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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SIPCORE O. Johansson 3 Internet-Draft Edvina AB 4 Intended status: Standards Track G. Salgueiro 5 Expires: June 15, 2017 Cisco Systems 6 D. Worley 7 Ariadne 8 December 12, 2016 10 Happy EarBalls: Success with Dual-Stack, Connection-Oriented SIP 11 draft-worley-sip-he-connection-01 13 Abstract 15 The Session Initiation Protocol (SIP) supports multiple transports 16 running both over IPv4 and IPv6 protocols. In more and more cases, a 17 SIP user agent (UA) is connected to multiple network interfaces. In 18 these cases setting up a connection from a dual stack client to a 19 dual stack server may suffer from the issues described in RFC 6555 20 [RFC6555] ("Happy Eyeballs") - significant delays in the process of 21 setting up a working flow to a server. This negatively affects user 22 experience. 24 This document builds on RFC 6555 and explains how a [RFC3261] 25 compliant SIP implementation can minimize delays when contacting a 26 host name (obtained by using DNS NAPTR and SRV lookups) in a dual 27 stack network using connection-oriented transport protocols. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on June 15, 2017. 46 Copyright Notice 48 Copyright (c) 2016 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 Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminology and Conventions Used in This Document . . . . . . 3 65 3. DNS Procedures in a Dual-Stack Network . . . . . . . . . . . 4 66 4. Establishing a Connection . . . . . . . . . . . . . . . . . . 5 67 4.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 6 68 4.1.1. Address Preferences . . . . . . . . . . . . . . . . . 6 69 4.1.2. Stateful Behavior . . . . . . . . . . . . . . . . . . 6 70 4.1.3. Reset on Network (Re-)Initialization . . . . . . . . 7 71 4.1.4. Abandon Non-Winning Connections . . . . . . . . . . . 7 72 5. Using an Existing Connection . . . . . . . . . . . . . . . . 8 73 6. Additional Considerations . . . . . . . . . . . . . . . . . . 8 74 6.1. Preemtive Actions . . . . . . . . . . . . . . . . . . . . 8 75 6.2. Determining the Type of an Address . . . . . . . . . . . 9 76 6.3. Debugging and Troubleshooting . . . . . . . . . . . . . . 9 77 6.4. Three or More Interfaces . . . . . . . . . . . . . . . . 9 78 6.5. Multiple A and AAAA Resource Records . . . . . . . . . . 9 79 6.6. Connection Timeout . . . . . . . . . . . . . . . . . . . 10 80 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 81 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 82 9. History . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 83 9.1. Changes from draft-worley-sip-he-connection-00 to draft- 84 worley-sip-he-connection-01 . . . . . . . . . . . . . . . 11 85 9.2. Changes from draft-johansson-sip-he-connection-01 to 86 draft-worley-sip-he-connection-00 . . . . . . . . . . . . 11 87 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 88 10.1. Normative References . . . . . . . . . . . . . . . . . . 11 89 10.2. Informative References . . . . . . . . . . . . . . . . . 11 90 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 93 1. Introduction 95 The Session Initiation Protocol (SIP) [RFC3261] and the documents 96 that extended it provide support for both IPv4 and IPv6. However, 97 this support has problems with environments that are characteristic 98 of the transitional migratory phase from IPv4 to IPv6 networks. 99 During this phase, many server and client implementations run on 100 dual-stack hosts. In such environments, a dual-stack host will 101 likely suffer greater connection delay, and by extension an inferior 102 user experience, than an IPv4-only host. The need to remedy this 103 diminished performance of dual-stack hosts led to the development of 104 the "Happy Eyeballs" [RFC6555] algorithm, which has since been 105 implemented in many protocols and applications. 107 This document revises the the [RFC3263] procedures to apply the 108 "Happy Eyeballs" framework. A dual-stack client using connection- 109 oriented transport should set up multiple connections in parallel, to 110 targets based on the result of DNS queries. This document starts at 111 the point where a SIP implementation has a host name that resolves 112 using A and AAAA records. Such a host name can either be the host 113 part of a SIP URI (possibly including a port number) or the result of 114 a lookup using DNS NAPTR and SRV records as described in RFC 3263 (as 115 updated by RFC 7984[RFC7984]). 117 Procedures for connectionless transport protocols for SIP are outside 118 the scope of this document. Procedures allowing a client to change 119 the order of contacting targets that were derived from different host 120 names are outside the scope of this document. 122 The concepts in this document are elaborated from those developed in 123 [RFC6555], and so some background information in RFC 6555 is not 124 repeated here. The reader is encouraged to read the available 125 documentation regarding implementations of RFC 6555, as well as study 126 Open Source implementations, in order to learn from the experience 127 accumulated since the publishing of RFC 6555 in 2012. 129 2. Terminology and Conventions Used in This Document 131 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 132 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 133 document are to be interpreted as described in RFC 2119 [RFC2119]. 135 RFC 3261 [RFC3261] defines additional terms used in this document 136 that are specific to the SIP domain such as "proxy"; "registrar"; 137 "redirect server"; "user agent server" or "UAS"; "user agent client" 138 or "UAC"; "back-to-back user agent" or "B2BUA"; "dialog"; 139 "transaction"; "server transaction". 141 This document uses the term "SIP Server" that is defined to include 142 the following SIP entities: user agent server, registrar, redirect 143 server, a SIP proxy in the role of user agent server, and a B2BUA in 144 the role of a user agent server. 146 This document also uses the following terminology to make clear 147 distinction between SIP entities supporting only IPv4, only IPv6 or 148 supporting both IPv4 and IPv6. 150 IPv4-only UA/UAC/UAS: An IPv4-only UA/UAC/UAS supports SIP signaling 151 and media only on the IPv4 network. It does not understand IPv6 152 addresses. 154 IPv6-only UA/UAC/UAS: An IPv6-only UA/UAC/UAS supports SIP signaling 155 and media only on the IPv6 network. It does not understand IPv4 156 addresses. 158 IPv4/IPv6 UA/UAC/UAS: A UA/UAC/UAS that supports SIP signaling and 159 media on both IPv4 and IPv6 networks; such a UA/UAC/UAS is known 160 (and will be referred to in this document) as a "dual-stack" 161 [RFC4213] UA/UAC/UAS. 163 Discussion: Do we need special handling of websocket transport? 165 While this document uses the term "dual-stack" based on RFC 6555 and 166 earlier terminology, the authors acknowledge that the same solution 167 can be applied to multi-interface environments as well as future 168 versions of IP alongside with the current ones. 170 3. DNS Procedures in a Dual-Stack Network 172 A SIP client uses DNS to find a server based on a SIP URI. This 173 process is described in [RFC3263] and updated in [RFC7984]. Using 174 this process, a list of "targets" is constructed, where each target 175 consists of an IP address, a port number, and a protocol (e.g., TCP, 176 UDP, TLS) by which to contact that address/port. The process 177 proceeds by constructing a sequence of host names, possibly by 178 looking up NAPTR and/or SRV DNS records, and then for each host name 179 looking up DNS address records (for all address families supported by 180 the client) to generate the list of IP addresses for targets that are 181 derived from that host name. The addresses for each host name are 182 ordered using the client's destination selection rules[RFC6724]. The 183 sorted targets for all the host names are then concatenated into the 184 sequence of targets to which the client will attempt to send the SIP 185 message. 187 Previously, the client contacts the targets in order until one is 188 contacted successfully. In order to contact a target, the client 189 establishes a transport connection (if necessary), sends the message 190 using the transport (possibly resending the message several times), 191 and then (for requests) waits for a response (either provisional or 192 final). The process ends successfully if the client receives a 193 response. The process ends unsuccessfully if the client receives a 194 permanent error from the transport layer or if a SIP timer (Timer B 195 or Timer F in [RFC3261]) expires. Timeouts generally default to 32 196 seconds. 198 If the user has to wait for even one timeout, this will seriously 199 degrade the user experience. Thus, it is desirable to minimize the 200 number of times the client has timeouts when sending requests. 202 If the target list contains both IPv6 addresses and IPv4 addresses, 203 this procedure can degrade the user's experience in common 204 situations. Typically, this problem arises when the client has an 205 IPv6 interface, the server's preferred address is an IPv6 address, 206 but the transit networks between the client and server do not carry 207 IPv6. This can cause the client to attempt to send a SIP request for 208 32 seconds before it times out that target and continues with an IPv4 209 target. This problem parallels a problem that was widely seen in web 210 browsers that was cured by specifying that web browsers should use a 211 "Happy Eyeballs" algorithm[RFC6555] to determine the order in which 212 to contact target addresses. 214 This document specifies an amendment to these procedures, by which 215 the subsequences of targets derived from individual host names may be 216 contacted in a different order than is specified by the destination 217 selection rules. As in [RFC6555], the algorithm that the client uses 218 is not specified by this document, but this document places 219 requirements on the algorithm that improve the user's experience 220 without unduly burdening the Internet infrastructure. By analogy 221 with the name "Happy Eyeballs" for similar algorithms in web 222 browsers, we label these algorithms "Happy EarBalls"[UD]. 224 This document modifies the transport procedures only in the case when 225 all targets for a host name have connection-oriented protocols 226 (currently, TCP, TLS, and SCTP). Other cases are outside the scope 227 of this document. The case of SIP using WebSocket transport is 228 outside the scope of this document because there is only one 229 transport target, the WebSocket transport provided by the context. 231 4. Establishing a Connection 233 This section discusses the situation that most closely resembles RFC 234 6555, which is when the SIP client has no active connection to any of 235 the targets in a subsequence of targets derived from one host name. 236 This specification allows the client to attempt to send a request to 237 targets in the subsequence in a different order than is prescribed by 238 RFC 3262 and RFC 6724. In addition, this specification allows the 239 client to attempt to initiate a connection to a target without 240 subsequently sending a request to the target. However, the algorithm 241 which the client uses use meet the constraints in this section. 243 Typically, the SIP client will set up two connections, with some head 244 start for one address family (which is possibly be configurable) and 245 then select the first completed connection for use and close the 246 other one. The SIP message is sent on the selected connection only. 248 The reason for this approach is to avoid the timeout associated with 249 sending an unsuccessful SIP request, requiring the client to wait for 250 a timeout before the request can be sent on a connection to another 251 target - which in the case of SIP with default timers is 32 seconds. 252 Waiting for timeout before trying with a secondary address will lead 253 to a very poor user experience. 255 4.1. Requirements 257 The following requirements apply to any implementation that takes 258 advantage of the relaxed requirements on message transmission 259 specified by this document. 261 4.1.1. Address Preferences 263 An implementation MUST prefer the first IP address family returned by 264 the host's address preference policy, unless it implements a stateful 265 algorithm as described in Section 4.1.2. This usually means giving 266 preference to IPv6 over IPv4, although that preference can be 267 overridden by user configuration or by network configuration. If the 268 host's policy is unknown or not attainable, the implementation MUST 269 prefer IPv6 over IPv4. 271 4.1.2. Stateful Behavior 273 The algorithm may be stateful -- that is, the algorithm will remember 274 that IPv6 always fails, or that IPv6 to certain prefixes always 275 fails, and so on. This section constrains such algorithms. 276 Stateless algorithms, which do not remember the success/failure of 277 previous connections, are not discussed in this section. 279 After making a connection attempt using the preferred address family 280 (e.g., IPv6) and failing to establish a connection within a certain 281 time period (see Section 6.6), a Happy EarBalls implementation will 282 decide to initiate a second connection attempt using the same address 283 family or the other address family. 285 Such an implementation MAY make prioritize making subsequent 286 connection attempts (to the same host or to other hosts) using the 287 successful address family (e.g., IPv4). So long as new connections 288 are being attempted by the host, such an implementation MUST 289 occasionally make connection attempts using the host's preferred 290 address family, as that family may have become functional again, and 291 the client SHOULD do so every 10 minutes. The 10-minute delay before 292 retrying a failed address family avoids the simple doubling of 293 connection attempts on both IPv6 and IPv4. This can be achieved by 294 flushing Happy EarBalls state every 10 minutes, which does not 295 significantly harm the application's subsequent connection setup 296 time. If connections using the preferred address family are again 297 successful, the preferred address family MUST be used for subsequent 298 connections. A stateful implementation MAY track connection success 299 and failure based on IPv6 or IPv4 prefix. E.g., connections to 300 addresses with the same prefix as the interface's address may be 301 successful whereas connections to addresses with different prefixes 302 fail. 304 4.1.3. Reset on Network (Re-)Initialization 306 Because every network has different characteristics (e.g., working or 307 broken IPv6 or IPv4 connectivity), a Happy EarBalls algorithm SHOULD 308 re-initialize when the interface is connected to a new network. 309 Interfaces can determine network (re-)initialization by a variety of 310 mechanisms (e.g., Detecting Network Attachment in IPv4 (DNAv4) 311 [RFC4436], DNAv6 [RFC6059]). 313 4.1.4. Abandon Non-Winning Connections 315 Non-winning connections that are not assigned as flows for the 316 purposes of [RFC5626] SHOULD be abandoned, even though they could -- 317 in some cases -- be put to reasonable use. 319 Justification: This reduces the load on the server (file descriptors, 320 TCP control blocks) and stateful middleboxes (NAT and firewalls). 321 Also, if the abandoned connection is IPv4, this reduces IPv4 address 322 sharing contention. 324 (There are some unlikely situations where a non-winning connection 325 could be useful in the future: If at a later time, the client must 326 send a request to a different host name, but one which has as a 327 target the peer of the non-winning connection and does not have as a 328 target the peer of the winning connection.) 330 5. Using an Existing Connection 332 When a client desires to send a message to a target that is within a 333 subsequence of targets derived from one host name, the client may 334 already have a connection established to one of the targets through 335 either SIP Outbound[RFC5626] or the procedures of Section 4. The 336 client SHOULD attempt to send the message using the existing 337 connection in preference to using a new connection to one of the 338 targets. 340 If, in the client's operational environment, there is a significant 341 risk that the connection has become unusable without the client 342 becoming aware of it, the client SHOULD consider testing whether the 343 connection is usable before sending the message using the connection. 344 Some possible ways to probe a connection to determine if it is still 345 usable are: 347 o Send a keep-alive, as specified by the protocol of the connection. 349 o Send a CR-LF-CR-LF keep-alive on a SIP Outbound 350 connection[RFC5626]. 352 o Send an OPTIONS request with "Max-Forwards: 0". 354 (Note that a probe using an OPTIONS request can be used with any 355 protocol. If the OPTIONS reaches the target, the target is required 356 to respond with either a 200 or 483 response[RFC3261] without 357 forwarding it to another entity. Conveniently, a server can respond 358 to such a request statelessly, so such requests are low-overhead. 359 (Although the [RFC5626] keep-alive methods have even lower 360 overhead.)) 362 6. Additional Considerations 364 This section discusses additional considerations related to Happy 365 EarBalls. 367 6.1. Preemtive Actions 369 A client may be in a situation where it has advance notice that it is 370 likely to need to send a message to a particular host name, for 371 instance, if the user of a UA begins dialing an outgoing call which 372 will be routed through a particular outgoing proxy. In such a 373 situation, the client SHOULD consider preemptively establishing a 374 connection (Section 4) or probing an existing connection (Section 5). 376 6.2. Determining the Type of an Address 378 For some transitional technologies, such as a dual-stack host, it is 379 easy for the application to recognize a native IPv6 address (learned 380 via a AAAA query) and a native IPv4 address (learned via an A query). 381 The use of IPv6/IPv4 translation in the local network makes it 382 difficult or impossible to determine the address family by which the 383 connection will traverse the global network. However, IPv6/IPv4 384 translators do not need to be deployed on networks with dual-stack 385 clients because dual-stack clients can use their native IP address 386 family. Environments where IPv6/IPv4 translation is active will 387 degrade the ability of Happy EarBalls algorithms to establish working 388 connections. 390 6.3. Debugging and Troubleshooting 392 Happy EarBalls is aimed at ensuring a reliable user experience 393 regardless of connectivity problems affecting any single transport. 394 However, this naturally means that applications employing these 395 techniques are by default less useful for diagnosing issues with a 396 particular address family. To assist in that regard, an 397 implementation MAY provide a mechanism to disable their Happy 398 EarBalls behavior via a user setting, and to provide data useful for 399 debugging (e.g., a log or way to review current preferences). 401 6.4. Three or More Interfaces 403 A dual-stack host normally has one physical interface, and all 404 network access is done via IPv4 and IPv6 addresses assigned to that 405 interface. However, a dual-stack host might have additional physical 406 interfaces or additional logical interfaces (e.g., because of a VPN). 407 Additional Happy EarBalls considerations for optimal operation with 408 additional physical or logical interfaces is for further study and is 409 outside the scope of this document. 411 6.5. Multiple A and AAAA Resource Records 413 It is possible that a DNS query for an A or AAAA resource record will 414 return more than one A or AAAA address. When this occurs, it is 415 RECOMMENDED that a Happy EarBalls implementation order the responses 416 following the host's address preference policy and then try the first 417 target. If that fails after a certain time (see Section 6.6), the 418 next target SHOULD be chosen from the other address family. 420 If the second attempt fails to connect, a Happy EarBalls 421 implementation SHOULD try the other targets; the order of these 422 connection attempts is not important. 424 Servers sometimes have multiple A records to provide load-balancing 425 across their servers (although load-balancing is better obtained 426 using SRV records). This same technique can be used for AAAA 427 records, as well. However, if multiple AAAA records are returned to 428 a client that is not using Happy EarBalls and that has broken IPv6 429 connectivity, the multiple AAAA records will further increase the 430 delay to fall back to IPv4, as the client will attempt to connect to 431 all of their addresses first. Thus, SIP server operators with native 432 IPv6 connectivity SHOULD NOT offer multiple AAAA records. If Happy 433 EarBalls is widely deployed in the future, this recommendation might 434 be revisited. 436 6.6. Connection Timeout 438 The primary purpose of Happy EarBalls is to reduce the wait time for 439 a dual-stack connection to complete, especially when the IPv6 path is 440 broken and IPv6 is preferred. Using a short timeout between 441 initiating an IPv6 connection and initiating an IPv4 connection (on 442 the order of tens of milliseconds) achieves this goal, but at the 443 cost of network traffic. This network traffic may be billable on 444 certain networks, will create state on some middleboxes (e.g., 445 firewalls, intrusion detection systems, NATs), and will consume ports 446 if IPv4 addresses are shared. For these reasons, it is RECOMMENDED 447 that connection attempts be paced to give connections a chance to 448 complete. It is RECOMMENDED that connection attempts be paced 449 150-250 ms apart to balance human factors against network load. A 450 stateful algorithm MAY be more aggressive (that is, make connection 451 attempts closer together), if it maintains estimates of the expected 452 connection completion times. 454 7. Security Considerations 456 This document places additional restrictions on the existing 457 procedures in the SIP protocol. The specific security 458 vulnerabilities, attacks and threat models of the various protocols 459 discussed in this document (SIP, DNS, SRV records, etc.) are well- 460 documented in their respective specifications. 462 8. IANA Considerations 464 This document does not require any actions by IANA. 466 9. History 468 Note to RFC Editor: Upon publication, remove this section. 470 9.1. Changes from draft-worley-sip-he-connection-00 to draft-worley- 471 sip-he-connection-01 473 9.2. Changes from draft-johansson-sip-he-connection-01 to draft-worley- 474 sip-he-connection-00 476 This version has a different name for technical reasons. It is, in 477 reality, the successor to draft-johansson-sip-he-connection-01. 479 Move Acknowledgments after References, as that is the style the 480 Editor prefers. 482 Updated Security Considerations: This increment of the H.E. work does 483 not make normative changes in existing SIP. 485 Copy a lot of text from RFC 6555, as this I-D is parallel to RFC 486 6555. 488 Changed "hostname" to "host name", as the latter form is more common 489 in RFCs by a moderate margin. 491 Revised some of the introduction text to parallel the introduction of 492 RFC 7984. 494 Changed name of algorithm to "Happy EarBalls", added reference to 495 Urban Dictionary. 497 Many expansions of the discussion and revisions of the wording. 499 10. References 501 10.1. Normative References 503 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 504 Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April 505 2012, . 507 10.2. Informative References 509 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 510 Requirement Levels", BCP 14, RFC 2119, 511 DOI 10.17487/RFC2119, March 1997, 512 . 514 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 515 A., Peterson, J., Sparks, R., Handley, M., and E. 516 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 517 DOI 10.17487/RFC3261, June 2002, 518 . 520 [RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation 521 Protocol (SIP): Locating SIP Servers", RFC 3263, 522 DOI 10.17487/RFC3263, June 2002, 523 . 525 [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms 526 for IPv6 Hosts and Routers", RFC 4213, 527 DOI 10.17487/RFC4213, October 2005, 528 . 530 [RFC5626] Jennings, C., Ed., Mahy, R., Ed., and F. Audet, Ed., 531 "Managing Client-Initiated Connections in the Session 532 Initiation Protocol (SIP)", RFC 5626, 533 DOI 10.17487/RFC5626, October 2009, 534 . 536 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 537 "Default Address Selection for Internet Protocol Version 6 538 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, 539 . 541 [RFC7984] Johansson, O., Salgueiro, G., Gurbani, V., and D. Worley, 542 Ed., "Locating Session Initiation Protocol (SIP) Servers 543 in a Dual-Stack IP Network", RFC 7984, 544 DOI 10.17487/RFC7984, September 2016, 545 . 547 [UD] The Jews Who Stole Christmas, , "Urban Dictionary, entry 548 'Earballs'", December 2011, 549 . 551 Acknowledgements 553 The authors would like to acknowledge the support and contribution of 554 the SIP Forum IPv6 Working Group. This document is based on a lot of 555 tests and discussions at SIPit events, organized by the SIP Forum. 557 Most of the material in Section 4 and Section 6 is taken from 558 [RFC6555], whose authors are Dan Wing and Andrew Yourtchenko. 560 Authors' Addresses 562 Olle E. Johansson 563 Edvina AB 564 Runbovaegen 10 565 Sollentuna SE-192 48 566 SE 568 Email: oej@edvina.net 570 Gonzalo Salgueiro 571 Cisco Systems 572 7200-12 Kit Creek Road 573 Research Triangle Park, NC 27709 574 US 576 Email: gsalguei@cisco.com 578 Dale R. Worley 579 Ariadne Internet Services 580 738 Main St. 581 Waltham, MA 02451 582 US 584 Email: worley@ariadne.com