idnits 2.17.1 draft-ietf-lisp-12.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 (April 26, 2011) is 4742 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** 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 (-10) exists of draft-ietf-lisp-alt-06 == 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-07 == Outdated reference: A later version (-14) exists of draft-ietf-lisp-multicast-05 == 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 (~~), 18 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: October 28, 2011 D. Lewis 6 cisco Systems 7 April 26, 2011 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-12 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 October 28, 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 12.1. IETF Security Area Statement . . . . . . . . . . . . . . . 69 120 13. Network Management Considerations . . . . . . . . . . . . . . 70 121 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 71 122 14.1. LISP Address Type Codes . . . . . . . . . . . . . . . . . 71 123 14.2. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 71 124 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 72 125 15.1. Normative References . . . . . . . . . . . . . . . . . . . 72 126 15.2. Informative References . . . . . . . . . . . . . . . . . . 73 127 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 76 128 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 77 129 B.1. Changes to draft-ietf-lisp-12.txt . . . . . . . . . . . . 77 130 B.2. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 78 131 B.3. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 79 132 B.4. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 79 133 B.5. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 80 134 B.6. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 81 135 B.7. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 83 136 B.8. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 84 137 B.9. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 85 138 B.10. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 86 139 B.11. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 87 140 B.12. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 87 141 B.13. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 87 142 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 88 144 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 which would be required for an Internet standard 210 equivalent. See Section 12.1 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. This would 269 require coordination and cooperation with the entities managing 270 the mapping infrastructure. Once this has been done, that block 271 could be removed from the globally routed IP system, if other 272 suitable transition and access mechanisms are in place. The 273 converse is not supported. That is, a site which receives an 274 explicitly allocated EID-prefix may not use that EID-prefix as a 275 globally prefix. 277 End-system: An end-system is an IPv4 or IPv6 device that originates 278 packets with a single IPv4 or IPv6 header. The end-system 279 supplies an EID value for the destination address field of the IP 280 header when communicating globally (i.e. outside of its routing 281 domain). An end-system can be a host computer, a switch or router 282 device, or any network appliance. 284 Ingress Tunnel Router (ITR): An ITR is a router which accepts an IP 285 packet with a single IP header (more precisely, an IP packet that 286 does not contain a LISP header). The router treats this "inner" 287 IP destination address as an EID and performs an EID-to-RLOC 288 mapping lookup. The router then prepends an "outer" IP header 289 with one of its globally-routable RLOCs in the source address 290 field and the result of the mapping lookup in the destination 291 address field. Note that this destination RLOC may be an 292 intermediate, proxy device that has better knowledge of the EID- 293 to-RLOC mapping closer to the destination EID. In general, an ITR 294 receives IP packets from site end-systems on one side and sends 295 LISP-encapsulated IP packets toward the Internet on the other 296 side. 298 Specifically, when a service provider prepends a LISP header for 299 Traffic Engineering purposes, the router that does this is also 300 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 301 on the outer destination address (the originating ITR's supplied 302 RLOC) or the inner destination address (the originating hosts 303 supplied EID). 305 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 306 network that prepends an additional LISP header for Traffic 307 Engineering purposes. 309 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 310 packet where the destination address in the "outer" IP header is 311 one of its own RLOCs. The router strips the "outer" header and 312 forwards the packet based on the next IP header found. In 313 general, an ETR receives LISP-encapsulated IP packets from the 314 Internet on one side and sends decapsulated IP packets to site 315 end-systems on the other side. ETR functionality does not have to 316 be limited to a router device. A server host can be the endpoint 317 of a LISP tunnel as well. 319 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 320 network that strips an outer LISP header for Traffic Engineering 321 purposes. 323 xTR: A xTR is a reference to an ITR or ETR when direction of data 324 flow is not part of the context description. xTR refers to the 325 router that is the tunnel endpoint. Used synonymously with the 326 term "Tunnel Router". For example, "An xTR can be located at the 327 Customer Edge (CE) router", meaning both ITR and ETR functionality 328 is at the CE router. 330 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 331 demand table in an ITR that stores, tracks, and is responsible for 332 timing-out and otherwise validating EID-to-RLOC mappings. This 333 cache is distinct from the full "database" of EID-to-RLOC 334 mappings, it is dynamic, local to the ITR(s), and relatively small 335 while the database is distributed, relatively static, and much 336 more global in scope. 338 EID-to-RLOC Database: The EID-to-RLOC database is a global 339 distributed database that contains all known EID-prefix to RLOC 340 mappings. Each potential ETR typically contains a small piece of 341 the database: the EID-to-RLOC mappings for the EID prefixes 342 "behind" the router. These map to one of the router's own, 343 globally-visible, IP addresses. The same database mapping entries 344 MUST be configured on all ETRs for a given site. In a steady 345 state the EID-prefixes for the site and the locator-set for each 346 EID-prefix MUST be the same on all ETRs. Procedures to enforce 347 and/or verify this are outside the scope of this document. Note 348 that there may be transient conditions when the EID-prefix for the 349 site and locator-set for each EID-prefix may not be the same on 350 all ETRs. This has no negative implications. 352 Recursive Tunneling: Recursive tunneling occurs when a packet has 353 more than one LISP IP header. Additional layers of tunneling may 354 be employed to implement traffic engineering or other re-routing 355 as needed. When this is done, an additional "outer" LISP header 356 is added and the original RLOCs are preserved in the "inner" 357 header. Any references to tunnels in this specification refers to 358 dynamic encapsulating tunnels and never are they statically 359 configured. 361 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 362 ETR removes a LISP header, then acts as an ITR to prepend another 363 LISP header. Doing this allows a packet to be re-routed by the 364 re-encapsulating router without adding the overhead of additional 365 tunnel headers. Any references to tunnels in this specification 366 refers to dynamic encapsulating tunnels and never are they 367 statically configured. 369 LISP Header: a term used in this document to refer to the outer 370 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-byte 371 header that follows the UDP header, an ITR prepends or an ETR 372 strips. 374 Address Family Identifier (AFI): a term used to describe an address 375 encoding in a packet. An address family currently pertains to an 376 IPv4 or IPv6 address. See [AFI] and [RFC1700] for details. An 377 AFI value of 0 used in this specification indicates an unspecified 378 encoded address where the length of the address is 0 bytes 379 following the 16-bit AFI value of 0. 381 Negative Mapping Entry: A negative mapping entry, also known as a 382 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 383 is advertised or stored with no RLOCs. That is, the locator-set 384 for the EID-to-RLOC entry is empty or has an encoded locator count 385 of 0. This type of entry could be used to describe a prefix from 386 a non-LISP site, which is explicitly not in the mapping database. 387 There are a set of well defined actions that are encoded in a 388 Negative Map-Reply. 390 Data Probe: A data-probe is a LISP-encapsulated data packet where 391 the inner header destination address equals the outer header 392 destination address used to trigger a Map-Reply by a decapsulating 393 ETR. In addition, the original packet is decapsulated and 394 delivered to the destination host. A Data Probe is used in some 395 of the mapping database designs to "probe" or request a Map-Reply 396 from an ETR; in other cases, Map-Requests are used. See each 397 mapping database design for details. 399 Proxy ITR (PITR): A PITR is also known as a PTR is defined and 400 described in [INTERWORK], a PITR acts like an ITR but does so on 401 behalf of non-LISP sites which send packets to destinations at 402 LISP sites. 404 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 405 PETR acts like an ETR but does so on behalf of LISP sites which 406 send packets to destinations at non-LISP sites. 408 Route-returnability: is an assumption that the underlying routing 409 system will deliver packets to the destination. When combined 410 with a nonce that is provided by a sender and returned by a 411 receiver limits off-path data insertion. 413 LISP site: is a set of routers in an edge network that are under a 414 single technical administration. LISP routers which reside in the 415 edge network are the demarcation points to separate the edge 416 network from the core network. 418 Client-side: a term used in this document to indicate a connection 419 initiation attempt by an EID. The ITR(s) at the LISP site are the 420 first to get involved in obtaining database map cache entries by 421 sending Map-Request messages. 423 Server-side: a term used in this document to indicate a connection 424 initiation attempt is being accepted for a destination EID. The 425 ETR(s) at the destination LISP site are the first to send Map- 426 Replies to the source site initiating the connection. The ETR(s) 427 at this destination site can obtain mappings by gleaning 428 information from Map-Requests, Data-Probes, or encapsulated 429 packets. 431 Locator-Status-Bits (LSBs): Locator status bits are present in the 432 LISP header. They are used by ITRs to inform ETRs about the up/ 433 down status of all ITRs at the local site. These bits are used as 434 a hint to convey up/down router status and not path reachability 435 status. The LSBs can be verified by use of one of the Locator 436 Reachability Algoriths described in Section 6.3. 438 4. Basic Overview 440 One key concept of LISP is that end-systems (hosts) operate the same 441 way they do today. The IP addresses that hosts use for tracking 442 sockets, connections, and for sending and receiving packets do not 443 change. In LISP terminology, these IP addresses are called Endpoint 444 Identifiers (EIDs). 446 Routers continue to forward packets based on IP destination 447 addresses. When a packet is LISP encapsulated, these addresses are 448 referred to as Routing Locators (RLOCs). Most routers along a path 449 between two hosts will not change; they continue to perform routing/ 450 forwarding lookups on the destination addresses. For routers between 451 the source host and the ITR as well as routers from the ETR to the 452 destination host, the destination address is an EID. For the routers 453 between the ITR and the ETR, the destination address is an RLOC. 455 Another key LISP concept is the "Tunnel Router". A tunnel router 456 prepends LISP headers on host-originated packets and strip them prior 457 to final delivery to their destination. The IP addresses in this 458 "outer header" are RLOCs. During end-to-end packet exchange between 459 two Internet hosts, an ITR prepends a new LISP header to each packet 460 and an egress tunnel router strips the new header. The ITR performs 461 EID-to-RLOC lookups to determine the routing path to the ETR, which 462 has the RLOC as one of its IP addresses. 464 Some basic rules governing LISP are: 466 o End-systems (hosts) only send to addresses which are EIDs. They 467 don't know addresses are EIDs versus RLOCs but assume packets get 468 to LISP routers, which in turn, deliver packets to the destination 469 the end-system has specified. 471 o EIDs are always IP addresses assigned to hosts. 473 o LISP routers mostly deal with Routing Locator addresses. See 474 details later in Section 4.1 to clarify what is meant by "mostly". 476 o RLOCs are always IP addresses assigned to routers; preferably, 477 topologically-oriented addresses from provider CIDR blocks. 479 o When a router originates packets it may use as a source address 480 either an EID or RLOC. When acting as a host (e.g. when 481 terminating a transport session such as SSH, TELNET, or SNMP), it 482 may use an EID that is explicitly assigned for that purpose. An 483 EID that identifies the router as a host MUST NOT be used as an 484 RLOC; an EID is only routable within the scope of a site. A 485 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 486 usage where a router could use its "host-like" EID to terminate 487 iBGP sessions to other routers in a site while at the same time 488 using RLOCs to terminate eBGP sessions to routers outside the 489 site. 491 o EIDs are not expected to be usable for global end-to-end 492 communication in the absence of an EID-to-RLOC mapping operation. 493 They are expected to be used locally for intra-site communication. 495 o EID prefixes are likely to be hierarchically assigned in a manner 496 which is optimized for administrative convenience and to 497 facilitate scaling of the EID-to-RLOC mapping database. The 498 hierarchy is based on a address allocation hierarchy which is 499 independent of the network topology. 501 o EIDs may also be structured (subnetted) in a manner suitable for 502 local routing within an autonomous system. 504 An additional LISP header may be prepended to packets by a TE-ITR 505 when re-routing of the path for a packet is desired. An obvious 506 instance of this would be an ISP router that needs to perform traffic 507 engineering for packets flowing through its network. In such a 508 situation, termed Recursive Tunneling, an ISP transit acts as an 509 additional ingress tunnel router and the RLOC it uses for the new 510 prepended header would be either a TE-ETR within the ISP (along 511 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 512 inter-ISP traffic engineered path, where an agreement to build such a 513 path exists). 515 In order to avoid excessive packet overhead as well as possible 516 encapsulation loops, this document mandates that a maximum of two 517 LISP headers can be prepended to a packet. It is believed two 518 headers is sufficient, where the first prepended header is used at a 519 site for Location/Identity separation and second prepended header is 520 used inside a service provider for Traffic Engineering purposes. 522 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 523 For example, the ITR for a particular end-to-end packet exchange 524 might be the first-hop or default router within a site for the source 525 host. Similarly, the egress tunnel router might be the last-hop 526 router directly-connected to the destination host. Another example, 527 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 528 could be the site's border router at the service provider attachment 529 point. Mixing and matching of site-operated, ISP-operated, and other 530 tunnel routers is allowed for maximum flexibility. See Section 8 for 531 more details. 533 4.1. Packet Flow Sequence 535 This section provides an example of the unicast packet flow with the 536 following conditions: 538 o Source host "host1.abc.com" is sending a packet to 539 "host2.xyz.com", exactly what host1 would do if the site was not 540 using LISP. 542 o Each site is multi-homed, so each tunnel router has an address 543 (RLOC) assigned from the service provider address block for each 544 provider to which that particular tunnel router is attached. 546 o The ITR(s) and ETR(s) are directly connected to the source and 547 destination, respectively, but the source and destination can be 548 located anywhere in LISP site. 550 o Map-Requests can be sent on the underlying routing system topology 551 or over an alternative topology [ALT]. 553 o Map-Replies are sent on the underlying routing system topology. 555 Client host1.abc.com wants to communicate with server host2.xyz.com: 557 1. host1.abc.com wants to open a TCP connection to host2.xyz.com. 558 It does a DNS lookup on host2.xyz.com. An A/AAAA record is 559 returned. This address is the destination EID. The locally- 560 assigned address of host1.abc.com is used as the source EID. An 561 IPv4 or IPv6 packet is built and forwarded through the LISP site 562 as a normal IP packet until it reaches a LISP ITR. 564 2. The LISP ITR must be able to map the EID destination to an RLOC 565 of one of the ETRs at the destination site. The specific method 566 used to do this is not described in this example. See [ALT] or 567 [CONS] for possible solutions. 569 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 570 rate-limited. 572 4. When an alternate mapping system is not in use, the Map-Request 573 packet is routed through the underlying routing system. 574 Otherwise, the Map-Request packet is routed on an alternate 575 logical topology. In either case, when the Map-Request arrives 576 at one of the ETRs at the destination site, it will process the 577 packet as a control message. 579 5. The ETR looks at the destination EID of the Map-Request and 580 matches it against the prefixes in the ETR's configured EID-to- 581 RLOC mapping database. This is the list of EID-prefixes the ETR 582 is supporting for the site it resides in. If there is no match, 583 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 584 returned to the ITR. 586 6. The ITR receives the Map-Reply message, parses the message (to 587 check for format validity) and stores the mapping information 588 from the packet. This information is stored in the ITR's EID-to- 589 RLOC mapping cache. Note that the map cache is an on-demand 590 cache. An ITR will manage its map cache in such a way that 591 optimizes for its resource constraints. 593 7. Subsequent packets from host1.abc.com to host2.xyz.com will have 594 a LISP header prepended by the ITR using the appropriate RLOC as 595 the LISP header destination address learned from the ETR. Note 596 the packet may be sent to a different ETR than the one which 597 returned the Map-Reply due to the source site's hashing policy or 598 the destination site's locator-set policy. 600 8. The ETR receives these packets directly (since the destination 601 address is one of its assigned IP addresses), strips the LISP 602 header and forwards the packets to the attached destination host. 604 In order to defer the need for a mapping lookup in the reverse 605 direction, an ETR MAY create a cache entry that maps the source EID 606 (inner header source IP address) to the source RLOC (outer header 607 source IP address) in a received LISP packet. Such a cache entry is 608 termed a "gleaned" mapping and only contains a single RLOC for the 609 EID in question. More complete information about additional RLOCs 610 SHOULD be verified by sending a LISP Map-Request for that EID. Both 611 ITR and the ETR may also influence the decision the other makes in 612 selecting an RLOC. See Section 6 for more details. 614 5. LISP Encapsulation Details 616 Since additional tunnel headers are prepended, the packet becomes 617 larger and can exceed the MTU of any link traversed from the ITR to 618 the ETR. It is recommended in IPv4 that packets do not get 619 fragmented as they are encapsulated by the ITR. Instead, the packet 620 is dropped and an ICMP Too Big message is returned to the source. 622 This specification recommends that implementations support for one of 623 the proposed fragmentation and reassembly schemes. These two 624 existing schemes are detailed in Section 5.4. 626 5.1. LISP IPv4-in-IPv4 Header Format 628 0 1 2 3 629 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 1 630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 631 / |Version| IHL |Type of Service| Total Length | 632 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 | | Identification |Flags| Fragment Offset | 634 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 OH | Time to Live | Protocol = 17 | Header Checksum | 636 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 637 | | Source Routing Locator | 638 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 639 \ | Destination Routing Locator | 640 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 641 / | Source Port = xxxx | Dest Port = 4341 | 642 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 643 \ | UDP Length | UDP Checksum | 644 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 645 L |N|L|E|V|I|flags| Nonce/Map-Version | 646 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 647 S / | Instance ID/Locator Status Bits | 648 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 / |Version| IHL |Type of Service| Total Length | 650 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 651 | | Identification |Flags| Fragment Offset | 652 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 653 IH | Time to Live | Protocol | Header Checksum | 654 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 | | Source EID | 656 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 \ | Destination EID | 658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 660 5.2. LISP IPv6-in-IPv6 Header Format 662 0 1 2 3 663 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 665 / |Version| Traffic Class | Flow Label | 666 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 668 | | Payload Length | Next Header=17| Hop Limit | 669 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 670 | | 671 O + + 672 u | | 673 t + Source Routing Locator + 674 e | | 675 r + + 676 | | 677 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 678 d | | 679 r + + 680 | | 681 ^ + Destination Routing Locator + 682 | | | 683 \ + + 684 \ | | 685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 686 / | Source Port = xxxx | Dest Port = 4341 | 687 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 688 \ | UDP Length | UDP Checksum | 689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 690 L |N|L|E|V|I|flags| Nonce/Map-Version | 691 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 692 S / | Instance ID/Locator Status Bits | 693 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 694 / |Version| Traffic Class | Flow Label | 695 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 696 / | Payload Length | Next Header | Hop Limit | 697 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 698 | | 699 I + + 700 n | | 701 n + Source EID + 702 e | | 703 r + + 704 | | 705 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 706 d | | 707 r + + 708 | | 709 ^ + Destination EID + 710 \ | | 711 \ + + 712 \ | | 713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 715 5.3. Tunnel Header Field Descriptions 717 Inner Header: The inner header is the header on the datagram 718 received from the originating host. The source and destination IP 719 addresses are EIDs. 721 Outer Header: The outer header is a new header prepended by an ITR. 722 The address fields contain RLOCs obtained from the ingress 723 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 724 from [RFC0768]. The DF bit of the Flags field is set to 0 when 725 the method in Section 5.4.1 is used and set to 1 when the method 726 in Section 5.4.2 is used. 728 UDP Header: The UDP header contains a ITR selected source port when 729 encapsulating a packet. See Section 6.5 for details on the hash 730 algorithm used to select a source port based on the 5-tuple of the 731 inner header. The destination port MUST be set to the well-known 732 IANA assigned port value 4341. 734 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 735 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 736 [UDP-TUNNELS]. When a packet with a zero UDP checksum is received 737 by an ETR, the ETR MUST accept the packet for decapsulation. When 738 an ITR transmits a non-zero value for the UDP checksum, it MUST 739 send a correctly computed value in this field. When an ETR 740 receives a packet with a non-zero UDP checksum, it MAY choose to 741 verify the checksum value. If it chooses to perform such 742 verification, and the verification fails, the packet MUST be 743 silently dropped. If the ETR chooses not to perform the 744 verification, or performs the verification successfully, the 745 packet MUST be accepted for decapsulation. The handling of UDP 746 checksums for all tunneling protocols, including LISP, is under 747 active discussion within the IETF. When that discussion 748 concludes, any necessary changes will be made to align LISP with 749 the outcome of the broader discussion. 751 UDP Length: The UDP length field is for an IPv4 encapsulated packet, 752 the inner header Total Length plus the UDP and LISP header lengths 753 are used. For an IPv6 encapsulated packet, the inner header 754 Payload Length plus the size of the IPv6 header (40 bytes) plus 755 the size of the UDP and LISP headers are used. The UDP header 756 length is 8 bytes. 758 N: The N bit is the nonce-present bit. When this bit is set to 1, 759 the low-order 24-bits of the first 32-bits of the LISP header 760 contains a Nonce. See Section 6.3.1 for details. Both N and V 761 bits MUST NOT be set in the same packet. If they are, a 762 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 763 having a Nonce value present. 765 L: The L bit is the Locator-Status-Bits field enabled bit. When this 766 bit is set to 1, the Locator-Status-Bits in the second 32-bits of 767 the LISP header are in use. 769 x 1 x x 0 x x x 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 771 |N|L|E|V|I|flags| Nonce/Map-Version | 772 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 773 | Locator Status Bits | 774 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 776 E: The E bit is the echo-nonce-request bit. When this bit is set to 777 1, the N bit MUST be 1. This bit SHOULD be ignored and has no 778 meaning when the N bit is set to 0. See Section 6.3.1 for 779 details. 781 V: The V bit is the Map-Version present bit. When this bit is set to 782 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 783 This bit indicates that the first 4 bytes of the LISP header is 784 encoded as: 786 0 x 0 1 x x x x 787 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 788 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 790 | Instance ID/Locator Status Bits | 791 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 793 I: The I bit is the Instance ID bit. See Section 5.5 for more 794 details. When this bit is set to 1, the Locator Status Bits field 795 is reduced to 8-bits and the high-order 24-bits are used as an 796 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 797 are transmitted as zero and ignored on receipt. The format of the 798 last 4 bytes of the LISP header would look like: 800 x x x x 1 x x x 801 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 802 |N|L|E|V|I|flags| Nonce/Map-Version | 803 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 804 | Instance ID | LSBs | 805 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 807 flags: The flags field is a 3-bit field is reserved for future flag 808 use. It is set to 0 on transmit and ignored on receipt. 810 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 811 generated by an ITR when the N-bit is set to 1. The nonce is also 812 used when the E-bit is set to request the nonce value to be echoed 813 by the other side when packets are returned. When the E-bit is 814 clear but the N-bit is set, a remote ITR is either echoing a 815 previously requested echo-nonce or providing a random nonce. See 816 Section 6.3.1 for more details. 818 LISP Locator Status Bits: The locator status bits field in the LISP 819 header is set by an ITR to indicate to an ETR the up/down status 820 of the Locators in the source site. Each RLOC in a Map-Reply is 821 assigned an ordinal value from 0 to n-1 (when there are n RLOCs in 822 a mapping entry). The Locator Status Bits are numbered from 0 to 823 n-1 from the least significant bit of field. The field is 32-bits 824 when the I-bit is set to 0 and is 8 bits when the I-bit is set to 825 1. When a Locator Status Bit is set to 1, the ITR is indicating 826 to the ETR the RLOC associated with the bit ordinal has up status. 827 See Section 6.3 for details on how an ITR can determine the status 828 of other ITRs at the same site. When a site has multiple EID- 829 prefixes which result in multiple mappings (where each could have 830 a different locator-set), the Locator Status Bits setting in an 831 encapsulated packet MUST reflect the mapping for the EID-prefix 832 that the inner-header source EID address matches. If the LSB for 833 an anycast locator is set to 1, then there is at least one RLOC 834 with that address that the ETR is considered 'up'. 836 When doing ITR/PITR encapsulation: 838 o The outer header Time to Live field (or Hop Limit field, in case 839 of IPv6) SHOULD be copied from the inner header Time to Live 840 field. 842 o The outer header Type of Service field (or the Traffic Class 843 field, in the case of IPv6) SHOULD be copied from the inner header 844 Type of Service field (with one caveat, see below). 846 When doing ETR/PETR decapsulation: 848 o The inner header Time to Live field (or Hop Limit field, in case 849 of IPv6) SHOULD be copied from the outer header Time to Live 850 field, when the Time to Live field of the outer header is less 851 than the Time to Live of the inner header. Failing to perform 852 this check can cause the Time to Live of the inner header to 853 increment across encapsulation/decapsulation cycle. This check is 854 also performed when doing initial encapsulation when a packet 855 comes to an ITR or PITR destined for a LISP site. 857 o The inner header Type of Service field (or the Traffic Class 858 field, in the case of IPv6) SHOULD be copied from the outer header 859 Type of Service field (with one caveat, see below). 861 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 862 after decapsulating, the net effect of this is that the new outer 863 header will carry the same Time to Live as the old outer header. 865 Copying the TTL serves two purposes: first, it preserves the distance 866 the host intended the packet to travel; second, and more importantly, 867 it provides for suppression of looping packets in the event there is 868 a loop of concatenated tunnels due to misconfiguration. See 869 Section 9.3 for TTL exception handling for traceroute packets. 871 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 872 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 873 requires special treatment in order to avoid discarding indications 874 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 875 field from the inner header to the outer header. Re-encapsulation 876 MUST copy the 2-bit ECN field from the stripped outer header to the 877 new outer header. If the ECN field contains a congestion indication 878 codepoint (the value is '11', the Congestion Experienced (CE) 879 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 880 the stripped outer header to the surviving inner header that is used 881 to forward the packet beyond the ETR. These requirements preserve 882 Congestion Experienced (CE) indications when a packet that uses ECN 883 traverses a LISP tunnel and becomes marked with a CE indication due 884 to congestion between the tunnel endpoints. 886 5.4. Dealing with Large Encapsulated Packets 888 This section proposes two mechanisms to deal with packets that exceed 889 the path MTU between the ITR and ETR. 891 It is left to the implementor to decide if the stateless or stateful 892 mechanism should be implemented. Both or neither can be used since 893 it is a local decision in the ITR regarding how to deal with MTU 894 issues, and sites can interoperate with differing mechanisms. 896 Both stateless and stateful mechanisms also apply to Reencapsulating 897 and Recursive Tunneling. So any actions below referring to an ITR 898 also apply to an TE-ITR. 900 5.4.1. A Stateless Solution to MTU Handling 902 An ITR stateless solution to handle MTU issues is described as 903 follows: 905 1. Define an architectural constant S for the maximum size of a 906 packet, in bytes, an ITR would like to receive from a source 907 inside of its site. 909 2. Define L to be the maximum size, in bytes, a packet of size S 910 would be after the ITR prepends the LISP header, UDP header, and 911 outer network layer header of size H. 913 3. Calculate: S + H = L. 915 When an ITR receives a packet from a site-facing interface and adds H 916 bytes worth of encapsulation to yield a packet size greater than L 917 bytes, it resolves the MTU issue by first splitting the original 918 packet into 2 equal-sized fragments. A LISP header is then prepended 919 to each fragment. The size of the encapsulated fragments is then 920 (S/2 + H), which is less than the ITR's estimate of the path MTU 921 between the ITR and its correspondent ETR. 923 When an ETR receives encapsulated fragments, it treats them as two 924 individually encapsulated packets. It strips the LISP headers then 925 forwards each fragment to the destination host of the destination 926 site. The two fragments are reassembled at the destination host into 927 the single IP datagram that was originated by the source host. 929 This behavior is performed by the ITR when the source host originates 930 a packet with the DF field of the IP header is set to 0. When the DF 931 field of the IP header is set to 1, or the packet is an IPv6 packet 932 originated by the source host, the ITR will drop the packet when the 933 size is greater than L, and sends an ICMP Too Big message to the 934 source with a value of S, where S is (L - H). 936 When the outer header encapsulation uses an IPv4 header, an 937 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 938 can be avoided. An implementation MAY set the DF bit in such headers 939 to 0 if it has good reason to believe there are unresolvable path MTU 940 issues between the sending ITR and the receiving ETR. 942 This specification recommends that L be defined as 1500. 944 5.4.2. A Stateful Solution to MTU Handling 946 An ITR stateful solution to handle MTU issues is described as follows 947 and was first introduced in [OPENLISP]: 949 1. The ITR will keep state of the effective MTU for each locator per 950 mapping cache entry. The effective MTU is what the core network 951 can deliver along the path between ITR and ETR. 953 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 954 with DF bit set to 1, exceeds what the core network can deliver, 955 one of the intermediate routers on the path will send an ICMP Too 956 Big message to the ITR. The ITR will parse the ICMP message to 957 determine which locator is affected by the effective MTU change 958 and then record the new effective MTU value in the mapping cache 959 entry. 961 3. When a packet is received by the ITR from a source inside of the 962 site and the size of the packet is greater than the effective MTU 963 stored with the mapping cache entry associated with the 964 destination EID the packet is for, the ITR will send an ICMP Too 965 Big message back to the source. The packet size advertised by 966 the ITR in the ICMP Too Big message is the effective MTU minus 967 the LISP encapsulation length. 969 Even though this mechanism is stateful, it has advantages over the 970 stateless IP fragmentation mechanism, by not involving the 971 destination host with reassembly of ITR fragmented packets. 973 5.5. Using Virtualization and Segmentation with LISP 975 When multiple organizations inside of a LISP site are using private 976 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 977 segregated due to possible address duplication. An Instance ID in 978 the address encoding can aid in making the entire AFI based address 979 unique. See IANA Considerations Section 14.1 for details for 980 possible address encodings. 982 An Instance ID can be carried in a LISP encapsulated packet. An ITR 983 that prepends a LISP header, will copy a 24-bit value, used by the 984 LISP router to uniquely identify the address space. The value is 985 copied to the Instance ID field of the LISP header and the I-bit is 986 set to 1. 988 When an ETR decapsulates a packet, the Instance ID from the LISP 989 header is used as a table identifier to locate the forwarding table 990 to use for the inner destination EID lookup. 992 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 993 24-bit Instance ID. 995 6. EID-to-RLOC Mapping 997 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 999 The following new UDP packet types are used to retrieve EID-to-RLOC 1000 mappings: 1002 0 1 2 3 1003 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 1004 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1005 |Version| IHL |Type of Service| Total Length | 1006 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1007 | Identification |Flags| Fragment Offset | 1008 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1009 | Time to Live | Protocol = 17 | Header Checksum | 1010 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1011 | Source Routing Locator | 1012 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1013 | Destination Routing Locator | 1014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1015 / | Source Port | Dest Port | 1016 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1017 \ | UDP Length | UDP Checksum | 1018 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1019 | | 1020 | LISP Message | 1021 | | 1022 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1024 0 1 2 3 1025 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 1026 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1027 |Version| Traffic Class | Flow Label | 1028 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1029 | Payload Length | Next Header=17| Hop Limit | 1030 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1031 | | 1032 + + 1033 | | 1034 + Source Routing Locator + 1035 | | 1036 + + 1037 | | 1038 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1039 | | 1040 + + 1041 | | 1042 + Destination Routing Locator + 1043 | | 1044 + + 1045 | | 1046 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1047 / | Source Port | Dest Port | 1048 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1049 \ | UDP Length | UDP Checksum | 1050 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1051 | | 1052 | LISP Message | 1053 | | 1054 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1056 The LISP UDP-based messages are the Map-Request and Map-Reply 1057 messages. When a UDP Map-Request is sent, the UDP source port is 1058 chosen by the sender and the destination UDP port number is set to 1059 4342. When a UDP Map-Reply is sent, the source UDP port number is 1060 set to 4342 and the destination UDP port number is copied from the 1061 source port of either the Map-Request or the invoking data packet. 1062 Implementations MUST be prepared to accept packets when either the 1063 source port or destination UDP port is set to 4342 due to NATs 1064 changing port number values. 1066 The UDP Length field will reflect the length of the UDP header and 1067 the LISP Message payload. 1069 The UDP Checksum is computed and set to non-zero for Map-Request, 1070 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1071 on receipt and if the checksum fails, the packet MUST be dropped. 1073 LISP-CONS [CONS] uses TCP to send LISP control messages. The format 1074 of control messages includes the UDP header so the checksum and 1075 length fields can be used to protect and delimit message boundaries. 1077 This main LISP specification is the authoritative source for message 1078 format definitions for the Map-Request and Map-Reply messages. 1080 6.1.1. LISP Packet Type Allocations 1082 This section will be the authoritative source for allocating LISP 1083 Type values. Current allocations are: 1085 Reserved: 0 b'0000' 1086 LISP Map-Request: 1 b'0001' 1087 LISP Map-Reply: 2 b'0010' 1088 LISP Map-Register: 3 b'0011' 1089 LISP Map-Notify: 4 b'0100' 1090 LISP Encapsulated Control Message: 8 b'1000' 1092 6.1.2. Map-Request Message Format 1094 0 1 2 3 1095 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 1096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1097 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1098 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1099 | Nonce . . . | 1100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1101 | . . . Nonce | 1102 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1103 | Source-EID-AFI | Source EID Address ... | 1104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1105 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1107 | ... | 1108 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1109 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1111 / | Reserved | EID mask-len | EID-prefix-AFI | 1112 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1113 \ | EID-prefix ... | 1114 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1115 | Map-Reply Record ... | 1116 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1117 | Mapping Protocol Data | 1118 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1120 Packet field descriptions: 1122 Type: 1 (Map-Request) 1124 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1125 Requests sent by an ITR. 1127 M: When set, it indicates a Map-Reply Record segment is included in 1128 the Map-Request. 1130 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1131 treated as a locator reachability probe. The receiver SHOULD 1132 respond with a Map-Reply with the probe-bit set, indicating the 1133 Map-Reply is a locator reachability probe reply, with the nonce 1134 copied from the Map-Request. See Section 6.3.2 for more details. 1136 S: This is the SMR bit. See Section 6.6.2 for details. 1138 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1139 Map-Request. 1141 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1142 sending a Map-Request in response to a received SMR-based Map- 1143 Request. 1145 Reserved: Set to 0 on transmission and ignored on receipt. 1147 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1148 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1149 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1150 Address) pair must always be encoded. Multiple ITR-RLOC Address 1151 fields are used so a Map-Replier can select which destination 1152 address to use for a Map-Reply. The IRC value ranges from 0 to 1153 31, and for a value of 1, there are 2 ITR-RLOC addresses encoded 1154 and so on up to 31 which encodes a total of 32 ITR-RLOC addresses. 1156 Record Count: The number of records in this Map-Request message. A 1157 record is comprised of the portion of the packet that is labeled 1158 'Rec' above and occurs the number of times equal to Record Count. 1159 For this version of the protocol, a receiver MUST accept and 1160 process Map-Requests that contain one or more records, but a 1161 sender MUST only send Map-Requests containing one record. Support 1162 for requesting multiple EIDs in a single Map-Request message will 1163 be specified in a future version of the protocol. 1165 Nonce: An 8-byte random value created by the sender of the Map- 1166 Request. This nonce will be returned in the Map-Reply. The 1167 security of the LISP mapping protocol depends critically on the 1168 strength of the nonce in the Map-Request message. The nonce 1169 SHOULD be generated by a properly seeded pseudo-random (or strong 1170 random) source. See [RFC4086] for advice on generating security- 1171 sensitive random data. 1173 Source-EID-AFI: Address family of the "Source EID Address" field. 1175 Source EID Address: This is the EID of the source host which 1176 originated the packet which is invoking this Map-Request. When 1177 Map-Requests are used for refreshing a map-cache entry or for 1178 RLOC-probing, an AFI value 0 is used and this field is of zero 1179 length. 1181 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1182 follows this field. 1184 ITR-RLOC Address: Used to give the ETR the option of selecting the 1185 destination address from any address family for the Map-Reply 1186 message. This address MUST be a routable RLOC address of the 1187 sender of the Map-Request message. 1189 EID mask-len: Mask length for EID prefix. 1191 EID-prefix-AFI: Address family of EID-prefix according to [AFI] 1193 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1194 address-family. When a Map-Request is sent by an ITR because a 1195 data packet is received for a destination where there is no 1196 mapping entry, the EID-prefix is set to the destination IP address 1197 of the data packet. And the 'EID mask-len' is set to 32 or 128 1198 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1199 about the status of a mapping it already has cached, the EID- 1200 prefix used in the Map-Request has the same mask-length as the 1201 EID-prefix returned from the site when it sent a Map-Reply 1202 message. 1204 Map-Reply Record: When the M bit is set, this field is the size of a 1205 single "Record" in the Map-Reply format. This Map-Reply record 1206 contains the EID-to-RLOC mapping entry associated with the Source 1207 EID. This allows the ETR which will receive this Map-Request to 1208 cache the data if it chooses to do so. 1210 Mapping Protocol Data: See [CONS] for details. This field is 1211 optional and present when the UDP length indicates there is enough 1212 space in the packet to include it. 1214 6.1.3. EID-to-RLOC UDP Map-Request Message 1216 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1217 wants to test an RLOC for reachability, or wants to refresh a mapping 1218 before TTL expiration. For the initial case, the destination IP 1219 address used for the Map-Request is the destination-EID from the 1220 packet which had a mapping cache lookup failure. For the latter 2 1221 cases, the destination IP address used for the Map-Request is one of 1222 the RLOC addresses from the locator-set of the map cache entry. The 1223 source address is either an IPv4 or IPv6 RLOC address depending if 1224 the Map-Request is using an IPv4 versus IPv6 header, respectively. 1225 In all cases, the UDP source port number for the Map-Request message 1226 is an ITR/PITR selected 16-bit value and the UDP destination port 1227 number is set to the well-known destination port number 4342. A 1228 successful Map-Reply updates the cached set of RLOCs associated with 1229 the EID prefix range. 1231 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1232 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1233 be placed in the IRC field. The ITR MAY include all locally 1234 configured locators in this list or just provide one locator address 1235 from each address family it supports. If the ITR erroneously 1236 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1237 Request. 1239 Map-Requests can also be LISP encapsulated using UDP destination port 1240 4342 with a LISP type value set to "Encapsulated Control Message", 1241 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1242 LISP encapsulated the same way from a Map-Server to an ETR. Details 1243 on encapsulated Map-Requests and Map-Resolvers can be found in 1244 [LISP-MS]. 1246 Map-Requests MUST be rate-limited. It is recommended that a Map- 1247 Request for the same EID-prefix be sent no more than once per second. 1249 An ITR that is configured with mapping database information (i.e. it 1250 is also an ETR) may optionally include those mappings in a Map- 1251 Request. When an ETR configured to accept and verify such 1252 "piggybacked" mapping data receives such a Map-Request and it does 1253 not have this mapping in the map-cache, it may originate a "verifying 1254 Map-Request", addressed to the map-requesting ITR. If the ETR has a 1255 map-cache entry that matches the "piggybacked" EID and the RLOC is in 1256 the locator-set for the entry, then it may send the "verifying Map- 1257 Request" directly to the originating Map-Request source. If the RLOC 1258 is not in the locator-set, then the ETR MUST send the "verifying Map- 1259 Request" to the "piggybacked" EID. Doing this forces the "verifying 1260 Map-Request" to go through the mapping database system to reach the 1261 authoritative source of information about that EID, guarding against 1262 RLOC-spoofing in in the "piggybacked" mapping data. 1264 6.1.4. Map-Reply Message Format 1266 0 1 2 3 1267 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 1268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1269 |Type=2 |P|E|S| Reserved | Record Count | 1270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1271 | Nonce . . . | 1272 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1273 | . . . Nonce | 1274 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1275 | | Record TTL | 1276 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1277 R | Locator Count | EID mask-len | ACT |A| Reserved | 1278 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1279 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1280 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1281 r | EID-prefix | 1282 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1283 | /| Priority | Weight | M Priority | M Weight | 1284 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1285 | o | Unused Flags |L|p|R| Loc-AFI | 1286 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1287 | \| Locator | 1288 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1289 | Mapping Protocol Data | 1290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1292 Packet field descriptions: 1294 Type: 2 (Map-Reply) 1296 P: This is the probe-bit which indicates that the Map-Reply is in 1297 response to a locator reachability probe Map-Request. The nonce 1298 field MUST contain a copy of the nonce value from the original 1299 Map-Request. See Section 6.3.2 for more details. 1301 E: Indicates that the ETR which sends this Map-Reply message is 1302 advertising that the site is enabled for the Echo-Nonce locator 1303 reachability algorithm. See Section 6.3.1 for more details. 1305 S: This is the Security bit. When set to 1 the field following the 1306 Mapping Protocol Data field will have the following format. The 1307 detailed format of the Authentication Data Content field can be 1308 found in [LISP-SEC] when AD Type is equal to 1. 1310 0 1 2 3 1311 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 1312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1313 | AD Type | Authentication Data Content . . . | 1314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1316 Reserved: Set to 0 on transmission and ignored on receipt. 1318 Record Count: The number of records in this reply message. A record 1319 is comprised of that portion of the packet labeled 'Record' above 1320 and occurs the number of times equal to Record count. 1322 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1323 from the Map-Request is echoed in this Nonce field of the Map- 1324 Reply. 1326 Record TTL: The time in minutes the recipient of the Map-Reply will 1327 store the mapping. If the TTL is 0, the entry SHOULD be removed 1328 from the cache immediately. If the value is 0xffffffff, the 1329 recipient can decide locally how long to store the mapping. 1331 Locator Count: The number of Locator entries. A locator entry 1332 comprises what is labeled above as 'Loc'. The locator count can 1333 be 0 indicating there are no locators for the EID-prefix. 1335 EID mask-len: Mask length for EID prefix. 1337 ACT: This 3-bit field describes negative Map-Reply actions. These 1338 bits are used only when the 'Locator Count' field is set to 0. 1339 The action bits are encoded only in Map-Reply messages. The 1340 actions defined are used by an ITR or PTR when a destination EID 1341 matches a negative mapping cache entry. Unassigned values should 1342 cause a map-cache entry to be created and, when packets match this 1343 negative cache entry, they will be dropped. The current assigned 1344 values are: 1346 (0) No-Action: The map-cache is kept alive and packet 1347 encapsulation occurs. 1349 (1) Natively-Forward: The packet is not encapsulated or dropped 1350 but natively forwarded. 1352 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1354 (3) Drop: A packet that matches this map-cache entry is dropped. 1356 A: The Authoritative bit, when sent by a UDP-based message is always 1357 set to 1 by an ETR. See [CONS] for TCP-based Map-Replies. When a 1358 Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, the 1359 Authoritative bit is set to 0. This indicates to requesting ITRs 1360 that the Map-Reply was not originated by a LISP node managed at 1361 the site that owns the EID-prefix. 1363 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1364 sender is informing the ITR what the version number is for the 1365 EID-record contained in the Map-Reply. The ETR can allocate this 1366 number internally but MUST coordinate this value with other ETRs 1367 for the site. When this value is 0, there is no versioning 1368 information conveyed. The Map-Version Number can be included in 1369 Map-Request and Map-Register messages. See Section 6.6.3 for more 1370 details. 1372 EID-prefix-AFI: Address family of EID-prefix according to [AFI]. 1374 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1375 address-family. 1377 Priority: each RLOC is assigned a unicast priority. Lower values 1378 are more preferable. When multiple RLOCs have the same priority, 1379 they may be used in a load-split fashion. A value of 255 means 1380 the RLOC MUST NOT be used for unicast forwarding. 1382 Weight: when priorities are the same for multiple RLOCs, the weight 1383 indicates how to balance unicast traffic between them. Weight is 1384 encoded as a relative weight of total unicast packets that match 1385 the mapping entry. For example if there are 4 locators in a 1386 locator set, where the weights assigned are 30, 20, 20, and 10, 1387 the first locator will get 37.5% of the traffic, the 2nd and 3rd 1388 locators will get 25% of traffic and the 4th locator will get 1389 12.5% of the traffic. If all weights for a locator-set are equal, 1390 receiver of the Map-Reply will decide how to load-split traffic. 1391 See Section 6.5 for a suggested hash algorithm to distribute load 1392 across locators with same priority and equal weight values. 1394 M Priority: each RLOC is assigned a multicast priority used by an 1395 ETR in a receiver multicast site to select an ITR in a source 1396 multicast site for building multicast distribution trees. A value 1397 of 255 means the RLOC MUST NOT be used for joining a multicast 1398 distribution tree. 1400 M Weight: when priorities are the same for multiple RLOCs, the 1401 weight indicates how to balance building multicast distribution 1402 trees across multiple ITRs. The weight is encoded as a relative 1403 weight (similar to the unicast Weights) of total number of trees 1404 built to the source site identified by the EID-prefix. If all 1405 weights for a locator-set are equal, the receiver of the Map-Reply 1406 will decide how to distribute multicast state across ITRs. 1408 Unused Flags: set to 0 when sending and ignored on receipt. 1410 L: when this bit is set, the locator is flagged as a local locator to 1411 the ETR that is sending the Map-Reply. When a Map-Server is doing 1412 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1413 0 for all locators in this locator-set. 1415 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1416 locator address, for which this bit is set, is the one being RLOC- 1417 probed and may be different from the source address of the Map- 1418 Reply. An ITR that RLOC-probes a particular locator, MUST use 1419 this locator for retrieving the data structure used to store the 1420 fact that the locator is reachable. The "p" bit is set for a 1421 single locator in the same locator set. If an implementation sets 1422 more than one "p" bit erroneously, the receiver of the Map-Reply 1423 MUST select the first locator. The "p" bit MUST NOT be set for 1424 locator-set records sent in Map-Request and Map-Register messages. 1426 R: set when the sender of a Map-Reply has a route to the locator in 1427 the locator data record. This receiver may find this useful to 1428 know if the locator is up but not necessarily reachable from the 1429 receiver's point of view. See also Section 6.4 for another way 1430 the R-bit may be used. 1432 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1433 assigned to an ETR. Note that the destination RLOC address MAY be 1434 an anycast address. A source RLOC can be an anycast address as 1435 well. The source or destination RLOC MUST NOT be the broadcast 1436 address (255.255.255.255 or any subnet broadcast address known to 1437 the router), and MUST NOT be a link-local multicast address. The 1438 source RLOC MUST NOT be a multicast address. The destination RLOC 1439 SHOULD be a multicast address if it is being mapped from a 1440 multicast destination EID. 1442 Mapping Protocol Data: See [CONS] or [ALT] for details. This field 1443 is optional and present when the UDP length indicates there is 1444 enough space in the packet to include it. The Mapping Protocol 1445 Data is used when needed by the particular mapping system. 1447 6.1.5. EID-to-RLOC UDP Map-Reply Message 1449 A Map-Reply returns an EID-prefix with a prefix length that is less 1450 than or equal to the EID being requested. The EID being requested is 1451 either from the destination field of an IP header of a Data-Probe or 1452 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1453 globally-routable IP addresses of all ETRs for the LISP site. Each 1454 RLOC conveys status reachability but does not convey path 1455 reachability from a requesters perspective. Separate testing of path 1456 reachability is required, See Section 6.3 for details. 1458 Note that a Map-Reply may contain different EID-prefix granularity 1459 (prefix + length) than the Map-Request which triggers it. This might 1460 occur if a Map-Request were for a prefix that had been returned by an 1461 earlier Map-Reply. In such a case, the requester updates its cache 1462 with the new prefix information and granularity. For example, a 1463 requester with two cached EID-prefixes that are covered by a Map- 1464 Reply containing one, less-specific prefix, replaces the entry with 1465 the less-specific EID-prefix. Note that the reverse, replacement of 1466 one less-specific prefix with multiple more-specific prefixes, can 1467 also occur but not by removing the less-specific prefix rather by 1468 adding the more-specific prefixes which during a lookup will override 1469 the less-specific prefix. 1471 When an ETR is configured with overlapping EID-prefixes, a Map- 1472 Request with an EID that longest matches any EID-prefix MUST be 1473 returned in a single Map-Reply message. For instance, if an ETR had 1474 database mapping entries for EID-prefixes: 1476 10.0.0.0/8 1477 10.1.0.0/16 1478 10.1.1.0/24 1479 10.1.2.0/24 1481 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1482 count of 1 to be returned with a mapping record EID-prefix of 1483 10.1.1.0/24. 1485 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1486 count of 3 to be returned with mapping records for EID-prefixes 1487 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1489 Note that not all overlapping EID-prefixes need to be returned, only 1490 the more specifics (note in the second example above 10.0.0.0/8 was 1491 not returned for requesting EID 10.1.5.5) entries for the matching 1492 EID-prefix of the requesting EID. When more than one EID-prefix is 1493 returned, all SHOULD use the same Time-to-Live value so they can all 1494 time out at the same time. When a more specific EID-prefix is 1495 received later, its Time-to-Live value in the Map-Reply record can be 1496 stored even when other less specifics exist. When a less specific 1497 EID-prefix is received later, its map-cache expiration time SHOULD be 1498 set to the minimum expiration time of any more specific EID-prefix in 1499 the map-cache. 1501 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1502 per second to the same requesting router. For scalability, it is 1503 expected that aggregation of EID addresses into EID-prefixes will 1504 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1505 prefix range thereby reducing the number of Map-Request messages. 1507 Map-Reply records can have an empty locator-set. A negative Map- 1508 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1509 convey special actions by the sender to the ITR or PTR which have 1510 solicited the Map-Reply. There are two primary applications for 1511 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1512 ITR or PTR when a destination is for a LISP site versus a non-LISP 1513 site. And the other is to source quench Map-Requests which are sent 1514 for non-allocated EIDs. 1516 For each Map-Reply record, the list of locators in a locator-set MUST 1517 appear in the same order for each ETR that originates a Map-Reply 1518 message. The locator-set MUST be sorted in order of ascending IP 1519 address where an IPv4 locator address is considered numerically 'less 1520 than' an IPv6 locator address. 1522 When sending a Map-Reply message, the destination address is copied 1523 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1524 can choose a locator address from one of the address families it 1525 supports. For Data-Probes, the destination address of the Map-Reply 1526 is copied from the source address of the Data-Probe message which is 1527 invoking the reply. The source address of the Map-Reply is one of 1528 the local IP addresses chosen to allow uRPF checks to succeed in the 1529 upstream service provider. The destination port of a Map-Reply 1530 message is copied from the source port of the Map-Request or Data- 1531 Probe and the source port of the Map-Reply message is set to the 1532 well-known UDP port 4342. 1534 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1536 When an ETR is misconfigured or compromised, it could return coarse 1537 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1538 cover EID-prefixes which are allocated to other sites redirecting 1539 their traffic to the locators of the compromised site. 1541 To solve this problem, there are two basic solutions that could be 1542 used. The first is to have Map-Servers proxy-map-reply on behalf of 1543 ETRs so their registered EID-prefixes are the ones returned in Map- 1544 Replies. Since the interaction between an ETR and Map-Server is 1545 secured with shared-keys, it is more difficult for an ETR to 1546 misbehave. The second solution is to have ITRs and PTRs cache EID- 1547 prefixes with mask-lengths that are greater than or equal to a 1548 configured prefix length. This limits the damage to a specific width 1549 of any EID-prefix advertised, but needs to be coordinated with the 1550 allocation of site prefixes. These solutions can be used 1551 independently or at the same time. 1553 At the time of this writing, other approaches are being considered 1554 and researched. 1556 6.1.6. Map-Register Message Format 1558 The usage details of the Map-Register message can be found in 1559 specification [LISP-MS]. This section solely defines the message 1560 format. 1562 The message is sent in UDP with a destination UDP port of 4342 and a 1563 randomly selected UDP source port number. 1565 The Map-Register message format is: 1567 0 1 2 3 1568 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 1569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1570 |Type=3 |P| Reserved |M| Record Count | 1571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1572 | Nonce . . . | 1573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1574 | . . . Nonce | 1575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1576 | Key ID | Authentication Data Length | 1577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1578 ~ Authentication Data ~ 1579 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1580 | | Record TTL | 1581 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1582 R | Locator Count | EID mask-len | ACT |A| Reserved | 1583 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1584 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1585 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1586 r | EID-prefix | 1587 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1588 | /| Priority | Weight | M Priority | M Weight | 1589 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1590 | o | Unused Flags |L|p|R| Loc-AFI | 1591 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1592 | \| Locator | 1593 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1595 Packet field descriptions: 1597 Type: 3 (Map-Register) 1599 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1600 Register message requesting for the Map-Server to proxy Map-Reply. 1601 The Map-Server will send non-authoritative Map-Replies on behalf 1602 of the ETR. Details on this usage will be provided in a future 1603 version of this draft. 1605 Reserved: Set to 0 on transmission and ignored on receipt. 1607 M: This is the want-map-notify bit, when set to 1 an ETR is 1608 requesting for a Map-Notify message to be returned in response to 1609 sending a Map-Register message. The Map-Notify message sent by a 1610 Map-Server is used to an acknowledge receipt of a Map-Register 1611 message. 1613 Record Count: The number of records in this Map-Register message. A 1614 record is comprised of that portion of the packet labeled 'Record' 1615 above and occurs the number of times equal to Record count. 1617 Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages. 1619 Key ID: A configured ID to find the configured Message 1620 Authentication Code (MAC) algorithm and key value used for the 1621 authentication function. 1623 Authentication Data Length: The length in bytes of the 1624 Authentication Data field that follows this field. The length of 1625 the Authentication Data field is dependent on the Message 1626 Authentication Code (MAC) algorithm used. The length field allows 1627 a device that doesn't know the MAC algorithm to correctly parse 1628 the packet. 1630 Authentication Data: The message digest used from the output of the 1631 Message Authentication Code (MAC) algorithm. The entire Map- 1632 Register payload is authenticated with this field preset to 0. 1633 After the MAC is computed, it is placed in this field. 1634 Implementations of this specification MUST include support for 1635 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-128-256 [RFC4634] 1636 is recommended. 1638 The definition of the rest of the Map-Register can be found in the 1639 Map-Reply section. 1641 6.1.7. Map-Notify Message Format 1643 The usage details of the Map-Notify message can be found in 1644 specification [LISP-MS]. This section solely defines the message 1645 format. 1647 The message is sent inside a UDP packet with a source UDP port equal 1648 to 4342 and a destination port equal to the source port from the Map- 1649 Register message this Map-Notify message is responding to. 1651 The Map-Notify message format is: 1653 0 1 2 3 1654 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 1655 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1656 |Type=4 | Reserved | Record Count | 1657 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1658 | Nonce . . . | 1659 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1660 | . . . Nonce | 1661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1662 | Key ID | Authentication Data Length | 1663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1664 ~ Authentication Data ~ 1665 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1666 | | Record TTL | 1667 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1668 R | Locator Count | EID mask-len | ACT |A| Reserved | 1669 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1670 c | Rsvd | Map-Version Number | EID-prefix-AFI | 1671 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1672 r | EID-prefix | 1673 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1674 | /| Priority | Weight | M Priority | M Weight | 1675 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1676 | o | Unused Flags |L|p|R| Loc-AFI | 1677 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1678 | \| Locator | 1679 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1681 Packet field descriptions: 1683 Type: 4 (Map-Notify) 1685 The Map-Notify message has the same contents as a Map-Register 1686 message. See Map-Register section for field descriptions. 1688 6.1.8. Encapsulated Control Message Format 1690 An Encapsulated Control Message is used to encapsulate control 1691 packets sent between xTRs and the mapping database system described 1692 in [LISP-MS]. 1694 0 1 2 3 1695 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 1696 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1697 / | IPv4 or IPv6 Header | 1698 OH | (uses RLOC addresses) | 1699 \ | | 1700 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1701 / | Source Port = xxxx | Dest Port = 4342 | 1702 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1703 \ | UDP Length | UDP Checksum | 1704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1705 LH |Type=8 |S| Reserved | 1706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1707 / | IPv4 or IPv6 Header | 1708 IH | (uses RLOC or EID addresses) | 1709 \ | | 1710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1711 / | Source Port = xxxx | Dest Port = yyyy | 1712 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1713 \ | UDP Length | UDP Checksum | 1714 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1715 LCM | LISP Control Message | 1716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1718 Packet header descriptions: 1720 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1721 source and destination header address fields. 1723 UDP: The outer UDP header with destination port 4342. The source 1724 port is randomly allocated. The checksum field MUST be non-zero. 1726 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1727 and what follows is either an IPv4 or IPv6 header as encoded by 1728 the first 4 bits after the reserved field. 1730 S: This is the Security bit. When set to 1 the field following the 1731 Reserved field will have the following format. The detailed 1732 format of the Authentication Data Content field can be found in 1733 [LISP-SEC] when AD Type is equal to 1. 1735 0 1 2 3 1736 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 1737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1738 | AD Type | Authentication Data Content . . . | 1739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1741 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1742 addresses in the header address fields. When a Map-Request is 1743 encapsulated in this packet format the destination address in this 1744 header is an EID. 1746 UDP: The inner UDP header where the port assignments depends on the 1747 control packet being encapsulated. When the control packet is a 1748 Map-Request or Map-Register, the source port is ITR/PITR selected 1749 and the destination port is 4342. When the control packet is a 1750 Map-Reply, the source port is 4342 and the destination port is 1751 assigned from the source port of the invoking Map-Request. Port 1752 number 4341 MUST NOT be assigned to either port. The checksum 1753 field MUST be non-zero. 1755 LCM: The format is one of the control message formats described in 1756 this section. At this time, only Map-Request messages and PIM 1757 Join-Prune messages [MLISP] are allowed to be encapsulated. 1758 Encapsulating other types of LISP control messages are for further 1759 study. When Map-Requests are sent for RLOC-probing purposes (i.e 1760 the probe-bit is set), they MUST NOT be sent inside Encapsulated 1761 Control Messages. 1763 6.2. Routing Locator Selection 1765 Both client-side and server-side may need control over the selection 1766 of RLOCs for conversations between them. This control is achieved by 1767 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1768 messages. Alternatively, RLOC information may be gleaned from 1769 received tunneled packets or EID-to-RLOC Map-Request messages. 1771 The following enumerates different scenarios for choosing RLOCs and 1772 the controls that are available: 1774 o Server-side returns one RLOC. Client-side can only use one RLOC. 1775 Server-side has complete control of the selection. 1777 o Server-side returns a list of RLOC where a subset of the list has 1778 the same best priority. Client can only use the subset list 1779 according to the weighting assigned by the server-side. In this 1780 case, the server-side controls both the subset list and load- 1781 splitting across its members. The client-side can use RLOCs 1782 outside of the subset list if it determines that the subset list 1783 is unreachable (unless RLOCs are set to a Priority of 255). Some 1784 sharing of control exists: the server-side determines the 1785 destination RLOC list and load distribution while the client-side 1786 has the option of using alternatives to this list if RLOCs in the 1787 list are unreachable. 1789 o Server-side sets weight of 0 for the RLOC subset list. In this 1790 case, the client-side can choose how the traffic load is spread 1791 across the subset list. Control is shared by the server-side 1792 determining the list and the client determining load distribution. 1793 Again, the client can use alternative RLOCs if the server-provided 1794 list of RLOCs are unreachable. 1796 o Either side (more likely on the server-side ETR) decides not to 1797 send a Map-Request. For example, if the server-side ETR does not 1798 send Map-Requests, it gleans RLOCs from the client-side ITR, 1799 giving the client-side ITR responsibility for bidirectional RLOC 1800 reachability and preferability. Server-side ETR gleaning of the 1801 client-side ITR RLOC is done by caching the inner header source 1802 EID and the outer header source RLOC of received packets. The 1803 client-side ITR controls how traffic is returned and can alternate 1804 using an outer header source RLOC, which then can be added to the 1805 list the server-side ETR uses to return traffic. Since no 1806 Priority or Weights are provided using this method, the server- 1807 side ETR MUST assume each client-side ITR RLOC uses the same best 1808 Priority with a Weight of zero. In addition, since EID-prefix 1809 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1810 on tunnel routers can grow to be very large. 1812 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1813 received encapsulated packet, is only stored and used for a few 1814 seconds, pending verification. Verification is performed by 1815 sending a Map-Request to the source EID (the inner header IP 1816 source address) of the received encapsulated packet. A reply to 1817 this "verifying Map-Request" is used to fully populate the map- 1818 cache entry for the "gleaned" EID and is stored and used for the 1819 time indicated from the TTL field of a received Map-Reply. When a 1820 verified map-cache entry is stored, data gleaning no longer occurs 1821 for subsequent packets which have a source EID that matches the 1822 EID-prefix of the verified entry. 1824 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1825 reachable when the R-bit for the locator record is set to 1. When 1826 the R-bit is set to 0, an ITR or PITR MUST not encapsulate to the 1827 RLOC. Neither the information contained in a Map-Reply or that 1828 stored in the mapping database system provides reachability 1829 information for RLOCs. Note that reachability is not part of the 1830 mapping system and is determined using one or more of the Routing 1831 Locator Reachability Algorithms described in the next section. 1833 6.3. Routing Locator Reachability 1835 Several mechanisms for determining RLOC reachability are currently 1836 defined: 1838 1. An ETR may examine the Loc-Status-Bits in the LISP header of an 1839 encapsulated data packet received from an ITR. If the ETR is 1840 also acting as an ITR and has traffic to return to the original 1841 ITR site, it can use this status information to help select an 1842 RLOC. 1844 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1845 message for an RLOC it is using. This indicates that the RLOC is 1846 likely down. 1848 3. An ITR which participates in the global routing system can 1849 determine that an RLOC is down if no BGP RIB route exists that 1850 matches the RLOC IP address. 1852 4. An ITR may receive an ICMP Port Unreachable message from a 1853 destination host. This occurs if an ITR attempts to use 1854 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1855 non-LISP-capable site. 1857 5. An ITR may receive a Map-Reply from a ETR in response to a 1858 previously sent Map-Request. The RLOC source of the Map-Reply is 1859 likely up since the ETR was able to send the Map-Reply to the 1860 ITR. 1862 6. When an ETR receives an encapsulated packet from an ITR, the 1863 source RLOC from the outer header of the packet is likely up. 1865 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1866 described in this section, namely Echo-Noncing or RLOC-Probing. 1868 When determining Locator up/down reachability by examining the Loc- 1869 Status-Bits from the LISP encapsulated data packet, an ETR will 1870 receive up to date status from an encapsulating ITR about 1871 reachability for all ETRs at the site. CE-based ITRs at the source 1872 site can determine reachability relative to each other using the site 1873 IGP as follows: 1875 o Under normal circumstances, each ITR will advertise a default 1876 route into the site IGP. 1878 o If an ITR fails or if the upstream link to its PE fails, its 1879 default route will either time-out or be withdrawn. 1881 Each ITR can thus observe the presence or lack of a default route 1882 originated by the others to determine the Locator Status Bits it sets 1883 for them. 1885 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1886 Loc-Status-Bits in a LISP encapsulated packet are numbered from 0 to 1887 n-1 starting with the least significant bit. For example, if an RLOC 1888 listed in the 3rd position of the Map-Reply goes down (ordinal value 1889 2), then all ITRs at the site will clear the 3rd least significant 1890 bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they 1891 encapsulate. 1893 When an ETR decapsulates a packet, it will check for any change in 1894 the Loc-Status-Bits field. When a bit goes from 1 to 0, the ETR will 1895 refrain from encapsulating packets to an RLOC that is indicated as 1896 down. It will only resume using that RLOC if the corresponding Loc- 1897 Status-Bit returns to a value of 1. Loc-Status-Bits are associated 1898 with a locator-set per EID-prefix. Therefore, when a locator becomes 1899 unreachable, the Loc-Status-Bit that corresponds to that locator's 1900 position in the list returned by the last Map-Reply will be set to 1901 zero for that particular EID-prefix. 1903 When ITRs at the site are not deployed in CE routers, the IGP can 1904 still be used to determine the reachability of Locators provided they 1905 are injected into the IGP. This is typically done when a /32 address 1906 is configured on a loopback interface. 1908 When ITRs receive ICMP Network or Host Unreachable messages as a 1909 method to determine unreachability, they will refrain from using 1910 Locators which are described in Locator lists of Map-Replies. 1911 However, using this approach is unreliable because many network 1912 operators turn off generation of ICMP Unreachable messages. 1914 If an ITR does receive an ICMP Network or Host Unreachable message, 1915 it MAY originate its own ICMP Unreachable message destined for the 1916 host that originated the data packet the ITR encapsulated. 1918 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 1919 locator address from a locator-set in a mapping entry matches a 1920 prefix. If it does not find one and BGP is running in the Default 1921 Free Zone (DFZ), it can decide to not use the locator even though the 1922 Loc-Status-Bits indicate the locator is up. In this case, the path 1923 from the ITR to the ETR that is assigned the locator is not 1924 available. More details are in [LOC-ID-ARCH]. 1926 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 1927 Reply is returned, reachability of the Locator has been determined. 1928 Obviously, sending such probes increases the number of control 1929 messages originated by tunnel routers for active flows, so Locators 1930 are assumed to be reachable when they are advertised. 1932 This assumption does create a dependency: Locator unreachability is 1933 detected by the receipt of ICMP Host Unreachable messages. When an 1934 Locator has been determined to be unreachable, it is not used for 1935 active traffic; this is the same as if it were listed in a Map-Reply 1936 with priority 255. 1938 The ITR can test the reachability of the unreachable Locator by 1939 sending periodic Requests. Both Requests and Replies MUST be rate- 1940 limited. Locator reachability testing is never done with data 1941 packets since that increases the risk of packet loss for end-to-end 1942 sessions. 1944 When an ETR decapsulates a packet, it knows that it is reachable from 1945 the encapsulating ITR because that is how the packet arrived. In 1946 most cases, the ETR can also reach the ITR but cannot assume this to 1947 be true due to the possibility of path asymmetry. In the presence of 1948 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 1949 use the lack of return traffic as an indication that the ETR is 1950 unreachable. Instead, it MUST use an alternate mechanisms to 1951 determine reachability. 1953 6.3.1. Echo Nonce Algorithm 1955 When data flows bidirectionally between locators from different 1956 sites, a data-plane mechanism called "nonce echoing" can be used to 1957 determine reachability between an ITR and ETR. When an ITR wants to 1958 solicit a nonce echo, it sets the N and E bits and places a 24-bit 1959 nonce in the LISP header of the next encapsulated data packet. 1961 When this packet is received by the ETR, the encapsulated packet is 1962 forwarded as normal. When the ETR next sends a data packet to the 1963 ITR, it includes the nonce received earlier with the N bit set and E 1964 bit cleared. The ITR sees this "echoed nonce" and knows the path to 1965 and from the ETR is up. 1967 The ITR will set the E-bit and N-bit for every packet it sends while 1968 in echo-nonce-request state. The time the ITR waits to process the 1969 echoed nonce before it determines the path is unreachable is variable 1970 and a choice left for the implementation. 1972 If the ITR is receiving packets from the ETR but does not see the 1973 nonce echoed while being in echo-nonce-request state, then the path 1974 to the ETR is unreachable. This decision may be overridden by other 1975 locator reachability algorithms. Once the ITR determines the path to 1976 the ETR is down it can switch to another locator for that EID-prefix. 1978 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1979 be implementing both ITR and ETR functionality for the echo nonce 1980 mechanism to operate. 1982 The ITR and ETR may both go into echo-nonce-request state at the same 1983 time. The number of packets sent or the time during which echo nonce 1984 requests are sent is an implementation specific setting. However, 1985 when an ITR is in echo-nonce-request state, it can echo the ETR's 1986 nonce in the next set of packets that it encapsulates and then 1987 subsequently, continue sending echo-nonce-request packets. 1989 This mechanism does not completely solve the forward path 1990 reachability problem as traffic may be unidirectional. That is, the 1991 ETR receiving traffic at a site may not be the same device as an ITR 1992 which transmits traffic from that site or the site to site traffic is 1993 unidirectional so there is no ITR returning traffic. 1995 The echo-nonce algorithm is bilateral. That is, if one side sets the 1996 E-bit and the other side is not enabled for echo-noncing, then the 1997 echoing of the nonce does not occur and the requesting side may 1998 regard the locator unreachable erroneously. An ITR SHOULD only set 1999 the E-bit in a encapsulated data packet when it knows the ETR is 2000 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 2001 Reply message. 2003 Note that other locator reachability mechanisms are being researched 2004 and can be used to compliment or even override the Echo Nonce 2005 Algorithm. See next section for an example of control-plane probing. 2007 6.3.2. RLOC Probing Algorithm 2009 RLOC Probing is a method that an ITR or PTR can use to determine the 2010 reachability status of one or more locators that it has cached in a 2011 map-cache entry. The probe-bit of the Map-Request and Map-Reply 2012 messages are used for RLOC Probing. 2014 RLOC probing is done in the control-plane on a timer basis where an 2015 ITR or PTR will originate a Map-Request destined to a locator address 2016 from one of its own locator addresses. A Map-Request used as an 2017 RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the 2018 ALT like one would when soliciting mapping data. The EID record 2019 encoded in the Map-Request is the EID-prefix of the map-cache entry 2020 cached by the ITR or PTR. The ITR may include a mapping data record 2021 for its own database mapping information which contains the local 2022 EID-prefixes and RLOCs for its site. 2024 When an ETR receives a Map-Request message with the probe-bit set, it 2025 returns a Map-Reply with the probe-bit set. The source address of 2026 the Map-Reply is set from the destination address of the Map-Request 2027 and the destination address of the Map-Reply is set from the source 2028 address of the Map-Request. The Map-Reply SHOULD contain mapping 2029 data for the EID-prefix contained in the Map-Request. This provides 2030 the opportunity for the ITR or PTR, which sent the RLOC-probe to get 2031 mapping updates if there were changes to the ETR's database mapping 2032 entries. 2034 There are advantages and disadvantages of RLOC Probing. The greatest 2035 benefit of RLOC Probing is that it can handle many failure scenarios 2036 allowing the ITR to determine when the path to a specific locator is 2037 reachable or has become unreachable, thus providing a robust 2038 mechanism for switching to using another locator from the cached 2039 locator. RLOC Probing can also provide rough RTT estimates between a 2040 pair of locators which can be useful for network management purposes 2041 as well as for selecting low delay paths. The major disadvantage of 2042 RLOC Probing is in the number of control messages required and the 2043 amount of bandwidth used to obtain those benefits, especially if the 2044 requirement for failure detection times are very small. 2046 Continued research and testing will attempt to characterize the 2047 tradeoffs of failure detection times versus message overhead. 2049 6.4. EID Reachability within a LISP Site 2051 A site may be multihomed using two or more ETRs. The hosts and 2052 infrastructure within a site will be addressed using one or more EID 2053 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2054 mapping system. One possible failure mode is for an ETR to lose 2055 reachability to one or more of the EID prefixes within its own site. 2056 When this occurs when the ETR sends Map-Replies, it can clear the 2057 R-bit associated with its own locator. And when the ETR is also an 2058 ITR, it can clear its locator-status-bit in the encapsulation data 2059 header. 2061 It is recognized there are no simple solutions to the site 2062 partitioning problem because it is hard to know which part of the 2063 EID-prefix range is partitioned. And which locators can reach any 2064 sub-ranges of the EID-prefixes. This problem is under investigation 2065 with the expectation that experiments will tell us more. Note, this 2066 is not a new problem introduced by the LISP architecture. The 2067 problem exists today when a multi-homed site uses BGP to advertise 2068 its reachability upstream. 2070 6.5. Routing Locator Hashing 2072 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2073 a requesting ITR, the locator-set for the EID-prefix may contain 2074 different priority values for each locator address. When more than 2075 one best priority locator exists, the ITR can decide how to load 2076 share traffic against the corresponding locators. 2078 The following hash algorithm may be used by an ITR to select a 2079 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2081 1. Either a source and destination address hash can be used or the 2082 traditional 5-tuple hash which includes the source and 2083 destination addresses, source and destination TCP, UDP, or SCTP 2084 port numbers and the IP protocol number field or IPv6 next- 2085 protocol fields of a packet a host originates from within a LISP 2086 site. When a packet is not a TCP, UDP, or SCTP packet, the 2087 source and destination addresses only from the header are used to 2088 compute the hash. 2090 2. Take the hash value and divide it by the number of locators 2091 stored in the locator-set for the EID-to-RLOC mapping. 2093 3. The remainder will be yield a value of 0 to "number of locators 2094 minus 1". Use the remainder to select the locator in the 2095 locator-set. 2097 Note that when a packet is LISP encapsulated, the source port number 2098 in the outer UDP header needs to be set. Selecting a hashed value 2099 allows core routers which are attached to Link Aggregation Groups 2100 (LAGs) to load-split the encapsulated packets across member links of 2101 such LAGs. Otherwise, core routers would see a single flow, since 2102 packets have a source address of the ITR, for packets which are 2103 originated by different EIDs at the source site. A suggested setting 2104 for the source port number computed by an ITR is a 5-tuple hash 2105 function on the inner header, as described above. 2107 Many core router implementations use a 5-tuple hash to decide how to 2108 balance packet load across members of a LAG. The 5-tuple hash 2109 includes the source and destination addresses of the packet and the 2110 source and destination ports when the protocol number in the packet 2111 is TCP or UDP. For this reason, UDP encoding is used for LISP 2112 encapsulation. 2114 6.6. Changing the Contents of EID-to-RLOC Mappings 2116 Since the LISP architecture uses a caching scheme to retrieve and 2117 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2118 date mapping is to re-request the mapping. However, the ITRs do not 2119 know when the mappings change and the ETRs do not keep track of which 2120 ITRs requested its mappings. For scalability reasons, we want to 2121 maintain this approach but need to provide a way for ETRs change 2122 their mappings and inform the sites that are currently communicating 2123 with the ETR site using such mappings. 2125 When adding a new locator record in lexiographic order to the end of 2126 a locator-set, it is easy to update mappings. We assume new mappings 2127 will maintain the same locator ordering as the old mapping but just 2128 have new locators appended to the end of the list. So some ITRs can 2129 have a new mapping while other ITRs have only an old mapping that is 2130 used until they time out. When an ITR has only an old mapping but 2131 detects bits set in the loc-status-bits that correspond to locators 2132 beyond the list it has cached, it simply ignores them. However, this 2133 can only happen for locator addresses that are lexicographically 2134 greater than the locator addresses in the existing locator-set. 2136 When a locator record is inserted in the middle of a locator-set, to 2137 maintain lexiographic order, the SMR procedure in Section 6.6.2 is 2138 used to inform ITRs and PTRs of the new locator-status-bit mappings. 2140 When a locator record is removed from a locator-set, ITRs that have 2141 the mapping cached will not use the removed locator because the xTRs 2142 will set the loc-status-bit to 0. So even if the locator is in the 2143 list, it will not be used. For new mapping requests, the xTRs can 2144 set the locator AFI to 0 (indicating an unspecified address), as well 2145 as setting the corresponding loc-status-bit to 0. This forces ITRs 2146 with old or new mappings to avoid using the removed locator. 2148 If many changes occur to a mapping over a long period of time, one 2149 will find empty record slots in the middle of the locator-set and new 2150 records appended to the locator-set. At some point, it would be 2151 useful to compact the locator-set so the loc-status-bit settings can 2152 be efficiently packed. 2154 We propose here three approaches for locator-set compaction, one 2155 operational and two protocol mechanisms. The operational approach 2156 uses a clock sweep method. The protocol approaches use the concept 2157 of Solicit-Map-Requests and Map-Versioning. 2159 6.6.1. Clock Sweep 2161 The clock sweep approach uses planning in advance and the use of 2162 count-down TTLs to time out mappings that have already been cached. 2163 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2164 there is a 24 hour window to time out old mappings. The following 2165 clock sweep procedure is used: 2167 1. 24 hours before a mapping change is to take effect, a network 2168 administrator configures the ETRs at a site to start the clock 2169 sweep window. 2171 2. During the clock sweep window, ETRs continue to send Map-Reply 2172 messages with the current (unchanged) mapping records. The TTL 2173 for these mappings is set to 1 hour. 2175 3. 24 hours later, all previous cache entries will have timed out, 2176 and any active cache entries will time out within 1 hour. During 2177 this 1 hour window the ETRs continue to send Map-Reply messages 2178 with the current (unchanged) mapping records with the TTL set to 2179 1 minute. 2181 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2182 messages with the new (changed) mapping records. So any active 2183 caches can get the new mapping contents right away if not cached, 2184 or in 1 minute if they had the mapping cached. The new mappings 2185 are cached with a time to live equal to the TTL in the Map-Reply. 2187 6.6.2. Solicit-Map-Request (SMR) 2189 Soliciting a Map-Request is a selective way for ETRs, at the site 2190 where mappings change, to control the rate they receive requests for 2191 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2192 the mappings they have cached. 2194 Since the ETRs don't keep track of remote ITRs that have cached their 2195 mappings, they do not know which ITRs need to have their mappings 2196 updated. As a result, an ETR will solicit Map-Requests (called an 2197 SMR message) from those sites to which it has been sending 2198 encapsulated data to for the last minute. In particular, an ETR will 2199 send an SMR an ITR to which it has recently sent encapsulated data. 2201 An SMR message is simply a bit set in a Map-Request message. An ITR 2202 or PTR will send a Map-Request when they receive an SMR message. 2203 Both the SMR sender and the Map-Request responder MUST rate-limited 2204 these messages. Rate-limiting can be implemented as a global rate- 2205 limiter or one rate-limiter per SMR destination. 2207 The following procedure shows how a SMR exchange occurs when a site 2208 is doing locator-set compaction for an EID-to-RLOC mapping: 2210 1. When the database mappings in an ETR change, the ETRs at the site 2211 begin to send Map-Requests with the SMR bit set for each locator 2212 in each map-cache entry the ETR caches. 2214 2. A remote ITR which receives the SMR message will schedule sending 2215 a Map-Request message to the source locator address of the SMR 2216 message or to the mapping database system. A newly allocated 2217 random nonce is selected and the EID-prefix used is the one 2218 copied from the SMR message. If the source locator is the only 2219 locator in the cached locator-set, the remote ITR SHOULD send a 2220 Map-Request to the database mapping system just in case the 2221 single locator has changed and may no longer be reachable to 2222 accept the Map-Request. 2224 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2225 Map-Reply while continuing to use the cached mapping. When Map 2226 Versioning is used, described in Section 6.6.3, an SMR sender can 2227 detect if an ITR is using the most up to date database mapping. 2229 4. The ETRs at the site with the changed mapping will reply to the 2230 Map-Request with a Map-Reply message that has a nonce from the 2231 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2232 limited. This is important to avoid Map-Reply implosion. 2234 5. The ETRs, at the site with the changed mapping, record the fact 2235 that the site that sent the Map-Request has received the new 2236 mapping data in the mapping cache entry for the remote site so 2237 the loc-status-bits are reflective of the new mapping for packets 2238 going to the remote site. The ETR then stops sending SMR 2239 messages. 2241 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2242 To avoid map-cache entry corruption by a third-party, a sender of an 2243 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2244 based Map-Request and the source is not in the locator-set for the 2245 stored map-cache entry, then the responding Map-Request MUST be sent 2246 with an EID destination to the mapping database system. Since the 2247 mapping database system is more secure to reach an authoritative ETR, 2248 it will deliver the Map-Request to the authoritative source of the 2249 mapping data. 2251 When an ITR receives an SMR-based Map-Request for which it does not 2252 have a cached mapping for the EID in the SMR message, it MAY not send 2253 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2254 SMR messages to all locators in the locator-set it has stored in its 2255 map-cache but the remote ITRs that receive the SMR may not be sending 2256 packets to the site. There is no point in updating the ITRs until 2257 they need to send, in which case, they will send Map-Requests to 2258 obtain a map-cache entry. 2260 6.6.3. Database Map Versioning 2262 When there is unidirectional packet flow between an ITR and ETR, and 2263 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2264 ITR so encapsulation can stop to a removed locator and start to a new 2265 locator in the locator-set. 2267 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2268 number. This is known as the Destination Map-Version Number. ITRs 2269 include the Destination Map-Version Number in packets they 2270 encapsulate to the site. When an ETR decapsulates a packet and 2271 detects the Destination Map-Version Number is less than the current 2272 version for its mapping, the SMR procedure described in Section 6.6.2 2273 occurs. 2275 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2276 Version number. This is known as the Source Map-Version Number. 2277 When an ETR decapsulates a packet and detects the Source Map-Version 2278 Number is greater than the last Map-Version Number sent in a Map- 2279 Reply from the ITR's site, the ETR will send a Map-Request to one of 2280 the ETRs for the source site. 2282 A Map-Version Number is used as a sequence number per EID-prefix. So 2283 values that are greater, are considered to be more recent. A value 2284 of 0 for the Source Map-Version Number or the Destination Map-Version 2285 Number conveys no versioning information and an ITR does no 2286 comparison with previously received Map-Version Numbers. 2288 A Map-Version Number can be included in Map-Register messages as 2289 well. This is a good way for the Map-Server can assure that all ETRs 2290 for a site registering to it will be Map-Version number synchronized. 2292 See [VERSIONING] for a more detailed analysis and description of 2293 Database Map Versioning. 2295 7. Router Performance Considerations 2297 LISP is designed to be very hardware-based forwarding friendly. A 2298 few implementation techniques can be used to incrementally implement 2299 LISP: 2301 o When a tunnel encapsulated packet is received by an ETR, the outer 2302 destination address may not be the address of the router. This 2303 makes it challenging for the control plane to get packets from the 2304 hardware. This may be mitigated by creating special FIB entries 2305 for the EID-prefixes of EIDs served by the ETR (those for which 2306 the router provides an RLOC translation). These FIB entries are 2307 marked with a flag indicating that control plane processing should 2308 be performed. The forwarding logic of testing for particular IP 2309 protocol number value is not necessary. There are a few proven 2310 cases where no changes to existing deployed hardware were needed 2311 to support the LISP data-plane. 2313 o On an ITR, prepending a new IP header consists of adding more 2314 bytes to a MAC rewrite string and prepending the string as part of 2315 the outgoing encapsulation procedure. Routers that support GRE 2316 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2317 support this action. 2319 o A packet's source address or interface the packet was received on 2320 can be used to select a VRF (Virtual Routing/Forwarding). The 2321 VRF's routing table can be used to find EID-to-RLOC mappings. 2323 8. Deployment Scenarios 2325 This section will explore how and where ITRs and ETRs can be deployed 2326 and will discuss the pros and cons of each deployment scenario. For 2327 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2329 There are two basic deployment trade-offs to consider: centralized 2330 versus distributed caches and flat, recursive, or re-encapsulating 2331 tunneling. When deciding on centralized versus distributed caching, 2332 the following issues should be considered: 2334 o Are the tunnel routers spread out so that the caches are spread 2335 across all the memories of each router? 2337 o Should management "touch points" be minimized by choosing few 2338 tunnel routers, just enough for redundancy? 2340 o In general, using more ITRs doesn't increase management load, 2341 since caches are built and stored dynamically. On the other hand, 2342 more ETRs does require more management since EID-prefix-to-RLOC 2343 mappings need to be explicitly configured. 2345 When deciding on flat, recursive, or re-encapsulation tunneling, the 2346 following issues should be considered: 2348 o Flat tunneling implements a single tunnel between source site and 2349 destination site. This generally offers better paths between 2350 sources and destinations with a single tunnel path. 2352 o Recursive tunneling is when tunneled traffic is again further 2353 encapsulated in another tunnel, either to implement VPNs or to 2354 perform Traffic Engineering. When doing VPN-based tunneling, the 2355 site has some control since the site is prepending a new tunnel 2356 header. In the case of TE-based tunneling, the site may have 2357 control if it is prepending a new tunnel header, but if the site's 2358 ISP is doing the TE, then the site has no control. Recursive 2359 tunneling generally will result in suboptimal paths but at the 2360 benefit of steering traffic to resource available parts of the 2361 network. 2363 o The technique of re-encapsulation ensures that packets only 2364 require one tunnel header. So if a packet needs to be rerouted, 2365 it is first decapsulated by the ETR and then re-encapsulated with 2366 a new tunnel header using a new RLOC. 2368 The next sub-sections will survey where tunnel routers can reside in 2369 the network. 2371 8.1. First-hop/Last-hop Tunnel Routers 2373 By locating tunnel routers close to hosts, the EID-prefix set is at 2374 the granularity of an IP subnet. So at the expense of more EID- 2375 prefix-to-RLOC sets for the site, the caches in each tunnel router 2376 can remain relatively small. But caches always depend on the number 2377 of non-aggregated EID destination flows active through these tunnel 2378 routers. 2380 With more tunnel routers doing encapsulation, the increase in control 2381 traffic grows as well: since the EID-granularity is greater, more 2382 Map-Requests and Map-Replies are traveling between more routers. 2384 The advantage of placing the caches and databases at these stub 2385 routers is that the products deployed in this part of the network 2386 have better price-memory ratios then their core router counterparts. 2387 Memory is typically less expensive in these devices and fewer routes 2388 are stored (only IGP routes). These devices tend to have excess 2389 capacity, both for forwarding and routing state. 2391 LISP functionality can also be deployed in edge switches. These 2392 devices generally have layer-2 ports facing hosts and layer-3 ports 2393 facing the Internet. Spare capacity is also often available in these 2394 devices as well. 2396 8.2. Border/Edge Tunnel Routers 2398 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2399 space associated with a site to be reachable via a small set of RLOCs 2400 assigned to the CE routers for that site. This is the default 2401 behavior envisioned in the rest of this specification. 2403 This offers the opposite benefit of the first-hop/last-hop tunnel 2404 router scenario: the number of mapping entries and network management 2405 touch points are reduced, allowing better scaling. 2407 One disadvantage is that less of the network's resources are used to 2408 reach host endpoints thereby centralizing the point-of-failure domain 2409 and creating network choke points at the CE router. 2411 Note that more than one CE router at a site can be configured with 2412 the same IP address. In this case an RLOC is an anycast address. 2413 This allows resilience between the CE routers. That is, if a CE 2414 router fails, traffic is automatically routed to the other routers 2415 using the same anycast address. However, this comes with the 2416 disadvantage where the site cannot control the entrance point when 2417 the anycast route is advertised out from all border routers. Another 2418 disadvantage of using anycast locators is the limited advertisement 2419 scope of /32 (or /128 for IPv6) routes. 2421 8.3. ISP Provider-Edge (PE) Tunnel Routers 2423 Use of ISP PE routers as tunnel endpoint routers is not the typical 2424 deployment scenario envisioned in the specification. This section 2425 attempts to capture some of reasoning behind this preference of 2426 implementing LISP on CE routers. 2428 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2429 than a site, control over the location of the egress tunnel 2430 endpoints. That is, the ISP can decide if the tunnel endpoints are 2431 in the destination site (in either CE routers or last-hop routers 2432 within a site) or at other PE edges. The advantage of this case is 2433 that two tunnel headers can be avoided. By having the PE be the 2434 first router on the path to encapsulate, it can choose a TE path 2435 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2436 the destination end site. 2438 An obvious disadvantage is that the end site has no control over 2439 where its packets flow or the RLOCs used. Other disadvantages 2440 include the difficulty in synchronizing path liveness updates between 2441 CE and PE routers. 2443 As mentioned in earlier sections a combination of these scenarios is 2444 possible at the expense of extra packet header overhead, if both site 2445 and provider want control, then recursive or re-encapsulating tunnels 2446 are used. 2448 8.4. LISP Functionality with Conventional NATs 2450 LISP routers can be deployed behind Network Address Translator (NAT) 2451 devices to provide the same set of packet services hosts have today 2452 when they are addressed out of private address space. 2454 It is important to note that a locator address in any LISP control 2455 message MUST be a globally routable address and therefore SHOULD NOT 2456 contain [RFC1918] addresses. If a LISP router is configured with 2457 private addresses, they MUST be used only in the outer IP header so 2458 the NAT device can translate properly. Otherwise, EID addresses MUST 2459 be translated before encapsulation is performed. Both NAT 2460 translation and LISP encapsulation functions could be co-located in 2461 the same device. 2463 More details on LISP address translation can be found in [INTERWORK]. 2465 8.5. Packets Egressing a LISP Site 2467 When a LISP site is using two ITRs for redundancy, the failure of one 2468 ITR will likely shift outbound traffic to the second. This second 2469 ITR's cache may not not be populated with the same EID-to-RLOC 2470 mapping entries as the first. If this second ITR does not have these 2471 mappings, traffic will be dropped while the mappings are retrieved 2472 from the mapping system. The retrieval of these messages may 2473 increase the load of requests being sent into the mapping system. 2474 While this is not anticipated this will be a problem, the deployment 2475 and experimentation will determine if there is an issue requiring 2476 more attention. 2478 9. Traceroute Considerations 2480 When a source host in a LISP site initiates a traceroute to a 2481 destination host in another LISP site, it is highly desirable for it 2482 to see the entire path. Since packets are encapsulated from ITR to 2483 ETR, the hop across the tunnel could be viewed as a single hop. 2484 However, LISP traceroute will provide the entire path so the user can 2485 see 3 distinct segments of the path from a source LISP host to a 2486 destination LISP host: 2488 Segment 1 (in source LISP site based on EIDs): 2490 source-host ---> first-hop ... next-hop ---> ITR 2492 Segment 2 (in the core network based on RLOCs): 2494 ITR ---> next-hop ... next-hop ---> ETR 2496 Segment 3 (in the destination LISP site based on EIDs): 2498 ETR ---> next-hop ... last-hop ---> destination-host 2500 For segment 1 of the path, ICMP Time Exceeded messages are returned 2501 in the normal matter as they are today. The ITR performs a TTL 2502 decrement and test for 0 before encapsulating. So the ITR hop is 2503 seen by the traceroute source has an EID address (the address of 2504 site-facing interface). 2506 For segment 2 of the path, ICMP Time Exceeded messages are returned 2507 to the ITR because the TTL decrement to 0 is done on the outer 2508 header, so the destination of the ICMP messages are to the ITR RLOC 2509 address, the source RLOC address of the encapsulated traceroute 2510 packet. The ITR looks inside of the ICMP payload to inspect the 2511 traceroute source so it can return the ICMP message to the address of 2512 the traceroute client as well as retaining the core router IP address 2513 in the ICMP message. This is so the traceroute client can display 2514 the core router address (the RLOC address) in the traceroute output. 2515 The ETR returns its RLOC address and responds to the TTL decrement to 2516 0 like the previous core routers did. 2518 For segment 3, the next-hop router downstream from the ETR will be 2519 decrementing the TTL for the packet that was encapsulated, sent into 2520 the core, decapsulated by the ETR, and forwarded because it isn't the 2521 final destination. If the TTL is decremented to 0, any router on the 2522 path to the destination of the traceroute, including the next-hop 2523 router or destination, will send an ICMP Time Exceeded message to the 2524 source EID of the traceroute client. The ICMP message will be 2525 encapsulated by the local ITR and sent back to the ETR in the 2526 originated traceroute source site, where the packet will be delivered 2527 to the host. 2529 9.1. IPv6 Traceroute 2531 IPv6 traceroute follows the procedure described above since the 2532 entire traceroute data packet is included in ICMP Time Exceeded 2533 message payload. Therefore, only the ITR needs to pay special 2534 attention for forwarding ICMP messages back to the traceroute source. 2536 9.2. IPv4 Traceroute 2538 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2539 ICMP Time Exceeded messages only include the invoking IP header and 8 2540 bytes that follow the IP header. Therefore, when a core router sends 2541 an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP 2542 payload is the encapsulated header it prepended followed by a UDP 2543 header. The original invoking IP header, and therefore the identity 2544 of the traceroute source is lost. 2546 The solution we propose to solve this problem is to cache traceroute 2547 IPv4 headers in the ITR and to match them up with corresponding IPv4 2548 Time Exceeded messages received from core routers and the ETR. The 2549 ITR will use a circular buffer for caching the IPv4 and UDP headers 2550 of traceroute packets. It will select a 16-bit number as a key to 2551 find them later when the IPv4 Time Exceeded messages are received. 2552 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2553 16-bit number as the UDP source port in the encapsulating header. 2554 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2555 header of the encapsulating header is present in the ICMP payload 2556 thereby allowing the ITR to find the cached headers for the 2557 traceroute source. The ITR puts the cached headers in the payload 2558 and sends the ICMP Time Exceeded message to the traceroute source 2559 retaining the source address of the original ICMP Time Exceeded 2560 message (a core router or the ETR of the site of the traceroute 2561 destination). 2563 The signature of a traceroute packet comes in two forms. The first 2564 form is encoded as a UDP message where the destination port is 2565 inspected for a range of values. The second form is encoded as an 2566 ICMP message where the IP identification field is inspected for a 2567 well-known value. 2569 9.3. Traceroute using Mixed Locators 2571 When either an IPv4 traceroute or IPv6 traceroute is originated and 2572 the ITR encapsulates it in the other address family header, you 2573 cannot get all 3 segments of the traceroute. Segment 2 of the 2574 traceroute can not be conveyed to the traceroute source since it is 2575 expecting addresses from intermediate hops in the same address format 2576 for the type of traceroute it originated. Therefore, in this case, 2577 segment 2 will make the tunnel look like one hop. All the ITR has to 2578 do to make this work is to not copy the inner TTL to the outer, 2579 encapsulating header's TTL when a traceroute packet is encapsulated 2580 using an RLOC from a different address family. This will cause no 2581 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2583 10. Mobility Considerations 2585 There are several kinds of mobility of which only some might be of 2586 concern to LISP. Essentially they are as follows. 2588 10.1. Site Mobility 2590 A site wishes to change its attachment points to the Internet, and 2591 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2592 providers. Changes in EID-RLOC mappings for sites are expected to be 2593 handled by configuration, outside of the LISP protocol. 2595 10.2. Slow Endpoint Mobility 2597 An individual endpoint wishes to move, but is not concerned about 2598 maintaining session continuity. Renumbering is involved. LISP can 2599 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2600 decoupling the address space used by a site from the address spaces 2601 used by its ISPs. [RFC4984] 2603 10.3. Fast Endpoint Mobility 2605 Fast endpoint mobility occurs when an endpoint moves relatively 2606 rapidly, changing its IP layer network attachment point. Maintenance 2607 of session continuity is a goal. This is where the Mobile IPv4 2608 [RFC3344bis] and Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used, 2609 and primarily where interactions with LISP need to be explored. 2611 The problem is that as an endpoint moves, it may require changes to 2612 the mapping between its EID and a set of RLOCs for its new network 2613 location. When this is added to the overhead of mobile IP binding 2614 updates, some packets might be delayed or dropped. 2616 In IPv4 mobility, when an endpoint is away from home, packets to it 2617 are encapsulated and forwarded via a home agent which resides in the 2618 home area the endpoint's address belongs to. The home agent will 2619 encapsulate and forward packets either directly to the endpoint or to 2620 a foreign agent which resides where the endpoint has moved to. 2621 Packets from the endpoint may be sent directly to the correspondent 2622 node, may be sent via the foreign agent, or may be reverse-tunneled 2623 back to the home agent for delivery to the mobile node. As the 2624 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2625 mappings are required for communication between the mobile node and 2626 the home agent, whether via foreign agent or not. As a mobile 2627 endpoint changes networks, up to three LISP mapping changes may be 2628 required: 2630 o The mobile node moves from an old location to a new visited 2631 network location and notifies its home agent that it has done so. 2632 The Mobile IPv4 control packets the mobile node sends pass through 2633 one of the new visited network's ITRs, which needs a EID-RLOC 2634 mapping for the home agent. 2636 o The home agent might not have the EID-RLOC mappings for the mobile 2637 node's "care-of" address or its foreign agent in the new visited 2638 network, in which case it will need to acquire them. 2640 o When packets are sent directly to the correspondent node, it may 2641 be that no traffic has been sent from the new visited network to 2642 the correspondent node's network, and the new visited network's 2643 ITR will need to obtain an EID-RLOC mapping for the correspondent 2644 node's site. 2646 In addition, if the IPv4 endpoint is sending packets from the new 2647 visited network using its original EID, then LISP will need to 2648 perform a route-returnability check on the new EID-RLOC mapping for 2649 that EID. 2651 In IPv6 mobility, packets can flow directly between the mobile node 2652 and the correspondent node in either direction. The mobile node uses 2653 its "care-of" address (EID). In this case, the route-returnability 2654 check would not be needed but one more LISP mapping lookup may be 2655 required instead: 2657 o As above, three mapping changes may be needed for the mobile node 2658 to communicate with its home agent and to send packets to the 2659 correspondent node. 2661 o In addition, another mapping will be needed in the correspondent 2662 node's ITR, in order for the correspondent node to send packets to 2663 the mobile node's "care-of" address (EID) at the new network 2664 location. 2666 When both endpoints are mobile the number of potential mapping 2667 lookups increases accordingly. 2669 As a mobile node moves there are not only mobility state changes in 2670 the mobile node, correspondent node, and home agent, but also state 2671 changes in the ITRs and ETRs for at least some EID-prefixes. 2673 The goal is to support rapid adaptation, with little delay or packet 2674 loss for the entire system. Also IP mobility can be modified to 2675 require fewer mapping changes. In order to increase overall system 2676 performance, there may be a need to reduce the optimization of one 2677 area in order to place fewer demands on another. 2679 In LISP, one possibility is to "glean" information. When a packet 2680 arrives, the ETR could examine the EID-RLOC mapping and use that 2681 mapping for all outgoing traffic to that EID. It can do this after 2682 performing a route-returnability check, to ensure that the new 2683 network location does have a internal route to that endpoint. 2684 However, this does not cover the case where an ITR (the node assigned 2685 the RLOC) at the mobile-node location has been compromised. 2687 Mobile IP packet exchange is designed for an environment in which all 2688 routing information is disseminated before packets can be forwarded. 2689 In order to allow the Internet to grow to support expected future 2690 use, we are moving to an environment where some information may have 2691 to be obtained after packets are in flight. Modifications to IP 2692 mobility should be considered in order to optimize the behavior of 2693 the overall system. Anything which decreases the number of new EID- 2694 RLOC mappings needed when a node moves, or maintains the validity of 2695 an EID-RLOC mapping for a longer time, is useful. 2697 10.4. Fast Network Mobility 2699 In addition to endpoints, a network can be mobile, possibly changing 2700 xTRs. A "network" can be as small as a single router and as large as 2701 a whole site. This is different from site mobility in that it is 2702 fast and possibly short-lived, but different from endpoint mobility 2703 in that a whole prefix is changing RLOCs. However, the mechanisms 2704 are the same and there is no new overhead in LISP. A map request for 2705 any endpoint will return a binding for the entire mobile prefix. 2707 If mobile networks become a more common occurrence, it may be useful 2708 to revisit the design of the mapping service and allow for dynamic 2709 updates of the database. 2711 The issue of interactions between mobility and LISP needs to be 2712 explored further. Specific improvements to the entire system will 2713 depend on the details of mapping mechanisms. Mapping mechanisms 2714 should be evaluated on how well they support session continuity for 2715 mobile nodes. 2717 10.5. LISP Mobile Node Mobility 2719 A mobile device can use the LISP infrastructure to achieve mobility 2720 by implementing the LISP encapsulation and decapsulation functions 2721 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2722 node" can use topologically-independent EID IP addresses that are not 2723 advertised into and do not impose a cost on the global routing 2724 system. These EIDs are maintained at the edges of the mapping system 2725 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2726 only the correspondents of the LISP mobile node. 2728 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2729 more details. 2731 11. Multicast Considerations 2733 A multicast group address, as defined in the original Internet 2734 architecture is an identifier of a grouping of topologically 2735 independent receiver host locations. The address encoding itself 2736 does not determine the location of the receiver(s). The multicast 2737 routing protocol, and the network-based state the protocol creates, 2738 determines where the receivers are located. 2740 In the context of LISP, a multicast group address is both an EID and 2741 a Routing Locator. Therefore, no specific semantic or action needs 2742 to be taken for a destination address, as it would appear in an IP 2743 header. Therefore, a group address that appears in an inner IP 2744 header built by a source host will be used as the destination EID. 2745 The outer IP header (the destination Routing Locator address), 2746 prepended by a LISP router, will use the same group address as the 2747 destination Routing Locator. 2749 Having said that, only the source EID and source Routing Locator 2750 needs to be dealt with. Therefore, an ITR merely needs to put its 2751 own IP address in the source Routing Locator field when prepending 2752 the outer IP header. This source Routing Locator address, like any 2753 other Routing Locator address MUST be globally routable. 2755 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2756 ITR when a received data packet is a multicast data packet or when 2757 processing a source-specific Join (either by IGMPv3 or PIM). But the 2758 source Routing Locator is decided by the multicast routing protocol 2759 in a receiver site. That is, an EID to Routing Locator translation 2760 is done at control-time. 2762 Another approach is to have the ITR not encapsulate a multicast 2763 packet and allow the host built packet to flow into the core even if 2764 the source address is allocated out of the EID namespace. If the 2765 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2766 routers can RPF to the ITR (the Locator address which is injected 2767 into core routing) rather than the host source address (the EID 2768 address which is not injected into core routing). 2770 To avoid any EID-based multicast state in the network core, the first 2771 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2772 and Interworking with non-LISP sites is described in specification 2773 [MLISP]. 2775 12. Security Considerations 2777 It is believed that most of the security mechanisms will be part of 2778 the mapping database service when using control plane procedures for 2779 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2780 as described in this specification, protection is provided against 2781 ETR spoofing by using Return- Routability mechanisms evidenced by the 2782 use of a 24-bit Nonce field in the LISP encapsulation header and a 2783 64-bit Nonce field in the LISP control message. The nonce, coupled 2784 with the ITR accepting only solicited Map-Replies goes a long way 2785 toward providing decent authentication. 2787 LISP does not rely on a PKI infrastructure or a more heavy weight 2788 authentication system. These systems challenge the scalability of 2789 LISP which was a primary design goal. 2791 DoS attack prevention will depend on implementations rate-limiting 2792 Map-Requests and Map-Replies to the control plane as well as rate- 2793 limiting the number of data-triggered Map-Replies. 2795 An incorrectly implemented or malicious ITR might choose to ignore 2796 the priority and weights provided by the ETR in its Map-Reply. This 2797 traffic steering would be limited to the traffic that is sent by this 2798 ITR's site, and no more severe than if the site initiated a bandwidth 2799 DoS attack on (one of) the ETR's ingress links. The ITR's site would 2800 typically gain no benefit from not respecting the weights, and would 2801 likely to receive better service by abiding by them. 2803 To deal with map-cache exhaustion attempts in an ITR/PTR, the 2804 implementation should consider putting a maximum cap on the number of 2805 entries stored with a reserve list for special or frequently accessed 2806 sites. This should be a configuration policy control set by the 2807 network administrator who manages ITRs and PTRs. 2809 Given that the ITR/PTR maintains a cache of EID-to-RLOC mappings, 2810 cache sizing and maintenance is an issue to be kept in mind during 2811 implementation. It is a good idea to have instrumentation in place 2812 to detect thrashing of the cache. Implementation experimentation 2813 will be used to determine which cache management strategies work 2814 best. It should be noted that an undersized cache in an ITR/PTR not 2815 only causes adverse affect on the site or region they support, but 2816 may also cause increased Map-Request load on the mapping system. 2818 There is a potential security risk implicit in the fact that ETRs 2819 generate the EID prefix to which they are responding. In theory, an 2820 ETR can claim a shorter prefix than it is actually responsible for. 2821 Various mechanisms to ameliorate or resolve this issue will be 2822 examined in the future, [LISP-SEC]. 2824 Spoofing of inner header addresses of LISP encapsulated packets is 2825 possible like with any tunneling mechanism. ITRs MUST verify the 2826 source address of a packet to be an EID that belongs to the site's 2827 EID-prefix range prior to encapsulation. ETRs MUST NOT decapsulate 2828 and forward packets into their site where the inner header 2829 destination EID does not belong to the ETR's EID-prefix range for the 2830 site. If a LISP encapsulated packet arrives at an ETR, it MAY 2831 compare the inner header source EID address and the outer header 2832 source RLOC address with the mapping that exists in the mapping 2833 database. Then when spoofing attacks occur, the outer header source 2834 RLOC address can be used to trace back the attack to the source site, 2835 using existing operational tools. 2837 12.1. IETF Security Area Statement 2839 This document represents the thinking of the LISP working group. The 2840 Security Area of the IETF believes there is an open security issue 2841 how LISP interacts with BCP 107's guidance on automated key 2842 management. This and other issues would need to be resolved before 2843 standardization of LISP. Accounting for these concerns may change 2844 the underlying design of LISP. It is important that deferring these 2845 discussions in order to publish an experimental protocol sooner not 2846 restrict a standardized solution that balances concerns of all areas 2847 of the IETF. 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 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 2897 August 1980. 2899 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 2900 STD 13, RFC 1034, November 1987. 2902 [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700, 2903 October 1994. 2905 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 2906 E. Lear, "Address Allocation for Private Internets", 2907 BCP 5, RFC 1918, February 1996. 2909 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2910 Requirement Levels", BCP 14, RFC 2119, March 1997. 2912 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 2913 ESP and AH", RFC 2404, November 1998. 2915 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 2916 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 2917 March 2000. 2919 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 2920 via IPv4 Clouds", RFC 3056, February 2001. 2922 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 2923 of Explicit Congestion Notification (ECN) to IP", 2924 RFC 3168, September 2001. 2926 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 2927 A., Peterson, J., Sparks, R., Handley, M., and E. 2928 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 2929 June 2002. 2931 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 2932 in IPv6", RFC 3775, June 2004. 2934 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 2935 Requirements for Security", BCP 106, RFC 4086, June 2005. 2937 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 2938 (CIDR): The Internet Address Assignment and Aggregation 2939 Plan", BCP 122, RFC 4632, August 2006. 2941 [RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 2942 (SHA and HMAC-SHA)", RFC 4634, July 2006. 2944 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 2945 Optimization for Mobile IPv6", RFC 4866, May 2007. 2947 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 2948 Workshop on Routing and Addressing", RFC 4984, 2949 September 2007. 2951 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2952 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2953 May 2008. 2955 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 2956 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 2958 [UDP-TUNNELS] 2959 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 2960 Packets"", draft-eubanks-chimento-6man-01.txt (work in 2961 progress), October 2010. 2963 15.2. Informative References 2965 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 2966 NUMBERS http://www.iana.org/.../address-family-numbers, 2967 Febuary 2007. 2969 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 2970 Alternative Topology (LISP-ALT)", 2971 draft-ietf-lisp-alt-06.txt (work in progress), March 2011. 2973 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 2974 Enhancement to the Internet Architecture", Internet- 2975 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt, 2976 1999. 2978 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 2979 Content distribution Overlay Network Service for LISP", 2980 draft-meyer-lisp-cons-03.txt (work in progress), 2981 November 2007. 2983 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 2984 Mappings Multicast Across Cooperating Systems for LISP", 2985 draft-curran-lisp-emacs-00.txt (work in progress), 2986 November 2007. 2988 [INTERWORK] 2989 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 2990 "Interworking LISP with IPv4 and IPv6", 2991 draft-ietf-lisp-interworking-02.txt (work in progress), 2992 March 2011. 2994 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 2995 Address Format", draft-farinacci-lisp-lcaf-04.txt (work in 2996 progress), October 2010. 2998 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 2999 "Renumbering: Threat or Menace?", Usenix , September 1996. 3001 [LISP-DEPLOY] 3002 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 3003 "LISP Network Element Deployment Considerations", 3004 draft-jakab-lisp-deployment-02.txt (work in progress), 3005 February 2011. 3007 [LISP-LIG] 3008 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 3009 draft-ietf-lisp-lig-01.txt (work in progress), 3010 October 2010. 3012 [LISP-MAIN] 3013 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 3014 "Locator/ID Separation Protocol (LISP)", 3015 draft-farinacci-lisp-12.txt (work in progress), 3016 March 2009. 3018 [LISP-MIB] 3019 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 3020 draft-ietf-lisp-mib-01.txt (work in progress), March 2011. 3022 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 3023 Mobility Architecture", draft-meyer-lisp-mn-04.txt (work 3024 in progress), October 2010. 3026 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 3027 draft-ietf-lisp-ms-07.txt (work in progress), March 2011. 3029 [LISP-SEC] 3030 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 3031 Bonaventure, "LISP-Security (LISP-SEC)", 3032 draft-maino-lisp-sec-00.txt (work in progress), 3033 February 2011. 3035 [LOC-ID-ARCH] 3036 Meyer, D. and D. Lewis, "Architectural Implications of 3037 Locator/ID Separation", 3038 draft-meyer-loc-id-implications-01.txt (work in progress), 3039 Januaryr 2009. 3041 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 3042 "LISP for Multicast Environments", 3043 draft-ietf-lisp-multicast-05.txt (work in progress), 3044 April 2011. 3046 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 3047 draft-lear-lisp-nerd-08.txt (work in progress), 3048 March 2010. 3050 [OPENLISP] 3051 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 3052 Report", draft-iannone-openlisp-implementation-01.txt 3053 (work in progress), July 2008. 3055 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 3056 draft-narten-radir-problem-statement-00.txt (work in 3057 progress), July 2007. 3059 [RFC3344bis] 3060 Perkins, C., "IP Mobility Support for IPv4, revised", 3061 draft-ietf-mip4-rfc3344bis-05 (work in progress), 3062 July 2007. 3064 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 3065 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 3066 September 2005. 3068 [RPMD] Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol 3069 for Routing Protocol Meta-data Dissemination", 3070 draft-handley-p2ppush-unpublished-2007726.txt (work in 3071 progress), July 2007. 3073 [VERSIONING] 3074 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3075 Versioning", draft-ietf-lisp-map-versioning-01.txt (work 3076 in progress), March 2011. 3078 Appendix A. Acknowledgments 3080 An initial thank you goes to Dave Oran for planting the seeds for the 3081 initial ideas for LISP. His consultation continues to provide value 3082 to the LISP authors. 3084 A special and appreciative thank you goes to Noel Chiappa for 3085 providing architectural impetus over the past decades on separation 3086 of location and identity, as well as detailed review of the LISP 3087 architecture and documents, coupled with enthusiasm for making LISP a 3088 practical and incremental transition for the Internet. 3090 The authors would like to gratefully acknowledge many people who have 3091 contributed discussion and ideas to the making of this proposal. 3092 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3093 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3094 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3095 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3096 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3097 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3098 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3099 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3100 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3101 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3102 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3103 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3104 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3105 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3106 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3107 Clarence Filsfils, and Alia Atlas. 3109 This work originated in the Routing Research Group (RRG) of the IRTF. 3110 The individual submission [LISP-MAIN] was converted into this IETF 3111 LISP working group draft. 3113 Appendix B. Document Change Log 3115 B.1. Changes to draft-ietf-lisp-12.txt 3117 o Posted April 2011. 3119 o Tracker item 87. Provided rewording how an EID-prefix can be 3120 resued in the definition section of "EID-prefix". 3122 o Tracker item 95. Change "eliminate" to "defer" in section 4.1. 3124 o Tracker item 110. Added that the Mapping Protocol Data field in 3125 the Map-Reply message is only used when needed by the particular 3126 Mapping Database System. 3128 o Tracker item 111. Indicate that if an LSB that is assocaited with 3129 an anycast address, that there is at least one RLOC that is up. 3131 o Tracker item 108. Make clear the R-bit does not define RLOC path 3132 reachability. 3134 o Tracker item 107. Indicate that weights are relative to each 3135 other versus requiring an addition of up to 100%. 3137 o Tracker item 46. Add a sentence how LISP products should be sized 3138 for the appropriate demand so cache thrashing is avoided. 3140 o Change some references of RFC 5226 to [AFI] per Luigi. 3142 o Per Luigi, make reference to "EID-AFI" consistent to "EID-prefix- 3143 AFI". 3145 o Tracker item 66. Indicate that appending locators to a locator- 3146 set is done when the added locators are lexiographically greater 3147 than the previous ones in the set. 3149 o Tracker item 87. Once again reword the definition of the EID- 3150 prefix to reflect recent comments. 3152 o Tracker item 70. Added text to security section on what the 3153 implications could be if an ITR does not obey priority and weights 3154 from a Map-Reply message. 3156 o Tracker item 54. Added text to the new section titled "Packets 3157 Egressing a LISP Site" to describe the implications when two or 3158 more ITRs exist at a site where only one ITR is used for egress 3159 traffic and when there is a shift of traffic to the others, how 3160 the map-cache will need to be populated in those new egress ITRs. 3162 o Tracker item 33. Make more clear in the Routing Locator Selection 3163 section what an ITR should do when it sees an R-bit of 0 in a 3164 locator-record of a Map-Reply. 3166 o Tracker item 33. Add paragraph to the EID Reachability section 3167 indicating that site parittioning is under investigation. 3169 o Tracker item 58. Added last paragraph of Security Considerations 3170 section about how to protect inner header EID address spoofing 3171 attacks. 3173 o Add suggested Sam text to indicate that all security concerns need 3174 not be addressed for moving document to Experimental RFC status. 3175 Put this in a subsection of the Secuirty Considerations section. 3177 B.2. Changes to draft-ietf-lisp-11.txt 3179 o Posted March 30, 2011. 3181 o Change IANA URL. The URL we had pointed to a general protocol 3182 numbers page. 3184 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3185 Requests to be sent to a MN ETR via the map-server. 3187 o Generalize text for the defintion of Reencapsuatling tunnels. 3189 o Add pargraph suggested by Joel to explain how implementation 3190 experimentation will be used to determine the proper cache 3191 management techniques. 3193 o Add Yakov provided text for the definition of "EID-to-RLOC 3194 "Database". 3196 o Add reference in Section 8, Deployment Scenarios, to the 3197 draft-jakab-lisp-deploy-02.txt draft. 3199 o Clarify sentence about no hardware changes needed to support LISP 3200 encapsulation. 3202 o Add paragraph about what is the procedure when a locator is 3203 inserted in the middle of a locator-set. 3205 o Add a definition for Locator-Status-Bits so we can emphasize they 3206 are used as a hint for router up/down status and not path 3207 reachability. 3209 o Change "BGP RIB" to "RIB" per Clarence's comment. 3211 o Fixed complaints by IDnits. 3213 o Add subsection to Security Considerations section indicating how 3214 EID-prefix overclaiming in Map-Replies is for further study and 3215 add a reference to LISP-SEC. 3217 B.3. Changes to draft-ietf-lisp-10.txt 3219 o Posted March 2011. 3221 o Add p-bit to Map-Request so there is documentary reasons to know 3222 when a PITR has sent a Map-Request to an ETR. 3224 o Add Map-Notify message which is used to acknowledge a Map-Register 3225 message sent to a Map-Server. 3227 o Add M-bit to the Map-Register message so an ETR that wants an 3228 acknowledgment for the Map-Register can request one. 3230 o Add S-bit to the ECM and Map-Reply messages to describe security 3231 data that can be present in each message. Then refer to 3232 [LISP-SEC] for expansive details. 3234 o Add Network Management Considerations section and point to the MIB 3235 and LIG drafts. 3237 o Remove the word "simple" per Yakov's comments. 3239 B.4. Changes to draft-ietf-lisp-09.txt 3241 o Posted October 2010. 3243 o Add to IANA Consideration section about the use of LCAF Type 3244 values that accepted and maintained by the IANA registry and not 3245 the LCAF specification. 3247 o Indicate that implementations should be able to receive LISP 3248 control messages when either UDP port is 4342, so they can be 3249 robust in the face of intervening NAT boxes. 3251 o Add paragraph to SMR section to indicate that an ITR does not need 3252 to respond to an SMR-based Map-Request when it has no map-cache 3253 entry for the SMR source's EID-prefix. 3255 B.5. Changes to draft-ietf-lisp-08.txt 3257 o Posted August 2010. 3259 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3260 Register messages. 3262 o Clarify language in section 6.1.5 about Map-Replying to Data- 3263 Probes or Map-Requests. 3265 o Indicate that outer TTL should only be copied to inner TTL when it 3266 is less than inner TTL. 3268 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3269 value of 0. 3271 o Indicate that SMRs can have a global or per SMR destination rate- 3272 limiter. 3274 o Add clarifications to the SMR procedures. 3276 o Add definitions for "client-side" and 'server-side" terms used in 3277 this specification. 3279 o Clear up language in section 6.4, last paragraph. 3281 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3282 probe a PETR and have it return a Map-Reply with a locator-set of 3283 size 0. The way it is spec'ed the map-cache entry has action 3284 "dropped". Drop-action is set to 3. 3286 o Add statement about normalizing locator weights. 3288 o Clarify R-bit definition in the Map-Reply locator record. 3290 o Add section on EID Reachability within a LISP site. 3292 o Clarify another disadvantage of using anycast locators. 3294 o Reworded Abstract. 3296 o Change section 2.0 Introduction to remove obsolete information 3297 such as the LISP variant definitions. 3299 o Change section 5 title from "Tunneling Details" to "LISP 3300 Encapsulation Details". 3302 o Changes to section 5 to include results of network deployment 3303 experience with MTU. Recommend that implementations use either 3304 the stateful or stateless handling. 3306 o Make clarification wordsmithing to Section 7 and 8. 3308 o Identify that if there is one locator in the locator-set of a map- 3309 cache entry, that an SMR from that locator should be responded to 3310 by sending the the SMR-invoked Map-Request to the database mapping 3311 system rather than to the RLOC itself (which may be unreachable). 3313 o When describing Unicast and Multicast Weights indicate the the 3314 values are relative weights rather than percentages. So it 3315 doesn't imply the sum of all locator weights in the locator-set 3316 need to be 100. 3318 o Do some wordsmithing on copying TTL and TOS fields. 3320 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3321 combed the spec. 3323 o Removed Section 14 "Prototype Plans and Status". We felt this 3324 type of section is no longer appropriate for a protocol 3325 specification. 3327 o Add clarification text for the IRC description per Damien's 3328 commentary. 3330 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3331 per Vina's comment about a possible DoS vector. 3333 o Clarify (S/2 + H) in the stateless MTU section. 3335 o Add text to reflect Damien's comment about the description of the 3336 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3337 addresses are local addresses of the Map-Requester. 3339 B.6. Changes to draft-ietf-lisp-07.txt 3341 o Posted April 2010. 3343 o Added I-bit to data header so LSB field can also be used as an 3344 Instance ID field. When this occurs, the LSB field is reduced to 3345 8-bits (from 32-bits). 3347 o Added V-bit to the data header so the 24-bit nonce field can also 3348 be used for source and destination version numbers. 3350 o Added Map-Version 12-bit value to the EID-record to be used in all 3351 of Map-Request, Map-Reply, and Map-Register messages. 3353 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3354 can decide what address to select for the destination of a Map- 3355 Reply. 3357 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3358 the Locator-Set record of an EID-record for a Map-Reply message. 3359 The L-bit indicates which RLOCs in the locator-set are local to 3360 the sender of the message. The P-bit indicates which RLOC is the 3361 source of a RLOC-probe Reply (Map-Reply) message. 3363 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3365 o Made editorial and clarification changes based on comments from 3366 Dhirendra Trivedi. 3368 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3370 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3371 6.3.1. 3373 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3374 for Map-Register messages. 3376 o Add NAT section per Ron Bonica comments. 3378 o Fix IDnits issues per Ron Bonica. 3380 o Added section on Virtualization and Segmentation to explain the 3381 use if the Instance ID field in the data header. 3383 o There are too many P-bits, keep their scope to the packet format 3384 description and refer to them by name every where else in the 3385 spec. 3387 o Scanned all occurrences of "should", "should not", "must" and 3388 "must not" and uppercased them. 3390 o John Zwiebel offered text for section 4.1 to modernize the 3391 example. Thanks Z! 3393 o Make it more clear in the definition of "EID-to-RLOC Database" 3394 that all ETRs need to have the same database mapping. This 3395 reflects a comment from John Scudder. 3397 o Add a definition "Route-returnability" to the Definition of Terms 3398 section. 3400 o In section 9.2, add text to describe what the signature of 3401 traceroute packets can look like. 3403 o Removed references to Data Probe for introductory example. Data- 3404 probes are still part of the LISP design but not encouraged. 3406 o Added the definition for "LISP site" to the Definition of Terms" 3407 section. 3409 B.7. Changes to draft-ietf-lisp-06.txt 3411 Editorial based changes: 3413 o Posted December 2009. 3415 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3417 o Add text to indicate that Map-Register messages must contain a 3418 computed UDP checksum. 3420 o Add definitions for PITR and PETR. 3422 o Indicate an AFI value of 0 is an unspecified address. 3424 o Indicate that the TTL field of a Map-Register is not used and set 3425 to 0 by the sender. This change makes this spec consistent with 3426 [LISP-MS]. 3428 o Change "... yield a packet size of L bytes" to "... yield a packet 3429 size greater than L bytes". 3431 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3432 Reply messages. 3434 o Clarify that LSBs that go beyond the number of locators do not to 3435 be SMRed when the locator addresses are greater lexicographically 3436 than the locator in the existing locator-set. 3438 o Add Gregg, Srini, and Amit to acknowledgment section. 3440 o Clarify in the definition of a LISP header what is following the 3441 UDP header. 3443 o Clarify "verifying Map-Request" text in section 6.1.3. 3445 o Add Xu Xiaohu to the acknowledgment section for introducing the 3446 problem of overlapping EID-prefixes among multiple sites in an RRG 3447 email message. 3449 Design based changes: 3451 o Use stronger language to have the outer IPv4 header set DF=1 so we 3452 can avoid fragment reassembly in an ETR or PETR. This will also 3453 make IPv4 and IPv6 encapsulation have consistent behavior. 3455 o Map-Requests should not be sent in ECM with the Probe bit is set. 3456 These type of Map-Requests are used as RLOC-probes and are sent 3457 directly to locator addresses in the underlying network. 3459 o Add text in section 6.1.5 about returning all EID-prefixes in a 3460 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3461 configure. 3463 o Add text in a new subsection of section 6.1.5 about dealing with 3464 Map-Replies with coarse EID-prefixes. 3466 B.8. Changes to draft-ietf-lisp-05.txt 3468 o Posted September 2009. 3470 o Added this Document Change Log appendix. 3472 o Added section indicating that encapsulated Map-Requests must use 3473 destination UDP port 4342. 3475 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3476 data in Map-Register payload. 3478 o Added Jari to acknowledgment section. 3480 o State the source-EID is set to 0 when using Map-Requests to 3481 refresh or RLOC-probe. 3483 o Make more clear what source-RLOC should be for a Map-Request. 3485 o The LISP-CONS authors thought that the Type definitions for CONS 3486 should be removed from this specification. 3488 o Removed nonce from Map-Register message, it wasn't used so no need 3489 for it. 3491 o Clarify what to do for unspecified Action bits for negative Map- 3492 Replies. Since No Action is a drop, make value 0 Drop. 3494 B.9. Changes to draft-ietf-lisp-04.txt 3496 o Posted September 2009. 3498 o How do deal with record count greater than 1 for a Map-Request. 3499 Damien and Joel comment. Joel suggests: 1) Specify that senders 3500 compliant with the current document will always set the count to 3501 1, and note that the count is included for future extensibility. 3502 2) Specify what a receiver compliant with the draft should do if 3503 it receives a request with a count greater than 1. Presumably, it 3504 should send some error back? 3506 o Add Fred Templin in acknowledgment section. 3508 o Add Margaret and Sam to the acknowledgment section for their great 3509 comments. 3511 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3513 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3514 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3515 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3516 ignore the checksum completely. And of course we'd need to 3517 confirm that can actually be implemented. In particular, hardware 3518 that verifies UDP checksums on receive needs to be checked to make 3519 sure it permits 0 checksums." 3521 o Margaret wants a reference to 3522 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3524 o Fix description in Map-Request section. Where we describe Map- 3525 Reply Record, change "R-bit" to "M-bit". 3527 o Add the mobility bit to Map-Replies. So PTRs don't probe so often 3528 for MNs but often enough to get mapping updates. 3530 o Indicate SHA1 can be used as well for Map-Registers. 3532 o More Fred comments on MTU handling. 3534 o Isidor comment about spec'ing better periodic Map-Registers. Will 3535 be fixed in draft-ietf-lisp-ms-02.txt. 3537 o Margaret's comment on gleaning: "The current specification does 3538 not make it clear how long gleaned map entries should be retained 3539 in the cache, nor does it make it clear how/ when they will be 3540 validated. The LISP spec should, at the very least, include a 3541 (short) default lifetime for gleaned entries, require that they be 3542 validated within a short period of time, and state that a new 3543 gleaned entry should never overwrite an entry that was obtained 3544 from the mapping system. The security implications of storing 3545 "gleaned" entries should also be explored in detail." 3547 o Add section on RLOC-probing per working group feedback. 3549 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3550 Noel. 3552 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3553 control plane only. 3555 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3556 fields can be turned off and used for another future purpose. For 3557 Luigi et al versioning convergence. 3559 o Add a N-bit to the data header suggested by Noel. Then the nonce 3560 field could be used when N is not 1. 3562 o Clarify that when E-bit is 0, the nonce field can be an echoed 3563 nonce or a random nonce. Comment from Jesper. 3565 o Indicate when doing data-gleaning that a verifying Map-Request is 3566 sent to the source-EID of the gleaned data packet so we can avoid 3567 map-cache corruption by a 3rd party. Comment from Pedro. 3569 o Indicate that a verifying Map-Request, for accepting mapping data, 3570 should be sent over the ALT (or to the EID). 3572 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3574 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3575 noncing. Comment by Pedro and Dino. 3577 o Jesper made a comment to loosen the language about requiring the 3578 copy of inner TTL to outer TTL since the text to get mixed-AF 3579 traceroute to work would violate the "MUST" clause. Changed from 3580 MUST to SHOULD in section 5.3. 3582 B.10. Changes to draft-ietf-lisp-03.txt 3584 o Posted July 2009. 3586 o Removed loc-reach-bits longword from control packets per Damien 3587 comment. 3589 o Clarifications in MTU text from Roque. 3591 o Added text to indicate that the locator-set be sorted by locator 3592 address from Isidor. 3594 o Clarification text from John Zwiebel in Echo-Nonce section. 3596 B.11. Changes to draft-ietf-lisp-02.txt 3598 o Posted July 2009. 3600 o Encapsulation packet format change to add E-bit and make loc- 3601 reach-bits 32-bits in length. 3603 o Added Echo-Nonce Algorithm section. 3605 o Clarification how ECN bits are copied. 3607 o Moved S-bit in Map-Request. 3609 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3610 RLOC-Probe Algorithm. 3612 o Added to Mobility section to reference [LISP-MN]. 3614 B.12. Changes to draft-ietf-lisp-01.txt 3616 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3618 o Defined LEID to be a "LISP EID". 3620 o Indicate encapsulation use IPv4 DF=0. 3622 o Added negative Map-Reply messages with drop, native-forward, and 3623 send-map-request actions. 3625 o Added Proxy-Map-Reply bit to Map-Register. 3627 B.13. Changes to draft-ietf-lisp-00.txt 3629 o Posted May 2009. 3631 o Rename of draft-farinacci-lisp-12.txt. 3633 o Acknowledgment to RRG. 3635 Authors' Addresses 3637 Dino Farinacci 3638 cisco Systems 3639 Tasman Drive 3640 San Jose, CA 95134 3641 USA 3643 Email: dino@cisco.com 3645 Vince Fuller 3646 cisco Systems 3647 Tasman Drive 3648 San Jose, CA 95134 3649 USA 3651 Email: vaf@cisco.com 3653 Dave Meyer 3654 cisco Systems 3655 170 Tasman Drive 3656 San Jose, CA 3657 USA 3659 Email: dmm@cisco.com 3661 Darrel Lewis 3662 cisco Systems 3663 170 Tasman Drive 3664 San Jose, CA 3665 USA 3667 Email: darlewis@cisco.com