idnits 2.17.1 draft-ermagan-lisp-nat-traversal-16.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 : ---------------------------------------------------------------------------- == There are 25 instances of lines with non-RFC6890-compliant IPv4 addresses in the document. If these are example addresses, they should be changed. == There are 11 instances of lines with private range IPv4 addresses in the document. If these are generic example addresses, they should be changed to use any of the ranges defined in RFC 6890 (or successor): 192.0.2.x, 198.51.100.x or 203.0.113.x. ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 368: '... nonce SHOULD be generated by a p...' RFC 2119 keyword, line 432: '...n xTR-ID or site-ID, it MUST set the I...' RFC 2119 keyword, line 446: '...-zero value), it MUST copy the XTR-ID ...' RFC 2119 keyword, line 487: '...). A Map-Server MUST set the I bit in...' RFC 2119 keyword, line 534: '...ementations of this specification MUST...' (5 more instances...) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (June 2, 2019) is 1790 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Missing Reference: 'RFC2404' is mentioned on line 535, but not defined == Missing Reference: 'RFC6234' is mentioned on line 536, but not defined == Outdated reference: A later version (-38) exists of draft-ietf-lisp-rfc6830bis-26 == Outdated reference: A later version (-31) exists of draft-ietf-lisp-rfc6833bis-24 ** Obsolete normative reference: RFC 5245 (ref. 'ICE') (Obsoleted by RFC 8445, RFC 8839) ** Obsolete normative reference: RFC 5389 (ref. 'STUN') (Obsoleted by RFC 8489) ** Obsolete normative reference: RFC 5766 (ref. 'TURN') (Obsoleted by RFC 8656) Summary: 4 errors (**), 0 flaws (~~), 7 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group V. Ermagan 3 Internet-Draft Google 4 Intended status: Experimental D. Farinacci 5 Expires: December 4, 2019 lispers.net 6 D. Lewis 7 F. Maino 8 M. Portoles 9 Cisco Systems, Inc. 10 J. Skriver 11 Arista 12 C. White 13 Logicalelegance, Inc. 14 June 2, 2019 16 NAT traversal for LISP 17 draft-ermagan-lisp-nat-traversal-16 19 Abstract 21 This document describes a mechanism for IPv4 NAT traversal for LISP 22 tunnel routers (xTR) and LISP Mobile Nodes (LISP-MN) behind a NAT 23 device. A LISP device both detects the NAT and initializes its 24 state. Forwarding to the LISP device through a NAT is enabled by the 25 LISP Re-encapsulating Tunnel Router (RTR) network element, which acts 26 as an anchor point in the data plane, forwarding traffic from 27 unmodified LISP devices through the NAT. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on December 4, 2019. 46 Copyright Notice 48 Copyright (c) 2019 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 64 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 65 3. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . 5 66 3.1. LISP NAT Traversal Overview . . . . . . . . . . . . . . . 6 67 4. LISP RTR Message Details . . . . . . . . . . . . . . . . . . 7 68 4.1. Info-Request Message . . . . . . . . . . . . . . . . . . 7 69 4.2. LISP Info-Reply . . . . . . . . . . . . . . . . . . . . . 9 70 4.3. LISP Map-Register Message . . . . . . . . . . . . . . . . 10 71 4.4. LISP Map-Notify . . . . . . . . . . . . . . . . . . . . . 11 72 4.5. LISP Data-Map-Notify Message . . . . . . . . . . . . . . 12 73 5. Protocol Operations . . . . . . . . . . . . . . . . . . . . . 14 74 5.1. xTR Processing . . . . . . . . . . . . . . . . . . . . . 14 75 5.1.1. ETR Registration . . . . . . . . . . . . . . . . . . 15 76 5.1.2. Map-Request and Map-Reply Handling . . . . . . . . . 16 77 5.1.3. xTR Sending and Receiving Data . . . . . . . . . . . 17 78 5.2. Map-Server Processing . . . . . . . . . . . . . . . . . . 18 79 5.3. RTR Processing . . . . . . . . . . . . . . . . . . . . . 19 80 5.3.1. RTR Data Forwarding . . . . . . . . . . . . . . . . . 21 81 5.4. Multi-homed xTRs . . . . . . . . . . . . . . . . . . . . 21 82 5.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 22 83 6. Security Considerations . . . . . . . . . . . . . . . . . . . 25 84 6.1. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 26 85 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 86 8. Normative References . . . . . . . . . . . . . . . . . . . . 26 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 89 1. Introduction 91 The Locator/ID Separation Protocol [I-D.ietf-lisp-rfc6830bis] 92 [I-D.ietf-lisp-rfc6833bis]defines a set of functions for 93 encapsulating routers to exchange information used to map from 94 Endpoint Identifiers (EIDs) to routable Routing Locators (RLOCs). 95 The assumption that the LISP Tunnel Routers are reachable at their 96 RLOC breaks when a LISP device is behind a NAT. LISP relies on the 97 xTR being able to receive traffic at its RLOC on destination port 98 4341. However nodes behind a NAT are only reachable through the 99 NAT's public address and in most cases only after the appropriate 100 mapping state is set up in the NAT. Depending on the type of the NAT 101 device, this mapping state may be address and port dependent. In 102 other words, the mapping state in the NAT device may be associated 103 with the 5 tuple that forms a specific flow, preventing incoming 104 traffic from any LISP router other than the one associated with the 5 105 tuple. A NAT traversal mechanism is needed to make the LISP device 106 behind a NAT reachable. 108 This document briefly discusses available NAT traversal options, and 109 then it introduces in detail a NAT traversal mechanism for LISP. Two 110 new LISP control messages - LISP Info-Request and LISP Info-Reply - 111 are introduced in order to detect whether a LISP device is behind a 112 NAT, and discover the global IP address and global ephemeral port 113 used by the NAT to forward LISP packets sent by the LISP device. A 114 new LISP component, the LISP Re-encapsulating Tunnel Router (RTR), 115 acts as a re-encapsulating LISP tunnel router 116 [I-D.ietf-lisp-rfc6830bis] to pass traffic through the NAT, to and 117 from the LISP device. A modification to how the LISP Map-Register 118 messages are sent allows LISP device to initialize NAT state to use 119 the RTR services. This mechanism addresses the scenario where the 120 LISP device is behind the NAT, but the associated Map-Server 121 [I-D.ietf-lisp-rfc6833bis] is on the public side of the NAT. 123 2. Definition of Terms 125 LISP Info-Request: A LISP control message sent by a LISP device to 126 its Map-Server. 128 LISP Info-Reply: A LISP control message sent by a Map Server to a 129 LISP device in response to an Info-Request control message. 131 LISP Re-encapsulating Tunnel Router (RTR): An RTR is a re- 132 encapsulating LISP Router (see [I-D.ietf-lisp-rfc6830bis]). One 133 function that an RTR provides is enabling a LISP device to 134 traverse NATs. 136 LISP Data-Map-Notify: A LISP Map-Notify message encapsulated in a 137 LISP data header. 139 LISP xTR-ID A 128-bit field that, together with a site-ID, can be 140 appended at the end of a Map-Register or Map-Notify message. An 141 xTR-ID is used as a unique identifier of the xTR that is sending 142 the Map-Register and is especially useful for identifying multiple 143 xTRs serving the same site/EID-prefix. A value of all zeros 144 indicate the xTR-ID is unspecified. 146 LISP site-ID A 64-bit field that, together with a xTR-ID, can be 147 appended at the end of a Map-Register or Map-Notify message. A 148 site-ID is used as a unique identifier of a group of xTRs 149 belonging to the same site. A value of 0 indicate the site-ID is 150 unspecified. 152 NAT: "Network Address Translation is a method by which IP addresses 153 are mapped from one address realm to another, providing 154 transparent routing to end hosts". "Traditional NAT would allow 155 hosts within a private network to transparently access hosts in 156 the external network, in most cases. In a traditional NAT, 157 sessions are uni-directional, outbound from the private network." 158 --RFC 2663 [NAT]. Basic NAT and NAPT are two varieties of 159 traditional NAT. 161 Basic NAT: "With Basic NAT, a block of external addresses are set 162 aside for translating addresses of hosts in a private domain as 163 they originate sessions to the external domain. For packets 164 outbound from the private network, the source IP address and 165 related fields such as IP, TCP, UDP and ICMP header checksums are 166 translated. For inbound packets, the destination IP address and 167 the checksums as listed above are translated." --RFC 2663[NAT]. 169 NAPT: "NAPT extends the notion of translation one step further by 170 also translating transport identifier (e.g., TCP and UDP port 171 numbers, ICMP query identifiers). This allows the transport 172 identifiers of a number of private hosts to be multiplexed into 173 the transport identifiers of a single external address. NAPT 174 allows a set of hosts to share a single external address. Note 175 that NAPT can be combined with Basic NAT so that a pool of 176 external addresses are used in conjunction with port translation." 177 --RFC 2663[NAT]. Transport identifiers of the destination hosts 178 are not modified by the NAPT. 180 In this document the general term NAT is used to refer to both Basic 181 NAT and NAPT. 183 While this document specifies LISP NAT Traversal for LISP tunnel 184 routers, a LISP-MN can also use the same procedure for NAT traversal. 185 The modifications attributed to a LISP-Device, xTR, ETR, and ITR must 186 be supported by a LISP-MN where applicable, in order to achieve NAT 187 traversal for such a LISP node. A NAT traversal mechanism for LISP- 188 MN is also proposed in [NAT-MN]. 190 For definitions of other terms, notably Map-Request, Map-Reply, 191 Ingress Tunnel Router (ITR), and Egress Tunnel Router (ETR), please 192 consult the LISP specification [I-D.ietf-lisp-rfc6833bis]. 194 3. Basic Overview 196 There are a variety of NAT devices and a variety of network 197 topologies utilizing NAT devices in deployments. Most NAT devices 198 deployed today are designed primarily around the client/server 199 paradigm, where client machines inside a private network initiate 200 connections to public servers with public IP addresses. As such, any 201 protocol requiring a device or host in a private network behind a NAT 202 to receive packets or accept sessions from destinations without first 203 initiating a session or sending packets towards those destinations, 204 will be challenged by deployed NAT devices. 206 NAT devices are loosely classified based on how restrictive they are. 207 These classifications are essentially identifying the type of mapping 208 state that the NAT device is requiring to allow incoming traffic. 209 For instance, the mapping state may be end-point independent: once 210 device A inside the private network sends traffic to a destination 211 outside, a mapping state in the NAT is created that only includes 212 information about device A, namely its IP address and perhaps its 213 port number. Once this mapping is established in the NAT device, any 214 external device with any IP address could send packets to device A. 215 More restrictive NAT devices could include the 5 tuple information of 216 the flow as part of the mapping state, in other words, the mapping 217 state in the NAT is dependent upon Source IP and Port, as well as 218 destination IP and port (symmetric NAT or Endpoint-dependent NAT). 219 Such a NAT only allows traffic from the specified destination IP and 220 port to reach the specified source device on the specified source 221 port. Traffic with a different 5 tuple signature will not be allowed 222 to pass. In general, in the case of less restrictive NATs it may be 223 possible to eventually establish direct peer-to-peer connections, by 224 means of various hole punching techniques and initial rendezvous 225 servers. However, in the case of symmetric NATs or NATs with 226 endpoint-address-and-port-dependent mappings, direct connection may 227 prove impossible. In such cases a relay device is required that is 228 in the public Network and can relay packets between the two 229 endpoints. 231 Various methods have been designed to address NAT traversal 232 challenges, mostly in the context of peer-to-peer applications and 233 protocols. Among these, the Interactive Connectivity Establishment 234 (ICE) [ICE] seems the most comprehensive, which defines a protocol 235 that leverages other protocols such as Session Traversal Utilities 236 for NAT(STUN) [STUN] and Traversal Using Relays around NAT (TURN) 237 [TURN], as well as a rendezvous server to identify and exchange a 238 list of potential transport (IP and Port) addresses between the two 239 endpoints. All possible pairs of transport addresses are 240 exhaustively tested to find the best possible option for 241 communication, preferring direct connection to connections using a 242 relay. In the case of most restrictive NATs, ICE leads to use of 243 TURN servers as relay for the traffic. TURN requires a list of 244 allowed peer IP addresses defined as permissions, before allowing a 245 peer to use the relay server to reach a TURN client. 247 Common NAT traversal techniques such as ICE generally assume bi- 248 directional traffic with the same 5 tuple. LISP, however, requires 249 traffic to use destination UDP port 4341, without specifying the 250 source port. As a result, LISP traffic is generally uni-directional. 251 This means that, in the case of symmetric or endpoint-address-and- 252 port-dependent mapping NATs, even when an outgoing mapping is 253 established, still incoming traffic may not match the established 254 mapping and will not be allowed to pass. As a result, while ICE may 255 be used to traverse less restrictive NATs, use of standard TURN 256 servers as relays to traverse symmetric NATs for LISP protocol is not 257 possible. The rest of this document specifies a NAT traversal 258 technique for the LISP protocol that enables LISP protocol to 259 traverse multiple types of NATs including symmetric NATs. 261 3.1. LISP NAT Traversal Overview 263 There are two attributes of a LISP device behind a typical NAT that 264 requires special consideration in LISP protocol behavior in order to 265 make the device reachable. First, the RLOC assigned to the device is 266 typically not globally unique nor globally routable. The NAT likely 267 has a restrictive translation table and forwarding policy, requiring 268 outbound packets to create state before the NAT accepts inbound 269 packets. Second, LISP protocol requires an xTR to receive traffic on 270 a specific UDP port 4341, so the random UDP port allocated by the NAT 271 on its public side to associate with a xTR behind the NAT can not be 272 used by other xTRs to send LISP traffic to. This section provides an 273 overview of the LISP NAT traversal mechanism which deals with these 274 conditions. The following sections specify the mechanism in more 275 detail. 277 When a LISP device receives a new RLOC and wants to register it with 278 the mapping system, it needs to first discover whether it is behind a 279 NAT. To do this, an ETR queries its Map-Server to discover the ETR's 280 translated global RLOC and port via the two new LISP messages: Info- 281 Request and Info-Reply. Once an ETR detects that it is behind a NAT, 282 it uses a LISP Re-encapsulating Tunnel Router (RTR) entity as an 283 anchor point for sending and receiving data plane traffic through the 284 NAT device. The ETR registers the RTR RLOC(s) to its Map-Server 285 using the RTR as a proxy for the Map-Register message. The ETR 286 encapsulates the Map-Register message in a LISP ECM header destined 287 to the RTR's RLOC. The RTR strips the LISP ECM header, re-originates 288 the Map-Register message, and sends it to the Map-Server. This 289 initializes state in the NAT device so the ETR can receive traffic on 290 port 4341 from the RTR. The ETR also registers the RTR RLOC as the 291 RLOC where the ETR EID prefix is reachable. As a result, all packets 292 destined to the ETR's EID will go to its RTR. The RTR will then re- 293 encapsulate and forward the ETR's traffic via the existing NAT state 294 to the ETR. 296 Outbound LISP data traffic from the xTR is also encapsulated to the 297 RTR, where the RTR de-capsulates the LISP packets, and then re- 298 encapsulates them or forwards them natively depending on their 299 destination. 301 In the next sections these procedures are discussed in more detail. 303 4. LISP RTR Message Details 305 The main modifications in the LISP protocol to enable LISP NAT 306 traversal via an RTR include: (1) two new messages used for NAT 307 discovery (Info-Request and Info-Reply), and (2) encapsulation of two 308 LISP control messages (Map-Register and Map-Notify) between the xTR 309 and the RTR. Map-Register is encapsulated in an ECM header while 310 Map-Notify is encapsulated in a LISP data header (Data-Map-Notify). 311 This section describes the message formats and details of the Info- 312 Request, Info-Reply, and Data-Map-Notify messages, as well as 313 encapsulation details and minor changes to Map-Register and Map- 314 Notify messages. 316 4.1. Info-Request Message 318 An ETR sends an Info-Request message to its Map-Server in order to 320 1. detect whether there is a NAT on the path to its Map-Server 322 2. obtain a list of RTR RLOCs that can be used for LISP data plane 323 NAT traversal. 325 An Info-Request message is a LISP control message, its source port is 326 chosen by the xTR and its destination port is set to 4342. 328 0 1 2 3 329 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 1 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 |Type=7 |R| Reserved | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | Nonce . . . | 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 | . . . Nonce | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | Key ID | Authentication Data Length | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 ~ Authentication Data ~ 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 341 | TTL | 342 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 343 | Reserved | EID mask-len | EID-prefix-AFI | 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 | EID-prefix | 346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 347 | AFI = 0 | | 348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 LISP Info-Request Message Format 352 Type: 7 (Info-Request) 354 R: R bit indicates this is a reply to an Info-Request (Info- 355 Reply). R bit is set to 0 in an Info-Request. When R bit is set 356 to 0, the AFI field (following the EID-prefix field) must be set 357 to 0. When R bit is set to 1, the packet contents follow the 358 format for an Info-Reply, as described below. 360 Reserved: Must be set to 0 on transmit and must be ignored on 361 receipt. 363 TTL: The time in minutes the recipient of the Info-Reply will 364 store the RTR Information. 366 Nonce: An 8-byte random value created by the sender of the Info- 367 Request. This nonce will be returned in the Info-Reply. The 368 nonce SHOULD be generated by a properly seeded pseudo-random (or 369 strong random) source. 371 Descriptions for other fields can be found in the Map-Register 372 section of [I-D.ietf-lisp-rfc6833bis]. Field descriptions for the 373 LCAF AFI = 0 can be found in the LISP LCAF draft [LCAF] . 375 4.2. LISP Info-Reply 377 When a Map-Server receives an Info-Request message, it responds with 378 an Info-Reply message. The Info-Reply message source port is 4342, 379 and destination port is taken from the source port of the triggering 380 Info-Request. Map-Server fills the NAT LCAF (LCAF Type = 7) fields 381 according to their description. The Map-Server uses AFI=0 for the 382 Private ETR RLOC Address field in the NAT LCAF. 384 0 1 2 3 385 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 1 386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 |Type=7 |R| Reserved | 388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 | Nonce . . . | 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 | . . . Nonce | 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | Key ID | Authentication Data Length | 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 ~ Authentication Data ~ 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 397 | TTL | 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 | Reserved | EID mask-len | EID-prefix-AFI | 400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 401 | EID-prefix | 402 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 403 | | AFI = 16387 | Rsvd1 | Flags | 404 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 405 | | Type = 7 | Rsvd2 | 4 + n | 406 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 407 N | MS UDP Port Number | ETR UDP Port Number | 408 A +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 T | AFI = x | Global ETR RLOC Address ... | 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 L | AFI = x | MS RLOC Address ... | 412 C +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 A | AFI = x | Private ETR RLOC Address ... | 414 F +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 | | AFI = x | RTR RLOC Address 1 ... | 416 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 417 | | AFI = x | RTR RLOC Address n ... | 418 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 LISP Info-Reply Message Format 422 Type: 7 , R = 1, (Info-Reply) 423 The format is similar to the Info-Request message. See Info-Request 424 section for field descriptions. Field descriptions for the NAT LCAF 425 section can be found in the LISP LCAF draft [LCAF] . 427 4.3. LISP Map-Register Message 429 The third bit after the Type field in the Map-Register message is 430 allocated as "I" bit. I bit indicates that a 128 bit xTR-ID and a 64 431 bit site-ID field are present at the end of the Map-Register message. 432 If an xTR is configured with an xTR-ID or site-ID, it MUST set the I 433 bit to 1 and include its xTR-ID and site-ID in the Map-Register 434 messages it generates. If either the xTR-ID or site-ID is not 435 configured an unspecified value is encoded for whichever ID that is 436 not configured. 438 xTR-ID is a 128 bit field at the end of the Map-Register message, 439 starting after the final Record in the message. The xTR-ID is used 440 to identify the intended recipient xTR for a Map-Notify message, 441 especially in the case where a site has more than one xTR. A value 442 of all zeros indicate that an xTR-ID is not specified, though encoded 443 in the message. This is useful in the case where a site-ID is 444 specified, but no xTR-ID is configured. When a Map-Server receives a 445 Map-Register with an xTR-ID specified (I bit set and xTR-ID has a 446 non-zero value), it MUST copy the XTR-ID from the Map-Register to the 447 associated Map-Notify message. When a Map-Server is sending an 448 unsolicited Map-Notify to an xTR to notify the xTR of a change in 449 locators, the Map-Server must include the xTR-ID for the intended 450 recipient xTR, if it has one stored locally. 452 site-ID is a 64 bit field at the end of the Map-Register message, 453 following the xTR-ID. site-ID is used by the Map-Server receiving the 454 Map-Register message to identify which xTRs belong to the same site. 455 A value of 0 indicate that a site-ID is not specified, though encoded 456 in the message. When a Map-Server receives a Map-Register with a 457 site-ID specified (I bit set and site-ID has non-zero value), it must 458 copy the site-ID from the Map-Register to the associated Map-Notify 459 message. When a Map-Server is sending an unsolicited Map-Notify to 460 an xTR to notify the xTR of a change in locators, the Map-Server must 461 include the site-ID for the intended recipient xTR, if it has one 462 stored locally. 464 A LISP device that sends a Map-Register to an RTR must encapsulate 465 the Map-Register message using an Encapsulated Control Message (ECM) 466 [I-D.ietf-lisp-rfc6833bis]. The 6th bit in the ECM LISP header is 467 allocated as the "R" bit. The R bit indicates that the encapsulated 468 Map-Register is to be processed by an RTR. The 7th bit in the ECM 469 header is allocated as the "N" bit. The N bit indicates that this 470 Map-Register is being relayed by an RTR. When an RTR relays the ECM- 471 ed Map-Register to a Map-Server, the N bit must be set to 1. 473 The outer header source RLOC of the ECM is set to the LISP device's 474 local RLOC, and the outer header source port is set to 4341. The 475 outer header destination RLOC and port are set to RTR RLOC and 4342 476 respectively. The inner header source RLOC is set to LISP device's 477 local RLOC, and the inner source port is picked at random. The inner 478 header destination RLOC is set to the xTR's Map-Server RLOC, and 479 inner header destination port is set to 4342. 481 4.4. LISP Map-Notify 483 The first bit after the Type field in a Map-Notify message is 484 allocated as the "I" bit. I bit indicates that a 128 bit xTR-ID and 485 64 bit site-ID field is present at the end of the Map-Notify message, 486 following the final Record in the Map-Notify (See Section 4.3 for 487 details on xTR-ID and site-ID). A Map-Server MUST set the I bit in a 488 Map-Notify and include the xTR-ID and/or site-ID of the intended 489 recipient xTR if the associated Map-Register has an xTR-ID and/or 490 site-ID specified, or when the Map-Server has previously cached an 491 xTR-ID and/or site-ID for the destination xTR. 493 A LISP device that sends a Map-Notify to an RTR must encapsulate the 494 Map-Notify message using an ECM. The 6th bit in the ECM LISP header, 495 allocated as the "R" bit, must be set when the encapsulated Map- 496 Notify is to be processed by an RTR. If the S bit is also set in the 497 Map-Notify ECM header, it indicates that additional MS-RTR 498 authentication data is included after the LISP header in the ECM. If 499 the I bit is also set in the Map-Notify, the xTR-ID and site-ID 500 fields are included in the Map-Notify. If a Map-Server receiving an 501 ECM-ed Map-Register has a shared key associated with the sending RTR, 502 it must generate a Map-Notify message with the S bit in the ECM 503 header set to 1, and with the additional MS-RTR authentication 504 related fields described below. 506 0 1 2 3 507 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 1 508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 | AD Type | Reserved | 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 511 | MS-RTR Key ID | MS-RTR Auth. Data Length | 512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 ~ MS-RTR Authentication Data ~ 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 Changes to LISP Map-Notify Message 518 AD Type: 2 (RTR Authentication Data) 520 MS-RTR Key ID: A configured ID to find the configured Message 521 Authentication Code (MAC) algorithm and key value used for the 522 authentication function. See [I-D.ietf-lisp-rfc6833bis] section 12.5 523 for code point assignments. 525 MS-RTR Authentication Data Length: The length in bytes of the MS-RTR 526 Authentication Data field that follows this field. The length of the 527 Authentication Data field is dependent on the Message Authentication 528 Code (MAC) algorithm used. The length field allows a device that 529 doesn't know the MAC algorithm to correctly parse the packet. 531 MS-RTR Authentication Data: The message digest used from the output 532 of the Message Authentication Code (MAC) algorithm. The entire Map- 533 Notify payload is authenticated. After the MAC is computed, it is 534 placed in this field. Implementations of this specification MUST 535 support HMAC-SHA-1-96 [RFC2404] and SHOULD support HMAC-SHA-256-128 536 [RFC6234]. 538 For a full description of all fields in the Map-Notify message refer 539 to Map-Notify section in [I-D.ietf-lisp-rfc6833bis]. 541 4.5. LISP Data-Map-Notify Message 543 When an RTR receives an ECM-ed Map-Notify message with R bit in the 544 ECM header set to 1, it has to relay the Map-Notify payload to the 545 registering LISP device. After removing the ECM header and 546 processing the Map-Notify message as described in Section 5.3, the 547 RTR encapsulates the Map-Notify in a LISP data header and sends it to 548 the associated LISP device. This Map-Notify inside a LISP data 549 header is referred to as a Data-Map-Notify message. 551 0 1 2 3 552 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 1 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 / | IPv4 or IPv6 Header | 555 OH | (uses RLOC addresses) | 556 \ | | 557 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 558 / | Source Port = 4342 | Dest Port = xxxx | 559 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 560 \ | UDP Length | UDP Checksum | 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 L | LISP Header ~ | 563 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 564 S / | ~ LISP Header | 565 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 / | IPv4 or IPv6 Header | 567 IH | (uses RLOC or EID addresses) | 568 \ | | 569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 570 / | Source Port = 4342 | Dest Port = 4342 | 571 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 \ | UDP Length | UDP Checksum | 573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 574 LCM | LISP Map-Notify Message ~ 575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 577 LISP Data-Map-Notify Message 579 In a Data-Map-Notify, the outer header source RLOC is set to the 580 RTR's RLOC that was used in the associated Map-Register. This is 581 previously cached by the RTR. The outer header source port is set to 582 4342. The outer header destination RLOC and port are filled based on 583 the translated global RLOC and port of the registering LISP device 584 previously stored locally at the RTR. The inner header source 585 address is Map-Server's RLOC, and inner header source port is 4342. 586 The inner header destination address is set to the LISP device's 587 local RLOC also previously cached by the RTR (See Section 5.3 for 588 details.). The inner header destination port is 4342. 590 Since a Data-Map-Notify is a control message encapsulated in a LISP 591 data header, a special Instance ID is used as a signal for the xTR to 592 trigger processing of the control packet inside the data header. The 593 Instance ID value 0xFFFFFF is reserved for this purpose. The 594 Instance ID field in a Data-Map-Notify must be set to 0xFFFFFF. 596 5. Protocol Operations 598 There are two main steps in the NAT traversal procedure. First, the 599 ETR's translated global RLOC must be discovered. Second, the NAT 600 translation table must be primed to accept incoming connections. At 601 the same time, the Map-Server and the RTR must be informed of the 602 ETR's translated global RLOC including the translated ephemeral port 603 number(s) at which the Map-Server and RTR can reach the LISP device. 605 5.1. xTR Processing 607 Upon receiving a new local RLOC, an ETR first has to detect whether 608 the new RLOC is behind a NAT device. For this purpose the ETR sends 609 an Info-Request message to its Map-Server in order to discover the 610 ETR's translated global RLOC as it is visible to the Map-Server. The 611 ETR uses its new local RLOC as the source RLOC of the message. The 612 Map-Server, after authenticating the message, responds with an Info- 613 Reply message. The Map-Server includes the source RLOC and port from 614 the Info-Request message in the Global ETR RLOC Address and ETR UDP 615 Port Number fields of the Info-Reply. The Map Server also includes 616 the destination RLOC and port number of the Info-Request message in 617 the MS RLOC Address and MS UDP Port Number fields of the Info-Reply. 618 In addition, the Map-Server provides a list of RTR RLOCs that the ETR 619 may use in case it needs NAT traversal services. The source port of 620 the Info-Reply is set to 4342 and the destination port is copied from 621 the source port of the triggering Info-Request message. 623 Upon receiving the Info-Reply message, the ETR compares the source 624 RLOC and source port used for the Info-Request message with the 625 Global ETR RLOC Address and ETR UDP Port Number fields of the Info- 626 Reply message. If the two are not identical, the ETR concludes that 627 its new local RLOC is behind a NAT and that it requires an RTR for 628 NAT traversal services in order to be reachable at that RLOC. An ETR 629 behind other statefull devices (e.g. statefull firewalls) may also 630 use an RTR and the procedure specified here for traversing the 631 statefull device. Detecting existence of such devices are beyond 632 scope of this document. 634 It is worth noting that a STUN server can also be used to do NAT 635 detection and to discover the NAT-translated public IP address and 636 port number for the ETR behind NAT. If a STUN server is used, list 637 of RTR devices that can be used by the xTR for NAT traversal must be 638 provisioned to the xTR via other means which are outside the scope of 639 this document. 641 If there is no NAT on the path identified by an info-Request and an 642 Info-Reply, the ETR registers the associated RLOC with its Map-Server 643 as described in [I-D.ietf-lisp-rfc6833bis]. 645 5.1.1. ETR Registration 647 Once an ETR has detected that it is behind a NAT, based on local 648 policy the ETR selects one (or more) RTR(s) from the RTR RLOCs 649 provided in the Info-Reply and initializes state in the NAT device in 650 order to receive LISP data traffic on UDP port 4341 from the selected 651 RTR. To do so, the ETR sends a Map-Register encapsulated in an ECM 652 header to the selected RTR(s). The Map-Register message is created 653 as specified in [I-D.ietf-lisp-rfc6833bis]. More specifically, the 654 source RLOC of the Map-Register is set to ETR's local RLOC, while the 655 destination RLOC is set to the ETR's Map-Server RLOC, and destination 656 port is set to 4342. The ETR sets the M bit (want-Map-Notify) in 657 Map-Register to 1, and it includes the selected RTR RLOC(s) as the 658 locators in the Map-Register message. The ETR can also include its 659 local RLOCs as locators in the Map-Register, including weight and 660 priorities, while setting the R bit to 0 for each local RLOC. This 661 can be used by the RTR for load balancing when forwarding data to a 662 multi-homed xTR behind a NAT. The R bit is set to 1 for all RTR 663 locators included in the Map-Register. The ETR must also set the I 664 bit in the Map-Register message to 1 and include its xTR-ID in t he 665 corresponding field. In the ECM header of this Map-Register the 666 source RLOC is set to ETR's local RLOC and the source port is set to 667 4341, while the destination RLOC is the RTR's RLOC and the 668 destination port is set to LISP control port 4342. The R bit in the 669 ECM header is also set to 1, to indicate that this EDCM-ed Map- 670 Register is to be processed by an RTR. 672 This ECM-ed Map-Register is then sent to the RTR. The RTR removes 673 the ECM header, re-originates the Map-Register message, encapsulates 674 the new Map-Register in a new ECM header with R bit set to 0, and 675 sends it to the associated Map-Server. The RTR then encapsulates the 676 corresponding Map-Notify message in a LISP data header (Data-Map- 677 Notify) and sends it back to the xTR. 679 Upon receiving a Data-Map-Notify from the RTR, the ETR must strip the 680 outer LISP data header, and process the inner Map-Notify message as 681 described in [I-D.ietf-lisp-rfc6833bis]. Since outer header 682 destination port in Data-Map-Notify is set to LISP data port 4341, 683 the Instance ID 0xFFFFFF in the LISP header of the Data-Map-Notify is 684 used by the ETR to detect and process the Data-Map-Notify as a 685 control message encapsulated in a LISP data header. While processing 686 the Data-Map-Notify, the xTR also stores the RTR RLOC(s) as its data 687 plane proxy for the interface/RLOC behind the NAT. 689 If the xTR is not multi-homed, or if all its interfaces are behind 690 the NAT and will use the same RTR, then the xTR MAY map the EID 691 prefix 0/0 to this RTR RLOC(s) in its map-cache. This results in the 692 xTR encapsulating all LISP data plane traffic to this RTR, reducing 693 the state created in the NAT. Note that not installing the default 694 map-cache entry will lead to normal Map-Request and Map-Reply 695 messages for EID mapping lookups. If outgoing traffic is sent 696 directly to destinations without passing through the RTR, this will 697 result in additional state to be created in the NAT device. 699 At this point the registration and state initialization is complete 700 and the xTR can use the RTR services. The state created in the NAT 701 device based on the ECM-ed Map-Register and corresponding Data-Map- 702 Notify is used by the xTR behind the NAT to send and receive LISP 703 control packets to/from the RTR, as well as for receiving LISP data 704 packets form the RTR. 706 If ETR receives a Data-Map-Notify with a xTR-ID specified, but the 707 xTR-ID is not equal to its local xTR-ID, it must log this as an 708 error. The ETR should discard such Data-Map-Notify message. 710 The ETR must periodically send ECM-ed Map-Register messages to its 711 RTR in order to both refresh its registration to the RTR and the Map- 712 Server, and as a keep alive in order to preserve the state in the NAT 713 device. RFC 2663 [NAT] points out that the period for sending the 714 keep alives can be set to default value of two minutes, however since 715 shorter timeouts may exist in some NAT deployments, the interval for 716 sending periodic ECM-ed Map-Registers must be configurable. 718 5.1.2. Map-Request and Map-Reply Handling 720 The ETR is in control of how to handle the Map-Requests and Map- 721 Replies. If the ETR wants the Map-Server to proxy-reply as described 722 in [I-D.ietf-lisp-rfc6833bis], it can register its locators, 723 including the RTR RLOC(s), via the ECM-ed Map-Register message. In 724 this case, if the proxy bit is set in the Map-Register, the Map- 725 Server will proxy reply to all Map-Requests for the ETR. As a result 726 traffic for the ETR can be encapsulated to its RTR(s). 728 If the proxy bit in the ECM-ed Map-Register message is not set, and 729 the ETR chooses to receive Map-Requests, the ETR must also initiate 730 and preserve state in the NAT device to receive LISP control packets 731 from its Map-Server. To do this, the ETR must periodically send 732 Info-Request messages to its Map-Server, and receive Info-Reply 733 messages from the Map-Server. As pointed in RFC 2663 [NAT] the 734 default assumption of two minute period for session lifetime can be 735 used, however since shorter timeouts may exist in some NAT 736 deployments, the interval for sending periodic Info-Requests must be 737 configurable. Furthermore, the ETR must also provide its Map-Server 738 with the ETR's translated global RLOC and port as visible to the Map- 739 Server. To do this, ETR includes a copy of the NAT LCAF section of 740 the Info-Reply message as one of the locators in its Map-Register 741 along with the RTR(s) RLOC(s). The ETR can set the priorities of RTR 742 RLOC(s) in this Map-Register to 255, resulting in the Map Server 743 encapsulating Map-Requests to the ETR's translated global RLOC and 744 port so it can receive them through the NAT device. 746 If an ETR behind a NAT chooses to receive Map-Requests from the Map- 747 Server, it must send Map-Replies to requesting ITRs. Note that this 748 configuration will result in excessive state in the NAT device and is 749 not recommended. ETR must include its RTR RLOC(s) as its locator set 750 in the Map-Reply in order to receive data through the NAT device. 752 When an ITR behind a NAT is encapsulating outbound LISP traffic, it 753 can use its RTR RLOC as the locator for all destination EIDs that it 754 wishes to send data to. As such, the ITR does not need to send Map- 755 Requests for the purpose of finding EID-to-RLOC mappings. However, 756 the ITR can choose to send Map-Requests, specially if the ITR is 757 multihomed, and could use other interfaces not behind the NAT. It 758 should be noted that sending packets directly to destination RLOCs 759 through the interface behind the NAT will result in creating 760 additional state in the NAT device. 762 For RLOC-probing, the periodic ECM-ed Map-Register and Data-Map- 763 Notify messages between xTR and RTR can also serve the purpose of 764 RLOC probes. However, if RLOC-probing is used, no changes are 765 required to the RLOC-probing specification in 766 [I-D.ietf-lisp-rfc6833bis], except that the LISP device behind a NAT 767 only needs to probe the RTR's RLOC. 769 5.1.3. xTR Sending and Receiving Data 771 When a Map-Request for a LISP device behind a NAT is received by its 772 Map-Server or the LISP device itself, the Map-Server, or the LISP 773 device (ETR), responds with a Map-Reply including RTR's RLOC as the 774 locator for the requested EID. As a result, all LISP data traffic 775 destined for the ETR's EID behind the NAT is encapsulated to its RTR. 776 The RTR re-encapsulates the LISP data packets to the ETR's translated 777 global RLOC and port number so the data can pass through the NAT 778 device and reach the ETR. As a result the ETR receives LISP data 779 traffic with outer header destination port set to 4341 as specified 780 in [I-D.ietf-lisp-rfc6830bis]. 782 For sending outbound LISP data, an ITR behind a NAT SHOULD use the 783 RTR RLOC as the locator for all EIDs that it wishes to send data to 784 via the interface behind the NAT. The ITR then encapsulates the LISP 785 traffic in a LISP data header with outer header destination set to 786 RTR RLOC and outer header destination port set to 4341. This may 787 create a secondary state in the NAT device. ITR SHOULD set the outer 788 header source port in all egress LISP data packets to a random but 789 static port number in order to avoid creating excessive state in the 790 NAT device. 792 If the ITR and ETR of a site are not collocated, the RTR RLOC must be 793 configured in the ITR via an out-of-band mechanism. Other procedures 794 specified here would still apply. 796 5.2. Map-Server Processing 798 Upon receiving an Info-Request message a Map-Server first verifies 799 the authenticity of the message. Next the Map-Server creates an 800 Info-Reply message and copies the source RLOC and port number of the 801 Info-Request message to the Global ETR RLOC Address and ETR UDP Port 802 Number fields of the Info-Reply message. The Map-Server also 803 includes a list of RTR RLOCs that the ETR may use for NAT traversal 804 services. The Map-Server sends the Info-Reply message to the ETR, by 805 setting the destination RLOC and port of the Info-Reply to the source 806 RLOC and port of the triggering Info-Request. The Map-Server sets 807 the source port of the Info-Reply to 4342. 809 Upon receiving an ECM-ed Map-Register message with the N bit in the 810 ECM header set to 1, the Map-Server removes the ECM header and if the 811 M bit in the Map-Register is set, the Map-Server processes the Map- 812 Register message and generates the resulting Map-Notify as described 813 in [I-D.ietf-lisp-rfc6833bis]. The Map-Server encapsulates the Map- 814 Notify in an ECM header and sets the R bit in the ECM header to 1. 815 This indicates that the ECM-ed Map-Notify is to be processed by an 816 RTR. If the Map-Server has a shared secret configured with the RTR 817 sending the Map-Register, the Map-Server also sets the S bit in the 818 ECM header of the Map-Notify and includes the MS-RTR authentication 819 data after the ECM LISP header. See Security Considerations 820 Section for more details. If the I bit is set in the Map-Register 821 message, the Map-Server also locally stores the xTR-ID from the Map- 822 Register, and sets the I bit in the corresponding Map-Notify message 823 and includes the same xTR-ID in the Map-Notify. The ECM-ed Map- 824 Notify is then sent to the RTR sending the corresponding Map- 825 Register. 827 If a Map-Server is forwarding Map-Requests to an ETR which has 828 registered its RLOC in a NAT LCAF, Map-Server must use the ETR Global 829 RLOC Address and ETR UDP Port as the destination RLOC and port for 830 outer header of the encapsulated Map-Requests. If more than one NAT 831 LCAF is registered for the same EID prefix, the Map-Server must use 832 the NAT LCAF corresponding to the RLOC of this Map-Server. 834 5.3. RTR Processing 836 Upon receiving an ECM-encapsulated Map-Register with the R bit set in 837 the ECM header, the RTR creates a map-cache entry for the EID-prefix 838 that was specified in the Map-Register message. The RTR stores the 839 outer header source RLOC and outer header source port, the outer 840 header destination RLOC (RTR's own RLOC), the inner header source 841 RLOC (xTR's local RLOC), the xTR-ID, the weight and priority 842 associated with the xTR's local RLOC that was used to send this Map- 843 Register if present, and the nonce field of the Map-Register in this 844 local map-cache entry. The RTR uses the inner header source address 845 to identify which xTR local RLOC (R bit =0) was used by the xTR to 846 send this Map-Register. The outer header source RLOC and outer 847 header source port is the ETR's translated global RLOC and port 848 number visible to the RTR. Once the registration process is 849 complete, this map-cache entry can be used to send LISP data traffic 850 to the ETR. The inner header source RLOC of the Map-Register is the 851 ETR's local RLOC behind the NAT, and the outer header destination 852 RLOC is the RTR's RLOC used by the ETR. The RTR can later use these 853 fields as the inner header destination RLOC and source RLOC 854 correspondingly, for sending data-encapsulated control messages 855 (Data-Map-Notify) back to the ETR. The nonce field is used for 856 security purposes and is matched with the nonce field in the 857 corresponding Map-Notify message. This map-cache entry is stored as 858 an "unverified" mapping, until the corresponding Map-Notify message 859 is received. 861 In the cases where the xTR has multiple RLOCs behind the NAT, and 862 requires the RTR to load balance the traffic across those interfaces, 863 the xTR must include the local RLOCs associated with each interface 864 behind the NAT with the R bit in the locator record set to 0 in the 865 ECM-ed Map-Register sent to the RTR. The RTR uses the weight and 866 priority policies of the RLOCs with R=0 in the Map-Register to load 867 balance the traffic from the RTR to the xTR behind the NAT. The RTR 868 compares the RLOCs with the R bit set to 0 in the Map-Register to the 869 inner header source address of the Map-Register to find the matching 870 RLOC that the xTR used to send the Map-Register from. The RTR 871 associates the weight and priority policies of this local RLOC with 872 the NAT-translated RLOC and xTR-ID for this map-cache entry. For all 873 other local RLOCs included in the Map-Register, that the Map-Register 874 is not originating from, the RTR only updates previously cached 875 weight and priority policies if it already has those local RLOCs 876 previously stored for that EID prefix and xTR-ID. In other words, 877 the RTR only adds new local RLOCs and their weight and priority 878 policies to its cache if the Map-Register is actually originating 879 from that RLOC. The TTL for every map-cache is also only updated 880 when a Map-Register is originating from the same RLOC. However, the 881 weight and priorities of all previously cached local RLOCs will be 882 updated by every Map-Register, whether it is originating from that 883 RLOC or not. The xTR-ID is used to define the Merge domain for these 884 RLOCs. In other words, a Map-Register originating from a unique xTR- 885 ID will always overwrite previously stored policies for that xTR-ID. 886 However it does not modify in any way the policies indicated by any 887 other xTR-ID serving the same EID prefix. As a result, in the case 888 of a renumbering or xTR reboot, the xTR uses its unique xTR-ID to 889 send a new Map-Register, overwriting the previously stored policies 890 for that xTR. Using this method the xTR can immediately remove any 891 RLOCs from the RTR cache that are no longer active. In order to 892 implement this, the RTR must compare the list of local RLOCs in the 893 Map-Register (R=0) with the ones it has previously cached associated 894 with the same xTR-ID. If there is any RLOC previously cached that 895 does not appear in the newly received Map-Register, the RTR must 896 remove that RLOC together with the associated translated RLOC and 897 associated policies, because removal of a local (behind-the-NAT) RLOC 898 also invalidates the NAT-ed address associated with it. . 900 After filling the local map-cache entry, the RTR strips the outer 901 header and extracts the Map-Register message, re-originates the 902 message by rewriting the source RLOC of the Map-Register to RTR's 903 RLOC, encapsulated in a new ECM header with the R bit set to 0, and N 904 bit set to 1, and sends the ECM-ed Map-Register to destination Map- 905 Server. 907 Map-Server responds with a ECM-ed Map-Notify message to the RTR. 909 Upon receiving an ECM-ed Map-Notify message with R bit set to 1 in 910 the ECM header, if the S bit in ECM header is set to 1, RTR uses the 911 MS-RTR Key ID to verify the MS-RTR Authentication Data included after 912 the ECM header. If the MS-RTR authentication fails, the RTR must 913 drop the packet. Once the authenticity of the message is verified, 914 RTR can confirm that the Map-Register message for the ETR with the 915 matching xTR-ID was accepted by the Map-Server. At this point the 916 RTR can change the state of the associated map-cache entry to 917 verified for the duration of the Map-Register TTL. 919 The RTR then uses the information in the associated map-cache entry 920 to create a Data-Map-Notify message according to the following 921 procedure: RTR rewrites the inner header destination RLOC of the Map- 922 Notify message to ETR's local RLOC. Inner header destination port is 923 4342. The RTR encapsulates the Map-Notify in a LISP data header, 924 where the outer header destination RLOC and port number are set to 925 the ETR's translated global RLOC and port number. If more than one 926 ETR translated RLOC and port exists in the map-cache entry for the 927 same EID prefix specified in the Map-Notify, the RTR can use the xTR- 928 ID from the Map-Notify to identify which ETR is the correct 929 destination for the Data-Map-Notify. The RTR sets the outer header 930 source RLOC to RTR's RLOC from the map-cache entry and the outer 931 header source port is set to 4342. The RTR also sets the Instance ID 932 field in the LISP header of the Data-Map-Notify to 0xFFFFFF. The RTR 933 then sends the Data-Map-Notify to the ETR. 935 If the S bit is set to 0 in the ECM header of the Map-Notify, and the 936 RTR has a shared key configured locally with the sending Map-Server, 937 the RTR must drop the packet. If the S bit is set to 0, and the RTR 938 does not have a shared key configured with the associated Map-Server, 939 according to local policy, the RTR may drop the packet. If the Map- 940 Notify with S bit set to 0 is processed, the RTR must match the nonce 941 field from this Map-Notify with the nonce stored in the local map- 942 cache entry with the matching xTR-ID. If the nonces do not match, 943 the RTR must drop the packet. 945 5.3.1. RTR Data Forwarding 947 For all LISP data packets encapsulated to RTR's RLOC and outer header 948 destination port 4341, the RTR first verifies whether the source or 949 destination EID is a previously registered EID. If so, the RTR must 950 process the packet according to the following. If the destination or 951 source EID is not a registered EID, the RTR can drop or process the 952 packets based on local policy. 954 In the case where the destination EID is a previously registered EID, 955 the RTR must strip the LISP data header and re-encapsulate the packet 956 in a new LISP data header. The outer header RLOCs and UDP ports are 957 then filled based on the matching map-cache entry for the associated 958 destination EID prefix. The RTR uses the RTR RLOC from the map-cache 959 entry as the outer header source RLOC. The outer header source port 960 is set to 4342. The RTR sets the outer header destination RLOC and 961 outer header destination port based on the ETR translated global RLOC 962 and port stored in the map-cache entry. Then the RTR forwards the 963 LISP data packet. 965 In the case where the source EID is a previously registered EID, the 966 RTR process the packet as if it is a Proxy ETR (PETR). The RTR must 967 strip the LISP data header, and process the packet based on its inner 968 header destination address. The packet may be forwarded natively, it 969 may be LISP encapsulated to the destination ETR, or it may trigger 970 the RTR to send a LISP Map-Request. 972 5.4. Multi-homed xTRs 974 In the case where an xTR has multiple interfaces and RLOCs, info- 975 Requests can be sent per each interface and NAT discovery is done per 976 each interface. NAT traversal is accomplished by following state and 977 processes described above per each interface/RLOC. In other words, 978 if multiple interfaces of an xTR are behind a NAT, the ECM-ed Map- 979 Register messages should be sent via each xTR interface behind NAT if 980 the xTR desires to receive traffic via that interface. This is 981 required to establish the state in the NAT device for that interface. 982 The M bit (want Map-Notify) must be set in ECM-ed Map-Register 983 messages sent from at least one of xTR interfaces behind the NAT. If 984 additional interfaces behind the NAT are using the same RTR for NAT 985 traversal, no Map-Notify processing is required for such interfaces 986 and M bit in Map-Register can be set to 0 for these to reduce 987 processing on the RTR and the Map-Server. 989 The RLOCs included in Map-Register messages when the xTR has multiple 990 interfaces SHOULD be the union of the locators (behind NAT or not) 991 resulting from the process defined above per each RLOC of the xTR, 992 according to the specifics of that interface (whether it is behind 993 the NAT or not). 995 In cases where some xTR interfaces are behind NAT while others are 996 not, ECM-ed Map-Register messages should be sent via interfaces 997 behind the NAT through the selected RTRs. xTR can receive traffic via 998 both types of interfaces by including the associated RLOCs (as well 999 as the RTR RLOCs) in its ECM-ed Map-Register messages. 1001 5.5. Example 1003 What follows is an example of an ETR initiating a registration of a 1004 new RLOC to its Map-Server, when there is a NAT device on the path 1005 between the ETR and the Map-Server. 1007 In this example, the ETR (site1-ETR) is configured with the local 1008 RLOC of 192.168.1.2. The NAT's global (external) addresses are from 1009 2.0.0.1/24 prefix. The Map-Server is at 3.0.0.1. And one potential 1010 RTR has an IP address of 1.0.0.1. The site1-ETR has an EID Prefix of 1011 128.1.0.0/16. 1013 An example of the registration process follows: 1015 1. The Site1-ETR receives the private IP address, 192.168.1.2 as 1016 its RLOC via DHCP. 1018 2. The Site1-ETR sends an Info-Request message with the destination 1019 RLOC of the Map-Server, 3.0.0.1, and source RLOC of 192.168.1.2. 1020 This packet has the destination port set to 4342 and the source 1021 port is set to (for example) 5001. 1023 3. The NAT device translates the source IP from 192.168.1.2 to 1024 2.0.0.1, and source port to (for example) 20001 global ephemeral 1025 source port. 1027 4. The Map-Server receives and responds to this Info-Request with 1028 an Info-Reply message. This Info-Reply has the destination 1029 address set to ETR's translated address of 2.0.0.1 and the 1030 source address is the Map-Server's RLOC, namely 3.0.0.1. The 1031 destination port is 20001 and the source port is 4342. Map- 1032 Server includes a copy of the source address and port of the 1033 Info-Request message (2.0.0.1:20001), and a list of RTR RLOCs 1034 including RTR RLOC 1.0.0.1 in the Info-Reply contents. 1036 5. The NAT translates the Info-Reply packet's destination IP from 1037 2.0.0.1 to 192.168.1.2, and translates the destination port from 1038 20001 to 5001, and forwards the Info-Reply to site1-ETR at 1039 192.168.1.2. 1041 6. The Site1-ETR detects that it is behind a NAT by comparing its 1042 local RLOC (192.168.1.2) with the Global ETR RLOC Address in the 1043 Info-Reply (2.0.0.2) . Then site1-ETR picks the RTR 1.0.0.1 from 1044 the list of RTR RLOCs in the Info-Reply. ETR stores the RTR 1045 RLOC in a default map-cache entry to periodically send ECM-ed 1046 Map-Registers to. 1048 7. The ETR sends an ECM encapsulated Map-Register to RTR at 1049 1.0.0.1. The outer header source RLOC of this Map-Register is 1050 set to 192.168.1.2 and the outer header source port is set to 1051 4341. The outer header destination RLOC and port are set to RTR 1052 RLOC at 1.0.0.1 and 4342 respectively. The R bit in ECM header 1053 is set to 1. The inner header destination RLOC is set to ETR's 1054 Map-Server 3.0.0.1, and the inner header destination port is set 1055 to 4342. The inner header source RLOC is set to ETR's local 1056 RLOC 192.168.1.2. In the Map-Register message the RTR RLOC 1057 1.0.0.1 appears as the locator set for the ETR's EID prefix 1058 (128.1.0.0/16). In this example ETR also sets the Proxy bit in 1059 the Map-Register to 1, and sets I bit to 1, and includes its 1060 xTR-ID in the Map-Register. 1062 8. The NAT translates the source RLOC in the ECM header of the Map- 1063 Register, by changing it from 192.168.1.2 to 2.0.0.2, and 1064 translates the source port in the ECM header from 4341 to (for 1065 example) 20002, and forwards the Map-Register to RTR. 1067 9. The RTR receives the Map-Register and creates a map-cache entry 1068 with the ETR's xTR-ID, EID prefix, and the source RLOC and port 1069 of the ECM header of the Map-Register as the locator 1070 (128.1.0.0/16 is mapped to 2.0.0.2:20002). RTR also caches the 1071 inner header source RLOC of the Map-Register namely 192.168.1.2, 1072 and the outer header destination RLOC of the ECM header in the 1073 Map-Register (this would be RTR's RLOC 1.0.0.1 ) to use for 1074 sending back a Data-Map-Notify. RTR then removes the outer 1075 header, re-writes the source RLOC of the Map-Register message to 1076 its own RLOC 1.0.0.1, adds a new ECM header with R=0, and N=1, 1077 and forwards the Map-Register to the destination Map-Server. 1079 10. The Map-Server receives the ECM-ed Map-Register with N bit set 1080 to 1, removes the ECM header, and processes it according to 1081 [I-D.ietf-lisp-rfc6833bis]. Since Map-Server has a shared 1082 secret with the sending RTR, after registering the ETR, Map- 1083 Server responds with a ECM-ed Map-Notify with the R bit and S 1084 bit both set to 1 in the ECM header and including the MS-RTR 1085 authentication data. Since the I bit is set in the Map- 1086 Register, the Map-Server also sets the I bit in the Map-Notify 1087 and copies the xTR-ID from the Map-Register to the Map-Notify. 1088 The source address of this Map-Notify is set to 3.0.0.1. The 1089 destination is RTR 1.0.0.1, and both source and destination 1090 ports are set to 4342. 1092 11. The RTR receives the ECM-ed Map-Notify and verifies the MS-RTR 1093 authentication data. The RTR data-encapsulates the Map-Notify 1094 and sends the resulting Data-Map-Notify to site1-ETR with a 1095 matching xTR-ID. The outer header source RLOC and port of the 1096 Data-Map-Notify are set to 1.0.0.1:4342. The outer header 1097 destination RLOC and port are retrieved from previously cached 1098 map-cache entry in step 9 namely 2.0.0.2:20002. RTR also sets 1099 the inner header destination address to site1-ETR's local 1100 address namely 192.168.1.2. RTR sets the Instance ID in the 1101 LISP header to 0xFFFFFF. At this point RTR marks ETR's EID 1102 prefix as "Registered" status and forwards the Data-Map-Notify 1103 to ETR. 1105 12. The NAT device translates the destination RLOC and port of the 1106 Data-Map-Notify to 192.168.1.2:4341 and forwards the packet to 1107 ETR. 1109 13. The Site1-ETR receives the packet with a destination port 4341, 1110 and processes the packet as a control packet after observing the 1111 Instance ID value 0xFFFFFF in the LISP header. At this point 1112 ETR's registration to the RTR is complete. 1114 Assume a requesting ITR in a second LISP (site2-ITR) site has an RLOC 1115 of 74.0.0.1. The following is an example process of an EID behind 1116 site2-ITR sending a data packet to an EID behind the site1-ETR: 1118 1. The ITR sends a Map-Request which arrives via the LISP mapping 1119 system to the ETR's Map Server. 1121 2. The Map-Server sends a Map-Reply on behalf of the ETR, using the 1122 RTR's RLOC (1.0.0.1) in the Map-Reply's Locator Set. 1124 3. The ITR encapsulates a LISP data packet with ITR's local RLOC 1125 (74.0.0.1) as the source RLOC and the RTR as the destination RLOC 1126 (1.0.0.1) in the outer header. 1128 4. The RTR decapsulates the packet, evaluates the inner header 1129 against its map-cache and then re-encapsulates the packet. The 1130 new outer header's source RLOC is the RTR's RLOC 1.0.0.1 and the 1131 new outer header's destination RLOC is the Global NAT address 1132 2.0.0.2. The destination port of the packet is set to 20002 1133 (discovered above during the registration phase) and the source 1134 port is 4342. 1136 5. The NAT translates the LISP data packet's destination IP from to 1137 2.0.0.2 to 192.168.1.2, and translates the destination port from 1138 20002 to 4341, and forwards the LISP data packet to the ETR at 1139 192.168.1.2. 1141 6. For the reverse path the ITR uses its local map-cache entry with 1142 the RTR RLOC as the default locator and encapsulates the LISP 1143 data packets using RTR RLOC, and 4341 as destination RLOC and 1144 port. The ITR must pick a random source port to use for all 1145 outbound LISP data traffic in order to avoid creating excessive 1146 state in the NAT. 1148 6. Security Considerations 1150 By having the RTR relay the ECM-ed Map-Register message from an ETR 1151 to its Map-Server, the RTR can restrict access to the RTR services, 1152 only to those ETRs that are registered with a given Map-Server. To 1153 do so, the RTR and the Map-Server may be configured with a shared key 1154 that is used to authenticate the origin and to protect the integrity 1155 of the Map-Notify messages sent by the Map Server to the RTR. This 1156 prevents an on-path attacker from impersonating the Map-Server to the 1157 RTR, and allows the RTR to cryptographically verify that the ETR is 1158 properly registered with the Map-Server. 1160 Having the RTR re-encapsulate traffic only when the source or the 1161 destination are registered EIDs, protects against the adverse use of 1162 an RTR for EID spoofing. 1164 Upon receiving a Data-Map-Notify, an xTR can authenticate the origin 1165 of the Map-Notify message using the key that the ETR shares with the 1166 Map-Server. This enables the ETR to verify that the ECM-ed Map- 1167 Register was indeed forwarded by the RTR to the Map-Server, and was 1168 accepted by the Map-Server. 1170 6.1. Acknowledgments 1172 The authors would like to thank Noel Chiappa, Alberto Rodriguez 1173 Natal, Lorand Jakab, Albert Cabellos, Dominik Klein, Matthias 1174 Hartmann, and Michael Menth for their previous work, feedback and 1175 helpful suggestions. 1177 7. IANA Considerations 1179 This document does not request any IANA actions. 1181 8. Normative References 1183 [I-D.ietf-lisp-rfc6830bis] 1184 Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A. 1185 Cabellos-Aparicio, "The Locator/ID Separation Protocol 1186 (LISP)", draft-ietf-lisp-rfc6830bis-26 (work in progress), 1187 November 2018. 1189 [I-D.ietf-lisp-rfc6833bis] 1190 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1191 "Locator/ID Separation Protocol (LISP) Control-Plane", 1192 draft-ietf-lisp-rfc6833bis-24 (work in progress), February 1193 2019. 1195 [ICE] Rosenberg, J., "Interactive Connectivity Establishment 1196 (ICE)", RFC rfc5245, October 2008. 1198 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1199 Address Format (LCAF)", RFC 8060, December 2015. 1201 [NAT] Srisuresh, P. and M. Holdrege, "IP Network Address 1202 Translator (NAT) Terminology and Considerations", RFC 1203 2663, August 1999. 1205 [NAT-MN] Klein, D., Hartmann, M., and M. Menth, "NAT traversal for 1206 LISP mobile node, In Proceedings of the Re-Architecting 1207 the Internet Workshop (ReARCH '10).", 2010. 1209 [STUN] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, 1210 "Session Traversal Utilities for NAT (STUN)", RFC rfc5389, 1211 October 2008. 1213 [TURN] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using 1214 Relays around NAT (TURN)", RFC rfc5766, April 2010. 1216 Authors' Addresses 1218 Vina Ermagan 1219 Google 1221 Email: ermagan@gmail.com 1223 Dino Farinacci 1224 lispers.net 1226 Email: farinacci@gmail.com 1228 Darrel Lewis 1229 Cisco Systems, Inc. 1231 Email: darlewis@cisco.com 1233 Fabio Maino 1234 Cisco Systems, Inc. 1236 Email: fmaino@cisco.com 1238 Marc Portoles Comeras 1239 Cisco Systems, Inc. 1241 Email: mportole@cisco.com 1243 Jesper Skriver 1244 Arista 1246 Email: jesper@skrever.dk 1248 Chris White 1249 Logicalelegance, Inc. 1251 Email: chris@logicalelegance.com