idnits 2.17.1 draft-camarillo-mmusic-alt-02.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** Looks like you're using RFC 2026 boilerplate. This must be updated to follow RFC 3978/3979, as updated by RFC 4748. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- ** The document seems to lack a 1id_guidelines paragraph about the list of Shadow Directories. == No 'Intended status' indicated for this document; assuming Proposed Standard == It seems as if not all pages are separated by form feeds - found 0 form feeds but 8 pages Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 1 instance of lines with non-RFC3849-compliant IPv6 addresses in the document. If these are example addresses, they should be changed. -- The document has examples using IPv4 documentation addresses according to RFC6890, but does not use any IPv6 documentation addresses. Maybe there should be IPv6 examples, too? Miscellaneous warnings: ---------------------------------------------------------------------------- == The document seems to lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- 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 (October 17, 2003) is 7497 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) -- Looks like a reference, but probably isn't: 'RFCxxxx' on line 190 ** Obsolete normative reference: RFC 2327 (ref. '1') (Obsoleted by RFC 4566) ** Obsolete normative reference: RFC 3388 (ref. '2') (Obsoleted by RFC 5888) -- Possible downref: Non-RFC (?) normative reference: ref. '6' Summary: 4 errors (**), 0 flaws (~~), 4 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force SIP WG 3 Internet Draft G. Camarillo 4 Ericsson 5 J. Rosenberg 6 dynamicsoft 7 draft-camarillo-mmusic-alt-02.txt 8 October 17, 2003 9 Expires: April 2004 11 The Alternative IP Versions Semantics for the 12 Session Description Protocol Grouping Framework 14 STATUS OF THIS MEMO 16 This document is an Internet-Draft and is in full conformance with 17 all provisions of Section 10 of RFC2026. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress". 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt 32 To view the list Internet-Draft Shadow Directories, see 33 http://www.ietf.org/shadow.html. 35 Abstract 37 This document defines the alternative IP versions (IPV) semantics for 38 the SDP grouping framework. The IPV semantics allow offering 39 alternative transport addresses that use different IP versions to 40 establish a particular media stream. 42 Table of Contents 44 1 Introduction ........................................ 3 45 1.1 Scope and Relation with ICE ......................... 3 46 1.2 Terminology ......................................... 3 47 2 IPV Semantics ....................................... 4 48 3 Preference .......................................... 4 49 4 Offer/Answer and IPV ................................ 4 50 4.1 IPV and Media Configurations ........................ 4 51 5 Backwards Compatibility ............................. 5 52 6 Example ............................................. 5 53 7 IANA Considerations ................................. 5 54 8 Security Considerations ............................. 6 55 9 Authors' Addresses .................................. 6 56 10 Normative References ................................ 6 57 11 Informative References .............................. 7 59 1 Introduction 61 An SDP [1] session description contains the media parameters to be 62 used to establish a number of media streams. For a particular media 63 stream, an SDP session description contains, among other parameters, 64 the transport addresses and the codec to be used to transfer media. 65 SDP allows providing a set of codecs per media stream, but only one 66 transport address. 68 Being able to offer a set of transport addresses to establish a media 69 stream is useful in environments with both IPv4-only hosts and IPv6- 70 only hosts. 72 This document defines the alternative IP versions (IPV) semantics for 73 the SDP grouping framework [2]. The IPV semantics allow expressing 74 alternative transport addresses with different IP versions for a 75 particular media stream. 77 1.1 Scope and Relation with ICE 79 The IPV semantics are intended to address scenarios that involve 80 different IP versions. They are not intended to provide alternative 81 transport addresses with the same IP version. Systems that need to 82 provide different transport addresses with the same IP version should 83 use the SDP format defined in ICE (Interactive Connectivity 84 Establishment) [6] instead. 86 ICE is used by systems that cannot determine their own transport 87 address as seen from the remote end but that can provide several 88 possible alternatives. ICE encodes the address that is most likely to 89 be valid in an m= line and the rest of addresses as a= lines after 90 that m= line. This way, systems that do not support ICE simply ignore 91 the a= lines and only use the address in the m= line. This achieves 92 good backwards compatibility. 94 We have chosen to group m= lines with different IP versions at the m= 95 level (IPV semantics) rather than at the a= level (ICE format) in 96 order to keep the IPv6 syntax free from ICE parameters used for 97 legacy (IPv4) NATs (Network Address Translators). This yields a 98 syntax much closer to vanilla SDP, where IPv6 addresses are defined 99 in their own m= line, rather than in parameters belonging to a 100 different m= line. 102 In addition to that, the separation between IPV and ICE helps systems 103 that support IPv4 and IPv6 but that do not need to support ICE (e.g., 104 a multicast server). 106 1.2 Terminology 107 In this document, the key words "MUST", "MUST NOT", "REQUIRED", 108 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", 109 and "OPTIONAL" are to be interpreted as described in RFC 2119 [4] and 110 indicate requirement levels for compliant SIP implementations. 112 2 IPV Semantics 114 We define a new "semantics" attribute within the SDP grouping 115 framework [2]: IPV (Alternative IP Versions). 117 Media lines grouped using IPV semantics provide alternative transport 118 addresses with different IP versions for a single logical media 119 stream. The entity creating a session description with an IPV group 120 MUST be ready to receive (or send) media over any of the grouped m 121 lines. 123 3 Preference 125 The entity generating a session description may have an order of 126 preference for the alternative IP versions offered. The identifiers 127 of the media streams MUST be listed in order of preference in the 128 group line. In the example below, the m line with mid=1 has a higher 129 preference than the m line with mid=2. 131 a=group:IPV 1 2 133 4 Offer/Answer and IPV 135 When ICE is used, the ICE spec [6] explains how to choose a 136 particular IP address among all the alternatives received. When ICE 137 is not used, an answerer receiving a session description that uses 138 the IPV semantics SHOULD use the address with highest priority it 139 understands and set the ports of the rest of the m= lines of the 140 group to zero. 142 4.1 IPV and Media Configurations 144 The creator of a session description MAY want to use different media 145 configurations (e.g., audio codec) for different transport addresses 146 in the same IPV group. The receiver of such a session may find some 147 of the m lines unacceptable. They may contain codecs that the 148 answerer does not support or contain any other parameter that makes 149 them unacceptable. The answerer should, following normal SIP 150 procedures, set their ports to zero in the answer. 152 5 Backwards Compatibility 154 IPv4-only and IPv6-only systems would only understand one of m= lines 155 of the IPV group. Therefore, they will not have any problem 156 establishing sessions that use IPV. 158 It is STRONGLY RECOMMENDED that dual-stack IPv6/IPv4 hosts implement 159 the IPV semantics. Dual-stack hosts that failed to implement IPV 160 would need more RTTs to establish a session with a single-stack host. 161 When acting as answerers, they would establish more media streams 162 than needed. This could increase the session bandwidth in the first 163 instants of the session, until the remote end could issue a new offer 164 with only one m= line. 166 6 Example 168 The session description below contains an IPv4 address and an IPv6 169 address grouped using IPV. 171 v=0 172 o=bob 280744730 28977631 IN IP4 host.example.com 173 s= 174 t=0 0 175 a=group:IPV 1 2 176 m=audio 6886 RTP/AVP 0 177 c=IN IP6 2201:056D::112E:144A:1E24 178 a=mid:1 179 m=audio 22334 RTP/AVP 0 180 c=IN IP4 192.0.2.2 181 a=mid:2 183 7 IANA Considerations 185 IANA needs to register the following new "semantics" attribute for 186 the SDP grouping framework [2]: 188 Semantics Token Reference 189 ----------------------- ----- --------- 190 Alternative IP Versions IPV [RFCxxxx] 192 It should be registered in the SDP parameters registry 193 (http://www.iana.org/assignments/sdp-parameters) under Semantics for 194 the "group" SDP Attribute. 196 8 Security Considerations 198 An attacker adding group lines using the IPV semantics to an SDP 199 session description could make an end-point use only one out of all 200 the streams offered by the remote end, when the intention of the 201 remote-end might have been to establish all the streams. 203 An attacker removing group lines using IPV semantics could make and 204 end-point establish a higher number of media streams. If the end- 205 point sends media over all of them, the session bandwidth may 206 increase dramatically. 208 It is thus STRONGLY RECOMMENDED that integrity protection be applied 209 to the SDP session descriptions. For session descriptions carried in 210 SIP [5], S/MIME is the natural choice to provide such end-to-end 211 integrity protection, as described in RFC 3261. Other applications 212 MAY use a different form of integrity protection. 214 9 Authors' Addresses 216 Gonzalo Camarillo 217 Ericsson 218 Advanced Signalling Research Lab. 219 FIN-02420 Jorvas 220 Finland 221 electronic mail: Gonzalo.Camarillo@ericsson.com 223 Jonathan Rosenberg 224 dynamicsoft 225 72 Eagle Rock Ave 226 East Hanover, NJ 07936 227 USA 228 electronic mail: jdrosen@dynamicsoft.com 230 10 Normative References 232 [1] M. Handley and V. Jacobson, "SDP: session description protocol," 233 RFC 2327, Internet Engineering Task Force, Apr. 1998. 235 [2] G. Camarillo, G. Eriksson, J. Holler, and H. Schulzrinne, 236 "Grouping of media lines in the session description protocol (SDP)," 237 RFC 3388, Internet Engineering Task Force, Dec. 2002. 239 [6] J. Rosenberg, "Interactive connectivity establishment (ICE): a 240 methodology for nettwork address translator (NAT) traversal for the 241 session initiation protocol (SIP)," internet draft, Internet 242 Engineering Task Force, July 2003. Work in progress. 244 [4] S. Bradner, "Key words for use in RFCs to indicate requirement 245 levels," RFC 2119, Internet Engineering Task Force, Mar. 1997. 247 [5] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. R. Johnston, J. 248 Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP: session 249 initiation protocol," RFC 3261, Internet Engineering Task Force, June 250 2002. 252 11 Informative References 254 The IETF takes no position regarding the validity or scope of any 255 intellectual property or other rights that might be claimed to 256 pertain to the implementation or use of the technology described in 257 this document or the extent to which any license under such rights 258 might or might not be available; neither does it represent that it 259 has made any effort to identify any such rights. Information on the 260 IETF's procedures with respect to rights in standards-track and 261 standards-related documentation can be found in BCP-11. Copies of 262 claims of rights made available for publication and any assurances of 263 licenses to be made available, or the result of an attempt made to 264 obtain a general license or permission for the use of such 265 proprietary rights by implementors or users of this specification can 266 be obtained from the IETF Secretariat. 268 The IETF invites any interested party to bring to its attention any 269 copyrights, patents or patent applications, or other proprietary 270 rights which may cover technology that may be required to practice 271 this standard. Please address the information to the IETF Executive 272 Director. 274 Full Copyright Statement 276 Copyright (c) The Internet Society (2003). All Rights Reserved. 278 This document and translations of it may be copied and furnished to 279 others, and derivative works that comment on or otherwise explain it 280 or assist in its implementation may be prepared, copied, published 281 and distributed, in whole or in part, without restriction of any 282 kind, provided that the above copyright notice and this paragraph are 283 included on all such copies and derivative works. However, this 284 document itself may not be modified in any way, such as by removing 285 the copyright notice or references to the Internet Society or other 286 Internet organizations, except as needed for the purpose of 287 developing Internet standards in which case the procedures for 288 copyrights defined in the Internet Standards process must be 289 followed, or as required to translate it into languages other than 290 English. 292 The limited permissions granted above are perpetual and will not be 293 revoked by the Internet Society or its successors or assigns. 295 This document and the information contained herein is provided on an 296 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 297 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 298 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 299 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 300 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.