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As required by the SIP change process draft-tsvarea-sipchange [7] the SIP extension header field name "Service-Route" should also be registered in association with this extension. However, "Service-Route" MUST not be used until documented by a standards-track RFC. Expert review as required for this process is to be provided by the SIP Working Group. -- 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 (May 16, 2002) is 8016 days in the past. Is this intentional? 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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SIP -- Session Initiation Protocol D. Willis 3 Working Group dynamicsoft Inc. 4 Internet-Draft B. Hoeneisen 5 Expires: November 14, 2002 Nokia 6 May 16, 2002 8 SIP Extension Header Field for Service Route Discovery in Private 9 Networks 10 draft-willis-sip-scvrtdisco-05 12 Status of this Memo 14 This document is an Internet-Draft and is in full conformance with 15 all provisions of Section 10 of RFC2026. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at http:// 28 www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on November 14, 2002. 35 Copyright Notice 37 Copyright (C) The Internet Society (2002). All Rights Reserved. 39 Abstract 41 This document proposes a private SIP extension header field used in 42 conjunction with responses to REGISTER requests to provide a 43 mechanism by which a registrar may inform a registering UA of a 44 service route that the UA may use to request outbound services from 45 the registrar's domain. 47 Table of Contents 49 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 3. Discussion of Mechanism . . . . . . . . . . . . . . . . . . 4 55 4. Applicability Statement . . . . . . . . . . . . . . . . . . 5 57 5. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 59 6. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 60 6.1 Procedures at the UA . . . . . . . . . . . . . . . . . . . . 6 61 6.2 Procedures at the Proxy . . . . . . . . . . . . . . . . . . 6 62 6.3 Procedures at the Registrar . . . . . . . . . . . . . . . . 7 63 6.4 Examples of Usage . . . . . . . . . . . . . . . . . . . . . 8 64 6.4.1 Example of Mechanism in REGISTER Transaction . . . . . . . . 8 65 6.4.2 Example of Mechanism in INVITE Transaction . . . . . . . . . 10 67 7. Security Considerations . . . . . . . . . . . . . . . . . . 12 69 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 13 71 Normative References . . . . . . . . . . . . . . . . . . . . 13 73 Non-Normative References . . . . . . . . . . . . . . . . . . 14 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14 77 Full Copyright Statement . . . . . . . . . . . . . . . . . . 15 79 1. Terminology 81 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 82 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 83 document are to be interpreted as described in RFC 2119 [3]. 85 2. Background 87 3GPP established a requirement for discovering home proxies during 88 SIP registration and published this requirement in draft-garcia- 89 sipping-3gpp-reqs [6]. Unlike many other network environments, the 90 3GPP network dynamically assigns a home service proxy to each 91 address-of-record. This assignment may occur in conjunction with a 92 REGISTER operation, or out-of-band as needed to support call services 93 when the address-of-record has no registrations. This home service 94 proxy may provide both inbound (UA terminated) and outbound (UA 95 originated) services. 97 For inbound (UA terminated) session cases, the home proxy network 98 routes requests having a request-URI targeting the address-of-record 99 associated with the UA to the assigned home service proxy by using 100 some sort of look-up-mechanism outside the scope of this document. 102 Outbound (UA originated) session cases raise another issue. 103 Specifically, "How does the UA know which service proxy to use and 104 how to get there?" 106 Several mechanisms have been proposed in list discussions, including: 108 1. Configuration data in the UA. This raises questions of UA 109 configuration management and updating, especially if proxy 110 assignment is very dynamic, such as in load-balancing scenarios. 111 2. Use of some other protocol, such as HTTP, to get configuration 112 data from a configuration server in the home network. While 113 functional, this solution requires additional protocol engines, 114 firewall complexity, operations overhead, and a significant 115 additional "over the air" traffic. 116 3. Use of lookup tables in the home network, as is done for inbound 117 requests. This has a relatively high overhead in terms of 118 database operations. 119 4. Returning a 302 response indicating the service proxy as a new 120 contact, causing the upstream node processing the 302 (ostensibly 121 the UA) to retransmit the request toward the service proxy. 122 While this shares the database operation of the previous 123 alternative, it does explicitly allow for caching the 302 124 response thereby potentially reducing the frequency and number of 125 database operations. 126 5. Performing an operation equivalent to record-routing in a 127 REGISTER transaction between the UA and the associated registrar, 128 then storing that route in the UA and reusing it as a service 129 route on future requests originating from the UA. While 130 efficient, this constrains the service route for proxy operations 131 to be congruent with the route taken by the REGISTER message. 132 6. Returning service route information as the value of a header 133 field in the REGISTER response. While similar to the previous 134 alternative, this approach grants the ability for the registrar 135 to selectively apply knowledge about the topology of the home 136 network in constructing the service route. 138 This document discusses this final alternative: using a header field 139 in the REGISTER response to indicate a service route that the UA may 140 wish to use if requesting services from the proxy network associated 141 with the registrar generating the response. 143 Scenario 145 UA1----P1-----| |--R-------| 146 | | | 147 P2---| DBMS 148 | | | 149 UA2-----------| |--HSP-----| 151 In this scenario, we have a "home network" containing routing proxy 152 P2, registrar R, home service proxy HSP, and database DBMS used by 153 both R and HSP. P2 represents the "edge" of the home network from a 154 SIP perspective, and might be called an "edge proxy". UA1 is an 155 external UA behind proxy P1. UA1 discovers P1 via DHCP. UA2 is 156 another UA on the Internet, and does not use a default outbound 157 proxy. We do not show DNS elements in this diagram, but will assume 158 their reasonable availability in the discussion. The mission is for 159 UA1 to discover HSP so that outbound requests from UA1 may be routed 160 (at the discretion of UA1) through HSP, thereby receiving outbound 161 services from HSP. 163 3. Discussion of Mechanism 165 The proposed mechanism uses a private header field "P-Service-Route" 166 in the REGISTER response to indicate a service route that the UA may 167 wish to use if requesting services from the proxy network associated 168 with the registrar generating the response. The routing established 169 by the P-Service-Route mechanism applies only to requests originating 170 in the user agent. 172 Simply put, the registrar generates a service route for the 173 registering UA and returns it in the response to each successful 174 REGISTER request. This service route has the form of a Route header 175 field that the registering UA may use to send requests through the 176 service proxy selected by the registrar. The UA would use this route 177 by inserting it as a preloaded Route header field in requests 178 originated by the UA intended for routing through the service proxy. 180 The mechanism by which the registrar constructs the header field 181 value is specific to the local implementation and outside the scope 182 of this document. 184 4. Applicability Statement 186 The P-Service-Route mechanism is applicable when: 188 1. The UA registers with a REGISTRAR in a given domain. 189 2. The domain dynamically assigns a service proxy for the UA. 190 3. The registrar(s) in the domain has/have sufficient knowledge of 191 the network topology, policy, and situation such that a 192 reasonable service route can be constructed. 193 4. Other mechanisms for proposing a service route to the UA are not 194 available or are inappropriate for use within the administrative 195 domain. 197 5. Syntax 199 The syntax for the P-Service-Route header field is: 201 P-Service-Route = "P-Service-Route" HCOLON 1#( p-sr-value) 203 p-sr-value = name-addr *( SEMI rr-param ) 205 rr-param = generic-param 207 The allowable usage of header fields is described in Tables 2 and 3 208 of SIPbis [1]. The following additions to this table are needed for 209 P-Service-Route. 211 Addition of P-Service-Route to SIP Table 3: 213 Header field where proxy ACK BYE CAN INV OPT REG PRA 214 _______________________________________________________________ 215 P-Service-Route 2xx ar - - - - - o - 217 6. Usage 219 6.1 Procedures at the UA 221 The UA performs a register as usual. The register response may 222 contain a P-Service-Route header field. If so, the UA MAY store the 223 value of the P-Service-Route header field in an association with the 224 address-of-record for which the REGISTER transaction had registered a 225 contact. If the UA supports multiple address of records, it may be 226 able to store multiple service routes, one per address-of-record. If 227 the UA refreshes the registration, the stored value of the P-Service- 228 Route is updated according to the P-Service-Route header field of the 229 latest 200 OK response. If there is no P-Service-Route header field 230 in the response, the UA clears any service route for that registrar 231 previously stored by the UA. 233 The UA MAY choose to exercise a service route for future requests 234 associated with a given address-of-record for which a service route 235 is known. If so, it uses the content of the P-Service-Route header 236 field as a preloaded Route header field in outgoing requests [1]. 237 The UA MUST preserve the order, in case there is more than one P- 238 Service-Route header field or header field value. 240 Loose routes may interact with routing policy in interesting ways. 241 The specifics of how the service route set integrates with any 242 locally required default route and local policy are implementation 243 dependent. For example, some devices will use locally-configured 244 explicit loose routing to reach a next-hop proxy, and others will use 245 a default outbound-proxy routing rule. However, for the result to 246 function, the combination MUST provide valid routing in the local 247 environment. In general, the service route set is appended to any 248 locally configured route needed to egress the access proxy chain. 249 Systems designers must match the service routing policy of their 250 nodes with the basic SIP routing policy in order to get a workable 251 system. 253 6.2 Procedures at the Proxy 255 The P-Service-Route header field is generally treated like any other 256 unknown header field by intermediate proxies. They simply forward it 257 on towards the destination. 259 There is a question of whether proxies processing a REGISTER response 260 may add themselves to the route set in the P-Service-Route header 261 field. While this would enable dynamic construction of service 262 routes, it has two significant problems. The first is one of 263 transparency, as seen by the registrar: Intermediate proxies could 264 add themselves without the knowledge or consent of the registrar. 266 The second problem is interaction with end-to-end security. If the 267 registrar uses S/MIME techniques to protect the REGISTER response, 268 such additions would be visible to the UA as "man in the middle" 269 alterations in the response. Consequently, intermediate proxies 270 SHOULD NOT alter the value of P-Service-Route in REGISTER responses, 271 and if they do, acceptance of the alteration by the UA MUST NOT be 272 required. 274 6.3 Procedures at the Registrar 276 When a registrar receives a successful REGISTER request, it MAY 277 choose to return one or more P-Service-Route header field(s) in the 278 200 OK response. The determinations of whether to include these 279 header fields(s) into the 200 OK response and what value(s) to insert 280 are a matter of local policy and outside the scope of this document. 282 Having inserted a P-Service-Route header field or fields, the 283 registrar returns the 200 OK response to the UA in accordance with 284 standard procedures. 286 A REGISTER operation performing a Fetching Bindings (i.e. no Contact 287 header field is present in the request) SHOULD return the same value 288 of P-Service-Route as returned in the corresponding previous REGISTER 289 response for the address-of-record in question. 291 Note: A Fetching Bindings operation could be used by the UA to 292 recover a lost value of P-Service-Route. 294 Certain network topologies MAY require a specific proxy (e.g. 295 firewall proxy) to be traversed before the home service proxy. Thus, 296 a registrar with specific knowledge of the network topology MAY 297 return more than one P-Service-Route header field or element in the 298 200 OK response; the order is specified as top-down, meaning the 299 topmost P-Service-Route entry will be visited first. Such 300 constructions are implementation specific and outside the scope of 301 this document. 303 In general, the P-Service-Route header field contains references to 304 elements strictly within the administrative domain of the registrar 305 and home service proxy. For example, consider a case where a user 306 leaves the "home" network and roams into a "visited" network. The 307 registrar cannot be assumed to have knowledge of the topology of the 308 visited network, so the P-Service-Route it returns contains elements 309 only within the home network. 311 Note that the inserted P-Service-Route element(s) MUST conform to the 312 syntax of a Route element as defined in [1]. As suggested therein, 313 such route elements MUST include the loose-routing indicator 314 parameter ";lr" for full compliance with [1] 316 6.4 Examples of Usage 318 We present an example in the context of the scenario presented in the 319 Background section earlier in this document. The network diagram is 320 replicated below: 322 Scenario 324 UA1----P1-----| |--R-------| 325 | | | 326 P2---| DBMS 327 | | | 328 UA2-----------| |--HSP-----| 330 6.4.1 Example of Mechanism in REGISTER Transaction 332 This example shows the message sequence for user agent UA1 333 registering to HOMEDOMAIN using registrar R. R returns a P-Service- 334 Route indicating that UA1 may use home service proxy HSP to receive 335 outbound services from HOMEDOMAIN. 337 Please note that the name UA1, HOMEDOMAIN, etc. are placeholders for 338 appropriate user and host names or addresses. 340 Message sequence for REGISTER returning P-Service-Route: 342 F1 Register UA1 -> P1 344 REGISTER sip:HOMEDOMAIN SIP/2.0 345 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 346 To: UA1@HOMEDOMAIN 347 From: UA1@HOMEDOMAIN ;tag=456248 348 Call-ID: 843817637684230@998sdasdh09 349 CSeq: 1826 REGISTER 350 Contact: 351 . . . 353 F2 Register P1 -> P2 354 REGISTER sip:HOMEDOMAIN SIP/2.0 355 Via: SIP/2.0/UDP P1:5060;branch=z9hG4bK34ghi7ab04 356 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 357 To: UA1@HOMEDOMAIN 358 From: UA1@REGISTAR ;tag=456248 359 Call-ID: 843817637684230@998sdasdh09 360 CSeq: 1826 REGISTER 361 Contact: 362 . . . 364 F3 Register P2 -> R 366 REGISTER sip:HOMEDOMAIN SIP/2.0 367 Via: SIP/2.0/UDP P2:5060;branch=z9hG4bKiokioukju908 368 Via: SIP/2.0/UDP P1:5060;branch=z9hG4bK34ghi7ab04 369 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 370 To: UA1@HOMEDOMAIN 371 From: UA1@HOMEDOMAIN ;tag=456248 372 Call-ID: 843817637684230@998sdasdh09 373 CSeq: 1826 REGISTER 374 Contact: 375 . . . 377 F4 R executes Register 379 R Stores: 380 For 381 Contact = 383 F5 R calculates Service Route 385 In this example, R is statically configured to reference HSP as a 386 service route, so P-Service-Route = 388 F6 Register Response r -> P2 390 SIP/2.0 200 OK 391 Via: SIP/2.0/UDP P2:5060;branch=z9hG4bKiokioukju908 392 Via: SIP/2.0/UDP P1:5060;branch=z9hG4bK34ghi7ab04 393 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 394 To: UA1@HOMEDOMAIN 395 From: UA1@HOMEDOMAIN ;tag=456248 396 Call-ID: 843817637684230@998sdasdh09 397 CSeq: 1826 REGISTER 398 Contact: 399 P-Service-Route: 400 . . . 402 F7 Register Response P2 -> P1 404 SIP/2.0 200 OK 405 Via: SIP/2.0/UDP P1:5060;branch=z9hG4bK34ghi7ab04 406 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 407 To: UA1@HOMEDOMAIN 408 From: UA1@HOMEDOMAIN ;tag=456248 409 Call-ID: 843817637684230@998sdasdh09 410 CSeq: 1826 REGISTER 411 Contact: 412 P-Service-Route: 413 . . . 415 F8 Register Response P1 -> UA1 417 SIP/2.0 200 OK 418 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 419 To: UA1@HOMEDOMAIN 420 From: UA1@HOMEDOMAIN ;tag=456248 421 Call-ID: 843817637684230@998sdasdh09 422 CSeq: 1826 REGISTER 423 Contact: 424 P-Service-Route: 425 . . . 427 F9 UA1 stores service route for HOMEDOMAIN 429 6.4.2 Example of Mechanism in INVITE Transaction 431 This example shows the message sequence for an INVITE transaction 432 originating from UA1 eventually arriving at UA2 using outbound 433 services from HOMEDOMAIN, where UA1 has previously registered with 434 HOMEDOMAIN and been informed of a service route through HSP. The 435 service being provided by HOMEDOMAIN is a "logging" service, which 436 provides a record of the call for UA1's use (perhaps the user of UA1 437 is an attorney who bills for calls to customers). 439 Message sequence for INVITE using P-Service-Route: 441 F1 INVITE UA1 -> P1 443 INVITE sip:UA2@HOMEDOMAIN SIP/2.0 444 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 445 To: Customer 446 From: Lawyer ;tag=456248 447 Call-ID: 843817637684230@998sdasdh09 448 CSeq: 18 INVITE 449 Contact: 450 Route: 451 . . . 453 Note: P1 is selected using the "outbound proxy" rule in UA1. 455 F2 INVITE P1 -> P2 457 INVITE sip:UA2@HOMEDOMAIN SIP/2.0 458 Via: SIP/2.0/UDP P1:5060;branch=z9hG4bK34ghi7ab04 459 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 460 To: Customer 461 From: Lawyer ;tag=456248 462 Call-ID: 843817637684230@998sdasdh09 463 CSeq: 18 INVITE 464 Contact: 465 Record-Route: 466 Route: 467 . . . 469 Note: P2 is selected using a DNS lookup on the domain of HSP. 470 P1 has added itself to the Record Route. 472 F3 INVITE P2 -> HSP 474 INVITE sip:UA2@HOMEDOMAIN SIP/2.0 475 Via: SIP/2.0/UDP P2:5060;branch=z9hG4bKiokioukju908 476 Via: SIP/2.0/UDP P1:5060;branch=z9hG4bK34ghi7ab04 477 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 478 To: Customer 479 From: Lawyer ;tag=456248 480 Call-ID: 843817637684230@998sdasdh09 481 CSeq: 18 INVITE 482 Contact: 483 Record-Route: 484 Record-Route: 485 Route: 486 . . . 488 Note: HSP is selected using a DNS lookup for HSP within HOMEDOMAIN. 489 P2 has addded itself to the Record Route. 491 F4 HSP executes service 493 HSP identifies the service to be executed from UA1's stored 494 profile. The specifics of this are outside the scope of this 495 document. HSP writes a record to "Lawyer"s log book, then looks up 496 name "sip:UA2@HOMEDOMAIN" and discovers that the current contact for 497 UA2 is address 18.19.20.21. This will be the request-URI of the 498 next-hop INVITE 500 F5 INVITE HSP->P2 502 INVITE sip:UA2@18.19.20.21 503 Via: SIP/2.0/USP HSP:5060;branch=z9hG4bKHSP10120323 504 Via: SIP/2.0/UDP P2:5060;branch=z9hG4bKiokioukju908 505 Via: SIP/2.0/UDP P1:5060;branch=z9hG4bK34ghi7ab04 506 Via: SIP/2.0/UDP 192.0.2.4:5060;branch=z9hG4bKnashds7 507 To: Customer 508 From: UA1@HOMEDOMAIN ;tag=456248 509 Call-ID: 843817637684230@998sdasdh09 510 CSeq: 18 INVITE 511 Contact: 512 Record-Route: 513 Record-Route: 514 Record-Route: 515 . . . 517 Note: P2 selected by outbound proxy rule on HSP. 519 INVITE propagates toward UA2 as usual. 521 7. Security Considerations 523 It is possible for proxies between the UA and the registrar during 524 the REGISTER transaction to modify the value of P-Service-Route 525 returned by the registrar, or to insert a P-Service-Route even when 526 one was not returned by the registrar. It is also possible for 527 proxies on the INVITE path to execute many different attacks. It is 528 therefore desirable to apply transitive mutual authentication using 529 sips: or other available mechanisms in order to prevent such attacks. 531 The "sips:" URI as defined in [1] defines a mechanism by which a UA 532 may request transport-level message integrity and mutual 533 authentication. Since there is no requirement for proxies to modify 534 message, S/MIME signed bodies may be used to provide end-to-end 535 protection for the returned value. 537 Systems using P-Service-Route SHOULD provide hop-by-hop message 538 integrity and mutual authentication. UAs SHOULD request this support 539 by using a "sips:" URI. Registrars returning a P-Service-Route 540 SHOULD provide end-to-end protection on the return using S/MIME. UAs 541 receiving P-Service-Route SHOULD authenticate attached S/MIME bodies. 543 8. IANA Considerations 545 This document defines the SIP extension header field "P-Service- 546 Route" which should be included in the registry of SIP header fields 547 defined in SIP bis [1]. As required by the SIP change process draft- 548 tsvarea-sipchange [7] the SIP extension header field name "Service- 549 Route" should also be registered in association with this extension. 550 However, "Service-Route" MUST not be used until documented by a 551 standards-track RFC. Expert review as required for this process is 552 to be provided by the SIP Working Group. 554 The following is the registration for the P-Service-Route header 555 field: 557 RFC Number: RFCXXXX [Note to IANA: Fill in with the RFC number of 558 this specification.] 560 Header Field Name: P-Service-Route 562 Compact Form: none 564 The following is the registration for the Service-Route header field: 566 RFC Number: RFCXXXX [Note to IANA: Fill in with the RFC number of 567 this specification.] (not yet specified, only reserved) 569 Header Field Name: Service-Route 571 Compact Form: none 573 Normative References 575 [1] Rosenberg, J., "SIP: Session Initiation Protocol", draft-ietf- 576 sip-rfc2543bis-09 (work in progress), March 2002. 578 [2] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 579 9, RFC 2026, October 1996. 581 [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement 582 Levels", BCP 14, RFC 2119, March 1997. 584 [4] Postel, J. and J. Reynolds, "Instructions to RFC Authors", RFC 585 2223, October 1997. 587 [5] Handley, M., Schulzrinne, H., Schooler, E. and J. Rosenberg, 588 "SIP: Session Initiation Protocol", RFC 2543, March 1999. 590 Non-Normative References 592 [6] Garcia-Martin, MA., "3GPP Requirements On SIP", draft-garcia- 593 sipping-3gpp-reqs-03 (work in progress), March 2002. 595 [7] Mankin, A., "SIP Change Process", draft-tsvarea-sipchange-01 596 (work in progress), March 2002. 598 Authors' Addresses 600 Dean Willis 601 dynamicsoft Inc. 602 5100 Tennyson Parkway 603 Suite 1200 604 Plano, TX 75028 605 US 607 Phone: +1 972 473 5455 608 EMail: dwillis@dynamicsoft.com 609 URI: http://www.dynamicsoft.com/ 611 Bernie Hoeneisen 612 Nokia 613 Helsinki, Hiomo 3/6 614 P.O. Box 312 615 00045 NOKIA Group 616 Finland 618 Phone: +358-40-821 9 831 619 EMail: bernhard.honeisen@nokia.com, b.hoeneisen@ieee.org 620 URI: http://www.nokia.com/ 622 Full Copyright Statement 624 Copyright (C) The Internet Society (2002). 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