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That text should be removed or replaced: By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, or will be disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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'11' == Outdated reference: A later version (-02) exists of draft-nikander-hip-mm-01 -- Possible downref: Normative reference to a draft: ref. '12' -- Possible downref: Normative reference to a draft: ref. '13' == Outdated reference: A later version (-03) exists of draft-iab-sec-cons-00 == Outdated reference: A later version (-12) exists of draft-ietf-ipseckey-rr-09 Summary: 12 errors (**), 0 flaws (~~), 11 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group P. Nikander 2 Internet-Draft Ericsson Research Nomadic Lab 3 Expires: October 30, 2004 J. Laganier 4 LIP / Sun Microsystems 5 May 2004 7 Host Identity Protocol (HIP) Domain Name System (DNS) Extensions 8 draft-nikander-hip-dns-00 10 Status of this Memo 12 By submitting this Internet-Draft, I certify that any applicable 13 patent or other IPR claims of which I am aware have been disclosed, 14 and any of which I become aware will be disclosed, in accordance with 15 RFC 3668. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that other 19 groups may also distribute working documents as Internet-Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at http:// 27 www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on October 30, 2004. 34 Copyright Notice 36 Copyright (C) The Internet Society (2004). All Rights Reserved. 38 Abstract 40 This document specifies two new resource records for the Domain Name 41 System, and how to use them with the Host Identity Protocol. These 42 records allow a HIP node to store in the DNS its Host Identity (i.e., 43 its public key), Host Identity Tag (i.e., a truncated hash of its 44 public key), and Rendezvous Servers (RVS). 46 Table of Contents 48 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 49 2. Conventions used in this document . . . . . . . . . . . . . . 5 50 3. Usage scenarios . . . . . . . . . . . . . . . . . . . . . . . 6 51 3.1 Simple static singly homed end-host . . . . . . . . . . . 7 52 3.2 Mobile end-host . . . . . . . . . . . . . . . . . . . . . 7 53 3.3 Multi-homed end-host . . . . . . . . . . . . . . . . . . . 7 54 3.4 Multi-homed site . . . . . . . . . . . . . . . . . . . . . 7 55 3.5 Site with a HAA . . . . . . . . . . . . . . . . . . . . . 7 56 4. Overview of using the DNS with HIP . . . . . . . . . . . . . . 8 57 4.1 Different types of HITs . . . . . . . . . . . . . . . . . 8 58 4.1.1 Host Assigning Authority (HAA) field . . . . . . . . . 8 59 4.1.2 Reverse lookup based on Type 2 (HAA-based) HITs . . . 9 60 4.2 Storing HI and HIT in DNS . . . . . . . . . . . . . . . . 9 61 4.3 Storing HAA in DNS . . . . . . . . . . . . . . . . . . . . 9 62 4.4 Providing multiple IP addresses . . . . . . . . . . . . . 9 63 4.4.1 Storing Rendezvous Servers in the DNS . . . . . . . . 10 64 4.5 Initiating connections based on DNS names . . . . . . . . 10 65 4.6 Address verification . . . . . . . . . . . . . . . . . . . 10 66 5. Storage Format . . . . . . . . . . . . . . . . . . . . . . . . 11 67 5.1 HIPHI RDATA format . . . . . . . . . . . . . . . . . . . . 11 68 5.1.1 RDATA format HIT type . . . . . . . . . . . . . . . . 11 69 5.1.2 RDATA format algorithm type . . . . . . . . . . . . . 11 70 5.1.3 RDATA format HIT . . . . . . . . . . . . . . . . . . . 11 71 5.1.4 RDATA format public key . . . . . . . . . . . . . . . 12 72 5.2 HIPRVS RDATA format . . . . . . . . . . . . . . . . . . . 12 73 5.2.1 RDATA format precedence . . . . . . . . . . . . . . . 13 74 5.2.2 RDATA format Rendezvous server type . . . . . . . . . 13 75 5.2.3 RDATA format Rendezvous server . . . . . . . . . . . . 13 76 6. Policy considerations . . . . . . . . . . . . . . . . . . . . 14 77 7. Conjunction of multiple HIs with mutiple IPs . . . . . . . . . 15 78 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 79 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 80 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 18 81 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 82 11.1 Normative references . . . . . . . . . . . . . . . . . . . . 19 83 11.2 Informative references . . . . . . . . . . . . . . . . . . . 20 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 20 85 Intellectual Property and Copyright Statements . . . . . . . . 21 87 1. Introduction 89 This document specifies two new resource records (RRs) for the Domain 90 Name System (DNS) [8], and how to use them with the Host Identity 91 Protocol (HIP) [10]. These records allow a HIP node to store in the 92 DNS its Host Identity (i.e., its public key), Host Identity Tag 93 (i.e., a truncated hash of its public key), and Rendezvous Servers 94 (RVS) [13]. 96 The current Internet architecture defines two global namespaces: IP 97 addresses and domain names. The Domain Name System provides a two way 98 lookup between these two namespaces. 100 The HIP architecture [11] defines a new third namespace called Host 101 Identity Namespace. This namespace is composed of the Host Identity 102 (HI) of HIP nodes. The Host Identity Tag (HIT) is one local 103 representation of a HI (the others being the IPv4-compatible and 104 IPv6-compatible Local Scope Identifiers - LSIs). This local 105 representation is obtained by taking the output of a secure hash 106 function applied to the HI, truncated to the IPv6 address size. HITs 107 are supposed to be used instead of IP addresses in some ULPs and 108 applications. 110 The Host Identity Protocol [10] allows two HIP nodes to establish a 111 pair of unidirectional IPsec Security Association. These SAs are 112 bound to HI instead of regular IP addresses. 114 The proposed HIP multi-homing mechanisms [12] allow a node to 115 dynamically change its set of underlying IP addresses while 116 maintaining transport layer session survivability. 118 The HIP rendezvous extensions [13] proposal allows a HIP node to 119 maintain HIP reachability while not relying on dynamic DNS updates to 120 make its peers aware of its current location (i.e., its set of IP 121 address(es)). 123 Although a HIP node can initiate a HIP communication 124 "opportunistically" (i.e., without a priori knowledge of its peer's 125 HI), doing so expose both endpoints to Man-in-the-Middle attacks on 126 the HIP handshake. Hence, there is a desire to gain knowledge of 127 peers' HI before applications and ULPs initiate communication. 129 Currently, most of the Internet applications which need to 130 communicate with a remote host first translate a domain name (often 131 obtained via user input) into one or more IP address(es). This step 132 occurs prior to communication with the remote host, and relies on a 133 DNS lookup. 135 With HIP, IP addresses are expected to be used mostly for on-the-wire 136 communication between end hosts, while most ULPs and applications 137 uses HIs or HITs instead (ICMP might be an example of an ULP not 138 using them). Consequently, we need a means to translate a domain name 139 into an HI. Using the DNS for this translation is pretty 140 straightforward: We define a new HIPHI (HIP HI) resource record. Upon 141 query by an application or ULP for a FQDN -> IP lookup, the resolver 142 would then additionaly perform an FQDN -> HI lookup, and use it to 143 construct the resulting HI -> IP mapping (which is internal to the 144 HIP layer). The HIP layer uses the HI -> IP mapping to translate HIs 145 and their local representations (HITs, IPv4 and IPv6-compatible LSIs) 146 into IP addresses and vice versa. 148 2. Conventions used in this document 150 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 151 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 152 document are to be interpreted as described in RFC2119 [2]. 154 3. Usage scenarios 156 In this section we briefly introduce a number of usage scenarios 157 where the DNS is useful with the Host Identity Protocol. 159 With HIP, most application and ULPs are unaware of the IP addresses 160 used to carry packets on the wire. Consequently, a HIP node could 161 take advantage of having multiple IP addresses for fail-over, 162 redundancy, mobility or renumbering, in a manner which is transparent 163 to most ULPs and applications (because they are bound to HIs, hence 164 they are agnostic to these IP address(es) changes). 166 In these situations, a node wishing to be reachable by reference to 167 its FQDN MAY store the following informations in the DNS: 169 o Its set of IP address(es). 170 o Its Host Identity (HI) and/or Host Identity Tag (HIT). 171 o Its Host Assigning Authority (HAA). 172 o The IP address(es) or DNS name(s) of its Rendezvous Server(s) 173 (RVS). 175 When a HIP node wants to initiate a communication with another HIP 176 node, it first needs to perform a HIP base exchange to set-up a HIP 177 association towards its peer. Although such an exchange can be 178 initiated opportunistically, i.e., without a priori knowledge of the 179 responder's HI, by doing so both nodes knowingly risk 180 man-in-the-middle attacks on the HIP exchange. To prevent these 181 attacks, it is recommended that the initiator first obtain the HI of 182 the responder, and then initiate the exchange. This can be done 183 through manual configuration, or DNS lookups, hence the introduction 184 of the new HIPHI RR. 186 When a HIP node is frequently changing its IP address(es), the 187 dynamic DNS update latency may prevent it from publishing globally 188 its new IP address(es). For solving this problem, the HIP 189 architecture introduce Rendezvous Servers (RVS). A HIP responder uses 190 a Rendezvous Server as a Rendezvous point, to maintain reachability 191 with possible HIP initiators. Such a HIP node would publish in the 192 DNS its RVS' IP address or DNS name in a HIPRVS RR, while keeping its 193 RVS up-to-date with its current set of IP addresses. 195 Then, when some HIP node wants to initiate an HIP exchange with such 196 a responder, it retrieves its RVS IP address by looking up a HIPRVS 197 RR at the FQDN of the responder, and sends an I1 to this IP address. 198 The I1 will then be relayed by the RVS to the responder, which will 199 then complete the HIP exchange, either directly or via the RVS [13]. 201 Note that storing HIP RR informations in the DNS at a FQDN which is 202 assigned to a non-HIP node might have very bad effects on its 203 reachability by HIP nodes. 205 3.1 Simple static singly homed end-host 207 A HIP node having a single static network attachment, wishing to be 208 reachable by reference to its FQDN, would store in the DNS, in 209 addition to its IP address(es), its Host Identity (HI) in a HIPHI 210 resource record. 212 3.2 Mobile end-host 214 A mobile HIP node wishing to be reachable by reference to its FQDN 215 would store in the DNS, instead of its IP address(es), its HI in a 216 HIPHI RR, and the IP address(es) of its Rendezvous Server(s) in 217 HIPRVS resource record(s). The mobile HIP node also need to notify 218 its Rendezvous Servers of any change in its set of IP address(es). 220 A host wanting to reach this mobile host would then send an I1 to one 221 of its RVS. Following, the RVS will relay the I1 up to the mobile 222 node, which will complete the HIP exchange. 224 3.3 Multi-homed end-host 226 A HIP node having several distinct network attachments is 227 multi-homed. Such a HIP node might also be reachable via several 228 distinct Rendezvous Servers. In addition to its set of IP 229 address(es), a multi-homed end-host would store in the DNS its HI in 230 a HIPHI RR, and possibly the IP address(es) of its RVS(s) in HIPRVS 231 RRs. 233 3.4 Multi-homed site 235 A HIP node being attached to the network of a multi-homed site will 236 possibly have multiple prefixes and addresses. This site might also 237 be reachable via several distinct Rendezvous Servers. In addition to 238 its set of IP address(es), a multi-homed end-host would store in the 239 DNS its HI in a HIPHI RR, and possibly the IP address(es) of its site 240 RVS(s) in HIPRVS RRs. 242 3.5 Site with a HAA 244 A site which has an assigned HAA might store this HAA in a HIPHI RR. 245 This might be useful to verify that a HIP node with a given "Type 2" 246 HIT belongs to a site referenced by a given HAA. 248 4. Overview of using the DNS with HIP 250 4.1 Different types of HITs 252 There are _currently_ two types of HITs. HITs of the first type 253 consists just of the SHA-1 hash of the public key. HITs of the second 254 type consist of a 63 bits Host Assigning Authority (HAA) field, and 255 only the last 64 bits come from a SHA-1 hash of the Host Identity. 256 This latter format for HIT is recommended for 'well known' systems. 257 It is possible to support a resolution mechanism for these names in 258 directories like DNS. Another use of HAA is in policy controls, see 259 Section 6. 261 The first bit of a HIT is used to differentiate between Type 1 and 262 Type 2 format. If the first bit is 0 then the rest of a HIT is the 263 127 upper bits of a SHA-1 hash of the Host Identity. If the first bit 264 is 1 then the next 63 bits is the HAA field, and only the last 64 265 bits come from the hash of the Host Identity. 267 Additionnaly, this document defines an internal IPv6-compatible LSI 268 representation format, to be used within the legacy IPv6-compatible 269 API (e.g., socket over AF_INET6). The format of these IPv6-compatible 270 LSIs is designed to avoid the most commonly occurring IPv6 addresses 271 in RFC3596 [9]. An IPv6-compatible LSI representation is easily 272 computed by replacing in the corresponding HIT the Bit 1 with NOT(Bit 273 0). That way if Bit 0 is zero and Bit 1 is one, then the rest of the 274 LSI is a 126 bits of a SHA-1 hash of the Host Identity. If Bit 0 is 275 one and Bit 1 is zero, then the next 62 bits come from the HAA field, 276 and only the last 64 bits come from the hash of the Host Identity. 277 The figure belows shows how the specified IPv6-compatible LSI format 278 tries to avoid collision: 280 Allocation Prefix Fraction of IPv6 281 (binary) Address Space 282 ------------------------ -------- ------------- 284 IPv6 Address space 00 1/4 285 Type 1 IPv6-compatible LSI 01 1/4 286 Type 2 IPv6-compatible LSI 10 1/4 287 IPv6 Address space 11 1/4 289 4.1.1 Host Assigning Authority (HAA) field 291 The 63 bits of HAA supports two levels of delegation. The first is a 292 registered assigning authority (RAA). The second is a registered 293 identity (RI, commonly a company). The RAA is 23 bits with values 294 assign sequentially by ICANN. The RI is 40 bits, also assigned 295 sequentially but by the RAA. 297 As IPv6 "global site-local" addresses were proposed in the IPv6 WG to 298 replace IPv6 site-local address, it is questionable if HIP needs a 299 kind of "global site-local" HAA, which would be generated by a given 300 site by setting the RAA field to 0 while the RI field is filled by 301 either random or EUI-48 bits. 303 4.1.2 Reverse lookup based on Type 2 (HAA-based) HITs 305 This can be used to create a resolution mechanism in the DNS. For 306 example if FOO is RAA number 100 and BAR is FOO's 50th registered 307 identity, and if 1385D17FC63961F5 is the hash of the Host Identity 308 for www.bar.com, then by using DNS Binary Labels [5] there could be a 309 reverse lookup record like: 311 \[x1385D17FC63961F5/64].\[x32/40].\[x64/23].HIT.int IN PTR 312 www.bar.com. 314 (Note that RFC2673 [5] is Experimental, and that there are some bad 315 experiences with binary DNS labels. [7]) 317 4.2 Storing HI and HIT in DNS 319 Any conforming implementation might store Host Identifiers in a DNS 320 HIPHI RDATA format. An implementation may also store a HIT along with 321 its associated HI. If a particular form of a HI or HIT does not 322 already have a specified RDATA format, a new RDATA-like format SHOULD 323 be defined for the HI or HIT. 325 During a transition period, instead of storing the HI or HIT in a 326 HIPHI RR, the HIT MAY be stored in an AAAA RR. If a HIT is stored in 327 an AAAA RR, it MUST be returned as the last item in the set of AAAA 328 RRs returned to avoid as most as possible conflicts with non-HIP IPv6 329 nodes. 331 4.3 Storing HAA in DNS 333 Any conforming implementation might store a site's Host Assigning 334 Authority in a DNS HIPHI RDATA format. A HAA MUST be stored similarly 335 to a Type 2 HIT, while the least significant 64-bit are set to 0. If 336 a particular form of a HAA does not already have an associated HIT 337 specified RDATA format, a new RDATA-like format SHOULD be defined for 338 the HIT/HAA. 340 4.4 Providing multiple IP addresses 341 4.4.1 Storing Rendezvous Servers in the DNS 343 The Rendezvous server (RVS) resource record indicates an address (or 344 a FQDN resolvable into an address) towards which a HIP I1 packet 345 might be sent to trigger the establishment of an association with the 346 entity named by this resource record. 348 An RVS receiving such an I1 would then forward it to the appropriate 349 responder (i.e., the owner of the destination HIT in this I1). The 350 responder will then complete the exchange with the initiator, 351 possibly without ongoing help from the RVS. 353 Any conforming implementation may store Rendezvous Server's IP 354 address(es) or DNS name in a DNS HIPRVS RDATA format. If a particular 355 form of a RVS reference does not already have a specified RDATA 356 format, a new RDATA-like format SHOULD be defined for the RVS. 358 During a transition period, similarly to what may happen with HITs, 359 the RVS's IP address might be stored in an A or AAAA RR instead of a 360 HIPRVS RR. If a RVS IP address is stored in an A or AAAA RR, it MUST 361 be returned as the last item in the set of returned RRs to avoid as 362 most as possible conflicts with non-HIP IPv6 nodes. 364 4.5 Initiating connections based on DNS names 366 A Host Identity Protocol exchange SHOULD be initiated whenever the 367 DNS lookup returns HIPHI resource records. Furthermore, if the DNS 368 lookups also returns HIPRVS resource records, the addresses of these 369 RVS SHOULD be put in the destination IP addresses list while 370 initiating the afore mentioned HIP exchange. Since some hosts may 371 choose not to have HIPHI information in DNS, hosts MAY implement 372 support opportunistic HIP. 374 4.6 Address verification 376 Upon return of an HIPHI RR, a host MUST always calculate the 377 HI-derivative HIT to be used in the HIP exchange, as specified in the 378 HIP architecture [11], while the HIT possibly embedded along SHOULD 379 only be used as an optimisation (e.g., table lookup). 381 5. Storage Format 383 5.1 HIPHI RDATA format 385 The RDATA for a HIPHI RR consists of a HIT type, an algorithm type, a 386 HIT and a public key. 388 0 1 2 3 389 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 1 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 | HIT type | algorithm | | 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ HIT | 393 ~ ~ 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | / 396 / public key / 397 / / 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 400 5.1.1 RDATA format HIT type 402 The algorithm type indicates the Host Identity Tag (HIT) type and the 403 implied HIT format. 405 The following values are defined: 407 0 No HIT is present. 408 1 A 128-bit Type 1 HIT is present. 409 2 A 128-bit Type 2 HIT is present. 410 3 A 128-bit HAA is present. 412 5.1.2 RDATA format algorithm type 414 The algorithm type indicates the public key cryptographic algorithm 415 and the implied public key field format. 417 The following values are defined: 419 0 No key is present. 420 1 A DSA key is present, in the format defined in RFC2536 [4]. 421 2 A RSA key is present, in the format defined in RFC3110 [6]. 423 5.1.3 RDATA format HIT 425 There's currently two types of HITs, both 128-bit long, and a single 426 type of HAA. Both of them are stored within a a single RDATA format. 428 This Field contain either: 430 o A *Type 1* HIT: binary prefix 0 concatenated with least 431 significant 127-bit of the hash (e.g., SHA1) of the public key 432 (Host Identity), which is possibly following in the HIPHI RR. 433 o A *Type 2* HIT: binary prefix 1 concatenated with a 63-bit HAA, 434 and the least significant 64-bit of the hash (e.g., SHA1) of the 435 public key (Host Identity), which is possibly following in the 436 HIPHI RR. 437 o A HAA: binary prefix 1 concatenated with a 63-bit HAA, and the 438 remaining 64-bit are set to 0. 440 5.1.4 RDATA format public key 442 Both of the public key types defined in this document (RSA and DSA) 443 inherit their public key formats from the corresponding KEY RR 444 formats. The public key field contains the algorithm-specific portion 445 of the KEY RR RDATA (i.e., all of the KEY RR DATA after the first 446 four octets, corresponding to the same portion of the KEY RR that 447 must be specified by documents that define a DNSSEC algorithm). 449 In the future, if a new algorithm is to be used both by DNSSEC's KEY 450 RR and HIPHI RR, it would probably use the same public key encodings 451 for both RRs. Unless specified otherwise, the HIPHI public key field 452 would contain the algorithm-specific portion of the KEY RR RDATA for 453 the corresponding algorithm. Such an algorithm must still be 454 designated for use with the HIP protocol and an algorithm type number 455 must be assigned to it. Similarly to what happened with public key 456 encodings, this algorithm type number is likely to be the same than 457 the one used in DNSSEC, though it might not always be the case. 459 The DSA key format is defined in RFC2536 [4]. 461 The RSA key format is defined in RFC3110 [6]. 463 5.2 HIPRVS RDATA format 465 The RDATA for a HIPRVS RR consists of a preference value, a 466 Rendezvous server type and a Rendezvous server address. 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 | preference | type | | 472 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rendezvous server | 473 ~ ~ 474 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 476 5.2.1 RDATA format precedence 478 This is an 8-bit preference order for this record. This used to 479 specify the preference given to this RR amongst others at the same 480 owner. Lower values are preferred, and if there is a tie with some 481 RRs, the order should be non-deterministic (e.g., round-robin). 483 5.2.2 RDATA format Rendezvous server type 485 The Rendezvous server type indicates the format of the information 486 stored in the Rendezvous server field. 488 The following values are defined: 490 0 Reserved. 491 1 A 4-byte IPv4 address in network byte order is present. 492 2 A 16-byte IPv6 address in network byte order is present. 493 3 A variable length wire-encoded domain name as described in 494 section 3.3 of RFC1035 [1]. The domain name MUST NOT be 495 compressed. 497 5.2.3 RDATA format Rendezvous server 499 The Rendezvous server field indicates an address (or a FQDN 500 resolvable into an address) towards which a HIP I1 packet might be 501 send in order to reach the entity named by this resource record. 503 There are three different formats for the data portion of the 504 Rendezvous server field: 506 o A 32-bit IPv4 address in network byte order. 507 o A 128-bit IPv6 address in network byte order. 508 o A variable length wire-encoded domain name as described in section 509 3.3 of RFC1035 [1]. The domain name MUST NOT be compressed. 511 6. Policy considerations 513 There are a number of variables that will influence the HIP exchanges 514 that each host must support. All HIP implementations MUST support at 515 least 2 HIs, one to publish in the DNS and one for anonymous usage. 516 Although anonymous HIs will be rarely used as responder HIs, they 517 will be common for initiators. Support for multiple HIs is 518 RECOMMENDED. 520 7. Conjunction of multiple HIs with mutiple IPs 522 The RRs defined in this document are "flat", in the sense that the IP 523 addresses and HIs are associated to an FQDN on an equality basis. In 524 the case where an FQDN is resolved into multiple HIs (HIPHI RRs) and 525 IP addresses (A, AAAA or HIPRVS RRs), the requester cannot associate 526 an IP address with a specific HI, nor the opposite. 528 Considering the following DNS-IP load balancing model: Multiple 529 initiators are querying a DNS server with A or AAAA RRs at a given 530 FQDN. The DNS server replies with a round-robin ordered set of IP 531 addresses, causing each initiator to connect to a different address 532 (the first address of the set they received from the DNS). This model 533 can be extended to HIP by having the DNS returning a round-robin 534 ordered set of HIs, and IP addresses. But then the problem is that 535 the initiator would need to map each of these HIs to a subset of the 536 returned set of IP addresses. Hence, perhaps there is a need for 537 having a "hierarchical" model for these RRs, which will allows to tie 538 an HI to a specific subset of IP addresses, as illustrated in the 539 figure below: 541 FQDN FQDN 542 | / \ 543 +-----+-----+-----+ HI1 HI2 544 / / \ \ \ / \ \ 545 IP1 IP2 IP3 HI1 HI2 IP1 IP2 IP3 547 "Flat" model Vs. "Hierarchical" model 549 However, as HIs and Type 1 HITs are not yet resolvable using the DNS, 550 implementing such a model would certainly prove to be difficult. The 551 use of Distributed Hash Tables (DHTs) might help to resolve HIs, but 552 at this point the whole story isn't known. In the absence of HI 553 resolvability, a solution might be to index each IP addresses and HIs 554 with a descriptor. This descriptor might be the HIT, or more 555 efficiently, an additional 8-bit field. That way each HIPHI, HIPRVS, 556 and HIPLOC (a new to-be-defined RR carrying the IP address of a HIP 557 node) would contain an additionnal HI index field allowing to link a 558 HI with a subset of IP addresses and vice versa. 560 8. Security Considerations 562 The security considerations of the HIP DNS extensions still need to 563 be investigated and documented. 565 Man-in-the-middle attacks are difficult to defend against, without 566 third-party authentication. A skillful MitM could easily handle all 567 parts of HIP; but HIP indirectly provides the following protection 568 from a MitM attack. If the responder's HI is retrieved from a signed 569 DNS zone by the initiator, the initiator can use this to validate the 570 R1 HIP packet. 572 Likewise, if the initiator's HI is in a secure DNS zone, the 573 responder can retrieve it after it gets the I2 HIP packet and 574 validate that. However, since an initiator may choose to use an 575 anonymous HI, it knowingly risks a MitM attack. The responder may 576 choose not to accept a HIP exchange with an anonymous initiator. 578 9. IANA Considerations 580 IANA needs to allocate two new RR type code for HIPHI and HIPRVS from 581 the standard RR type space. 583 IANA needs to open a new registry for the HIPHI RR type for public 584 key algorithms. Defined types are: 586 0 is reserved 587 1 is RSA 588 2 is DSA 590 Adding new reservations requires IETF consensus RFC2434 [1]. 592 IANA needs to open a new registry for the HIPHI RR HIT type. Defined 593 types are: 595 0 No HIT is present 596 1 A 128-bit Type 1 HIT is present 597 2 A 128-bit Type 2 HIT is present 598 3 A 128-bit HAA is present 600 Adding new reservations requires IETF consensus RFC2434 [1]. 602 IANA needs to open a new registry for the HIPRVS RR Rendezvous server 603 type. Defined types are: 605 0 is reserved 606 1 is IPv4 607 2 is IPv6 608 3 is a wire-encoded uncompressed domain name 610 Adding new reservations requires IETF consensus RFC2434 [1]. 612 10. Acknowledgments 614 Some parts of this draft stem from [10]. This work is heavily 615 influenced by [15], which serves as a model for this document. 617 The authors would like to thanks the following people, who have 618 provided thoughtful and helpful discussions and/or suggestions, that 619 have improved this document: Rob Austein, Hannu Flinck, Miika Komu, 620 Gabriel Montenegro. 622 11. References 624 11.1 Normative references 626 [1] Mockapetris, P., "Domain names - implementation and 627 specification", STD 13, RFC 1035, November 1987. 629 [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement 630 Levels", BCP 14, RFC 2119, March 1997. 632 [3] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 633 Considerations Section in RFCs", BCP 26, RFC 2434, October 634 1998. 636 [4] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System 637 (DNS)", RFC 2536, March 1999. 639 [5] Crawford, M., "Binary Labels in the Domain Name System", RFC 640 2673, August 1999. 642 [6] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name 643 System (DNS)", RFC 3110, May 2001. 645 [7] Bush, R., Durand, A., Fink, B., Gudmundsson, O. and T. Hain, 646 "Representing Internet Protocol version 6 (IPv6) Addresses in 647 the Domain Name System (DNS)", RFC 3363, August 2002. 649 [8] Klensin, J., "Role of the Domain Name System (DNS)", RFC 3467, 650 February 2003. 652 [9] Thomson, S., Huitema, C., Ksinant, V. and M. Souissi, "DNS 653 Extensions to Support IP Version 6", RFC 3596, October 2003. 655 [10] Moskowitz, R., Nikander, P. and P. Jokela, "Host Identity 656 Protocol", draft-moskowitz-hip-09 (work in progress), February 657 2004. 659 [11] Moskowitz, R., "Host Identity Protocol Architecture", 660 draft-moskowitz-hip-arch-05 (work in progress), October 2003. 662 [12] Nikander, P., "End-Host Mobility and Multi-Homing with Host 663 Identity Protocol", draft-nikander-hip-mm-01 (work in 664 progress), January 2004. 666 [13] Eggert, L. and J. Laganier, "Host Identity Protocol (HIP) 667 Rendezvous Extensions", draft-eggert-hip-rvs-00 (work in 668 progress), July 2004. 670 11.2 Informative references 672 [14] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on 673 Security Considerations", draft-iab-sec-cons-00 (work in 674 progress), August 2002. 676 [15] Richardson, M., "A method for storing IPsec keying material in 677 DNS", draft-ietf-ipseckey-rr-09 (work in progress), February 678 2004. 680 Authors' Addresses 682 Pekka Nikander 683 Ericsson Research Nomadic Lab 685 JORVAS FIN-02420 686 FINLAND 688 Phone: +358 9 299 1 689 EMail: pekka.nikander@nomadiclab.com 691 Julien Laganier 692 LIP (CNRS-INRIA-ENSL-UCBL) & Sun Labs (Sun Microsystems) 693 180, Avenue de l'Europe 694 Saint Ismier CEDEX 38334 695 France 697 Phone: +33 476 188 815 698 EMail: ju@sun.com 700 Intellectual Property Statement 702 The IETF takes no position regarding the validity or scope of any 703 Intellectual Property Rights or other rights that might be claimed to 704 pertain to the implementation or use of the technology described in 705 this document or the extent to which any license under such rights 706 might or might not be available; nor does it represent that it has 707 made any independent effort to identify any such rights. 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