Uniform Resource Identifiers for Television Broadcasts
RFC 2838

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 03

Network Working Group                                        D. Zigmond
Request for Comments: 2838                         WebTV Networks, Inc.
Category: Informational                                      M. Vickers
                                            Liberate Technologies, Inc.
                                                               May 2000

        Uniform Resource Identifiers for Television Broadcasts

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

1. Introduction

   World-Wide Web browsers are starting to appear on a variety of
   consumer electronic devices, such as television sets and television
   set-top boxes, which are capable of receiving television programming
   from either terrestrial broadcast, satellite broadcast, or cable. In
   this context there is a need to reference television broadcasts using
   the URI format described in [RFC 2396]. This document describes a
   widely-implemented URI scheme to refer to such broadcasts.

2. Television URI

   The basic structure of a television URI is:

        tv:<broadcast>

   where broadcast is a description of the data source. The description
   takes the form of a DNS-style identifier for a particular broadcaster
   or television network. For example:

        tv:wqed.org           the WQED station
        tv:nbc.com            the NBC network

Zigmond & Vickers            Informational                      [Page 1]
RFC 2838                 URIs for TV Broadcasts                 May 2000

3.1. Scheme-only form

   A simplest form of the "tv:" URI scheme is used to refer to the
   "current" or "default" channel:

        tv:

   This URI refers to whichever television broadcast is currently being
   received by the device. It is often used in combination with HTML
   content that is actually being broadcast along with the audio and
   video, where the meaning of "current broadcast" is quite unambiguous
   (because it is the broadcast along with which the content containing
   the URI was received). This is in fact the most common usage of the
   "tv:" scheme today, and is explicitly referenced by the recently
   published specification of the Advanced Television Enhancement Forum
   [ATVEF 1.1].

3.2 DNS-style identifiers

   Television broadcasts traditionally have been identified in a variety
   of ways.  All terrestrial television broadcasters are assigned call
   signs (such as "KDKA" or "WQED") to identify their signal. These are
   generally assigned by national authorities (such as the Federal
   Communications Commission in the United States) and are world unique.
   The global namespace is managed by the International
   Telecommunications Union, which assigns portions to member countries
   (see [ITU RR]).

   Many modern television networks are not broadcasted over-the-air, but
   available only through cable or satellite subscriptions.  The
   identifiers for these networks (such as the familiar "CNN" and "HBO")
   are not regulated at this time.  In some countries, even over-the-air
   broadcasters use these sorts of identifiers, rather than call signs.

   Unfortunately, these two namespaces overlap, with most network
   identifiers also being valid call signs.  Furthermore, network
   identifiers are not world unique, and many cases exist of name
   collisions.  (For example, both the Australian Broadcast Corporation
   and the American Broadcasting Company identify themselves as "ABC".)
   In order to ensure uniqueness, the "tv:" scheme uses DNS-style
   identifiers for all broadcast streams.  Because these build on the
   existing registration system for DNS hostname, all name collisions
   can be resolved through the existing DNS dispute resolution
   processes.

Zigmond & Vickers            Informational                      [Page 2]
RFC 2838                 URIs for TV Broadcasts                 May 2000

   In the simplest form, domain names themselves are used as broadcast
   identifiers.  For example:

          tv:abc.com          the American Broadcast Company
          tv:abc.co.au        the Australian Broadcast Corporation

   In some cases, networks have multiple broadcast streams that need to
   be distinguished.  This is also handled in DNS style:

          tv:east.hbo.com     HBO East
          tv:west.hbo.com     HBO West

   It is important to note that these DNS-style identifiers need not
   match real hostnames; they should not be resolved to IP addresses
   using DNS.  Thus, using the terms as defined in RFC 2396, the "tv:"
   scheme is a Uniform Resource Identifier and not a Uniform Resource
   Locator.

   In order to support these identifiers in a "tv:" URI, a receiver must
   implement a means to map known identifiers to frequencies. The nature