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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: September 30, 2011 D. Lewis 6 cisco Systems 7 March 29, 2011 9 Locator/ID Separation Protocol (LISP) 10 draft-ietf-lisp-11 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 September 30, 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 . . . . . . . . . . . . . . . . . 49 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 . . . . . . . . . . . . . . . 53 100 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 9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 59 107 9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 60 108 9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 60 109 9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 60 110 10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 62 111 10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 62 112 10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 62 113 10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 62 114 10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 64 115 10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 64 116 11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 66 117 12. Security Considerations . . . . . . . . . . . . . . . . . . . 67 118 13. Network Management Considerations . . . . . . . . . . . . . . 68 119 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 69 120 14.1. LISP Address Type Codes . . . . . . . . . . . . . . . . . 69 121 14.2. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 69 122 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 70 123 15.1. Normative References . . . . . . . . . . . . . . . . . . . 70 124 15.2. Informative References . . . . . . . . . . . . . . . . . . 71 125 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 74 126 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 75 127 B.1. Changes to draft-ietf-lisp-11.txt . . . . . . . . . . . . 75 128 B.2. Changes to draft-ietf-lisp-10.txt . . . . . . . . . . . . 75 129 B.3. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 76 130 B.4. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 76 131 B.5. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 78 132 B.6. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 80 133 B.7. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 81 134 B.8. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 81 135 B.9. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 83 136 B.10. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 83 137 B.11. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 84 138 B.12. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 84 139 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 85 141 1. Requirements Notation 143 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 144 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 145 document are to be interpreted as described in [RFC2119]. 147 2. Introduction 149 This document describes the Locator/Identifier Separation Protocol 150 (LISP), which provides a set of functions for routers to exchange 151 information used to map from non-routeable Endpoint Identifiers 152 (EIDs) to routeable Routing Locators (RLOCs). It also defines a 153 mechanism for these LISP routers to encapsulate IP packets addressed 154 with EIDs for transmission across an Internet that uses RLOCs for 155 routing and forwarding. 157 Creation of LISP was initially motivated by discussions during the 158 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 159 October, 2006 (see [RFC4984]). A key conclusion of the workshop was 160 that the Internet routing and addressing system was not scaling well 161 in the face of the explosive growth of new sites; one reason for this 162 poor scaling is the increasing number of multi-homed and other sites 163 that cannot be addressed as part of topologically- or provider-based 164 aggregated prefixes. Additional work that more completely described 165 the problem statement may be found in [RADIR]. 167 A basic observation, made many years ago in early networking research 168 such as that documented in [CHIAPPA] and [RFC4984], is that using a 169 single address field for both identifying a device and for 170 determining where it is topologically located in the network requires 171 optimization along two conflicting axes: for routing to be efficient, 172 the address must be assigned topologically; for collections of 173 devices to be easily and effectively managed, without the need for 174 renumbering in response to topological change (such as that caused by 175 adding or removing attachment points to the network or by mobility 176 events), the address must explicitly not be tied to the topology. 178 The approach that LISP takes to solving the routing scalability 179 problem is to replace IP addresses with two new types of numbers: 180 Routing Locators (RLOCs), which are topologically assigned to network 181 attachment points (and are therefore amenable to aggregation) and 182 used for routing and forwarding of packets through the network; and 183 Endpoint Identifiers (EIDs), which are assigned independently from 184 the network topology, are used for numbering devices, and are 185 aggregated along administrative boundaries. LISP then defines 186 functions for mapping between the two numbering spaces and for 187 encapsulating traffic originated by devices using non-routeable EIDs 188 for transport across a network infrastructure that routes and 189 forwards using RLOCs. Both RLOCs and EIDs are syntactically- 190 identical to IP addresses; it is the semantics of how they are used 191 that differs. 193 This document describes the protocol that implements these functions. 194 The database which stores the mappings between EIDs and RLOCs is 195 explicitly a separate "module" to facilitate experimentation with a 196 variety of approaches. One database design that is being developed 197 and prototyped as part of the LISP working group work is [ALT]. 198 Others that have been described but not implemented include [CONS], 199 [EMACS], [RPMD], [NERD]. Finally, [LISP-MS], documents a general- 200 purpose service interface for accessing a mapping database; this 201 interface is intended to make the mapping database modular so that 202 different approaches can be tried without the need to modify 203 installed xTRs. 205 3. Definition of Terms 207 Provider Independent (PI) Addresses: PI addresses are an address 208 block assigned from a pool where blocks are not associated with 209 any particular location in the network (e.g. from a particular 210 service provider), and is therefore not topologically aggregatable 211 in the routing system. 213 Provider Assigned (PA) Addresses: PA addresses are an a address 214 block assigned to a site by each service provider to which a site 215 connects. Typically, each block is sub-block of a service 216 provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and 217 is aggregated into the larger block before being advertised into 218 the global Internet. Traditionally, IP multihoming has been 219 implemented by each multi-homed site acquiring its own, globally- 220 visible prefix. LISP uses only topologically-assigned and 221 aggregatable address blocks for RLOCs, eliminating this 222 demonstrably non-scalable practice. 224 Routing Locator (RLOC): A RLOC is an IPv4 or IPv6 address of an 225 egress tunnel router (ETR). A RLOC is the output of a EID-to-RLOC 226 mapping lookup. An EID maps to one or more RLOCs. Typically, 227 RLOCs are numbered from topologically-aggregatable blocks that are 228 assigned to a site at each point to which it attaches to the 229 global Internet; where the topology is defined by the connectivity 230 of provider networks, RLOCs can be thought of as PA addresses. 231 Multiple RLOCs can be assigned to the same ETR device or to 232 multiple ETR devices at a site. 234 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 235 IPv6) value used in the source and destination address fields of 236 the first (most inner) LISP header of a packet. The host obtains 237 a destination EID the same way it obtains an destination address 238 today, for example through a Domain Name System (DNS) [RFC1034] 239 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 240 The source EID is obtained via existing mechanisms used to set a 241 host's "local" IP address. An EID is allocated to a host from an 242 EID-prefix block associated with the site where the host is 243 located. An EID can be used by a host to refer to other hosts. 244 EIDs MUST NOT be used as LISP RLOCs. Note that EID blocks may be 245 assigned in a hierarchical manner, independent of the network 246 topology, to facilitate scaling of the mapping database. In 247 addition, an EID block assigned to a site may have site-local 248 structure (subnetting) for routing within the site; this structure 249 is not visible to the global routing system. When used in 250 discussions with other Locator/ID separation proposals, a LISP EID 251 will be called a "LEID". Throughout this document, any references 252 to "EID" refers to an LEID. 254 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are 255 allocated to a site by an address allocation authority. EID- 256 prefixes are associated with a set of RLOC addresses which make up 257 a "database mapping". EID-prefix allocations can be broken up 258 into smaller blocks when an RLOC set is to be associated with the 259 smaller EID-prefix. A globally routed address block (whether PI 260 or PA) is not an EID-prefix. However, a globally routed address 261 block may be removed from global routing and reused as an EID- 262 prefix. A site that receives an explicitly allocated EID-prefix 263 may not use that EID-prefix as a globally routed prefix assigned 264 to RLOCs. 266 End-system: An end-system is an IPv4 or IPv6 device that originates 267 packets with a single IPv4 or IPv6 header. The end-system 268 supplies an EID value for the destination address field of the IP 269 header when communicating globally (i.e. outside of its routing 270 domain). An end-system can be a host computer, a switch or router 271 device, or any network appliance. 273 Ingress Tunnel Router (ITR): An ITR is a router which accepts an IP 274 packet with a single IP header (more precisely, an IP packet that 275 does not contain a LISP header). The router treats this "inner" 276 IP destination address as an EID and performs an EID-to-RLOC 277 mapping lookup. The router then prepends an "outer" IP header 278 with one of its globally-routable RLOCs in the source address 279 field and the result of the mapping lookup in the destination 280 address field. Note that this destination RLOC may be an 281 intermediate, proxy device that has better knowledge of the EID- 282 to-RLOC mapping closer to the destination EID. In general, an ITR 283 receives IP packets from site end-systems on one side and sends 284 LISP-encapsulated IP packets toward the Internet on the other 285 side. 287 Specifically, when a service provider prepends a LISP header for 288 Traffic Engineering purposes, the router that does this is also 289 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 290 on the outer destination address (the originating ITR's supplied 291 RLOC) or the inner destination address (the originating hosts 292 supplied EID). 294 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 295 network that prepends an additional LISP header for Traffic 296 Engineering purposes. 298 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 299 packet where the destination address in the "outer" IP header is 300 one of its own RLOCs. The router strips the "outer" header and 301 forwards the packet based on the next IP header found. In 302 general, an ETR receives LISP-encapsulated IP packets from the 303 Internet on one side and sends decapsulated IP packets to site 304 end-systems on the other side. ETR functionality does not have to 305 be limited to a router device. A server host can be the endpoint 306 of a LISP tunnel as well. 308 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 309 network that strips an outer LISP header for Traffic Engineering 310 purposes. 312 xTR: A xTR is a reference to an ITR or ETR when direction of data 313 flow is not part of the context description. xTR refers to the 314 router that is the tunnel endpoint. Used synonymously with the 315 term "Tunnel Router". For example, "An xTR can be located at the 316 Customer Edge (CE) router", meaning both ITR and ETR functionality 317 is at the CE router. 319 EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- 320 demand table in an ITR that stores, tracks, and is responsible for 321 timing-out and otherwise validating EID-to-RLOC mappings. This 322 cache is distinct from the full "database" of EID-to-RLOC 323 mappings, it is dynamic, local to the ITR(s), and relatively small 324 while the database is distributed, relatively static, and much 325 more global in scope. 327 EID-to-RLOC Database: The EID-to-RLOC database is a global 328 distributed database that contains all known EID-prefix to RLOC 329 mappings. Each potential ETR typically contains a small piece of 330 the database: the EID-to-RLOC mappings for the EID prefixes 331 "behind" the router. These map to one of the router's own, 332 globally-visible, IP addresses. The same database mapping entries 333 MUST be configured on all ETRs for a given site. In a steady 334 state the EID-prefixes for the site and the locator-set for each 335 EID-prefix MUST be the same on all ETRs. Procedures to enforce 336 and/or verify this are outside the scope of this document. Note 337 that there may be transient conditions when the EID-prefix for the 338 site and locator-set for each EID-prefix may not be the same on 339 all ETRs. This has no negative implications. 341 Recursive Tunneling: Recursive tunneling occurs when a packet has 342 more than one LISP IP header. Additional layers of tunneling may 343 be employed to implement traffic engineering or other re-routing 344 as needed. When this is done, an additional "outer" LISP header 345 is added and the original RLOCs are preserved in the "inner" 346 header. Any references to tunnels in this specification refers to 347 dynamic encapsulating tunnels and never are they statically 348 configured. 350 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 351 ETR removes a LISP header, then acts as an ITR to prepend another 352 LISP header. Doing this allows a packet to be re-routed by the 353 re-encapsulating router without adding the overhead of additional 354 tunnel headers. Any references to tunnels in this specification 355 refers to dynamic encapsulating tunnels and never are they 356 statically configured. 358 LISP Header: a term used in this document to refer to the outer 359 IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-byte 360 header that follows the UDP header, an ITR prepends or an ETR 361 strips. 363 Address Family Identifier (AFI): a term used to describe an address 364 encoding in a packet. An address family currently pertains to an 365 IPv4 or IPv6 address. See [AFI] and [RFC1700] for details. An 366 AFI value of 0 used in this specification indicates an unspecified 367 encoded address where the length of the address is 0 bytes 368 following the 16-bit AFI value of 0. 370 Negative Mapping Entry: A negative mapping entry, also known as a 371 negative cache entry, is an EID-to-RLOC entry where an EID-prefix 372 is advertised or stored with no RLOCs. That is, the locator-set 373 for the EID-to-RLOC entry is empty or has an encoded locator count 374 of 0. This type of entry could be used to describe a prefix from 375 a non-LISP site, which is explicitly not in the mapping database. 376 There are a set of well defined actions that are encoded in a 377 Negative Map-Reply. 379 Data Probe: A data-probe is a LISP-encapsulated data packet where 380 the inner header destination address equals the outer header 381 destination address used to trigger a Map-Reply by a decapsulating 382 ETR. In addition, the original packet is decapsulated and 383 delivered to the destination host. A Data Probe is used in some 384 of the mapping database designs to "probe" or request a Map-Reply 385 from an ETR; in other cases, Map-Requests are used. See each 386 mapping database design for details. 388 Proxy ITR (PITR): A PITR is also known as a PTR is defined and 389 described in [INTERWORK], a PITR acts like an ITR but does so on 390 behalf of non-LISP sites which send packets to destinations at 391 LISP sites. 393 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a 394 PETR acts like an ETR but does so on behalf of LISP sites which 395 send packets to destinations at non-LISP sites. 397 Route-returnability: is an assumption that the underlying routing 398 system will deliver packets to the destination. When combined 399 with a nonce that is provided by a sender and returned by a 400 receiver limits off-path data insertion. 402 LISP site: is a set of routers in an edge network that are under a 403 single technical administration. LISP routers which reside in the 404 edge network are the demarcation points to separate the edge 405 network from the core network. 407 Client-side: a term used in this document to indicate a connection 408 initiation attempt by an EID. The ITR(s) at the LISP site are the 409 first to get involved in obtaining database map cache entries by 410 sending Map-Request messages. 412 Server-side: a term used in this document to indicate a connection 413 initiation attempt is being accepted for a destination EID. The 414 ETR(s) at the destination LISP site are the first to send Map- 415 Replies to the source site initiating the connection. The ETR(s) 416 at this destination site can obtain mappings by gleaning 417 information from Map-Requests, Data-Probes, or encapsulated 418 packets. 420 Locator-Status-Bits (LSBs): Locator status bits are present in the 421 LISP header. They are used by ITRs to inform ETRs about the up/ 422 down status of all ITRs at the local site. These bits are used as 423 a hint to convey up/down router status and not path reachability 424 status. The LSBs can be verified by use of one of the Locator 425 Reachability Algoriths described in Section 6.3. 427 4. Basic Overview 429 One key concept of LISP is that end-systems (hosts) operate the same 430 way they do today. The IP addresses that hosts use for tracking 431 sockets, connections, and for sending and receiving packets do not 432 change. In LISP terminology, these IP addresses are called Endpoint 433 Identifiers (EIDs). 435 Routers continue to forward packets based on IP destination 436 addresses. When a packet is LISP encapsulated, these addresses are 437 referred to as Routing Locators (RLOCs). Most routers along a path 438 between two hosts will not change; they continue to perform routing/ 439 forwarding lookups on the destination addresses. For routers between 440 the source host and the ITR as well as routers from the ETR to the 441 destination host, the destination address is an EID. For the routers 442 between the ITR and the ETR, the destination address is an RLOC. 444 Another key LISP concept is the "Tunnel Router". A tunnel router 445 prepends LISP headers on host-originated packets and strip them prior 446 to final delivery to their destination. The IP addresses in this 447 "outer header" are RLOCs. During end-to-end packet exchange between 448 two Internet hosts, an ITR prepends a new LISP header to each packet 449 and an egress tunnel router strips the new header. The ITR performs 450 EID-to-RLOC lookups to determine the routing path to the ETR, which 451 has the RLOC as one of its IP addresses. 453 Some basic rules governing LISP are: 455 o End-systems (hosts) only send to addresses which are EIDs. They 456 don't know addresses are EIDs versus RLOCs but assume packets get 457 to LISP routers, which in turn, deliver packets to the destination 458 the end-system has specified. 460 o EIDs are always IP addresses assigned to hosts. 462 o LISP routers mostly deal with Routing Locator addresses. See 463 details later in Section 4.1 to clarify what is meant by "mostly". 465 o RLOCs are always IP addresses assigned to routers; preferably, 466 topologically-oriented addresses from provider CIDR blocks. 468 o When a router originates packets it may use as a source address 469 either an EID or RLOC. When acting as a host (e.g. when 470 terminating a transport session such as SSH, TELNET, or SNMP), it 471 may use an EID that is explicitly assigned for that purpose. An 472 EID that identifies the router as a host MUST NOT be used as an 473 RLOC; an EID is only routable within the scope of a site. A 474 typical BGP configuration might demonstrate this "hybrid" EID/RLOC 475 usage where a router could use its "host-like" EID to terminate 476 iBGP sessions to other routers in a site while at the same time 477 using RLOCs to terminate eBGP sessions to routers outside the 478 site. 480 o EIDs are not expected to be usable for global end-to-end 481 communication in the absence of an EID-to-RLOC mapping operation. 482 They are expected to be used locally for intra-site communication. 484 o EID prefixes are likely to be hierarchically assigned in a manner 485 which is optimized for administrative convenience and to 486 facilitate scaling of the EID-to-RLOC mapping database. The 487 hierarchy is based on a address allocation hierarchy which is 488 independent of the network topology. 490 o EIDs may also be structured (subnetted) in a manner suitable for 491 local routing within an autonomous system. 493 An additional LISP header may be prepended to packets by a TE-ITR 494 when re-routing of the path for a packet is desired. An obvious 495 instance of this would be an ISP router that needs to perform traffic 496 engineering for packets flowing through its network. In such a 497 situation, termed Recursive Tunneling, an ISP transit acts as an 498 additional ingress tunnel router and the RLOC it uses for the new 499 prepended header would be either a TE-ETR within the ISP (along 500 intra-ISP traffic engineered path) or a TE-ETR within another ISP (an 501 inter-ISP traffic engineered path, where an agreement to build such a 502 path exists). 504 In order to avoid excessive packet overhead as well as possible 505 encapsulation loops, this document mandates that a maximum of two 506 LISP headers can be prepended to a packet. It is believed two 507 headers is sufficient, where the first prepended header is used at a 508 site for Location/Identity separation and second prepended header is 509 used inside a service provider for Traffic Engineering purposes. 511 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 512 For example, the ITR for a particular end-to-end packet exchange 513 might be the first-hop or default router within a site for the source 514 host. Similarly, the egress tunnel router might be the last-hop 515 router directly-connected to the destination host. Another example, 516 perhaps for a VPN service out-sourced to an ISP by a site, the ITR 517 could be the site's border router at the service provider attachment 518 point. Mixing and matching of site-operated, ISP-operated, and other 519 tunnel routers is allowed for maximum flexibility. See Section 8 for 520 more details. 522 4.1. Packet Flow Sequence 524 This section provides an example of the unicast packet flow with the 525 following conditions: 527 o Source host "host1.abc.com" is sending a packet to 528 "host2.xyz.com", exactly what host1 would do if the site was not 529 using LISP. 531 o Each site is multi-homed, so each tunnel router has an address 532 (RLOC) assigned from the service provider address block for each 533 provider to which that particular tunnel router is attached. 535 o The ITR(s) and ETR(s) are directly connected to the source and 536 destination, respectively, but the source and destination can be 537 located anywhere in LISP site. 539 o Map-Requests can be sent on the underlying routing system topology 540 or over an alternative topology [ALT]. 542 o Map-Replies are sent on the underlying routing system topology. 544 Client host1.abc.com wants to communicate with server host2.xyz.com: 546 1. host1.abc.com wants to open a TCP connection to host2.xyz.com. 547 It does a DNS lookup on host2.xyz.com. An A/AAAA record is 548 returned. This address is the destination EID. The locally- 549 assigned address of host1.abc.com is used as the source EID. An 550 IPv4 or IPv6 packet is built and forwarded through the LISP site 551 as a normal IP packet until it reaches a LISP ITR. 553 2. The LISP ITR must be able to map the EID destination to an RLOC 554 of one of the ETRs at the destination site. The specific method 555 used to do this is not described in this example. See [ALT] or 556 [CONS] for possible solutions. 558 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be 559 rate-limited. 561 4. When an alternate mapping system is not in use, the Map-Request 562 packet is routed through the underlying routing system. 563 Otherwise, the Map-Request packet is routed on an alternate 564 logical topology. In either case, when the Map-Request arrives 565 at one of the ETRs at the destination site, it will process the 566 packet as a control message. 568 5. The ETR looks at the destination EID of the Map-Request and 569 matches it against the prefixes in the ETR's configured EID-to- 570 RLOC mapping database. This is the list of EID-prefixes the ETR 571 is supporting for the site it resides in. If there is no match, 572 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 573 returned to the ITR. 575 6. The ITR receives the Map-Reply message, parses the message (to 576 check for format validity) and stores the mapping information 577 from the packet. This information is stored in the ITR's EID-to- 578 RLOC mapping cache. Note that the map cache is an on-demand 579 cache. An ITR will manage its map cache in such a way that 580 optimizes for its resource constraints. 582 7. Subsequent packets from host1.abc.com to host2.xyz.com will have 583 a LISP header prepended by the ITR using the appropriate RLOC as 584 the LISP header destination address learned from the ETR. Note 585 the packet may be sent to a different ETR than the one which 586 returned the Map-Reply due to the source site's hashing policy or 587 the destination site's locator-set policy. 589 8. The ETR receives these packets directly (since the destination 590 address is one of its assigned IP addresses), strips the LISP 591 header and forwards the packets to the attached destination host. 593 In order to eliminate the need for a mapping lookup in the reverse 594 direction, an ETR MAY create a cache entry that maps the source EID 595 (inner header source IP address) to the source RLOC (outer header 596 source IP address) in a received LISP packet. Such a cache entry is 597 termed a "gleaned" mapping and only contains a single RLOC for the 598 EID in question. More complete information about additional RLOCs 599 SHOULD be verified by sending a LISP Map-Request for that EID. Both 600 ITR and the ETR may also influence the decision the other makes in 601 selecting an RLOC. See Section 6 for more details. 603 5. LISP Encapsulation Details 605 Since additional tunnel headers are prepended, the packet becomes 606 larger and can exceed the MTU of any link traversed from the ITR to 607 the ETR. It is recommended in IPv4 that packets do not get 608 fragmented as they are encapsulated by the ITR. Instead, the packet 609 is dropped and an ICMP Too Big message is returned to the source. 611 This specification recommends that implementations support for one of 612 the proposed fragmentation and reassembly schemes. These two 613 existing schemes are detailed in Section 5.4. 615 5.1. LISP IPv4-in-IPv4 Header Format 617 0 1 2 3 618 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 1 619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 620 / |Version| IHL |Type of Service| Total Length | 621 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 | | Identification |Flags| Fragment Offset | 623 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 624 OH | Time to Live | Protocol = 17 | Header Checksum | 625 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 626 | | Source Routing Locator | 627 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 628 \ | Destination Routing Locator | 629 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 630 / | Source Port = xxxx | Dest Port = 4341 | 631 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 632 \ | UDP Length | UDP Checksum | 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 634 L |N|L|E|V|I|flags| Nonce/Map-Version | 635 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 636 S / | Instance ID/Locator Status Bits | 637 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 638 / |Version| IHL |Type of Service| Total Length | 639 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 640 | | Identification |Flags| Fragment Offset | 641 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 IH | Time to Live | Protocol | Header Checksum | 643 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 | | Source EID | 645 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 646 \ | Destination EID | 647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 5.2. LISP IPv6-in-IPv6 Header Format 651 0 1 2 3 652 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 1 653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 654 / |Version| Traffic Class | Flow Label | 655 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 | | Payload Length | Next Header=17| Hop Limit | 658 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 | | 660 O + + 661 u | | 662 t + Source Routing Locator + 663 e | | 664 r + + 665 | | 666 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 667 d | | 668 r + + 669 | | 670 ^ + Destination Routing Locator + 671 | | | 672 \ + + 673 \ | | 674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 675 / | Source Port = xxxx | Dest Port = 4341 | 676 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 677 \ | UDP Length | UDP Checksum | 678 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 679 L |N|L|E|V|I|flags| Nonce/Map-Version | 680 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 681 S / | Instance ID/Locator Status Bits | 682 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 683 / |Version| Traffic Class | Flow Label | 684 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 685 / | Payload Length | Next Header | Hop Limit | 686 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 | | 688 I + + 689 n | | 690 n + Source EID + 691 e | | 692 r + + 693 | | 694 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 695 d | | 696 r + + 697 | | 698 ^ + Destination EID + 699 \ | | 700 \ + + 701 \ | | 702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 704 5.3. Tunnel Header Field Descriptions 706 Inner Header: The inner header is the header on the datagram 707 received from the originating host. The source and destination IP 708 addresses are EIDs. 710 Outer Header: The outer header is a new header prepended by an ITR. 711 The address fields contain RLOCs obtained from the ingress 712 router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" 713 from [RFC0768]. The DF bit of the Flags field is set to 0 when 714 the method in Section 5.4.1 is used and set to 1 when the method 715 in Section 5.4.2 is used. 717 UDP Header: The UDP header contains a ITR selected source port when 718 encapsulating a packet. See Section 6.5 for details on the hash 719 algorithm used to select a source port based on the 5-tuple of the 720 inner header. The destination port MUST be set to the well-known 721 IANA assigned port value 4341. 723 UDP Checksum: The UDP checksum field SHOULD be transmitted as zero 724 by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation 725 [UDP-TUNNELS]. When a packet with a zero UDP checksum is received 726 by an ETR, the ETR MUST accept the packet for decapsulation. When 727 an ITR transmits a non-zero value for the UDP checksum, it MUST 728 send a correctly computed value in this field. When an ETR 729 receives a packet with a non-zero UDP checksum, it MAY choose to 730 verify the checksum value. If it chooses to perform such 731 verification, and the verification fails, the packet MUST be 732 silently dropped. If the ETR chooses not to perform the 733 verification, or performs the verification successfully, the 734 packet MUST be accepted for decapsulation. The handling of UDP 735 checksums for all tunneling protocols, including LISP, is under 736 active discussion within the IETF. When that discussion 737 concludes, any necessary changes will be made to align LISP with 738 the outcome of the broader discussion. 740 UDP Length: The UDP length field is for an IPv4 encapsulated packet, 741 the inner header Total Length plus the UDP and LISP header lengths 742 are used. For an IPv6 encapsulated packet, the inner header 743 Payload Length plus the size of the IPv6 header (40 bytes) plus 744 the size of the UDP and LISP headers are used. The UDP header 745 length is 8 bytes. 747 N: The N bit is the nonce-present bit. When this bit is set to 1, 748 the low-order 24-bits of the first 32-bits of the LISP header 749 contains a Nonce. See Section 6.3.1 for details. Both N and V 750 bits MUST NOT be set in the same packet. If they are, a 751 decapsulating ETR MUST treat the "Nonce/Map-Version" field as 752 having a Nonce value present. 754 L: The L bit is the Locator-Status-Bits field enabled bit. When this 755 bit is set to 1, the Locator-Status-Bits in the second 32-bits of 756 the LISP header are in use. 758 x 1 x x 0 x x x 759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 760 |N|L|E|V|I|flags| Nonce/Map-Version | 761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 762 | Locator Status Bits | 763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 765 E: The E bit is the echo-nonce-request bit. When this bit is set to 766 1, the N bit MUST be 1. This bit SHOULD be ignored and has no 767 meaning when the N bit is set to 0. See Section 6.3.1 for 768 details. 770 V: The V bit is the Map-Version present bit. When this bit is set to 771 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. 772 This bit indicates that the first 4 bytes of the LISP header is 773 encoded as: 775 0 x 0 1 x x x x 776 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 777 |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | 778 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 779 | Instance ID/Locator Status Bits | 780 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 782 I: The I bit is the Instance ID bit. See Section 5.5 for more 783 details. When this bit is set to 1, the Locator Status Bits field 784 is reduced to 8-bits and the high-order 24-bits are used as an 785 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 786 are transmitted as zero and ignored on receipt. The format of the 787 last 4 bytes of the LISP header would look like: 789 x x x x 1 x x x 790 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 791 |N|L|E|V|I|flags| Nonce/Map-Version | 792 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 793 | Instance ID | LSBs | 794 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 796 flags: The flags field is a 3-bit field is reserved for future flag 797 use. It is set to 0 on transmit and ignored on receipt. 799 LISP Nonce: The LISP nonce field is a 24-bit value that is randomly 800 generated by an ITR when the N-bit is set to 1. The nonce is also 801 used when the E-bit is set to request the nonce value to be echoed 802 by the other side when packets are returned. When the E-bit is 803 clear but the N-bit is set, a remote ITR is either echoing a 804 previously requested echo-nonce or providing a random nonce. See 805 Section 6.3.1 for more details. 807 LISP Locator Status Bits: The locator status bits field in the LISP 808 header is set by an ITR to indicate to an ETR the up/down status 809 of the Locators in the source site. Each RLOC in a Map-Reply is 810 assigned an ordinal value from 0 to n-1 (when there are n RLOCs in 811 a mapping entry). The Locator Status Bits are numbered from 0 to 812 n-1 from the least significant bit of field. The field is 32-bits 813 when the I-bit is set to 0 and is 8 bits when the I-bit is set to 814 1. When a Locator Status Bit is set to 1, the ITR is indicating 815 to the ETR the RLOC associated with the bit ordinal has up status. 816 See Section 6.3 for details on how an ITR can determine the status 817 of other ITRs at the same site. When a site has multiple EID- 818 prefixes which result in multiple mappings (where each could have 819 a different locator-set), the Locator Status Bits setting in an 820 encapsulated packet MUST reflect the mapping for the EID-prefix 821 that the inner-header source EID address matches. 823 When doing ITR/PITR encapsulation: 825 o The outer header Time to Live field (or Hop Limit field, in case 826 of IPv6) SHOULD be copied from the inner header Time to Live 827 field. 829 o The outer header Type of Service field (or the Traffic Class 830 field, in the case of IPv6) SHOULD be copied from the inner header 831 Type of Service field (with one caveat, see below). 833 When doing ETR/PETR decapsulation: 835 o The inner header Time to Live field (or Hop Limit field, in case 836 of IPv6) SHOULD be copied from the outer header Time to Live 837 field, when the Time to Live field of the outer header is less 838 than the Time to Live of the inner header. Failing to perform 839 this check can cause the Time to Live of the inner header to 840 increment across encapsulation/decapsulation cycle. This check is 841 also performed when doing initial encapsulation when a packet 842 comes to an ITR or PITR destined for a LISP site. 844 o The inner header Type of Service field (or the Traffic Class 845 field, in the case of IPv6) SHOULD be copied from the outer header 846 Type of Service field (with one caveat, see below). 848 Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate 849 after decapsulating, the net effect of this is that the new outer 850 header will carry the same Time to Live as the old outer header. 852 Copying the TTL serves two purposes: first, it preserves the distance 853 the host intended the packet to travel; second, and more importantly, 854 it provides for suppression of looping packets in the event there is 855 a loop of concatenated tunnels due to misconfiguration. See 856 Section 9.3 for TTL exception handling for traceroute packets. 858 The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service 859 field and the IPv6 Traffic Class field [RFC3168]. The ECN field 860 requires special treatment in order to avoid discarding indications 861 of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN 862 field from the inner header to the outer header. Re-encapsulation 863 MUST copy the 2-bit ECN field from the stripped outer header to the 864 new outer header. If the ECN field contains a congestion indication 865 codepoint (the value is '11', the Congestion Experienced (CE) 866 codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from 867 the stripped outer header to the surviving inner header that is used 868 to forward the packet beyond the ETR. These requirements preserve 869 Congestion Experienced (CE) indications when a packet that uses ECN 870 traverses a LISP tunnel and becomes marked with a CE indication due 871 to congestion between the tunnel endpoints. 873 5.4. Dealing with Large Encapsulated Packets 875 This section proposes two mechanisms to deal with packets that exceed 876 the path MTU between the ITR and ETR. 878 It is left to the implementor to decide if the stateless or stateful 879 mechanism should be implemented. Both or neither can be used since 880 it is a local decision in the ITR regarding how to deal with MTU 881 issues, and sites can interoperate with differing mechanisms. 883 Both stateless and stateful mechanisms also apply to Reencapsulating 884 and Recursive Tunneling. So any actions below referring to an ITR 885 also apply to an TE-ITR. 887 5.4.1. A Stateless Solution to MTU Handling 889 An ITR stateless solution to handle MTU issues is described as 890 follows: 892 1. Define an architectural constant S for the maximum size of a 893 packet, in bytes, an ITR would like to receive from a source 894 inside of its site. 896 2. Define L to be the maximum size, in bytes, a packet of size S 897 would be after the ITR prepends the LISP header, UDP header, and 898 outer network layer header of size H. 900 3. Calculate: S + H = L. 902 When an ITR receives a packet from a site-facing interface and adds H 903 bytes worth of encapsulation to yield a packet size greater than L 904 bytes, it resolves the MTU issue by first splitting the original 905 packet into 2 equal-sized fragments. A LISP header is then prepended 906 to each fragment. The size of the encapsulated fragments is then 907 (S/2 + H), which is less than the ITR's estimate of the path MTU 908 between the ITR and its correspondent ETR. 910 When an ETR receives encapsulated fragments, it treats them as two 911 individually encapsulated packets. It strips the LISP headers then 912 forwards each fragment to the destination host of the destination 913 site. The two fragments are reassembled at the destination host into 914 the single IP datagram that was originated by the source host. 916 This behavior is performed by the ITR when the source host originates 917 a packet with the DF field of the IP header is set to 0. When the DF 918 field of the IP header is set to 1, or the packet is an IPv6 packet 919 originated by the source host, the ITR will drop the packet when the 920 size is greater than L, and sends an ICMP Too Big message to the 921 source with a value of S, where S is (L - H). 923 When the outer header encapsulation uses an IPv4 header, an 924 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 925 can be avoided. An implementation MAY set the DF bit in such headers 926 to 0 if it has good reason to believe there are unresolvable path MTU 927 issues between the sending ITR and the receiving ETR. 929 This specification recommends that L be defined as 1500. 931 5.4.2. A Stateful Solution to MTU Handling 933 An ITR stateful solution to handle MTU issues is described as follows 934 and was first introduced in [OPENLISP]: 936 1. The ITR will keep state of the effective MTU for each locator per 937 mapping cache entry. The effective MTU is what the core network 938 can deliver along the path between ITR and ETR. 940 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet 941 with DF bit set to 1, exceeds what the core network can deliver, 942 one of the intermediate routers on the path will send an ICMP Too 943 Big message to the ITR. The ITR will parse the ICMP message to 944 determine which locator is affected by the effective MTU change 945 and then record the new effective MTU value in the mapping cache 946 entry. 948 3. When a packet is received by the ITR from a source inside of the 949 site and the size of the packet is greater than the effective MTU 950 stored with the mapping cache entry associated with the 951 destination EID the packet is for, the ITR will send an ICMP Too 952 Big message back to the source. The packet size advertised by 953 the ITR in the ICMP Too Big message is the effective MTU minus 954 the LISP encapsulation length. 956 Even though this mechanism is stateful, it has advantages over the 957 stateless IP fragmentation mechanism, by not involving the 958 destination host with reassembly of ITR fragmented packets. 960 5.5. Using Virtualization and Segmentation with LISP 962 When multiple organizations inside of a LISP site are using private 963 addresses [RFC1918] as EID-prefixes, their address spaces MUST remain 964 segregated due to possible address duplication. An Instance ID in 965 the address encoding can aid in making the entire AFI based address 966 unique. See IANA Considerations Section 14.1 for details for 967 possible address encodings. 969 An Instance ID can be carried in a LISP encapsulated packet. An ITR 970 that prepends a LISP header, will copy a 24-bit value, used by the 971 LISP router to uniquely identify the address space. The value is 972 copied to the Instance ID field of the LISP header and the I-bit is 973 set to 1. 975 When an ETR decapsulates a packet, the Instance ID from the LISP 976 header is used as a table identifier to locate the forwarding table 977 to use for the inner destination EID lookup. 979 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 980 24-bit Instance ID. 982 6. EID-to-RLOC Mapping 984 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats 986 The following new UDP packet types are used to retrieve EID-to-RLOC 987 mappings: 989 0 1 2 3 990 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 1 991 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 992 |Version| IHL |Type of Service| Total Length | 993 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 994 | Identification |Flags| Fragment Offset | 995 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 996 | Time to Live | Protocol = 17 | Header Checksum | 997 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 998 | Source Routing Locator | 999 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1000 | Destination Routing Locator | 1001 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1002 / | Source Port | Dest Port | 1003 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1004 \ | UDP Length | UDP Checksum | 1005 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1006 | | 1007 | LISP Message | 1008 | | 1009 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1011 0 1 2 3 1012 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 1013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1014 |Version| Traffic Class | Flow Label | 1015 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1016 | Payload Length | Next Header=17| Hop Limit | 1017 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1018 | | 1019 + + 1020 | | 1021 + Source Routing Locator + 1022 | | 1023 + + 1024 | | 1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1026 | | 1027 + + 1028 | | 1029 + Destination Routing Locator + 1030 | | 1031 + + 1032 | | 1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1034 / | Source Port | Dest Port | 1035 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1036 \ | UDP Length | UDP Checksum | 1037 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1038 | | 1039 | LISP Message | 1040 | | 1041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1043 The LISP UDP-based messages are the Map-Request and Map-Reply 1044 messages. When a UDP Map-Request is sent, the UDP source port is 1045 chosen by the sender and the destination UDP port number is set to 1046 4342. When a UDP Map-Reply is sent, the source UDP port number is 1047 set to 4342 and the destination UDP port number is copied from the 1048 source port of either the Map-Request or the invoking data packet. 1049 Implementations MUST be prepared to accept packets when either the 1050 source port or destination UDP port is set to 4342 due to NATs 1051 changing port number values. 1053 The UDP Length field will reflect the length of the UDP header and 1054 the LISP Message payload. 1056 The UDP Checksum is computed and set to non-zero for Map-Request, 1057 Map-Reply, Map-Register and ECM control messages. It MUST be checked 1058 on receipt and if the checksum fails, the packet MUST be dropped. 1060 LISP-CONS [CONS] uses TCP to send LISP control messages. The format 1061 of control messages includes the UDP header so the checksum and 1062 length fields can be used to protect and delimit message boundaries. 1064 This main LISP specification is the authoritative source for message 1065 format definitions for the Map-Request and Map-Reply messages. 1067 6.1.1. LISP Packet Type Allocations 1069 This section will be the authoritative source for allocating LISP 1070 Type values. Current allocations are: 1072 Reserved: 0 b'0000' 1073 LISP Map-Request: 1 b'0001' 1074 LISP Map-Reply: 2 b'0010' 1075 LISP Map-Register: 3 b'0011' 1076 LISP Map-Notify: 4 b'0100' 1077 LISP Encapsulated Control Message: 8 b'1000' 1079 6.1.2. Map-Request Message Format 1081 0 1 2 3 1082 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1083 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1084 |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | 1085 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1086 | Nonce . . . | 1087 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1088 | . . . Nonce | 1089 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1090 | Source-EID-AFI | Source EID Address ... | 1091 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1092 | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | 1093 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1094 | ... | 1095 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1096 | ITR-RLOC-AFI n | ITR-RLOC Address n ... | 1097 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1098 / | Reserved | EID mask-len | EID-prefix-AFI | 1099 Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1100 \ | EID-prefix ... | 1101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1102 | Map-Reply Record ... | 1103 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1104 | Mapping Protocol Data | 1105 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1107 Packet field descriptions: 1109 Type: 1 (Map-Request) 1111 A: This is an authoritative bit, which is set to 0 for UDP-based Map- 1112 Requests sent by an ITR. 1114 M: When set, it indicates a Map-Reply Record segment is included in 1115 the Map-Request. 1117 P: This is the probe-bit which indicates that a Map-Request SHOULD be 1118 treated as a locator reachability probe. The receiver SHOULD 1119 respond with a Map-Reply with the probe-bit set, indicating the 1120 Map-Reply is a locator reachability probe reply, with the nonce 1121 copied from the Map-Request. See Section 6.3.2 for more details. 1123 S: This is the SMR bit. See Section 6.6.2 for details. 1125 p: This is the PITR bit. This bit is set to 1 when a PITR sends a 1126 Map-Request. 1128 s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is 1129 sending a Map-Request in response to a received SMR-based Map- 1130 Request. 1132 Reserved: Set to 0 on transmission and ignored on receipt. 1134 IRC: This 5-bit field is the ITR-RLOC Count which encodes the 1135 additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields 1136 present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- 1137 Address) pair must always be encoded. Multiple ITR-RLOC Address 1138 fields are used so a Map-Replier can select which destination 1139 address to use for a Map-Reply. The IRC value ranges from 0 to 1140 31, and for a value of 1, there are 2 ITR-RLOC addresses encoded 1141 and so on up to 31 which encodes a total of 32 ITR-RLOC addresses. 1143 Record Count: The number of records in this Map-Request message. A 1144 record is comprised of the portion of the packet that is labeled 1145 'Rec' above and occurs the number of times equal to Record Count. 1146 For this version of the protocol, a receiver MUST accept and 1147 process Map-Requests that contain one or more records, but a 1148 sender MUST only send Map-Requests containing one record. Support 1149 for requesting multiple EIDs in a single Map-Request message will 1150 be specified in a future version of the protocol. 1152 Nonce: An 8-byte random value created by the sender of the Map- 1153 Request. This nonce will be returned in the Map-Reply. The 1154 security of the LISP mapping protocol depends critically on the 1155 strength of the nonce in the Map-Request message. The nonce 1156 SHOULD be generated by a properly seeded pseudo-random (or strong 1157 random) source. See [RFC4086] for advice on generating security- 1158 sensitive random data. 1160 Source-EID-AFI: Address family of the "Source EID Address" field. 1162 Source EID Address: This is the EID of the source host which 1163 originated the packet which is invoking this Map-Request. When 1164 Map-Requests are used for refreshing a map-cache entry or for 1165 RLOC-probing, an AFI value 0 is used and this field is of zero 1166 length. 1168 ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that 1169 follows this field. 1171 ITR-RLOC Address: Used to give the ETR the option of selecting the 1172 destination address from any address family for the Map-Reply 1173 message. This address MUST be a routable RLOC address of the 1174 sender of the Map-Request message. 1176 EID mask-len: Mask length for EID prefix. 1178 EID-prefix-AFI: Address family of EID-prefix according to [RFC5226] 1180 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1181 address-family. When a Map-Request is sent by an ITR because a 1182 data packet is received for a destination where there is no 1183 mapping entry, the EID-prefix is set to the destination IP address 1184 of the data packet. And the 'EID mask-len' is set to 32 or 128 1185 for IPv4 or IPv6, respectively. When an xTR wants to query a site 1186 about the status of a mapping it already has cached, the EID- 1187 prefix used in the Map-Request has the same mask-length as the 1188 EID-prefix returned from the site when it sent a Map-Reply 1189 message. 1191 Map-Reply Record: When the M bit is set, this field is the size of a 1192 single "Record" in the Map-Reply format. This Map-Reply record 1193 contains the EID-to-RLOC mapping entry associated with the Source 1194 EID. This allows the ETR which will receive this Map-Request to 1195 cache the data if it chooses to do so. 1197 Mapping Protocol Data: See [CONS] for details. This field is 1198 optional and present when the UDP length indicates there is enough 1199 space in the packet to include it. 1201 6.1.3. EID-to-RLOC UDP Map-Request Message 1203 A Map-Request is sent from an ITR when it needs a mapping for an EID, 1204 wants to test an RLOC for reachability, or wants to refresh a mapping 1205 before TTL expiration. For the initial case, the destination IP 1206 address used for the Map-Request is the destination-EID from the 1207 packet which had a mapping cache lookup failure. For the latter 2 1208 cases, the destination IP address used for the Map-Request is one of 1209 the RLOC addresses from the locator-set of the map cache entry. The 1210 source address is either an IPv4 or IPv6 RLOC address depending if 1211 the Map-Request is using an IPv4 versus IPv6 header, respectively. 1212 In all cases, the UDP source port number for the Map-Request message 1213 is an ITR/PITR selected 16-bit value and the UDP destination port 1214 number is set to the well-known destination port number 4342. A 1215 successful Map-Reply updates the cached set of RLOCs associated with 1216 the EID prefix range. 1218 One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST 1219 be filled in by the ITR. The number of fields (minus 1) encoded MUST 1220 be placed in the IRC field. The ITR MAY include all locally 1221 configured locators in this list or just provide one locator address 1222 from each address family it supports. If the ITR erroneously 1223 provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- 1224 Request. 1226 Map-Requests can also be LISP encapsulated using UDP destination port 1227 4342 with a LISP type value set to "Encapsulated Control Message", 1228 when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are 1229 LISP encapsulated the same way from a Map-Server to an ETR. Details 1230 on encapsulated Map-Requests and Map-Resolvers can be found in 1231 [LISP-MS]. 1233 Map-Requests MUST be rate-limited. It is recommended that a Map- 1234 Request for the same EID-prefix be sent no more than once per second. 1236 An ITR that is configured with mapping database information (i.e. it 1237 is also an ETR) may optionally include those mappings in a Map- 1238 Request. When an ETR configured to accept and verify such 1239 "piggybacked" mapping data receives such a Map-Request and it does 1240 not have this mapping in the map-cache, it may originate a "verifying 1241 Map-Request", addressed to the map-requesting ITR. If the ETR has a 1242 map-cache entry that matches the "piggybacked" EID and the RLOC is in 1243 the locator-set for the entry, then it may send the "verifying Map- 1244 Request" directly to the originating Map-Request source. If the RLOC 1245 is not in the locator-set, then the ETR MUST send the "verifying Map- 1246 Request" to the "piggybacked" EID. Doing this forces the "verifying 1247 Map-Request" to go through the mapping database system to reach the 1248 authoritative source of information about that EID, guarding against 1249 RLOC-spoofing in in the "piggybacked" mapping data. 1251 6.1.4. Map-Reply Message Format 1253 0 1 2 3 1254 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 1255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1256 |Type=2 |P|E|S| Reserved | Record Count | 1257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1258 | Nonce . . . | 1259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1260 | . . . Nonce | 1261 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1262 | | Record TTL | 1263 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1264 R | Locator Count | EID mask-len | ACT |A| Reserved | 1265 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1266 c | Rsvd | Map-Version Number | EID-AFI | 1267 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1268 r | EID-prefix | 1269 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1270 | /| Priority | Weight | M Priority | M Weight | 1271 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1272 | o | Unused Flags |L|p|R| Loc-AFI | 1273 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1274 | \| Locator | 1275 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1276 | Mapping Protocol Data | 1277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1279 Packet field descriptions: 1281 Type: 2 (Map-Reply) 1283 P: This is the probe-bit which indicates that the Map-Reply is in 1284 response to a locator reachability probe Map-Request. The nonce 1285 field MUST contain a copy of the nonce value from the original 1286 Map-Request. See Section 6.3.2 for more details. 1288 E: Indicates that the ETR which sends this Map-Reply message is 1289 advertising that the site is enabled for the Echo-Nonce locator 1290 reachability algorithm. See Section 6.3.1 for more details. 1292 S: This is the Security bit. When set to 1 the field following the 1293 Mapping Protocol Data field will have the following format. The 1294 detailed format of the Authentication Data Content field can be 1295 found in [LISP-SEC] when AD Type is equal to 1. 1297 0 1 2 3 1298 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 1299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1300 | AD Type | Authentication Data Content . . . | 1301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1303 Reserved: Set to 0 on transmission and ignored on receipt. 1305 Record Count: The number of records in this reply message. A record 1306 is comprised of that portion of the packet labeled 'Record' above 1307 and occurs the number of times equal to Record count. 1309 Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value 1310 from the Map-Request is echoed in this Nonce field of the Map- 1311 Reply. 1313 Record TTL: The time in minutes the recipient of the Map-Reply will 1314 store the mapping. If the TTL is 0, the entry SHOULD be removed 1315 from the cache immediately. If the value is 0xffffffff, the 1316 recipient can decide locally how long to store the mapping. 1318 Locator Count: The number of Locator entries. A locator entry 1319 comprises what is labeled above as 'Loc'. The locator count can 1320 be 0 indicating there are no locators for the EID-prefix. 1322 EID mask-len: Mask length for EID prefix. 1324 ACT: This 3-bit field describes negative Map-Reply actions. These 1325 bits are used only when the 'Locator Count' field is set to 0. 1326 The action bits are encoded only in Map-Reply messages. The 1327 actions defined are used by an ITR or PTR when a destination EID 1328 matches a negative mapping cache entry. Unassigned values should 1329 cause a map-cache entry to be created and, when packets match this 1330 negative cache entry, they will be dropped. The current assigned 1331 values are: 1333 (0) No-Action: The map-cache is kept alive and packet 1334 encapsulation occurs. 1336 (1) Natively-Forward: The packet is not encapsulated or dropped 1337 but natively forwarded. 1339 (2) Send-Map-Request: The packet invokes sending a Map-Request. 1341 (3) Drop: A packet that matches this map-cache entry is dropped. 1343 A: The Authoritative bit, when sent by a UDP-based message is always 1344 set to 1 by an ETR. See [CONS] for TCP-based Map-Replies. When a 1345 Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, the 1346 Authoritative bit is set to 0. This indicates to requesting ITRs 1347 that the Map-Reply was not originated by a LISP node managed at 1348 the site that owns the EID-prefix. 1350 Map-Version Number: When this 12-bit value is non-zero the Map-Reply 1351 sender is informing the ITR what the version number is for the 1352 EID-record contained in the Map-Reply. The ETR can allocate this 1353 number internally but MUST coordinate this value with other ETRs 1354 for the site. When this value is 0, there is no versioning 1355 information conveyed. The Map-Version Number can be included in 1356 Map-Request and Map-Register messages. See Section 6.6.3 for more 1357 details. 1359 EID-AFI: Address family of EID-prefix according to [RFC5226]. 1361 EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 1362 address-family. 1364 Priority: each RLOC is assigned a unicast priority. Lower values 1365 are more preferable. When multiple RLOCs have the same priority, 1366 they may be used in a load-split fashion. A value of 255 means 1367 the RLOC MUST NOT be used for unicast forwarding. 1369 Weight: when priorities are the same for multiple RLOCs, the weight 1370 indicates how to balance unicast traffic between them. Weight is 1371 encoded as a relative weight of total unicast packets that match 1372 the mapping entry. If a non-zero weight value is used for any 1373 RLOC, then all RLOCs MUST use a non-zero weight value and then the 1374 sum of all weight values MUST equal 100. If a zero value is used 1375 for any RLOC weight, then all weights MUST be zero and the 1376 receiver of the Map-Reply will decide how to load-split traffic. 1377 See Section 6.5 for a suggested hash algorithm to distribute load 1378 across locators with same priority and equal weight values. 1380 M Priority: each RLOC is assigned a multicast priority used by an 1381 ETR in a receiver multicast site to select an ITR in a source 1382 multicast site for building multicast distribution trees. A value 1383 of 255 means the RLOC MUST NOT be used for joining a multicast 1384 distribution tree. 1386 M Weight: when priorities are the same for multiple RLOCs, the 1387 weight indicates how to balance building multicast distribution 1388 trees across multiple ITRs. The weight is encoded as a relative 1389 weight of total number of trees built to the source site 1390 identified by the EID-prefix. If a non-zero weight value is used 1391 for any RLOC, then all RLOCs MUST use a non-zero weight value and 1392 then the sum of all weight values MUST equal 100. If a zero value 1393 is used for any RLOC weight, then all weights MUST be zero and the 1394 receiver of the Map-Reply will decide how to distribute multicast 1395 state across ITRs. 1397 Unused Flags: set to 0 when sending and ignored on receipt. 1399 L: when this bit is set, the locator is flagged as a local locator to 1400 the ETR that is sending the Map-Reply. When a Map-Server is doing 1401 proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 1402 0 for all locators in this locator-set. 1404 p: when this bit is set, an ETR informs the RLOC-probing ITR that the 1405 locator address, for which this bit is set, is the one being RLOC- 1406 probed and may be different from the source address of the Map- 1407 Reply. An ITR that RLOC-probes a particular locator, MUST use 1408 this locator for retrieving the data structure used to store the 1409 fact that the locator is reachable. The "p" bit is set for a 1410 single locator in the same locator set. If an implementation sets 1411 more than one "p" bit erroneously, the receiver of the Map-Reply 1412 MUST select the first locator. The "p" bit MUST NOT be set for 1413 locator-set records sent in Map-Request and Map-Register messages. 1415 R: set when the sender of a Map-Reply has a route to the locator in 1416 the locator data record. This receiver may find this useful to 1417 know when determining if the locator is reachable from the 1418 receiver. See also Section 6.4 for another way the R-bit may be 1419 used. 1421 Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) 1422 assigned to an ETR. Note that the destination RLOC address MAY be 1423 an anycast address. A source RLOC can be an anycast address as 1424 well. The source or destination RLOC MUST NOT be the broadcast 1425 address (255.255.255.255 or any subnet broadcast address known to 1426 the router), and MUST NOT be a link-local multicast address. The 1427 source RLOC MUST NOT be a multicast address. The destination RLOC 1428 SHOULD be a multicast address if it is being mapped from a 1429 multicast destination EID. 1431 Mapping Protocol Data: See [CONS] or [ALT] for details. This field 1432 is optional and present when the UDP length indicates there is 1433 enough space in the packet to include it. 1435 6.1.5. EID-to-RLOC UDP Map-Reply Message 1437 A Map-Reply returns an EID-prefix with a prefix length that is less 1438 than or equal to the EID being requested. The EID being requested is 1439 either from the destination field of an IP header of a Data-Probe or 1440 the EID record of a Map-Request. The RLOCs in the Map-Reply are 1441 globally-routable IP addresses of all ETRs for the LISP site. Each 1442 RLOC conveys status reachability but does not convey path 1443 reachability from a requesters perspective. Separate testing of path 1444 reachability is required, See Section 6.3 for details. 1446 Note that a Map-Reply may contain different EID-prefix granularity 1447 (prefix + length) than the Map-Request which triggers it. This might 1448 occur if a Map-Request were for a prefix that had been returned by an 1449 earlier Map-Reply. In such a case, the requester updates its cache 1450 with the new prefix information and granularity. For example, a 1451 requester with two cached EID-prefixes that are covered by a Map- 1452 Reply containing one, less-specific prefix, replaces the entry with 1453 the less-specific EID-prefix. Note that the reverse, replacement of 1454 one less-specific prefix with multiple more-specific prefixes, can 1455 also occur but not by removing the less-specific prefix rather by 1456 adding the more-specific prefixes which during a lookup will override 1457 the less-specific prefix. 1459 When an ETR is configured with overlapping EID-prefixes, a Map- 1460 Request with an EID that longest matches any EID-prefix MUST be 1461 returned in a single Map-Reply message. For instance, if an ETR had 1462 database mapping entries for EID-prefixes: 1464 10.0.0.0/8 1465 10.1.0.0/16 1466 10.1.1.0/24 1467 10.1.2.0/24 1469 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record 1470 count of 1 to be returned with a mapping record EID-prefix of 1471 10.1.1.0/24. 1473 A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record 1474 count of 3 to be returned with mapping records for EID-prefixes 1475 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. 1477 Note that not all overlapping EID-prefixes need to be returned, only 1478 the more specifics (note in the second example above 10.0.0.0/8 was 1479 not returned for requesting EID 10.1.5.5) entries for the matching 1480 EID-prefix of the requesting EID. When more than one EID-prefix is 1481 returned, all SHOULD use the same Time-to-Live value so they can all 1482 time out at the same time. When a more specific EID-prefix is 1483 received later, its Time-to-Live value in the Map-Reply record can be 1484 stored even when other less specifics exist. When a less specific 1485 EID-prefix is received later, its map-cache expiration time SHOULD be 1486 set to the minimum expiration time of any more specific EID-prefix in 1487 the map-cache. 1489 Map-Replies SHOULD be sent for an EID-prefix no more often than once 1490 per second to the same requesting router. For scalability, it is 1491 expected that aggregation of EID addresses into EID-prefixes will 1492 allow one Map-Reply to satisfy a mapping for the EID addresses in the 1493 prefix range thereby reducing the number of Map-Request messages. 1495 Map-Reply records can have an empty locator-set. A negative Map- 1496 Reply is a Map-Reply with an empty locator-set. Negative Map-Replies 1497 convey special actions by the sender to the ITR or PTR which have 1498 solicited the Map-Reply. There are two primary applications for 1499 Negative Map-Replies. The first is for a Map-Resolver to instruct an 1500 ITR or PTR when a destination is for a LISP site versus a non-LISP 1501 site. And the other is to source quench Map-Requests which are sent 1502 for non-allocated EIDs. 1504 For each Map-Reply record, the list of locators in a locator-set MUST 1505 appear in the same order for each ETR that originates a Map-Reply 1506 message. The locator-set MUST be sorted in order of ascending IP 1507 address where an IPv4 locator address is considered numerically 'less 1508 than' an IPv6 locator address. 1510 When sending a Map-Reply message, the destination address is copied 1511 from the one of the ITR-RLOC fields from the Map-Request. The ETR 1512 can choose a locator address from one of the address families it 1513 supports. For Data-Probes, the destination address of the Map-Reply 1514 is copied from the source address of the Data-Probe message which is 1515 invoking the reply. The source address of the Map-Reply is one of 1516 the local IP addresses chosen to allow uRPF checks to succeed in the 1517 upstream service provider. The destination port of a Map-Reply 1518 message is copied from the source port of the Map-Request or Data- 1519 Probe and the source port of the Map-Reply message is set to the 1520 well-known UDP port 4342. 1522 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes 1524 When an ETR is misconfigured or compromised, it could return coarse 1525 EID-prefixes in Map-Reply messages it sends. The EID-prefix could 1526 cover EID-prefixes which are allocated to other sites redirecting 1527 their traffic to the locators of the compromised site. 1529 To solve this problem, there are two basic solutions that could be 1530 used. The first is to have Map-Servers proxy-map-reply on behalf of 1531 ETRs so their registered EID-prefixes are the ones returned in Map- 1532 Replies. Since the interaction between an ETR and Map-Server is 1533 secured with shared-keys, it is more difficult for an ETR to 1534 misbehave. The second solution is to have ITRs and PTRs cache EID- 1535 prefixes with mask-lengths that are greater than or equal to a 1536 configured prefix length. This limits the damage to a specific width 1537 of any EID-prefix advertised, but needs to be coordinated with the 1538 allocation of site prefixes. These solutions can be used 1539 independently or at the same time. 1541 At the time of this writing, other approaches are being considered 1542 and researched. 1544 6.1.6. Map-Register Message Format 1546 The usage details of the Map-Register message can be found in 1547 specification [LISP-MS]. This section solely defines the message 1548 format. 1550 The message is sent in UDP with a destination UDP port of 4342 and a 1551 randomly selected UDP source port number. 1553 The Map-Register message format is: 1555 0 1 2 3 1556 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 1557 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1558 |Type=3 |P| Reserved |M| Record Count | 1559 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1560 | Nonce . . . | 1561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1562 | . . . Nonce | 1563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1564 | Key ID | Authentication Data Length | 1565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1566 ~ Authentication Data ~ 1567 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1568 | | Record TTL | 1569 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1570 R | Locator Count | EID mask-len | ACT |A| Reserved | 1571 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1572 c | Rsvd | Map-Version Number | EID-AFI | 1573 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1574 r | EID-prefix | 1575 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1576 | /| Priority | Weight | M Priority | M Weight | 1577 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1578 | o | Unused Flags |L|p|R| Loc-AFI | 1579 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1580 | \| Locator | 1581 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1583 Packet field descriptions: 1585 Type: 3 (Map-Register) 1587 P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- 1588 Register message requesting for the Map-Server to proxy Map-Reply. 1589 The Map-Server will send non-authoritative Map-Replies on behalf 1590 of the ETR. Details on this usage will be provided in a future 1591 version of this draft. 1593 Reserved: Set to 0 on transmission and ignored on receipt. 1595 M: This is the want-map-notify bit, when set to 1 an ETR is 1596 requesting for a Map-Notify message to be returned in response to 1597 sending a Map-Register message. The Map-Notify message sent by a 1598 Map-Server is used to an acknowledge receipt of a Map-Register 1599 message. 1601 Record Count: The number of records in this Map-Register message. A 1602 record is comprised of that portion of the packet labeled 'Record' 1603 above and occurs the number of times equal to Record count. 1605 Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages. 1607 Key ID: A configured ID to find the configured Message 1608 Authentication Code (MAC) algorithm and key value used for the 1609 authentication function. 1611 Authentication Data Length: The length in bytes of the 1612 Authentication Data field that follows this field. The length of 1613 the Authentication Data field is dependent on the Message 1614 Authentication Code (MAC) algorithm used. The length field allows 1615 a device that doesn't know the MAC algorithm to correctly parse 1616 the packet. 1618 Authentication Data: The message digest used from the output of the 1619 Message Authentication Code (MAC) algorithm. The entire Map- 1620 Register payload is authenticated with this field preset to 0. 1621 After the MAC is computed, it is placed in this field. 1622 Implementations of this specification MUST include support for 1623 HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-128-256 [RFC4634] 1624 is recommended. 1626 The definition of the rest of the Map-Register can be found in the 1627 Map-Reply section. 1629 6.1.7. Map-Notify Message Format 1631 The usage details of the Map-Notify message can be found in 1632 specification [LISP-MS]. This section solely defines the message 1633 format. 1635 The message is sent inside a UDP packet with a source UDP port equal 1636 to 4342 and a destination port equal to the source port from the Map- 1637 Register message this Map-Notify message is responding to. 1639 The Map-Notify message format is: 1641 0 1 2 3 1642 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 1643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1644 |Type=4 | Reserved | Record Count | 1645 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1646 | Nonce . . . | 1647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1648 | . . . Nonce | 1649 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1650 | Key ID | Authentication Data Length | 1651 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1652 ~ Authentication Data ~ 1653 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1654 | | Record TTL | 1655 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1656 R | Locator Count | EID mask-len | ACT |A| Reserved | 1657 e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1658 c | Rsvd | Map-Version Number | EID-AFI | 1659 o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1660 r | EID-prefix | 1661 d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1662 | /| Priority | Weight | M Priority | M Weight | 1663 | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1664 | o | Unused Flags |L|p|R| Loc-AFI | 1665 | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1666 | \| Locator | 1667 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1669 Packet field descriptions: 1671 Type: 4 (Map-Notify) 1673 The Map-Notify message has the same contents as a Map-Register 1674 message. See Map-Register section for field descriptions. 1676 6.1.8. Encapsulated Control Message Format 1678 An Encapsulated Control Message is used to encapsulate control 1679 packets sent between xTRs and the mapping database system described 1680 in [LISP-MS]. 1682 0 1 2 3 1683 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 1684 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1685 / | IPv4 or IPv6 Header | 1686 OH | (uses RLOC addresses) | 1687 \ | | 1688 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1689 / | Source Port = xxxx | Dest Port = 4342 | 1690 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1691 \ | UDP Length | UDP Checksum | 1692 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1693 LH |Type=8 |S| Reserved | 1694 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1695 / | IPv4 or IPv6 Header | 1696 IH | (uses RLOC or EID addresses) | 1697 \ | | 1698 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1699 / | Source Port = xxxx | Dest Port = yyyy | 1700 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1701 \ | UDP Length | UDP Checksum | 1702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1703 LCM | LISP Control Message | 1704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1706 Packet header descriptions: 1708 OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the 1709 source and destination header address fields. 1711 UDP: The outer UDP header with destination port 4342. The source 1712 port is randomly allocated. The checksum field MUST be non-zero. 1714 LH: Type 8 is defined to be a "LISP Encapsulated Control Message" 1715 and what follows is either an IPv4 or IPv6 header as encoded by 1716 the first 4 bits after the reserved field. 1718 S: This is the Security bit. When set to 1 the field following the 1719 Reserved field will have the following format. The detailed 1720 format of the Authentication Data Content field can be found in 1721 [LISP-SEC] when AD Type is equal to 1. 1723 0 1 2 3 1724 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 1725 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1726 | AD Type | Authentication Data Content . . . | 1727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1729 IH: The inner IPv4 or IPv6 header which can use either RLOC or EID 1730 addresses in the header address fields. When a Map-Request is 1731 encapsulated in this packet format the destination address in this 1732 header is an EID. 1734 UDP: The inner UDP header where the port assignments depends on the 1735 control packet being encapsulated. When the control packet is a 1736 Map-Request or Map-Register, the source port is ITR/PITR selected 1737 and the destination port is 4342. When the control packet is a 1738 Map-Reply, the source port is 4342 and the destination port is 1739 assigned from the source port of the invoking Map-Request. Port 1740 number 4341 MUST NOT be assigned to either port. The checksum 1741 field MUST be non-zero. 1743 LCM: The format is one of the control message formats described in 1744 this section. At this time, only Map-Request messages and PIM 1745 Join-Prune messages [MLISP] are allowed to be encapsulated. 1746 Encapsulating other types of LISP control messages are for further 1747 study. When Map-Requests are sent for RLOC-probing purposes (i.e 1748 the probe-bit is set), they MUST NOT be sent inside Encapsulated 1749 Control Messages. 1751 6.2. Routing Locator Selection 1753 Both client-side and server-side may need control over the selection 1754 of RLOCs for conversations between them. This control is achieved by 1755 manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply 1756 messages. Alternatively, RLOC information may be gleaned from 1757 received tunneled packets or EID-to-RLOC Map-Request messages. 1759 The following enumerates different scenarios for choosing RLOCs and 1760 the controls that are available: 1762 o Server-side returns one RLOC. Client-side can only use one RLOC. 1763 Server-side has complete control of the selection. 1765 o Server-side returns a list of RLOC where a subset of the list has 1766 the same best priority. Client can only use the subset list 1767 according to the weighting assigned by the server-side. In this 1768 case, the server-side controls both the subset list and load- 1769 splitting across its members. The client-side can use RLOCs 1770 outside of the subset list if it determines that the subset list 1771 is unreachable (unless RLOCs are set to a Priority of 255). Some 1772 sharing of control exists: the server-side determines the 1773 destination RLOC list and load distribution while the client-side 1774 has the option of using alternatives to this list if RLOCs in the 1775 list are unreachable. 1777 o Server-side sets weight of 0 for the RLOC subset list. In this 1778 case, the client-side can choose how the traffic load is spread 1779 across the subset list. Control is shared by the server-side 1780 determining the list and the client determining load distribution. 1781 Again, the client can use alternative RLOCs if the server-provided 1782 list of RLOCs are unreachable. 1784 o Either side (more likely on the server-side ETR) decides not to 1785 send a Map-Request. For example, if the server-side ETR does not 1786 send Map-Requests, it gleans RLOCs from the client-side ITR, 1787 giving the client-side ITR responsibility for bidirectional RLOC 1788 reachability and preferability. Server-side ETR gleaning of the 1789 client-side ITR RLOC is done by caching the inner header source 1790 EID and the outer header source RLOC of received packets. The 1791 client-side ITR controls how traffic is returned and can alternate 1792 using an outer header source RLOC, which then can be added to the 1793 list the server-side ETR uses to return traffic. Since no 1794 Priority or Weights are provided using this method, the server- 1795 side ETR MUST assume each client-side ITR RLOC uses the same best 1796 Priority with a Weight of zero. In addition, since EID-prefix 1797 encoding cannot be conveyed in data packets, the EID-to-RLOC cache 1798 on tunnel routers can grow to be very large. 1800 o A "gleaned" map-cache entry, one learned from the source RLOC of a 1801 received encapsulated packet, is only stored and used for a few 1802 seconds, pending verification. Verification is performed by 1803 sending a Map-Request to the source EID (the inner header IP 1804 source address) of the received encapsulated packet. A reply to 1805 this "verifying Map-Request" is used to fully populate the map- 1806 cache entry for the "gleaned" EID and is stored and used for the 1807 time indicated from the TTL field of a received Map-Reply. When a 1808 verified map-cache entry is stored, data gleaning no longer occurs 1809 for subsequent packets which have a source EID that matches the 1810 EID-prefix of the verified entry. 1812 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1813 reachable when the R-bit for the locator record is set to 1. Neither 1814 the information contained in a Map-Reply or that stored in the 1815 mapping database system provides reachability information for RLOCs. 1816 Note that reachability is not part of the mapping system and is 1817 determined using one or more of the Routing Locator Reachability 1818 Algorithms described in the next section. 1820 6.3. Routing Locator Reachability 1822 Several mechanisms for determining RLOC reachability are currently 1823 defined: 1825 1. An ETR may examine the Loc-Status-Bits in the LISP header of an 1826 encapsulated data packet received from an ITR. If the ETR is 1827 also acting as an ITR and has traffic to return to the original 1828 ITR site, it can use this status information to help select an 1829 RLOC. 1831 2. An ITR may receive an ICMP Network or ICMP Host Unreachable 1832 message for an RLOC it is using. This indicates that the RLOC is 1833 likely down. 1835 3. An ITR which participates in the global routing system can 1836 determine that an RLOC is down if no BGP RIB route exists that 1837 matches the RLOC IP address. 1839 4. An ITR may receive an ICMP Port Unreachable message from a 1840 destination host. This occurs if an ITR attempts to use 1841 interworking [INTERWORK] and LISP-encapsulated data is sent to a 1842 non-LISP-capable site. 1844 5. An ITR may receive a Map-Reply from a ETR in response to a 1845 previously sent Map-Request. The RLOC source of the Map-Reply is 1846 likely up since the ETR was able to send the Map-Reply to the 1847 ITR. 1849 6. When an ETR receives an encapsulated packet from an ITR, the 1850 source RLOC from the outer header of the packet is likely up. 1852 7. An ITR/ETR pair can use the Locator Reachability Algorithms 1853 described in this section, namely Echo-Noncing or RLOC-Probing. 1855 When determining Locator up/down reachability by examining the Loc- 1856 Status-Bits from the LISP encapsulated data packet, an ETR will 1857 receive up to date status from an encapsulating ITR about 1858 reachability for all ETRs at the site. CE-based ITRs at the source 1859 site can determine reachability relative to each other using the site 1860 IGP as follows: 1862 o Under normal circumstances, each ITR will advertise a default 1863 route into the site IGP. 1865 o If an ITR fails or if the upstream link to its PE fails, its 1866 default route will either time-out or be withdrawn. 1868 Each ITR can thus observe the presence or lack of a default route 1869 originated by the others to determine the Locator Status Bits it sets 1870 for them. 1872 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1873 Loc-Status-Bits in a LISP encapsulated packet are numbered from 0 to 1874 n-1 starting with the least significant bit. For example, if an RLOC 1875 listed in the 3rd position of the Map-Reply goes down (ordinal value 1876 2), then all ITRs at the site will clear the 3rd least significant 1877 bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they 1878 encapsulate. 1880 When an ETR decapsulates a packet, it will check for any change in 1881 the Loc-Status-Bits field. When a bit goes from 1 to 0, the ETR will 1882 refrain from encapsulating packets to an RLOC that is indicated as 1883 down. It will only resume using that RLOC if the corresponding Loc- 1884 Status-Bit returns to a value of 1. Loc-Status-Bits are associated 1885 with a locator-set per EID-prefix. Therefore, when a locator becomes 1886 unreachable, the Loc-Status-Bit that corresponds to that locator's 1887 position in the list returned by the last Map-Reply will be set to 1888 zero for that particular EID-prefix. 1890 When ITRs at the site are not deployed in CE routers, the IGP can 1891 still be used to determine the reachability of Locators provided they 1892 are injected into the IGP. This is typically done when a /32 address 1893 is configured on a loopback interface. 1895 When ITRs receive ICMP Network or Host Unreachable messages as a 1896 method to determine unreachability, they will refrain from using 1897 Locators which are described in Locator lists of Map-Replies. 1898 However, using this approach is unreliable because many network 1899 operators turn off generation of ICMP Unreachable messages. 1901 If an ITR does receive an ICMP Network or Host Unreachable message, 1902 it MAY originate its own ICMP Unreachable message destined for the 1903 host that originated the data packet the ITR encapsulated. 1905 Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a 1906 locator address from a locator-set in a mapping entry matches a 1907 prefix. If it does not find one and BGP is running in the Default 1908 Free Zone (DFZ), it can decide to not use the locator even though the 1909 Loc-Status-Bits indicate the locator is up. In this case, the path 1910 from the ITR to the ETR that is assigned the locator is not 1911 available. More details are in [LOC-ID-ARCH]. 1913 Optionally, an ITR can send a Map-Request to a Locator and if a Map- 1914 Reply is returned, reachability of the Locator has been determined. 1915 Obviously, sending such probes increases the number of control 1916 messages originated by tunnel routers for active flows, so Locators 1917 are assumed to be reachable when they are advertised. 1919 This assumption does create a dependency: Locator unreachability is 1920 detected by the receipt of ICMP Host Unreachable messages. When an 1921 Locator has been determined to be unreachable, it is not used for 1922 active traffic; this is the same as if it were listed in a Map-Reply 1923 with priority 255. 1925 The ITR can test the reachability of the unreachable Locator by 1926 sending periodic Requests. Both Requests and Replies MUST be rate- 1927 limited. Locator reachability testing is never done with data 1928 packets since that increases the risk of packet loss for end-to-end 1929 sessions. 1931 When an ETR decapsulates a packet, it knows that it is reachable from 1932 the encapsulating ITR because that is how the packet arrived. In 1933 most cases, the ETR can also reach the ITR but cannot assume this to 1934 be true due to the possibility of path asymmetry. In the presence of 1935 unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT 1936 use the lack of return traffic as an indication that the ETR is 1937 unreachable. Instead, it MUST use an alternate mechanisms to 1938 determine reachability. 1940 6.3.1. Echo Nonce Algorithm 1942 When data flows bidirectionally between locators from different 1943 sites, a data-plane mechanism called "nonce echoing" can be used to 1944 determine reachability between an ITR and ETR. When an ITR wants to 1945 solicit a nonce echo, it sets the N and E bits and places a 24-bit 1946 nonce in the LISP header of the next encapsulated data packet. 1948 When this packet is received by the ETR, the encapsulated packet is 1949 forwarded as normal. When the ETR next sends a data packet to the 1950 ITR, it includes the nonce received earlier with the N bit set and E 1951 bit cleared. The ITR sees this "echoed nonce" and knows the path to 1952 and from the ETR is up. 1954 The ITR will set the E-bit and N-bit for every packet it sends while 1955 in echo-nonce-request state. The time the ITR waits to process the 1956 echoed nonce before it determines the path is unreachable is variable 1957 and a choice left for the implementation. 1959 If the ITR is receiving packets from the ETR but does not see the 1960 nonce echoed while being in echo-nonce-request state, then the path 1961 to the ETR is unreachable. This decision may be overridden by other 1962 locator reachability algorithms. Once the ITR determines the path to 1963 the ETR is down it can switch to another locator for that EID-prefix. 1965 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1966 be implementing both ITR and ETR functionality for the echo nonce 1967 mechanism to operate. 1969 The ITR and ETR may both go into echo-nonce-request state at the same 1970 time. The number of packets sent or the time during which echo nonce 1971 requests are sent is an implementation specific setting. However, 1972 when an ITR is in echo-nonce-request state, it can echo the ETR's 1973 nonce in the next set of packets that it encapsulates and then 1974 subsequently, continue sending echo-nonce-request packets. 1976 This mechanism does not completely solve the forward path 1977 reachability problem as traffic may be unidirectional. That is, the 1978 ETR receiving traffic at a site may not be the same device as an ITR 1979 which transmits traffic from that site or the site to site traffic is 1980 unidirectional so there is no ITR returning traffic. 1982 The echo-nonce algorithm is bilateral. That is, if one side sets the 1983 E-bit and the other side is not enabled for echo-noncing, then the 1984 echoing of the nonce does not occur and the requesting side may 1985 regard the locator unreachable erroneously. An ITR SHOULD only set 1986 the E-bit in a encapsulated data packet when it knows the ETR is 1987 enabled for echo-noncing. This is conveyed by the E-bit in the Map- 1988 Reply message. 1990 Note that other locator reachability mechanisms are being researched 1991 and can be used to compliment or even override the Echo Nonce 1992 Algorithm. See next section for an example of control-plane probing. 1994 6.3.2. RLOC Probing Algorithm 1996 RLOC Probing is a method that an ITR or PTR can use to determine the 1997 reachability status of one or more locators that it has cached in a 1998 map-cache entry. The probe-bit of the Map-Request and Map-Reply 1999 messages are used for RLOC Probing. 2001 RLOC probing is done in the control-plane on a timer basis where an 2002 ITR or PTR will originate a Map-Request destined to a locator address 2003 from one of its own locator addresses. A Map-Request used as an 2004 RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the 2005 ALT like one would when soliciting mapping data. The EID record 2006 encoded in the Map-Request is the EID-prefix of the map-cache entry 2007 cached by the ITR or PTR. The ITR may include a mapping data record 2008 for its own database mapping information which contains the local 2009 EID-prefixes and RLOCs for its site. 2011 When an ETR receives a Map-Request message with the probe-bit set, it 2012 returns a Map-Reply with the probe-bit set. The source address of 2013 the Map-Reply is set from the destination address of the Map-Request 2014 and the destination address of the Map-Reply is set from the source 2015 address of the Map-Request. The Map-Reply SHOULD contain mapping 2016 data for the EID-prefix contained in the Map-Request. This provides 2017 the opportunity for the ITR or PTR, which sent the RLOC-probe to get 2018 mapping updates if there were changes to the ETR's database mapping 2019 entries. 2021 There are advantages and disadvantages of RLOC Probing. The greatest 2022 benefit of RLOC Probing is that it can handle many failure scenarios 2023 allowing the ITR to determine when the path to a specific locator is 2024 reachable or has become unreachable, thus providing a robust 2025 mechanism for switching to using another locator from the cached 2026 locator. RLOC Probing can also provide rough RTT estimates between a 2027 pair of locators which can be useful for network management purposes 2028 as well as for selecting low delay paths. The major disadvantage of 2029 RLOC Probing is in the number of control messages required and the 2030 amount of bandwidth used to obtain those benefits, especially if the 2031 requirement for failure detection times are very small. 2033 Continued research and testing will attempt to characterize the 2034 tradeoffs of failure detection times versus message overhead. 2036 6.4. EID Reachability within a LISP Site 2038 A site may be multihomed using two or more ETRs. The hosts and 2039 infrastructure within a site will be addressed using one or more EID 2040 prefixes that are mapped to the RLOCs of the relevant ETRs in the 2041 mapping system. One possible failure mode is for an ETR to lose 2042 reachability to one or more of the EID prefixes within its own site. 2043 When this occurs when the ETR sends Map-Replies, it can clear the 2044 R-bit associated with its own locator. And when the ETR is also an 2045 ITR, it can clear its locator-status-bit in the encapsulation data 2046 header. 2048 6.5. Routing Locator Hashing 2050 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to 2051 a requesting ITR, the locator-set for the EID-prefix may contain 2052 different priority values for each locator address. When more than 2053 one best priority locator exists, the ITR can decide how to load 2054 share traffic against the corresponding locators. 2056 The following hash algorithm may be used by an ITR to select a 2057 locator for a packet destined to an EID for the EID-to-RLOC mapping: 2059 1. Either a source and destination address hash can be used or the 2060 traditional 5-tuple hash which includes the source and 2061 destination addresses, source and destination TCP, UDP, or SCTP 2062 port numbers and the IP protocol number field or IPv6 next- 2063 protocol fields of a packet a host originates from within a LISP 2064 site. When a packet is not a TCP, UDP, or SCTP packet, the 2065 source and destination addresses only from the header are used to 2066 compute the hash. 2068 2. Take the hash value and divide it by the number of locators 2069 stored in the locator-set for the EID-to-RLOC mapping. 2071 3. The remainder will be yield a value of 0 to "number of locators 2072 minus 1". Use the remainder to select the locator in the 2073 locator-set. 2075 Note that when a packet is LISP encapsulated, the source port number 2076 in the outer UDP header needs to be set. Selecting a hashed value 2077 allows core routers which are attached to Link Aggregation Groups 2078 (LAGs) to load-split the encapsulated packets across member links of 2079 such LAGs. Otherwise, core routers would see a single flow, since 2080 packets have a source address of the ITR, for packets which are 2081 originated by different EIDs at the source site. A suggested setting 2082 for the source port number computed by an ITR is a 5-tuple hash 2083 function on the inner header, as described above. 2085 Many core router implementations use a 5-tuple hash to decide how to 2086 balance packet load across members of a LAG. The 5-tuple hash 2087 includes the source and destination addresses of the packet and the 2088 source and destination ports when the protocol number in the packet 2089 is TCP or UDP. For this reason, UDP encoding is used for LISP 2090 encapsulation. 2092 6.6. Changing the Contents of EID-to-RLOC Mappings 2094 Since the LISP architecture uses a caching scheme to retrieve and 2095 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 2096 date mapping is to re-request the mapping. However, the ITRs do not 2097 know when the mappings change and the ETRs do not keep track of which 2098 ITRs requested its mappings. For scalability reasons, we want to 2099 maintain this approach but need to provide a way for ETRs change 2100 their mappings and inform the sites that are currently communicating 2101 with the ETR site using such mappings. 2103 When a locator record is added to the end of a locator-set, it is 2104 easy to update mappings. We assume new mappings will maintain the 2105 same locator ordering as the old mapping but just have new locators 2106 appended to the end of the list. So some ITRs can have a new mapping 2107 while other ITRs have only an old mapping that is used until they 2108 time out. When an ITR has only an old mapping but detects bits set 2109 in the loc-status-bits that correspond to locators beyond the list it 2110 has cached, it simply ignores them. However, this can only happen 2111 for locator addresses that are lexicographically greater than the 2112 locator addresses in the existing locator-set. 2114 When a locator record is inserted in the middle of a locator-set, to 2115 maintain lexiographic order, the SMR procedure in Section 6.6.2 is 2116 used to inform ITRs and PTRs of the new locator-status-bit mappings. 2118 When a locator record is removed from a locator-set, ITRs that have 2119 the mapping cached will not use the removed locator because the xTRs 2120 will set the loc-status-bit to 0. So even if the locator is in the 2121 list, it will not be used. For new mapping requests, the xTRs can 2122 set the locator AFI to 0 (indicating an unspecified address), as well 2123 as setting the corresponding loc-status-bit to 0. This forces ITRs 2124 with old or new mappings to avoid using the removed locator. 2126 If many changes occur to a mapping over a long period of time, one 2127 will find empty record slots in the middle of the locator-set and new 2128 records appended to the locator-set. At some point, it would be 2129 useful to compact the locator-set so the loc-status-bit settings can 2130 be efficiently packed. 2132 We propose here three approaches for locator-set compaction, one 2133 operational and two protocol mechanisms. The operational approach 2134 uses a clock sweep method. The protocol approaches use the concept 2135 of Solicit-Map-Requests and Map-Versioning. 2137 6.6.1. Clock Sweep 2139 The clock sweep approach uses planning in advance and the use of 2140 count-down TTLs to time out mappings that have already been cached. 2141 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So 2142 there is a 24 hour window to time out old mappings. The following 2143 clock sweep procedure is used: 2145 1. 24 hours before a mapping change is to take effect, a network 2146 administrator configures the ETRs at a site to start the clock 2147 sweep window. 2149 2. During the clock sweep window, ETRs continue to send Map-Reply 2150 messages with the current (unchanged) mapping records. The TTL 2151 for these mappings is set to 1 hour. 2153 3. 24 hours later, all previous cache entries will have timed out, 2154 and any active cache entries will time out within 1 hour. During 2155 this 1 hour window the ETRs continue to send Map-Reply messages 2156 with the current (unchanged) mapping records with the TTL set to 2157 1 minute. 2159 4. At the end of the 1 hour window, the ETRs will send Map-Reply 2160 messages with the new (changed) mapping records. So any active 2161 caches can get the new mapping contents right away if not cached, 2162 or in 1 minute if they had the mapping cached. The new mappings 2163 are cached with a time to live equal to the TTL in the Map-Reply. 2165 6.6.2. Solicit-Map-Request (SMR) 2167 Soliciting a Map-Request is a selective way for ETRs, at the site 2168 where mappings change, to control the rate they receive requests for 2169 Map-Reply messages. SMRs are also used to tell remote ITRs to update 2170 the mappings they have cached. 2172 Since the ETRs don't keep track of remote ITRs that have cached their 2173 mappings, they do not know which ITRs need to have their mappings 2174 updated. As a result, an ETR will solicit Map-Requests (called an 2175 SMR message) from those sites to which it has been sending 2176 encapsulated data to for the last minute. In particular, an ETR will 2177 send an SMR an ITR to which it has recently sent encapsulated data. 2179 An SMR message is simply a bit set in a Map-Request message. An ITR 2180 or PTR will send a Map-Request when they receive an SMR message. 2181 Both the SMR sender and the Map-Request responder MUST rate-limited 2182 these messages. Rate-limiting can be implemented as a global rate- 2183 limiter or one rate-limiter per SMR destination. 2185 The following procedure shows how a SMR exchange occurs when a site 2186 is doing locator-set compaction for an EID-to-RLOC mapping: 2188 1. When the database mappings in an ETR change, the ETRs at the site 2189 begin to send Map-Requests with the SMR bit set for each locator 2190 in each map-cache entry the ETR caches. 2192 2. A remote ITR which receives the SMR message will schedule sending 2193 a Map-Request message to the source locator address of the SMR 2194 message or to the mapping database system. A newly allocated 2195 random nonce is selected and the EID-prefix used is the one 2196 copied from the SMR message. If the source locator is the only 2197 locator in the cached locator-set, the remote ITR SHOULD send a 2198 Map-Request to the database mapping system just in case the 2199 single locator has changed and may no longer be reachable to 2200 accept the Map-Request. 2202 3. The remote ITR MUST rate-limit the Map-Request until it gets a 2203 Map-Reply while continuing to use the cached mapping. When Map 2204 Versioning is used, described in Section 6.6.3, an SMR sender can 2205 detect if an ITR is using the most up to date database mapping. 2207 4. The ETRs at the site with the changed mapping will reply to the 2208 Map-Request with a Map-Reply message that has a nonce from the 2209 SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate 2210 limited. This is important to avoid Map-Reply implosion. 2212 5. The ETRs, at the site with the changed mapping, record the fact 2213 that the site that sent the Map-Request has received the new 2214 mapping data in the mapping cache entry for the remote site so 2215 the loc-status-bits are reflective of the new mapping for packets 2216 going to the remote site. The ETR then stops sending SMR 2217 messages. 2219 For security reasons an ITR MUST NOT process unsolicited Map-Replies. 2220 To avoid map-cache entry corruption by a third-party, a sender of an 2221 SMR-based Map-Request MUST be verified. If an ITR receives an SMR- 2222 based Map-Request and the source is not in the locator-set for the 2223 stored map-cache entry, then the responding Map-Request MUST be sent 2224 with an EID destination to the mapping database system. Since the 2225 mapping database system is more secure to reach an authoritative ETR, 2226 it will deliver the Map-Request to the authoritative source of the 2227 mapping data. 2229 When an ITR receives an SMR-based Map-Request for which it does not 2230 have a cached mapping for the EID in the SMR message, it MAY not send 2231 a SMR-invoked Map-Request. This scenario can occur when an ETR sends 2232 SMR messages to all locators in the locator-set it has stored in its 2233 map-cache but the remote ITRs that receive the SMR may not be sending 2234 packets to the site. There is no point in updating the ITRs until 2235 they need to send, in which case, they will send Map-Requests to 2236 obtain a map-cache entry. 2238 6.6.3. Database Map Versioning 2240 When there is unidirectional packet flow between an ITR and ETR, and 2241 the EID-to-RLOC mappings change on the ETR, it needs to inform the 2242 ITR so encapsulation can stop to a removed locator and start to a new 2243 locator in the locator-set. 2245 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 2246 number. This is known as the Destination Map-Version Number. ITRs 2247 include the Destination Map-Version Number in packets they 2248 encapsulate to the site. When an ETR decapsulates a packet and 2249 detects the Destination Map-Version Number is less than the current 2250 version for its mapping, the SMR procedure described in Section 6.6.2 2251 occurs. 2253 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 2254 Version number. This is known as the Source Map-Version Number. 2255 When an ETR decapsulates a packet and detects the Source Map-Version 2256 Number is greater than the last Map-Version Number sent in a Map- 2257 Reply from the ITR's site, the ETR will send a Map-Request to one of 2258 the ETRs for the source site. 2260 A Map-Version Number is used as a sequence number per EID-prefix. So 2261 values that are greater, are considered to be more recent. A value 2262 of 0 for the Source Map-Version Number or the Destination Map-Version 2263 Number conveys no versioning information and an ITR does no 2264 comparison with previously received Map-Version Numbers. 2266 A Map-Version Number can be included in Map-Register messages as 2267 well. This is a good way for the Map-Server can assure that all ETRs 2268 for a site registering to it will be Map-Version number synchronized. 2270 See [VERSIONING] for a more detailed analysis and description of 2271 Database Map Versioning. 2273 7. Router Performance Considerations 2275 LISP is designed to be very hardware-based forwarding friendly. A 2276 few implementation techniques can be used to incrementally implement 2277 LISP: 2279 o When a tunnel encapsulated packet is received by an ETR, the outer 2280 destination address may not be the address of the router. This 2281 makes it challenging for the control plane to get packets from the 2282 hardware. This may be mitigated by creating special FIB entries 2283 for the EID-prefixes of EIDs served by the ETR (those for which 2284 the router provides an RLOC translation). These FIB entries are 2285 marked with a flag indicating that control plane processing should 2286 be performed. The forwarding logic of testing for particular IP 2287 protocol number value is not necessary. There are a few proven 2288 cases where no changes to existing deployed hardware were needed 2289 to support the LISP data-plane. 2291 o On an ITR, prepending a new IP header consists of adding more 2292 bytes to a MAC rewrite string and prepending the string as part of 2293 the outgoing encapsulation procedure. Routers that support GRE 2294 tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already 2295 support this action. 2297 o A packet's source address or interface the packet was received on 2298 can be used to select a VRF (Virtual Routing/Forwarding). The 2299 VRF's routing table can be used to find EID-to-RLOC mappings. 2301 8. Deployment Scenarios 2303 This section will explore how and where ITRs and ETRs can be deployed 2304 and will discuss the pros and cons of each deployment scenario. For 2305 a more detailed deployment recommendation, refer to [LISP-DEPLOY]. 2307 There are two basic deployment trade-offs to consider: centralized 2308 versus distributed caches and flat, recursive, or re-encapsulating 2309 tunneling. When deciding on centralized versus distributed caching, 2310 the following issues should be considered: 2312 o Are the tunnel routers spread out so that the caches are spread 2313 across all the memories of each router? 2315 o Should management "touch points" be minimized by choosing few 2316 tunnel routers, just enough for redundancy? 2318 o In general, using more ITRs doesn't increase management load, 2319 since caches are built and stored dynamically. On the other hand, 2320 more ETRs does require more management since EID-prefix-to-RLOC 2321 mappings need to be explicitly configured. 2323 When deciding on flat, recursive, or re-encapsulation tunneling, the 2324 following issues should be considered: 2326 o Flat tunneling implements a single tunnel between source site and 2327 destination site. This generally offers better paths between 2328 sources and destinations with a single tunnel path. 2330 o Recursive tunneling is when tunneled traffic is again further 2331 encapsulated in another tunnel, either to implement VPNs or to 2332 perform Traffic Engineering. When doing VPN-based tunneling, the 2333 site has some control since the site is prepending a new tunnel 2334 header. In the case of TE-based tunneling, the site may have 2335 control if it is prepending a new tunnel header, but if the site's 2336 ISP is doing the TE, then the site has no control. Recursive 2337 tunneling generally will result in suboptimal paths but at the 2338 benefit of steering traffic to resource available parts of the 2339 network. 2341 o The technique of re-encapsulation ensures that packets only 2342 require one tunnel header. So if a packet needs to be rerouted, 2343 it is first decapsulated by the ETR and then re-encapsulated with 2344 a new tunnel header using a new RLOC. 2346 The next sub-sections will survey where tunnel routers can reside in 2347 the network. 2349 8.1. First-hop/Last-hop Tunnel Routers 2351 By locating tunnel routers close to hosts, the EID-prefix set is at 2352 the granularity of an IP subnet. So at the expense of more EID- 2353 prefix-to-RLOC sets for the site, the caches in each tunnel router 2354 can remain relatively small. But caches always depend on the number 2355 of non-aggregated EID destination flows active through these tunnel 2356 routers. 2358 With more tunnel routers doing encapsulation, the increase in control 2359 traffic grows as well: since the EID-granularity is greater, more 2360 Map-Requests and Map-Replies are traveling between more routers. 2362 The advantage of placing the caches and databases at these stub 2363 routers is that the products deployed in this part of the network 2364 have better price-memory ratios then their core router counterparts. 2365 Memory is typically less expensive in these devices and fewer routes 2366 are stored (only IGP routes). These devices tend to have excess 2367 capacity, both for forwarding and routing state. 2369 LISP functionality can also be deployed in edge switches. These 2370 devices generally have layer-2 ports facing hosts and layer-3 ports 2371 facing the Internet. Spare capacity is also often available in these 2372 devices as well. 2374 8.2. Border/Edge Tunnel Routers 2376 Using customer-edge (CE) routers for tunnel endpoints allows the EID 2377 space associated with a site to be reachable via a small set of RLOCs 2378 assigned to the CE routers for that site. This is the default 2379 behavior envisioned in the rest of this specification. 2381 This offers the opposite benefit of the first-hop/last-hop tunnel 2382 router scenario: the number of mapping entries and network management 2383 touch points are reduced, allowing better scaling. 2385 One disadvantage is that less of the network's resources are used to 2386 reach host endpoints thereby centralizing the point-of-failure domain 2387 and creating network choke points at the CE router. 2389 Note that more than one CE router at a site can be configured with 2390 the same IP address. In this case an RLOC is an anycast address. 2391 This allows resilience between the CE routers. That is, if a CE 2392 router fails, traffic is automatically routed to the other routers 2393 using the same anycast address. However, this comes with the 2394 disadvantage where the site cannot control the entrance point when 2395 the anycast route is advertised out from all border routers. Another 2396 disadvantage of using anycast locators is the limited advertisement 2397 scope of /32 (or /128 for IPv6) routes. 2399 8.3. ISP Provider-Edge (PE) Tunnel Routers 2401 Use of ISP PE routers as tunnel endpoint routers is not the typical 2402 deployment scenario envisioned in the specification. This section 2403 attempts to capture some of reasoning behind this preference of 2404 implementing LISP on CE routers. 2406 Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather 2407 than a site, control over the location of the egress tunnel 2408 endpoints. That is, the ISP can decide if the tunnel endpoints are 2409 in the destination site (in either CE routers or last-hop routers 2410 within a site) or at other PE edges. The advantage of this case is 2411 that two tunnel headers can be avoided. By having the PE be the 2412 first router on the path to encapsulate, it can choose a TE path 2413 first, and the ETR can decapsulate and re-encapsulate for a tunnel to 2414 the destination end site. 2416 An obvious disadvantage is that the end site has no control over 2417 where its packets flow or the RLOCs used. Other disadvantages 2418 include the difficulty in synchronizing path liveness updates between 2419 CE and PE routers. 2421 As mentioned in earlier sections a combination of these scenarios is 2422 possible at the expense of extra packet header overhead, if both site 2423 and provider want control, then recursive or re-encapsulating tunnels 2424 are used. 2426 8.4. LISP Functionality with Conventional NATs 2428 LISP routers can be deployed behind Network Address Translator (NAT) 2429 devices to provide the same set of packet services hosts have today 2430 when they are addressed out of private address space. 2432 It is important to note that a locator address in any LISP control 2433 message MUST be a globally routable address and therefore SHOULD NOT 2434 contain [RFC1918] addresses. If a LISP router is configured with 2435 private addresses, they MUST be used only in the outer IP header so 2436 the NAT device can translate properly. Otherwise, EID addresses MUST 2437 be translated before encapsulation is performed. Both NAT 2438 translation and LISP encapsulation functions could be co-located in 2439 the same device. 2441 More details on LISP address translation can be found in [INTERWORK]. 2443 9. Traceroute Considerations 2445 When a source host in a LISP site initiates a traceroute to a 2446 destination host in another LISP site, it is highly desirable for it 2447 to see the entire path. Since packets are encapsulated from ITR to 2448 ETR, the hop across the tunnel could be viewed as a single hop. 2449 However, LISP traceroute will provide the entire path so the user can 2450 see 3 distinct segments of the path from a source LISP host to a 2451 destination LISP host: 2453 Segment 1 (in source LISP site based on EIDs): 2455 source-host ---> first-hop ... next-hop ---> ITR 2457 Segment 2 (in the core network based on RLOCs): 2459 ITR ---> next-hop ... next-hop ---> ETR 2461 Segment 3 (in the destination LISP site based on EIDs): 2463 ETR ---> next-hop ... last-hop ---> destination-host 2465 For segment 1 of the path, ICMP Time Exceeded messages are returned 2466 in the normal matter as they are today. The ITR performs a TTL 2467 decrement and test for 0 before encapsulating. So the ITR hop is 2468 seen by the traceroute source has an EID address (the address of 2469 site-facing interface). 2471 For segment 2 of the path, ICMP Time Exceeded messages are returned 2472 to the ITR because the TTL decrement to 0 is done on the outer 2473 header, so the destination of the ICMP messages are to the ITR RLOC 2474 address, the source RLOC address of the encapsulated traceroute 2475 packet. The ITR looks inside of the ICMP payload to inspect the 2476 traceroute source so it can return the ICMP message to the address of 2477 the traceroute client as well as retaining the core router IP address 2478 in the ICMP message. This is so the traceroute client can display 2479 the core router address (the RLOC address) in the traceroute output. 2480 The ETR returns its RLOC address and responds to the TTL decrement to 2481 0 like the previous core routers did. 2483 For segment 3, the next-hop router downstream from the ETR will be 2484 decrementing the TTL for the packet that was encapsulated, sent into 2485 the core, decapsulated by the ETR, and forwarded because it isn't the 2486 final destination. If the TTL is decremented to 0, any router on the 2487 path to the destination of the traceroute, including the next-hop 2488 router or destination, will send an ICMP Time Exceeded message to the 2489 source EID of the traceroute client. The ICMP message will be 2490 encapsulated by the local ITR and sent back to the ETR in the 2491 originated traceroute source site, where the packet will be delivered 2492 to the host. 2494 9.1. IPv6 Traceroute 2496 IPv6 traceroute follows the procedure described above since the 2497 entire traceroute data packet is included in ICMP Time Exceeded 2498 message payload. Therefore, only the ITR needs to pay special 2499 attention for forwarding ICMP messages back to the traceroute source. 2501 9.2. IPv4 Traceroute 2503 For IPv4 traceroute, we cannot follow the above procedure since IPv4 2504 ICMP Time Exceeded messages only include the invoking IP header and 8 2505 bytes that follow the IP header. Therefore, when a core router sends 2506 an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP 2507 payload is the encapsulated header it prepended followed by a UDP 2508 header. The original invoking IP header, and therefore the identity 2509 of the traceroute source is lost. 2511 The solution we propose to solve this problem is to cache traceroute 2512 IPv4 headers in the ITR and to match them up with corresponding IPv4 2513 Time Exceeded messages received from core routers and the ETR. The 2514 ITR will use a circular buffer for caching the IPv4 and UDP headers 2515 of traceroute packets. It will select a 16-bit number as a key to 2516 find them later when the IPv4 Time Exceeded messages are received. 2517 When an ITR encapsulates an IPv4 traceroute packet, it will use the 2518 16-bit number as the UDP source port in the encapsulating header. 2519 When the ICMP Time Exceeded message is returned to the ITR, the UDP 2520 header of the encapsulating header is present in the ICMP payload 2521 thereby allowing the ITR to find the cached headers for the 2522 traceroute source. The ITR puts the cached headers in the payload 2523 and sends the ICMP Time Exceeded message to the traceroute source 2524 retaining the source address of the original ICMP Time Exceeded 2525 message (a core router or the ETR of the site of the traceroute 2526 destination). 2528 The signature of a traceroute packet comes in two forms. The first 2529 form is encoded as a UDP message where the destination port is 2530 inspected for a range of values. The second form is encoded as an 2531 ICMP message where the IP identification field is inspected for a 2532 well-known value. 2534 9.3. Traceroute using Mixed Locators 2536 When either an IPv4 traceroute or IPv6 traceroute is originated and 2537 the ITR encapsulates it in the other address family header, you 2538 cannot get all 3 segments of the traceroute. Segment 2 of the 2539 traceroute can not be conveyed to the traceroute source since it is 2540 expecting addresses from intermediate hops in the same address format 2541 for the type of traceroute it originated. Therefore, in this case, 2542 segment 2 will make the tunnel look like one hop. All the ITR has to 2543 do to make this work is to not copy the inner TTL to the outer, 2544 encapsulating header's TTL when a traceroute packet is encapsulated 2545 using an RLOC from a different address family. This will cause no 2546 TTL decrement to 0 to occur in core routers between the ITR and ETR. 2548 10. Mobility Considerations 2550 There are several kinds of mobility of which only some might be of 2551 concern to LISP. Essentially they are as follows. 2553 10.1. Site Mobility 2555 A site wishes to change its attachment points to the Internet, and 2556 its LISP Tunnel Routers will have new RLOCs when it changes upstream 2557 providers. Changes in EID-RLOC mappings for sites are expected to be 2558 handled by configuration, outside of the LISP protocol. 2560 10.2. Slow Endpoint Mobility 2562 An individual endpoint wishes to move, but is not concerned about 2563 maintaining session continuity. Renumbering is involved. LISP can 2564 help with the issues surrounding renumbering [RFC4192] [LISA96] by 2565 decoupling the address space used by a site from the address spaces 2566 used by its ISPs. [RFC4984] 2568 10.3. Fast Endpoint Mobility 2570 Fast endpoint mobility occurs when an endpoint moves relatively 2571 rapidly, changing its IP layer network attachment point. Maintenance 2572 of session continuity is a goal. This is where the Mobile IPv4 2573 [RFC3344bis] and Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used, 2574 and primarily where interactions with LISP need to be explored. 2576 The problem is that as an endpoint moves, it may require changes to 2577 the mapping between its EID and a set of RLOCs for its new network 2578 location. When this is added to the overhead of mobile IP binding 2579 updates, some packets might be delayed or dropped. 2581 In IPv4 mobility, when an endpoint is away from home, packets to it 2582 are encapsulated and forwarded via a home agent which resides in the 2583 home area the endpoint's address belongs to. The home agent will 2584 encapsulate and forward packets either directly to the endpoint or to 2585 a foreign agent which resides where the endpoint has moved to. 2586 Packets from the endpoint may be sent directly to the correspondent 2587 node, may be sent via the foreign agent, or may be reverse-tunneled 2588 back to the home agent for delivery to the mobile node. As the 2589 mobile node's EID or available RLOC changes, LISP EID-to-RLOC 2590 mappings are required for communication between the mobile node and 2591 the home agent, whether via foreign agent or not. As a mobile 2592 endpoint changes networks, up to three LISP mapping changes may be 2593 required: 2595 o The mobile node moves from an old location to a new visited 2596 network location and notifies its home agent that it has done so. 2597 The Mobile IPv4 control packets the mobile node sends pass through 2598 one of the new visited network's ITRs, which needs a EID-RLOC 2599 mapping for the home agent. 2601 o The home agent might not have the EID-RLOC mappings for the mobile 2602 node's "care-of" address or its foreign agent in the new visited 2603 network, in which case it will need to acquire them. 2605 o When packets are sent directly to the correspondent node, it may 2606 be that no traffic has been sent from the new visited network to 2607 the correspondent node's network, and the new visited network's 2608 ITR will need to obtain an EID-RLOC mapping for the correspondent 2609 node's site. 2611 In addition, if the IPv4 endpoint is sending packets from the new 2612 visited network using its original EID, then LISP will need to 2613 perform a route-returnability check on the new EID-RLOC mapping for 2614 that EID. 2616 In IPv6 mobility, packets can flow directly between the mobile node 2617 and the correspondent node in either direction. The mobile node uses 2618 its "care-of" address (EID). In this case, the route-returnability 2619 check would not be needed but one more LISP mapping lookup may be 2620 required instead: 2622 o As above, three mapping changes may be needed for the mobile node 2623 to communicate with its home agent and to send packets to the 2624 correspondent node. 2626 o In addition, another mapping will be needed in the correspondent 2627 node's ITR, in order for the correspondent node to send packets to 2628 the mobile node's "care-of" address (EID) at the new network 2629 location. 2631 When both endpoints are mobile the number of potential mapping 2632 lookups increases accordingly. 2634 As a mobile node moves there are not only mobility state changes in 2635 the mobile node, correspondent node, and home agent, but also state 2636 changes in the ITRs and ETRs for at least some EID-prefixes. 2638 The goal is to support rapid adaptation, with little delay or packet 2639 loss for the entire system. Also IP mobility can be modified to 2640 require fewer mapping changes. In order to increase overall system 2641 performance, there may be a need to reduce the optimization of one 2642 area in order to place fewer demands on another. 2644 In LISP, one possibility is to "glean" information. When a packet 2645 arrives, the ETR could examine the EID-RLOC mapping and use that 2646 mapping for all outgoing traffic to that EID. It can do this after 2647 performing a route-returnability check, to ensure that the new 2648 network location does have a internal route to that endpoint. 2649 However, this does not cover the case where an ITR (the node assigned 2650 the RLOC) at the mobile-node location has been compromised. 2652 Mobile IP packet exchange is designed for an environment in which all 2653 routing information is disseminated before packets can be forwarded. 2654 In order to allow the Internet to grow to support expected future 2655 use, we are moving to an environment where some information may have 2656 to be obtained after packets are in flight. Modifications to IP 2657 mobility should be considered in order to optimize the behavior of 2658 the overall system. Anything which decreases the number of new EID- 2659 RLOC mappings needed when a node moves, or maintains the validity of 2660 an EID-RLOC mapping for a longer time, is useful. 2662 10.4. Fast Network Mobility 2664 In addition to endpoints, a network can be mobile, possibly changing 2665 xTRs. A "network" can be as small as a single router and as large as 2666 a whole site. This is different from site mobility in that it is 2667 fast and possibly short-lived, but different from endpoint mobility 2668 in that a whole prefix is changing RLOCs. However, the mechanisms 2669 are the same and there is no new overhead in LISP. A map request for 2670 any endpoint will return a binding for the entire mobile prefix. 2672 If mobile networks become a more common occurrence, it may be useful 2673 to revisit the design of the mapping service and allow for dynamic 2674 updates of the database. 2676 The issue of interactions between mobility and LISP needs to be 2677 explored further. Specific improvements to the entire system will 2678 depend on the details of mapping mechanisms. Mapping mechanisms 2679 should be evaluated on how well they support session continuity for 2680 mobile nodes. 2682 10.5. LISP Mobile Node Mobility 2684 A mobile device can use the LISP infrastructure to achieve mobility 2685 by implementing the LISP encapsulation and decapsulation functions 2686 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 2687 node" can use topologically-independent EID IP addresses that are not 2688 advertised into and do not impose a cost on the global routing 2689 system. These EIDs are maintained at the edges of the mapping system 2690 (in LISP Map-Servers and Map-Resolvers) and are provided on demand to 2691 only the correspondents of the LISP mobile node. 2693 Refer to the LISP Mobility Architecture specification [LISP-MN] for 2694 more details. 2696 11. Multicast Considerations 2698 A multicast group address, as defined in the original Internet 2699 architecture is an identifier of a grouping of topologically 2700 independent receiver host locations. The address encoding itself 2701 does not determine the location of the receiver(s). The multicast 2702 routing protocol, and the network-based state the protocol creates, 2703 determines where the receivers are located. 2705 In the context of LISP, a multicast group address is both an EID and 2706 a Routing Locator. Therefore, no specific semantic or action needs 2707 to be taken for a destination address, as it would appear in an IP 2708 header. Therefore, a group address that appears in an inner IP 2709 header built by a source host will be used as the destination EID. 2710 The outer IP header (the destination Routing Locator address), 2711 prepended by a LISP router, will use the same group address as the 2712 destination Routing Locator. 2714 Having said that, only the source EID and source Routing Locator 2715 needs to be dealt with. Therefore, an ITR merely needs to put its 2716 own IP address in the source Routing Locator field when prepending 2717 the outer IP header. This source Routing Locator address, like any 2718 other Routing Locator address MUST be globally routable. 2720 Therefore, an EID-to-RLOC mapping does not need to be performed by an 2721 ITR when a received data packet is a multicast data packet or when 2722 processing a source-specific Join (either by IGMPv3 or PIM). But the 2723 source Routing Locator is decided by the multicast routing protocol 2724 in a receiver site. That is, an EID to Routing Locator translation 2725 is done at control-time. 2727 Another approach is to have the ITR not encapsulate a multicast 2728 packet and allow the host built packet to flow into the core even if 2729 the source address is allocated out of the EID namespace. If the 2730 RPF-Vector TLV [RFC5496] is used by PIM in the core, then core 2731 routers can RPF to the ITR (the Locator address which is injected 2732 into core routing) rather than the host source address (the EID 2733 address which is not injected into core routing). 2735 To avoid any EID-based multicast state in the network core, the first 2736 approach is chosen for LISP-Multicast. Details for LISP-Multicast 2737 and Interworking with non-LISP sites is described in specification 2738 [MLISP]. 2740 12. Security Considerations 2742 It is believed that most of the security mechanisms will be part of 2743 the mapping database service when using control plane procedures for 2744 obtaining EID-to-RLOC mappings. For data plane triggered mappings, 2745 as described in this specification, protection is provided against 2746 ETR spoofing by using Return- Routability mechanisms evidenced by the 2747 use of a 24-bit Nonce field in the LISP encapsulation header and a 2748 64-bit Nonce field in the LISP control message. The nonce, coupled 2749 with the ITR accepting only solicited Map-Replies goes a long way 2750 toward providing decent authentication. 2752 LISP does not rely on a PKI infrastructure or a more heavy weight 2753 authentication system. These systems challenge the scalability of 2754 LISP which was a primary design goal. 2756 DoS attack prevention will depend on implementations rate-limiting 2757 Map-Requests and Map-Replies to the control plane as well as rate- 2758 limiting the number of data-triggered Map-Replies. 2760 To deal with map-cache exhaustion attempts in an ITR/PTR, the 2761 implementation should consider putting a maximum cap on the number of 2762 entries stored with a reserve list for special or frequently accessed 2763 sites. This should be a configuration policy control set by the 2764 network administrator who manages ITRs and PTRs. 2766 Given that the ITR/PTR maintains a cache of EID-to-RLOC mappings, 2767 cache sizing and maintenance is an issue to be kept in mind during 2768 implementation. It is a good idea to have instrumentation in place 2769 to detect thrashing of the cache. Implementation experimentation 2770 will be used to determine which cache management strategies work 2771 best. 2773 There is a potential security risk implicit in the fact that ETRs 2774 generate the EID prefix to which they are responding. In theory, an 2775 ETR can claim a shorter prefix than it is actually responsible for. 2776 Various mechanisms to ameliorate or resolve this issue will be 2777 examined in the future, [LISP-SEC]. 2779 13. Network Management Considerations 2781 Considerations for Network Management tools exist so the LISP 2782 protocol suite can be operationally managed. The mechanisms can be 2783 found in [LISP-MIB] and [LISP-LIG]. 2785 14. IANA Considerations 2787 This section provides guidance to the Internet Assigned Numbers 2788 Authority (IANA) regarding registration of values related to the LISP 2789 specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. 2791 There are two name spaces in LISP that require registration: 2793 o LISP IANA registry allocations should not be made for purposes 2794 unrelated to LISP routing or transport protocols. 2796 o The following policies are used here with the meanings defined in 2797 BCP 26: "Specification Required", "IETF Consensus", "Experimental 2798 Use", "First Come First Served". 2800 14.1. LISP Address Type Codes 2802 Instance ID type codes have a range from 0 to 15, of which 0 and 1 2803 have been allocated [LCAF]. New Type Codes MUST be allocated 2804 starting at 2. Type Codes 2 - 10 are to be assigned by IETF Review. 2805 Type Codes 11 - 15 are available on a First Come First Served policy. 2807 The following codes have been allocated: 2809 Type 0: Null Body Type 2811 Type 1: AFI List Type 2813 See [LCAF] for details for other possible unapproved address 2814 encodings. The unapproved LCAF encodings are an area for further 2815 study and experimentation. 2817 14.2. LISP UDP Port Numbers 2819 The IANA registry has allocated UDP port numbers 4341 and 4342 for 2820 LISP data-plane and control-plane operation, respectively. 2822 15. References 2824 15.1. Normative References 2826 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 2827 August 1980. 2829 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 2830 STD 13, RFC 1034, November 1987. 2832 [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700, 2833 October 1994. 2835 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 2836 E. Lear, "Address Allocation for Private Internets", 2837 BCP 5, RFC 1918, February 1996. 2839 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2840 Requirement Levels", BCP 14, RFC 2119, March 1997. 2842 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within 2843 ESP and AH", RFC 2404, November 1998. 2845 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 2846 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 2847 March 2000. 2849 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 2850 via IPv4 Clouds", RFC 3056, February 2001. 2852 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 2853 of Explicit Congestion Notification (ECN) to IP", 2854 RFC 3168, September 2001. 2856 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 2857 A., Peterson, J., Sparks, R., Handley, M., and E. 2858 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 2859 June 2002. 2861 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 2862 in IPv6", RFC 3775, June 2004. 2864 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 2865 Requirements for Security", BCP 106, RFC 4086, June 2005. 2867 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 2868 (CIDR): The Internet Address Assignment and Aggregation 2869 Plan", BCP 122, RFC 4632, August 2006. 2871 [RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 2872 (SHA and HMAC-SHA)", RFC 4634, July 2006. 2874 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 2875 Optimization for Mobile IPv6", RFC 4866, May 2007. 2877 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 2878 Workshop on Routing and Addressing", RFC 4984, 2879 September 2007. 2881 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2882 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2883 May 2008. 2885 [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path 2886 Forwarding (RPF) Vector TLV", RFC 5496, March 2009. 2888 [UDP-TUNNELS] 2889 Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled 2890 Packets"", draft-eubanks-chimento-6man-00.txt (work in 2891 progress), February 2009. 2893 15.2. Informative References 2895 [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY 2896 NUMBERS http://www.iana.org/.../address-family-numbers, 2897 Febuary 2007. 2899 [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP 2900 Alternative Topology (LISP-ALT)", 2901 draft-ietf-lisp-alt-06.txt (work in progress), March 2011. 2903 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed 2904 Enhancement to the Internet Architecture", Internet- 2905 Draft http://www.chiappa.net/~jnc/tech/endpoints.txt, 2906 1999. 2908 [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A 2909 Content distribution Overlay Network Service for LISP", 2910 draft-meyer-lisp-cons-03.txt (work in progress), 2911 November 2007. 2913 [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 2914 Mappings Multicast Across Cooperating Systems for LISP", 2915 draft-curran-lisp-emacs-00.txt (work in progress), 2916 November 2007. 2918 [INTERWORK] 2919 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 2920 "Interworking LISP with IPv4 and IPv6", 2921 draft-ietf-lisp-interworking-02.txt (work in progress), 2922 March 2011. 2924 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 2925 Address Format", draft-farinacci-lisp-lcaf-04.txt (work in 2926 progress), October 2010. 2928 [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, 2929 "Renumbering: Threat or Menace?", Usenix , September 1996. 2931 [LISP-DEPLOY] 2932 Jakab, L., Coras, F., Domingo-Pascual, J., and D. Lewis, 2933 "LISP Network Element Deployment Considerations", 2934 draft-jakab-lisp-deployment-02.txt (work in progress), 2935 February 2011. 2937 [LISP-LIG] 2938 Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)", 2939 draft-ietf-lisp-lig-01.txt (work in progress), 2940 October 2010. 2942 [LISP-MAIN] 2943 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 2944 "Locator/ID Separation Protocol (LISP)", 2945 draft-farinacci-lisp-12.txt (work in progress), 2946 March 2009. 2948 [LISP-MIB] 2949 Schudel, G., Jain, A., and V. Moreno, "LISP MIB", 2950 draft-ietf-lisp-mib-01.txt (work in progress), March 2011. 2952 [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP 2953 Mobility Architecture", draft-meyer-lisp-mn-04.txt (work 2954 in progress), October 2010. 2956 [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", 2957 draft-ietf-lisp-ms-07.txt (work in progress), March 2011. 2959 [LISP-SEC] 2960 Maino, F., Ermagon, V., Cabellos, A., Sausez, D., and O. 2961 Bonaventure, "LISP-Security (LISP-SEC)", 2962 draft-maino-lisp-sec-00.txt (work in progress), 2963 February 2011. 2965 [LOC-ID-ARCH] 2966 Meyer, D. and D. Lewis, "Architectural Implications of 2967 Locator/ID Separation", 2968 draft-meyer-loc-id-implications-01.txt (work in progress), 2969 Januaryr 2009. 2971 [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, 2972 "LISP for Multicast Environments", 2973 draft-ietf-lisp-multicast-04.txt (work in progress), 2974 October 2010. 2976 [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", 2977 draft-lear-lisp-nerd-08.txt (work in progress), 2978 March 2010. 2980 [OPENLISP] 2981 Iannone, L. and O. Bonaventure, "OpenLISP Implementation 2982 Report", draft-iannone-openlisp-implementation-01.txt 2983 (work in progress), July 2008. 2985 [RADIR] Narten, T., "Routing and Addressing Problem Statement", 2986 draft-narten-radir-problem-statement-00.txt (work in 2987 progress), July 2007. 2989 [RFC3344bis] 2990 Perkins, C., "IP Mobility Support for IPv4, revised", 2991 draft-ietf-mip4-rfc3344bis-05 (work in progress), 2992 July 2007. 2994 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 2995 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 2996 September 2005. 2998 [RPMD] Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol 2999 for Routing Protocol Meta-data Dissemination", 3000 draft-handley-p2ppush-unpublished-2007726.txt (work in 3001 progress), July 2007. 3003 [VERSIONING] 3004 Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping 3005 Versioning", draft-ietf-lisp-map-versioning-01.txt (work 3006 in progress), March 2011. 3008 Appendix A. Acknowledgments 3010 An initial thank you goes to Dave Oran for planting the seeds for the 3011 initial ideas for LISP. His consultation continues to provide value 3012 to the LISP authors. 3014 A special and appreciative thank you goes to Noel Chiappa for 3015 providing architectural impetus over the past decades on separation 3016 of location and identity, as well as detailed review of the LISP 3017 architecture and documents, coupled with enthusiasm for making LISP a 3018 practical and incremental transition for the Internet. 3020 The authors would like to gratefully acknowledge many people who have 3021 contributed discussion and ideas to the making of this proposal. 3022 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 3023 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 3024 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 3025 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 3026 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 3027 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 3028 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 3029 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 3030 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 3031 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 3032 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 3033 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 3034 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 3035 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 3036 Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, 3037 and Clarence Filsfils. 3039 This work originated in the Routing Research Group (RRG) of the IRTF. 3040 The individual submission [LISP-MAIN] was converted into this IETF 3041 LISP working group draft. 3043 Appendix B. Document Change Log 3045 B.1. Changes to draft-ietf-lisp-11.txt 3047 o Posted April 2011. 3049 o Change IANA URL. The URL we had pointed to a general protocol 3050 numbers page. 3052 o Added the "s" bit to the Map-Request to allow SMR-invoked Map- 3053 Requests to be sent to a MN ETR via the map-server. 3055 o Generalize text for the defintion of Reencapsuatling tunnels. 3057 o Add pargraph suggested by Joel to explain how implementation 3058 experimentation will be used to determine the proper cache 3059 management techniques. 3061 o Add Yakov provided text for the definition of "EID-to-RLOC 3062 "Database". 3064 o Add reference in Section 8, Deployment Scenarios, to the 3065 draft-jakab-lisp-deploy-02.txt draft. 3067 o Clarify sentence about no hardware changes needed to support LISP 3068 encapsulation. 3070 o Add paragraph about what is the procedure when a locator is 3071 inserted in the middle of a locator-set. 3073 o Add a definition for Locator-Status-Bits so we can emphasize they 3074 are used as a hint for router up/down status and not path 3075 reachability. 3077 o Change "BGP RIB" to "RIB" per Clarence's comment. 3079 o Fixed complaints by IDnits. 3081 o Add paragraph to Security Considerations section indicating how 3082 EID-prefix overclaiming in Map-Replies is for further study and 3083 add a reference to LISP-SEC. 3085 B.2. Changes to draft-ietf-lisp-10.txt 3087 o Posted March 2011. 3089 o Add p-bit to Map-Request so there is documentary reasons to know 3090 when a PITR has sent a Map-Request to an ETR. 3092 o Add Map-Notify message which is used to acknowledge a Map-Register 3093 message sent to a Map-Server. 3095 o Add M-bit to the Map-Register message so an ETR that wants an 3096 acknowledgment for the Map-Register can request one. 3098 o Add S-bit to the ECM and Map-Reply messages to describe security 3099 data that can be present in each message. Then refer to 3100 [LISP-SEC] for expansive details. 3102 o Add Network Management Considerations section and point to the MIB 3103 and LIG drafts. 3105 o Remove the word "simple" per Yakov's comments. 3107 B.3. Changes to draft-ietf-lisp-09.txt 3109 o Posted October 2010. 3111 o Add to IANA Consideration section about the use of LCAF Type 3112 values that accepted and maintained by the IANA registry and not 3113 the LCAF specification. 3115 o Indicate that implementations should be able to receive LISP 3116 control messages when either UDP port is 4342, so they can be 3117 robust in the face of intervening NAT boxes. 3119 o Add paragraph to SMR section to indicate that an ITR does not need 3120 to respond to an SMR-based Map-Request when it has no map-cache 3121 entry for the SMR source's EID-prefix. 3123 B.4. Changes to draft-ietf-lisp-08.txt 3125 o Posted August 2010. 3127 o In section 6.1.6, remove statement about setting TTL to 0 in Map- 3128 Register messages. 3130 o Clarify language in section 6.1.5 about Map-Replying to Data- 3131 Probes or Map-Requests. 3133 o Indicate that outer TTL should only be copied to inner TTL when it 3134 is less than inner TTL. 3136 o Indicate a source-EID for RLOC-probes are encoded with an AFI 3137 value of 0. 3139 o Indicate that SMRs can have a global or per SMR destination rate- 3140 limiter. 3142 o Add clarifications to the SMR procedures. 3144 o Add definitions for "client-side" and 'server-side" terms used in 3145 this specification. 3147 o Clear up language in section 6.4, last paragraph. 3149 o Change ACT of value 0 to "no-action". This is so we can RLOC- 3150 probe a PETR and have it return a Map-Reply with a locator-set of 3151 size 0. The way it is spec'ed the map-cache entry has action 3152 "dropped". Drop-action is set to 3. 3154 o Add statement about normalizing locator weights. 3156 o Clarify R-bit definition in the Map-Reply locator record. 3158 o Add section on EID Reachability within a LISP site. 3160 o Clarify another disadvantage of using anycast locators. 3162 o Reworded Abstract. 3164 o Change section 2.0 Introduction to remove obsolete information 3165 such as the LISP variant definitions. 3167 o Change section 5 title from "Tunneling Details" to "LISP 3168 Encapsulation Details". 3170 o Changes to section 5 to include results of network deployment 3171 experience with MTU. Recommend that implementations use either 3172 the stateful or stateless handling. 3174 o Make clarification wordsmithing to Section 7 and 8. 3176 o Identify that if there is one locator in the locator-set of a map- 3177 cache entry, that an SMR from that locator should be responded to 3178 by sending the the SMR-invoked Map-Request to the database mapping 3179 system rather than to the RLOC itself (which may be unreachable). 3181 o When describing Unicast and Multicast Weights indicate the the 3182 values are relative weights rather than percentages. So it 3183 doesn't imply the sum of all locator weights in the locator-set 3184 need to be 100. 3186 o Do some wordsmithing on copying TTL and TOS fields. 3188 o Numerous wordsmithing changes from Dave Meyer. He fine toothed 3189 combed the spec. 3191 o Removed Section 14 "Prototype Plans and Status". We felt this 3192 type of section is no longer appropriate for a protocol 3193 specification. 3195 o Add clarification text for the IRC description per Damien's 3196 commentary. 3198 o Remove text on copying nonce from SMR to SMR-invoked Map- Request 3199 per Vina's comment about a possible DoS vector. 3201 o Clarify (S/2 + H) in the stateless MTU section. 3203 o Add text to reflect Damien's comment about the description of the 3204 "ITR-RLOC Address" field in the Map-Request. that the list of RLOC 3205 addresses are local addresses of the Map-Requester. 3207 B.5. Changes to draft-ietf-lisp-07.txt 3209 o Posted April 2010. 3211 o Added I-bit to data header so LSB field can also be used as an 3212 Instance ID field. When this occurs, the LSB field is reduced to 3213 8-bits (from 32-bits). 3215 o Added V-bit to the data header so the 24-bit nonce field can also 3216 be used for source and destination version numbers. 3218 o Added Map-Version 12-bit value to the EID-record to be used in all 3219 of Map-Request, Map-Reply, and Map-Register messages. 3221 o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR 3222 can decide what address to select for the destination of a Map- 3223 Reply. 3225 o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to 3226 the Locator-Set record of an EID-record for a Map-Reply message. 3227 The L-bit indicates which RLOCs in the locator-set are local to 3228 the sender of the message. The P-bit indicates which RLOC is the 3229 source of a RLOC-probe Reply (Map-Reply) message. 3231 o Add reference to the LISP Canonical Address Format [LCAF] draft. 3233 o Made editorial and clarification changes based on comments from 3234 Dhirendra Trivedi. 3236 o Added wordsmithing comments from Joel Halpern on DF=1 setting. 3238 o Add John Zwiebel clarification to Echo Nonce Algorithm section 3239 6.3.1. 3241 o Add John Zwiebel comment about expanding on proxy-map-reply bit 3242 for Map-Register messages. 3244 o Add NAT section per Ron Bonica comments. 3246 o Fix IDnits issues per Ron Bonica. 3248 o Added section on Virtualization and Segmentation to explain the 3249 use if the Instance ID field in the data header. 3251 o There are too many P-bits, keep their scope to the packet format 3252 description and refer to them by name every where else in the 3253 spec. 3255 o Scanned all occurrences of "should", "should not", "must" and 3256 "must not" and uppercased them. 3258 o John Zwiebel offered text for section 4.1 to modernize the 3259 example. Thanks Z! 3261 o Make it more clear in the definition of "EID-to-RLOC Database" 3262 that all ETRs need to have the same database mapping. This 3263 reflects a comment from John Scudder. 3265 o Add a definition "Route-returnability" to the Definition of Terms 3266 section. 3268 o In section 9.2, add text to describe what the signature of 3269 traceroute packets can look like. 3271 o Removed references to Data Probe for introductory example. Data- 3272 probes are still part of the LISP design but not encouraged. 3274 o Added the definition for "LISP site" to the Definition of Terms" 3275 section. 3277 B.6. Changes to draft-ietf-lisp-06.txt 3279 Editorial based changes: 3281 o Posted December 2009. 3283 o Fix typo for flags in LISP data header. Changed from "4" to "5". 3285 o Add text to indicate that Map-Register messages must contain a 3286 computed UDP checksum. 3288 o Add definitions for PITR and PETR. 3290 o Indicate an AFI value of 0 is an unspecified address. 3292 o Indicate that the TTL field of a Map-Register is not used and set 3293 to 0 by the sender. This change makes this spec consistent with 3294 [LISP-MS]. 3296 o Change "... yield a packet size of L bytes" to "... yield a packet 3297 size greater than L bytes". 3299 o Clarify section 6.1.5 on what addresses and ports are used in Map- 3300 Reply messages. 3302 o Clarify that LSBs that go beyond the number of locators do not to 3303 be SMRed when the locator addresses are greater lexicographically 3304 than the locator in the existing locator-set. 3306 o Add Gregg, Srini, and Amit to acknowledgment section. 3308 o Clarify in the definition of a LISP header what is following the 3309 UDP header. 3311 o Clarify "verifying Map-Request" text in section 6.1.3. 3313 o Add Xu Xiaohu to the acknowledgment section for introducing the 3314 problem of overlapping EID-prefixes among multiple sites in an RRG 3315 email message. 3317 Design based changes: 3319 o Use stronger language to have the outer IPv4 header set DF=1 so we 3320 can avoid fragment reassembly in an ETR or PETR. This will also 3321 make IPv4 and IPv6 encapsulation have consistent behavior. 3323 o Map-Requests should not be sent in ECM with the Probe bit is set. 3324 These type of Map-Requests are used as RLOC-probes and are sent 3325 directly to locator addresses in the underlying network. 3327 o Add text in section 6.1.5 about returning all EID-prefixes in a 3328 Map-Reply sent by an ETR when there are overlapping EID-prefixes 3329 configure. 3331 o Add text in a new subsection of section 6.1.5 about dealing with 3332 Map-Replies with coarse EID-prefixes. 3334 B.7. Changes to draft-ietf-lisp-05.txt 3336 o Posted September 2009. 3338 o Added this Document Change Log appendix. 3340 o Added section indicating that encapsulated Map-Requests must use 3341 destination UDP port 4342. 3343 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- 3344 data in Map-Register payload. 3346 o Added Jari to acknowledgment section. 3348 o State the source-EID is set to 0 when using Map-Requests to 3349 refresh or RLOC-probe. 3351 o Make more clear what source-RLOC should be for a Map-Request. 3353 o The LISP-CONS authors thought that the Type definitions for CONS 3354 should be removed from this specification. 3356 o Removed nonce from Map-Register message, it wasn't used so no need 3357 for it. 3359 o Clarify what to do for unspecified Action bits for negative Map- 3360 Replies. Since No Action is a drop, make value 0 Drop. 3362 B.8. Changes to draft-ietf-lisp-04.txt 3364 o Posted September 2009. 3366 o How do deal with record count greater than 1 for a Map-Request. 3367 Damien and Joel comment. Joel suggests: 1) Specify that senders 3368 compliant with the current document will always set the count to 3369 1, and note that the count is included for future extensibility. 3370 2) Specify what a receiver compliant with the draft should do if 3371 it receives a request with a count greater than 1. Presumably, it 3372 should send some error back? 3374 o Add Fred Templin in acknowledgment section. 3376 o Add Margaret and Sam to the acknowledgment section for their great 3377 comments. 3379 o Say more about LAGs in the UDP section per Sam Hartman's comment. 3381 o Sam wants to use MAY instead of SHOULD for ignoring checksums on 3382 ETR. From the mailing list: "You'd need to word it as an ITR MAY 3383 send a zero checksum, an ETR MUST accept a 0 checksum and MAY 3384 ignore the checksum completely. And of course we'd need to 3385 confirm that can actually be implemented. In particular, hardware 3386 that verifies UDP checksums on receive needs to be checked to make 3387 sure it permits 0 checksums." 3389 o Margaret wants a reference to 3390 http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. 3392 o Fix description in Map-Request section. Where we describe Map- 3393 Reply Record, change "R-bit" to "M-bit". 3395 o Add the mobility bit to Map-Replies. So PTRs don't probe so often 3396 for MNs but often enough to get mapping updates. 3398 o Indicate SHA1 can be used as well for Map-Registers. 3400 o More Fred comments on MTU handling. 3402 o Isidor comment about spec'ing better periodic Map-Registers. Will 3403 be fixed in draft-ietf-lisp-ms-02.txt. 3405 o Margaret's comment on gleaning: "The current specification does 3406 not make it clear how long gleaned map entries should be retained 3407 in the cache, nor does it make it clear how/ when they will be 3408 validated. The LISP spec should, at the very least, include a 3409 (short) default lifetime for gleaned entries, require that they be 3410 validated within a short period of time, and state that a new 3411 gleaned entry should never overwrite an entry that was obtained 3412 from the mapping system. The security implications of storing 3413 "gleaned" entries should also be explored in detail." 3415 o Add section on RLOC-probing per working group feedback. 3417 o Change "loc-reach-bits" to "loc-status-bits" per comment from 3418 Noel. 3420 o Remove SMR-bit from data-plane. Dino prefers to have it in the 3421 control plane only. 3423 o Change LISP header to allow a "Research Bit" so the Nonce and LSB 3424 fields can be turned off and used for another future purpose. For 3425 Luigi et al versioning convergence. 3427 o Add a N-bit to the data header suggested by Noel. Then the nonce 3428 field could be used when N is not 1. 3430 o Clarify that when E-bit is 0, the nonce field can be an echoed 3431 nonce or a random nonce. Comment from Jesper. 3433 o Indicate when doing data-gleaning that a verifying Map-Request is 3434 sent to the source-EID of the gleaned data packet so we can avoid 3435 map-cache corruption by a 3rd party. Comment from Pedro. 3437 o Indicate that a verifying Map-Request, for accepting mapping data, 3438 should be sent over the ALT (or to the EID). 3440 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. 3442 o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- 3443 noncing. Comment by Pedro and Dino. 3445 o Jesper made a comment to loosen the language about requiring the 3446 copy of inner TTL to outer TTL since the text to get mixed-AF 3447 traceroute to work would violate the "MUST" clause. Changed from 3448 MUST to SHOULD in section 5.3. 3450 B.9. Changes to draft-ietf-lisp-03.txt 3452 o Posted July 2009. 3454 o Removed loc-reach-bits longword from control packets per Damien 3455 comment. 3457 o Clarifications in MTU text from Roque. 3459 o Added text to indicate that the locator-set be sorted by locator 3460 address from Isidor. 3462 o Clarification text from John Zwiebel in Echo-Nonce section. 3464 B.10. Changes to draft-ietf-lisp-02.txt 3466 o Posted July 2009. 3468 o Encapsulation packet format change to add E-bit and make loc- 3469 reach-bits 32-bits in length. 3471 o Added Echo-Nonce Algorithm section. 3473 o Clarification how ECN bits are copied. 3475 o Moved S-bit in Map-Request. 3477 o Added P-bit in Map-Request and Map-Reply messages to anticipate 3478 RLOC-Probe Algorithm. 3480 o Added to Mobility section to reference [LISP-MN]. 3482 B.11. Changes to draft-ietf-lisp-01.txt 3484 o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. 3486 o Defined LEID to be a "LISP EID". 3488 o Indicate encapsulation use IPv4 DF=0. 3490 o Added negative Map-Reply messages with drop, native-forward, and 3491 send-map-request actions. 3493 o Added Proxy-Map-Reply bit to Map-Register. 3495 B.12. Changes to draft-ietf-lisp-00.txt 3497 o Posted May 2009. 3499 o Rename of draft-farinacci-lisp-12.txt. 3501 o Acknowledgment to RRG. 3503 Authors' Addresses 3505 Dino Farinacci 3506 cisco Systems 3507 Tasman Drive 3508 San Jose, CA 95134 3509 USA 3511 Email: dino@cisco.com 3513 Vince Fuller 3514 cisco Systems 3515 Tasman Drive 3516 San Jose, CA 95134 3517 USA 3519 Email: vaf@cisco.com 3521 Dave Meyer 3522 cisco Systems 3523 170 Tasman Drive 3524 San Jose, CA 3525 USA 3527 Email: dmm@cisco.com 3529 Darrel Lewis 3530 cisco Systems 3531 170 Tasman Drive 3532 San Jose, CA 3533 USA 3535 Email: darlewis@cisco.com