The Transmission of IP Over the Vertical Blanking Interval of a Television Signal
RFC 2728

Document Type RFC - Proposed Standard (November 1999; No errata)
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Network Working Group                                    R. Panabaker
Request for Comments: 2728                                  Microsoft
Category: Standards Track                                  S. Wegerif
                                               Philips Semiconductors
                                                           D. Zigmond
                                                       WebTV Networks
                                                        November 1999

    The Transmission of IP Over the Vertical Blanking Interval of a
                           Television Signal

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 Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

1. Abstract

   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
   structures.

2. Introduction

   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
   applications.

Panabaker, et al.           Standards Track                     [Page 2]
RFC 2728                         IPVBI                     November 1999

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