The Transmission of IP Over the Vertical Blanking Interval of a Television Signal
Network Working Group R. Panabaker
Request for Comments: 2728 Microsoft
Category: Standards Track S. Wegerif
The Transmission of IP Over the Vertical Blanking Interval of a
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document describes a method for broadcasting IP data in a
unidirectional manner using the vertical blanking interval of
television signals. It includes a description for compressing IP
headers on unidirectional networks, a framing protocol identical to
SLIP, a forward error correction scheme, and the NABTS byte
This RFC proposes several protocols to be used in the transmission of
IP datagrams using the Vertical Blanking Interval (VBI) of a
television signal. The VBI is a non-viewable portion of the
television signal that can be used to provide point-to-multipoint IP
data services which will relieve congestion and traffic in the
traditional Internet access networks. Wherever possible these
protocols make use of existing RFC standards and non-standards.
Traditionally, point-to-point connections (TCP/IP) have been used
even for the transmission of broadcast type data. Distribution of
the same content--news feeds, stock quotes, newsgroups, weather
Panabaker, et al. Standards Track [Page 1]
RFC 2728 IPVBI November 1999
reports, and the like--are typically sent repeatedly to individual
clients rather than being broadcast to the large number of users who
want to receive such data.
Today, IP is quickly becoming the preferred method of distributing
one-to-many data on intranets and the Internet. The coming
availability of low cost PC hardware for receiving television signals
accompanied by broadcast data streams makes a defined standard for
the transmission of data over traditional broadcast networks
imperative. A lack of standards in this area as well as the expense
of hardware has prevented traditional broadcast networks from
becoming effective deliverers of data to the home and office.
This document describes the transmission of IP using the North
American Basic Teletext Standard (NABTS), a recognized and industry-
supported method of transporting data on the VBI. NABTS is
traditionally used on 525-line television systems such as NTSC.
Another byte structure, WST, is traditionally used on 625-line
systems such as PAL and SECAM. These generalizations have
exceptions, and countries should be treated on an individual basis.
These existing television system standards will enable the television
and Internet communities to provide inexpensive broadcast data
services. A set of existing protocols will be layered above the
specific FEC for NABTS including a serial stream framing protocol
similar to SLIP (RFC 1055 [Romkey 1988]) and a compression technique
for unidirectional UDP/IP headers.
The protocols described in this document are intended for the
unidirectional delivery of IP datagrams using the VBI. That is, no
return channel is described, or for that matter possible, in the VBI.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
3. Proposed protocol stack
The following protocol stack demonstrates the layers used in the
transmission of VBI data. Each layer has no knowledge of the data it
encapsulates, and is therefore abstracted from the other layers. At
the link layer, the NABTS protocol defines the modulation scheme used
to transport data on the VBI. At the network layer, IP handles the
movement of data to the appropriate clients. In the transport layer,
UDP determines the flow of data to the appropriate processes and
Panabaker, et al. Standards Track [Page 2]
RFC 2728 IPVBI November 1999
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