idnits 2.17.1 draft-ietf-lisp-14.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** You're using the IETF Trust Provisions' Section 6.b License Notice from 12 Sep 2009 rather than the newer Notice from 28 Dec 2009. (See https://trustee.ietf.org/license-info/) 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 5 instances of lines with non-RFC2606-compliant FQDNs in the document. == 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 == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be reachable when the R-bit for the locator record is set to 1. When the R-bit is set to 0, an ITR or PITR MUST not encapsulate to the RLOC. Neither the information contained in a Map-Reply or that stored in the mapping database system provides reachability information for RLOCs. Note that reachability is not part of the mapping system and is determined using one or more of the Routing Locator Reachability Algorithms described in the next section. -- The document date (June 29, 2011) is 4678 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-karp-design-guide-02 ** Obsolete normative reference: RFC 1700 (Obsoleted by RFC 3232) ** Obsolete normative reference: RFC 3775 (Obsoleted by RFC 6275) ** Obsolete normative reference: RFC 4634 (Obsoleted by RFC 6234) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) == Outdated reference: A later version (-13) exists of draft-ietf-sidr-arch-12 == Outdated reference: A later version (-10) exists of draft-ietf-lisp-alt-07 == Outdated reference: A later version (-04) exists of draft-meyer-lisp-cons-03 == Outdated reference: A later version (-06) exists of draft-ietf-lisp-interworking-02 == Outdated reference: A later version (-10) exists of draft-farinacci-lisp-lcaf-04 == Outdated reference: A later version (-03) exists of draft-jakab-lisp-deployment-02 == Outdated reference: A later version (-06) exists of draft-ietf-lisp-lig-01 == Outdated reference: A later version (-13) exists of draft-ietf-lisp-mib-01 == Outdated reference: A later version (-16) exists of draft-meyer-lisp-mn-04 == Outdated reference: A later version (-16) exists of draft-ietf-lisp-ms-09 == Outdated reference: A later version (-29) exists of draft-ietf-lisp-sec-00 == Outdated reference: A later version (-14) exists of draft-ietf-lisp-multicast-06 == Outdated reference: A later version (-09) exists of draft-lear-lisp-nerd-08 == Outdated reference: A later version (-05) exists of draft-narten-radir-problem-statement-00 == Outdated reference: A later version (-10) exists of draft-ietf-mip4-rfc3344bis-05 -- No information found for draft-handley-p2ppush-unpublished-2007726 - is the name correct? == Outdated reference: A later version (-09) exists of draft-ietf-lisp-map-versioning-01 Summary: 5 errors (**), 0 flaws (~~), 21 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: December 31, 2011 D. Lewis 6 cisco Systems 7 June 29, 2011 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-14 12 Abstract 14 This draft describes a network-based protocol that enables separation 15 of IP addresses into two new numbering spaces: Endpoint Identifiers 16 (EIDs) and Routing Locators (RLOCs). No changes are required to 17 either host protocol stacks or to the "core" of the Internet 18 infrastructure. LISP can be incrementally deployed, without a "flag 19 day", and offers traffic engineering, multi-homing, and mobility 20 benefits even to early adopters, when there are relatively few LISP- 21 capable sites. 23 Design and development of LISP was largely motivated by the problem 24 statement produced by the October, 2006 IAB Routing and Addressing 25 Workshop. 27 Status of this Memo 29 This Internet-Draft is submitted to IETF 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), its areas, and its working groups. Note that 34 other groups may also distribute working documents as Internet- 35 Drafts. 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 The list of current Internet-Drafts can be accessed at 43 http://www.ietf.org/ietf/1id-abstracts.txt. 45 The list of Internet-Draft Shadow Directories can be accessed at 46 http://www.ietf.org/shadow.html. 48 This Internet-Draft will expire on December 31, 2011. 50 Copyright Notice 52 Copyright (c) 2011 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the BSD License. 65 Table of Contents 67 1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 68 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 7 70 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 12 71 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 14 72 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . . 16 73 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 17 74 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 17 75 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . . 19 76 5.4. Dealing with Large Encapsulated Packets . . . . . . . . . 22 77 5.4.1. A Stateless Solution to MTU Handling . . . . . . . . . 23 78 5.4.2. A Stateful Solution to MTU Handling . . . . . . . . . 24 79 5.5. Using Virtualization and Segmentation with LISP . . . . . 24 80 6. EID-to-RLOC Mapping . . . . . . . . . . . . . . . . . . . . . 26 81 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats . . . . . 26 82 6.1.1. LISP Packet Type Allocations . . . . . . . . . . . . . 28 83 6.1.2. Map-Request Message Format . . . . . . . . . . . . . . 28 84 6.1.3. EID-to-RLOC UDP Map-Request Message . . . . . . . . . 31 85 6.1.4. Map-Reply Message Format . . . . . . . . . . . . . . . 32 86 6.1.5. EID-to-RLOC UDP Map-Reply Message . . . . . . . . . . 36 87 6.1.6. Map-Register Message Format . . . . . . . . . . . . . 38 88 6.1.7. Map-Notify Message Format . . . . . . . . . . . . . . 40 89 6.1.8. Encapsulated Control Message Format . . . . . . . . . 41 90 6.2. Routing Locator Selection . . . . . . . . . . . . . . . . 43 91 6.3. Routing Locator Reachability . . . . . . . . . . . . . . . 45 92 6.3.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 47 93 6.3.2. RLOC Probing Algorithm . . . . . . . . . . . . . . . . 48 94 6.4. EID Reachability within a LISP Site . . . . . . . . . . . 49 95 6.5. Routing Locator Hashing . . . . . . . . . . . . . . . . . 50 96 6.6. Changing the Contents of EID-to-RLOC Mappings . . . . . . 50 97 6.6.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . 51 98 6.6.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . 52 99 6.6.3. Database Map Versioning . . . . . . . . . . . . . . . 54 100 7. Router Performance Considerations . . . . . . . . . . . . . . 55 101 8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 56 102 8.1. First-hop/Last-hop Tunnel Routers . . . . . . . . . . . . 57 103 8.2. Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 57 104 8.3. ISP Provider-Edge (PE) Tunnel Routers . . . . . . . . . . 58 105 8.4. LISP Functionality with Conventional NATs . . . . . . . . 58 106 8.5. Packets Egressing a LISP Site . . . . . . . . . . . . . . 59 107 9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 60 108 9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 61 109 9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 61 110 9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 61 111 10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 63 112 10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 63 113 10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 63 114 10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 63 115 10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 65 116 10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 65 117 11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 67 118 12. Security Considerations . . . . . . . . . . . . . . . . . . . 68 119 13. Network Management Considerations . . . . . . . . . . . . . . 70 120 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 71 121 14.1. LISP Address Type Codes . . . . . . . . . . . . . . . . . 71 122 14.2. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 71 123 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 72 124 15.1. Normative References . . . . . . . . . . . . . . . . . . . 72 125 15.2. Informative References . . . . . . . . . . . . . . . . . . 73 126 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 77 127 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 78 128 B.1. Changes to draft-ietf-lisp-14.txt . . . . . . . . . . . . 78 129 B.2. Changes to draft-ietf-lisp-13.txt . . . . . . . . . . . . 78 130 B.3. Changes to draft-ietf-lisp-12.txt . . . . . . . . . . . . 79 131 B.4. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 80 132 B.5. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 81 133 B.6. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 81 134 B.7. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 82 135 B.8. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 84 136 B.9. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 85 137 B.10. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 86 138 B.11. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 87 139 B.12. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 89 140 B.13. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 89 141 B.14. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 89 142 B.15. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 90 143 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 91 145 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-routeable Endpoint Identifiers 156 (EIDs) to routeable Routing Locators (RLOCs). It also defines a 157 mechanism for these LISP routers to encapsulate IP packets addressed 158 with EIDs for transmission across an Internet that uses RLOCs for 159 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], [RPMD], [NERD]. Finally, [LISP-MS], documents a general- 204 purpose service interface for accessing a mapping database; this 205 interface is intended to make the mapping database modular so that 206 different approaches can be tried without the need to modify 207 installed xTRs. 209 This experimental specification does not address automated key 210 management. Addressing automated key management is necessary for 211 Internet standards. See Section 12 for further security details. 213 3. Definition of Terms 215 Provider Independent (PI) Addresses: PI addresses are an address 216 block assigned from a pool where blocks are not associated with 217 any particular location in the network (e.g. from a particular 218 service provider), and is therefore not topologically aggregatable 219 in the routing system. 221 Provider Assigned (PA) Addresses: PA addresses are an a address 222 block assigned to a site by each service provider to which a site 223 connects. Typically, each block is sub-block of a service 224 provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and 225 is aggregated into the larger block before being advertised into 226 the global Internet. Traditionally, IP multihoming has been 227 implemented by each multi-homed site acquiring its own, globally- 228 visible prefix. LISP uses only topologically-assigned and 229 aggregatable address blocks for RLOCs, eliminating this 230 demonstrably non-scalable practice. 232 Routing Locator (RLOC): A RLOC is an IPv4 or IPv6 address of an 233 egress tunnel router (ETR). A RLOC is the output of a EID-to-RLOC 234 mapping lookup. An EID maps to one or more RLOCs. Typically, 235 RLOCs are numbered from topologically-aggregatable blocks that are 236 assigned to a site at each point to which it attaches to the 237 global Internet; where the topology is defined by the connectivity 238 of provider networks, RLOCs can be thought of as PA addresses. 239 Multiple RLOCs can be assigned to the same ETR device or to 240 multiple ETR devices at a site. 242 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 243 IPv6) value used in the source and destination address fields of 244 the first (most inner) LISP header of a packet. The host obtains 245 a destination EID the same way it obtains an destination address 246 today, for example through a Domain Name System (DNS) [RFC1034] 247 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 248 The source EID is obtained via existing mechanisms used to set a 249 host's "local" IP address. An EID is allocated to a host from an 250 EID-prefix block associated with the site where the host is 251 located. An EID can be used by a host to refer to other hosts. 252 EIDs MUST NOT be used as LISP RLOCs. Note that EID blocks may be 253 assigned in a hierarchical manner, independent of the network 254 topology, to facilitate scaling of the mapping database. In 255 addition, an EID block assigned to a site may have site-local 256 structure (subnetting) for routing within the site; this structure 257 is not visible to the global routing system. In theory, the bit 258 string that represents an EID for one device can represent an RLOC 259 for a different device. As the architecture is realized, if a 260 given bit string is both an RLOC and an EID, it must refer to the 261 same entity in both cases. When used in discussions with other 262 Locator/ID separation proposals, a LISP EID will be called a 263 "LEID". Throughout this document, any references to "EID" refers 264 to an LEID. 266 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are 267 allocated to a site by an address allocation authority. EID- 268 prefixes are associated with a set of RLOC addresses which make up 269 a "database mapping". EID-prefix allocations can be broken up 270 into smaller blocks when an RLOC set is to be associated with the 271 smaller EID-prefix. A globally routed address block (whether PI 272 or PA) is not inherently an EID-prefix. A globally routed address 273 block may be used by its assignee as an EID block. The converse 274 is not supported. That is, a site which receives an explicitly 275 allocated EID-prefix may not use that EID-prefix as a globally 276 prefix. This would require coordination and cooperation with the 277 entities managing the mapping infrastructure. Once this has been 278 done, that block could be removed from the globally routed IP 279 system, if other suitable transition and access mechanisms are in 280 place. Discussion of such transition and access mechanisms can be 281 found in [INTERWORK] and [LISP-DEPLOY]. 283 End-system: An end-system is an IPv4 or IPv6 device that originates 284 packets with a single IPv4 or IPv6 header. The end-system 285 supplies an EID value for the destination address field of the IP 286 header when communicating globally (i.e. outside of its routing 287 domain). An end-system can be a host computer, a switch or router 288 device, or any network appliance. 290 Ingress Tunnel Router (ITR): An ITR is a router which accepts an IP 291 packet with a single IP header (more precisely, an IP packet that 292 does not contain a LISP header). The router treats this "inner" 293 IP destination address as an EID and performs an EID-to-RLOC 294 mapping lookup. The router then prepends an "outer" IP header 295 with one of its globally-routable RLOCs in the source address 296 field and the result of the mapping lookup in the destination 297 address field. Note that this destination RLOC may be an 298 intermediate, proxy device that has better knowledge of the EID- 299 to-RLOC mapping closer to the destination EID. In general, an ITR 300 receives IP packets from site end-systems on one side and sends 301 LISP-encapsulated IP packets toward the Internet on the other 302 side. 304 Specifically, when a service provider prepends a LISP header for 305 Traffic Engineering purposes, the router that does this is also 306 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 307 on the outer destination address (the originating ITR's supplied 308 RLOC) or the inner destination address (the originating hosts 309 supplied EID). 311 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 312 network that prepends an additional LISP header for Traffic 313 Engineering purposes. 315 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 316 packet where the destination address in the "outer" IP header is 317 one of its own RLOCs. The router strips the "outer" header and 318 forwards the packet based on the next IP header found. In 319 general, an ETR receives LISP-encapsulated IP packets from the 320 Internet on one side and sends decapsulated IP packets to site 321 end-systems on the other side. ETR functionality does not have to 322 be limited to a router device. A server host can be the endpoint 323 of a LISP tunnel as well. 325 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 326 network that strips an outer LISP header for Traffic Engineering 327 purposes. 329 xTR: A xTR is a reference to an ITR or ETR when direction of data 330 flow is not part of the context description. xTR refers to the 331 router that is the tunnel endpoint. Used synonymously with the 332 term "Tunnel Router". For example, "An xTR can be located at the 333 Customer Edge (CE) router", meaning both ITR and ETR functionality 334 is at the CE router. 336 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 337 demand table in an ITR that stores, tracks, and is responsible for 338 timing-out and otherwise validating EID-to-RLOC mappings. This 339 cache is distinct from the full "database" of EID-to-RLOC 340 mappings, it is dynamic, local to the ITR(s), and relatively small 341 while the database is distributed, relatively static, and much 342 more global in scope. 344 EID-to-RLOC Database: The EID-to-RLOC database is a global 345 distributed database that contains all known EID-prefix to RLOC 346 mappings. Each potential ETR typically contains a small piece of 347 the database: the EID-to-RLOC mappings for the EID prefixes 348 "behind" the router. These map to one of the router's own, 349 globally-visible, IP addresses. The same database mapping entries 350 MUST be configured on all ETRs for a given site. In a steady 351 state the EID-prefixes for the site and the locator-set for each 352 EID-prefix MUST be the same on all ETRs. Procedures to enforce 353 and/or verify this are outside the scope of this document. Note 354 that there may be transient conditions when the EID-prefix for the 355 site and locator-set for each EID-prefix may not be the same on 356 all ETRs. This has no negative implications. 358 Recursive Tunneling: Recursive tunneling occurs when a packet has 359 more than one LISP IP header. Additional layers of tunneling may 360 be employed to implement traffic engineering or other re-routing 361 as needed. When this is done, an additional "outer" LISP header 362 is added and the original RLOCs are preserved in the "inner" 363 header. Any references to tunnels in this specification refers to 364 dynamic encapsulating tunnels and never are they statically 365 configured. 367 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 368 ETR removes a LISP header, then acts as an ITR to prepend another 369 LISP header. Doing this allows a packet to be re-routed by the 370 re-encapsulating router without adding the overhead of additional 371 tunnel headers. Any references to tunnels in this specification 372 refers to dynamic encapsulating tunnels and never are they 373 statically configured. When using multiple mapping database 374 systems, care must be taken to not create reencapsulation loops. 376 LISP Header: a term used in this document to refer to the outer 377 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-byte 378 header that follows the UDP header, an ITR prepends or an ETR 379 strips. 381 Address Family Identifier (AFI): a term used to describe an address 382 encoding in a packet. An address family currently pertains to an 383 IPv4 or IPv6 address. See [AFI]/[AFI-REGISTRY] and [RFC1700] for 384 details. An AFI value of 0 used in this specification indicates 385 an unspecified encoded address where the length of the address is 386 0 bytes following the 16-bit AFI value of 0. 388 Negative Mapping Entry: A negative mapping entry, also known as a 389 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 390 is advertised or stored with no RLOCs. That is, the locator-set 391 for the EID-to-RLOC entry is empty or has an encoded locator count 392 of 0. This type of entry could be used to describe a prefix from 393 a non-LISP site, which is explicitly not in the mapping database. 394 There are a set of well defined actions that are encoded in a 395 Negative Map-Reply. 397 Data Probe: A data-probe is a LISP-encapsulated data packet where 398 the inner header destination address equals the outer header 399 destination address used to trigger a Map-Reply by a decapsulating 400 ETR. In addition, the original packet is decapsulated and 401 delivered to the destination host if the destination EID is in the 402 EID-prefix range configured on the ETR. Otherwise, the packet is 403 discarded. A Data Probe is used in some of the mapping database 404 designs to "probe" or request a Map-Reply from an ETR; in other 405 cases, Map-Requests are used. See each mapping database design 406 for details. 408 Proxy ITR (PITR): A PITR is also known as a PTR is defined and 409 described in [INTERWORK], a PITR acts like an ITR but does so on 410 behalf of non-LISP sites which send packets to destinations at 411 LISP sites. 413 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 414 PETR acts like an ETR but does so on behalf of LISP sites which 415 send packets to destinations at non-LISP sites. 417 Route-returnability: is an assumption that the underlying routing 418 system will deliver packets to the destination. When combined 419 with a nonce that is provided by a sender and returned by a 420 receiver limits off-path data insertion. 422 LISP site: is a set of routers in an edge network that are under a 423 single technical administration. LISP routers which reside in the 424 edge network are the demarcation points to separate the edge 425 network from the core network. 427 Client-side: a term used in this document to indicate a connection 428 initiation attempt by an EID. The ITR(s) at the LISP site are the 429 first to get involved in obtaining database map cache entries by 430 sending Map-Request messages. 432 Server-side: a term used in this document to indicate a connection 433 initiation attempt is being accepted for a destination EID. The 434 ETR(s) at the destination LISP site are the first to send Map- 435 Replies to the source site initiating the connection. The ETR(s) 436 at this destination site can obtain mappings by gleaning 437 information from Map-Requests, Data-Probes, or encapsulated 438 packets. 440 Locator-Status-Bits (LSBs): Locator status bits are present in the 441 LISP header. They are used by ITRs to inform ETRs about the up/ 442 down status of all ETRs at the local site. These bits are used as 443 a hint to convey up/down router status and not path reachability 444 status. The LSBs can be verified by use of one of the Locator 445 Reachability Algoriths described in Section 6.3. 447 4. Basic Overview 449 One key concept of LISP is that end-systems (hosts) operate the same 450 way they do today. The IP addresses that hosts use for tracking 451 sockets, connections, and for sending and receiving packets do not 452 change. In LISP terminology, these IP addresses are called Endpoint 453 Identifiers (EIDs). 455 Routers continue to forward packets based on IP destination 456 addresses. When a packet is LISP encapsulated, these addresses are 457 referred to as Routing Locators (RLOCs). Most routers along a path 458 between two hosts will not change; they continue to perform routing/ 459 forwarding lookups on the destination addresses. For routers between 460 the source host and the ITR as well as routers from the ETR to the 461 destination host, the destination address is an EID. For the routers 462 between the ITR and the ETR, the destination address is an RLOC. 464 Another key LISP concept is the "Tunnel Router". A tunnel router 465 prepends LISP headers on host-originated packets and strip them prior 466 to final delivery to their destination. The IP addresses in this 467 "outer header" are RLOCs. During end-to-end packet exchange between 468 two Internet hosts, an ITR prepends a new LISP header to each packet 469 and an egress tunnel router strips the new header. The ITR performs 470 EID-to-RLOC lookups to determine the routing path to the ETR, which 471 has the RLOC as one of its IP addresses. 473 Some basic rules governing LISP are: 475 o End-systems (hosts) only send to addresses which are EIDs. They 476 don't know addresses are EIDs versus RLOCs but assume packets get 477 to LISP routers, which in turn, deliver packets to the destination 478 the end-system has specified. 480 o EIDs are always IP addresses assigned to hosts. 482 o LISP routers mostly deal with Routing Locator addresses. See 483 details later in Section 4.1 to clarify what is meant by "mostly". 485 o RLOCs are always IP addresses assigned to routers; preferably, 486 topologically-oriented addresses from provider CIDR blocks. 488 o When a router originates packets it may use as a source address 489 either an EID or RLOC. When acting as a host (e.g. when 490 terminating a transport session such as SSH, TELNET, or SNMP), it 491 may use an EID that is explicitly assigned for that purpose. An 492 EID that identifies the router as a host MUST NOT be used as an 493 RLOC; an EID is only routable within the scope of a site. A 494 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 495 usage where a router could use its "host-like" EID to terminate 496 iBGP sessions to other routers in a site while at the same time 497 using RLOCs to terminate eBGP sessions to routers outside the 498 site. 500 o EIDs are not expected to be usable for global end-to-end 501 communication in the absence of an EID-to-RLOC mapping operation. 502 They are expected to be used locally for intra-site communication. 504 o EID prefixes are likely to be hierarchically assigned in a manner 505 which is optimized for administrative convenience and to 506 facilitate scaling of the EID-to-RLOC mapping database. The 507 hierarchy is based on a address allocation hierarchy which is 508 independent of the network topology. 510 o EIDs may also be structured (subnetted) in a manner suitable for 511 local routing within an autonomous system. 513 An additional LISP header may be prepended to packets by a TE-ITR 514 when re-routing of the path for a packet is desired. A potential 515 use-case for this would be an ISP router that needs to perform 516 traffic engineering for packets flowing through its network. In such 517 a situation, termed Recursive Tunneling, an ISP transit acts as an 518 additional ingress tunnel router and the RLOC it uses for the new 519 prepended header would be either a TE-ETR within the ISP (along 520 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 521 inter-ISP traffic engineered path, where an agreement to build such a 522 path exists). 524 In order to avoid excessive packet overhead as well as possible 525 encapsulation loops, this document mandates that a maximum of two 526 LISP headers can be prepended to a packet. For initial LISP 527 deployments, it is assumed two headers is sufficient, where the first 528 prepended header is used at a site for Location/Identity separation 529 and second prepended header is used inside a service provider for 530 Traffic Engineering purposes. 532 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 533 For example, the ITR for a particular end-to-end packet exchange 534 might be the first-hop or default router within a site for the source 535 host. Similarly, the egress tunnel router might be the last-hop 536 router directly-connected to the destination host. Another example, 537 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 538 could be the site's border router at the service provider attachment 539 point. Mixing and matching of site-operated, ISP-operated, and other 540 tunnel routers is allowed for maximum flexibility. See Section 8 for 541 more details. 543 4.1. Packet Flow Sequence 545 This section provides an example of the unicast packet flow with the 546 following conditions: 548 o Source host "host1.abc.com" is sending a packet to 549 "host2.xyz.com", exactly what host1 would do if the site was not 550 using LISP. 552 o Each site is multi-homed, so each tunnel router has an address 553 (RLOC) assigned from the service provider address block for each 554 provider to which that particular tunnel router is attached. 556 o The ITR(s) and ETR(s) are directly connected to the source and 557 destination, respectively, but the source and destination can be 558 located anywhere in LISP site. 560 o Map-Requests can be sent on the underlying routing system topology 561 or over an alternative topology [ALT]. 563 o Map-Replies are sent on the underlying routing system topology. 565 Client host1.abc.com wants to communicate with server host2.xyz.com: 567 1. host1.abc.com wants to open a TCP connection to host2.xyz.com. 568 It does a DNS lookup on host2.xyz.com. An A/AAAA record is 569 returned. This address is the destination EID. The locally- 570 assigned address of host1.abc.com is used as the source EID. An 571 IPv4 or IPv6 packet is built and forwarded through the LISP site 572 as a normal IP packet until it reaches a LISP ITR. 574 2. The LISP ITR must be able to map the EID destination to an RLOC 575 of one of the ETRs at the destination site. The specific method 576 used to do this is not described in this example. See [ALT] or 577 [CONS] for possible solutions. 579 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 580 rate-limited. 582 4. When an alternate mapping system is not in use, the Map-Request 583 packet is routed through the underlying routing system. 584 Otherwise, the Map-Request packet is routed on an alternate 585 logical topology. In either case, when the Map-Request arrives 586 at one of the ETRs at the destination site, it will process the 587 packet as a control message. 589 5. The ETR looks at the destination EID of the Map-Request and 590 matches it against the prefixes in the ETR's configured EID-to- 591 RLOC mapping database. This is the list of EID-prefixes the ETR 592 is supporting for the site it resides in. If there is no match, 593 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 594 returned to the ITR. 596 6. The ITR receives the Map-Reply message, parses the message (to 597 check for format validity) and stores the mapping information 598 from the packet. This information is stored in the ITR's EID-to- 599 RLOC mapping cache. Note that the map cache is an on-demand 600 cache. An ITR will manage its map cache in such a way that 601 optimizes for its resource constraints. 603 7. Subsequent packets from host1.abc.com to host2.xyz.com will have 604 a LISP header prepended by the ITR using the appropriate RLOC as 605 the LISP header destination address learned from the ETR. Note 606 the packet may be sent to a different ETR than the one which 607 returned the Map-Reply due to the source site's hashing policy or 608 the destination site's locator-set policy. 610 8. The ETR receives these packets directly (since the destination 611 address is one of its assigned IP addresses), strips the LISP 612 header and forwards the packets to the attached destination host. 614 In order to defer the need for a mapping lookup in the reverse 615 direction, an ETR MAY create a cache entry that maps the source EID 616 (inner header source IP address) to the source RLOC (outer header 617 source IP address) in a received LISP packet. Such a cache entry is 618 termed a "gleaned" mapping and only contains a single RLOC for the 619 EID in question. More complete information about additional RLOCs 620 SHOULD be verified by sending a LISP Map-Request for that EID. Both 621 ITR and the ETR may also influence the decision the other makes in 622 selecting an RLOC. See Section 6 for more details. 624 5. LISP Encapsulation Details 626 Since additional tunnel headers are prepended, the packet becomes 627 larger and can exceed the MTU of any link traversed from the ITR to 628 the ETR. It is recommended in IPv4 that packets do not get 629 fragmented as they are encapsulated by the ITR. Instead, the packet 630 is dropped and an ICMP Too Big message is returned to the source. 632 This specification recommends that implementations support for one of 633 the proposed fragmentation and reassembly schemes. These two 634 existing schemes are detailed in Section 5.4. 636 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 637 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 638 header is in IPv4 packet format and the other header is in IPv6 639 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 640 is in IPv6 packet format and the other header is in IPv4 packet 641 format). The next sub-sections illustrate packet formats for the 642 homogenous case (IPv4-in-IPv4 and IPv6-in-IPv6) but all 4 643 combinations SHOULD be supported. 645 5.1. LISP IPv4-in-IPv4 Header Format 647 0 1 2 3 648 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 1 649 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 650 / |Version| IHL |Type of Service| Total Length | 651 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 652 | | Identification |Flags| Fragment Offset | 653 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 654 OH | Time to Live | Protocol = 17 | Header Checksum | 655 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 656 | | Source Routing Locator | 657 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 658 \ | Destination Routing Locator | 659 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 660 / | Source Port = xxxx | Dest Port = 4341 | 661 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 662 \ | UDP Length | UDP Checksum | 663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 664 L |N|L|E|V|I|flags| Nonce/Map-Version | 665 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 666 S / | Instance ID/Locator Status Bits | 667 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 668 / |Version| IHL |Type of Service| Total Length | 669 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 670 | | Identification |Flags| Fragment Offset | 671 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 672 IH | Time to Live | Protocol | Header Checksum | 673 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 674 | | Source EID | 675 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 676 \ | Destination EID | 677 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 679 5.2. LISP IPv6-in-IPv6 Header Format 681 0 1 2 3 682 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 1 683 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 684 / |Version| Traffic Class | Flow Label | 685 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 | | Payload Length | Next Header=17| Hop Limit | 688 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 689 | | 690 O + + 691 u | | 692 t + Source Routing Locator + 693 e | | 694 r + + 695 | | 696 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 697 d | | 698 r + + 699 | | 700 ^ + Destination Routing Locator + 701 | | | 702 \ + + 703 \ | | 704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 705 / | Source Port = xxxx | Dest Port = 4341 | 706 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 707 \ | UDP Length | UDP Checksum | 708 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 709 L |N|L|E|V|I|flags| Nonce/Map-Version | 710 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 711 S / | Instance ID/Locator Status Bits | 712 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 713 / |Version| Traffic Class | Flow Label | 714 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 715 / | Payload Length | Next Header | Hop Limit | 716 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 | | 718 I + + 719 n | | 720 n + Source EID + 721 e | | 722 r + + 723 | | 724 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 725 d | | 726 r + + 727 | | 728 ^ + Destination EID + 729 \ | | 730 \ + + 731 \ | | 732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 734 5.3. Tunnel Header Field Descriptions 736 Inner Header: The inner header is the header on the datagram 737 received from the originating host. The source and destination IP 738 addresses are EIDs. 740 Outer Header: The outer header is a new header prepended by an ITR. 741 The address fields contain RLOCs obtained from the ingress 742 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 743 from [RFC0768]. The DF bit of the Flags field is set to 0 when 744 the method in Section 5.4.1 is used and set to 1 when the method 745 in Section 5.4.2 is used. 747 UDP Header: The UDP header contains a ITR selected source port when 748 encapsulating a packet. See Section 6.5 for details on the hash 749 algorithm used to select a source port based on the 5-tuple of the 750 inner header. The destination port MUST be set to the well-known 751 IANA assigned port value 4341. 753 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 754 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 755 [UDP-TUNNELS]. When a packet with a zero UDP checksum is received 756 by an ETR, the ETR MUST accept the packet for decapsulation. When 757 an ITR transmits a non-zero value for the UDP checksum, it MUST 758 send a correctly computed value in this field. When an ETR 759 receives a packet with a non-zero UDP checksum, it MAY choose to 760 verify the checksum value. If it chooses to perform such 761 verification, and the verification fails, the packet MUST be 762 silently dropped. If the ETR chooses not to perform the 763 verification, or performs the verification successfully, the 764 packet MUST be accepted for decapsulation. The handling of UDP 765 checksums for all tunneling protocols, including LISP, is under 766 active discussion within the IETF. When that discussion 767 concludes, any necessary changes will be made to align LISP with 768 the outcome of the broader discussion. 770 UDP Length: The UDP length field is for an IPv4 encapsulated packet, 771 the inner header Total Length plus the UDP and LISP header lengths 772 are used. For an IPv6 encapsulated packet, the inner header 773 Payload Length plus the size of the IPv6 header (40 bytes) plus 774 the size of the UDP and LISP headers are used. The UDP header 775 length is 8 bytes. 777 N: The N bit is the nonce-present bit. When this bit is set to 1, 778 the low-order 24-bits of the first 32-bits of the LISP header 779 contains a Nonce. See Section 6.3.1 for details. Both N and V 780 bits MUST NOT be set in the same packet. If they are, a 781 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 782 having a Nonce value present. 784 L: The L bit is the Locator-Status-Bits field enabled bit. When this 785 bit is set to 1, the Locator-Status-Bits in the second 32-bits of 786 the LISP header are in use. 788 x 1 x x 0 x x x 789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 790 |N|L|E|V|I|flags| Nonce/Map-Version | 791 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 792 | Locator Status Bits | 793 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 795 E: The E bit is the echo-nonce-request bit. When this bit is set to 796 1, the N bit MUST be 1. This bit SHOULD be ignored and has no 797 meaning when the N bit is set to 0. See Section 6.3.1 for 798 details. 800 V: The V bit is the Map-Version present bit. When this bit is set to 801 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 802 This bit indicates that the first 4 bytes of the LISP header is 803 encoded as: 805 0 x 0 1 x x x x 806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 807 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 808 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 809 | Instance ID/Locator Status Bits | 810 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 812 I: The I bit is the Instance ID bit. See Section 5.5 for more 813 details. When this bit is set to 1, the Locator Status Bits field 814 is reduced to 8-bits and the high-order 24-bits are used as an 815 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 816 are transmitted as zero and ignored on receipt. The format of the 817 last 4 bytes of the LISP header would look like: 819 x x x x 1 x x x 820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 821 |N|L|E|V|I|flags| Nonce/Map-Version | 822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 823 | Instance ID | LSBs | 824 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 826 flags: The flags field is a 3-bit field is reserved for future flag 827 use. It MUST be set to 0 on transmit and MUST be ignored on 828 receipt. 830 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 831 generated by an ITR when the N-bit is set to 1. The nonce is also 832 used when the E-bit is set to request the nonce value to be echoed 833 by the other side when packets are returned. When the E-bit is 834 clear but the N-bit is set, a remote ITR is either echoing a 835 previously requested echo-nonce or providing a random nonce. See 836 Section 6.3.1 for more details. 838 LISP Locator Status Bits: The locator status bits field in the LISP 839 header is set by an ITR to indicate to an ETR the up/down status 840 of the Locators in the source site. Each RLOC in a Map-Reply is 841 assigned an ordinal value from 0 to n-1 (when there are n RLOCs in 842 a mapping entry). The Locator Status Bits are numbered from 0 to 843 n-1 from the least significant bit of field. The field is 32-bits 844 when the I-bit is set to 0 and is 8 bits when the I-bit is set to 845 1. When a Locator Status Bit is set to 1, the ITR is indicating 846 to the ETR the RLOC associated with the bit ordinal has up status. 847 See Section 6.3 for details on how an ITR can determine the status 848 of the ETRs at the same site. When a site has multiple EID- 849 prefixes which result in multiple mappings (where each could have 850 a different locator-set), the Locator Status Bits setting in an 851 encapsulated packet MUST reflect the mapping for the EID-prefix 852 that the inner-header source EID address matches. If the LSB for 853 an anycast locator is set to 1, then there is at least one RLOC 854 with that address the ETR is considered 'up'. 856 When doing ITR/PITR encapsulation: 858 o The outer header Time to Live field (or Hop Limit field, in case 859 of IPv6) SHOULD be copied from the inner header Time to Live 860 field. 862 o The outer header Type of Service field (or the Traffic Class 863 field, in the case of IPv6) SHOULD be copied from the inner header 864 Type of Service field (with one caveat, see below). 866 When doing ETR/PETR decapsulation: 868 o The inner header Time to Live field (or Hop Limit field, in case 869 of IPv6) SHOULD be copied from the outer header Time to Live 870 field, when the Time to Live field of the outer header is less 871 than the Time to Live of the inner header. Failing to perform 872 this check can cause the Time to Live of the inner header to 873 increment across encapsulation/decapsulation cycle. This check is 874 also performed when doing initial encapsulation when a packet 875 comes to an ITR or PITR destined for a LISP site. 877 o The inner header Type of Service field (or the Traffic Class 878 field, in the case of IPv6) SHOULD be copied from the outer header 879 Type of Service field (with one caveat, see below). 881 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 882 after decapsulating, the net effect of this is that the new outer 883 header will carry the same Time to Live as the old outer header. 885 Copying the TTL serves two purposes: first, it preserves the distance 886 the host intended the packet to travel; second, and more importantly, 887 it provides for suppression of looping packets in the event there is 888 a loop of concatenated tunnels due to misconfiguration. See 889 Section 9.3 for TTL exception handling for traceroute packets. 891 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 892 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 893 requires special treatment in order to avoid discarding indications 894 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 895 field from the inner header to the outer header. Re-encapsulation 896 MUST copy the 2-bit ECN field from the stripped outer header to the 897 new outer header. If the ECN field contains a congestion indication 898 codepoint (the value is '11', the Congestion Experienced (CE) 899 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 900 the stripped outer header to the surviving inner header that is used 901 to forward the packet beyond the ETR. These requirements preserve 902 Congestion Experienced (CE) indications when a packet that uses ECN 903 traverses a LISP tunnel and becomes marked with a CE indication due 904 to congestion between the tunnel endpoints. 906 5.4. Dealing with Large Encapsulated Packets 908 This section proposes two mechanisms to deal with packets that exceed 909 the path MTU between the ITR and ETR. 911 It is left to the implementor to decide if the stateless or stateful 912 mechanism should be implemented. Both or neither can be used since 913 it is a local decision in the ITR regarding how to deal with MTU 914 issues, and sites can interoperate with differing mechanisms. 916 Both stateless and stateful mechanisms also apply to Reencapsulating 917 and Recursive Tunneling. So any actions below referring to an ITR 918 also apply to an TE-ITR. 920 5.4.1. A Stateless Solution to MTU Handling 922 An ITR stateless solution to handle MTU issues is described as 923 follows: 925 1. Define an architectural constant S for the maximum size of a 926 packet, in bytes, an ITR would like to receive from a source 927 inside of its site. 929 2. Define L to be the maximum size, in bytes, a packet of size S 930 would be after the ITR prepends the LISP header, UDP header, and 931 outer network layer header of size H. 933 3. Calculate: S + H = L. 935 When an ITR receives a packet from a site-facing interface and adds H 936 bytes worth of encapsulation to yield a packet size greater than L 937 bytes, it resolves the MTU issue by first splitting the original 938 packet into 2 equal-sized fragments. A LISP header is then prepended 939 to each fragment. The size of the encapsulated fragments is then 940 (S/2 + H), which is less than the ITR's estimate of the path MTU 941 between the ITR and its correspondent ETR. 943 When an ETR receives encapsulated fragments, it treats them as two 944 individually encapsulated packets. It strips the LISP headers then 945 forwards each fragment to the destination host of the destination 946 site. The two fragments are reassembled at the destination host into 947 the single IP datagram that was originated by the source host. 949 This behavior is performed by the ITR when the source host originates 950 a packet with the DF field of the IP header is set to 0. When the DF 951 field of the IP header is set to 1, or the packet is an IPv6 packet 952 originated by the source host, the ITR will drop the packet when the 953 size is greater than L, and sends an ICMP Too Big message to the 954 source with a value of S, where S is (L - H). 956 When the outer header encapsulation uses an IPv4 header, an 957 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 958 can be avoided. An implementation MAY set the DF bit in such headers 959 to 0 if it has good reason to believe there are unresolvable path MTU 960 issues between the sending ITR and the receiving ETR. 962 This specification recommends that L be defined as 1500. 964 5.4.2. A Stateful Solution to MTU Handling 966 An ITR stateful solution to handle MTU issues is described as follows 967 and was first introduced in [OPENLISP]: 969 1. The ITR will keep state of the effective MTU for each locator per 970 mapping cache entry. The effective MTU is what the core network 971 can deliver along the path between ITR and ETR. 973 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 974 with DF bit set to 1, exceeds what the core network can deliver, 975 one of the intermediate routers on the path will send an ICMP Too 976 Big message to the ITR. The ITR will parse the ICMP message to 977 determine which locator is affected by the effective MTU change 978 and then record the new effective MTU value in the mapping cache 979 entry. 981 3. When a packet is received by the ITR from a source inside of the 982 site and the size of the packet is greater than the effective MTU 983 stored with the mapping cache entry associated with the 984 destination EID the packet is for, the ITR will send an ICMP Too 985 Big message back to the source. The packet size advertised by 986 the ITR in the ICMP Too Big message is the effective MTU minus 987 the LISP encapsulation length. 989 Even though this mechanism is stateful, it has advantages over the 990 stateless IP fragmentation mechanism, by not involving the 991 destination host with reassembly of ITR fragmented packets. 993 5.5. Using Virtualization and Segmentation with LISP 995 When multiple organizations inside of a LISP site are using private 996 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 997 segregated due to possible address duplication. An Instance ID in 998 the address encoding can aid in making the entire AFI based address 999 unique. See IANA Considerations Section 14.1 for details for 1000 possible address encodings. 1002 An Instance ID can be carried in a LISP encapsulated packet. An ITR 1003 that prepends a LISP header, will copy a 24-bit value, used by the 1004 LISP router to uniquely identify the address space. The value is 1005 copied to the Instance ID field of the LISP header and the I-bit is 1006 set to 1. 1008 When an ETR decapsulates a packet, the Instance ID from the LISP 1009 header is used as a table identifier to locate the forwarding table 1010 to use for the inner destination EID lookup. 1012 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 1013 24-bit Instance ID. 1015 6. EID-to-RLOC Mapping 1017 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 1019 The following UDP packet formats are used by the LISP control-plane. 1021 0 1 2 3 1022 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 1023 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1024 |Version| IHL |Type of Service| Total Length | 1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1026 | Identification |Flags| Fragment Offset | 1027 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1028 | Time to Live | Protocol = 17 | Header Checksum | 1029 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1030 | Source Routing Locator | 1031 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1032 | Destination Routing Locator | 1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1034 / | Source Port | Dest Port | 1035 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1036 \ | UDP Length | UDP Checksum | 1037 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1038 | | 1039 | LISP Message | 1040 | | 1041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1043 0 1 2 3 1044 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 1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1046 |Version| Traffic Class | Flow Label | 1047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1048 | Payload Length | Next Header=17| Hop Limit | 1049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1050 | | 1051 + + 1052 | | 1053 + Source Routing Locator + 1054 | | 1055 + + 1056 | | 1057 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1058 | | 1059 + + 1060 | | 1061 + Destination Routing Locator + 1062 | | 1063 + + 1064 | | 1065 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1066 / | Source Port | Dest Port | 1067 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1068 \ | UDP Length | UDP Checksum | 1069 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1070 | | 1071 | LISP Message | 1072 | | 1073 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1075 The LISP UDP-based messages are the Map-Request and Map-Reply 1076 messages. When a UDP Map-Request is sent, the UDP source port is 1077 chosen by the sender and the destination UDP port number is set to 1078 4342. When a UDP Map-Reply is sent, the source UDP port number is 1079 set to 4342 and the destination UDP port number is copied from the 1080 source port of either the Map-Request or the invoking data packet. 1081 Implementations MUST be prepared to accept packets when either the 1082 source port or destination UDP port is set to 4342 due to NATs 1083 changing port number values. 1085 The UDP Length field will reflect the length of the UDP header and 1086 the LISP Message payload. 1088 The UDP Checksum is computed and set to non-zero for Map-Request, 1089 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1090 on receipt and if the checksum fails, the packet MUST be dropped. 1092 LISP-CONS [CONS] uses TCP to send LISP control messages. The format 1093 of control messages includes the UDP header so the checksum and 1094 length fields can be used to protect and delimit message boundaries. 1096 This main LISP specification is the authoritative source for message 1097 format definitions for the Map-Request and Map-Reply messages. 1099 6.1.1. LISP Packet Type Allocations 1101 This section will be the authoritative source for allocating LISP 1102 Type values. Current allocations are: 1104 Reserved: 0 b'0000' 1105 LISP Map-Request: 1 b'0001' 1106 LISP Map-Reply: 2 b'0010' 1107 LISP Map-Register: 3 b'0011' 1108 LISP Map-Notify: 4 b'0100' 1109 LISP Encapsulated Control Message: 8 b'1000' 1111 6.1.2. Map-Request Message Format 1113 0 1 2 3 1114 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 1115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1116 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1118 | Nonce . . . | 1119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1120 | . . . Nonce | 1121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1122 | Source-EID-AFI | Source EID Address ... | 1123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1124 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1126 | ... | 1127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1128 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1130 / | Reserved | EID mask-len | EID-prefix-AFI | 1131 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1132 \ | EID-prefix ... | 1133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1134 | Map-Reply Record ... | 1135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1136 | Mapping Protocol Data | 1137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1139 Packet field descriptions: 1141 Type: 1 (Map-Request) 1143 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1144 Requests sent by an ITR. 1146 M: When set, it indicates a Map-Reply Record segment is included in 1147 the Map-Request. 1149 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1150 treated as a locator reachability probe. The receiver SHOULD 1151 respond with a Map-Reply with the probe-bit set, indicating the 1152 Map-Reply is a locator reachability probe reply, with the nonce 1153 copied from the Map-Request. See Section 6.3.2 for more details. 1155 S: This is the SMR bit. See Section 6.6.2 for details. 1157 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1158 Map-Request. 1160 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1161 sending a Map-Request in response to a received SMR-based Map- 1162 Request. 1164 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1165 receipt. 1167 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1168 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1169 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1170 Address) pair must always be encoded. Multiple ITR-RLOC Address 1171 fields are used so a Map-Replier can select which destination 1172 address to use for a Map-Reply. The IRC value ranges from 0 to 1173 31, and for a value of 1, there are 2 ITR-RLOC addresses encoded 1174 and so on up to 31 which encodes a total of 32 ITR-RLOC addresses. 1176 Record Count: The number of records in this Map-Request message. A 1177 record is comprised of the portion of the packet that is labeled 1178 'Rec' above and occurs the number of times equal to Record Count. 1179 For this version of the protocol, a receiver MUST accept and 1180 process Map-Requests that contain one or more records, but a 1181 sender MUST only send Map-Requests containing one record. Support 1182 for requesting multiple EIDs in a single Map-Request message will 1183 be specified in a future version of the protocol. 1185 Nonce: An 8-byte random value created by the sender of the Map- 1186 Request. This nonce will be returned in the Map-Reply. The 1187 security of the LISP mapping protocol depends critically on the 1188 strength of the nonce in the Map-Request message. The nonce 1189 SHOULD be generated by a properly seeded pseudo-random (or strong 1190 random) source. See [RFC4086] for advice on generating security- 1191 sensitive random data. 1193 Source-EID-AFI: Address family of the "Source EID Address" field. 1195 Source EID Address: This is the EID of the source host which 1196 originated the packet which is invoking this Map-Request. When 1197 Map-Requests are used for refreshing a map-cache entry or for 1198 RLOC-probing, an AFI value 0 is used and this field is of zero 1199 length. 1201 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1202 follows this field. 1204 ITR-RLOC Address: Used to give the ETR the option of selecting the 1205 destination address from any address family for the Map-Reply 1206 message. This address MUST be a routable RLOC address of the 1207 sender of the Map-Request message. 1209 EID mask-len: Mask length for EID prefix. 1211 EID-prefix-AFI: Address family of EID-prefix according to [AFI] 1213 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1214 address-family. When a Map-Request is sent by an ITR because a 1215 data packet is received for a destination where there is no 1216 mapping entry, the EID-prefix is set to the destination IP address 1217 of the data packet. And the 'EID mask-len' is set to 32 or 128 1218 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1219 about the status of a mapping it already has cached, the EID- 1220 prefix used in the Map-Request has the same mask-length as the 1221 EID-prefix returned from the site when it sent a Map-Reply 1222 message. 1224 Map-Reply Record: When the M bit is set, this field is the size of a 1225 single "Record" in the Map-Reply format. This Map-Reply record 1226 contains the EID-to-RLOC mapping entry associated with the Source 1227 EID. This allows the ETR which will receive this Map-Request to 1228 cache the data if it chooses to do so. 1230 Mapping Protocol Data: See [CONS] for details. This field is 1231 optional and present when the UDP length indicates there is enough 1232 space in the packet to include it. 1234 6.1.3. EID-to-RLOC UDP Map-Request Message 1236 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1237 wants to test an RLOC for reachability, or wants to refresh a mapping 1238 before TTL expiration. For the initial case, the destination IP 1239 address used for the Map-Request is the destination-EID from the 1240 packet which had a mapping cache lookup failure. For the latter 2 1241 cases, the destination IP address used for the Map-Request is one of 1242 the RLOC addresses from the locator-set of the map cache entry. The 1243 source address is either an IPv4 or IPv6 RLOC address depending if 1244 the Map-Request is using an IPv4 versus IPv6 header, respectively. 1245 In all cases, the UDP source port number for the Map-Request message 1246 is an ITR/PITR selected 16-bit value and the UDP destination port 1247 number is set to the well-known destination port number 4342. A 1248 successful Map-Reply updates the cached set of RLOCs associated with 1249 the EID prefix range. 1251 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1252 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1253 be placed in the IRC field. The ITR MAY include all locally 1254 configured locators in this list or just provide one locator address 1255 from each address family it supports. If the ITR erroneously 1256 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1257 Request. 1259 Map-Requests can also be LISP encapsulated using UDP destination port 1260 4342 with a LISP type value set to "Encapsulated Control Message", 1261 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1262 LISP encapsulated the same way from a Map-Server to an ETR. Details 1263 on encapsulated Map-Requests and Map-Resolvers can be found in 1264 [LISP-MS]. 1266 Map-Requests MUST be rate-limited. It is recommended that a Map- 1267 Request for the same EID-prefix be sent no more than once per second. 1269 An ITR that is configured with mapping database information (i.e. it 1270 is also an ETR) may optionally include those mappings in a Map- 1271 Request. When an ETR configured to accept and verify such 1272 "piggybacked" mapping data receives such a Map-Request and it does 1273 not have this mapping in the map-cache, it may originate a "verifying 1274 Map-Request", addressed to the map-requesting ITR. If the ETR has a 1275 map-cache entry that matches the "piggybacked" EID and the RLOC is in 1276 the locator-set for the entry, then it may send the "verifying Map- 1277 Request" directly to the originating Map-Request source. If the RLOC 1278 is not in the locator-set, then the ETR MUST send the "verifying Map- 1279 Request" to the "piggybacked" EID. Doing this forces the "verifying 1280 Map-Request" to go through the mapping database system to reach the 1281 authoritative source of information about that EID, guarding against 1282 RLOC-spoofing in in the "piggybacked" mapping data. 1284 6.1.4. Map-Reply Message Format 1286 0 1 2 3 1287 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 1288 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1289 |Type=2 |P|E|S| Reserved | Record Count | 1290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1291 | Nonce . . . | 1292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1293 | . . . Nonce | 1294 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1295 | | Record TTL | 1296 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1297 R | Locator Count | EID mask-len | ACT |A| Reserved | 1298 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1299 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1300 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1301 r | EID-prefix | 1302 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1303 | /| Priority | Weight | M Priority | M Weight | 1304 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1305 | o | Unused Flags |L|p|R| Loc-AFI | 1306 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1307 | \| Locator | 1308 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1309 | Mapping Protocol Data | 1310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1312 Packet field descriptions: 1314 Type: 2 (Map-Reply) 1316 P: This is the probe-bit which indicates that the Map-Reply is in 1317 response to a locator reachability probe Map-Request. The nonce 1318 field MUST contain a copy of the nonce value from the original 1319 Map-Request. See Section 6.3.2 for more details. 1321 E: Indicates that the ETR which sends this Map-Reply message is 1322 advertising that the site is enabled for the Echo-Nonce locator 1323 reachability algorithm. See Section 6.3.1 for more details. 1325 S: This is the Security bit. When set to 1 the field following the 1326 Mapping Protocol Data field will have the following format. The 1327 detailed format of the Authentication Data Content is for further 1328 study. 1330 0 1 2 3 1331 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 1332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1333 | AD Type | Authentication Data Content . . . | 1334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1336 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1337 receipt. 1339 Record Count: The number of records in this reply message. A record 1340 is comprised of that portion of the packet labeled 'Record' above 1341 and occurs the number of times equal to Record count. 1343 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1344 from the Map-Request is echoed in this Nonce field of the Map- 1345 Reply. 1347 Record TTL: The time in minutes the recipient of the Map-Reply will 1348 store the mapping. If the TTL is 0, the entry SHOULD be removed 1349 from the cache immediately. If the value is 0xffffffff, the 1350 recipient can decide locally how long to store the mapping. 1352 Locator Count: The number of Locator entries. A locator entry 1353 comprises what is labeled above as 'Loc'. The locator count can 1354 be 0 indicating there are no locators for the EID-prefix. 1356 EID mask-len: Mask length for EID prefix. 1358 ACT: This 3-bit field describes negative Map-Reply actions. These 1359 bits are used only when the 'Locator Count' field is set to 0. 1360 The action bits are encoded only in Map-Reply messages. The 1361 actions defined are used by an ITR or PTR when a destination EID 1362 matches a negative mapping cache entry. Unassigned values should 1363 cause a map-cache entry to be created and, when packets match this 1364 negative cache entry, they will be dropped. The current assigned 1365 values are: 1367 (0) No-Action: The map-cache is kept alive and no packet 1368 encapsulation occurs. 1370 (1) Natively-Forward: The packet is not encapsulated or dropped 1371 but natively forwarded. 1373 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1375 (3) Drop: A packet that matches this map-cache entry is dropped. 1376 An ICMP Unreachable message SHOULD be sent. 1378 A: The Authoritative bit, when sent by a UDP-based message is always 1379 set to 1 by an ETR. See [CONS] for TCP-based Map-Replies. When a 1380 Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, the 1381 Authoritative bit is set to 0. This indicates to requesting ITRs 1382 that the Map-Reply was not originated by a LISP node managed at 1383 the site that owns the EID-prefix. 1385 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1386 sender is informing the ITR what the version number is for the 1387 EID-record contained in the Map-Reply. The ETR can allocate this 1388 number internally but MUST coordinate this value with other ETRs 1389 for the site. When this value is 0, there is no versioning 1390 information conveyed. The Map-Version Number can be included in 1391 Map-Request and Map-Register messages. See Section 6.6.3 for more 1392 details. 1394 EID-prefix-AFI: Address family of EID-prefix according to [AFI]. 1396 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1397 address-family. 1399 Priority: each RLOC is assigned a unicast priority. Lower values 1400 are more preferable. When multiple RLOCs have the same priority, 1401 they may be used in a load-split fashion. A value of 255 means 1402 the RLOC MUST NOT be used for unicast forwarding. 1404 Weight: when priorities are the same for multiple RLOCs, the weight 1405 indicates how to balance unicast traffic between them. Weight is 1406 encoded as a relative weight of total unicast packets that match 1407 the mapping entry. For example if there are 4 locators in a 1408 locator set, where the weights assigned are 30, 20, 20, and 10, 1409 the first locator will get 37.5% of the traffic, the 2nd and 3rd 1410 locators will get 25% of traffic and the 4th locator will get 1411 12.5% of the traffic. If all weights for a locator-set are equal, 1412 receiver of the Map-Reply will decide how to load-split traffic. 1413 See Section 6.5 for a suggested hash algorithm to distribute load 1414 across locators with same priority and equal weight values. 1416 M Priority: each RLOC is assigned a multicast priority used by an 1417 ETR in a receiver multicast site to select an ITR in a source 1418 multicast site for building multicast distribution trees. A value 1419 of 255 means the RLOC MUST NOT be used for joining a multicast 1420 distribution tree. 1422 M Weight: when priorities are the same for multiple RLOCs, the 1423 weight indicates how to balance building multicast distribution 1424 trees across multiple ITRs. The weight is encoded as a relative 1425 weight (similar to the unicast Weights) of total number of trees 1426 built to the source site identified by the EID-prefix. If all 1427 weights for a locator-set are equal, the receiver of the Map-Reply 1428 will decide how to distribute multicast state across ITRs. 1430 Unused Flags: set to 0 when sending and ignored on receipt. 1432 L: when this bit is set, the locator is flagged as a local locator to 1433 the ETR that is sending the Map-Reply. When a Map-Server is doing 1434 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1435 0 for all locators in this locator-set. 1437 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1438 locator address, for which this bit is set, is the one being RLOC- 1439 probed and may be different from the source address of the Map- 1440 Reply. An ITR that RLOC-probes a particular locator, MUST use 1441 this locator for retrieving the data structure used to store the 1442 fact that the locator is reachable. The "p" bit is set for a 1443 single locator in the same locator set. If an implementation sets 1444 more than one "p" bit erroneously, the receiver of the Map-Reply 1445 MUST select the first locator. The "p" bit MUST NOT be set for 1446 locator-set records sent in Map-Request and Map-Register messages. 1448 R: set when the sender of a Map-Reply has a route to the locator in 1449 the locator data record. This receiver may find this useful to 1450 know if the locator is up but not necessarily reachable from the 1451 receiver's point of view. See also Section 6.4 for another way 1452 the R-bit may be used. 1454 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1455 assigned to an ETR. Note that the destination RLOC address MAY be 1456 an anycast address. A source RLOC can be an anycast address as 1457 well. The source or destination RLOC MUST NOT be the broadcast 1458 address (255.255.255.255 or any subnet broadcast address known to 1459 the router), and MUST NOT be a link-local multicast address. The 1460 source RLOC MUST NOT be a multicast address. The destination RLOC 1461 SHOULD be a multicast address if it is being mapped from a 1462 multicast destination EID. 1464 Mapping Protocol Data: See [CONS] for details. This field is 1465 optional and present when the UDP length indicates there is enough 1466 space in the packet to include it. The Mapping Protocol Data is 1467 used when needed by the particular mapping system. 1469 6.1.5. EID-to-RLOC UDP Map-Reply Message 1471 A Map-Reply returns an EID-prefix with a prefix length that is less 1472 than or equal to the EID being requested. The EID being requested is 1473 either from the destination field of an IP header of a Data-Probe or 1474 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1475 globally-routable IP addresses of all ETRs for the LISP site. Each 1476 RLOC conveys status reachability but does not convey path 1477 reachability from a requesters perspective. Separate testing of path 1478 reachability is required, See Section 6.3 for details. 1480 Note that a Map-Reply may contain different EID-prefix granularity 1481 (prefix + length) than the Map-Request which triggers it. This might 1482 occur if a Map-Request were for a prefix that had been returned by an 1483 earlier Map-Reply. In such a case, the requester updates its cache 1484 with the new prefix information and granularity. For example, a 1485 requester with two cached EID-prefixes that are covered by a Map- 1486 Reply containing one, less-specific prefix, replaces the entry with 1487 the less-specific EID-prefix. Note that the reverse, replacement of 1488 one less-specific prefix with multiple more-specific prefixes, can 1489 also occur but not by removing the less-specific prefix rather by 1490 adding the more-specific prefixes which during a lookup will override 1491 the less-specific prefix. 1493 When an ETR is configured with overlapping EID-prefixes, a Map- 1494 Request with an EID that longest matches any EID-prefix MUST be 1495 returned in a single Map-Reply message. For instance, if an ETR had 1496 database mapping entries for EID-prefixes: 1498 10.0.0.0/8 1499 10.1.0.0/16 1500 10.1.1.0/24 1501 10.1.2.0/24 1503 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1504 count of 1 to be returned with a mapping record EID-prefix of 1505 10.1.1.0/24. 1507 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1508 count of 3 to be returned with mapping records for EID-prefixes 1509 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1511 Note that not all overlapping EID-prefixes need to be returned, only 1512 the more specifics (note in the second example above 10.0.0.0/8 was 1513 not returned for requesting EID 10.1.5.5) entries for the matching 1514 EID-prefix of the requesting EID. When more than one EID-prefix is 1515 returned, all SHOULD use the same Time-to-Live value so they can all 1516 time out at the same time. When a more specific EID-prefix is 1517 received later, its Time-to-Live value in the Map-Reply record can be 1518 stored even when other less specifics exist. When a less specific 1519 EID-prefix is received later, its map-cache expiration time SHOULD be 1520 set to the minimum expiration time of any more specific EID-prefix in 1521 the map-cache. This is done so the integrity of the EID-prefix set 1522 is wholly maintained so no more-specific entries are removed from the 1523 map-cache while keeping less-specific entries. 1525 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1526 per second to the same requesting router. For scalability, it is 1527 expected that aggregation of EID addresses into EID-prefixes will 1528 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1529 prefix range thereby reducing the number of Map-Request messages. 1531 Map-Reply records can have an empty locator-set. A negative Map- 1532 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1533 convey special actions by the sender to the ITR or PTR which have 1534 solicited the Map-Reply. There are two primary applications for 1535 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1536 ITR or PTR when a destination is for a LISP site versus a non-LISP 1537 site. And the other is to source quench Map-Requests which are sent 1538 for non-allocated EIDs. 1540 For each Map-Reply record, the list of locators in a locator-set MUST 1541 appear in the same order for each ETR that originates a Map-Reply 1542 message. The locator-set MUST be sorted in order of ascending IP 1543 address where an IPv4 locator address is considered numerically 'less 1544 than' an IPv6 locator address. 1546 When sending a Map-Reply message, the destination address is copied 1547 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1548 can choose a locator address from one of the address families it 1549 supports. For Data-Probes, the destination address of the Map-Reply 1550 is copied from the source address of the Data-Probe message which is 1551 invoking the reply. The source address of the Map-Reply is one of 1552 the local IP addresses chosen to allow uRPF checks to succeed in the 1553 upstream service provider. The destination port of a Map-Reply 1554 message is copied from the source port of the Map-Request or Data- 1555 Probe and the source port of the Map-Reply message is set to the 1556 well-known UDP port 4342. 1558 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1560 When an ETR is misconfigured or compromised, it could return coarse 1561 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1562 cover EID-prefixes which are allocated to other sites redirecting 1563 their traffic to the locators of the compromised site. 1565 To solve this problem, there are two basic solutions that could be 1566 used. The first is to have Map-Servers proxy-map-reply on behalf of 1567 ETRs so their registered EID-prefixes are the ones returned in Map- 1568 Replies. Since the interaction between an ETR and Map-Server is 1569 secured with shared-keys, it is more difficult for an ETR to 1570 misbehave. The second solution is to have ITRs and PTRs cache EID- 1571 prefixes with mask-lengths that are greater than or equal to a 1572 configured prefix length. This limits the damage to a specific width 1573 of any EID-prefix advertised, but needs to be coordinated with the 1574 allocation of site prefixes. These solutions can be used 1575 independently or at the same time. 1577 At the time of this writing, other approaches are being considered 1578 and researched. 1580 6.1.6. Map-Register Message Format 1582 The usage details of the Map-Register message can be found in 1583 specification [LISP-MS]. This section solely defines the message 1584 format. 1586 The message is sent in UDP with a destination UDP port of 4342 and a 1587 randomly selected UDP source port number. 1589 The Map-Register message format is: 1591 0 1 2 3 1592 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 1593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1594 |Type=3 |P| Reserved |M| Record Count | 1595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1596 | Nonce . . . | 1597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1598 | . . . Nonce | 1599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1600 | Key ID | Authentication Data Length | 1601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1602 ~ Authentication Data ~ 1603 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1604 | | Record TTL | 1605 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1606 R | Locator Count | EID mask-len | ACT |A| Reserved | 1607 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1608 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1609 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1610 r | EID-prefix | 1611 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1612 | /| Priority | Weight | M Priority | M Weight | 1613 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1614 | o | Unused Flags |L|p|R| Loc-AFI | 1615 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1616 | \| Locator | 1617 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1619 Packet field descriptions: 1621 Type: 3 (Map-Register) 1623 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1624 Register message requesting for the Map-Server to proxy Map-Reply. 1625 The Map-Server will send non-authoritative Map-Replies on behalf 1626 of the ETR. Details on this usage will be provided in a future 1627 version of this draft. 1629 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1630 receipt. 1632 M: This is the want-map-notify bit, when set to 1 an ETR is 1633 requesting for a Map-Notify message to be returned in response to 1634 sending a Map-Register message. The Map-Notify message sent by a 1635 Map-Server is used to an acknowledge receipt of a Map-Register 1636 message. 1638 Record Count: The number of records in this Map-Register message. A 1639 record is comprised of that portion of the packet labeled 'Record' 1640 above and occurs the number of times equal to Record count. 1642 Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages. 1644 Key ID: A configured ID to find the configured Message 1645 Authentication Code (MAC) algorithm and key value used for the 1646 authentication function. 1648 Authentication Data Length: The length in bytes of the 1649 Authentication Data field that follows this field. The length of 1650 the Authentication Data field is dependent on the Message 1651 Authentication Code (MAC) algorithm used. The length field allows 1652 a device that doesn't know the MAC algorithm to correctly parse 1653 the packet. 1655 Authentication Data: The message digest used from the output of the 1656 Message Authentication Code (MAC) algorithm. The entire Map- 1657 Register payload is authenticated with this field preset to 0. 1658 After the MAC is computed, it is placed in this field. 1659 Implementations of this specification MUST include support for 1660 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-128-256 [RFC4634] 1661 is recommended. 1663 The definition of the rest of the Map-Register can be found in the 1664 Map-Reply section. 1666 6.1.7. Map-Notify Message Format 1668 The usage details of the Map-Notify message can be found in 1669 specification [LISP-MS]. This section solely defines the message 1670 format. 1672 The message is sent inside a UDP packet with a source UDP port equal 1673 to 4342 and a destination port equal to the source port from the Map- 1674 Register message this Map-Notify message is responding to. 1676 The Map-Notify message format is: 1678 0 1 2 3 1679 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 1680 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1681 |Type=4 | Reserved | Record Count | 1682 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1683 | Nonce . . . | 1684 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1685 | . . . Nonce | 1686 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1687 | Key ID | Authentication Data Length | 1688 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1689 ~ Authentication Data ~ 1690 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1691 | | Record TTL | 1692 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1693 R | Locator Count | EID mask-len | ACT |A| Reserved | 1694 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1695 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1696 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1697 r | EID-prefix | 1698 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1699 | /| Priority | Weight | M Priority | M Weight | 1700 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1701 | o | Unused Flags |L|p|R| Loc-AFI | 1702 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1703 | \| Locator | 1704 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1706 Packet field descriptions: 1708 Type: 4 (Map-Notify) 1710 The Map-Notify message has the same contents as a Map-Register 1711 message. See Map-Register section for field descriptions. 1713 6.1.8. Encapsulated Control Message Format 1715 An Encapsulated Control Message is used to encapsulate control 1716 packets sent between xTRs and the mapping database system described 1717 in [LISP-MS]. 1719 0 1 2 3 1720 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 1721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1722 / | IPv4 or IPv6 Header | 1723 OH | (uses RLOC addresses) | 1724 \ | | 1725 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1726 / | Source Port = xxxx | Dest Port = 4342 | 1727 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1728 \ | UDP Length | UDP Checksum | 1729 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1730 LH |Type=8 |S| Reserved | 1731 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1732 / | IPv4 or IPv6 Header | 1733 IH | (uses RLOC or EID addresses) | 1734 \ | | 1735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1736 / | Source Port = xxxx | Dest Port = yyyy | 1737 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1738 \ | UDP Length | UDP Checksum | 1739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1740 LCM | LISP Control Message | 1741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1743 Packet header descriptions: 1745 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1746 source and destination header address fields. 1748 UDP: The outer UDP header with destination port 4342. The source 1749 port is randomly allocated. The checksum field MUST be non-zero. 1751 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1752 and what follows is either an IPv4 or IPv6 header as encoded by 1753 the first 4 bits after the reserved field. 1755 S: This is the Security bit. When set to 1 the field following the 1756 Reserved field will have the following format. The detailed 1757 format of the Authentication Data Content is for further study. 1759 0 1 2 3 1760 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 1761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1762 | AD Type | Authentication Data Content . . . | 1763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1765 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1766 addresses in the header address fields. When a Map-Request is 1767 encapsulated in this packet format the destination address in this 1768 header is an EID. 1770 UDP: The inner UDP header where the port assignments depends on the 1771 control packet being encapsulated. When the control packet is a 1772 Map-Request or Map-Register, the source port is ITR/PITR selected 1773 and the destination port is 4342. When the control packet is a 1774 Map-Reply, the source port is 4342 and the destination port is 1775 assigned from the source port of the invoking Map-Request. Port 1776 number 4341 MUST NOT be assigned to either port. The checksum 1777 field MUST be non-zero. 1779 LCM: The format is one of the control message formats described in 1780 this section. At this time, only Map-Request messages and PIM 1781 Join-Prune messages [MLISP] are allowed to be encapsulated. 1782 Encapsulating other types of LISP control messages are for further 1783 study. When Map-Requests are sent for RLOC-probing purposes (i.e 1784 the probe-bit is set), they MUST NOT be sent inside Encapsulated 1785 Control Messages. 1787 6.2. Routing Locator Selection 1789 Both client-side and server-side may need control over the selection 1790 of RLOCs for conversations between them. This control is achieved by 1791 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1792 messages. Alternatively, RLOC information may be gleaned from 1793 received tunneled packets or EID-to-RLOC Map-Request messages. 1795 The following enumerates different scenarios for choosing RLOCs and 1796 the controls that are available: 1798 o Server-side returns one RLOC. Client-side can only use one RLOC. 1799 Server-side has complete control of the selection. 1801 o Server-side returns a list of RLOC where a subset of the list has 1802 the same best priority. Client can only use the subset list 1803 according to the weighting assigned by the server-side. In this 1804 case, the server-side controls both the subset list and load- 1805 splitting across its members. The client-side can use RLOCs 1806 outside of the subset list if it determines that the subset list 1807 is unreachable (unless RLOCs are set to a Priority of 255). Some 1808 sharing of control exists: the server-side determines the 1809 destination RLOC list and load distribution while the client-side 1810 has the option of using alternatives to this list if RLOCs in the 1811 list are unreachable. 1813 o Server-side sets weight of 0 for the RLOC subset list. In this 1814 case, the client-side can choose how the traffic load is spread 1815 across the subset list. Control is shared by the server-side 1816 determining the list and the client determining load distribution. 1817 Again, the client can use alternative RLOCs if the server-provided 1818 list of RLOCs are unreachable. 1820 o Either side (more likely on the server-side ETR) decides not to 1821 send a Map-Request. For example, if the server-side ETR does not 1822 send Map-Requests, it gleans RLOCs from the client-side ITR, 1823 giving the client-side ITR responsibility for bidirectional RLOC 1824 reachability and preferability. Server-side ETR gleaning of the 1825 client-side ITR RLOC is done by caching the inner header source 1826 EID and the outer header source RLOC of received packets. The 1827 client-side ITR controls how traffic is returned and can alternate 1828 using an outer header source RLOC, which then can be added to the 1829 list the server-side ETR uses to return traffic. Since no 1830 Priority or Weights are provided using this method, the server- 1831 side ETR MUST assume each client-side ITR RLOC uses the same best 1832 Priority with a Weight of zero. In addition, since EID-prefix 1833 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1834 on tunnel routers can grow to be very large. 1836 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1837 received encapsulated packet, is only stored and used for a few 1838 seconds, pending verification. Verification is performed by 1839 sending a Map-Request to the source EID (the inner header IP 1840 source address) of the received encapsulated packet. A reply to 1841 this "verifying Map-Request" is used to fully populate the map- 1842 cache entry for the "gleaned" EID and is stored and used for the 1843 time indicated from the TTL field of a received Map-Reply. When a 1844 verified map-cache entry is stored, data gleaning no longer occurs 1845 for subsequent packets which have a source EID that matches the 1846 EID-prefix of the verified entry. 1848 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1849 reachable when the R-bit for the locator record is set to 1. When 1850 the R-bit is set to 0, an ITR or PITR MUST not encapsulate to the 1851 RLOC. Neither the information contained in a Map-Reply or that 1852 stored in the mapping database system provides reachability 1853 information for RLOCs. Note that reachability is not part of the 1854 mapping system and is determined using one or more of the Routing 1855 Locator Reachability Algorithms described in the next section. 1857 6.3. Routing Locator Reachability 1859 Several mechanisms for determining RLOC reachability are currently 1860 defined: 1862 1. An ETR may examine the Loc-Status-Bits in the LISP header of an 1863 encapsulated data packet received from an ITR. If the ETR is 1864 also acting as an ITR and has traffic to return to the original 1865 ITR site, it can use this status information to help select an 1866 RLOC. 1868 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1869 message for an RLOC it is using. This indicates that the RLOC is 1870 likely down. 1872 3. An ITR which participates in the global routing system can 1873 determine that an RLOC is down if no BGP RIB route exists that 1874 matches the RLOC IP address. 1876 4. An ITR may receive an ICMP Port Unreachable message from a 1877 destination host. This occurs if an ITR attempts to use 1878 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1879 non-LISP-capable site. 1881 5. An ITR may receive a Map-Reply from a ETR in response to a 1882 previously sent Map-Request. The RLOC source of the Map-Reply is 1883 likely up since the ETR was able to send the Map-Reply to the 1884 ITR. 1886 6. When an ETR receives an encapsulated packet from an ITR, the 1887 source RLOC from the outer header of the packet is likely up. 1889 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1890 described in this section, namely Echo-Noncing or RLOC-Probing. 1892 When determining Locator up/down reachability by examining the Loc- 1893 Status-Bits from the LISP encapsulated data packet, an ETR will 1894 receive up to date status from an encapsulating ITR about 1895 reachability for all ETRs at the site. CE-based ITRs at the source 1896 site can determine reachability relative to each other using the site 1897 IGP as follows: 1899 o Under normal circumstances, each ITR will advertise a default 1900 route into the site IGP. 1902 o If an ITR fails or if the upstream link to its PE fails, its 1903 default route will either time-out or be withdrawn. 1905 Each ITR can thus observe the presence or lack of a default route 1906 originated by the others to determine the Locator Status Bits it sets 1907 for them. 1909 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1910 Loc-Status-Bits in a LISP encapsulated packet are numbered from 0 to 1911 n-1 starting with the least significant bit. For example, if an RLOC 1912 listed in the 3rd position of the Map-Reply goes down (ordinal value 1913 2), then all ITRs at the site will clear the 3rd least significant 1914 bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they 1915 encapsulate. 1917 When an ETR decapsulates a packet, it will check for any change in 1918 the Loc-Status-Bits field. When a bit goes from 1 to 0, the ETR will 1919 refrain from encapsulating packets to an RLOC that is indicated as 1920 down. It will only resume using that RLOC if the corresponding Loc- 1921 Status-Bit returns to a value of 1. Loc-Status-Bits are associated 1922 with a locator-set per EID-prefix. Therefore, when a locator becomes 1923 unreachable, the Loc-Status-Bit that corresponds to that locator's 1924 position in the list returned by the last Map-Reply will be set to 1925 zero for that particular EID-prefix. 1927 When ITRs at the site are not deployed in CE routers, the IGP can 1928 still be used to determine the reachability of Locators provided they 1929 are injected into the IGP. This is typically done when a /32 address 1930 is configured on a loopback interface. 1932 When ITRs receive ICMP Network or Host Unreachable messages as a 1933 method to determine unreachability, they will refrain from using 1934 Locators which are described in Locator lists of Map-Replies. 1935 However, using this approach is unreliable because many network 1936 operators turn off generation of ICMP Unreachable messages. 1938 If an ITR does receive an ICMP Network or Host Unreachable message, 1939 it MAY originate its own ICMP Unreachable message destined for the 1940 host that originated the data packet the ITR encapsulated. 1942 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 1943 locator address from a locator-set in a mapping entry matches a 1944 prefix. If it does not find one and BGP is running in the Default 1945 Free Zone (DFZ), it can decide to not use the locator even though the 1946 Loc-Status-Bits indicate the locator is up. In this case, the path 1947 from the ITR to the ETR that is assigned the locator is not 1948 available. More details are in [LOC-ID-ARCH]. 1950 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 1951 Reply is returned, reachability of the Locator has been determined. 1952 Obviously, sending such probes increases the number of control 1953 messages originated by tunnel routers for active flows, so Locators 1954 are assumed to be reachable when they are advertised. 1956 This assumption does create a dependency: Locator unreachability is 1957 detected by the receipt of ICMP Host Unreachable messages. When an 1958 Locator has been determined to be unreachable, it is not used for 1959 active traffic; this is the same as if it were listed in a Map-Reply 1960 with priority 255. 1962 The ITR can test the reachability of the unreachable Locator by 1963 sending periodic Requests. Both Requests and Replies MUST be rate- 1964 limited. Locator reachability testing is never done with data 1965 packets since that increases the risk of packet loss for end-to-end 1966 sessions. 1968 When an ETR decapsulates a packet, it knows that it is reachable from 1969 the encapsulating ITR because that is how the packet arrived. In 1970 most cases, the ETR can also reach the ITR but cannot assume this to 1971 be true due to the possibility of path asymmetry. In the presence of 1972 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 1973 use the lack of return traffic as an indication that the ETR is 1974 unreachable. Instead, it MUST use an alternate mechanisms to 1975 determine reachability. 1977 6.3.1. Echo Nonce Algorithm 1979 When data flows bidirectionally between locators from different 1980 sites, a data-plane mechanism called "nonce echoing" can be used to 1981 determine reachability between an ITR and ETR. When an ITR wants to 1982 solicit a nonce echo, it sets the N and E bits and places a 24-bit 1983 nonce in the LISP header of the next encapsulated data packet. 1985 When this packet is received by the ETR, the encapsulated packet is 1986 forwarded as normal. When the ETR next sends a data packet to the 1987 ITR, it includes the nonce received earlier with the N bit set and E 1988 bit cleared. The ITR sees this "echoed nonce" and knows the path to 1989 and from the ETR is up. 1991 The ITR will set the E-bit and N-bit for every packet it sends while 1992 in echo-nonce-request state. The time the ITR waits to process the 1993 echoed nonce before it determines the path is unreachable is variable 1994 and a choice left for the implementation. 1996 If the ITR is receiving packets from the ETR but does not see the 1997 nonce echoed while being in echo-nonce-request state, then the path 1998 to the ETR is unreachable. This decision may be overridden by other 1999 locator reachability algorithms. Once the ITR determines the path to 2000 the ETR is down it can switch to another locator for that EID-prefix. 2002 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 2003 be implementing both ITR and ETR functionality for the echo nonce 2004 mechanism to operate. 2006 The ITR and ETR may both go into echo-nonce-request state at the same 2007 time. The number of packets sent or the time during which echo nonce 2008 requests are sent is an implementation specific setting. However, 2009 when an ITR is in echo-nonce-request state, it can echo the ETR's 2010 nonce in the next set of packets that it encapsulates and then 2011 subsequently, continue sending echo-nonce-request packets. 2013 This mechanism does not completely solve the forward path 2014 reachability problem as traffic may be unidirectional. That is, the 2015 ETR receiving traffic at a site may not be the same device as an ITR 2016 which transmits traffic from that site or the site to site traffic is 2017 unidirectional so there is no ITR returning traffic. 2019 The echo-nonce algorithm is bilateral. That is, if one side sets the 2020 E-bit and the other side is not enabled for echo-noncing, then the 2021 echoing of the nonce does not occur and the requesting side may 2022 regard the locator unreachable erroneously. An ITR SHOULD only set 2023 the E-bit in a encapsulated data packet when it knows the ETR is 2024 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 2025 Reply message. 2027 Note that other locator reachability mechanisms are being researched 2028 and can be used to compliment or even override the Echo Nonce 2029 Algorithm. See next section for an example of control-plane probing. 2031 6.3.2. RLOC Probing Algorithm 2033 RLOC Probing is a method that an ITR or PTR can use to determine the 2034 reachability status of one or more locators that it has cached in a 2035 map-cache entry. The probe-bit of the Map-Request and Map-Reply 2036 messages are used for RLOC Probing. 2038 RLOC probing is done in the control-plane on a timer basis where an 2039 ITR or PTR will originate a Map-Request destined to a locator address 2040 from one of its own locator addresses. A Map-Request used as an 2041 RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the 2042 ALT like one would when soliciting mapping data. The EID record 2043 encoded in the Map-Request is the EID-prefix of the map-cache entry 2044 cached by the ITR or PTR. The ITR may include a mapping data record 2045 for its own database mapping information which contains the local 2046 EID-prefixes and RLOCs for its site. 2048 When an ETR receives a Map-Request message with the probe-bit set, it 2049 returns a Map-Reply with the probe-bit set. The source address of 2050 the Map-Reply is set from the destination address of the Map-Request 2051 and the destination address of the Map-Reply is set from the source 2052 address of the Map-Request. The Map-Reply SHOULD contain mapping 2053 data for the EID-prefix contained in the Map-Request. This provides 2054 the opportunity for the ITR or PTR, which sent the RLOC-probe to get 2055 mapping updates if there were changes to the ETR's database mapping 2056 entries. 2058 There are advantages and disadvantages of RLOC Probing. The greatest 2059 benefit of RLOC Probing is that it can handle many failure scenarios 2060 allowing the ITR to determine when the path to a specific locator is 2061 reachable or has become unreachable, thus providing a robust 2062 mechanism for switching to using another locator from the cached 2063 locator. RLOC Probing can also provide rough RTT estimates between a 2064 pair of locators which can be useful for network management purposes 2065 as well as for selecting low delay paths. The major disadvantage of 2066 RLOC Probing is in the number of control messages required and the 2067 amount of bandwidth used to obtain those benefits, especially if the 2068 requirement for failure detection times are very small. 2070 Continued research and testing will attempt to characterize the 2071 tradeoffs of failure detection times versus message overhead. 2073 6.4. EID Reachability within a LISP Site 2075 A site may be multihomed using two or more ETRs. The hosts and 2076 infrastructure within a site will be addressed using one or more EID 2077 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2078 mapping system. One possible failure mode is for an ETR to lose 2079 reachability to one or more of the EID prefixes within its own site. 2080 When this occurs when the ETR sends Map-Replies, it can clear the 2081 R-bit associated with its own locator. And when the ETR is also an 2082 ITR, it can clear its locator-status-bit in the encapsulation data 2083 header. 2085 It is recognized there are no simple solutions to the site 2086 partitioning problem because it is hard to know which part of the 2087 EID-prefix range is partitioned. And which locators can reach any 2088 sub-ranges of the EID-prefixes. This problem is under investigation 2089 with the expectation that experiments will tell us more. Note, this 2090 is not a new problem introduced by the LISP architecture. The 2091 problem exists today when a multi-homed site uses BGP to advertise 2092 its reachability upstream. 2094 6.5. Routing Locator Hashing 2096 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2097 a requesting ITR, the locator-set for the EID-prefix may contain 2098 different priority values for each locator address. When more than 2099 one best priority locator exists, the ITR can decide how to load 2100 share traffic against the corresponding locators. 2102 The following hash algorithm may be used by an ITR to select a 2103 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2105 1. Either a source and destination address hash can be used or the 2106 traditional 5-tuple hash which includes the source and 2107 destination addresses, source and destination TCP, UDP, or SCTP 2108 port numbers and the IP protocol number field or IPv6 next- 2109 protocol fields of a packet a host originates from within a LISP 2110 site. When a packet is not a TCP, UDP, or SCTP packet, the 2111 source and destination addresses only from the header are used to 2112 compute the hash. 2114 2. Take the hash value and divide it by the number of locators 2115 stored in the locator-set for the EID-to-RLOC mapping. 2117 3. The remainder will be yield a value of 0 to "number of locators 2118 minus 1". Use the remainder to select the locator in the 2119 locator-set. 2121 Note that when a packet is LISP encapsulated, the source port number 2122 in the outer UDP header needs to be set. Selecting a hashed value 2123 allows core routers which are attached to Link Aggregation Groups 2124 (LAGs) to load-split the encapsulated packets across member links of 2125 such LAGs. Otherwise, core routers would see a single flow, since 2126 packets have a source address of the ITR, for packets which are 2127 originated by different EIDs at the source site. A suggested setting 2128 for the source port number computed by an ITR is a 5-tuple hash 2129 function on the inner header, as described above. 2131 Many core router implementations use a 5-tuple hash to decide how to 2132 balance packet load across members of a LAG. The 5-tuple hash 2133 includes the source and destination addresses of the packet and the 2134 source and destination ports when the protocol number in the packet 2135 is TCP or UDP. For this reason, UDP encoding is used for LISP 2136 encapsulation. 2138 6.6. Changing the Contents of EID-to-RLOC Mappings 2140 Since the LISP architecture uses a caching scheme to retrieve and 2141 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2142 date mapping is to re-request the mapping. However, the ITRs do not 2143 know when the mappings change and the ETRs do not keep track of which 2144 ITRs requested its mappings. For scalability reasons, we want to 2145 maintain this approach but need to provide a way for ETRs change 2146 their mappings and inform the sites that are currently communicating 2147 with the ETR site using such mappings. 2149 When adding a new locator record in lexicographic order to the end of 2150 a locator-set, it is easy to update mappings. We assume new mappings 2151 will maintain the same locator ordering as the old mapping but just 2152 have new locators appended to the end of the list. So some ITRs can 2153 have a new mapping while other ITRs have only an old mapping that is 2154 used until they time out. When an ITR has only an old mapping but 2155 detects bits set in the loc-status-bits that correspond to locators 2156 beyond the list it has cached, it simply ignores them. However, this 2157 can only happen for locator addresses that are lexicographically 2158 greater than the locator addresses in the existing locator-set. 2160 When a locator record is inserted in the middle of a locator-set, to 2161 maintain lexicographic order, the SMR procedure in Section 6.6.2 is 2162 used to inform ITRs and PTRs of the new locator-status-bit mappings. 2164 When a locator record is removed from a locator-set, ITRs that have 2165 the mapping cached will not use the removed locator because the xTRs 2166 will set the loc-status-bit to 0. So even if the locator is in the 2167 list, it will not be used. For new mapping requests, the xTRs can 2168 set the locator AFI to 0 (indicating an unspecified address), as well 2169 as setting the corresponding loc-status-bit to 0. This forces ITRs 2170 with old or new mappings to avoid using the removed locator. 2172 If many changes occur to a mapping over a long period of time, one 2173 will find empty record slots in the middle of the locator-set and new 2174 records appended to the locator-set. At some point, it would be 2175 useful to compact the locator-set so the loc-status-bit settings can 2176 be efficiently packed. 2178 We propose here three approaches for locator-set compaction, one 2179 operational and two protocol mechanisms. The operational approach 2180 uses a clock sweep method. The protocol approaches use the concept 2181 of Solicit-Map-Requests and Map-Versioning. 2183 6.6.1. Clock Sweep 2185 The clock sweep approach uses planning in advance and the use of 2186 count-down TTLs to time out mappings that have already been cached. 2187 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2188 there is a 24 hour window to time out old mappings. The following 2189 clock sweep procedure is used: 2191 1. 24 hours before a mapping change is to take effect, a network 2192 administrator configures the ETRs at a site to start the clock 2193 sweep window. 2195 2. During the clock sweep window, ETRs continue to send Map-Reply 2196 messages with the current (unchanged) mapping records. The TTL 2197 for these mappings is set to 1 hour. 2199 3. 24 hours later, all previous cache entries will have timed out, 2200 and any active cache entries will time out within 1 hour. During 2201 this 1 hour window the ETRs continue to send Map-Reply messages 2202 with the current (unchanged) mapping records with the TTL set to 2203 1 minute. 2205 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2206 messages with the new (changed) mapping records. So any active 2207 caches can get the new mapping contents right away if not cached, 2208 or in 1 minute if they had the mapping cached. The new mappings 2209 are cached with a time to live equal to the TTL in the Map-Reply. 2211 6.6.2. Solicit-Map-Request (SMR) 2213 Soliciting a Map-Request is a selective way for ETRs, at the site 2214 where mappings change, to control the rate they receive requests for 2215 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2216 the mappings they have cached. 2218 Since the ETRs don't keep track of remote ITRs that have cached their 2219 mappings, they do not know which ITRs need to have their mappings 2220 updated. As a result, an ETR will solicit Map-Requests (called an 2221 SMR message) from those sites to which it has been sending 2222 encapsulated data to for the last minute. In particular, an ETR will 2223 send an SMR an ITR to which it has recently sent encapsulated data. 2225 An SMR message is simply a bit set in a Map-Request message. An ITR 2226 or PTR will send a Map-Request when they receive an SMR message. 2227 Both the SMR sender and the Map-Request responder MUST rate-limited 2228 these messages. Rate-limiting can be implemented as a global rate- 2229 limiter or one rate-limiter per SMR destination. 2231 The following procedure shows how a SMR exchange occurs when a site 2232 is doing locator-set compaction for an EID-to-RLOC mapping: 2234 1. When the database mappings in an ETR change, the ETRs at the site 2235 begin to send Map-Requests with the SMR bit set for each locator 2236 in each map-cache entry the ETR caches. 2238 2. A remote ITR which receives the SMR message will schedule sending 2239 a Map-Request message to the source locator address of the SMR 2240 message or to the mapping database system. A newly allocated 2241 random nonce is selected and the EID-prefix used is the one 2242 copied from the SMR message. If the source locator is the only 2243 locator in the cached locator-set, the remote ITR SHOULD send a 2244 Map-Request to the database mapping system just in case the 2245 single locator has changed and may no longer be reachable to 2246 accept the Map-Request. 2248 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2249 Map-Reply while continuing to use the cached mapping. When Map 2250 Versioning is used, described in Section 6.6.3, an SMR sender can 2251 detect if an ITR is using the most up to date database mapping. 2253 4. The ETRs at the site with the changed mapping will reply to the 2254 Map-Request with a Map-Reply message that has a nonce from the 2255 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2256 limited. This is important to avoid Map-Reply implosion. 2258 5. The ETRs, at the site with the changed mapping, record the fact 2259 that the site that sent the Map-Request has received the new 2260 mapping data in the mapping cache entry for the remote site so 2261 the loc-status-bits are reflective of the new mapping for packets 2262 going to the remote site. The ETR then stops sending SMR 2263 messages. 2265 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2266 To avoid map-cache entry corruption by a third-party, a sender of an 2267 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2268 based Map-Request and the source is not in the locator-set for the 2269 stored map-cache entry, then the responding Map-Request MUST be sent 2270 with an EID destination to the mapping database system. Since the 2271 mapping database system is more secure to reach an authoritative ETR, 2272 it will deliver the Map-Request to the authoritative source of the 2273 mapping data. 2275 When an ITR receives an SMR-based Map-Request for which it does not 2276 have a cached mapping for the EID in the SMR message, it MAY not send 2277 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2278 SMR messages to all locators in the locator-set it has stored in its 2279 map-cache but the remote ITRs that receive the SMR may not be sending 2280 packets to the site. There is no point in updating the ITRs until 2281 they need to send, in which case, they will send Map-Requests to 2282 obtain a map-cache entry. 2284 6.6.3. Database Map Versioning 2286 When there is unidirectional packet flow between an ITR and ETR, and 2287 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2288 ITR so encapsulation can stop to a removed locator and start to a new 2289 locator in the locator-set. 2291 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2292 number. This is known as the Destination Map-Version Number. ITRs 2293 include the Destination Map-Version Number in packets they 2294 encapsulate to the site. When an ETR decapsulates a packet and 2295 detects the Destination Map-Version Number is less than the current 2296 version for its mapping, the SMR procedure described in Section 6.6.2 2297 occurs. 2299 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2300 Version number. This is known as the Source Map-Version Number. 2301 When an ETR decapsulates a packet and detects the Source Map-Version 2302 Number is greater than the last Map-Version Number sent in a Map- 2303 Reply from the ITR's site, the ETR will send a Map-Request to one of 2304 the ETRs for the source site. 2306 A Map-Version Number is used as a sequence number per EID-prefix. So 2307 values that are greater, are considered to be more recent. A value 2308 of 0 for the Source Map-Version Number or the Destination Map-Version 2309 Number conveys no versioning information and an ITR does no 2310 comparison with previously received Map-Version Numbers. 2312 A Map-Version Number can be included in Map-Register messages as 2313 well. This is a good way for the Map-Server can assure that all ETRs 2314 for a site registering to it will be Map-Version number synchronized. 2316 See [VERSIONING] for a more detailed analysis and description of 2317 Database Map Versioning. 2319 7. Router Performance Considerations 2321 LISP is designed to be very hardware-based forwarding friendly. A 2322 few implementation techniques can be used to incrementally implement 2323 LISP: 2325 o When a tunnel encapsulated packet is received by an ETR, the outer 2326 destination address may not be the address of the router. This 2327 makes it challenging for the control plane to get packets from the 2328 hardware. This may be mitigated by creating special FIB entries 2329 for the EID-prefixes of EIDs served by the ETR (those for which 2330 the router provides an RLOC translation). These FIB entries are 2331 marked with a flag indicating that control plane processing should 2332 be performed. The forwarding logic of testing for particular IP 2333 protocol number value is not necessary. There are a few proven 2334 cases where no changes to existing deployed hardware were needed 2335 to support the LISP data-plane. 2337 o On an ITR, prepending a new IP header consists of adding more 2338 bytes to a MAC rewrite string and prepending the string as part of 2339 the outgoing encapsulation procedure. Routers that support GRE 2340 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2341 support this action. 2343 o A packet's source address or interface the packet was received on 2344 can be used to select a VRF (Virtual Routing/Forwarding). The 2345 VRF's routing table can be used to find EID-to-RLOC mappings. 2347 8. Deployment Scenarios 2349 This section will explore how and where ITRs and ETRs can be deployed 2350 and will discuss the pros and cons of each deployment scenario. For 2351 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2353 There are two basic deployment trade-offs to consider: centralized 2354 versus distributed caches and flat, recursive, or re-encapsulating 2355 tunneling. When deciding on centralized versus distributed caching, 2356 the following issues should be considered: 2358 o Are the tunnel routers spread out so that the caches are spread 2359 across all the memories of each router? 2361 o Should management "touch points" be minimized by choosing few 2362 tunnel routers, just enough for redundancy? 2364 o In general, using more ITRs doesn't increase management load, 2365 since caches are built and stored dynamically. On the other hand, 2366 more ETRs does require more management since EID-prefix-to-RLOC 2367 mappings need to be explicitly configured. 2369 When deciding on flat, recursive, or re-encapsulation tunneling, the 2370 following issues should be considered: 2372 o Flat tunneling implements a single tunnel between source site and 2373 destination site. This generally offers better paths between 2374 sources and destinations with a single tunnel path. 2376 o Recursive tunneling is when tunneled traffic is again further 2377 encapsulated in another tunnel, either to implement VPNs or to 2378 perform Traffic Engineering. When doing VPN-based tunneling, the 2379 site has some control since the site is prepending a new tunnel 2380 header. In the case of TE-based tunneling, the site may have 2381 control if it is prepending a new tunnel header, but if the site's 2382 ISP is doing the TE, then the site has no control. Recursive 2383 tunneling generally will result in suboptimal paths but at the 2384 benefit of steering traffic to resource available parts of the 2385 network. 2387 o The technique of re-encapsulation ensures that packets only 2388 require one tunnel header. So if a packet needs to be rerouted, 2389 it is first decapsulated by the ETR and then re-encapsulated with 2390 a new tunnel header using a new RLOC. 2392 The next sub-sections will survey where tunnel routers can reside in 2393 the network. 2395 8.1. First-hop/Last-hop Tunnel Routers 2397 By locating tunnel routers close to hosts, the EID-prefix set is at 2398 the granularity of an IP subnet. So at the expense of more EID- 2399 prefix-to-RLOC sets for the site, the caches in each tunnel router 2400 can remain relatively small. But caches always depend on the number 2401 of non-aggregated EID destination flows active through these tunnel 2402 routers. 2404 With more tunnel routers doing encapsulation, the increase in control 2405 traffic grows as well: since the EID-granularity is greater, more 2406 Map-Requests and Map-Replies are traveling between more routers. 2408 The advantage of placing the caches and databases at these stub 2409 routers is that the products deployed in this part of the network 2410 have better price-memory ratios then their core router counterparts. 2411 Memory is typically less expensive in these devices and fewer routes 2412 are stored (only IGP routes). These devices tend to have excess 2413 capacity, both for forwarding and routing state. 2415 LISP functionality can also be deployed in edge switches. These 2416 devices generally have layer-2 ports facing hosts and layer-3 ports 2417 facing the Internet. Spare capacity is also often available in these 2418 devices as well. 2420 8.2. Border/Edge Tunnel Routers 2422 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2423 space associated with a site to be reachable via a small set of RLOCs 2424 assigned to the CE routers for that site. This is the default 2425 behavior envisioned in the rest of this specification. 2427 This offers the opposite benefit of the first-hop/last-hop tunnel 2428 router scenario: the number of mapping entries and network management 2429 touch points are reduced, allowing better scaling. 2431 One disadvantage is that less of the network's resources are used to 2432 reach host endpoints thereby centralizing the point-of-failure domain 2433 and creating network choke points at the CE router. 2435 Note that more than one CE router at a site can be configured with 2436 the same IP address. In this case an RLOC is an anycast address. 2437 This allows resilience between the CE routers. That is, if a CE 2438 router fails, traffic is automatically routed to the other routers 2439 using the same anycast address. However, this comes with the 2440 disadvantage where the site cannot control the entrance point when 2441 the anycast route is advertised out from all border routers. Another 2442 disadvantage of using anycast locators is the limited advertisement 2443 scope of /32 (or /128 for IPv6) routes. 2445 8.3. ISP Provider-Edge (PE) Tunnel Routers 2447 Use of ISP PE routers as tunnel endpoint routers is not the typical 2448 deployment scenario envisioned in the specification. This section 2449 attempts to capture some of reasoning behind this preference of 2450 implementing LISP on CE routers. 2452 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2453 than a site, control over the location of the egress tunnel 2454 endpoints. That is, the ISP can decide if the tunnel endpoints are 2455 in the destination site (in either CE routers or last-hop routers 2456 within a site) or at other PE edges. The advantage of this case is 2457 that two tunnel headers can be avoided. By having the PE be the 2458 first router on the path to encapsulate, it can choose a TE path 2459 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2460 the destination end site. 2462 An obvious disadvantage is that the end site has no control over 2463 where its packets flow or the RLOCs used. Other disadvantages 2464 include the difficulty in synchronizing path liveness updates between 2465 CE and PE routers. 2467 As mentioned in earlier sections a combination of these scenarios is 2468 possible at the expense of extra packet header overhead, if both site 2469 and provider want control, then recursive or re-encapsulating tunnels 2470 are used. 2472 8.4. LISP Functionality with Conventional NATs 2474 LISP routers can be deployed behind Network Address Translator (NAT) 2475 devices to provide the same set of packet services hosts have today 2476 when they are addressed out of private address space. 2478 It is important to note that a locator address in any LISP control 2479 message MUST be a globally routable address and therefore SHOULD NOT 2480 contain [RFC1918] addresses. If a LISP router is configured with 2481 private addresses, they MUST be used only in the outer IP header so 2482 the NAT device can translate properly. Otherwise, EID addresses MUST 2483 be translated before encapsulation is performed. Both NAT 2484 translation and LISP encapsulation functions could be co-located in 2485 the same device. 2487 More details on LISP address translation can be found in [INTERWORK]. 2489 8.5. Packets Egressing a LISP Site 2491 When a LISP site is using two ITRs for redundancy, the failure of one 2492 ITR will likely shift outbound traffic to the second. This second 2493 ITR's cache may not not be populated with the same EID-to-RLOC 2494 mapping entries as the first. If this second ITR does not have these 2495 mappings, traffic will be dropped while the mappings are retrieved 2496 from the mapping system. The retrieval of these messages may 2497 increase the load of requests being sent into the mapping system. 2498 Deployment and experimentation will determine whether this issue 2499 requires more attention. 2501 9. Traceroute Considerations 2503 When a source host in a LISP site initiates a traceroute to a 2504 destination host in another LISP site, it is highly desirable for it 2505 to see the entire path. Since packets are encapsulated from ITR to 2506 ETR, the hop across the tunnel could be viewed as a single hop. 2507 However, LISP traceroute will provide the entire path so the user can 2508 see 3 distinct segments of the path from a source LISP host to a 2509 destination LISP host: 2511 Segment 1 (in source LISP site based on EIDs): 2513 source-host ---> first-hop ... next-hop ---> ITR 2515 Segment 2 (in the core network based on RLOCs): 2517 ITR ---> next-hop ... next-hop ---> ETR 2519 Segment 3 (in the destination LISP site based on EIDs): 2521 ETR ---> next-hop ... last-hop ---> destination-host 2523 For segment 1 of the path, ICMP Time Exceeded messages are returned 2524 in the normal matter as they are today. The ITR performs a TTL 2525 decrement and test for 0 before encapsulating. So the ITR hop is 2526 seen by the traceroute source has an EID address (the address of 2527 site-facing interface). 2529 For segment 2 of the path, ICMP Time Exceeded messages are returned 2530 to the ITR because the TTL decrement to 0 is done on the outer 2531 header, so the destination of the ICMP messages are to the ITR RLOC 2532 address, the source RLOC address of the encapsulated traceroute 2533 packet. The ITR looks inside of the ICMP payload to inspect the 2534 traceroute source so it can return the ICMP message to the address of 2535 the traceroute client as well as retaining the core router IP address 2536 in the ICMP message. This is so the traceroute client can display 2537 the core router address (the RLOC address) in the traceroute output. 2538 The ETR returns its RLOC address and responds to the TTL decrement to 2539 0 like the previous core routers did. 2541 For segment 3, the next-hop router downstream from the ETR will be 2542 decrementing the TTL for the packet that was encapsulated, sent into 2543 the core, decapsulated by the ETR, and forwarded because it isn't the 2544 final destination. If the TTL is decremented to 0, any router on the 2545 path to the destination of the traceroute, including the next-hop 2546 router or destination, will send an ICMP Time Exceeded message to the 2547 source EID of the traceroute client. The ICMP message will be 2548 encapsulated by the local ITR and sent back to the ETR in the 2549 originated traceroute source site, where the packet will be delivered 2550 to the host. 2552 9.1. IPv6 Traceroute 2554 IPv6 traceroute follows the procedure described above since the 2555 entire traceroute data packet is included in ICMP Time Exceeded 2556 message payload. Therefore, only the ITR needs to pay special 2557 attention for forwarding ICMP messages back to the traceroute source. 2559 9.2. IPv4 Traceroute 2561 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2562 ICMP Time Exceeded messages only include the invoking IP header and 8 2563 bytes that follow the IP header. Therefore, when a core router sends 2564 an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP 2565 payload is the encapsulated header it prepended followed by a UDP 2566 header. The original invoking IP header, and therefore the identity 2567 of the traceroute source is lost. 2569 The solution we propose to solve this problem is to cache traceroute 2570 IPv4 headers in the ITR and to match them up with corresponding IPv4 2571 Time Exceeded messages received from core routers and the ETR. The 2572 ITR will use a circular buffer for caching the IPv4 and UDP headers 2573 of traceroute packets. It will select a 16-bit number as a key to 2574 find them later when the IPv4 Time Exceeded messages are received. 2575 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2576 16-bit number as the UDP source port in the encapsulating header. 2577 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2578 header of the encapsulating header is present in the ICMP payload 2579 thereby allowing the ITR to find the cached headers for the 2580 traceroute source. The ITR puts the cached headers in the payload 2581 and sends the ICMP Time Exceeded message to the traceroute source 2582 retaining the source address of the original ICMP Time Exceeded 2583 message (a core router or the ETR of the site of the traceroute 2584 destination). 2586 The signature of a traceroute packet comes in two forms. The first 2587 form is encoded as a UDP message where the destination port is 2588 inspected for a range of values. The second form is encoded as an 2589 ICMP message where the IP identification field is inspected for a 2590 well-known value. 2592 9.3. Traceroute using Mixed Locators 2594 When either an IPv4 traceroute or IPv6 traceroute is originated and 2595 the ITR encapsulates it in the other address family header, you 2596 cannot get all 3 segments of the traceroute. Segment 2 of the 2597 traceroute can not be conveyed to the traceroute source since it is 2598 expecting addresses from intermediate hops in the same address format 2599 for the type of traceroute it originated. Therefore, in this case, 2600 segment 2 will make the tunnel look like one hop. All the ITR has to 2601 do to make this work is to not copy the inner TTL to the outer, 2602 encapsulating header's TTL when a traceroute packet is encapsulated 2603 using an RLOC from a different address family. This will cause no 2604 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2606 10. Mobility Considerations 2608 There are several kinds of mobility of which only some might be of 2609 concern to LISP. Essentially they are as follows. 2611 10.1. Site Mobility 2613 A site wishes to change its attachment points to the Internet, and 2614 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2615 providers. Changes in EID-RLOC mappings for sites are expected to be 2616 handled by configuration, outside of the LISP protocol. 2618 10.2. Slow Endpoint Mobility 2620 An individual endpoint wishes to move, but is not concerned about 2621 maintaining session continuity. Renumbering is involved. LISP can 2622 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2623 decoupling the address space used by a site from the address spaces 2624 used by its ISPs. [RFC4984] 2626 10.3. Fast Endpoint Mobility 2628 Fast endpoint mobility occurs when an endpoint moves relatively 2629 rapidly, changing its IP layer network attachment point. Maintenance 2630 of session continuity is a goal. This is where the Mobile IPv4 2631 [RFC3344bis] and Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used, 2632 and primarily where interactions with LISP need to be explored. 2634 The problem is that as an endpoint moves, it may require changes to 2635 the mapping between its EID and a set of RLOCs for its new network 2636 location. When this is added to the overhead of mobile IP binding 2637 updates, some packets might be delayed or dropped. 2639 In IPv4 mobility, when an endpoint is away from home, packets to it 2640 are encapsulated and forwarded via a home agent which resides in the 2641 home area the endpoint's address belongs to. The home agent will 2642 encapsulate and forward packets either directly to the endpoint or to 2643 a foreign agent which resides where the endpoint has moved to. 2644 Packets from the endpoint may be sent directly to the correspondent 2645 node, may be sent via the foreign agent, or may be reverse-tunneled 2646 back to the home agent for delivery to the mobile node. As the 2647 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2648 mappings are required for communication between the mobile node and 2649 the home agent, whether via foreign agent or not. As a mobile 2650 endpoint changes networks, up to three LISP mapping changes may be 2651 required: 2653 o The mobile node moves from an old location to a new visited 2654 network location and notifies its home agent that it has done so. 2655 The Mobile IPv4 control packets the mobile node sends pass through 2656 one of the new visited network's ITRs, which needs a EID-RLOC 2657 mapping for the home agent. 2659 o The home agent might not have the EID-RLOC mappings for the mobile 2660 node's "care-of" address or its foreign agent in the new visited 2661 network, in which case it will need to acquire them. 2663 o When packets are sent directly to the correspondent node, it may 2664 be that no traffic has been sent from the new visited network to 2665 the correspondent node's network, and the new visited network's 2666 ITR will need to obtain an EID-RLOC mapping for the correspondent 2667 node's site. 2669 In addition, if the IPv4 endpoint is sending packets from the new 2670 visited network using its original EID, then LISP will need to 2671 perform a route-returnability check on the new EID-RLOC mapping for 2672 that EID. 2674 In IPv6 mobility, packets can flow directly between the mobile node 2675 and the correspondent node in either direction. The mobile node uses 2676 its "care-of" address (EID). In this case, the route-returnability 2677 check would not be needed but one more LISP mapping lookup may be 2678 required instead: 2680 o As above, three mapping changes may be needed for the mobile node 2681 to communicate with its home agent and to send packets to the 2682 correspondent node. 2684 o In addition, another mapping will be needed in the correspondent 2685 node's ITR, in order for the correspondent node to send packets to 2686 the mobile node's "care-of" address (EID) at the new network 2687 location. 2689 When both endpoints are mobile the number of potential mapping 2690 lookups increases accordingly. 2692 As a mobile node moves there are not only mobility state changes in 2693 the mobile node, correspondent node, and home agent, but also state 2694 changes in the ITRs and ETRs for at least some EID-prefixes. 2696 The goal is to support rapid adaptation, with little delay or packet 2697 loss for the entire system. Also IP mobility can be modified to 2698 require fewer mapping changes. In order to increase overall system 2699 performance, there may be a need to reduce the optimization of one 2700 area in order to place fewer demands on another. 2702 In LISP, one possibility is to "glean" information. When a packet 2703 arrives, the ETR could examine the EID-RLOC mapping and use that 2704 mapping for all outgoing traffic to that EID. It can do this after 2705 performing a route-returnability check, to ensure that the new 2706 network location does have a internal route to that endpoint. 2707 However, this does not cover the case where an ITR (the node assigned 2708 the RLOC) at the mobile-node location has been compromised. 2710 Mobile IP packet exchange is designed for an environment in which all 2711 routing information is disseminated before packets can be forwarded. 2712 In order to allow the Internet to grow to support expected future 2713 use, we are moving to an environment where some information may have 2714 to be obtained after packets are in flight. Modifications to IP 2715 mobility should be considered in order to optimize the behavior of 2716 the overall system. Anything which decreases the number of new EID- 2717 RLOC mappings needed when a node moves, or maintains the validity of 2718 an EID-RLOC mapping for a longer time, is useful. 2720 10.4. Fast Network Mobility 2722 In addition to endpoints, a network can be mobile, possibly changing 2723 xTRs. A "network" can be as small as a single router and as large as 2724 a whole site. This is different from site mobility in that it is 2725 fast and possibly short-lived, but different from endpoint mobility 2726 in that a whole prefix is changing RLOCs. However, the mechanisms 2727 are the same and there is no new overhead in LISP. A map request for 2728 any endpoint will return a binding for the entire mobile prefix. 2730 If mobile networks become a more common occurrence, it may be useful 2731 to revisit the design of the mapping service and allow for dynamic 2732 updates of the database. 2734 The issue of interactions between mobility and LISP needs to be 2735 explored further. Specific improvements to the entire system will 2736 depend on the details of mapping mechanisms. Mapping mechanisms 2737 should be evaluated on how well they support session continuity for 2738 mobile nodes. 2740 10.5. LISP Mobile Node Mobility 2742 A mobile device can use the LISP infrastructure to achieve mobility 2743 by implementing the LISP encapsulation and decapsulation functions 2744 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2745 node" can use topologically-independent EID IP addresses that are not 2746 advertised into and do not impose a cost on the global routing 2747 system. These EIDs are maintained at the edges of the mapping system 2748 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2749 only the correspondents of the LISP mobile node. 2751 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2752 more details. 2754 11. Multicast Considerations 2756 A multicast group address, as defined in the original Internet 2757 architecture is an identifier of a grouping of topologically 2758 independent receiver host locations. The address encoding itself 2759 does not determine the location of the receiver(s). The multicast 2760 routing protocol, and the network-based state the protocol creates, 2761 determines where the receivers are located. 2763 In the context of LISP, a multicast group address is both an EID and 2764 a Routing Locator. Therefore, no specific semantic or action needs 2765 to be taken for a destination address, as it would appear in an IP 2766 header. Therefore, a group address that appears in an inner IP 2767 header built by a source host will be used as the destination EID. 2768 The outer IP header (the destination Routing Locator address), 2769 prepended by a LISP router, will use the same group address as the 2770 destination Routing Locator. 2772 Having said that, only the source EID and source Routing Locator 2773 needs to be dealt with. Therefore, an ITR merely needs to put its 2774 own IP address in the source Routing Locator field when prepending 2775 the outer IP header. This source Routing Locator address, like any 2776 other Routing Locator address MUST be globally routable. 2778 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2779 ITR when a received data packet is a multicast data packet or when 2780 processing a source-specific Join (either by IGMPv3 or PIM). But the 2781 source Routing Locator is decided by the multicast routing protocol 2782 in a receiver site. That is, an EID to Routing Locator translation 2783 is done at control-time. 2785 Another approach is to have the ITR not encapsulate a multicast 2786 packet and allow the host built packet to flow into the core even if 2787 the source address is allocated out of the EID namespace. If the 2788 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2789 routers can RPF to the ITR (the Locator address which is injected 2790 into core routing) rather than the host source address (the EID 2791 address which is not injected into core routing). 2793 To avoid any EID-based multicast state in the network core, the first 2794 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2795 and Interworking with non-LISP sites is described in specification 2796 [MLISP]. 2798 12. Security Considerations 2800 It is believed that most of the security mechanisms will be part of 2801 the mapping database service when using control plane procedures for 2802 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2803 as described in this specification, protection is provided against 2804 ETR spoofing by using Return- Routability mechanisms evidenced by the 2805 use of a 24-bit Nonce field in the LISP encapsulation header and a 2806 64-bit Nonce field in the LISP control message. The nonce, coupled 2807 with the ITR accepting only solicited Map-Replies goes a long way 2808 toward providing decent authentication. 2810 LISP does not rely on a PKI infrastructure or a more heavy weight 2811 authentication system. These systems challenge the scalability of 2812 LISP which was a primary design goal. 2814 DoS attack prevention will depend on implementations rate-limiting 2815 Map-Requests and Map-Replies to the control plane as well as rate- 2816 limiting the number of data-triggered Map-Replies. 2818 An incorrectly implemented or malicious ITR might choose to ignore 2819 the priority and weights provided by the ETR in its Map-Reply. This 2820 traffic steering would be limited to the traffic that is sent by this 2821 ITR's site, and no more severe than if the site initiated a bandwidth 2822 DoS attack on (one of) the ETR's ingress links. The ITR's site would 2823 typically gain no benefit from not respecting the weights, and would 2824 likely to receive better service by abiding by them. 2826 To deal with map-cache exhaustion attempts in an ITR/PTR, the 2827 implementation should consider putting a maximum cap on the number of 2828 entries stored with a reserve list for special or frequently accessed 2829 sites. This should be a configuration policy control set by the 2830 network administrator who manages ITRs and PTRs. When overlapping 2831 EID-prefixes occur across multiple map-cache entries, the integrity 2832 of the set must be wholly maintained. So if a more-specific entry 2833 cannot be added due to reaching the maximum cap, then none of the 2834 less specifics should be stored in the map-cache. 2836 Given that the ITR/PTR maintains a cache of EID-to-RLOC mappings, 2837 cache sizing and maintenance is an issue to be kept in mind during 2838 implementation. It is a good idea to have instrumentation in place 2839 to detect thrashing of the cache. Implementation experimentation 2840 will be used to determine which cache management strategies work 2841 best. It should be noted that an undersized cache in an ITR/PTR not 2842 only causes adverse affect on the site or region they support, but 2843 may also cause increased Map-Request load on the mapping system. 2845 There is a security risk implicit in the fact that ETRs generate the 2846 EID prefix to which they are responding. An ETR can claim a shorter 2847 prefix than it is actually responsible for. Various mechanisms to 2848 ameliorate or resolve this issue will be examined in the future, 2849 [LISP-SEC]. 2851 Spoofing of inner header addresses of LISP encapsulated packets is 2852 possible like with any tunneling mechanism. ITRs MUST verify the 2853 source address of a packet to be an EID that belongs to the site's 2854 EID-prefix range prior to encapsulation. An ETR must only 2855 decapsulate and forward datagrams with an inner header destination 2856 that matches one of its EID-prefix ranges. If, upon receipt and 2857 decapsulation, the destination EID of a datagram does not match one 2858 of the ETR's configured EID-prefixes, the ETR MUST drop the 2859 datragram. If a LISP encapsulated packet arrives at an ETR, it MAY 2860 compare the inner header source EID address and the outer header 2861 source RLOC address with the mapping that exists in the mapping 2862 database. Then when spoofing attacks occur, the outer header source 2863 RLOC address can be used to trace back the attack to the source site, 2864 using existing operational tools. 2866 This experimental specification does not address automated key 2867 management (AKM). BCP 107 provides guidance in this area. In 2868 addition, at the time of this writing, substantial work is being 2869 undertaken to improve security of the routing system [KARP], [RPKI], 2870 [BGP-SEC], [LISP-SEC], Future work on LISP should address BCP-107 as 2871 well as other open security considerations, which may require changes 2872 to this specification. 2874 13. Network Management Considerations 2876 Considerations for Network Management tools exist so the LISP 2877 protocol suite can be operationally managed. The mechanisms can be 2878 found in [LISP-MIB] and [LISP-LIG]. 2880 14. IANA Considerations 2882 This section provides guidance to the Internet Assigned Numbers 2883 Authority (IANA) regarding registration of values related to the LISP 2884 specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. 2886 There are two name spaces in LISP that require registration: 2888 o LISP IANA registry allocations should not be made for purposes 2889 unrelated to LISP routing or transport protocols. 2891 o The following policies are used here with the meanings defined in 2892 BCP 26: "Specification Required", "IETF Consensus", "Experimental 2893 Use", "First Come First Served". 2895 14.1. LISP Address Type Codes 2897 Instance ID type codes have a range from 0 to 15, of which 0 and 1 2898 have been allocated [LCAF]. New Type Codes MUST be allocated 2899 starting at 2. Type Codes 2 - 10 are to be assigned by IETF Review. 2900 Type Codes 11 - 15 are available on a First Come First Served policy. 2902 The following codes have been allocated: 2904 Type 0: Null Body Type 2906 Type 1: AFI List Type 2908 See [LCAF] for details for other possible unapproved address 2909 encodings. The unapproved LCAF encodings are an area for further 2910 study and experimentation. 2912 14.2. LISP UDP Port Numbers 2914 The IANA registry has allocated UDP port numbers 4341 and 4342 for 2915 LISP data-plane and control-plane operation, respectively. 2917 15. References 2919 15.1. Normative References 2921 [BGP-SEC] Lepinski, M., "An Overview of BGPSEC", 2922 draft-lepinski-bgpsec-overview-00.txt (work in progress), 2923 March 2011. 2925 [KARP] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 2926 Routing Protocols (KARP)Design Guidelines", 2927 draft-ietf-karp-design-guide-02.txt (work in progress), 2928 March 2011. 2930 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 2931 August 1980. 2933 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 2934 STD 13, RFC 1034, November 1987. 2936 [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700, 2937 October 1994. 2939 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 2940 E. Lear, "Address Allocation for Private Internets", 2941 BCP 5, RFC 1918, February 1996. 2943 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2944 Requirement Levels", BCP 14, RFC 2119, March 1997. 2946 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 2947 ESP and AH", RFC 2404, November 1998. 2949 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 2950 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 2951 March 2000. 2953 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 2954 via IPv4 Clouds", RFC 3056, February 2001. 2956 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 2957 of Explicit Congestion Notification (ECN) to IP", 2958 RFC 3168, September 2001. 2960 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 2961 A., Peterson, J., Sparks, R., Handley, M., and E. 2962 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 2963 June 2002. 2965 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 2966 in IPv6", RFC 3775, June 2004. 2968 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 2969 Requirements for Security", BCP 106, RFC 4086, June 2005. 2971 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 2972 (CIDR): The Internet Address Assignment and Aggregation 2973 Plan", BCP 122, RFC 4632, August 2006. 2975 [RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 2976 (SHA and HMAC-SHA)", RFC 4634, July 2006. 2978 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 2979 Optimization for Mobile IPv6", RFC 4866, May 2007. 2981 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 2982 Workshop on Routing and Addressing", RFC 4984, 2983 September 2007. 2985 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2986 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2987 May 2008. 2989 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 2990 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 2992 [RPKI] Lepinski, M., "An Infrastructure to Support Secure 2993 Internet Routing", draft-ietf-sidr-arch-12.txt (work in 2994 progress), February 2011. 2996 [UDP-TUNNELS] 2997 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 2998 Packets", draft-eubanks-chimento-6man-01.txt (work in 2999 progress), October 2010. 3001 15.2. Informative References 3003 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3004 NUMBERS 3005 http://www.iana.org/assignments/address-family-numbers, 3006 January 2011. 3008 [AFI-REGISTRY] 3009 IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 3010 NUMBER registry http://www.iana.org/assignments/ 3011 address-family-numbers/ 3012 address-family-numbers.xml#address-family-numbers-1, 3013 January 2011. 3015 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 3016 Alternative Topology (LISP-ALT)", 3017 draft-ietf-lisp-alt-07.txt (work in progress), June 2011. 3019 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 3020 Enhancement to the Internet Architecture", Internet- 3021 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt, 3022 1999. 3024 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 3025 Content distribution Overlay Network Service for LISP", 3026 draft-meyer-lisp-cons-03.txt (work in progress), 3027 November 2007. 3029 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 3030 Mappings Multicast Across Cooperating Systems for LISP", 3031 draft-curran-lisp-emacs-00.txt (work in progress), 3032 November 2007. 3034 [INTERWORK] 3035 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 3036 "Interworking LISP with IPv4 and IPv6", 3037 draft-ietf-lisp-interworking-02.txt (work in progress), 3038 June 2011. 3040 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 3041 Address Format", draft-farinacci-lisp-lcaf-04.txt (work in 3042 progress), October 2010. 3044 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 3045 "Renumbering: Threat or Menace?", Usenix , September 1996. 3047 [LISP-DEPLOY] 3048 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 3049 "LISP Network Element Deployment Considerations", 3050 draft-jakab-lisp-deployment-02.txt (work in progress), 3051 February 2011. 3053 [LISP-LIG] 3054 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 3055 draft-ietf-lisp-lig-01.txt (work in progress), 3056 October 2010. 3058 [LISP-MAIN] 3059 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 3060 "Locator/ID Separation Protocol (LISP)", 3061 draft-farinacci-lisp-12.txt (work in progress), 3062 March 2009. 3064 [LISP-MIB] 3065 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 3066 draft-ietf-lisp-mib-01.txt (work in progress), March 2011. 3068 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 3069 Mobility Architecture", draft-meyer-lisp-mn-04.txt (work 3070 in progress), October 2010. 3072 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 3073 draft-ietf-lisp-ms-09.txt (work in progress), June 2011. 3075 [LISP-SEC] 3076 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 3077 Bonaventure, "LISP-Security (LISP-SEC)", 3078 draft-ietf-lisp-sec-00.txt (work in progress), June 2011. 3080 [LOC-ID-ARCH] 3081 Meyer, D. and D. Lewis, "Architectural Implications of 3082 Locator/ID Separation", 3083 draft-meyer-loc-id-implications-01.txt (work in progress), 3084 Januaryr 2009. 3086 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 3087 "LISP for Multicast Environments", 3088 draft-ietf-lisp-multicast-06.txt (work in progress), 3089 June 2011. 3091 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 3092 draft-lear-lisp-nerd-08.txt (work in progress), 3093 March 2010. 3095 [OPENLISP] 3096 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 3097 Report", draft-iannone-openlisp-implementation-01.txt 3098 (work in progress), July 2008. 3100 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 3101 draft-narten-radir-problem-statement-00.txt (work in 3102 progress), July 2007. 3104 [RFC3344bis] 3105 Perkins, C., "IP Mobility Support for IPv4, revised", 3106 draft-ietf-mip4-rfc3344bis-05 (work in progress), 3107 July 2007. 3109 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 3110 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 3111 September 2005. 3113 [RPMD] Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol 3114 for Routing Protocol Meta-data Dissemination", 3115 draft-handley-p2ppush-unpublished-2007726.txt (work in 3116 progress), July 2007. 3118 [VERSIONING] 3119 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3120 Versioning", draft-ietf-lisp-map-versioning-01.txt (work 3121 in progress), March 2011. 3123 Appendix A. Acknowledgments 3125 An initial thank you goes to Dave Oran for planting the seeds for the 3126 initial ideas for LISP. His consultation continues to provide value 3127 to the LISP authors. 3129 A special and appreciative thank you goes to Noel Chiappa for 3130 providing architectural impetus over the past decades on separation 3131 of location and identity, as well as detailed review of the LISP 3132 architecture and documents, coupled with enthusiasm for making LISP a 3133 practical and incremental transition for the Internet. 3135 The authors would like to gratefully acknowledge many people who have 3136 contributed discussion and ideas to the making of this proposal. 3137 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3138 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3139 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3140 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3141 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3142 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3143 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3144 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3145 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3146 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3147 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3148 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3149 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3150 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3151 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3152 Clarence Filsfils, and Alia Atlas. 3154 This work originated in the Routing Research Group (RRG) of the IRTF. 3155 The individual submission [LISP-MAIN] was converted into this IETF 3156 LISP working group draft. 3158 Appendix B. Document Change Log 3160 B.1. Changes to draft-ietf-lisp-14.txt 3162 o Post working group last call and pre-IESG last call review. 3164 o Indicate that an ICMP Unreachable message should be sent when a 3165 packet matches a drop-based negative map-cache entry. 3167 o Indicate how a map-cache set of overlapping EID-prefixes must 3168 maintian integrity when the map-cache maximum cap is reached. 3170 o Add Joel's description for the definition of an EID, that the bit 3171 string value can be an RLOC for another device in abstract but the 3172 architecture allows it to be an EID of one device and the same 3173 value as an RLOC for another device. 3175 o In the "Tunnel Encapsulation Details" section, indicate that 4 3176 combinations of encapsulation are supported. 3178 o Add what ETR should do for a Data-Probe when received for a 3179 destination EID outside of its EID-prefix range. This was added 3180 in the Data Probe definition section. 3182 o Added text indicating that more-specific EID-prefixes must not be 3183 removed when less-specific entries stay in the map-cache. This is 3184 to preserve the integrity of the EID-prefix set. 3186 o Add clarifying text in the Security Considerations section about 3187 how an ETR must not decapsulate and forward a packet that is not 3188 for its configured EID-prefix range. 3190 B.2. Changes to draft-ietf-lisp-13.txt 3192 o Posted June 2011 to complete working group last call. 3194 o Tracker item 87. Put Yakov suggested wording in the EID-prefix 3195 definition section to reference [INTERWORK] and [LISP-DEPLOY] 3196 about discussion on transition and access mechanisms. 3198 o Change "ITRs" to "ETRs" in the Locator Status Bit definition 3199 section and data packet description section per Damien's comment. 3201 o Remove the normative reference to [LISP-SEC] when describing the 3202 S-bit in the ECM and Map-Reply headers. 3204 o Tracker item 54. Added text from John Scudder in the "Packets 3205 Egressing a LISP Site" section. 3207 o Add sentence to the "Reencapsulating Tunnel" definition about how 3208 reencapsulation loops can occur when not coordinating among 3209 multiple mapping database systems. 3211 o Remove "In theory" from a sentence in the Security Considerations 3212 section. 3214 o Remove Security Area Statement title and reword section with 3215 Eliot's provided text. The text was agreed upon by LISP-WG chairs 3216 and Security ADs. 3218 o Remove word "potential" from the over-claiming paragraph of the 3219 Security Considerations section per Stephen's request. 3221 o Wordsmithing and other editorial comments from Alia. 3223 B.3. Changes to draft-ietf-lisp-12.txt 3225 o Posted April 2011. 3227 o Tracker item 87. Provided rewording how an EID-prefix can be 3228 resued in the definition section of "EID-prefix". 3230 o Tracker item 95. Change "eliminate" to "defer" in section 4.1. 3232 o Tracker item 110. Added that the Mapping Protocol Data field in 3233 the Map-Reply message is only used when needed by the particular 3234 Mapping Database System. 3236 o Tracker item 111. Indicate that if an LSB that is assocaited with 3237 an anycast address, that there is at least one RLOC that is up. 3239 o Tracker item 108. Make clear the R-bit does not define RLOC path 3240 reachability. 3242 o Tracker item 107. Indicate that weights are relative to each 3243 other versus requiring an addition of up to 100%. 3245 o Tracker item 46. Add a sentence how LISP products should be sized 3246 for the appropriate demand so cache thrashing is avoided. 3248 o Change some references of RFC 5226 to [AFI] per Luigi. 3250 o Per Luigi, make reference to "EID-AFI" consistent to "EID-prefix- 3251 AFI". 3253 o Tracker item 66. Indicate that appending locators to a locator- 3254 set is done when the added locators are lexicographically greater 3255 than the previous ones in the set. 3257 o Tracker item 87. Once again reword the definition of the EID- 3258 prefix to reflect recent comments. 3260 o Tracker item 70. Added text to security section on what the 3261 implications could be if an ITR does not obey priority and weights 3262 from a Map-Reply message. 3264 o Tracker item 54. Added text to the new section titled "Packets 3265 Egressing a LISP Site" to describe the implications when two or 3266 more ITRs exist at a site where only one ITR is used for egress 3267 traffic and when there is a shift of traffic to the others, how 3268 the map-cache will need to be populated in those new egress ITRs. 3270 o Tracker item 33. Make more clear in the Routing Locator Selection 3271 section what an ITR should do when it sees an R-bit of 0 in a 3272 locator-record of a Map-Reply. 3274 o Tracker item 33. Add paragraph to the EID Reachability section 3275 indicating that site parittioning is under investigation. 3277 o Tracker item 58. Added last paragraph of Security Considerations 3278 section about how to protect inner header EID address spoofing 3279 attacks. 3281 o Add suggested Sam text to indicate that all security concerns need 3282 not be addressed for moving document to Experimental RFC status. 3283 Put this in a subsection of the Secuirty Considerations section. 3285 B.4. Changes to draft-ietf-lisp-11.txt 3287 o Posted March 30, 2011. 3289 o Change IANA URL. The URL we had pointed to a general protocol 3290 numbers page. 3292 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3293 Requests to be sent to a MN ETR via the map-server. 3295 o Generalize text for the defintion of Reencapsuatling tunnels. 3297 o Add pargraph suggested by Joel to explain how implementation 3298 experimentation will be used to determine the proper cache 3299 management techniques. 3301 o Add Yakov provided text for the definition of "EID-to-RLOC 3302 "Database". 3304 o Add reference in Section 8, Deployment Scenarios, to the 3305 draft-jakab-lisp-deploy-02.txt draft. 3307 o Clarify sentence about no hardware changes needed to support LISP 3308 encapsulation. 3310 o Add paragraph about what is the procedure when a locator is 3311 inserted in the middle of a locator-set. 3313 o Add a definition for Locator-Status-Bits so we can emphasize they 3314 are used as a hint for router up/down status and not path 3315 reachability. 3317 o Change "BGP RIB" to "RIB" per Clarence's comment. 3319 o Fixed complaints by IDnits. 3321 o Add subsection to Security Considerations section indicating how 3322 EID-prefix overclaiming in Map-Replies is for further study and 3323 add a reference to LISP-SEC. 3325 B.5. Changes to draft-ietf-lisp-10.txt 3327 o Posted March 2011. 3329 o Add p-bit to Map-Request so there is documentary reasons to know 3330 when a PITR has sent a Map-Request to an ETR. 3332 o Add Map-Notify message which is used to acknowledge a Map-Register 3333 message sent to a Map-Server. 3335 o Add M-bit to the Map-Register message so an ETR that wants an 3336 acknowledgment for the Map-Register can request one. 3338 o Add S-bit to the ECM and Map-Reply messages to describe security 3339 data that can be present in each message. Then refer to 3340 [LISP-SEC] for expansive details. 3342 o Add Network Management Considerations section and point to the MIB 3343 and LIG drafts. 3345 o Remove the word "simple" per Yakov's comments. 3347 B.6. Changes to draft-ietf-lisp-09.txt 3349 o Posted October 2010. 3351 o Add to IANA Consideration section about the use of LCAF Type 3352 values that accepted and maintained by the IANA registry and not 3353 the LCAF specification. 3355 o Indicate that implementations should be able to receive LISP 3356 control messages when either UDP port is 4342, so they can be 3357 robust in the face of intervening NAT boxes. 3359 o Add paragraph to SMR section to indicate that an ITR does not need 3360 to respond to an SMR-based Map-Request when it has no map-cache 3361 entry for the SMR source's EID-prefix. 3363 B.7. Changes to draft-ietf-lisp-08.txt 3365 o Posted August 2010. 3367 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3368 Register messages. 3370 o Clarify language in section 6.1.5 about Map-Replying to Data- 3371 Probes or Map-Requests. 3373 o Indicate that outer TTL should only be copied to inner TTL when it 3374 is less than inner TTL. 3376 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3377 value of 0. 3379 o Indicate that SMRs can have a global or per SMR destination rate- 3380 limiter. 3382 o Add clarifications to the SMR procedures. 3384 o Add definitions for "client-side" and 'server-side" terms used in 3385 this specification. 3387 o Clear up language in section 6.4, last paragraph. 3389 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3390 probe a PETR and have it return a Map-Reply with a locator-set of 3391 size 0. The way it is spec'ed the map-cache entry has action 3392 "dropped". Drop-action is set to 3. 3394 o Add statement about normalizing locator weights. 3396 o Clarify R-bit definition in the Map-Reply locator record. 3398 o Add section on EID Reachability within a LISP site. 3400 o Clarify another disadvantage of using anycast locators. 3402 o Reworded Abstract. 3404 o Change section 2.0 Introduction to remove obsolete information 3405 such as the LISP variant definitions. 3407 o Change section 5 title from "Tunneling Details" to "LISP 3408 Encapsulation Details". 3410 o Changes to section 5 to include results of network deployment 3411 experience with MTU. Recommend that implementations use either 3412 the stateful or stateless handling. 3414 o Make clarification wordsmithing to Section 7 and 8. 3416 o Identify that if there is one locator in the locator-set of a map- 3417 cache entry, that an SMR from that locator should be responded to 3418 by sending the the SMR-invoked Map-Request to the database mapping 3419 system rather than to the RLOC itself (which may be unreachable). 3421 o When describing Unicast and Multicast Weights indicate the the 3422 values are relative weights rather than percentages. So it 3423 doesn't imply the sum of all locator weights in the locator-set 3424 need to be 100. 3426 o Do some wordsmithing on copying TTL and TOS fields. 3428 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3429 combed the spec. 3431 o Removed Section 14 "Prototype Plans and Status". We felt this 3432 type of section is no longer appropriate for a protocol 3433 specification. 3435 o Add clarification text for the IRC description per Damien's 3436 commentary. 3438 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3439 per Vina's comment about a possible DoS vector. 3441 o Clarify (S/2 + H) in the stateless MTU section. 3443 o Add text to reflect Damien's comment about the description of the 3444 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3445 addresses are local addresses of the Map-Requester. 3447 B.8. Changes to draft-ietf-lisp-07.txt 3449 o Posted April 2010. 3451 o Added I-bit to data header so LSB field can also be used as an 3452 Instance ID field. When this occurs, the LSB field is reduced to 3453 8-bits (from 32-bits). 3455 o Added V-bit to the data header so the 24-bit nonce field can also 3456 be used for source and destination version numbers. 3458 o Added Map-Version 12-bit value to the EID-record to be used in all 3459 of Map-Request, Map-Reply, and Map-Register messages. 3461 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3462 can decide what address to select for the destination of a Map- 3463 Reply. 3465 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3466 the Locator-Set record of an EID-record for a Map-Reply message. 3467 The L-bit indicates which RLOCs in the locator-set are local to 3468 the sender of the message. The P-bit indicates which RLOC is the 3469 source of a RLOC-probe Reply (Map-Reply) message. 3471 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3473 o Made editorial and clarification changes based on comments from 3474 Dhirendra Trivedi. 3476 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3478 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3479 6.3.1. 3481 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3482 for Map-Register messages. 3484 o Add NAT section per Ron Bonica comments. 3486 o Fix IDnits issues per Ron Bonica. 3488 o Added section on Virtualization and Segmentation to explain the 3489 use if the Instance ID field in the data header. 3491 o There are too many P-bits, keep their scope to the packet format 3492 description and refer to them by name every where else in the 3493 spec. 3495 o Scanned all occurrences of "should", "should not", "must" and 3496 "must not" and uppercased them. 3498 o John Zwiebel offered text for section 4.1 to modernize the 3499 example. Thanks Z! 3501 o Make it more clear in the definition of "EID-to-RLOC Database" 3502 that all ETRs need to have the same database mapping. This 3503 reflects a comment from John Scudder. 3505 o Add a definition "Route-returnability" to the Definition of Terms 3506 section. 3508 o In section 9.2, add text to describe what the signature of 3509 traceroute packets can look like. 3511 o Removed references to Data Probe for introductory example. Data- 3512 probes are still part of the LISP design but not encouraged. 3514 o Added the definition for "LISP site" to the Definition of Terms" 3515 section. 3517 B.9. Changes to draft-ietf-lisp-06.txt 3519 Editorial based changes: 3521 o Posted December 2009. 3523 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3525 o Add text to indicate that Map-Register messages must contain a 3526 computed UDP checksum. 3528 o Add definitions for PITR and PETR. 3530 o Indicate an AFI value of 0 is an unspecified address. 3532 o Indicate that the TTL field of a Map-Register is not used and set 3533 to 0 by the sender. This change makes this spec consistent with 3534 [LISP-MS]. 3536 o Change "... yield a packet size of L bytes" to "... yield a packet 3537 size greater than L bytes". 3539 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3540 Reply messages. 3542 o Clarify that LSBs that go beyond the number of locators do not to 3543 be SMRed when the locator addresses are greater lexicographically 3544 than the locator in the existing locator-set. 3546 o Add Gregg, Srini, and Amit to acknowledgment section. 3548 o Clarify in the definition of a LISP header what is following the 3549 UDP header. 3551 o Clarify "verifying Map-Request" text in section 6.1.3. 3553 o Add Xu Xiaohu to the acknowledgment section for introducing the 3554 problem of overlapping EID-prefixes among multiple sites in an RRG 3555 email message. 3557 Design based changes: 3559 o Use stronger language to have the outer IPv4 header set DF=1 so we 3560 can avoid fragment reassembly in an ETR or PETR. This will also 3561 make IPv4 and IPv6 encapsulation have consistent behavior. 3563 o Map-Requests should not be sent in ECM with the Probe bit is set. 3564 These type of Map-Requests are used as RLOC-probes and are sent 3565 directly to locator addresses in the underlying network. 3567 o Add text in section 6.1.5 about returning all EID-prefixes in a 3568 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3569 configure. 3571 o Add text in a new subsection of section 6.1.5 about dealing with 3572 Map-Replies with coarse EID-prefixes. 3574 B.10. Changes to draft-ietf-lisp-05.txt 3576 o Posted September 2009. 3578 o Added this Document Change Log appendix. 3580 o Added section indicating that encapsulated Map-Requests must use 3581 destination UDP port 4342. 3583 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3584 data in Map-Register payload. 3586 o Added Jari to acknowledgment section. 3588 o State the source-EID is set to 0 when using Map-Requests to 3589 refresh or RLOC-probe. 3591 o Make more clear what source-RLOC should be for a Map-Request. 3593 o The LISP-CONS authors thought that the Type definitions for CONS 3594 should be removed from this specification. 3596 o Removed nonce from Map-Register message, it wasn't used so no need 3597 for it. 3599 o Clarify what to do for unspecified Action bits for negative Map- 3600 Replies. Since No Action is a drop, make value 0 Drop. 3602 B.11. Changes to draft-ietf-lisp-04.txt 3604 o Posted September 2009. 3606 o How do deal with record count greater than 1 for a Map-Request. 3607 Damien and Joel comment. Joel suggests: 1) Specify that senders 3608 compliant with the current document will always set the count to 3609 1, and note that the count is included for future extensibility. 3610 2) Specify what a receiver compliant with the draft should do if 3611 it receives a request with a count greater than 1. Presumably, it 3612 should send some error back? 3614 o Add Fred Templin in acknowledgment section. 3616 o Add Margaret and Sam to the acknowledgment section for their great 3617 comments. 3619 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3621 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3622 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3623 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3624 ignore the checksum completely. And of course we'd need to 3625 confirm that can actually be implemented. In particular, hardware 3626 that verifies UDP checksums on receive needs to be checked to make 3627 sure it permits 0 checksums." 3629 o Margaret wants a reference to 3630 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3632 o Fix description in Map-Request section. Where we describe Map- 3633 Reply Record, change "R-bit" to "M-bit". 3635 o Add the mobility bit to Map-Replies. So PTRs don't probe so often 3636 for MNs but often enough to get mapping updates. 3638 o Indicate SHA1 can be used as well for Map-Registers. 3640 o More Fred comments on MTU handling. 3642 o Isidor comment about spec'ing better periodic Map-Registers. Will 3643 be fixed in draft-ietf-lisp-ms-02.txt. 3645 o Margaret's comment on gleaning: "The current specification does 3646 not make it clear how long gleaned map entries should be retained 3647 in the cache, nor does it make it clear how/ when they will be 3648 validated. The LISP spec should, at the very least, include a 3649 (short) default lifetime for gleaned entries, require that they be 3650 validated within a short period of time, and state that a new 3651 gleaned entry should never overwrite an entry that was obtained 3652 from the mapping system. The security implications of storing 3653 "gleaned" entries should also be explored in detail." 3655 o Add section on RLOC-probing per working group feedback. 3657 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3658 Noel. 3660 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3661 control plane only. 3663 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3664 fields can be turned off and used for another future purpose. For 3665 Luigi et al versioning convergence. 3667 o Add a N-bit to the data header suggested by Noel. Then the nonce 3668 field could be used when N is not 1. 3670 o Clarify that when E-bit is 0, the nonce field can be an echoed 3671 nonce or a random nonce. Comment from Jesper. 3673 o Indicate when doing data-gleaning that a verifying Map-Request is 3674 sent to the source-EID of the gleaned data packet so we can avoid 3675 map-cache corruption by a 3rd party. Comment from Pedro. 3677 o Indicate that a verifying Map-Request, for accepting mapping data, 3678 should be sent over the ALT (or to the EID). 3680 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3682 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3683 noncing. Comment by Pedro and Dino. 3685 o Jesper made a comment to loosen the language about requiring the 3686 copy of inner TTL to outer TTL since the text to get mixed-AF 3687 traceroute to work would violate the "MUST" clause. Changed from 3688 MUST to SHOULD in section 5.3. 3690 B.12. Changes to draft-ietf-lisp-03.txt 3692 o Posted July 2009. 3694 o Removed loc-reach-bits longword from control packets per Damien 3695 comment. 3697 o Clarifications in MTU text from Roque. 3699 o Added text to indicate that the locator-set be sorted by locator 3700 address from Isidor. 3702 o Clarification text from John Zwiebel in Echo-Nonce section. 3704 B.13. Changes to draft-ietf-lisp-02.txt 3706 o Posted July 2009. 3708 o Encapsulation packet format change to add E-bit and make loc- 3709 reach-bits 32-bits in length. 3711 o Added Echo-Nonce Algorithm section. 3713 o Clarification how ECN bits are copied. 3715 o Moved S-bit in Map-Request. 3717 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3718 RLOC-Probe Algorithm. 3720 o Added to Mobility section to reference [LISP-MN]. 3722 B.14. Changes to draft-ietf-lisp-01.txt 3724 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3726 o Defined LEID to be a "LISP EID". 3728 o Indicate encapsulation use IPv4 DF=0. 3730 o Added negative Map-Reply messages with drop, native-forward, and 3731 send-map-request actions. 3733 o Added Proxy-Map-Reply bit to Map-Register. 3735 B.15. Changes to draft-ietf-lisp-00.txt 3737 o Posted May 2009. 3739 o Rename of draft-farinacci-lisp-12.txt. 3741 o Acknowledgment to RRG. 3743 Authors' Addresses 3745 Dino Farinacci 3746 cisco Systems 3747 Tasman Drive 3748 San Jose, CA 95134 3749 USA 3751 Email: dino@cisco.com 3753 Vince Fuller 3754 cisco Systems 3755 Tasman Drive 3756 San Jose, CA 95134 3757 USA 3759 Email: vaf@cisco.com 3761 Dave Meyer 3762 cisco Systems 3763 170 Tasman Drive 3764 San Jose, CA 3765 USA 3767 Email: dmm@cisco.com 3769 Darrel Lewis 3770 cisco Systems 3771 170 Tasman Drive 3772 San Jose, CA 3773 USA 3775 Email: darlewis@cisco.com