1. Introduction

   This document identifies requirements and an architecture for the
   transport of IP Datagrams over ISO MPEG-2 Transport Streams
   [ISO-MPEG].  The prime focus is the efficient and flexible delivery
   of IP services over those subnetworks that use the MPEG-2 Transport
   Stream (TS).

   The architecture is designed to be compatible with services based on
   MPEG-2, for example the Digital Video Broadcast (DVB) architecture,
   the Advanced Television Systems Committee (ATSC) system [ATSC,ATSC-G], and other similar MPEG-2-based transmission systems.  Such
   systems typically provide unidirectional (simplex) physical and link
   layer standards, and have been defined for a wide range of physical
   media (e.g., Terrestrial TV [ETSI-DVBT,ATSC-PSIP-TC], Satellite TV
   [ETSI-DVBS,ETSI-DVBS2,ATSC-S], Cable Transmission [ETSI-DVBC,ATSC-PSIP-TC,OPEN-CABLE], and data transmission over MPEG-2
   [ETSI-MHP].

             +-+-+-+-+------+------------+---+--+--+---------+
             |T|V|A|O|  O   |            | O |S |O |         |
             |e|i|u|t|  t   |            | t |I |t |         |
             |l|d|d|h|  h   |     IP     | h |  |h | Other   |
             |e|e|i|e|  e   |            | e |T |e |protocols|
             |t|o|o|r|  r   |            | r |a |r | native  |
             |e| | | |      |            |   |b |  |  over   |
             |x| | | |      |   +---+----+-+ |l |  |MPEG-2 TS|
             |t| | | |      |   |   | MPE  | |e |  |         |
             | | | | |   +--+---+   +------+ |  |  |         |
             | | | | |   | AAL5 |ULE|Priv. | |  |  |         |
             +-+-+-+-+---+------+   |      +-+--+--+         |
             |  PES  |   ATM    |   |Sect. |Section|         |
             +-------+----------+---+------+-------+---------+
             |                  MPEG-2 TS                    |
             +---------+-------+----------------+------------+
             |Satellite| Cable | Terrestrial TV | Other PHY  |
             +---------+-------+----------------+------------+

       Figure 1: Overview of the MPEG-2 protocol stack

   Although many MPEG-2 systems carry a mixture of data types, MPEG-2
   components may be, and are, also used to build IP-only networks.
   Standard system components offer advantages of improved
   interoperability and larger deployment.  However, some MPEG-2
   networks do not implement all parts of a DVB / ATSC system, and may,
   for instance, support minimal, or no, signalling of Service
   Information (SI) tables.

1.1. Salient Features of the Architecture

   The architecture defined in this document describes a set of
   protocols that support transmission of IP packets over the MPEG-2 TS.
   Key characteristics of these networks are that they may provide
   link-level broadcast capability, and that many supported applications
   require access to a very large number of subnetwork nodes.

   Some, or all, of these protocols may also be applicable to other
   subnetworks, e.g., other MPEG-2 transmission networks, regenerative
   satellite links [ETSI-BSM], and some types of broadcast wireless
   links.  The key goals of the architecture are to reduce complexity
   when using the system, while improving performance, increasing
   flexibility for IP services, and providing opportunities for better
   integration with IP services.

   Since a majority of MPEG-2 transmission networks are bandwidth-
   limited, encapsulation protocols must therefore add minimal overhead
   to ensure good link efficiency while providing adequate network
   services.  They also need to be simple to minimize processing, robust
   to errors and security threats, and extensible to a wide range of
   services.

   In MPEG-2 systems, TS Logical Channels, are identified by their PID
   and provide multiplexing, addressing, and error reporting.  The TS
   Logical Channel may also be used to provide Quality of Service (QoS).
   Mapping functions are required to relate TS Logical Channels to IP
   addresses, to map TS Logical Channels to IP-level QoS, and to
   associate IP flows with specific subnetwork capabilities.  An
   important feature of the architecture is that these functions may be
   provided in a dynamic way, allowing transparent integration with
   other IP-layer protocols.  Collectively, these will form an MPEG-2 TS
   Address Resolution (AR) protocol suite [IPDVB-AR].