idnits 2.17.1 draft-ermagan-lisp-nat-traversal-04.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 24 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 284: '... nonce SHOULD be generated by a p...' RFC 2119 keyword, line 349: '...n xTR-ID or site-ID, it MUST set the I...' RFC 2119 keyword, line 363: '...-zero value), it MUST copy the XTR-ID ...' RFC 2119 keyword, line 404: '...). A Map-Server MUST set the I bit in...' RFC 2119 keyword, line 451: '...ementations of this specification MUST...' (1 more instance...) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 01, 2013) is 3852 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Missing Reference: 'RFC2404' is mentioned on line 452, but not defined == Missing Reference: 'RFC6234' is mentioned on line 453, but not defined == Unused Reference: 'RFC1918' is defined on line 1070, but no explicit reference was found in the text == Unused Reference: 'RFC4632' is defined on line 1074, but no explicit reference was found in the text == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-03 ** Obsolete normative reference: RFC 6833 (ref. 'LISP-MS') (Obsoleted by RFC 9301) ** Obsolete normative reference: RFC 6830 (ref. 'LISP') (Obsoleted by RFC 9300, RFC 9301) Summary: 3 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: April 04, 2014 lispers.net 6 D. Lewis 7 J. Skriver 8 F. Maino 9 Cisco Systems, Inc. 10 C. White 11 Logicalelegance, Inc. 12 October 01, 2013 14 NAT traversal for LISP 15 draft-ermagan-lisp-nat-traversal-04.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 April 04, 2014. 44 Copyright Notice 46 Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . 4 64 4. LISP RTR Message Details . . . . . . . . . . . . . . . . . . 5 65 4.1. Info-Request Message . . . . . . . . . . . . . . . . . . 5 66 4.2. LISP Info-Reply . . . . . . . . . . . . . . . . . . . . . 7 67 4.3. LISP Map-Register Message . . . . . . . . . . . . . . . . 8 68 4.4. LISP Map-Notify . . . . . . . . . . . . . . . . . . . . . 9 69 4.5. LISP Data-Map-Notify Message . . . . . . . . . . . . . . 10 70 5. Protocol Operations . . . . . . . . . . . . . . . . . . . . . 11 71 5.1. xTR Processing . . . . . . . . . . . . . . . . . . . . . 11 72 5.1.1. ETR Registration . . . . . . . . . . . . . . . . . . 12 73 5.1.2. Map-Request and Map-Reply Handling . . . . . . . . . 14 74 5.1.3. xTR Sending and Receiving Data . . . . . . . . . . . 15 75 5.2. Map-Server Processing . . . . . . . . . . . . . . . . . . 15 76 5.3. RTR Processing . . . . . . . . . . . . . . . . . . . . . 16 77 5.3.1. RTR Data Forwarding . . . . . . . . . . . . . . . . . 18 78 5.4. Example . . . . . . . . . . . . . . . . . . . . . . . . . 19 79 6. Security Considerations . . . . . . . . . . . . . . . . . . . 22 80 6.1. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 22 81 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 82 8. Normative References . . . . . . . . . . . . . . . . . . . . 23 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 85 1. Introduction 87 The Locator/ID Separation Protocol [LISP] defines a set of functions 88 for encapsulating routers to exchange information used to map from 89 Endpoint Identifiers (EIDs) to routable Routing Locators (RLOCs). 90 The assumption that the LISP Tunnel Routers are reachable at their 91 RLOC breaks when a LISP device is behind a NAT. LISP relies on the 92 xTR being able to receive traffic at its RLOC on destination port 93 4341. However nodes behind a NAT are only reachable through the 94 NAT's public address and in most cases only after the appropriate 95 mapping state is set up in the NAT. A NAT traversal mechanism is 96 needed to make the LISP device behind a NAT reachable. 98 This document introduces a NAT traversal mechanism for LISP. Two new 99 LISP control messages - LISP Info-Request and LISP Info-Reply - are 100 introduced in order to detect whether a LISP device is behind a NAT, 101 and discover the global IP address and global ephemeral port used by 102 the NAT to forward LISP packets sent by the LISP device. A new LISP 103 component, the LISP Re-encapsulating Tunnel Router (RTR), acts as a 104 re-encapsulating LISP tunnel router [LISP] to pass traffic through 105 the NAT, to and from the LISP device. A modification to how the LISP 106 Map-Register messages are sent allows LISP device to initialize NAT 107 state to use the RTR services. This mechanism addresses the scenario 108 where the LISP device is behind the NAT, but the associated Map- 109 Server [LISP-MS] is on the public side of the NAT. 111 2. Definition of Terms 113 LISP Info-Request: A LISP control message sent by a LISP device to 114 its Map-Server. 116 LISP Info-Reply: A LISP control message sent by a Map Server to a 117 LISP device in response to an Info-Request control message. 119 LISP Re-encapsulating Tunnel Router (RTR): An RTR is a re- 120 encapsulating LISP Router (see section 8 of the main LISP 121 specification) [LISP]. One function that an RTR provides is 122 enabling a LISP device to traverse NATs. 124 LISP Data-Map-Notify: A LISP Map-Notify message encapsulated in a 125 LISP data header. 127 LISP xTR-ID A 128-bit field that, together with a site-ID, can be 128 appended at the end of a Map-Register or Map-Notify message. An 129 xTR-ID is used as a unique identifier of the xTR that is sending 130 the Map-Register and is especially useful for identifying multiple 131 xTRs serving the same site/EID-prefix. A value of all zeros 132 indicate the xTR-ID is unspecified. 134 LISP site-ID A 64-bit field that, together with a xTR-ID, can be 135 appended at the end of a Map-Register or Map-Notify message. A 136 site-ID is used as a unique identifier of a group of xTRs 137 belonging to the same site. A value of 0 indicate the site-ID is 138 unspecified. 140 NAT: "Network Address Translation is a method by which IP addresses 141 are mapped from one address realm to another, providing 142 transparent routing to end hosts". "Traditional NAT would allow 143 hosts within a private network to transparently access hosts in 144 the external network, in most cases. In a traditional NAT, 145 sessions are uni-directional, outbound from the private network." 146 --RFC 2663 [NAT]. Basic NAT and NAPT are two varieties of 147 traditional NAT. 149 Basic NAT: "With Basic NAT, a block of external addresses are set 150 aside for translating addresses of hosts in a private domain as 151 they originate sessions to the external domain. For packets 152 outbound from the private network, the source IP address and 153 related fields such as IP, TCP, UDP and ICMP header checksums are 154 translated. For inbound packets, the destination IP address and 155 the checksums as listed above are translated." --RFC 2663[NAT]. 157 NAPT: "NAPT extends the notion of translation one step further by 158 also translating transport identifier (e.g., TCP and UDP port 159 numbers, ICMP query identifiers). This allows the transport 160 identifiers of a number of private hosts to be multiplexed into 161 the transport identifiers of a single external address. NAPT 162 allows a set of hosts to share a single external address. Note 163 that NAPT can be combined with Basic NAT so that a pool of 164 external addresses are used in conjunction with port translation." 165 --RFC 2663[NAT]. Transport identifiers of the destination hosts 166 are not modified by the NAPT. 168 In this document the general term NAT is used to refer to both Basic 169 NAT and NAPT. 171 While this document specifies LISP NAT Traversal for LISP tunnel 172 routers, a LISP-MN can also use the same procedure for NAT traversal. 173 The modifications attributed to a LISP-Device, xTR, ETR, and ITR must 174 be supported by a LISP-MN where applicable, in order to achieve NAT 175 traversal for such a LISP node. A NAT traversal mechanism for LISP- 176 MN is also proposed in [NAT-MN]. 178 For definitions of other terms, notably Map-Request, Map-Reply, 179 Ingress Tunnel Router (ITR), and Egress Tunnel Router (ETR), please 180 consult the LISP specification [LISP]. 182 3. Basic Overview 184 There are two attributes of a LISP device behind a typical NAT that 185 requires special consideration in LISP protocol behavior in order to 186 make the device reachable. First, the RLOC assigned to the device is 187 typically not globally unique nor globally routable. Second, the NAT 188 likely has a restrictive translation table and forwarding policy, 189 requiring outbound packets to create state before the NAT accepts 190 inbound packets. This section provides an overview of the LISP NAT 191 traversal mechanism which deals with these conditions. The following 192 sections specify the mechanism in more detail. 194 When a LISP device receives a new RLOC and wants to register it with 195 the mapping system, it needs to first discover whether it is behind a 196 NAT. To do this, an ETR queries its Map-Server to discover the ETR's 197 translated global RLOC and port via the two new LISP messages: Info- 198 Request and Info-Reply. Once an ETR detects that it is behind a NAT, 199 it uses a LISP Re-encapsulating Tunnel Router (RTR) entity as an 200 anchor point for sending and receiving data plane traffic through the 201 NAT device. The ETR registers the RTR RLOC(s) to its Map-Server 202 using the RTR as a proxy for the Map-Register message. The ETR 203 encapsulates the Map-Register message in a LISP ECM header destined 204 to the RTR's RLOC. The RTR strips the LISP ECM header, re-originates 205 the Map-Register message, and sends it to the Map-Server. This 206 initializes state in the NAT device so the ETR can receive traffic on 207 port 4341 from the RTR. The ETR also registers the RTR RLOC as the 208 RLOC where the ETR EID prefix is reachable. As a result, all packets 209 destined to the ETR's EID will go to its RTR. The RTR will then re- 210 encapsulate and forward the ETR's traffic via the existing NAT state 211 to the ETR. 213 Outbound LISP data traffic from the xTR is also encapsulated to the 214 RTR, where the RTR de-capsulates the LISP packets, and then re- 215 encapsulates them or forwards them natively depending on their 216 destination. 218 In the next sections these procedures are discussed in more detail. 220 4. LISP RTR Message Details 222 The main modifications in the LISP protocol to enable LISP NAT 223 traversal via an RTR include: (1) two new messages used for NAT 224 discovery (Info-Request and Info-Reply), and (2) encapsulation of two 225 LISP control messages (Map-Register and Map-Notify) between the xTR 226 and the RTR. Map-Register is encapsulated in an ECM header while 227 Map-Notify is encapsulated in a LISP data header (Data-Map-Notify). 228 This section describes the message formats and details of the Info- 229 Request, Info-Reply, and Data-Map-Notify messages, as well as 230 encapsulation details and minor changes to Map-Register and Map- 231 Notify messages. 233 4.1. Info-Request Message 235 An ETR sends an Info-Request message to its Map-Server in order to 236 1. detect whether there is a NAT on the path to its Map-Server 238 2. obtain a list of RTR RLOCs that can be used for LISP data plane 239 NAT traversal. 241 An Info-Request message is a LISP control message, its source port is 242 chosen by the xTR and its destination port is set to 4342. 244 0 1 2 3 245 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 1 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 |Type=7 |R| Reserved | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | Nonce . . . | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | . . . Nonce | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | Key ID | Authentication Data Length | 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 ~ Authentication Data ~ 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | TTL | 258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 259 | Reserved | EID mask-len | EID-prefix-AFI | 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | EID-prefix | 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 263 | AFI = 0 | | 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 LISP Info-Request Message Format 268 Type: 7 (Info-Request) 270 R: R bit indicates this is a reply to an Info-Request (Info- 271 Reply). R bit is set to 0 in an Info-Request. When R bit is set 272 to 0, the AFI field (following the EID-prefix field) must be set 273 to 0. When R bit is set to 1, the packet contents follow the 274 format for an Info-Reply, as described below. 276 Reserved: Must be set to 0 on transmit and must be ignored on 277 receipt. 279 TTL: The time in minutes the recipient of the Info-Reply will 280 store the RTR Information. 282 Nonce: An 8-byte random value created by the sender of the Info- 283 Request. This nonce will be returned in the Info-Reply. The 284 nonce SHOULD be generated by a properly seeded pseudo-random (or 285 strong random) source. 287 Descriptions for other fields can be found in the Map-Register 288 section of the main LISP draft [LISP]. Field descriptions for the 289 LCAF AFI = 0 can be found in the LISP LCAF draft [LCAF] . 291 4.2. LISP Info-Reply 293 When a Map-Server receives an Info-Request message, it responds with 294 an Info-Reply message. The Info-Reply message source port is 4342, 295 and destination port is taken from the source port of the triggering 296 Info-Request. Map-Server fills the NAT LCAF (LCAF Type = 7) fields 297 according to their description. The Map-Server uses AFI=0 for the 298 Private ETR RLOC Address field in the NAT LCAF. 300 0 1 2 3 301 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 1 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 303 |Type=7 |R| Reserved | 304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 305 | Nonce . . . | 306 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 307 | . . . Nonce | 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 309 | Key ID | Authentication Data Length | 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 ~ Authentication Data ~ 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 | TTL | 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 315 | Reserved | EID mask-len | EID-prefix-AFI | 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 317 | EID-prefix | 318 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 319 | | AFI = 16387 | Rsvd1 | Flags | 320 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 321 | | Type = 7 | Rsvd2 | 4 + n | 322 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 N | MS UDP Port Number | ETR UDP Port Number | 324 A +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 325 T | AFI = x | Global ETR RLOC Address ... | 326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 L | AFI = x | MS RLOC Address ... | 328 C +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 A | AFI = x | Private ETR RLOC Address ... | 330 F +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | | AFI = x | RTR RLOC Address 1 ... | 332 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | | AFI = x | RTR RLOC Address n ... | 334 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 336 LISP Info-Reply Message Format 338 Type: 7 , R = 1, (Info-Reply) 340 The format is similar to the Info-Request message. See Info-Request 341 section for field descriptions. Field descriptions for the NAT LCAF 342 section can be found in the LISP LCAF draft [LCAF] . 344 4.3. LISP Map-Register Message 346 The third bit after the Type field in the Map-Register message is 347 allocated as "I" bit. I bit indicates that a 128 bit xTR-ID and a 64 348 bit site-ID field are present at the end of the Map-Register message. 349 If an xTR is configured with an xTR-ID or site-ID, it MUST set the I 350 bit to 1 and include its xTR-ID and site-ID in the Map-Register 351 messages it generates. If either the xTR-ID or site-ID is not 352 configured an unspecified value is encoded for whichever ID that is 353 not configured. 355 xTR-ID is a 128 bit field at the end of the Map-Register message, 356 starting after the final Record in the message. The xTR-ID is used 357 to identify the intended recipient xTR for a Map-Notify message, 358 especially in the case where a site has more than one xTR. A value 359 of all zeros indicate that an xTR-ID is not specified, though encoded 360 in the message. This is useful in the case where a site-ID is 361 specified, but no xTR-ID is configured. When a Map-Server receives a 362 Map-Register with an xTR-ID specified (I bit set and xTR-ID has a 363 non-zero value), it MUST copy the XTR-ID from the Map-Register to the 364 associated Map-Notify message. When a Map-Server is sending an 365 unsolicited Map-Notify to an xTR to notify the xTR of a change in 366 locators, the Map-Server must include the xTR-ID for the intended 367 recipient xTR, if it has one stored locally. 369 site-ID is a 64 bit field at the end of the Map-Register message, 370 following the xTR-ID. site-ID is used by the Map-Server receiving the 371 Map-Register message to identify which xTRs belong to the same site. 372 A value of 0 indicate that a site-ID is not specified, though encoded 373 in the message. When a Map-Server receives a Map-Register with a 374 site-ID specified (I bit set and site-ID has non-zero value), it must 375 copy the site-ID from the Map-Register to the associated Map-Notify 376 message. When a Map-Server is sending an unsolicited Map-Notify to 377 an xTR to notify the xTR of a change in locators, the Map-Server must 378 include the site-ID for the intended recipient xTR, if it has one 379 stored locally. 381 A LISP device that sends a Map-Register to an RTR must encapsulate 382 the Map-Register message using an Encapsulated Control Message (ECM) 383 [LISP]. The 6th bit in the ECM LISP header is allocated as the "R" 384 bit. The R bit indicates that the encapsulated Map-Register is to be 385 processed by an RTR. The 7th bit in the ECM header is allocated as 386 the "N" bit. The N bit indicates that this Map-REgister is being 387 relayed by an RTR. When an RTR relays the ECM-ed Map-Register to a 388 Map-Server, the N bit must be set to 1. 390 The outer header source RLOC of the ECM is set to the LISP device's 391 local RLOC, and the outer header source port is set to 4341. The 392 outer header destination RLOC and port are set to RTR RLOC and 4342 393 respectively. The inner header source RLOC is set to LISP device's 394 local RLOC, and the inner source port is picked at random. The inner 395 header destination RLOC is set to the xTR's Map-Server RLOC, and 396 inner header destination port is set to 4342. 398 4.4. LISP Map-Notify 400 The first bit after the Type field in a Map-Notify message is 401 allocated as the "I" bit. I bit indicates that a 128 bit xTR-ID and 402 64 bit site-ID field is present at the end of the Map-Notify message, 403 following the final Record in the Map-Notify (See Section 4.3 for 404 details on xTR-ID and site-ID). A Map-Server MUST set the I bit in a 405 Map-Notify and include the xTR-ID and/or site-ID of the intended 406 recipient xTR if the associated Map-Register has an xTR-ID and/or 407 site-ID specified, or when the Map-Server has previously cached an 408 xTR-ID and/or site-ID for the destination xTR. 410 A LISP device that sends a Map-Notify to an RTR must encapsulate the 411 Map-Notify message using an ECM. the 6th bit in the ECM LISP header, 412 allocated as the "R" bit, must be set when the encapsulated Map- 413 Notify is to be processed by an RTR. If the S bit is also set in the 414 Map-Notify ECM header, it indicates that additional MS-RTR 415 authentication data is included after the LISP header in the ECM. If 416 the I bit is also set in the Map-Notify, the xTR-ID and site-ID 417 fields are included in the Map-Notify. If a Map-Server receiving an 418 ECM-ed Map-Register has a shared key associated with the sending RTR, 419 it must generate a Map-Notify message with the S bit in the ECM 420 header set to 1, and with the additional MS-RTR authentication 421 related fields described below. 423 0 1 2 3 424 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 1 425 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 426 |AD Type| Reserved | 427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 428 | MS-RTR Key ID | MS-RTR Auth. Data Length | 429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 430 ~ MS-RTR Authentication Data ~ 431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 Changes to LISP Map-Notify Message 435 AD Type: 2 (RTR Authentication Data) 437 MS-RTR Key ID: A configured ID to find the configured Message 438 Authentication Code (MAC) algorithm and key value used for the 439 authentication function. See [LISP] section 14.4 for code point 440 assignments. 442 MS-RTR Authentication Data Length: The length in bytes of the MS-RTR 443 Authentication Data field that follows this field. The length of the 444 Authentication Data field is dependent on the Message Authentication 445 Code (MAC) algorithm used. The length field allows a device that 446 doesn't know the MAC algorithm to correctly parse the packet. 448 MS-RTR Authentication Data: The message digest used from the output 449 of the Message Authentication Code (MAC) algorithm. The entire Map- 450 Notify payload is authenticated. After the MAC is computed, it is 451 placed in this field. Implementations of this specification MUST 452 support HMAC-SHA-1-96 [RFC2404] and SHOULD support HMAC-SHA-256-128 453 [RFC6234]. 455 For a full description of all fields in the Map-Notify message refer 456 to Map-Notify section in the main LISP draft [LISP]. 458 4.5. LISP Data-Map-Notify Message 460 When an RTR receives an ECM-ed Map-Notify message with R bit in the 461 ECM header set to 1, it has to relay the Map-Notify payload to the 462 registering LISP device. After removing the ECM header and 463 processing the Map-Notify message as described in Section 5.3, the 464 RTR encapsulates the Map-Notify in a LISP data header and sends it to 465 the associated LISP device. This Map-Notify inside a LISP data 466 header is referred to as a Data-Map-Notify message. 468 0 1 2 3 469 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 1 470 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 471 / | IPv4 or IPv6 Header | 472 OH | (uses RLOC addresses) | 473 \ | | 474 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 475 / | Source Port = 4342 | Dest Port = xxxx | 476 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 477 \ | UDP Length | UDP Checksum | 478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 479 L | LISP Header ~ | 480 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 481 S / | ~ LISP Header | 482 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 483 / | IPv4 or IPv6 Header | 484 IH | (uses RLOC or EID addresses) | 485 \ | | 486 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 487 / | Source Port = 4342 | Dest Port = 4342 | 488 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 \ | UDP Length | UDP Checksum | 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 LCM | LISP Map-Notify Message ~ 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 494 LISP Data-Map-Notify Message 496 In a Data-Map-Notify, the outer header source RLOC is set to the 497 RTR's RLOC that was used in the associated Map-Register. This is 498 previously cached by the RTR. The outer header source port is set to 499 4342. The outer header destination RLOC and port are filled based on 500 the translated global RLOC and port of the registering LISP device 501 previously stored locally at the RTR. The inner header source 502 address is Map-Server's RLOC, and inner header source port is 4342. 503 The inner header destination address is set to the LISP device's 504 local RLOC also previously cached by the RTR (See Section 5.3 for 505 details.). The inner header destination port is 4342. 507 Since a Data-Map-Notify is a control message encapsulated in a LISP 508 data header, a special Instance ID is used as a signal for the xTR to 509 trigger processing of the control packet inside the data header. The 510 Instance ID value 0xFFFFFF is reserved for this purpose. The 511 Instance ID field in a Data-Map-Notify must be set to 0xFFFFFF. 513 5. Protocol Operations 515 There are two main steps in the NAT traversal procedure. First, the 516 ETR's translated global RLOC must be discovered. Second, the NAT 517 translation table must be primed to accept incoming connections. At 518 the same time, the Map-Server and the RTR must be informed of the 519 ETR's translated global RLOC including the translated ephemeral port 520 number(s) at which the Map-Server and RTR can reach the LISP device. 522 5.1. xTR Processing 523 Upon receiving a new local RLOC, an ETR first has to detect whether 524 the new RLOC is behind a NAT device. For this purpose the ETR sends 525 an Info-Request message to its Map-Server in order to discover the 526 ETR's translated global RLOC as it is visible to the Map-Server. The 527 ETR uses its new local RLOC as the source RLOC of the message. The 528 Map-Server, after authenticating the message, responds with an Info- 529 Reply message. The Map-Server includes the source RLOC and port from 530 the Info-Request message in the Global ETR RLOC Address and ETR UDP 531 Port Number fields of the Info-Reply. The Map Server also includes 532 the destination RLOC and port number of the Info-Request message in 533 the MS RLOC Address and MS UDP Port Number fields of the Info-Reply. 534 In addition, the Map-Server provides a list of RTR RLOCs that the ETR 535 may use in case it needs NAT traversal services. The source port of 536 the Info-Reply is set to 4342 and the destination port is copied from 537 the source port of the triggering Info-Request message. 539 Upon receiving the Info-Reply message, the ETR compares the source 540 RLOC and source port used for the Info-Request message with the 541 Global ETR RLOC Address and ETR UDP Port Number fields of the Info- 542 Reply message. If the two are not identical, the ETR concludes that 543 its new local RLOC is behind a NAT and that it requires an RTR for 544 NAT traversal services in order to be reachable at that RLOC. An ETR 545 behind other statefull devices (e.g. statefull firewalls) may also 546 use an RTR and the procedure specified here for traversing the 547 statefull device. Detecting existence of such devices are beyond 548 scope of this document. 550 In the case where an xTR has multiple RLOCs, info-Requests must be 551 sent per each RLOC and the state and processes described below must 552 be followed per each RLOC. The RLOCs included in Map-Register 553 messages in such cases will be the union of the locators resulting 554 from the process below per each RLOC of the xTR, according to the 555 specifics of that interface (whether it is behind the NAT or not). 557 If there is no NAT on the path identified by an info-Request and an 558 Info-Reply, the ETR registers the associated RLOC with its Map-Server 559 as described in the main LISP draft [LISP]. 561 5.1.1. ETR Registration 563 Once an ETR has detected that it is behind a NAT, based on local 564 policy the ETR selects one (or more) RTR(s) from the RTR RLOCs 565 provided in the Info-Reply and initializes state in the NAT device in 566 order to receive LISP data traffic on UDP port 4341 from the selected 567 RTR. To do so, the ETR sends a Map-Register encapsulated in an ECM 568 header to the selected RTR(s). The Map-Register message is created 569 as specified in [LISP]. More specifically, the source RLOC of the 570 Map-Register is set to ETR's local RLOC, while the destination RLOC 571 is set to the ETR's Map-Server RLOC, and destination port is set to 572 4342. The ETR sets the M bit in Map-Register to 1, and it includes 573 the selected RTR RLOC(s) as the locators in the Map-Register message. 574 The ETR can also include its local RLOCs as locators in the Map- 575 Register, including weight and priorities, while setting the R bit to 576 0 for each local RLOC. This can be used by the RTR for load 577 balancing when forwarding data to a multi-homed xTR behind a NAT. 578 The R bit is set to 1 for all RTR locators included in the Map- 579 Register. The ETR must also set the I bit in the Map-Register 580 message to 1 and include its xTR-ID in t he corresponding field. In 581 the ECM header of this Map-Register the source RLOC is set to ETR's 582 local RLOC and the source port is set to 4341, while the destination 583 RLOC is the RTR's RLOC and the destination port is set to LISP 584 control port 4342. The R bit in the ECM header is also set to 1, to 585 indicate that this EDCM-ed Map-Register is to be processed by an RTR. 587 This ECM-ed Map-Register is then sent to the RTR. The RTR removes 588 the EMC header, re-originates the Map-Register message, encapsulates 589 the new Map-Register in a new ECM header with R bit set to 0, and 590 sends it to the associated Map-Server. The RTR then encapsulates the 591 corresponding Map-Notify message in a LISP data header (Data-Map- 592 Notify) and sends it back to the xTR. 594 Upon receiving a Data-Map-Notify from the RTR, the ETR must strip the 595 outer LISP data header, and process the inner Map-Notify message as 596 described in [LISP]. Since outer header destination port in Data- 597 Map-Notify is set to LISP data port 4341, the Instance ID 0xFFFFFF in 598 the LISP header of the Data-Map-Notify is used by the ETR to detect 599 and process the Data-Map-Notify as a control message encapsulated in 600 a LISP data header. While processing the Data-Map-Notify, the xTR 601 also stores the RTR RLOC(s) as its data plane proxy, by storing a 602 default map-cache entry with the RTR RLOC(s) as its locator set. The 603 xTR may map the EID prefix 0/0 to this RTR RLOC(s). This results in 604 the xTR encapsulating all LISP data plane traffic to this RTR. At 605 this point the registration and state initialization is complete and 606 the xTR can use the RTR services. The state created in the NAT 607 device based on the ECM-ed Map-Register and corresponding Data-Map- 608 Notify is used by the xTR behind the NAT to send and receive LISP 609 control packets to/from the RTR, as well as for receiving LISP data 610 packets form the RTR. 612 If ETR receives a Data-Map-Notify with a xTR-ID specified, but the 613 xTR-ID is not equal to its local xTR-ID, it must log this as an 614 error. The ETR should discard such Data-Map-Notify message. 616 The ETR must periodically send ECM-ed Map-Register messages to its 617 RTR in order to both refresh its registration to the RTR and the Map- 618 Server, and as a keep alive in order to preserve the state in the NAT 619 device. RFC 2663 [NAT] points out that the period for sending the 620 keep alives can be set to default value of two minutes, however since 621 shorter timeouts may exist in some NAT deployments, the interval for 622 sending periodic ECM-ed Map-Registers must be configurable. 624 5.1.2. Map-Request and Map-Reply Handling 626 The ETR is in control of how to handle the Map-Requests and Map- 627 Replies. If the ETR wants the Map-Server to proxy-reply as described 628 in [LISP], it can register the RTR RLOC(s) as its locator via the 629 ECM-ed Map-Register message. In this case, if the proxy bit is set 630 in the Map-Register, the Map-Server will proxy reply with RTR's RLOC 631 to all Map-Requests for the ETR. As a result all traffic for the ETR 632 is encapsulated to its RTR(s). 634 If the proxy bit in the ECM-ed Map-Register message is not set, and 635 the ETR chooses to receive Map-Requests, the ETR must also initiate 636 and preserve state in the NAT device to receive LISP control packets 637 from its Map-Server. To do this, the ETR must periodically send 638 Info-Request messages to its Map-Server, and receive Info-Reply 639 messages from the Map-Server. As pointed in RFC 2663 [NAT] the 640 default assumption of two minute period for session lifetime can be 641 used, however since shorter timeouts may exist in some NAT 642 deployments, the interval for sending periodic Info-Requests must be 643 configurable. Furthermore, the ETR must also provide its Map-Server 644 with the ETR's translated global RLOC and port as visible to the Map- 645 Server. To do this, ETR includes a copy of the NAT LCAF section of 646 the Info-Reply message as one of the locators in its Map-Register 647 along with the RTR(s) RLOC(s). The ETR can set the priorities of RTR 648 RLOC(s) in this Map-Register to 255, resulting in the Map Server 649 encapsulating Map-Requests to the ETR's translated global RLOC and 650 port so it can receive them through the NAT device. 652 If an ETR behind a NAT chooses to receive Map-Requests from the Map- 653 Server, it must send Map-Replies to requesting ITRs. Note that this 654 configuration will result in excessive state in the NAT device and is 655 not recommended. ETR must include its RTR RLOC(s) as its locator set 656 in the Map-Reply in order to receive data through the NAT device. 658 When an ITR behind a NAT is encapsulating outbound LISP traffic, it 659 must use its RTR RLOC as the locator for all destination EIDs that it 660 wishes to send data to. As such, the ITR does not need to send Map- 661 Requests for the purpose of finding EID-to-RLOC mappings. For RLOC- 662 probing, the periodic ECM-ed Map-Register and Data-Map-Notify 663 messages between xTR and RTR can also serve the purpose of RLOC 664 probes. However, if RLOC-probing is used, no changes are required to 665 the RLOC-probing specification in [LISP], except that the LISP device 666 behind a NAT only needs to probe the RTR's RLOC. 668 5.1.3. xTR Sending and Receiving Data 670 When a Map-Request for a LISP device behind a NAT is received by its 671 Map-Server or the LISP device itself, the Map-Server, or the LISP 672 device (ETR), responds with a Map-Reply including RTR's RLOC as the 673 locator for the requested EID. As a result, all LISP data traffic 674 destined for the ETR's EID behind the NAT is encapsulated to its RTR. 675 The RTR re-encapsulates the LISP data packets to the ETR's translated 676 global RLOC and port number so the data can pass through the NAT 677 device and reach the ETR. As a result the ETR receives LISP data 678 traffic with outer header destination port set to 4341 as specified 679 in [LISP]. 681 For sending outbound LISP data, an ITR behind a NAT must use the RTR 682 RLOC as the locator for all EIDs that it wishes to send data to 683 according to the installed default map-cache entry. The ITR then 684 encapsulates the LISP traffic in a LISP data header with outer header 685 destination set to RTR RLOC and outer header destination port set to 686 4341. This may create a secondary state in the NAT device. ITR must 687 set the outer header source port in all egress LISP data packets to a 688 random but static port number in order to avoid creating excessive 689 state in the NAT device. 691 If the ITR and ETR of a site are not collocated, the RTR RLOC must be 692 configured in the ITR via an out-of-band mechanism. Other procedures 693 specified here would still apply. 695 5.2. Map-Server Processing 697 Upon receiving an Info-Request message a Map-Server first verifies 698 the authenticity of the message. Next the Map-Server creates an 699 Info-Reply message and copies the source RLOC and port number of the 700 Info-Request message to the Global ETR RLOC Address and ETR UDP Port 701 Number fields of the Info-Reply message. The Map-Server also 702 includes a list of RTR RLOCs that the ETR may use for NAT traversal 703 services. The Map-Server sends the Info-Reply message to the ETR, by 704 setting the destination RLOC and port of the Info-Reply to the source 705 RLOC and port of the triggering Info-Request. The Map-Server sets 706 the source port of the Info-Reply to 4342. 708 Upon receiving an ECM-ed Map-Register message with the N bit in the 709 ECM header set to 1, the Map-Server removes the ECM header and if the 710 M bit in the Map-Register is set, the Map-Server processes the Map- 711 Register message and generates the resulting Map-Notify as described 712 in [LISP]. The Map-Server encapsulates the Map-Notify in an ECM 713 header and sets the R bit in the ECM header to 1. This indicates 714 that the ECM-ed Map-Notify is to be processed by an RTR. If the Map- 715 Server has a shared secret configured with the RTR sending the Map- 716 Register, the Map-Server also sets the S bit in the ECM header of the 717 Map-Notify and includes the MS-RTR authentication data after the ECM 718 LISP header. See Security Considerations Section for more details. 719 If the I bit is set in the Map-Register message, the Map-Server also 720 locally stores the xTR-ID from the Map-Register, and sets the I bit 721 in the corresponding Map-Notify message and includes the same xTR-ID 722 in the Map-Notify. The ECM-ed Map-Notify is then sent to the RTR 723 sending the corresponding Map-Register. 725 If a Map-Server is forwarding Map-Requests to an ETR which has 726 registered its RLOC in a NAT LCAF, Map-Server must use the ETR Global 727 RLOC Address and ETR UDP Port as the destination RLOC and port for 728 outer header of the encapsulated Map-Requests. If more than one NAT 729 LCAF is registered for the same EID prefix, the Map-Server must use 730 the NAT LCAF corresponding to the RLOC of this Map-Server. 732 5.3. RTR Processing 734 Upon receiving an ECM-encapsulated Map-Register with the R bit set in 735 the ECM header, the RTR creates a map-cache entry for the EID-prefix 736 that was specified in the Map-Register message. The RTR stores the 737 outer header source RLOC and outer header source port, the outer 738 header destination RLOC (RTR's own RLOC), the inner header source 739 RLOC (xTR's local RLOC), the xTR-ID, the weight and priority 740 associated with the xTR's local RLOC that was used to send this Map- 741 Register if present, and the nonce field of the Map-Register in this 742 local map-cache entry. The RTR uses the inner header source address 743 to identify which xTR local RLOC (R bit =0) was used by the xTR to 744 send this Map-Register. The outer header source RLOC and outer 745 header source port is the ETR's translated global RLOC and port 746 number visible to the RTR. Once the registration process is 747 complete, this map-cache entry can be used to send LISP data traffic 748 to the ETR. The inner header destination RLOC is the RTR's RLOC, and 749 the inner header source RLOC is the ETR's local RLOC behind the NAT, 750 and the RTR can later use these fields as the inner header source 751 RLOC and destination RLOC correspondingly, for sending data- 752 encapsulated control messages (Data-Map-Notify) back to the ETR. The 753 nonce field is used for security purposes and is matched with the 754 nonce field in the corresponding Map-Notify message. This map-cache 755 entry is stored as an "unverified" mapping, until the corresponding 756 Map-Notify message is received. 758 In the cases where the xTR has multiple RLOCs behind the NAT, and 759 requires the RTR to load balance the traffic across those interfaces, 760 the xTR must include the local RLOCs associated with each interface 761 behind the NAT with the R bit in the locator record set to 0 in the 762 ECM-ed Map-Register sent to the RTR. The RTR uses the weight and 763 priority policies of the RLOCs with R=0 in the Map-Register to load 764 balance the traffic from the RTR to the xTR behind the NAT. The RTR 765 compares the RLOCs with the R bit set to 0 in the Map-Register to the 766 inner header source address of the Map-Register to find the matching 767 RLOC that the xTR used to send the Map-Register from. The RTR 768 associates the weight and priority policies of this local RLOC with 769 the NAT-translated RLOC and xTR-ID for this map-cache entry. For all 770 other local RLOCs included in the Map-Register, that the Map-Register 771 is not originating from, the RTR only updates previously cached 772 weight and priority policies if it already has those local RLOCs 773 previously stored for that EID prefix and xTR-ID. In other words, 774 the RTR only adds new local RLOCs and their weight and priority 775 policies to its cache if the Map-Register is actually originating 776 from that RLOC. The TTL for every map-cache is also only updated 777 when a Map-Register is originating from the same RLOC. However, the 778 weight and priorities of all previously cached local RLOCs will be 779 updated by every Map-Register, whether it is originating from that 780 RLOC or not. The xTR-ID is used to define the Merge domain for these 781 RLOCs. In other words, a Map-Register originating from a unique xTR- 782 ID will always overwrite previously stored policies for that xTR-ID. 783 However it does not modify in any way the policies indicated by any 784 other xTR-ID serving the same EID prefix. As a result, in the case 785 of a renumbering or xTR reboot, the xTR uses its unique xTR-ID to 786 send a new Map-Register, overwriting the previously stored policies 787 for that xTR. Using this method the xTR can immediately remove any 788 RLOCs from the RTR cache that are no longer active. In order to 789 implement this, the RTR must compare the list of local RLOCs in the 790 Map-Register (R=0) with the ones it has previously cached associated 791 with the same xTR-ID. If there is any RLOC previously cached that 792 does not appear in the newly received Map-Register, the RTR must 793 remove that RLOC together with the associated translated RLOC and 794 associated policies, because removal of a local (behind-the-NAT) RLOC 795 also invalidates the NAT-ed address associated with it. . 797 After filling the local map-cache entry, the RTR strips the outer 798 header and extracts the Map-Register message, re-originates the 799 message by rewriting the source RLOC of the Map-Register to RTR's 800 RLOC, encapsulated in a new ECM header with the R bit set to 0, and N 801 bit set to 1, and sends the ECM-ed Map-Register to destination Map- 802 Server. 804 Map-Server responds with a ECM-ed Map-Notify message to the RTR. 806 Upon receiving an ECM-ed Map-Notify message with R bit set to 1 in 807 the ECM header, if the S bit in ECM header is set to 1, RTR uses the 808 MS-RTR Key ID to verify the MS-RTR Authentication Data included after 809 the ECM header. If the MS-RTR authentication fails, the RTR must 810 drop the packet. Once the authenticity of the message is verified, 811 RTR can confirm that the Map-Register message for the ETR with the 812 matching xTR-ID was accepted by the Map-Server. At this point the 813 RTR can change the state of the associated map-cache entry to 814 verified for the duration of the Map-Register TTL. 816 The RTR then uses the information in the associated map-cache entry 817 to create a Data-Map-Notify message according to the following 818 procedure: RTR rewrites the inner header destination RLOC of the Map- 819 Notify message to ETR's local RLOC. Inner header destination port is 820 4342. The RTR encapsulates the Map-Notify in a LISP data header, 821 where the outer header destination RLOC and port number are set to 822 the ETR's translated global RLOC and port number. If more than one 823 ETR translated RLOC and port exists in the map-cache entry for the 824 same EID prefix specified in the Map-Notify, the RTR can use the xTR- 825 ID from the Map-Notify to identify which ETR is the correct 826 destination for the Data-Map-Notify. The RTR sets the outer header 827 source RLOC to RTR's RLOC from the map-cache entry and the outer 828 header source port is set to 4342. The RTR also sets the Instance ID 829 field in the LISP header of the Data-Map-Notify to 0xFFFFFF. The RTR 830 then sends the Data-Map-Notify to the ETR. 832 If the S bit is set to 0 in the ECM header of the Map-Notify, and the 833 RTR has a shared key configured locally with the sending Map-Server, 834 the RTR must drop the packet. If the S bit is set to 0, and the RTR 835 does not have a shared key configured with the associated Map-Server, 836 according to local policy, the RTR may drop the packet. If the Map- 837 Notify with S bit set to 0 is processed, the RTR must match the nonce 838 field from this Map-Notify with the nonce stored in the local map- 839 cache entry with the matching xTR-ID. If the nonces do not match, 840 the RTR must drop the packet. 842 5.3.1. RTR Data Forwarding 844 For all LISP data packets encapsulated to RTR's RLOC and outer header 845 destination port 4341, the RTR first verifies whether the source or 846 destination EID is a previously registered EID. If so, the RTR must 847 process the packet according to the following. If the destination or 848 source EID is not a registered EID, the RTR can drop or process the 849 packets based on local policy. 851 In the case where the destination EID is a previously registered EID, 852 the RTR must strip the LISP data header and re-encapsulate the packet 853 in a new LISP data header. The outer header RLOCs and UDP ports are 854 then filled based on the matching map-cache entry for the associated 855 destination EID prefix. The RTR uses the RTR RLOC from the map-cache 856 entry as the outer header source RLOC. The outer header source port 857 is set to 4342. The RTR sets the outer header destination RLOC and 858 outer header destination port based on the ETR translated global RLOC 859 and port stored in the map-cache entry. Then the RTR forwards the 860 LISP data packet. 862 In the case where the source EID is a previously registered EID, the 863 RTR process the packet as if it is a Proxy ETR (PETR). The RTR must 864 strip the LISP data header, and process the packet based on its inner 865 header destination address. The packet may be forwarded natively, it 866 may be LISP encapsulated to the destination ETR, or it may trigger 867 the RTR to send a LISP Map-Request. 869 5.4. Example 871 What follows is an example of an ETR initiating a registration of a 872 new RLOC to its Map-Server, when there is a NAT device on the path 873 between the ETR and the Map-Server. 875 In this example, the ETR (site1-ETR) is configured with the local 876 RLOC of 192.168.1.2. The NAT's global (external) addresses are from 877 2.0.0.1/24 prefix. The Map-Server is at 3.0.0.1. And one potential 878 RTR has an IP address of 1.0.0.1. The site1-ETR has an EID Prefix of 879 128.1.0.0/16. 881 An example of the registration process follows: 883 1. The Site1-ETR receives the private IP address, 192.168.1.2 as 884 its RLOC via DHCP. 886 2. The Site1-ETR sends an Info-Request message with the destination 887 RLOC of the Map-Server, 3.0.0.1, and source RLOC of 192.168.1.2. 888 This packet has the destination port set to 4342 and the source 889 port is set to (for example) 5001. 891 3. The NAT device translates the source IP from 192.168.1.2 to 892 2.0.0.1, and source port to (for example) 20001 global ephemeral 893 source port. 895 4. The Map-Server receives and responds to this Info-Request with 896 an Info-Reply message. This Info-Reply has the destination 897 address set to ETR's translated address of 2.0.0.1 and the 898 source address is the Map-Server's RLOC, namely 3.0.0.1. The 899 destination port is 20001 and the source port is 4342. Map- 900 Server includes a copy of the source address and port of the 901 Info-Request message (2.0.0.1:20001), and a list of RTR RLOCs 902 including RTR RLOC 1.0.0.1 in the Info-Reply contents. 904 5. The NAT translates the Info-Reply packet's destination IP from 905 2.0.0.1 to 192.168.1.2, and translates the destination port from 906 20001 to 5001, and forwards the Info-Reply to site1-ETR at 907 192.168.1.2. 909 6. The Site1-ETR detects that it is behind a NAT by comparing its 910 local RLOC (192.168.1.2) with the Global ETR RLOC Address in the 911 Info-Reply (2.0.0.2) . Then site1-ETR picks the RTR 1.0.0.1 from 912 the list of RTR RLOCs in the Info-Reply. ETR stores the RTR 913 RLOC in a default map-cache entry to periodically send ECM-ed 914 Map-Registers to. 916 7. The ETR sends an ECM encapsulated Map-Register to RTR at 917 1.0.0.1. The outer header source RLOC of this Map-Register is 918 set to 192.168.1.2 and the outer header source port is set to 919 4341. The outer header destination RLOC and port are set to RTR 920 RLOC at 1.0.0.1 and 4342 respectively. The R bit in ECM header 921 is set to 1. The inner header destination RLOC is set to ETR's 922 Map-Server 3.0.0.1, and the inner header destination port is set 923 to 4342. The inner header source RLOC is set to ETR's local 924 RLOC 192.168.1.2. In the Map-Register message the RTR RLOC 925 1.0.0.1 appears as the locator set for the ETR's EID prefix 926 (128.1.0.0/16). In this example ETR also sets the Proxy bit in 927 the Map-Register to 1, and sets I bit to 1, and includes its 928 xTR-ID in the Map-Register. 930 8. The NAT translates the source RLOC in the ECM header of the Map- 931 Register, by changing it from 192.168.1.2 to 2.0.0.2, and 932 translates the source port in the ECM header from 4341 to (for 933 example) 20002, and forwards the Map-Register to RTR. 935 9. The RTR receives the Map-Register and creates a map-cache entry 936 with the ETR's xTR-ID, EID prefix, and the source RLOC and port 937 of the ECM header of the Map-Register as the locator (128.1.0.0/ 938 16 is mapped to 2.0.0.2:20002). RTR also caches the inner 939 header source RLOC of the Map-Register namely 192.168.1.2, and 940 the outer header destination RLOC of the ECM header in the Map- 941 Register (this would be RTR's RLOC 1.0.0.1 ) to use for sending 942 back a Data-Map-Notify. RTR then removes the outer header, re- 943 writes the source RLOC of the Map-Register message to its own 944 RLOC 1.0.0.1, adds a new ECM header with R=0, and N=1, and 945 forwards the Map-Register to the destination Map-Server. 947 10. The Map-Server receives the ECM-ed Map-Register with N bit set 948 to 1, removes the ECM header, and processes it according to 949 [LISP]. Since Map-Server has a shared secret with the sending 950 RTR, after registering the ETR, Map-Server responds with a ECM- 951 ed Map-Notify with the R bit and S bit both set to 1 in the ECM 952 header and including the MS-RTR authentication data. Since the 953 I bit is set in the Map-Register, the Map-Server also sets the I 954 bit in the Map-Notify and copies the xTR-ID from the Map- 955 Register to the Map-Notify. The source address of this Map- 956 Notify is set to 3.0.0.1. The destination is RTR 1.0.0.1, and 957 both source and destination ports are set to 4342. 959 11. The RTR receives the ECM-ed Map-Notify and verifies the MS-RTR 960 authentication data. The RTR data-encapsulates the Map-Notify 961 and sends the resulting Data-Map-Notify to site1-ETR with a 962 matching xTR-ID. The outer header source RLOC and port of the 963 Data-Map-Notify are set to 1.0.0.1:4342. The outer header 964 destination RLOC and port are retrieved from previously cached 965 map-cache entry in step 9 namely 2.0.0.2:20002. RTR also sets 966 the inner header destination address to site1-ETR's local 967 address namely 192.168.1.2. RTR sets the Instance ID in the 968 LISP header to 0xFFFFFF. At this point RTR marks ETR's EID 969 prefix as "Registered" status and forwards the Data-Map-Notify 970 to ETR. 972 12. The NAT device translates the destination RLOC and port of the 973 Data-Map-Notify to 192.168.1.2:4341 and forwards the packet to 974 ETR. 976 13. The Site1-ETR receives the packet with a destination port 4341, 977 and processes the packet as a control packet after observing the 978 Instance ID value 0xFFFFFF in the LISP header. At this point 979 ETR's registration to the RTR is complete. 981 Assume a requesting ITR in a second LISP (site2-ITR) site has an RLOC 982 of 74.0.0.1. The following is an example process of an EID behind 983 site2-ITR sending a data packet to an EID behind the site1-ETR: 985 1. The ITR sends a Map-Request which arrives via the LISP mapping 986 system to the ETR's Map Server. 988 2. The Map-Server sends a Map-Reply on behalf of the ETR, using the 989 RTR's RLOC (1.0.0.1) in the Map-Reply's Locator Set. 991 3. The ITR encapsulates a LISP data packet with ITR's local RLOC 992 (74.0.0.1) as the source RLOC and the RTR as the destination RLOC 993 (1.0.0.1) in the outer header. 995 4. The RTR decapsulates the packet, evaluates the inner header 996 against its map-cache and then re-encapsulates the packet. The 997 new outer header's source RLOC is the RTR's RLOC 1.0.0.1 and the 998 new outer header's destination RLOC is the Global NAT address 999 2.0.0.2. The destination port of the packet is set to 20002 1000 (discovered above during the registration phase) and the source 1001 port is 4342. 1003 5. The NAT translates the LISP data packet's destination IP from to 1004 2.0.0.2 to 192.168.1.2, and translates the destination port from 1005 20002 to 4341, and forwards the LISP data packet to the ETR at 1006 192.168.1.2. 1008 6. For the reverse path the ITR uses its local map-cache entry with 1009 the RTR RLOC as the default locator and encapsulates the LISP 1010 data packets using RTR RLOC, and 4341 as destination RLOC and 1011 port. The ITR must pick a random source port to use for all 1012 outbound LISP data traffic in order to avoid creating excessive 1013 state in the NAT. 1015 6. Security Considerations 1017 By having the RTR relay the ECM-ed Map-Register message from an ETR 1018 to its Map-Server, the RTR can restrict access to the RTR services, 1019 only to those ETRs that are registered with a given Map-Server. To 1020 do so, the RTR and the Map-Server may be configured with a shared key 1021 that is used to authenticate the origin and to protect the integrity 1022 of the Map-Notify messages sent by the Map Server to the RTR. This 1023 prevents an on-path attacker from impersonating the Map-Server to the 1024 RTR, and allows the RTR to cryptographically verify that the ETR is 1025 properly registered with the Map-Server. 1027 Having the RTR re-encapsulate traffic only when the source or the 1028 destination are registered EIDs, protects against the adverse use of 1029 an RTR for EID spoofing. 1031 Upon receiving a Data-Map-Notify, an xTR can authenticate the origin 1032 of the Map-Notify message using the key that the ETR shares with the 1033 Map-Server. This enables the ETR to verify that the ECM-ed Map- 1034 Register was indeed forwarded by the RTR to the Map-Server, and was 1035 accepted by the Map-Server. 1037 6.1. Acknowledgments 1039 The authors would like to thank Noel Chiappa, Alberto Rodriguez 1040 Natal, Lorand Jakab, Albert Cabellos, Dominik Klein, Matthias 1041 Hartmann, and Michael Menth for their previous work, feedback and 1042 helpful suggestions. 1044 7. IANA Considerations 1046 This document does not request any IANA actions. 1048 8. Normative References 1050 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1051 Address Format (LCAF)", draft-ietf-lisp-lcaf-03 (work in 1052 progress), September 2013. 1054 [LISP-MS] Farinacci, D. and V. Fuller, "Locator/ID Separation 1055 Protocol (LISP) Map-Server Interface", RFC 6833, January 1056 2013. 1058 [LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 1059 "Locator/ID Separation Protocol (LISP)", RFC 6830, January 1060 2013. 1062 [NAT-MN] Klein, D., Hartmann, M., and M. Menth, "NAT traversal for 1063 LISP mobile node, In Proceedings of the Re-Architecting 1064 the Internet Workshop (ReARCH '10).", 2010. 1066 [NAT] Srisuresh, P. and M. Holdrege, "IP Network Address 1067 Translator (NAT) Terminology and Considerations", RFC 1068 2663, August 1999. 1070 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 1071 E. Lear, "Address Allocation for Private Internets", BCP 1072 5, RFC 1918, February 1996. 1074 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 1075 (CIDR): The Internet Address Assignment and Aggregation 1076 Plan", BCP 122, RFC 4632, August 2006. 1078 Authors' Addresses 1080 Vina Ermagan 1081 Cisco Systems, Inc. 1083 Email: vermagan@cisco.com 1085 Dino Farinacci 1086 lispers.net 1088 Email: farinacci@gmail.com 1089 Darrel Lewis 1090 Cisco Systems, Inc. 1092 Email: darlewis@cisco.com 1094 Jesper Skriver 1095 Cisco Systems, Inc. 1097 Email: jesper@cisco.com 1099 Fabio Maino 1100 Cisco Systems, Inc. 1102 Email: fmaino@cisco.com 1104 Chris White 1105 Logicalelegance, Inc. 1107 Email: chris@logicalelegance.com