idnits 2.17.1 draft-ietf-lisp-rfc6830bis-17.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 (September 11, 2018) is 2053 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-14) exists of draft-ietf-lisp-6834bis-02 == Outdated reference: A later version (-31) exists of draft-ietf-lisp-rfc6833bis-13 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-introduction-13 == Outdated reference: A later version (-12) exists of draft-ietf-lisp-vpn-02 Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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: March 15, 2019 Cisco Systems 7 A. Cabellos (Ed.) 8 UPC/BarcelonaTech 9 September 11, 2018 11 The Locator/ID Separation Protocol (LISP) 12 draft-ietf-lisp-rfc6830bis-17 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 March 15, 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 . . . . . . . . . . . . . 14 72 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . 15 73 6. LISP EID-to-RLOC Map-Cache . . . . . . . . . . . . . . . . . 20 74 7. Dealing with Large Encapsulated Packets . . . . . . . . . . . 20 75 7.1. A Stateless Solution to MTU Handling . . . . . . . . . . 21 76 7.2. A Stateful Solution to MTU Handling . . . . . . . . . . . 22 77 8. Using Virtualization and Segmentation with LISP . . . . . . . 22 78 9. Routing Locator Selection . . . . . . . . . . . . . . . . . . 23 79 10. Routing Locator Reachability . . . . . . . . . . . . . . . . 25 80 10.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . . 26 81 11. EID Reachability within a LISP Site . . . . . . . . . . . . . 27 82 12. Routing Locator Hashing . . . . . . . . . . . . . . . . . . . 28 83 13. Changing the Contents of EID-to-RLOC Mappings . . . . . . . . 29 84 13.1. Database Map-Versioning . . . . . . . . . . . . . . . . 30 85 14. Multicast Considerations . . . . . . . . . . . . . . . . . . 30 86 15. Router Performance Considerations . . . . . . . . . . . . . . 31 87 16. Security Considerations . . . . . . . . . . . . . . . . . . . 32 88 17. Network Management Considerations . . . . . . . . . . . . . . 33 89 18. Changes since RFC 6830 . . . . . . . . . . . . . . . . . . . 33 90 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33 91 19.1. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . 33 92 20. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 93 20.1. Normative References . . . . . . . . . . . . . . . . . . 34 94 20.2. Informative References . . . . . . . . . . . . . . . . . 35 96 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 39 97 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 39 98 B.1. Changes to draft-ietf-lisp-rfc6830bis-17 . . . . . . . . 40 99 B.2. Changes to draft-ietf-lisp-rfc6830bis-16 . . . . . . . . 40 100 B.3. Changes to draft-ietf-lisp-rfc6830bis-15 . . . . . . . . 40 101 B.4. Changes to draft-ietf-lisp-rfc6830bis-14 . . . . . . . . 40 102 B.5. Changes to draft-ietf-lisp-rfc6830bis-13 . . . . . . . . 40 103 B.6. Changes to draft-ietf-lisp-rfc6830bis-12 . . . . . . . . 41 104 B.7. Changes to draft-ietf-lisp-rfc6830bis-11 . . . . . . . . 41 105 B.8. Changes to draft-ietf-lisp-rfc6830bis-10 . . . . . . . . 41 106 B.9. Changes to draft-ietf-lisp-rfc6830bis-09 . . . . . . . . 41 107 B.10. Changes to draft-ietf-lisp-rfc6830bis-08 . . . . . . . . 42 108 B.11. Changes to draft-ietf-lisp-rfc6830bis-07 . . . . . . . . 42 109 B.12. Changes to draft-ietf-lisp-rfc6830bis-06 . . . . . . . . 42 110 B.13. Changes to draft-ietf-lisp-rfc6830bis-05 . . . . . . . . 42 111 B.14. Changes to draft-ietf-lisp-rfc6830bis-04 . . . . . . . . 43 112 B.15. Changes to draft-ietf-lisp-rfc6830bis-03 . . . . . . . . 43 113 B.16. Changes to draft-ietf-lisp-rfc6830bis-02 . . . . . . . . 43 114 B.17. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 43 115 B.18. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 43 116 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43 118 1. Introduction 120 This document describes the Locator/Identifier Separation Protocol 121 (LISP). LISP is an encapsulation protocol built around the 122 fundamental idea of separating the topological location of a network 123 attachment point from the node's identity [CHIAPPA]. As a result 124 LISP creates two namespaces: Endpoint Identifiers (EIDs), that are 125 used to identify end-hosts (e.g., nodes or Virtual Machines) and 126 routable Routing Locators (RLOCs), used to identify network 127 attachment points. LISP then defines functions for mapping between 128 the two namespaces and for encapsulating traffic originated by 129 devices using non-routable EIDs for transport across a network 130 infrastructure that routes and forwards using RLOCs. LISP 131 encapsulation uses a dynamic form of tunneling where no static 132 provisioning is required or necessary. 134 LISP is an overlay protocol that separates control from Data-Plane, 135 this document specifies the Data-Plane, how LISP-capable routers 136 (Tunnel Routers) exchange packets by encapsulating them to the 137 appropriate location. Tunnel routers are equipped with a cache, 138 called Map-Cache, that contains EID-to-RLOC mappings. The Map-Cache 139 is populated using the LISP Control-Plane protocol 140 [I-D.ietf-lisp-rfc6833bis]. 142 LISP does not require changes to either host protocol stack or to 143 underlay routers. By separating the EID from the RLOC space, LISP 144 offers native Traffic Engineering, multihoming and mobility, among 145 other features. 147 Creation of LISP was initially motivated by discussions during the 148 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 149 October 2006 (see [RFC4984]). 151 This document specifies the LISP Data-Plane encapsulation and other 152 LISP forwarding node functionality while [I-D.ietf-lisp-rfc6833bis] 153 specifies the LISP control plane. LISP deployment guidelines can be 154 found in [RFC7215] and [RFC6835] describes considerations for network 155 operational management. Finally, [I-D.ietf-lisp-introduction] 156 describes the LISP architecture. 158 This document obsoletes RFC 6830. 160 2. Requirements Notation 162 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 163 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 164 document are to be interpreted as described in [RFC2119] and 165 [RFC8174]. 167 3. Definition of Terms 169 Address Family Identifier (AFI): AFI is a term used to describe an 170 address encoding in a packet. An address family that pertains to 171 the Data-Plane. See [AFN] and [RFC3232] for details. An AFI 172 value of 0 used in this specification indicates an unspecified 173 encoded address where the length of the address is 0 octets 174 following the 16-bit AFI value of 0. 176 Anycast Address: Anycast Address is a term used in this document to 177 refer to the same IPv4 or IPv6 address configured and used on 178 multiple systems at the same time. An EID or RLOC can be an 179 anycast address in each of their own address spaces. 181 Client-side: Client-side is a term used in this document to indicate 182 a connection initiation attempt by an end-system represented by an 183 EID. 185 Data-Probe: A Data-Probe is a LISP-encapsulated data packet where 186 the inner-header destination address equals the outer-header 187 destination address used to trigger a Map-Reply by a decapsulating 188 ETR. In addition, the original packet is decapsulated and 189 delivered to the destination host if the destination EID is in the 190 EID-Prefix range configured on the ETR. Otherwise, the packet is 191 discarded. A Data-Probe is used in some of the mapping database 192 designs to "probe" or request a Map-Reply from an ETR; in other 193 cases, Map-Requests are used. See each mapping database design 194 for details. When using Data-Probes, by sending Map-Requests on 195 the underlying routing system, EID-Prefixes must be advertised. 197 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 198 packet where the destination address in the "outer" IP header is 199 one of its own RLOCs. The router strips the "outer" header and 200 forwards the packet based on the next IP header found. In 201 general, an ETR receives LISP-encapsulated IP packets from the 202 Internet on one side and sends decapsulated IP packets to site 203 end-systems on the other side. ETR functionality does not have to 204 be limited to a router device. A server host can be the endpoint 205 of a LISP tunnel as well. 207 EID-to-RLOC Database: The EID-to-RLOC Database is a global 208 distributed database that contains all known EID-Prefix-to-RLOC 209 mappings. Each potential ETR typically contains a small piece of 210 the database: the EID-to-RLOC mappings for the EID-Prefixes 211 "behind" the router. These map to one of the router's own 212 globally visible IP addresses. Note that there MAY be transient 213 conditions when the EID-Prefix for the site and Locator-Set for 214 each EID-Prefix may not be the same on all ETRs. This has no 215 negative implications, since a partial set of Locators can be 216 used. 218 EID-to-RLOC Map-Cache: The EID-to-RLOC Map-Cache is generally 219 short-lived, on-demand table in an ITR that stores, tracks, and is 220 responsible for timing out and otherwise validating EID-to-RLOC 221 mappings. This cache is distinct from the full "database" of EID- 222 to-RLOC mappings; it is dynamic, local to the ITR(s), and 223 relatively small, while the database is distributed, relatively 224 static, and much more global in scope. 226 EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are 227 allocated to a site by an address allocation authority. EID- 228 Prefixes are associated with a set of RLOC addresses. EID-Prefix 229 allocations can be broken up into smaller blocks when an RLOC set 230 is to be associated with the larger EID-Prefix block. 232 End-System: An end-system is an IPv4 or IPv6 device that originates 233 packets with a single IPv4 or IPv6 header. The end-system 234 supplies an EID value for the destination address field of the IP 235 header when communicating globally (i.e., outside of its routing 236 domain). An end-system can be a host computer, a switch or router 237 device, or any network appliance. 239 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 240 IPv6) value used in the source and destination address fields of 241 the first (most inner) LISP header of a packet. The host obtains 242 a destination EID the same way it obtains a destination address 243 today, for example, through a Domain Name System (DNS) [RFC1034] 244 lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. 245 The source EID is obtained via existing mechanisms used to set a 246 host's "local" IP address. An EID used on the public Internet 247 MUST have the same properties as any other IP address used in that 248 manner; this means, among other things, that it MUST be globally 249 unique. An EID is allocated to a host from an EID-Prefix block 250 associated with the site where the host is located. An EID can be 251 used by a host to refer to other hosts. Note that EID blocks MAY 252 be assigned in a hierarchical manner, independent of the network 253 topology, to facilitate scaling of the mapping database. In 254 addition, an EID block assigned to a site MAY have site-local 255 structure (subnetting) for routing within the site; this structure 256 is not visible to the global routing system. In theory, the bit 257 string that represents an EID for one device can represent an RLOC 258 for a different device. When used in discussions with other 259 Locator/ID separation proposals, a LISP EID will be called an 260 "LEID". Throughout this document, any references to "EID" refer 261 to an LEID. 263 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 264 LISP site. Packets sent by sources inside of the LISP site to 265 destinations outside of the site are candidates for encapsulation 266 by the ITR. The ITR treats the IP destination address as an EID 267 and performs an EID-to-RLOC mapping lookup. The router then 268 prepends an "outer" IP header with one of its routable RLOCs (in 269 the RLOC space) in the source address field and the result of the 270 mapping lookup in the destination address field. Note that this 271 destination RLOC MAY be an intermediate, proxy device that has 272 better knowledge of the EID-to-RLOC mapping closer to the 273 destination EID. In general, an ITR receives IP packets from site 274 end-systems on one side and sends LISP-encapsulated IP packets 275 toward the Internet on the other side. 277 Specifically, when a service provider prepends a LISP header for 278 Traffic Engineering purposes, the router that does this is also 279 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 280 on the outer destination address (the originating ITR's supplied 281 RLOC) or the inner destination address (the originating host's 282 supplied EID). 284 LISP Header: LISP header is a term used in this document to refer 285 to the outer IPv4 or IPv6 header, a UDP header, and a LISP- 286 specific 8-octet header that follow the UDP header and that an ITR 287 prepends or an ETR strips. 289 LISP Router: A LISP router is a router that performs the functions 290 of any or all of the following: ITR, ETR, RTR, Proxy-ITR (PITR), 291 or Proxy-ETR (PETR). 293 LISP Site: LISP site is a set of routers in an edge network that are 294 under a single technical administration. LISP routers that reside 295 in the edge network are the demarcation points to separate the 296 edge network from the core network. 298 Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the 299 LISP header. They are used by ITRs to inform ETRs about the up/ 300 down status of all ETRs at the local site. These bits are used as 301 a hint to convey up/down router status and not path reachability 302 status. The LSBs can be verified by use of one of the Locator 303 reachability algorithms described in Section 10. 305 Negative Mapping Entry: A negative mapping entry, also known as a 306 negative cache entry, is an EID-to-RLOC entry where an EID-Prefix 307 is advertised or stored with no RLOCs. That is, the Locator-Set 308 for the EID-to-RLOC entry is empty or has an encoded Locator count 309 of 0. This type of entry could be used to describe a prefix from 310 a non-LISP site, which is explicitly not in the mapping database. 311 There are a set of well-defined actions that are encoded in a 312 Negative Map-Reply. 314 Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A 315 PETR acts like an ETR but does so on behalf of LISP sites that 316 send packets to destinations at non-LISP sites. 318 Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A 319 PITR acts like an ITR but does so on behalf of non-LISP sites that 320 send packets to destinations at LISP sites. 322 Recursive Tunneling: Recursive Tunneling occurs when a packet has 323 more than one LISP IP header. Additional layers of tunneling MAY 324 be employed to implement Traffic Engineering or other re-routing 325 as needed. When this is done, an additional "outer" LISP header 326 is added, and the original RLOCs are preserved in the "inner" 327 header. 329 Re-Encapsulating Tunneling Router (RTR): An RTR acts like an ETR to 330 remove a LISP header, then acts as an ITR to prepend a new LISP 331 header. This is known as Re-encapsulating Tunneling. Doing this 332 allows a packet to be re-routed by the RTR without adding the 333 overhead of additional tunnel headers. When using multiple 334 mapping database systems, care must be taken to not create re- 335 encapsulation loops through misconfiguration. 337 Route-Returnability: Route-returnability is an assumption that the 338 underlying routing system will deliver packets to the destination. 339 When combined with a nonce that is provided by a sender and 340 returned by a receiver, this limits off-path data insertion. A 341 route-returnability check is verified when a message is sent with 342 a nonce, another message is returned with the same nonce, and the 343 destination of the original message appears as the source of the 344 returned message. 346 Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 347 [RFC8200] address of an Egress Tunnel Router (ETR). An RLOC is 348 the output of an EID-to-RLOC mapping lookup. An EID maps to zero 349 or more RLOCs. Typically, RLOCs are numbered from blocks that are 350 assigned to a site at each point to which it attaches to the 351 underlay network; where the topology is defined by the 352 connectivity of provider networks. Multiple RLOCs can be assigned 353 to the same ETR device or to multiple ETR devices at a site. 355 Server-side: Server-side is a term used in this document to indicate 356 that a connection initiation attempt is being accepted for a 357 destination EID. 359 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 360 network that strips an outer LISP header for Traffic Engineering 361 purposes. 363 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 364 network that prepends an additional LISP header for Traffic 365 Engineering purposes. 367 xTR: An xTR is a reference to an ITR or ETR when direction of data 368 flow is not part of the context description. "xTR" refers to the 369 router that is the tunnel endpoint and is used synonymously with 370 the term "Tunnel Router". For example, "An xTR can be located at 371 the Customer Edge (CE) router" indicates both ITR and ETR 372 functionality at the CE router. 374 4. Basic Overview 376 One key concept of LISP is that end-systems operate the same way they 377 do today. The IP addresses that hosts use for tracking sockets and 378 connections, and for sending and receiving packets, do not change. 379 In LISP terminology, these IP addresses are called Endpoint 380 Identifiers (EIDs). 382 Routers continue to forward packets based on IP destination 383 addresses. When a packet is LISP encapsulated, these addresses are 384 referred to as Routing Locators (RLOCs). Most routers along a path 385 between two hosts will not change; they continue to perform routing/ 386 forwarding lookups on the destination addresses. For routers between 387 the source host and the ITR as well as routers from the ETR to the 388 destination host, the destination address is an EID. For the routers 389 between the ITR and the ETR, the destination address is an RLOC. 391 Another key LISP concept is the "Tunnel Router". A Tunnel Router 392 prepends LISP headers on host-originated packets and strips them 393 prior to final delivery to their destination. The IP addresses in 394 this "outer header" are RLOCs. During end-to-end packet exchange 395 between two Internet hosts, an ITR prepends a new LISP header to each 396 packet, and an ETR strips the new header. The ITR performs EID-to- 397 RLOC lookups to determine the routing path to the ETR, which has the 398 RLOC as one of its IP addresses. 400 Some basic rules governing LISP are: 402 o End-systems only send to addresses that are EIDs. EIDs are 403 typically IP addresses assigned to hosts (other types of EID are 404 supported by LISP, see [RFC8060] for further information). End- 405 systems don't know that addresses are EIDs versus RLOCs but assume 406 that packets get to their intended destinations. In a system 407 where LISP is deployed, LISP routers intercept EID-addressed 408 packets and assist in delivering them across the network core 409 where EIDs cannot be routed. The procedure a host uses to send IP 410 packets does not change. 412 o LISP routers mostly deal with Routing Locator addresses. See 413 details in Section 4.1 to clarify what is meant by "mostly". 415 o RLOCs are always IP addresses assigned to routers, preferably 416 topologically oriented addresses from provider CIDR (Classless 417 Inter-Domain Routing) blocks. 419 o When a router originates packets, it MAY use as a source address 420 either an EID or RLOC. When acting as a host (e.g., when 421 terminating a transport session such as Secure SHell (SSH), 422 TELNET, or the Simple Network Management Protocol (SNMP)), it MAY 423 use an EID that is explicitly assigned for that purpose. An EID 424 that identifies the router as a host MUST NOT be used as an RLOC; 425 an EID is only routable within the scope of a site. A typical BGP 426 configuration might demonstrate this "hybrid" EID/RLOC usage where 427 a router could use its "host-like" EID to terminate iBGP sessions 428 to other routers in a site while at the same time using RLOCs to 429 terminate eBGP sessions to routers outside the site. 431 o Packets with EIDs in them are not expected to be delivered end-to- 432 end in the absence of an EID-to-RLOC mapping operation. They are 433 expected to be used locally for intra-site communication or to be 434 encapsulated for inter-site communication. 436 o EIDs MAY also be structured (subnetted) in a manner suitable for 437 local routing within an Autonomous System (AS). 439 An additional LISP header MAY be prepended to packets by a TE-ITR 440 when re-routing of the path for a packet is desired. A potential 441 use-case for this would be an ISP router that needs to perform 442 Traffic Engineering for packets flowing through its network. In such 443 a situation, termed "Recursive Tunneling", an ISP transit acts as an 444 additional ITR, and the RLOC it uses for the new prepended header 445 would be either a TE-ETR within the ISP (along an intra-ISP traffic 446 engineered path) or a TE-ETR within another ISP (an inter-ISP traffic 447 engineered path, where an agreement to build such a path exists). 449 In order to avoid excessive packet overhead as well as possible 450 encapsulation loops, this document recommends that a maximum of two 451 LISP headers can be prepended to a packet. For initial LISP 452 deployments, it is assumed that two headers is sufficient, where the 453 first prepended header is used at a site for Location/Identity 454 separation and the second prepended header is used inside a service 455 provider for Traffic Engineering purposes. 457 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 458 For example, the ITR for a particular end-to-end packet exchange 459 might be the first-hop or default router within a site for the source 460 host. Similarly, the ETR might be the last-hop router directly 461 connected to the destination host. Another example, perhaps for a 462 VPN service outsourced to an ISP by a site, the ITR could be the 463 site's border router at the service provider attachment point. 464 Mixing and matching of site-operated, ISP-operated, and other Tunnel 465 Routers is allowed for maximum flexibility. 467 4.1. Packet Flow Sequence 469 This section provides an example of the unicast packet flow, 470 including also Control-Plane information as specified in 471 [I-D.ietf-lisp-rfc6833bis]. The example also assumes the following 472 conditions: 474 o Source host "host1.abc.example.com" is sending a packet to 475 "host2.xyz.example.com", exactly what host1 would do if the site 476 was not using LISP. 478 o Each site is multihomed, so each Tunnel Router has an address 479 (RLOC) assigned from the service provider address block for each 480 provider to which that particular Tunnel Router is attached. 482 o The ITR(s) and ETR(s) are directly connected to the source and 483 destination, respectively, but the source and destination can be 484 located anywhere in the LISP site. 486 o A Map-Request is sent for an external destination when the 487 destination is not found in the forwarding table or matches a 488 default route. Map-Requests are sent to the mapping database 489 system by using the LISP Control-Plane protocol documented in 490 [I-D.ietf-lisp-rfc6833bis]. 492 o Map-Replies are sent on the underlying routing system topology 493 using the [I-D.ietf-lisp-rfc6833bis] Control-Plane protocol. 495 Client host1.abc.example.com wants to communicate with server 496 host2.xyz.example.com: 498 1. host1.abc.example.com wants to open a TCP connection to 499 host2.xyz.example.com. It does a DNS lookup on 500 host2.xyz.example.com. An A/AAAA record is returned. This 501 address is the destination EID. The locally assigned address of 502 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 503 packet is built and forwarded through the LISP site as a normal 504 IP packet until it reaches a LISP ITR. 506 2. The LISP ITR must be able to map the destination EID to an RLOC 507 of one of the ETRs at the destination site. The specific method 508 used to do this is not described in this example. See 509 [I-D.ietf-lisp-rfc6833bis] for further information. 511 3. The ITR sends a LISP Map-Request as specified in 512 [I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited. 514 4. The mapping system helps forwarding the Map-Request to the 515 corresponding ETR. When the Map-Request arrives at one of the 516 ETRs at the destination site, it will process the packet as a 517 control message. 519 5. The ETR looks at the destination EID of the Map-Request and 520 matches it against the prefixes in the ETR's configured EID-to- 521 RLOC mapping database. This is the list of EID-Prefixes the ETR 522 is supporting for the site it resides in. If there is no match, 523 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 524 returned to the ITR. 526 6. The ITR receives the Map-Reply message, parses the message (to 527 check for format validity), and stores the mapping information 528 from the packet. This information is stored in the ITR's EID-to- 529 RLOC Map-Cache. Note that the Map-Cache is an on-demand cache. 530 An ITR will manage its Map-Cache in such a way that optimizes for 531 its resource constraints. 533 7. Subsequent packets from host1.abc.example.com to 534 host2.xyz.example.com will have a LISP header prepended by the 535 ITR using the appropriate RLOC as the LISP header destination 536 address learned from the ETR. Note that the packet MAY be sent 537 to a different ETR than the one that returned the Map-Reply due 538 to the source site's hashing policy or the destination site's 539 Locator-Set policy. 541 8. The ETR receives these packets directly (since the destination 542 address is one of its assigned IP addresses), checks the validity 543 of the addresses, strips the LISP header, and forwards packets to 544 the attached destination host. 546 9. In order to defer the need for a mapping lookup in the reverse 547 direction, an ETR can OPTIONALLY create a cache entry that maps 548 the source EID (inner-header source IP address) to the source 549 RLOC (outer-header source IP address) in a received LISP packet. 550 Such a cache entry is termed a "glean mapping" and only contains 551 a single RLOC for the EID in question. More complete information 552 about additional RLOCs SHOULD be verified by sending a LISP Map- 553 Request for that EID. Both the ITR and the ETR MAY also 554 influence the decision the other makes in selecting an RLOC. 556 5. LISP Encapsulation Details 558 Since additional tunnel headers are prepended, the packet becomes 559 larger and can exceed the MTU of any link traversed from the ITR to 560 the ETR. It is RECOMMENDED in IPv4 that packets do not get 561 fragmented as they are encapsulated by the ITR. Instead, the packet 562 is dropped and an ICMP Unreachable/Fragmentation-Needed message is 563 returned to the source. 565 In the case when fragmentation is needed, this specification 566 RECOMMENDS that implementations provide support for one of the 567 proposed fragmentation and reassembly schemes. Two existing schemes 568 are detailed in Section 7. 570 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 571 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 572 header is in IPv4 packet format and the outer header is in IPv6 573 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 574 is in IPv6 packet format and the outer header is in IPv4 packet 575 format). The next sub-sections illustrate packet formats for the 576 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 577 combinations MUST be supported. Additional types of EIDs are defined 578 in [RFC8060]. 580 As LISP uses UDP encapsulation to carry traffic between xTRs across 581 the Internet, implementors should be aware of the provisions of 582 [RFC8085], especially those given in section 3.1.11 on congestion 583 control for UDP tunneling. 585 Implementors are encouraged to consider UDP checksum usage guidelines 586 in section 3.4 of [RFC8085] when it is desirable to protect UDP and 587 LISP headers against corruption. 589 5.1. LISP IPv4-in-IPv4 Header Format 590 0 1 2 3 591 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 1 592 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 / |Version| IHL | DSCP |ECN| Total Length | 594 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 | | Identification |Flags| Fragment Offset | 596 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 OH | Time to Live | Protocol = 17 | Header Checksum | 598 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 | | Source Routing Locator | 600 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 \ | Destination Routing Locator | 602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 / | Source Port = xxxx | Dest Port = 4341 | 604 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 605 \ | UDP Length | UDP Checksum | 606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 608 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 S / | Instance ID/Locator-Status-Bits | 610 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 611 / |Version| IHL | DSCP |ECN| Total Length | 612 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 | | Identification |Flags| Fragment Offset | 614 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 615 IH | Time to Live | Protocol | Header Checksum | 616 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 617 | | Source EID | 618 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 \ | Destination EID | 620 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 IHL = IP-Header-Length 624 5.2. LISP IPv6-in-IPv6 Header Format 626 0 1 2 3 627 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 1 628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 / |Version| DSCP |ECN| Flow Label | 630 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 631 | | Payload Length | Next Header=17| Hop Limit | 632 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 | | 634 O + + 635 u | | 636 t + Source Routing Locator + 637 e | | 638 r + + 639 | | 640 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 641 d | | 642 r + + 643 | | 644 ^ + Destination Routing Locator + 645 | | | 646 \ + + 647 \ | | 648 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 / | Source Port = xxxx | Dest Port = 4341 | 650 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 651 \ | UDP Length | UDP Checksum | 652 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 653 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 654 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 S / | Instance ID/Locator-Status-Bits | 656 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 / |Version| DSCP |ECN| Flow Label | 658 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 / | Payload Length | Next Header | Hop Limit | 660 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 661 | | 662 I + + 663 n | | 664 n + Source EID + 665 e | | 666 r + + 667 | | 668 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 669 d | | 670 r + + 671 | | 672 ^ + Destination EID + 673 \ | | 674 \ + + 675 \ | | 676 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 678 5.3. Tunnel Header Field Descriptions 680 Inner Header (IH): The inner header is the header on the 681 datagram received from the originating host [RFC0791] [RFC8200] 682 [RFC2474]. The source and destination IP addresses are EIDs. 684 Outer Header: (OH) The outer header is a new header prepended by an 685 ITR. The address fields contain RLOCs obtained from the ingress 686 router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" 687 from [RFC0768]. The setting of the Don't Fragment (DF) bit 688 'Flags' field is according to rules listed in Sections 7.1 and 689 7.2. 691 UDP Header: The UDP header contains an ITR selected source port when 692 encapsulating a packet. See Section 12 for details on the hash 693 algorithm used to select a source port based on the 5-tuple of the 694 inner header. The destination port MUST be set to the well-known 695 IANA-assigned port value 4341. 697 UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero 698 by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation 699 [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is 700 received by an ETR, the ETR MUST accept the packet for 701 decapsulation. When an ITR transmits a non-zero value for the UDP 702 checksum, it MUST send a correctly computed value in this field. 703 When an ETR receives a packet with a non-zero UDP checksum, it MAY 704 choose to verify the checksum value. If it chooses to perform 705 such verification, and the verification fails, the packet MUST be 706 silently dropped. If the ETR chooses not to perform the 707 verification, or performs the verification successfully, the 708 packet MUST be accepted for decapsulation. The handling of UDP 709 zero checksums over IPv6 for all tunneling protocols, including 710 LISP, is subject to the applicability statement in [RFC6936]. 712 UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated 713 packet to be the sum of the inner-header IPv4 Total Length plus 714 the UDP and LISP header lengths. For an IPv6-encapsulated packet, 715 the 'UDP Length' field is the sum of the inner-header IPv6 Payload 716 Length, the size of the IPv6 header (40 octets), and the size of 717 the UDP and LISP headers. 719 N: The N-bit is the nonce-present bit. When this bit is set to 1, 720 the low-order 24 bits of the first 32 bits of the LISP header 721 contain a Nonce. See Section 10.1 for details. Both N- and 722 V-bits MUST NOT be set in the same packet. If they are, a 723 decapsulating ETR MUST treat the 'Nonce/Map-Version' field as 724 having a Nonce value present. 726 L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When 727 this bit is set to 1, the Locator-Status-Bits in the second 728 32 bits of the LISP header are in use. 730 x 1 x x 0 x x x 731 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 732 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 734 | Locator-Status-Bits | 735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 737 E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored 738 and has no meaning when the N-bit is set to 0. When the N-bit is 739 set to 1 and this bit is set to 1, an ITR is requesting that the 740 nonce value in the 'Nonce' field be echoed back in LISP- 741 encapsulated packets when the ITR is also an ETR. See 742 Section 10.1 for details. 744 V: The V-bit is the Map-Version present bit. When this bit is set to 745 1, the N-bit MUST be 0. Refer to Section 13.1 for more details. 746 This bit indicates that the LISP header is encoded in this 747 case as: 749 0 x 0 1 x x x x 750 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 751 |N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version | 752 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 753 | Instance ID/Locator-Status-Bits | 754 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 756 I: The I-bit is the Instance ID bit. See Section 8 for more details. 757 When this bit is set to 1, the 'Locator-Status-Bits' field is 758 reduced to 8 bits and the high-order 24 bits are used as an 759 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 760 are transmitted as zero and ignored on receipt. The format of the 761 LISP header would look like this: 763 x x x x 1 x x x 764 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 765 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 767 | Instance ID | LSBs | 768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 770 R: The R-bit is a Reserved bit for future use. It MUST be set to 0 771 on transmit and MUST be ignored on receipt. 773 KK: The KK-bits are a 2-bit field used when encapsulated packets are 774 encrypted. The field is set to 00 when the packet is not 775 encrypted. See [RFC8061] for further information. 777 LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is 778 randomly generated by an ITR when the N-bit is set to 1. Nonce 779 generation algorithms are an implementation matter but are 780 required to generate different nonces when sending to different 781 RLOCs. However, the same nonce can be used for a period of time 782 when encapsulating to the same ETR. The nonce is also used when 783 the E-bit is set to request the nonce value to be echoed by the 784 other side when packets are returned. When the E-bit is clear but 785 the N-bit is set, a remote ITR is either echoing a previously 786 requested echo-nonce or providing a random nonce. See 787 Section 10.1 for more details. 789 LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the 790 'Locator-Status-Bits' field in the LISP header is set by an ITR to 791 indicate to an ETR the up/down status of the Locators in the 792 source site. Each RLOC in a Map-Reply is assigned an ordinal 793 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 794 The Locator-Status-Bits are numbered from 0 to n-1 from the least 795 significant bit of the field. The field is 32 bits when the I-bit 796 is set to 0 and is 8 bits when the I-bit is set to 1. When a 797 Locator-Status-Bit is set to 1, the ITR is indicating to the ETR 798 that the RLOC associated with the bit ordinal has up status. See 799 Section 10 for details on how an ITR can determine the status of 800 the ETRs at the same site. When a site has multiple EID-Prefixes 801 that result in multiple mappings (where each could have a 802 different Locator-Set), the Locator-Status-Bits setting in an 803 encapsulated packet MUST reflect the mapping for the EID-Prefix 804 that the inner-header source EID address matches. If the LSB for 805 an anycast Locator is set to 1, then there is at least one RLOC 806 with that address, and the ETR is considered 'up'. 808 When doing ITR/PITR encapsulation: 810 o The outer-header 'Time to Live' field (or 'Hop Limit' field, in 811 the case of IPv6) SHOULD be copied from the inner-header 'Time to 812 Live' field. 814 o The outer-header 'Differentiated Services Code Point' (DSCP) field 815 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 816 copied from the inner-header DSCP field ('Traffic Class' field, in 817 the case of IPv6) considering the exception listed below. 819 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 820 of the IPv6 'Traffic Class' field) requires special treatment in 821 order to avoid discarding indications of congestion [RFC3168]. 822 ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 823 header to the outer header. Re-encapsulation MUST copy the 2-bit 824 'ECN' field from the stripped outer header to the new outer 825 header. 827 When doing ETR/PETR decapsulation: 829 o The inner-header 'Time to Live' field (or 'Hop Limit' field, in 830 the case of IPv6) SHOULD be copied from the outer-header 'Time to 831 Live' field, when the Time to Live value of the outer header is 832 less than the Time to Live value of the inner header. Failing to 833 perform this check can cause the Time to Live of the inner header 834 to increment across encapsulation/decapsulation cycles. This 835 check is also performed when doing initial encapsulation, when a 836 packet comes to an ITR or PITR destined for a LISP site. 838 o The inner-header 'Differentiated Services Code Point' (DSCP) field 839 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 840 copied from the outer-header DSCP field ('Traffic Class' field, in 841 the case of IPv6) to the inner-header. 843 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 844 of the IPv6 'Traffic Class' field) requires special treatment in 845 order to avoid discarding indications of congestion [RFC3168]. If 846 the 'ECN' field contains a congestion indication codepoint (the 847 value is '11', the Congestion Experienced (CE) codepoint), then 848 ETR decapsulation MUST copy the 2-bit 'ECN' field from the 849 stripped outer header to the surviving inner header that is used 850 to forward the packet beyond the ETR. These requirements preserve 851 CE indications when a packet that uses ECN traverses a LISP tunnel 852 and becomes marked with a CE indication due to congestion between 853 the tunnel endpoints. 855 Note that if an ETR/PETR is also an ITR/PITR and chooses to re- 856 encapsulate after decapsulating, the net effect of this is that the 857 new outer header will carry the same Time to Live as the old outer 858 header minus 1. 860 Copying the Time to Live (TTL) serves two purposes: first, it 861 preserves the distance the host intended the packet to travel; 862 second, and more importantly, it provides for suppression of looping 863 packets in the event there is a loop of concatenated tunnels due to 864 misconfiguration. 866 The Explicit Congestion Notification ('ECN') field occupies bits 6 867 and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic 868 Class' field [RFC3168]. The 'ECN' field requires special treatment 869 in order to avoid discarding indications of congestion [RFC3168]. An 870 ITR/PITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 871 header to the outer header. Re-encapsulation MUST copy the 2-bit 872 'ECN' field from the stripped outer header to the new outer header. 873 If the 'ECN' field contains a congestion indication codepoint (the 874 value is '11', the Congestion Experienced (CE) codepoint), then ETR/ 875 PETR decapsulation MUST copy the 2-bit 'ECN' field from the stripped 876 outer header to the surviving inner header that is used to forward 877 the packet beyond the ETR. These requirements preserve CE 878 indications when a packet that uses ECN traverses a LISP tunnel and 879 becomes marked with a CE indication due to congestion between the 880 tunnel endpoints. 882 6. LISP EID-to-RLOC Map-Cache 884 ITRs and PITRs maintain an on-demand cache, referred as LISP EID-to- 885 RLOC Map-Cache, that contains mappings from EID-prefixes to locator 886 sets. The cache is used to encapsulate packets from the EID space to 887 the corresponding RLOC network attachment point. 889 When an ITR/PITR receives a packet from inside of the LISP site to 890 destinations outside of the site a longest-prefix match lookup of the 891 EID is done to the Map-Cache. 893 When the lookup succeeds, the Locator-Set retrieved from the Map- 894 Cache is used to send the packet to the EID's topological location. 896 If the lookup fails, the ITR/PITR needs to retrieve the mapping using 897 the LISP Control-Plane protocol [I-D.ietf-lisp-rfc6833bis]. The 898 mapping is then stored in the local Map-Cache to forward subsequent 899 packets addressed to the same EID-prefix. 901 The Map-Cache is a local cache of mappings, entries are expired based 902 on the associated Time to live. In addition, entries can be updated 903 with more current information, see Section 13 for further information 904 on this. Finally, the Map-Cache also contains reachability 905 information about EIDs and RLOCs, and uses LISP reachability 906 information mechanisms to determine the reachability of RLOCs, see 907 Section 10 for the specific mechanisms. 909 7. Dealing with Large Encapsulated Packets 911 This section proposes two mechanisms to deal with packets that exceed 912 the path MTU between the ITR and ETR. 914 It is left to the implementor to decide if the stateless or stateful 915 mechanism SHOULD be implemented. Both or neither can be used, since 916 it is a local decision in the ITR regarding how to deal with MTU 917 issues, and sites can interoperate with differing mechanisms. 919 Both stateless and stateful mechanisms also apply to Re-encapsulating 920 and Recursive Tunneling, so any actions below referring to an ITR 921 also apply to a TE-ITR. 923 7.1. A Stateless Solution to MTU Handling 925 An ITR stateless solution to handle MTU issues is described as 926 follows: 928 1. Define H to be the size, in octets, of the outer header an ITR 929 prepends to a packet. This includes the UDP and LISP header 930 lengths. 932 2. Define L to be the size, in octets, of the maximum-sized packet 933 an ITR can send to an ETR without the need for the ITR or any 934 intermediate routers to fragment the packet. 936 3. Define an architectural constant S for the maximum size of a 937 packet, in octets, an ITR MUST receive from the source so the 938 effective MTU can be met. That is, L = S + H. 940 When an ITR receives a packet from a site-facing interface and adds H 941 octets worth of encapsulation to yield a packet size greater than L 942 octets (meaning the received packet size was greater than S octets 943 from the source), it resolves the MTU issue by first splitting the 944 original packet into 2 equal-sized fragments. A LISP header is then 945 prepended to each fragment. The size of the encapsulated fragments 946 is then (S/2 + H), which is less than the ITR's estimate of the path 947 MTU between the ITR and its correspondent ETR. 949 When an ETR receives encapsulated fragments, it treats them as two 950 individually encapsulated packets. It strips the LISP headers and 951 then forwards each fragment to the destination host of the 952 destination site. The two fragments are reassembled at the 953 destination host into the single IP datagram that was originated by 954 the source host. Note that reassembly can happen at the ETR if the 955 encapsulated packet was fragmented at or after the ITR. 957 This behavior MAY be performed by the ITR only when the source host 958 originates a packet with the 'DF' field of the IP header set to 0. 959 When the 'DF' field of the IP header is set to 1, or the packet is an 960 IPv6 packet originated by the source host, the ITR will drop the 961 packet when the size is greater than L and send an ICMP Unreachable/ 962 Fragmentation-Needed message to the source with a value of S, where S 963 is (L - H). 965 When the outer-header encapsulation uses an IPv4 header, an 966 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 967 can be avoided. An implementation MAY set the DF bit in such headers 968 to 0 if it has good reason to believe there are unresolvable path MTU 969 issues between the sending ITR and the receiving ETR. 971 This specification RECOMMENDS that L be defined as 1500. 973 7.2. A Stateful Solution to MTU Handling 975 An ITR stateful solution to handle MTU issues is described as follows 976 and was first introduced in [OPENLISP]: 978 1. The ITR will keep state of the effective MTU for each Locator per 979 Map-Cache entry. The effective MTU is what the core network can 980 deliver along the path between the ITR and ETR. 982 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet 983 with the DF bit set to 1, exceeds what the core network can 984 deliver, one of the intermediate routers on the path will send an 985 ICMPv6 "Packet Too Big" message to the ITR. The ITR will parse 986 the ICMPv6 message to determine which Locator is affected by the 987 effective MTU change and then record the new effective MTU value 988 in the Map-Cache entry. 990 3. When a packet is received by the ITR from a source inside of the 991 site and the size of the packet is greater than the effective MTU 992 stored with the Map-Cache entry associated with the destination 993 EID the packet is for, the ITR will send an ICMPv6 "Packet Too 994 Big" message back to the source. The packet size advertised by 995 the ITR in the ICMPv6 message is the effective MTU minus the LISP 996 encapsulation length. 998 Even though this mechanism is stateful, it has advantages over the 999 stateless IP fragmentation mechanism, by not involving the 1000 destination host with reassembly of ITR fragmented packets. 1002 8. Using Virtualization and Segmentation with LISP 1004 There are several cases where segregation is needed at the EID level. 1005 For instance, this is the case for deployments containing overlapping 1006 addresses, traffic isolation policies or multi-tenant virtualization. 1007 For these and other scenarios where segregation is needed, Instance 1008 IDs are used. 1010 An Instance ID can be carried in a LISP-encapsulated packet. An ITR 1011 that prepends a LISP header will copy a 24-bit value used by the LISP 1012 router to uniquely identify the address space. The value is copied 1013 to the 'Instance ID' field of the LISP header, and the I-bit is set 1014 to 1. 1016 When an ETR decapsulates a packet, the Instance ID from the LISP 1017 header is used as a table identifier to locate the forwarding table 1018 to use for the inner destination EID lookup. 1020 For example, an 802.1Q VLAN tag or VPN identifier could be used as a 1021 24-bit Instance ID. See [I-D.ietf-lisp-vpn] for LISP VPN use-case 1022 details. 1024 The Instance ID that is stored in the mapping database when LISP-DDT 1025 [RFC8111] is used is 32 bits in length. That means the Control-Plane 1026 can store more instances than a given Data-Plane can use. Multiple 1027 Data-Planes can use the same 32-bit space as long as the low-order 24 1028 bits don't overlap among xTRs. 1030 9. Routing Locator Selection 1032 The Map-Cache contains the state used by ITRs and PITRs to 1033 encapsulate packets. When an ITR/PITR receives a packet from inside 1034 the LISP site to a destination outside of the site a longest-prefix 1035 match lookup of the EID is done to the Map-Cache (see Section 6). 1036 The lookup returns a single Locator-Set containing a list of RLOCs 1037 corresponding to the EID's topological location. Each RLOC in the 1038 Locator-Set is associated with a 'Priority' and 'Weight', this 1039 information is used to select the RLOC to encapsulate. 1041 The RLOC with the lowest 'Priority' is selected. An RLOC with 1042 'Priority' 255 means that MUST NOT be used for forwarding. When 1043 multiple RLOC have the same 'Priority' then the 'Weight' states how 1044 to load balance traffic among them. The value of the 'Weight' 1045 represents the relative weight of the total packets that match the 1046 maping entry. 1048 The following are different scenarios for choosing RLOCs and the 1049 controls that are available: 1051 o The server-side returns one RLOC. The client-side can only use 1052 one RLOC. The server-side has complete control of the selection. 1054 o The server-side returns a list of RLOCs where a subset of the list 1055 has the same best Priority. The client can only use the subset 1056 list according to the weighting assigned by the server-side. In 1057 this case, the server-side controls both the subset list and load- 1058 splitting across its members. The client-side can use RLOCs 1059 outside of the subset list if it determines that the subset list 1060 is unreachable (unless RLOCs are set to a Priority of 255). Some 1061 sharing of control exists: the server-side determines the 1062 destination RLOC list and load distribution while the client-side 1063 has the option of using alternatives to this list if RLOCs in the 1064 list are unreachable. 1066 o The server-side sets a Weight of zero for the RLOC subset list. 1067 In this case, the client-side can choose how the traffic load is 1068 spread across the subset list. Control is shared by the server- 1069 side determining the list and the client-side determining load 1070 distribution. Again, the client can use alternative RLOCs if the 1071 server-provided list of RLOCs is unreachable. 1073 o Either side (more likely the server-side ETR) decides not to send 1074 a Map-Request. For example, if the server-side ETR does not send 1075 Map-Requests, it gleans RLOCs from the client-side ITR, giving the 1076 client-side ITR responsibility for bidirectional RLOC reachability 1077 and preferability. Server-side ETR gleaning of the client-side 1078 ITR RLOC is done by caching the inner-header source EID and the 1079 outer-header source RLOC of received packets. The client-side ITR 1080 controls how traffic is returned and can alternate using an outer- 1081 header source RLOC, which then can be added to the list the 1082 server-side ETR uses to return traffic. Since no Priority or 1083 Weights are provided using this method, the server-side ETR MUST 1084 assume that each client-side ITR RLOC uses the same best Priority 1085 with a Weight of zero. In addition, since EID-Prefix encoding 1086 cannot be conveyed in data packets, the EID-to-RLOC Cache on 1087 Tunnel Routers can grow to be very large. 1089 Alternatively, RLOC information MAY be gleaned from received tunneled 1090 packets or EID-to-RLOC Map-Request messages. A "gleaned" Map-Cache 1091 entry, one learned from the source RLOC of a received encapsulated 1092 packet, is only stored and used for a few seconds, pending 1093 verification. Verification is performed by sending a Map-Request to 1094 the source EID (the inner-header IP source address) of the received 1095 encapsulated packet. A reply to this "verifying Map-Request" is used 1096 to fully populate the Map-Cache entry for the "gleaned" EID and is 1097 stored and used for the time indicated from the 'TTL' field of a 1098 received Map-Reply. When a verified Map-Cache entry is stored, data 1099 gleaning no longer occurs for subsequent packets that have a source 1100 EID that matches the EID-Prefix of the verified entry. This 1101 "gleaning" mechanism is OPTIONAL, refer to Section 16 for security 1102 issues regarding this mechanism. 1104 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1105 reachable when the R-bit for the Locator record is set to 1. When 1106 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1107 RLOC. Neither the information contained in a Map-Reply nor that 1108 stored in the mapping database system provides reachability 1109 information for RLOCs. Note that reachability is not part of the 1110 mapping system and is determined using one or more of the Routing 1111 Locator reachability algorithms described in the next section. 1113 10. Routing Locator Reachability 1115 Several Data-Plane mechanisms for determining RLOC reachability are 1116 currently defined. Please note that additional Control-Plane based 1117 reachability mechanisms are defined in [I-D.ietf-lisp-rfc6833bis]. 1119 1. An ETR MAY examine the Locator-Status-Bits in the LISP header of 1120 an encapsulated data packet received from an ITR. If the ETR is 1121 also acting as an ITR and has traffic to return to the original 1122 ITR site, it can use this status information to help select an 1123 RLOC. 1125 2. When an ETR receives an encapsulated packet from an ITR, the 1126 source RLOC from the outer header of the packet is likely up. 1128 3. An ITR/ETR pair can use the 'Echo-Noncing' Locator reachability 1129 algorithms described in this section. 1131 When determining Locator up/down reachability by examining the 1132 Locator-Status-Bits from the LISP-encapsulated data packet, an ETR 1133 will receive up-to-date status from an encapsulating ITR about 1134 reachability for all ETRs at the site. CE-based ITRs at the source 1135 site can determine reachability relative to each other using the site 1136 IGP as follows: 1138 o Under normal circumstances, each ITR will advertise a default 1139 route into the site IGP. 1141 o If an ITR fails or if the upstream link to its PE fails, its 1142 default route will either time out or be withdrawn. 1144 Each ITR can thus observe the presence or lack of a default route 1145 originated by the others to determine the Locator-Status-Bits it sets 1146 for them. 1148 When ITRs at the site are not deployed in CE routers, the IGP can 1149 still be used to determine the reachability of Locators, provided 1150 they are injected into the IGP. This is typically done when a /32 1151 address is configured on a loopback interface. 1153 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1154 Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 1155 to n-1 starting with the least significant bit. For example, if an 1156 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1157 value 2), then all ITRs at the site will clear the 3rd least 1158 significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for 1159 the packets they encapsulate. 1161 When an ETR decapsulates a packet, it will check for any change in 1162 the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the 1163 ETR, if acting also as an ITR, will refrain from encapsulating 1164 packets to an RLOC that is indicated as down. It will only resume 1165 using that RLOC if the corresponding Locator-Status-Bit returns to a 1166 value of 1. Locator-Status-Bits are associated with a Locator-Set 1167 per EID-Prefix. Therefore, when a Locator becomes unreachable, the 1168 Locator-Status-Bit that corresponds to that Locator's position in the 1169 list returned by the last Map-Reply will be set to zero for that 1170 particular EID-Prefix. Refer to Section 16 for security related 1171 issues regarding Locator-Status-Bits. 1173 When an ETR decapsulates a packet, it knows that it is reachable from 1174 the encapsulating ITR because that is how the packet arrived. In 1175 most cases, the ETR can also reach the ITR but cannot assume this to 1176 be true, due to the possibility of path asymmetry. In the presence 1177 of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD 1178 NOT use the lack of return traffic as an indication that the ETR is 1179 unreachable. Instead, it MUST use an alternate mechanism to 1180 determine reachability. 1182 10.1. Echo Nonce Algorithm 1184 When data flows bidirectionally between Locators from different 1185 sites, a Data-Plane mechanism called "nonce echoing" can be used to 1186 determine reachability between an ITR and ETR. When an ITR wants to 1187 solicit a nonce echo, it sets the N- and E-bits and places a 24-bit 1188 nonce [RFC4086] in the LISP header of the next encapsulated data 1189 packet. 1191 When this packet is received by the ETR, the encapsulated packet is 1192 forwarded as normal. When the ETR next sends a data packet to the 1193 ITR, it includes the nonce received earlier with the N-bit set and 1194 E-bit cleared. The ITR sees this "echoed nonce" and knows that the 1195 path to and from the ETR is up. 1197 The ITR will set the E-bit and N-bit for every packet it sends while 1198 in the echo-nonce-request state. The time the ITR waits to process 1199 the echoed nonce before it determines the path is unreachable is 1200 variable and is a choice left for the implementation. 1202 If the ITR is receiving packets from the ETR but does not see the 1203 nonce echoed while being in the echo-nonce-request state, then the 1204 path to the ETR is unreachable. This decision MAY be overridden by 1205 other Locator reachability algorithms. Once the ITR determines that 1206 the path to the ETR is down, it can switch to another Locator for 1207 that EID-Prefix. 1209 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1210 be implementing both ITR and ETR functionality for the echo nonce 1211 mechanism to operate. 1213 The ITR and ETR MAY both go into the echo-nonce-request state at the 1214 same time. The number of packets sent or the time during which echo 1215 nonce requests are sent is an implementation-specific setting. 1216 However, when an ITR is in the echo-nonce-request state, it can echo 1217 the ETR's nonce in the next set of packets that it encapsulates and 1218 subsequently continue sending echo-nonce-request packets. 1220 This mechanism does not completely solve the forward path 1221 reachability problem, as traffic may be unidirectional. That is, the 1222 ETR receiving traffic at a site MAY not be the same device as an ITR 1223 that transmits traffic from that site, or the site-to-site traffic is 1224 unidirectional so there is no ITR returning traffic. 1226 The echo-nonce algorithm is bilateral. That is, if one side sets the 1227 E-bit and the other side is not enabled for echo-noncing, then the 1228 echoing of the nonce does not occur and the requesting side may 1229 erroneously consider the Locator unreachable. An ITR SHOULD only set 1230 the E-bit in an encapsulated data packet when it knows the ETR is 1231 enabled for echo-noncing. This is conveyed by the E-bit in the RLOC- 1232 probe Map-Reply message. 1234 11. EID Reachability within a LISP Site 1236 A site MAY be multihomed using two or more ETRs. The hosts and 1237 infrastructure within a site will be addressed using one or more EID- 1238 Prefixes that are mapped to the RLOCs of the relevant ETRs in the 1239 mapping system. One possible failure mode is for an ETR to lose 1240 reachability to one or more of the EID-Prefixes within its own site. 1241 When this occurs when the ETR sends Map-Replies, it can clear the 1242 R-bit associated with its own Locator. And when the ETR is also an 1243 ITR, it can clear its Locator-Status-Bit in the encapsulation data 1244 header. 1246 It is recognized that there are no simple solutions to the site 1247 partitioning problem because it is hard to know which part of the 1248 EID-Prefix range is partitioned and which Locators can reach any sub- 1249 ranges of the EID-Prefixes. Note that this is not a new problem 1250 introduced by the LISP architecture. The problem exists today when a 1251 multihomed site uses BGP to advertise its reachability upstream. 1253 12. Routing Locator Hashing 1255 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message 1256 that is stored in the Map-Cache of a requesting ITR, the Locator-Set 1257 for the EID-Prefix MAY contain different Priority and Weight values 1258 for each locator address. When more than one best Priority Locator 1259 exists, the ITR can decide how to load-share traffic against the 1260 corresponding Locators. 1262 The following hash algorithm MAY be used by an ITR to select a 1263 Locator for a packet destined to an EID for the EID-to-RLOC mapping: 1265 1. Either a source and destination address hash or the traditional 1266 5-tuple hash can be used. The traditional 5-tuple hash includes 1267 the source and destination addresses; source and destination TCP, 1268 UDP, or Stream Control Transmission Protocol (SCTP) port numbers; 1269 and the IP protocol number field or IPv6 next-protocol fields of 1270 a packet that a host originates from within a LISP site. When a 1271 packet is not a TCP, UDP, or SCTP packet, the source and 1272 destination addresses only from the header are used to compute 1273 the hash. 1275 2. Take the hash value and divide it by the number of Locators 1276 stored in the Locator-Set for the EID-to-RLOC mapping. 1278 3. The remainder will yield a value of 0 to "number of Locators 1279 minus 1". Use the remainder to select the Locator in the 1280 Locator-Set. 1282 Note that when a packet is LISP encapsulated, the source port number 1283 in the outer UDP header needs to be set. Selecting a hashed value 1284 allows core routers that are attached to Link Aggregation Groups 1285 (LAGs) to load-split the encapsulated packets across member links of 1286 such LAGs. Otherwise, core routers would see a single flow, since 1287 packets have a source address of the ITR, for packets that are 1288 originated by different EIDs at the source site. A suggested setting 1289 for the source port number computed by an ITR is a 5-tuple hash 1290 function on the inner header, as described above. The source port 1291 SHOULD be the same for all packets belonging to the same flow. 1293 Many core router implementations use a 5-tuple hash to decide how to 1294 balance packet load across members of a LAG. The 5-tuple hash 1295 includes the source and destination addresses of the packet and the 1296 source and destination ports when the protocol number in the packet 1297 is TCP or UDP. For this reason, UDP encoding is used for LISP 1298 encapsulation. 1300 13. Changing the Contents of EID-to-RLOC Mappings 1302 Since the LISP architecture uses a caching scheme to retrieve and 1303 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 1304 date mapping is to re-request the mapping. However, the ITRs do not 1305 know when the mappings change, and the ETRs do not keep track of 1306 which ITRs requested its mappings. For scalability reasons, it is 1307 desirable to maintain this approach but need to provide a way for 1308 ETRs to change their mappings and inform the sites that are currently 1309 communicating with the ETR site using such mappings. 1311 This section defines a Data-Plane mechanism for updating EID-to-RLOC 1312 mappings. Additionally, the Solicit-Map Request (SMR) Control-Plane 1313 updating mechanism is specified in [I-D.ietf-lisp-rfc6833bis]. 1315 When adding a new Locator record in lexicographic order to the end of 1316 a Locator-Set, it is easy to update mappings. We assume that new 1317 mappings will maintain the same Locator ordering as the old mapping 1318 but will just have new Locators appended to the end of the list. So, 1319 some ITRs can have a new mapping while other ITRs have only an old 1320 mapping that is used until they time out. When an ITR has only an 1321 old mapping but detects bits set in the Locator-Status-Bits that 1322 correspond to Locators beyond the list it has cached, it simply 1323 ignores them. However, this can only happen for locator addresses 1324 that are lexicographically greater than the locator addresses in the 1325 existing Locator-Set. 1327 When a Locator record is inserted in the middle of a Locator-Set, to 1328 maintain lexicographic order, SMR procedure 1329 [I-D.ietf-lisp-rfc6833bis] is used to inform ITRs and PITRs of the 1330 new Locator-Status-Bit mappings. 1332 When a Locator record is removed from a Locator-Set, ITRs that have 1333 the mapping cached will not use the removed Locator because the xTRs 1334 will set the Locator-Status-Bit to 0. So, even if the Locator is in 1335 the list, it will not be used. For new mapping requests, the xTRs 1336 can set the Locator AFI to 0 (indicating an unspecified address), as 1337 well as setting the corresponding Locator-Status-Bit to 0. This 1338 forces ITRs with old or new mappings to avoid using the removed 1339 Locator. 1341 If many changes occur to a mapping over a long period of time, one 1342 will find empty record slots in the middle of the Locator-Set and new 1343 records appended to the Locator-Set. At some point, it would be 1344 useful to compact the Locator-Set so the Locator-Status-Bit settings 1345 can be efficiently packed. 1347 We propose here a Data-Plane mechanism (Map-Versioning specified in 1348 [I-D.ietf-lisp-6834bis]) to update the contents of EID-to-RLOC 1349 mappings. Please note that in addition the Solicit-Map Request 1350 (specified in [I-D.ietf-lisp-rfc6833bis]) is a Control-Plane 1351 mechanisms that can be used to update EID-to-RLOC mappings. 1353 13.1. Database Map-Versioning 1355 When there is unidirectional packet flow between an ITR and ETR, and 1356 the EID-to-RLOC mappings change on the ETR, it needs to inform the 1357 ITR so encapsulation to a removed Locator can stop and can instead be 1358 started to a new Locator in the Locator-Set. 1360 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 1361 Number. This is known as the Destination Map-Version Number. ITRs 1362 include the Destination Map-Version Number in packets they 1363 encapsulate to the site. When an ETR decapsulates a packet and 1364 detects that the Destination Map-Version Number is less than the 1365 current version for its mapping, the SMR procedure described in 1366 [I-D.ietf-lisp-rfc6833bis] occurs. 1368 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 1369 Version Number. This is known as the Source Map-Version Number. 1370 When an ETR decapsulates a packet and detects that the Source Map- 1371 Version Number is greater than the last Map-Version Number sent in a 1372 Map-Reply from the ITR's site, the ETR will send a Map-Request to one 1373 of the ETRs for the source site. 1375 A Map-Version Number is used as a sequence number per EID-Prefix, so 1376 values that are greater are considered to be more recent. A value of 1377 0 for the Source Map-Version Number or the Destination Map-Version 1378 Number conveys no versioning information, and an ITR does no 1379 comparison with previously received Map-Version Numbers. 1381 A Map-Version Number can be included in Map-Register messages as 1382 well. This is a good way for the Map-Server to assure that all ETRs 1383 for a site registering to it will be synchronized according to Map- 1384 Version Number. 1386 See [I-D.ietf-lisp-6834bis] for a more detailed analysis and 1387 description of Database Map-Versioning. 1389 14. Multicast Considerations 1391 A multicast group address, as defined in the original Internet 1392 architecture, is an identifier of a grouping of topologically 1393 independent receiver host locations. The address encoding itself 1394 does not determine the location of the receiver(s). The multicast 1395 routing protocol, and the network-based state the protocol creates, 1396 determine where the receivers are located. 1398 In the context of LISP, a multicast group address is both an EID and 1399 a Routing Locator. Therefore, no specific semantic or action needs 1400 to be taken for a destination address, as it would appear in an IP 1401 header. Therefore, a group address that appears in an inner IP 1402 header built by a source host will be used as the destination EID. 1403 The outer IP header (the destination Routing Locator address), 1404 prepended by a LISP router, can use the same group address as the 1405 destination Routing Locator, use a multicast or unicast Routing 1406 Locator obtained from a Mapping System lookup, or use other means to 1407 determine the group address mapping. 1409 With respect to the source Routing Locator address, the ITR prepends 1410 its own IP address as the source address of the outer IP header. 1411 Just like it would if the destination EID was a unicast address. 1412 This source Routing Locator address, like any other Routing Locator 1413 address, MUST be globally routable. 1415 There are two approaches for LISP-Multicast, one that uses native 1416 multicast routing in the underlay with no support from the Mapping 1417 System and the other that uses only unicast routing in the underlay 1418 with support from the Mapping System. See [RFC6831] and [RFC8378], 1419 respectively, for details. Details for LISP-Multicast and 1420 interworking with non-LISP sites are described in [RFC6831] and 1421 [RFC6832]. 1423 15. Router Performance Considerations 1425 LISP is designed to be very "hardware-based forwarding friendly". A 1426 few implementation techniques can be used to incrementally implement 1427 LISP: 1429 o When a tunnel-encapsulated packet is received by an ETR, the outer 1430 destination address may not be the address of the router. This 1431 makes it challenging for the control plane to get packets from the 1432 hardware. This may be mitigated by creating special Forwarding 1433 Information Base (FIB) entries for the EID-Prefixes of EIDs served 1434 by the ETR (those for which the router provides an RLOC 1435 translation). These FIB entries are marked with a flag indicating 1436 that Control-Plane processing SHOULD be performed. The forwarding 1437 logic of testing for particular IP protocol number values is not 1438 necessary. There are a few proven cases where no changes to 1439 existing deployed hardware were needed to support the LISP Data- 1440 Plane. 1442 o On an ITR, prepending a new IP header consists of adding more 1443 octets to a MAC rewrite string and prepending the string as part 1444 of the outgoing encapsulation procedure. Routers that support 1445 Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 1446 tunneling [RFC3056] may already support this action. 1448 o A packet's source address or interface the packet was received on 1449 can be used to select VRF (Virtual Routing/Forwarding). The VRF's 1450 routing table can be used to find EID-to-RLOC mappings. 1452 For performance issues related to Map-Cache management, see 1453 Section 16. 1455 16. Security Considerations 1457 Security considerations for LISP are discussed in [RFC7833]. 1459 A complete LISP threat analysis can be found in [RFC7835], in what 1460 follows we provide a summary. 1462 The optional mechanisms of gleaning is offered to directly obtain a 1463 mapping from the LISP encapsulated packets. Specifically, an xTR can 1464 learn the EID-to-RLOC mapping by inspecting the source RLOC and 1465 source EID of an encapsulated packet, and insert this new mapping 1466 into its Map-Cache. An off-path attacker can spoof the source EID 1467 address to divert the traffic sent to the victim's spoofed EID. If 1468 the attacker spoofs the source RLOC, it can mount a DoS attack by 1469 redirecting traffic to the spoofed victim's RLOC, potentially 1470 overloading it. 1472 The LISP Data-Plane defines several mechanisms to monitor RLOC Data- 1473 Plane reachability, in this context Locator-Status Bits, Nonce- 1474 Present and Echo-Nonce bits of the LISP encapsulation header can be 1475 manipulated by an attacker to mount a DoS attack. An off-path 1476 attacker able to spoof the RLOC of a victim's xTR can manipulate such 1477 mechanisms to declare a set of RLOCs unreachable. This can be used 1478 also, for instance, to declare only one RLOC reachable with the aim 1479 of overload it. 1481 Map-Versioning is a Data-Plane mechanism used to signal a peering xTR 1482 that a local EID-to-RLOC mapping has been updated, so that the 1483 peering xTR uses LISP Control-Plane signaling message to retrieve a 1484 fresh mapping. This can be used by an attacker to forge the map- 1485 versioning field of a LISP encapsulated header and force an excessive 1486 amount of signaling between xTRs that may overload them. 1488 Most of the attack vectors can be mitigated with careful deployment 1489 and configuration, information learned opportunistically (such as LSB 1490 or gleaning) SHOULD be verified with other reachability mechanisms. 1491 In addition, systematic rate-limitation and filtering is an effective 1492 technique to mitigate attacks that aim to overload the Control-Plane. 1494 17. Network Management Considerations 1496 Considerations for network management tools exist so the LISP 1497 protocol suite can be operationally managed. These mechanisms can be 1498 found in [RFC7052] and [RFC6835]. 1500 18. Changes since RFC 6830 1502 For implementation considerations, the following changes have been 1503 made to this document since RFC 6830 was published: 1505 o It is no longer mandated that a maximum number of 2 LISP headers 1506 be prepended to a packet. If there is a application need for more 1507 than 2 LISP headers, an implementation can support more. However, 1508 it is RECOMMENDED that a maximum of two LISP headers can be 1509 prepended to a packet. 1511 o The 3 reserved flag bits in the LISP header have been allocated 1512 for [RFC8061]. The low-order 2 bits of the 3-bit field (now named 1513 the KK bits) are used as a key identifier. The 1 remaining bit is 1514 still documented as reserved. 1516 o Data-Plane gleaning for creating map-cache entries has been made 1517 optional. If any ITR implementations depend or assume the remote 1518 ETR is gleaning should not do so. This does not create any 1519 interoperability problems since the control-plane map-cache 1520 population procedures are unilateral and are the typical method 1521 for map-cache population. 1523 o The bulk of the changes to this document which reduces its length 1524 are due to moving the LISP control-plane messaging and procedures 1525 to [I-D.ietf-lisp-rfc6833bis]. 1527 19. IANA Considerations 1529 This section provides guidance to the Internet Assigned Numbers 1530 Authority (IANA) regarding registration of values related to this 1531 Data-Plane LISP specification, in accordance with BCP 26 [RFC8126]. 1533 19.1. LISP UDP Port Numbers 1535 The IANA registry has allocated UDP port number 4341 for the LISP 1536 Data-Plane. IANA has updated the description for UDP port 4341 as 1537 follows: 1539 lisp-data 4341 udp LISP Data Packets 1541 20. References 1543 20.1. Normative References 1545 [I-D.ietf-lisp-6834bis] 1546 Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1547 Separation Protocol (LISP) Map-Versioning", draft-ietf- 1548 lisp-6834bis-02 (work in progress), September 2018. 1550 [I-D.ietf-lisp-rfc6833bis] 1551 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1552 "Locator/ID Separation Protocol (LISP) Control-Plane", 1553 draft-ietf-lisp-rfc6833bis-13 (work in progress), August 1554 2018. 1556 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1557 DOI 10.17487/RFC0768, August 1980, 1558 . 1560 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1561 DOI 10.17487/RFC0791, September 1981, 1562 . 1564 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1565 Requirement Levels", BCP 14, RFC 2119, 1566 DOI 10.17487/RFC2119, March 1997, 1567 . 1569 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1570 "Definition of the Differentiated Services Field (DS 1571 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1572 DOI 10.17487/RFC2474, December 1998, 1573 . 1575 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1576 of Explicit Congestion Notification (ECN) to IP", 1577 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1578 . 1580 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1581 Writing an IANA Considerations Section in RFCs", BCP 26, 1582 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1583 . 1585 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1586 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1587 May 2017, . 1589 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1590 (IPv6) Specification", STD 86, RFC 8200, 1591 DOI 10.17487/RFC8200, July 2017, 1592 . 1594 20.2. Informative References 1596 [AFN] IANA, "Address Family Numbers", August 2016, 1597 . 1599 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed", 1600 1999, 1601 . 1603 [I-D.ietf-lisp-introduction] 1604 Cabellos-Aparicio, A. and D. Saucez, "An Architectural 1605 Introduction to the Locator/ID Separation Protocol 1606 (LISP)", draft-ietf-lisp-introduction-13 (work in 1607 progress), April 2015. 1609 [I-D.ietf-lisp-vpn] 1610 Moreno, V. and D. Farinacci, "LISP Virtual Private 1611 Networks (VPNs)", draft-ietf-lisp-vpn-02 (work in 1612 progress), May 2018. 1614 [OPENLISP] 1615 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 1616 Implementation Report", Work in Progress, July 2008. 1618 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1619 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1620 . 1622 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1623 and E. Lear, "Address Allocation for Private Internets", 1624 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1625 . 1627 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1628 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1629 DOI 10.17487/RFC2784, March 2000, 1630 . 1632 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 1633 via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 1634 2001, . 1636 [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced 1637 by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, 1638 January 2002, . 1640 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1641 A., Peterson, J., Sparks, R., Handley, M., and E. 1642 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1643 DOI 10.17487/RFC3261, June 2002, 1644 . 1646 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1647 "Randomness Requirements for Security", BCP 106, RFC 4086, 1648 DOI 10.17487/RFC4086, June 2005, 1649 . 1651 [RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report 1652 from the IAB Workshop on Routing and Addressing", 1653 RFC 4984, DOI 10.17487/RFC4984, September 2007, 1654 . 1656 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1657 Locator/ID Separation Protocol (LISP) for Multicast 1658 Environments", RFC 6831, DOI 10.17487/RFC6831, January 1659 2013, . 1661 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1662 "Interworking between Locator/ID Separation Protocol 1663 (LISP) and Non-LISP Sites", RFC 6832, 1664 DOI 10.17487/RFC6832, January 2013, 1665 . 1667 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1668 Protocol Internet Groper (LIG)", RFC 6835, 1669 DOI 10.17487/RFC6835, January 2013, 1670 . 1672 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1673 UDP Checksums for Tunneled Packets", RFC 6935, 1674 DOI 10.17487/RFC6935, April 2013, 1675 . 1677 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1678 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1679 RFC 6936, DOI 10.17487/RFC6936, April 2013, 1680 . 1682 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1683 Separation Protocol (LISP) MIB", RFC 7052, 1684 DOI 10.17487/RFC7052, October 2013, 1685 . 1687 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1688 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1689 Protocol (LISP) Network Element Deployment 1690 Considerations", RFC 7215, DOI 10.17487/RFC7215, April 1691 2014, . 1693 [RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A 1694 RADIUS Attribute, Binding, Profiles, Name Identifier 1695 Format, and Confirmation Methods for the Security 1696 Assertion Markup Language (SAML)", RFC 7833, 1697 DOI 10.17487/RFC7833, May 2016, 1698 . 1700 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 1701 Separation Protocol (LISP) Threat Analysis", RFC 7835, 1702 DOI 10.17487/RFC7835, April 2016, 1703 . 1705 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1706 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 1707 February 2017, . 1709 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 1710 (LISP) Data-Plane Confidentiality", RFC 8061, 1711 DOI 10.17487/RFC8061, February 2017, 1712 . 1714 [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage 1715 Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, 1716 March 2017, . 1718 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 1719 Smirnov, "Locator/ID Separation Protocol Delegated 1720 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 1721 May 2017, . 1723 [RFC8378] Moreno, V. and D. Farinacci, "Signal-Free Locator/ID 1724 Separation Protocol (LISP) Multicast", RFC 8378, 1725 DOI 10.17487/RFC8378, May 2018, 1726 . 1728 Appendix A. Acknowledgments 1730 An initial thank you goes to Dave Oran for planting the seeds for the 1731 initial ideas for LISP. His consultation continues to provide value 1732 to the LISP authors. 1734 A special and appreciative thank you goes to Noel Chiappa for 1735 providing architectural impetus over the past decades on separation 1736 of location and identity, as well as detailed reviews of the LISP 1737 architecture and documents, coupled with enthusiasm for making LISP a 1738 practical and incremental transition for the Internet. 1740 The authors would like to gratefully acknowledge many people who have 1741 contributed discussions and ideas to the making of this proposal. 1742 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 1743 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 1744 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 1745 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 1746 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 1747 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 1748 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 1749 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 1750 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 1751 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 1752 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 1753 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 1754 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 1755 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 1756 Ermagan, Fabio Maino, Victor Moreno, Chris White, Clarence Filsfils, 1757 Alia Atlas, Florin Coras and Alberto Rodriguez. 1759 This work originated in the Routing Research Group (RRG) of the IRTF. 1760 An individual submission was converted into the IETF LISP working 1761 group document that became this RFC. 1763 The LISP working group would like to give a special thanks to Jari 1764 Arkko, the Internet Area AD at the time that the set of LISP 1765 documents were being prepared for IESG last call, and for his 1766 meticulous reviews and detailed commentaries on the 7 working group 1767 last call documents progressing toward standards-track RFCs. 1769 Appendix B. Document Change Log 1771 [RFC Editor: Please delete this section on publication as RFC.] 1773 B.1. Changes to draft-ietf-lisp-rfc6830bis-17 1775 o Posted September 2018. 1777 o Indicate in the "Changes since RFC 6830" section why the document 1778 has been shortened in length. 1780 o Make reference to RFC 8085 about UDP congestion control. 1782 o More editorial changes from multiple IESG reviews. 1784 B.2. Changes to draft-ietf-lisp-rfc6830bis-16 1786 o Posted late August 2018. 1788 o Distinguish the message type names between ICMP for IPv4 and ICMP 1789 for IPv6 for handling MTU issues. 1791 B.3. Changes to draft-ietf-lisp-rfc6830bis-15 1793 o Posted August 2018. 1795 o Final editorial changes before RFC submission for Proposed 1796 Standard. 1798 o Added section "Changes since RFC 6830" so implementators are 1799 informed of any changes since the last RFC publication. 1801 B.4. Changes to draft-ietf-lisp-rfc6830bis-14 1803 o Posted July 2018 IETF week. 1805 o Put obsolete of RFC 6830 in Intro section in addition to abstract. 1807 B.5. Changes to draft-ietf-lisp-rfc6830bis-13 1809 o Posted March IETF Week 2018. 1811 o Clarified that a new nonce is required per RLOC. 1813 o Removed 'Clock Sweep' section. This text must be placed in a new 1814 OAM document. 1816 o Some references changed from normative to informative 1818 B.6. Changes to draft-ietf-lisp-rfc6830bis-12 1820 o Posted July 2018. 1822 o Fixed Luigi editorial comments to ready draft for RFC status. 1824 B.7. Changes to draft-ietf-lisp-rfc6830bis-11 1826 o Posted March 2018. 1828 o Removed sections 16, 17 and 18 (Mobility, Deployment and 1829 Traceroute considerations). This text must be placed in a new OAM 1830 document. 1832 B.8. Changes to draft-ietf-lisp-rfc6830bis-10 1834 o Posted March 2018. 1836 o Updated section 'Router Locator Selection' stating that the Data- 1837 Plane MUST follow what's stored in the Map-Cache (priorities and 1838 weights). 1840 o Section 'Routing Locator Reachability': Removed bullet point 2 1841 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP Port 1842 Unreachable),5 (receive a Map-Reply as a response) and RLOC 1843 probing 1845 o Removed 'Solicit-Map Request'. 1847 B.9. Changes to draft-ietf-lisp-rfc6830bis-09 1849 o Posted January 2018. 1851 o Add more details in section 5.3 about DSCP processing during 1852 encapsulation and decapsulation. 1854 o Added clarity to definitions in the Definition of Terms section 1855 from various commenters. 1857 o Removed PA and PI definitions from Definition of Terms section. 1859 o More editorial changes. 1861 o Removed 4342 from IANA section and move to RFC6833 IANA section. 1863 B.10. Changes to draft-ietf-lisp-rfc6830bis-08 1865 o Posted January 2018. 1867 o Remove references to research work for any protocol mechanisms. 1869 o Document scanned to make sure it is RFC 2119 compliant. 1871 o Made changes to reflect comments from document WG shepherd Luigi 1872 Iannone. 1874 o Ran IDNITs on the document. 1876 B.11. Changes to draft-ietf-lisp-rfc6830bis-07 1878 o Posted November 2017. 1880 o Rephrase how Instance-IDs are used and don't refer to [RFC1918] 1881 addresses. 1883 B.12. Changes to draft-ietf-lisp-rfc6830bis-06 1885 o Posted October 2017. 1887 o Put RTR definition before it is used. 1889 o Rename references that are now working group drafts. 1891 o Remove "EIDs MUST NOT be used as used by a host to refer to other 1892 hosts. Note that EID blocks MAY LISP RLOCs". 1894 o Indicate what address-family can appear in data packets. 1896 o ETRs may, rather than will, be the ones to send Map-Replies. 1898 o Recommend, rather than mandate, max encapsulation headers to 2. 1900 o Reference VPN draft when introducing Instance-ID. 1902 o Indicate that SMRs can be sent when ITR/ETR are in the same node. 1904 o Clarify when private addreses can be used. 1906 B.13. Changes to draft-ietf-lisp-rfc6830bis-05 1908 o Posted August 2017. 1910 o Make it clear that a Reencapsulating Tunnel Router is an RTR. 1912 B.14. Changes to draft-ietf-lisp-rfc6830bis-04 1914 o Posted July 2017. 1916 o Changed reference of IPv6 RFC2460 to RFC8200. 1918 o Indicate that the applicability statement for UDP zero checksums 1919 over IPv6 adheres to RFC6936. 1921 B.15. Changes to draft-ietf-lisp-rfc6830bis-03 1923 o Posted May 2017. 1925 o Move the control-plane related codepoints in the IANA 1926 Considerations section to RFC6833bis. 1928 B.16. Changes to draft-ietf-lisp-rfc6830bis-02 1930 o Posted April 2017. 1932 o Reflect some editorial comments from Damien Sausez. 1934 B.17. Changes to draft-ietf-lisp-rfc6830bis-01 1936 o Posted March 2017. 1938 o Include references to new RFCs published. 1940 o Change references from RFC6833 to RFC6833bis. 1942 o Clarified LCAF text in the IANA section. 1944 o Remove references to "experimental". 1946 B.18. Changes to draft-ietf-lisp-rfc6830bis-00 1948 o Posted December 2016. 1950 o Created working group document from draft-farinacci-lisp 1951 -rfc6830-00 individual submission. No other changes made. 1953 Authors' Addresses 1954 Dino Farinacci 1955 Cisco Systems 1956 Tasman Drive 1957 San Jose, CA 95134 1958 USA 1960 EMail: farinacci@gmail.com 1962 Vince Fuller 1963 Cisco Systems 1964 Tasman Drive 1965 San Jose, CA 95134 1966 USA 1968 EMail: vince.fuller@gmail.com 1970 Dave Meyer 1971 Cisco Systems 1972 170 Tasman Drive 1973 San Jose, CA 1974 USA 1976 EMail: dmm@1-4-5.net 1978 Darrel Lewis 1979 Cisco Systems 1980 170 Tasman Drive 1981 San Jose, CA 1982 USA 1984 EMail: darlewis@cisco.com 1986 Albert Cabellos 1987 UPC/BarcelonaTech 1988 Campus Nord, C. Jordi Girona 1-3 1989 Barcelona, Catalunya 1990 Spain 1992 EMail: acabello@ac.upc.edu