idnits 2.17.1 draft-ietf-hip-bone-02.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** The document seems to lack a License Notice according IETF Trust Provisions of 28 Dec 2009, Section 6.b.i or Provisions of 12 Sep 2009 Section 6.b -- however, there's a paragraph with a matching beginning. Boilerplate error? (You're using the IETF Trust Provisions' Section 6.b License Notice from 12 Feb 2009 rather than one of the newer Notices. See https://trustee.ietf.org/license-info/.) Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (July 6, 2009) is 5407 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 4843 (Obsoleted by RFC 7343) ** Obsolete normative reference: RFC 5201 (Obsoleted by RFC 7401) ** Obsolete normative reference: RFC 5202 (Obsoleted by RFC 7402) ** Obsolete normative reference: RFC 5204 (Obsoleted by RFC 8004) ** Obsolete normative reference: RFC 5205 (Obsoleted by RFC 8005) ** Obsolete normative reference: RFC 5206 (Obsoleted by RFC 8046) == Outdated reference: A later version (-12) exists of draft-ietf-hip-native-api-06 == Outdated reference: A later version (-09) exists of draft-ietf-hip-nat-traversal-08 == Outdated reference: A later version (-04) exists of draft-nikander-hip-hiccups-01 -- Obsolete informational reference (is this intentional?): RFC 5389 (Obsoleted by RFC 8489) == Outdated reference: A later version (-26) exists of draft-ietf-p2psip-base-02 Summary: 7 errors (**), 0 flaws (~~), 5 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 HIP Working Group G. Camarillo 3 Internet-Draft P. Nikander 4 Intended status: Experimental J. Hautakorpi 5 Expires: January 7, 2010 Ericsson 6 A. Johnston 7 Avaya 8 July 6, 2009 10 HIP BONE: Host Identity Protocol (HIP) Based Overlay Networking 11 Environment 12 draft-ietf-hip-bone-02.txt 14 Status of this Memo 16 This Internet-Draft is submitted to IETF in full conformance with the 17 provisions of BCP 78 and BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on January 7, 2010. 37 Copyright Notice 39 Copyright (c) 2009 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents in effect on the date of 44 publication of this document (http://trustee.ietf.org/license-info). 45 Please review these documents carefully, as they describe your rights 46 and restrictions with respect to this document. 48 Abstract 50 This document specifies a framework to build HIP (Host Identity 51 Protocol)-based overlay networks. This framework uses HIP to perform 52 connection management. Other functions, such as data storage and 53 retrieval or overlay maintenance, are implemented using protocols 54 other than HIP. These protocols are loosely referred to as peer 55 protocols. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Background on HIP . . . . . . . . . . . . . . . . . . . . . . 3 61 2.1. ID/locator Split . . . . . . . . . . . . . . . . . . . . . 3 62 2.1.1. Identifier Format . . . . . . . . . . . . . . . . . . 4 63 2.1.2. HIP Base Exchange . . . . . . . . . . . . . . . . . . 4 64 2.1.3. Locator Management . . . . . . . . . . . . . . . . . . 5 65 2.2. NAT Traversal . . . . . . . . . . . . . . . . . . . . . . 5 66 2.3. Security . . . . . . . . . . . . . . . . . . . . . . . . . 6 67 2.3.1. DoS Protection . . . . . . . . . . . . . . . . . . . . 6 68 2.3.2. Identifier Assignment and Authentication . . . . . . . 6 69 2.3.3. Connection Security . . . . . . . . . . . . . . . . . 7 70 2.4. HIP Deployability and Legacy Applications . . . . . . . . 7 71 3. The HIP BONE Framework . . . . . . . . . . . . . . . . . . . . 8 72 3.1. Peer ID Assignment and Bootstrap . . . . . . . . . . . . . 9 73 3.2. Connection Establishment . . . . . . . . . . . . . . . . . 10 74 3.3. Lightweight Message Exchanges . . . . . . . . . . . . . . 11 75 3.4. HIP BONE Instantiation . . . . . . . . . . . . . . . . . . 11 76 4. Advantages of Using HIP BONE . . . . . . . . . . . . . . . . . 12 77 5. Architectural Considerations . . . . . . . . . . . . . . . . . 12 78 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 80 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 81 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 82 9.1. Normative References . . . . . . . . . . . . . . . . . . . 15 83 9.2. Informative References . . . . . . . . . . . . . . . . . . 16 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 86 1. Introduction 88 The Host Identity Protocol (HIP) [RFC5201] defines a new name space 89 between the network and transport layers. HIP provides upper layers 90 with mobility, multihoming, NAT (Network Address Translation) 91 traversal, and security functionality. HIP implements the so called 92 identifier/locator (ID/locator) split, which implies that IP 93 addresses are only used as locators, not as host identifiers. This 94 split makes HIP a suitable protocol to build overlay networks that 95 implement identifier-based overlay routing over IP networks, which in 96 turn implement locator-based routing. 98 The remainder of this document is organized as follows. Section 2 99 provides background information on HIP. Section 3 describes the HIP 100 BONE (HIP-Based Overlay Networking Environment) framework. Section 4 101 discusses some of the advantages derived from using the HIP BONE 102 framework. Finally, before the customary sections, Section 5 103 attempts to put the presented proposal into a larger architectural 104 context. 106 2. Background on HIP 108 This section provides background on HIP. Given the tutorial nature 109 of this section, readers that are familiar with what HIP provides and 110 how HIP works may want to skip it. All descriptions contain 111 references to the relevant HIP specifications where readers can find 112 detailed explanations on the different topics discussed in this 113 section. 115 2.1. ID/locator Split 117 In an IP network, IP addresses typically serve two roles: they are 118 used as host identifiers and as host locators. IP addresses are 119 locators because a given host's IP address indicates where in the 120 network that host is located. IP networks route based on these 121 locators. Additionally, IP addresses are used to identify remote 122 hosts. The simultaneous use of IP addresses as host identifiers and 123 locators makes mobility and multihoming complicated. For example, 124 when a host opens a TCP connection, the host identifies the remote 125 end of the connection by the remote IP address (plus port). If the 126 remote host changes its IP address, the TCP connection will not 127 survive, since the transport layer identifier of the remote end of 128 the connection has changed. 130 Mobility solutions such as Mobile IP keep the remote IP address from 131 changing so that it can still be used as an identifier. HIP, on the 132 other hand, uses IP addresses as only locators and defines a new 133 identifier space. This approach is referred to as the ID/locator 134 split and makes the implementation of mobility and multihoming more 135 natural. In the previous example, the TCP connection would be bound 136 to the remote host's identifier, which would not change when the 137 remote hosts moves to a new IP address (i.e., to a new locator). The 138 TCP connection is able to survive locator changes because the remote 139 host's identifier does not change. 141 2.1.1. Identifier Format 143 HIP uses 128-bit ORCHIDs (Overlay Routable Cryptographic Hash 144 Identifiers) [RFC4843] as identifiers. ORCHIDs look like IPv6 145 addresses but cannot collide with regular IPv6 addresses because 146 ORCHID spaces are registered with the IANA. That is, a portion of 147 the IPv6 address space is reserved for ORCHIDs. The ORCHID 148 specification allows creating multiple disjoint identifier spaces. 149 Each such space is identified by a separate Context Identifier. The 150 Context Identifier can be either drawn implicitly from the context 151 the ORCHID is used in or carried explicitly in a protocol. 153 HIP defines a native socket API [I-D.ietf-hip-native-api] that 154 applications can use to establish and manage connections. 155 Additionally, HIP can also be used through the traditional IPv4 and 156 IPv6 TCP/IP socket APIs. Section 2.4 describes how an application 157 using these traditional APIs can make use of HIP. Figure 1 shows all 158 these APIs between the application and the transport layers. 160 +-----------------------------------------+ 161 | Application | 162 +----------------+------------------------+ 163 | HIP Native API | Traditional Socket API | 164 +----------------+------------------------+ 165 | Transport Layer | 166 +-----------------------------------------+ 168 Figure 1: HIP API 170 2.1.2. HIP Base Exchange 172 Before two HIP hosts exchange upper-layer traffic, they perform a 173 four-way handshake that is referred to as the HIP base exchange. 174 Figure 2 illustrates the HIP base exchange. The initiator sends an 175 I1 packet and receives an R1 packet from the responder. After that, 176 the initiator sends an I2 packet and receives an R2 packet from the 177 responder. 179 Initiator Responder 181 | I1 | 182 | -------------------------->| 183 | R1 | 184 | <--------------------------| 185 | I2 | 186 | -------------------------->| 187 | R2 | 188 | <--------------------------| 190 Figure 2: HIP base exchange 192 Of course, the initiator needs the responder's locator (or locators) 193 in order to send its I1 packet. The initiator can obtain locators 194 for the responder in multiple ways. For example, according to the 195 current HIP specifications the initiator can get the locators 196 directly from the DNS [RFC5205] or indirectly by sending packets 197 through a HIP rendezvous server [RFC5204]. However, as an 198 architecture HIP is open ended, and allows the locators to be 199 obtained by any means (e.g., from packets traversing an overlay 200 network or as part of the candidate address collection process in a 201 NAT traversal scenario). 203 2.1.3. Locator Management 205 Once a HIP connection between two hosts has been established with a 206 HIP base exchange, the hosts can start exchanging higher-layer 207 traffic. If any of the hosts changes its set of locators, it runs an 208 update exchange [RFC5206], which consists of three messages. If a 209 host is multihomed, it simply provides more than one locator in its 210 exchanges. However, if both of the end points move at the same time, 211 or through some other reason both lose track of the peers' currently 212 active locators, they need to resort to using a rendezvous server or 213 getting new peer locators by some other means. 215 2.2. NAT Traversal 217 HIP's NAT traversal mechanism [I-D.ietf-hip-nat-traversal] is based 218 on ICE (Interactive Connectivity Establishment) 219 [I-D.ietf-mmusic-ice]. Hosts gather address candidates and, as part 220 of the HIP base exchange, hosts perform an ICE offer/answer exchange 221 where they exchange their respective address candidates. Hosts 222 perform end-to-end STUN [RFC5389] based connectivity checks in order 223 to discover which address candidate pairs yield connectivity. 225 Even though, architecturally, HIP lies below the transport layer 226 (i.e., HIP packets are carried directly in IP packets), in presence 227 of NATs, HIP sometimes needs to be tunneled in a transport protocol 228 (i.e., HIP packets are carried by a transport protocol such as UDP). 230 2.3. Security 232 Security is an essential part of HIP. The following sections 233 describe the security-related functionality provided by HIP. 235 2.3.1. DoS Protection 237 HIP provides protection against DoS (Denial of Service) attacks by 238 having initiators resolve a cryptographic puzzle before the responder 239 stores any state. On receiving an I1 packet, a responder sends a 240 pre-generated R1 packet that contains a cryptographic puzzle and 241 deletes all the state associated with the processing of this I1 242 packet. The initiator needs to resolve the puzzle in the R1 packet 243 in order to generate an I2 packet. The difficulty of the puzzle can 244 be adjusted so that, if a receiver is under a DoS attack, it can 245 increase the difficulty of its puzzles. 247 On receiving an I2 packet, a receiver checks that the solution in the 248 packet corresponds to a puzzle generated by the receiver and that the 249 solution is correct. If it is, the receiver processes the I2 packet. 250 Otherwise, it silently discards it. 252 In an overlay scenario, there are multiple ways how this mechanism 253 can be utilised within the overlay. One possibility is to cache the 254 pre-generated R1 packets within the overlay and let the overlay 255 directly respond with R1s to I1s. In that way the responder is not 256 bothered at all until the initiator sends an I2 packet, with the 257 puzzle solution. Furthermore, a more sophisticated overlay could 258 verify that an I2 packet has a correctly solved puzzle before 259 forwarding the packet to the responder. 261 2.3.2. Identifier Assignment and Authentication 263 As discussed earlier, HIP uses ORCHIDs [RFC4843] as the main 264 representation for identifiers. Potentially, HIP can use different 265 types of ORCHIDs as long as the probability of finding collisions 266 (i.e., two nodes with the same ORCHID) is low enough. One way to 267 completely avoid this type of collision is to have a central 268 authority generate and assign ORCHIDs to nodes. To secure the 269 binding between ORCHIDs and any higher-layer identifiers, every time 270 the central authority assigns an ORCHID to a node, it also generates 271 and signs a certificate stating who is the owner of the ORCHID. The 272 owner of the ORCHID then includes the corresponding certificate in 273 its R1 (when acting as responder) and I2 packets (when acting 274 initiator) to prove that it is actually allowed to use the ORCHID 275 and, implicitly, the associated public key. 277 Having a central authority works well to completely avoid collisions. 278 However, having a central authority is impractical in some scenarios. 279 As defined today, HIP systems generally use a self-certifying ORCHID 280 type called HIT (Host Identity Tag) that does not require a central 281 authority (but still allows one to be used). 283 A HIT is the hash of a node's public key. A node proves that it has 284 the right to use a HIT by showing its ability to sign data with its 285 associated private key. This scheme is secure due to the so called 286 second-preimage resistance property of hash functions. That is, 287 given a fixed public key K1, finding a different public key K2 such 288 that hash(K1) = hash(K2) is computationally very hard. Optimally, a 289 preimage attack on the 100-bit hash function used in ORCHIDs will 290 take an order of 2^100 operations to be successful, and can be 291 expected to take in the average 2^99 operations. Given that each 292 operation requires the attacker to generate a new key pair, the 293 attack is completely impractical (see [RFC4843]). 295 HIP nodes using HITs as ORCHIDs do not typically use certificates 296 during their base exchanges. Instead, the use a leap-of-faith 297 mechanism, similar to SSH, whereby a node authenticates somehow 298 remote nodes the first time they connect it and, then, remembers 299 their public keys. While user-assisted leap-of-faith (such as in 300 SSH) can be used to facilitate a human-operated offline path (such as 301 a telephone call), automated leap-of-faith can be combined with a 302 reputation management system to create an incentive to behave. 303 However, such considerations go well beyond the current HIP 304 architecture and even beyond this proposal. For the purposes of the 305 present document, we merely want to point out that architecturally 306 HIP supports both self-generated opportunistic identifiers and 307 administratively assigned ones. 309 2.3.3. Connection Security 311 Once two nodes complete a base exchange between them, the traffic 312 they exchange is encrypted and integrity protected. The security 313 mechanism used to protect the traffic is IPsec ESP [RFC5202]. 314 However, there is ongoing work to specify how to use different 315 protection mechanisms. 317 2.4. HIP Deployability and Legacy Applications 319 As discussed earlier, HIP defines a native socket API 320 [I-D.ietf-hip-native-api] that applications can use to establish and 321 manage connections. New applications can implement this API to get 322 full advantage of HIP. However, in most cases, legacy (i.e., non-HIP 323 aware) applications [RFC5338] can use HIP through the traditional 324 IPv4 and IPv6 socket APIs. 326 The idea is that when a legacy IPv6 application tries and obtains a 327 remote host's IP address (e.g., by querying the DNS) the DNS resolver 328 passes the remote host's ORCHID (which was also stored in the DNS) to 329 the legacy application. At the same time, the DNS resolver stores 330 the remote host's IP address internally at the HIP module. Since the 331 ORCHID looks like an IPv6 address, the legacy application treats it 332 as such. It opens a connection (e.g., TCP) using the traditional 333 IPv6 socket API. The HIP module running in the same host as the 334 legacy application intercepts this call somehow (e.g., using an 335 interception library or setting up the host's routing tables so that 336 the HIP module receives the traffic) and runs HIP (on behalf of the 337 legacy application) towards the IP address corresponding to the 338 ORCHID. This mechanism works well in almost all cases. However, 339 applications involving referrals (i.e., passing of IPv6 addresses 340 between applications) present issues, to be discussed in Section 3 341 below. Additionally, management applications that care about the 342 exact IP address format may not work well with such straigthforward 343 approach. 345 In order to make HIP work through the traditional IPv4 socket API, 346 the HIP module passes an LSI (Local Scope Identifier), instead of a 347 regular IPv4 address, to the legacy IPv4 application. The LSI looks 348 like an IPv4 address, but is locally bound to an ORCHID. That is, 349 when the legacy application uses the LSI in a socket call, the HIP 350 module intercepts it and replaces the LSI with its corresponding 351 ORCHID. Therefore, LSIs always have local scope. They do not have 352 any meaning outside the host running the application. The ORCHID is 353 used on the wire; not the LSI. In the referral case, if it is not 354 possible to rewrite the application level packets to use ORCHIDs 355 instead of LSIs, it may be hard to make IPv4 referrals work in 356 Internet-wide settings. IPv4 LSIs have been succesfully used in 357 existing HIP deployments within a single corporate network. 359 3. The HIP BONE Framework 361 An overlay typically requires three types of operations: 363 o overlay maintenance. 364 o data storage and retrieval. 365 o connection management. 367 Overlay maintenance operations deal with nodes joining and leaving 368 the overlay and with the maintenance of the overlay's routing tables. 369 Data storage and retrieval operations deal with nodes storing, 370 retrieving, and removing information in or from the overlay. 371 Connection management operations deal with the establishment of 372 connections and the exchange of lightweight messages among the nodes 373 of the overlay, potentially in the presence of NATs. 375 The HIP BONE framework uses HIP to perform connection management. 376 Data storage and retrieval and overlay maintenance are to be 377 implemented using protocols other than HIP. For lack of a better 378 name, these protocols are referred to as peer protocols. 380 HIP BONE is a generic framework that allows the use of different peer 381 protocols. A particular HIP BONE instance uses a particular peer 382 protocol. The details on how to implement a HIP BONE using a given 383 peer protocol need to be specified in a, so called, HIP BONE instance 384 specification. Section 3.4 discusses what details need to be 385 specified by HIP BONE instance specifications. For example, the HIP 386 BONE instance specification for RELOAD [I-D.ietf-p2psip-base] is 387 specified in [I-D.keranen-hip-reload-instance]. 389 3.1. Peer ID Assignment and Bootstrap 391 Nodes in an overlay are primarily identified by their Peer IDs. 392 (Note that the Peer ID concept here is a peer-layer protocol concept, 393 distinct from the HIP-layer node identifiers. Peer IDs may be long, 394 may have some structure, and may consist of multiple parts.) 395 Overlays typically have an enrollment server that can generate Peer 396 IDs, or at least some part of the Peer ID, and sign certificates. A 397 certificate generated by an enrollment server authorizes a particular 398 user to use a particular Peer ID in a particular overlay. The way 399 users and overlays are identified and the format for Peer IDs are 400 defined by the peer protocol. 402 The enrollment server of an overlay that were to use plain public 403 keys as Peer IDs could just authorize users to use the public keys 404 and HITs associated to their nodes. This works well as long as the 405 enrollment server is the one generating the public/private key pairs 406 for all those nodes. If the enrollment server authorizes users to 407 use HITs that are generated directly by the nodes themselves, the 408 system is open to a type of chosen-peer-ID attack. 410 However, in some cases it is impractical to have the enrollment 411 server generate public/private key pairs for devices. In these 412 cases, the enrollment server simply generates Peer IDs whose format 413 is defined by the peer protocol used in the overlay. Since HIP needs 414 ORCHIDs (and not any type of Peer ID) to work, hosts in the overlay 415 will transform their Peer IDs into ORCHIDs, for example, by taking a 416 hash of the Peer IDs or taking a hash of the Peer ID and the public 417 key. That is a similar process to the one a host follows to generate 418 a HIT from a public key. In such scenarios, each host will need a 419 certificate (e.g., in their HIP base exchanges) provided by the 420 enrollment server to prove that they are authorized to use a 421 particular ORCHID in the overlay. Depending on how the certificates 422 are constructed, they typically also need to contain the host's self- 423 generated public key. Depending on how the Peer IDs and public keys 424 are attributed, different scenarios become possible. For example, 425 the Peer IDs may be attributed to users, there may be user public key 426 identifiers, and there may be separate host public key identifiers. 427 Authorisation certificates can be used to bind the different types of 428 identifiers together. 430 Bootstrap issues such as how to locate an enrollment or a bootstrap 431 server belong to the peer protocol. 433 3.2. Connection Establishment 435 Nodes in an overlay need to establish connection with other nodes in 436 different cases. For example, a node typically has connections to 437 the nodes in its forwarding table. Nodes also need to establish 438 connections with other nodes in order to exchange application-layer 439 messages. 441 As discussed earlier, HIP uses the base exchange to establish 442 connections. A HIP endpoint (the initiator) initiates a HIP base 443 exchange with a remote endpoint by sending an I1 packet. The 444 initiator sends the I1 packet to the remote endpoint's locator. 445 Initiators that do not have any locator for the remote endpoint need 446 to use a rendezvous service. Traditionally, a HIP rendezvous server 447 [RFC5204] has provided such a rendezvous service. In HIP BONE, the 448 overlay itself provides the rendezvous service. 450 Therefore, in HIP BONE, a node uses an I1 packet (as usual) to 451 establish a connection with another node in the overlay. Nodes in 452 the overlay forward I1 packets in a hop-by-hop fashion according to 453 the overlay's routing table towards its destination. This way, the 454 overlay provides a rendezvous service between the nodes establishing 455 the connection. If the overlay nodes have active connections with 456 other nodes in their forwarding tables and if those connections are 457 protected (typically with IPsec ESP), I1 packets may be sent over 458 protected connections between nodes. Alternatively, if there is no 459 such an active connection but the node forwarding the I1 packet has a 460 valid locator for the next hop, the I1 packets may be forwarded 461 directly, in a similar fashion to how I1 packets are today forwarded 462 by a HIP rendezvous server. 464 Since HIP supports NAT traversal, a HIP base exchange over the 465 overlay will perform an ICE [I-D.ietf-mmusic-ice] offer/answer 466 exchange between the nodes that are establishing the connection. In 467 order to perform this exchange, the nodes need to first gather 468 candidate addresses. Which nodes can be used to obtain reflexive 469 address candidates and which ones can be used to obtain relayed 470 candidates is defined by the peer protocol. 472 3.3. Lightweight Message Exchanges 474 In some cases, nodes need to perform a lightweight query to another 475 node (e.g., a request followed by a single response). In this 476 situation, establishing a connection using the mechanisms in 477 Section 3.2 for a simple query would be an overkill. A better 478 solution is to forward a HIP message through the overlay with the 479 query and another one with the response to the query. The payload of 480 such HIP packets is integrity protected [I-D.nikander-hip-hiccups]. 481 Nodes in the overlay forward this HIP packet in a hop-by-hop fashion 482 according to the overlay's routing table towards its destination, 483 typically through the protected connections established between them. 484 Again, the overlay acts as a rendezvous server between the nodes 485 exchanging the messages. 487 3.4. HIP BONE Instantiation 489 As discussed in Section 3, HIP BONE is a generic framework that 490 allows using different peer protocols. A particular HIP BONE 491 instance uses a particular peer protocol. The details on how to 492 implement a HIP BONE using a given peer protocol need to be specified 493 in a, so called, HIP BONE instance specification. A HIP BONE 494 instance specification needs to define, minimally: 496 o the peer protocol to be used. 497 o how to transform the peer IDs used by the peer protocol into the 498 ORCHIDs that will be used in HIP. 499 o which peer protocol primitives trigger HIP messages. 501 Additionally, a HIP BONE instance specification may need to specify 502 other details that are specific to the peer protocol used. 504 As an example, the HIP BONE instance specification for RELOAD 505 [I-D.ietf-p2psip-base] is specified in 506 [I-D.keranen-hip-reload-instance]. 508 It is assumed that areas not covered by a particular HIP BONE 509 instance specification are specified by the peer protocol or 510 elsewhere. These areas include: 512 o the algorithm to create the overlay (e.g., a DHT). 513 o overlay maintenance functions. 514 o data storage and retrieval functions. 515 o format and structure of peer IDs. 516 o the process for obtaining a peer ID. 517 o overlay identification. 518 o bootstrap function 519 o how to select STUN and TURN servers for the candidate address 520 collection process in NAT traversal scenarios. 521 o for what type of traffic or messages it is appropriate to use 522 lightweight message exchanges. 524 Note that the border between HIP BONE instance specification and a 525 peer protocol specifications is blurry. Depending on how generic the 526 specification of a given peer protocol is, its associated HIP BONE 527 instance specification may need to specify more or less details. 528 Also, a particular HIP BONE instance specification left certain areas 529 unspecified in order to leave their configuration up to each 530 particular overlay. 532 4. Advantages of Using HIP BONE 534 Using HIP BONE, as opposed to a peer protocol, to perform connection 535 management in an overlay has a set of advantages. HIP BONE can be 536 used by any peer protocol. This keeps each peer protocol from 537 defining primitives needed for connection management (e.g., 538 primitives to establish connections and to tunnel messages through 539 the overlay) and NAT traversal. Having this functionality at a lower 540 layer allows multiple upper-layer protocols to take advantage of it. 542 Additionally, having a solution that integrates mobility and 543 multihoming is useful in many scenarios. Peer protocols do not 544 typically specify mobility and multihoming solutions. Combining a 545 peer protocol including NAT traversal with a separate mobility 546 mechanism and a separate multihoming mechanism can easily lead to 547 unexpected (and unpleasant) interactions. 549 5. Architectural Considerations 551 Architecturally, HIP can be considered to create a new thin "waist" 552 layer on the top of the IPv4 and IPv6 networks; see Figure 3. The 553 HIP layer itself consists of the HIP signalling protocol and one or 554 more data transport protocols; see Figure 4. The HIP signalling 555 packets and the data transport packets can take different routes. In 556 the HIP BONE, the HIP signalling packets are typically first routed 557 through the overlay and then directly (if possible), while the data 558 transport packets are typically routed only directly between the end 559 points. 561 +--------------------------------------+ 562 | Transport (using HITs or LSIs) | 563 +--------------------------------------+ 564 | HIP | 565 +------------------+-------------------+ 566 | IPv4 | IPv6 | 567 +------------------+-------------------+ 569 Figure 3: HIP as a thin waist 571 +------------------+-------------------+ 572 | HIP signalling | data transports | 573 +------------------+-------------------+ 575 Figure 4: HIP layer structure 577 In HIP BONE, the peer protocol creates a new signalling layer on the 578 top of HIP. It is used to set up forwarding paths for HIP signalling 579 messages. This is a similar relationship that an IP routing 580 protocol, such as OSPF, has to the IP protocol itself. In the HIP 581 BONE case, the peer protocol plays a role similar to OSPF, and HIP 582 plays a role similar to IP. The ORCHIDs are used for forwarding HIP 583 packets according to the information in the routing tables. The peer 584 protocols are used to exchange routing information based on Peer IDs 585 and public keys, and to construct the routing tables. 587 Architecturally, routing tables are located between the peer protocol 588 and HIP, as shown in Figure 5. The peer protocol constructs the 589 routing table and keeps it updated. The HIP layer accesses the 590 routing table in order to make routing decisions. The bootstrap of a 591 HIP BONE overlay does not create circular dependencies between the 592 peer protocol (which needs to use HIP to establish connections with 593 other nodes) and HIP (which needs the peer protocol to know how to 594 route messages to other nodes) for the same reasons as the bootstrap 595 of an IP network does not create circular dependencies between OSPF 596 and IP. The first connections established by the peer protocol are 597 with nodes whose locators are known. HIP establishes those 598 connections as any connection between two HIP nodes where no overlays 599 are present. That is, there is no need for the overlay to provide a 600 rendezvous service for those connections. 602 +--------------------------------------+ 603 | Peer protocol | 604 +--------------------------------------+ 605 | Routing table | 606 +--------------------------------------+ 607 | HIP | 608 +--------------------------------------+ 610 Figure 5: Routing tables 612 It is possible that different overlays use different routing table 613 formats. For example, the structure of the routing tables of two 614 overlays based on different DHTs (Distributed Hash Tables) may be 615 very different. In order to make routing decisions, the HIP layer 616 needs to convert the routing table generated by the peer protocol 617 into a forwarding table that allows the HIP layer select a next-hop 618 for any packet being routed. 620 In HIP BONE, the HIP usage of public keys and deriving ORCHIDs 621 through a hash function can be utilised at the peer protocol side to 622 better secure routing table maintenance and to protect against 623 chosen-peer-ID attacks. 625 The HIP BONE provides quite a lot of flexibility with regards to how 626 to arrange the different protocols in detail. Figure 6 shows one 627 potential stack structure. 629 +-----------------------+--------------+ 630 | peer protocols | media | 631 +------------------+----+--------------+ 632 | HIP signalling | data transport | 633 | | 634 +------------------+-------------------+ 635 | NAT | non-NAT | | 636 | | | 637 | IPv4 | IPv6 | 638 +------------------+-------------------+ 640 Figure 6: Example HIP BONE stack structure 642 6. Security Considerations 644 This document provides a high-level framework to build HIP-based 645 overlays. The security properties of HIP and its extensions used in 646 this framework are discussed in their respective specifications. 647 Those security properties can be affected by the way HIP is used in a 648 particular overlay (e.g., by how ORCHIDs are derived from Peer IDs). 649 However, those properties are mostly affected by the design decisions 650 made to build a particular overlay; not so much by how this high- 651 level framework is specified in this document. Such design decisions 652 are typically documented in a HIP BONE instance specification, which 653 will describe the security properties of the resulting overlay. 655 7. Acknowledgements 657 HIP BONE is based on ideas coming from conversations and discussions 658 with a number of people in the HIP and P2PSIP communities. In 659 particular, Philip Matthews, Eric Cooper, Joakim Koskela, Thomas 660 Henderson, Bruce Lowekamp, and Miika Komu provided useful input on 661 HIP BONE. 663 8. IANA Considerations 665 This document does not contain any IANA actions. 667 9. References 669 9.1. Normative References 671 [RFC4843] Nikander, P., Laganier, J., and F. Dupont, "An IPv6 Prefix 672 for Overlay Routable Cryptographic Hash Identifiers 673 (ORCHID)", RFC 4843, April 2007. 675 [RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson, 676 "Host Identity Protocol", RFC 5201, April 2008. 678 [RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the 679 Encapsulating Security Payload (ESP) Transport Format with 680 the Host Identity Protocol (HIP)", RFC 5202, April 2008. 682 [RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 683 Rendezvous Extension", RFC 5204, April 2008. 685 [RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol 686 (HIP) Domain Name System (DNS) Extensions", RFC 5205, 687 April 2008. 689 [RFC5206] Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "End- 690 Host Mobility and Multihoming with the Host Identity 691 Protocol", RFC 5206, April 2008. 693 [RFC5338] Henderson, T., Nikander, P., and M. Komu, "Using the Host 694 Identity Protocol with Legacy Applications", RFC 5338, 695 September 2008. 697 [I-D.ietf-hip-native-api] 698 Komu, M. and T. Henderson, "Basic Socket Interface 699 Extensions for Host Identity Protocol (HIP)", 700 draft-ietf-hip-native-api-06 (work in progress), May 2009. 702 [I-D.ietf-hip-nat-traversal] 703 Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. 704 Keraenen, "Basic HIP Extensions for Traversal of Network 705 Address Translators", draft-ietf-hip-nat-traversal-08 706 (work in progress), June 2009. 708 [I-D.nikander-hip-hiccups] 709 Nikander, P., Camarillo, G., and J. Melen, "HIP (Host 710 Identity Protocol) Immediate Carriage and Conveyance of 711 Upper- layer Protocol Signaling (HICCUPS)", 712 draft-nikander-hip-hiccups-01 (work in progress), 713 November 2008. 715 9.2. Informative References 717 [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, 718 "Session Traversal Utilities for NAT (STUN)", RFC 5389, 719 October 2008. 721 [I-D.ietf-mmusic-ice] 722 Rosenberg, J., "Interactive Connectivity Establishment 723 (ICE): A Protocol for Network Address Translator (NAT) 724 Traversal for Offer/Answer Protocols", 725 draft-ietf-mmusic-ice-19 (work in progress), October 2007. 727 [I-D.ietf-p2psip-base] 728 Jennings, C., Lowekamp, B., Rescorla, E., Baset, S., and 729 H. Schulzrinne, "REsource LOcation And Discovery (RELOAD) 730 Base Protocol", draft-ietf-p2psip-base-02 (work in 731 progress), March 2009. 733 [I-D.keranen-hip-reload-instance] 734 Keranen, A. and G. Camarillo, "HIP BONE Instance 735 Specification for RELOAD", 736 draft-keranen-hip-reload-instance-00 (work in progress), 737 July 2009. 739 Authors' Addresses 741 Gonzalo Camarillo 742 Ericsson 743 Hirsalantie 11 744 Jorvas 02420 745 Finland 747 Email: Gonzalo.Camarillo@ericsson.com 749 Pekka Nikander 750 Ericsson 751 Hirsalantie 11 752 Jorvas 02420 753 Finland 755 Email: Pekka.Nikander@ericsson.com 757 Jani Hautakorpi 758 Ericsson 759 Hirsalantie 11 760 Jorvas 02420 761 Finland 763 Email: Jani.Hautakorpi@ericsson.com 765 Alan Johnston 766 Avaya 767 St. Louis, MO 63124 769 Email: alan@sipstation.com