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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: Standards Track D. Meyer 5 Expires: September 5, 2018 D. Lewis 6 Cisco Systems 7 A. Cabellos (Ed.) 8 UPC/BarcelonaTech 9 March 4, 2018 11 The Locator/ID Separation Protocol (LISP) 12 draft-ietf-lisp-rfc6830bis-10 14 Abstract 16 This document describes the data-plane protocol for the Locator/ID 17 Separation Protocol (LISP). LISP defines two namespaces, End-point 18 Identifiers (EIDs) that identify end-hosts and Routing Locators 19 (RLOCs) that identify network attachment points. With this, LISP 20 effectively separates control from data, and allows routers to create 21 overlay networks. LISP-capable routers exchange encapsulated packets 22 according to EID-to-RLOC mappings stored in a local map-cache. 24 LISP requires no change to either host protocol stacks or to underlay 25 routers and offers Traffic Engineering, multihoming and mobility, 26 among other features. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on September 5, 2018. 45 Copyright Notice 47 Copyright (c) 2018 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 64 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4 65 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . 8 66 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . 10 67 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . 12 68 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 13 69 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 14 70 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . 15 71 6. LISP EID-to-RLOC Map-Cache . . . . . . . . . . . . . . . . . 19 72 7. Dealing with Large Encapsulated Packets . . . . . . . . . . . 20 73 7.1. A Stateless Solution to MTU Handling . . . . . . . . . . 20 74 7.2. A Stateful Solution to MTU Handling . . . . . . . . . . . 21 75 8. Using Virtualization and Segmentation with LISP . . . . . . . 22 76 9. Routing Locator Selection . . . . . . . . . . . . . . . . . . 22 77 10. Routing Locator Reachability . . . . . . . . . . . . . . . . 24 78 10.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . . 25 79 11. EID Reachability within a LISP Site . . . . . . . . . . . . . 27 80 12. Routing Locator Hashing . . . . . . . . . . . . . . . . . . . 27 81 13. Changing the Contents of EID-to-RLOC Mappings . . . . . . . . 28 82 13.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . . 29 83 13.2. Database Map-Versioning . . . . . . . . . . . . . . . . 30 84 14. Multicast Considerations . . . . . . . . . . . . . . . . . . 30 85 15. Router Performance Considerations . . . . . . . . . . . . . . 31 86 16. Mobility Considerations . . . . . . . . . . . . . . . . . . . 32 87 16.1. Slow Mobility . . . . . . . . . . . . . . . . . . . . . 32 88 16.2. Fast Mobility . . . . . . . . . . . . . . . . . . . . . 32 89 16.3. LISP Mobile Node Mobility . . . . . . . . . . . . . . . 33 90 17. LISP xTR Placement and Encapsulation Methods . . . . . . . . 33 91 17.1. First-Hop/Last-Hop xTRs . . . . . . . . . . . . . . . . 35 92 17.2. Border/Edge xTRs . . . . . . . . . . . . . . . . . . . . 35 93 17.3. ISP Provider Edge (PE) xTRs . . . . . . . . . . . . . . 36 94 17.4. LISP Functionality with Conventional NATs . . . . . . . 36 95 17.5. Packets Egressing a LISP Site . . . . . . . . . . . . . 37 96 18. Traceroute Considerations . . . . . . . . . . . . . . . . . . 37 97 18.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . 38 98 18.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . 38 99 18.3. Traceroute Using Mixed Locators . . . . . . . . . . . . 39 100 19. Security Considerations . . . . . . . . . . . . . . . . . . . 39 101 20. Network Management Considerations . . . . . . . . . . . . . . 40 102 21. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40 103 21.1. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . 40 104 22. References . . . . . . . . . . . . . . . . . . . . . . . . . 40 105 22.1. Normative References . . . . . . . . . . . . . . . . . . 40 106 22.2. Informative References . . . . . . . . . . . . . . . . . 41 107 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 46 108 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 46 109 B.1. Changes to draft-ietf-lisp-rfc6830bis-10 . . . . . . . . 47 110 B.2. Changes to draft-ietf-lisp-rfc6830bis-09 . . . . . . . . 47 111 B.3. Changes to draft-ietf-lisp-rfc6830bis-08 . . . . . . . . 47 112 B.4. Changes to draft-ietf-lisp-rfc6830bis-07 . . . . . . . . 48 113 B.5. Changes to draft-ietf-lisp-rfc6830bis-06 . . . . . . . . 48 114 B.6. Changes to draft-ietf-lisp-rfc6830bis-05 . . . . . . . . 48 115 B.7. Changes to draft-ietf-lisp-rfc6830bis-04 . . . . . . . . 48 116 B.8. Changes to draft-ietf-lisp-rfc6830bis-03 . . . . . . . . 49 117 B.9. Changes to draft-ietf-lisp-rfc6830bis-02 . . . . . . . . 49 118 B.10. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 49 119 B.11. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 49 120 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 49 122 1. Introduction 124 This document describes the Locator/Identifier Separation Protocol 125 (LISP). LISP is an encapsulation protocol built around the 126 fundamental idea of separating the topological location of a network 127 attachment point from the node's identity [CHIAPPA]. As a result 128 LISP creates two namespaces: Endpoint Identifiers (EIDs), that are 129 used to identify end-hosts (e.g., nodes or Virtual Machines) and 130 routable Routing Locators (RLOCs), used to identify network 131 attachment points. LISP then defines functions for mapping between 132 the two namespaces and for encapsulating traffic originated by 133 devices using non-routable EIDs for transport across a network 134 infrastructure that routes and forwards using RLOCs. LISP 135 encapsulation uses a dynamic form of tunneling where no static 136 provisioning is required or necessary. 138 LISP is an overlay protocol that separates control from data-plane, 139 this document specifies the data-plane, how LISP-capable routers 140 (Tunnel Routers) exchange packets by encapsulating them to the 141 appropriate location. Tunnel routers are equipped with a cache, 142 called map-cache, that contains EID-to-RLOC mappings. The map-cache 143 is populated using the LISP Control-Plane protocol 144 [I-D.ietf-lisp-rfc6833bis]. 146 LISP does not require changes to either host protocol stack or to 147 underlay routers. By separating the EID from the RLOC space, LISP 148 offers native Traffic Engineering, multihoming and mobility, among 149 other features. 151 Creation of LISP was initially motivated by discussions during the 152 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 153 October 2006 (see [RFC4984]). 155 This document specifies the LISP data-plane encapsulation and other 156 LISP forwarding node functionality while [I-D.ietf-lisp-rfc6833bis] 157 specifies the LISP control plane. LISP deployment guidelines can be 158 found in [RFC7215] and [RFC6835] describes considerations for network 159 operational management. Finally, [I-D.ietf-lisp-introduction] 160 describes the LISP architecture. 162 2. Requirements Notation 164 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 165 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 166 document are to be interpreted as described in [RFC2119]. 168 3. Definition of Terms 170 Address Family Identifier (AFI): AFI is a term used to describe an 171 address encoding in a packet. An address family that pertains to 172 the data-plane. See [AFN] and [RFC3232] for details. An AFI 173 value of 0 used in this specification indicates an unspecified 174 encoded address where the length of the address is 0 octets 175 following the 16-bit AFI value of 0. 177 Anycast Address: Anycast Address is a term used in this document to 178 refer to the same IPv4 or IPv6 address configured and used on 179 multiple systems at the same time. An EID or RLOC can be an 180 anycast address in each of their own address spaces. 182 Client-side: Client-side is a term used in this document to indicate 183 a connection initiation attempt by an end-system represented by an 184 EID. 186 Data-Probe: A Data-Probe is a LISP-encapsulated data packet where 187 the inner-header destination address equals the outer-header 188 destination address used to trigger a Map-Reply by a decapsulating 189 ETR. In addition, the original packet is decapsulated and 190 delivered to the destination host if the destination EID is in the 191 EID-Prefix range configured on the ETR. Otherwise, the packet is 192 discarded. A Data-Probe is used in some of the mapping database 193 designs to "probe" or request a Map-Reply from an ETR; in other 194 cases, Map-Requests are used. See each mapping database design 195 for details. When using Data-Probes, by sending Map-Requests on 196 the underlying routing system, EID-Prefixes must be advertised. 198 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 199 packet where the destination address in the "outer" IP header is 200 one of its own RLOCs. The router strips the "outer" header and 201 forwards the packet based on the next IP header found. In 202 general, an ETR receives LISP-encapsulated IP packets from the 203 Internet on one side and sends decapsulated IP packets to site 204 end-systems on the other side. ETR functionality does not have to 205 be limited to a router device. A server host can be the endpoint 206 of a LISP tunnel as well. 208 EID-to-RLOC Database: The EID-to-RLOC Database is a global 209 distributed database that contains all known EID-Prefix-to-RLOC 210 mappings. Each potential ETR typically contains a small piece of 211 the database: the EID-to-RLOC mappings for the EID-Prefixes 212 "behind" the router. These map to one of the router's own 213 globally visible IP addresses. Note that there MAY be transient 214 conditions when the EID-Prefix for the site and Locator-Set for 215 each EID-Prefix may not be the same on all ETRs. This has no 216 negative implications, since a partial set of Locators can be 217 used. 219 EID-to-RLOC Map-Cache: The EID-to-RLOC map-cache is generally 220 short-lived, on-demand table in an ITR that stores, tracks, and is 221 responsible for timing out and otherwise validating EID-to-RLOC 222 mappings. This cache is distinct from the full "database" of EID- 223 to-RLOC mappings; it is dynamic, local to the ITR(s), and 224 relatively small, while the database is distributed, relatively 225 static, and much more global in scope. 227 EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are 228 allocated to a site by an address allocation authority. EID- 229 Prefixes are associated with a set of RLOC addresses. EID-Prefix 230 allocations can be broken up into smaller blocks when an RLOC set 231 is to be associated with the larger EID-Prefix block. 233 End-System: An end-system is an IPv4 or IPv6 device that originates 234 packets with a single IPv4 or IPv6 header. The end-system 235 supplies an EID value for the destination address field of the IP 236 header when communicating globally (i.e., outside of its routing 237 domain). An end-system can be a host computer, a switch or router 238 device, or any network appliance. 240 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 241 IPv6) value used in the source and destination address fields of 242 the first (most inner) LISP header of a packet. The host obtains 243 a destination EID the same way it obtains a destination address 244 today, for example, through a Domain Name System (DNS) [RFC1034] 245 lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. 246 The source EID is obtained via existing mechanisms used to set a 247 host's "local" IP address. An EID used on the public Internet 248 MUST have the same properties as any other IP address used in that 249 manner; this means, among other things, that it MUST be globally 250 unique. An EID is allocated to a host from an EID-Prefix block 251 associated with the site where the host is located. An EID can be 252 used by a host to refer to other hosts. Note that EID blocks MAY 253 be assigned in a hierarchical manner, independent of the network 254 topology, to facilitate scaling of the mapping database. In 255 addition, an EID block assigned to a site MAY have site-local 256 structure (subnetting) for routing within the site; this structure 257 is not visible to the global routing system. In theory, the bit 258 string that represents an EID for one device can represent an RLOC 259 for a different device. When used in discussions with other 260 Locator/ID separation proposals, a LISP EID will be called an 261 "LEID". Throughout this document, any references to "EID" refer 262 to an LEID. 264 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 265 LISP site. Packets sent by sources inside of the LISP site to 266 destinations outside of the site are candidates for encapsulation 267 by the ITR. The ITR treats the IP destination address as an EID 268 and performs an EID-to-RLOC mapping lookup. The router then 269 prepends an "outer" IP header with one of its routable RLOCs (in 270 the RLOC space) in the source address field and the result of the 271 mapping lookup in the destination address field. Note that this 272 destination RLOC MAY be an intermediate, proxy device that has 273 better knowledge of the EID-to-RLOC mapping closer to the 274 destination EID. In general, an ITR receives IP packets from site 275 end-systems on one side and sends LISP-encapsulated IP packets 276 toward the Internet on the other side. 278 Specifically, when a service provider prepends a LISP header for 279 Traffic Engineering purposes, the router that does this is also 280 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 281 on the outer destination address (the originating ITR's supplied 282 RLOC) or the inner destination address (the originating host's 283 supplied EID). 285 LISP Header: LISP header is a term used in this document to refer 286 to the outer IPv4 or IPv6 header, a UDP header, and a LISP- 287 specific 8-octet header that follow the UDP header and that an ITR 288 prepends or an ETR strips. 290 LISP Router: A LISP router is a router that performs the functions 291 of any or all of the following: ITR, ETR, RTR, Proxy-ITR (PITR), 292 or Proxy-ETR (PETR). 294 LISP Site: LISP site is a set of routers in an edge network that are 295 under a single technical administration. LISP routers that reside 296 in the edge network are the demarcation points to separate the 297 edge network from the core network. 299 Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the 300 LISP header. They are used by ITRs to inform ETRs about the up/ 301 down status of all ETRs at the local site. These bits are used as 302 a hint to convey up/down router status and not path reachability 303 status. The LSBs can be verified by use of one of the Locator 304 reachability algorithms described in Section 10. 306 Negative Mapping Entry: A negative mapping entry, also known as a 307 negative cache entry, is an EID-to-RLOC entry where an EID-Prefix 308 is advertised or stored with no RLOCs. That is, the Locator-Set 309 for the EID-to-RLOC entry is empty or has an encoded Locator count 310 of 0. This type of entry could be used to describe a prefix from 311 a non-LISP site, which is explicitly not in the mapping database. 312 There are a set of well-defined actions that are encoded in a 313 Negative Map-Reply. 315 Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A 316 PETR acts like an ETR but does so on behalf of LISP sites that 317 send packets to destinations at non-LISP sites. 319 Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A 320 PITR acts like an ITR but does so on behalf of non-LISP sites that 321 send packets to destinations at LISP sites. 323 Recursive Tunneling: Recursive Tunneling occurs when a packet has 324 more than one LISP IP header. Additional layers of tunneling MAY 325 be employed to implement Traffic Engineering or other re-routing 326 as needed. When this is done, an additional "outer" LISP header 327 is added, and the original RLOCs are preserved in the "inner" 328 header. 330 Re-Encapsulating Tunneling Router (RTR): An RTR acts like an ETR to 331 remove a LISP header, then acts as an ITR to prepend a new LISP 332 header. This is known as Re-encapsulating Tunneling. Doing this 333 allows a packet to be re-routed by the RTR without adding the 334 overhead of additional tunnel headers. When using multiple 335 mapping database systems, care must be taken to not create re- 336 encapsulation loops through misconfiguration. 338 Route-Returnability: Route-returnability is an assumption that the 339 underlying routing system will deliver packets to the destination. 340 When combined with a nonce that is provided by a sender and 341 returned by a receiver, this limits off-path data insertion. A 342 route-returnability check is verified when a message is sent with 343 a nonce, another message is returned with the same nonce, and the 344 destination of the original message appears as the source of the 345 returned message. 347 Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 348 [RFC8200] address of an Egress Tunnel Router (ETR). An RLOC is 349 the output of an EID-to-RLOC mapping lookup. An EID maps to zero 350 or more RLOCs. Typically, RLOCs are numbered from blocks that are 351 assigned to a site at each point to which it attaches to the 352 underlay network; where the topology is defined by the 353 connectivity of provider networks. Multiple RLOCs can be assigned 354 to the same ETR device or to multiple ETR devices at a site. 356 Server-side: Server-side is a term used in this document to indicate 357 that a connection initiation attempt is being accepted for a 358 destination EID. 360 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 361 network that strips an outer LISP header for Traffic Engineering 362 purposes. 364 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 365 network that prepends an additional LISP header for Traffic 366 Engineering purposes. 368 xTR: An xTR is a reference to an ITR or ETR when direction of data 369 flow is not part of the context description. "xTR" refers to the 370 router that is the tunnel endpoint and is used synonymously with 371 the term "Tunnel Router". For example, "An xTR can be located at 372 the Customer Edge (CE) router" indicates both ITR and ETR 373 functionality at the CE router. 375 4. Basic Overview 377 One key concept of LISP is that end-systems operate the same way they 378 do today. The IP addresses that hosts use for tracking sockets and 379 connections, and for sending and receiving packets, do not change. 381 In LISP terminology, these IP addresses are called Endpoint 382 Identifiers (EIDs). 384 Routers continue to forward packets based on IP destination 385 addresses. When a packet is LISP encapsulated, these addresses are 386 referred to as Routing Locators (RLOCs). Most routers along a path 387 between two hosts will not change; they continue to perform routing/ 388 forwarding lookups on the destination addresses. For routers between 389 the source host and the ITR as well as routers from the ETR to the 390 destination host, the destination address is an EID. For the routers 391 between the ITR and the ETR, the destination address is an RLOC. 393 Another key LISP concept is the "Tunnel Router". A Tunnel Router 394 prepends LISP headers on host-originated packets and strips them 395 prior to final delivery to their destination. The IP addresses in 396 this "outer header" are RLOCs. During end-to-end packet exchange 397 between two Internet hosts, an ITR prepends a new LISP header to each 398 packet, and an ETR strips the new header. The ITR performs EID-to- 399 RLOC lookups to determine the routing path to the ETR, which has the 400 RLOC as one of its IP addresses. 402 Some basic rules governing LISP are: 404 o End-systems only send to addresses that are EIDs. EIDs are 405 typically IP addresses assigned to hosts (other types of EID are 406 supported by LISP, see [RFC8060] for further information). End- 407 systems don't know that addresses are EIDs versus RLOCs but assume 408 that packets get to their intended destinations. In a system 409 where LISP is deployed, LISP routers intercept EID-addressed 410 packets and assist in delivering them across the network core 411 where EIDs cannot be routed. The procedure a host uses to send IP 412 packets does not change. 414 o LISP routers mostly deal with Routing Locator addresses. See 415 details in Section 4.1 to clarify what is meant by "mostly". 417 o RLOCs are always IP addresses assigned to routers, preferably 418 topologically oriented addresses from provider CIDR (Classless 419 Inter-Domain Routing) blocks. 421 o When a router originates packets, it MAY use as a source address 422 either an EID or RLOC. When acting as a host (e.g., when 423 terminating a transport session such as Secure SHell (SSH), 424 TELNET, or the Simple Network Management Protocol (SNMP)), it MAY 425 use an EID that is explicitly assigned for that purpose. An EID 426 that identifies the router as a host MUST NOT be used as an RLOC; 427 an EID is only routable within the scope of a site. A typical BGP 428 configuration might demonstrate this "hybrid" EID/RLOC usage where 429 a router could use its "host-like" EID to terminate iBGP sessions 430 to other routers in a site while at the same time using RLOCs to 431 terminate eBGP sessions to routers outside the site. 433 o Packets with EIDs in them are not expected to be delivered end-to- 434 end in the absence of an EID-to-RLOC mapping operation. They are 435 expected to be used locally for intra-site communication or to be 436 encapsulated for inter-site communication. 438 o EIDs MAY also be structured (subnetted) in a manner suitable for 439 local routing within an Autonomous System (AS). 441 An additional LISP header MAY be prepended to packets by a TE-ITR 442 when re-routing of the path for a packet is desired. A potential 443 use-case for this would be an ISP router that needs to perform 444 Traffic Engineering for packets flowing through its network. In such 445 a situation, termed "Recursive Tunneling", an ISP transit acts as an 446 additional ITR, and the RLOC it uses for the new prepended header 447 would be either a TE-ETR within the ISP (along an intra-ISP traffic 448 engineered path) or a TE-ETR within another ISP (an inter-ISP traffic 449 engineered path, where an agreement to build such a path exists). 451 In order to avoid excessive packet overhead as well as possible 452 encapsulation loops, this document recommends that a maximum of two 453 LISP headers can be prepended to a packet. For initial LISP 454 deployments, it is assumed that two headers is sufficient, where the 455 first prepended header is used at a site for Location/Identity 456 separation and the second prepended header is used inside a service 457 provider for Traffic Engineering purposes. 459 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 460 For example, the ITR for a particular end-to-end packet exchange 461 might be the first-hop or default router within a site for the source 462 host. Similarly, the ETR might be the last-hop router directly 463 connected to the destination host. Another example, perhaps for a 464 VPN service outsourced to an ISP by a site, the ITR could be the 465 site's border router at the service provider attachment point. 466 Mixing and matching of site-operated, ISP-operated, and other Tunnel 467 Routers is allowed for maximum flexibility. 469 4.1. Packet Flow Sequence 471 This section provides an example of the unicast packet flow, 472 including also control-plane information as specified in 473 [I-D.ietf-lisp-rfc6833bis]. The example also assumes the following 474 conditions: 476 o Source host "host1.abc.example.com" is sending a packet to 477 "host2.xyz.example.com", exactly what host1 would do if the site 478 was not using LISP. 480 o Each site is multihomed, so each Tunnel Router has an address 481 (RLOC) assigned from the service provider address block for each 482 provider to which that particular Tunnel Router is attached. 484 o The ITR(s) and ETR(s) are directly connected to the source and 485 destination, respectively, but the source and destination can be 486 located anywhere in the LISP site. 488 o A Map-Request is sent for an external destination when the 489 destination is not found in the forwarding table or matches a 490 default route. Map-Requests are sent to the mapping database 491 system by using the LISP control-plane protocol documented in 492 [I-D.ietf-lisp-rfc6833bis]. 494 o Map-Replies are sent on the underlying routing system topology 495 using the [I-D.ietf-lisp-rfc6833bis] control-plane protocol. 497 Client host1.abc.example.com wants to communicate with server 498 host2.xyz.example.com: 500 1. host1.abc.example.com wants to open a TCP connection to 501 host2.xyz.example.com. It does a DNS lookup on 502 host2.xyz.example.com. An A/AAAA record is returned. This 503 address is the destination EID. The locally assigned address of 504 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 505 packet is built and forwarded through the LISP site as a normal 506 IP packet until it reaches a LISP ITR. 508 2. The LISP ITR must be able to map the destination EID to an RLOC 509 of one of the ETRs at the destination site. The specific method 510 used to do this is not described in this example. See 511 [I-D.ietf-lisp-rfc6833bis] for further information. 513 3. The ITR sends a LISP Map-Request as specified in 514 [I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited. 516 4. The mapping system helps forwarding the Map-Request to the 517 corresponding ETR. When the Map-Request arrives at one of the 518 ETRs at the destination site, it will process the packet as a 519 control message. 521 5. The ETR looks at the destination EID of the Map-Request and 522 matches it against the prefixes in the ETR's configured EID-to- 523 RLOC mapping database. This is the list of EID-Prefixes the ETR 524 is supporting for the site it resides in. If there is no match, 525 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 526 returned to the ITR. 528 6. The ITR receives the Map-Reply message, parses the message (to 529 check for format validity), and stores the mapping information 530 from the packet. This information is stored in the ITR's EID-to- 531 RLOC map-cache. Note that the map-cache is an on-demand cache. 532 An ITR will manage its map-cache in such a way that optimizes for 533 its resource constraints. 535 7. Subsequent packets from host1.abc.example.com to 536 host2.xyz.example.com will have a LISP header prepended by the 537 ITR using the appropriate RLOC as the LISP header destination 538 address learned from the ETR. Note that the packet MAY be sent 539 to a different ETR than the one that returned the Map-Reply due 540 to the source site's hashing policy or the destination site's 541 Locator-Set policy. 543 8. The ETR receives these packets directly (since the destination 544 address is one of its assigned IP addresses), checks the validity 545 of the addresses, strips the LISP header, and forwards packets to 546 the attached destination host. 548 9. In order to defer the need for a mapping lookup in the reverse 549 direction, an ETR can OPTIONALLY create a cache entry that maps 550 the source EID (inner-header source IP address) to the source 551 RLOC (outer-header source IP address) in a received LISP packet. 552 Such a cache entry is termed a "glean mapping" and only contains 553 a single RLOC for the EID in question. More complete information 554 about additional RLOCs SHOULD be verified by sending a LISP Map- 555 Request for that EID. Both the ITR and the ETR MAY also 556 influence the decision the other makes in selecting an RLOC. 558 5. LISP Encapsulation Details 560 Since additional tunnel headers are prepended, the packet becomes 561 larger and can exceed the MTU of any link traversed from the ITR to 562 the ETR. It is RECOMMENDED in IPv4 that packets do not get 563 fragmented as they are encapsulated by the ITR. Instead, the packet 564 is dropped and an ICMP Unreachable/Fragmentation-Needed message is 565 returned to the source. 567 In the case when fragmentation is needed, this specification 568 RECOMMENDS that implementations provide support for one of the 569 proposed fragmentation and reassembly schemes. Two existing schemes 570 are detailed in Section 7. 572 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 573 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 574 header is in IPv4 packet format and the outer header is in IPv6 575 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 576 is in IPv6 packet format and the outer header is in IPv4 packet 577 format). The next sub-sections illustrate packet formats for the 578 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 579 combinations MUST be supported. Additional types of EIDs are defined 580 in [RFC8060]. 582 5.1. LISP IPv4-in-IPv4 Header Format 584 0 1 2 3 585 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 1 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 / |Version| IHL | DSCP |ECN| Total Length | 588 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 589 | | Identification |Flags| Fragment Offset | 590 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 591 OH | Time to Live | Protocol = 17 | Header Checksum | 592 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 | | Source Routing Locator | 594 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 \ | Destination Routing Locator | 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 / | Source Port = xxxx | Dest Port = 4341 | 598 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 \ | UDP Length | UDP Checksum | 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 602 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 S / | Instance ID/Locator-Status-Bits | 604 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 605 / |Version| IHL | DSCP |ECN| Total Length | 606 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 | | Identification |Flags| Fragment Offset | 608 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 IH | Time to Live | Protocol | Header Checksum | 610 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 611 | | Source EID | 612 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 \ | Destination EID | 614 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 616 IHL = IP-Header-Length 618 5.2. LISP IPv6-in-IPv6 Header Format 620 0 1 2 3 621 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 1 622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 / |Version| DSCP |ECN| Flow Label | 624 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 625 | | Payload Length | Next Header=17| Hop Limit | 626 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 627 | | 628 O + + 629 u | | 630 t + Source Routing Locator + 631 e | | 632 r + + 633 | | 634 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 d | | 636 r + + 637 | | 638 ^ + Destination Routing Locator + 639 | | | 640 \ + + 641 \ | | 642 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 643 / | Source Port = xxxx | Dest Port = 4341 | 644 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 645 \ | UDP Length | UDP Checksum | 646 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 647 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 648 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 S / | Instance ID/Locator-Status-Bits | 650 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 651 / |Version| DSCP |ECN| Flow Label | 652 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 653 / | Payload Length | Next Header | Hop Limit | 654 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 | | 656 I + + 657 n | | 658 n + Source EID + 659 e | | 660 r + + 661 | | 662 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 663 d | | 664 r + + 665 | | 667 ^ + Destination EID + 668 \ | | 669 \ + + 670 \ | | 671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 673 5.3. Tunnel Header Field Descriptions 675 Inner Header (IH): The inner header is the header on the 676 datagram received from the originating host [RFC0791] [RFC8200] 677 [RFC2474]. The source and destination IP addresses are EIDs. 679 Outer Header: (OH) The outer header is a new header prepended by an 680 ITR. The address fields contain RLOCs obtained from the ingress 681 router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" 682 from [RFC0768]. The setting of the Don't Fragment (DF) bit 683 'Flags' field is according to rules listed in Sections 7.1 and 684 7.2. 686 UDP Header: The UDP header contains an ITR selected source port when 687 encapsulating a packet. See Section 12 for details on the hash 688 algorithm used to select a source port based on the 5-tuple of the 689 inner header. The destination port MUST be set to the well-known 690 IANA-assigned port value 4341. 692 UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero 693 by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation 694 [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is 695 received by an ETR, the ETR MUST accept the packet for 696 decapsulation. When an ITR transmits a non-zero value for the UDP 697 checksum, it MUST send a correctly computed value in this field. 698 When an ETR receives a packet with a non-zero UDP checksum, it MAY 699 choose to verify the checksum value. If it chooses to perform 700 such verification, and the verification fails, the packet MUST be 701 silently dropped. If the ETR chooses not to perform the 702 verification, or performs the verification successfully, the 703 packet MUST be accepted for decapsulation. The handling of UDP 704 zero checksums over IPv6 for all tunneling protocols, including 705 LISP, is subject to the applicability statement in [RFC6936]. 707 UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated 708 packet to be the sum of the inner-header IPv4 Total Length plus 709 the UDP and LISP header lengths. For an IPv6-encapsulated packet, 710 the 'UDP Length' field is the sum of the inner-header IPv6 Payload 711 Length, the size of the IPv6 header (40 octets), and the size of 712 the UDP and LISP headers. 714 N: The N-bit is the nonce-present bit. When this bit is set to 1, 715 the low-order 24 bits of the first 32 bits of the LISP header 716 contain a Nonce. See Section 10.1 for details. Both N- and 717 V-bits MUST NOT be set in the same packet. If they are, a 718 decapsulating ETR MUST treat the 'Nonce/Map-Version' field as 719 having a Nonce value present. 721 L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When 722 this bit is set to 1, the Locator-Status-Bits in the second 723 32 bits of the LISP header are in use. 725 x 1 x x 0 x x x 726 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 727 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 728 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 729 | Locator-Status-Bits | 730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 732 E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored 733 and has no meaning when the N-bit is set to 0. When the N-bit is 734 set to 1 and this bit is set to 1, an ITR is requesting that the 735 nonce value in the 'Nonce' field be echoed back in LISP- 736 encapsulated packets when the ITR is also an ETR. See 737 Section 10.1 for details. 739 V: The V-bit is the Map-Version present bit. When this bit is set to 740 1, the N-bit MUST be 0. Refer to Section 13.2 for more details. 741 This bit indicates that the LISP header is encoded in this 742 case as: 744 0 x 0 1 x x x x 745 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 746 |N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version | 747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 748 | Instance ID/Locator-Status-Bits | 749 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 751 I: The I-bit is the Instance ID bit. See Section 8 for more details. 752 When this bit is set to 1, the 'Locator-Status-Bits' field is 753 reduced to 8 bits and the high-order 24 bits are used as an 754 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 755 are transmitted as zero and ignored on receipt. The format of the 756 LISP header would look like this: 758 x x x x 1 x x x 759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 760 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 762 | Instance ID | LSBs | 763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 765 R: The R-bit is a Reserved bit for future use. It MUST be set to 0 766 on transmit and MUST be ignored on receipt. 768 KK: The KK-bits are a 2-bit field used when encapsulated packets are 769 encrypted. The field is set to 00 when the packet is not 770 encrypted. See [RFC8061] for further information. 772 LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is 773 randomly generated by an ITR when the N-bit is set to 1. Nonce 774 generation algorithms are an implementation matter but are 775 required to generate different nonces when sending to different 776 destinations. However, the same nonce can be used for a period of 777 time when encapsulating to the same ETR. The nonce is also used 778 when the E-bit is set to request the nonce value to be echoed by 779 the other side when packets are returned. When the E-bit is clear 780 but the N-bit is set, a remote ITR is either echoing a previously 781 requested echo-nonce or providing a random nonce. See 782 Section 10.1 for more details. 784 LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the 785 'Locator-Status-Bits' field in the LISP header is set by an ITR to 786 indicate to an ETR the up/down status of the Locators in the 787 source site. Each RLOC in a Map-Reply is assigned an ordinal 788 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 789 The Locator-Status-Bits are numbered from 0 to n-1 from the least 790 significant bit of the field. The field is 32 bits when the I-bit 791 is set to 0 and is 8 bits when the I-bit is set to 1. When a 792 Locator-Status-Bit is set to 1, the ITR is indicating to the ETR 793 that the RLOC associated with the bit ordinal has up status. See 794 Section 10 for details on how an ITR can determine the status of 795 the ETRs at the same site. When a site has multiple EID-Prefixes 796 that result in multiple mappings (where each could have a 797 different Locator-Set), the Locator-Status-Bits setting in an 798 encapsulated packet MUST reflect the mapping for the EID-Prefix 799 that the inner-header source EID address matches. If the LSB for 800 an anycast Locator is set to 1, then there is at least one RLOC 801 with that address, and the ETR is considered 'up'. 803 When doing ITR/PITR encapsulation: 805 o The outer-header 'Time to Live' field (or 'Hop Limit' field, in 806 the case of IPv6) SHOULD be copied from the inner-header 'Time to 807 Live' field. 809 o The outer-header 'Differentiated Services Code Point' (DSCP) field 810 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 811 copied from the inner-header DSCP field ('Traffic Class' field, in 812 the case of IPv6) considering the exception listed below. 814 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 815 of the IPv6 'Traffic Class' field) requires special treatment in 816 order to avoid discarding indications of congestion [RFC3168]. 817 ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 818 header to the outer header. Re-encapsulation MUST copy the 2-bit 819 'ECN' field from the stripped outer header to the new outer 820 header. 822 When doing ETR/PETR decapsulation: 824 o The inner-header 'Time to Live' field (or 'Hop Limit' field, in 825 the case of IPv6) SHOULD be copied from the outer-header 'Time to 826 Live' field, when the Time to Live value of the outer header is 827 less than the Time to Live value of the inner header. Failing to 828 perform this check can cause the Time to Live of the inner header 829 to increment across encapsulation/decapsulation cycles. This 830 check is also performed when doing initial encapsulation, when a 831 packet comes to an ITR or PITR destined for a LISP site. 833 o The inner-header 'Differentiated Services Code Point' (DSCP) field 834 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 835 copied from the outer-header DSCP field ('Traffic Class' field, in 836 the case of IPv6) considering the exception listed below. 838 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 839 of the IPv6 'Traffic Class' field) requires special treatment in 840 order to avoid discarding indications of congestion [RFC3168]. If 841 the 'ECN' field contains a congestion indication codepoint (the 842 value is '11', the Congestion Experienced (CE) codepoint), then 843 ETR decapsulation MUST copy the 2-bit 'ECN' field from the 844 stripped outer header to the surviving inner header that is used 845 to forward the packet beyond the ETR. These requirements preserve 846 CE indications when a packet that uses ECN traverses a LISP tunnel 847 and becomes marked with a CE indication due to congestion between 848 the tunnel endpoints. 850 Note that if an ETR/PETR is also an ITR/PITR and chooses to re- 851 encapsulate after decapsulating, the net effect of this is that the 852 new outer header will carry the same Time to Live as the old outer 853 header minus 1. 855 Copying the Time to Live (TTL) serves two purposes: first, it 856 preserves the distance the host intended the packet to travel; 857 second, and more importantly, it provides for suppression of looping 858 packets in the event there is a loop of concatenated tunnels due to 859 misconfiguration. See Section 18.3 for TTL exception handling for 860 traceroute packets. 862 The Explicit Congestion Notification ('ECN') field occupies bits 6 863 and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic 864 Class' field [RFC3168]. The 'ECN' field requires special treatment 865 in order to avoid discarding indications of congestion [RFC3168]. An 866 ITR/PITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 867 header to the outer header. Re-encapsulation MUST copy the 2-bit 868 'ECN' field from the stripped outer header to the new outer header. 869 If the 'ECN' field contains a congestion indication codepoint (the 870 value is '11', the Congestion Experienced (CE) codepoint), then ETR/ 871 PETR decapsulation MUST copy the 2-bit 'ECN' field from the stripped 872 outer header to the surviving inner header that is used to forward 873 the packet beyond the ETR. These requirements preserve CE 874 indications when a packet that uses ECN traverses a LISP tunnel and 875 becomes marked with a CE indication due to congestion between the 876 tunnel endpoints. 878 6. LISP EID-to-RLOC Map-Cache 880 ITRs and PITRs maintain an on-demand cache, referred as LISP EID-to- 881 RLOC Map-Cache, that contains mappings from EID-prefixes to locator 882 sets. The cache is used to encapsulate packets from the EID space to 883 the corresponding RLOC network attachment point. 885 When an ITR/PITR receives a packet from inside of the LISP site to 886 destinations outside of the site a longest-prefix match lookup of the 887 EID is done to the map-cache. 889 When the lookup succeeds, the Locator-Set retrieved from the map- 890 cache is used to send the packet to the EID's topological location. 892 If the lookup fails, the ITR/PITR needs to retrieve the mapping using 893 the LISP control-plane protocol [I-D.ietf-lisp-rfc6833bis]. The 894 mapping is then stored in the local map-cache to forward subsequent 895 packets addressed to the same EID-prefix. 897 The map-cache is a local cache of mappings, entries are expired based 898 on the associated Time to live. In addition, entries can be updated 899 with more current information, see Section 13 for further information 900 on this. Finally, the map-cache also contains reachability 901 information about EIDs and RLOCs, and uses LISP reachability 902 information mechanisms to determine the reachability of RLOCs, see 903 Section 10 for the specific mechanisms. 905 7. Dealing with Large Encapsulated Packets 907 This section proposes two mechanisms to deal with packets that exceed 908 the path MTU between the ITR and ETR. 910 It is left to the implementor to decide if the stateless or stateful 911 mechanism SHOULD be implemented. Both or neither can be used, since 912 it is a local decision in the ITR regarding how to deal with MTU 913 issues, and sites can interoperate with differing mechanisms. 915 Both stateless and stateful mechanisms also apply to Re-encapsulating 916 and Recursive Tunneling, so any actions below referring to an ITR 917 also apply to a TE-ITR. 919 7.1. A Stateless Solution to MTU Handling 921 An ITR stateless solution to handle MTU issues is described as 922 follows: 924 1. Define H to be the size, in octets, of the outer header an ITR 925 prepends to a packet. This includes the UDP and LISP header 926 lengths. 928 2. Define L to be the size, in octets, of the maximum-sized packet 929 an ITR can send to an ETR without the need for the ITR or any 930 intermediate routers to fragment the packet. 932 3. Define an architectural constant S for the maximum size of a 933 packet, in octets, an ITR MUST receive from the source so the 934 effective MTU can be met. That is, L = S + H. 936 When an ITR receives a packet from a site-facing interface and adds H 937 octets worth of encapsulation to yield a packet size greater than L 938 octets (meaning the received packet size was greater than S octets 939 from the source), it resolves the MTU issue by first splitting the 940 original packet into 2 equal-sized fragments. A LISP header is then 941 prepended to each fragment. The size of the encapsulated fragments 942 is then (S/2 + H), which is less than the ITR's estimate of the path 943 MTU between the ITR and its correspondent ETR. 945 When an ETR receives encapsulated fragments, it treats them as two 946 individually encapsulated packets. It strips the LISP headers and 947 then forwards each fragment to the destination host of the 948 destination site. The two fragments are reassembled at the 949 destination host into the single IP datagram that was originated by 950 the source host. Note that reassembly can happen at the ETR if the 951 encapsulated packet was fragmented at or after the ITR. 953 This behavior is performed by the ITR when the source host originates 954 a packet with the 'DF' field of the IP header set to 0. When the 955 'DF' field of the IP header is set to 1, or the packet is an IPv6 956 packet originated by the source host, the ITR will drop the packet 957 when the size is greater than L and send an ICMP Unreachable/ 958 Fragmentation-Needed message to the source with a value of S, where S 959 is (L - H). 961 When the outer-header encapsulation uses an IPv4 header, an 962 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 963 can be avoided. An implementation MAY set the DF bit in such headers 964 to 0 if it has good reason to believe there are unresolvable path MTU 965 issues between the sending ITR and the receiving ETR. 967 This specification RECOMMENDS that L be defined as 1500. 969 7.2. A Stateful Solution to MTU Handling 971 An ITR stateful solution to handle MTU issues is described as follows 972 and was first introduced in [OPENLISP]: 974 1. The ITR will keep state of the effective MTU for each Locator per 975 Map-Cache entry. The effective MTU is what the core network can 976 deliver along the path between the ITR and ETR. 978 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet 979 with the DF bit set to 1, exceeds what the core network can 980 deliver, one of the intermediate routers on the path will send an 981 ICMP Unreachable/Fragmentation-Needed message to the ITR. The 982 ITR will parse the ICMP message to determine which Locator is 983 affected by the effective MTU change and then record the new 984 effective MTU value in the Map-Cache entry. 986 3. When a packet is received by the ITR from a source inside of the 987 site and the size of the packet is greater than the effective MTU 988 stored with the Map-Cache entry associated with the destination 989 EID the packet is for, the ITR will send an ICMP Unreachable/ 990 Fragmentation-Needed message back to the source. The packet size 991 advertised by the ITR in the ICMP Unreachable/Fragmentation- 992 Needed message is the effective MTU minus the LISP encapsulation 993 length. 995 Even though this mechanism is stateful, it has advantages over the 996 stateless IP fragmentation mechanism, by not involving the 997 destination host with reassembly of ITR fragmented packets. 999 8. Using Virtualization and Segmentation with LISP 1001 There are several cases where segregation is needed at the EID level. 1002 For instance, this is the case for deployments containing overlapping 1003 addresses, traffic isolation policies or multi-tenant virtualization. 1004 For these and other scenarios where segregation is needed, Instance 1005 IDs are used. 1007 An Instance ID can be carried in a LISP-encapsulated packet. An ITR 1008 that prepends a LISP header will copy a 24-bit value used by the LISP 1009 router to uniquely identify the address space. The value is copied 1010 to the 'Instance ID' field of the LISP header, and the I-bit is set 1011 to 1. 1013 When an ETR decapsulates a packet, the Instance ID from the LISP 1014 header is used as a table identifier to locate the forwarding table 1015 to use for the inner destination EID lookup. 1017 For example, an 802.1Q VLAN tag or VPN identifier could be used as a 1018 24-bit Instance ID. See [I-D.ietf-lisp-vpn] for LISP VPN use-case 1019 details. 1021 The Instance ID that is stored in the mapping database when LISP-DDT 1022 [RFC8111] is used is 32 bits in length. That means the control-plane 1023 can store more instances than a given data-plane can use. Multiple 1024 data-planes can use the same 32-bit space as long as the low-order 24 1025 bits don't overlap among xTRs. 1027 9. Routing Locator Selection 1029 The map-cache contains the state used by ITRs and PITRs to 1030 encapsulate packets. When an ITR/PITR receives a packet from inside 1031 the LISP site to a destination outside of the site a longest-prefix 1032 match lookup of the EID is done to the map-cache (see Section 6). 1033 The lookup returns a single Locator-Set containing a list of RLOCs 1034 corresponding to the EID's topological location. Each RLOC in the 1035 Locator-Set is associated with a 'Priority' and 'Weight', this 1036 information is used to select the RLOC to encapsulate. 1038 The RLOC with the lowest 'Priority' is selected. An RLOC with 1039 'Priority' 255 means that MUST NOT be used for forwarding. When 1040 multiple RLOC have the same 'Priority' then the 'Weight' states how 1041 to load balance traffic among them. The value of the 'Weight' 1042 represents the relative weight of the total packets that match the 1043 maping entry. 1045 The following are different scenarios for choosing RLOCs and the 1046 controls that are available: 1048 o The server-side returns one RLOC. The client-side can only use 1049 one RLOC. The server-side has complete control of the selection. 1051 o The server-side returns a list of RLOCs where a subset of the list 1052 has the same best Priority. The client can only use the subset 1053 list according to the weighting assigned by the server-side. In 1054 this case, the server-side controls both the subset list and load- 1055 splitting across its members. The client-side can use RLOCs 1056 outside of the subset list if it determines that the subset list 1057 is unreachable (unless RLOCs are set to a Priority of 255). Some 1058 sharing of control exists: the server-side determines the 1059 destination RLOC list and load distribution while the client-side 1060 has the option of using alternatives to this list if RLOCs in the 1061 list are unreachable. 1063 o The server-side sets a Weight of zero for the RLOC subset list. 1064 In this case, the client-side can choose how the traffic load is 1065 spread across the subset list. Control is shared by the server- 1066 side determining the list and the client-side determining load 1067 distribution. Again, the client can use alternative RLOCs if the 1068 server-provided list of RLOCs is unreachable. 1070 o Either side (more likely the server-side ETR) decides not to send 1071 a Map-Request. For example, if the server-side ETR does not send 1072 Map-Requests, it gleans RLOCs from the client-side ITR, giving the 1073 client-side ITR responsibility for bidirectional RLOC reachability 1074 and preferability. Server-side ETR gleaning of the client-side 1075 ITR RLOC is done by caching the inner-header source EID and the 1076 outer-header source RLOC of received packets. The client-side ITR 1077 controls how traffic is returned and can alternate using an outer- 1078 header source RLOC, which then can be added to the list the 1079 server-side ETR uses to return traffic. Since no Priority or 1080 Weights are provided using this method, the server-side ETR MUST 1081 assume that each client-side ITR RLOC uses the same best Priority 1082 with a Weight of zero. In addition, since EID-Prefix encoding 1083 cannot be conveyed in data packets, the EID-to-RLOC Cache on 1084 Tunnel Routers can grow to be very large. 1086 Alternatively, RLOC information MAY be gleaned from received tunneled 1087 packets or EID-to-RLOC Map-Request messages. A "gleaned" Map-Cache 1088 entry, one learned from the source RLOC of a received encapsulated 1089 packet, is only stored and used for a few seconds, pending 1090 verification. Verification is performed by sending a Map-Request to 1091 the source EID (the inner-header IP source address) of the received 1092 encapsulated packet. A reply to this "verifying Map-Request" is used 1093 to fully populate the Map-Cache entry for the "gleaned" EID and is 1094 stored and used for the time indicated from the 'TTL' field of a 1095 received Map-Reply. When a verified Map-Cache entry is stored, data 1096 gleaning no longer occurs for subsequent packets that have a source 1097 EID that matches the EID-Prefix of the verified entry. This 1098 "gleaning" mechanism is OPTIONAL, refer to Section 19 for security 1099 issues regarding this mechanism. 1101 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1102 reachable when the R-bit for the Locator record is set to 1. When 1103 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1104 RLOC. Neither the information contained in a Map-Reply nor that 1105 stored in the mapping database system provides reachability 1106 information for RLOCs. Note that reachability is not part of the 1107 mapping system and is determined using one or more of the Routing 1108 Locator reachability algorithms described in the next section. 1110 10. Routing Locator Reachability 1112 Several data-plane mechanisms for determining RLOC reachability are 1113 currently defined. Please note that additional control-plane based 1114 reachability mechanisms are defined in [I-D.ietf-lisp-rfc6833bis]. 1116 1. An ETR MAY examine the Locator-Status-Bits in the LISP header of 1117 an encapsulated data packet received from an ITR. If the ETR is 1118 also acting as an ITR and has traffic to return to the original 1119 ITR site, it can use this status information to help select an 1120 RLOC. 1122 2. When an ETR receives an encapsulated packet from an ITR, the 1123 source RLOC from the outer header of the packet is likely up. 1125 3. An ITR/ETR pair can use the 'Echo-Noncing' Locator reachability 1126 algorithms described in this section. 1128 When determining Locator up/down reachability by examining the 1129 Locator-Status-Bits from the LISP-encapsulated data packet, an ETR 1130 will receive up-to-date status from an encapsulating ITR about 1131 reachability for all ETRs at the site. CE-based ITRs at the source 1132 site can determine reachability relative to each other using the site 1133 IGP as follows: 1135 o Under normal circumstances, each ITR will advertise a default 1136 route into the site IGP. 1138 o If an ITR fails or if the upstream link to its PE fails, its 1139 default route will either time out or be withdrawn. 1141 Each ITR can thus observe the presence or lack of a default route 1142 originated by the others to determine the Locator-Status-Bits it sets 1143 for them. 1145 When ITRs at the site are not deployed in CE routers, the IGP can 1146 still be used to determine the reachability of Locators, provided 1147 they are injected into the IGP. This is typically done when a /32 1148 address is configured on a loopback interface. 1150 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1151 Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 1152 to n-1 starting with the least significant bit. For example, if an 1153 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1154 value 2), then all ITRs at the site will clear the 3rd least 1155 significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for 1156 the packets they encapsulate. 1158 When an ETR decapsulates a packet, it will check for any change in 1159 the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the 1160 ETR, if acting also as an ITR, will refrain from encapsulating 1161 packets to an RLOC that is indicated as down. It will only resume 1162 using that RLOC if the corresponding Locator-Status-Bit returns to a 1163 value of 1. Locator-Status-Bits are associated with a Locator-Set 1164 per EID-Prefix. Therefore, when a Locator becomes unreachable, the 1165 Locator-Status-Bit that corresponds to that Locator's position in the 1166 list returned by the last Map-Reply will be set to zero for that 1167 particular EID-Prefix. Refer to Section 19 for security related 1168 issues regarding Locator-Status-Bits. 1170 When an ETR decapsulates a packet, it knows that it is reachable from 1171 the encapsulating ITR because that is how the packet arrived. In 1172 most cases, the ETR can also reach the ITR but cannot assume this to 1173 be true, due to the possibility of path asymmetry. In the presence 1174 of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD 1175 NOT use the lack of return traffic as an indication that the ETR is 1176 unreachable. Instead, it MUST use an alternate mechanism to 1177 determine reachability. 1179 10.1. Echo Nonce Algorithm 1181 When data flows bidirectionally between Locators from different 1182 sites, a data-plane mechanism called "nonce echoing" can be used to 1183 determine reachability between an ITR and ETR. When an ITR wants to 1184 solicit a nonce echo, it sets the N- and E-bits and places a 24-bit 1185 nonce [RFC4086] in the LISP header of the next encapsulated data 1186 packet. 1188 When this packet is received by the ETR, the encapsulated packet is 1189 forwarded as normal. When the ETR next sends a data packet to the 1190 ITR, it includes the nonce received earlier with the N-bit set and 1191 E-bit cleared. The ITR sees this "echoed nonce" and knows that the 1192 path to and from the ETR is up. 1194 The ITR will set the E-bit and N-bit for every packet it sends while 1195 in the echo-nonce-request state. The time the ITR waits to process 1196 the echoed nonce before it determines the path is unreachable is 1197 variable and is a choice left for the implementation. 1199 If the ITR is receiving packets from the ETR but does not see the 1200 nonce echoed while being in the echo-nonce-request state, then the 1201 path to the ETR is unreachable. This decision MAY be overridden by 1202 other Locator reachability algorithms. Once the ITR determines that 1203 the path to the ETR is down, it can switch to another Locator for 1204 that EID-Prefix. 1206 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1207 be implementing both ITR and ETR functionality for the echo nonce 1208 mechanism to operate. 1210 The ITR and ETR MAY both go into the echo-nonce-request state at the 1211 same time. The number of packets sent or the time during which echo 1212 nonce requests are sent is an implementation-specific setting. 1213 However, when an ITR is in the echo-nonce-request state, it can echo 1214 the ETR's nonce in the next set of packets that it encapsulates and 1215 subsequently continue sending echo-nonce-request packets. 1217 This mechanism does not completely solve the forward path 1218 reachability problem, as traffic may be unidirectional. That is, the 1219 ETR receiving traffic at a site MAY not be the same device as an ITR 1220 that transmits traffic from that site, or the site-to-site traffic is 1221 unidirectional so there is no ITR returning traffic. 1223 The echo-nonce algorithm is bilateral. That is, if one side sets the 1224 E-bit and the other side is not enabled for echo-noncing, then the 1225 echoing of the nonce does not occur and the requesting side may 1226 erroneously consider the Locator unreachable. An ITR SHOULD only set 1227 the E-bit in an encapsulated data packet when it knows the ETR is 1228 enabled for echo-noncing. This is conveyed by the E-bit in the RLOC- 1229 probe Map-Reply message. 1231 11. EID Reachability within a LISP Site 1233 A site MAY be multihomed using two or more ETRs. The hosts and 1234 infrastructure within a site will be addressed using one or more EID- 1235 Prefixes that are mapped to the RLOCs of the relevant ETRs in the 1236 mapping system. One possible failure mode is for an ETR to lose 1237 reachability to one or more of the EID-Prefixes within its own site. 1238 When this occurs when the ETR sends Map-Replies, it can clear the 1239 R-bit associated with its own Locator. And when the ETR is also an 1240 ITR, it can clear its Locator-Status-Bit in the encapsulation data 1241 header. 1243 It is recognized that there are no simple solutions to the site 1244 partitioning problem because it is hard to know which part of the 1245 EID-Prefix range is partitioned and which Locators can reach any sub- 1246 ranges of the EID-Prefixes. Note that this is not a new problem 1247 introduced by the LISP architecture. The problem exists today when a 1248 multihomed site uses BGP to advertise its reachability upstream. 1250 12. Routing Locator Hashing 1252 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message 1253 that is stored in the map-cache of a requesting ITR, the Locator-Set 1254 for the EID-Prefix MAY contain different Priority and Weight values 1255 for each locator address. When more than one best Priority Locator 1256 exists, the ITR can decide how to load-share traffic against the 1257 corresponding Locators. 1259 The following hash algorithm MAY be used by an ITR to select a 1260 Locator for a packet destined to an EID for the EID-to-RLOC mapping: 1262 1. Either a source and destination address hash or the traditional 1263 5-tuple hash can be used. The traditional 5-tuple hash includes 1264 the source and destination addresses; source and destination TCP, 1265 UDP, or Stream Control Transmission Protocol (SCTP) port numbers; 1266 and the IP protocol number field or IPv6 next-protocol fields of 1267 a packet that a host originates from within a LISP site. When a 1268 packet is not a TCP, UDP, or SCTP packet, the source and 1269 destination addresses only from the header are used to compute 1270 the hash. 1272 2. Take the hash value and divide it by the number of Locators 1273 stored in the Locator-Set for the EID-to-RLOC mapping. 1275 3. The remainder will yield a value of 0 to "number of Locators 1276 minus 1". Use the remainder to select the Locator in the 1277 Locator-Set. 1279 Note that when a packet is LISP encapsulated, the source port number 1280 in the outer UDP header needs to be set. Selecting a hashed value 1281 allows core routers that are attached to Link Aggregation Groups 1282 (LAGs) to load-split the encapsulated packets across member links of 1283 such LAGs. Otherwise, core routers would see a single flow, since 1284 packets have a source address of the ITR, for packets that are 1285 originated by different EIDs at the source site. A suggested setting 1286 for the source port number computed by an ITR is a 5-tuple hash 1287 function on the inner header, as described above. 1289 Many core router implementations use a 5-tuple hash to decide how to 1290 balance packet load across members of a LAG. The 5-tuple hash 1291 includes the source and destination addresses of the packet and the 1292 source and destination ports when the protocol number in the packet 1293 is TCP or UDP. For this reason, UDP encoding is used for LISP 1294 encapsulation. 1296 13. Changing the Contents of EID-to-RLOC Mappings 1298 Since the LISP architecture uses a caching scheme to retrieve and 1299 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 1300 date mapping is to re-request the mapping. However, the ITRs do not 1301 know when the mappings change, and the ETRs do not keep track of 1302 which ITRs requested its mappings. For scalability reasons, it is 1303 desirable to maintain this approach but need to provide a way for 1304 ETRs to change their mappings and inform the sites that are currently 1305 communicating with the ETR site using such mappings. 1307 This section defines data-plane mechanisms for updating EID-to-RLOC 1308 mappings. Additionally, the Solicit-Map Request (SMR) control-plane 1309 updating mechanism is specified in [I-D.ietf-lisp-rfc6833bis]. 1311 When adding a new Locator record in lexicographic order to the end of 1312 a Locator-Set, it is easy to update mappings. We assume that new 1313 mappings will maintain the same Locator ordering as the old mapping 1314 but will just have new Locators appended to the end of the list. So, 1315 some ITRs can have a new mapping while other ITRs have only an old 1316 mapping that is used until they time out. When an ITR has only an 1317 old mapping but detects bits set in the Locator-Status-Bits that 1318 correspond to Locators beyond the list it has cached, it simply 1319 ignores them. However, this can only happen for locator addresses 1320 that are lexicographically greater than the locator addresses in the 1321 existing Locator-Set. 1323 When a Locator record is inserted in the middle of a Locator-Set, to 1324 maintain lexicographic order, SMR procedure 1325 [I-D.ietf-lisp-rfc6833bis] is used to inform ITRs and PITRs of the 1326 new Locator-Status-Bit mappings. 1328 When a Locator record is removed from a Locator-Set, ITRs that have 1329 the mapping cached will not use the removed Locator because the xTRs 1330 will set the Locator-Status-Bit to 0. So, even if the Locator is in 1331 the list, it will not be used. For new mapping requests, the xTRs 1332 can set the Locator AFI to 0 (indicating an unspecified address), as 1333 well as setting the corresponding Locator-Status-Bit to 0. This 1334 forces ITRs with old or new mappings to avoid using the removed 1335 Locator. 1337 If many changes occur to a mapping over a long period of time, one 1338 will find empty record slots in the middle of the Locator-Set and new 1339 records appended to the Locator-Set. At some point, it would be 1340 useful to compact the Locator-Set so the Locator-Status-Bit settings 1341 can be efficiently packed. 1343 We propose here two approaches for Locator-Set compaction: one 1344 operational mechanism (clock sweep) and one protocol mechanisms (Map- 1345 Versioning). Please note that in addition the Solicit-Map Request 1346 (specified in [I-D.ietf-lisp-rfc6833bis]) is a control-plane 1347 mechanisms that can be used to update EID-to-RLOC mappings. 1349 13.1. Clock Sweep 1351 The clock sweep approach uses planning in advance and the use of 1352 count-down TTLs to time out mappings that have already been cached. 1353 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So, 1354 there is a 24-hour window to time out old mappings. The following 1355 clock sweep procedure is used: 1357 1. 24 hours before a mapping change is to take effect, a network 1358 administrator configures the ETRs at a site to start the clock 1359 sweep window. 1361 2. During the clock sweep window, ETRs continue to send Map-Reply 1362 messages with the current (unchanged) mapping records. The TTL 1363 for these mappings is set to 1 hour. 1365 3. 24 hours later, all previous cache entries will have timed out, 1366 and any active cache entries will time out within 1 hour. During 1367 this 1-hour window, the ETRs continue to send Map-Reply messages 1368 with the current (unchanged) mapping records with the TTL set to 1369 1 minute. 1371 4. At the end of the 1-hour window, the ETRs will send Map-Reply 1372 messages with the new (changed) mapping records. So, any active 1373 caches can get the new mapping contents right away if not cached, 1374 or in 1 minute if they had the mapping cached. The new mappings 1375 are cached with a TTL equal to the TTL in the Map-Reply. 1377 13.2. Database Map-Versioning 1379 When there is unidirectional packet flow between an ITR and ETR, and 1380 the EID-to-RLOC mappings change on the ETR, it needs to inform the 1381 ITR so encapsulation to a removed Locator can stop and can instead be 1382 started to a new Locator in the Locator-Set. 1384 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 1385 Number. This is known as the Destination Map-Version Number. ITRs 1386 include the Destination Map-Version Number in packets they 1387 encapsulate to the site. When an ETR decapsulates a packet and 1388 detects that the Destination Map-Version Number is less than the 1389 current version for its mapping, the SMR procedure described in 1390 [I-D.ietf-lisp-rfc6833bis] occurs. 1392 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 1393 Version Number. This is known as the Source Map-Version Number. 1394 When an ETR decapsulates a packet and detects that the Source Map- 1395 Version Number is greater than the last Map-Version Number sent in a 1396 Map-Reply from the ITR's site, the ETR will send a Map-Request to one 1397 of the ETRs for the source site. 1399 A Map-Version Number is used as a sequence number per EID-Prefix, so 1400 values that are greater are considered to be more recent. A value of 1401 0 for the Source Map-Version Number or the Destination Map-Version 1402 Number conveys no versioning information, and an ITR does no 1403 comparison with previously received Map-Version Numbers. 1405 A Map-Version Number can be included in Map-Register messages as 1406 well. This is a good way for the Map-Server to assure that all ETRs 1407 for a site registering to it will be synchronized according to Map- 1408 Version Number. 1410 See [RFC6834] for a more detailed analysis and description of 1411 Database Map-Versioning. 1413 14. Multicast Considerations 1415 A multicast group address, as defined in the original Internet 1416 architecture, is an identifier of a grouping of topologically 1417 independent receiver host locations. The address encoding itself 1418 does not determine the location of the receiver(s). The multicast 1419 routing protocol, and the network-based state the protocol creates, 1420 determine where the receivers are located. 1422 In the context of LISP, a multicast group address is both an EID and 1423 a Routing Locator. Therefore, no specific semantic or action needs 1424 to be taken for a destination address, as it would appear in an IP 1425 header. Therefore, a group address that appears in an inner IP 1426 header built by a source host will be used as the destination EID. 1427 The outer IP header (the destination Routing Locator address), 1428 prepended by a LISP router, can use the same group address as the 1429 destination Routing Locator, use a multicast or unicast Routing 1430 Locator obtained from a Mapping System lookup, or use other means to 1431 determine the group address mapping. 1433 With respect to the source Routing Locator address, the ITR prepends 1434 its own IP address as the source address of the outer IP header. 1435 Just like it would if the destination EID was a unicast address. 1436 This source Routing Locator address, like any other Routing Locator 1437 address, MUST be globally routable. 1439 There are two approaches for LISP-Multicast, one that uses native 1440 multicast routing in the underlay with no support from the Mapping 1441 System and the other that uses only unicast routing in the underlay 1442 with support from the Mapping System. See [RFC6831] and 1443 [I-D.ietf-lisp-signal-free-multicast], respectively, for details. 1444 Details for LISP-Multicast and interworking with non-LISP sites are 1445 described in [RFC6831] and [RFC6832]. 1447 15. Router Performance Considerations 1449 LISP is designed to be very "hardware-based forwarding friendly". A 1450 few implementation techniques can be used to incrementally implement 1451 LISP: 1453 o When a tunnel-encapsulated packet is received by an ETR, the outer 1454 destination address may not be the address of the router. This 1455 makes it challenging for the control plane to get packets from the 1456 hardware. This may be mitigated by creating special Forwarding 1457 Information Base (FIB) entries for the EID-Prefixes of EIDs served 1458 by the ETR (those for which the router provides an RLOC 1459 translation). These FIB entries are marked with a flag indicating 1460 that control-plane processing SHOULD be performed. The forwarding 1461 logic of testing for particular IP protocol number values is not 1462 necessary. There are a few proven cases where no changes to 1463 existing deployed hardware were needed to support the LISP data- 1464 plane. 1466 o On an ITR, prepending a new IP header consists of adding more 1467 octets to a MAC rewrite string and prepending the string as part 1468 of the outgoing encapsulation procedure. Routers that support 1469 Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 1470 tunneling [RFC3056] may already support this action. 1472 o A packet's source address or interface the packet was received on 1473 can be used to select VRF (Virtual Routing/Forwarding). The VRF's 1474 routing table can be used to find EID-to-RLOC mappings. 1476 For performance issues related to map-cache management, see 1477 Section 19. 1479 16. Mobility Considerations 1481 There are several kinds of mobility, of which only some might be of 1482 concern to LISP. Essentially, they are as follows. 1484 16.1. Slow Mobility 1486 A site wishes to change its attachment points to the Internet, and 1487 its LISP Tunnel Routers will have new RLOCs when it changes upstream 1488 providers. Changes in EID-to-RLOC mappings for sites are expected to 1489 be handled by configuration, outside of LISP. 1491 An individual endpoint wishes to move but is not concerned about 1492 maintaining session continuity. Renumbering is involved. LISP can 1493 help with the issues surrounding renumbering [RFC4192] [LISA96] by 1494 decoupling the address space used by a site from the address spaces 1495 used by its ISPs [RFC4984]. 1497 16.2. Fast Mobility 1499 Fast endpoint mobility occurs when an endpoint moves relatively 1500 rapidly, changing its IP-layer network attachment point. Maintenance 1501 of session continuity is a goal. This is where the Mobile IPv4 1502 [RFC5944] and Mobile IPv6 [RFC6275] [RFC4866] mechanisms are used and 1503 primarily where interactions with LISP need to be explored, such as 1504 the mechanisms in [I-D.ietf-lisp-eid-mobility] when the EID moves but 1505 the RLOC is in the network infrastructure. 1507 In LISP, one possibility is to "glean" information. When a packet 1508 arrives, the ETR could examine the EID-to-RLOC mapping and use that 1509 mapping for all outgoing traffic to that EID. It can do this after 1510 performing a route-returnability check, to ensure that the new 1511 network location does have an internal route to that endpoint. 1512 However, this does not cover the case where an ITR (the node assigned 1513 the RLOC) at the mobile-node location has been compromised. 1515 Mobile IP packet exchange is designed for an environment in which all 1516 routing information is disseminated before packets can be forwarded. 1517 In order to allow the Internet to grow to support expected future 1518 use, we are moving to an environment where some information may have 1519 to be obtained after packets are in flight. Modifications to IP 1520 mobility should be considered in order to optimize the behavior of 1521 the overall system. Anything that decreases the number of new EID- 1522 to-RLOC mappings needed when a node moves, or maintains the validity 1523 of an EID-to-RLOC mapping for a longer time, is useful. 1525 In addition to endpoints, a network can be mobile, possibly changing 1526 xTRs. A "network" can be as small as a single router and as large as 1527 a whole site. This is different from site mobility in that it is 1528 fast and possibly short-lived, but different from endpoint mobility 1529 in that a whole prefix is changing RLOCs. However, the mechanisms 1530 are the same, and there is no new overhead in LISP. A map request 1531 for any endpoint will return a binding for the entire mobile prefix. 1533 If mobile networks become a more common occurrence, it may be useful 1534 to revisit the design of the mapping service and allow for dynamic 1535 updates of the database. 1537 The issue of interactions between mobility and LISP needs to be 1538 explored further. Specific improvements to the entire system will 1539 depend on the details of mapping mechanisms. Mapping mechanisms 1540 should be evaluated on how well they support session continuity for 1541 mobile nodes. See [I-D.ietf-lisp-predictive-rlocs] for more recent 1542 mechanisms which can provide near-zero packet loss during handoffs. 1544 16.3. LISP Mobile Node Mobility 1546 A mobile device can use the LISP infrastructure to achieve mobility 1547 by implementing the LISP encapsulation and decapsulation functions 1548 and acting as a simple ITR/ETR. By doing this, such a "LISP mobile 1549 node" can use topologically independent EID IP addresses that are not 1550 advertised into and do not impose a cost on the global routing 1551 system. These EIDs are maintained at the edges of the mapping system 1552 in LISP Map-Servers and Map-Resolvers) and are provided on demand to 1553 only the correspondents of the LISP mobile node. 1555 Refer to [I-D.ietf-lisp-mn] for more details for when the EID and 1556 RLOC are co-located in the roaming node. 1558 17. LISP xTR Placement and Encapsulation Methods 1560 This section will explore how and where ITRs and ETRs can be placed 1561 in the network and will discuss the pros and cons of each scenario. 1562 For a more detailed network design deployment recommendation, refer 1563 to [RFC7215]. 1565 There are two basic deployment tradeoffs to consider: centralized 1566 versus distributed caches; and flat, Recursive, or Re-encapsulating 1567 Tunneling. When deciding on centralized versus distributed caching, 1568 the following issues SHOULD be considered: 1570 o Are the xTRs spread out so that the caches are spread across all 1571 the memories of each router? A centralized cache is when an ITR 1572 keeps a cache for all the EIDs it is encapsulating to. The packet 1573 takes a direct path to the destination Locator. A distributed 1574 cache is when an ITR needs help from other Re-Encapsulating Tunnel 1575 Routers (RTRs) because it does not store all the cache entries for 1576 the EIDs it is encapsulating to. So, the packet takes a path 1577 through RTRs that have a different set of cache entries. 1579 o Should management "touch points" be minimized by only choosing a 1580 few xTRs, just enough for redundancy? 1582 o In general, using more ITRs doesn't increase management load, 1583 since caches are built and stored dynamically. On the other hand, 1584 using more ETRs does require more management, since EID-Prefix-to- 1585 RLOC mappings need to be explicitly configured. 1587 When deciding on flat, Recursive, or Re-Encapsulating Tunneling, the 1588 following issues SHOULD be considered: 1590 o Flat tunneling implements a single encapsulation path between the 1591 source site and destination site. This generally offers better 1592 paths between sources and destinations with a single encapsulation 1593 path. 1595 o Recursive Tunneling is when encapsulated traffic is again further 1596 encapsulated in another tunnel, either to implement VPNs or to 1597 perform Traffic Engineering. When doing VPN-based tunneling, the 1598 site has some control, since the site is prepending a new 1599 encapsulation header. In the case of TE-based tunneling, the site 1600 MAY have control if it is prepending a new tunnel header, but if 1601 the site's ISP is doing the TE, then the site has no control. 1602 Recursive Tunneling generally will result in suboptimal paths but 1603 with the benefit of steering traffic to parts of the network that 1604 have more resources available. 1606 o The technique of Re-Encapsulation ensures that packets only 1607 require one encapsulation header. So, if a packet needs to be re- 1608 routed, it is first decapsulated by the RTR and then Re- 1609 Encapsulated with a new encapsulation header using a new RLOC. 1611 The next sub-sections will examine where xTRs and RTRs can reside in 1612 the network. 1614 17.1. First-Hop/Last-Hop xTRs 1616 By locating xTRs close to hosts, the EID-Prefix set is at the 1617 granularity of an IP subnet. So, at the expense of more EID-Prefix- 1618 to-RLOC sets for the site, the caches in each xTR can remain 1619 relatively small. But caches always depend on the number of non- 1620 aggregated EID destination flows active through these xTRs. 1622 With more xTRs doing encapsulation, the increase in control traffic 1623 grows as well: since the EID granularity is greater, more Map- 1624 Requests and Map-Replies are traveling between more routers. 1626 The advantage of placing the caches and databases at these stub 1627 routers is that the products deployed in this part of the network 1628 have better price-memory ratios than their core router counterparts. 1629 Memory is typically less expensive in these devices, and fewer routes 1630 are stored (only IGP routes). These devices tend to have excess 1631 capacity, both for forwarding and routing states. 1633 LISP functionality can also be deployed in edge switches. These 1634 devices generally have layer-2 ports facing hosts and layer-3 ports 1635 facing the Internet. Spare capacity is also often available in these 1636 devices. 1638 17.2. Border/Edge xTRs 1640 Using Customer Edge (CE) routers for xTR placement allows the EID 1641 space associated with a site to be reachable via a small set of RLOCs 1642 assigned to the CE-based xTRs for that site. 1644 This offers the opposite benefit of the first-hop/last-hop xTR 1645 scenario: the number of mapping entries and network management touch 1646 points is reduced, allowing better scaling. 1648 One disadvantage is that fewer network resources are used to reach 1649 host endpoints, thereby centralizing the point-of-failure domain and 1650 creating network choke points at the CE xTR. 1652 Note that more than one CE xTR at a site can be configured with the 1653 same IP address. In this case, an RLOC is an anycast address. This 1654 allows resilience between the CE xTRs. That is, if a CE xTR fails, 1655 traffic is automatically routed to the other xTRs using the same 1656 anycast address. However, this comes with the disadvantage where the 1657 site cannot control the entrance point when the anycast route is 1658 advertised out from all border routers. Another disadvantage of 1659 using anycast Locators is the limited advertisement scope of /32 (or 1660 /128 for IPv6) routes. 1662 17.3. ISP Provider Edge (PE) xTRs 1664 The use of ISP PE routers as xTRs is not the typical deployment 1665 scenario envisioned in this specification. This section attempts to 1666 capture some of the reasoning behind this preference for implementing 1667 LISP on CE routers. 1669 The use of ISP PE routers for xTR placement gives an ISP, rather than 1670 a site, control over the location of the ETRs. That is, the ISP can 1671 decide whether the xTRs are in the destination site (in either CE 1672 xTRs or last-hop xTRs within a site) or at other PE edges. The 1673 advantage of this case is that two encapsulation headers can be 1674 avoided. By having the PE be the first router on the path to 1675 encapsulate, it can choose a TE path first, and the ETR can 1676 decapsulate and Re-Encapsulate for a new encapsulation path to the 1677 destination end site. 1679 An obvious disadvantage is that the end site has no control over 1680 where its packets flow or over the RLOCs used. Other disadvantages 1681 include difficulty in synchronizing path liveness updates between CE 1682 and PE routers. 1684 As mentioned in earlier sections, a combination of these scenarios is 1685 possible at the expense of extra packet header overhead; if both site 1686 and provider want control, then Recursive or Re-Encapsulating Tunnels 1687 are used. 1689 17.4. LISP Functionality with Conventional NATs 1691 LISP routers can be deployed behind Network Address Translator (NAT) 1692 devices to provide the same set of packet services hosts have today 1693 when they are addressed out of private address space. 1695 It is important to note that a locator address in any LISP control 1696 message MUST be a routable address and therefore [RFC1918] addresses 1697 SHOULD only be presence when running in a local environment. When a 1698 LISP xTR is configured with private RLOC addresses and resides behind 1699 a NAT device and desires to communicate on the Internet, the private 1700 addresses MUST be used only in the outer IP header so the NAT device 1701 can translate properly. Otherwise, EID addresses MUST be translated 1702 before encapsulation is performed when LISP VPNs are not in use. 1703 Both NAT translation and LISP encapsulation functions could be co- 1704 located in the same device. 1706 17.5. Packets Egressing a LISP Site 1708 When a LISP site is using two ITRs for redundancy, the failure of one 1709 ITR will likely shift outbound traffic to the second. This second 1710 ITR's cache MAY not be populated with the same EID-to-RLOC mapping 1711 entries as the first. If this second ITR does not have these 1712 mappings, traffic will be dropped while the mappings are retrieved 1713 from the mapping system. The retrieval of these messages may 1714 increase the load of requests being sent into the mapping system. 1716 18. Traceroute Considerations 1718 When a source host in a LISP site initiates a traceroute to a 1719 destination host in another LISP site, it is highly desirable for it 1720 to see the entire path. Since packets are encapsulated from the ITR 1721 to the ETR, the hop across the tunnel could be viewed as a single 1722 hop. However, LISP traceroute will provide the entire path so the 1723 user can see 3 distinct segments of the path from a source LISP host 1724 to a destination LISP host: 1726 Segment 1 (in source LISP site based on EIDs): 1728 source host ---> first hop ... next hop ---> ITR 1730 Segment 2 (in the core network based on RLOCs): 1732 ITR ---> next hop ... next hop ---> ETR 1734 Segment 3 (in the destination LISP site based on EIDs): 1736 ETR ---> next hop ... last hop ---> destination host 1738 For segment 1 of the path, ICMP Time Exceeded messages are returned 1739 in the normal manner as they are today. The ITR performs a TTL 1740 decrement and tests for 0 before encapsulating. Therefore, the ITR's 1741 hop is seen by the traceroute source as having an EID address (the 1742 address of the site-facing interface). 1744 For segment 2 of the path, ICMP Time Exceeded messages are returned 1745 to the ITR because the TTL decrement to 0 is done on the outer 1746 header, so the destinations of the ICMP messages are the ITR RLOC 1747 address and the source RLOC address of the encapsulated traceroute 1748 packet. The ITR looks inside of the ICMP payload to inspect the 1749 traceroute source so it can return the ICMP message to the address of 1750 the traceroute client and also retain the core router IP address in 1751 the ICMP message. This is so the traceroute client can display the 1752 core router address (the RLOC address) in the traceroute output. The 1753 ETR returns its RLOC address and responds to the TTL decrement to 0, 1754 as the previous core routers did. 1756 For segment 3, the next-hop router downstream from the ETR will be 1757 decrementing the TTL for the packet that was encapsulated, sent into 1758 the core, decapsulated by the ETR, and forwarded because it isn't the 1759 final destination. If the TTL is decremented to 0, any router on the 1760 path to the destination of the traceroute, including the next-hop 1761 router or destination, will send an ICMP Time Exceeded message to the 1762 source EID of the traceroute client. The ICMP message will be 1763 encapsulated by the local ITR and sent back to the ETR in the 1764 originated traceroute source site, where the packet will be delivered 1765 to the host. 1767 18.1. IPv6 Traceroute 1769 IPv6 traceroute follows the procedure described above, since the 1770 entire traceroute data packet is included in the ICMP Time Exceeded 1771 message payload. Therefore, only the ITR needs to pay special 1772 attention to forwarding ICMP messages back to the traceroute source. 1774 18.2. IPv4 Traceroute 1776 For IPv4 traceroute, we cannot follow the above procedure, since IPv4 1777 ICMP Time Exceeded messages only include the invoking IP header and 1778 8 octets that follow the IP header. Therefore, when a core router 1779 sends an IPv4 Time Exceeded message to an ITR, all the ITR has in the 1780 ICMP payload is the encapsulated header it prepended, followed by a 1781 UDP header. The original invoking IP header, and therefore the 1782 identity of the traceroute source, is lost. 1784 The solution we propose to solve this problem is to cache traceroute 1785 IPv4 headers in the ITR and to match them up with corresponding IPv4 1786 Time Exceeded messages received from core routers and the ETR. The 1787 ITR will use a circular buffer for caching the IPv4 and UDP headers 1788 of traceroute packets. It will select a 16-bit number as a key to 1789 find them later when the IPv4 Time Exceeded messages are received. 1790 When an ITR encapsulates an IPv4 traceroute packet, it will use the 1791 16-bit number as the UDP source port in the encapsulating header. 1792 When the ICMP Time Exceeded message is returned to the ITR, the UDP 1793 header of the encapsulating header is present in the ICMP payload, 1794 thereby allowing the ITR to find the cached headers for the 1795 traceroute source. The ITR puts the cached headers in the payload 1796 and sends the ICMP Time Exceeded message to the traceroute source 1797 retaining the source address of the original ICMP Time Exceeded 1798 message (a core router or the ETR of the site of the traceroute 1799 destination). 1801 The signature of a traceroute packet comes in two forms. The first 1802 form is encoded as a UDP message where the destination port is 1803 inspected for a range of values. The second form is encoded as an 1804 ICMP message where the IP identification field is inspected for a 1805 well-known value. 1807 18.3. Traceroute Using Mixed Locators 1809 When either an IPv4 traceroute or IPv6 traceroute is originated and 1810 the ITR encapsulates it in the other address family header, one 1811 cannot get all 3 segments of the traceroute. Segment 2 of the 1812 traceroute cannot be conveyed to the traceroute source, since it is 1813 expecting addresses from intermediate hops in the same address format 1814 for the type of traceroute it originated. Therefore, in this case, 1815 segment 2 will make the tunnel look like one hop. All the ITR has to 1816 do to make this work is to not copy the inner TTL to the outer, 1817 encapsulating header's TTL when a traceroute packet is encapsulated 1818 using an RLOC from a different address family. This will cause no 1819 TTL decrement to 0 to occur in core routers between the ITR and ETR. 1821 19. Security Considerations 1823 Security considerations for LISP are discussed in [RFC7833]. 1825 A complete LISP threat analysis can be found in [RFC7835], in what 1826 follows we provide a summary. 1828 The optional mechanisms of gleaning is offered to directly obtain a 1829 mapping from the LISP encapsulated packets. Specifically, an xTR can 1830 learn the EID-to-RLOC mapping by inspecting the source RLOC and 1831 source EID of an encapsulated packet, and insert this new mapping 1832 into its map-cache. An off-path attacker can spoof the source EID 1833 address to divert the traffic sent to the victim's spoofed EID. If 1834 the attacker spoofs the source RLOC, it can mount a DoS attack by 1835 redirecting traffic to the spoofed victim's RLOC, potentially 1836 overloading it. 1838 The LISP Data-Plane defines several mechanisms to monitor RLOC data- 1839 plane reachability, in this context Locator-Status Bits, Nonce- 1840 Present and Echo-Nonce bits of the LISP encapsulation header can be 1841 manipulated by an attacker to mount a DoS attack. An off-path 1842 attacker able to spoof the RLOC of a victim's xTR can manipulate such 1843 mechanisms to declare a set of RLOCs unreachable. This can be used 1844 also, for instance, to declare only one RLOC reachable with the aim 1845 of overload it. 1847 Map-Versioning is a data-plane mechanism used to signal a peering xTR 1848 that a local EID-to-RLOC mapping has been updated, so that the 1849 peering xTR uses LISP Control-Plane signaling message to retrieve a 1850 fresh mapping. This can be used by an attacker to forge the map- 1851 versioning field of a LISP encapsulated header and force an excessive 1852 amount of signaling between xTRs that may overload them. 1854 Most of the attack vectors can be mitigated with careful deployment 1855 and configuration, information learned opportunistically (such as LSB 1856 or gleaning) SHOULD be verified with other reachability mechanisms. 1857 In addition, systematic rate-limitation and filtering is an effective 1858 technique to mitigate attacks that aim to overload the control-plane. 1860 20. Network Management Considerations 1862 Considerations for network management tools exist so the LISP 1863 protocol suite can be operationally managed. These mechanisms can be 1864 found in [RFC7052] and [RFC6835]. 1866 21. IANA Considerations 1868 This section provides guidance to the Internet Assigned Numbers 1869 Authority (IANA) regarding registration of values related to this 1870 data-plane LISP specification, in accordance with BCP 26 [RFC8126]. 1872 21.1. LISP UDP Port Numbers 1874 The IANA registry has allocated UDP port number 4341 for the LISP 1875 data-plane. IANA has updated the description for UDP port 4341 as 1876 follows: 1878 lisp-data 4341 udp LISP Data Packets 1880 22. References 1882 22.1. Normative References 1884 [I-D.ietf-lisp-rfc6833bis] 1885 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1886 "Locator/ID Separation Protocol (LISP) Control-Plane", 1887 draft-ietf-lisp-rfc6833bis-07 (work in progress), December 1888 2017. 1890 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1891 DOI 10.17487/RFC0768, August 1980, 1892 . 1894 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1895 DOI 10.17487/RFC0791, September 1981, 1896 . 1898 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1899 "Definition of the Differentiated Services Field (DS 1900 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1901 DOI 10.17487/RFC2474, December 1998, 1902 . 1904 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1905 of Explicit Congestion Notification (ECN) to IP", 1906 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1907 . 1909 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1910 "Randomness Requirements for Security", BCP 106, RFC 4086, 1911 DOI 10.17487/RFC4086, June 2005, 1912 . 1914 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1915 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 1916 2011, . 1918 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1919 (IPv6) Specification", STD 86, RFC 8200, 1920 DOI 10.17487/RFC8200, July 2017, 1921 . 1923 22.2. Informative References 1925 [AFN] IANA, "Address Family Numbers", August 2016, 1926 . 1928 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed", 1929 1999, 1930 . 1932 [I-D.ietf-lisp-eid-mobility] 1933 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 1934 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 1935 Unified Control Plane", draft-ietf-lisp-eid-mobility-01 1936 (work in progress), November 2017. 1938 [I-D.ietf-lisp-introduction] 1939 Cabellos-Aparicio, A. and D. Saucez, "An Architectural 1940 Introduction to the Locator/ID Separation Protocol 1941 (LISP)", draft-ietf-lisp-introduction-13 (work in 1942 progress), April 2015. 1944 [I-D.ietf-lisp-mn] 1945 Farinacci, D., Lewis, D., Meyer, D., and C. White, "LISP 1946 Mobile Node", draft-ietf-lisp-mn-01 (work in progress), 1947 October 2017. 1949 [I-D.ietf-lisp-predictive-rlocs] 1950 Farinacci, D. and P. Pillay-Esnault, "LISP Predictive 1951 RLOCs", draft-ietf-lisp-predictive-rlocs-01 (work in 1952 progress), November 2017. 1954 [I-D.ietf-lisp-sec] 1955 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 1956 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-14 1957 (work in progress), October 2017. 1959 [I-D.ietf-lisp-signal-free-multicast] 1960 Moreno, V. and D. Farinacci, "Signal-Free LISP Multicast", 1961 draft-ietf-lisp-signal-free-multicast-08 (work in 1962 progress), February 2018. 1964 [I-D.ietf-lisp-vpn] 1965 Moreno, V. and D. Farinacci, "LISP Virtual Private 1966 Networks (VPNs)", draft-ietf-lisp-vpn-01 (work in 1967 progress), November 2017. 1969 [LISA96] Lear, E., Tharp, D., Katinsky, J., and J. Coffin, 1970 "Renumbering: Threat or Menace?", Usenix Tenth System 1971 Administration Conference (LISA 96), October 1996. 1973 [OPENLISP] 1974 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 1975 Implementation Report", Work in Progress, July 2008. 1977 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1978 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1979 . 1981 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1982 and E. Lear, "Address Allocation for Private Internets", 1983 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1984 . 1986 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1987 Requirement Levels", BCP 14, RFC 2119, 1988 DOI 10.17487/RFC2119, March 1997, 1989 . 1991 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1992 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1993 DOI 10.17487/RFC2784, March 2000, 1994 . 1996 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 1997 via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 1998 2001, . 2000 [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced 2001 by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, 2002 January 2002, . 2004 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 2005 A., Peterson, J., Sparks, R., Handley, M., and E. 2006 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 2007 DOI 10.17487/RFC3261, June 2002, 2008 . 2010 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 2011 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 2012 DOI 10.17487/RFC4192, September 2005, 2013 . 2015 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 2016 (CIDR): The Internet Address Assignment and Aggregation 2017 Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 2018 2006, . 2020 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 2021 Optimization for Mobile IPv6", RFC 4866, 2022 DOI 10.17487/RFC4866, May 2007, 2023 . 2025 [RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report 2026 from the IAB Workshop on Routing and Addressing", 2027 RFC 4984, DOI 10.17487/RFC4984, September 2007, 2028 . 2030 [RFC5944] Perkins, C., Ed., "IP Mobility Support for IPv4, Revised", 2031 RFC 5944, DOI 10.17487/RFC5944, November 2010, 2032 . 2034 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 2035 Locator/ID Separation Protocol (LISP) for Multicast 2036 Environments", RFC 6831, DOI 10.17487/RFC6831, January 2037 2013, . 2039 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 2040 "Interworking between Locator/ID Separation Protocol 2041 (LISP) and Non-LISP Sites", RFC 6832, 2042 DOI 10.17487/RFC6832, January 2013, 2043 . 2045 [RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 2046 Separation Protocol (LISP) Map-Versioning", RFC 6834, 2047 DOI 10.17487/RFC6834, January 2013, 2048 . 2050 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 2051 Protocol Internet Groper (LIG)", RFC 6835, 2052 DOI 10.17487/RFC6835, January 2013, 2053 . 2055 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 2056 UDP Checksums for Tunneled Packets", RFC 6935, 2057 DOI 10.17487/RFC6935, April 2013, 2058 . 2060 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 2061 for the Use of IPv6 UDP Datagrams with Zero Checksums", 2062 RFC 6936, DOI 10.17487/RFC6936, April 2013, 2063 . 2065 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 2066 Separation Protocol (LISP) MIB", RFC 7052, 2067 DOI 10.17487/RFC7052, October 2013, 2068 . 2070 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 2071 Pascual, J., and D. Lewis, "Locator/Identifier Separation 2072 Protocol (LISP) Network Element Deployment 2073 Considerations", RFC 7215, DOI 10.17487/RFC7215, April 2074 2014, . 2076 [RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A 2077 RADIUS Attribute, Binding, Profiles, Name Identifier 2078 Format, and Confirmation Methods for the Security 2079 Assertion Markup Language (SAML)", RFC 7833, 2080 DOI 10.17487/RFC7833, May 2016, 2081 . 2083 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 2084 Separation Protocol (LISP) Threat Analysis", RFC 7835, 2085 DOI 10.17487/RFC7835, April 2016, 2086 . 2088 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 2089 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 2090 February 2017, . 2092 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 2093 (LISP) Data-Plane Confidentiality", RFC 8061, 2094 DOI 10.17487/RFC8061, February 2017, 2095 . 2097 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 2098 Smirnov, "Locator/ID Separation Protocol Delegated 2099 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 2100 May 2017, . 2102 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 2103 Writing an IANA Considerations Section in RFCs", BCP 26, 2104 RFC 8126, DOI 10.17487/RFC8126, June 2017, 2105 . 2107 Appendix A. Acknowledgments 2109 An initial thank you goes to Dave Oran for planting the seeds for the 2110 initial ideas for LISP. His consultation continues to provide value 2111 to the LISP authors. 2113 A special and appreciative thank you goes to Noel Chiappa for 2114 providing architectural impetus over the past decades on separation 2115 of location and identity, as well as detailed reviews of the LISP 2116 architecture and documents, coupled with enthusiasm for making LISP a 2117 practical and incremental transition for the Internet. 2119 The authors would like to gratefully acknowledge many people who have 2120 contributed discussions and ideas to the making of this proposal. 2121 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 2122 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 2123 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 2124 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 2125 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 2126 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 2127 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 2128 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 2129 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 2130 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 2131 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 2132 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 2133 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 2134 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 2135 Ermagan, Fabio Maino, Victor Moreno, Chris White, Clarence Filsfils, 2136 Alia Atlas, Florin Coras and Alberto Rodriguez. 2138 This work originated in the Routing Research Group (RRG) of the IRTF. 2139 An individual submission was converted into the IETF LISP working 2140 group document that became this RFC. 2142 The LISP working group would like to give a special thanks to Jari 2143 Arkko, the Internet Area AD at the time that the set of LISP 2144 documents were being prepared for IESG last call, and for his 2145 meticulous reviews and detailed commentaries on the 7 working group 2146 last call documents progressing toward standards-track RFCs. 2148 Appendix B. Document Change Log 2150 [RFC Editor: Please delete this section on publication as RFC.] 2152 B.1. Changes to draft-ietf-lisp-rfc6830bis-10 2154 o Posted March 2018. 2156 o Updated section 'Router Locator Selection' stating that the data- 2157 plane MUST follow what's stored in the map-cache (priorities and 2158 weights). 2160 o Section 'Routing Locator Reachability': Removed bullet point 2 2161 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP Port 2162 Unreachable),5 (receive a Map-Reply as a response) and RLOC 2163 probing 2165 o Removed 'Solicit-Map Request'. 2167 B.2. Changes to draft-ietf-lisp-rfc6830bis-09 2169 o Posted January 2018. 2171 o Add more details in section 5.3 about DSCP processing during 2172 encapsulation and decapsulation. 2174 o Added clarity to definitions in the Definition of Terms section 2175 from various commenters. 2177 o Removed PA and PI definitions from Definition of Terms section. 2179 o More editorial changes. 2181 o Removed 4342 from IANA section and move to RFC6833 IANA section. 2183 B.3. Changes to draft-ietf-lisp-rfc6830bis-08 2185 o Posted January 2018. 2187 o Remove references to research work for any protocol mechanisms. 2189 o Document scanned to make sure it is RFC 2119 compliant. 2191 o Made changes to reflect comments from document WG shepherd Luigi 2192 Iannone. 2194 o Ran IDNITs on the document. 2196 B.4. Changes to draft-ietf-lisp-rfc6830bis-07 2198 o Posted November 2017. 2200 o Rephrase how Instance-IDs are used and don't refer to [RFC1918] 2201 addresses. 2203 B.5. Changes to draft-ietf-lisp-rfc6830bis-06 2205 o Posted October 2017. 2207 o Put RTR definition before it is used. 2209 o Rename references that are now working group drafts. 2211 o Remove "EIDs MUST NOT be used as used by a host to refer to other 2212 hosts. Note that EID blocks MAY LISP RLOCs". 2214 o Indicate what address-family can appear in data packets. 2216 o ETRs may, rather than will, be the ones to send Map-Replies. 2218 o Recommend, rather than mandate, max encapsulation headers to 2. 2220 o Reference VPN draft when introducing Instance-ID. 2222 o Indicate that SMRs can be sent when ITR/ETR are in the same node. 2224 o Clarify when private addreses can be used. 2226 B.6. Changes to draft-ietf-lisp-rfc6830bis-05 2228 o Posted August 2017. 2230 o Make it clear that a Reencapsulating Tunnel Router is an RTR. 2232 B.7. Changes to draft-ietf-lisp-rfc6830bis-04 2234 o Posted July 2017. 2236 o Changed reference of IPv6 RFC2460 to RFC8200. 2238 o Indicate that the applicability statement for UDP zero checksums 2239 over IPv6 adheres to RFC6936. 2241 B.8. Changes to draft-ietf-lisp-rfc6830bis-03 2243 o Posted May 2017. 2245 o Move the control-plane related codepoints in the IANA 2246 Considerations section to RFC6833bis. 2248 B.9. Changes to draft-ietf-lisp-rfc6830bis-02 2250 o Posted April 2017. 2252 o Reflect some editorial comments from Damien Sausez. 2254 B.10. Changes to draft-ietf-lisp-rfc6830bis-01 2256 o Posted March 2017. 2258 o Include references to new RFCs published. 2260 o Change references from RFC6833 to RFC6833bis. 2262 o Clarified LCAF text in the IANA section. 2264 o Remove references to "experimental". 2266 B.11. Changes to draft-ietf-lisp-rfc6830bis-00 2268 o Posted December 2016. 2270 o Created working group document from draft-farinacci-lisp 2271 -rfc6830-00 individual submission. No other changes made. 2273 Authors' Addresses 2275 Dino Farinacci 2276 Cisco Systems 2277 Tasman Drive 2278 San Jose, CA 95134 2279 USA 2281 EMail: farinacci@gmail.com 2282 Vince Fuller 2283 Cisco Systems 2284 Tasman Drive 2285 San Jose, CA 95134 2286 USA 2288 EMail: vince.fuller@gmail.com 2290 Dave Meyer 2291 Cisco Systems 2292 170 Tasman Drive 2293 San Jose, CA 2294 USA 2296 EMail: dmm@1-4-5.net 2298 Darrel Lewis 2299 Cisco Systems 2300 170 Tasman Drive 2301 San Jose, CA 2302 USA 2304 EMail: darlewis@cisco.com 2306 Albert Cabellos 2307 UPC/BarcelonaTech 2308 Campus Nord, C. Jordi Girona 1-3 2309 Barcelona, Catalunya 2310 Spain 2312 EMail: acabello@ac.upc.edu