idnits 2.17.1 draft-ietf-lisp-rfc6830bis-13.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 15, 2018) is 2105 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-14) exists of draft-ietf-lisp-6834bis-00 == Outdated reference: A later version (-31) exists of draft-ietf-lisp-rfc6833bis-10 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-introduction-13 == Outdated reference: A later version (-12) exists of draft-ietf-lisp-vpn-02 Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--). 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 Obsoletes: 6830 (if approved) D. Meyer 5 Intended status: Standards Track D. Lewis 6 Expires: January 16, 2019 Cisco Systems 7 A. Cabellos (Ed.) 8 UPC/BarcelonaTech 9 July 15, 2018 11 The Locator/ID Separation Protocol (LISP) 12 draft-ietf-lisp-rfc6830bis-13 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 This document obsoletes RFC 6830. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on January 16, 2019. 47 Copyright Notice 49 Copyright (c) 2018 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 66 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4 67 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . 8 68 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . 10 69 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . 12 70 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 13 71 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 13 72 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . 15 73 6. LISP EID-to-RLOC Map-Cache . . . . . . . . . . . . . . . . . 19 74 7. Dealing with Large Encapsulated Packets . . . . . . . . . . . 19 75 7.1. A Stateless Solution to MTU Handling . . . . . . . . . . 20 76 7.2. A Stateful Solution to MTU Handling . . . . . . . . . . . 21 77 8. Using Virtualization and Segmentation with LISP . . . . . . . 21 78 9. Routing Locator Selection . . . . . . . . . . . . . . . . . . 22 79 10. Routing Locator Reachability . . . . . . . . . . . . . . . . 24 80 10.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . . 25 81 11. EID Reachability within a LISP Site . . . . . . . . . . . . . 26 82 12. Routing Locator Hashing . . . . . . . . . . . . . . . . . . . 27 83 13. Changing the Contents of EID-to-RLOC Mappings . . . . . . . . 28 84 13.1. Database Map-Versioning . . . . . . . . . . . . . . . . 29 85 14. Multicast Considerations . . . . . . . . . . . . . . . . . . 29 86 15. Router Performance Considerations . . . . . . . . . . . . . . 30 87 16. Security Considerations . . . . . . . . . . . . . . . . . . . 31 88 17. Network Management Considerations . . . . . . . . . . . . . . 32 89 18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 90 18.1. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . 32 91 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 92 19.1. Normative References . . . . . . . . . . . . . . . . . . 32 93 19.2. Informative References . . . . . . . . . . . . . . . . . 33 94 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 37 95 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 37 96 B.1. Changes to draft-ietf-lisp-rfc6830bis-13 . . . . . . . . 38 97 B.2. Changes to draft-ietf-lisp-rfc6830bis-12 . . . . . . . . 38 98 B.3. Changes to draft-ietf-lisp-rfc6830bis-11 . . . . . . . . 38 99 B.4. Changes to draft-ietf-lisp-rfc6830bis-10 . . . . . . . . 38 100 B.5. Changes to draft-ietf-lisp-rfc6830bis-09 . . . . . . . . 38 101 B.6. Changes to draft-ietf-lisp-rfc6830bis-08 . . . . . . . . 39 102 B.7. Changes to draft-ietf-lisp-rfc6830bis-07 . . . . . . . . 39 103 B.8. Changes to draft-ietf-lisp-rfc6830bis-06 . . . . . . . . 39 104 B.9. Changes to draft-ietf-lisp-rfc6830bis-05 . . . . . . . . 40 105 B.10. Changes to draft-ietf-lisp-rfc6830bis-04 . . . . . . . . 40 106 B.11. Changes to draft-ietf-lisp-rfc6830bis-03 . . . . . . . . 40 107 B.12. Changes to draft-ietf-lisp-rfc6830bis-02 . . . . . . . . 40 108 B.13. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 40 109 B.14. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 41 110 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 112 1. Introduction 114 This document describes the Locator/Identifier Separation Protocol 115 (LISP). LISP is an encapsulation protocol built around the 116 fundamental idea of separating the topological location of a network 117 attachment point from the node's identity [CHIAPPA]. As a result 118 LISP creates two namespaces: Endpoint Identifiers (EIDs), that are 119 used to identify end-hosts (e.g., nodes or Virtual Machines) and 120 routable Routing Locators (RLOCs), used to identify network 121 attachment points. LISP then defines functions for mapping between 122 the two namespaces and for encapsulating traffic originated by 123 devices using non-routable EIDs for transport across a network 124 infrastructure that routes and forwards using RLOCs. LISP 125 encapsulation uses a dynamic form of tunneling where no static 126 provisioning is required or necessary. 128 LISP is an overlay protocol that separates control from Data-Plane, 129 this document specifies the Data-Plane, how LISP-capable routers 130 (Tunnel Routers) exchange packets by encapsulating them to the 131 appropriate location. Tunnel routers are equipped with a cache, 132 called Map-Cache, that contains EID-to-RLOC mappings. The Map-Cache 133 is populated using the LISP Control-Plane protocol 134 [I-D.ietf-lisp-rfc6833bis]. 136 LISP does not require changes to either host protocol stack or to 137 underlay routers. By separating the EID from the RLOC space, LISP 138 offers native Traffic Engineering, multihoming and mobility, among 139 other features. 141 Creation of LISP was initially motivated by discussions during the 142 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 143 October 2006 (see [RFC4984]). 145 This document specifies the LISP Data-Plane encapsulation and other 146 LISP forwarding node functionality while [I-D.ietf-lisp-rfc6833bis] 147 specifies the LISP control plane. LISP deployment guidelines can be 148 found in [RFC7215] and [RFC6835] describes considerations for network 149 operational management. Finally, [I-D.ietf-lisp-introduction] 150 describes the LISP architecture. 152 2. Requirements Notation 154 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 155 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 156 document are to be interpreted as described in [RFC2119]. 158 3. Definition of Terms 160 Address Family Identifier (AFI): AFI is a term used to describe an 161 address encoding in a packet. An address family that pertains to 162 the Data-Plane. See [AFN] and [RFC3232] for details. An AFI 163 value of 0 used in this specification indicates an unspecified 164 encoded address where the length of the address is 0 octets 165 following the 16-bit AFI value of 0. 167 Anycast Address: Anycast Address is a term used in this document to 168 refer to the same IPv4 or IPv6 address configured and used on 169 multiple systems at the same time. An EID or RLOC can be an 170 anycast address in each of their own address spaces. 172 Client-side: Client-side is a term used in this document to indicate 173 a connection initiation attempt by an end-system represented by an 174 EID. 176 Data-Probe: A Data-Probe is a LISP-encapsulated data packet where 177 the inner-header destination address equals the outer-header 178 destination address used to trigger a Map-Reply by a decapsulating 179 ETR. In addition, the original packet is decapsulated and 180 delivered to the destination host if the destination EID is in the 181 EID-Prefix range configured on the ETR. Otherwise, the packet is 182 discarded. A Data-Probe is used in some of the mapping database 183 designs to "probe" or request a Map-Reply from an ETR; in other 184 cases, Map-Requests are used. See each mapping database design 185 for details. When using Data-Probes, by sending Map-Requests on 186 the underlying routing system, EID-Prefixes must be advertised. 188 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 189 packet where the destination address in the "outer" IP header is 190 one of its own RLOCs. The router strips the "outer" header and 191 forwards the packet based on the next IP header found. In 192 general, an ETR receives LISP-encapsulated IP packets from the 193 Internet on one side and sends decapsulated IP packets to site 194 end-systems on the other side. ETR functionality does not have to 195 be limited to a router device. A server host can be the endpoint 196 of a LISP tunnel as well. 198 EID-to-RLOC Database: The EID-to-RLOC Database is a global 199 distributed database that contains all known EID-Prefix-to-RLOC 200 mappings. Each potential ETR typically contains a small piece of 201 the database: the EID-to-RLOC mappings for the EID-Prefixes 202 "behind" the router. These map to one of the router's own 203 globally visible IP addresses. Note that there MAY be transient 204 conditions when the EID-Prefix for the site and Locator-Set for 205 each EID-Prefix may not be the same on all ETRs. This has no 206 negative implications, since a partial set of Locators can be 207 used. 209 EID-to-RLOC Map-Cache: The EID-to-RLOC Map-Cache is generally 210 short-lived, on-demand table in an ITR that stores, tracks, and is 211 responsible for timing out and otherwise validating EID-to-RLOC 212 mappings. This cache is distinct from the full "database" of EID- 213 to-RLOC mappings; it is dynamic, local to the ITR(s), and 214 relatively small, while the database is distributed, relatively 215 static, and much more global in scope. 217 EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are 218 allocated to a site by an address allocation authority. EID- 219 Prefixes are associated with a set of RLOC addresses. EID-Prefix 220 allocations can be broken up into smaller blocks when an RLOC set 221 is to be associated with the larger EID-Prefix block. 223 End-System: An end-system is an IPv4 or IPv6 device that originates 224 packets with a single IPv4 or IPv6 header. The end-system 225 supplies an EID value for the destination address field of the IP 226 header when communicating globally (i.e., outside of its routing 227 domain). An end-system can be a host computer, a switch or router 228 device, or any network appliance. 230 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 231 IPv6) value used in the source and destination address fields of 232 the first (most inner) LISP header of a packet. The host obtains 233 a destination EID the same way it obtains a destination address 234 today, for example, through a Domain Name System (DNS) [RFC1034] 235 lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. 237 The source EID is obtained via existing mechanisms used to set a 238 host's "local" IP address. An EID used on the public Internet 239 MUST have the same properties as any other IP address used in that 240 manner; this means, among other things, that it MUST be globally 241 unique. An EID is allocated to a host from an EID-Prefix block 242 associated with the site where the host is located. An EID can be 243 used by a host to refer to other hosts. Note that EID blocks MAY 244 be assigned in a hierarchical manner, independent of the network 245 topology, to facilitate scaling of the mapping database. In 246 addition, an EID block assigned to a site MAY have site-local 247 structure (subnetting) for routing within the site; this structure 248 is not visible to the global routing system. In theory, the bit 249 string that represents an EID for one device can represent an RLOC 250 for a different device. When used in discussions with other 251 Locator/ID separation proposals, a LISP EID will be called an 252 "LEID". Throughout this document, any references to "EID" refer 253 to an LEID. 255 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 256 LISP site. Packets sent by sources inside of the LISP site to 257 destinations outside of the site are candidates for encapsulation 258 by the ITR. The ITR treats the IP destination address as an EID 259 and performs an EID-to-RLOC mapping lookup. The router then 260 prepends an "outer" IP header with one of its routable RLOCs (in 261 the RLOC space) in the source address field and the result of the 262 mapping lookup in the destination address field. Note that this 263 destination RLOC MAY be an intermediate, proxy device that has 264 better knowledge of the EID-to-RLOC mapping closer to the 265 destination EID. In general, an ITR receives IP packets from site 266 end-systems on one side and sends LISP-encapsulated IP packets 267 toward the Internet on the other side. 269 Specifically, when a service provider prepends a LISP header for 270 Traffic Engineering purposes, the router that does this is also 271 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 272 on the outer destination address (the originating ITR's supplied 273 RLOC) or the inner destination address (the originating host's 274 supplied EID). 276 LISP Header: LISP header is a term used in this document to refer 277 to the outer IPv4 or IPv6 header, a UDP header, and a LISP- 278 specific 8-octet header that follow the UDP header and that an ITR 279 prepends or an ETR strips. 281 LISP Router: A LISP router is a router that performs the functions 282 of any or all of the following: ITR, ETR, RTR, Proxy-ITR (PITR), 283 or Proxy-ETR (PETR). 285 LISP Site: LISP site is a set of routers in an edge network that are 286 under a single technical administration. LISP routers that reside 287 in the edge network are the demarcation points to separate the 288 edge network from the core network. 290 Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the 291 LISP header. They are used by ITRs to inform ETRs about the up/ 292 down status of all ETRs at the local site. These bits are used as 293 a hint to convey up/down router status and not path reachability 294 status. The LSBs can be verified by use of one of the Locator 295 reachability algorithms described in Section 10. 297 Negative Mapping Entry: A negative mapping entry, also known as a 298 negative cache entry, is an EID-to-RLOC entry where an EID-Prefix 299 is advertised or stored with no RLOCs. That is, the Locator-Set 300 for the EID-to-RLOC entry is empty or has an encoded Locator count 301 of 0. This type of entry could be used to describe a prefix from 302 a non-LISP site, which is explicitly not in the mapping database. 303 There are a set of well-defined actions that are encoded in a 304 Negative Map-Reply. 306 Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A 307 PETR acts like an ETR but does so on behalf of LISP sites that 308 send packets to destinations at non-LISP sites. 310 Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A 311 PITR acts like an ITR but does so on behalf of non-LISP sites that 312 send packets to destinations at LISP sites. 314 Recursive Tunneling: Recursive Tunneling occurs when a packet has 315 more than one LISP IP header. Additional layers of tunneling MAY 316 be employed to implement Traffic Engineering or other re-routing 317 as needed. When this is done, an additional "outer" LISP header 318 is added, and the original RLOCs are preserved in the "inner" 319 header. 321 Re-Encapsulating Tunneling Router (RTR): An RTR acts like an ETR to 322 remove a LISP header, then acts as an ITR to prepend a new LISP 323 header. This is known as Re-encapsulating Tunneling. Doing this 324 allows a packet to be re-routed by the RTR without adding the 325 overhead of additional tunnel headers. When using multiple 326 mapping database systems, care must be taken to not create re- 327 encapsulation loops through misconfiguration. 329 Route-Returnability: Route-returnability is an assumption that the 330 underlying routing system will deliver packets to the destination. 331 When combined with a nonce that is provided by a sender and 332 returned by a receiver, this limits off-path data insertion. A 333 route-returnability check is verified when a message is sent with 334 a nonce, another message is returned with the same nonce, and the 335 destination of the original message appears as the source of the 336 returned message. 338 Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 339 [RFC8200] address of an Egress Tunnel Router (ETR). An RLOC is 340 the output of an EID-to-RLOC mapping lookup. An EID maps to zero 341 or more RLOCs. Typically, RLOCs are numbered from blocks that are 342 assigned to a site at each point to which it attaches to the 343 underlay network; where the topology is defined by the 344 connectivity of provider networks. Multiple RLOCs can be assigned 345 to the same ETR device or to multiple ETR devices at a site. 347 Server-side: Server-side is a term used in this document to indicate 348 that a connection initiation attempt is being accepted for a 349 destination EID. 351 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 352 network that strips an outer LISP header for Traffic Engineering 353 purposes. 355 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 356 network that prepends an additional LISP header for Traffic 357 Engineering purposes. 359 xTR: An xTR is a reference to an ITR or ETR when direction of data 360 flow is not part of the context description. "xTR" refers to the 361 router that is the tunnel endpoint and is used synonymously with 362 the term "Tunnel Router". For example, "An xTR can be located at 363 the Customer Edge (CE) router" indicates both ITR and ETR 364 functionality at the CE router. 366 4. Basic Overview 368 One key concept of LISP is that end-systems operate the same way they 369 do today. The IP addresses that hosts use for tracking sockets and 370 connections, and for sending and receiving packets, do not change. 371 In LISP terminology, these IP addresses are called Endpoint 372 Identifiers (EIDs). 374 Routers continue to forward packets based on IP destination 375 addresses. When a packet is LISP encapsulated, these addresses are 376 referred to as Routing Locators (RLOCs). Most routers along a path 377 between two hosts will not change; they continue to perform routing/ 378 forwarding lookups on the destination addresses. For routers between 379 the source host and the ITR as well as routers from the ETR to the 380 destination host, the destination address is an EID. For the routers 381 between the ITR and the ETR, the destination address is an RLOC. 383 Another key LISP concept is the "Tunnel Router". A Tunnel Router 384 prepends LISP headers on host-originated packets and strips them 385 prior to final delivery to their destination. The IP addresses in 386 this "outer header" are RLOCs. During end-to-end packet exchange 387 between two Internet hosts, an ITR prepends a new LISP header to each 388 packet, and an ETR strips the new header. The ITR performs EID-to- 389 RLOC lookups to determine the routing path to the ETR, which has the 390 RLOC as one of its IP addresses. 392 Some basic rules governing LISP are: 394 o End-systems only send to addresses that are EIDs. EIDs are 395 typically IP addresses assigned to hosts (other types of EID are 396 supported by LISP, see [RFC8060] for further information). End- 397 systems don't know that addresses are EIDs versus RLOCs but assume 398 that packets get to their intended destinations. In a system 399 where LISP is deployed, LISP routers intercept EID-addressed 400 packets and assist in delivering them across the network core 401 where EIDs cannot be routed. The procedure a host uses to send IP 402 packets does not change. 404 o LISP routers mostly deal with Routing Locator addresses. See 405 details in Section 4.1 to clarify what is meant by "mostly". 407 o RLOCs are always IP addresses assigned to routers, preferably 408 topologically oriented addresses from provider CIDR (Classless 409 Inter-Domain Routing) blocks. 411 o When a router originates packets, it MAY use as a source address 412 either an EID or RLOC. When acting as a host (e.g., when 413 terminating a transport session such as Secure SHell (SSH), 414 TELNET, or the Simple Network Management Protocol (SNMP)), it MAY 415 use an EID that is explicitly assigned for that purpose. An EID 416 that identifies the router as a host MUST NOT be used as an RLOC; 417 an EID is only routable within the scope of a site. A typical BGP 418 configuration might demonstrate this "hybrid" EID/RLOC usage where 419 a router could use its "host-like" EID to terminate iBGP sessions 420 to other routers in a site while at the same time using RLOCs to 421 terminate eBGP sessions to routers outside the site. 423 o Packets with EIDs in them are not expected to be delivered end-to- 424 end in the absence of an EID-to-RLOC mapping operation. They are 425 expected to be used locally for intra-site communication or to be 426 encapsulated for inter-site communication. 428 o EIDs MAY also be structured (subnetted) in a manner suitable for 429 local routing within an Autonomous System (AS). 431 An additional LISP header MAY be prepended to packets by a TE-ITR 432 when re-routing of the path for a packet is desired. A potential 433 use-case for this would be an ISP router that needs to perform 434 Traffic Engineering for packets flowing through its network. In such 435 a situation, termed "Recursive Tunneling", an ISP transit acts as an 436 additional ITR, and the RLOC it uses for the new prepended header 437 would be either a TE-ETR within the ISP (along an intra-ISP traffic 438 engineered path) or a TE-ETR within another ISP (an inter-ISP traffic 439 engineered path, where an agreement to build such a path exists). 441 In order to avoid excessive packet overhead as well as possible 442 encapsulation loops, this document recommends that a maximum of two 443 LISP headers can be prepended to a packet. For initial LISP 444 deployments, it is assumed that two headers is sufficient, where the 445 first prepended header is used at a site for Location/Identity 446 separation and the second prepended header is used inside a service 447 provider for Traffic Engineering purposes. 449 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 450 For example, the ITR for a particular end-to-end packet exchange 451 might be the first-hop or default router within a site for the source 452 host. Similarly, the ETR might be the last-hop router directly 453 connected to the destination host. Another example, perhaps for a 454 VPN service outsourced to an ISP by a site, the ITR could be the 455 site's border router at the service provider attachment point. 456 Mixing and matching of site-operated, ISP-operated, and other Tunnel 457 Routers is allowed for maximum flexibility. 459 4.1. Packet Flow Sequence 461 This section provides an example of the unicast packet flow, 462 including also Control-Plane information as specified in 463 [I-D.ietf-lisp-rfc6833bis]. The example also assumes the following 464 conditions: 466 o Source host "host1.abc.example.com" is sending a packet to 467 "host2.xyz.example.com", exactly what host1 would do if the site 468 was not using LISP. 470 o Each site is multihomed, so each Tunnel Router has an address 471 (RLOC) assigned from the service provider address block for each 472 provider to which that particular Tunnel Router is attached. 474 o The ITR(s) and ETR(s) are directly connected to the source and 475 destination, respectively, but the source and destination can be 476 located anywhere in the LISP site. 478 o A Map-Request is sent for an external destination when the 479 destination is not found in the forwarding table or matches a 480 default route. Map-Requests are sent to the mapping database 481 system by using the LISP Control-Plane protocol documented in 482 [I-D.ietf-lisp-rfc6833bis]. 484 o Map-Replies are sent on the underlying routing system topology 485 using the [I-D.ietf-lisp-rfc6833bis] Control-Plane protocol. 487 Client host1.abc.example.com wants to communicate with server 488 host2.xyz.example.com: 490 1. host1.abc.example.com wants to open a TCP connection to 491 host2.xyz.example.com. It does a DNS lookup on 492 host2.xyz.example.com. An A/AAAA record is returned. This 493 address is the destination EID. The locally assigned address of 494 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 495 packet is built and forwarded through the LISP site as a normal 496 IP packet until it reaches a LISP ITR. 498 2. The LISP ITR must be able to map the destination EID to an RLOC 499 of one of the ETRs at the destination site. The specific method 500 used to do this is not described in this example. See 501 [I-D.ietf-lisp-rfc6833bis] for further information. 503 3. The ITR sends a LISP Map-Request as specified in 504 [I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited. 506 4. The mapping system helps forwarding the Map-Request to the 507 corresponding ETR. When the Map-Request arrives at one of the 508 ETRs at the destination site, it will process the packet as a 509 control message. 511 5. The ETR looks at the destination EID of the Map-Request and 512 matches it against the prefixes in the ETR's configured EID-to- 513 RLOC mapping database. This is the list of EID-Prefixes the ETR 514 is supporting for the site it resides in. If there is no match, 515 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 516 returned to the ITR. 518 6. The ITR receives the Map-Reply message, parses the message (to 519 check for format validity), and stores the mapping information 520 from the packet. This information is stored in the ITR's EID-to- 521 RLOC Map-Cache. Note that the Map-Cache is an on-demand cache. 523 An ITR will manage its Map-Cache in such a way that optimizes for 524 its resource constraints. 526 7. Subsequent packets from host1.abc.example.com to 527 host2.xyz.example.com will have a LISP header prepended by the 528 ITR using the appropriate RLOC as the LISP header destination 529 address learned from the ETR. Note that the packet MAY be sent 530 to a different ETR than the one that returned the Map-Reply due 531 to the source site's hashing policy or the destination site's 532 Locator-Set policy. 534 8. The ETR receives these packets directly (since the destination 535 address is one of its assigned IP addresses), checks the validity 536 of the addresses, strips the LISP header, and forwards packets to 537 the attached destination host. 539 9. In order to defer the need for a mapping lookup in the reverse 540 direction, an ETR can OPTIONALLY create a cache entry that maps 541 the source EID (inner-header source IP address) to the source 542 RLOC (outer-header source IP address) in a received LISP packet. 543 Such a cache entry is termed a "glean mapping" and only contains 544 a single RLOC for the EID in question. More complete information 545 about additional RLOCs SHOULD be verified by sending a LISP Map- 546 Request for that EID. Both the ITR and the ETR MAY also 547 influence the decision the other makes in selecting an RLOC. 549 5. LISP Encapsulation Details 551 Since additional tunnel headers are prepended, the packet becomes 552 larger and can exceed the MTU of any link traversed from the ITR to 553 the ETR. It is RECOMMENDED in IPv4 that packets do not get 554 fragmented as they are encapsulated by the ITR. Instead, the packet 555 is dropped and an ICMP Unreachable/Fragmentation-Needed message is 556 returned to the source. 558 In the case when fragmentation is needed, this specification 559 RECOMMENDS that implementations provide support for one of the 560 proposed fragmentation and reassembly schemes. Two existing schemes 561 are detailed in Section 7. 563 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 564 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 565 header is in IPv4 packet format and the outer header is in IPv6 566 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 567 is in IPv6 packet format and the outer header is in IPv4 packet 568 format). The next sub-sections illustrate packet formats for the 569 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 570 combinations MUST be supported. Additional types of EIDs are defined 571 in [RFC8060]. 573 5.1. LISP IPv4-in-IPv4 Header Format 575 0 1 2 3 576 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 1 577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 578 / |Version| IHL | DSCP |ECN| Total Length | 579 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 580 | | Identification |Flags| Fragment Offset | 581 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 582 OH | Time to Live | Protocol = 17 | Header Checksum | 583 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 584 | | Source Routing Locator | 585 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 586 \ | Destination Routing Locator | 587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 / | Source Port = xxxx | Dest Port = 4341 | 589 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 590 \ | UDP Length | UDP Checksum | 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 593 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 S / | Instance ID/Locator-Status-Bits | 595 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 / |Version| IHL | DSCP |ECN| Total Length | 597 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 | | Identification |Flags| Fragment Offset | 599 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 600 IH | Time to Live | Protocol | Header Checksum | 601 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 | | Source EID | 603 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 604 \ | Destination EID | 605 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 IHL = IP-Header-Length 609 5.2. LISP IPv6-in-IPv6 Header Format 611 0 1 2 3 612 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 1 613 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 614 / |Version| DSCP |ECN| Flow Label | 615 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 616 | | Payload Length | Next Header=17| Hop Limit | 617 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 618 | | 619 O + + 620 u | | 621 t + Source Routing Locator + 622 e | | 623 r + + 624 | | 625 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 626 d | | 627 r + + 628 | | 629 ^ + Destination Routing Locator + 630 | | | 631 \ + + 632 \ | | 633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 634 / | Source Port = xxxx | Dest Port = 4341 | 635 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 636 \ | UDP Length | UDP Checksum | 637 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 638 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 639 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 640 S / | Instance ID/Locator-Status-Bits | 641 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 642 / |Version| DSCP |ECN| Flow Label | 643 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 / | Payload Length | Next Header | Hop Limit | 645 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 646 | | 647 I + + 648 n | | 649 n + Source EID + 650 e | | 651 r + + 652 | | 653 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 654 d | | 655 r + + 656 | | 657 ^ + Destination EID + 658 \ | | 659 \ + + 660 \ | | 661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 663 5.3. Tunnel Header Field Descriptions 665 Inner Header (IH): The inner header is the header on the 666 datagram received from the originating host [RFC0791] [RFC8200] 667 [RFC2474]. The source and destination IP addresses are EIDs. 669 Outer Header: (OH) The outer header is a new header prepended by an 670 ITR. The address fields contain RLOCs obtained from the ingress 671 router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" 672 from [RFC0768]. The setting of the Don't Fragment (DF) bit 673 'Flags' field is according to rules listed in Sections 7.1 and 674 7.2. 676 UDP Header: The UDP header contains an ITR selected source port when 677 encapsulating a packet. See Section 12 for details on the hash 678 algorithm used to select a source port based on the 5-tuple of the 679 inner header. The destination port MUST be set to the well-known 680 IANA-assigned port value 4341. 682 UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero 683 by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation 684 [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is 685 received by an ETR, the ETR MUST accept the packet for 686 decapsulation. When an ITR transmits a non-zero value for the UDP 687 checksum, it MUST send a correctly computed value in this field. 688 When an ETR receives a packet with a non-zero UDP checksum, it MAY 689 choose to verify the checksum value. If it chooses to perform 690 such verification, and the verification fails, the packet MUST be 691 silently dropped. If the ETR chooses not to perform the 692 verification, or performs the verification successfully, the 693 packet MUST be accepted for decapsulation. The handling of UDP 694 zero checksums over IPv6 for all tunneling protocols, including 695 LISP, is subject to the applicability statement in [RFC6936]. 697 UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated 698 packet to be the sum of the inner-header IPv4 Total Length plus 699 the UDP and LISP header lengths. For an IPv6-encapsulated packet, 700 the 'UDP Length' field is the sum of the inner-header IPv6 Payload 701 Length, the size of the IPv6 header (40 octets), and the size of 702 the UDP and LISP headers. 704 N: The N-bit is the nonce-present bit. When this bit is set to 1, 705 the low-order 24 bits of the first 32 bits of the LISP header 706 contain a Nonce. See Section 10.1 for details. Both N- and 707 V-bits MUST NOT be set in the same packet. If they are, a 708 decapsulating ETR MUST treat the 'Nonce/Map-Version' field as 709 having a Nonce value present. 711 L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When 712 this bit is set to 1, the Locator-Status-Bits in the second 713 32 bits of the LISP header are in use. 715 x 1 x x 0 x x x 716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 718 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 719 | Locator-Status-Bits | 720 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 722 E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored 723 and has no meaning when the N-bit is set to 0. When the N-bit is 724 set to 1 and this bit is set to 1, an ITR is requesting that the 725 nonce value in the 'Nonce' field be echoed back in LISP- 726 encapsulated packets when the ITR is also an ETR. See 727 Section 10.1 for details. 729 V: The V-bit is the Map-Version present bit. When this bit is set to 730 1, the N-bit MUST be 0. Refer to Section 13.1 for more details. 731 This bit indicates that the LISP header is encoded in this 732 case as: 734 0 x 0 1 x x x x 735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 736 |N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version | 737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 738 | Instance ID/Locator-Status-Bits | 739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 741 I: The I-bit is the Instance ID bit. See Section 8 for more details. 742 When this bit is set to 1, the 'Locator-Status-Bits' field is 743 reduced to 8 bits and the high-order 24 bits are used as an 744 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 745 are transmitted as zero and ignored on receipt. The format of the 746 LISP header would look like this: 748 x x x x 1 x x x 749 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 750 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 751 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 752 | Instance ID | LSBs | 753 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 755 R: The R-bit is a Reserved bit for future use. It MUST be set to 0 756 on transmit and MUST be ignored on receipt. 758 KK: The KK-bits are a 2-bit field used when encapsulated packets are 759 encrypted. The field is set to 00 when the packet is not 760 encrypted. See [RFC8061] for further information. 762 LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is 763 randomly generated by an ITR when the N-bit is set to 1. Nonce 764 generation algorithms are an implementation matter but are 765 required to generate different nonces when sending to different 766 RLOCs. However, the same nonce can be used for a period of time 767 when encapsulating to the same ETR. The nonce is also used when 768 the E-bit is set to request the nonce value to be echoed by the 769 other side when packets are returned. When the E-bit is clear but 770 the N-bit is set, a remote ITR is either echoing a previously 771 requested echo-nonce or providing a random nonce. See 772 Section 10.1 for more details. 774 LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the 775 'Locator-Status-Bits' field in the LISP header is set by an ITR to 776 indicate to an ETR the up/down status of the Locators in the 777 source site. Each RLOC in a Map-Reply is assigned an ordinal 778 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 779 The Locator-Status-Bits are numbered from 0 to n-1 from the least 780 significant bit of the field. The field is 32 bits when the I-bit 781 is set to 0 and is 8 bits when the I-bit is set to 1. When a 782 Locator-Status-Bit is set to 1, the ITR is indicating to the ETR 783 that the RLOC associated with the bit ordinal has up status. See 784 Section 10 for details on how an ITR can determine the status of 785 the ETRs at the same site. When a site has multiple EID-Prefixes 786 that result in multiple mappings (where each could have a 787 different Locator-Set), the Locator-Status-Bits setting in an 788 encapsulated packet MUST reflect the mapping for the EID-Prefix 789 that the inner-header source EID address matches. If the LSB for 790 an anycast Locator is set to 1, then there is at least one RLOC 791 with that address, and the ETR is considered 'up'. 793 When doing ITR/PITR encapsulation: 795 o The outer-header 'Time to Live' field (or 'Hop Limit' field, in 796 the case of IPv6) SHOULD be copied from the inner-header 'Time to 797 Live' field. 799 o The outer-header 'Differentiated Services Code Point' (DSCP) field 800 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 801 copied from the inner-header DSCP field ('Traffic Class' field, in 802 the case of IPv6) considering the exception listed below. 804 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 805 of the IPv6 'Traffic Class' field) requires special treatment in 806 order to avoid discarding indications of congestion [RFC3168]. 807 ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 808 header to the outer header. Re-encapsulation MUST copy the 2-bit 809 'ECN' field from the stripped outer header to the new outer 810 header. 812 When doing ETR/PETR decapsulation: 814 o The inner-header 'Time to Live' field (or 'Hop Limit' field, in 815 the case of IPv6) SHOULD be copied from the outer-header 'Time to 816 Live' field, when the Time to Live value of the outer header is 817 less than the Time to Live value of the inner header. Failing to 818 perform this check can cause the Time to Live of the inner header 819 to increment across encapsulation/decapsulation cycles. This 820 check is also performed when doing initial encapsulation, when a 821 packet comes to an ITR or PITR destined for a LISP site. 823 o The inner-header 'Differentiated Services Code Point' (DSCP) field 824 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 825 copied from the outer-header DSCP field ('Traffic Class' field, in 826 the case of IPv6) considering the exception listed below. 828 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 829 of the IPv6 'Traffic Class' field) requires special treatment in 830 order to avoid discarding indications of congestion [RFC3168]. If 831 the 'ECN' field contains a congestion indication codepoint (the 832 value is '11', the Congestion Experienced (CE) codepoint), then 833 ETR decapsulation MUST copy the 2-bit 'ECN' field from the 834 stripped outer header to the surviving inner header that is used 835 to forward the packet beyond the ETR. These requirements preserve 836 CE indications when a packet that uses ECN traverses a LISP tunnel 837 and becomes marked with a CE indication due to congestion between 838 the tunnel endpoints. 840 Note that if an ETR/PETR is also an ITR/PITR and chooses to re- 841 encapsulate after decapsulating, the net effect of this is that the 842 new outer header will carry the same Time to Live as the old outer 843 header minus 1. 845 Copying the Time to Live (TTL) serves two purposes: first, it 846 preserves the distance the host intended the packet to travel; 847 second, and more importantly, it provides for suppression of looping 848 packets in the event there is a loop of concatenated tunnels due to 849 misconfiguration. 851 The Explicit Congestion Notification ('ECN') field occupies bits 6 852 and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic 853 Class' field [RFC3168]. The 'ECN' field requires special treatment 854 in order to avoid discarding indications of congestion [RFC3168]. An 855 ITR/PITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 856 header to the outer header. Re-encapsulation MUST copy the 2-bit 857 'ECN' field from the stripped outer header to the new outer header. 858 If the 'ECN' field contains a congestion indication codepoint (the 859 value is '11', the Congestion Experienced (CE) codepoint), then ETR/ 860 PETR decapsulation MUST copy the 2-bit 'ECN' field from the stripped 861 outer header to the surviving inner header that is used to forward 862 the packet beyond the ETR. These requirements preserve CE 863 indications when a packet that uses ECN traverses a LISP tunnel and 864 becomes marked with a CE indication due to congestion between the 865 tunnel endpoints. 867 6. LISP EID-to-RLOC Map-Cache 869 ITRs and PITRs maintain an on-demand cache, referred as LISP EID-to- 870 RLOC Map-Cache, that contains mappings from EID-prefixes to locator 871 sets. The cache is used to encapsulate packets from the EID space to 872 the corresponding RLOC network attachment point. 874 When an ITR/PITR receives a packet from inside of the LISP site to 875 destinations outside of the site a longest-prefix match lookup of the 876 EID is done to the Map-Cache. 878 When the lookup succeeds, the Locator-Set retrieved from the Map- 879 Cache is used to send the packet to the EID's topological location. 881 If the lookup fails, the ITR/PITR needs to retrieve the mapping using 882 the LISP Control-Plane protocol [I-D.ietf-lisp-rfc6833bis]. The 883 mapping is then stored in the local Map-Cache to forward subsequent 884 packets addressed to the same EID-prefix. 886 The Map-Cache is a local cache of mappings, entries are expired based 887 on the associated Time to live. In addition, entries can be updated 888 with more current information, see Section 13 for further information 889 on this. Finally, the Map-Cache also contains reachability 890 information about EIDs and RLOCs, and uses LISP reachability 891 information mechanisms to determine the reachability of RLOCs, see 892 Section 10 for the specific mechanisms. 894 7. Dealing with Large Encapsulated Packets 896 This section proposes two mechanisms to deal with packets that exceed 897 the path MTU between the ITR and ETR. 899 It is left to the implementor to decide if the stateless or stateful 900 mechanism SHOULD be implemented. Both or neither can be used, since 901 it is a local decision in the ITR regarding how to deal with MTU 902 issues, and sites can interoperate with differing mechanisms. 904 Both stateless and stateful mechanisms also apply to Re-encapsulating 905 and Recursive Tunneling, so any actions below referring to an ITR 906 also apply to a TE-ITR. 908 7.1. A Stateless Solution to MTU Handling 910 An ITR stateless solution to handle MTU issues is described as 911 follows: 913 1. Define H to be the size, in octets, of the outer header an ITR 914 prepends to a packet. This includes the UDP and LISP header 915 lengths. 917 2. Define L to be the size, in octets, of the maximum-sized packet 918 an ITR can send to an ETR without the need for the ITR or any 919 intermediate routers to fragment the packet. 921 3. Define an architectural constant S for the maximum size of a 922 packet, in octets, an ITR MUST receive from the source so the 923 effective MTU can be met. That is, L = S + H. 925 When an ITR receives a packet from a site-facing interface and adds H 926 octets worth of encapsulation to yield a packet size greater than L 927 octets (meaning the received packet size was greater than S octets 928 from the source), it resolves the MTU issue by first splitting the 929 original packet into 2 equal-sized fragments. A LISP header is then 930 prepended to each fragment. The size of the encapsulated fragments 931 is then (S/2 + H), which is less than the ITR's estimate of the path 932 MTU between the ITR and its correspondent ETR. 934 When an ETR receives encapsulated fragments, it treats them as two 935 individually encapsulated packets. It strips the LISP headers and 936 then forwards each fragment to the destination host of the 937 destination site. The two fragments are reassembled at the 938 destination host into the single IP datagram that was originated by 939 the source host. Note that reassembly can happen at the ETR if the 940 encapsulated packet was fragmented at or after the ITR. 942 This behavior is performed by the ITR when the source host originates 943 a packet with the 'DF' field of the IP header set to 0. When the 944 'DF' field of the IP header is set to 1, or the packet is an IPv6 945 packet originated by the source host, the ITR will drop the packet 946 when the size is greater than L and send an ICMP Unreachable/ 947 Fragmentation-Needed message to the source with a value of S, where S 948 is (L - H). 950 When the outer-header encapsulation uses an IPv4 header, an 951 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 952 can be avoided. An implementation MAY set the DF bit in such headers 953 to 0 if it has good reason to believe there are unresolvable path MTU 954 issues between the sending ITR and the receiving ETR. 956 This specification RECOMMENDS that L be defined as 1500. 958 7.2. A Stateful Solution to MTU Handling 960 An ITR stateful solution to handle MTU issues is described as follows 961 and was first introduced in [OPENLISP]: 963 1. The ITR will keep state of the effective MTU for each Locator per 964 Map-Cache entry. The effective MTU is what the core network can 965 deliver along the path between the ITR and ETR. 967 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet 968 with the DF bit set to 1, exceeds what the core network can 969 deliver, one of the intermediate routers on the path will send an 970 ICMP Unreachable/Fragmentation-Needed message to the ITR. The 971 ITR will parse the ICMP message to determine which Locator is 972 affected by the effective MTU change and then record the new 973 effective MTU value in the Map-Cache entry. 975 3. When a packet is received by the ITR from a source inside of the 976 site and the size of the packet is greater than the effective MTU 977 stored with the Map-Cache entry associated with the destination 978 EID the packet is for, the ITR will send an ICMP Unreachable/ 979 Fragmentation-Needed message back to the source. The packet size 980 advertised by the ITR in the ICMP Unreachable/Fragmentation- 981 Needed message is the effective MTU minus the LISP encapsulation 982 length. 984 Even though this mechanism is stateful, it has advantages over the 985 stateless IP fragmentation mechanism, by not involving the 986 destination host with reassembly of ITR fragmented packets. 988 8. Using Virtualization and Segmentation with LISP 990 There are several cases where segregation is needed at the EID level. 991 For instance, this is the case for deployments containing overlapping 992 addresses, traffic isolation policies or multi-tenant virtualization. 993 For these and other scenarios where segregation is needed, Instance 994 IDs are used. 996 An Instance ID can be carried in a LISP-encapsulated packet. An ITR 997 that prepends a LISP header will copy a 24-bit value used by the LISP 998 router to uniquely identify the address space. The value is copied 999 to the 'Instance ID' field of the LISP header, and the I-bit is set 1000 to 1. 1002 When an ETR decapsulates a packet, the Instance ID from the LISP 1003 header is used as a table identifier to locate the forwarding table 1004 to use for the inner destination EID lookup. 1006 For example, an 802.1Q VLAN tag or VPN identifier could be used as a 1007 24-bit Instance ID. See [I-D.ietf-lisp-vpn] for LISP VPN use-case 1008 details. 1010 The Instance ID that is stored in the mapping database when LISP-DDT 1011 [RFC8111] is used is 32 bits in length. That means the Control-Plane 1012 can store more instances than a given Data-Plane can use. Multiple 1013 Data-Planes can use the same 32-bit space as long as the low-order 24 1014 bits don't overlap among xTRs. 1016 9. Routing Locator Selection 1018 The Map-Cache contains the state used by ITRs and PITRs to 1019 encapsulate packets. When an ITR/PITR receives a packet from inside 1020 the LISP site to a destination outside of the site a longest-prefix 1021 match lookup of the EID is done to the Map-Cache (see Section 6). 1022 The lookup returns a single Locator-Set containing a list of RLOCs 1023 corresponding to the EID's topological location. Each RLOC in the 1024 Locator-Set is associated with a 'Priority' and 'Weight', this 1025 information is used to select the RLOC to encapsulate. 1027 The RLOC with the lowest 'Priority' is selected. An RLOC with 1028 'Priority' 255 means that MUST NOT be used for forwarding. When 1029 multiple RLOC have the same 'Priority' then the 'Weight' states how 1030 to load balance traffic among them. The value of the 'Weight' 1031 represents the relative weight of the total packets that match the 1032 maping entry. 1034 The following are different scenarios for choosing RLOCs and the 1035 controls that are available: 1037 o The server-side returns one RLOC. The client-side can only use 1038 one RLOC. The server-side has complete control of the selection. 1040 o The server-side returns a list of RLOCs where a subset of the list 1041 has the same best Priority. The client can only use the subset 1042 list according to the weighting assigned by the server-side. In 1043 this case, the server-side controls both the subset list and load- 1044 splitting across its members. The client-side can use RLOCs 1045 outside of the subset list if it determines that the subset list 1046 is unreachable (unless RLOCs are set to a Priority of 255). Some 1047 sharing of control exists: the server-side determines the 1048 destination RLOC list and load distribution while the client-side 1049 has the option of using alternatives to this list if RLOCs in the 1050 list are unreachable. 1052 o The server-side sets a Weight of zero for the RLOC subset list. 1053 In this case, the client-side can choose how the traffic load is 1054 spread across the subset list. Control is shared by the server- 1055 side determining the list and the client-side determining load 1056 distribution. Again, the client can use alternative RLOCs if the 1057 server-provided list of RLOCs is unreachable. 1059 o Either side (more likely the server-side ETR) decides not to send 1060 a Map-Request. For example, if the server-side ETR does not send 1061 Map-Requests, it gleans RLOCs from the client-side ITR, giving the 1062 client-side ITR responsibility for bidirectional RLOC reachability 1063 and preferability. Server-side ETR gleaning of the client-side 1064 ITR RLOC is done by caching the inner-header source EID and the 1065 outer-header source RLOC of received packets. The client-side ITR 1066 controls how traffic is returned and can alternate using an outer- 1067 header source RLOC, which then can be added to the list the 1068 server-side ETR uses to return traffic. Since no Priority or 1069 Weights are provided using this method, the server-side ETR MUST 1070 assume that each client-side ITR RLOC uses the same best Priority 1071 with a Weight of zero. In addition, since EID-Prefix encoding 1072 cannot be conveyed in data packets, the EID-to-RLOC Cache on 1073 Tunnel Routers can grow to be very large. 1075 Alternatively, RLOC information MAY be gleaned from received tunneled 1076 packets or EID-to-RLOC Map-Request messages. A "gleaned" Map-Cache 1077 entry, one learned from the source RLOC of a received encapsulated 1078 packet, is only stored and used for a few seconds, pending 1079 verification. Verification is performed by sending a Map-Request to 1080 the source EID (the inner-header IP source address) of the received 1081 encapsulated packet. A reply to this "verifying Map-Request" is used 1082 to fully populate the Map-Cache entry for the "gleaned" EID and is 1083 stored and used for the time indicated from the 'TTL' field of a 1084 received Map-Reply. When a verified Map-Cache entry is stored, data 1085 gleaning no longer occurs for subsequent packets that have a source 1086 EID that matches the EID-Prefix of the verified entry. This 1087 "gleaning" mechanism is OPTIONAL, refer to Section 16 for security 1088 issues regarding this mechanism. 1090 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1091 reachable when the R-bit for the Locator record is set to 1. When 1092 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1093 RLOC. Neither the information contained in a Map-Reply nor that 1094 stored in the mapping database system provides reachability 1095 information for RLOCs. Note that reachability is not part of the 1096 mapping system and is determined using one or more of the Routing 1097 Locator reachability algorithms described in the next section. 1099 10. Routing Locator Reachability 1101 Several Data-Plane mechanisms for determining RLOC reachability are 1102 currently defined. Please note that additional Control-Plane based 1103 reachability mechanisms are defined in [I-D.ietf-lisp-rfc6833bis]. 1105 1. An ETR MAY examine the Locator-Status-Bits in the LISP header of 1106 an encapsulated data packet received from an ITR. If the ETR is 1107 also acting as an ITR and has traffic to return to the original 1108 ITR site, it can use this status information to help select an 1109 RLOC. 1111 2. When an ETR receives an encapsulated packet from an ITR, the 1112 source RLOC from the outer header of the packet is likely up. 1114 3. An ITR/ETR pair can use the 'Echo-Noncing' Locator reachability 1115 algorithms described in this section. 1117 When determining Locator up/down reachability by examining the 1118 Locator-Status-Bits from the LISP-encapsulated data packet, an ETR 1119 will receive up-to-date status from an encapsulating ITR about 1120 reachability for all ETRs at the site. CE-based ITRs at the source 1121 site can determine reachability relative to each other using the site 1122 IGP as follows: 1124 o Under normal circumstances, each ITR will advertise a default 1125 route into the site IGP. 1127 o If an ITR fails or if the upstream link to its PE fails, its 1128 default route will either time out or be withdrawn. 1130 Each ITR can thus observe the presence or lack of a default route 1131 originated by the others to determine the Locator-Status-Bits it sets 1132 for them. 1134 When ITRs at the site are not deployed in CE routers, the IGP can 1135 still be used to determine the reachability of Locators, provided 1136 they are injected into the IGP. This is typically done when a /32 1137 address is configured on a loopback interface. 1139 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1140 Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 1141 to n-1 starting with the least significant bit. For example, if an 1142 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1143 value 2), then all ITRs at the site will clear the 3rd least 1144 significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for 1145 the packets they encapsulate. 1147 When an ETR decapsulates a packet, it will check for any change in 1148 the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the 1149 ETR, if acting also as an ITR, will refrain from encapsulating 1150 packets to an RLOC that is indicated as down. It will only resume 1151 using that RLOC if the corresponding Locator-Status-Bit returns to a 1152 value of 1. Locator-Status-Bits are associated with a Locator-Set 1153 per EID-Prefix. Therefore, when a Locator becomes unreachable, the 1154 Locator-Status-Bit that corresponds to that Locator's position in the 1155 list returned by the last Map-Reply will be set to zero for that 1156 particular EID-Prefix. Refer to Section 16 for security related 1157 issues regarding Locator-Status-Bits. 1159 When an ETR decapsulates a packet, it knows that it is reachable from 1160 the encapsulating ITR because that is how the packet arrived. In 1161 most cases, the ETR can also reach the ITR but cannot assume this to 1162 be true, due to the possibility of path asymmetry. In the presence 1163 of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD 1164 NOT use the lack of return traffic as an indication that the ETR is 1165 unreachable. Instead, it MUST use an alternate mechanism to 1166 determine reachability. 1168 10.1. Echo Nonce Algorithm 1170 When data flows bidirectionally between Locators from different 1171 sites, a Data-Plane mechanism called "nonce echoing" can be used to 1172 determine reachability between an ITR and ETR. When an ITR wants to 1173 solicit a nonce echo, it sets the N- and E-bits and places a 24-bit 1174 nonce [RFC4086] in the LISP header of the next encapsulated data 1175 packet. 1177 When this packet is received by the ETR, the encapsulated packet is 1178 forwarded as normal. When the ETR next sends a data packet to the 1179 ITR, it includes the nonce received earlier with the N-bit set and 1180 E-bit cleared. The ITR sees this "echoed nonce" and knows that the 1181 path to and from the ETR is up. 1183 The ITR will set the E-bit and N-bit for every packet it sends while 1184 in the echo-nonce-request state. The time the ITR waits to process 1185 the echoed nonce before it determines the path is unreachable is 1186 variable and is a choice left for the implementation. 1188 If the ITR is receiving packets from the ETR but does not see the 1189 nonce echoed while being in the echo-nonce-request state, then the 1190 path to the ETR is unreachable. This decision MAY be overridden by 1191 other Locator reachability algorithms. Once the ITR determines that 1192 the path to the ETR is down, it can switch to another Locator for 1193 that EID-Prefix. 1195 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1196 be implementing both ITR and ETR functionality for the echo nonce 1197 mechanism to operate. 1199 The ITR and ETR MAY both go into the echo-nonce-request state at the 1200 same time. The number of packets sent or the time during which echo 1201 nonce requests are sent is an implementation-specific setting. 1202 However, when an ITR is in the echo-nonce-request state, it can echo 1203 the ETR's nonce in the next set of packets that it encapsulates and 1204 subsequently continue sending echo-nonce-request packets. 1206 This mechanism does not completely solve the forward path 1207 reachability problem, as traffic may be unidirectional. That is, the 1208 ETR receiving traffic at a site MAY not be the same device as an ITR 1209 that transmits traffic from that site, or the site-to-site traffic is 1210 unidirectional so there is no ITR returning traffic. 1212 The echo-nonce algorithm is bilateral. That is, if one side sets the 1213 E-bit and the other side is not enabled for echo-noncing, then the 1214 echoing of the nonce does not occur and the requesting side may 1215 erroneously consider the Locator unreachable. An ITR SHOULD only set 1216 the E-bit in an encapsulated data packet when it knows the ETR is 1217 enabled for echo-noncing. This is conveyed by the E-bit in the RLOC- 1218 probe Map-Reply message. 1220 11. EID Reachability within a LISP Site 1222 A site MAY be multihomed using two or more ETRs. The hosts and 1223 infrastructure within a site will be addressed using one or more EID- 1224 Prefixes that are mapped to the RLOCs of the relevant ETRs in the 1225 mapping system. One possible failure mode is for an ETR to lose 1226 reachability to one or more of the EID-Prefixes within its own site. 1227 When this occurs when the ETR sends Map-Replies, it can clear the 1228 R-bit associated with its own Locator. And when the ETR is also an 1229 ITR, it can clear its Locator-Status-Bit in the encapsulation data 1230 header. 1232 It is recognized that there are no simple solutions to the site 1233 partitioning problem because it is hard to know which part of the 1234 EID-Prefix range is partitioned and which Locators can reach any sub- 1235 ranges of the EID-Prefixes. Note that this is not a new problem 1236 introduced by the LISP architecture. The problem exists today when a 1237 multihomed site uses BGP to advertise its reachability upstream. 1239 12. Routing Locator Hashing 1241 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message 1242 that is stored in the Map-Cache of a requesting ITR, the Locator-Set 1243 for the EID-Prefix MAY contain different Priority and Weight values 1244 for each locator address. When more than one best Priority Locator 1245 exists, the ITR can decide how to load-share traffic against the 1246 corresponding Locators. 1248 The following hash algorithm MAY be used by an ITR to select a 1249 Locator for a packet destined to an EID for the EID-to-RLOC mapping: 1251 1. Either a source and destination address hash or the traditional 1252 5-tuple hash can be used. The traditional 5-tuple hash includes 1253 the source and destination addresses; source and destination TCP, 1254 UDP, or Stream Control Transmission Protocol (SCTP) port numbers; 1255 and the IP protocol number field or IPv6 next-protocol fields of 1256 a packet that a host originates from within a LISP site. When a 1257 packet is not a TCP, UDP, or SCTP packet, the source and 1258 destination addresses only from the header are used to compute 1259 the hash. 1261 2. Take the hash value and divide it by the number of Locators 1262 stored in the Locator-Set for the EID-to-RLOC mapping. 1264 3. The remainder will yield a value of 0 to "number of Locators 1265 minus 1". Use the remainder to select the Locator in the 1266 Locator-Set. 1268 Note that when a packet is LISP encapsulated, the source port number 1269 in the outer UDP header needs to be set. Selecting a hashed value 1270 allows core routers that are attached to Link Aggregation Groups 1271 (LAGs) to load-split the encapsulated packets across member links of 1272 such LAGs. Otherwise, core routers would see a single flow, since 1273 packets have a source address of the ITR, for packets that are 1274 originated by different EIDs at the source site. A suggested setting 1275 for the source port number computed by an ITR is a 5-tuple hash 1276 function on the inner header, as described above. 1278 Many core router implementations use a 5-tuple hash to decide how to 1279 balance packet load across members of a LAG. The 5-tuple hash 1280 includes the source and destination addresses of the packet and the 1281 source and destination ports when the protocol number in the packet 1282 is TCP or UDP. For this reason, UDP encoding is used for LISP 1283 encapsulation. 1285 13. Changing the Contents of EID-to-RLOC Mappings 1287 Since the LISP architecture uses a caching scheme to retrieve and 1288 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 1289 date mapping is to re-request the mapping. However, the ITRs do not 1290 know when the mappings change, and the ETRs do not keep track of 1291 which ITRs requested its mappings. For scalability reasons, it is 1292 desirable to maintain this approach but need to provide a way for 1293 ETRs to change their mappings and inform the sites that are currently 1294 communicating with the ETR site using such mappings. 1296 This section defines a Data-Plane mechanism for updating EID-to-RLOC 1297 mappings. Additionally, the Solicit-Map Request (SMR) Control-Plane 1298 updating mechanism is specified in [I-D.ietf-lisp-rfc6833bis]. 1300 When adding a new Locator record in lexicographic order to the end of 1301 a Locator-Set, it is easy to update mappings. We assume that new 1302 mappings will maintain the same Locator ordering as the old mapping 1303 but will just have new Locators appended to the end of the list. So, 1304 some ITRs can have a new mapping while other ITRs have only an old 1305 mapping that is used until they time out. When an ITR has only an 1306 old mapping but detects bits set in the Locator-Status-Bits that 1307 correspond to Locators beyond the list it has cached, it simply 1308 ignores them. However, this can only happen for locator addresses 1309 that are lexicographically greater than the locator addresses in the 1310 existing Locator-Set. 1312 When a Locator record is inserted in the middle of a Locator-Set, to 1313 maintain lexicographic order, SMR procedure 1314 [I-D.ietf-lisp-rfc6833bis] is used to inform ITRs and PITRs of the 1315 new Locator-Status-Bit mappings. 1317 When a Locator record is removed from a Locator-Set, ITRs that have 1318 the mapping cached will not use the removed Locator because the xTRs 1319 will set the Locator-Status-Bit to 0. So, even if the Locator is in 1320 the list, it will not be used. For new mapping requests, the xTRs 1321 can set the Locator AFI to 0 (indicating an unspecified address), as 1322 well as setting the corresponding Locator-Status-Bit to 0. This 1323 forces ITRs with old or new mappings to avoid using the removed 1324 Locator. 1326 If many changes occur to a mapping over a long period of time, one 1327 will find empty record slots in the middle of the Locator-Set and new 1328 records appended to the Locator-Set. At some point, it would be 1329 useful to compact the Locator-Set so the Locator-Status-Bit settings 1330 can be efficiently packed. 1332 We propose here a Data-Plane mechanism (Map-Versioning) to update the 1333 contents of EID-to-RLOC mappings. Please note that in addition the 1334 Solicit-Map Request (specified in [I-D.ietf-lisp-rfc6833bis]) is a 1335 Control-Plane mechanisms that can be used to update EID-to-RLOC 1336 mappings. 1338 13.1. Database Map-Versioning 1340 When there is unidirectional packet flow between an ITR and ETR, and 1341 the EID-to-RLOC mappings change on the ETR, it needs to inform the 1342 ITR so encapsulation to a removed Locator can stop and can instead be 1343 started to a new Locator in the Locator-Set. 1345 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 1346 Number. This is known as the Destination Map-Version Number. ITRs 1347 include the Destination Map-Version Number in packets they 1348 encapsulate to the site. When an ETR decapsulates a packet and 1349 detects that the Destination Map-Version Number is less than the 1350 current version for its mapping, the SMR procedure described in 1351 [I-D.ietf-lisp-rfc6833bis] occurs. 1353 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 1354 Version Number. This is known as the Source Map-Version Number. 1355 When an ETR decapsulates a packet and detects that the Source Map- 1356 Version Number is greater than the last Map-Version Number sent in a 1357 Map-Reply from the ITR's site, the ETR will send a Map-Request to one 1358 of the ETRs for the source site. 1360 A Map-Version Number is used as a sequence number per EID-Prefix, so 1361 values that are greater are considered to be more recent. A value of 1362 0 for the Source Map-Version Number or the Destination Map-Version 1363 Number conveys no versioning information, and an ITR does no 1364 comparison with previously received Map-Version Numbers. 1366 A Map-Version Number can be included in Map-Register messages as 1367 well. This is a good way for the Map-Server to assure that all ETRs 1368 for a site registering to it will be synchronized according to Map- 1369 Version Number. 1371 See [I-D.ietf-lisp-6834bis] for a more detailed analysis and 1372 description of Database Map-Versioning. 1374 14. Multicast Considerations 1376 A multicast group address, as defined in the original Internet 1377 architecture, is an identifier of a grouping of topologically 1378 independent receiver host locations. The address encoding itself 1379 does not determine the location of the receiver(s). The multicast 1380 routing protocol, and the network-based state the protocol creates, 1381 determine where the receivers are located. 1383 In the context of LISP, a multicast group address is both an EID and 1384 a Routing Locator. Therefore, no specific semantic or action needs 1385 to be taken for a destination address, as it would appear in an IP 1386 header. Therefore, a group address that appears in an inner IP 1387 header built by a source host will be used as the destination EID. 1388 The outer IP header (the destination Routing Locator address), 1389 prepended by a LISP router, can use the same group address as the 1390 destination Routing Locator, use a multicast or unicast Routing 1391 Locator obtained from a Mapping System lookup, or use other means to 1392 determine the group address mapping. 1394 With respect to the source Routing Locator address, the ITR prepends 1395 its own IP address as the source address of the outer IP header. 1396 Just like it would if the destination EID was a unicast address. 1397 This source Routing Locator address, like any other Routing Locator 1398 address, MUST be globally routable. 1400 There are two approaches for LISP-Multicast, one that uses native 1401 multicast routing in the underlay with no support from the Mapping 1402 System and the other that uses only unicast routing in the underlay 1403 with support from the Mapping System. See [RFC6831] and [RFC8378], 1404 respectively, for details. Details for LISP-Multicast and 1405 interworking with non-LISP sites are described in [RFC6831] and 1406 [RFC6832]. 1408 15. Router Performance Considerations 1410 LISP is designed to be very "hardware-based forwarding friendly". A 1411 few implementation techniques can be used to incrementally implement 1412 LISP: 1414 o When a tunnel-encapsulated packet is received by an ETR, the outer 1415 destination address may not be the address of the router. This 1416 makes it challenging for the control plane to get packets from the 1417 hardware. This may be mitigated by creating special Forwarding 1418 Information Base (FIB) entries for the EID-Prefixes of EIDs served 1419 by the ETR (those for which the router provides an RLOC 1420 translation). These FIB entries are marked with a flag indicating 1421 that Control-Plane processing SHOULD be performed. The forwarding 1422 logic of testing for particular IP protocol number values is not 1423 necessary. There are a few proven cases where no changes to 1424 existing deployed hardware were needed to support the LISP Data- 1425 Plane. 1427 o On an ITR, prepending a new IP header consists of adding more 1428 octets to a MAC rewrite string and prepending the string as part 1429 of the outgoing encapsulation procedure. Routers that support 1430 Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 1431 tunneling [RFC3056] may already support this action. 1433 o A packet's source address or interface the packet was received on 1434 can be used to select VRF (Virtual Routing/Forwarding). The VRF's 1435 routing table can be used to find EID-to-RLOC mappings. 1437 For performance issues related to Map-Cache management, see 1438 Section 16. 1440 16. Security Considerations 1442 Security considerations for LISP are discussed in [RFC7833]. 1444 A complete LISP threat analysis can be found in [RFC7835], in what 1445 follows we provide a summary. 1447 The optional mechanisms of gleaning is offered to directly obtain a 1448 mapping from the LISP encapsulated packets. Specifically, an xTR can 1449 learn the EID-to-RLOC mapping by inspecting the source RLOC and 1450 source EID of an encapsulated packet, and insert this new mapping 1451 into its Map-Cache. An off-path attacker can spoof the source EID 1452 address to divert the traffic sent to the victim's spoofed EID. If 1453 the attacker spoofs the source RLOC, it can mount a DoS attack by 1454 redirecting traffic to the spoofed victim's RLOC, potentially 1455 overloading it. 1457 The LISP Data-Plane defines several mechanisms to monitor RLOC Data- 1458 Plane reachability, in this context Locator-Status Bits, Nonce- 1459 Present and Echo-Nonce bits of the LISP encapsulation header can be 1460 manipulated by an attacker to mount a DoS attack. An off-path 1461 attacker able to spoof the RLOC of a victim's xTR can manipulate such 1462 mechanisms to declare a set of RLOCs unreachable. This can be used 1463 also, for instance, to declare only one RLOC reachable with the aim 1464 of overload it. 1466 Map-Versioning is a Data-Plane mechanism used to signal a peering xTR 1467 that a local EID-to-RLOC mapping has been updated, so that the 1468 peering xTR uses LISP Control-Plane signaling message to retrieve a 1469 fresh mapping. This can be used by an attacker to forge the map- 1470 versioning field of a LISP encapsulated header and force an excessive 1471 amount of signaling between xTRs that may overload them. 1473 Most of the attack vectors can be mitigated with careful deployment 1474 and configuration, information learned opportunistically (such as LSB 1475 or gleaning) SHOULD be verified with other reachability mechanisms. 1476 In addition, systematic rate-limitation and filtering is an effective 1477 technique to mitigate attacks that aim to overload the Control-Plane. 1479 17. Network Management Considerations 1481 Considerations for network management tools exist so the LISP 1482 protocol suite can be operationally managed. These mechanisms can be 1483 found in [RFC7052] and [RFC6835]. 1485 18. IANA Considerations 1487 This section provides guidance to the Internet Assigned Numbers 1488 Authority (IANA) regarding registration of values related to this 1489 Data-Plane LISP specification, in accordance with BCP 26 [RFC8126]. 1491 18.1. LISP UDP Port Numbers 1493 The IANA registry has allocated UDP port number 4341 for the LISP 1494 Data-Plane. IANA has updated the description for UDP port 4341 as 1495 follows: 1497 lisp-data 4341 udp LISP Data Packets 1499 19. References 1501 19.1. Normative References 1503 [I-D.ietf-lisp-6834bis] 1504 Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1505 Separation Protocol (LISP) Map-Versioning", draft-ietf- 1506 lisp-6834bis-00 (work in progress), July 2018. 1508 [I-D.ietf-lisp-rfc6833bis] 1509 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1510 "Locator/ID Separation Protocol (LISP) Control-Plane", 1511 draft-ietf-lisp-rfc6833bis-10 (work in progress), March 1512 2018. 1514 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1515 DOI 10.17487/RFC0768, August 1980, 1516 . 1518 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1519 DOI 10.17487/RFC0791, September 1981, 1520 . 1522 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1523 "Definition of the Differentiated Services Field (DS 1524 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1525 DOI 10.17487/RFC2474, December 1998, 1526 . 1528 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1529 of Explicit Congestion Notification (ECN) to IP", 1530 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1531 . 1533 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1534 (IPv6) Specification", STD 86, RFC 8200, 1535 DOI 10.17487/RFC8200, July 2017, 1536 . 1538 19.2. Informative References 1540 [AFN] IANA, "Address Family Numbers", August 2016, 1541 . 1543 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed", 1544 1999, 1545 . 1547 [I-D.ietf-lisp-introduction] 1548 Cabellos-Aparicio, A. and D. Saucez, "An Architectural 1549 Introduction to the Locator/ID Separation Protocol 1550 (LISP)", draft-ietf-lisp-introduction-13 (work in 1551 progress), April 2015. 1553 [I-D.ietf-lisp-vpn] 1554 Moreno, V. and D. Farinacci, "LISP Virtual Private 1555 Networks (VPNs)", draft-ietf-lisp-vpn-02 (work in 1556 progress), May 2018. 1558 [OPENLISP] 1559 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 1560 Implementation Report", Work in Progress, July 2008. 1562 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1563 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1564 . 1566 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1567 and E. Lear, "Address Allocation for Private Internets", 1568 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1569 . 1571 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1572 Requirement Levels", BCP 14, RFC 2119, 1573 DOI 10.17487/RFC2119, March 1997, 1574 . 1576 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1577 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1578 DOI 10.17487/RFC2784, March 2000, 1579 . 1581 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 1582 via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 1583 2001, . 1585 [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced 1586 by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, 1587 January 2002, . 1589 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1590 A., Peterson, J., Sparks, R., Handley, M., and E. 1591 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1592 DOI 10.17487/RFC3261, June 2002, 1593 . 1595 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1596 "Randomness Requirements for Security", BCP 106, RFC 4086, 1597 DOI 10.17487/RFC4086, June 2005, 1598 . 1600 [RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report 1601 from the IAB Workshop on Routing and Addressing", 1602 RFC 4984, DOI 10.17487/RFC4984, September 2007, 1603 . 1605 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1606 Locator/ID Separation Protocol (LISP) for Multicast 1607 Environments", RFC 6831, DOI 10.17487/RFC6831, January 1608 2013, . 1610 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1611 "Interworking between Locator/ID Separation Protocol 1612 (LISP) and Non-LISP Sites", RFC 6832, 1613 DOI 10.17487/RFC6832, January 2013, 1614 . 1616 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1617 Protocol Internet Groper (LIG)", RFC 6835, 1618 DOI 10.17487/RFC6835, January 2013, 1619 . 1621 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1622 UDP Checksums for Tunneled Packets", RFC 6935, 1623 DOI 10.17487/RFC6935, April 2013, 1624 . 1626 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1627 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1628 RFC 6936, DOI 10.17487/RFC6936, April 2013, 1629 . 1631 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1632 Separation Protocol (LISP) MIB", RFC 7052, 1633 DOI 10.17487/RFC7052, October 2013, 1634 . 1636 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1637 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1638 Protocol (LISP) Network Element Deployment 1639 Considerations", RFC 7215, DOI 10.17487/RFC7215, April 1640 2014, . 1642 [RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A 1643 RADIUS Attribute, Binding, Profiles, Name Identifier 1644 Format, and Confirmation Methods for the Security 1645 Assertion Markup Language (SAML)", RFC 7833, 1646 DOI 10.17487/RFC7833, May 2016, 1647 . 1649 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 1650 Separation Protocol (LISP) Threat Analysis", RFC 7835, 1651 DOI 10.17487/RFC7835, April 2016, 1652 . 1654 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1655 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 1656 February 2017, . 1658 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 1659 (LISP) Data-Plane Confidentiality", RFC 8061, 1660 DOI 10.17487/RFC8061, February 2017, 1661 . 1663 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 1664 Smirnov, "Locator/ID Separation Protocol Delegated 1665 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 1666 May 2017, . 1668 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1669 Writing an IANA Considerations Section in RFCs", BCP 26, 1670 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1671 . 1673 [RFC8378] Moreno, V. and D. Farinacci, "Signal-Free Locator/ID 1674 Separation Protocol (LISP) Multicast", RFC 8378, 1675 DOI 10.17487/RFC8378, May 2018, 1676 . 1678 Appendix A. Acknowledgments 1680 An initial thank you goes to Dave Oran for planting the seeds for the 1681 initial ideas for LISP. His consultation continues to provide value 1682 to the LISP authors. 1684 A special and appreciative thank you goes to Noel Chiappa for 1685 providing architectural impetus over the past decades on separation 1686 of location and identity, as well as detailed reviews of the LISP 1687 architecture and documents, coupled with enthusiasm for making LISP a 1688 practical and incremental transition for the Internet. 1690 The authors would like to gratefully acknowledge many people who have 1691 contributed discussions and ideas to the making of this proposal. 1692 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 1693 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 1694 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 1695 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 1696 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 1697 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 1698 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 1699 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 1700 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 1701 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 1702 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 1703 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 1704 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 1705 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 1706 Ermagan, Fabio Maino, Victor Moreno, Chris White, Clarence Filsfils, 1707 Alia Atlas, Florin Coras and Alberto Rodriguez. 1709 This work originated in the Routing Research Group (RRG) of the IRTF. 1710 An individual submission was converted into the IETF LISP working 1711 group document that became this RFC. 1713 The LISP working group would like to give a special thanks to Jari 1714 Arkko, the Internet Area AD at the time that the set of LISP 1715 documents were being prepared for IESG last call, and for his 1716 meticulous reviews and detailed commentaries on the 7 working group 1717 last call documents progressing toward standards-track RFCs. 1719 Appendix B. Document Change Log 1721 [RFC Editor: Please delete this section on publication as RFC.] 1723 B.1. Changes to draft-ietf-lisp-rfc6830bis-13 1725 o Posted March IETF Week 2018. 1727 o Clarified that a new nonce is required per RLOC. 1729 o Removed 'Clock Sweep' section. This text must be placed in a new 1730 OAM document. 1732 o Some references changed from normative to informative 1734 B.2. Changes to draft-ietf-lisp-rfc6830bis-12 1736 o Posted July 2018. 1738 o Fixed Luigi editorial comments to ready draft for RFC status. 1740 B.3. Changes to draft-ietf-lisp-rfc6830bis-11 1742 o Posted March 2018. 1744 o Removed sections 16, 17 and 18 (Mobility, Deployment and 1745 Traceroute considerations). This text must be placed in a new OAM 1746 document. 1748 B.4. Changes to draft-ietf-lisp-rfc6830bis-10 1750 o Posted March 2018. 1752 o Updated section 'Router Locator Selection' stating that the Data- 1753 Plane MUST follow what's stored in the Map-Cache (priorities and 1754 weights). 1756 o Section 'Routing Locator Reachability': Removed bullet point 2 1757 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP Port 1758 Unreachable),5 (receive a Map-Reply as a response) and RLOC 1759 probing 1761 o Removed 'Solicit-Map Request'. 1763 B.5. Changes to draft-ietf-lisp-rfc6830bis-09 1765 o Posted January 2018. 1767 o Add more details in section 5.3 about DSCP processing during 1768 encapsulation and decapsulation. 1770 o Added clarity to definitions in the Definition of Terms section 1771 from various commenters. 1773 o Removed PA and PI definitions from Definition of Terms section. 1775 o More editorial changes. 1777 o Removed 4342 from IANA section and move to RFC6833 IANA section. 1779 B.6. Changes to draft-ietf-lisp-rfc6830bis-08 1781 o Posted January 2018. 1783 o Remove references to research work for any protocol mechanisms. 1785 o Document scanned to make sure it is RFC 2119 compliant. 1787 o Made changes to reflect comments from document WG shepherd Luigi 1788 Iannone. 1790 o Ran IDNITs on the document. 1792 B.7. Changes to draft-ietf-lisp-rfc6830bis-07 1794 o Posted November 2017. 1796 o Rephrase how Instance-IDs are used and don't refer to [RFC1918] 1797 addresses. 1799 B.8. Changes to draft-ietf-lisp-rfc6830bis-06 1801 o Posted October 2017. 1803 o Put RTR definition before it is used. 1805 o Rename references that are now working group drafts. 1807 o Remove "EIDs MUST NOT be used as used by a host to refer to other 1808 hosts. Note that EID blocks MAY LISP RLOCs". 1810 o Indicate what address-family can appear in data packets. 1812 o ETRs may, rather than will, be the ones to send Map-Replies. 1814 o Recommend, rather than mandate, max encapsulation headers to 2. 1816 o Reference VPN draft when introducing Instance-ID. 1818 o Indicate that SMRs can be sent when ITR/ETR are in the same node. 1820 o Clarify when private addreses can be used. 1822 B.9. Changes to draft-ietf-lisp-rfc6830bis-05 1824 o Posted August 2017. 1826 o Make it clear that a Reencapsulating Tunnel Router is an RTR. 1828 B.10. Changes to draft-ietf-lisp-rfc6830bis-04 1830 o Posted July 2017. 1832 o Changed reference of IPv6 RFC2460 to RFC8200. 1834 o Indicate that the applicability statement for UDP zero checksums 1835 over IPv6 adheres to RFC6936. 1837 B.11. Changes to draft-ietf-lisp-rfc6830bis-03 1839 o Posted May 2017. 1841 o Move the control-plane related codepoints in the IANA 1842 Considerations section to RFC6833bis. 1844 B.12. Changes to draft-ietf-lisp-rfc6830bis-02 1846 o Posted April 2017. 1848 o Reflect some editorial comments from Damien Sausez. 1850 B.13. Changes to draft-ietf-lisp-rfc6830bis-01 1852 o Posted March 2017. 1854 o Include references to new RFCs published. 1856 o Change references from RFC6833 to RFC6833bis. 1858 o Clarified LCAF text in the IANA section. 1860 o Remove references to "experimental". 1862 B.14. Changes to draft-ietf-lisp-rfc6830bis-00 1864 o Posted December 2016. 1866 o Created working group document from draft-farinacci-lisp 1867 -rfc6830-00 individual submission. No other changes made. 1869 Authors' Addresses 1871 Dino Farinacci 1872 Cisco Systems 1873 Tasman Drive 1874 San Jose, CA 95134 1875 USA 1877 EMail: farinacci@gmail.com 1879 Vince Fuller 1880 Cisco Systems 1881 Tasman Drive 1882 San Jose, CA 95134 1883 USA 1885 EMail: vince.fuller@gmail.com 1887 Dave Meyer 1888 Cisco Systems 1889 170 Tasman Drive 1890 San Jose, CA 1891 USA 1893 EMail: dmm@1-4-5.net 1895 Darrel Lewis 1896 Cisco Systems 1897 170 Tasman Drive 1898 San Jose, CA 1899 USA 1901 EMail: darlewis@cisco.com 1902 Albert Cabellos 1903 UPC/BarcelonaTech 1904 Campus Nord, C. Jordi Girona 1-3 1905 Barcelona, Catalunya 1906 Spain 1908 EMail: acabello@ac.upc.edu