for packets flowing through its network. In such 526 a situation, termed Recursive Tunneling, an ISP transit acts as an 527 additional ingress tunnel router and the RLOC it uses for the new 528 prepended header would be either a TE-ETR within the ISP (along 529 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 530 inter-ISP traffic engineered path, where an agreement to build such a 531 path exists). 533 In order to avoid excessive packet overhead as well as possible 534 encapsulation loops, this document mandates that a maximum of two 535 LISP headers can be prepended to a packet. For initial LISP 536 deployments, it is assumed two headers is sufficient, where the first 537 prepended header is used at a site for Location/Identity separation 538 and second prepended header is used inside a service provider for 539 Traffic Engineering purposes. 541 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 542 For example, the ITR for a particular end-to-end packet exchange 543 might be the first-hop or default router within a site for the source 544 host. Similarly, the egress tunnel router might be the last-hop 545 router directly-connected to the destination host. Another example, 546 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 547 could be the site's border router at the service provider attachment 548 point. Mixing and matching of site-operated, ISP-operated, and other 549 tunnel routers is allowed for maximum flexibility. See Section 8 for 550 more details. 552 4.1. Packet Flow Sequence 554 This section provides an example of the unicast packet flow with the 555 following conditions: 557 o Source host "host1.abc.example.com" is sending a packet to 558 "host2.xyz.example.com", exactly what host1 would do if the site 559 was not using LISP. 561 o Each site is multi-homed, so each tunnel router has an address 562 (RLOC) assigned from the service provider address block for each 563 provider to which that particular tunnel router is attached. 565 o The ITR(s) and ETR(s) are directly connected to the source and 566 destination, respectively, but the source and destination can be 567 located anywhere in LISP site. 569 o Map-Requests can be sent on the underlying routing system 570 topology, to a mapping database system, or directly over an 571 alternative topology [ALT]. 573 o Map-Replies are sent on the underlying routing system topology. 575 Client host1.abc.example.com wants to communicate with server 576 host2.xyz.example.com: 578 1. host1.abc.example.com wants to open a TCP connection to 579 host2.xyz.example.com. It does a DNS lookup on 580 host2.xyz.example.com. An A/AAAA record is returned. This 581 address is the destination EID. The locally-assigned address of 582 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 583 packet is built and forwarded through the LISP site as a normal 584 IP packet until it reaches a LISP ITR. 586 2. The LISP ITR must be able to map the destination EID to an RLOC 587 of one of the ETRs at the destination site. The specific method 588 used to do this is not described in this example. See [ALT] or 589 [CONS] for possible solutions. 591 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 592 rate-limited. 594 4. When an alternate mapping system is not in use, the Map-Request 595 packet is routed through the underlying routing system. 596 Otherwise, the Map-Request packet is routed on an alternate 597 logical topology, for example the [ALT] database mapping system. 598 In either case, when the Map-Request arrives at one of the ETRs 599 at the destination site, it will process the packet as a control 600 message. 602 5. The ETR looks at the destination EID of the Map-Request and 603 matches it against the prefixes in the ETR's configured EID-to- 604 RLOC mapping database. This is the list of EID-prefixes the ETR 605 is supporting for the site it resides in. If there is no match, 606 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 607 returned to the ITR. 609 6. The ITR receives the Map-Reply message, parses the message (to 610 check for format validity) and stores the mapping information 611 from the packet. This information is stored in the ITR's EID-to- 612 RLOC mapping cache. Note that the map cache is an on-demand 613 cache. An ITR will manage its map cache in such a way that 614 optimizes for its resource constraints. 616 7. Subsequent packets from host1.abc.example.com to 617 host2.xyz.example.com will have a LISP header prepended by the 618 ITR using the appropriate RLOC as the LISP header destination 619 address learned from the ETR. Note the packet MAY be sent to a 620 different ETR than the one which returned the Map-Reply due to 621 the source site's hashing policy or the destination site's 622 locator-set policy. 624 8. The ETR receives these packets directly (since the destination 625 address is one of its assigned IP addresses), checks the validity 626 of the addresses, strips the LISP header, and forwards packets to 627 the attached destination host. 629 In order to defer the need for a mapping lookup in the reverse 630 direction, an ETR MAY create a cache entry that maps the source EID 631 (inner header source IP address) to the source RLOC (outer header 632 source IP address) in a received LISP packet. Such a cache entry is 633 termed a "gleaned" mapping and only contains a single RLOC for the 634 EID in question. More complete information about additional RLOCs 635 SHOULD be verified by sending a LISP Map-Request for that EID. Both 636 ITR and the ETR may also influence the decision the other makes in 637 selecting an RLOC. See Section 6 for more details. 639 5. LISP Encapsulation Details 641 Since additional tunnel headers are prepended, the packet becomes 642 larger and can exceed the MTU of any link traversed from the ITR to 643 the ETR. It is RECOMMENDED in IPv4 that packets do not get 644 fragmented as they are encapsulated by the ITR. Instead, the packet 645 is dropped and an ICMP Too Big message is returned to the source. 647 This specification RECOMMENDS that implementations provide support 648 for one of the proposed fragmentation and reassembly schemes. Two 649 existing schemes are detailed in Section 5.4. 651 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 652 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 653 header is in IPv4 packet format and the other header is in IPv6 654 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 655 is in IPv6 packet format and the other header is in IPv4 packet 656 format). The next sub-sections illustrate packet formats for the 657 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6) but all 4 658 combinations MUST be supported. 660 5.1. LISP IPv4-in-IPv4 Header Format 662 0 1 2 3 663 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 1 664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 665 / |Version| IHL |Type of Service| Total Length | 666 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 667 | | Identification |Flags| Fragment Offset | 668 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 669 OH | Time to Live | Protocol = 17 | Header Checksum | 670 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 671 | | Source Routing Locator | 672 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 673 \ | Destination Routing Locator | 674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 675 / | Source Port = xxxx | Dest Port = 4341 | 676 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 677 \ | UDP Length | UDP Checksum | 678 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 679 L |N|L|E|V|I|flags| Nonce/Map-Version | 680 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 681 S / | Instance ID/Locator Status Bits | 682 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 683 / |Version| IHL |Type of Service| Total Length | 684 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 685 | | Identification |Flags| Fragment Offset | 686 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 IH | Time to Live | Protocol | Header Checksum | 688 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 689 | | Source EID | 690 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 691 \ | Destination EID | 692 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 694 5.2. LISP IPv6-in-IPv6 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| Traffic Class | Flow Label | 700 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 702 | | Payload Length | Next Header=17| Hop Limit | 703 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 704 | | 705 O + + 706 u | | 707 t + Source Routing Locator + 708 e | | 709 r + + 710 | | 711 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 d | | 713 r + + 714 | | 715 ^ + Destination Routing Locator + 716 | | | 717 \ + + 718 \ | | 719 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 720 / | Source Port = xxxx | Dest Port = 4341 | 721 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 722 \ | UDP Length | UDP Checksum | 723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 724 L |N|L|E|V|I|flags| Nonce/Map-Version | 725 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 726 S / | Instance ID/Locator Status Bits | 727 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 728 / |Version| Traffic Class | Flow Label | 729 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 730 / | Payload Length | Next Header | Hop Limit | 731 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 732 | | 733 I + + 734 n | | 735 n + Source EID + 736 e | | 737 r + + 738 | | 739 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 740 d | | 741 r + + 742 | | 743 ^ + Destination EID + 744 \ | | 745 \ + + 746 \ | | 747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 749 5.3. Tunnel Header Field Descriptions 751 Inner Header: The inner header is the header on the datagram 752 received from the originating host. The source and destination IP 753 addresses are EIDs, [RFC0791], [RFC2460]. 755 Outer Header: The outer header is a new header prepended by an ITR. 756 The address fields contain RLOCs obtained from the ingress 757 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 758 from [RFC0768]. The DF bit of the Flags field is set to 0 when 759 the method in Section 5.4.1 is used and set to 1 when the method 760 in Section 5.4.2 is used. 762 UDP Header: The UDP header contains an ITR selected source port when 763 encapsulating a packet. See Section 6.5 for details on the hash 764 algorithm used to select a source port based on the 5-tuple of the 765 inner header. The destination port MUST be set to the well-known 766 IANA assigned port value 4341. 768 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 769 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 770 [UDP-TUNNELS] [UDP-ZERO]. When a packet with a zero UDP checksum 771 is received by an ETR, the ETR MUST accept the packet for 772 decapsulation. When an ITR transmits a non-zero value for the UDP 773 checksum, it MUST send a correctly computed value in this field. 774 When an ETR receives a packet with a non-zero UDP checksum, it MAY 775 choose to verify the checksum value. If it chooses to perform 776 such verification, and the verification fails, the packet MUST be 777 silently dropped. If the ETR chooses not to perform the 778 verification, or performs the verification successfully, the 779 packet MUST be accepted for decapsulation. The handling of UDP 780 checksums for all tunneling protocols, including LISP, is under 781 active discussion within the IETF. When that discussion 782 concludes, any necessary changes will be made to align LISP with 783 the outcome of the broader discussion. 785 UDP Length: The UDP length field is set for an IPv4 encapsulated 786 packet to be the sum of the inner header IPv4 Total Length plus 787 the UDP and LISP header lengths. For an IPv6 encapsulated packet, 788 the UDP length field is the sum of the inner header IPv6 Payload 789 Length, the size of the IPv6 header (40 bytes), and the size of 790 the UDP and LISP headers. 792 N: The N bit is the nonce-present bit. When this bit is set to 1, 793 the low-order 24-bits of the first 32-bits of the LISP header 794 contains a Nonce. See Section 6.3.1 for details. Both N and V 795 bits MUST NOT be set in the same packet. If they are, a 796 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 797 having a Nonce value present. 799 L: The L bit is the Locator Status Bits field enabled bit. When this 800 bit is set to 1, the Locator Status Bits in the second 32-bits of 801 the LISP header are in use. 803 x 1 x x 0 x x x 804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 805 |N|L|E|V|I|flags| Nonce/Map-Version | 806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 807 | Locator Status Bits | 808 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 810 E: The E bit is the echo-nonce-request bit. This bit MUST be ignored 811 and has no meaning when the N bit is set to 0. When the N bit is 812 set to 1 and this bit is set to 1, means an ITR is requesting for 813 the nonce value in the Nonce field to be echoed back in LISP 814 encapsulated packets when the ITR is also an ETR. See 815 Section 6.3.1 for details. 817 V: The V bit is the Map-Version present bit. When this bit is set to 818 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 819 This bit indicates that the LISP header is encoded in this case 820 as: 822 0 x 0 1 x x x x 823 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 824 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 825 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 826 | Instance ID/Locator Status Bits | 827 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 829 I: The I bit is the Instance ID bit. See Section 5.5 for more 830 details. When this bit is set to 1, the Locator Status Bits field 831 is reduced to 8-bits and the high-order 24-bits are used as an 832 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 833 are transmitted as zero and ignored on receipt. The format of the 834 LISP header would look like in this case: 836 x x x x 1 x x x 837 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 838 |N|L|E|V|I|flags| Nonce/Map-Version | 839 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 840 | Instance ID | LSBs | 841 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 843 flags: The flags field is a 3-bit field is reserved for future flag 844 use. It MUST be set to 0 on transmit and MUST be ignored on 845 receipt. 847 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 848 generated by an ITR when the N-bit is set to 1. Nonce generation 849 algorithms are an implementation matter but are required to 850 generate different nonces when sending to different destinations. 851 However, the same nonce can be used for a period of time to the 852 same destination. The nonce is also used when the E-bit is set to 853 request the nonce value to be echoed by the other side when 854 packets are returned. When the E-bit is clear but the N-bit is 855 set, a remote ITR is either echoing a previously requested echo- 856 nonce or providing a random nonce. See Section 6.3.1 for more 857 details. 859 LISP Locator Status Bits (LSBs): When the L-bit is also set, the 860 locator status bits field in the LISP header is set by an ITR to 861 indicate to an ETR the up/down status of the Locators in the 862 source site. Each RLOC in a Map-Reply is assigned an ordinal 863 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 864 The Locator Status Bits are numbered from 0 to n-1 from the least 865 significant bit of field. The field is 32-bits when the I-bit is 866 set to 0 and is 8 bits when the I-bit is set to 1. When a Locator 867 Status Bit is set to 1, the ITR is indicating to the ETR the RLOC 868 associated with the bit ordinal has up status. See Section 6.3 869 for details on how an ITR can determine the status of the ETRs at 870 the same site. When a site has multiple EID-prefixes which result 871 in multiple mappings (where each could have a different locator- 872 set), the Locator Status Bits setting in an encapsulated packet 873 MUST reflect the mapping for the EID-prefix that the inner-header 874 source EID address matches. If the LSB for an anycast locator is 875 set to 1, then there is at least one RLOC with that address the 876 ETR is considered 'up'. 878 When doing ITR/PITR encapsulation: 880 o The outer header Time to Live field (or Hop Limit field, in case 881 of IPv6) SHOULD be copied from the inner header Time to Live 882 field. 884 o The outer header Type of Service field (or the Traffic Class 885 field, in the case of IPv6) SHOULD be copied from the inner header 886 Type of Service field (with one caveat, see below). 888 When doing ETR/PETR decapsulation: 890 o The inner header Time to Live field (or Hop Limit field, in case 891 of IPv6) SHOULD be copied from the outer header Time to Live 892 field, when the Time to Live field of the outer header is less 893 than the Time to Live of the inner header. Failing to perform 894 this check can cause the Time to Live of the inner header to 895 increment across encapsulation/decapsulation cycle. This check is 896 also performed when doing initial encapsulation when a packet 897 comes to an ITR or PITR destined for a LISP site. 899 o The inner header Type of Service field (or the Traffic Class 900 field, in the case of IPv6) SHOULD be copied from the outer header 901 Type of Service field (with one caveat, see below). 903 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 904 after decapsulating, the net effect of this is that the new outer 905 header will carry the same Time to Live as the old outer header minus 906 1. 908 Copying the TTL serves two purposes: first, it preserves the distance 909 the host intended the packet to travel; second, and more importantly, 910 it provides for suppression of looping packets in the event there is 911 a loop of concatenated tunnels due to misconfiguration. See 912 Section 9.3 for TTL exception handling for traceroute packets. 914 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 915 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 916 requires special treatment in order to avoid discarding indications 917 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 918 field from the inner header to the outer header. Re-encapsulation 919 MUST copy the 2-bit ECN field from the stripped outer header to the 920 new outer header. If the ECN field contains a congestion indication 921 codepoint (the value is '11', the Congestion Experienced (CE) 922 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 923 the stripped outer header to the surviving inner header that is used 924 to forward the packet beyond the ETR. These requirements preserve 925 Congestion Experienced (CE) indications when a packet that uses ECN 926 traverses a LISP tunnel and becomes marked with a CE indication due 927 to congestion between the tunnel endpoints. 929 5.4. Dealing with Large Encapsulated Packets 931 This section proposes two mechanisms to deal with packets that exceed 932 the path MTU between the ITR and ETR. 934 It is left to the implementor to decide if the stateless or stateful 935 mechanism should be implemented. Both or neither can be used since 936 it is a local decision in the ITR regarding how to deal with MTU 937 issues, and sites can interoperate with differing mechanisms. 939 Both stateless and stateful mechanisms also apply to Reencapsulating 940 and Recursive Tunneling. So any actions below referring to an ITR 941 also apply to an TE-ITR. 943 5.4.1. A Stateless Solution to MTU Handling 945 An ITR stateless solution to handle MTU issues is described as 946 follows: 948 1. Define an architectural constant S for the maximum size of a 949 packet, in bytes, an ITR would like to receive from a source 950 inside of its site. 952 2. Define L to be the maximum size, in bytes, a packet of size S 953 would be after the ITR prepends the LISP header, UDP header, and 954 outer network layer header of size H. Therefore, S + H = L. 956 When an ITR receives a packet from a site-facing interface and adds H 957 bytes worth of encapsulation to yield a packet size greater than L 958 bytes, it resolves the MTU issue by first splitting the original 959 packet into 2 equal-sized fragments. A LISP header is then prepended 960 to each fragment. The size of the encapsulated fragments is then 961 (S/2 + H), which is less than the ITR's estimate of the path MTU 962 between the ITR and its correspondent ETR. 964 When an ETR receives encapsulated fragments, it treats them as two 965 individually encapsulated packets. It strips the LISP headers then 966 forwards each fragment to the destination host of the destination 967 site. The two fragments are reassembled at the destination host into 968 the single IP datagram that was originated by the source host. 970 This behavior is performed by the ITR when the source host originates 971 a packet with the DF field of the IP header is set to 0. When the DF 972 field of the IP header is set to 1, or the packet is an IPv6 packet 973 originated by the source host, the ITR will drop the packet when the 974 size is greater than L, and sends an ICMP Too Big message to the 975 source with a value of S, where S is (L - H). 977 When the outer header encapsulation uses an IPv4 header, an 978 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 979 can be avoided. An implementation MAY set the DF bit in such headers 980 to 0 if it has good reason to believe there are unresolvable path MTU 981 issues between the sending ITR and the receiving ETR. 983 This specification RECOMMENDS that L be defined as 1500. 985 5.4.2. A Stateful Solution to MTU Handling 987 An ITR stateful solution to handle MTU issues is described as follows 988 and was first introduced in [OPENLISP]: 990 1. The ITR will keep state of the effective MTU for each locator per 991 mapping cache entry. The effective MTU is what the core network 992 can deliver along the path between ITR and ETR. 994 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 995 with DF bit set to 1, exceeds what the core network can deliver, 996 one of the intermediate routers on the path will send an ICMP Too 997 Big message to the ITR. The ITR will parse the ICMP message to 998 determine which locator is affected by the effective MTU change 999 and then record the new effective MTU value in the mapping cache 1000 entry. 1002 3. When a packet is received by the ITR from a source inside of the 1003 site and the size of the packet is greater than the effective MTU 1004 stored with the mapping cache entry associated with the 1005 destination EID the packet is for, the ITR will send an ICMP Too 1006 Big message back to the source. The packet size advertised by 1007 the ITR in the ICMP Too Big message is the effective MTU minus 1008 the LISP encapsulation length. 1010 Even though this mechanism is stateful, it has advantages over the 1011 stateless IP fragmentation mechanism, by not involving the 1012 destination host with reassembly of ITR fragmented packets. 1014 5.5. Using Virtualization and Segmentation with LISP 1016 When multiple organizations inside of a LISP site are using private 1017 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 1018 segregated due to possible address duplication. An Instance ID in 1019 the address encoding can aid in making the entire AFI based address 1020 unique. See IANA Considerations Section 14.2 for details for 1021 possible address encodings. 1023 An Instance ID can be carried in a LISP encapsulated packet. An ITR 1024 that prepends a LISP header, will copy a 24-bit value, used by the 1025 LISP router to uniquely identify the address space. The value is 1026 copied to the Instance ID field of the LISP header and the I-bit is 1027 set to 1. 1029 When an ETR decapsulates a packet, the Instance ID from the LISP 1030 header is used as a table identifier to locate the forwarding table 1031 to use for the inner destination EID lookup. 1033 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 1034 24-bit Instance ID. 1036 6. EID-to-RLOC Mapping 1038 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 1040 The following UDP packet formats are used by the LISP control-plane. 1042 0 1 2 3 1043 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 1044 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1045 |Version| IHL |Type of Service| Total Length | 1046 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1047 | Identification |Flags| Fragment Offset | 1048 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1049 | Time to Live | Protocol = 17 | Header Checksum | 1050 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1051 | Source Routing Locator | 1052 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1053 | Destination Routing Locator | 1054 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1055 / | Source Port | Dest Port | 1056 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1057 \ | UDP Length | UDP Checksum | 1058 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1059 | | 1060 | LISP Message | 1061 | | 1062 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1064 0 1 2 3 1065 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 1066 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1067 |Version| Traffic Class | Flow Label | 1068 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1069 | Payload Length | Next Header=17| Hop Limit | 1070 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1071 | | 1072 + + 1073 | | 1074 + Source Routing Locator + 1075 | | 1076 + + 1077 | | 1078 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1079 | | 1080 + + 1081 | | 1082 + Destination Routing Locator + 1083 | | 1084 + + 1085 | | 1086 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1087 / | Source Port | Dest Port | 1088 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1089 \ | UDP Length | UDP Checksum | 1090 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1091 | | 1092 | LISP Message | 1093 | | 1094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1096 The LISP UDP-based messages are the Map-Request and Map-Reply 1097 messages. When a UDP Map-Request is sent, the UDP source port is 1098 chosen by the sender and the destination UDP port number is set to 1099 4342. When a UDP Map-Reply is sent, the source UDP port number is 1100 set to 4342 and the destination UDP port number is copied from the 1101 source port of either the Map-Request or the invoking data packet. 1102 Implementations MUST be prepared to accept packets when either the 1103 source port or destination UDP port is set to 4342 due to NATs 1104 changing port number values. 1106 The UDP Length field will reflect the length of the UDP header and 1107 the LISP Message payload. 1109 The UDP Checksum is computed and set to non-zero for Map-Request, 1110 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1111 on receipt and if the checksum fails, the packet MUST be dropped. 1113 The format of control messages includes the UDP header so the 1114 checksum and length fields can be used to protect and delimit message 1115 boundaries. 1117 This main LISP specification is the authoritative source for message 1118 format definitions for the Map-Request and Map-Reply messages. 1120 6.1.1. LISP Packet Type Allocations 1122 This section will be the authoritative source for allocating LISP 1123 Type values. Current allocations are: 1125 Reserved: 0 b'0000' 1126 LISP Map-Request: 1 b'0001' 1127 LISP Map-Reply: 2 b'0010' 1128 LISP Map-Register: 3 b'0011' 1129 LISP Map-Notify: 4 b'0100' 1130 LISP Encapsulated Control Message: 8 b'1000' 1132 6.1.2. Map-Request Message Format 1134 0 1 2 3 1135 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 1136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1137 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1139 | Nonce . . . | 1140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1141 | . . . Nonce | 1142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1143 | Source-EID-AFI | Source EID Address ... | 1144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1145 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1146 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1147 | ... | 1148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1149 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1151 / | Reserved | EID mask-len | EID-prefix-AFI | 1152 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1153 \ | EID-prefix ... | 1154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1155 | Map-Reply Record ... | 1156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1157 | Mapping Protocol Data | 1158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1160 Packet field descriptions: 1162 Type: 1 (Map-Request) 1164 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1165 Requests sent by an ITR. Set to 1 when an ITR wants the 1166 destination site to return the Map-Reply rather than the mapping 1167 database system. 1169 M: This is the map-data-present bit, when set, it indicates a Map- 1170 Reply Record segment is included in the Map-Request. 1172 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1173 treated as a locator reachability probe. The receiver SHOULD 1174 respond with a Map-Reply with the probe-bit set, indicating the 1175 Map-Reply is a locator reachability probe reply, with the nonce 1176 copied from the Map-Request. See Section 6.3.2 for more details. 1178 S: This is the Solicit-Map-Request (SMR) bit. See Section 6.6.2 for 1179 details. 1181 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1182 Map-Request. 1184 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1185 sending a Map-Request in response to a received SMR-based Map- 1186 Request. 1188 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1189 receipt. 1191 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1192 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1193 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1194 Address) pair MUST be encoded. Multiple ITR-RLOC Address fields 1195 are used so a Map-Replier can select which destination address to 1196 use for a Map-Reply. The IRC value ranges from 0 to 31. For a 1197 value of 0, there is 1 ITR-RLOC address encoded, and for a value 1198 of 1, there are 2 ITR-RLOC addresses encoded and so on up to 31 1199 which encodes a total of 32 ITR-RLOC addresses. 1201 Record Count: The number of records in this Map-Request message. A 1202 record is comprised of the portion of the packet that is labeled 1203 'Rec' above and occurs the number of times equal to Record Count. 1204 For this version of the protocol, a receiver MUST accept and 1205 process Map-Requests that contain one or more records, but a 1206 sender MUST only send Map-Requests containing one record. Support 1207 for requesting multiple EIDs in a single Map-Request message will 1208 be specified in a future version of the protocol. 1210 Nonce: An 8-byte random value created by the sender of the Map- 1211 Request. This nonce will be returned in the Map-Reply. The 1212 security of the LISP mapping protocol depends critically on the 1213 strength of the nonce in the Map-Request message. The nonce 1214 SHOULD be generated by a properly seeded pseudo-random (or strong 1215 random) source. See [RFC4086] for advice on generating security- 1216 sensitive random data. 1218 Source-EID-AFI: Address family of the "Source EID Address" field. 1220 Source EID Address: This is the EID of the source host which 1221 originated the packet which is caused the Map-Request. When Map- 1222 Requests are used for refreshing a map-cache entry or for RLOC- 1223 probing, an AFI value 0 is used and this field is of zero length. 1225 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1226 follows this field. 1228 ITR-RLOC Address: Used to give the ETR the option of selecting the 1229 destination address from any address family for the Map-Reply 1230 message. This address MUST be a routable RLOC address of the 1231 sender of the Map-Request message. 1233 EID mask-len: Mask length for EID prefix. 1235 EID-prefix-AFI: Address family of EID-prefix according to [AFI] 1237 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1238 address-family. When a Map-Request is sent by an ITR because a 1239 data packet is received for a destination where there is no 1240 mapping entry, the EID-prefix is set to the destination IP address 1241 of the data packet. And the 'EID mask-len' is set to 32 or 128 1242 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1243 about the status of a mapping it already has cached, the EID- 1244 prefix used in the Map-Request has the same mask-length as the 1245 EID-prefix returned from the site when it sent a Map-Reply 1246 message. 1248 Map-Reply Record: When the M bit is set, this field is the size of a 1249 single "Record" in the Map-Reply format. This Map-Reply record 1250 contains the EID-to-RLOC mapping entry associated with the Source 1251 EID. This allows the ETR which will receive this Map-Request to 1252 cache the data if it chooses to do so. 1254 Mapping Protocol Data: This field is optional and present when the 1255 UDP length indicates there is enough space in the packet to 1256 include it. 1258 6.1.3. EID-to-RLOC UDP Map-Request Message 1260 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1261 wants to test an RLOC for reachability, or wants to refresh a mapping 1262 before TTL expiration. For the initial case, the destination IP 1263 address used for the Map-Request is the destination-EID from the 1264 packet which had a mapping cache lookup failure. For the latter two 1265 cases, the destination IP address used for the Map-Request is one of 1266 the RLOC addresses from the locator-set of the map cache entry. The 1267 source address is either an IPv4 or IPv6 RLOC address depending if 1268 the Map-Request is using an IPv4 versus IPv6 header, respectively. 1269 In all cases, the UDP source port number for the Map-Request message 1270 is an ITR/PITR selected 16-bit value and the UDP destination port 1271 number is set to the well-known destination port number 4342. A 1272 successful Map-Reply, which is one that has a nonce that matches an 1273 outstanding Map-Request nonce, will update the cached set of RLOCs 1274 associated with the EID prefix range. 1276 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1277 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1278 be placed in the IRC field. The ITR MAY include all locally 1279 configured locators in this list or just provide one locator address 1280 from each address family it supports. If the ITR erroneously 1281 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1282 Request. 1284 Map-Requests can also be LISP encapsulated using UDP destination port 1285 4342 with a LISP type value set to "Encapsulated Control Message", 1286 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1287 LISP encapsulated the same way from a Map-Server to an ETR. Details 1288 on encapsulated Map-Requests and Map-Resolvers can be found in 1289 [LISP-MS]. 1291 Map-Requests MUST be rate-limited. It is RECOMMENDED that a Map- 1292 Request for the same EID-prefix be sent no more than once per second. 1294 An ITR that is configured with mapping database information (i.e. it 1295 is also an ETR) MAY optionally include those mappings in a Map- 1296 Request. When an ETR configured to accept and verify such 1297 "piggybacked" mapping data receives such a Map-Request and it does 1298 not have this mapping in the map-cache, it may originate a "verifying 1299 Map-Request", addressed to the map-requesting ITR. If the ETR has a 1300 map-cache entry that matches the "piggybacked" EID and the RLOC is in 1301 the locator-set for the entry, then it may send the "verifying Map- 1302 Request" directly to the originating Map-Request source. If the RLOC 1303 is not in the locator-set, then the ETR MUST send the "verifying Map- 1304 Request" to the "piggybacked" EID. Doing this forces the "verifying 1305 Map-Request" to go through the mapping database system to reach the 1306 authoritative source of information about that EID, guarding against 1307 RLOC-spoofing in in the "piggybacked" mapping data. 1309 6.1.4. Map-Reply Message Format 1311 0 1 2 3 1312 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 1313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1314 |Type=2 |P|E|S| Reserved | Record Count | 1315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1316 | Nonce . . . | 1317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1318 | . . . Nonce | 1319 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1320 | | Record TTL | 1321 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1322 R | Locator Count | EID mask-len | ACT |A| Reserved | 1323 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1324 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1325 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1326 r | EID-prefix | 1327 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1328 | /| Priority | Weight | M Priority | M Weight | 1329 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1330 | o | Unused Flags |L|p|R| Loc-AFI | 1331 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1332 | \| Locator | 1333 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1334 | Mapping Protocol Data | 1335 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1337 Packet field descriptions: 1339 Type: 2 (Map-Reply) 1341 P: This is the probe-bit which indicates that the Map-Reply is in 1342 response to a locator reachability probe Map-Request. The nonce 1343 field MUST contain a copy of the nonce value from the original 1344 Map-Request. See Section 6.3.2 for more details. 1346 E: Indicates that the ETR which sends this Map-Reply message is 1347 advertising that the site is enabled for the Echo-Nonce locator 1348 reachability algorithm. See Section 6.3.1 for more details. 1350 S: This is the Security bit. When set to 1 the field following the 1351 Mapping Protocol Data field will have the following format. The 1352 detailed format of the Authentication Data Content is for further 1353 study. 1355 0 1 2 3 1356 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 1357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1358 | AD Type | Authentication Data Content . . . | 1359 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1361 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1362 receipt. 1364 Record Count: The number of records in this reply message. A record 1365 is comprised of that portion of the packet labeled 'Record' above 1366 and occurs the number of times equal to Record count. 1368 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1369 from the Map-Request is echoed in this Nonce field of the Map- 1370 Reply. When a 24-bit value is supplied, it resides in the low- 1371 order 64 bits of the nonce field. 1373 Record TTL: The time in minutes the recipient of the Map-Reply will 1374 store the mapping. If the TTL is 0, the entry SHOULD be removed 1375 from the cache immediately. If the value is 0xffffffff, the 1376 recipient can decide locally how long to store the mapping. 1378 Locator Count: The number of Locator entries. A locator entry 1379 comprises what is labeled above as 'Loc'. The locator count can 1380 be 0 indicating there are no locators for the EID-prefix. 1382 EID mask-len: Mask length for EID prefix. 1384 ACT: This 3-bit field describes negative Map-Reply actions. In any 1385 other message type, these bits are set to 0 and ignored on 1386 receipt. These bits are used only when the 'Locator Count' field 1387 is set to 0. The action bits are encoded only in Map-Reply 1388 messages. The actions defined are used by an ITR or PITR when a 1389 destination EID matches a negative mapping cache entry. 1390 Unassigned values should cause a map-cache entry to be created 1391 and, when packets match this negative cache entry, they will be 1392 dropped. The current assigned values are: 1394 (0) No-Action: The map-cache is kept alive and no packet 1395 encapsulation occurs. 1397 (1) Natively-Forward: The packet is not encapsulated or dropped 1398 but natively forwarded. 1400 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1402 (3) Drop: A packet that matches this map-cache entry is dropped. 1403 An ICMP Unreachable message SHOULD be sent. 1405 A: The Authoritative bit, when sent is always set to 1 by an ETR. 1406 When a Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, 1407 the Authoritative bit is set to 0. This indicates to requesting 1408 ITRs that the Map-Reply was not originated by a LISP node managed 1409 at the site that owns the EID-prefix. 1411 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1412 sender is informing the ITR what the version number is for the 1413 EID-record contained in the Map-Reply. The ETR can allocate this 1414 number internally but MUST coordinate this value with other ETRs 1415 for the site. When this value is 0, there is no versioning 1416 information conveyed. The Map-Version Number can be included in 1417 Map-Request and Map-Register messages. See Section 6.6.3 for more 1418 details. 1420 EID-prefix-AFI: Address family of EID-prefix according to [AFI]. 1422 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1423 address-family. 1425 Priority: each RLOC is assigned a unicast priority. Lower values 1426 are more preferable. When multiple RLOCs have the same priority, 1427 they MAY be used in a load-split fashion. A value of 255 means 1428 the RLOC MUST NOT be used for unicast forwarding. 1430 Weight: when priorities are the same for multiple RLOCs, the weight 1431 indicates how to balance unicast traffic between them. Weight is 1432 encoded as a relative weight of total unicast packets that match 1433 the mapping entry. For example if there are 4 locators in a 1434 locator set, where the weights assigned are 30, 20, 20, and 10, 1435 the first locator will get 37.5% of the traffic, the 2nd and 3rd 1436 locators will get 25% of traffic and the 4th locator will get 1437 12.5% of the traffic. If all weights for a locator-set are equal, 1438 receiver of the Map-Reply will decide how to load-split traffic. 1439 See Section 6.5 for a suggested hash algorithm to distribute load 1440 across locators with same priority and equal weight values. 1442 M Priority: each RLOC is assigned a multicast priority used by an 1443 ETR in a receiver multicast site to select an ITR in a source 1444 multicast site for building multicast distribution trees. A value 1445 of 255 means the RLOC MUST NOT be used for joining a multicast 1446 distribution tree. 1448 M Weight: when priorities are the same for multiple RLOCs, the 1449 weight indicates how to balance building multicast distribution 1450 trees across multiple ITRs. The weight is encoded as a relative 1451 weight (similar to the unicast Weights) of total number of trees 1452 built to the source site identified by the EID-prefix. If all 1453 weights for a locator-set are equal, the receiver of the Map-Reply 1454 will decide how to distribute multicast state across ITRs. 1456 Unused Flags: set to 0 when sending and ignored on receipt. 1458 L: when this bit is set, the locator is flagged as a local locator to 1459 the ETR that is sending the Map-Reply. When a Map-Server is doing 1460 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1461 0 for all locators in this locator-set. 1463 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1464 locator address, for which this bit is set, is the one being RLOC- 1465 probed and MAY be different from the source address of the Map- 1466 Reply. An ITR that RLOC-probes a particular locator, MUST use 1467 this locator for retrieving the data structure used to store the 1468 fact that the locator is reachable. The "p" bit is set for a 1469 single locator in the same locator set. If an implementation sets 1470 more than one "p" bit erroneously, the receiver of the Map-Reply 1471 MUST select the first locator. The "p" bit MUST NOT be set for 1472 locator-set records sent in Map-Request and Map-Register messages. 1474 R: set when the sender of a Map-Reply has a route to the locator in 1475 the locator data record. This receiver may find this useful to 1476 know if the locator is up but not necessarily reachable from the 1477 receiver's point of view. See also Section 6.4 for another way 1478 the R-bit may be used. 1480 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1481 assigned to an ETR. Note that the destination RLOC address MAY be 1482 an anycast address. A source RLOC can be an anycast address as 1483 well. The source or destination RLOC MUST NOT be the broadcast 1484 address (255.255.255.255 or any subnet broadcast address known to 1485 the router), and MUST NOT be a link-local multicast address. The 1486 source RLOC MUST NOT be a multicast address. The destination RLOC 1487 SHOULD be a multicast address if it is being mapped from a 1488 multicast destination EID. 1490 Mapping Protocol Data: This field is optional and present when the 1491 UDP length indicates there is enough space in the packet to 1492 include it. 1494 6.1.5. EID-to-RLOC UDP Map-Reply Message 1496 A Map-Reply returns an EID-prefix with a prefix length that is less 1497 than or equal to the EID being requested. The EID being requested is 1498 either from the destination field of an IP header of a Data-Probe or 1499 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1500 globally-routable IP addresses of all ETRs for the LISP site. Each 1501 RLOC conveys status reachability but does not convey path 1502 reachability from a requesters perspective. Separate testing of path 1503 reachability is required, See Section 6.3 for details. 1505 Note that a Map-Reply may contain different EID-prefix granularity 1506 (prefix + length) than the Map-Request which triggers it. This might 1507 occur if a Map-Request were for a prefix that had been returned by an 1508 earlier Map-Reply. In such a case, the requester updates its cache 1509 with the new prefix information and granularity. For example, a 1510 requester with two cached EID-prefixes that are covered by a Map- 1511 Reply containing one, less-specific prefix, replaces the entry with 1512 the less-specific EID-prefix. Note that the reverse, replacement of 1513 one less-specific prefix with multiple more-specific prefixes, can 1514 also occur but not by removing the less-specific prefix rather by 1515 adding the more-specific prefixes which during a lookup will override 1516 the less-specific prefix. 1518 When an ETR is configured with overlapping EID-prefixes, a Map- 1519 Request with an EID that longest matches any EID-prefix MUST be 1520 returned in a single Map-Reply message. For instance, if an ETR had 1521 database mapping entries for EID-prefixes: 1523 10.0.0.0/8 1524 10.1.0.0/16 1525 10.1.1.0/24 1526 10.1.2.0/24 1528 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1529 count of 1 to be returned with a mapping record EID-prefix of 1530 10.1.1.0/24. 1532 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1533 count of 3 to be returned with mapping records for EID-prefixes 1534 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1536 Note that not all overlapping EID-prefixes need to be returned, only 1537 the more specifics (note in the second example above 10.0.0.0/8 was 1538 not returned for requesting EID 10.1.5.5) entries for the matching 1539 EID-prefix of the requesting EID. When more than one EID-prefix is 1540 returned, all SHOULD use the same Time-to-Live value so they can all 1541 time out at the same time. When a more specific EID-prefix is 1542 received later, its Time-to-Live value in the Map-Reply record can be 1543 stored even when other less specifics exist. When a less specific 1544 EID-prefix is received later, its map-cache expiration time SHOULD be 1545 set to the minimum expiration time of any more specific EID-prefix in 1546 the map-cache. This is done so the integrity of the EID-prefix set 1547 is wholly maintained so no more-specific entries are removed from the 1548 map-cache while keeping less-specific entries. 1550 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1551 per second to the same requesting router. For scalability, it is 1552 expected that aggregation of EID addresses into EID-prefixes will 1553 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1554 prefix range thereby reducing the number of Map-Request messages. 1556 Map-Reply records can have an empty locator-set. A negative Map- 1557 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1558 convey special actions by the sender to the ITR or PITR which have 1559 solicited the Map-Reply. There are two primary applications for 1560 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1561 ITR or PITR when a destination is for a LISP site versus a non-LISP 1562 site. And the other is to source quench Map-Requests which are sent 1563 for non-allocated EIDs. 1565 For each Map-Reply record, the list of locators in a locator-set MUST 1566 appear in the same order for each ETR that originates a Map-Reply 1567 message. The locator-set MUST be sorted in order of ascending IP 1568 address where an IPv4 locator address is considered numerically 'less 1569 than' an IPv6 locator address. 1571 When sending a Map-Reply message, the destination address is copied 1572 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1573 can choose a locator address from one of the address families it 1574 supports. For Data-Probes, the destination address of the Map-Reply 1575 is copied from the source address of the Data-Probe message which is 1576 invoking the reply. The source address of the Map-Reply is one of 1577 the local IP addresses chosen to allow uRPF checks to succeed in the 1578 upstream service provider. The destination port of a Map-Reply 1579 message is copied from the source port of the Map-Request or Data- 1580 Probe and the source port of the Map-Reply message is set to the 1581 well-known UDP port 4342. 1583 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1585 When an ETR is misconfigured or compromised, it could return coarse 1586 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1587 cover EID-prefixes which are allocated to other sites redirecting 1588 their traffic to the locators of the compromised site. 1590 To solve this problem, there are two basic solutions that could be 1591 used. The first is to have Map-Servers proxy-map-reply on behalf of 1592 ETRs so their registered EID-prefixes are the ones returned in Map- 1593 Replies. Since the interaction between an ETR and Map-Server is 1594 secured with shared-keys, it is easier for an ETR to detect 1595 misbehavior. The second solution is to have ITRs and PITRs cache 1596 EID-prefixes with mask-lengths that are greater than or equal to a 1597 configured prefix length. This limits the damage to a specific width 1598 of any EID-prefix advertised, but needs to be coordinated with the 1599 allocation of site prefixes. These solutions can be used 1600 independently or at the same time. 1602 At the time of this writing, other approaches are being considered 1603 and researched. 1605 6.1.6. Map-Register Message Format 1607 The usage details of the Map-Register message can be found in 1608 specification [LISP-MS]. This section solely defines the message 1609 format. 1611 The message is sent in UDP with a destination UDP port of 4342 and a 1612 randomly selected UDP source port number. 1614 The Map-Register message format is: 1616 0 1 2 3 1617 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 1618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1619 |Type=3 |P| Reserved |M| Record Count | 1620 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1621 | Nonce . . . | 1622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1623 | . . . Nonce | 1624 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1625 | Key ID | Authentication Data Length | 1626 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1627 ~ Authentication Data ~ 1628 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1629 | | Record TTL | 1630 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1631 R | Locator Count | EID mask-len | ACT |A| Reserved | 1632 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1633 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1634 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1635 r | EID-prefix | 1636 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1637 | /| Priority | Weight | M Priority | M Weight | 1638 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1639 | o | Unused Flags |L|p|R| Loc-AFI | 1640 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1641 | \| Locator | 1642 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1644 Packet field descriptions: 1646 Type: 3 (Map-Register) 1648 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1649 Register message requesting for the Map-Server to proxy Map-Reply. 1650 The Map-Server will send non-authoritative Map-Replies on behalf 1651 of the ETR. Details on this usage can be found in [LISP-MS]. 1653 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1654 receipt. 1656 M: This is the want-map-notify bit, when set to 1 an ETR is 1657 requesting for a Map-Notify message to be returned in response to 1658 sending a Map-Register message. The Map-Notify message sent by a 1659 Map-Server is used to an acknowledge receipt of a Map-Register 1660 message. 1662 Record Count: The number of records in this Map-Register message. A 1663 record is comprised of that portion of the packet labeled 'Record' 1664 above and occurs the number of times equal to Record count. 1666 Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages. 1667 Since the Map-Register message is authenticated, the nonce field 1668 is not needed for any security function. 1670 Key ID: A configured ID to find the configured Message 1671 Authentication Code (MAC) algorithm and key value used for the 1672 authentication function. See Section 14.4 for codepoint 1673 assignments. 1675 Authentication Data Length: The length in bytes of the 1676 Authentication Data field that follows this field. The length of 1677 the Authentication Data field is dependent on the Message 1678 Authentication Code (MAC) algorithm used. The length field allows 1679 a device that doesn't know the MAC algorithm to correctly parse 1680 the packet. 1682 Authentication Data: The message digest used from the output of the 1683 Message Authentication Code (MAC) algorithm. The entire Map- 1684 Register payload is authenticated with this field preset to 0. 1685 After the MAC is computed, it is placed in this field. 1686 Implementations of this specification MUST include support for 1687 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-256-128 [RFC6234] 1688 is RECOMMENDED. 1690 The definition of the rest of the Map-Register can be found in the 1691 Map-Reply section. 1693 6.1.7. Map-Notify Message Format 1695 The usage details of the Map-Notify message can be found in 1696 specification [LISP-MS]. This section solely defines the message 1697 format. 1699 The message is sent inside a UDP packet with source and destination 1700 UDP ports equal to 4342. 1702 The Map-Notify message format is: 1704 0 1 2 3 1705 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 1706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1707 |Type=4 | Reserved | Record Count | 1708 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1709 | Nonce . . . | 1710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1711 | . . . Nonce | 1712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1713 | Key ID | Authentication Data Length | 1714 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1715 ~ Authentication Data ~ 1716 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1717 | | Record TTL | 1718 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1719 R | Locator Count | EID mask-len | ACT |A| Reserved | 1720 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1721 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1722 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1723 r | EID-prefix | 1724 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1725 | /| Priority | Weight | M Priority | M Weight | 1726 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1727 | o | Unused Flags |L|p|R| Loc-AFI | 1728 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1729 | \| Locator | 1730 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1732 Packet field descriptions: 1734 Type: 4 (Map-Notify) 1736 The Map-Notify message has the same contents as a Map-Register 1737 message. See Map-Register section for field descriptions. 1739 6.1.8. Encapsulated Control Message Format 1741 An Encapsulated Control Message (ECM) is used to encapsulate control 1742 packets sent between xTRs and the mapping database system described 1743 in [LISP-MS]. 1745 0 1 2 3 1746 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 1747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1748 / | IPv4 or IPv6 Header | 1749 OH | (uses RLOC addresses) | 1750 \ | | 1751 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1752 / | Source Port = xxxx | Dest Port = 4342 | 1753 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1754 \ | UDP Length | UDP Checksum | 1755 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1756 LH |Type=8 |S| Reserved | 1757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1758 / | IPv4 or IPv6 Header | 1759 IH | (uses RLOC or EID addresses) | 1760 \ | | 1761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1762 / | Source Port = xxxx | Dest Port = yyyy | 1763 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1764 \ | UDP Length | UDP Checksum | 1765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1766 LCM | LISP Control Message | 1767 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1769 Packet header descriptions: 1771 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1772 source and destination header address fields. 1774 UDP: The outer UDP header with destination port 4342. The source 1775 port is randomly allocated. The checksum field MUST be non-zero. 1777 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1778 and what follows is either an IPv4 or IPv6 header as encoded by 1779 the first 4 bits after the reserved field. 1781 S: This is the Security bit. When set to 1 the field following the 1782 Reserved field will have the following format. The detailed 1783 format of the Authentication Data Content is for further study. 1785 0 1 2 3 1786 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 1787 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1788 | AD Type | Authentication Data Content . . . | 1789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1791 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1792 addresses in the header address fields. When a Map-Request is 1793 encapsulated in this packet format the destination address in this 1794 header is an EID. 1796 UDP: The inner UDP header where the port assignments depends on the 1797 control packet being encapsulated. When the control packet is a 1798 Map-Request or Map-Register, the source port is ITR/PITR selected 1799 and the destination port is 4342. When the control packet is a 1800 Map-Reply, the source port is 4342 and the destination port is 1801 assigned from the source port of the invoking Map-Request. Port 1802 number 4341 MUST NOT be assigned to either port. The checksum 1803 field MUST be non-zero. 1805 LCM: The format is one of the control message formats described in 1806 this section. At this time, only Map-Request messages are allowed 1807 to be encapsulated. And in the future, PIM Join-Prune messages 1808 [MLISP] might be allowed. Encapsulating other types of LISP 1809 control messages are for further study. When Map-Requests are 1810 sent for RLOC-probing purposes (i.e the probe-bit is set), they 1811 MUST NOT be sent inside Encapsulated Control Messages. 1813 6.2. Routing Locator Selection 1815 Both client-side and server-side may need control over the selection 1816 of RLOCs for conversations between them. This control is achieved by 1817 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1818 messages. Alternatively, RLOC information MAY be gleaned from 1819 received tunneled packets or EID-to-RLOC Map-Request messages. 1821 The following enumerates different scenarios for choosing RLOCs and 1822 the controls that are available: 1824 o Server-side returns one RLOC. Client-side can only use one RLOC. 1825 Server-side has complete control of the selection. 1827 o Server-side returns a list of RLOC where a subset of the list has 1828 the same best priority. Client can only use the subset list 1829 according to the weighting assigned by the server-side. In this 1830 case, the server-side controls both the subset list and load- 1831 splitting across its members. The client-side can use RLOCs 1832 outside of the subset list if it determines that the subset list 1833 is unreachable (unless RLOCs are set to a Priority of 255). Some 1834 sharing of control exists: the server-side determines the 1835 destination RLOC list and load distribution while the client-side 1836 has the option of using alternatives to this list if RLOCs in the 1837 list are unreachable. 1839 o Server-side sets weight of 0 for the RLOC subset list. In this 1840 case, the client-side can choose how the traffic load is spread 1841 across the subset list. Control is shared by the server-side 1842 determining the list and the client determining load distribution. 1843 Again, the client can use alternative RLOCs if the server-provided 1844 list of RLOCs are unreachable. 1846 o Either side (more likely on the server-side ETR) decides not to 1847 send a Map-Request. For example, if the server-side ETR does not 1848 send Map-Requests, it gleans RLOCs from the client-side ITR, 1849 giving the client-side ITR responsibility for bidirectional RLOC 1850 reachability and preferability. Server-side ETR gleaning of the 1851 client-side ITR RLOC is done by caching the inner header source 1852 EID and the outer header source RLOC of received packets. The 1853 client-side ITR controls how traffic is returned and can alternate 1854 using an outer header source RLOC, which then can be added to the 1855 list the server-side ETR uses to return traffic. Since no 1856 Priority or Weights are provided using this method, the server- 1857 side ETR MUST assume each client-side ITR RLOC uses the same best 1858 Priority with a Weight of zero. In addition, since EID-prefix 1859 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1860 on tunnel routers can grow to be very large. 1862 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1863 received encapsulated packet, is only stored and used for a few 1864 seconds, pending verification. Verification is performed by 1865 sending a Map-Request to the source EID (the inner header IP 1866 source address) of the received encapsulated packet. A reply to 1867 this "verifying Map-Request" is used to fully populate the map- 1868 cache entry for the "gleaned" EID and is stored and used for the 1869 time indicated from the TTL field of a received Map-Reply. When a 1870 verified map-cache entry is stored, data gleaning no longer occurs 1871 for subsequent packets which have a source EID that matches the 1872 EID-prefix of the verified entry. 1874 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1875 reachable when the R-bit for the locator record is set to 1. When 1876 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1877 RLOC. Neither the information contained in a Map-Reply or that 1878 stored in the mapping database system provides reachability 1879 information for RLOCs. Note that reachability is not part of the 1880 mapping system and is determined using one or more of the Routing 1881 Locator Reachability Algorithms described in the next section. 1883 6.3. Routing Locator Reachability 1885 Several mechanisms for determining RLOC reachability are currently 1886 defined: 1888 1. An ETR may examine the Locator Status Bits in the LISP header of 1889 an encapsulated data packet received from an ITR. If the ETR is 1890 also acting as an ITR and has traffic to return to the original 1891 ITR site, it can use this status information to help select an 1892 RLOC. 1894 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1895 message for an RLOC it is using. This indicates that the RLOC is 1896 likely down. Note, trusting ICMP messages may not be desirable 1897 but neither is ignoring them completely. Implementations are 1898 encouraged to follow current best practices in treating these 1899 conditions. 1901 3. An ITR which participates in the global routing system can 1902 determine that an RLOC is down if no BGP RIB route exists that 1903 matches the RLOC IP address. 1905 4. An ITR may receive an ICMP Port Unreachable message from a 1906 destination host. This occurs if an ITR attempts to use 1907 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1908 non-LISP-capable site. 1910 5. An ITR may receive a Map-Reply from an ETR in response to a 1911 previously sent Map-Request. The RLOC source of the Map-Reply is 1912 likely up since the ETR was able to send the Map-Reply to the 1913 ITR. 1915 6. When an ETR receives an encapsulated packet from an ITR, the 1916 source RLOC from the outer header of the packet is likely up. 1918 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1919 described in this section, namely Echo-Noncing or RLOC-Probing. 1921 When determining Locator up/down reachability by examining the 1922 Locator Status Bits from the LISP encapsulated data packet, an ETR 1923 will receive up to date status from an encapsulating ITR about 1924 reachability for all ETRs at the site. CE-based ITRs at the source 1925 site can determine reachability relative to each other using the site 1926 IGP as follows: 1928 o Under normal circumstances, each ITR will advertise a default 1929 route into the site IGP. 1931 o If an ITR fails or if the upstream link to its PE fails, its 1932 default route will either time-out or be withdrawn. 1934 Each ITR can thus observe the presence or lack of a default route 1935 originated by the others to determine the Locator Status Bits it sets 1936 for them. 1938 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1939 Locator Status Bits in a LISP encapsulated packet are numbered from 0 1940 to n-1 starting with the least significant bit. For example, if an 1941 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1942 value 2), then all ITRs at the site will clear the 3rd least 1943 significant bit (xxxx x0xx) of the Locator Status Bits field for the 1944 packets they encapsulate. 1946 When an ETR decapsulates a packet, it will check for any change in 1947 the Locator Status Bits field. When a bit goes from 1 to 0, the ETR 1948 if acting also as an ITR, will refrain from encapsulating packets to 1949 an RLOC that is indicated as down. It will only resume using that 1950 RLOC if the corresponding Locator Status Bit returns to a value of 1. 1951 Locator Status Bits are associated with a locator-set per EID-prefix. 1952 Therefore, when a locator becomes unreachable, the Locator Status Bit 1953 that corresponds to that locator's position in the list returned by 1954 the last Map-Reply will be set to zero for that particular EID- 1955 prefix. 1957 When ITRs at the site are not deployed in CE routers, the IGP can 1958 still be used to determine the reachability of Locators provided they 1959 are injected into the IGP. This is typically done when a /32 address 1960 is configured on a loopback interface. 1962 When ITRs receive ICMP Network or Host Unreachable messages as a 1963 method to determine unreachability, they will refrain from using 1964 Locators which are described in Locator lists of Map-Replies. 1965 However, using this approach is unreliable because many network 1966 operators turn off generation of ICMP Unreachable messages. 1968 If an ITR does receive an ICMP Network or Host Unreachable message, 1969 it MAY originate its own ICMP Unreachable message destined for the 1970 host that originated the data packet the ITR encapsulated. 1972 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 1973 locator address from a locator-set in a mapping entry matches a 1974 prefix. If it does not find one and BGP is running in the Default 1975 Free Zone (DFZ), it can decide to not use the locator even though the 1976 Locator Status Bits indicate the locator is up. In this case, the 1977 path from the ITR to the ETR that is assigned the locator is not 1978 available. More details are in [LOC-ID-ARCH]. 1980 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 1981 Reply is returned, reachability of the Locator has been determined. 1982 Obviously, sending such probes increases the number of control 1983 messages originated by tunnel routers for active flows, so Locators 1984 are assumed to be reachable when they are advertised. 1986 This assumption does create a dependency: Locator unreachability is 1987 detected by the receipt of ICMP Host Unreachable messages. When an 1988 Locator has been determined to be unreachable, it is not used for 1989 active traffic; this is the same as if it were listed in a Map-Reply 1990 with priority 255. 1992 The ITR can test the reachability of the unreachable Locator by 1993 sending periodic Requests. Both Requests and Replies MUST be rate- 1994 limited. Locator reachability testing is never done with data 1995 packets since that increases the risk of packet loss for end-to-end 1996 sessions. 1998 When an ETR decapsulates a packet, it knows that it is reachable from 1999 the encapsulating ITR because that is how the packet arrived. In 2000 most cases, the ETR can also reach the ITR but cannot assume this to 2001 be true due to the possibility of path asymmetry. In the presence of 2002 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 2003 use the lack of return traffic as an indication that the ETR is 2004 unreachable. Instead, it MUST use an alternate mechanisms to 2005 determine reachability. 2007 6.3.1. Echo Nonce Algorithm 2009 When data flows bidirectionally between locators from different 2010 sites, a data-plane mechanism called "nonce echoing" can be used to 2011 determine reachability between an ITR and ETR. When an ITR wants to 2012 solicit a nonce echo, it sets the N and E bits and places a 24-bit 2013 nonce [RFC4086] in the LISP header of the next encapsulated data 2014 packet. 2016 When this packet is received by the ETR, the encapsulated packet is 2017 forwarded as normal. When the ETR next sends a data packet to the 2018 ITR, it includes the nonce received earlier with the N bit set and E 2019 bit cleared. The ITR sees this "echoed nonce" and knows the path to 2020 and from the ETR is up. 2022 The ITR will set the E-bit and N-bit for every packet it sends while 2023 in echo-nonce-request state. The time the ITR waits to process the 2024 echoed nonce before it determines the path is unreachable is variable 2025 and a choice left for the implementation. 2027 If the ITR is receiving packets from the ETR but does not see the 2028 nonce echoed while being in echo-nonce-request state, then the path 2029 to the ETR is unreachable. This decision may be overridden by other 2030 locator reachability algorithms. Once the ITR determines the path to 2031 the ETR is down it can switch to another locator for that EID-prefix. 2033 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 2034 be implementing both ITR and ETR functionality for the echo nonce 2035 mechanism to operate. 2037 The ITR and ETR may both go into echo-nonce-request state at the same 2038 time. The number of packets sent or the time during which echo nonce 2039 requests are sent is an implementation specific setting. However, 2040 when an ITR is in echo-nonce-request state, it can echo the ETR's 2041 nonce in the next set of packets that it encapsulates and then 2042 subsequently, continue sending echo-nonce-request packets. 2044 This mechanism does not completely solve the forward path 2045 reachability problem as traffic may be unidirectional. That is, the 2046 ETR receiving traffic at a site may not be the same device as an ITR 2047 which transmits traffic from that site or the site to site traffic is 2048 unidirectional so there is no ITR returning traffic. 2050 The echo-nonce algorithm is bilateral. That is, if one side sets the 2051 E-bit and the other side is not enabled for echo-noncing, then the 2052 echoing of the nonce does not occur and the requesting side may 2053 regard the locator unreachable erroneously. An ITR SHOULD only set 2054 the E-bit in a encapsulated data packet when it knows the ETR is 2055 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 2056 Reply message. 2058 Note that other locator reachability mechanisms are being researched 2059 and can be used to compliment or even override the Echo Nonce 2060 Algorithm. See next section for an example of control-plane probing. 2062 6.3.2. RLOC Probing Algorithm 2064 RLOC Probing is a method that an ITR or PITR can use to determine the 2065 reachability status of one or more locators that it has cached in a 2066 map-cache entry. The probe-bit of the Map-Request and Map-Reply 2067 messages are used for RLOC Probing. 2069 RLOC probing is done in the control-plane on a timer basis where an 2070 ITR or PITR will originate a Map-Request destined to a locator 2071 address from one of its own locator addresses. A Map-Request used as 2072 an RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on 2073 the ALT like one would when soliciting mapping data. The EID record 2074 encoded in the Map-Request is the EID-prefix of the map-cache entry 2075 cached by the ITR or PITR. The ITR may include a mapping data record 2076 for its own database mapping information which contains the local 2077 EID-prefixes and RLOCs for its site. 2079 When an ETR receives a Map-Request message with the probe-bit set, it 2080 returns a Map-Reply with the probe-bit set. The source address of 2081 the Map-Reply is set according to the procedure described in 2082 Section 6.1.5. The Map-Reply SHOULD contain mapping data for the 2083 EID-prefix contained in the Map-Request. This provides the 2084 opportunity for the ITR or PITR, which sent the RLOC-probe to get 2085 mapping updates if there were changes to the ETR's database mapping 2086 entries. 2088 There are advantages and disadvantages of RLOC Probing. The greatest 2089 benefit of RLOC Probing is that it can handle many failure scenarios 2090 allowing the ITR to determine when the path to a specific locator is 2091 reachable or has become unreachable, thus providing a robust 2092 mechanism for switching to using another locator from the cached 2093 locator. RLOC Probing can also provide rough RTT estimates between a 2094 pair of locators which can be useful for network management purposes 2095 as well as for selecting low delay paths. The major disadvantage of 2096 RLOC Probing is in the number of control messages required and the 2097 amount of bandwidth used to obtain those benefits, especially if the 2098 requirement for failure detection times are very small. 2100 Continued research and testing will attempt to characterize the 2101 tradeoffs of failure detection times versus message overhead. 2103 6.4. EID Reachability within a LISP Site 2105 A site may be multihomed using two or more ETRs. The hosts and 2106 infrastructure within a site will be addressed using one or more EID 2107 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2108 mapping system. One possible failure mode is for an ETR to lose 2109 reachability to one or more of the EID prefixes within its own site. 2110 When this occurs when the ETR sends Map-Replies, it can clear the 2111 R-bit associated with its own locator. And when the ETR is also an 2112 ITR, it can clear its locator-status-bit in the encapsulation data 2113 header. 2115 It is recognized there are no simple solutions to the site 2116 partitioning problem because it is hard to know which part of the 2117 EID-prefix range is partitioned. And which locators can reach any 2118 sub-ranges of the EID-prefixes. This problem is under investigation 2119 with the expectation that experiments will tell us more. Note, this 2120 is not a new problem introduced by the LISP architecture. The 2121 problem exists today when a multi-homed site uses BGP to advertise 2122 its reachability upstream. 2124 6.5. Routing Locator Hashing 2126 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2127 a requesting ITR, the locator-set for the EID-prefix may contain 2128 different priority values for each locator address. When more than 2129 one best priority locator exists, the ITR can decide how to load 2130 share traffic against the corresponding locators. 2132 The following hash algorithm may be used by an ITR to select a 2133 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2135 1. Either a source and destination address hash can be used or the 2136 traditional 5-tuple hash which includes the source and 2137 destination addresses, source and destination TCP, UDP, or SCTP 2138 port numbers and the IP protocol number field or IPv6 next- 2139 protocol fields of a packet a host originates from within a LISP 2140 site. When a packet is not a TCP, UDP, or SCTP packet, the 2141 source and destination addresses only from the header are used to 2142 compute the hash. 2144 2. Take the hash value and divide it by the number of locators 2145 stored in the locator-set for the EID-to-RLOC mapping. 2147 3. The remainder will yield a value of 0 to "number of locators 2148 minus 1". Use the remainder to select the locator in the 2149 locator-set. 2151 Note that when a packet is LISP encapsulated, the source port number 2152 in the outer UDP header needs to be set. Selecting a hashed value 2153 allows core routers which are attached to Link Aggregation Groups 2154 (LAGs) to load-split the encapsulated packets across member links of 2155 such LAGs. Otherwise, core routers would see a single flow, since 2156 packets have a source address of the ITR, for packets which are 2157 originated by different EIDs at the source site. A suggested setting 2158 for the source port number computed by an ITR is a 5-tuple hash 2159 function on the inner header, as described above. 2161 Many core router implementations use a 5-tuple hash to decide how to 2162 balance packet load across members of a LAG. The 5-tuple hash 2163 includes the source and destination addresses of the packet and the 2164 source and destination ports when the protocol number in the packet 2165 is TCP or UDP. For this reason, UDP encoding is used for LISP 2166 encapsulation. 2168 6.6. Changing the Contents of EID-to-RLOC Mappings 2170 Since the LISP architecture uses a caching scheme to retrieve and 2171 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2172 date mapping is to re-request the mapping. However, the ITRs do not 2173 know when the mappings change and the ETRs do not keep track of which 2174 ITRs requested its mappings. For scalability reasons, we want to 2175 maintain this approach but need to provide a way for ETRs change 2176 their mappings and inform the sites that are currently communicating 2177 with the ETR site using such mappings. 2179 When adding a new locator record in lexicographic order to the end of 2180 a locator-set, it is easy to update mappings. We assume new mappings 2181 will maintain the same locator ordering as the old mapping but just 2182 have new locators appended to the end of the list. So some ITRs can 2183 have a new mapping while other ITRs have only an old mapping that is 2184 used until they time out. When an ITR has only an old mapping but 2185 detects bits set in the loc-status-bits that correspond to locators 2186 beyond the list it has cached, it simply ignores them. However, this 2187 can only happen for locator addresses that are lexicographically 2188 greater than the locator addresses in the existing locator-set. 2190 When a locator record is inserted in the middle of a locator-set, to 2191 maintain lexicographic order, the SMR procedure in Section 6.6.2 is 2192 used to inform ITRs and PITRs of the new locator-status-bit mappings. 2194 When a locator record is removed from a locator-set, ITRs that have 2195 the mapping cached will not use the removed locator because the xTRs 2196 will set the loc-status-bit to 0. So even if the locator is in the 2197 list, it will not be used. For new mapping requests, the xTRs can 2198 set the locator AFI to 0 (indicating an unspecified address), as well 2199 as setting the corresponding loc-status-bit to 0. This forces ITRs 2200 with old or new mappings to avoid using the removed locator. 2202 If many changes occur to a mapping over a long period of time, one 2203 will find empty record slots in the middle of the locator-set and new 2204 records appended to the locator-set. At some point, it would be 2205 useful to compact the locator-set so the loc-status-bit settings can 2206 be efficiently packed. 2208 We propose here three approaches for locator-set compaction, one 2209 operational and two protocol mechanisms. The operational approach 2210 uses a clock sweep method. The protocol approaches use the concept 2211 of Solicit-Map-Requests and Map-Versioning. 2213 6.6.1. Clock Sweep 2215 The clock sweep approach uses planning in advance and the use of 2216 count-down TTLs to time out mappings that have already been cached. 2217 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2218 there is a 24 hour window to time out old mappings. The following 2219 clock sweep procedure is used: 2221 1. 24 hours before a mapping change is to take effect, a network 2222 administrator configures the ETRs at a site to start the clock 2223 sweep window. 2225 2. During the clock sweep window, ETRs continue to send Map-Reply 2226 messages with the current (unchanged) mapping records. The TTL 2227 for these mappings is set to 1 hour. 2229 3. 24 hours later, all previous cache entries will have timed out, 2230 and any active cache entries will time out within 1 hour. During 2231 this 1 hour window the ETRs continue to send Map-Reply messages 2232 with the current (unchanged) mapping records with the TTL set to 2233 1 minute. 2235 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2236 messages with the new (changed) mapping records. So any active 2237 caches can get the new mapping contents right away if not cached, 2238 or in 1 minute if they had the mapping cached. The new mappings 2239 are cached with a time to live equal to the TTL in the Map-Reply. 2241 6.6.2. Solicit-Map-Request (SMR) 2243 Soliciting a Map-Request is a selective way for ETRs, at the site 2244 where mappings change, to control the rate they receive requests for 2245 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2246 the mappings they have cached. 2248 Since the ETRs don't keep track of remote ITRs that have cached their 2249 mappings, they do not know which ITRs need to have their mappings 2250 updated. As a result, an ETR will solicit Map-Requests (called an 2251 SMR message) from those sites to which it has been sending 2252 encapsulated data to for the last minute. In particular, an ETR will 2253 send an SMR an ITR to which it has recently sent encapsulated data. 2255 An SMR message is simply a bit set in a Map-Request message. An ITR 2256 or PITR will send a Map-Request when they receive an SMR message. 2257 Both the SMR sender and the Map-Request responder MUST rate-limited 2258 these messages. Rate-limiting can be implemented as a global rate- 2259 limiter or one rate-limiter per SMR destination. 2261 The following procedure shows how a SMR exchange occurs when a site 2262 is doing locator-set compaction for an EID-to-RLOC mapping: 2264 1. When the database mappings in an ETR change, the ETRs at the site 2265 begin to send Map-Requests with the SMR bit set for each locator 2266 in each map-cache entry the ETR caches. 2268 2. A remote ITR which receives the SMR message will schedule sending 2269 a Map-Request message to the source locator address of the SMR 2270 message or to the mapping database system. A newly allocated 2271 random nonce is selected and the EID-prefix used is the one 2272 copied from the SMR message. If the source locator is the only 2273 locator in the cached locator-set, the remote ITR SHOULD send a 2274 Map-Request to the database mapping system just in case the 2275 single locator has changed and may no longer be reachable to 2276 accept the Map-Request. 2278 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2279 Map-Reply while continuing to use the cached mapping. When Map 2280 Versioning is used, described in Section 6.6.3, an SMR sender can 2281 detect if an ITR is using the most up to date database mapping. 2283 4. The ETRs at the site with the changed mapping will reply to the 2284 Map-Request with a Map-Reply message that has a nonce from the 2285 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2286 limited. This is important to avoid Map-Reply implosion. 2288 5. The ETRs, at the site with the changed mapping, record the fact 2289 that the site that sent the Map-Request has received the new 2290 mapping data in the mapping cache entry for the remote site so 2291 the loc-status-bits are reflective of the new mapping for packets 2292 going to the remote site. The ETR then stops sending SMR 2293 messages. 2295 Experimentation is in progress to determine the appropriate rate- 2296 limit parameters. 2298 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2299 To avoid map-cache entry corruption by a third-party, a sender of an 2300 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2301 based Map-Request and the source is not in the locator-set for the 2302 stored map-cache entry, then the responding Map-Request MUST be sent 2303 with an EID destination to the mapping database system. Since the 2304 mapping database system is more secure to reach an authoritative ETR, 2305 it will deliver the Map-Request to the authoritative source of the 2306 mapping data. 2308 When an ITR receives an SMR-based Map-Request for which it does not 2309 have a cached mapping for the EID in the SMR message, it MAY not send 2310 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2311 SMR messages to all locators in the locator-set it has stored in its 2312 map-cache but the remote ITRs that receive the SMR may not be sending 2313 packets to the site. There is no point in updating the ITRs until 2314 they need to send, in which case, they will send Map-Requests to 2315 obtain a map-cache entry. 2317 6.6.3. Database Map Versioning 2319 When there is unidirectional packet flow between an ITR and ETR, and 2320 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2321 ITR so encapsulation can stop to a removed locator and start to a new 2322 locator in the locator-set. 2324 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2325 number. This is known as the Destination Map-Version Number. ITRs 2326 include the Destination Map-Version Number in packets they 2327 encapsulate to the site. When an ETR decapsulates a packet and 2328 detects the Destination Map-Version Number is less than the current 2329 version for its mapping, the SMR procedure described in Section 6.6.2 2330 occurs. 2332 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2333 Version number. This is known as the Source Map-Version Number. 2334 When an ETR decapsulates a packet and detects the Source Map-Version 2335 Number is greater than the last Map-Version Number sent in a Map- 2336 Reply from the ITR's site, the ETR will send a Map-Request to one of 2337 the ETRs for the source site. 2339 A Map-Version Number is used as a sequence number per EID-prefix. So 2340 values that are greater, are considered to be more recent. A value 2341 of 0 for the Source Map-Version Number or the Destination Map-Version 2342 Number conveys no versioning information and an ITR does no 2343 comparison with previously received Map-Version Numbers. 2345 A Map-Version Number can be included in Map-Register messages as 2346 well. This is a good way for the Map-Server can assure that all ETRs 2347 for a site registering to it will be Map-Version number synchronized. 2349 See [VERSIONING] for a more detailed analysis and description of 2350 Database Map Versioning. 2352 7. Router Performance Considerations 2354 LISP is designed to be very hardware-based forwarding friendly. A 2355 few implementation techniques can be used to incrementally implement 2356 LISP: 2358 o When a tunnel encapsulated packet is received by an ETR, the outer 2359 destination address may not be the address of the router. This 2360 makes it challenging for the control plane to get packets from the 2361 hardware. This may be mitigated by creating special FIB entries 2362 for the EID-prefixes of EIDs served by the ETR (those for which 2363 the router provides an RLOC translation). These FIB entries are 2364 marked with a flag indicating that control plane processing should 2365 be performed. The forwarding logic of testing for particular IP 2366 protocol number value is not necessary. There are a few proven 2367 cases where no changes to existing deployed hardware were needed 2368 to support the LISP data-plane. 2370 o On an ITR, prepending a new IP header consists of adding more 2371 bytes to a MAC rewrite string and prepending the string as part of 2372 the outgoing encapsulation procedure. Routers that support GRE 2373 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2374 support this action. 2376 o A packet's source address or interface the packet was received on 2377 can be used to select a VRF (Virtual Routing/Forwarding). The 2378 VRF's routing table can be used to find EID-to-RLOC mappings. 2380 For performance issues related to map-cache management, see section 2381 Section 12. 2383 8. Deployment Scenarios 2385 This section will explore how and where ITRs and ETRs can be deployed 2386 and will discuss the pros and cons of each deployment scenario. For 2387 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2389 There are two basic deployment trade-offs to consider: centralized 2390 versus distributed caches and flat, recursive, or re-encapsulating 2391 tunneling. When deciding on centralized versus distributed caching, 2392 the following issues should be considered: 2394 o Are the tunnel routers spread out so that the caches are spread 2395 across all the memories of each router? A centralized cache is 2396 when an ITR keeps a cache for all the EIDs it is encapsulating to. 2397 The packet takes a direct path to the destination locator. A 2398 distributed cache is when an ITR needs help from other re- 2399 encapsulating routers because it does not store all the cache 2400 entries for the EIDs is it encapsulating to. So the packet takes 2401 a path through re-encapsulating routers that have a different set 2402 of cache entries. 2404 o Should management "touch points" be minimized by choosing few 2405 tunnel routers, just enough for redundancy? 2407 o In general, using more ITRs doesn't increase management load, 2408 since caches are built and stored dynamically. On the other hand, 2409 more ETRs does require more management since EID-prefix-to-RLOC 2410 mappings need to be explicitly configured. 2412 When deciding on flat, recursive, or re-encapsulation tunneling, the 2413 following issues should be considered: 2415 o Flat tunneling implements a single tunnel between source site and 2416 destination site. This generally offers better paths between 2417 sources and destinations with a single tunnel path. 2419 o Recursive tunneling is when tunneled traffic is again further 2420 encapsulated in another tunnel, either to implement VPNs or to 2421 perform Traffic Engineering. When doing VPN-based tunneling, the 2422 site has some control since the site is prepending a new tunnel 2423 header. In the case of TE-based tunneling, the site may have 2424 control if it is prepending a new tunnel header, but if the site's 2425 ISP is doing the TE, then the site has no control. Recursive 2426 tunneling generally will result in suboptimal paths but at the 2427 benefit of steering traffic to resource available parts of the 2428 network. 2430 o The technique of re-encapsulation ensures that packets only 2431 require one tunnel header. So if a packet needs to be rerouted, 2432 it is first decapsulated by the ETR and then re-encapsulated with 2433 a new tunnel header using a new RLOC. 2435 The next sub-sections will survey where tunnel routers can reside in 2436 the network. 2438 8.1. First-hop/Last-hop Tunnel Routers 2440 By locating tunnel routers close to hosts, the EID-prefix set is at 2441 the granularity of an IP subnet. So at the expense of more EID- 2442 prefix-to-RLOC sets for the site, the caches in each tunnel router 2443 can remain relatively small. But caches always depend on the number 2444 of non-aggregated EID destination flows active through these tunnel 2445 routers. 2447 With more tunnel routers doing encapsulation, the increase in control 2448 traffic grows as well: since the EID-granularity is greater, more 2449 Map-Requests and Map-Replies are traveling between more routers. 2451 The advantage of placing the caches and databases at these stub 2452 routers is that the products deployed in this part of the network 2453 have better price-memory ratios then their core router counterparts. 2454 Memory is typically less expensive in these devices and fewer routes 2455 are stored (only IGP routes). These devices tend to have excess 2456 capacity, both for forwarding and routing state. 2458 LISP functionality can also be deployed in edge switches. These 2459 devices generally have layer-2 ports facing hosts and layer-3 ports 2460 facing the Internet. Spare capacity is also often available in these 2461 devices as well. 2463 8.2. Border/Edge Tunnel Routers 2465 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2466 space associated with a site to be reachable via a small set of RLOCs 2467 assigned to the CE routers for that site. This is the default 2468 behavior envisioned in the rest of this specification. 2470 This offers the opposite benefit of the first-hop/last-hop tunnel 2471 router scenario: the number of mapping entries and network management 2472 touch points are reduced, allowing better scaling. 2474 One disadvantage is that less of the network's resources are used to 2475 reach host endpoints thereby centralizing the point-of-failure domain 2476 and creating network choke points at the CE router. 2478 Note that more than one CE router at a site can be configured with 2479 the same IP address. In this case an RLOC is an anycast address. 2480 This allows resilience between the CE routers. That is, if a CE 2481 router fails, traffic is automatically routed to the other routers 2482 using the same anycast address. However, this comes with the 2483 disadvantage where the site cannot control the entrance point when 2484 the anycast route is advertised out from all border routers. Another 2485 disadvantage of using anycast locators is the limited advertisement 2486 scope of /32 (or /128 for IPv6) routes. 2488 8.3. ISP Provider-Edge (PE) Tunnel Routers 2490 Use of ISP PE routers as tunnel endpoint routers is not the typical 2491 deployment scenario envisioned in the specification. This section 2492 attempts to capture some of reasoning behind this preference of 2493 implementing LISP on CE routers. 2495 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2496 than a site, control over the location of the egress tunnel 2497 endpoints. That is, the ISP can decide if the tunnel endpoints are 2498 in the destination site (in either CE routers or last-hop routers 2499 within a site) or at other PE edges. The advantage of this case is 2500 that two tunnel headers can be avoided. By having the PE be the 2501 first router on the path to encapsulate, it can choose a TE path 2502 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2503 the destination end site. 2505 An obvious disadvantage is that the end site has no control over 2506 where its packets flow or the RLOCs used. Other disadvantages 2507 include the difficulty in synchronizing path liveness updates between 2508 CE and PE routers. 2510 As mentioned in earlier sections a combination of these scenarios is 2511 possible at the expense of extra packet header overhead, if both site 2512 and provider want control, then recursive or re-encapsulating tunnels 2513 are used. 2515 8.4. LISP Functionality with Conventional NATs 2517 LISP routers can be deployed behind Network Address Translator (NAT) 2518 devices to provide the same set of packet services hosts have today 2519 when they are addressed out of private address space. 2521 It is important to note that a locator address in any LISP control 2522 message MUST be a globally routable address and therefore SHOULD NOT 2523 contain [RFC1918] addresses. If a LISP router is configured with 2524 private addresses, they MUST be used only in the outer IP header so 2525 the NAT device can translate properly. Otherwise, EID addresses MUST 2526 be translated before encapsulation is performed. Both NAT 2527 translation and LISP encapsulation functions could be co-located in 2528 the same device. 2530 More details on LISP address translation can be found in [INTERWORK]. 2532 8.5. Packets Egressing a LISP Site 2534 When a LISP site is using two ITRs for redundancy, the failure of one 2535 ITR will likely shift outbound traffic to the second. This second 2536 ITR's cache may not not be populated with the same EID-to-RLOC 2537 mapping entries as the first. If this second ITR does not have these 2538 mappings, traffic will be dropped while the mappings are retrieved 2539 from the mapping system. The retrieval of these messages may 2540 increase the load of requests being sent into the mapping system. 2541 Deployment and experimentation will determine whether this issue 2542 requires more attention. 2544 9. Traceroute Considerations 2546 When a source host in a LISP site initiates a traceroute to a 2547 destination host in another LISP site, it is highly desirable for it 2548 to see the entire path. Since packets are encapsulated from ITR to 2549 ETR, the hop across the tunnel could be viewed as a single hop. 2550 However, LISP traceroute will provide the entire path so the user can 2551 see 3 distinct segments of the path from a source LISP host to a 2552 destination LISP host: 2554 Segment 1 (in source LISP site based on EIDs): 2556 source-host ---> first-hop ... next-hop ---> ITR 2558 Segment 2 (in the core network based on RLOCs): 2560 ITR ---> next-hop ... next-hop ---> ETR 2562 Segment 3 (in the destination LISP site based on EIDs): 2564 ETR ---> next-hop ... last-hop ---> destination-host 2566 For segment 1 of the path, ICMP Time Exceeded messages are returned 2567 in the normal manner as they are today. The ITR performs a TTL 2568 decrement and test for 0 before encapsulating. So the ITR hop is 2569 seen by the traceroute source has an EID address (the address of 2570 site-facing interface). 2572 For segment 2 of the path, ICMP Time Exceeded messages are returned 2573 to the ITR because the TTL decrement to 0 is done on the outer 2574 header, so the destination of the ICMP messages are to the ITR RLOC 2575 address, the source RLOC address of the encapsulated traceroute 2576 packet. The ITR looks inside of the ICMP payload to inspect the 2577 traceroute source so it can return the ICMP message to the address of 2578 the traceroute client as well as retaining the core router IP address 2579 in the ICMP message. This is so the traceroute client can display 2580 the core router address (the RLOC address) in the traceroute output. 2581 The ETR returns its RLOC address and responds to the TTL decrement to 2582 0 like the previous core routers did. 2584 For segment 3, the next-hop router downstream from the ETR will be 2585 decrementing the TTL for the packet that was encapsulated, sent into 2586 the core, decapsulated by the ETR, and forwarded because it isn't the 2587 final destination. If the TTL is decremented to 0, any router on the 2588 path to the destination of the traceroute, including the next-hop 2589 router or destination, will send an ICMP Time Exceeded message to the 2590 source EID of the traceroute client. The ICMP message will be 2591 encapsulated by the local ITR and sent back to the ETR in the 2592 originated traceroute source site, where the packet will be delivered 2593 to the host. 2595 9.1. IPv6 Traceroute 2597 IPv6 traceroute follows the procedure described above since the 2598 entire traceroute data packet is included in ICMP Time Exceeded 2599 message payload. Therefore, only the ITR needs to pay special 2600 attention for forwarding ICMP messages back to the traceroute source. 2602 9.2. IPv4 Traceroute 2604 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2605 ICMP Time Exceeded messages only include the invoking IP header and 8 2606 bytes that follow the IP header. Therefore, when a core router sends 2607 an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP 2608 payload is the encapsulated header it prepended followed by a UDP 2609 header. The original invoking IP header, and therefore the identity 2610 of the traceroute source is lost. 2612 The solution we propose to solve this problem is to cache traceroute 2613 IPv4 headers in the ITR and to match them up with corresponding IPv4 2614 Time Exceeded messages received from core routers and the ETR. The 2615 ITR will use a circular buffer for caching the IPv4 and UDP headers 2616 of traceroute packets. It will select a 16-bit number as a key to 2617 find them later when the IPv4 Time Exceeded messages are received. 2618 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2619 16-bit number as the UDP source port in the encapsulating header. 2620 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2621 header of the encapsulating header is present in the ICMP payload 2622 thereby allowing the ITR to find the cached headers for the 2623 traceroute source. The ITR puts the cached headers in the payload 2624 and sends the ICMP Time Exceeded message to the traceroute source 2625 retaining the source address of the original ICMP Time Exceeded 2626 message (a core router or the ETR of the site of the traceroute 2627 destination). 2629 The signature of a traceroute packet comes in two forms. The first 2630 form is encoded as a UDP message where the destination port is 2631 inspected for a range of values. The second form is encoded as an 2632 ICMP message where the IP identification field is inspected for a 2633 well-known value. 2635 9.3. Traceroute using Mixed Locators 2637 When either an IPv4 traceroute or IPv6 traceroute is originated and 2638 the ITR encapsulates it in the other address family header, you 2639 cannot get all 3 segments of the traceroute. Segment 2 of the 2640 traceroute can not be conveyed to the traceroute source since it is 2641 expecting addresses from intermediate hops in the same address format 2642 for the type of traceroute it originated. Therefore, in this case, 2643 segment 2 will make the tunnel look like one hop. All the ITR has to 2644 do to make this work is to not copy the inner TTL to the outer, 2645 encapsulating header's TTL when a traceroute packet is encapsulated 2646 using an RLOC from a different address family. This will cause no 2647 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2649 10. Mobility Considerations 2651 There are several kinds of mobility of which only some might be of 2652 concern to LISP. Essentially they are as follows. 2654 10.1. Site Mobility 2656 A site wishes to change its attachment points to the Internet, and 2657 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2658 providers. Changes in EID-RLOC mappings for sites are expected to be 2659 handled by configuration, outside of the LISP protocol. 2661 10.2. Slow Endpoint Mobility 2663 An individual endpoint wishes to move, but is not concerned about 2664 maintaining session continuity. Renumbering is involved. LISP can 2665 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2666 decoupling the address space used by a site from the address spaces 2667 used by its ISPs. [RFC4984] 2669 10.3. Fast Endpoint Mobility 2671 Fast endpoint mobility occurs when an endpoint moves relatively 2672 rapidly, changing its IP layer network attachment point. Maintenance 2673 of session continuity is a goal. This is where the Mobile IPv4 2674 [RFC5944] and Mobile IPv6 [RFC6275] [RFC4866] mechanisms are used, 2675 and primarily where interactions with LISP need to be explored. 2677 The problem is that as an endpoint moves, it may require changes to 2678 the mapping between its EID and a set of RLOCs for its new network 2679 location. When this is added to the overhead of mobile IP binding 2680 updates, some packets might be delayed or dropped. 2682 In IPv4 mobility, when an endpoint is away from home, packets to it 2683 are encapsulated and forwarded via a home agent which resides in the 2684 home area the endpoint's address belongs to. The home agent will 2685 encapsulate and forward packets either directly to the endpoint or to 2686 a foreign agent which resides where the endpoint has moved to. 2687 Packets from the endpoint may be sent directly to the correspondent 2688 node, may be sent via the foreign agent, or may be reverse-tunneled 2689 back to the home agent for delivery to the mobile node. As the 2690 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2691 mappings are required for communication between the mobile node and 2692 the home agent, whether via foreign agent or not. As a mobile 2693 endpoint changes networks, up to three LISP mapping changes may be 2694 required: 2696 o The mobile node moves from an old location to a new visited 2697 network location and notifies its home agent that it has done so. 2698 The Mobile IPv4 control packets the mobile node sends pass through 2699 one of the new visited network's ITRs, which needs an EID-RLOC 2700 mapping for the home agent. 2702 o The home agent might not have the EID-RLOC mappings for the mobile 2703 node's "care-of" address or its foreign agent in the new visited 2704 network, in which case it will need to acquire them. 2706 o When packets are sent directly to the correspondent node, it may 2707 be that no traffic has been sent from the new visited network to 2708 the correspondent node's network, and the new visited network's 2709 ITR will need to obtain an EID-RLOC mapping for the correspondent 2710 node's site. 2712 In addition, if the IPv4 endpoint is sending packets from the new 2713 visited network using its original EID, then LISP will need to 2714 perform a route-returnability check on the new EID-RLOC mapping for 2715 that EID. 2717 In IPv6 mobility, packets can flow directly between the mobile node 2718 and the correspondent node in either direction. The mobile node uses 2719 its "care-of" address (EID). In this case, the route-returnability 2720 check would not be needed but one more LISP mapping lookup may be 2721 required instead: 2723 o As above, three mapping changes may be needed for the mobile node 2724 to communicate with its home agent and to send packets to the 2725 correspondent node. 2727 o In addition, another mapping will be needed in the correspondent 2728 node's ITR, in order for the correspondent node to send packets to 2729 the mobile node's "care-of" address (EID) at the new network 2730 location. 2732 When both endpoints are mobile the number of potential mapping 2733 lookups increases accordingly. 2735 As a mobile node moves there are not only mobility state changes in 2736 the mobile node, correspondent node, and home agent, but also state 2737 changes in the ITRs and ETRs for at least some EID-prefixes. 2739 The goal is to support rapid adaptation, with little delay or packet 2740 loss for the entire system. Also IP mobility can be modified to 2741 require fewer mapping changes. In order to increase overall system 2742 performance, there may be a need to reduce the optimization of one 2743 area in order to place fewer demands on another. 2745 In LISP, one possibility is to "glean" information. When a packet 2746 arrives, the ETR could examine the EID-RLOC mapping and use that 2747 mapping for all outgoing traffic to that EID. It can do this after 2748 performing a route-returnability check, to ensure that the new 2749 network location does have a internal route to that endpoint. 2750 However, this does not cover the case where an ITR (the node assigned 2751 the RLOC) at the mobile-node location has been compromised. 2753 Mobile IP packet exchange is designed for an environment in which all 2754 routing information is disseminated before packets can be forwarded. 2755 In order to allow the Internet to grow to support expected future 2756 use, we are moving to an environment where some information may have 2757 to be obtained after packets are in flight. Modifications to IP 2758 mobility should be considered in order to optimize the behavior of 2759 the overall system. Anything which decreases the number of new EID- 2760 RLOC mappings needed when a node moves, or maintains the validity of 2761 an EID-RLOC mapping for a longer time, is useful. 2763 10.4. Fast Network Mobility 2765 In addition to endpoints, a network can be mobile, possibly changing 2766 xTRs. A "network" can be as small as a single router and as large as 2767 a whole site. This is different from site mobility in that it is 2768 fast and possibly short-lived, but different from endpoint mobility 2769 in that a whole prefix is changing RLOCs. However, the mechanisms 2770 are the same and there is no new overhead in LISP. A map request for 2771 any endpoint will return a binding for the entire mobile prefix. 2773 If mobile networks become a more common occurrence, it may be useful 2774 to revisit the design of the mapping service and allow for dynamic 2775 updates of the database. 2777 The issue of interactions between mobility and LISP needs to be 2778 explored further. Specific improvements to the entire system will 2779 depend on the details of mapping mechanisms. Mapping mechanisms 2780 should be evaluated on how well they support session continuity for 2781 mobile nodes. 2783 10.5. LISP Mobile Node Mobility 2785 A mobile device can use the LISP infrastructure to achieve mobility 2786 by implementing the LISP encapsulation and decapsulation functions 2787 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2788 node" can use topologically-independent EID IP addresses that are not 2789 advertised into and do not impose a cost on the global routing 2790 system. These EIDs are maintained at the edges of the mapping system 2791 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2792 only the correspondents of the LISP mobile node. 2794 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2795 more details. 2797 11. Multicast Considerations 2799 A multicast group address, as defined in the original Internet 2800 architecture is an identifier of a grouping of topologically 2801 independent receiver host locations. The address encoding itself 2802 does not determine the location of the receiver(s). The multicast 2803 routing protocol, and the network-based state the protocol creates, 2804 determines where the receivers are located. 2806 In the context of LISP, a multicast group address is both an EID and 2807 a Routing Locator. Therefore, no specific semantic or action needs 2808 to be taken for a destination address, as it would appear in an IP 2809 header. Therefore, a group address that appears in an inner IP 2810 header built by a source host will be used as the destination EID. 2811 The outer IP header (the destination Routing Locator address), 2812 prepended by a LISP router, will use the same group address as the 2813 destination Routing Locator. 2815 Having said that, only the source EID and source Routing Locator 2816 needs to be dealt with. Therefore, an ITR merely needs to put its 2817 own IP address in the source Routing Locator field when prepending 2818 the outer IP header. This source Routing Locator address, like any 2819 other Routing Locator address MUST be globally routable. 2821 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2822 ITR when a received data packet is a multicast data packet or when 2823 processing a source-specific Join (either by IGMPv3 or PIM). But the 2824 source Routing Locator is decided by the multicast routing protocol 2825 in a receiver site. That is, an EID to Routing Locator translation 2826 is done at control-time. 2828 Another approach is to have the ITR not encapsulate a multicast 2829 packet and allow the host built packet to flow into the core even if 2830 the source address is allocated out of the EID namespace. If the 2831 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2832 routers can RPF to the ITR (the Locator address which is injected 2833 into core routing) rather than the host source address (the EID 2834 address which is not injected into core routing). 2836 To avoid any EID-based multicast state in the network core, the first 2837 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2838 and Interworking with non-LISP sites is described in specification 2839 [MLISP]. 2841 12. Security Considerations 2843 It is believed that most of the security mechanisms will be part of 2844 the mapping database service when using control plane procedures for 2845 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2846 as described in this specification, protection is provided against 2847 ETR spoofing by using Return-Routability mechanisms evidenced by the 2848 use of a 24-bit Nonce field in the LISP encapsulation header and a 2849 64-bit Nonce field in the LISP control message. 2851 The nonce, coupled with the ITR accepting only solicited Map-Replies 2852 provides a basic level of security, in many ways similar to the 2853 security experienced in the current Internet routing system. It is 2854 hard for off-path attackers to launch attacks against these LISP 2855 mechanisms, as they do not have the nonce values. Sending a large 2856 number of packets to accidentally find the right nonce value is 2857 possible, but would already by itself be a denial-of-service attack. 2858 On-path attackers can perform far more serious attacks, but on-path 2859 attackers can launch serious attacks in the current Internet as well, 2860 including eavesdropping, blocking or redirecting traffic. 2862 LISP does not rely on a PKI or a more heavy weight authentication 2863 system. These systems challenge the scalability of LISP which was a 2864 primary design goal. 2866 DoS attack prevention will depend on implementations rate-limiting 2867 Map-Requests and Map-Replies to the control plane as well as rate- 2868 limiting the number of data-triggered Map-Replies. 2870 An incorrectly implemented or malicious ITR might choose to ignore 2871 the priority and weights provided by the ETR in its Map-Reply. This 2872 traffic steering would be limited to the traffic that is sent by this 2873 ITR's site, and no more severe than if the site initiated a bandwidth 2874 DoS attack on (one of) the ETR's ingress links. The ITR's site would 2875 typically gain no benefit from not respecting the weights, and would 2876 likely to receive better service by abiding by them. 2878 To deal with map-cache exhaustion attempts in an ITR/PITR, the 2879 implementation should consider putting a maximum cap on the number of 2880 entries stored with a reserve list for special or frequently accessed 2881 sites. This should be a configuration policy control set by the 2882 network administrator who manages ITRs and PITRs. When overlapping 2883 EID-prefixes occur across multiple map-cache entries, the integrity 2884 of the set must be wholly maintained. So if a more-specific entry 2885 cannot be added due to reaching the maximum cap, then none of the 2886 less specifics should be stored in the map-cache. 2888 Given that the ITR/PITR maintains a cache of EID-to-RLOC mappings, 2889 cache sizing and maintenance is an issue to be kept in mind during 2890 implementation. It is a good idea to have instrumentation in place 2891 to detect thrashing of the cache. Implementation experimentation 2892 will be used to determine which cache management strategies work 2893 best. In general, it is difficult to defend against cache trashing 2894 attacks. It should be noted that an undersized cache in an ITR/PITR 2895 not only causes adverse affect on the site or region they support, 2896 but may also cause increased Map-Request load on the mapping system. 2898 There is a security risk implicit in the fact that ETRs generate the 2899 EID prefix to which they are responding. An ETR can claim a shorter 2900 prefix than it is actually responsible for. Various mechanisms to 2901 ameliorate or resolve this issue will be examined in the future, 2902 [LISP-SEC]. 2904 Spoofing of inner header addresses of LISP encapsulated packets is 2905 possible like with any tunneling mechanism. ITRs MUST verify the 2906 source address of a packet to be an EID that belongs to the site's 2907 EID-prefix range prior to encapsulation. An ETR must only 2908 decapsulate and forward datagrams with an inner header destination 2909 that matches one of its EID-prefix ranges. If, upon receipt and 2910 decapsulation, the destination EID of a datagram does not match one 2911 of the ETR's configured EID-prefixes, the ETR MUST drop the datagram. 2912 If a LISP encapsulated packet arrives at an ETR, it SHOULD compare 2913 the inner header source EID address and the outer header source RLOC 2914 address with the mapping that exists in the mapping database. Then 2915 when spoofing attacks occur, the outer header source RLOC address can 2916 be used to trace back the attack to the source site, using existing 2917 operational tools. 2919 This experimental specification does not address automated key 2920 management (AKM). BCP 107 provides guidance in this area. In 2921 addition, at the time of this writing, substantial work is being 2922 undertaken to improve security of the routing system [KARP], [RPKI], 2923 [BGP-SEC], [LISP-SEC]. Future work on LISP should address BCP-107 as 2924 well as other open security considerations, which may require changes 2925 to this specification. 2927 13. Network Management Considerations 2929 Considerations for Network Management tools exist so the LISP 2930 protocol suite can be operationally managed. The mechanisms can be 2931 found in [LISP-MIB] and [LISP-LIG]. 2933 14. IANA Considerations 2935 This section provides guidance to the Internet Assigned Numbers 2936 Authority (IANA) regarding registration of values related to the LISP 2937 specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. 2939 There are two name spaces in LISP that require registration: 2941 o LISP IANA registry allocations should not be made for purposes 2942 unrelated to LISP routing or transport protocols. 2944 o The following policies are used here with the meanings defined in 2945 BCP 26: "Specification Required", "IETF Review", "Experimental 2946 Use", "First Come First Served". 2948 14.1. LISP ACT and Flag Fields 2950 New ACT values (Section 6.1.5) can be allocated through IETF review 2951 or IESG approval. Four values have already been allocated by this 2952 specification (Section 6.1.5). 2954 In addition, the LISP protocol has a number of flag and reserved 2955 fields, such as the LISP header flags field (Section 5.3). New bits 2956 for flags can be taken into use from these fields through IETF review 2957 or IESG approval, but these need not be managed by IANA. 2959 14.2. LISP Address Type Codes 2961 LISP Address [LCAF] type codes have a range from 0 to 255. New type 2962 codes MUST be allocated consecutively starting at 0. Type Codes 0 - 2963 127 are to be assigned by IETF review or IESG approval. 2965 Type Codes 128 - 255 are available on a First Come First Served 2966 policy. 2968 This registry, initially empty, is constructed for future-use 2969 experimental work of LCAF values. See [LCAF] for details for other 2970 possible unapproved address encodings. The unapproved LCAF encodings 2971 are an area for further study and experimentation. 2973 14.3. LISP UDP Port Numbers 2975 The IANA registry has allocated UDP port numbers 4341 and 4342 for 2976 LISP data-plane and control-plane operation, respectively. 2978 14.4. LISP Key ID Numbers 2980 The following Key ID values are defined by this specification as used 2981 in any packet type that references a Key ID field: 2983 Name Number Defined in 2984 ----------------------------------------------- 2985 None 0 n/a 2986 HMAC-SHA-1-96 1 [RFC2404] 2987 HMAC-SHA-256-128 2 [RFC6234] 2989 15. Known Open Issues and Areas of Future Work 2991 As an experimental specification, this work is, by definition, 2992 incomplete. Specific areas where additional experience and work are 2993 needed include: 2995 o At present, only [ALT] is defined for implementing a database of 2996 EID-to-RLOC mapping information. Additional research on other 2997 mapping database systems is strongly encouraged. 2999 o Failure and recovery of LISP site partitioning (see Section 6.4), 3000 in the presence of redundant configuration (see Section 8.5) needs 3001 further research and experimentation. 3003 o The characteristics of map-cache management under exceptional 3004 conditions, such as denial-of-service attacks are not fully 3005 understood. Further experience is needed to determine whether 3006 current caching methods are practical or in need of further 3007 development. In particular, the performance, scaling and security 3008 characteristics of the map-cache will be discovered as part of 3009 this experiment. Performance metrics to be observed are packet 3010 reordering associated with the LISP data probe and loss of the 3011 first packet in a flow associated with map-caching. The impact of 3012 these upon TCP will be observed. See Section 12 for additional 3013 thoughts and considerations. 3015 o Preliminary work has been done to ensure that sites employing LISP 3016 can interconnect with the rest of the Internet. This work is 3017 documented in [INTERWORK] but further experimentation and 3018 experience is needed. 3020 o At present, no mechanism for automated key management for message 3021 authentication is defined. Addressing automated key management is 3022 necessary before this specification could be developed into a 3023 standards track RFC. See Section 12 for further details regarding 3024 security considerations. 3026 o In order to maintain security and stability, Internet Protocols 3027 typically isolate the control and data planes. Therefore, user 3028 activity cannot cause control plane state to be created or 3029 destroyed. LISP does not maintain this separation. The degree to 3030 which the loss of separation impacts security and stability is a 3031 topic for experimental observation. 3033 o LISP allows for different mapping database systems to be used. 3034 While only one [ALT] is currently well-defined, each mapping 3035 database will likely have some impact on the security of the EID- 3036 to-RLOC mappings. How each mapping database system's security 3037 properties impact on LISP overall is for further study. 3039 16. References 3041 16.1. Normative References 3043 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 3044 Alternative Topology (LISP-ALT)", 3045 draft-ietf-lisp-alt-09.txt (work in progress). 3047 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 3048 draft-ietf-lisp-ms-12.txt (work in progress). 3050 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 3051 August 1980. 3053 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 3054 September 1981. 3056 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 3057 E. Lear, "Address Allocation for Private Internets", 3058 BCP 5, RFC 1918, February 1996. 3060 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3061 Requirement Levels", BCP 14, RFC 2119, March 1997. 3063 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 3064 ESP and AH", RFC 2404, November 1998. 3066 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 3067 (IPv6) Specification", RFC 2460, December 1998. 3069 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 3070 of Explicit Congestion Notification (ECN) to IP", 3071 RFC 3168, September 2001. 3073 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 3074 an On-line Database", RFC 3232, January 2002. 3076 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 3077 Requirements for Security", BCP 106, RFC 4086, June 2005. 3079 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 3080 (CIDR): The Internet Address Assignment and Aggregation 3081 Plan", BCP 122, RFC 4632, August 2006. 3083 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3084 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 3085 May 2008. 3087 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 3088 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 3090 [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", 3091 RFC 5944, November 2010. 3093 [RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 3094 (SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011. 3096 [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support 3097 in IPv6", RFC 6275, July 2011. 3099 [UDP-TUNNELS] 3100 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 3101 Packets", draft-eubanks-chimento-6man-01.txt (work in 3102 progress), October 2010. 3104 [UDP-ZERO] 3105 Fairhurst, G. and M. Westerland, "IPv6 UDP Checksum 3106 Considerations", draft-ietf-6man-udpzero-04.txt (work in 3107 progress), October 2011. 3109 [VERSIONING] 3110 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3111 Versioning", draft-ietf-lisp-map-versioning-05.txt (work 3112 in progress). 3114 16.2. Informative References 3116 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3117 NUMBERS 3118 http://www.iana.org/assignments/address-family-numbers. 3120 [AFI-REGISTRY] 3121 IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3122 NUMBER registry http://www.iana.org/assignments/ 3123 address-family-numbers/ 3124 address-family-numbers.xml#address-family-numbers-1. 3126 [BGP-SEC] Lepinski, M., "An Overview of BGPSEC", 3127 draft-lepinski-bgpsec-overview-00.txt (work in progress), 3128 March 2011. 3130 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 3131 Enhancement to the Internet Architecture", Internet- 3132 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt. 3134 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 3135 Content distribution Overlay Network Service for LISP", 3136 draft-meyer-lisp-cons-04.txt (work in progress). 3138 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 3139 Mappings Multicast Across Cooperating Systems for LISP", 3140 draft-curran-lisp-emacs-00.txt (work in progress). 3142 [INTERWORK] 3143 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 3144 "Interworking LISP with IPv4 and IPv6", 3145 draft-ietf-lisp-interworking-02.txt (work in progress). 3147 [KARP] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 3148 Routing Protocols (KARP)Design Guidelines", 3149 draft-ietf-karp-design-guide-06.txt (work in progress), 3150 October 2011. 3152 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 3153 Address Format", draft-farinacci-lisp-lcaf-06.txt (work in 3154 progress). 3156 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 3157 "Renumbering: Threat or Menace?", Usenix . 3159 [LISP-DEPLOY] 3160 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 3161 "LISP Network Element Deployment Considerations", 3162 draft-ietf-lisp-deployment-02.txt (work in progress). 3164 [LISP-LIG] 3165 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 3166 draft-ietf-lisp-lig-06.txt (work in progress). 3168 [LISP-MAIN] 3169 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 3170 "Locator/ID Separation Protocol (LISP)", 3171 draft-farinacci-lisp-12.txt (work in progress). 3173 [LISP-MIB] 3174 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 3175 draft-ietf-lisp-mib-02.txt (work in progress). 3177 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 3178 Mobility Architecture", draft-meyer-lisp-mn-06.txt (work 3179 in progress). 3181 [LISP-SEC] 3182 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 3184 Bonaventure, "LISP-Security (LISP-SEC)", 3185 draft-ietf-lisp-sec-00.txt (work in progress). 3187 [LOC-ID-ARCH] 3188 Meyer, D. and D. Lewis, "Architectural Implications of 3189 Locator/ID Separation", 3190 draft-meyer-loc-id-implications-02.txt (work in progress). 3192 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 3193 "LISP for Multicast Environments", 3194 draft-ietf-lisp-multicast-10.txt (work in progress). 3196 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 3197 draft-lear-lisp-nerd-08.txt (work in progress). 3199 [OPENLISP] 3200 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 3201 Report", draft-iannone-openlisp-implementation-01.txt 3202 (work in progress). 3204 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 3205 draft-narten-radir-problem-statement-05.txt (work in 3206 progress). 3208 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 3209 STD 13, RFC 1034, November 1987. 3211 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 3212 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 3213 March 2000. 3215 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 3216 via IPv4 Clouds", RFC 3056, February 2001. 3218 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 3219 A., Peterson, J., Sparks, R., Handley, M., and E. 3220 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 3221 June 2002. 3223 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 3224 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 3225 September 2005. 3227 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 3228 Optimization for Mobile IPv6", RFC 4866, May 2007. 3230 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 3231 Workshop on Routing and Addressing", RFC 4984, 3232 September 2007. 3234 [RPKI] Lepinski, M., "An Infrastructure to Support Secure 3235 Internet Routing", draft-ietf-sidr-arch-13.txt (work in 3236 progress), February 2011. 3238 Appendix A. Acknowledgments 3240 An initial thank you goes to Dave Oran for planting the seeds for the 3241 initial ideas for LISP. His consultation continues to provide value 3242 to the LISP authors. 3244 A special and appreciative thank you goes to Noel Chiappa for 3245 providing architectural impetus over the past decades on separation 3246 of location and identity, as well as detailed review of the LISP 3247 architecture and documents, coupled with enthusiasm for making LISP a 3248 practical and incremental transition for the Internet. 3250 The authors would like to gratefully acknowledge many people who have 3251 contributed discussion and ideas to the making of this proposal. 3252 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3253 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3254 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3255 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3256 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3257 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3258 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3259 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3260 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3261 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3262 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3263 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3264 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3265 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3266 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3267 Clarence Filsfils, and Alia Atlas. 3269 This work originated in the Routing Research Group (RRG) of the IRTF. 3270 The individual submission [LISP-MAIN] was converted into this IETF 3271 LISP working group draft. 3273 The LISP working group would like to give a special thanks to Jari 3274 Arkko, the Internet Area AD at the time the set of LISP documents 3275 were being prepared for IESG last call, for his meticulous review and 3276 detail commentary on the 7 working group last call drafts progressing 3277 toward experimental RFCs. 3279 Appendix B. Document Change Log 3281 B.1. Changes to draft-ietf-lisp-17.txt 3283 o Posted December 2011 after IETF last call comments. 3285 o Make Map-Notify port assignment be 4342 in both source and 3286 destination ports. This change was agreed on and put in [LISP-MS] 3287 but was not updated in this spec. 3289 B.2. Changes to draft-ietf-lisp-16.txt 3291 o Posted October 2011 after AD review by Jari. 3293 B.3. Changes to draft-ietf-lisp-15.txt 3295 o Posted July 2011. Fixing IDnits errors. 3297 o Change description on how to select a source address for RLOC- 3298 probe Map-Replies to refer to the "EID-to-RLOC Map-Reply Message" 3299 section. 3301 B.4. Changes to draft-ietf-lisp-14.txt 3303 o Post working group last call and pre-IESG last call review. 3305 o Indicate that an ICMP Unreachable message should be sent when a 3306 packet matches a drop-based negative map-cache entry. 3308 o Indicate how a map-cache set of overlapping EID-prefixes must 3309 maintain integrity when the map-cache maximum cap is reached. 3311 o Add Joel's description for the definition of an EID, that the bit 3312 string value can be an RLOC for another device in abstract but the 3313 architecture allows it to be an EID of one device and the same 3314 value as an RLOC for another device. 3316 o In the "Tunnel Encapsulation Details" section, indicate that 4 3317 combinations of encapsulation are supported. 3319 o Add what ETR should do for a Data-Probe when received for a 3320 destination EID outside of its EID-prefix range. This was added 3321 in the Data Probe definition section. 3323 o Added text indicating that more-specific EID-prefixes must not be 3324 removed when less-specific entries stay in the map-cache. This is 3325 to preserve the integrity of the EID-prefix set. 3327 o Add clarifying text in the Security Considerations section about 3328 how an ETR must not decapsulate and forward a packet that is not 3329 for its configured EID-prefix range. 3331 B.5. Changes to draft-ietf-lisp-13.txt 3333 o Posted June 2011 to complete working group last call. 3335 o Tracker item 87. Put Yakov suggested wording in the EID-prefix 3336 definition section to reference [INTERWORK] and [LISP-DEPLOY] 3337 about discussion on transition and access mechanisms. 3339 o Change "ITRs" to "ETRs" in the Locator Status Bit definition 3340 section and data packet description section per Damien's comment. 3342 o Remove the normative reference to [LISP-SEC] when describing the 3343 S-bit in the ECM and Map-Reply headers. 3345 o Tracker item 54. Added text from John Scudder in the "Packets 3346 Egressing a LISP Site" section. 3348 o Add sentence to the "Reencapsulating Tunnel" definition about how 3349 reencapsulation loops can occur when not coordinating among 3350 multiple mapping database systems. 3352 o Remove "In theory" from a sentence in the Security Considerations 3353 section. 3355 o Remove Security Area Statement title and reword section with 3356 Eliot's provided text. The text was agreed upon by LISP-WG chairs 3357 and Security ADs. 3359 o Remove word "potential" from the over-claiming paragraph of the 3360 Security Considerations section per Stephen's request. 3362 o Wordsmithing and other editorial comments from Alia. 3364 B.6. Changes to draft-ietf-lisp-12.txt 3366 o Posted April 2011. 3368 o Tracker item 87. Provided rewording how an EID-prefix can be 3369 reused in the definition section of "EID-prefix". 3371 o Tracker item 95. Change "eliminate" to "defer" in section 4.1. 3373 o Tracker item 110. Added that the Mapping Protocol Data field in 3374 the Map-Reply message is only used when needed by the particular 3375 Mapping Database System. 3377 o Tracker item 111. Indicate that if an LSB that is associated with 3378 an anycast address, that there is at least one RLOC that is up. 3380 o Tracker item 108. Make clear the R-bit does not define RLOC path 3381 reachability. 3383 o Tracker item 107. Indicate that weights are relative to each 3384 other versus requiring an addition of up to 100%. 3386 o Tracker item 46. Add a sentence how LISP products should be sized 3387 for the appropriate demand so cache thrashing is avoided. 3389 o Change some references of RFC 5226 to [AFI] per Luigi. 3391 o Per Luigi, make reference to "EID-AFI" consistent to "EID-prefix- 3392 AFI". 3394 o Tracker item 66. Indicate that appending locators to a locator- 3395 set is done when the added locators are lexicographically greater 3396 than the previous ones in the set. 3398 o Tracker item 87. Once again reword the definition of the EID- 3399 prefix to reflect recent comments. 3401 o Tracker item 70. Added text to security section on what the 3402 implications could be if an ITR does not obey priority and weights 3403 from a Map-Reply message. 3405 o Tracker item 54. Added text to the new section titled "Packets 3406 Egressing a LISP Site" to describe the implications when two or 3407 more ITRs exist at a site where only one ITR is used for egress 3408 traffic and when there is a shift of traffic to the others, how 3409 the map-cache will need to be populated in those new egress ITRs. 3411 o Tracker item 33. Make more clear in the Routing Locator Selection 3412 section what an ITR should do when it sees an R-bit of 0 in a 3413 locator-record of a Map-Reply. 3415 o Tracker item 33. Add paragraph to the EID Reachability section 3416 indicating that site partitioning is under investigation. 3418 o Tracker item 58. Added last paragraph of Security Considerations 3419 section about how to protect inner header EID address spoofing 3420 attacks. 3422 o Add suggested Sam text to indicate that all security concerns need 3423 not be addressed for moving document to Experimental RFC status. 3424 Put this in a subsection of the Security Considerations section. 3426 B.7. Changes to draft-ietf-lisp-11.txt 3428 o Posted March 30, 2011. 3430 o Change IANA URL. The URL we had pointed to a general protocol 3431 numbers page. 3433 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3434 Requests to be sent to a MN ETR via the map-server. 3436 o Generalize text for the definition of Reencapsuatling tunnels. 3438 o Add paragraph suggested by Joel to explain how implementation 3439 experimentation will be used to determine the proper cache 3440 management techniques. 3442 o Add Yakov provided text for the definition of "EID-to-RLOC 3443 "Database". 3445 o Add reference in Section 8, Deployment Scenarios, to the 3446 draft-jakab-lisp-deploy-02.txt draft. 3448 o Clarify sentence about no hardware changes needed to support LISP 3449 encapsulation. 3451 o Add paragraph about what is the procedure when a locator is 3452 inserted in the middle of a locator-set. 3454 o Add a definition for Locator Status Bits so we can emphasize they 3455 are used as a hint for router up/down status and not path 3456 reachability. 3458 o Change "BGP RIB" to "RIB" per Clarence's comment. 3460 o Fixed complaints by IDnits. 3462 o Add subsection to Security Considerations section indicating how 3463 EID-prefix overclaiming in Map-Replies is for further study and 3464 add a reference to LISP-SEC. 3466 B.8. Changes to draft-ietf-lisp-10.txt 3468 o Posted March 2011. 3470 o Add p-bit to Map-Request so there is documentary reasons to know 3471 when a PITR has sent a Map-Request to an ETR. 3473 o Add Map-Notify message which is used to acknowledge a Map-Register 3474 message sent to a Map-Server. 3476 o Add M-bit to the Map-Register message so an ETR that wants an 3477 acknowledgment for the Map-Register can request one. 3479 o Add S-bit to the ECM and Map-Reply messages to describe security 3480 data that can be present in each message. Then refer to 3481 [LISP-SEC] for expansive details. 3483 o Add Network Management Considerations section and point to the MIB 3484 and LIG drafts. 3486 o Remove the word "simple" per Yakov's comments. 3488 B.9. Changes to draft-ietf-lisp-09.txt 3490 o Posted October 2010. 3492 o Add to IANA Consideration section about the use of LCAF Type 3493 values that accepted and maintained by the IANA registry and not 3494 the LCAF specification. 3496 o Indicate that implementations should be able to receive LISP 3497 control messages when either UDP port is 4342, so they can be 3498 robust in the face of intervening NAT boxes. 3500 o Add paragraph to SMR section to indicate that an ITR does not need 3501 to respond to an SMR-based Map-Request when it has no map-cache 3502 entry for the SMR source's EID-prefix. 3504 B.10. Changes to draft-ietf-lisp-08.txt 3506 o Posted August 2010. 3508 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3509 Register messages. 3511 o Clarify language in section 6.1.5 about Map-Replying to Data- 3512 Probes or Map-Requests. 3514 o Indicate that outer TTL should only be copied to inner TTL when it 3515 is less than inner TTL. 3517 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3518 value of 0. 3520 o Indicate that SMRs can have a global or per SMR destination rate- 3521 limiter. 3523 o Add clarifications to the SMR procedures. 3525 o Add definitions for "client-side" and 'server-side" terms used in 3526 this specification. 3528 o Clear up language in section 6.4, last paragraph. 3530 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3531 probe a PETR and have it return a Map-Reply with a locator-set of 3532 size 0. The way it is spec'ed the map-cache entry has action 3533 "dropped". Drop-action is set to 3. 3535 o Add statement about normalizing locator weights. 3537 o Clarify R-bit definition in the Map-Reply locator record. 3539 o Add section on EID Reachability within a LISP site. 3541 o Clarify another disadvantage of using anycast locators. 3543 o Reworded Abstract. 3545 o Change section 2.0 Introduction to remove obsolete information 3546 such as the LISP variant definitions. 3548 o Change section 5 title from "Tunneling Details" to "LISP 3549 Encapsulation Details". 3551 o Changes to section 5 to include results of network deployment 3552 experience with MTU. Recommend that implementations use either 3553 the stateful or stateless handling. 3555 o Make clarification wordsmithing to Section 7 and 8. 3557 o Identify that if there is one locator in the locator-set of a map- 3558 cache entry, that an SMR from that locator should be responded to 3559 by sending the the SMR-invoked Map-Request to the database mapping 3560 system rather than to the RLOC itself (which may be unreachable). 3562 o When describing Unicast and Multicast Weights indicate the the 3563 values are relative weights rather than percentages. So it 3564 doesn't imply the sum of all locator weights in the locator-set 3565 need to be 100. 3567 o Do some wordsmithing on copying TTL and TOS fields. 3569 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3570 combed the spec. 3572 o Removed Section 14 "Prototype Plans and Status". We felt this 3573 type of section is no longer appropriate for a protocol 3574 specification. 3576 o Add clarification text for the IRC description per Damien's 3577 commentary. 3579 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3580 per Vina's comment about a possible DoS vector. 3582 o Clarify (S/2 + H) in the stateless MTU section. 3584 o Add text to reflect Damien's comment about the description of the 3585 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3586 addresses are local addresses of the Map-Requester. 3588 B.11. Changes to draft-ietf-lisp-07.txt 3590 o Posted April 2010. 3592 o Added I-bit to data header so LSB field can also be used as an 3593 Instance ID field. When this occurs, the LSB field is reduced to 3594 8-bits (from 32-bits). 3596 o Added V-bit to the data header so the 24-bit nonce field can also 3597 be used for source and destination version numbers. 3599 o Added Map-Version 12-bit value to the EID-record to be used in all 3600 of Map-Request, Map-Reply, and Map-Register messages. 3602 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3603 can decide what address to select for the destination of a Map- 3604 Reply. 3606 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3607 the Locator-Set record of an EID-record for a Map-Reply message. 3608 The L-bit indicates which RLOCs in the locator-set are local to 3609 the sender of the message. The P-bit indicates which RLOC is the 3610 source of a RLOC-probe Reply (Map-Reply) message. 3612 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3614 o Made editorial and clarification changes based on comments from 3615 Dhirendra Trivedi. 3617 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3619 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3620 6.3.1. 3622 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3623 for Map-Register messages. 3625 o Add NAT section per Ron Bonica comments. 3627 o Fix IDnits issues per Ron Bonica. 3629 o Added section on Virtualization and Segmentation to explain the 3630 use if the Instance ID field in the data header. 3632 o There are too many P-bits, keep their scope to the packet format 3633 description and refer to them by name every where else in the 3634 spec. 3636 o Scanned all occurrences of "should", "should not", "must" and 3637 "must not" and uppercased them. 3639 o John Zwiebel offered text for section 4.1 to modernize the 3640 example. Thanks Z! 3642 o Make it more clear in the definition of "EID-to-RLOC Database" 3643 that all ETRs need to have the same database mapping. This 3644 reflects a comment from John Scudder. 3646 o Add a definition "Route-returnability" to the Definition of Terms 3647 section. 3649 o In section 9.2, add text to describe what the signature of 3650 traceroute packets can look like. 3652 o Removed references to Data Probe for introductory example. Data- 3653 probes are still part of the LISP design but not encouraged. 3655 o Added the definition for "LISP site" to the Definition of Terms" 3656 section. 3658 B.12. Changes to draft-ietf-lisp-06.txt 3660 Editorial based changes: 3662 o Posted December 2009. 3664 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3666 o Add text to indicate that Map-Register messages must contain a 3667 computed UDP checksum. 3669 o Add definitions for PITR and PETR. 3671 o Indicate an AFI value of 0 is an unspecified address. 3673 o Indicate that the TTL field of a Map-Register is not used and set 3674 to 0 by the sender. This change makes this spec consistent with 3675 [LISP-MS]. 3677 o Change "... yield a packet size of L bytes" to "... yield a packet 3678 size greater than L bytes". 3680 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3681 Reply messages. 3683 o Clarify that LSBs that go beyond the number of locators do not to 3684 be SMRed when the locator addresses are greater lexicographically 3685 than the locator in the existing locator-set. 3687 o Add Gregg, Srini, and Amit to acknowledgment section. 3689 o Clarify in the definition of a LISP header what is following the 3690 UDP header. 3692 o Clarify "verifying Map-Request" text in section 6.1.3. 3694 o Add Xu Xiaohu to the acknowledgment section for introducing the 3695 problem of overlapping EID-prefixes among multiple sites in an RRG 3696 email message. 3698 Design based changes: 3700 o Use stronger language to have the outer IPv4 header set DF=1 so we 3701 can avoid fragment reassembly in an ETR or PETR. This will also 3702 make IPv4 and IPv6 encapsulation have consistent behavior. 3704 o Map-Requests should not be sent in ECM with the Probe bit is set. 3705 These type of Map-Requests are used as RLOC-probes and are sent 3706 directly to locator addresses in the underlying network. 3708 o Add text in section 6.1.5 about returning all EID-prefixes in a 3709 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3710 configure. 3712 o Add text in a new subsection of section 6.1.5 about dealing with 3713 Map-Replies with coarse EID-prefixes. 3715 B.13. Changes to draft-ietf-lisp-05.txt 3717 o Posted September 2009. 3719 o Added this Document Change Log appendix. 3721 o Added section indicating that encapsulated Map-Requests must use 3722 destination UDP port 4342. 3724 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3725 data in Map-Register payload. 3727 o Added Jari to acknowledgment section. 3729 o State the source-EID is set to 0 when using Map-Requests to 3730 refresh or RLOC-probe. 3732 o Make more clear what source-RLOC should be for a Map-Request. 3734 o The LISP-CONS authors thought that the Type definitions for CONS 3735 should be removed from this specification. 3737 o Removed nonce from Map-Register message, it wasn't used so no need 3738 for it. 3740 o Clarify what to do for unspecified Action bits for negative Map- 3741 Replies. Since No Action is a drop, make value 0 Drop. 3743 B.14. Changes to draft-ietf-lisp-04.txt 3745 o Posted September 2009. 3747 o How do deal with record count greater than 1 for a Map-Request. 3748 Damien and Joel comment. Joel suggests: 1) Specify that senders 3749 compliant with the current document will always set the count to 3750 1, and note that the count is included for future extensibility. 3751 2) Specify what a receiver compliant with the draft should do if 3752 it receives a request with a count greater than 1. Presumably, it 3753 should send some error back? 3755 o Add Fred Templin in acknowledgment section. 3757 o Add Margaret and Sam to the acknowledgment section for their great 3758 comments. 3760 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3762 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3763 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3764 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3765 ignore the checksum completely. And of course we'd need to 3766 confirm that can actually be implemented. In particular, hardware 3767 that verifies UDP checksums on receive needs to be checked to make 3768 sure it permits 0 checksums." 3770 o Margaret wants a reference to 3771 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3773 o Fix description in Map-Request section. Where we describe Map- 3774 Reply Record, change "R-bit" to "M-bit". 3776 o Add the mobility bit to Map-Replies. So PITRs don't probe so 3777 often for MNs but often enough to get mapping updates. 3779 o Indicate SHA1 can be used as well for Map-Registers. 3781 o More Fred comments on MTU handling. 3783 o Isidor comment about spec'ing better periodic Map-Registers. Will 3784 be fixed in draft-ietf-lisp-ms-02.txt. 3786 o Margaret's comment on gleaning: "The current specification does 3787 not make it clear how long gleaned map entries should be retained 3788 in the cache, nor does it make it clear how/ when they will be 3789 validated. The LISP spec should, at the very least, include a 3790 (short) default lifetime for gleaned entries, require that they be 3791 validated within a short period of time, and state that a new 3792 gleaned entry should never overwrite an entry that was obtained 3793 from the mapping system. The security implications of storing 3794 "gleaned" entries should also be explored in detail." 3796 o Add section on RLOC-probing per working group feedback. 3798 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3799 Noel. 3801 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3802 control plane only. 3804 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3805 fields can be turned off and used for another future purpose. For 3806 Luigi et al versioning convergence. 3808 o Add a N-bit to the data header suggested by Noel. Then the nonce 3809 field could be used when N is not 1. 3811 o Clarify that when E-bit is 0, the nonce field can be an echoed 3812 nonce or a random nonce. Comment from Jesper. 3814 o Indicate when doing data-gleaning that a verifying Map-Request is 3815 sent to the source-EID of the gleaned data packet so we can avoid 3816 map-cache corruption by a 3rd party. Comment from Pedro. 3818 o Indicate that a verifying Map-Request, for accepting mapping data, 3819 should be sent over the ALT (or to the EID). 3821 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3823 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3824 noncing. Comment by Pedro and Dino. 3826 o Jesper made a comment to loosen the language about requiring the 3827 copy of inner TTL to outer TTL since the text to get mixed-AF 3828 traceroute to work would violate the "MUST" clause. Changed from 3829 MUST to SHOULD in section 5.3. 3831 B.15. Changes to draft-ietf-lisp-03.txt 3833 o Posted July 2009. 3835 o Removed loc-reach-bits longword from control packets per Damien 3836 comment. 3838 o Clarifications in MTU text from Roque. 3840 o Added text to indicate that the locator-set be sorted by locator 3841 address from Isidor. 3843 o Clarification text from John Zwiebel in Echo-Nonce section. 3845 B.16. Changes to draft-ietf-lisp-02.txt 3847 o Posted July 2009. 3849 o Encapsulation packet format change to add E-bit and make loc- 3850 reach-bits 32-bits in length. 3852 o Added Echo-Nonce Algorithm section. 3854 o Clarification how ECN bits are copied. 3856 o Moved S-bit in Map-Request. 3858 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3859 RLOC-Probe Algorithm. 3861 o Added to Mobility section to reference [LISP-MN]. 3863 B.17. Changes to draft-ietf-lisp-01.txt 3865 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3867 o Defined LEID to be a "LISP EID". 3869 o Indicate encapsulation use IPv4 DF=0. 3871 o Added negative Map-Reply messages with drop, native-forward, and 3872 send-map-request actions. 3874 o Added Proxy-Map-Reply bit to Map-Register. 3876 B.18. Changes to draft-ietf-lisp-00.txt 3878 o Posted May 2009. 3880 o Rename of draft-farinacci-lisp-12.txt. 3882 o Acknowledgment to RRG. 3884 Authors' Addresses 3886 Dino Farinacci 3887 cisco Systems 3888 Tasman Drive 3889 San Jose, CA 95134 3890 USA 3892 Email: dino@cisco.com 3894 Vince Fuller 3895 cisco Systems 3896 Tasman Drive 3897 San Jose, CA 95134 3898 USA 3900 Email: vaf@cisco.com 3902 Dave Meyer 3903 cisco Systems 3904 170 Tasman Drive 3905 San Jose, CA 3906 USA 3908 Email: dmm@cisco.com 3910 Darrel Lewis 3911 cisco Systems 3912 170 Tasman Drive 3913 San Jose, CA 3914 USA 3916 Email: darlewis@cisco.com