idnits 2.17.1 draft-ietf-lisp-13.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 21, 2011) is 4690 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for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-karp-design-guide-02 ** Obsolete normative reference: RFC 1700 (Obsoleted by RFC 3232) ** Obsolete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 23, 2011 D. Lewis 6 cisco Systems 7 June 21, 2011 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-13 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 23, 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-13.txt . . . . . . . . . . . . 78 129 B.2. Changes to draft-ietf-lisp-12.txt . . . . . . . . . . . . 78 130 B.3. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 80 131 B.4. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 80 132 B.5. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 81 133 B.6. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 81 134 B.7. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 83 135 B.8. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 85 136 B.9. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 86 137 B.10. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 86 138 B.11. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 88 139 B.12. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 88 140 B.13. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 89 141 B.14. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 89 142 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 90 144 1. Requirements Notation 146 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 147 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 148 document are to be interpreted as described in [RFC2119]. 150 2. Introduction 152 This document describes the Locator/Identifier Separation Protocol 153 (LISP), which provides a set of functions for routers to exchange 154 information used to map from non-routeable Endpoint Identifiers 155 (EIDs) to routeable Routing Locators (RLOCs). It also defines a 156 mechanism for these LISP routers to encapsulate IP packets addressed 157 with EIDs for transmission across an Internet that uses RLOCs for 158 routing and forwarding. 160 Creation of LISP was initially motivated by discussions during the 161 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 162 October, 2006 (see [RFC4984]). A key conclusion of the workshop was 163 that the Internet routing and addressing system was not scaling well 164 in the face of the explosive growth of new sites; one reason for this 165 poor scaling is the increasing number of multi-homed and other sites 166 that cannot be addressed as part of topologically- or provider-based 167 aggregated prefixes. Additional work that more completely described 168 the problem statement may be found in [RADIR]. 170 A basic observation, made many years ago in early networking research 171 such as that documented in [CHIAPPA] and [RFC4984], is that using a 172 single address field for both identifying a device and for 173 determining where it is topologically located in the network requires 174 optimization along two conflicting axes: for routing to be efficient, 175 the address must be assigned topologically; for collections of 176 devices to be easily and effectively managed, without the need for 177 renumbering in response to topological change (such as that caused by 178 adding or removing attachment points to the network or by mobility 179 events), the address must explicitly not be tied to the topology. 181 The approach that LISP takes to solving the routing scalability 182 problem is to replace IP addresses with two new types of numbers: 183 Routing Locators (RLOCs), which are topologically assigned to network 184 attachment points (and are therefore amenable to aggregation) and 185 used for routing and forwarding of packets through the network; and 186 Endpoint Identifiers (EIDs), which are assigned independently from 187 the network topology, are used for numbering devices, and are 188 aggregated along administrative boundaries. LISP then defines 189 functions for mapping between the two numbering spaces and for 190 encapsulating traffic originated by devices using non-routeable EIDs 191 for transport across a network infrastructure that routes and 192 forwards using RLOCs. Both RLOCs and EIDs are syntactically- 193 identical to IP addresses; it is the semantics of how they are used 194 that differs. 196 This document describes the protocol that implements these functions. 197 The database which stores the mappings between EIDs and RLOCs is 198 explicitly a separate "module" to facilitate experimentation with a 199 variety of approaches. One database design that is being developed 200 and prototyped as part of the LISP working group work is [ALT]. 201 Others that have been described but not implemented include [CONS], 202 [EMACS], [RPMD], [NERD]. Finally, [LISP-MS], documents a general- 203 purpose service interface for accessing a mapping database; this 204 interface is intended to make the mapping database modular so that 205 different approaches can be tried without the need to modify 206 installed xTRs. 208 This experimental specification does not address automated key 209 management. Addressing automated key management is necessary for 210 Internet standards. See Section 12 for further security details. 212 3. Definition of Terms 214 Provider Independent (PI) Addresses: PI addresses are an address 215 block assigned from a pool where blocks are not associated with 216 any particular location in the network (e.g. from a particular 217 service provider), and is therefore not topologically aggregatable 218 in the routing system. 220 Provider Assigned (PA) Addresses: PA addresses are an a address 221 block assigned to a site by each service provider to which a site 222 connects. Typically, each block is sub-block of a service 223 provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and 224 is aggregated into the larger block before being advertised into 225 the global Internet. Traditionally, IP multihoming has been 226 implemented by each multi-homed site acquiring its own, globally- 227 visible prefix. LISP uses only topologically-assigned and 228 aggregatable address blocks for RLOCs, eliminating this 229 demonstrably non-scalable practice. 231 Routing Locator (RLOC): A RLOC is an IPv4 or IPv6 address of an 232 egress tunnel router (ETR). A RLOC is the output of a EID-to-RLOC 233 mapping lookup. An EID maps to one or more RLOCs. Typically, 234 RLOCs are numbered from topologically-aggregatable blocks that are 235 assigned to a site at each point to which it attaches to the 236 global Internet; where the topology is defined by the connectivity 237 of provider networks, RLOCs can be thought of as PA addresses. 238 Multiple RLOCs can be assigned to the same ETR device or to 239 multiple ETR devices at a site. 241 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 242 IPv6) value used in the source and destination address fields of 243 the first (most inner) LISP header of a packet. The host obtains 244 a destination EID the same way it obtains an destination address 245 today, for example through a Domain Name System (DNS) [RFC1034] 246 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 247 The source EID is obtained via existing mechanisms used to set a 248 host's "local" IP address. An EID is allocated to a host from an 249 EID-prefix block associated with the site where the host is 250 located. An EID can be used by a host to refer to other hosts. 251 EIDs MUST NOT be used as LISP RLOCs. Note that EID blocks may be 252 assigned in a hierarchical manner, independent of the network 253 topology, to facilitate scaling of the mapping database. In 254 addition, an EID block assigned to a site may have site-local 255 structure (subnetting) for routing within the site; this structure 256 is not visible to the global routing system. When used in 257 discussions with other Locator/ID separation proposals, a LISP EID 258 will be called a "LEID". Throughout this document, any references 259 to "EID" refers to an LEID. 261 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are 262 allocated to a site by an address allocation authority. EID- 263 prefixes are associated with a set of RLOC addresses which make up 264 a "database mapping". EID-prefix allocations can be broken up 265 into smaller blocks when an RLOC set is to be associated with the 266 smaller EID-prefix. A globally routed address block (whether PI 267 or PA) is not inherently an EID-prefix. A globally routed address 268 block may be used by its assignee as an EID block. The converse 269 is not supported. That is, a site which receives an explicitly 270 allocated EID-prefix may not use that EID-prefix as a globally 271 prefix. This would require coordination and cooperation with the 272 entities managing the mapping infrastructure. Once this has been 273 done, that block could be removed from the globally routed IP 274 system, if other suitable transition and access mechanisms are in 275 place. Discussion of such transition and access mechanisms can be 276 found in [INTERWORK] and [LISP-DEPLOY]. 278 End-system: An end-system is an IPv4 or IPv6 device that originates 279 packets with a single IPv4 or IPv6 header. The end-system 280 supplies an EID value for the destination address field of the IP 281 header when communicating globally (i.e. outside of its routing 282 domain). An end-system can be a host computer, a switch or router 283 device, or any network appliance. 285 Ingress Tunnel Router (ITR): An ITR is a router which accepts an IP 286 packet with a single IP header (more precisely, an IP packet that 287 does not contain a LISP header). The router treats this "inner" 288 IP destination address as an EID and performs an EID-to-RLOC 289 mapping lookup. The router then prepends an "outer" IP header 290 with one of its globally-routable RLOCs in the source address 291 field and the result of the mapping lookup in the destination 292 address field. Note that this destination RLOC may be an 293 intermediate, proxy device that has better knowledge of the EID- 294 to-RLOC mapping closer to the destination EID. In general, an ITR 295 receives IP packets from site end-systems on one side and sends 296 LISP-encapsulated IP packets toward the Internet on the other 297 side. 299 Specifically, when a service provider prepends a LISP header for 300 Traffic Engineering purposes, the router that does this is also 301 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 302 on the outer destination address (the originating ITR's supplied 303 RLOC) or the inner destination address (the originating hosts 304 supplied EID). 306 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 307 network that prepends an additional LISP header for Traffic 308 Engineering purposes. 310 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 311 packet where the destination address in the "outer" IP header is 312 one of its own RLOCs. The router strips the "outer" header and 313 forwards the packet based on the next IP header found. In 314 general, an ETR receives LISP-encapsulated IP packets from the 315 Internet on one side and sends decapsulated IP packets to site 316 end-systems on the other side. ETR functionality does not have to 317 be limited to a router device. A server host can be the endpoint 318 of a LISP tunnel as well. 320 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 321 network that strips an outer LISP header for Traffic Engineering 322 purposes. 324 xTR: A xTR is a reference to an ITR or ETR when direction of data 325 flow is not part of the context description. xTR refers to the 326 router that is the tunnel endpoint. Used synonymously with the 327 term "Tunnel Router". For example, "An xTR can be located at the 328 Customer Edge (CE) router", meaning both ITR and ETR functionality 329 is at the CE router. 331 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 332 demand table in an ITR that stores, tracks, and is responsible for 333 timing-out and otherwise validating EID-to-RLOC mappings. This 334 cache is distinct from the full "database" of EID-to-RLOC 335 mappings, it is dynamic, local to the ITR(s), and relatively small 336 while the database is distributed, relatively static, and much 337 more global in scope. 339 EID-to-RLOC Database: The EID-to-RLOC database is a global 340 distributed database that contains all known EID-prefix to RLOC 341 mappings. Each potential ETR typically contains a small piece of 342 the database: the EID-to-RLOC mappings for the EID prefixes 343 "behind" the router. These map to one of the router's own, 344 globally-visible, IP addresses. The same database mapping entries 345 MUST be configured on all ETRs for a given site. In a steady 346 state the EID-prefixes for the site and the locator-set for each 347 EID-prefix MUST be the same on all ETRs. Procedures to enforce 348 and/or verify this are outside the scope of this document. Note 349 that there may be transient conditions when the EID-prefix for the 350 site and locator-set for each EID-prefix may not be the same on 351 all ETRs. This has no negative implications. 353 Recursive Tunneling: Recursive tunneling occurs when a packet has 354 more than one LISP IP header. Additional layers of tunneling may 355 be employed to implement traffic engineering or other re-routing 356 as needed. When this is done, an additional "outer" LISP header 357 is added and the original RLOCs are preserved in the "inner" 358 header. Any references to tunnels in this specification refers to 359 dynamic encapsulating tunnels and never are they statically 360 configured. 362 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 363 ETR removes a LISP header, then acts as an ITR to prepend another 364 LISP header. Doing this allows a packet to be re-routed by the 365 re-encapsulating router without adding the overhead of additional 366 tunnel headers. Any references to tunnels in this specification 367 refers to dynamic encapsulating tunnels and never are they 368 statically configured. When using multiple mapping database 369 systems, care must be taken to not create reencapsulation loops. 371 LISP Header: a term used in this document to refer to the outer 372 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-byte 373 header that follows the UDP header, an ITR prepends or an ETR 374 strips. 376 Address Family Identifier (AFI): a term used to describe an address 377 encoding in a packet. An address family currently pertains to an 378 IPv4 or IPv6 address. See [AFI]/[AFI-REGISTRY] and [RFC1700] for 379 details. An AFI value of 0 used in this specification indicates 380 an unspecified encoded address where the length of the address is 381 0 bytes following the 16-bit AFI value of 0. 383 Negative Mapping Entry: A negative mapping entry, also known as a 384 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 385 is advertised or stored with no RLOCs. That is, the locator-set 386 for the EID-to-RLOC entry is empty or has an encoded locator count 387 of 0. This type of entry could be used to describe a prefix from 388 a non-LISP site, which is explicitly not in the mapping database. 389 There are a set of well defined actions that are encoded in a 390 Negative Map-Reply. 392 Data Probe: A data-probe is a LISP-encapsulated data packet where 393 the inner header destination address equals the outer header 394 destination address used to trigger a Map-Reply by a decapsulating 395 ETR. In addition, the original packet is decapsulated and 396 delivered to the destination host. A Data Probe is used in some 397 of the mapping database designs to "probe" or request a Map-Reply 398 from an ETR; in other cases, Map-Requests are used. See each 399 mapping database design for details. 401 Proxy ITR (PITR): A PITR is also known as a PTR is defined and 402 described in [INTERWORK], a PITR acts like an ITR but does so on 403 behalf of non-LISP sites which send packets to destinations at 404 LISP sites. 406 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 407 PETR acts like an ETR but does so on behalf of LISP sites which 408 send packets to destinations at non-LISP sites. 410 Route-returnability: is an assumption that the underlying routing 411 system will deliver packets to the destination. When combined 412 with a nonce that is provided by a sender and returned by a 413 receiver limits off-path data insertion. 415 LISP site: is a set of routers in an edge network that are under a 416 single technical administration. LISP routers which reside in the 417 edge network are the demarcation points to separate the edge 418 network from the core network. 420 Client-side: a term used in this document to indicate a connection 421 initiation attempt by an EID. The ITR(s) at the LISP site are the 422 first to get involved in obtaining database map cache entries by 423 sending Map-Request messages. 425 Server-side: a term used in this document to indicate a connection 426 initiation attempt is being accepted for a destination EID. The 427 ETR(s) at the destination LISP site are the first to send Map- 428 Replies to the source site initiating the connection. The ETR(s) 429 at this destination site can obtain mappings by gleaning 430 information from Map-Requests, Data-Probes, or encapsulated 431 packets. 433 Locator-Status-Bits (LSBs): Locator status bits are present in the 434 LISP header. They are used by ITRs to inform ETRs about the up/ 435 down status of all ETRs at the local site. These bits are used as 436 a hint to convey up/down router status and not path reachability 437 status. The LSBs can be verified by use of one of the Locator 438 Reachability Algoriths described in Section 6.3. 440 4. Basic Overview 442 One key concept of LISP is that end-systems (hosts) operate the same 443 way they do today. The IP addresses that hosts use for tracking 444 sockets, connections, and for sending and receiving packets do not 445 change. In LISP terminology, these IP addresses are called Endpoint 446 Identifiers (EIDs). 448 Routers continue to forward packets based on IP destination 449 addresses. When a packet is LISP encapsulated, these addresses are 450 referred to as Routing Locators (RLOCs). Most routers along a path 451 between two hosts will not change; they continue to perform routing/ 452 forwarding lookups on the destination addresses. For routers between 453 the source host and the ITR as well as routers from the ETR to the 454 destination host, the destination address is an EID. For the routers 455 between the ITR and the ETR, the destination address is an RLOC. 457 Another key LISP concept is the "Tunnel Router". A tunnel router 458 prepends LISP headers on host-originated packets and strip them prior 459 to final delivery to their destination. The IP addresses in this 460 "outer header" are RLOCs. During end-to-end packet exchange between 461 two Internet hosts, an ITR prepends a new LISP header to each packet 462 and an egress tunnel router strips the new header. The ITR performs 463 EID-to-RLOC lookups to determine the routing path to the ETR, which 464 has the RLOC as one of its IP addresses. 466 Some basic rules governing LISP are: 468 o End-systems (hosts) only send to addresses which are EIDs. They 469 don't know addresses are EIDs versus RLOCs but assume packets get 470 to LISP routers, which in turn, deliver packets to the destination 471 the end-system has specified. 473 o EIDs are always IP addresses assigned to hosts. 475 o LISP routers mostly deal with Routing Locator addresses. See 476 details later in Section 4.1 to clarify what is meant by "mostly". 478 o RLOCs are always IP addresses assigned to routers; preferably, 479 topologically-oriented addresses from provider CIDR blocks. 481 o When a router originates packets it may use as a source address 482 either an EID or RLOC. When acting as a host (e.g. when 483 terminating a transport session such as SSH, TELNET, or SNMP), it 484 may use an EID that is explicitly assigned for that purpose. An 485 EID that identifies the router as a host MUST NOT be used as an 486 RLOC; an EID is only routable within the scope of a site. A 487 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 488 usage where a router could use its "host-like" EID to terminate 489 iBGP sessions to other routers in a site while at the same time 490 using RLOCs to terminate eBGP sessions to routers outside the 491 site. 493 o EIDs are not expected to be usable for global end-to-end 494 communication in the absence of an EID-to-RLOC mapping operation. 495 They are expected to be used locally for intra-site communication. 497 o EID prefixes are likely to be hierarchically assigned in a manner 498 which is optimized for administrative convenience and to 499 facilitate scaling of the EID-to-RLOC mapping database. The 500 hierarchy is based on a address allocation hierarchy which is 501 independent of the network topology. 503 o EIDs may also be structured (subnetted) in a manner suitable for 504 local routing within an autonomous system. 506 An additional LISP header may be prepended to packets by a TE-ITR 507 when re-routing of the path for a packet is desired. A potential 508 use-case for this would be an ISP router that needs to perform 509 traffic engineering for packets flowing through its network. In such 510 a situation, termed Recursive Tunneling, an ISP transit acts as an 511 additional ingress tunnel router and the RLOC it uses for the new 512 prepended header would be either a TE-ETR within the ISP (along 513 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 514 inter-ISP traffic engineered path, where an agreement to build such a 515 path exists). 517 In order to avoid excessive packet overhead as well as possible 518 encapsulation loops, this document mandates that a maximum of two 519 LISP headers can be prepended to a packet. For initial LISP 520 deployments, it is assumed two headers is sufficient, where the first 521 prepended header is used at a site for Location/Identity separation 522 and second prepended header is used inside a service provider for 523 Traffic Engineering purposes. 525 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 526 For example, the ITR for a particular end-to-end packet exchange 527 might be the first-hop or default router within a site for the source 528 host. Similarly, the egress tunnel router might be the last-hop 529 router directly-connected to the destination host. Another example, 530 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 531 could be the site's border router at the service provider attachment 532 point. Mixing and matching of site-operated, ISP-operated, and other 533 tunnel routers is allowed for maximum flexibility. See Section 8 for 534 more details. 536 4.1. Packet Flow Sequence 538 This section provides an example of the unicast packet flow with the 539 following conditions: 541 o Source host "host1.abc.com" is sending a packet to 542 "host2.xyz.com", exactly what host1 would do if the site was not 543 using LISP. 545 o Each site is multi-homed, so each tunnel router has an address 546 (RLOC) assigned from the service provider address block for each 547 provider to which that particular tunnel router is attached. 549 o The ITR(s) and ETR(s) are directly connected to the source and 550 destination, respectively, but the source and destination can be 551 located anywhere in LISP site. 553 o Map-Requests can be sent on the underlying routing system topology 554 or over an alternative topology [ALT]. 556 o Map-Replies are sent on the underlying routing system topology. 558 Client host1.abc.com wants to communicate with server host2.xyz.com: 560 1. host1.abc.com wants to open a TCP connection to host2.xyz.com. 561 It does a DNS lookup on host2.xyz.com. An A/AAAA record is 562 returned. This address is the destination EID. The locally- 563 assigned address of host1.abc.com is used as the source EID. An 564 IPv4 or IPv6 packet is built and forwarded through the LISP site 565 as a normal IP packet until it reaches a LISP ITR. 567 2. The LISP ITR must be able to map the EID destination to an RLOC 568 of one of the ETRs at the destination site. The specific method 569 used to do this is not described in this example. See [ALT] or 570 [CONS] for possible solutions. 572 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 573 rate-limited. 575 4. When an alternate mapping system is not in use, the Map-Request 576 packet is routed through the underlying routing system. 577 Otherwise, the Map-Request packet is routed on an alternate 578 logical topology. In either case, when the Map-Request arrives 579 at one of the ETRs at the destination site, it will process the 580 packet as a control message. 582 5. The ETR looks at the destination EID of the Map-Request and 583 matches it against the prefixes in the ETR's configured EID-to- 584 RLOC mapping database. This is the list of EID-prefixes the ETR 585 is supporting for the site it resides in. If there is no match, 586 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 587 returned to the ITR. 589 6. The ITR receives the Map-Reply message, parses the message (to 590 check for format validity) and stores the mapping information 591 from the packet. This information is stored in the ITR's EID-to- 592 RLOC mapping cache. Note that the map cache is an on-demand 593 cache. An ITR will manage its map cache in such a way that 594 optimizes for its resource constraints. 596 7. Subsequent packets from host1.abc.com to host2.xyz.com will have 597 a LISP header prepended by the ITR using the appropriate RLOC as 598 the LISP header destination address learned from the ETR. Note 599 the packet may be sent to a different ETR than the one which 600 returned the Map-Reply due to the source site's hashing policy or 601 the destination site's locator-set policy. 603 8. The ETR receives these packets directly (since the destination 604 address is one of its assigned IP addresses), strips the LISP 605 header and forwards the packets to the attached destination host. 607 In order to defer the need for a mapping lookup in the reverse 608 direction, an ETR MAY create a cache entry that maps the source EID 609 (inner header source IP address) to the source RLOC (outer header 610 source IP address) in a received LISP packet. Such a cache entry is 611 termed a "gleaned" mapping and only contains a single RLOC for the 612 EID in question. More complete information about additional RLOCs 613 SHOULD be verified by sending a LISP Map-Request for that EID. Both 614 ITR and the ETR may also influence the decision the other makes in 615 selecting an RLOC. See Section 6 for more details. 617 5. LISP Encapsulation Details 619 Since additional tunnel headers are prepended, the packet becomes 620 larger and can exceed the MTU of any link traversed from the ITR to 621 the ETR. It is recommended in IPv4 that packets do not get 622 fragmented as they are encapsulated by the ITR. Instead, the packet 623 is dropped and an ICMP Too Big message is returned to the source. 625 This specification recommends that implementations support for one of 626 the proposed fragmentation and reassembly schemes. These two 627 existing schemes are detailed in Section 5.4. 629 5.1. LISP IPv4-in-IPv4 Header Format 631 0 1 2 3 632 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 1 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 634 / |Version| IHL |Type of Service| Total Length | 635 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 636 | | Identification |Flags| Fragment Offset | 637 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 638 OH | Time to Live | Protocol = 17 | Header Checksum | 639 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 640 | | Source Routing Locator | 641 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 \ | Destination Routing Locator | 643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 / | Source Port = xxxx | Dest Port = 4341 | 645 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 646 \ | UDP Length | UDP Checksum | 647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 648 L |N|L|E|V|I|flags| Nonce/Map-Version | 649 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 650 S / | Instance ID/Locator Status Bits | 651 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 652 / |Version| IHL |Type of Service| Total Length | 653 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 654 | | Identification |Flags| Fragment Offset | 655 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 656 IH | Time to Live | Protocol | Header Checksum | 657 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 658 | | Source EID | 659 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 660 \ | Destination EID | 661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 663 5.2. LISP IPv6-in-IPv6 Header Format 665 0 1 2 3 666 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 1 667 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 668 / |Version| Traffic Class | Flow Label | 669 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 671 | | Payload Length | Next Header=17| Hop Limit | 672 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 673 | | 674 O + + 675 u | | 676 t + Source Routing Locator + 677 e | | 678 r + + 679 | | 680 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 681 d | | 682 r + + 683 | | 684 ^ + Destination Routing Locator + 685 | | | 686 \ + + 687 \ | | 688 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 689 / | Source Port = xxxx | Dest Port = 4341 | 690 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 691 \ | UDP Length | UDP Checksum | 692 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 693 L |N|L|E|V|I|flags| Nonce/Map-Version | 694 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 695 S / | Instance ID/Locator Status Bits | 696 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 697 / |Version| Traffic Class | Flow Label | 698 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 699 / | Payload Length | Next Header | Hop Limit | 700 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 701 | | 702 I + + 703 n | | 704 n + Source EID + 705 e | | 706 r + + 707 | | 708 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 709 d | | 710 r + + 711 | | 712 ^ + Destination EID + 713 \ | | 714 \ + + 715 \ | | 716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 718 5.3. Tunnel Header Field Descriptions 720 Inner Header: The inner header is the header on the datagram 721 received from the originating host. The source and destination IP 722 addresses are EIDs. 724 Outer Header: The outer header is a new header prepended by an ITR. 725 The address fields contain RLOCs obtained from the ingress 726 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 727 from [RFC0768]. The DF bit of the Flags field is set to 0 when 728 the method in Section 5.4.1 is used and set to 1 when the method 729 in Section 5.4.2 is used. 731 UDP Header: The UDP header contains a ITR selected source port when 732 encapsulating a packet. See Section 6.5 for details on the hash 733 algorithm used to select a source port based on the 5-tuple of the 734 inner header. The destination port MUST be set to the well-known 735 IANA assigned port value 4341. 737 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 738 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 739 [UDP-TUNNELS]. When a packet with a zero UDP checksum is received 740 by an ETR, the ETR MUST accept the packet for decapsulation. When 741 an ITR transmits a non-zero value for the UDP checksum, it MUST 742 send a correctly computed value in this field. When an ETR 743 receives a packet with a non-zero UDP checksum, it MAY choose to 744 verify the checksum value. If it chooses to perform such 745 verification, and the verification fails, the packet MUST be 746 silently dropped. If the ETR chooses not to perform the 747 verification, or performs the verification successfully, the 748 packet MUST be accepted for decapsulation. The handling of UDP 749 checksums for all tunneling protocols, including LISP, is under 750 active discussion within the IETF. When that discussion 751 concludes, any necessary changes will be made to align LISP with 752 the outcome of the broader discussion. 754 UDP Length: The UDP length field is for an IPv4 encapsulated packet, 755 the inner header Total Length plus the UDP and LISP header lengths 756 are used. For an IPv6 encapsulated packet, the inner header 757 Payload Length plus the size of the IPv6 header (40 bytes) plus 758 the size of the UDP and LISP headers are used. The UDP header 759 length is 8 bytes. 761 N: The N bit is the nonce-present bit. When this bit is set to 1, 762 the low-order 24-bits of the first 32-bits of the LISP header 763 contains a Nonce. See Section 6.3.1 for details. Both N and V 764 bits MUST NOT be set in the same packet. If they are, a 765 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 766 having a Nonce value present. 768 L: The L bit is the Locator-Status-Bits field enabled bit. When this 769 bit is set to 1, the Locator-Status-Bits in the second 32-bits of 770 the LISP header are in use. 772 x 1 x x 0 x x x 773 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 774 |N|L|E|V|I|flags| Nonce/Map-Version | 775 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 776 | Locator Status Bits | 777 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 779 E: The E bit is the echo-nonce-request bit. When this bit is set to 780 1, the N bit MUST be 1. This bit SHOULD be ignored and has no 781 meaning when the N bit is set to 0. See Section 6.3.1 for 782 details. 784 V: The V bit is the Map-Version present bit. When this bit is set to 785 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 786 This bit indicates that the first 4 bytes of the LISP header is 787 encoded as: 789 0 x 0 1 x x x x 790 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 791 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 792 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 793 | Instance ID/Locator Status Bits | 794 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 796 I: The I bit is the Instance ID bit. See Section 5.5 for more 797 details. When this bit is set to 1, the Locator Status Bits field 798 is reduced to 8-bits and the high-order 24-bits are used as an 799 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 800 are transmitted as zero and ignored on receipt. The format of the 801 last 4 bytes of the LISP header would look like: 803 x x x x 1 x x x 804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 805 |N|L|E|V|I|flags| Nonce/Map-Version | 806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 807 | Instance ID | LSBs | 808 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 810 flags: The flags field is a 3-bit field is reserved for future flag 811 use. It MUST be set to 0 on transmit and MUST be ignored on 812 receipt. 814 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 815 generated by an ITR when the N-bit is set to 1. The nonce is also 816 used when the E-bit is set to request the nonce value to be echoed 817 by the other side when packets are returned. When the E-bit is 818 clear but the N-bit is set, a remote ITR is either echoing a 819 previously requested echo-nonce or providing a random nonce. See 820 Section 6.3.1 for more details. 822 LISP Locator Status Bits: The locator status bits field in the LISP 823 header is set by an ITR to indicate to an ETR the up/down status 824 of the Locators in the source site. Each RLOC in a Map-Reply is 825 assigned an ordinal value from 0 to n-1 (when there are n RLOCs in 826 a mapping entry). The Locator Status Bits are numbered from 0 to 827 n-1 from the least significant bit of field. The field is 32-bits 828 when the I-bit is set to 0 and is 8 bits when the I-bit is set to 829 1. When a Locator Status Bit is set to 1, the ITR is indicating 830 to the ETR the RLOC associated with the bit ordinal has up status. 831 See Section 6.3 for details on how an ITR can determine the status 832 of the ETRs at the same site. When a site has multiple EID- 833 prefixes which result in multiple mappings (where each could have 834 a different locator-set), the Locator Status Bits setting in an 835 encapsulated packet MUST reflect the mapping for the EID-prefix 836 that the inner-header source EID address matches. If the LSB for 837 an anycast locator is set to 1, then there is at least one RLOC 838 with that address the ETR is considered 'up'. 840 When doing ITR/PITR encapsulation: 842 o The outer header Time to Live field (or Hop Limit field, in case 843 of IPv6) SHOULD be copied from the inner header Time to Live 844 field. 846 o The outer header Type of Service field (or the Traffic Class 847 field, in the case of IPv6) SHOULD be copied from the inner header 848 Type of Service field (with one caveat, see below). 850 When doing ETR/PETR decapsulation: 852 o The inner header Time to Live field (or Hop Limit field, in case 853 of IPv6) SHOULD be copied from the outer header Time to Live 854 field, when the Time to Live field of the outer header is less 855 than the Time to Live of the inner header. Failing to perform 856 this check can cause the Time to Live of the inner header to 857 increment across encapsulation/decapsulation cycle. This check is 858 also performed when doing initial encapsulation when a packet 859 comes to an ITR or PITR destined for a LISP site. 861 o The inner header Type of Service field (or the Traffic Class 862 field, in the case of IPv6) SHOULD be copied from the outer header 863 Type of Service field (with one caveat, see below). 865 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 866 after decapsulating, the net effect of this is that the new outer 867 header will carry the same Time to Live as the old outer header. 869 Copying the TTL serves two purposes: first, it preserves the distance 870 the host intended the packet to travel; second, and more importantly, 871 it provides for suppression of looping packets in the event there is 872 a loop of concatenated tunnels due to misconfiguration. See 873 Section 9.3 for TTL exception handling for traceroute packets. 875 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 876 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 877 requires special treatment in order to avoid discarding indications 878 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 879 field from the inner header to the outer header. Re-encapsulation 880 MUST copy the 2-bit ECN field from the stripped outer header to the 881 new outer header. If the ECN field contains a congestion indication 882 codepoint (the value is '11', the Congestion Experienced (CE) 883 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 884 the stripped outer header to the surviving inner header that is used 885 to forward the packet beyond the ETR. These requirements preserve 886 Congestion Experienced (CE) indications when a packet that uses ECN 887 traverses a LISP tunnel and becomes marked with a CE indication due 888 to congestion between the tunnel endpoints. 890 5.4. Dealing with Large Encapsulated Packets 892 This section proposes two mechanisms to deal with packets that exceed 893 the path MTU between the ITR and ETR. 895 It is left to the implementor to decide if the stateless or stateful 896 mechanism should be implemented. Both or neither can be used since 897 it is a local decision in the ITR regarding how to deal with MTU 898 issues, and sites can interoperate with differing mechanisms. 900 Both stateless and stateful mechanisms also apply to Reencapsulating 901 and Recursive Tunneling. So any actions below referring to an ITR 902 also apply to an TE-ITR. 904 5.4.1. A Stateless Solution to MTU Handling 906 An ITR stateless solution to handle MTU issues is described as 907 follows: 909 1. Define an architectural constant S for the maximum size of a 910 packet, in bytes, an ITR would like to receive from a source 911 inside of its site. 913 2. Define L to be the maximum size, in bytes, a packet of size S 914 would be after the ITR prepends the LISP header, UDP header, and 915 outer network layer header of size H. 917 3. Calculate: S + H = L. 919 When an ITR receives a packet from a site-facing interface and adds H 920 bytes worth of encapsulation to yield a packet size greater than L 921 bytes, it resolves the MTU issue by first splitting the original 922 packet into 2 equal-sized fragments. A LISP header is then prepended 923 to each fragment. The size of the encapsulated fragments is then 924 (S/2 + H), which is less than the ITR's estimate of the path MTU 925 between the ITR and its correspondent ETR. 927 When an ETR receives encapsulated fragments, it treats them as two 928 individually encapsulated packets. It strips the LISP headers then 929 forwards each fragment to the destination host of the destination 930 site. The two fragments are reassembled at the destination host into 931 the single IP datagram that was originated by the source host. 933 This behavior is performed by the ITR when the source host originates 934 a packet with the DF field of the IP header is set to 0. When the DF 935 field of the IP header is set to 1, or the packet is an IPv6 packet 936 originated by the source host, the ITR will drop the packet when the 937 size is greater than L, and sends an ICMP Too Big message to the 938 source with a value of S, where S is (L - H). 940 When the outer header encapsulation uses an IPv4 header, an 941 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 942 can be avoided. An implementation MAY set the DF bit in such headers 943 to 0 if it has good reason to believe there are unresolvable path MTU 944 issues between the sending ITR and the receiving ETR. 946 This specification recommends that L be defined as 1500. 948 5.4.2. A Stateful Solution to MTU Handling 950 An ITR stateful solution to handle MTU issues is described as follows 951 and was first introduced in [OPENLISP]: 953 1. The ITR will keep state of the effective MTU for each locator per 954 mapping cache entry. The effective MTU is what the core network 955 can deliver along the path between ITR and ETR. 957 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 958 with DF bit set to 1, exceeds what the core network can deliver, 959 one of the intermediate routers on the path will send an ICMP Too 960 Big message to the ITR. The ITR will parse the ICMP message to 961 determine which locator is affected by the effective MTU change 962 and then record the new effective MTU value in the mapping cache 963 entry. 965 3. When a packet is received by the ITR from a source inside of the 966 site and the size of the packet is greater than the effective MTU 967 stored with the mapping cache entry associated with the 968 destination EID the packet is for, the ITR will send an ICMP Too 969 Big message back to the source. The packet size advertised by 970 the ITR in the ICMP Too Big message is the effective MTU minus 971 the LISP encapsulation length. 973 Even though this mechanism is stateful, it has advantages over the 974 stateless IP fragmentation mechanism, by not involving the 975 destination host with reassembly of ITR fragmented packets. 977 5.5. Using Virtualization and Segmentation with LISP 979 When multiple organizations inside of a LISP site are using private 980 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 981 segregated due to possible address duplication. An Instance ID in 982 the address encoding can aid in making the entire AFI based address 983 unique. See IANA Considerations Section 14.1 for details for 984 possible address encodings. 986 An Instance ID can be carried in a LISP encapsulated packet. An ITR 987 that prepends a LISP header, will copy a 24-bit value, used by the 988 LISP router to uniquely identify the address space. The value is 989 copied to the Instance ID field of the LISP header and the I-bit is 990 set to 1. 992 When an ETR decapsulates a packet, the Instance ID from the LISP 993 header is used as a table identifier to locate the forwarding table 994 to use for the inner destination EID lookup. 996 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 997 24-bit Instance ID. 999 6. EID-to-RLOC Mapping 1001 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 1003 The following UDP packet formats are used by the LISP control-plane. 1005 0 1 2 3 1006 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 1007 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1008 |Version| IHL |Type of Service| Total Length | 1009 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1010 | Identification |Flags| Fragment Offset | 1011 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1012 | Time to Live | Protocol = 17 | Header Checksum | 1013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1014 | Source Routing Locator | 1015 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1016 | Destination Routing Locator | 1017 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1018 / | Source Port | Dest Port | 1019 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1020 \ | UDP Length | UDP Checksum | 1021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1022 | | 1023 | LISP Message | 1024 | | 1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1027 0 1 2 3 1028 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 1029 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1030 |Version| Traffic Class | Flow Label | 1031 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1032 | Payload Length | Next Header=17| Hop Limit | 1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1034 | | 1035 + + 1036 | | 1037 + Source Routing Locator + 1038 | | 1039 + + 1040 | | 1041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1042 | | 1043 + + 1044 | | 1045 + Destination Routing Locator + 1046 | | 1047 + + 1048 | | 1049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1050 / | Source Port | Dest Port | 1051 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1052 \ | UDP Length | UDP Checksum | 1053 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1054 | | 1055 | LISP Message | 1056 | | 1057 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1059 The LISP UDP-based messages are the Map-Request and Map-Reply 1060 messages. When a UDP Map-Request is sent, the UDP source port is 1061 chosen by the sender and the destination UDP port number is set to 1062 4342. When a UDP Map-Reply is sent, the source UDP port number is 1063 set to 4342 and the destination UDP port number is copied from the 1064 source port of either the Map-Request or the invoking data packet. 1065 Implementations MUST be prepared to accept packets when either the 1066 source port or destination UDP port is set to 4342 due to NATs 1067 changing port number values. 1069 The UDP Length field will reflect the length of the UDP header and 1070 the LISP Message payload. 1072 The UDP Checksum is computed and set to non-zero for Map-Request, 1073 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1074 on receipt and if the checksum fails, the packet MUST be dropped. 1076 LISP-CONS [CONS] uses TCP to send LISP control messages. The format 1077 of control messages includes the UDP header so the checksum and 1078 length fields can be used to protect and delimit message boundaries. 1080 This main LISP specification is the authoritative source for message 1081 format definitions for the Map-Request and Map-Reply messages. 1083 6.1.1. LISP Packet Type Allocations 1085 This section will be the authoritative source for allocating LISP 1086 Type values. Current allocations are: 1088 Reserved: 0 b'0000' 1089 LISP Map-Request: 1 b'0001' 1090 LISP Map-Reply: 2 b'0010' 1091 LISP Map-Register: 3 b'0011' 1092 LISP Map-Notify: 4 b'0100' 1093 LISP Encapsulated Control Message: 8 b'1000' 1095 6.1.2. Map-Request Message Format 1097 0 1 2 3 1098 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 1099 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1100 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1102 | Nonce . . . | 1103 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1104 | . . . Nonce | 1105 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1106 | Source-EID-AFI | Source EID Address ... | 1107 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1108 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1109 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1110 | ... | 1111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1112 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1114 / | Reserved | EID mask-len | EID-prefix-AFI | 1115 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1116 \ | EID-prefix ... | 1117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1118 | Map-Reply Record ... | 1119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1120 | Mapping Protocol Data | 1121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1123 Packet field descriptions: 1125 Type: 1 (Map-Request) 1127 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1128 Requests sent by an ITR. 1130 M: When set, it indicates a Map-Reply Record segment is included in 1131 the Map-Request. 1133 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1134 treated as a locator reachability probe. The receiver SHOULD 1135 respond with a Map-Reply with the probe-bit set, indicating the 1136 Map-Reply is a locator reachability probe reply, with the nonce 1137 copied from the Map-Request. See Section 6.3.2 for more details. 1139 S: This is the SMR bit. See Section 6.6.2 for details. 1141 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1142 Map-Request. 1144 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1145 sending a Map-Request in response to a received SMR-based Map- 1146 Request. 1148 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1149 receipt. 1151 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1152 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1153 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1154 Address) pair must always be encoded. Multiple ITR-RLOC Address 1155 fields are used so a Map-Replier can select which destination 1156 address to use for a Map-Reply. The IRC value ranges from 0 to 1157 31, and for a value of 1, there are 2 ITR-RLOC addresses encoded 1158 and so on up to 31 which encodes a total of 32 ITR-RLOC addresses. 1160 Record Count: The number of records in this Map-Request message. A 1161 record is comprised of the portion of the packet that is labeled 1162 'Rec' above and occurs the number of times equal to Record Count. 1163 For this version of the protocol, a receiver MUST accept and 1164 process Map-Requests that contain one or more records, but a 1165 sender MUST only send Map-Requests containing one record. Support 1166 for requesting multiple EIDs in a single Map-Request message will 1167 be specified in a future version of the protocol. 1169 Nonce: An 8-byte random value created by the sender of the Map- 1170 Request. This nonce will be returned in the Map-Reply. The 1171 security of the LISP mapping protocol depends critically on the 1172 strength of the nonce in the Map-Request message. The nonce 1173 SHOULD be generated by a properly seeded pseudo-random (or strong 1174 random) source. See [RFC4086] for advice on generating security- 1175 sensitive random data. 1177 Source-EID-AFI: Address family of the "Source EID Address" field. 1179 Source EID Address: This is the EID of the source host which 1180 originated the packet which is invoking this Map-Request. When 1181 Map-Requests are used for refreshing a map-cache entry or for 1182 RLOC-probing, an AFI value 0 is used and this field is of zero 1183 length. 1185 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1186 follows this field. 1188 ITR-RLOC Address: Used to give the ETR the option of selecting the 1189 destination address from any address family for the Map-Reply 1190 message. This address MUST be a routable RLOC address of the 1191 sender of the Map-Request message. 1193 EID mask-len: Mask length for EID prefix. 1195 EID-prefix-AFI: Address family of EID-prefix according to [AFI] 1197 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1198 address-family. When a Map-Request is sent by an ITR because a 1199 data packet is received for a destination where there is no 1200 mapping entry, the EID-prefix is set to the destination IP address 1201 of the data packet. And the 'EID mask-len' is set to 32 or 128 1202 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1203 about the status of a mapping it already has cached, the EID- 1204 prefix used in the Map-Request has the same mask-length as the 1205 EID-prefix returned from the site when it sent a Map-Reply 1206 message. 1208 Map-Reply Record: When the M bit is set, this field is the size of a 1209 single "Record" in the Map-Reply format. This Map-Reply record 1210 contains the EID-to-RLOC mapping entry associated with the Source 1211 EID. This allows the ETR which will receive this Map-Request to 1212 cache the data if it chooses to do so. 1214 Mapping Protocol Data: See [CONS] for details. This field is 1215 optional and present when the UDP length indicates there is enough 1216 space in the packet to include it. 1218 6.1.3. EID-to-RLOC UDP Map-Request Message 1220 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1221 wants to test an RLOC for reachability, or wants to refresh a mapping 1222 before TTL expiration. For the initial case, the destination IP 1223 address used for the Map-Request is the destination-EID from the 1224 packet which had a mapping cache lookup failure. For the latter 2 1225 cases, the destination IP address used for the Map-Request is one of 1226 the RLOC addresses from the locator-set of the map cache entry. The 1227 source address is either an IPv4 or IPv6 RLOC address depending if 1228 the Map-Request is using an IPv4 versus IPv6 header, respectively. 1229 In all cases, the UDP source port number for the Map-Request message 1230 is an ITR/PITR selected 16-bit value and the UDP destination port 1231 number is set to the well-known destination port number 4342. A 1232 successful Map-Reply updates the cached set of RLOCs associated with 1233 the EID prefix range. 1235 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1236 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1237 be placed in the IRC field. The ITR MAY include all locally 1238 configured locators in this list or just provide one locator address 1239 from each address family it supports. If the ITR erroneously 1240 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1241 Request. 1243 Map-Requests can also be LISP encapsulated using UDP destination port 1244 4342 with a LISP type value set to "Encapsulated Control Message", 1245 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1246 LISP encapsulated the same way from a Map-Server to an ETR. Details 1247 on encapsulated Map-Requests and Map-Resolvers can be found in 1248 [LISP-MS]. 1250 Map-Requests MUST be rate-limited. It is recommended that a Map- 1251 Request for the same EID-prefix be sent no more than once per second. 1253 An ITR that is configured with mapping database information (i.e. it 1254 is also an ETR) may optionally include those mappings in a Map- 1255 Request. When an ETR configured to accept and verify such 1256 "piggybacked" mapping data receives such a Map-Request and it does 1257 not have this mapping in the map-cache, it may originate a "verifying 1258 Map-Request", addressed to the map-requesting ITR. If the ETR has a 1259 map-cache entry that matches the "piggybacked" EID and the RLOC is in 1260 the locator-set for the entry, then it may send the "verifying Map- 1261 Request" directly to the originating Map-Request source. If the RLOC 1262 is not in the locator-set, then the ETR MUST send the "verifying Map- 1263 Request" to the "piggybacked" EID. Doing this forces the "verifying 1264 Map-Request" to go through the mapping database system to reach the 1265 authoritative source of information about that EID, guarding against 1266 RLOC-spoofing in in the "piggybacked" mapping data. 1268 6.1.4. Map-Reply Message Format 1270 0 1 2 3 1271 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 1272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1273 |Type=2 |P|E|S| Reserved | Record Count | 1274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1275 | Nonce . . . | 1276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1277 | . . . Nonce | 1278 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1279 | | Record TTL | 1280 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1281 R | Locator Count | EID mask-len | ACT |A| Reserved | 1282 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1283 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1284 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1285 r | EID-prefix | 1286 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1287 | /| Priority | Weight | M Priority | M Weight | 1288 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1289 | o | Unused Flags |L|p|R| Loc-AFI | 1290 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1291 | \| Locator | 1292 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1293 | Mapping Protocol Data | 1294 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1296 Packet field descriptions: 1298 Type: 2 (Map-Reply) 1300 P: This is the probe-bit which indicates that the Map-Reply is in 1301 response to a locator reachability probe Map-Request. The nonce 1302 field MUST contain a copy of the nonce value from the original 1303 Map-Request. See Section 6.3.2 for more details. 1305 E: Indicates that the ETR which sends this Map-Reply message is 1306 advertising that the site is enabled for the Echo-Nonce locator 1307 reachability algorithm. See Section 6.3.1 for more details. 1309 S: This is the Security bit. When set to 1 the field following the 1310 Mapping Protocol Data field will have the following format. The 1311 detailed format of the Authentication Data Content is for further 1312 study. 1314 0 1 2 3 1315 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 1316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1317 | AD Type | Authentication Data Content . . . | 1318 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1320 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1321 receipt. 1323 Record Count: The number of records in this reply message. A record 1324 is comprised of that portion of the packet labeled 'Record' above 1325 and occurs the number of times equal to Record count. 1327 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1328 from the Map-Request is echoed in this Nonce field of the Map- 1329 Reply. 1331 Record TTL: The time in minutes the recipient of the Map-Reply will 1332 store the mapping. If the TTL is 0, the entry SHOULD be removed 1333 from the cache immediately. If the value is 0xffffffff, the 1334 recipient can decide locally how long to store the mapping. 1336 Locator Count: The number of Locator entries. A locator entry 1337 comprises what is labeled above as 'Loc'. The locator count can 1338 be 0 indicating there are no locators for the EID-prefix. 1340 EID mask-len: Mask length for EID prefix. 1342 ACT: This 3-bit field describes negative Map-Reply actions. These 1343 bits are used only when the 'Locator Count' field is set to 0. 1344 The action bits are encoded only in Map-Reply messages. The 1345 actions defined are used by an ITR or PTR when a destination EID 1346 matches a negative mapping cache entry. Unassigned values should 1347 cause a map-cache entry to be created and, when packets match this 1348 negative cache entry, they will be dropped. The current assigned 1349 values are: 1351 (0) No-Action: The map-cache is kept alive and no packet 1352 encapsulation occurs. 1354 (1) Natively-Forward: The packet is not encapsulated or dropped 1355 but natively forwarded. 1357 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1359 (3) Drop: A packet that matches this map-cache entry is dropped. 1361 A: The Authoritative bit, when sent by a UDP-based message is always 1362 set to 1 by an ETR. See [CONS] for TCP-based Map-Replies. When a 1363 Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, the 1364 Authoritative bit is set to 0. This indicates to requesting ITRs 1365 that the Map-Reply was not originated by a LISP node managed at 1366 the site that owns the EID-prefix. 1368 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1369 sender is informing the ITR what the version number is for the 1370 EID-record contained in the Map-Reply. The ETR can allocate this 1371 number internally but MUST coordinate this value with other ETRs 1372 for the site. When this value is 0, there is no versioning 1373 information conveyed. The Map-Version Number can be included in 1374 Map-Request and Map-Register messages. See Section 6.6.3 for more 1375 details. 1377 EID-prefix-AFI: Address family of EID-prefix according to [AFI]. 1379 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1380 address-family. 1382 Priority: each RLOC is assigned a unicast priority. Lower values 1383 are more preferable. When multiple RLOCs have the same priority, 1384 they may be used in a load-split fashion. A value of 255 means 1385 the RLOC MUST NOT be used for unicast forwarding. 1387 Weight: when priorities are the same for multiple RLOCs, the weight 1388 indicates how to balance unicast traffic between them. Weight is 1389 encoded as a relative weight of total unicast packets that match 1390 the mapping entry. For example if there are 4 locators in a 1391 locator set, where the weights assigned are 30, 20, 20, and 10, 1392 the first locator will get 37.5% of the traffic, the 2nd and 3rd 1393 locators will get 25% of traffic and the 4th locator will get 1394 12.5% of the traffic. If all weights for a locator-set are equal, 1395 receiver of the Map-Reply will decide how to load-split traffic. 1396 See Section 6.5 for a suggested hash algorithm to distribute load 1397 across locators with same priority and equal weight values. 1399 M Priority: each RLOC is assigned a multicast priority used by an 1400 ETR in a receiver multicast site to select an ITR in a source 1401 multicast site for building multicast distribution trees. A value 1402 of 255 means the RLOC MUST NOT be used for joining a multicast 1403 distribution tree. 1405 M Weight: when priorities are the same for multiple RLOCs, the 1406 weight indicates how to balance building multicast distribution 1407 trees across multiple ITRs. The weight is encoded as a relative 1408 weight (similar to the unicast Weights) of total number of trees 1409 built to the source site identified by the EID-prefix. If all 1410 weights for a locator-set are equal, the receiver of the Map-Reply 1411 will decide how to distribute multicast state across ITRs. 1413 Unused Flags: set to 0 when sending and ignored on receipt. 1415 L: when this bit is set, the locator is flagged as a local locator to 1416 the ETR that is sending the Map-Reply. When a Map-Server is doing 1417 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1418 0 for all locators in this locator-set. 1420 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1421 locator address, for which this bit is set, is the one being RLOC- 1422 probed and may be different from the source address of the Map- 1423 Reply. An ITR that RLOC-probes a particular locator, MUST use 1424 this locator for retrieving the data structure used to store the 1425 fact that the locator is reachable. The "p" bit is set for a 1426 single locator in the same locator set. If an implementation sets 1427 more than one "p" bit erroneously, the receiver of the Map-Reply 1428 MUST select the first locator. The "p" bit MUST NOT be set for 1429 locator-set records sent in Map-Request and Map-Register messages. 1431 R: set when the sender of a Map-Reply has a route to the locator in 1432 the locator data record. This receiver may find this useful to 1433 know if the locator is up but not necessarily reachable from the 1434 receiver's point of view. See also Section 6.4 for another way 1435 the R-bit may be used. 1437 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1438 assigned to an ETR. Note that the destination RLOC address MAY be 1439 an anycast address. A source RLOC can be an anycast address as 1440 well. The source or destination RLOC MUST NOT be the broadcast 1441 address (255.255.255.255 or any subnet broadcast address known to 1442 the router), and MUST NOT be a link-local multicast address. The 1443 source RLOC MUST NOT be a multicast address. The destination RLOC 1444 SHOULD be a multicast address if it is being mapped from a 1445 multicast destination EID. 1447 Mapping Protocol Data: See [CONS] for details. This field is 1448 optional and present when the UDP length indicates there is enough 1449 space in the packet to include it. The Mapping Protocol Data is 1450 used when needed by the particular mapping system. 1452 6.1.5. EID-to-RLOC UDP Map-Reply Message 1454 A Map-Reply returns an EID-prefix with a prefix length that is less 1455 than or equal to the EID being requested. The EID being requested is 1456 either from the destination field of an IP header of a Data-Probe or 1457 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1458 globally-routable IP addresses of all ETRs for the LISP site. Each 1459 RLOC conveys status reachability but does not convey path 1460 reachability from a requesters perspective. Separate testing of path 1461 reachability is required, See Section 6.3 for details. 1463 Note that a Map-Reply may contain different EID-prefix granularity 1464 (prefix + length) than the Map-Request which triggers it. This might 1465 occur if a Map-Request were for a prefix that had been returned by an 1466 earlier Map-Reply. In such a case, the requester updates its cache 1467 with the new prefix information and granularity. For example, a 1468 requester with two cached EID-prefixes that are covered by a Map- 1469 Reply containing one, less-specific prefix, replaces the entry with 1470 the less-specific EID-prefix. Note that the reverse, replacement of 1471 one less-specific prefix with multiple more-specific prefixes, can 1472 also occur but not by removing the less-specific prefix rather by 1473 adding the more-specific prefixes which during a lookup will override 1474 the less-specific prefix. 1476 When an ETR is configured with overlapping EID-prefixes, a Map- 1477 Request with an EID that longest matches any EID-prefix MUST be 1478 returned in a single Map-Reply message. For instance, if an ETR had 1479 database mapping entries for EID-prefixes: 1481 10.0.0.0/8 1482 10.1.0.0/16 1483 10.1.1.0/24 1484 10.1.2.0/24 1486 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1487 count of 1 to be returned with a mapping record EID-prefix of 1488 10.1.1.0/24. 1490 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1491 count of 3 to be returned with mapping records for EID-prefixes 1492 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1494 Note that not all overlapping EID-prefixes need to be returned, only 1495 the more specifics (note in the second example above 10.0.0.0/8 was 1496 not returned for requesting EID 10.1.5.5) entries for the matching 1497 EID-prefix of the requesting EID. When more than one EID-prefix is 1498 returned, all SHOULD use the same Time-to-Live value so they can all 1499 time out at the same time. When a more specific EID-prefix is 1500 received later, its Time-to-Live value in the Map-Reply record can be 1501 stored even when other less specifics exist. When a less specific 1502 EID-prefix is received later, its map-cache expiration time SHOULD be 1503 set to the minimum expiration time of any more specific EID-prefix in 1504 the map-cache. 1506 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1507 per second to the same requesting router. For scalability, it is 1508 expected that aggregation of EID addresses into EID-prefixes will 1509 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1510 prefix range thereby reducing the number of Map-Request messages. 1512 Map-Reply records can have an empty locator-set. A negative Map- 1513 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1514 convey special actions by the sender to the ITR or PTR which have 1515 solicited the Map-Reply. There are two primary applications for 1516 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1517 ITR or PTR when a destination is for a LISP site versus a non-LISP 1518 site. And the other is to source quench Map-Requests which are sent 1519 for non-allocated EIDs. 1521 For each Map-Reply record, the list of locators in a locator-set MUST 1522 appear in the same order for each ETR that originates a Map-Reply 1523 message. The locator-set MUST be sorted in order of ascending IP 1524 address where an IPv4 locator address is considered numerically 'less 1525 than' an IPv6 locator address. 1527 When sending a Map-Reply message, the destination address is copied 1528 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1529 can choose a locator address from one of the address families it 1530 supports. For Data-Probes, the destination address of the Map-Reply 1531 is copied from the source address of the Data-Probe message which is 1532 invoking the reply. The source address of the Map-Reply is one of 1533 the local IP addresses chosen to allow uRPF checks to succeed in the 1534 upstream service provider. The destination port of a Map-Reply 1535 message is copied from the source port of the Map-Request or Data- 1536 Probe and the source port of the Map-Reply message is set to the 1537 well-known UDP port 4342. 1539 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1541 When an ETR is misconfigured or compromised, it could return coarse 1542 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1543 cover EID-prefixes which are allocated to other sites redirecting 1544 their traffic to the locators of the compromised site. 1546 To solve this problem, there are two basic solutions that could be 1547 used. The first is to have Map-Servers proxy-map-reply on behalf of 1548 ETRs so their registered EID-prefixes are the ones returned in Map- 1549 Replies. Since the interaction between an ETR and Map-Server is 1550 secured with shared-keys, it is more difficult for an ETR to 1551 misbehave. The second solution is to have ITRs and PTRs cache EID- 1552 prefixes with mask-lengths that are greater than or equal to a 1553 configured prefix length. This limits the damage to a specific width 1554 of any EID-prefix advertised, but needs to be coordinated with the 1555 allocation of site prefixes. These solutions can be used 1556 independently or at the same time. 1558 At the time of this writing, other approaches are being considered 1559 and researched. 1561 6.1.6. Map-Register Message Format 1563 The usage details of the Map-Register message can be found in 1564 specification [LISP-MS]. This section solely defines the message 1565 format. 1567 The message is sent in UDP with a destination UDP port of 4342 and a 1568 randomly selected UDP source port number. 1570 The Map-Register message format is: 1572 0 1 2 3 1573 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 1574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1575 |Type=3 |P| Reserved |M| Record Count | 1576 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1577 | Nonce . . . | 1578 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1579 | . . . Nonce | 1580 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1581 | Key ID | Authentication Data Length | 1582 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1583 ~ Authentication Data ~ 1584 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1585 | | Record TTL | 1586 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1587 R | Locator Count | EID mask-len | ACT |A| Reserved | 1588 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1589 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1590 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1591 r | EID-prefix | 1592 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1593 | /| Priority | Weight | M Priority | M Weight | 1594 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1595 | o | Unused Flags |L|p|R| Loc-AFI | 1596 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1597 | \| Locator | 1598 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1600 Packet field descriptions: 1602 Type: 3 (Map-Register) 1604 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1605 Register message requesting for the Map-Server to proxy Map-Reply. 1606 The Map-Server will send non-authoritative Map-Replies on behalf 1607 of the ETR. Details on this usage will be provided in a future 1608 version of this draft. 1610 Reserved: It MUST be set to 0 on transmit and MUST be ignored on 1611 receipt. 1613 M: This is the want-map-notify bit, when set to 1 an ETR is 1614 requesting for a Map-Notify message to be returned in response to 1615 sending a Map-Register message. The Map-Notify message sent by a 1616 Map-Server is used to an acknowledge receipt of a Map-Register 1617 message. 1619 Record Count: The number of records in this Map-Register message. A 1620 record is comprised of that portion of the packet labeled 'Record' 1621 above and occurs the number of times equal to Record count. 1623 Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages. 1625 Key ID: A configured ID to find the configured Message 1626 Authentication Code (MAC) algorithm and key value used for the 1627 authentication function. 1629 Authentication Data Length: The length in bytes of the 1630 Authentication Data field that follows this field. The length of 1631 the Authentication Data field is dependent on the Message 1632 Authentication Code (MAC) algorithm used. The length field allows 1633 a device that doesn't know the MAC algorithm to correctly parse 1634 the packet. 1636 Authentication Data: The message digest used from the output of the 1637 Message Authentication Code (MAC) algorithm. The entire Map- 1638 Register payload is authenticated with this field preset to 0. 1639 After the MAC is computed, it is placed in this field. 1640 Implementations of this specification MUST include support for 1641 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-128-256 [RFC4634] 1642 is recommended. 1644 The definition of the rest of the Map-Register can be found in the 1645 Map-Reply section. 1647 6.1.7. Map-Notify Message Format 1649 The usage details of the Map-Notify message can be found in 1650 specification [LISP-MS]. This section solely defines the message 1651 format. 1653 The message is sent inside a UDP packet with a source UDP port equal 1654 to 4342 and a destination port equal to the source port from the Map- 1655 Register message this Map-Notify message is responding to. 1657 The Map-Notify message format is: 1659 0 1 2 3 1660 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 1661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1662 |Type=4 | Reserved | Record Count | 1663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1664 | Nonce . . . | 1665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1666 | . . . Nonce | 1667 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1668 | Key ID | Authentication Data Length | 1669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1670 ~ Authentication Data ~ 1671 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1672 | | Record TTL | 1673 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1674 R | Locator Count | EID mask-len | ACT |A| Reserved | 1675 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1676 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1677 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1678 r | EID-prefix | 1679 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1680 | /| Priority | Weight | M Priority | M Weight | 1681 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1682 | o | Unused Flags |L|p|R| Loc-AFI | 1683 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1684 | \| Locator | 1685 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1687 Packet field descriptions: 1689 Type: 4 (Map-Notify) 1691 The Map-Notify message has the same contents as a Map-Register 1692 message. See Map-Register section for field descriptions. 1694 6.1.8. Encapsulated Control Message Format 1696 An Encapsulated Control Message is used to encapsulate control 1697 packets sent between xTRs and the mapping database system described 1698 in [LISP-MS]. 1700 0 1 2 3 1701 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 1702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1703 / | IPv4 or IPv6 Header | 1704 OH | (uses RLOC addresses) | 1705 \ | | 1706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1707 / | Source Port = xxxx | Dest Port = 4342 | 1708 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1709 \ | UDP Length | UDP Checksum | 1710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1711 LH |Type=8 |S| Reserved | 1712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1713 / | IPv4 or IPv6 Header | 1714 IH | (uses RLOC or EID addresses) | 1715 \ | | 1716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1717 / | Source Port = xxxx | Dest Port = yyyy | 1718 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1719 \ | UDP Length | UDP Checksum | 1720 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1721 LCM | LISP Control Message | 1722 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1724 Packet header descriptions: 1726 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1727 source and destination header address fields. 1729 UDP: The outer UDP header with destination port 4342. The source 1730 port is randomly allocated. The checksum field MUST be non-zero. 1732 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1733 and what follows is either an IPv4 or IPv6 header as encoded by 1734 the first 4 bits after the reserved field. 1736 S: This is the Security bit. When set to 1 the field following the 1737 Reserved field will have the following format. The detailed 1738 format of the Authentication Data Content is for further study. 1740 0 1 2 3 1741 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 1742 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1743 | AD Type | Authentication Data Content . . . | 1744 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1746 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1747 addresses in the header address fields. When a Map-Request is 1748 encapsulated in this packet format the destination address in this 1749 header is an EID. 1751 UDP: The inner UDP header where the port assignments depends on the 1752 control packet being encapsulated. When the control packet is a 1753 Map-Request or Map-Register, the source port is ITR/PITR selected 1754 and the destination port is 4342. When the control packet is a 1755 Map-Reply, the source port is 4342 and the destination port is 1756 assigned from the source port of the invoking Map-Request. Port 1757 number 4341 MUST NOT be assigned to either port. The checksum 1758 field MUST be non-zero. 1760 LCM: The format is one of the control message formats described in 1761 this section. At this time, only Map-Request messages and PIM 1762 Join-Prune messages [MLISP] are allowed to be encapsulated. 1763 Encapsulating other types of LISP control messages are for further 1764 study. When Map-Requests are sent for RLOC-probing purposes (i.e 1765 the probe-bit is set), they MUST NOT be sent inside Encapsulated 1766 Control Messages. 1768 6.2. Routing Locator Selection 1770 Both client-side and server-side may need control over the selection 1771 of RLOCs for conversations between them. This control is achieved by 1772 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1773 messages. Alternatively, RLOC information may be gleaned from 1774 received tunneled packets or EID-to-RLOC Map-Request messages. 1776 The following enumerates different scenarios for choosing RLOCs and 1777 the controls that are available: 1779 o Server-side returns one RLOC. Client-side can only use one RLOC. 1780 Server-side has complete control of the selection. 1782 o Server-side returns a list of RLOC where a subset of the list has 1783 the same best priority. Client can only use the subset list 1784 according to the weighting assigned by the server-side. In this 1785 case, the server-side controls both the subset list and load- 1786 splitting across its members. The client-side can use RLOCs 1787 outside of the subset list if it determines that the subset list 1788 is unreachable (unless RLOCs are set to a Priority of 255). Some 1789 sharing of control exists: the server-side determines the 1790 destination RLOC list and load distribution while the client-side 1791 has the option of using alternatives to this list if RLOCs in the 1792 list are unreachable. 1794 o Server-side sets weight of 0 for the RLOC subset list. In this 1795 case, the client-side can choose how the traffic load is spread 1796 across the subset list. Control is shared by the server-side 1797 determining the list and the client determining load distribution. 1798 Again, the client can use alternative RLOCs if the server-provided 1799 list of RLOCs are unreachable. 1801 o Either side (more likely on the server-side ETR) decides not to 1802 send a Map-Request. For example, if the server-side ETR does not 1803 send Map-Requests, it gleans RLOCs from the client-side ITR, 1804 giving the client-side ITR responsibility for bidirectional RLOC 1805 reachability and preferability. Server-side ETR gleaning of the 1806 client-side ITR RLOC is done by caching the inner header source 1807 EID and the outer header source RLOC of received packets. The 1808 client-side ITR controls how traffic is returned and can alternate 1809 using an outer header source RLOC, which then can be added to the 1810 list the server-side ETR uses to return traffic. Since no 1811 Priority or Weights are provided using this method, the server- 1812 side ETR MUST assume each client-side ITR RLOC uses the same best 1813 Priority with a Weight of zero. In addition, since EID-prefix 1814 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1815 on tunnel routers can grow to be very large. 1817 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1818 received encapsulated packet, is only stored and used for a few 1819 seconds, pending verification. Verification is performed by 1820 sending a Map-Request to the source EID (the inner header IP 1821 source address) of the received encapsulated packet. A reply to 1822 this "verifying Map-Request" is used to fully populate the map- 1823 cache entry for the "gleaned" EID and is stored and used for the 1824 time indicated from the TTL field of a received Map-Reply. When a 1825 verified map-cache entry is stored, data gleaning no longer occurs 1826 for subsequent packets which have a source EID that matches the 1827 EID-prefix of the verified entry. 1829 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1830 reachable when the R-bit for the locator record is set to 1. When 1831 the R-bit is set to 0, an ITR or PITR MUST not encapsulate to the 1832 RLOC. Neither the information contained in a Map-Reply or that 1833 stored in the mapping database system provides reachability 1834 information for RLOCs. Note that reachability is not part of the 1835 mapping system and is determined using one or more of the Routing 1836 Locator Reachability Algorithms described in the next section. 1838 6.3. Routing Locator Reachability 1840 Several mechanisms for determining RLOC reachability are currently 1841 defined: 1843 1. An ETR may examine the Loc-Status-Bits in the LISP header of an 1844 encapsulated data packet received from an ITR. If the ETR is 1845 also acting as an ITR and has traffic to return to the original 1846 ITR site, it can use this status information to help select an 1847 RLOC. 1849 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1850 message for an RLOC it is using. This indicates that the RLOC is 1851 likely down. 1853 3. An ITR which participates in the global routing system can 1854 determine that an RLOC is down if no BGP RIB route exists that 1855 matches the RLOC IP address. 1857 4. An ITR may receive an ICMP Port Unreachable message from a 1858 destination host. This occurs if an ITR attempts to use 1859 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1860 non-LISP-capable site. 1862 5. An ITR may receive a Map-Reply from a ETR in response to a 1863 previously sent Map-Request. The RLOC source of the Map-Reply is 1864 likely up since the ETR was able to send the Map-Reply to the 1865 ITR. 1867 6. When an ETR receives an encapsulated packet from an ITR, the 1868 source RLOC from the outer header of the packet is likely up. 1870 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1871 described in this section, namely Echo-Noncing or RLOC-Probing. 1873 When determining Locator up/down reachability by examining the Loc- 1874 Status-Bits from the LISP encapsulated data packet, an ETR will 1875 receive up to date status from an encapsulating ITR about 1876 reachability for all ETRs at the site. CE-based ITRs at the source 1877 site can determine reachability relative to each other using the site 1878 IGP as follows: 1880 o Under normal circumstances, each ITR will advertise a default 1881 route into the site IGP. 1883 o If an ITR fails or if the upstream link to its PE fails, its 1884 default route will either time-out or be withdrawn. 1886 Each ITR can thus observe the presence or lack of a default route 1887 originated by the others to determine the Locator Status Bits it sets 1888 for them. 1890 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1891 Loc-Status-Bits in a LISP encapsulated packet are numbered from 0 to 1892 n-1 starting with the least significant bit. For example, if an RLOC 1893 listed in the 3rd position of the Map-Reply goes down (ordinal value 1894 2), then all ITRs at the site will clear the 3rd least significant 1895 bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they 1896 encapsulate. 1898 When an ETR decapsulates a packet, it will check for any change in 1899 the Loc-Status-Bits field. When a bit goes from 1 to 0, the ETR will 1900 refrain from encapsulating packets to an RLOC that is indicated as 1901 down. It will only resume using that RLOC if the corresponding Loc- 1902 Status-Bit returns to a value of 1. Loc-Status-Bits are associated 1903 with a locator-set per EID-prefix. Therefore, when a locator becomes 1904 unreachable, the Loc-Status-Bit that corresponds to that locator's 1905 position in the list returned by the last Map-Reply will be set to 1906 zero for that particular EID-prefix. 1908 When ITRs at the site are not deployed in CE routers, the IGP can 1909 still be used to determine the reachability of Locators provided they 1910 are injected into the IGP. This is typically done when a /32 address 1911 is configured on a loopback interface. 1913 When ITRs receive ICMP Network or Host Unreachable messages as a 1914 method to determine unreachability, they will refrain from using 1915 Locators which are described in Locator lists of Map-Replies. 1916 However, using this approach is unreliable because many network 1917 operators turn off generation of ICMP Unreachable messages. 1919 If an ITR does receive an ICMP Network or Host Unreachable message, 1920 it MAY originate its own ICMP Unreachable message destined for the 1921 host that originated the data packet the ITR encapsulated. 1923 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 1924 locator address from a locator-set in a mapping entry matches a 1925 prefix. If it does not find one and BGP is running in the Default 1926 Free Zone (DFZ), it can decide to not use the locator even though the 1927 Loc-Status-Bits indicate the locator is up. In this case, the path 1928 from the ITR to the ETR that is assigned the locator is not 1929 available. More details are in [LOC-ID-ARCH]. 1931 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 1932 Reply is returned, reachability of the Locator has been determined. 1933 Obviously, sending such probes increases the number of control 1934 messages originated by tunnel routers for active flows, so Locators 1935 are assumed to be reachable when they are advertised. 1937 This assumption does create a dependency: Locator unreachability is 1938 detected by the receipt of ICMP Host Unreachable messages. When an 1939 Locator has been determined to be unreachable, it is not used for 1940 active traffic; this is the same as if it were listed in a Map-Reply 1941 with priority 255. 1943 The ITR can test the reachability of the unreachable Locator by 1944 sending periodic Requests. Both Requests and Replies MUST be rate- 1945 limited. Locator reachability testing is never done with data 1946 packets since that increases the risk of packet loss for end-to-end 1947 sessions. 1949 When an ETR decapsulates a packet, it knows that it is reachable from 1950 the encapsulating ITR because that is how the packet arrived. In 1951 most cases, the ETR can also reach the ITR but cannot assume this to 1952 be true due to the possibility of path asymmetry. In the presence of 1953 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 1954 use the lack of return traffic as an indication that the ETR is 1955 unreachable. Instead, it MUST use an alternate mechanisms to 1956 determine reachability. 1958 6.3.1. Echo Nonce Algorithm 1960 When data flows bidirectionally between locators from different 1961 sites, a data-plane mechanism called "nonce echoing" can be used to 1962 determine reachability between an ITR and ETR. When an ITR wants to 1963 solicit a nonce echo, it sets the N and E bits and places a 24-bit 1964 nonce in the LISP header of the next encapsulated data packet. 1966 When this packet is received by the ETR, the encapsulated packet is 1967 forwarded as normal. When the ETR next sends a data packet to the 1968 ITR, it includes the nonce received earlier with the N bit set and E 1969 bit cleared. The ITR sees this "echoed nonce" and knows the path to 1970 and from the ETR is up. 1972 The ITR will set the E-bit and N-bit for every packet it sends while 1973 in echo-nonce-request state. The time the ITR waits to process the 1974 echoed nonce before it determines the path is unreachable is variable 1975 and a choice left for the implementation. 1977 If the ITR is receiving packets from the ETR but does not see the 1978 nonce echoed while being in echo-nonce-request state, then the path 1979 to the ETR is unreachable. This decision may be overridden by other 1980 locator reachability algorithms. Once the ITR determines the path to 1981 the ETR is down it can switch to another locator for that EID-prefix. 1983 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1984 be implementing both ITR and ETR functionality for the echo nonce 1985 mechanism to operate. 1987 The ITR and ETR may both go into echo-nonce-request state at the same 1988 time. The number of packets sent or the time during which echo nonce 1989 requests are sent is an implementation specific setting. However, 1990 when an ITR is in echo-nonce-request state, it can echo the ETR's 1991 nonce in the next set of packets that it encapsulates and then 1992 subsequently, continue sending echo-nonce-request packets. 1994 This mechanism does not completely solve the forward path 1995 reachability problem as traffic may be unidirectional. That is, the 1996 ETR receiving traffic at a site may not be the same device as an ITR 1997 which transmits traffic from that site or the site to site traffic is 1998 unidirectional so there is no ITR returning traffic. 2000 The echo-nonce algorithm is bilateral. That is, if one side sets the 2001 E-bit and the other side is not enabled for echo-noncing, then the 2002 echoing of the nonce does not occur and the requesting side may 2003 regard the locator unreachable erroneously. An ITR SHOULD only set 2004 the E-bit in a encapsulated data packet when it knows the ETR is 2005 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 2006 Reply message. 2008 Note that other locator reachability mechanisms are being researched 2009 and can be used to compliment or even override the Echo Nonce 2010 Algorithm. See next section for an example of control-plane probing. 2012 6.3.2. RLOC Probing Algorithm 2014 RLOC Probing is a method that an ITR or PTR can use to determine the 2015 reachability status of one or more locators that it has cached in a 2016 map-cache entry. The probe-bit of the Map-Request and Map-Reply 2017 messages are used for RLOC Probing. 2019 RLOC probing is done in the control-plane on a timer basis where an 2020 ITR or PTR will originate a Map-Request destined to a locator address 2021 from one of its own locator addresses. A Map-Request used as an 2022 RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the 2023 ALT like one would when soliciting mapping data. The EID record 2024 encoded in the Map-Request is the EID-prefix of the map-cache entry 2025 cached by the ITR or PTR. The ITR may include a mapping data record 2026 for its own database mapping information which contains the local 2027 EID-prefixes and RLOCs for its site. 2029 When an ETR receives a Map-Request message with the probe-bit set, it 2030 returns a Map-Reply with the probe-bit set. The source address of 2031 the Map-Reply is set from the destination address of the Map-Request 2032 and the destination address of the Map-Reply is set from the source 2033 address of the Map-Request. The Map-Reply SHOULD contain mapping 2034 data for the EID-prefix contained in the Map-Request. This provides 2035 the opportunity for the ITR or PTR, which sent the RLOC-probe to get 2036 mapping updates if there were changes to the ETR's database mapping 2037 entries. 2039 There are advantages and disadvantages of RLOC Probing. The greatest 2040 benefit of RLOC Probing is that it can handle many failure scenarios 2041 allowing the ITR to determine when the path to a specific locator is 2042 reachable or has become unreachable, thus providing a robust 2043 mechanism for switching to using another locator from the cached 2044 locator. RLOC Probing can also provide rough RTT estimates between a 2045 pair of locators which can be useful for network management purposes 2046 as well as for selecting low delay paths. The major disadvantage of 2047 RLOC Probing is in the number of control messages required and the 2048 amount of bandwidth used to obtain those benefits, especially if the 2049 requirement for failure detection times are very small. 2051 Continued research and testing will attempt to characterize the 2052 tradeoffs of failure detection times versus message overhead. 2054 6.4. EID Reachability within a LISP Site 2056 A site may be multihomed using two or more ETRs. The hosts and 2057 infrastructure within a site will be addressed using one or more EID 2058 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2059 mapping system. One possible failure mode is for an ETR to lose 2060 reachability to one or more of the EID prefixes within its own site. 2061 When this occurs when the ETR sends Map-Replies, it can clear the 2062 R-bit associated with its own locator. And when the ETR is also an 2063 ITR, it can clear its locator-status-bit in the encapsulation data 2064 header. 2066 It is recognized there are no simple solutions to the site 2067 partitioning problem because it is hard to know which part of the 2068 EID-prefix range is partitioned. And which locators can reach any 2069 sub-ranges of the EID-prefixes. This problem is under investigation 2070 with the expectation that experiments will tell us more. Note, this 2071 is not a new problem introduced by the LISP architecture. The 2072 problem exists today when a multi-homed site uses BGP to advertise 2073 its reachability upstream. 2075 6.5. Routing Locator Hashing 2077 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2078 a requesting ITR, the locator-set for the EID-prefix may contain 2079 different priority values for each locator address. When more than 2080 one best priority locator exists, the ITR can decide how to load 2081 share traffic against the corresponding locators. 2083 The following hash algorithm may be used by an ITR to select a 2084 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2086 1. Either a source and destination address hash can be used or the 2087 traditional 5-tuple hash which includes the source and 2088 destination addresses, source and destination TCP, UDP, or SCTP 2089 port numbers and the IP protocol number field or IPv6 next- 2090 protocol fields of a packet a host originates from within a LISP 2091 site. When a packet is not a TCP, UDP, or SCTP packet, the 2092 source and destination addresses only from the header are used to 2093 compute the hash. 2095 2. Take the hash value and divide it by the number of locators 2096 stored in the locator-set for the EID-to-RLOC mapping. 2098 3. The remainder will be yield a value of 0 to "number of locators 2099 minus 1". Use the remainder to select the locator in the 2100 locator-set. 2102 Note that when a packet is LISP encapsulated, the source port number 2103 in the outer UDP header needs to be set. Selecting a hashed value 2104 allows core routers which are attached to Link Aggregation Groups 2105 (LAGs) to load-split the encapsulated packets across member links of 2106 such LAGs. Otherwise, core routers would see a single flow, since 2107 packets have a source address of the ITR, for packets which are 2108 originated by different EIDs at the source site. A suggested setting 2109 for the source port number computed by an ITR is a 5-tuple hash 2110 function on the inner header, as described above. 2112 Many core router implementations use a 5-tuple hash to decide how to 2113 balance packet load across members of a LAG. The 5-tuple hash 2114 includes the source and destination addresses of the packet and the 2115 source and destination ports when the protocol number in the packet 2116 is TCP or UDP. For this reason, UDP encoding is used for LISP 2117 encapsulation. 2119 6.6. Changing the Contents of EID-to-RLOC Mappings 2121 Since the LISP architecture uses a caching scheme to retrieve and 2122 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2123 date mapping is to re-request the mapping. However, the ITRs do not 2124 know when the mappings change and the ETRs do not keep track of which 2125 ITRs requested its mappings. For scalability reasons, we want to 2126 maintain this approach but need to provide a way for ETRs change 2127 their mappings and inform the sites that are currently communicating 2128 with the ETR site using such mappings. 2130 When adding a new locator record in lexicographic order to the end of 2131 a locator-set, it is easy to update mappings. We assume new mappings 2132 will maintain the same locator ordering as the old mapping but just 2133 have new locators appended to the end of the list. So some ITRs can 2134 have a new mapping while other ITRs have only an old mapping that is 2135 used until they time out. When an ITR has only an old mapping but 2136 detects bits set in the loc-status-bits that correspond to locators 2137 beyond the list it has cached, it simply ignores them. However, this 2138 can only happen for locator addresses that are lexicographically 2139 greater than the locator addresses in the existing locator-set. 2141 When a locator record is inserted in the middle of a locator-set, to 2142 maintain lexicographic order, the SMR procedure in Section 6.6.2 is 2143 used to inform ITRs and PTRs of the new locator-status-bit mappings. 2145 When a locator record is removed from a locator-set, ITRs that have 2146 the mapping cached will not use the removed locator because the xTRs 2147 will set the loc-status-bit to 0. So even if the locator is in the 2148 list, it will not be used. For new mapping requests, the xTRs can 2149 set the locator AFI to 0 (indicating an unspecified address), as well 2150 as setting the corresponding loc-status-bit to 0. This forces ITRs 2151 with old or new mappings to avoid using the removed locator. 2153 If many changes occur to a mapping over a long period of time, one 2154 will find empty record slots in the middle of the locator-set and new 2155 records appended to the locator-set. At some point, it would be 2156 useful to compact the locator-set so the loc-status-bit settings can 2157 be efficiently packed. 2159 We propose here three approaches for locator-set compaction, one 2160 operational and two protocol mechanisms. The operational approach 2161 uses a clock sweep method. The protocol approaches use the concept 2162 of Solicit-Map-Requests and Map-Versioning. 2164 6.6.1. Clock Sweep 2166 The clock sweep approach uses planning in advance and the use of 2167 count-down TTLs to time out mappings that have already been cached. 2168 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2169 there is a 24 hour window to time out old mappings. The following 2170 clock sweep procedure is used: 2172 1. 24 hours before a mapping change is to take effect, a network 2173 administrator configures the ETRs at a site to start the clock 2174 sweep window. 2176 2. During the clock sweep window, ETRs continue to send Map-Reply 2177 messages with the current (unchanged) mapping records. The TTL 2178 for these mappings is set to 1 hour. 2180 3. 24 hours later, all previous cache entries will have timed out, 2181 and any active cache entries will time out within 1 hour. During 2182 this 1 hour window the ETRs continue to send Map-Reply messages 2183 with the current (unchanged) mapping records with the TTL set to 2184 1 minute. 2186 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2187 messages with the new (changed) mapping records. So any active 2188 caches can get the new mapping contents right away if not cached, 2189 or in 1 minute if they had the mapping cached. The new mappings 2190 are cached with a time to live equal to the TTL in the Map-Reply. 2192 6.6.2. Solicit-Map-Request (SMR) 2194 Soliciting a Map-Request is a selective way for ETRs, at the site 2195 where mappings change, to control the rate they receive requests for 2196 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2197 the mappings they have cached. 2199 Since the ETRs don't keep track of remote ITRs that have cached their 2200 mappings, they do not know which ITRs need to have their mappings 2201 updated. As a result, an ETR will solicit Map-Requests (called an 2202 SMR message) from those sites to which it has been sending 2203 encapsulated data to for the last minute. In particular, an ETR will 2204 send an SMR an ITR to which it has recently sent encapsulated data. 2206 An SMR message is simply a bit set in a Map-Request message. An ITR 2207 or PTR will send a Map-Request when they receive an SMR message. 2208 Both the SMR sender and the Map-Request responder MUST rate-limited 2209 these messages. Rate-limiting can be implemented as a global rate- 2210 limiter or one rate-limiter per SMR destination. 2212 The following procedure shows how a SMR exchange occurs when a site 2213 is doing locator-set compaction for an EID-to-RLOC mapping: 2215 1. When the database mappings in an ETR change, the ETRs at the site 2216 begin to send Map-Requests with the SMR bit set for each locator 2217 in each map-cache entry the ETR caches. 2219 2. A remote ITR which receives the SMR message will schedule sending 2220 a Map-Request message to the source locator address of the SMR 2221 message or to the mapping database system. A newly allocated 2222 random nonce is selected and the EID-prefix used is the one 2223 copied from the SMR message. If the source locator is the only 2224 locator in the cached locator-set, the remote ITR SHOULD send a 2225 Map-Request to the database mapping system just in case the 2226 single locator has changed and may no longer be reachable to 2227 accept the Map-Request. 2229 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2230 Map-Reply while continuing to use the cached mapping. When Map 2231 Versioning is used, described in Section 6.6.3, an SMR sender can 2232 detect if an ITR is using the most up to date database mapping. 2234 4. The ETRs at the site with the changed mapping will reply to the 2235 Map-Request with a Map-Reply message that has a nonce from the 2236 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2237 limited. This is important to avoid Map-Reply implosion. 2239 5. The ETRs, at the site with the changed mapping, record the fact 2240 that the site that sent the Map-Request has received the new 2241 mapping data in the mapping cache entry for the remote site so 2242 the loc-status-bits are reflective of the new mapping for packets 2243 going to the remote site. The ETR then stops sending SMR 2244 messages. 2246 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2247 To avoid map-cache entry corruption by a third-party, a sender of an 2248 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2249 based Map-Request and the source is not in the locator-set for the 2250 stored map-cache entry, then the responding Map-Request MUST be sent 2251 with an EID destination to the mapping database system. Since the 2252 mapping database system is more secure to reach an authoritative ETR, 2253 it will deliver the Map-Request to the authoritative source of the 2254 mapping data. 2256 When an ITR receives an SMR-based Map-Request for which it does not 2257 have a cached mapping for the EID in the SMR message, it MAY not send 2258 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2259 SMR messages to all locators in the locator-set it has stored in its 2260 map-cache but the remote ITRs that receive the SMR may not be sending 2261 packets to the site. There is no point in updating the ITRs until 2262 they need to send, in which case, they will send Map-Requests to 2263 obtain a map-cache entry. 2265 6.6.3. Database Map Versioning 2267 When there is unidirectional packet flow between an ITR and ETR, and 2268 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2269 ITR so encapsulation can stop to a removed locator and start to a new 2270 locator in the locator-set. 2272 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2273 number. This is known as the Destination Map-Version Number. ITRs 2274 include the Destination Map-Version Number in packets they 2275 encapsulate to the site. When an ETR decapsulates a packet and 2276 detects the Destination Map-Version Number is less than the current 2277 version for its mapping, the SMR procedure described in Section 6.6.2 2278 occurs. 2280 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2281 Version number. This is known as the Source Map-Version Number. 2282 When an ETR decapsulates a packet and detects the Source Map-Version 2283 Number is greater than the last Map-Version Number sent in a Map- 2284 Reply from the ITR's site, the ETR will send a Map-Request to one of 2285 the ETRs for the source site. 2287 A Map-Version Number is used as a sequence number per EID-prefix. So 2288 values that are greater, are considered to be more recent. A value 2289 of 0 for the Source Map-Version Number or the Destination Map-Version 2290 Number conveys no versioning information and an ITR does no 2291 comparison with previously received Map-Version Numbers. 2293 A Map-Version Number can be included in Map-Register messages as 2294 well. This is a good way for the Map-Server can assure that all ETRs 2295 for a site registering to it will be Map-Version number synchronized. 2297 See [VERSIONING] for a more detailed analysis and description of 2298 Database Map Versioning. 2300 7. Router Performance Considerations 2302 LISP is designed to be very hardware-based forwarding friendly. A 2303 few implementation techniques can be used to incrementally implement 2304 LISP: 2306 o When a tunnel encapsulated packet is received by an ETR, the outer 2307 destination address may not be the address of the router. This 2308 makes it challenging for the control plane to get packets from the 2309 hardware. This may be mitigated by creating special FIB entries 2310 for the EID-prefixes of EIDs served by the ETR (those for which 2311 the router provides an RLOC translation). These FIB entries are 2312 marked with a flag indicating that control plane processing should 2313 be performed. The forwarding logic of testing for particular IP 2314 protocol number value is not necessary. There are a few proven 2315 cases where no changes to existing deployed hardware were needed 2316 to support the LISP data-plane. 2318 o On an ITR, prepending a new IP header consists of adding more 2319 bytes to a MAC rewrite string and prepending the string as part of 2320 the outgoing encapsulation procedure. Routers that support GRE 2321 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2322 support this action. 2324 o A packet's source address or interface the packet was received on 2325 can be used to select a VRF (Virtual Routing/Forwarding). The 2326 VRF's routing table can be used to find EID-to-RLOC mappings. 2328 8. Deployment Scenarios 2330 This section will explore how and where ITRs and ETRs can be deployed 2331 and will discuss the pros and cons of each deployment scenario. For 2332 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2334 There are two basic deployment trade-offs to consider: centralized 2335 versus distributed caches and flat, recursive, or re-encapsulating 2336 tunneling. When deciding on centralized versus distributed caching, 2337 the following issues should be considered: 2339 o Are the tunnel routers spread out so that the caches are spread 2340 across all the memories of each router? 2342 o Should management "touch points" be minimized by choosing few 2343 tunnel routers, just enough for redundancy? 2345 o In general, using more ITRs doesn't increase management load, 2346 since caches are built and stored dynamically. On the other hand, 2347 more ETRs does require more management since EID-prefix-to-RLOC 2348 mappings need to be explicitly configured. 2350 When deciding on flat, recursive, or re-encapsulation tunneling, the 2351 following issues should be considered: 2353 o Flat tunneling implements a single tunnel between source site and 2354 destination site. This generally offers better paths between 2355 sources and destinations with a single tunnel path. 2357 o Recursive tunneling is when tunneled traffic is again further 2358 encapsulated in another tunnel, either to implement VPNs or to 2359 perform Traffic Engineering. When doing VPN-based tunneling, the 2360 site has some control since the site is prepending a new tunnel 2361 header. In the case of TE-based tunneling, the site may have 2362 control if it is prepending a new tunnel header, but if the site's 2363 ISP is doing the TE, then the site has no control. Recursive 2364 tunneling generally will result in suboptimal paths but at the 2365 benefit of steering traffic to resource available parts of the 2366 network. 2368 o The technique of re-encapsulation ensures that packets only 2369 require one tunnel header. So if a packet needs to be rerouted, 2370 it is first decapsulated by the ETR and then re-encapsulated with 2371 a new tunnel header using a new RLOC. 2373 The next sub-sections will survey where tunnel routers can reside in 2374 the network. 2376 8.1. First-hop/Last-hop Tunnel Routers 2378 By locating tunnel routers close to hosts, the EID-prefix set is at 2379 the granularity of an IP subnet. So at the expense of more EID- 2380 prefix-to-RLOC sets for the site, the caches in each tunnel router 2381 can remain relatively small. But caches always depend on the number 2382 of non-aggregated EID destination flows active through these tunnel 2383 routers. 2385 With more tunnel routers doing encapsulation, the increase in control 2386 traffic grows as well: since the EID-granularity is greater, more 2387 Map-Requests and Map-Replies are traveling between more routers. 2389 The advantage of placing the caches and databases at these stub 2390 routers is that the products deployed in this part of the network 2391 have better price-memory ratios then their core router counterparts. 2392 Memory is typically less expensive in these devices and fewer routes 2393 are stored (only IGP routes). These devices tend to have excess 2394 capacity, both for forwarding and routing state. 2396 LISP functionality can also be deployed in edge switches. These 2397 devices generally have layer-2 ports facing hosts and layer-3 ports 2398 facing the Internet. Spare capacity is also often available in these 2399 devices as well. 2401 8.2. Border/Edge Tunnel Routers 2403 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2404 space associated with a site to be reachable via a small set of RLOCs 2405 assigned to the CE routers for that site. This is the default 2406 behavior envisioned in the rest of this specification. 2408 This offers the opposite benefit of the first-hop/last-hop tunnel 2409 router scenario: the number of mapping entries and network management 2410 touch points are reduced, allowing better scaling. 2412 One disadvantage is that less of the network's resources are used to 2413 reach host endpoints thereby centralizing the point-of-failure domain 2414 and creating network choke points at the CE router. 2416 Note that more than one CE router at a site can be configured with 2417 the same IP address. In this case an RLOC is an anycast address. 2418 This allows resilience between the CE routers. That is, if a CE 2419 router fails, traffic is automatically routed to the other routers 2420 using the same anycast address. However, this comes with the 2421 disadvantage where the site cannot control the entrance point when 2422 the anycast route is advertised out from all border routers. Another 2423 disadvantage of using anycast locators is the limited advertisement 2424 scope of /32 (or /128 for IPv6) routes. 2426 8.3. ISP Provider-Edge (PE) Tunnel Routers 2428 Use of ISP PE routers as tunnel endpoint routers is not the typical 2429 deployment scenario envisioned in the specification. This section 2430 attempts to capture some of reasoning behind this preference of 2431 implementing LISP on CE routers. 2433 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2434 than a site, control over the location of the egress tunnel 2435 endpoints. That is, the ISP can decide if the tunnel endpoints are 2436 in the destination site (in either CE routers or last-hop routers 2437 within a site) or at other PE edges. The advantage of this case is 2438 that two tunnel headers can be avoided. By having the PE be the 2439 first router on the path to encapsulate, it can choose a TE path 2440 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2441 the destination end site. 2443 An obvious disadvantage is that the end site has no control over 2444 where its packets flow or the RLOCs used. Other disadvantages 2445 include the difficulty in synchronizing path liveness updates between 2446 CE and PE routers. 2448 As mentioned in earlier sections a combination of these scenarios is 2449 possible at the expense of extra packet header overhead, if both site 2450 and provider want control, then recursive or re-encapsulating tunnels 2451 are used. 2453 8.4. LISP Functionality with Conventional NATs 2455 LISP routers can be deployed behind Network Address Translator (NAT) 2456 devices to provide the same set of packet services hosts have today 2457 when they are addressed out of private address space. 2459 It is important to note that a locator address in any LISP control 2460 message MUST be a globally routable address and therefore SHOULD NOT 2461 contain [RFC1918] addresses. If a LISP router is configured with 2462 private addresses, they MUST be used only in the outer IP header so 2463 the NAT device can translate properly. Otherwise, EID addresses MUST 2464 be translated before encapsulation is performed. Both NAT 2465 translation and LISP encapsulation functions could be co-located in 2466 the same device. 2468 More details on LISP address translation can be found in [INTERWORK]. 2470 8.5. Packets Egressing a LISP Site 2472 When a LISP site is using two ITRs for redundancy, the failure of one 2473 ITR will likely shift outbound traffic to the second. This second 2474 ITR's cache may not not be populated with the same EID-to-RLOC 2475 mapping entries as the first. If this second ITR does not have these 2476 mappings, traffic will be dropped while the mappings are retrieved 2477 from the mapping system. The retrieval of these messages may 2478 increase the load of requests being sent into the mapping system. 2479 Deployment and experimentation will determine whether this issue 2480 requires more attention. 2482 9. Traceroute Considerations 2484 When a source host in a LISP site initiates a traceroute to a 2485 destination host in another LISP site, it is highly desirable for it 2486 to see the entire path. Since packets are encapsulated from ITR to 2487 ETR, the hop across the tunnel could be viewed as a single hop. 2488 However, LISP traceroute will provide the entire path so the user can 2489 see 3 distinct segments of the path from a source LISP host to a 2490 destination LISP host: 2492 Segment 1 (in source LISP site based on EIDs): 2494 source-host ---> first-hop ... next-hop ---> ITR 2496 Segment 2 (in the core network based on RLOCs): 2498 ITR ---> next-hop ... next-hop ---> ETR 2500 Segment 3 (in the destination LISP site based on EIDs): 2502 ETR ---> next-hop ... last-hop ---> destination-host 2504 For segment 1 of the path, ICMP Time Exceeded messages are returned 2505 in the normal matter as they are today. The ITR performs a TTL 2506 decrement and test for 0 before encapsulating. So the ITR hop is 2507 seen by the traceroute source has an EID address (the address of 2508 site-facing interface). 2510 For segment 2 of the path, ICMP Time Exceeded messages are returned 2511 to the ITR because the TTL decrement to 0 is done on the outer 2512 header, so the destination of the ICMP messages are to the ITR RLOC 2513 address, the source RLOC address of the encapsulated traceroute 2514 packet. The ITR looks inside of the ICMP payload to inspect the 2515 traceroute source so it can return the ICMP message to the address of 2516 the traceroute client as well as retaining the core router IP address 2517 in the ICMP message. This is so the traceroute client can display 2518 the core router address (the RLOC address) in the traceroute output. 2519 The ETR returns its RLOC address and responds to the TTL decrement to 2520 0 like the previous core routers did. 2522 For segment 3, the next-hop router downstream from the ETR will be 2523 decrementing the TTL for the packet that was encapsulated, sent into 2524 the core, decapsulated by the ETR, and forwarded because it isn't the 2525 final destination. If the TTL is decremented to 0, any router on the 2526 path to the destination of the traceroute, including the next-hop 2527 router or destination, will send an ICMP Time Exceeded message to the 2528 source EID of the traceroute client. The ICMP message will be 2529 encapsulated by the local ITR and sent back to the ETR in the 2530 originated traceroute source site, where the packet will be delivered 2531 to the host. 2533 9.1. IPv6 Traceroute 2535 IPv6 traceroute follows the procedure described above since the 2536 entire traceroute data packet is included in ICMP Time Exceeded 2537 message payload. Therefore, only the ITR needs to pay special 2538 attention for forwarding ICMP messages back to the traceroute source. 2540 9.2. IPv4 Traceroute 2542 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2543 ICMP Time Exceeded messages only include the invoking IP header and 8 2544 bytes that follow the IP header. Therefore, when a core router sends 2545 an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP 2546 payload is the encapsulated header it prepended followed by a UDP 2547 header. The original invoking IP header, and therefore the identity 2548 of the traceroute source is lost. 2550 The solution we propose to solve this problem is to cache traceroute 2551 IPv4 headers in the ITR and to match them up with corresponding IPv4 2552 Time Exceeded messages received from core routers and the ETR. The 2553 ITR will use a circular buffer for caching the IPv4 and UDP headers 2554 of traceroute packets. It will select a 16-bit number as a key to 2555 find them later when the IPv4 Time Exceeded messages are received. 2556 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2557 16-bit number as the UDP source port in the encapsulating header. 2558 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2559 header of the encapsulating header is present in the ICMP payload 2560 thereby allowing the ITR to find the cached headers for the 2561 traceroute source. The ITR puts the cached headers in the payload 2562 and sends the ICMP Time Exceeded message to the traceroute source 2563 retaining the source address of the original ICMP Time Exceeded 2564 message (a core router or the ETR of the site of the traceroute 2565 destination). 2567 The signature of a traceroute packet comes in two forms. The first 2568 form is encoded as a UDP message where the destination port is 2569 inspected for a range of values. The second form is encoded as an 2570 ICMP message where the IP identification field is inspected for a 2571 well-known value. 2573 9.3. Traceroute using Mixed Locators 2575 When either an IPv4 traceroute or IPv6 traceroute is originated and 2576 the ITR encapsulates it in the other address family header, you 2577 cannot get all 3 segments of the traceroute. Segment 2 of the 2578 traceroute can not be conveyed to the traceroute source since it is 2579 expecting addresses from intermediate hops in the same address format 2580 for the type of traceroute it originated. Therefore, in this case, 2581 segment 2 will make the tunnel look like one hop. All the ITR has to 2582 do to make this work is to not copy the inner TTL to the outer, 2583 encapsulating header's TTL when a traceroute packet is encapsulated 2584 using an RLOC from a different address family. This will cause no 2585 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2587 10. Mobility Considerations 2589 There are several kinds of mobility of which only some might be of 2590 concern to LISP. Essentially they are as follows. 2592 10.1. Site Mobility 2594 A site wishes to change its attachment points to the Internet, and 2595 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2596 providers. Changes in EID-RLOC mappings for sites are expected to be 2597 handled by configuration, outside of the LISP protocol. 2599 10.2. Slow Endpoint Mobility 2601 An individual endpoint wishes to move, but is not concerned about 2602 maintaining session continuity. Renumbering is involved. LISP can 2603 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2604 decoupling the address space used by a site from the address spaces 2605 used by its ISPs. [RFC4984] 2607 10.3. Fast Endpoint Mobility 2609 Fast endpoint mobility occurs when an endpoint moves relatively 2610 rapidly, changing its IP layer network attachment point. Maintenance 2611 of session continuity is a goal. This is where the Mobile IPv4 2612 [RFC3344bis] and Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used, 2613 and primarily where interactions with LISP need to be explored. 2615 The problem is that as an endpoint moves, it may require changes to 2616 the mapping between its EID and a set of RLOCs for its new network 2617 location. When this is added to the overhead of mobile IP binding 2618 updates, some packets might be delayed or dropped. 2620 In IPv4 mobility, when an endpoint is away from home, packets to it 2621 are encapsulated and forwarded via a home agent which resides in the 2622 home area the endpoint's address belongs to. The home agent will 2623 encapsulate and forward packets either directly to the endpoint or to 2624 a foreign agent which resides where the endpoint has moved to. 2625 Packets from the endpoint may be sent directly to the correspondent 2626 node, may be sent via the foreign agent, or may be reverse-tunneled 2627 back to the home agent for delivery to the mobile node. As the 2628 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2629 mappings are required for communication between the mobile node and 2630 the home agent, whether via foreign agent or not. As a mobile 2631 endpoint changes networks, up to three LISP mapping changes may be 2632 required: 2634 o The mobile node moves from an old location to a new visited 2635 network location and notifies its home agent that it has done so. 2636 The Mobile IPv4 control packets the mobile node sends pass through 2637 one of the new visited network's ITRs, which needs a EID-RLOC 2638 mapping for the home agent. 2640 o The home agent might not have the EID-RLOC mappings for the mobile 2641 node's "care-of" address or its foreign agent in the new visited 2642 network, in which case it will need to acquire them. 2644 o When packets are sent directly to the correspondent node, it may 2645 be that no traffic has been sent from the new visited network to 2646 the correspondent node's network, and the new visited network's 2647 ITR will need to obtain an EID-RLOC mapping for the correspondent 2648 node's site. 2650 In addition, if the IPv4 endpoint is sending packets from the new 2651 visited network using its original EID, then LISP will need to 2652 perform a route-returnability check on the new EID-RLOC mapping for 2653 that EID. 2655 In IPv6 mobility, packets can flow directly between the mobile node 2656 and the correspondent node in either direction. The mobile node uses 2657 its "care-of" address (EID). In this case, the route-returnability 2658 check would not be needed but one more LISP mapping lookup may be 2659 required instead: 2661 o As above, three mapping changes may be needed for the mobile node 2662 to communicate with its home agent and to send packets to the 2663 correspondent node. 2665 o In addition, another mapping will be needed in the correspondent 2666 node's ITR, in order for the correspondent node to send packets to 2667 the mobile node's "care-of" address (EID) at the new network 2668 location. 2670 When both endpoints are mobile the number of potential mapping 2671 lookups increases accordingly. 2673 As a mobile node moves there are not only mobility state changes in 2674 the mobile node, correspondent node, and home agent, but also state 2675 changes in the ITRs and ETRs for at least some EID-prefixes. 2677 The goal is to support rapid adaptation, with little delay or packet 2678 loss for the entire system. Also IP mobility can be modified to 2679 require fewer mapping changes. In order to increase overall system 2680 performance, there may be a need to reduce the optimization of one 2681 area in order to place fewer demands on another. 2683 In LISP, one possibility is to "glean" information. When a packet 2684 arrives, the ETR could examine the EID-RLOC mapping and use that 2685 mapping for all outgoing traffic to that EID. It can do this after 2686 performing a route-returnability check, to ensure that the new 2687 network location does have a internal route to that endpoint. 2688 However, this does not cover the case where an ITR (the node assigned 2689 the RLOC) at the mobile-node location has been compromised. 2691 Mobile IP packet exchange is designed for an environment in which all 2692 routing information is disseminated before packets can be forwarded. 2693 In order to allow the Internet to grow to support expected future 2694 use, we are moving to an environment where some information may have 2695 to be obtained after packets are in flight. Modifications to IP 2696 mobility should be considered in order to optimize the behavior of 2697 the overall system. Anything which decreases the number of new EID- 2698 RLOC mappings needed when a node moves, or maintains the validity of 2699 an EID-RLOC mapping for a longer time, is useful. 2701 10.4. Fast Network Mobility 2703 In addition to endpoints, a network can be mobile, possibly changing 2704 xTRs. A "network" can be as small as a single router and as large as 2705 a whole site. This is different from site mobility in that it is 2706 fast and possibly short-lived, but different from endpoint mobility 2707 in that a whole prefix is changing RLOCs. However, the mechanisms 2708 are the same and there is no new overhead in LISP. A map request for 2709 any endpoint will return a binding for the entire mobile prefix. 2711 If mobile networks become a more common occurrence, it may be useful 2712 to revisit the design of the mapping service and allow for dynamic 2713 updates of the database. 2715 The issue of interactions between mobility and LISP needs to be 2716 explored further. Specific improvements to the entire system will 2717 depend on the details of mapping mechanisms. Mapping mechanisms 2718 should be evaluated on how well they support session continuity for 2719 mobile nodes. 2721 10.5. LISP Mobile Node Mobility 2723 A mobile device can use the LISP infrastructure to achieve mobility 2724 by implementing the LISP encapsulation and decapsulation functions 2725 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2726 node" can use topologically-independent EID IP addresses that are not 2727 advertised into and do not impose a cost on the global routing 2728 system. These EIDs are maintained at the edges of the mapping system 2729 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2730 only the correspondents of the LISP mobile node. 2732 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2733 more details. 2735 11. Multicast Considerations 2737 A multicast group address, as defined in the original Internet 2738 architecture is an identifier of a grouping of topologically 2739 independent receiver host locations. The address encoding itself 2740 does not determine the location of the receiver(s). The multicast 2741 routing protocol, and the network-based state the protocol creates, 2742 determines where the receivers are located. 2744 In the context of LISP, a multicast group address is both an EID and 2745 a Routing Locator. Therefore, no specific semantic or action needs 2746 to be taken for a destination address, as it would appear in an IP 2747 header. Therefore, a group address that appears in an inner IP 2748 header built by a source host will be used as the destination EID. 2749 The outer IP header (the destination Routing Locator address), 2750 prepended by a LISP router, will use the same group address as the 2751 destination Routing Locator. 2753 Having said that, only the source EID and source Routing Locator 2754 needs to be dealt with. Therefore, an ITR merely needs to put its 2755 own IP address in the source Routing Locator field when prepending 2756 the outer IP header. This source Routing Locator address, like any 2757 other Routing Locator address MUST be globally routable. 2759 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2760 ITR when a received data packet is a multicast data packet or when 2761 processing a source-specific Join (either by IGMPv3 or PIM). But the 2762 source Routing Locator is decided by the multicast routing protocol 2763 in a receiver site. That is, an EID to Routing Locator translation 2764 is done at control-time. 2766 Another approach is to have the ITR not encapsulate a multicast 2767 packet and allow the host built packet to flow into the core even if 2768 the source address is allocated out of the EID namespace. If the 2769 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2770 routers can RPF to the ITR (the Locator address which is injected 2771 into core routing) rather than the host source address (the EID 2772 address which is not injected into core routing). 2774 To avoid any EID-based multicast state in the network core, the first 2775 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2776 and Interworking with non-LISP sites is described in specification 2777 [MLISP]. 2779 12. Security Considerations 2781 It is believed that most of the security mechanisms will be part of 2782 the mapping database service when using control plane procedures for 2783 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2784 as described in this specification, protection is provided against 2785 ETR spoofing by using Return- Routability mechanisms evidenced by the 2786 use of a 24-bit Nonce field in the LISP encapsulation header and a 2787 64-bit Nonce field in the LISP control message. The nonce, coupled 2788 with the ITR accepting only solicited Map-Replies goes a long way 2789 toward providing decent authentication. 2791 LISP does not rely on a PKI infrastructure or a more heavy weight 2792 authentication system. These systems challenge the scalability of 2793 LISP which was a primary design goal. 2795 DoS attack prevention will depend on implementations rate-limiting 2796 Map-Requests and Map-Replies to the control plane as well as rate- 2797 limiting the number of data-triggered Map-Replies. 2799 An incorrectly implemented or malicious ITR might choose to ignore 2800 the priority and weights provided by the ETR in its Map-Reply. This 2801 traffic steering would be limited to the traffic that is sent by this 2802 ITR's site, and no more severe than if the site initiated a bandwidth 2803 DoS attack on (one of) the ETR's ingress links. The ITR's site would 2804 typically gain no benefit from not respecting the weights, and would 2805 likely to receive better service by abiding by them. 2807 To deal with map-cache exhaustion attempts in an ITR/PTR, the 2808 implementation should consider putting a maximum cap on the number of 2809 entries stored with a reserve list for special or frequently accessed 2810 sites. This should be a configuration policy control set by the 2811 network administrator who manages ITRs and PTRs. 2813 Given that the ITR/PTR maintains a cache of EID-to-RLOC mappings, 2814 cache sizing and maintenance is an issue to be kept in mind during 2815 implementation. It is a good idea to have instrumentation in place 2816 to detect thrashing of the cache. Implementation experimentation 2817 will be used to determine which cache management strategies work 2818 best. It should be noted that an undersized cache in an ITR/PTR not 2819 only causes adverse affect on the site or region they support, but 2820 may also cause increased Map-Request load on the mapping system. 2822 There is a security risk implicit in the fact that ETRs generate the 2823 EID prefix to which they are responding. An ETR can claim a shorter 2824 prefix than it is actually responsible for. Various mechanisms to 2825 ameliorate or resolve this issue will be examined in the future, 2826 [LISP-SEC]. 2828 Spoofing of inner header addresses of LISP encapsulated packets is 2829 possible like with any tunneling mechanism. ITRs MUST verify the 2830 source address of a packet to be an EID that belongs to the site's 2831 EID-prefix range prior to encapsulation. ETRs MUST NOT decapsulate 2832 and forward packets into their site where the inner header 2833 destination EID does not belong to the ETR's EID-prefix range for the 2834 site. If a LISP encapsulated packet arrives at an ETR, it MAY 2835 compare the inner header source EID address and the outer header 2836 source RLOC address with the mapping that exists in the mapping 2837 database. Then when spoofing attacks occur, the outer header source 2838 RLOC address can be used to trace back the attack to the source site, 2839 using existing operational tools. 2841 This experimental specification does not address automated key 2842 management (AKM). BCP 107 provides guidance in this area. In 2843 addition, at the time of this writing, substantial work is being 2844 undertaken to improve security of the routing system [KARP], [RPKI], 2845 [BGP-SEC], [LISP-SEC], Future work on LISP should address BCP-107 as 2846 well as other open security considerations, which may require changes 2847 to this specification. 2849 13. Network Management Considerations 2851 Considerations for Network Management tools exist so the LISP 2852 protocol suite can be operationally managed. The mechanisms can be 2853 found in [LISP-MIB] and [LISP-LIG]. 2855 14. IANA Considerations 2857 This section provides guidance to the Internet Assigned Numbers 2858 Authority (IANA) regarding registration of values related to the LISP 2859 specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. 2861 There are two name spaces in LISP that require registration: 2863 o LISP IANA registry allocations should not be made for purposes 2864 unrelated to LISP routing or transport protocols. 2866 o The following policies are used here with the meanings defined in 2867 BCP 26: "Specification Required", "IETF Consensus", "Experimental 2868 Use", "First Come First Served". 2870 14.1. LISP Address Type Codes 2872 Instance ID type codes have a range from 0 to 15, of which 0 and 1 2873 have been allocated [LCAF]. New Type Codes MUST be allocated 2874 starting at 2. Type Codes 2 - 10 are to be assigned by IETF Review. 2875 Type Codes 11 - 15 are available on a First Come First Served policy. 2877 The following codes have been allocated: 2879 Type 0: Null Body Type 2881 Type 1: AFI List Type 2883 See [LCAF] for details for other possible unapproved address 2884 encodings. The unapproved LCAF encodings are an area for further 2885 study and experimentation. 2887 14.2. LISP UDP Port Numbers 2889 The IANA registry has allocated UDP port numbers 4341 and 4342 for 2890 LISP data-plane and control-plane operation, respectively. 2892 15. References 2894 15.1. Normative References 2896 [BGP-SEC] Lepinski, M., "An Overview of BGPSEC", 2897 draft-lepinski-bgpsec-overview-00.txt (work in progress), 2898 March 2011. 2900 [KARP] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 2901 Routing Protocols (KARP)Design Guidelines", 2902 draft-ietf-karp-design-guide-02.txt (work in progress), 2903 March 2011. 2905 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 2906 August 1980. 2908 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 2909 STD 13, RFC 1034, November 1987. 2911 [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700, 2912 October 1994. 2914 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 2915 E. Lear, "Address Allocation for Private Internets", 2916 BCP 5, RFC 1918, February 1996. 2918 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2919 Requirement Levels", BCP 14, RFC 2119, March 1997. 2921 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 2922 ESP and AH", RFC 2404, November 1998. 2924 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 2925 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 2926 March 2000. 2928 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 2929 via IPv4 Clouds", RFC 3056, February 2001. 2931 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 2932 of Explicit Congestion Notification (ECN) to IP", 2933 RFC 3168, September 2001. 2935 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 2936 A., Peterson, J., Sparks, R., Handley, M., and E. 2937 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 2938 June 2002. 2940 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 2941 in IPv6", RFC 3775, June 2004. 2943 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 2944 Requirements for Security", BCP 106, RFC 4086, June 2005. 2946 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 2947 (CIDR): The Internet Address Assignment and Aggregation 2948 Plan", BCP 122, RFC 4632, August 2006. 2950 [RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 2951 (SHA and HMAC-SHA)", RFC 4634, July 2006. 2953 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 2954 Optimization for Mobile IPv6", RFC 4866, May 2007. 2956 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 2957 Workshop on Routing and Addressing", RFC 4984, 2958 September 2007. 2960 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2961 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2962 May 2008. 2964 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 2965 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 2967 [RPKI] Lepinski, M., "An Infrastructure to Support Secure 2968 Internet Routing", draft-ietf-sidr-arch-12.txt (work in 2969 progress), February 2011. 2971 [UDP-TUNNELS] 2972 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 2973 Packets", draft-eubanks-chimento-6man-01.txt (work in 2974 progress), October 2010. 2976 15.2. Informative References 2978 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 2979 NUMBERS 2980 http://www.iana.org/assignments/address-family-numbers, 2981 January 2011. 2983 [AFI-REGISTRY] 2984 IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 2985 NUMBER registry http://www.iana.org/assignments/ 2986 address-family-numbers/ 2987 address-family-numbers.xml#address-family-numbers-1, 2988 January 2011. 2990 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 2991 Alternative Topology (LISP-ALT)", 2992 draft-ietf-lisp-alt-07.txt (work in progress), June 2011. 2994 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 2995 Enhancement to the Internet Architecture", Internet- 2996 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt, 2997 1999. 2999 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 3000 Content distribution Overlay Network Service for LISP", 3001 draft-meyer-lisp-cons-03.txt (work in progress), 3002 November 2007. 3004 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 3005 Mappings Multicast Across Cooperating Systems for LISP", 3006 draft-curran-lisp-emacs-00.txt (work in progress), 3007 November 2007. 3009 [INTERWORK] 3010 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 3011 "Interworking LISP with IPv4 and IPv6", 3012 draft-ietf-lisp-interworking-02.txt (work in progress), 3013 June 2011. 3015 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 3016 Address Format", draft-farinacci-lisp-lcaf-04.txt (work in 3017 progress), October 2010. 3019 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 3020 "Renumbering: Threat or Menace?", Usenix , September 1996. 3022 [LISP-DEPLOY] 3023 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 3024 "LISP Network Element Deployment Considerations", 3025 draft-jakab-lisp-deployment-02.txt (work in progress), 3026 February 2011. 3028 [LISP-LIG] 3029 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 3030 draft-ietf-lisp-lig-01.txt (work in progress), 3031 October 2010. 3033 [LISP-MAIN] 3034 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 3035 "Locator/ID Separation Protocol (LISP)", 3036 draft-farinacci-lisp-12.txt (work in progress), 3037 March 2009. 3039 [LISP-MIB] 3040 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 3041 draft-ietf-lisp-mib-01.txt (work in progress), March 2011. 3043 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 3044 Mobility Architecture", draft-meyer-lisp-mn-04.txt (work 3045 in progress), October 2010. 3047 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 3048 draft-ietf-lisp-ms-09.txt (work in progress), June 2011. 3050 [LISP-SEC] 3051 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 3052 Bonaventure, "LISP-Security (LISP-SEC)", 3053 draft-ietf-lisp-sec-00.txt (work in progress), June 2011. 3055 [LOC-ID-ARCH] 3056 Meyer, D. and D. Lewis, "Architectural Implications of 3057 Locator/ID Separation", 3058 draft-meyer-loc-id-implications-01.txt (work in progress), 3059 Januaryr 2009. 3061 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 3062 "LISP for Multicast Environments", 3063 draft-ietf-lisp-multicast-06.txt (work in progress), 3064 June 2011. 3066 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 3067 draft-lear-lisp-nerd-08.txt (work in progress), 3068 March 2010. 3070 [OPENLISP] 3071 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 3072 Report", draft-iannone-openlisp-implementation-01.txt 3073 (work in progress), July 2008. 3075 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 3076 draft-narten-radir-problem-statement-00.txt (work in 3077 progress), July 2007. 3079 [RFC3344bis] 3080 Perkins, C., "IP Mobility Support for IPv4, revised", 3081 draft-ietf-mip4-rfc3344bis-05 (work in progress), 3082 July 2007. 3084 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 3085 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 3086 September 2005. 3088 [RPMD] Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol 3089 for Routing Protocol Meta-data Dissemination", 3090 draft-handley-p2ppush-unpublished-2007726.txt (work in 3091 progress), July 2007. 3093 [VERSIONING] 3094 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3095 Versioning", draft-ietf-lisp-map-versioning-01.txt (work 3096 in progress), March 2011. 3098 Appendix A. Acknowledgments 3100 An initial thank you goes to Dave Oran for planting the seeds for the 3101 initial ideas for LISP. His consultation continues to provide value 3102 to the LISP authors. 3104 A special and appreciative thank you goes to Noel Chiappa for 3105 providing architectural impetus over the past decades on separation 3106 of location and identity, as well as detailed review of the LISP 3107 architecture and documents, coupled with enthusiasm for making LISP a 3108 practical and incremental transition for the Internet. 3110 The authors would like to gratefully acknowledge many people who have 3111 contributed discussion and ideas to the making of this proposal. 3112 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3113 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3114 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3115 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3116 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3117 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3118 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3119 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3120 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3121 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3122 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3123 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3124 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3125 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3126 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3127 Clarence Filsfils, and Alia Atlas. 3129 This work originated in the Routing Research Group (RRG) of the IRTF. 3130 The individual submission [LISP-MAIN] was converted into this IETF 3131 LISP working group draft. 3133 Appendix B. Document Change Log 3135 B.1. Changes to draft-ietf-lisp-13.txt 3137 o Posted June 2011 to complete working group last call. 3139 o Tracker item 87. Put Yakov suggested wording in the EID-prefix 3140 definition section to reference [INTERWORK] and [LISP-DEPLOY] 3141 about discussion on transition and access mechanisms. 3143 o Change "ITRs" to "ETRs" in the Locator Status Bit definition 3144 section and data packet description section per Damien's comment. 3146 o Remove the normative reference to [LISP-SEC] when describing the 3147 S-bit in the ECM and Map-Reply headers. 3149 o Tracker item 54. Added text from John Scudder in the "Packets 3150 Egressing a LISP Site" section. 3152 o Add sentence to the "Reencapsulating Tunnel" definition about how 3153 reencapsulation loops can occur when not coordinating among 3154 multiple mapping database systems. 3156 o Remove "In theory" from a sentence in the Security Considerations 3157 section. 3159 o Remove Security Area Statement title and reword section with 3160 Eliot's provided text. The text was agreed upon by LISP-WG chairs 3161 and Security ADs. 3163 o Remove word "potential" from the over-claiming paragraph of the 3164 Security Considerations section per Stephen's request. 3166 o Wordsmithing and other editorial comments from Alia. 3168 B.2. Changes to draft-ietf-lisp-12.txt 3170 o Posted April 2011. 3172 o Tracker item 87. Provided rewording how an EID-prefix can be 3173 resued in the definition section of "EID-prefix". 3175 o Tracker item 95. Change "eliminate" to "defer" in section 4.1. 3177 o Tracker item 110. Added that the Mapping Protocol Data field in 3178 the Map-Reply message is only used when needed by the particular 3179 Mapping Database System. 3181 o Tracker item 111. Indicate that if an LSB that is assocaited with 3182 an anycast address, that there is at least one RLOC that is up. 3184 o Tracker item 108. Make clear the R-bit does not define RLOC path 3185 reachability. 3187 o Tracker item 107. Indicate that weights are relative to each 3188 other versus requiring an addition of up to 100%. 3190 o Tracker item 46. Add a sentence how LISP products should be sized 3191 for the appropriate demand so cache thrashing is avoided. 3193 o Change some references of RFC 5226 to [AFI] per Luigi. 3195 o Per Luigi, make reference to "EID-AFI" consistent to "EID-prefix- 3196 AFI". 3198 o Tracker item 66. Indicate that appending locators to a locator- 3199 set is done when the added locators are lexicographically greater 3200 than the previous ones in the set. 3202 o Tracker item 87. Once again reword the definition of the EID- 3203 prefix to reflect recent comments. 3205 o Tracker item 70. Added text to security section on what the 3206 implications could be if an ITR does not obey priority and weights 3207 from a Map-Reply message. 3209 o Tracker item 54. Added text to the new section titled "Packets 3210 Egressing a LISP Site" to describe the implications when two or 3211 more ITRs exist at a site where only one ITR is used for egress 3212 traffic and when there is a shift of traffic to the others, how 3213 the map-cache will need to be populated in those new egress ITRs. 3215 o Tracker item 33. Make more clear in the Routing Locator Selection 3216 section what an ITR should do when it sees an R-bit of 0 in a 3217 locator-record of a Map-Reply. 3219 o Tracker item 33. Add paragraph to the EID Reachability section 3220 indicating that site parittioning is under investigation. 3222 o Tracker item 58. Added last paragraph of Security Considerations 3223 section about how to protect inner header EID address spoofing 3224 attacks. 3226 o Add suggested Sam text to indicate that all security concerns need 3227 not be addressed for moving document to Experimental RFC status. 3228 Put this in a subsection of the Secuirty Considerations section. 3230 B.3. Changes to draft-ietf-lisp-11.txt 3232 o Posted March 30, 2011. 3234 o Change IANA URL. The URL we had pointed to a general protocol 3235 numbers page. 3237 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3238 Requests to be sent to a MN ETR via the map-server. 3240 o Generalize text for the defintion of Reencapsuatling tunnels. 3242 o Add pargraph suggested by Joel to explain how implementation 3243 experimentation will be used to determine the proper cache 3244 management techniques. 3246 o Add Yakov provided text for the definition of "EID-to-RLOC 3247 "Database". 3249 o Add reference in Section 8, Deployment Scenarios, to the 3250 draft-jakab-lisp-deploy-02.txt draft. 3252 o Clarify sentence about no hardware changes needed to support LISP 3253 encapsulation. 3255 o Add paragraph about what is the procedure when a locator is 3256 inserted in the middle of a locator-set. 3258 o Add a definition for Locator-Status-Bits so we can emphasize they 3259 are used as a hint for router up/down status and not path 3260 reachability. 3262 o Change "BGP RIB" to "RIB" per Clarence's comment. 3264 o Fixed complaints by IDnits. 3266 o Add subsection to Security Considerations section indicating how 3267 EID-prefix overclaiming in Map-Replies is for further study and 3268 add a reference to LISP-SEC. 3270 B.4. Changes to draft-ietf-lisp-10.txt 3272 o Posted March 2011. 3274 o Add p-bit to Map-Request so there is documentary reasons to know 3275 when a PITR has sent a Map-Request to an ETR. 3277 o Add Map-Notify message which is used to acknowledge a Map-Register 3278 message sent to a Map-Server. 3280 o Add M-bit to the Map-Register message so an ETR that wants an 3281 acknowledgment for the Map-Register can request one. 3283 o Add S-bit to the ECM and Map-Reply messages to describe security 3284 data that can be present in each message. Then refer to 3285 [LISP-SEC] for expansive details. 3287 o Add Network Management Considerations section and point to the MIB 3288 and LIG drafts. 3290 o Remove the word "simple" per Yakov's comments. 3292 B.5. Changes to draft-ietf-lisp-09.txt 3294 o Posted October 2010. 3296 o Add to IANA Consideration section about the use of LCAF Type 3297 values that accepted and maintained by the IANA registry and not 3298 the LCAF specification. 3300 o Indicate that implementations should be able to receive LISP 3301 control messages when either UDP port is 4342, so they can be 3302 robust in the face of intervening NAT boxes. 3304 o Add paragraph to SMR section to indicate that an ITR does not need 3305 to respond to an SMR-based Map-Request when it has no map-cache 3306 entry for the SMR source's EID-prefix. 3308 B.6. Changes to draft-ietf-lisp-08.txt 3310 o Posted August 2010. 3312 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3313 Register messages. 3315 o Clarify language in section 6.1.5 about Map-Replying to Data- 3316 Probes or Map-Requests. 3318 o Indicate that outer TTL should only be copied to inner TTL when it 3319 is less than inner TTL. 3321 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3322 value of 0. 3324 o Indicate that SMRs can have a global or per SMR destination rate- 3325 limiter. 3327 o Add clarifications to the SMR procedures. 3329 o Add definitions for "client-side" and 'server-side" terms used in 3330 this specification. 3332 o Clear up language in section 6.4, last paragraph. 3334 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3335 probe a PETR and have it return a Map-Reply with a locator-set of 3336 size 0. The way it is spec'ed the map-cache entry has action 3337 "dropped". Drop-action is set to 3. 3339 o Add statement about normalizing locator weights. 3341 o Clarify R-bit definition in the Map-Reply locator record. 3343 o Add section on EID Reachability within a LISP site. 3345 o Clarify another disadvantage of using anycast locators. 3347 o Reworded Abstract. 3349 o Change section 2.0 Introduction to remove obsolete information 3350 such as the LISP variant definitions. 3352 o Change section 5 title from "Tunneling Details" to "LISP 3353 Encapsulation Details". 3355 o Changes to section 5 to include results of network deployment 3356 experience with MTU. Recommend that implementations use either 3357 the stateful or stateless handling. 3359 o Make clarification wordsmithing to Section 7 and 8. 3361 o Identify that if there is one locator in the locator-set of a map- 3362 cache entry, that an SMR from that locator should be responded to 3363 by sending the the SMR-invoked Map-Request to the database mapping 3364 system rather than to the RLOC itself (which may be unreachable). 3366 o When describing Unicast and Multicast Weights indicate the the 3367 values are relative weights rather than percentages. So it 3368 doesn't imply the sum of all locator weights in the locator-set 3369 need to be 100. 3371 o Do some wordsmithing on copying TTL and TOS fields. 3373 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3374 combed the spec. 3376 o Removed Section 14 "Prototype Plans and Status". We felt this 3377 type of section is no longer appropriate for a protocol 3378 specification. 3380 o Add clarification text for the IRC description per Damien's 3381 commentary. 3383 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3384 per Vina's comment about a possible DoS vector. 3386 o Clarify (S/2 + H) in the stateless MTU section. 3388 o Add text to reflect Damien's comment about the description of the 3389 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3390 addresses are local addresses of the Map-Requester. 3392 B.7. Changes to draft-ietf-lisp-07.txt 3394 o Posted April 2010. 3396 o Added I-bit to data header so LSB field can also be used as an 3397 Instance ID field. When this occurs, the LSB field is reduced to 3398 8-bits (from 32-bits). 3400 o Added V-bit to the data header so the 24-bit nonce field can also 3401 be used for source and destination version numbers. 3403 o Added Map-Version 12-bit value to the EID-record to be used in all 3404 of Map-Request, Map-Reply, and Map-Register messages. 3406 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3407 can decide what address to select for the destination of a Map- 3408 Reply. 3410 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3411 the Locator-Set record of an EID-record for a Map-Reply message. 3412 The L-bit indicates which RLOCs in the locator-set are local to 3413 the sender of the message. The P-bit indicates which RLOC is the 3414 source of a RLOC-probe Reply (Map-Reply) message. 3416 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3418 o Made editorial and clarification changes based on comments from 3419 Dhirendra Trivedi. 3421 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3423 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3424 6.3.1. 3426 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3427 for Map-Register messages. 3429 o Add NAT section per Ron Bonica comments. 3431 o Fix IDnits issues per Ron Bonica. 3433 o Added section on Virtualization and Segmentation to explain the 3434 use if the Instance ID field in the data header. 3436 o There are too many P-bits, keep their scope to the packet format 3437 description and refer to them by name every where else in the 3438 spec. 3440 o Scanned all occurrences of "should", "should not", "must" and 3441 "must not" and uppercased them. 3443 o John Zwiebel offered text for section 4.1 to modernize the 3444 example. Thanks Z! 3446 o Make it more clear in the definition of "EID-to-RLOC Database" 3447 that all ETRs need to have the same database mapping. This 3448 reflects a comment from John Scudder. 3450 o Add a definition "Route-returnability" to the Definition of Terms 3451 section. 3453 o In section 9.2, add text to describe what the signature of 3454 traceroute packets can look like. 3456 o Removed references to Data Probe for introductory example. Data- 3457 probes are still part of the LISP design but not encouraged. 3459 o Added the definition for "LISP site" to the Definition of Terms" 3460 section. 3462 B.8. Changes to draft-ietf-lisp-06.txt 3464 Editorial based changes: 3466 o Posted December 2009. 3468 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3470 o Add text to indicate that Map-Register messages must contain a 3471 computed UDP checksum. 3473 o Add definitions for PITR and PETR. 3475 o Indicate an AFI value of 0 is an unspecified address. 3477 o Indicate that the TTL field of a Map-Register is not used and set 3478 to 0 by the sender. This change makes this spec consistent with 3479 [LISP-MS]. 3481 o Change "... yield a packet size of L bytes" to "... yield a packet 3482 size greater than L bytes". 3484 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3485 Reply messages. 3487 o Clarify that LSBs that go beyond the number of locators do not to 3488 be SMRed when the locator addresses are greater lexicographically 3489 than the locator in the existing locator-set. 3491 o Add Gregg, Srini, and Amit to acknowledgment section. 3493 o Clarify in the definition of a LISP header what is following the 3494 UDP header. 3496 o Clarify "verifying Map-Request" text in section 6.1.3. 3498 o Add Xu Xiaohu to the acknowledgment section for introducing the 3499 problem of overlapping EID-prefixes among multiple sites in an RRG 3500 email message. 3502 Design based changes: 3504 o Use stronger language to have the outer IPv4 header set DF=1 so we 3505 can avoid fragment reassembly in an ETR or PETR. This will also 3506 make IPv4 and IPv6 encapsulation have consistent behavior. 3508 o Map-Requests should not be sent in ECM with the Probe bit is set. 3509 These type of Map-Requests are used as RLOC-probes and are sent 3510 directly to locator addresses in the underlying network. 3512 o Add text in section 6.1.5 about returning all EID-prefixes in a 3513 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3514 configure. 3516 o Add text in a new subsection of section 6.1.5 about dealing with 3517 Map-Replies with coarse EID-prefixes. 3519 B.9. Changes to draft-ietf-lisp-05.txt 3521 o Posted September 2009. 3523 o Added this Document Change Log appendix. 3525 o Added section indicating that encapsulated Map-Requests must use 3526 destination UDP port 4342. 3528 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3529 data in Map-Register payload. 3531 o Added Jari to acknowledgment section. 3533 o State the source-EID is set to 0 when using Map-Requests to 3534 refresh or RLOC-probe. 3536 o Make more clear what source-RLOC should be for a Map-Request. 3538 o The LISP-CONS authors thought that the Type definitions for CONS 3539 should be removed from this specification. 3541 o Removed nonce from Map-Register message, it wasn't used so no need 3542 for it. 3544 o Clarify what to do for unspecified Action bits for negative Map- 3545 Replies. Since No Action is a drop, make value 0 Drop. 3547 B.10. Changes to draft-ietf-lisp-04.txt 3549 o Posted September 2009. 3551 o How do deal with record count greater than 1 for a Map-Request. 3552 Damien and Joel comment. Joel suggests: 1) Specify that senders 3553 compliant with the current document will always set the count to 3554 1, and note that the count is included for future extensibility. 3555 2) Specify what a receiver compliant with the draft should do if 3556 it receives a request with a count greater than 1. Presumably, it 3557 should send some error back? 3559 o Add Fred Templin in acknowledgment section. 3561 o Add Margaret and Sam to the acknowledgment section for their great 3562 comments. 3564 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3566 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3567 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3568 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3569 ignore the checksum completely. And of course we'd need to 3570 confirm that can actually be implemented. In particular, hardware 3571 that verifies UDP checksums on receive needs to be checked to make 3572 sure it permits 0 checksums." 3574 o Margaret wants a reference to 3575 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3577 o Fix description in Map-Request section. Where we describe Map- 3578 Reply Record, change "R-bit" to "M-bit". 3580 o Add the mobility bit to Map-Replies. So PTRs don't probe so often 3581 for MNs but often enough to get mapping updates. 3583 o Indicate SHA1 can be used as well for Map-Registers. 3585 o More Fred comments on MTU handling. 3587 o Isidor comment about spec'ing better periodic Map-Registers. Will 3588 be fixed in draft-ietf-lisp-ms-02.txt. 3590 o Margaret's comment on gleaning: "The current specification does 3591 not make it clear how long gleaned map entries should be retained 3592 in the cache, nor does it make it clear how/ when they will be 3593 validated. The LISP spec should, at the very least, include a 3594 (short) default lifetime for gleaned entries, require that they be 3595 validated within a short period of time, and state that a new 3596 gleaned entry should never overwrite an entry that was obtained 3597 from the mapping system. The security implications of storing 3598 "gleaned" entries should also be explored in detail." 3600 o Add section on RLOC-probing per working group feedback. 3602 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3603 Noel. 3605 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3606 control plane only. 3608 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3609 fields can be turned off and used for another future purpose. For 3610 Luigi et al versioning convergence. 3612 o Add a N-bit to the data header suggested by Noel. Then the nonce 3613 field could be used when N is not 1. 3615 o Clarify that when E-bit is 0, the nonce field can be an echoed 3616 nonce or a random nonce. Comment from Jesper. 3618 o Indicate when doing data-gleaning that a verifying Map-Request is 3619 sent to the source-EID of the gleaned data packet so we can avoid 3620 map-cache corruption by a 3rd party. Comment from Pedro. 3622 o Indicate that a verifying Map-Request, for accepting mapping data, 3623 should be sent over the ALT (or to the EID). 3625 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3627 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3628 noncing. Comment by Pedro and Dino. 3630 o Jesper made a comment to loosen the language about requiring the 3631 copy of inner TTL to outer TTL since the text to get mixed-AF 3632 traceroute to work would violate the "MUST" clause. Changed from 3633 MUST to SHOULD in section 5.3. 3635 B.11. Changes to draft-ietf-lisp-03.txt 3637 o Posted July 2009. 3639 o Removed loc-reach-bits longword from control packets per Damien 3640 comment. 3642 o Clarifications in MTU text from Roque. 3644 o Added text to indicate that the locator-set be sorted by locator 3645 address from Isidor. 3647 o Clarification text from John Zwiebel in Echo-Nonce section. 3649 B.12. Changes to draft-ietf-lisp-02.txt 3651 o Posted July 2009. 3653 o Encapsulation packet format change to add E-bit and make loc- 3654 reach-bits 32-bits in length. 3656 o Added Echo-Nonce Algorithm section. 3658 o Clarification how ECN bits are copied. 3660 o Moved S-bit in Map-Request. 3662 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3663 RLOC-Probe Algorithm. 3665 o Added to Mobility section to reference [LISP-MN]. 3667 B.13. Changes to draft-ietf-lisp-01.txt 3669 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3671 o Defined LEID to be a "LISP EID". 3673 o Indicate encapsulation use IPv4 DF=0. 3675 o Added negative Map-Reply messages with drop, native-forward, and 3676 send-map-request actions. 3678 o Added Proxy-Map-Reply bit to Map-Register. 3680 B.14. Changes to draft-ietf-lisp-00.txt 3682 o Posted May 2009. 3684 o Rename of draft-farinacci-lisp-12.txt. 3686 o Acknowledgment to RRG. 3688 Authors' Addresses 3690 Dino Farinacci 3691 cisco Systems 3692 Tasman Drive 3693 San Jose, CA 95134 3694 USA 3696 Email: dino@cisco.com 3698 Vince Fuller 3699 cisco Systems 3700 Tasman Drive 3701 San Jose, CA 95134 3702 USA 3704 Email: vaf@cisco.com 3706 Dave Meyer 3707 cisco Systems 3708 170 Tasman Drive 3709 San Jose, CA 3710 USA 3712 Email: dmm@cisco.com 3714 Darrel Lewis 3715 cisco Systems 3716 170 Tasman Drive 3717 San Jose, CA 3718 USA 3720 Email: darlewis@cisco.com