idnits 2.17.1 draft-ietf-lisp-rfc6830bis-19.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 22, 2018) is 2043 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in RFCs) == Unused Reference: 'RFC7833' is defined on line 1703, but no explicit reference was found in the text == Outdated reference: A later version (-14) exists of draft-ietf-lisp-6834bis-02 == Outdated reference: A later version (-31) exists of draft-ietf-lisp-rfc6833bis-15 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-introduction-13 == Outdated reference: A later version (-12) exists of draft-ietf-lisp-vpn-02 Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--).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 26, 2019 Cisco Systems 7 A. Cabellos (Ed.) 8 UPC/BarcelonaTech 9 September 22, 2018 11 The Locator/ID Separation Protocol (LISP) 12 draft-ietf-lisp-rfc6830bis-19 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 26, 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 . . . . . . . . . . . . . . . . . . 31 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 . . . . . . . . . . . . . . . . . 34 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-19 . . . . . . . . 40 99 B.2. Changes to draft-ietf-lisp-rfc6830bis-18 . . . . . . . . 40 100 B.3. Changes to draft-ietf-lisp-rfc6830bis-17 . . . . . . . . 40 101 B.4. Changes to draft-ietf-lisp-rfc6830bis-16 . . . . . . . . 40 102 B.5. Changes to draft-ietf-lisp-rfc6830bis-15 . . . . . . . . 40 103 B.6. Changes to draft-ietf-lisp-rfc6830bis-14 . . . . . . . . 40 104 B.7. Changes to draft-ietf-lisp-rfc6830bis-13 . . . . . . . . 41 105 B.8. Changes to draft-ietf-lisp-rfc6830bis-12 . . . . . . . . 41 106 B.9. Changes to draft-ietf-lisp-rfc6830bis-11 . . . . . . . . 41 107 B.10. Changes to draft-ietf-lisp-rfc6830bis-10 . . . . . . . . 41 108 B.11. Changes to draft-ietf-lisp-rfc6830bis-09 . . . . . . . . 41 109 B.12. Changes to draft-ietf-lisp-rfc6830bis-08 . . . . . . . . 42 110 B.13. Changes to draft-ietf-lisp-rfc6830bis-07 . . . . . . . . 42 111 B.14. Changes to draft-ietf-lisp-rfc6830bis-06 . . . . . . . . 42 112 B.15. Changes to draft-ietf-lisp-rfc6830bis-05 . . . . . . . . 43 113 B.16. Changes to draft-ietf-lisp-rfc6830bis-04 . . . . . . . . 43 114 B.17. Changes to draft-ietf-lisp-rfc6830bis-03 . . . . . . . . 43 115 B.18. Changes to draft-ietf-lisp-rfc6830bis-02 . . . . . . . . 43 116 B.19. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 43 117 B.20. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 44 118 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44 120 1. Introduction 122 This document describes the Locator/Identifier Separation Protocol 123 (LISP). LISP is an encapsulation protocol built around the 124 fundamental idea of separating the topological location of a network 125 attachment point from the node's identity [CHIAPPA]. As a result 126 LISP creates two namespaces: Endpoint Identifiers (EIDs), that are 127 used to identify end-hosts (e.g., nodes or Virtual Machines) and 128 routable Routing Locators (RLOCs), used to identify network 129 attachment points. LISP then defines functions for mapping between 130 the two namespaces and for encapsulating traffic originated by 131 devices using non-routable EIDs for transport across a network 132 infrastructure that routes and forwards using RLOCs. LISP 133 encapsulation uses a dynamic form of tunneling where no static 134 provisioning is required or necessary. 136 LISP is an overlay protocol that separates control from Data-Plane, 137 this document specifies the Data-Plane, how LISP-capable routers 138 (Tunnel Routers) exchange packets by encapsulating them to the 139 appropriate location. Tunnel routers are equipped with a cache, 140 called Map-Cache, that contains EID-to-RLOC mappings. The Map-Cache 141 is populated using the LISP Control-Plane protocol 142 [I-D.ietf-lisp-rfc6833bis]. 144 LISP does not require changes to either host protocol stack or to 145 underlay routers. By separating the EID from the RLOC space, LISP 146 offers native Traffic Engineering, multihoming and mobility, among 147 other features. 149 Creation of LISP was initially motivated by discussions during the 150 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 151 October 2006 (see [RFC4984]). 153 This document specifies the LISP Data-Plane encapsulation and other 154 LISP forwarding node functionality while [I-D.ietf-lisp-rfc6833bis] 155 specifies the LISP control plane. LISP deployment guidelines can be 156 found in [RFC7215] and [RFC6835] describes considerations for network 157 operational management. Finally, [I-D.ietf-lisp-introduction] 158 describes the LISP architecture. 160 This document obsoletes RFC 6830. 162 2. Requirements Notation 164 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 165 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 166 document are to be interpreted as described in [RFC2119] and 167 [RFC8174]. 169 3. Definition of Terms 171 Address Family Identifier (AFI): AFI is a term used to describe an 172 address encoding in a packet. An address family that pertains to 173 the Data-Plane. See [AFN] and [RFC3232] for details. An AFI 174 value of 0 used in this specification indicates an unspecified 175 encoded address where the length of the address is 0 octets 176 following the 16-bit AFI value of 0. 178 Anycast Address: Anycast Address is a term used in this document to 179 refer to the same IPv4 or IPv6 address configured and used on 180 multiple systems at the same time. An EID or RLOC can be an 181 anycast address in each of their own address spaces. 183 Client-side: Client-side is a term used in this document to indicate 184 a connection initiation attempt by an end-system represented by an 185 EID. 187 Data-Probe: A Data-Probe is a LISP-encapsulated data packet where 188 the inner-header destination address equals the outer-header 189 destination address used to trigger a Map-Reply by a decapsulating 190 ETR. In addition, the original packet is decapsulated and 191 delivered to the destination host if the destination EID is in the 192 EID-Prefix range configured on the ETR. Otherwise, the packet is 193 discarded. A Data-Probe is used in some of the mapping database 194 designs to "probe" or request a Map-Reply from an ETR; in other 195 cases, Map-Requests are used. See each mapping database design 196 for details. When using Data-Probes, by sending Map-Requests on 197 the underlying routing system, EID-Prefixes must be advertised. 199 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 200 packet where the destination address in the "outer" IP header is 201 one of its own RLOCs. The router strips the "outer" header and 202 forwards the packet based on the next IP header found. In 203 general, an ETR receives LISP-encapsulated IP packets from the 204 Internet on one side and sends decapsulated IP packets to site 205 end-systems on the other side. ETR functionality does not have to 206 be limited to a router device. A server host can be the endpoint 207 of a LISP tunnel as well. 209 EID-to-RLOC Database: The EID-to-RLOC Database is a global 210 distributed database that contains all known EID-Prefix-to-RLOC 211 mappings. Each potential ETR typically contains a small piece of 212 the database: the EID-to-RLOC mappings for the EID-Prefixes 213 "behind" the router. These map to one of the router's own 214 globally visible IP addresses. Note that there MAY be transient 215 conditions when the EID-Prefix for the site and Locator-Set for 216 each EID-Prefix may not be the same on all ETRs. This has no 217 negative implications, since a partial set of Locators can be 218 used. 220 EID-to-RLOC Map-Cache: The EID-to-RLOC Map-Cache is generally 221 short-lived, on-demand table in an ITR that stores, tracks, and is 222 responsible for timing out and otherwise validating EID-to-RLOC 223 mappings. This cache is distinct from the full "database" of EID- 224 to-RLOC mappings; it is dynamic, local to the ITR(s), and 225 relatively small, while the database is distributed, relatively 226 static, and much more global in scope. 228 EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are 229 allocated to a site by an address allocation authority. EID- 230 Prefixes are associated with a set of RLOC addresses. EID-Prefix 231 allocations can be broken up into smaller blocks when an RLOC set 232 is to be associated with the larger EID-Prefix block. 234 End-System: An end-system is an IPv4 or IPv6 device that originates 235 packets with a single IPv4 or IPv6 header. The end-system 236 supplies an EID value for the destination address field of the IP 237 header when communicating globally (i.e., outside of its routing 238 domain). An end-system can be a host computer, a switch or router 239 device, or any network appliance. 241 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 242 IPv6) value used in the source and destination address fields of 243 the first (most inner) LISP header of a packet. The host obtains 244 a destination EID the same way it obtains a destination address 245 today, for example, through a Domain Name System (DNS) [RFC1034] 246 lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. 247 The source EID is obtained via existing mechanisms used to set a 248 host's "local" IP address. An EID used on the public Internet 249 MUST have the same properties as any other IP address used in that 250 manner; this means, among other things, that it MUST be globally 251 unique. An EID is allocated to a host from an EID-Prefix block 252 associated with the site where the host is located. An EID can be 253 used by a host to refer to other hosts. Note that EID blocks MAY 254 be assigned in a hierarchical manner, independent of the network 255 topology, to facilitate scaling of the mapping database. In 256 addition, an EID block assigned to a site MAY have site-local 257 structure (subnetting) for routing within the site; this structure 258 is not visible to the global routing system. In theory, the bit 259 string that represents an EID for one device can represent an RLOC 260 for a different device. When used in discussions with other 261 Locator/ID separation proposals, a LISP EID will be called an 262 "LEID". Throughout this document, any references to "EID" refer 263 to an LEID. 265 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 266 LISP site. Packets sent by sources inside of the LISP site to 267 destinations outside of the site are candidates for encapsulation 268 by the ITR. The ITR treats the IP destination address as an EID 269 and performs an EID-to-RLOC mapping lookup. The router then 270 prepends an "outer" IP header with one of its routable RLOCs (in 271 the RLOC space) in the source address field and the result of the 272 mapping lookup in the destination address field. Note that this 273 destination RLOC MAY be an intermediate, proxy device that has 274 better knowledge of the EID-to-RLOC mapping closer to the 275 destination EID. In general, an ITR receives IP packets from site 276 end-systems on one side and sends LISP-encapsulated IP packets 277 toward the Internet on the other side. 279 Specifically, when a service provider prepends a LISP header for 280 Traffic Engineering purposes, the router that does this is also 281 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 282 on the outer destination address (the originating ITR's supplied 283 RLOC) or the inner destination address (the originating host's 284 supplied EID). 286 LISP Header: LISP header is a term used in this document to refer 287 to the outer IPv4 or IPv6 header, a UDP header, and a LISP- 288 specific 8-octet header that follow the UDP header and that an ITR 289 prepends or an ETR strips. 291 LISP Router: A LISP router is a router that performs the functions 292 of any or all of the following: ITR, ETR, RTR, Proxy-ITR (PITR), 293 or Proxy-ETR (PETR). 295 LISP Site: LISP site is a set of routers in an edge network that are 296 under a single technical administration. LISP routers that reside 297 in the edge network are the demarcation points to separate the 298 edge network from the core network. 300 Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the 301 LISP header. They are used by ITRs to inform ETRs about the up/ 302 down status of all ETRs at the local site. These bits are used as 303 a hint to convey up/down router status and not path reachability 304 status. The LSBs can be verified by use of one of the Locator 305 reachability algorithms described in Section 10. 307 Negative Mapping Entry: A negative mapping entry, also known as a 308 negative cache entry, is an EID-to-RLOC entry where an EID-Prefix 309 is advertised or stored with no RLOCs. That is, the Locator-Set 310 for the EID-to-RLOC entry is empty or has an encoded Locator count 311 of 0. This type of entry could be used to describe a prefix from 312 a non-LISP site, which is explicitly not in the mapping database. 313 There are a set of well-defined actions that are encoded in a 314 Negative Map-Reply. 316 Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A 317 PETR acts like an ETR but does so on behalf of LISP sites that 318 send packets to destinations at non-LISP sites. 320 Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A 321 PITR acts like an ITR but does so on behalf of non-LISP sites that 322 send packets to destinations at LISP sites. 324 Recursive Tunneling: Recursive Tunneling occurs when a packet has 325 more than one LISP IP header. Additional layers of tunneling MAY 326 be employed to implement Traffic Engineering or other re-routing 327 as needed. When this is done, an additional "outer" LISP header 328 is added, and the original RLOCs are preserved in the "inner" 329 header. 331 Re-Encapsulating Tunneling Router (RTR): An RTR acts like an ETR to 332 remove a LISP header, then acts as an ITR to prepend a new LISP 333 header. This is known as Re-encapsulating Tunneling. Doing this 334 allows a packet to be re-routed by the RTR without adding the 335 overhead of additional tunnel headers. When using multiple 336 mapping database systems, care must be taken to not create re- 337 encapsulation loops through misconfiguration. 339 Route-Returnability: Route-returnability is an assumption that the 340 underlying routing system will deliver packets to the destination. 341 When combined with a nonce that is provided by a sender and 342 returned by a receiver, this limits off-path data insertion. A 343 route-returnability check is verified when a message is sent with 344 a nonce, another message is returned with the same nonce, and the 345 destination of the original message appears as the source of the 346 returned message. 348 Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 349 [RFC8200] address of an Egress Tunnel Router (ETR). An RLOC is 350 the output of an EID-to-RLOC mapping lookup. An EID maps to zero 351 or more RLOCs. Typically, RLOCs are numbered from blocks that are 352 assigned to a site at each point to which it attaches to the 353 underlay network; where the topology is defined by the 354 connectivity of provider networks. Multiple RLOCs can be assigned 355 to the same ETR device or to multiple ETR devices at a site. 357 Server-side: Server-side is a term used in this document to indicate 358 that a connection initiation attempt is being accepted for a 359 destination EID. 361 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 362 network that strips an outer LISP header for Traffic Engineering 363 purposes. 365 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 366 network that prepends an additional LISP header for Traffic 367 Engineering purposes. 369 xTR: An xTR is a reference to an ITR or ETR when direction of data 370 flow is not part of the context description. "xTR" refers to the 371 router that is the tunnel endpoint and is used synonymously with 372 the term "Tunnel Router". For example, "An xTR can be located at 373 the Customer Edge (CE) router" indicates both ITR and ETR 374 functionality at the CE router. 376 4. Basic Overview 378 One key concept of LISP is that end-systems operate the same way they 379 do today. The IP addresses that hosts use for tracking sockets and 380 connections, and for sending and receiving packets, do not change. 381 In LISP terminology, these IP addresses are called Endpoint 382 Identifiers (EIDs). 384 Routers continue to forward packets based on IP destination 385 addresses. When a packet is LISP encapsulated, these addresses are 386 referred to as Routing Locators (RLOCs). Most routers along a path 387 between two hosts will not change; they continue to perform routing/ 388 forwarding lookups on the destination addresses. For routers between 389 the source host and the ITR as well as routers from the ETR to the 390 destination host, the destination address is an EID. For the routers 391 between the ITR and the ETR, the destination address is an RLOC. 393 Another key LISP concept is the "Tunnel Router". A Tunnel Router 394 prepends LISP headers on host-originated packets and strips them 395 prior to final delivery to their destination. The IP addresses in 396 this "outer header" are RLOCs. During end-to-end packet exchange 397 between two Internet hosts, an ITR prepends a new LISP header to each 398 packet, and an ETR strips the new header. The ITR performs EID-to- 399 RLOC lookups to determine the routing path to the ETR, which has the 400 RLOC as one of its IP addresses. 402 Some basic rules governing LISP are: 404 o End-systems only send to addresses that are EIDs. EIDs are 405 typically IP addresses assigned to hosts (other types of EID are 406 supported by LISP, see [RFC8060] for further information). End- 407 systems don't know that addresses are EIDs versus RLOCs but assume 408 that packets get to their intended destinations. In a system 409 where LISP is deployed, LISP routers intercept EID-addressed 410 packets and assist in delivering them across the network core 411 where EIDs cannot be routed. The procedure a host uses to send IP 412 packets does not change. 414 o LISP routers mostly deal with Routing Locator addresses. See 415 details in Section 4.1 to clarify what is meant by "mostly". 417 o RLOCs are always IP addresses assigned to routers, preferably 418 topologically oriented addresses from provider CIDR (Classless 419 Inter-Domain Routing) blocks. 421 o When a router originates packets, it MAY use as a source address 422 either an EID or RLOC. When acting as a host (e.g., when 423 terminating a transport session such as Secure SHell (SSH), 424 TELNET, or the Simple Network Management Protocol (SNMP)), it MAY 425 use an EID that is explicitly assigned for that purpose. An EID 426 that identifies the router as a host MUST NOT be used as an RLOC; 427 an EID is only routable within the scope of a site. A typical BGP 428 configuration might demonstrate this "hybrid" EID/RLOC usage where 429 a router could use its "host-like" EID to terminate iBGP sessions 430 to other routers in a site while at the same time using RLOCs to 431 terminate eBGP sessions to routers outside the site. 433 o Packets with EIDs in them are not expected to be delivered end-to- 434 end in the absence of an EID-to-RLOC mapping operation. They are 435 expected to be used locally for intra-site communication or to be 436 encapsulated for inter-site communication. 438 o EIDs MAY also be structured (subnetted) in a manner suitable for 439 local routing within an Autonomous System (AS). 441 An additional LISP header MAY be prepended to packets by a TE-ITR 442 when re-routing of the path for a packet is desired. A potential 443 use-case for this would be an ISP router that needs to perform 444 Traffic Engineering for packets flowing through its network. In such 445 a situation, termed "Recursive Tunneling", an ISP transit acts as an 446 additional ITR, and the RLOC it uses for the new prepended header 447 would be either a TE-ETR within the ISP (along an intra-ISP traffic 448 engineered path) or a TE-ETR within another ISP (an inter-ISP traffic 449 engineered path, where an agreement to build such a path exists). 451 In order to avoid excessive packet overhead as well as possible 452 encapsulation loops, this document recommends that a maximum of two 453 LISP headers can be prepended to a packet. For initial LISP 454 deployments, it is assumed that two headers is sufficient, where the 455 first prepended header is used at a site for Location/Identity 456 separation and the second prepended header is used inside a service 457 provider for Traffic Engineering purposes. 459 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 460 For example, the ITR for a particular end-to-end packet exchange 461 might be the first-hop or default router within a site for the source 462 host. Similarly, the ETR might be the last-hop router directly 463 connected to the destination host. Another example, perhaps for a 464 VPN service outsourced to an ISP by a site, the ITR could be the 465 site's border router at the service provider attachment point. 466 Mixing and matching of site-operated, ISP-operated, and other Tunnel 467 Routers is allowed for maximum flexibility. 469 4.1. Packet Flow Sequence 471 This section provides an example of the unicast packet flow, 472 including also Control-Plane information as specified in 473 [I-D.ietf-lisp-rfc6833bis]. The example also assumes the following 474 conditions: 476 o Source host "host1.abc.example.com" is sending a packet to 477 "host2.xyz.example.com", exactly what host1 would do if the site 478 was not using LISP. 480 o Each site is multihomed, so each Tunnel Router has an address 481 (RLOC) assigned from the service provider address block for each 482 provider to which that particular Tunnel Router is attached. 484 o The ITR(s) and ETR(s) are directly connected to the source and 485 destination, respectively, but the source and destination can be 486 located anywhere in the LISP site. 488 o A Map-Request is sent for an external destination when the 489 destination is not found in the forwarding table or matches a 490 default route. Map-Requests are sent to the mapping database 491 system by using the LISP Control-Plane protocol documented in 492 [I-D.ietf-lisp-rfc6833bis]. 494 o Map-Replies are sent on the underlying routing system topology 495 using the [I-D.ietf-lisp-rfc6833bis] Control-Plane protocol. 497 Client host1.abc.example.com wants to communicate with server 498 host2.xyz.example.com: 500 1. host1.abc.example.com wants to open a TCP connection to 501 host2.xyz.example.com. It does a DNS lookup on 502 host2.xyz.example.com. An A/AAAA record is returned. This 503 address is the destination EID. The locally assigned address of 504 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 505 packet is built and forwarded through the LISP site as a normal 506 IP packet until it reaches a LISP ITR. 508 2. The LISP ITR must be able to map the destination EID to an RLOC 509 of one of the ETRs at the destination site. The specific method 510 used to do this is not described in this example. See 511 [I-D.ietf-lisp-rfc6833bis] for further information. 513 3. The ITR sends a LISP Map-Request as specified in 514 [I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited. 516 4. The mapping system helps forwarding the Map-Request to the 517 corresponding ETR. When the Map-Request arrives at one of the 518 ETRs at the destination site, it will process the packet as a 519 control message. 521 5. The ETR looks at the destination EID of the Map-Request and 522 matches it against the prefixes in the ETR's configured EID-to- 523 RLOC mapping database. This is the list of EID-Prefixes the ETR 524 is supporting for the site it resides in. If there is no match, 525 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 526 returned to the ITR. 528 6. The ITR receives the Map-Reply message, parses the message (to 529 check for format validity), and stores the mapping information 530 from the packet. This information is stored in the ITR's EID-to- 531 RLOC Map-Cache. Note that the Map-Cache is an on-demand cache. 532 An ITR will manage its Map-Cache in such a way that optimizes for 533 its resource constraints. 535 7. Subsequent packets from host1.abc.example.com to 536 host2.xyz.example.com will have a LISP header prepended by the 537 ITR using the appropriate RLOC as the LISP header destination 538 address learned from the ETR. Note that the packet MAY be sent 539 to a different ETR than the one that returned the Map-Reply due 540 to the source site's hashing policy or the destination site's 541 Locator-Set policy. 543 8. The ETR receives these packets directly (since the destination 544 address is one of its assigned IP addresses), checks the validity 545 of the addresses, strips the LISP header, and forwards packets to 546 the attached destination host. 548 9. In order to defer the need for a mapping lookup in the reverse 549 direction, an ETR can OPTIONALLY create a cache entry that maps 550 the source EID (inner-header source IP address) to the source 551 RLOC (outer-header source IP address) in a received LISP packet. 552 Such a cache entry is termed a "glean mapping" and only contains 553 a single RLOC for the EID in question. More complete information 554 about additional RLOCs SHOULD be verified by sending a LISP Map- 555 Request for that EID. Both the ITR and the ETR MAY also 556 influence the decision the other makes in selecting an RLOC. 558 5. LISP Encapsulation Details 560 Since additional tunnel headers are prepended, the packet becomes 561 larger and can exceed the MTU of any link traversed from the ITR to 562 the ETR. It is RECOMMENDED in IPv4 that packets do not get 563 fragmented as they are encapsulated by the ITR. Instead, the packet 564 is dropped and an ICMP Unreachable/Fragmentation-Needed message is 565 returned to the source. 567 In the case when fragmentation is needed, this specification 568 RECOMMENDS that implementations provide support for one of the 569 proposed fragmentation and reassembly schemes. Two existing schemes 570 are detailed in Section 7. 572 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 573 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 574 header is in IPv4 packet format and the outer header is in IPv6 575 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 576 is in IPv6 packet format and the outer header is in IPv4 packet 577 format). The next sub-sections illustrate packet formats for the 578 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 579 combinations MUST be supported. Additional types of EIDs are defined 580 in [RFC8060]. 582 As LISP uses UDP encapsulation to carry traffic between xTRs across 583 the Internet, implementors should be aware of the provisions of 584 [RFC8085], especially those given in section 3.1.11 on congestion 585 control for UDP tunneling. 587 Implementors are encouraged to consider UDP checksum usage guidelines 588 in section 3.4 of [RFC8085] when it is desirable to protect UDP and 589 LISP headers against corruption. 591 5.1. LISP IPv4-in-IPv4 Header Format 592 0 1 2 3 593 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 1 594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 / |Version| IHL | DSCP |ECN| Total Length | 596 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | | Identification |Flags| Fragment Offset | 598 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 OH | Time to Live | Protocol = 17 | Header Checksum | 600 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 | | Source Routing Locator | 602 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 \ | Destination Routing Locator | 604 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 605 / | Source Port = xxxx | Dest Port = 4341 | 606 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 \ | UDP Length | UDP Checksum | 608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 610 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 611 S / | Instance ID/Locator-Status-Bits | 612 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 / |Version| IHL | DSCP |ECN| Total Length | 614 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 615 | | Identification |Flags| Fragment Offset | 616 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 617 IH | Time to Live | Protocol | Header Checksum | 618 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 | | Source EID | 620 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 \ | Destination EID | 622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 624 IHL = IP-Header-Length 626 5.2. LISP IPv6-in-IPv6 Header Format 628 0 1 2 3 629 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 631 / |Version| DSCP |ECN| Flow Label | 632 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 | | Payload Length | Next Header=17| Hop Limit | 634 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 | | 636 O + + 637 u | | 638 t + Source Routing Locator + 639 e | | 640 r + + 641 | | 642 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 643 d | | 644 r + + 645 | | 646 ^ + Destination Routing Locator + 647 | | | 648 \ + + 649 \ | | 650 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 651 / | Source Port = xxxx | Dest Port = 4341 | 652 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 653 \ | UDP Length | UDP Checksum | 654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 655 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 656 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 S / | Instance ID/Locator-Status-Bits | 658 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 / |Version| DSCP |ECN| Flow Label | 660 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 661 / | Payload Length | Next Header | Hop Limit | 662 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 663 | | 664 I + + 665 n | | 666 n + Source EID + 667 e | | 668 r + + 669 | | 670 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 671 d | | 672 r + + 673 | | 674 ^ + Destination EID + 675 \ | | 676 \ + + 677 \ | | 678 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 680 5.3. Tunnel Header Field Descriptions 682 Inner Header (IH): The inner header is the header on the 683 datagram received from the originating host [RFC0791] [RFC8200] 684 [RFC2474]. The source and destination IP addresses are EIDs. 686 Outer Header: (OH) The outer header is a new header prepended by an 687 ITR. The address fields contain RLOCs obtained from the ingress 688 router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" 689 from [RFC0768]. The setting of the Don't Fragment (DF) bit 690 'Flags' field is according to rules listed in Sections 7.1 and 691 7.2. 693 UDP Header: The UDP header contains an ITR selected source port when 694 encapsulating a packet. See Section 12 for details on the hash 695 algorithm used to select a source port based on the 5-tuple of the 696 inner header. The destination port MUST be set to the well-known 697 IANA-assigned port value 4341. 699 UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero 700 by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation 701 [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is 702 received by an ETR, the ETR MUST accept the packet for 703 decapsulation. When an ITR transmits a non-zero value for the UDP 704 checksum, it MUST send a correctly computed value in this field. 705 When an ETR receives a packet with a non-zero UDP checksum, it MAY 706 choose to verify the checksum value. If it chooses to perform 707 such verification, and the verification fails, the packet MUST be 708 silently dropped. If the ETR chooses not to perform the 709 verification, or performs the verification successfully, the 710 packet MUST be accepted for decapsulation. The handling of UDP 711 zero checksums over IPv6 for all tunneling protocols, including 712 LISP, is subject to the applicability statement in [RFC6936]. 714 UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated 715 packet to be the sum of the inner-header IPv4 Total Length plus 716 the UDP and LISP header lengths. For an IPv6-encapsulated packet, 717 the 'UDP Length' field is the sum of the inner-header IPv6 Payload 718 Length, the size of the IPv6 header (40 octets), and the size of 719 the UDP and LISP headers. 721 N: The N-bit is the nonce-present bit. When this bit is set to 1, 722 the low-order 24 bits of the first 32 bits of the LISP header 723 contain a Nonce. See Section 10.1 for details. Both N- and 724 V-bits MUST NOT be set in the same packet. If they are, a 725 decapsulating ETR MUST treat the 'Nonce/Map-Version' field as 726 having a Nonce value present. 728 L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When 729 this bit is set to 1, the Locator-Status-Bits in the second 730 32 bits of the LISP header are in use. 732 x 1 x x 0 x x x 733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 734 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 736 | Locator-Status-Bits | 737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 739 E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored 740 and has no meaning when the N-bit is set to 0. When the N-bit is 741 set to 1 and this bit is set to 1, an ITR is requesting that the 742 nonce value in the 'Nonce' field be echoed back in LISP- 743 encapsulated packets when the ITR is also an ETR. See 744 Section 10.1 for details. 746 V: The V-bit is the Map-Version present bit. When this bit is set to 747 1, the N-bit MUST be 0. Refer to Section 13.1 for more details. 748 This bit indicates that the LISP header is encoded in this 749 case as: 751 0 x 0 1 x x x x 752 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 753 |N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version | 754 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 755 | Instance ID/Locator-Status-Bits | 756 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 I: The I-bit is the Instance ID bit. See Section 8 for more details. 759 When this bit is set to 1, the 'Locator-Status-Bits' field is 760 reduced to 8 bits and the high-order 24 bits are used as an 761 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 762 are transmitted as zero and ignored on receipt. The format of the 763 LISP header would look like this: 765 x x x x 1 x x x 766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 767 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 768 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 769 | Instance ID | LSBs | 770 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 772 R: The R-bit is a Reserved bit for future use. It MUST be set to 0 773 on transmit and MUST be ignored on receipt. 775 KK: The KK-bits are a 2-bit field used when encapsulated packets are 776 encrypted. The field is set to 00 when the packet is not 777 encrypted. See [RFC8061] for further information. 779 LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is 780 randomly generated by an ITR when the N-bit is set to 1. Nonce 781 generation algorithms are an implementation matter but are 782 required to generate different nonces when sending to different 783 RLOCs. However, the same nonce can be used for a period of time 784 when encapsulating to the same ETR. The nonce is also used when 785 the E-bit is set to request the nonce value to be echoed by the 786 other side when packets are returned. When the E-bit is clear but 787 the N-bit is set, a remote ITR is either echoing a previously 788 requested echo-nonce or providing a random nonce. See 789 Section 10.1 for more details. 791 LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the 792 'Locator-Status-Bits' field in the LISP header is set by an ITR to 793 indicate to an ETR the up/down status of the Locators in the 794 source site. Each RLOC in a Map-Reply is assigned an ordinal 795 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 796 The Locator-Status-Bits are numbered from 0 to n-1 from the least 797 significant bit of the field. The field is 32 bits when the I-bit 798 is set to 0 and is 8 bits when the I-bit is set to 1. When a 799 Locator-Status-Bit is set to 1, the ITR is indicating to the ETR 800 that the RLOC associated with the bit ordinal has up status. See 801 Section 10 for details on how an ITR can determine the status of 802 the ETRs at the same site. When a site has multiple EID-Prefixes 803 that result in multiple mappings (where each could have a 804 different Locator-Set), the Locator-Status-Bits setting in an 805 encapsulated packet MUST reflect the mapping for the EID-Prefix 806 that the inner-header source EID address matches. If the LSB for 807 an anycast Locator is set to 1, then there is at least one RLOC 808 with that address, and the ETR is considered 'up'. 810 When doing ITR/PITR encapsulation: 812 o The outer-header 'Time to Live' field (or 'Hop Limit' field, in 813 the case of IPv6) SHOULD be copied from the inner-header 'Time to 814 Live' field. 816 o The outer-header 'Differentiated Services Code Point' (DSCP) field 817 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 818 copied from the inner-header DSCP field ('Traffic Class' field, in 819 the case of IPv6) to the outer-header. 821 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 822 of the IPv6 'Traffic Class' field) requires special treatment in 823 order to avoid discarding indications of congestion [RFC3168]. 824 ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 825 header to the outer header. Re-encapsulation MUST copy the 2-bit 826 'ECN' field from the stripped outer header to the new outer 827 header. 829 When doing ETR/PETR decapsulation: 831 o The inner-header 'Time to Live' field (or 'Hop Limit' field, in 832 the case of IPv6) SHOULD be copied from the outer-header 'Time to 833 Live' field, when the Time to Live value of the outer header is 834 less than the Time to Live value of the inner header. Failing to 835 perform this check can cause the Time to Live of the inner header 836 to increment across encapsulation/decapsulation cycles. This 837 check is also performed when doing initial encapsulation, when a 838 packet comes to an ITR or PITR destined for a LISP site. 840 o The inner-header 'Differentiated Services Code Point' (DSCP) field 841 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 842 copied from the outer-header DSCP field ('Traffic Class' field, in 843 the case of IPv6) to the inner-header. 845 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 846 of the IPv6 'Traffic Class' field) requires special treatment in 847 order to avoid discarding indications of congestion [RFC6040]. If 848 the 'ECN' field contains a congestion indication codepoint (the 849 value is '11', the Congestion Experienced (CE) codepoint), then 850 ETR decapsulation MUST copy the 2-bit 'ECN' field from the 851 stripped outer header to the surviving inner header that is used 852 to forward the packet beyond the ETR. These requirements preserve 853 CE indications when a packet that uses ECN traverses a LISP tunnel 854 and becomes marked with a CE indication due to congestion between 855 the tunnel endpoints. Implementations exist that copy the 'ECN' 856 field from the outer header to the inner header even though 857 [RFC6040] does not recommend this behavior. It is RECOMMENDED 858 that implementations change to support the behavior in [RFC6040]. 860 Note that if an ETR/PETR is also an ITR/PITR and chooses to re- 861 encapsulate after decapsulating, the net effect of this is that the 862 new outer header will carry the same Time to Live as the old outer 863 header minus 1. 865 Copying the Time to Live (TTL) serves two purposes: first, it 866 preserves the distance the host intended the packet to travel; 867 second, and more importantly, it provides for suppression of looping 868 packets in the event there is a loop of concatenated tunnels due to 869 misconfiguration. 871 The Explicit Congestion Notification ('ECN') field occupies bits 6 872 and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic 873 Class' field [RFC6040]. The 'ECN' field requires special treatment 874 in order to avoid discarding indications of congestion [RFC6040]. An 875 ITR/PITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 876 header to the outer header. Re-encapsulation MUST copy the 2-bit 877 'ECN' field from the stripped outer header to the new outer header. 878 If the 'ECN' field contains a congestion indication codepoint (the 879 value is '11', the Congestion Experienced (CE) codepoint), then ETR/ 880 PETR decapsulation MUST copy the 2-bit 'ECN' field from the stripped 881 outer header to the surviving inner header that is used to forward 882 the packet beyond the ETR. These requirements preserve CE 883 indications when a packet that uses ECN traverses a LISP tunnel and 884 becomes marked with a CE indication due to congestion between the 885 tunnel endpoints. 887 6. LISP EID-to-RLOC Map-Cache 889 ITRs and PITRs maintain an on-demand cache, referred as LISP EID-to- 890 RLOC Map-Cache, that contains mappings from EID-prefixes to locator 891 sets. The cache is used to encapsulate packets from the EID space to 892 the corresponding RLOC network attachment point. 894 When an ITR/PITR receives a packet from inside of the LISP site to 895 destinations outside of the site a longest-prefix match lookup of the 896 EID is done to the Map-Cache. 898 When the lookup succeeds, the Locator-Set retrieved from the Map- 899 Cache is used to send the packet to the EID's topological location. 901 If the lookup fails, the ITR/PITR needs to retrieve the mapping using 902 the LISP Control-Plane protocol [I-D.ietf-lisp-rfc6833bis]. The 903 mapping is then stored in the local Map-Cache to forward subsequent 904 packets addressed to the same EID-prefix. 906 The Map-Cache is a local cache of mappings, entries are expired based 907 on the associated Time to live. In addition, entries can be updated 908 with more current information, see Section 13 for further information 909 on this. Finally, the Map-Cache also contains reachability 910 information about EIDs and RLOCs, and uses LISP reachability 911 information mechanisms to determine the reachability of RLOCs, see 912 Section 10 for the specific mechanisms. 914 7. Dealing with Large Encapsulated Packets 916 This section proposes two mechanisms to deal with packets that exceed 917 the path MTU between the ITR and ETR. 919 It is left to the implementor to decide if the stateless or stateful 920 mechanism SHOULD be implemented. Both or neither can be used, since 921 it is a local decision in the ITR regarding how to deal with MTU 922 issues, and sites can interoperate with differing mechanisms. 924 Both stateless and stateful mechanisms also apply to Re-encapsulating 925 and Recursive Tunneling, so any actions below referring to an ITR 926 also apply to a TE-ITR. 928 7.1. A Stateless Solution to MTU Handling 930 An ITR stateless solution to handle MTU issues is described as 931 follows: 933 1. Define H to be the size, in octets, of the outer header an ITR 934 prepends to a packet. This includes the UDP and LISP header 935 lengths. 937 2. Define L to be the size, in octets, of the maximum-sized packet 938 an ITR can send to an ETR without the need for the ITR or any 939 intermediate routers to fragment the packet. 941 3. Define an architectural constant S for the maximum size of a 942 packet, in octets, an ITR MUST receive from the source so the 943 effective MTU can be met. That is, L = S + H. 945 When an ITR receives a packet from a site-facing interface and adds H 946 octets worth of encapsulation to yield a packet size greater than L 947 octets (meaning the received packet size was greater than S octets 948 from the source), it resolves the MTU issue by first splitting the 949 original packet into 2 equal-sized fragments. A LISP header is then 950 prepended to each fragment. The size of the encapsulated fragments 951 is then (S/2 + H), which is less than the ITR's estimate of the path 952 MTU between the ITR and its correspondent ETR. 954 When an ETR receives encapsulated fragments, it treats them as two 955 individually encapsulated packets. It strips the LISP headers and 956 then forwards each fragment to the destination host of the 957 destination site. The two fragments are reassembled at the 958 destination host into the single IP datagram that was originated by 959 the source host. Note that reassembly can happen at the ETR if the 960 encapsulated packet was fragmented at or after the ITR. 962 This behavior MAY be performed by the ITR only when the source host 963 originates a packet with the 'DF' field of the IP header set to 0. 964 When the 'DF' field of the IP header is set to 1, or the packet is an 965 IPv6 packet originated by the source host, the ITR will drop the 966 packet when the size is greater than L and send an ICMP Unreachable/ 967 Fragmentation-Needed message to the source with a value of S, where S 968 is (L - H). 970 When the outer-header encapsulation uses an IPv4 header, an 971 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 972 can be avoided. An implementation MAY set the DF bit in such headers 973 to 0 if it has good reason to believe there are unresolvable path MTU 974 issues between the sending ITR and the receiving ETR. 976 This specification RECOMMENDS that L be defined as 1500. 978 7.2. A Stateful Solution to MTU Handling 980 An ITR stateful solution to handle MTU issues is described as follows 981 and was first introduced in [OPENLISP]: 983 1. The ITR will keep state of the effective MTU for each Locator per 984 Map-Cache entry. The effective MTU is what the core network can 985 deliver along the path between the ITR and ETR. 987 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet 988 with the DF bit set to 1, exceeds what the core network can 989 deliver, one of the intermediate routers on the path will send an 990 ICMPv6 "Packet Too Big" message or an ICMPv4 Unreachable/ 991 Fragmentation-Needed to the ITR, respectively. The ITR will 992 parse the ICMP message to determine which Locator is affected by 993 the effective MTU change and then record the new effective MTU 994 value in the Map-Cache entry. 996 3. When a packet is received by the ITR from a source inside of the 997 site and the size of the packet is greater than the effective MTU 998 stored with the Map-Cache entry associated with the destination 999 EID the packet is for, the ITR will send an ICMPv4 ICMP 1000 Unreachable/Fragmentation-Needed or ICMPv6 "Packet Too Big" 1001 message back to the source. The packet size advertised by the 1002 ITR in the ICMP message is the effective MTU minus the LISP 1003 encapsulation length. 1005 Even though this mechanism is stateful, it has advantages over the 1006 stateless IP fragmentation mechanism, by not involving the 1007 destination host with reassembly of ITR fragmented packets. 1009 8. Using Virtualization and Segmentation with LISP 1011 There are several cases where segregation is needed at the EID level. 1012 For instance, this is the case for deployments containing overlapping 1013 addresses, traffic isolation policies or multi-tenant virtualization. 1014 For these and other scenarios where segregation is needed, Instance 1015 IDs are used. 1017 An Instance ID can be carried in a LISP-encapsulated packet. An ITR 1018 that prepends a LISP header will copy a 24-bit value used by the LISP 1019 router to uniquely identify the address space. The value is copied 1020 to the 'Instance ID' field of the LISP header, and the I-bit is set 1021 to 1. 1023 When an ETR decapsulates a packet, the Instance ID from the LISP 1024 header is used as a table identifier to locate the forwarding table 1025 to use for the inner destination EID lookup. 1027 For example, an 802.1Q VLAN tag or VPN identifier could be used as a 1028 24-bit Instance ID. See [I-D.ietf-lisp-vpn] for LISP VPN use-case 1029 details. 1031 The Instance ID that is stored in the mapping database when LISP-DDT 1032 [RFC8111] is used is 32 bits in length. That means the Control-Plane 1033 can store more instances than a given Data-Plane can use. Multiple 1034 Data-Planes can use the same 32-bit space as long as the low-order 24 1035 bits don't overlap among xTRs. 1037 9. Routing Locator Selection 1039 The Map-Cache contains the state used by ITRs and PITRs to 1040 encapsulate packets. When an ITR/PITR receives a packet from inside 1041 the LISP site to a destination outside of the site a longest-prefix 1042 match lookup of the EID is done to the Map-Cache (see Section 6). 1043 The lookup returns a single Locator-Set containing a list of RLOCs 1044 corresponding to the EID's topological location. Each RLOC in the 1045 Locator-Set is associated with a 'Priority' and 'Weight', this 1046 information is used to select the RLOC to encapsulate. 1048 The RLOC with the lowest 'Priority' is selected. An RLOC with 1049 'Priority' 255 means that MUST NOT be used for forwarding. When 1050 multiple RLOC have the same 'Priority' then the 'Weight' states how 1051 to load balance traffic among them. The value of the 'Weight' 1052 represents the relative weight of the total packets that match the 1053 maping entry. 1055 The following are different scenarios for choosing RLOCs and the 1056 controls that are available: 1058 o The server-side returns one RLOC. The client-side can only use 1059 one RLOC. The server-side has complete control of the selection. 1061 o The server-side returns a list of RLOCs where a subset of the list 1062 has the same best Priority. The client can only use the subset 1063 list according to the weighting assigned by the server-side. In 1064 this case, the server-side controls both the subset list and load- 1065 splitting across its members. The client-side can use RLOCs 1066 outside of the subset list if it determines that the subset list 1067 is unreachable (unless RLOCs are set to a Priority of 255). Some 1068 sharing of control exists: the server-side determines the 1069 destination RLOC list and load distribution while the client-side 1070 has the option of using alternatives to this list if RLOCs in the 1071 list are unreachable. 1073 o The server-side sets a Weight of zero for the RLOC subset list. 1074 In this case, the client-side can choose how the traffic load is 1075 spread across the subset list. Control is shared by the server- 1076 side determining the list and the client-side determining load 1077 distribution. Again, the client can use alternative RLOCs if the 1078 server-provided list of RLOCs is unreachable. 1080 o Either side (more likely the server-side ETR) decides not to send 1081 a Map-Request. For example, if the server-side ETR does not send 1082 Map-Requests, it gleans RLOCs from the client-side ITR, giving the 1083 client-side ITR responsibility for bidirectional RLOC reachability 1084 and preferability. Server-side ETR gleaning of the client-side 1085 ITR RLOC is done by caching the inner-header source EID and the 1086 outer-header source RLOC of received packets. The client-side ITR 1087 controls how traffic is returned and can alternate using an outer- 1088 header source RLOC, which then can be added to the list the 1089 server-side ETR uses to return traffic. Since no Priority or 1090 Weights are provided using this method, the server-side ETR MUST 1091 assume that each client-side ITR RLOC uses the same best Priority 1092 with a Weight of zero. In addition, since EID-Prefix encoding 1093 cannot be conveyed in data packets, the EID-to-RLOC Cache on 1094 Tunnel Routers can grow to be very large. 1096 Alternatively, RLOC information MAY be gleaned from received tunneled 1097 packets or EID-to-RLOC Map-Request messages. A "gleaned" Map-Cache 1098 entry, one learned from the source RLOC of a received encapsulated 1099 packet, is only stored and used for a few seconds, pending 1100 verification. Verification is performed by sending a Map-Request to 1101 the source EID (the inner-header IP source address) of the received 1102 encapsulated packet. A reply to this "verifying Map-Request" is used 1103 to fully populate the Map-Cache entry for the "gleaned" EID and is 1104 stored and used for the time indicated from the 'TTL' field of a 1105 received Map-Reply. When a verified Map-Cache entry is stored, data 1106 gleaning no longer occurs for subsequent packets that have a source 1107 EID that matches the EID-Prefix of the verified entry. This 1108 "gleaning" mechanism is OPTIONAL, refer to Section 16 for security 1109 issues regarding this mechanism. 1111 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1112 reachable when the R-bit for the Locator record is set to 1. When 1113 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1114 RLOC. Neither the information contained in a Map-Reply nor that 1115 stored in the mapping database system provides reachability 1116 information for RLOCs. Note that reachability is not part of the 1117 mapping system and is determined using one or more of the Routing 1118 Locator reachability algorithms described in the next section. 1120 10. Routing Locator Reachability 1122 Several Data-Plane mechanisms for determining RLOC reachability are 1123 currently defined. Please note that additional Control-Plane based 1124 reachability mechanisms are defined in [I-D.ietf-lisp-rfc6833bis]. 1126 1. An ETR MAY examine the Locator-Status-Bits in the LISP header of 1127 an encapsulated data packet received from an ITR. If the ETR is 1128 also acting as an ITR and has traffic to return to the original 1129 ITR site, it can use this status information to help select an 1130 RLOC. 1132 2. When an ETR receives an encapsulated packet from an ITR, the 1133 source RLOC from the outer header of the packet is likely up. 1135 3. An ITR/ETR pair can use the 'Echo-Noncing' Locator reachability 1136 algorithms described in this section. 1138 When determining Locator up/down reachability by examining the 1139 Locator-Status-Bits from the LISP-encapsulated data packet, an ETR 1140 will receive up-to-date status from an encapsulating ITR about 1141 reachability for all ETRs at the site. CE-based ITRs at the source 1142 site can determine reachability relative to each other using the site 1143 IGP as follows: 1145 o Under normal circumstances, each ITR will advertise a default 1146 route into the site IGP. 1148 o If an ITR fails or if the upstream link to its PE fails, its 1149 default route will either time out or be withdrawn. 1151 Each ITR can thus observe the presence or lack of a default route 1152 originated by the others to determine the Locator-Status-Bits it sets 1153 for them. 1155 When ITRs at the site are not deployed in CE routers, the IGP can 1156 still be used to determine the reachability of Locators, provided 1157 they are injected into the IGP. This is typically done when a /32 1158 address is configured on a loopback interface. 1160 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1161 Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 1162 to n-1 starting with the least significant bit. For example, if an 1163 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1164 value 2), then all ITRs at the site will clear the 3rd least 1165 significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for 1166 the packets they encapsulate. 1168 When an ETR decapsulates a packet, it will check for any change in 1169 the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the 1170 ETR, if acting also as an ITR, will refrain from encapsulating 1171 packets to an RLOC that is indicated as down. It will only resume 1172 using that RLOC if the corresponding Locator-Status-Bit returns to a 1173 value of 1. Locator-Status-Bits are associated with a Locator-Set 1174 per EID-Prefix. Therefore, when a Locator becomes unreachable, the 1175 Locator-Status-Bit that corresponds to that Locator's position in the 1176 list returned by the last Map-Reply will be set to zero for that 1177 particular EID-Prefix. Refer to Section 16 for security related 1178 issues regarding Locator-Status-Bits. 1180 When an ETR decapsulates a packet, it knows that it is reachable from 1181 the encapsulating ITR because that is how the packet arrived. In 1182 most cases, the ETR can also reach the ITR but cannot assume this to 1183 be true, due to the possibility of path asymmetry. In the presence 1184 of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD 1185 NOT use the lack of return traffic as an indication that the ETR is 1186 unreachable. Instead, it MUST use an alternate mechanism to 1187 determine reachability. 1189 10.1. Echo Nonce Algorithm 1191 When data flows bidirectionally between Locators from different 1192 sites, a Data-Plane mechanism called "nonce echoing" can be used to 1193 determine reachability between an ITR and ETR. When an ITR wants to 1194 solicit a nonce echo, it sets the N- and E-bits and places a 24-bit 1195 nonce [RFC4086] in the LISP header of the next encapsulated data 1196 packet. 1198 When this packet is received by the ETR, the encapsulated packet is 1199 forwarded as normal. When the ETR next sends a data packet to the 1200 ITR, it includes the nonce received earlier with the N-bit set and 1201 E-bit cleared. The ITR sees this "echoed nonce" and knows that the 1202 path to and from the ETR is up. 1204 The ITR will set the E-bit and N-bit for every packet it sends while 1205 in the echo-nonce-request state. The time the ITR waits to process 1206 the echoed nonce before it determines the path is unreachable is 1207 variable and is a choice left for the implementation. 1209 If the ITR is receiving packets from the ETR but does not see the 1210 nonce echoed while being in the echo-nonce-request state, then the 1211 path to the ETR is unreachable. This decision MAY be overridden by 1212 other Locator reachability algorithms. Once the ITR determines that 1213 the path to the ETR is down, it can switch to another Locator for 1214 that EID-Prefix. 1216 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1217 be implementing both ITR and ETR functionality for the echo nonce 1218 mechanism to operate. 1220 The ITR and ETR MAY both go into the echo-nonce-request state at the 1221 same time. The number of packets sent or the time during which echo 1222 nonce requests are sent is an implementation-specific setting. 1223 However, when an ITR is in the echo-nonce-request state, it can echo 1224 the ETR's nonce in the next set of packets that it encapsulates and 1225 subsequently continue sending echo-nonce-request packets. 1227 This mechanism does not completely solve the forward path 1228 reachability problem, as traffic may be unidirectional. That is, the 1229 ETR receiving traffic at a site MAY not be the same device as an ITR 1230 that transmits traffic from that site, or the site-to-site traffic is 1231 unidirectional so there is no ITR returning traffic. 1233 The echo-nonce algorithm is bilateral. That is, if one side sets the 1234 E-bit and the other side is not enabled for echo-noncing, then the 1235 echoing of the nonce does not occur and the requesting side may 1236 erroneously consider the Locator unreachable. An ITR SHOULD only set 1237 the E-bit in an encapsulated data packet when it knows the ETR is 1238 enabled for echo-noncing. This is conveyed by the E-bit in the RLOC- 1239 probe Map-Reply message. 1241 11. EID Reachability within a LISP Site 1243 A site MAY be multihomed using two or more ETRs. The hosts and 1244 infrastructure within a site will be addressed using one or more EID- 1245 Prefixes that are mapped to the RLOCs of the relevant ETRs in the 1246 mapping system. One possible failure mode is for an ETR to lose 1247 reachability to one or more of the EID-Prefixes within its own site. 1248 When this occurs when the ETR sends Map-Replies, it can clear the 1249 R-bit associated with its own Locator. And when the ETR is also an 1250 ITR, it can clear its Locator-Status-Bit in the encapsulation data 1251 header. 1253 It is recognized that there are no simple solutions to the site 1254 partitioning problem because it is hard to know which part of the 1255 EID-Prefix range is partitioned and which Locators can reach any sub- 1256 ranges of the EID-Prefixes. Note that this is not a new problem 1257 introduced by the LISP architecture. The problem exists today when a 1258 multihomed site uses BGP to advertise its reachability upstream. 1260 12. Routing Locator Hashing 1262 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message 1263 that is stored in the Map-Cache of a requesting ITR, the Locator-Set 1264 for the EID-Prefix MAY contain different Priority and Weight values 1265 for each locator address. When more than one best Priority Locator 1266 exists, the ITR can decide how to load-share traffic against the 1267 corresponding Locators. 1269 The following hash algorithm MAY be used by an ITR to select a 1270 Locator for a packet destined to an EID for the EID-to-RLOC mapping: 1272 1. Either a source and destination address hash or the traditional 1273 5-tuple hash can be used. The traditional 5-tuple hash includes 1274 the source and destination addresses; source and destination TCP, 1275 UDP, or Stream Control Transmission Protocol (SCTP) port numbers; 1276 and the IP protocol number field or IPv6 next-protocol fields of 1277 a packet that a host originates from within a LISP site. When a 1278 packet is not a TCP, UDP, or SCTP packet, the source and 1279 destination addresses only from the header are used to compute 1280 the hash. 1282 2. Take the hash value and divide it by the number of Locators 1283 stored in the Locator-Set for the EID-to-RLOC mapping. 1285 3. The remainder will yield a value of 0 to "number of Locators 1286 minus 1". Use the remainder to select the Locator in the 1287 Locator-Set. 1289 Note that when a packet is LISP encapsulated, the source port number 1290 in the outer UDP header needs to be set. Selecting a hashed value 1291 allows core routers that are attached to Link Aggregation Groups 1292 (LAGs) to load-split the encapsulated packets across member links of 1293 such LAGs. Otherwise, core routers would see a single flow, since 1294 packets have a source address of the ITR, for packets that are 1295 originated by different EIDs at the source site. A suggested setting 1296 for the source port number computed by an ITR is a 5-tuple hash 1297 function on the inner header, as described above. The source port 1298 SHOULD be the same for all packets belonging to the same flow. 1300 Many core router implementations use a 5-tuple hash to decide how to 1301 balance packet load across members of a LAG. The 5-tuple hash 1302 includes the source and destination addresses of the packet and the 1303 source and destination ports when the protocol number in the packet 1304 is TCP or UDP. For this reason, UDP encoding is used for LISP 1305 encapsulation. 1307 13. Changing the Contents of EID-to-RLOC Mappings 1309 Since the LISP architecture uses a caching scheme to retrieve and 1310 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 1311 date mapping is to re-request the mapping. However, the ITRs do not 1312 know when the mappings change, and the ETRs do not keep track of 1313 which ITRs requested its mappings. For scalability reasons, it is 1314 desirable to maintain this approach but need to provide a way for 1315 ETRs to change their mappings and inform the sites that are currently 1316 communicating with the ETR site using such mappings. 1318 This section defines a Data-Plane mechanism for updating EID-to-RLOC 1319 mappings. Additionally, the Solicit-Map Request (SMR) Control-Plane 1320 updating mechanism is specified in [I-D.ietf-lisp-rfc6833bis]. 1322 When adding a new Locator record in lexicographic order to the end of 1323 a Locator-Set, it is easy to update mappings. We assume that new 1324 mappings will maintain the same Locator ordering as the old mapping 1325 but will just have new Locators appended to the end of the list. So, 1326 some ITRs can have a new mapping while other ITRs have only an old 1327 mapping that is used until they time out. When an ITR has only an 1328 old mapping but detects bits set in the Locator-Status-Bits that 1329 correspond to Locators beyond the list it has cached, it simply 1330 ignores them. However, this can only happen for locator addresses 1331 that are lexicographically greater than the locator addresses in the 1332 existing Locator-Set. 1334 When a Locator record is inserted in the middle of a Locator-Set, to 1335 maintain lexicographic order, SMR procedure 1336 [I-D.ietf-lisp-rfc6833bis] is used to inform ITRs and PITRs of the 1337 new Locator-Status-Bit mappings. 1339 When a Locator record is removed from a Locator-Set, ITRs that have 1340 the mapping cached will not use the removed Locator because the xTRs 1341 will set the Locator-Status-Bit to 0. So, even if the Locator is in 1342 the list, it will not be used. For new mapping requests, the xTRs 1343 can set the Locator AFI to 0 (indicating an unspecified address), as 1344 well as setting the corresponding Locator-Status-Bit to 0. This 1345 forces ITRs with old or new mappings to avoid using the removed 1346 Locator. 1348 If many changes occur to a mapping over a long period of time, one 1349 will find empty record slots in the middle of the Locator-Set and new 1350 records appended to the Locator-Set. At some point, it would be 1351 useful to compact the Locator-Set so the Locator-Status-Bit settings 1352 can be efficiently packed. 1354 We propose here a Data-Plane mechanism (Map-Versioning specified in 1355 [I-D.ietf-lisp-6834bis]) to update the contents of EID-to-RLOC 1356 mappings. Please note that in addition the Solicit-Map Request 1357 (specified in [I-D.ietf-lisp-rfc6833bis]) is a Control-Plane 1358 mechanisms that can be used to update EID-to-RLOC mappings. 1360 13.1. Database Map-Versioning 1362 When there is unidirectional packet flow between an ITR and ETR, and 1363 the EID-to-RLOC mappings change on the ETR, it needs to inform the 1364 ITR so encapsulation to a removed Locator can stop and can instead be 1365 started to a new Locator in the Locator-Set. 1367 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 1368 Number. This is known as the Destination Map-Version Number. ITRs 1369 include the Destination Map-Version Number in packets they 1370 encapsulate to the site. When an ETR decapsulates a packet and 1371 detects that the Destination Map-Version Number is less than the 1372 current version for its mapping, the SMR procedure described in 1373 [I-D.ietf-lisp-rfc6833bis] occurs. 1375 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 1376 Version Number. This is known as the Source Map-Version Number. 1377 When an ETR decapsulates a packet and detects that the Source Map- 1378 Version Number is greater than the last Map-Version Number sent in a 1379 Map-Reply from the ITR's site, the ETR will send a Map-Request to one 1380 of the ETRs for the source site. 1382 A Map-Version Number is used as a sequence number per EID-Prefix, so 1383 values that are greater are considered to be more recent. A value of 1384 0 for the Source Map-Version Number or the Destination Map-Version 1385 Number conveys no versioning information, and an ITR does no 1386 comparison with previously received Map-Version Numbers. 1388 A Map-Version Number can be included in Map-Register messages as 1389 well. This is a good way for the Map-Server to assure that all ETRs 1390 for a site registering to it will be synchronized according to Map- 1391 Version Number. 1393 See [I-D.ietf-lisp-6834bis] for a more detailed analysis and 1394 description of Database Map-Versioning. 1396 14. Multicast Considerations 1398 A multicast group address, as defined in the original Internet 1399 architecture, is an identifier of a grouping of topologically 1400 independent receiver host locations. The address encoding itself 1401 does not determine the location of the receiver(s). The multicast 1402 routing protocol, and the network-based state the protocol creates, 1403 determine where the receivers are located. 1405 In the context of LISP, a multicast group address is both an EID and 1406 a Routing Locator. Therefore, no specific semantic or action needs 1407 to be taken for a destination address, as it would appear in an IP 1408 header. Therefore, a group address that appears in an inner IP 1409 header built by a source host will be used as the destination EID. 1410 The outer IP header (the destination Routing Locator address), 1411 prepended by a LISP router, can use the same group address as the 1412 destination Routing Locator, use a multicast or unicast Routing 1413 Locator obtained from a Mapping System lookup, or use other means to 1414 determine the group address mapping. 1416 With respect to the source Routing Locator address, the ITR prepends 1417 its own IP address as the source address of the outer IP header. 1418 Just like it would if the destination EID was a unicast address. 1419 This source Routing Locator address, like any other Routing Locator 1420 address, MUST be globally routable. 1422 There are two approaches for LISP-Multicast, one that uses native 1423 multicast routing in the underlay with no support from the Mapping 1424 System and the other that uses only unicast routing in the underlay 1425 with support from the Mapping System. See [RFC6831] and [RFC8378], 1426 respectively, for details. Details for LISP-Multicast and 1427 interworking with non-LISP sites are described in [RFC6831] and 1428 [RFC6832]. 1430 15. Router Performance Considerations 1432 LISP is designed to be very "hardware-based forwarding friendly". A 1433 few implementation techniques can be used to incrementally implement 1434 LISP: 1436 o When a tunnel-encapsulated packet is received by an ETR, the outer 1437 destination address may not be the address of the router. This 1438 makes it challenging for the control plane to get packets from the 1439 hardware. This may be mitigated by creating special Forwarding 1440 Information Base (FIB) entries for the EID-Prefixes of EIDs served 1441 by the ETR (those for which the router provides an RLOC 1442 translation). These FIB entries are marked with a flag indicating 1443 that Control-Plane processing SHOULD be performed. The forwarding 1444 logic of testing for particular IP protocol number values is not 1445 necessary. There are a few proven cases where no changes to 1446 existing deployed hardware were needed to support the LISP Data- 1447 Plane. 1449 o On an ITR, prepending a new IP header consists of adding more 1450 octets to a MAC rewrite string and prepending the string as part 1451 of the outgoing encapsulation procedure. Routers that support 1452 Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 1453 tunneling [RFC3056] may already support this action. 1455 o A packet's source address or interface the packet was received on 1456 can be used to select VRF (Virtual Routing/Forwarding). The VRF's 1457 routing table can be used to find EID-to-RLOC mappings. 1459 For performance issues related to Map-Cache management, see 1460 Section 16. 1462 16. Security Considerations 1464 A complete LISP threat analysis can be found in [RFC7835] in what 1465 follows we provide a summary when LISP is deployed in non-trustable 1466 environments. 1468 The optional mechanisms of gleaning is offered to directly obtain a 1469 mapping from the LISP encapsulated packets. Specifically, an xTR can 1470 learn the EID-to-RLOC mapping by inspecting the source RLOC and 1471 source EID of an encapsulated packet, and insert this new mapping 1472 into its Map-Cache. An off-path attacker can spoof the source EID 1473 address to divert the traffic sent to the victim's spoofed EID. If 1474 the attacker spoofs the source RLOC, it can mount a DoS attack by 1475 redirecting traffic to the spoofed victim's RLOC, potentially 1476 overloading it. 1478 The LISP Data-Plane defines several mechanisms to monitor RLOC Data- 1479 Plane reachability, in this context Locator-Status Bits, Nonce- 1480 Present and Echo-Nonce bits of the LISP encapsulation header can be 1481 manipulated by an attacker to mount a DoS attack. An off-path 1482 attacker able to spoof the RLOC of a victim's xTR can manipulate such 1483 mechanisms to declare a set of RLOCs unreachable. This can be used 1484 also, for instance, to declare only one RLOC reachable with the aim 1485 of overload it. 1487 Map-Versioning is a Data-Plane mechanism used to signal a peering xTR 1488 that a local EID-to-RLOC mapping has been updated, so that the 1489 peering xTR uses LISP Control-Plane signaling message to retrieve a 1490 fresh mapping. This can be used by an attacker to forge the map- 1491 versioning field of a LISP encapsulated header and force an excessive 1492 amount of signaling between xTRs that may overload them. 1494 Most of the attack vectors can be mitigated with careful deployment 1495 and configuration, information learned opportunistically (such as LSB 1496 or gleaning) SHOULD be verified with other reachability mechanisms. 1497 In addition, systematic rate-limitation and filtering is an effective 1498 technique to mitigate attacks that aim to overload the Control-Plane. 1500 17. Network Management Considerations 1502 Considerations for network management tools exist so the LISP 1503 protocol suite can be operationally managed. These mechanisms can be 1504 found in [RFC7052] and [RFC6835]. 1506 18. Changes since RFC 6830 1508 For implementation considerations, the following changes have been 1509 made to this document since RFC 6830 was published: 1511 o It is no longer mandated that a maximum number of 2 LISP headers 1512 be prepended to a packet. If there is a application need for more 1513 than 2 LISP headers, an implementation can support more. However, 1514 it is RECOMMENDED that a maximum of two LISP headers can be 1515 prepended to a packet. 1517 o The 3 reserved flag bits in the LISP header have been allocated 1518 for [RFC8061]. The low-order 2 bits of the 3-bit field (now named 1519 the KK bits) are used as a key identifier. The 1 remaining bit is 1520 still documented as reserved. 1522 o Data-Plane gleaning for creating map-cache entries has been made 1523 optional. If any ITR implementations depend or assume the remote 1524 ETR is gleaning should not do so. This does not create any 1525 interoperability problems since the control-plane map-cache 1526 population procedures are unilateral and are the typical method 1527 for map-cache population. 1529 o The bulk of the changes to this document which reduces its length 1530 are due to moving the LISP control-plane messaging and procedures 1531 to [I-D.ietf-lisp-rfc6833bis]. 1533 19. IANA Considerations 1535 This section provides guidance to the Internet Assigned Numbers 1536 Authority (IANA) regarding registration of values related to this 1537 Data-Plane LISP specification, in accordance with BCP 26 [RFC8126]. 1539 19.1. LISP UDP Port Numbers 1541 The IANA registry has allocated UDP port number 4341 for the LISP 1542 Data-Plane. IANA has updated the description for UDP port 4341 as 1543 follows: 1545 lisp-data 4341 udp LISP Data Packets 1547 20. References 1549 20.1. Normative References 1551 [I-D.ietf-lisp-6834bis] 1552 Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1553 Separation Protocol (LISP) Map-Versioning", draft-ietf- 1554 lisp-6834bis-02 (work in progress), September 2018. 1556 [I-D.ietf-lisp-rfc6833bis] 1557 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1558 "Locator/ID Separation Protocol (LISP) Control-Plane", 1559 draft-ietf-lisp-rfc6833bis-15 (work in progress), 1560 September 2018. 1562 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1563 DOI 10.17487/RFC0768, August 1980, 1564 . 1566 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1567 DOI 10.17487/RFC0791, September 1981, 1568 . 1570 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1571 Requirement Levels", BCP 14, RFC 2119, 1572 DOI 10.17487/RFC2119, March 1997, 1573 . 1575 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1576 "Definition of the Differentiated Services Field (DS 1577 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1578 DOI 10.17487/RFC2474, December 1998, 1579 . 1581 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1582 of Explicit Congestion Notification (ECN) to IP", 1583 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1584 . 1586 [RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion 1587 Notification", RFC 6040, DOI 10.17487/RFC6040, November 1588 2010, . 1590 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1591 Writing an IANA Considerations Section in RFCs", BCP 26, 1592 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1593 . 1595 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1596 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1597 May 2017, . 1599 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1600 (IPv6) Specification", STD 86, RFC 8200, 1601 DOI 10.17487/RFC8200, July 2017, 1602 . 1604 20.2. Informative References 1606 [AFN] IANA, "Address Family Numbers", August 2016, 1607 . 1609 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed", 1610 1999, 1611 . 1613 [I-D.ietf-lisp-introduction] 1614 Cabellos-Aparicio, A. and D. Saucez, "An Architectural 1615 Introduction to the Locator/ID Separation Protocol 1616 (LISP)", draft-ietf-lisp-introduction-13 (work in 1617 progress), April 2015. 1619 [I-D.ietf-lisp-vpn] 1620 Moreno, V. and D. Farinacci, "LISP Virtual Private 1621 Networks (VPNs)", draft-ietf-lisp-vpn-02 (work in 1622 progress), May 2018. 1624 [OPENLISP] 1625 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 1626 Implementation Report", Work in Progress, July 2008. 1628 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1629 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1630 . 1632 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1633 and E. Lear, "Address Allocation for Private Internets", 1634 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1635 . 1637 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1638 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1639 DOI 10.17487/RFC2784, March 2000, 1640 . 1642 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 1643 via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 1644 2001, . 1646 [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced 1647 by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, 1648 January 2002, . 1650 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1651 A., Peterson, J., Sparks, R., Handley, M., and E. 1652 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1653 DOI 10.17487/RFC3261, June 2002, 1654 . 1656 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1657 "Randomness Requirements for Security", BCP 106, RFC 4086, 1658 DOI 10.17487/RFC4086, June 2005, 1659 . 1661 [RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report 1662 from the IAB Workshop on Routing and Addressing", 1663 RFC 4984, DOI 10.17487/RFC4984, September 2007, 1664 . 1666 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1667 Locator/ID Separation Protocol (LISP) for Multicast 1668 Environments", RFC 6831, DOI 10.17487/RFC6831, January 1669 2013, . 1671 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1672 "Interworking between Locator/ID Separation Protocol 1673 (LISP) and Non-LISP Sites", RFC 6832, 1674 DOI 10.17487/RFC6832, January 2013, 1675 . 1677 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1678 Protocol Internet Groper (LIG)", RFC 6835, 1679 DOI 10.17487/RFC6835, January 2013, 1680 . 1682 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1683 UDP Checksums for Tunneled Packets", RFC 6935, 1684 DOI 10.17487/RFC6935, April 2013, 1685 . 1687 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1688 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1689 RFC 6936, DOI 10.17487/RFC6936, April 2013, 1690 . 1692 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1693 Separation Protocol (LISP) MIB", RFC 7052, 1694 DOI 10.17487/RFC7052, October 2013, 1695 . 1697 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1698 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1699 Protocol (LISP) Network Element Deployment 1700 Considerations", RFC 7215, DOI 10.17487/RFC7215, April 1701 2014, . 1703 [RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A 1704 RADIUS Attribute, Binding, Profiles, Name Identifier 1705 Format, and Confirmation Methods for the Security 1706 Assertion Markup Language (SAML)", RFC 7833, 1707 DOI 10.17487/RFC7833, May 2016, 1708 . 1710 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 1711 Separation Protocol (LISP) Threat Analysis", RFC 7835, 1712 DOI 10.17487/RFC7835, April 2016, 1713 . 1715 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1716 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 1717 February 2017, . 1719 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 1720 (LISP) Data-Plane Confidentiality", RFC 8061, 1721 DOI 10.17487/RFC8061, February 2017, 1722 . 1724 [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage 1725 Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, 1726 March 2017, . 1728 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 1729 Smirnov, "Locator/ID Separation Protocol Delegated 1730 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 1731 May 2017, . 1733 [RFC8378] Moreno, V. and D. Farinacci, "Signal-Free Locator/ID 1734 Separation Protocol (LISP) Multicast", RFC 8378, 1735 DOI 10.17487/RFC8378, May 2018, 1736 . 1738 Appendix A. Acknowledgments 1740 An initial thank you goes to Dave Oran for planting the seeds for the 1741 initial ideas for LISP. His consultation continues to provide value 1742 to the LISP authors. 1744 A special and appreciative thank you goes to Noel Chiappa for 1745 providing architectural impetus over the past decades on separation 1746 of location and identity, as well as detailed reviews of the LISP 1747 architecture and documents, coupled with enthusiasm for making LISP a 1748 practical and incremental transition for the Internet. 1750 The authors would like to gratefully acknowledge many people who have 1751 contributed discussions and ideas to the making of this proposal. 1752 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 1753 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 1754 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 1755 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 1756 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 1757 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 1758 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 1759 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 1760 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 1761 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 1762 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 1763 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 1764 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 1765 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 1766 Ermagan, Fabio Maino, Victor Moreno, Chris White, Clarence Filsfils, 1767 Alia Atlas, Florin Coras and Alberto Rodriguez. 1769 This work originated in the Routing Research Group (RRG) of the IRTF. 1770 An individual submission was converted into the IETF LISP working 1771 group document that became this RFC. 1773 The LISP working group would like to give a special thanks to Jari 1774 Arkko, the Internet Area AD at the time that the set of LISP 1775 documents were being prepared for IESG last call, and for his 1776 meticulous reviews and detailed commentaries on the 7 working group 1777 last call documents progressing toward standards-track RFCs. 1779 Appendix B. Document Change Log 1781 [RFC Editor: Please delete this section on publication as RFC.] 1783 B.1. Changes to draft-ietf-lisp-rfc6830bis-19 1785 o Posted late-September 2018. 1787 o More editorial changes. 1789 B.2. Changes to draft-ietf-lisp-rfc6830bis-18 1791 o Posted mid-September 2018. 1793 o Changes to reflect comments from Secdir review (Mirja). 1795 B.3. Changes to draft-ietf-lisp-rfc6830bis-17 1797 o Posted September 2018. 1799 o Indicate in the "Changes since RFC 6830" section why the document 1800 has been shortened in length. 1802 o Make reference to RFC 8085 about UDP congestion control. 1804 o More editorial changes from multiple IESG reviews. 1806 B.4. Changes to draft-ietf-lisp-rfc6830bis-16 1808 o Posted late August 2018. 1810 o Distinguish the message type names between ICMP for IPv4 and ICMP 1811 for IPv6 for handling MTU issues. 1813 B.5. Changes to draft-ietf-lisp-rfc6830bis-15 1815 o Posted August 2018. 1817 o Final editorial changes before RFC submission for Proposed 1818 Standard. 1820 o Added section "Changes since RFC 6830" so implementers are 1821 informed of any changes since the last RFC publication. 1823 B.6. Changes to draft-ietf-lisp-rfc6830bis-14 1825 o Posted July 2018 IETF week. 1827 o Put obsolete of RFC 6830 in Intro section in addition to abstract. 1829 B.7. Changes to draft-ietf-lisp-rfc6830bis-13 1831 o Posted March IETF Week 2018. 1833 o Clarified that a new nonce is required per RLOC. 1835 o Removed 'Clock Sweep' section. This text must be placed in a new 1836 OAM document. 1838 o Some references changed from normative to informative 1840 B.8. Changes to draft-ietf-lisp-rfc6830bis-12 1842 o Posted July 2018. 1844 o Fixed Luigi editorial comments to ready draft for RFC status. 1846 B.9. Changes to draft-ietf-lisp-rfc6830bis-11 1848 o Posted March 2018. 1850 o Removed sections 16, 17 and 18 (Mobility, Deployment and 1851 Traceroute considerations). This text must be placed in a new OAM 1852 document. 1854 B.10. Changes to draft-ietf-lisp-rfc6830bis-10 1856 o Posted March 2018. 1858 o Updated section 'Router Locator Selection' stating that the Data- 1859 Plane MUST follow what's stored in the Map-Cache (priorities and 1860 weights). 1862 o Section 'Routing Locator Reachability': Removed bullet point 2 1863 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP Port 1864 Unreachable),5 (receive a Map-Reply as a response) and RLOC 1865 probing 1867 o Removed 'Solicit-Map Request'. 1869 B.11. Changes to draft-ietf-lisp-rfc6830bis-09 1871 o Posted January 2018. 1873 o Add more details in section 5.3 about DSCP processing during 1874 encapsulation and decapsulation. 1876 o Added clarity to definitions in the Definition of Terms section 1877 from various commenters. 1879 o Removed PA and PI definitions from Definition of Terms section. 1881 o More editorial changes. 1883 o Removed 4342 from IANA section and move to RFC6833 IANA section. 1885 B.12. Changes to draft-ietf-lisp-rfc6830bis-08 1887 o Posted January 2018. 1889 o Remove references to research work for any protocol mechanisms. 1891 o Document scanned to make sure it is RFC 2119 compliant. 1893 o Made changes to reflect comments from document WG shepherd Luigi 1894 Iannone. 1896 o Ran IDNITs on the document. 1898 B.13. Changes to draft-ietf-lisp-rfc6830bis-07 1900 o Posted November 2017. 1902 o Rephrase how Instance-IDs are used and don't refer to [RFC1918] 1903 addresses. 1905 B.14. Changes to draft-ietf-lisp-rfc6830bis-06 1907 o Posted October 2017. 1909 o Put RTR definition before it is used. 1911 o Rename references that are now working group drafts. 1913 o Remove "EIDs MUST NOT be used as used by a host to refer to other 1914 hosts. Note that EID blocks MAY LISP RLOCs". 1916 o Indicate what address-family can appear in data packets. 1918 o ETRs may, rather than will, be the ones to send Map-Replies. 1920 o Recommend, rather than mandate, max encapsulation headers to 2. 1922 o Reference VPN draft when introducing Instance-ID. 1924 o Indicate that SMRs can be sent when ITR/ETR are in the same node. 1926 o Clarify when private addresses can be used. 1928 B.15. Changes to draft-ietf-lisp-rfc6830bis-05 1930 o Posted August 2017. 1932 o Make it clear that a Re-encapsulating Tunnel Router is an RTR. 1934 B.16. Changes to draft-ietf-lisp-rfc6830bis-04 1936 o Posted July 2017. 1938 o Changed reference of IPv6 RFC2460 to RFC8200. 1940 o Indicate that the applicability statement for UDP zero checksums 1941 over IPv6 adheres to RFC6936. 1943 B.17. Changes to draft-ietf-lisp-rfc6830bis-03 1945 o Posted May 2017. 1947 o Move the control-plane related codepoints in the IANA 1948 Considerations section to RFC6833bis. 1950 B.18. Changes to draft-ietf-lisp-rfc6830bis-02 1952 o Posted April 2017. 1954 o Reflect some editorial comments from Damien Sausez. 1956 B.19. Changes to draft-ietf-lisp-rfc6830bis-01 1958 o Posted March 2017. 1960 o Include references to new RFCs published. 1962 o Change references from RFC6833 to RFC6833bis. 1964 o Clarified LCAF text in the IANA section. 1966 o Remove references to "experimental". 1968 B.20. Changes to draft-ietf-lisp-rfc6830bis-00 1970 o Posted December 2016. 1972 o Created working group document from draft-farinacci-lisp 1973 -rfc6830-00 individual submission. No other changes made. 1975 Authors' Addresses 1977 Dino Farinacci 1978 Cisco Systems 1979 Tasman Drive 1980 San Jose, CA 95134 1981 USA 1983 EMail: farinacci@gmail.com 1985 Vince Fuller 1986 Cisco Systems 1987 Tasman Drive 1988 San Jose, CA 95134 1989 USA 1991 EMail: vince.fuller@gmail.com 1993 Dave Meyer 1994 Cisco Systems 1995 170 Tasman Drive 1996 San Jose, CA 1997 USA 1999 EMail: dmm@1-4-5.net 2001 Darrel Lewis 2002 Cisco Systems 2003 170 Tasman Drive 2004 San Jose, CA 2005 USA 2007 EMail: darlewis@cisco.com 2008 Albert Cabellos 2009 UPC/BarcelonaTech 2010 Campus Nord, C. Jordi Girona 1-3 2011 Barcelona, Catalunya 2012 Spain 2014 EMail: acabello@ac.upc.edu