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'IPV6') (Obsoleted by RFC 2460) ** Downref: Normative reference to an Informational RFC: RFC 2375 (ref. 'MASGN') -- Possible downref: Non-RFC (?) normative reference: ref. 'SMIL' ** Obsolete normative reference: RFC 2327 (Obsoleted by RFC 4566) Summary: 15 errors (**), 0 flaws (~~), 7 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force MMUSIC WG 3 Internet Draft Maryann P. Maher 4 draft-ietf-mmusic-sap-v2-00.txt ISI 5 16 November 1998 Colin Perkins 6 Expires: May 30, 1998 UCL 8 Session Announcement Protocol: Version 2 10 Status of this Memo 12 This document is an Internet Draft. Internet Drafts are working 13 documents of the Internet Engineering Task Force (IETF), its Areas, 14 and its Working Groups. Note that other groups may also distribute 15 working documents as Internet Drafts. 17 Internet Drafts are draft documents valid for a maximum of six 18 months. Internet Drafts may be updated, replaced, or obsoleted by 19 other documents at any time. It is not appropriate to use Internet 20 Drafts as reference material or to cite them other than as a "working 21 draft" or "work in progress." 23 To view the entire list of current Internet-Drafts, please check the 24 "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow 25 Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern 26 Europe), ftp.nic.it (Southern Europe), munnari.oz.au (Pacific Rim), 27 ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). 29 Abstract 31 This document describes modifications and enhancements to SAP, the 32 session directory announcement protocol, for support of IPv6 33 conferencing environments. Along with support for IPv6, a couple new 34 features are also introduced. This document compliments [SAP], which 35 fully describes SAP in the context of IPv4. Readers are assumed to be 36 familiar with [SAP]. 38 Note: At this time, this document presents an initial set of ideas 39 aimed solely at starting discussion within the working group. We 40 await the RFC publication of [SAP] before finalizing any protocol 41 specifications. 43 This document is a product of the Multiparty Multimedia Session 44 Control (MMUSIC) working group of the Internet Engineering Task 45 Force. Comments are solicited and should be addressed to the working 46 group's mailing list at confctrl@isi.edu and/or the author. 48 1. Overview 50 This document describes a new version of SAP, the session directory 51 announcement protocol, for support of IPv6 conferencing environments. 52 SAP is a protocol used for handling multicast and unicast session 53 description packets and defines an encapsulating packet format to be 54 used by session directory clients. As currently defined, only IPv4 55 session announcements are supported mainly due to the fact that an 56 IPv4 address field is contained in the SAP packet header. This docu- 57 ment describes the modifications to SAP for supporting IPv6 session 58 announcements and introduces some additional new features. The two 59 new features described in this document are: 61 1) a MIME Content-Type specifier, and 63 2) a URL scheme for referencing SAP announcements. 65 Note: At this time, this document presents an initial set of ideas 66 aimed solely at starting discussion within the working group. We 67 await the RFC publication of [SAP] before finalizing any protocol 68 specifications. 70 2. Modifications to the SAP Packet Format 72 Current SAPv1 data packets are of the following format: 74 0 1 2 3 75 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 76 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 77 | V=1 | MT |E|C| auth len | msg id hash | 78 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 79 | originating source | 80 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 81 | optional authentication header | 82 | .... | 83 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 84 | optional timeout | 85 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 86 | optional random field | 87 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 88 | text payload | 89 | .... | 90 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 91 In order to support session directory clients in IPv6 environments, 92 the SAP packet format must be modified to contain a 128-bit IPv6 93 source address instead of the 32-bit IPv4 address. 95 Therefore, SAP v2 data packets are of the following format: 97 0 1 2 3 98 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 99 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 100 | V=1 |A| MT|E|C| auth len | msg id hash | 101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 102 | | 103 | originating source | 104 | .... | 105 | | 106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 107 | optional authentication header | 108 | .... | 109 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 110 | optional timeout | 111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 112 | optional random field | 113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 114 | text payload | 115 | .... | 116 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 Note: the version number in the packet header has NOT changed. 120 A Address type: 0 = IPv4, 1 = IPv6 122 If the A bit is 0, the orig source contains a 32-bit IPv4 address. If 123 the A bit is 1, the orig source contains a 128-bit IPv6 address. 125 3. Scoping SAP Announcements 127 A SAP client that announces a conference session periodically multi- 128 casts an announcement packet to a well known multicast address and 129 port. The well known IPv6 SAP address is FF0X:0:0:0:0:0:2:7FFE, 130 where X is the 4-bit scope value. The following scope values are 131 currently defined in IPv6: 133 Value Scope Recommended Bandwidth Limit 134 ------ ----------- ----------------------------- 135 0x1 Node-local n/a 136 0x2 Link-local 20 Kbps 137 0x5 Site-local 10 Kbps 138 0x8 Organization-local 1 Kbps 139 0xE Global 200 bps 141 The announcement is multicast with the same scope as the session it 142 is announcing, ensuring that the recipients of the announcement can 143 also be potential recipients of the session being advertised. Having 144 a scope field within the address itself removes the need to carve out 145 scope ranges within the multicast address space or scope addresses 146 according to a corresponding TTL. Therefore, unlike in IPv4, TTL- 147 scoped announcements do not exist in IPv6 environments. The scope 148 value to be used in the well-know SAP address is simply the same used 149 in the multicast address assigned for the session. 151 For example, an announcement for a link-local session assigned the 152 multicast address of FF02:0:0:0:0:0:1234:5678, should be advertised 153 on SAP address FF02:0:0:0:0:0:2:7FFE. (Note: Issues related to IPv6 154 multicast address allocation are being addressed in the MALLOC work- 155 ing group.) 157 In the table above, recommended bandwidth limits are given for ses- 158 sions within the defined scopes. The total bandwidth to be used for 159 SAP announcements should be one-fourth of the session bandwidth, 160 though this may be inappropriate for some uses. 162 4. SAP Payload 164 In previous versions of SAP, the payload was required to be a session 165 description in the SDP format [RFC2327]. With the introduction of new 166 session description formats, such as SMIL [SMIL], it is believed that 167 that restriction is no longer appropriate. SAP v2 therefore allows 168 for other content to be carried. That content should begin with a 169 MIME Content-Type specifier. 171 Content-Type: application/sdp 173 v=0 174 o=... 176 If the content type is "application/sdp" the MIME header may be omit- 177 ted, for backwards compatibility with SAP v1 applications. If any 178 other content is carried the MIME header MUST be present. 180 5. SAP URL scheme 182 In certain cases, it is desirable to reference a SAP announcement. 183 For example, if it is desired that a new participant join an existing 184 session yet it is not known if that participant is within the scope 185 of the announcement then an explicit reference to the announcement 186 will enable them to determine if it can be received. Providing the 187 session description contained within that announcement merely allows 188 them to join the session, when they then notice that the media 189 streams are not visible. Moreover, the addresses contained in a ses- 190 sion description for one scope may not be valid outside that scope 191 zone. 193 We therefore define a URL scheme for SAP announcements. The combina- 194 tion of msg-id-hash and originating-source fields in the SAP header 195 is sufficient to identify a particular announcement. 197 sap:msg-id@orig-source 199 TBD: What is the effect of 10.x.x.x assignments on this? 201 6. Compatibility 203 SAPv2 announcement are backwards compatible with SAPv1 provided that 204 IPv4 sessions are announced, and that the payload is SDP with the 205 content-type omitted. 207 If IPv6 announcements are made, they will be discarded by SAPv1 tools 208 since they represent illegal MT values in that protocol. 210 If the Content-Type header is present in the payload, the announce- 211 ment is invalid in SAPv1. Those tools require that SDP is used, hence 212 the payload for a SAPv1 announcement MUST start with "v=". 214 7. Security Considerations 216 SAP contains mechanisms for ensuring integrity of session announce- 217 ments, for authenticating the origin of an announcement and for 218 encrypting such announcements. The strengths and limitations of these 219 mechanisms are described in the 'Security Considerations' section of 220 [SAP]. Those considerations apply to this document as well. 222 8. Acknowledgements 224 REFERENCES 226 [SAP] Handley, M.J., Session Announcement Protocol, draft-ietf- 227 mmusic-sap-01.txt, work in progress. 229 [ADDARCH] Hinden, R., and S. Deering, "IP Version 6 Addressing Archi- 230 tecture", RFC 2373, July 1998. 232 [IPV6] Deering, S., and R. Hinden, Editors, "Internet Protocol, Ver- 233 sion 6 (IPv6) Specification", RFC 1883, December 1995. 235 [MASGN] Hinden, R., and S. Deering, "IPv6 Multicast Address Assign- 236 ments", RFC 2375, July 1998. 238 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 239 Requirement Levels", BCP 14, RFC 2119, March 1997. 241 [SMIL] 243 [RFC2327] Handley, M., and Jacobson, V., "SDP: Session Description 244 Protocol", RFC2327, April 1998. 246 Author's Address 248 Maryann P. Maher 249 USC/ISI 250 4350 N. Fairfax Drive, Suite 620 251 Arlington VA 22203 253 Colin Perkins 254 Department of Computer Science 255 University College London 256 Gower Street 257 London WC1E 6BT