Internet DRAFT - draft-fujikawa-stream-uri

draft-fujikawa-stream-uri



INTERNET DRAFT                                            FUJIKAWA Kenji
draft-fujikawa-stream-uri-00.txt                          KURIYA Shinobu
                                                         TANAKA Tsuyoshi
                                                        Kyoto University

                                                            January 2000

                           Stream URI Scheme


Status of this Memo

       This document is an Internet-Draft and is in full conformance
       with all provisions of Section 10 of RFC2026.

       Internet-Drafts are working documents of the Internet Engineering
       Task Force (IETF), its areas, and its working groups.  Note that
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Abstract

   This document describes the Stream Uniform Resource Identifier which
   allows Internet clients to have direct access to multimedia streams.


1. Introduction

   This document defines the Stream URI which will allow Internet
   clients to have direct access to media streams.  It includes
   information for launching applications to join a session.  It should
   be included in HTML documents with other information about the
   session.  A Stream URI client which can be a extended WWW browser
   will launch applications to participate in the session when a user
   activate a Stream URI included in the HTML document.



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2. Overview of the Stream URI

   A session description, which describes information about sessions,
   including participating in sessions, is originally defined by Session
   Description Protocol (SDP) [RFC2327].  Stream URI is the URI which
   only includes information necessary to launch applications for a
   multimedia session.  It reuses some formats of SDP.  These formats
   are "m" that means media name and transport address, "t" that means
   time the session is active and "a" that means zero or more media
   attribute lines.  Stream URI doesn't include formats such as session
   information, email address and phone number, which can be written in
   HTML documents.

   Stream URI has an optional attribute for QoS routing (this attribute
   is not defined in SDP).  Specifying this attribute, the media
   application will be able to receive streams that QoS is satisfied.



3. Description of the Stream URI scheme

   Stream URI takes the following form:

       stream:// <connection address> [: <connection port>] / [<session name>]
            # [t = <start time> : <stop time> &]
            m = <media> : [<port>] : <transport> : <fmt list>
                 [& a = <attribute> [: <value list>]]
            *[& m = <media> : [<port>] : <transport> : <fmt list>
                 *[& a = <attribute> : [<value list>]]]

   <connection address> is the session IP address, to which the media
   streams are sent.  It is a unicast address or a multicast address.

   <connection port> is the transport port to which the media streams
   are sent. It can be omitted.

   <session name> is the session name. It must be represented by
   conventional URI encoding scheme [RFC2396]. It can be omitted.

   <start time> is the time the session will start.  <stop time> is the
   time the session will close.  They can be omitted.

   <media> is the type of media.  It is one of the terms "video,"
   "audio" and "wb," which means video stream, audio stream and white
   board stream, respectively.

   <port> is the transport port number for that media.  If it is
   omitted, <connection port> will be used instead.  Stream URI must



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   contain at least one of <connection port> and <port>.

   <transport> is the transport protocol.  It is one of the terms "RTP-
   AVP" and "udp," which means the RTP Audio/Video profile [RFC1890] and
   the UDP protocol, respectively.

   <fmt list> is a list of media formats divided by ":".  These formats
   are media payload types as defined in the RTP Audio/Video profile.
   The first one is the default format for the session.  For example,
   format "0" means u-law PCM coded channel audio sampled at 8KHz.

   <attribute> is attribute which is media specific.  <value list> is a
   list of values that is related to the attribute, which is divided by
   ":".  Each media can have any numbers of attribute.  Currently,
   attribute "framerate" can be used.  Refer to [RFC2327] for details.
   Besides, this draft defines "qos" attribute, which is described in a
   later section.


4. Examples

   The followings are some examples of Stream URIs.

   (1) internet phone

   o callee's host address is caravan.kuis.kyoto-u.ac.jp

   o callee's port is 23456

   o callee's name is "tanaka" and it is used as a session name.

   o voice is encoded into PCMU whose payload type is 0

       stream://caravan.kuis.kyoto-u.ac.jp:23456/tanaka#m=audio::RTP-AVP:0

   (2) audio and video meeting

   o meeting address is 224.130.54.22

   o audio port is 10000, video port is 10002

   o session name is "ikeda lab meeting"

   o audio encoding is PCMA whose payload type is 8

   o video encoding is JPEG whose payload type is 26

   o maximum framerate of video is 10



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       stream://224.130.54.22/ikeda+lab+meeting
            #m=audio:10000:RTP-AVP:8&m=video:10002:RTP-AVP:26&a=framerate:10

   Multicast addresses could be registered in DNS in [2].  In this case,
   the URI is also written as:

       stream://meeting.lab1.kuis.kyoto-u.ac.jp/ikeda+lab+meeting
            #m=audio:10000:RTP-AVP:8&m=video:10002:RTP-AVP:26&a=framerate:10

   where 'meeting.lab1.kuis.kyoto-u.ac.jp' is the domain name of the
   address 224.130.54.22 .


5. Proposed syntax

   The proposed BNF syntax is encoded as specified in [RFC1738].

       streamURI     = "stream://" connection "/" sessionname "#"
                       [time "&"] media *["&" media]

       connection    = address [":" port]
       address       = addressnumber | addressname
       addressnumber = digits "." digits "." digits "." digits
       digits        = 1*digit
       addressname   = *[domainlevel "."] toplevel
       domainlevel   = alphadigit |
                       alphadigit *[alphadigit | "-"] alphadigit
       toplevel      = alpha |
                       alpha *[alphadigit | "-"] alphadigit
       alphadigit    = alpha | digit

       sessioname    = 1*uchar

       time          = "t=" starttime ":" stoptime
       starttime     = digits
       stoptime      = digits

       media         = "m=" mediatype ":" [port] ":" transport ":" formatlist
                       *["&" attribute]
       mediatype     = "audio" | "video" | "application" | "data" | "control"
       transport     = 1*uchar
       formatlist    = format *[":" format]
       format        = 1*uchar
       attribute     = "a=" attributename *[":" value]
       attributename = 1*uchar
       value         = 1*uchar

       alpha, digit and uchar are defined in [RFC1738].



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6. QoS Attribute

   This documents defines attribute "qos."  It is an ascii caracter
   string format of REQ_QOS defined in [FK1999].  It takes the following
   form:

       qos_attribute = "a=qos" ":" R_PRI ":" R_MTU ":" R_PPS ":" R_UTU ":"
                       R_CDLY ":" R_CCHG ":" R_RDLY ":" R_RCHG
       R_PRI         = digits
       R_MTU         = digits
       R_PPS         = digits
       R_UTU         = digits
       R_CDLY        = digits
       R_CCHG        = digits
       R_RDLY        = digits
       R_RCHG        = digits

   Refer to [FK1999] for the meaning of each parameter.


7. Considerations of Scope rule

   Though the range of a session is limited by the scope of a multicast,
   a user can access a WWW server out of the range. Therefore, it is
   pointed out that there is a situation where a receiver may not join a
   session announced by WWW.

   However, it is shown in [OM1998] that this is not a problem actually
   and the conception of the scope itself have some problems.  Thus, we
   should omit the conception and the TTL management related to it.


8. Security Considerations

   Security considerations are not addressed in this document.


References

   [RFC2327] Handley, M., Jacobson, V., "SDP: Session Description Protocol,"
             RFC 2327, April 1998.

   [RFC1890] H. Shulzrinne, "RTP Profile Audio and Vidoe conferences with
             Minimal Control," RFC 1890, January 1996.

   [RFC1738] Berners-Lee, T., Masinter, L. and McCahill, M., "Uniform
             Resource Locators (URL)," RFC 1738, December 1994.




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   [RFC2396] Berners-Lee, T., Fielding, R., Masinter, L., "Uniform Resource
             Identifiers (URI): Generic Syntax," RFC 2396, August 1998.

   [OM1998]  Ohta, M. and Crowcroft, J., "Static Multicast," Internet Draft
             draft-ohta-static-multicast-00.txt (work in progress),
             March 1998.

   [FK1999]  Fujikawa, K., "Service Specification,"
             http://www.real-internet.org/draft/draft-ric-ss-00.txt,
             December 1999.



Authors' Address

   FUJIKAWA, Kenji
   Graduate School of Informatics, Kyoto University
   Yoshidahonmachi, Sakyo-ku, Kyoto City, 606-8501, Japan
   Phone : +81 75-753-5387
   Email : fujikawa@real-internet.org

   KURIYA, Shinobu
   Graduate School of Informatics, Kyoto University
   Yoshidahonmachi, Sakyo-ku, Kyoto City, 606-8501, Japan
   Phone : +81 75-753-5387
   Email : kuriya@kuis.kyoto-u.ac.jp

   TANAKA, Tsuyoshi
   Graduate School of Informatics, Kyoto University
   Yoshidahonmachi, Sakyo-ku, Kyoto City, 606-8501, Japan
   Phone : +81 75-753-5387
   Email : tanaka@kuis.kyoto-u.ac.jp



















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