idnits 2.17.1 draft-ietf-sipcore-dns-dual-stack-06.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document updates RFC3263, but the abstract doesn't seem to directly say this. It does mention RFC3263 though, so this could be OK. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year (Using the creation date from RFC3263, updated by this document, for RFC5378 checks: 2000-10-06) -- 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 2, 2016) is 2915 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 3484 (Obsoleted by RFC 6724) -- Obsolete informational reference (is this intentional?): RFC 6555 (Obsoleted by RFC 8305) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SIPCORE O. Johansson 3 Internet-Draft Edvina AB 4 Updates: 3263 (if approved) G. Salgueiro 5 Intended status: Standards Track Cisco Systems 6 Expires: November 3, 2016 V. Gurbani 7 Bell Labs, Alcatel-Lucent 8 D. Worley, Ed. 9 Ariadne 10 May 2, 2016 12 Locating Session Initiation Protocol (SIP) Servers in a Dual-Stack IP 13 Network 14 draft-ietf-sipcore-dns-dual-stack-06 16 Abstract 18 RFC 3263 defines how a Session Initiation Protocol (SIP) 19 implementation, given a SIP Uniform Resource Identifier (URI), should 20 locate the next-hop SIP server using Domain Name System (DNS) 21 procedures. As SIP networks increasingly transition from IPv4-only 22 to dual-stack, a quality user experience must be ensured for dual- 23 stack SIP implementations. This document updates the DNS procedures 24 described in RFC 3263 for dual-stack SIP implementations in 25 preparation for forthcoming specifications for applying Happy 26 Eyeballs principles to SIP. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at http://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on November 3, 2016. 45 Copyright Notice 47 Copyright (c) 2016 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 3. DNS Procedures in a Dual-Stack Network . . . . . . . . . . . 4 65 3.1. Dual-Stack SIP UA DNS Record Lookup Procedure . . . . . . 4 66 3.2. Indicating Address Family Preference in DNS SRV Records . 5 67 4. Clarification of interaction with RFC 6724 . . . . . . . . . 5 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 69 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 70 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 71 8. Revision History . . . . . . . . . . . . . . . . . . . . . . 7 72 8.1. Changes from draft-ietf-sipcore-dns-dual-stack-05 to 73 draft-ietf-sipcore-dns-dual-stack-06 . . . . . . . . . . 7 74 8.2. Changes from draft-ietf-sipcore-dns-dual-stack-04 to 75 draft-ietf-sipcore-dns-dual-stack-05 . . . . . . . . . . 8 76 8.3. Changes from draft-ietf-sipcore-dns-dual-stack-03 to 77 draft-ietf-sipcore-dns-dual-stack-04 . . . . . . . . . . 8 78 8.4. Changes from draft-ietf-sipcore-dns-dual-stack-02 to 79 draft-ietf-sipcore-dns-dual-stack-03 . . . . . . . . . . 8 80 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 81 9.1. Normative References . . . . . . . . . . . . . . . . . . 9 82 9.2. Informative References . . . . . . . . . . . . . . . . . 9 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 85 1. Introduction 87 The Session Initiation Protocol (SIP, [RFC3261]) and the additional 88 documents that extended it provide support for both IPv4 and IPv6. 89 However, this support does not fully extend to the highly hybridized 90 environments that are characteristic of the transitional migratory 91 phase from IPv4 to IPv6 networks. During this phase, many server and 92 client implementations run on dual-stack hosts. In such 93 environments, a dual-stack host will likely suffer greater connection 94 delay, and by extension an inferior user experience, than an 95 IPv4-only host. The need to remedy this diminished performance of 96 dual-stack hosts led to the development of the Happy Eyeballs 97 [RFC6555] algorithm, which has since been implemented in many 98 protocols and applications. 100 This document updates the DNS lookup procedures of RFC 3263 [RFC3263] 101 in preparation for the specification of the application of Happy 102 Eyeballs to SIP to provide enhanced performance, and consequently 103 user experience, in highly hybridized dual-stack SIP networks. The 104 procedures described herein are such that a dual-stack client should 105 look up both A and AAAA records in DNS and then select the best way 106 to set up a network flow. The details of how the latter is done is 107 considered out of scope for this document. See the Happy Eyeballs 108 algorithm and implementation and design considerations in RFC 6555 109 [RFC6555] for more information about issues with setting up dual- 110 stack network flows. 112 Section 4 of this document clarifies the interaction of [RFC3263] 113 with [RFC6157] and [RFC6724]. 115 2. Terminology 117 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 118 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 119 document are to be interpreted as described in RFC 2119 [RFC2119]. 121 RFC 3261 [RFC3261] defines additional terms used in this document 122 that are specific to the SIP domain such as "proxy", "registrar", 123 "redirect server", "user agent server" or "UAS", "user agent client" 124 or "UAC", "back-to-back user agent" or "B2BUA", "dialog", 125 "transaction", and "server transaction". 127 This document uses the term "SIP server" that is defined to include 128 the following SIP entities: user agent server, registrar, redirect 129 server, a SIP proxy in the role of user agent server, and a B2BUA in 130 the role of a user agent server. 132 This document also uses the following terminology to make clear 133 distinction between SIP entities supporting only IPv4, only IPv6 or 134 supporting both IPv4 and IPv6: 136 IPv4-only UA/UAC/UAS: An IPv4-only UA/UAC/UAS supports SIP signaling 137 and media only on the IPv4 network. It does not understand IPv6 138 addresses. 140 IPv6-only UA/UAC/UAS: An IPv6-only UA/UAC/UAS supports SIP signaling 141 and media only on the IPv6 network. It does not understand IPv4 142 addresses. 144 IPv4/IPv6 UA/UAC/UAS: A UA/UAC/UAS that supports SIP signaling and 145 media on both IPv4 and IPv6 networks; such a UA/UAC/UAS is known 146 (and will be referred to in this document) as a "dual-stack" 147 [RFC4213] UA/UAC/UAS. 149 The term "address records" means the DNS records which translate a 150 domain name into addresses within the address family(ies) that the 151 entity supports (as A records provide IPv4 addresses and AAAA records 152 provide IPv6 addresses), regardless of whether the address family was 153 defined before or after this document was approved. 155 3. DNS Procedures in a Dual-Stack Network 157 This specification introduces two normative DNS lookup procedures. 158 These are designed to improve the performance of dual-stack clients 159 in IPv4/IPv6 networks. 161 3.1. Dual-Stack SIP UA DNS Record Lookup Procedure 163 Once the transport protocol has been determined, the procedure for 164 discovering an IP address if the TARGET is not a numeric IP address 165 but the port is explicitly stated in the URI, is detailed in 166 Section 4.2 of RFC 3263 [RFC3263]. The piece relevant to this 167 discussion is: 169 If the TARGET was not a numeric IP address, but a port is present 170 in the URI, the client performs an A or AAAA record lookup of the 171 domain name. The result will be a list of IP addresses, each of 172 which can be contacted at the specific port from the URI and 173 transport protocol determined previously. 175 Section 4.2 of RFC 3263 [RFC3263] also goes on to describe the 176 procedure for discovering an IP address if the TARGET is not a 177 numeric IP address, and no port is present in the URI. The piece 178 relevant to to this discussion is: 180 If no SRV records were found, the client performs an A or AAAA 181 record lookup of the domain name. The result will be a list of IP 182 addresses, each of which can be contacted using the transport 183 protocol determined previously, at the default port for that 184 transport. Processing then proceeds as described above for an 185 explicit port once the A or AAAA records have been looked up. 187 Happy Eyeballs [RFC6555] documents that looking up the "A or AAAA 188 record" is not an effective practice for dual-stack clients and that 189 it can add significant connection delay and greatly degrade user 190 experience. Therefore, this document makes the following normative 191 addendum to the DNS lookup procedures of Section 4.2 of RFC 3263 192 [RFC3263] for IPv4/IPv6 hybrid SIP networks and recommends it as a 193 best practice for such dual-stack networks: 195 The dual-stack client SHOULD look up all address records (i.e., 196 for all address family(ies) that it supports) for the domain name 197 and add the resulting addresses to the list of IP addresses to be 198 contacted. A client MUST be prepared for DNS lookups to return 199 addresses in families that it does not support; such addresses 200 MUST be ignored as unusable and the supported addresses used as 201 specified herein. 203 3.2. Indicating Address Family Preference in DNS SRV Records 205 The Happy Eyeballs algorithm [RFC6555] is particularly effective when 206 dual-stack client applications have significant performance 207 differences in their IPv4 or IPv6 network paths. In this common 208 scenario it is often necessary for a dual-stack client to indicate a 209 preference for either IPv4 or IPv6. A service may use DNS SRV 210 records to indicate such a preference for an address family. This 211 way, a server with a high-latency and/or low-capacity IPv4 tunnel may 212 indicate a preference for being contacted using IPv6. A server that 213 wishes to do this can use the lowest SRV priority to publish 214 hostnames that only resolve in IPv6 and the next priority with host 215 names that resolve in both address families. 217 4. Clarification of interaction with RFC 6724 219 Section 5 of [RFC6157] specifies that the addresses from the address 220 records for a single target DNS name for a server's DNS name must be 221 contacted in the order specified by the Source and Destination 222 Address Selection algorithms defined in [RFC6724] (the successor of 223 [RFC3484]). Typically, this is done by using the getaddrinfo() 224 function to translate the target DNS name into a list of IPv4 and/or 225 IPv6 addresses in the order in which they are to be contacted, as 226 that function implements [RFC6724]. 228 Thus, if SRV lookup on the server's DNS name is successful, the major 229 ordering of the complete list of destination addresses is determined 230 by the priority and weight fields of the SRV records (as specified in 231 [RFC2782]) and the (minor) ordering among the destinations derived 232 from the "target" field of a single SRV record is determined by 233 [RFC6724]. 235 For example, consider a server with DNS name example.com, with TCP 236 transport specified. The relevant SRV records are: 238 _sip._tcp.example.com. 300 IN SRV 10 1 5060 sip-1.example.com. 239 _sip._tcp.example.com. 300 IN SRV 20 1 5060 sip-2.example.com. 241 The address records for sip-1.example.com, as ordered by [RFC6724], 242 are 244 sip-1.example.com. 300 IN AAAA 2001:0db8:58:c02::face 245 sip-1.example.com. 300 IN AAAA 2001:0db8:c:a06::2:cafe 246 sip-1.example.com. 300 IN AAAA 2001:0db8:44:204::d1ce 247 sip-1.example.com. 300 IN A 192.0.2.45 248 sip-1.example.com. 300 IN A 203.0.113.109 249 sip-1.example.com. 300 IN A 198.51.100.24 251 and the address records for sip-2.example.com, as ordered by 252 [RFC6724], are: 254 sip-2.example.com. 300 IN AAAA 2001:0db8:58:c02::dead 255 sip-2.example.com. 300 IN AAAA 2001:0db8:c:a06::2:beef 256 sip-2.example.com. 300 IN AAAA 2001:0db8:44:204::c0de 257 sip-2.example.com. 300 IN A 192.0.2.75 258 sip-2.example.com. 300 IN A 203.0.113.38 259 sip-2.example.com. 300 IN A 198.51.100.140 261 Thus, the complete list of destination addresses has this ordering: 263 2001:0db8:58:c02::face 264 2001:0db8:c:a06::2:cafe 265 2001:0db8:44:204::d1ce 266 192.0.2.45 267 203.0.113.109 268 198.51.100.24 269 2001:0db8:58:c02::dead 270 2001:0db8:c:a06::2:beef 271 2001:0db8:44:204::c0de 272 192.0.2.75 273 203.0.113.38 274 198.51.100.140 276 In particular, the destination addresses derived from sip- 277 1.example.com and those derived from sip-2.example.com are not 278 interleaved; [RFC6724] does not operate on the complete list. This 279 would be true even if the two SRV records had the same priority and 280 were (randomly) ordered based on their weights, as the address 281 records of two target DNS names are never interleaved. 283 5. Security Considerations 285 This document introduces two new normative procedures to the existing 286 DNS procedures used to locate SIP servers. While both of these 287 procedures are optimizations designed to improve the performance of 288 dual-stack clients, neither introduces any new security 289 considerations. 291 The specific security vulnerabilities, attacks and threat models of 292 the various protocols discussed in this document (SIP, DNS, SRV 293 records, Happy Eyeballs requirements and algorithm, etc.) are well 294 documented in their respective specifications. 296 6. IANA Considerations 298 This document does not require any actions by IANA. 300 7. Acknowledgments 302 The authors would like to acknowledge the support and contribution of 303 the SIP Forum IPv6 Working Group. This document is based on a lot of 304 tests and discussions at SIPit events, organized by the SIP Forum. 306 This document has benefited from the expertise and review feedback of 307 many participants of the IETF DISPATCH and SIPCORE WG mailing lists 308 as well as those on the SIP Forum IPv6 Task Group mailing list. The 309 authors wish to specifically call out the efforts and express their 310 gratitude for the detailed and thoughtful comments and corrections of 311 Dan Wing, Brett Tate, Rifaat Shekh-Yusef, Carl Klatsky, Mary Barnes, 312 Keith Drage, Cullen Jennings, Simon Perreault, Paul Kyzivat, Adam 313 Roach, and Richard Barnes. Adam Roach devised the example in 314 Section 4. 316 8. Revision History 318 [Note to RFC Editor: Please remove this entire section upon 319 publication as an RFC.] 321 8.1. Changes from draft-ietf-sipcore-dns-dual-stack-05 to draft-ietf- 322 sipcore-dns-dual-stack-06 324 Acknowledged Adam Roach for providing the example in Section 4. 326 Correct references to [RFC6157] vs. references to [RFC6724]. 328 8.2. Changes from draft-ietf-sipcore-dns-dual-stack-04 to draft-ietf- 329 sipcore-dns-dual-stack-05 331 Simplified the acknowledgments. 333 Improve wording and punctuation. 335 Rewrote Section 4 based on critiques on the Sipcore list. Included 336 an example by Adam Roach. 338 Replaced "RR's" with "records" per suggestion by Jean Mahoney. 340 8.3. Changes from draft-ietf-sipcore-dns-dual-stack-03 to draft-ietf- 341 sipcore-dns-dual-stack-04 343 Changed the "updates" specification to add RFC 3263 and remove RFC 344 6157. 346 Added Simon Perreault to the acknowledgments. 348 Minor wording changes. 350 8.4. Changes from draft-ietf-sipcore-dns-dual-stack-02 to draft-ietf- 351 sipcore-dns-dual-stack-03 353 Described the relationship to RFC 3263 as "update", since the 354 existing wording in 3263 is not what we want. Arguably, the new 355 wording is what was intended in 3263, but the existing wording either 356 does not say that or says it in a way that is easily misunderstood. 358 Described the relationship to RFC 6157 as "clarification", since the 359 described interaction between 3263 and 6157 appears to be the only 360 reasonable interpretation. 362 Revised wording, punctuation, and capitalization in various places. 364 Clarified that this draft does not document Happy Eyeballs for SIP, 365 but is preparatory for it. 367 Attempted to use "update" for text that is definitively a change to 368 the preexisting text and "clarify" for text that is a more clear 369 statement of the (presumed) intention of the preexisting text. 371 Removed normative words from section 1, the introduction. 373 Copied definition of "address records" from RFC 2782 (SRV records) to 374 allow the specifications to expand automatically to include any new 375 address families. 377 Relocated the text requiring a client to ignore addresses that it 378 discovers in address families it does not support from section 4.2 379 (which describes why the situation arises) to section 4.1 (which 380 describes how clients look up RRs). 382 Clarified the interaction with RFC 6157 (source and destination 383 address selection in IPv6) to specify what must have been intended: 384 The major sort of the destinations is the ordering determined by 385 priority/weight in the SRV records; the addresses derived from a 386 single SRV record's target are minorly sorted based on RFC 6157. 388 Removed editor's name from the acknowledgments list. 390 9. References 392 9.1. Normative References 394 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 395 Requirement Levels", BCP 14, RFC 2119, 396 DOI 10.17487/RFC2119, March 1997, 397 . 399 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for 400 specifying the location of services (DNS SRV)", RFC 2782, 401 DOI 10.17487/RFC2782, February 2000, 402 . 404 [RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation 405 Protocol (SIP): Locating SIP Servers", RFC 3263, 406 DOI 10.17487/RFC3263, June 2002, 407 . 409 [RFC6157] Camarillo, G., El Malki, K., and V. Gurbani, "IPv6 410 Transition in the Session Initiation Protocol (SIP)", 411 RFC 6157, DOI 10.17487/RFC6157, April 2011, 412 . 414 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 415 "Default Address Selection for Internet Protocol Version 6 416 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, 417 . 419 9.2. Informative References 421 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 422 A., Peterson, J., Sparks, R., Handley, M., and E. 423 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 424 DOI 10.17487/RFC3261, June 2002, 425 . 427 [RFC3484] Draves, R., "Default Address Selection for Internet 428 Protocol version 6 (IPv6)", RFC 3484, 429 DOI 10.17487/RFC3484, February 2003, 430 . 432 [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms 433 for IPv6 Hosts and Routers", RFC 4213, 434 DOI 10.17487/RFC4213, October 2005, 435 . 437 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 438 Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April 439 2012, . 441 Authors' Addresses 443 Olle E. Johansson 444 Edvina AB 445 Runbovaegen 10 446 Sollentuna SE-192 48 447 SE 449 Email: oej@edvina.net 451 Gonzalo Salgueiro 452 Cisco Systems 453 7200-12 Kit Creek Road 454 Research Triangle Park, NC 27709 455 US 457 Email: gsalguei@cisco.com 459 Vijay Gurbani 460 Bell Labs, Alcatel-Lucent 461 1960 Lucent Lane 462 Rm 9C-533 463 Naperville, IL 60563 464 US 466 Email: vkg@bell-labs.com 467 Dale R. Worley (editor) 468 Ariadne Internet Services 469 738 Main St. 470 Waltham, MA 02451 471 US 473 Email: worley@ariadne.com