Colin Perkins

draft-ietf-mmusic-sdp-new

IETF DataTracker: draft-ietf-mmusic-sdp-new

This draft is replaced by draft-ietf-mmusic-rfc4566bis

• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol, Internet Engineering Task Force, RFC 4566, July 2006. DOI:10.17487/RFC4566
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, January 2006, Work in progress (draft-ietf-mmusic-sdp-new-26.txt).

• This version is intended to address the GenART comments received during IESG review. In addition the discussion of sharing ports between "m=" lines has been removed from section 5.14, since there was no consensus on that approach.

  The complete list of changes is as follows:

  • fix reference to H.332;
  • in Section 1, clarify that this obsoletes RFC 2327 and RFC 3266, rather than just updating RFC 2327;
  • in Section 3, mention that SDP is used by SIP/RTSP use before mentioning its use with SAP; no longer say that SAP is "commonly used", and remove the mention of SAP when discussing use of SDP with email/WWW;
  • in section 4, clarify that sessions need not be continually active;
  • in Section 4.1, explain why it it NOT RECOMMENDED to redefine the semantics of the destination address/port; correct the use of RFC 2119 terms;
  • in Section 4.2, add cross reference to section 5.9;
  • in Section 4.3, fix grammar;
  • in Section 4.5, add cross reference to "a=cat:" in section 6;
  • in Section 5, correct use of RFC 2119 terms in penultimate paragraph;
  • in Section 5.2, clarify what is meant by "A local IP address MUST NOT be used in any context where the SDP description might leave the scope in which the address is meaningful";
  • in Section 5.9, note that permanent sessions are discouraged, rather than giving different degrees of discouragement for differing durations;
  • in Section 5.10, state that the "s" unit specification character is allowed for completeness, rather than also stating that its use is "NOT RECOMMENDED" (the RFC 2119 term is too strong here);
  • in Section 5.12, clarify that "k=uri:" often uses SSL/TLS-protected HTTP (i.e., "https:") and not secure HTTP (RFC2660);
  • in Section 5.12, remove last sentence of the section, that confused operational security with protocol security;
  • in Section 5.14, remove discussion of sharing ports between "m=" lines, and instead note that the semantics of this are currently undefined, and that no implicit grouping is implied; add reference to RFC 3388;
  • in Section 6, note that neither "a=cat:" nor "a=keywds:" have a central registry of legal values;
  • in Section 7, 1st paragraph, change "agree" to "agree on"; note that SAP is no longer frequently used;
  • in Section 7, 2nd paragraph, clarify the security issues with using an SDP file obtained via an untrusted transport; and
  • in Section 7, 6th paragraph, clarify interactions with intermediary systems that parse SDP contained in signalling messages.

  I believe this is now ready to go to the RFC Editor.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, July 2005, Work in progress (draft-ietf-mmusic-sdp-new-25.txt).

• This version corrects a problem with the email address ABNF.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, February 2005, Work in progress (draft-ietf-mmusic-sdp-new-24.txt).

• This version clarifies signalling of non-contiguous ports for RTP and RTCP.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, December 2004, Work in progress (draft-ietf-mmusic-sdp-new-23.txt).

• The changes in this version are to fix section references in IANA considerations, and expand "Encoding Considerations"; and to clarify that the username and unicast-address in "o=" lines may be chosen to obfuscate the actual values, provided this does not compromise the global uniqueness of the field.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, November 2004, Work in progress (draft-ietf-mmusic-sdp-new-22.txt).

• Changes in this version are:

  • fix typo in section 5.14;
  • allow "message" as a media type in "m=" lines;
  • update references;
  • note that internationalized domain names MUST use the ACE format defined in RFC 3490, rather than being directly represented in UTF-8;
  • note that the "control" and "data" media types are defined in RFC 3840 but not in this version of SDP or as top-level MIME types; and
  • add summary of changes from RFC 2327.
• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, October 2004, Work in progress (draft-ietf-mmusic-sdp-new-21.txt).

• Changes in this version are:

  • in section 4.1, clarify that the transport port for unicast IP sessions is the remote transport port;
  • in section 5.1, clarify that the media description is optional;
  • in section 5.7, clarify that "this memo only defines IP4 and IP6", rather than "currently only IP4 and IP6 are defined";
  • in section 5.7, note that TTL scoping is NOT RECOMMENDED for multicast, and one should use admin-scoped addresses instead;
  • rename section 6 from "Suggested Attributes" to "SDP Attributes";
  • in section 5.8, clarify that the bandwidth is in kilobits per second unless otherwise specified in the definition of a new bwtype modifier;
  • in section 5.9, clarify that the end time SHOULD be specified unless a session is unbounded;
  • in section 5.12, remove example of SIP-over-TLS, since that's not an end to end connection;
  • in section 5.13, remove example of use of attributes;
  • in section 5.14, clarify behaviour when two RTP sessions share the same transport address;
  • section 5.14 was missing a reference to the "application" top-level MIME type for the "udp" proto;
  • in section 6, generalise "a=orient" slightly;
  • in section 6, remove references to the "wb" application, which is of historical interest only;
  • in section 6, specify that "a=maxptime" is an integer multiple of the frame size for frame based codecs;
  • in section 7, reference SIP and offer/answer security considerations;
  • in section 7, note that firewall holes should only be opened when the user can be appropriately authenticated and is authorized to do so;
  • in ABNF, remove comment that suggested that UDP ports should either be 0 or in the range 1024-65535, since this conflicts with existing usage (e.g., port 9 is used by comedia) and isn't mandated by the text;
  • in ABNF, allow DNS names for multicast groups;
  • in ABNF, remove comment in the definition of "sess-version" that conflicted with the requirement in section 5.2 that an NTP-format timestamp SHOULD be used; and
  • in ABNF, allow 127.0.0.1 as a valid IPv4 address;
• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, September 2004, Work in progress (draft-ietf-mmusic-sdp-new-20.txt).

• There's a single change in this version: to remove the underspecified "control" and "data" media types, aligning the SDP media types with MIME media types. If there's a use for these media types they can be registered separately. They've been removed here in the interests of getting the base spec out.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, August 2004, Work in progress (draft-ietf-mmusic-sdp-new-19.txt).

• Running a diff with -18 will show many changes, due to differences in the way the latest version of xml2rfc formats drafts. The main items to note are:

  • minor editorial clarifications to Section 5.7 (clarify meaning of "slash notation");
  • add normative references to RS, RR and TIAS bandwidth modifiers to Section 5.8;
  • when using "k=clear:" clarify that the key can is interpreted as a text string according to charset, and that "k=base64:" should be used if the must contains non-text characters;
  • clarify that "i=" is not suitable for parsing by automata;
  • fix ABNF to disallow extensions to "k=";
  • allow non-IP multicast address formats, to match unicast rules;
  • the rules in section 5.6 say that phone numbers "SHOULD" be full E.164 numbers preceeded by a "+", whereas the ABNF required this form, and relax the ABNF to allow other forms of phone number;
  • clarify that time values in SDP are represented as unlimited length text strings that don't wrap in 2036 (unlike 64 bit binary NTP timestamps);
  • clarify that URIs may now contain literal IPv6 addresses;
  • rewrite description of the proto field in "m=" lines for clarity (move some of the text to IANA considerations);
  • rewrite description of the fmt field in "m=" lines for clarify, moving much of the text to the description of the "a=rtpmap:" attribute;
  • in section 9.2.6 and 9.2.7 clarify that any type of RFC is sufficient to register a new network or address type; and
  • make assorted minor clarifications and editorial fixes.

  These address the majority of comments received, although I have made no attempt to better specify the "control" and "data" media types.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, June 2004, Work in progress (draft-ietf-mmusic-sdp-new-18.txt).

• Changes in this version are: update ABNF for "proto"; clarify second paragraph of Section 9.2.3, regarding use of RTP payload types as "fmt" values; register the "RTP/SAVP" profile and its "fmt" namespace; and clarify that only a single "a=fmtp:" attribute is allowed for each format.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, June 2004, Work in progress (draft-ietf-mmusic-sdp-new-17.txt).

• This version removes TCP from allowable proto values, since this will be defined by the comedia spec; specifies that "a=rtpmap:" is not allowed at the session level; and clarifies the set of registered media types.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, May 2004, Work in progress (draft-ietf-mmusic-sdp-new-16.txt).

• Changes in this version:

  • Add support for "text" media;
  • Add the Macintosh File Type Code to the MIME registration;
  • Add IANA registrations for attributes and parameters in the draft;
  • Delete the definition "session advertisement" from section 2;
  • Make use of the terms "session announcement" and "session description" consistent;
  • Remove recommendations on use of SDP with SAP from definition of "i=" since they duplicated RFC 2974;
  • Reference RFC 2822 rather than RFC 822;
  • Clarify that the free-text name associated with email address and phone number MUST be enclosed in parenthesis, to match the ABNF;
  • Clarify that the X- prefix for bandwidth modifier names is for experimental purposes only;
  • Rename the top-level construct in the ABNF to "session-description" rather than "announcement";
  • Remove duplicate definition of "multimedia session" from section 4;
  • Clarify that the "conventional international format" for phone numbers is an E.164 number in section 5.6, and relax the requirement for a space or hyphen between the country code and the rest of the phone number;
  • Clarify what attributes and fields are dependent on charset; and
  • Better align the ABNF field names and those in the main document.
• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, October 2003, Work in progress (draft-ietf-mmusic-sdp-new-15.txt).

• The changes in this version are as follows:

  • Update references
  • Clarify that b= may be duplicated
  • Clarify that multiple addresses or "c=" lines can only be specified if they provide multicast addresses for different layers
  • Clarify use of b= with layered coding
  • Clarify which ports are associated with an m= line when layered coding is used
  • Remove extra ")" from the definition of m1 in the ABNF
  • Add reference to RFC2396 in definition of u=
  • Add MIME registration to the IANA Considerations section, and note that this draft updates RFC 2327
  • In the description of "k=", note that S/MIME email and TLS protected HTTP and SIP might be appropriate secure transports for SDP. Also note that it is necessary to "ensure that the secure channel is with the party that is authorized to join the session, not an intermediary" and "If a caching server is used, there ought to be a way to keep the server from accessing the key"
  • The recommendation that systems "SHOULD NOT deliver the user into an interactive multimedia session without the user being aware that this will happen" in the Security Considerations section was strengthened to "MUST NOT deliver the user into an interactive multimedia session unless the user has explicitly pre-authorized such action"
  • A comment in the ABNF for "token-char" allowed a larger set of characters than the actual definition. The comment has been removed, leaving the set of allowed characters as specified in the ABNF
  • Clarify that UTF-8 normalization is not needed because comparisons are not done on fields with UTF-8.
  • Clarify that k= is NOT RECOMMENDED and give pointers to the sdescriptions and key-mgmt drafts.
  • Clarify that k= does not include an algorithm identifier, key type, or any other information about the key.
  • Clarify that k= does not support the transfer of two keys
  • Remove reference to RFC 3551/1890 from the description of k=, since that nowhere specified how k= was used.
  • Note that a session description may contain URIs which may be dereferenced. This makes the SDP non-self contained.
  • Remove "Changes from RFC 2327" section, since it was very inaccurate and outdated.
• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, September 2003, Work in progress (draft-ietf-mmusic-sdp-new-14.txt).

• Reformat and add table of contents. No technical changes.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, May 2003, Work in progress (draft-ietf-mmusic-sdp-new-13.txt).

• Update IANA registration requirements for attributes and fmt values; clarify UDP port usage; disallow X- prefix payload format names (previously deprecated); update references and make other editorial fixes.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, March 2003, Work in progress (draft-ietf-mmusic-sdp-new-12.txt).

• Revert change to media-description ABNF, and instead fix the description of "c=" to be consistant. Add definition of decimal-uchar to ABNF (copied from RFC 3108) Clarify the limitations of the k= field. Split references into normative and informative sections Clarify and tighten the rules in the IANA considerations section. Editorial and formatting clean-ups.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, November 2002, Work in progress (draft-ietf-mmusic-sdp-new-11.txt).

• In the media-description ABNF definition, the "*" in connection-field was redundant and has been removed since connection-field defines itself as optional; the X- notation for experimental parameters has been deprecated; the example on page 23 has been corrected; the definition of email-safe in the ABNF has been corrected; and the ABNF for "r=" has been corrected to handle initial repeat of "0", matching examples.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, May 2002, Work in progress (draft-ietf-mmusic-sdp-new-10.txt).

• Notes that RFC 2044 is obsoleted by RFC 2279, and corrects a typo.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, May 2002, Work in progress (draft-ietf-mmusic-sdp-new-09.txt).

• Note relation to the offer/answer model, for use with SIP. Update use of RFC 2119 terms. Clarify that "a=sendrecv" is the default, if none of "sendonly", "recvonly", "inactive", or "sendrecv" is specified. Make assorted editorial clarifications.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, April 2002, Work in progress (draft-ietf-mmusic-sdp-new-08.txt).

• Editorial clean-ups.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, March 2002, Work in progress (draft-ietf-mmusic-sdp-new-07.txt).

• This version fixes the description of IPv6 multicast, especially around TTL vs hop count. It also allows "a=rtpmap:" to be a session level attribute, in addition to a media level, as discussed on the mailing list.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, February 2002, Work in progress (draft-ietf-mmusic-sdp-new-06.txt).

• Updates ABNF to be consistent with RFC 2234 and SDP/IPv6.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, February 2002, Work in progress (draft-ietf-mmusic-sdp-new-05.txt).

• Changes since previous version: clarify that RTCP is still sent in an a=recvonly session (similarly for sendonly and inactive); fix ABNF to include a unicast-address element, allowing comedia to align with both this and RFC2327; use "s= " rather than "s=-", fix ABNF to reflect that s= is mandatory, and clarify that s= lines needs to be non-empty and SHOULD contain ISO 10646 formatted content.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, November 2001, Work in progress (draft-ietf-mmusic-sdp-new-04.txt).

• Changes include:

  • Add Changes since RFC2327 section
  • Add a=inactive attribute
  • Note about b= AS field being the RTP session bandwidth
  • Note about a=maxptime: "Note that this attribute is introduced after RFC 2327, and non updated implementations will ignore this attribute." as suggested by Steve Casner.
  • Note that "s=-" SHOULD be used for sessions with no meaningful name.
  • Updated BNF from Jonathan Lennox
  • Note that a=rtpmap is a media attribute.
  • add c= example for IPv6

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, July 2001, Work in progress (draft-ietf-mmusic-sdp-new-03.txt).

• Changes in this version include:

  • e= and p= and mandatory, but should be made optional
  • maxptime
  • Remove references to "conference" from t=, to make it less SAP oriented
  • What about wrap-around of NTP timestamps in t=?
  • Merge draft-olson-sdp-ipv6-00.txt
• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, April 2001, Work in progress (draft-ietf-mmusic-sdp-new-02.txt).

• Changes in this version include:

  • References updated
  • Section 3.1 replaced with a reference to RFC 2119
  • Use of "application/sdp" as MIME type: SHOULD to MUST
  • Section 4 now mentions use of SIP and RTSP
  • Section 5.3 now mentions SIP and is less SAP centric
  • Section 6 comments about bandwidth limits rewritten to be less SAP specific
  • The section on concatenation of session descriptions (not allowed in SAP, allowed in other cases) has been removed. Assume transports of SDP specify this?
  • Section 6 has MUST, SHOULD, etc. Please comment.
  • c= talked about how "typically the address is a class D multicast address". Made less Mbone specific, to reflect common use of SDP.
  • b= no longer makes a normative reference to the Mbone FAQ for bandwidth limits at various TTLs
  • m= define relation to MIME types
• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, March 2001, Work in progress (draft-ietf-mmusic-sdp-new-01.txt).

• For "b=", note that modifiers may specify that alternate units are to be used, but that the modifiers specified in this draft use the default of kilobits per second. Clarify meaning when there are "c=" lines containing multiple addresses with multiple ports specified on the "m=" lines.

• (diff from previous version)
• Mark Handley, Van Jacobson, and Colin Perkins, SDP: Session Description Protocol (.txt|.pdf), Internet Engineering Task Force, November 2000, Work in progress (draft-ietf-mmusic-sdp-new-00.txt).

• This draft is essentially identical to RFC 2327. It is made available to stimulate discussion of corrections and clarifications which need to be made in order to advance SDP to a draft standard RFC.

This draft defines the Session Description Protocol, SDP. SDP is intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation. This draft is eventually intended to replace 2327.