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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 364: '... nonce SHOULD be generated by a p...' RFC 2119 keyword, line 428: '...n xTR-ID or site-ID, it MUST set the I...' RFC 2119 keyword, line 442: '...-zero value), it MUST copy the XTR-ID ...' RFC 2119 keyword, line 483: '...). A Map-Server MUST set the I bit in...' RFC 2119 keyword, line 530: '...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 (February 20, 2016) is 2981 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Missing Reference: 'RFC2404' is mentioned on line 531, but not defined == Missing Reference: 'RFC6234' is mentioned on line 532, but not defined == Unused Reference: 'RFC1918' is defined on line 1192, but no explicit reference was found in the text == Unused Reference: 'RFC4632' is defined on line 1197, but no explicit reference was found in the text ** Obsolete normative reference: RFC 5245 (ref. 'ICE') (Obsoleted by RFC 8445, RFC 8839) == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-10 ** Obsolete normative reference: RFC 6830 (ref. 'LISP') (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 6833 (ref. 'LISP-MS') (Obsoleted by RFC 9301) ** Obsolete normative reference: RFC 5389 (ref. 'STUN') (Obsoleted by RFC 8489) ** Obsolete normative reference: RFC 5766 (ref. 'TURN') (Obsoleted by RFC 8656) Summary: 6 errors (**), 0 flaws (~~), 8 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 Cisco Systems, Inc. 4 Intended status: Experimental D. Farinacci 5 Expires: August 23, 2016 lispers.net 6 D. Lewis 7 J. Skriver 8 F. Maino 9 Cisco Systems, Inc. 10 C. White 11 Logicalelegance, Inc. 12 February 20, 2016 14 NAT traversal for LISP 15 draft-ermagan-lisp-nat-traversal-09.txt 17 Abstract 19 This document describes a mechanism for IPv4 NAT traversal for LISP 20 tunnel routers (xTR) and LISP Mobile Nodes (LISP-MN) behind a NAT 21 device. A LISP device both detects the NAT and initializes its 22 state. Forwarding to the LISP device through a NAT is enabled by the 23 LISP Re-encapsulating Tunnel Router (RTR) network element, which acts 24 as an anchor point in the data plane, forwarding traffic from 25 unmodified LISP devices through the NAT. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on August 23, 2016. 44 Copyright Notice 46 Copyright (c) 2016 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 63 3. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . 5 64 3.1. LISP NAT Traversal Overview . . . . . . . . . . . . . . . 6 65 4. LISP RTR Message Details . . . . . . . . . . . . . . . . . . 7 66 4.1. Info-Request Message . . . . . . . . . . . . . . . . . . 7 67 4.2. LISP Info-Reply . . . . . . . . . . . . . . . . . . . . . 9 68 4.3. LISP Map-Register Message . . . . . . . . . . . . . . . . 10 69 4.4. LISP Map-Notify . . . . . . . . . . . . . . . . . . . . . 11 70 4.5. LISP Data-Map-Notify Message . . . . . . . . . . . . . . 12 71 5. Protocol Operations . . . . . . . . . . . . . . . . . . . . . 14 72 5.1. xTR Processing . . . . . . . . . . . . . . . . . . . . . 14 73 5.1.1. ETR Registration . . . . . . . . . . . . . . . . . . 15 74 5.1.2. Map-Request and Map-Reply Handling . . . . . . . . . 16 75 5.1.3. xTR Sending and Receiving Data . . . . . . . . . . . 17 76 5.2. Map-Server Processing . . . . . . . . . . . . . . . . . . 18 77 5.3. RTR Processing . . . . . . . . . . . . . . . . . . . . . 18 78 5.3.1. RTR Data Forwarding . . . . . . . . . . . . . . . . . 21 79 5.4. Multi-homed xTRs . . . . . . . . . . . . . . . . . . . . 21 80 5.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 22 81 6. Security Considerations . . . . . . . . . . . . . . . . . . . 25 82 6.1. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 25 83 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 84 8. Normative References . . . . . . . . . . . . . . . . . . . . 26 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 87 1. Introduction 89 The Locator/ID Separation Protocol [LISP] defines a set of functions 90 for encapsulating routers to exchange information used to map from 91 Endpoint Identifiers (EIDs) to routable Routing Locators (RLOCs). 92 The assumption that the LISP Tunnel Routers are reachable at their 93 RLOC breaks when a LISP device is behind a NAT. LISP relies on the 94 xTR being able to receive traffic at its RLOC on destination port 95 4341. However nodes behind a NAT are only reachable through the 96 NAT's public address and in most cases only after the appropriate 97 mapping state is set up in the NAT. Depending on the type of the NAT 98 device, this mapping state may be address and port dependent. In 99 other words, the mapping state in the NAT device may be associated 100 with the 5 tuple that forms a specific flow, preventing incoming 101 traffic from any LISP router other than the one associated with the 5 102 tuple. A NAT traversal mechanism is needed to make the LISP device 103 behind a NAT reachable. 105 This document briefly discusses available NAT traversal options, and 106 then it introduces in detail a NAT traversal mechanism for LISP. Two 107 new LISP control messages - LISP Info-Request and LISP Info-Reply - 108 are introduced in order to detect whether a LISP device is behind a 109 NAT, and discover the global IP address and global ephemeral port 110 used by the NAT to forward LISP packets sent by the LISP device. A 111 new LISP component, the LISP Re-encapsulating Tunnel Router (RTR), 112 acts as a re-encapsulating LISP tunnel router [LISP] to pass traffic 113 through the NAT, to and from the LISP device. A modification to how 114 the LISP Map-Register messages are sent allows LISP device to 115 initialize NAT state to use the RTR services. This mechanism 116 addresses the scenario where the LISP device is behind the NAT, but 117 the associated Map-Server [LISP-MS] is on the public side of the NAT. 119 2. Definition of Terms 121 LISP Info-Request: A LISP control message sent by a LISP device to 122 its Map-Server. 124 LISP Info-Reply: A LISP control message sent by a Map Server to a 125 LISP device in response to an Info-Request control message. 127 LISP Re-encapsulating Tunnel Router (RTR): An RTR is a re- 128 encapsulating LISP Router (see section 8 of the main LISP 129 specification) [LISP]. One function that an RTR provides is 130 enabling a LISP device to traverse NATs. 132 LISP Data-Map-Notify: A LISP Map-Notify message encapsulated in a 133 LISP data header. 135 LISP xTR-ID A 128-bit field that, together with a site-ID, can be 136 appended at the end of a Map-Register or Map-Notify message. An 137 xTR-ID is used as a unique identifier of the xTR that is sending 138 the Map-Register and is especially useful for identifying multiple 139 xTRs serving the same site/EID-prefix. A value of all zeros 140 indicate the xTR-ID is unspecified. 142 LISP site-ID A 64-bit field that, together with a xTR-ID, can be 143 appended at the end of a Map-Register or Map-Notify message. A 144 site-ID is used as a unique identifier of a group of xTRs 145 belonging to the same site. A value of 0 indicate the site-ID is 146 unspecified. 148 NAT: "Network Address Translation is a method by which IP addresses 149 are mapped from one address realm to another, providing 150 transparent routing to end hosts". "Traditional NAT would allow 151 hosts within a private network to transparently access hosts in 152 the external network, in most cases. In a traditional NAT, 153 sessions are uni-directional, outbound from the private network." 154 --RFC 2663 [NAT]. Basic NAT and NAPT are two varieties of 155 traditional NAT. 157 Basic NAT: "With Basic NAT, a block of external addresses are set 158 aside for translating addresses of hosts in a private domain as 159 they originate sessions to the external domain. For packets 160 outbound from the private network, the source IP address and 161 related fields such as IP, TCP, UDP and ICMP header checksums are 162 translated. For inbound packets, the destination IP address and 163 the checksums as listed above are translated." --RFC 2663[NAT]. 165 NAPT: "NAPT extends the notion of translation one step further by 166 also translating transport identifier (e.g., TCP and UDP port 167 numbers, ICMP query identifiers). This allows the transport 168 identifiers of a number of private hosts to be multiplexed into 169 the transport identifiers of a single external address. NAPT 170 allows a set of hosts to share a single external address. Note 171 that NAPT can be combined with Basic NAT so that a pool of 172 external addresses are used in conjunction with port translation." 173 --RFC 2663[NAT]. Transport identifiers of the destination hosts 174 are not modified by the NAPT. 176 In this document the general term NAT is used to refer to both Basic 177 NAT and NAPT. 179 While this document specifies LISP NAT Traversal for LISP tunnel 180 routers, a LISP-MN can also use the same procedure for NAT traversal. 181 The modifications attributed to a LISP-Device, xTR, ETR, and ITR must 182 be supported by a LISP-MN where applicable, in order to achieve NAT 183 traversal for such a LISP node. A NAT traversal mechanism for LISP- 184 MN is also proposed in [NAT-MN]. 186 For definitions of other terms, notably Map-Request, Map-Reply, 187 Ingress Tunnel Router (ITR), and Egress Tunnel Router (ETR), please 188 consult the LISP specification [LISP]. 190 3. Basic Overview 192 There are a variety of NAT devices and a variety of network 193 topologies utilizing NAT devices in deployments. Most NAT devices 194 deployed today are designed primarily around the client/server 195 paradigm, where client machines inside a private network initiate 196 connections to public servers with public IP addresses. As such, any 197 protocol requiring a device or host in a private network behind a NAT 198 to receive packets or accept sessions from destinations without first 199 initiating a session or sending packets towards those destinations, 200 will be challenged by deployed NAT devices. 202 NAT devices are loosely classified based on how restrictive they are. 203 These classifications are essentially identifying the type of mapping 204 state that the NAT device is requiring to allow incoming traffic. 205 For instance, the mapping state may be end-point independent: once 206 device A inside the private network sends traffic to a destination 207 outside, a mapping state in the NAT is created that only includes 208 information about device A, namely its IP address and perhaps its 209 port number. Once this mapping is established in the NAT device, any 210 external device with any IP address could send packets to device A. 211 More restrictive NAT devices could include the 5 tuple information of 212 the flow as part of the mapping state, in other words, the mapping 213 state in the NAT is dependent upon Source IP and Port, as well as 214 destination IP and port (symmetric NAT or Endpoint-dependent NAT). 215 Such a NAT only allows traffic from the specified destination IP and 216 port to reach the specified source device on the specified source 217 port. Traffic with a different 5 tuple signature will not be allowed 218 to pass. In general, in the case of less restrictive NATs it may be 219 possible to eventually establish direct peer-to-peer connections, by 220 means of various hole punching techniques and initial rendezvous 221 servers. However, in the case of symmetric NATs or NATs with 222 endpoint-address-and-port-dependent mappings, direct connection may 223 prove impossible. In such cases a relay device is required that is 224 in the public Network and can relay packets between the two 225 endpoints. 227 Various methods have been designed to address NAT traversal 228 challenges, mostly in the context of peer-to-peer applications and 229 protocols. Among these, the Interactive Connectivity Establishment 230 (ICE) [ICE] seems the most comprehensive, which defines a protocol 231 that leverages other protocols such as Session Traversal Utilities 232 for NAT(STUN) [STUN] and Traversal Using Relays around NAT (TURN) 233 [TURN], as well as a rendezvous server to identify and exchange a 234 list of potential transport (IP and Port) addresses between the two 235 endpoints. All possible pairs of transport addresses are 236 exhaustively tested to find the best possible option for 237 communication, preferring direct connection to connections using a 238 relay. In the case of most restrictive NATs, ICE leads to use of 239 TURN servers as relay for the traffic. TURN requires a list of 240 allowed peer IP addresses defined as permissions, before allowing a 241 peer to use the relay server to reach a TURN client. 243 Common NAT traversal techniques such as ICE generally assume bi- 244 directional traffic with the same 5 tuple. LISP, however, requires 245 traffic to use destination UDP port 4341, without specifying the 246 source port. As a result, LISP traffic is generally uni-directional. 247 This means that, in the case of symmetric or endpoint-address-and- 248 port-dependent mapping NATs, even when an outgoing mapping is 249 established, still incoming traffic may not match the established 250 mapping and will not be allowed to pass. As a result, while ICE may 251 be used to traverse less restrictive NATs, use of standard TURN 252 servers as relays to traverse symmetric NATs for LISP protocol is not 253 possible. The rest of this document specifies a NAT traversal 254 technique for the LISP protocol that enables LISP protocol to 255 traverse multiple types of NATs including symmetric NATs. 257 3.1. LISP NAT Traversal Overview 259 There are two attributes of a LISP device behind a typical NAT that 260 requires special consideration in LISP protocol behavior in order to 261 make the device reachable. First, the RLOC assigned to the device is 262 typically not globally unique nor globally routable. The NAT likely 263 has a restrictive translation table and forwarding policy, requiring 264 outbound packets to create state before the NAT accepts inbound 265 packets. Second, LISP protocol requires an xTR to receive traffic on 266 a specific UDP port 4341, so the random UDP port allocated by the NAT 267 on its public side to associate with a xTR behind the NAT can not be 268 used by other xTRs to send LISP traffic to. This section provides an 269 overview of the LISP NAT traversal mechanism which deals with these 270 conditions. The following sections specify the mechanism in more 271 detail. 273 When a LISP device receives a new RLOC and wants to register it with 274 the mapping system, it needs to first discover whether it is behind a 275 NAT. To do this, an ETR queries its Map-Server to discover the ETR's 276 translated global RLOC and port via the two new LISP messages: Info- 277 Request and Info-Reply. Once an ETR detects that it is behind a NAT, 278 it uses a LISP Re-encapsulating Tunnel Router (RTR) entity as an 279 anchor point for sending and receiving data plane traffic through the 280 NAT device. The ETR registers the RTR RLOC(s) to its Map-Server 281 using the RTR as a proxy for the Map-Register message. The ETR 282 encapsulates the Map-Register message in a LISP ECM header destined 283 to the RTR's RLOC. The RTR strips the LISP ECM header, re-originates 284 the Map-Register message, and sends it to the Map-Server. This 285 initializes state in the NAT device so the ETR can receive traffic on 286 port 4341 from the RTR. The ETR also registers the RTR RLOC as the 287 RLOC where the ETR EID prefix is reachable. As a result, all packets 288 destined to the ETR's EID will go to its RTR. The RTR will then re- 289 encapsulate and forward the ETR's traffic via the existing NAT state 290 to the ETR. 292 Outbound LISP data traffic from the xTR is also encapsulated to the 293 RTR, where the RTR de-capsulates the LISP packets, and then re- 294 encapsulates them or forwards them natively depending on their 295 destination. 297 In the next sections these procedures are discussed in more detail. 299 4. LISP RTR Message Details 301 The main modifications in the LISP protocol to enable LISP NAT 302 traversal via an RTR include: (1) two new messages used for NAT 303 discovery (Info-Request and Info-Reply), and (2) encapsulation of two 304 LISP control messages (Map-Register and Map-Notify) between the xTR 305 and the RTR. Map-Register is encapsulated in an ECM header while 306 Map-Notify is encapsulated in a LISP data header (Data-Map-Notify). 307 This section describes the message formats and details of the Info- 308 Request, Info-Reply, and Data-Map-Notify messages, as well as 309 encapsulation details and minor changes to Map-Register and Map- 310 Notify messages. 312 4.1. Info-Request Message 314 An ETR sends an Info-Request message to its Map-Server in order to 316 1. detect whether there is a NAT on the path to its Map-Server 318 2. obtain a list of RTR RLOCs that can be used for LISP data plane 319 NAT traversal. 321 An Info-Request message is a LISP control message, its source port is 322 chosen by the xTR and its destination port is set to 4342. 324 0 1 2 3 325 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 1 326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 |Type=7 |R| Reserved | 328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 | Nonce . . . | 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | . . . Nonce | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | Key ID | Authentication Data Length | 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 ~ Authentication Data ~ 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | TTL | 338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 339 | Reserved | EID mask-len | EID-prefix-AFI | 340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 341 | EID-prefix | 342 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 343 | AFI = 0 | | 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 346 LISP Info-Request Message Format 348 Type: 7 (Info-Request) 350 R: R bit indicates this is a reply to an Info-Request (Info- 351 Reply). R bit is set to 0 in an Info-Request. When R bit is set 352 to 0, the AFI field (following the EID-prefix field) must be set 353 to 0. When R bit is set to 1, the packet contents follow the 354 format for an Info-Reply, as described below. 356 Reserved: Must be set to 0 on transmit and must be ignored on 357 receipt. 359 TTL: The time in minutes the recipient of the Info-Reply will 360 store the RTR Information. 362 Nonce: An 8-byte random value created by the sender of the Info- 363 Request. This nonce will be returned in the Info-Reply. The 364 nonce SHOULD be generated by a properly seeded pseudo-random (or 365 strong random) source. 367 Descriptions for other fields can be found in the Map-Register 368 section of the main LISP draft [LISP]. Field descriptions for the 369 LCAF AFI = 0 can be found in the LISP LCAF draft [LCAF] . 371 4.2. LISP Info-Reply 373 When a Map-Server receives an Info-Request message, it responds with 374 an Info-Reply message. The Info-Reply message source port is 4342, 375 and destination port is taken from the source port of the triggering 376 Info-Request. Map-Server fills the NAT LCAF (LCAF Type = 7) fields 377 according to their description. The Map-Server uses AFI=0 for the 378 Private ETR RLOC Address field in the NAT LCAF. 380 0 1 2 3 381 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 1 382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 |Type=7 |R| Reserved | 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 385 | Nonce . . . | 386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 | . . . Nonce | 388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 | Key ID | Authentication Data Length | 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 ~ Authentication Data ~ 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | TTL | 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | Reserved | EID mask-len | EID-prefix-AFI | 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 397 | EID-prefix | 398 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 399 | | AFI = 16387 | Rsvd1 | Flags | 400 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 401 | | Type = 7 | Rsvd2 | 4 + n | 402 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 403 N | MS UDP Port Number | ETR UDP Port Number | 404 A +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 405 T | AFI = x | Global ETR RLOC Address ... | 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 407 L | AFI = x | MS RLOC Address ... | 408 C +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 A | AFI = x | Private ETR RLOC Address ... | 410 F +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | | AFI = x | RTR RLOC Address 1 ... | 412 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 | | AFI = x | RTR RLOC Address n ... | 414 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 416 LISP Info-Reply Message Format 418 Type: 7 , R = 1, (Info-Reply) 419 The format is similar to the Info-Request message. See Info-Request 420 section for field descriptions. Field descriptions for the NAT LCAF 421 section can be found in the LISP LCAF draft [LCAF] . 423 4.3. LISP Map-Register Message 425 The third bit after the Type field in the Map-Register message is 426 allocated as "I" bit. I bit indicates that a 128 bit xTR-ID and a 64 427 bit site-ID field are present at the end of the Map-Register message. 428 If an xTR is configured with an xTR-ID or site-ID, it MUST set the I 429 bit to 1 and include its xTR-ID and site-ID in the Map-Register 430 messages it generates. If either the xTR-ID or site-ID is not 431 configured an unspecified value is encoded for whichever ID that is 432 not configured. 434 xTR-ID is a 128 bit field at the end of the Map-Register message, 435 starting after the final Record in the message. The xTR-ID is used 436 to identify the intended recipient xTR for a Map-Notify message, 437 especially in the case where a site has more than one xTR. A value 438 of all zeros indicate that an xTR-ID is not specified, though encoded 439 in the message. This is useful in the case where a site-ID is 440 specified, but no xTR-ID is configured. When a Map-Server receives a 441 Map-Register with an xTR-ID specified (I bit set and xTR-ID has a 442 non-zero value), it MUST copy the XTR-ID from the Map-Register to the 443 associated Map-Notify message. When a Map-Server is sending an 444 unsolicited Map-Notify to an xTR to notify the xTR of a change in 445 locators, the Map-Server must include the xTR-ID for the intended 446 recipient xTR, if it has one stored locally. 448 site-ID is a 64 bit field at the end of the Map-Register message, 449 following the xTR-ID. site-ID is used by the Map-Server receiving the 450 Map-Register message to identify which xTRs belong to the same site. 451 A value of 0 indicate that a site-ID is not specified, though encoded 452 in the message. When a Map-Server receives a Map-Register with a 453 site-ID specified (I bit set and site-ID has non-zero value), it must 454 copy the site-ID from the Map-Register to the associated Map-Notify 455 message. When a Map-Server is sending an unsolicited Map-Notify to 456 an xTR to notify the xTR of a change in locators, the Map-Server must 457 include the site-ID for the intended recipient xTR, if it has one 458 stored locally. 460 A LISP device that sends a Map-Register to an RTR must encapsulate 461 the Map-Register message using an Encapsulated Control Message (ECM) 462 [LISP]. The 6th bit in the ECM LISP header is allocated as the "R" 463 bit. The R bit indicates that the encapsulated Map-Register is to be 464 processed by an RTR. The 7th bit in the ECM header is allocated as 465 the "N" bit. The N bit indicates that this Map-Register is being 466 relayed by an RTR. When an RTR relays the ECM-ed Map-Register to a 467 Map-Server, the N bit must be set to 1. 469 The outer header source RLOC of the ECM is set to the LISP device's 470 local RLOC, and the outer header source port is set to 4341. The 471 outer header destination RLOC and port are set to RTR RLOC and 4342 472 respectively. The inner header source RLOC is set to LISP device's 473 local RLOC, and the inner source port is picked at random. The inner 474 header destination RLOC is set to the xTR's Map-Server RLOC, and 475 inner header destination port is set to 4342. 477 4.4. LISP Map-Notify 479 The first bit after the Type field in a Map-Notify message is 480 allocated as the "I" bit. I bit indicates that a 128 bit xTR-ID and 481 64 bit site-ID field is present at the end of the Map-Notify message, 482 following the final Record in the Map-Notify (See Section 4.3 for 483 details on xTR-ID and site-ID). A Map-Server MUST set the I bit in a 484 Map-Notify and include the xTR-ID and/or site-ID of the intended 485 recipient xTR if the associated Map-Register has an xTR-ID and/or 486 site-ID specified, or when the Map-Server has previously cached an 487 xTR-ID and/or site-ID for the destination xTR. 489 A LISP device that sends a Map-Notify to an RTR must encapsulate the 490 Map-Notify message using an ECM. the 6th bit in the ECM LISP header, 491 allocated as the "R" bit, must be set when the encapsulated Map- 492 Notify is to be processed by an RTR. If the S bit is also set in the 493 Map-Notify ECM header, it indicates that additional MS-RTR 494 authentication data is included after the LISP header in the ECM. If 495 the I bit is also set in the Map-Notify, the xTR-ID and site-ID 496 fields are included in the Map-Notify. If a Map-Server receiving an 497 ECM-ed Map-Register has a shared key associated with the sending RTR, 498 it must generate a Map-Notify message with the S bit in the ECM 499 header set to 1, and with the additional MS-RTR authentication 500 related fields described below. 502 0 1 2 3 503 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 1 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | AD Type | Reserved | 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 507 | MS-RTR Key ID | MS-RTR Auth. Data Length | 508 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 509 ~ MS-RTR Authentication Data ~ 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 Changes to LISP Map-Notify Message 514 AD Type: 2 (RTR Authentication Data) 516 MS-RTR Key ID: A configured ID to find the configured Message 517 Authentication Code (MAC) algorithm and key value used for the 518 authentication function. See [LISP] section 14.4 for code point 519 assignments. 521 MS-RTR Authentication Data Length: The length in bytes of the MS-RTR 522 Authentication Data field that follows this field. The length of the 523 Authentication Data field is dependent on the Message Authentication 524 Code (MAC) algorithm used. The length field allows a device that 525 doesn't know the MAC algorithm to correctly parse the packet. 527 MS-RTR Authentication Data: The message digest used from the output 528 of the Message Authentication Code (MAC) algorithm. The entire Map- 529 Notify payload is authenticated. After the MAC is computed, it is 530 placed in this field. Implementations of this specification MUST 531 support HMAC-SHA-1-96 [RFC2404] and SHOULD support HMAC-SHA-256-128 532 [RFC6234]. 534 For a full description of all fields in the Map-Notify message refer 535 to Map-Notify section in the main LISP draft [LISP]. 537 4.5. LISP Data-Map-Notify Message 539 When an RTR receives an ECM-ed Map-Notify message with R bit in the 540 ECM header set to 1, it has to relay the Map-Notify payload to the 541 registering LISP device. After removing the ECM header and 542 processing the Map-Notify message as described in Section 5.3, the 543 RTR encapsulates the Map-Notify in a LISP data header and sends it to 544 the associated LISP device. This Map-Notify inside a LISP data 545 header is referred to as a Data-Map-Notify message. 547 0 1 2 3 548 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 1 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 / | IPv4 or IPv6 Header | 551 OH | (uses RLOC addresses) | 552 \ | | 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 / | Source Port = 4342 | Dest Port = xxxx | 555 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 \ | UDP Length | UDP Checksum | 557 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 558 L | LISP Header ~ | 559 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 560 S / | ~ LISP Header | 561 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 / | IPv4 or IPv6 Header | 563 IH | (uses RLOC or EID addresses) | 564 \ | | 565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 / | Source Port = 4342 | Dest Port = 4342 | 567 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 568 \ | UDP Length | UDP Checksum | 569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 570 LCM | LISP Map-Notify Message ~ 571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 573 LISP Data-Map-Notify Message 575 In a Data-Map-Notify, the outer header source RLOC is set to the 576 RTR's RLOC that was used in the associated Map-Register. This is 577 previously cached by the RTR. The outer header source port is set to 578 4342. The outer header destination RLOC and port are filled based on 579 the translated global RLOC and port of the registering LISP device 580 previously stored locally at the RTR. The inner header source 581 address is Map-Server's RLOC, and inner header source port is 4342. 582 The inner header destination address is set to the LISP device's 583 local RLOC also previously cached by the RTR (See Section 5.3 for 584 details.). The inner header destination port is 4342. 586 Since a Data-Map-Notify is a control message encapsulated in a LISP 587 data header, a special Instance ID is used as a signal for the xTR to 588 trigger processing of the control packet inside the data header. The 589 Instance ID value 0xFFFFFF is reserved for this purpose. The 590 Instance ID field in a Data-Map-Notify must be set to 0xFFFFFF. 592 5. Protocol Operations 594 There are two main steps in the NAT traversal procedure. First, the 595 ETR's translated global RLOC must be discovered. Second, the NAT 596 translation table must be primed to accept incoming connections. At 597 the same time, the Map-Server and the RTR must be informed of the 598 ETR's translated global RLOC including the translated ephemeral port 599 number(s) at which the Map-Server and RTR can reach the LISP device. 601 5.1. xTR Processing 603 Upon receiving a new local RLOC, an ETR first has to detect whether 604 the new RLOC is behind a NAT device. For this purpose the ETR sends 605 an Info-Request message to its Map-Server in order to discover the 606 ETR's translated global RLOC as it is visible to the Map-Server. The 607 ETR uses its new local RLOC as the source RLOC of the message. The 608 Map-Server, after authenticating the message, responds with an Info- 609 Reply message. The Map-Server includes the source RLOC and port from 610 the Info-Request message in the Global ETR RLOC Address and ETR UDP 611 Port Number fields of the Info-Reply. The Map Server also includes 612 the destination RLOC and port number of the Info-Request message in 613 the MS RLOC Address and MS UDP Port Number fields of the Info-Reply. 614 In addition, the Map-Server provides a list of RTR RLOCs that the ETR 615 may use in case it needs NAT traversal services. The source port of 616 the Info-Reply is set to 4342 and the destination port is copied from 617 the source port of the triggering Info-Request message. 619 Upon receiving the Info-Reply message, the ETR compares the source 620 RLOC and source port used for the Info-Request message with the 621 Global ETR RLOC Address and ETR UDP Port Number fields of the Info- 622 Reply message. If the two are not identical, the ETR concludes that 623 its new local RLOC is behind a NAT and that it requires an RTR for 624 NAT traversal services in order to be reachable at that RLOC. An ETR 625 behind other statefull devices (e.g. statefull firewalls) may also 626 use an RTR and the procedure specified here for traversing the 627 statefull device. Detecting existence of such devices are beyond 628 scope of this document. 630 It is worth noting that a STUN server can also be used to do NAT 631 detection and to discover the NAT-translated public IP address and 632 port number for the ETR behind NAT. If a STUN server is used, list 633 of RTR devices that can be used by the xTR for NAT traversal must be 634 provisioned to the xTR via other means which are outside the scope of 635 this document. 637 If there is no NAT on the path identified by an info-Request and an 638 Info-Reply, the ETR registers the associated RLOC with its Map-Server 639 as described in the main LISP draft [LISP]. 641 5.1.1. ETR Registration 643 Once an ETR has detected that it is behind a NAT, based on local 644 policy the ETR selects one (or more) RTR(s) from the RTR RLOCs 645 provided in the Info-Reply and initializes state in the NAT device in 646 order to receive LISP data traffic on UDP port 4341 from the selected 647 RTR. To do so, the ETR sends a Map-Register encapsulated in an ECM 648 header to the selected RTR(s). The Map-Register message is created 649 as specified in [LISP]. More specifically, the source RLOC of the 650 Map-Register is set to ETR's local RLOC, while the destination RLOC 651 is set to the ETR's Map-Server RLOC, and destination port is set to 652 4342. The ETR sets the M bit (want-Map-Notify) in Map-Register to 1, 653 and it includes the selected RTR RLOC(s) as the locators in the Map- 654 Register message. The ETR can also include its local RLOCs as 655 locators in the Map-Register, including weight and priorities, while 656 setting the R bit to 0 for each local RLOC. This can be used by the 657 RTR for load balancing when forwarding data to a multi-homed xTR 658 behind a NAT. The R bit is set to 1 for all RTR locators included in 659 the Map-Register. The ETR must also set the I bit in the Map- 660 Register message to 1 and include its xTR-ID in t he corresponding 661 field. In the ECM header of this Map-Register the source RLOC is set 662 to ETR's local RLOC and the source port is set to 4341, while the 663 destination RLOC is the RTR's RLOC and the destination port is set to 664 LISP control port 4342. The R bit in the ECM header is also set to 665 1, to indicate that this EDCM-ed Map-Register is to be processed by 666 an RTR. 668 This ECM-ed Map-Register is then sent to the RTR. The RTR removes 669 the EMC header, re-originates the Map-Register message, encapsulates 670 the new Map-Register in a new ECM header with R bit set to 0, and 671 sends it to the associated Map-Server. The RTR then encapsulates the 672 corresponding Map-Notify message in a LISP data header (Data-Map- 673 Notify) and sends it back to the xTR. 675 Upon receiving a Data-Map-Notify from the RTR, the ETR must strip the 676 outer LISP data header, and process the inner Map-Notify message as 677 described in [LISP]. Since outer header destination port in Data- 678 Map-Notify is set to LISP data port 4341, the Instance ID 0xFFFFFF in 679 the LISP header of the Data-Map-Notify is used by the ETR to detect 680 and process the Data-Map-Notify as a control message encapsulated in 681 a LISP data header. While processing the Data-Map-Notify, the xTR 682 also stores the RTR RLOC(s) as its data plane proxy for the 683 interface/RLOC behind the NAT. 685 If the xTR is not multi-homed, or if all its interfaces are behind 686 the NAT and will use the same RTR, then the xTR MAY map the EID 687 prefix 0/0 to this RTR RLOC(s) in its map-cache. This results in the 688 xTR encapsulating all LISP data plane traffic to this RTR, reducing 689 the state created in the NAT. Note that not installing the default 690 map-cache entry will lead to normal Map-Request and Map-Reply 691 messages for EID mapping lookups, and outgoing traffic could be sent 692 directly to destinations without passing through the RTR. This will 693 result in additional state to be created in the NAT device. 695 At this point the registration and state initialization is complete 696 and the xTR can use the RTR services. The state created in the NAT 697 device based on the ECM-ed Map-Register and corresponding Data-Map- 698 Notify is used by the xTR behind the NAT to send and receive LISP 699 control packets to/from the RTR, as well as for receiving LISP data 700 packets form the RTR. 702 If ETR receives a Data-Map-Notify with a xTR-ID specified, but the 703 xTR-ID is not equal to its local xTR-ID, it must log this as an 704 error. The ETR should discard such Data-Map-Notify message. 706 The ETR must periodically send ECM-ed Map-Register messages to its 707 RTR in order to both refresh its registration to the RTR and the Map- 708 Server, and as a keep alive in order to preserve the state in the NAT 709 device. RFC 2663 [NAT] points out that the period for sending the 710 keep alives can be set to default value of two minutes, however since 711 shorter timeouts may exist in some NAT deployments, the interval for 712 sending periodic ECM-ed Map-Registers must be configurable. 714 5.1.2. Map-Request and Map-Reply Handling 716 The ETR is in control of how to handle the Map-Requests and Map- 717 Replies. If the ETR wants the Map-Server to proxy-reply as described 718 in [LISP], it can register the RTR RLOC(s) as its locator via the 719 ECM-ed Map-Register message. In this case, if the proxy bit is set 720 in the Map-Register, the Map-Server will proxy reply with RTR's RLOC 721 to all Map-Requests for the ETR. As a result all traffic for the ETR 722 is encapsulated to its RTR(s). 724 If the proxy bit in the ECM-ed Map-Register message is not set, and 725 the ETR chooses to receive Map-Requests, the ETR must also initiate 726 and preserve state in the NAT device to receive LISP control packets 727 from its Map-Server. To do this, the ETR must periodically send 728 Info-Request messages to its Map-Server, and receive Info-Reply 729 messages from the Map-Server. As pointed in RFC 2663 [NAT] the 730 default assumption of two minute period for session lifetime can be 731 used, however since shorter timeouts may exist in some NAT 732 deployments, the interval for sending periodic Info-Requests must be 733 configurable. Furthermore, the ETR must also provide its Map-Server 734 with the ETR's translated global RLOC and port as visible to the Map- 735 Server. To do this, ETR includes a copy of the NAT LCAF section of 736 the Info-Reply message as one of the locators in its Map-Register 737 along with the RTR(s) RLOC(s). The ETR can set the priorities of RTR 738 RLOC(s) in this Map-Register to 255, resulting in the Map Server 739 encapsulating Map-Requests to the ETR's translated global RLOC and 740 port so it can receive them through the NAT device. 742 If an ETR behind a NAT chooses to receive Map-Requests from the Map- 743 Server, it must send Map-Replies to requesting ITRs. Note that this 744 configuration will result in excessive state in the NAT device and is 745 not recommended. ETR must include its RTR RLOC(s) as its locator set 746 in the Map-Reply in order to receive data through the NAT device. 748 When an ITR behind a NAT is encapsulating outbound LISP traffic, it 749 must use its RTR RLOC as the locator for all destination EIDs that it 750 wishes to send data to. As such, the ITR does not need to send Map- 751 Requests for the purpose of finding EID-to-RLOC mappings. For RLOC- 752 probing, the periodic ECM-ed Map-Register and Data-Map-Notify 753 messages between xTR and RTR can also serve the purpose of RLOC 754 probes. However, if RLOC-probing is used, no changes are required to 755 the RLOC-probing specification in [LISP], except that the LISP device 756 behind a NAT only needs to probe the RTR's RLOC. 758 5.1.3. xTR Sending and Receiving Data 760 When a Map-Request for a LISP device behind a NAT is received by its 761 Map-Server or the LISP device itself, the Map-Server, or the LISP 762 device (ETR), responds with a Map-Reply including RTR's RLOC as the 763 locator for the requested EID. As a result, all LISP data traffic 764 destined for the ETR's EID behind the NAT is encapsulated to its RTR. 765 The RTR re-encapsulates the LISP data packets to the ETR's translated 766 global RLOC and port number so the data can pass through the NAT 767 device and reach the ETR. As a result the ETR receives LISP data 768 traffic with outer header destination port set to 4341 as specified 769 in [LISP]. 771 For sending outbound LISP data, an ITR behind a NAT SHOULD use the 772 RTR RLOC as the locator for all EIDs that it wishes to send data to 773 via the interface behind the NAT. The ITR then encapsulates the LISP 774 traffic in a LISP data header with outer header destination set to 775 RTR RLOC and outer header destination port set to 4341. This may 776 create a secondary state in the NAT device. ITR SHOULD set the outer 777 header source port in all egress LISP data packets to a random but 778 static port number in order to avoid creating excessive state in the 779 NAT device. 781 If the ITR and ETR of a site are not collocated, the RTR RLOC must be 782 configured in the ITR via an out-of-band mechanism. Other procedures 783 specified here would still apply. 785 5.2. Map-Server Processing 787 Upon receiving an Info-Request message a Map-Server first verifies 788 the authenticity of the message. Next the Map-Server creates an 789 Info-Reply message and copies the source RLOC and port number of the 790 Info-Request message to the Global ETR RLOC Address and ETR UDP Port 791 Number fields of the Info-Reply message. The Map-Server also 792 includes a list of RTR RLOCs that the ETR may use for NAT traversal 793 services. The Map-Server sends the Info-Reply message to the ETR, by 794 setting the destination RLOC and port of the Info-Reply to the source 795 RLOC and port of the triggering Info-Request. The Map-Server sets 796 the source port of the Info-Reply to 4342. 798 Upon receiving an ECM-ed Map-Register message with the N bit in the 799 ECM header set to 1, the Map-Server removes the ECM header and if the 800 M bit in the Map-Register is set, the Map-Server processes the Map- 801 Register message and generates the resulting Map-Notify as described 802 in [LISP]. The Map-Server encapsulates the Map-Notify in an ECM 803 header and sets the R bit in the ECM header to 1. This indicates 804 that the ECM-ed Map-Notify is to be processed by an RTR. If the Map- 805 Server has a shared secret configured with the RTR sending the Map- 806 Register, the Map-Server also sets the S bit in the ECM header of the 807 Map-Notify and includes the MS-RTR authentication data after the ECM 808 LISP header. See Security Considerations Section for more details. 809 If the I bit is set in the Map-Register message, the Map-Server also 810 locally stores the xTR-ID from the Map-Register, and sets the I bit 811 in the corresponding Map-Notify message and includes the same xTR-ID 812 in the Map-Notify. The ECM-ed Map-Notify is then sent to the RTR 813 sending the corresponding Map-Register. 815 If a Map-Server is forwarding Map-Requests to an ETR which has 816 registered its RLOC in a NAT LCAF, Map-Server must use the ETR Global 817 RLOC Address and ETR UDP Port as the destination RLOC and port for 818 outer header of the encapsulated Map-Requests. If more than one NAT 819 LCAF is registered for the same EID prefix, the Map-Server must use 820 the NAT LCAF corresponding to the RLOC of this Map-Server. 822 5.3. RTR Processing 824 Upon receiving an ECM-encapsulated Map-Register with the R bit set in 825 the ECM header, the RTR creates a map-cache entry for the EID-prefix 826 that was specified in the Map-Register message. The RTR stores the 827 outer header source RLOC and outer header source port, the outer 828 header destination RLOC (RTR's own RLOC), the inner header source 829 RLOC (xTR's local RLOC), the xTR-ID, the weight and priority 830 associated with the xTR's local RLOC that was used to send this Map- 831 Register if present, and the nonce field of the Map-Register in this 832 local map-cache entry. The RTR uses the inner header source address 833 to identify which xTR local RLOC (R bit =0) was used by the xTR to 834 send this Map-Register. The outer header source RLOC and outer 835 header source port is the ETR's translated global RLOC and port 836 number visible to the RTR. Once the registration process is 837 complete, this map-cache entry can be used to send LISP data traffic 838 to the ETR. The inner header source RLOC of the Map-Register is the 839 ETR's local RLOC behind the NAT, and the outer header destination 840 RLOC is the RTR's RLOC used by the ETR. The RTR can later use these 841 fields as the inner header destination RLOC and source RLOC 842 correspondingly, for sending data-encapsulated control messages 843 (Data-Map-Notify) back to the ETR. The nonce field is used for 844 security purposes and is matched with the nonce field in the 845 corresponding Map-Notify message. This map-cache entry is stored as 846 an "unverified" mapping, until the corresponding Map-Notify message 847 is received. 849 In the cases where the xTR has multiple RLOCs behind the NAT, and 850 requires the RTR to load balance the traffic across those interfaces, 851 the xTR must include the local RLOCs associated with each interface 852 behind the NAT with the R bit in the locator record set to 0 in the 853 ECM-ed Map-Register sent to the RTR. The RTR uses the weight and 854 priority policies of the RLOCs with R=0 in the Map-Register to load 855 balance the traffic from the RTR to the xTR behind the NAT. The RTR 856 compares the RLOCs with the R bit set to 0 in the Map-Register to the 857 inner header source address of the Map-Register to find the matching 858 RLOC that the xTR used to send the Map-Register from. The RTR 859 associates the weight and priority policies of this local RLOC with 860 the NAT-translated RLOC and xTR-ID for this map-cache entry. For all 861 other local RLOCs included in the Map-Register, that the Map-Register 862 is not originating from, the RTR only updates previously cached 863 weight and priority policies if it already has those local RLOCs 864 previously stored for that EID prefix and xTR-ID. In other words, 865 the RTR only adds new local RLOCs and their weight and priority 866 policies to its cache if the Map-Register is actually originating 867 from that RLOC. The TTL for every map-cache is also only updated 868 when a Map-Register is originating from the same RLOC. However, the 869 weight and priorities of all previously cached local RLOCs will be 870 updated by every Map-Register, whether it is originating from that 871 RLOC or not. The xTR-ID is used to define the Merge domain for these 872 RLOCs. In other words, a Map-Register originating from a unique xTR- 873 ID will always overwrite previously stored policies for that xTR-ID. 874 However it does not modify in any way the policies indicated by any 875 other xTR-ID serving the same EID prefix. As a result, in the case 876 of a renumbering or xTR reboot, the xTR uses its unique xTR-ID to 877 send a new Map-Register, overwriting the previously stored policies 878 for that xTR. Using this method the xTR can immediately remove any 879 RLOCs from the RTR cache that are no longer active. In order to 880 implement this, the RTR must compare the list of local RLOCs in the 881 Map-Register (R=0) with the ones it has previously cached associated 882 with the same xTR-ID. If there is any RLOC previously cached that 883 does not appear in the newly received Map-Register, the RTR must 884 remove that RLOC together with the associated translated RLOC and 885 associated policies, because removal of a local (behind-the-NAT) RLOC 886 also invalidates the NAT-ed address associated with it. . 888 After filling the local map-cache entry, the RTR strips the outer 889 header and extracts the Map-Register message, re-originates the 890 message by rewriting the source RLOC of the Map-Register to RTR's 891 RLOC, encapsulated in a new ECM header with the R bit set to 0, and N 892 bit set to 1, and sends the ECM-ed Map-Register to destination Map- 893 Server. 895 Map-Server responds with a ECM-ed Map-Notify message to the RTR. 897 Upon receiving an ECM-ed Map-Notify message with R bit set to 1 in 898 the ECM header, if the S bit in ECM header is set to 1, RTR uses the 899 MS-RTR Key ID to verify the MS-RTR Authentication Data included after 900 the ECM header. If the MS-RTR authentication fails, the RTR must 901 drop the packet. Once the authenticity of the message is verified, 902 RTR can confirm that the Map-Register message for the ETR with the 903 matching xTR-ID was accepted by the Map-Server. At this point the 904 RTR can change the state of the associated map-cache entry to 905 verified for the duration of the Map-Register TTL. 907 The RTR then uses the information in the associated map-cache entry 908 to create a Data-Map-Notify message according to the following 909 procedure: RTR rewrites the inner header destination RLOC of the Map- 910 Notify message to ETR's local RLOC. Inner header destination port is 911 4342. The RTR encapsulates the Map-Notify in a LISP data header, 912 where the outer header destination RLOC and port number are set to 913 the ETR's translated global RLOC and port number. If more than one 914 ETR translated RLOC and port exists in the map-cache entry for the 915 same EID prefix specified in the Map-Notify, the RTR can use the xTR- 916 ID from the Map-Notify to identify which ETR is the correct 917 destination for the Data-Map-Notify. The RTR sets the outer header 918 source RLOC to RTR's RLOC from the map-cache entry and the outer 919 header source port is set to 4342. The RTR also sets the Instance ID 920 field in the LISP header of the Data-Map-Notify to 0xFFFFFF. The RTR 921 then sends the Data-Map-Notify to the ETR. 923 If the S bit is set to 0 in the ECM header of the Map-Notify, and the 924 RTR has a shared key configured locally with the sending Map-Server, 925 the RTR must drop the packet. If the S bit is set to 0, and the RTR 926 does not have a shared key configured with the associated Map-Server, 927 according to local policy, the RTR may drop the packet. If the Map- 928 Notify with S bit set to 0 is processed, the RTR must match the nonce 929 field from this Map-Notify with the nonce stored in the local map- 930 cache entry with the matching xTR-ID. If the nonces do not match, 931 the RTR must drop the packet. 933 5.3.1. RTR Data Forwarding 935 For all LISP data packets encapsulated to RTR's RLOC and outer header 936 destination port 4341, the RTR first verifies whether the source or 937 destination EID is a previously registered EID. If so, the RTR must 938 process the packet according to the following. If the destination or 939 source EID is not a registered EID, the RTR can drop or process the 940 packets based on local policy. 942 In the case where the destination EID is a previously registered EID, 943 the RTR must strip the LISP data header and re-encapsulate the packet 944 in a new LISP data header. The outer header RLOCs and UDP ports are 945 then filled based on the matching map-cache entry for the associated 946 destination EID prefix. The RTR uses the RTR RLOC from the map-cache 947 entry as the outer header source RLOC. The outer header source port 948 is set to 4342. The RTR sets the outer header destination RLOC and 949 outer header destination port based on the ETR translated global RLOC 950 and port stored in the map-cache entry. Then the RTR forwards the 951 LISP data packet. 953 In the case where the source EID is a previously registered EID, the 954 RTR process the packet as if it is a Proxy ETR (PETR). The RTR must 955 strip the LISP data header, and process the packet based on its inner 956 header destination address. The packet may be forwarded natively, it 957 may be LISP encapsulated to the destination ETR, or it may trigger 958 the RTR to send a LISP Map-Request. 960 5.4. Multi-homed xTRs 962 In the case where an xTR has multiple interfaces and RLOCs, info- 963 Requests can be sent per each interface and NAT discovery is done per 964 each interface. NAT traversal is accomplished by following state and 965 processes described above per each interface/RLOC. In other words, 966 if multiple interfaces of an xTR are behind a NAT, the ECM-ed Map- 967 Register messages should be sent via each xTR interface behind NAT if 968 the xTR desires to receive traffic via that interface. This is 969 required to establish the state in the NAT device for that interface. 970 The M bit (want Map-Notify) must be set in ECM-ed Map-Register 971 messages sent from at least one of xTR interfaces behind the NAT. If 972 additional interfaces behind the NAT are using the same RTR for NAT 973 traversal, no Map-Notify processing is required for such interfaces 974 and M bit in Ma-Register can be set to 0 for these to reduce 975 processing on the RTR and the Map-Server. 977 The RLOCs included in Map-Register messages in such cases SHOULD be 978 the union of the locators (behind NAT or not) resulting from the 979 process defined above per each RLOC of the xTR, according to the 980 specifics of that interface (whether it is behind the NAT or not). 982 In cases where some xTR interfaces are behind NAT while others are 983 not, ECM-ed Map-Register messages should be sent via interfaces 984 behind the NAT through the selected RTRs. xTR can receive traffic via 985 both types of interfaces by including the associated RLOCs (or RTR 986 RLOCs) in its ECM-ed Map-Register messages. 988 5.5. Example 990 What follows is an example of an ETR initiating a registration of a 991 new RLOC to its Map-Server, when there is a NAT device on the path 992 between the ETR and the Map-Server. 994 In this example, the ETR (site1-ETR) is configured with the local 995 RLOC of 192.168.1.2. The NAT's global (external) addresses are from 996 2.0.0.1/24 prefix. The Map-Server is at 3.0.0.1. And one potential 997 RTR has an IP address of 1.0.0.1. The site1-ETR has an EID Prefix of 998 128.1.0.0/16. 1000 An example of the registration process follows: 1002 1. The Site1-ETR receives the private IP address, 192.168.1.2 as 1003 its RLOC via DHCP. 1005 2. The Site1-ETR sends an Info-Request message with the destination 1006 RLOC of the Map-Server, 3.0.0.1, and source RLOC of 192.168.1.2. 1007 This packet has the destination port set to 4342 and the source 1008 port is set to (for example) 5001. 1010 3. The NAT device translates the source IP from 192.168.1.2 to 1011 2.0.0.1, and source port to (for example) 20001 global ephemeral 1012 source port. 1014 4. The Map-Server receives and responds to this Info-Request with 1015 an Info-Reply message. This Info-Reply has the destination 1016 address set to ETR's translated address of 2.0.0.1 and the 1017 source address is the Map-Server's RLOC, namely 3.0.0.1. The 1018 destination port is 20001 and the source port is 4342. Map- 1019 Server includes a copy of the source address and port of the 1020 Info-Request message (2.0.0.1:20001), and a list of RTR RLOCs 1021 including RTR RLOC 1.0.0.1 in the Info-Reply contents. 1023 5. The NAT translates the Info-Reply packet's destination IP from 1024 2.0.0.1 to 192.168.1.2, and translates the destination port from 1025 20001 to 5001, and forwards the Info-Reply to site1-ETR at 1026 192.168.1.2. 1028 6. The Site1-ETR detects that it is behind a NAT by comparing its 1029 local RLOC (192.168.1.2) with the Global ETR RLOC Address in the 1030 Info-Reply (2.0.0.2) . Then site1-ETR picks the RTR 1.0.0.1 from 1031 the list of RTR RLOCs in the Info-Reply. ETR stores the RTR 1032 RLOC in a default map-cache entry to periodically send ECM-ed 1033 Map-Registers to. 1035 7. The ETR sends an ECM encapsulated Map-Register to RTR at 1036 1.0.0.1. The outer header source RLOC of this Map-Register is 1037 set to 192.168.1.2 and the outer header source port is set to 1038 4341. The outer header destination RLOC and port are set to RTR 1039 RLOC at 1.0.0.1 and 4342 respectively. The R bit in ECM header 1040 is set to 1. The inner header destination RLOC is set to ETR's 1041 Map-Server 3.0.0.1, and the inner header destination port is set 1042 to 4342. The inner header source RLOC is set to ETR's local 1043 RLOC 192.168.1.2. In the Map-Register message the RTR RLOC 1044 1.0.0.1 appears as the locator set for the ETR's EID prefix 1045 (128.1.0.0/16). In this example ETR also sets the Proxy bit in 1046 the Map-Register to 1, and sets I bit to 1, and includes its 1047 xTR-ID in the Map-Register. 1049 8. The NAT translates the source RLOC in the ECM header of the Map- 1050 Register, by changing it from 192.168.1.2 to 2.0.0.2, and 1051 translates the source port in the ECM header from 4341 to (for 1052 example) 20002, and forwards the Map-Register to RTR. 1054 9. The RTR receives the Map-Register and creates a map-cache entry 1055 with the ETR's xTR-ID, EID prefix, and the source RLOC and port 1056 of the ECM header of the Map-Register as the locator 1057 (128.1.0.0/16 is mapped to 2.0.0.2:20002). RTR also caches the 1058 inner header source RLOC of the Map-Register namely 192.168.1.2, 1059 and the outer header destination RLOC of the ECM header in the 1060 Map-Register (this would be RTR's RLOC 1.0.0.1 ) to use for 1061 sending back a Data-Map-Notify. RTR then removes the outer 1062 header, re-writes the source RLOC of the Map-Register message to 1063 its own RLOC 1.0.0.1, adds a new ECM header with R=0, and N=1, 1064 and forwards the Map-Register to the destination Map-Server. 1066 10. The Map-Server receives the ECM-ed Map-Register with N bit set 1067 to 1, removes the ECM header, and processes it according to 1068 [LISP]. Since Map-Server has a shared secret with the sending 1069 RTR, after registering the ETR, Map-Server responds with a ECM- 1070 ed Map-Notify with the R bit and S bit both set to 1 in the ECM 1071 header and including the MS-RTR authentication data. Since the 1072 I bit is set in the Map-Register, the Map-Server also sets the I 1073 bit in the Map-Notify and copies the xTR-ID from the Map- 1074 Register to the Map-Notify. The source address of this Map- 1075 Notify is set to 3.0.0.1. The destination is RTR 1.0.0.1, and 1076 both source and destination ports are set to 4342. 1078 11. The RTR receives the ECM-ed Map-Notify and verifies the MS-RTR 1079 authentication data. The RTR data-encapsulates the Map-Notify 1080 and sends the resulting Data-Map-Notify to site1-ETR with a 1081 matching xTR-ID. The outer header source RLOC and port of the 1082 Data-Map-Notify are set to 1.0.0.1:4342. The outer header 1083 destination RLOC and port are retrieved from previously cached 1084 map-cache entry in step 9 namely 2.0.0.2:20002. RTR also sets 1085 the inner header destination address to site1-ETR's local 1086 address namely 192.168.1.2. RTR sets the Instance ID in the 1087 LISP header to 0xFFFFFF. At this point RTR marks ETR's EID 1088 prefix as "Registered" status and forwards the Data-Map-Notify 1089 to ETR. 1091 12. The NAT device translates the destination RLOC and port of the 1092 Data-Map-Notify to 192.168.1.2:4341 and forwards the packet to 1093 ETR. 1095 13. The Site1-ETR receives the packet with a destination port 4341, 1096 and processes the packet as a control packet after observing the 1097 Instance ID value 0xFFFFFF in the LISP header. At this point 1098 ETR's registration to the RTR is complete. 1100 Assume a requesting ITR in a second LISP (site2-ITR) site has an RLOC 1101 of 74.0.0.1. The following is an example process of an EID behind 1102 site2-ITR sending a data packet to an EID behind the site1-ETR: 1104 1. The ITR sends a Map-Request which arrives via the LISP mapping 1105 system to the ETR's Map Server. 1107 2. The Map-Server sends a Map-Reply on behalf of the ETR, using the 1108 RTR's RLOC (1.0.0.1) in the Map-Reply's Locator Set. 1110 3. The ITR encapsulates a LISP data packet with ITR's local RLOC 1111 (74.0.0.1) as the source RLOC and the RTR as the destination RLOC 1112 (1.0.0.1) in the outer header. 1114 4. The RTR decapsulates the packet, evaluates the inner header 1115 against its map-cache and then re-encapsulates the packet. The 1116 new outer header's source RLOC is the RTR's RLOC 1.0.0.1 and the 1117 new outer header's destination RLOC is the Global NAT address 1118 2.0.0.2. The destination port of the packet is set to 20002 1119 (discovered above during the registration phase) and the source 1120 port is 4342. 1122 5. The NAT translates the LISP data packet's destination IP from to 1123 2.0.0.2 to 192.168.1.2, and translates the destination port from 1124 20002 to 4341, and forwards the LISP data packet to the ETR at 1125 192.168.1.2. 1127 6. For the reverse path the ITR uses its local map-cache entry with 1128 the RTR RLOC as the default locator and encapsulates the LISP 1129 data packets using RTR RLOC, and 4341 as destination RLOC and 1130 port. The ITR must pick a random source port to use for all 1131 outbound LISP data traffic in order to avoid creating excessive 1132 state in the NAT. 1134 6. Security Considerations 1136 By having the RTR relay the ECM-ed Map-Register message from an ETR 1137 to its Map-Server, the RTR can restrict access to the RTR services, 1138 only to those ETRs that are registered with a given Map-Server. To 1139 do so, the RTR and the Map-Server may be configured with a shared key 1140 that is used to authenticate the origin and to protect the integrity 1141 of the Map-Notify messages sent by the Map Server to the RTR. This 1142 prevents an on-path attacker from impersonating the Map-Server to the 1143 RTR, and allows the RTR to cryptographically verify that the ETR is 1144 properly registered with the Map-Server. 1146 Having the RTR re-encapsulate traffic only when the source or the 1147 destination are registered EIDs, protects against the adverse use of 1148 an RTR for EID spoofing. 1150 Upon receiving a Data-Map-Notify, an xTR can authenticate the origin 1151 of the Map-Notify message using the key that the ETR shares with the 1152 Map-Server. This enables the ETR to verify that the ECM-ed Map- 1153 Register was indeed forwarded by the RTR to the Map-Server, and was 1154 accepted by the Map-Server. 1156 6.1. Acknowledgments 1158 The authors would like to thank Noel Chiappa, Alberto Rodriguez 1159 Natal, Lorand Jakab, Albert Cabellos, Dominik Klein, Matthias 1160 Hartmann, and Michael Menth for their previous work, feedback and 1161 helpful suggestions. 1163 7. IANA Considerations 1165 This document does not request any IANA actions. 1167 8. Normative References 1169 [ICE] Rosenberg, J., "Interactive Connectivity Establishment 1170 (ICE)", RFC rfc5245, October 2008. 1172 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1173 Address Format (LCAF)", draft-ietf-lisp-lcaf-10 (work in 1174 progress), December 2015. 1176 [LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 1177 "Locator/ID Separation Protocol (LISP)", RFC 6830, 1178 January 2013. 1180 [LISP-MS] Farinacci, D. and V. Fuller, "Locator/ID Separation 1181 Protocol (LISP) Map-Server Interface", RFC 6833, January 1182 2013. 1184 [NAT] Srisuresh, P. and M. Holdrege, "IP Network Address 1185 Translator (NAT) Terminology and Considerations", RFC 1186 2663, August 1999. 1188 [NAT-MN] Klein, D., Hartmann, M., and M. Menth, "NAT traversal for 1189 LISP mobile node, In Proceedings of the Re-Architecting 1190 the Internet Workshop (ReARCH '10).", 2010. 1192 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1193 and E. Lear, "Address Allocation for Private Internets", 1194 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1195 . 1197 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 1198 (CIDR): The Internet Address Assignment and Aggregation 1199 Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 1200 2006, . 1202 [STUN] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, 1203 "Session Traversal Utilities for NAT (STUN)", RFC rfc5389, 1204 October 2008. 1206 [TURN] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using 1207 Relays around NAT (TURN)", RFC rfc5766, April 2010. 1209 Authors' Addresses 1211 Vina Ermagan 1212 Cisco Systems, Inc. 1214 Email: vermagan@cisco.com 1215 Dino Farinacci 1216 lispers.net 1218 Email: farinacci@gmail.com 1220 Darrel Lewis 1221 Cisco Systems, Inc. 1223 Email: darlewis@cisco.com 1225 Jesper Skriver 1226 Cisco Systems, Inc. 1228 Email: jesper@cisco.com 1230 Fabio Maino 1231 Cisco Systems, Inc. 1233 Email: fmaino@cisco.com 1235 Chris White 1236 Logicalelegance, Inc. 1238 Email: chris@logicalelegance.com