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
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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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