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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: October 11, 2010 A. Keranen 6 Ericsson 7 A. Johnston 8 Avaya 9 April 9, 2010 11 HIP BONE: Host Identity Protocol (HIP) 12 Based Overlay Networking Environment 13 draft-ietf-hip-bone-06.txt 15 Abstract 17 This document specifies a framework to build HIP (Host Identity 18 Protocol)-based overlay networks. This framework uses HIP to perform 19 connection management. Other functions, such as data storage and 20 retrieval or overlay maintenance, are implemented using protocols 21 other than HIP. These protocols are loosely referred to as peer 22 protocols. 24 Status of this Memo 26 This Internet-Draft is submitted to IETF in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF), its areas, and its working groups. Note that 31 other groups may also distribute working documents as Internet- 32 Drafts. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 The list of current Internet-Drafts can be accessed at 40 http://www.ietf.org/ietf/1id-abstracts.txt. 42 The list of Internet-Draft Shadow Directories can be accessed at 43 http://www.ietf.org/shadow.html. 45 This Internet-Draft will expire on October 11, 2010. 47 Copyright Notice 48 Copyright (c) 2010 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 3. Background on HIP . . . . . . . . . . . . . . . . . . . . . . 4 66 3.1. ID/locator Split . . . . . . . . . . . . . . . . . . . . . 4 67 3.1.1. Identifier Format . . . . . . . . . . . . . . . . . . 5 68 3.1.2. HIP Base Exchange . . . . . . . . . . . . . . . . . . 5 69 3.1.3. Locator Management . . . . . . . . . . . . . . . . . . 6 70 3.2. NAT Traversal . . . . . . . . . . . . . . . . . . . . . . 6 71 3.3. Security . . . . . . . . . . . . . . . . . . . . . . . . . 7 72 3.3.1. DoS Protection . . . . . . . . . . . . . . . . . . . . 7 73 3.3.2. Identifier Assignment and Authentication . . . . . . . 7 74 3.3.3. Connection Security . . . . . . . . . . . . . . . . . 8 75 3.4. HIP Deployability and Legacy Applications . . . . . . . . 8 76 4. Framework Overview . . . . . . . . . . . . . . . . . . . . . . 9 77 5. The HIP BONE Framework . . . . . . . . . . . . . . . . . . . . 12 78 5.1. Node ID Assignment and Bootstrap . . . . . . . . . . . . . 13 79 5.2. Overlay Network Identification . . . . . . . . . . . . . . 14 80 5.3. Connection Establishment . . . . . . . . . . . . . . . . . 14 81 5.4. Lightweight Message Exchanges . . . . . . . . . . . . . . 15 82 5.5. HIP BONE Instantiation . . . . . . . . . . . . . . . . . . 15 83 6. Overlay HIP Parameters . . . . . . . . . . . . . . . . . . . . 16 84 6.1. Overlay Identifier . . . . . . . . . . . . . . . . . . . . 16 85 6.2. Overlay TTL . . . . . . . . . . . . . . . . . . . . . . . 17 86 7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 87 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 88 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 89 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 90 10.1. Normative References . . . . . . . . . . . . . . . . . . . 19 91 10.2. Informative References . . . . . . . . . . . . . . . . . . 19 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 94 1. Introduction 96 The Host Identity Protocol (HIP) [RFC5201] defines a new name space 97 between the network and transport layers. HIP provides upper layers 98 with mobility, multihoming, NAT (Network Address Translation) 99 traversal, and security functionality. HIP implements the so called 100 identifier/locator (ID/locator) split, which implies that IP 101 addresses are only used as locators, not as host identifiers. This 102 split makes HIP a suitable protocol to build overlay networks that 103 implement identifier-based overlay routing over IP networks, which in 104 turn implement locator-based routing. 106 Using HIP BONE, as opposed to a peer protocol, to perform connection 107 management in an overlay has a set of advantages. HIP BONE can be 108 used by any peer protocol. This keeps each peer protocol from 109 defining primitives needed for connection management (e.g., 110 primitives to establish connections and to tunnel messages through 111 the overlay) and NAT traversal. Having this functionality at a lower 112 layer allows multiple upper-layer protocols to take advantage of it. 114 Additionally, having a solution that integrates mobility and 115 multihoming is useful in many scenarios. Peer protocols do not 116 typically specify mobility and multihoming solutions. Combining a 117 peer protocol including NAT traversal with a separate mobility 118 mechanism and a separate multihoming mechanism can easily lead to 119 unexpected (and unpleasant) interactions. 121 The remainder of this document is organized as follows. Section 3 122 provides background information on HIP. Section 4 gives an overview 123 of the HIP BONE (HIP-Based Overlay Networking Environment) framework 124 and architecture and Section 5 describes the framework in more 125 detail. Finally, before the customary sections, Section 6 introduces 126 new HIP parameters for overlay usage. 128 2. Terminology 130 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 131 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 132 document are to be interpreted as described in RFC 2119 [RFC2119]. 134 The following terms are used in context of HIP BONEs: 136 Overlay network: A network built on top of another network. In case 137 of HIP BONEs, the underlying network is an IP network and the 138 overlay can be, e.g., a peer-to-peer (P2P) network. 140 Peer protocol: A protocol used by nodes in an overlay network for 141 performing, e.g., data storage and retrieval or overlay 142 maintenance. HIP is used for conveying the peer protocol messages 143 between the nodes in the overlay network. 145 HIP BONE instance: A HIP-based overlay network that uses a 146 particular peer protocol and is based on the framework presented 147 in this document. 149 Node ID: A value that uniquely identifies a node in an overlay 150 network. The value is not usually human-friendly, but for example 151 a hash of a public key. 153 Valid locator: A Locator (as defined in [RFC5206]; usually an IP 154 address or an address and a port number) that a host is known to 155 be reachable at, for example, because there is an active HIP 156 association with the host. 158 3. Background on HIP 160 This section provides background on HIP. Given the tutorial nature 161 of this section, readers that are familiar with what HIP provides and 162 how HIP works may want to skip it. All descriptions contain 163 references to the relevant HIP specifications where readers can find 164 detailed explanations on the different topics discussed in this 165 section. 167 3.1. ID/locator Split 169 In an IP network, IP addresses typically serve two roles: they are 170 used as host identifiers and as host locators. IP addresses are 171 locators because a given host's IP address indicates where in the 172 network that host is located. IP networks route based on these 173 locators. Additionally, IP addresses are used to identify remote 174 hosts. The simultaneous use of IP addresses as host identifiers and 175 locators makes mobility and multihoming complicated. For example, 176 when a host opens a TCP connection, the host identifies the remote 177 end of the connection by the remote IP address (plus port). If the 178 remote host changes its IP address, the TCP connection will not 179 survive, since the transport layer identifier of the remote end of 180 the connection has changed. 182 Mobility solutions such as Mobile IP keep the remote IP address from 183 changing so that it can still be used as an identifier. HIP, on the 184 other hand, uses IP addresses as only locators and defines a new 185 identifier space. This approach is referred to as the ID/locator 186 split and makes the implementation of mobility and multihoming more 187 natural. In the previous example, the TCP connection would be bound 188 to the remote host's identifier, which would not change when the 189 remote hosts moves to a new IP address (i.e., to a new locator). The 190 TCP connection is able to survive locator changes because the remote 191 host's identifier does not change. 193 3.1.1. Identifier Format 195 HIP uses 128-bit ORCHIDs (Overlay Routable Cryptographic Hash 196 Identifiers) [RFC4843] as identifiers. ORCHIDs look like IPv6 197 addresses but cannot collide with regular IPv6 addresses because 198 ORCHID spaces are registered with the IANA. That is, a portion of 199 the IPv6 address space is reserved for ORCHIDs. The ORCHID 200 specification allows creating multiple disjoint identifier spaces. 201 Each such space is identified by a separate Context Identifier. The 202 Context Identifier can be either drawn implicitly from the context 203 the ORCHID is used in or carried explicitly in a protocol. 205 HIP defines a native socket API [I-D.ietf-hip-native-api] that 206 applications can use to establish and manage connections. 207 Additionally, HIP can also be used through the traditional IPv4 and 208 IPv6 TCP/IP socket APIs. Section 3.4 describes how an application 209 using these traditional APIs can make use of HIP. Figure 1 shows all 210 these APIs between the application and the transport layers. 212 +-----------------------------------------+ 213 | Application | 214 +----------------+------------------------+ 215 | HIP Native API | Traditional Socket API | 216 +----------------+------------------------+ 217 | Transport Layer | 218 +-----------------------------------------+ 220 Figure 1: HIP API 222 3.1.2. HIP Base Exchange 224 Before two HIP hosts exchange upper-layer traffic, they perform a 225 four-way handshake that is referred to as the HIP base exchange. 226 Figure 2 illustrates the HIP base exchange. The initiator sends an 227 I1 packet and receives an R1 packet from the responder. After that, 228 the initiator sends an I2 packet and receives an R2 packet from the 229 responder. 231 Initiator Responder 233 | I1 | 234 | -------------------------->| 235 | R1 | 236 | <--------------------------| 237 | I2 | 238 | -------------------------->| 239 | R2 | 240 | <--------------------------| 242 Figure 2: HIP Base Exchange 244 Of course, the initiator needs the responder's locator (or locators) 245 in order to send its I1 packet. The initiator can obtain locators 246 for the responder in multiple ways. For example, according to the 247 current HIP specifications the initiator can get the locators 248 directly from the DNS [RFC5205] or indirectly by sending packets 249 through a HIP rendezvous server [RFC5204]. However, as an 250 architecture HIP is open ended, and allows the locators to be 251 obtained by any means (e.g., from packets traversing an overlay 252 network or as part of the candidate address collection process in a 253 NAT traversal scenario). 255 3.1.3. Locator Management 257 Once a HIP connection between two hosts has been established with a 258 HIP base exchange, the hosts can start exchanging higher-layer 259 traffic. If any of the hosts changes its set of locators, it runs an 260 update exchange [RFC5206], which consists of three messages. If a 261 host is multihomed, it simply provides more than one locator in its 262 exchanges. However, if both of the end points move at the same time, 263 or through some other reason both lose track of the peers' currently 264 active locators, they need to resort to using a rendezvous server or 265 getting new peer locators by some other means. 267 3.2. NAT Traversal 269 HIP's NAT traversal mechanism [I-D.ietf-hip-nat-traversal] is based 270 on ICE (Interactive Connectivity Establishment) 271 [I-D.ietf-mmusic-ice]. Hosts gather address candidates and, as part 272 of the HIP base exchange, hosts perform an ICE offer/answer exchange 273 where they exchange their respective address candidates. Hosts 274 perform end-to-end STUN [RFC5389] based connectivity checks in order 275 to discover which address candidate pairs yield connectivity. 277 Even though, architecturally, HIP lies below the transport layer 278 (i.e., HIP packets are carried directly in IP packets), in presence 279 of NATs, HIP sometimes needs to be tunneled in a transport protocol 280 (i.e., HIP packets are carried by a transport protocol such as UDP). 282 3.3. Security 284 Security is an essential part of HIP. The following sections 285 describe the security-related functionality provided by HIP. 287 3.3.1. DoS Protection 289 HIP provides protection against DoS (Denial of Service) attacks by 290 having initiators resolve a cryptographic puzzle before the responder 291 stores any state. On receiving an I1 packet, a responder sends a 292 pre-generated R1 packet that contains a cryptographic puzzle and 293 deletes all the state associated with the processing of this I1 294 packet. The initiator needs to resolve the puzzle in the R1 packet 295 in order to generate an I2 packet. The difficulty of the puzzle can 296 be adjusted so that, if a receiver is under a DoS attack, it can 297 increase the difficulty of its puzzles. 299 On receiving an I2 packet, a receiver checks that the solution in the 300 packet corresponds to a puzzle generated by the receiver and that the 301 solution is correct. If it is, the receiver processes the I2 packet. 302 Otherwise, it silently discards it. 304 In an overlay scenario, there are multiple ways how this mechanism 305 can be utilized within the overlay. One possibility is to cache the 306 pre-generated R1 packets within the overlay and let the overlay 307 directly respond with R1s to I1s. In that way the responder is not 308 bothered at all until the initiator sends an I2 packet, with the 309 puzzle solution. Furthermore, a more sophisticated overlay could 310 verify that an I2 packet has a correctly solved puzzle before 311 forwarding the packet to the responder. 313 3.3.2. Identifier Assignment and Authentication 315 As discussed earlier, HIP uses ORCHIDs [RFC4843] as the main 316 representation for identifiers. Potentially, HIP can use different 317 types of ORCHIDs as long as the probability of finding collisions 318 (i.e., two nodes with the same ORCHID) is low enough. One way to 319 completely avoid this type of collision is to have a central 320 authority generate and assign ORCHIDs to nodes. To secure the 321 binding between ORCHIDs and any higher-layer identifiers, every time 322 the central authority assigns an ORCHID to a node, it also generates 323 and signs a certificate stating who is the owner of the ORCHID. The 324 owner of the ORCHID then includes the corresponding certificate in 325 its R1 (when acting as responder) and I2 packets (when acting 326 initiator) to prove that it is actually allowed to use the ORCHID 327 and, implicitly, the associated public key. 329 Having a central authority works well to completely avoid collisions. 330 However, having a central authority is impractical in some scenarios. 331 As defined today, HIP systems generally use a self-certifying ORCHID 332 type called HIT (Host Identity Tag) that does not require a central 333 authority (but still allows one to be used). 335 A HIT is the hash of a node's public key. A node proves that it has 336 the right to use a HIT by showing its ability to sign data with its 337 associated private key. This scheme is secure due to the so called 338 second-preimage resistance property of hash functions. That is, 339 given a fixed public key K1, finding a different public key K2 such 340 that hash(K1) = hash(K2) is computationally very hard. Optimally, a 341 preimage attack on the 100-bit hash function used in ORCHIDs will 342 take an order of 2^100 operations to be successful, and can be 343 expected to take in the average 2^99 operations. Given that each 344 operation requires the attacker to generate a new key pair, the 345 attack is completely impractical (see [RFC4843]). 347 HIP nodes using HITs as ORCHIDs do not typically use certificates 348 during their base exchanges. Instead, the use a leap-of-faith 349 mechanism, similar to the Secure Shell (SSH) protocol [RFC4251], 350 whereby a node authenticates somehow remote nodes the first time they 351 connect it and, then, remembers their public keys. While user- 352 assisted leap-of-faith (such as in SSH) can be used to facilitate a 353 human-operated offline path (such as a telephone call), automated 354 leap-of-faith can be combined with a reputation management system to 355 create an incentive to behave. However, such considerations go well 356 beyond the current HIP architecture and even beyond this proposal. 357 For the purposes of the present document, we merely want to point out 358 that architecturally HIP supports both self-generated opportunistic 359 identifiers and administratively assigned ones. 361 3.3.3. Connection Security 363 Once two nodes complete a base exchange between them, the traffic 364 they exchange is encrypted and integrity protected. The security 365 mechanism used to protect the traffic is IPsec Encapsulating Security 366 Payload (ESP) [RFC5202]. However, there is ongoing work to specify 367 how to use different protection mechanisms. 369 3.4. HIP Deployability and Legacy Applications 371 As discussed earlier, HIP defines a native socket API 372 [I-D.ietf-hip-native-api] that applications can use to establish and 373 manage connections. New applications can implement this API to get 374 full advantage of HIP. However, in most cases, legacy (i.e., non-HIP 375 aware) applications [RFC5338] can use HIP through the traditional 376 IPv4 and IPv6 socket APIs. 378 The idea is that when a legacy IPv6 application tries and obtains a 379 remote host's IP address (e.g., by querying the DNS) the DNS resolver 380 passes the remote host's ORCHID (which was also stored in the DNS) to 381 the legacy application. At the same time, the DNS resolver stores 382 the remote host's IP address internally at the HIP module. Since the 383 ORCHID looks like an IPv6 address, the legacy application treats it 384 as such. It opens a connection (e.g., TCP) using the traditional 385 IPv6 socket API. The HIP module running in the same host as the 386 legacy application intercepts this call somehow (e.g., using an 387 interception library or setting up the host's routing tables so that 388 the HIP module receives the traffic) and runs HIP (on behalf of the 389 legacy application) towards the IP address corresponding to the 390 ORCHID. This mechanism works well in almost all cases. However, 391 applications involving referrals (i.e., passing of IPv6 addresses 392 between applications) present issues, to be discussed in Section 5 393 below. Additionally, management applications that care about the 394 exact IP address format may not work well with such straightforward 395 approach. 397 In order to make HIP work through the traditional IPv4 socket API, 398 the HIP module passes an LSI (Local Scope Identifier), instead of a 399 regular IPv4 address, to the legacy IPv4 application. The LSI looks 400 like an IPv4 address, but is locally bound to an ORCHID. That is, 401 when the legacy application uses the LSI in a socket call, the HIP 402 module intercepts it and replaces the LSI with its corresponding 403 ORCHID. Therefore, LSIs always have local scope. They do not have 404 any meaning outside the host running the application. The ORCHID is 405 used on the wire; not the LSI. In the referral case, if it is not 406 possible to rewrite the application level packets to use ORCHIDs 407 instead of LSIs, it may be hard to make IPv4 referrals work in 408 Internet-wide settings. IPv4 LSIs have been successfully used in 409 existing HIP deployments within a single corporate network. 411 4. Framework Overview 413 The HIP BONE framework combines HIP with different peer protocols to 414 provide robust and secure overlay network solutions. 416 Many overlays typically require three types of operations: 418 o overlay maintenance. 419 o data storage and retrieval. 421 o connection management. 423 Overlay maintenance operations deal with nodes joining and leaving 424 the overlay and with the maintenance of the overlay's routing tables. 425 Data storage and retrieval operations deal with nodes storing, 426 retrieving, and removing information in or from the overlay. 427 Connection management operations deal with the establishment of 428 connections and the exchange of lightweight messages among the nodes 429 of the overlay, potentially in the presence of NATs. 431 The HIP BONE framework uses HIP to perform connection management. 432 Data storage and retrieval and overlay maintenance are to be 433 implemented using protocols other than HIP. For lack of a better 434 name, these protocols are referred to as peer protocols. 436 One way to depict the relationship between the peer protocol and HIP 437 modules is shown in Figure 3. The peer protocol module implements 438 the overlay construction and maintenance features, and possibly 439 storage (if the particular protocol supports such a feature). The 440 HIP module consults the peer protocol's overlay topology part for 441 making routing decisions and the peer protocol uses HIP for 442 connection management and sending peer protocol messages to other 443 hosts. The HIP BONE API that applications use is a combination of 444 the HIP Native API and traditional socket API (as shown in Figure 1) 445 with any additional API a particular instance implementation 446 provides. 448 Application 449 -------------------------------- HIP BONE API 450 +---+ +--------------------+ 451 | | | Peer Protocol | 452 | | +--------+ +---------+ 453 | |<->|Topology| |(Storage)| 454 | | +---------+----------+ 455 | | ^ 456 | | v 457 | +------------------------+ 458 | HIP | 459 +----------------------------+ 461 Figure 3: HIP with Peer Protocol 463 Architecturally, HIP can be considered to create a new thin "waist" 464 layer on top of the IPv4 and IPv6 networks; see Figure 4. The HIP 465 layer itself consists of the HIP signaling protocol and one or more 466 data transport protocols; see Figure 5. The HIP signaling packets 467 and the data transport packets can take different routes. In the HIP 468 BONE, the HIP signaling packets are typically first routed through 469 the overlay and then directly (if possible), while the data transport 470 packets are typically routed only directly between the end points. 472 +--------------------------------------+ 473 | Transport (using HITs or LSIs) | 474 +--------------------------------------+ 475 | HIP | 476 +------------------+-------------------+ 477 | IPv4 | IPv6 | 478 +------------------+-------------------+ 480 Figure 4: HIP as a Thin Waist 482 +------------------+-------------------+ 483 | HIP signaling | data transports | 484 +------------------+-------------------+ 486 Figure 5: HIP Layer Structure 488 In HIP BONE, the peer protocol creates a new signaling layer on top 489 of HIP. It is used to set up forwarding paths for HIP signaling 490 messages. This is a similar relationship that an IP routing 491 protocol, such as OSPF, has to the IP protocol itself. In the HIP 492 BONE case, the peer protocol plays a role similar to OSPF, and HIP 493 plays a role similar to IP. The ORCHIDs (or, in general, Node IDs if 494 the ORCHID prefix is not used) are used for forwarding HIP packets 495 according to the information in the routing tables. The peer 496 protocols are used to exchange routing information based on Node IDs 497 and to construct the routing tables. 499 Architecturally, routing tables are located between the peer protocol 500 and HIP, as shown in Figure 6. The peer protocol constructs the 501 routing table and keeps it updated. The HIP layer accesses the 502 routing table in order to make routing decisions. The bootstrap of a 503 HIP BONE overlay does not create circular dependencies between the 504 peer protocol (which needs to use HIP to establish connections with 505 other nodes) and HIP (which needs the peer protocol to know how to 506 route messages to other nodes) for the same reasons as the bootstrap 507 of an IP network does not create circular dependencies between OSPF 508 and IP. The first connections established by the peer protocol are 509 with nodes whose locators are known. HIP establishes those 510 connections as any connection between two HIP nodes where no overlays 511 are present. That is, there is no need for the overlay to provide a 512 rendezvous service for those connections. 514 +--------------------------------------+ 515 | Peer protocol | 516 +--------------------------------------+ 517 | Routing table | 518 +--------------------------------------+ 519 | HIP | 520 +--------------------------------------+ 522 Figure 6: Routing Tables 524 It is possible that different overlays use different routing table 525 formats. For example, the structure of the routing tables of two 526 overlays based on different DHTs (Distributed Hash Tables) may be 527 very different. In order to make routing decisions, the HIP layer 528 needs to convert the routing table generated by the peer protocol 529 into a forwarding table that allows the HIP layer select a next-hop 530 for any packet being routed. 532 In HIP BONE, the HIP usage of public keys and deriving ORCHIDs 533 through a hash function can be utilized at the peer protocol side to 534 better secure routing table maintenance and to protect against 535 chosen-peer-ID attacks. 537 The HIP BONE provides quite a lot of flexibility with regards to how 538 to arrange the different protocols in detail. Figure 7 shows one 539 potential stack structure. 541 +-----------------------+--------------+ 542 | peer protocols | media | 543 +------------------+----+--------------+ 544 | HIP signaling | data transport | 545 | | 546 +------------------+-------------------+ 547 | NAT | non-NAT | | 548 | | | 549 | IPv4 | IPv6 | 550 +------------------+-------------------+ 552 Figure 7: Example HIP BONE Stack Structure 554 5. The HIP BONE Framework 556 HIP BONE is a generic framework that allows the use of different peer 557 protocols. A particular HIP BONE instance uses a particular peer 558 protocol. The details on how to implement a HIP BONE using a given 559 peer protocol need to be specified in a, so called, HIP BONE instance 560 specification. Section 5.5 discusses what details need to be 561 specified by HIP BONE instance specifications. For example, the HIP 562 BONE instance specification for RELOAD [I-D.ietf-p2psip-base] is 563 specified in [I-D.ietf-hip-reload-instance]. 565 5.1. Node ID Assignment and Bootstrap 567 Nodes in an overlay are primarily identified by their Node IDs. 568 Overlays typically have an enrollment server that can generate Node 569 IDs, or at least some part of the Node ID, and sign certificates. A 570 certificate generated by an enrollment server authorizes a particular 571 user to use a particular Node ID in a particular overlay. The way 572 users are identified is defined by the peer protocol and HIP BONE 573 instance specification. 575 The enrollment server of an overlay that were to use HITs derived 576 from public keys as Node IDs could just authorize users to use the 577 public keys and HITs associated to their nodes. Such a Node ID has 578 the same self-certifying property as HITs and the Node ID can also be 579 used in the HIP and legacy APIs as an ORCHID. This works well as 580 long as the enrollment server is the one generating the public/ 581 private key pairs for all those nodes. If the enrollment server 582 authorizes users to use HITs that are generated directly by the nodes 583 themselves, the system is open to a type of chosen-peer-ID attack. 585 If the overlay network or peer protocol has more specific 586 requirements for the Node ID value that prevent using HITs derived 587 from public keys, each host will need a certificate (e.g., in their 588 HIP base exchanges) provided by the enrollment server to prove that 589 they are authorized to use a particular identifier in the overlay. 590 Depending on how the certificates are constructed, they typically 591 also need to contain the host's self-generated public key. Depending 592 on how the Node IDs and public keys are attributed, different 593 scenarios become possible. For example, the Node IDs may be 594 attributed to users, there may be user public key identifiers, and 595 there may be separate host public key identifiers. Authorization 596 certificates can be used to bind the different types of identifiers 597 together. 599 HITs, as defined in [RFC5201], always start with the ORCHID prefix. 600 Therefore, there are 100 bits left in the HIT for different Node ID 601 values. If an overlay network requires larger address space, it is 602 also possible to use all the 128 bits of a HIT for addressing peer 603 layer identifiers. The benefit of using ORCHID prefix for Node IDs 604 is that it makes possible to use them with legacy socket APIs, but in 605 this context most of the applications are assumed to be HIP aware and 606 able to use a more advanced API supporting full 128-bit identifiers. 607 Even larger address spaces could be supported with an additional HIP 608 parameter giving the source and destination Node IDs, but defining 609 such a parameter, if needed, is left for future documents. 611 Bootstrap issues such as how to locate an enrollment or a bootstrap 612 server belong to the peer protocol. 614 5.2. Overlay Network Identification 616 It is possible for a HIP host to participate simultaneously in 617 multiple different overlay networks. It is also possible that some 618 HIP traffic is not intended to be forwarded over an overlay. 619 Therefore, a host needs to know to which overlay an incoming HIP 620 message belongs to and the outgoing HIP messages need to be labeled 621 belonging to a certain overlay. This document specifies a new 622 generic HIP parameter (in Section 6.1) for the purpose of directing 623 HIP messages to the right overlay. 625 In addition, an application using HIP BONE needs to define, either 626 implicitly or explicitly, the overlay to use for communication. 627 Explicit configuration can happen, e.g., by configuring certain local 628 HITs to be be bound to certain overlays or by defining the overlay 629 identifier using advanced HIP socket options or other suitable APIs. 630 On the other hand, if no explicit configuration for a HIP association 631 is used, a host may have a configured default overlay where all HIP 632 messages without a valid locator are sent. The specification for how 633 to implement this coordination for locally originated messages is out 634 of scope for this document. 636 5.3. Connection Establishment 638 Nodes in an overlay need to establish connection with other nodes in 639 different cases. For example, a node typically has connections to 640 the nodes in its forwarding table. Nodes also need to establish 641 connections with other nodes in order to exchange application-layer 642 messages. 644 As discussed earlier, HIP uses the base exchange to establish 645 connections. A HIP endpoint (the initiator) initiates a HIP base 646 exchange with a remote endpoint by sending an I1 packet. The 647 initiator sends the I1 packet to the remote endpoint's locator. 648 Initiators that do not have any locator for the remote endpoint need 649 to use a rendezvous service. Traditionally, a HIP rendezvous server 650 [RFC5204] has provided such a rendezvous service. In HIP BONE, the 651 overlay itself provides the rendezvous service. 653 Therefore, in HIP BONE, a node uses an I1 packet (as usual) to 654 establish a connection with another node in the overlay. Nodes in 655 the overlay forward I1 packets in a hop-by-hop fashion according to 656 the overlay's routing table towards its destination. This way, the 657 overlay provides a rendezvous service between the nodes establishing 658 the connection. If the overlay nodes have active connections with 659 other nodes in their forwarding tables and if those connections are 660 protected (typically with IPsec ESP), I1 packets may be sent over 661 protected connections between nodes. Alternatively, if there is no 662 such an active connection but the node forwarding the I1 packet has a 663 valid locator for the next hop, the I1 packets may be forwarded 664 directly, in a similar fashion to how I1 packets are today forwarded 665 by a HIP rendezvous server. 667 Since HIP supports NAT traversal, a HIP base exchange over the 668 overlay will perform an ICE [I-D.ietf-mmusic-ice] offer/answer 669 exchange between the nodes that are establishing the connection. In 670 order to perform this exchange, the nodes need to first gather 671 candidate addresses. Which nodes can be used to obtain reflexive 672 address candidates and which ones can be used to obtain relayed 673 candidates is defined by the peer protocol. 675 5.4. Lightweight Message Exchanges 677 In some cases, nodes need to perform a lightweight query to another 678 node (e.g., a request followed by a single response). In this 679 situation, establishing a connection using the mechanisms in 680 Section 5.3 for a simple query would be an overkill. A better 681 solution is to forward a HIP message through the overlay with the 682 query and another one with the response to the query. The payload of 683 such HIP packets is integrity protected [I-D.ietf-hip-hiccups]. 684 Nodes in the overlay forward this HIP packet in a hop-by-hop fashion 685 according to the overlay's routing table towards its destination, 686 typically through the protected connections established between them. 687 Again, the overlay acts as a rendezvous server between the nodes 688 exchanging the messages. 690 5.5. HIP BONE Instantiation 692 As discussed in Section 5, HIP BONE is a generic framework that 693 allows using different peer protocols. A particular HIP BONE 694 instance uses a particular peer protocol. The details on how to 695 implement a HIP BONE using a given peer protocol need to be specified 696 in a, so called, HIP BONE instance specification. A HIP BONE 697 instance specification needs to define, minimally: 699 o the peer protocol to be used. 700 o what kind of Node IDs are used and how they are derived. 701 o which peer protocol primitives trigger HIP messages. 703 o how the overlay identifier is generated. 705 Additionally, a HIP BONE instance specification may need to specify 706 other details that are specific to the peer protocol used. 708 As an example, the HIP BONE instance specification for RELOAD 709 [I-D.ietf-p2psip-base] is specified in 710 [I-D.ietf-hip-reload-instance]. 712 It is assumed that areas not covered by a particular HIP BONE 713 instance specification are specified by the peer protocol or 714 elsewhere. These areas include: 716 o the algorithm to create the overlay (e.g., a DHT). 717 o overlay maintenance functions. 718 o data storage and retrieval functions. 719 o the process for obtaining a Node ID. 720 o bootstrap function. 721 o how to select STUN and TURN servers for the candidate address 722 collection process in NAT traversal scenarios. 724 Note that the border between HIP BONE instance specification and a 725 peer protocol specifications is blurry. Depending on how generic the 726 specification of a given peer protocol is, its associated HIP BONE 727 instance specification may need to specify more or less details. 728 Also, a HIP BONE instance specification may leave certain areas 729 unspecified in order to leave their configuration up to each 730 particular overlay. 732 6. Overlay HIP Parameters 734 This section defines generic format and protocol behavior for the 735 Overlay Identifier and Overlay Time-to-Live (TTL) HIP parameters that 736 can be used in HIP based overlay networks. HIP BONE instance 737 specifications define the exact format and content of the Overlay 738 Identifier parameter, the cases when the Overlay TTL parameter should 739 be used, and any additional behavior for each packet. 741 6.1. Overlay Identifier 743 To identify to which overlay network a HIP message belongs to, all 744 HIP messages that are sent via an overlay, or as a part of operations 745 specific to a certain overlay, MUST contain an OVERLAY_ID parameter 746 with the identifier of the corresponding overlay network. Instance 747 specifications define how the identifier is generated for different 748 types of overlay networks. The generation mechanism MUST be such 749 that it is unlikely to generate the same identifier for two different 750 overlay instances and hence it is RECOMMENDED that the identifier 751 contains at least 32 bits of randomness. 753 The generic format of the OVERLAY_ID parameter is shown in Figure 8. 754 Instance specifications define valid length for the parameter and how 755 the identifier values are generated. 757 0 1 2 3 758 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 1 759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 760 | Type | Length | 761 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 762 | Identifier / 763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 764 / | Padding | 765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 767 Type [ TBD by IANA; 980 ] 768 Length Length of the Identifier in octets 769 Identifier The identifier value 770 Padding 0-7 bytes of padding if needed 772 Figure 8: Format of the OVERLAY_ID Parameter 774 6.2. Overlay TTL 776 HIP packets sent in an overlay network MAY contain an Overlay Time- 777 to-live (OVERLAY_TTL) parameter whose TTL value is decremented on 778 each overlay network hop. When a HIP host receives a HIP packet with 779 an OVERLAY_TTL parameter, and the host is not the final recipient of 780 the packet, it MUST decrement the TTL value in the parameter by one 781 before forwarding the packet. 783 If the TTL value in a received HIP packet is zero, and the receiving 784 host is not the final recipient, the packet MUST be dropped and the 785 host SHOULD send HIP Notify packet with type OVERLAY_TTL_EXCEEDED 786 (value [TBD by IANA; 70]) to the sender of the original HIP packet. 787 The Notification Data field for the OVERLAY_TTL_EXCEEDED 788 notifications SHOULD contain the HIP header and the TRANSACTION_ID 789 [I-D.ietf-hip-hiccups] parameter (if one exists) of the packet whose 790 TTL exceeded. 792 Figure 9 shows the format of the OVERLAY_TTL parameter. The TTL 793 value is given as the number of overlay hops this packet has left and 794 it is encoded as an unsigned integer. 796 0 1 2 3 797 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 1 798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 799 | Type | Length | 800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 801 | TTL | Reserved | 802 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 804 Type [ TBD by IANA; 64011 ] 805 Length 4 806 TTL The Time-to-live value 807 Reserved Reserved for future use 809 Figure 9: Format of the OVERLAY_TTL Parameter 811 The type of the OVERLAY_TTL parameter is critical (as defined in 812 Section 5.2.1 of [RFC5201]) and therefore the final recipient of the 813 packet, and all HIP hosts on the path, MUST support it. If the 814 parameter is used in a scenario where the final recipient does not 815 support the parameter, the parameter SHOULD be removed before 816 forwarding the packet to the final recipient. 818 7. Security Considerations 820 This document provides a high-level framework to build HIP-based 821 overlays. The security properties of HIP and its extensions used in 822 this framework are discussed in their respective specifications. 823 Those security properties can be affected by the way HIP is used in a 824 particular overlay. However, those properties are mostly affected by 825 the design decisions made to build a particular overlay; not so much 826 by the high-level framework specified in this document. Such design 827 decisions are typically documented in a HIP BONE instance 828 specification, which describes the security properties of the 829 resulting overlay. 831 8. Acknowledgements 833 HIP BONE is based on ideas coming from conversations and discussions 834 with a number of people in the HIP and P2PSIP communities. In 835 particular, Philip Matthews, Eric Cooper, Joakim Koskela, Thomas 836 Henderson, Bruce Lowekamp, and Miika Komu provided useful input on 837 HIP BONE. 839 9. IANA Considerations 841 This section is to be interpreted according to [RFC5226]. 843 This document updates the IANA Registry for HIP Parameter Types 844 [RFC5201] by assigning HIP Parameter Type values for the new HIP 845 Parameters OVERLAY_ID (defined in Section 6.1) and OVERLAY_TTL 846 (defined in Section 6.2). This document also defines a new HIP 847 Notify packet type [RFC5201] OVERLAY_TTL_EXCEEDED in Section 6.2. 849 10. References 851 10.1. Normative References 853 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 854 Requirement Levels", BCP 14, RFC 2119, March 1997. 856 [RFC4843] Nikander, P., Laganier, J., and F. Dupont, "An IPv6 Prefix 857 for Overlay Routable Cryptographic Hash Identifiers 858 (ORCHID)", RFC 4843, April 2007. 860 [RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson, 861 "Host Identity Protocol", RFC 5201, April 2008. 863 [RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the 864 Encapsulating Security Payload (ESP) Transport Format with 865 the Host Identity Protocol (HIP)", RFC 5202, April 2008. 867 [I-D.ietf-hip-nat-traversal] 868 Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. 869 Keranen, "Basic HIP Extensions for Traversal of Network 870 Address Translators", draft-ietf-hip-nat-traversal-09 871 (work in progress), October 2009. 873 [I-D.ietf-hip-hiccups] 874 Camarillo, G. and J. Melen, "HIP (Host Identity Protocol) 875 Immediate Carriage and Conveyance of Upper- layer Protocol 876 Signaling (HICCUPS)", draft-ietf-hip-hiccups-02 (work in 877 progress), March 2010. 879 10.2. Informative References 881 [RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) 882 Protocol Architecture", RFC 4251, January 2006. 884 [RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 885 Rendezvous Extension", RFC 5204, April 2008. 887 [RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol 888 (HIP) Domain Name System (DNS) Extensions", RFC 5205, 889 April 2008. 891 [RFC5206] Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "End- 892 Host Mobility and Multihoming with the Host Identity 893 Protocol", RFC 5206, April 2008. 895 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 896 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 897 May 2008. 899 [RFC5338] Henderson, T., Nikander, P., and M. Komu, "Using the Host 900 Identity Protocol with Legacy Applications", RFC 5338, 901 September 2008. 903 [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, 904 "Session Traversal Utilities for NAT (STUN)", RFC 5389, 905 October 2008. 907 [I-D.ietf-hip-native-api] 908 Komu, M. and T. Henderson, "Basic Socket Interface 909 Extensions for Host Identity Protocol (HIP)", 910 draft-ietf-hip-native-api-12 (work in progress), 911 January 2010. 913 [I-D.ietf-mmusic-ice] 914 Rosenberg, J., "Interactive Connectivity Establishment 915 (ICE): A Protocol for Network Address Translator (NAT) 916 Traversal for Offer/Answer Protocols", 917 draft-ietf-mmusic-ice-19 (work in progress), October 2007. 919 [I-D.ietf-p2psip-base] 920 Jennings, C., Lowekamp, B., Rescorla, E., Baset, S., and 921 H. Schulzrinne, "REsource LOcation And Discovery (RELOAD) 922 Base Protocol", draft-ietf-p2psip-base-08 (work in 923 progress), March 2010. 925 [I-D.ietf-hip-reload-instance] 926 Keranen, A., Camarillo, G., and J. Maenpaa, "Host Identity 927 Protocol-Based Overlay Networking Environment (HIP BONE) 928 Instance Specification for REsource LOcation And Discovery 929 (RELOAD)", draft-ietf-hip-reload-instance-01 (work in 930 progress), March 2010. 932 Authors' Addresses 934 Gonzalo Camarillo 935 Ericsson 936 Hirsalantie 11 937 Jorvas 02420 938 Finland 940 Email: Gonzalo.Camarillo@ericsson.com 942 Pekka Nikander 943 Ericsson 944 Hirsalantie 11 945 Jorvas 02420 946 Finland 948 Email: Pekka.Nikander@ericsson.com 950 Jani Hautakorpi 951 Ericsson 952 Hirsalantie 11 953 Jorvas 02420 954 Finland 956 Email: Jani.Hautakorpi@ericsson.com 958 Ari Keranen 959 Ericsson 960 Hirsalantie 11 961 02420 Jorvas 962 Finland 964 Email: Ari.Keranen@ericsson.com 966 Alan Johnston 967 Avaya 968 St. Louis, MO 63124 970 Email: alan@sipstation.com