GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc4259

Network Working Group M.-J. Montpetit Request for Comments: 4259 Motorola Connected Home Solutions Category: Informational G. Fairhurst

                                                University of Aberdeen
                                                            H. Clausen
                                                           TIC Systems
                                                     B. Collini-Nocker
                                                             H. Linder
                                                University of Salzburg
                                                         November 2005
 A Framework for Transmission of IP Datagrams over MPEG-2 Networks

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 (2005).

Abstract

 This document describes an architecture for the transport of IP
 Datagrams over ISO MPEG-2 Transport Streams (TS).  The MPEG-2 TS has
 been widely accepted not only for providing digital TV services but
 also as a subnetwork technology for building IP networks.  Examples
 of systems using MPEG-2 include the Digital Video Broadcast (DVB) and
 Advanced Television Systems Committee (ATSC) Standards for Digital
 Television.
 The document identifies the need for a set of Internet standards
 defining the interface between the MPEG-2 Transport Stream and an IP
 subnetwork.  It suggests a new encapsulation method for IP datagrams
 and proposes protocols to perform IPv6/IPv4 address resolution, to
 associate IP packets with the properties of the Logical Channels
 provided by an MPEG-2 TS.

Montpetit, et al. Informational [Page 1] RFC 4259 IP Transport over MPEG-2 Networks November 2005

Table of Contents

 1. Introduction ....................................................3
    1.1. Salient Features of the Architecture .......................4
 2. Conventions Used in This Document ...............................4
 3. Architecture ....................................................8
    3.1. MPEG-2 Transmission Networks ...............................8
    3.2. TS Logical Channels .......................................10
    3.3. Multiplexing and Re-Multiplexing ..........................12
    3.4. IP Datagram Transmission ..................................13
    3.5. Motivation ................................................14
 4. Encapsulation Protocol Requirements ............................16
    4.1. Payload Unit Delimitation .................................17
    4.2. Length Indicator ..........................................18
    4.3. Next Level Protocol Type ..................................19
    4.4. L2 Subnet Addressing ......................................19
    4.5. Integrity Check ...........................................21
    4.6. Identification of Scope. ..................................21
    4.7. Extension Headers .........................................21
    4.8. Summary of Requirements for Encapsulation .................22
 5. Address Resolution Functions ...................................22
    5.1. Address Resolution for MPEG-2 .............................23
    5.2. Scenarios for MPEG AR .....................................25
         5.2.1. Table-Based AR over MPEG-2 .........................25
         5.2.2. Table-Based AR over IP .............................26
         5.2.3. Query/Response AR over IP ..........................26
    5.3. Unicast Address Scoping ...................................26
    5.4. AR Authentication .........................................27
    5.5. Requirements for Unicast AR over MPEG-2 ...................28
 6. Multicast Support ..............................................28
    6.1. Multicast AR Functions ....................................29
    6.2. Multicast Address Scoping .................................30
    6.3. Requirements for Multicast over MPEG-2 ....................31
 7. Summary ........................................................31
 8. Security Considerations ........................................32
    8.1. Link Encryption ...........................................33
 9. IANA Considerations ............................................34
 10. Acknowledgements ..............................................34
 11. References ....................................................34
    11.1. Normative References .....................................34
    11.2. Informative References ...................................34
 Appendix A ........................................................39

Montpetit, et al. Informational [Page 2] RFC 4259 IP Transport over MPEG-2 Networks November 2005

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.

Montpetit, et al. Informational [Page 3] RFC 4259 IP Transport over MPEG-2 Networks November 2005

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].

2. Conventions Used in This Document

 Adaptation Field: An optional variable-length extension field of the
 fixed-length TS Packet header, intended to convey clock references
 and timing and synchronization information as well as stuffing over
 an MPEG-2 Multiplex [ISO-MPEG].
 ATSC: Advanced Television Systems Committee [ATSC].  A framework and
 a set of associated standards for the transmission of video, audio,
 and data using the ISO MPEG-2 standard [ISO-MPEG].
 DSM-CC: Digital Storage Media Command and Control [ISO-DSMCC].  A
 format for transmission of data and control information defined by
 the ISO MPEG-2 standard that is carried in an MPEG-2 Private Section.

Montpetit, et al. Informational [Page 4] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 DVB: Digital Video Broadcast [ETSI-DVBC, ETSI-DVBRCS, ETSI-DVBS].  A
 framework and set of associated standards published by the European
 Telecommunications Standards Institute (ETSI) for the transmission of
 video, audio, and data, using the ISO MPEG-2 Standard [ISO-MPEG].
 Encapsulator: A network device that receives PDUs and formats these
 into Payload Units (known here as SNDUs) for output as a stream of TS
 Packets.
 Forward Direction: The dominant direction of data transfer over a
 network path.  Data transfer in the forward direction is called
 "forward transfer".  Packets travelling in the forward direction
 follow the forward path through the IP network.
 MAC: Medium Access and Control.  The link layer header of the
 Ethernet IEEE 802 standard of protocols, consisting of a 6B
 destination address, 6B source address, and 2B type field (see also
 NPA).
 MPE: Multiprotocol Encapsulation [ETSI-DAT, ATSC-DAT, ATSC-DATG].  A
 scheme that encapsulates PDUs, forming a DSM-CC Table Section.  Each
 Section is sent in a series of TS Packets using a single TS Logical
 Channel.
 MPEG-2: A set of standards specified by the Motion Picture Experts
 Group (MPEG), and standardized by the International Standards
 Organisation (ISO) [ISO-MPEG].
 NPA: Network Point of Attachment.  Addresses primarily used for
 station (Receiver) identification within a local network (e.g., IEEE
 MAC address).  An address may identify individual Receivers or groups
 of Receivers.
 PAT: Program Association Table [ISO-MPEG].  An MPEG-2 PSI control
 table that associates program numbers with the PID value used to send
 the corresponding PMT.  The PAT is sent using the well-known PID
 value of zero.
 PDU: Protocol Data Unit.  Examples of a PDU include Ethernet frames,
 IPv4 or IPv6 datagrams, and other network packets.
 PES: Packetized Elementary Stream [ISO-MPEG].  A format of MPEG-2 TS
 packet payload usually used for video or audio information.
 PID: Packet Identifier [ISO-MPEG].  A 13 bit field carried in the
 header of TS Packets.  This is used to identify the TS Logical
 Channel to which a TS Packet belongs [ISO-MPEG].  The TS Packets
 forming the parts of a Table Section, PES, or other Payload Unit must

Montpetit, et al. Informational [Page 5] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 all carry the same PID value.  The all 1s PID value indicates a Null
 TS Packet introduced to maintain a constant bit rate of a TS
 Multiplex.  There is no required relationship between the PID values
 used for TS Logical Channels transmitted using different TS
 Multiplexes.
 PMT: Program Map Table.  An MPEG-2 PSI control table that associates
 the PID values used by the set of TS Logical Channels/Streams that
 comprise a program [ISO-MPEG].  The PID value which is used to send
 the PMT for a specific program is defined by an entry in the PAT.
 PP: Payload Pointer [ISO-MPEG].  An optional one byte pointer that
 directly follows the TS Packet header.  It contains the number of
 bytes between the end of the TS Packet header and the start of a
 Payload Unit.  The presence of the Payload Pointer is indicated by
 the value of the PUSI bit in the TS Packet header.  The Payload
 Pointer is present in DSM-CC and Table Sections; it is not present in
 TS Logical Channels that use the PES-format.
 Private Section: A syntactic structure constructed in accordance with
 Table 2-30 of [ISO-MPEG].  The structure may be used to identify
 private information (i.e., not defined by [ISO-MPEG]) relating to one
 or more elementary streams, or a specific MPEG-2 program, or the
 entire TS.  Other Standards bodies (e.g., ETSI, ATSC) have defined
 sets of table structures using the private_section structure.  A
 Private Section is transmitted as a sequence of TS Packets using a TS
 Logical Channel.  A TS Logical Channel may carry sections from more
 than one set of tables.
 PSI: Program Specific Information [ISO-MPEG].  PSI is used to convey
 information about services carried in a TS Multiplex.  It is carried
 in one of four specifically identified table section constructs
 [ISO-MPEG], see also SI Table.
 PU: Payload Unit.  A sequence of bytes sent using a TS.  Examples of
 Payload Units include: an MPEG-2 Table Section or a ULE SNDU.
 PUSI: Payload_Unit_Start_Indicator [ISO-MPEG].  A single bit flag
 carried in the TS Packet header.  A PUSI value of zero indicates that
 the TS Packet does not carry the start of a new Payload Unit.  A PUSI
 value of one indicates that the TS Packet does carry the start of a
 new Payload Unit.  In ULE, a PUSI bit set to 1 also indicates the
 presence of a one byte Payload Pointer (PP).
 Receiver: A piece of equipment that processes the signal from a TS
 Multiplex and performs filtering and forwarding of encapsulated PDUs
 to the network-layer service (or bridging module when operating at
 the link layer).

Montpetit, et al. Informational [Page 6] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 SI Table: Service Information Table [ISO-MPEG].  In this document,
 this term describes a table that is used to convey information about
 the services carried in a TS Multiplex, that has been defined by
 another standards body.  A Table may consist of one or more Table
 Sections, however all sections of a particular SI Table must be
 carried over a single TS Logical Channel [ISO-MPEG].
 SNDU: Sub-Network Data Unit.  An encapsulated PDU sent as an MPEG-2
 Payload Unit.
 STB: Set-Top Box.  A consumer equipment (Receiver) for reception of
 digital TV services.
 Table Section: A Payload Unit carrying all or a part of an SI or PSI
 Table [ISO-MPEG].
 TS: Transport Stream [ISO-MPEG], a method of transmission at the
 MPEG-2 level using TS Packets; it represents level 2 of the ISO/OSI
 reference model.  See also TS Logical Channel and TS Multiplex.
 TS Header: The 4-byte header of a TS Packet [ISO-MPEG].
 TS Logical Channel: Transport Stream Logical Channel.  In this
 document, this term identifies a channel at the MPEG-2 level
 [ISO-MPEG].  It exists at level 2 of the ISO/OSI reference model.
 All packets sent over a TS Logical Channel carry the same PID value
 (this value is unique within a specific TS Multiplex).  According to
 MPEG-2, some TS Logical Channels are reserved for specific
 signalling.  Other standards (e.g., ATSC, DVB) also reserve specific
 TS Logical Channels.
 TS Multiplex: In this document, this term defines a set of MPEG-2 TS
 Logical Channels sent over a single lower layer connection.  This may
 be a common physical link (i.e., a transmission at a specified symbol
 rate, FEC setting, and transmission frequency) or an encapsulation
 provided by another protocol layer (e.g., Ethernet, or RTP over IP).
 The same TS Logical Channel may be repeated over more than one TS
 Multiplex (possibly associated with a different PID value), for
 example to redistribute the same multicast content to two terrestrial
 TV transmission cells.
 TS Packet: A fixed-length 188B unit of data sent over a TS Multiplex
 [ISO-MPEG].  Each TS Packet carries a 4B header, plus optional
 overhead including an Adaptation Field, encryption details and time
 stamp information to synchronize a set of related TS Logical
 Channels.  It is also referred to as a TS_cell.  Each TS Packet
 carries a PID value to associate it with a single TS Logical Channel.

Montpetit, et al. Informational [Page 7] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 ULE: Unidirectional Lightweight Encapsulation (ULE) [IPDVB-ULE].  A
 scheme that encapsulates PDUs, into SNDUs that are sent in a series
 of TS Packets using a single TS Logical Channel.

3. Architecture

 The following sections introduce the components of the MPEG-2
 Transmission Network and relate these to a networking framework.

3.1. MPEG-2 Transmission Networks

 There are many possible topologies for MPEG-2 Transmission Networks.
 A number of example scenarios are briefly described below, and the
 following text relates specific functions to this set of scenarios.
 A) Broadcast TV and Radio Delivery
 The principal service in the Broadcast TV and Radio Delivery scenario
 is Digital TV and/or Radio and their associated data [MMUSIC-IMG,
 ETSI-IPDC].  Such networks typically contain two components: the
 contribution feed and the broadcast part.  Contribution feeds provide
 communication from a typically small number of individual sites
 (usually at high quality) to the Hub of a broadcast network.  The
 traffic carried on contribution feeds is typically encrypted, and is
 usually processed prior to being resent on the Broadcast part of the
 network.  The Broadcast part uses a star topology centered on the Hub
 to reach a typically large number of down-stream Receivers.  Although
 such networks may provide IP transmission, they do not necessarily
 provide access to the public Internet.
 B) Broadcast Networks used as an ISP
 Another scenario resembles that above, but includes the provision of
 IP services providing access to the public Internet.  The IP traffic
 in this scenario is typically not related to the digital TV/Radio
 content, and the service may be operated by an independent operator
 such as unidirectional file delivery or bidirectional ISP access.
 The IP service must adhere to the full system specification used for
 the broadcast transmission, including allocation of PIDs and
 generation of appropriate MPEG-2 control information (e.g., DVB and
 ATSC SI tables).
 C) Unidirectional Star IP Scenario
 The Unidirectional Star IP Scenario utilizes a Hub station to provide
 a data network delivering a common bit stream to typically medium-
 sized groups of Receivers.  MPEG-2 transmission technology provides
 the forward direction physical and link layers for this transmission;
 the return link (if required) is provided by other means.  IP

Montpetit, et al. Informational [Page 8] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 services typically form the main proportion of the transmission
 traffic.  Such networks do not necessarily implement the MPEG-2
 control plane, i.e., PSI/SI tables.
 D) Datacast Overlay
 The Datacast Overlay scenario employs MPEG-2 physical and link layers
 to provide additional connectivity such as unidirectional multicast
 to supplement an existing IP-based Internet service.  Examples of
 such a network includes IP Datacast to mobile wireless receivers
 [MMUSIC-IMG].
 E) Point-to-Point Links
 Point-to-Point connectivity may be provided using a pair of transmit
 and receive interfaces supporting the MPEG-2 physical and link
 layers.  Typically, the transmission from a sender is received by
 only one or a small number of Receivers.  Examples include the use of
 transmit/receive DVB-S terminals to provide satellite links between
 ISPs utilising BGP routing.
 F) Two-Way IP Networks
 Two-Way IP networks are typically satellite-based and star-based
 utilising a Hub station to deliver a common bit stream to medium-
 sized groups of receivers.  A bidirectional service is provided over
 a common air-interface.  The transmission technology in the forward
 direction at the physical and link layers is MPEG-2, which may also
 be used in the return direction.  Such systems also usually include a
 control plane element to manage the (shared) return link capacity.  A
 concrete example is the DVB-RCS system [ETSI-DVBRCS].  IP services
 typically form the main proportion of the transmission traffic.
 Scenarios A-D employ unidirectional MPEG-2 Transmission Networks.
 For satellite-based networks, these typically have a star topology,
 with a central Hub providing service to large numbers of down-stream
 Receivers.  Terrestrial networks may employ several transmission
 Hubs, each serving a particular coverage cell with a community of
 Receivers.
 From an IP viewpoint, the service is typically either unidirectional
 multicast, or a bidirectional service in which some complementary
 link technology (e.g., modem, Local Multipoint Distribution Service
 (LMDS), General Packet Radio Service (GPRS)) is used to provide the
 return path from Receivers to the Internet.  In this case, routing
 could be provided using UniDirectional Link Routing (UDLR) [RFC3077].
 Note that only Scenarios A-B actually carry MPEG-2 video and audio
 (intended for reception by digital Set Top Boxes (STBs)) as the
 primary traffic.  The other scenarios are IP-based data networks and
 need not necessarily implement the MPEG-2 control plane.

Montpetit, et al. Informational [Page 9] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 Scenarios E-F provide two-way connectivity using the MPEG-2
 Transmission Network.  Such networks provide direct support for
 bidirectional protocols above and below the IP layer.
 The complete MPEG-2 transmission network may be managed by a
 transmission service operator.  In such cases, the assignment of
 addresses and TS Logical Channels at Receivers are usually under the
 control of the service operator.  Examples include a TV operator
 (Scenario A), or an ISP (Scenarios B-F).  MPEG-2 transmission
 networks are also used for private networks.  These typically involve
 a smaller number of Receivers and do not require the same level of
 centralized control.  Examples include companies wishing to connect
 DVB-capable routers to form links within the Internet (Scenario B).

3.2. TS Logical Channels

 An MPEG-2 Transport Multiplex offers a number of parallel channels,
 which are known here as TS Logical Channels.  Each TS Logical Channel
 is uniquely identified by the Packet ID (PID) value that is carried
 in the header of each MPEG-2 TS Packet.  The PID value is a 13 bit
 field; thus, the number of available channels ranges from 0 to 8191
 decimal or 0x1FFF in hexadecimal, some of which are reserved for
 transmission of SI tables.  Non-reserved TS Logical Channels may be
 used to carry audio [ISO-AUD], video [ISO-VID], IP packets
 [ISO-DSMCC, ETSI-DAT, ATSC-DAT], or other data [ISO-DSMCC, ETSI-DAT,
 ATSC-DAT].  The value 8191 decimal (0x1FFF) indicates a null packet
 that is used to maintain the physical bearer bit rate when there are
 no other MPEG-2 TS packets to be sent.

Montpetit, et al. Informational [Page 10] RFC 4259 IP Transport over MPEG-2 Networks November 2005

            TS-LC-A-1         /---\--------------------/---\
                    \        /     \                  /     \
                     \      |       |                |       |
         TS-LC-A-2    -----------   |                | -------------
             --------------------   |                | -------------
                            |       |                |       |
                       /--------   /                 | -------------
                      /      \----/-------------------\----/
            TS-LC-A-3/               MPEG-2 TS MUX A
                    /
      TS-LC        /
      ------------X
                   \ TS-LC-B-3 /---\------------------------/---\
                    \         /     \                      /     \
                     \       |       |                    |       |
         TS-LC-B-2    \-----------   |                    | ---------
              --------------------   |                    | ---------
                             |       |                    |       |
                        /--------   /                     | ---------
                       /      \----/-----------------------\----/
                      /                 MPEG-2 TS MUX B
           TS-LC-B-1
       Figure 2: Example showing MPEG-2 TS Logical Channels carried
                 Over 2 MPEG-2 TS Multiplexes.
 TS Logical Channels are independently numbered on each MPEG-2 TS
 Multiplex (MUX).  In most cases, the data sent over the TS Logical
 Channels will differ for different multiplexes.  Figure 2 shows a set
 of TS Logical Channels sent using two MPEG-2 TS Multiplexes (A and
 B).
 There are cases where the same data may be distributed over two or
 more multiplexes (e.g., some SI tables; multicast content that needs
 to be received by Receivers tuned to either MPEG-2 TS; unicast data
 where the Receiver may be in either/both of two potentially
 overlapping MPEG-2 transmission cells).  In figure 2, each multiplex
 carries 3 MPEG-2 TS Logical Channels.  These TS Logical Channels may
 differ (TS-LC-A-1, TS-LC-A-2, TS-LC-B-2, TS-LC-B-1), or may be common
 to both MPEG-2 TS Multiplexes (i.e., TS-LC-A-3 and TS-LC-B-3 carry
 identical content).
 As can been seen, there are similarities between the way PIDs are
 used and the operation of virtual channels in ATM.  However, unlike
 ATM, a PID defines a unidirectional broadcast channel and not a
 point-to-point link.  Contrary to ATM, there is, as yet, no specified

Montpetit, et al. Informational [Page 11] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 standard interface for MPEG-2 connection setup, or for signaling
 mappings of IP flows to PIDs, or to set the Quality of Service, QoS,
 assigned to a TS Logical Channel.

3.3. Multiplexing and Re-Multiplexing

 In a simple example, one or more TS Logical Channels are processed by
 an MPEG-2 multiplexor, resulting in a TS Multiplex.  The TS Multiplex
 is forwarded over a physical bearer towards one or more Receivers
 (Figure 3).
 In a more complex example, the same TS may be fed to multiple MPEG-2
 multiplexors and these may, in turn, feed other MPEG-2 multiplexors
 (remultiplexing).  Remultiplexing may occur in several places (and is
 common in Scenarios A and B of Section 3.1).  One example is a
 satellite that provides on-board processing of the TS packets,
 multiplexing the TS Logical Channels received from one or more uplink
 physical bearers (TS Multiplex) to one (or more in the case of
 broadcast/multicast) down-link physical bearer (TS Multiplex).  As
 part of the remultiplexing process, a remultiplexor may renumber the
 PID values associated with one or more TS Logical Channels to prevent
 clashes between input TS Logical Channels with the same PID carried
 on different input multiplexes.  It may also modify and/or insert new
 SI data into the control plane.
 In all cases, the final result is a "TS Multiplex" that is
 transmitted over the physical bearer towards the Receiver.

Montpetit, et al. Informational [Page 12] RFC 4259 IP Transport over MPEG-2 Networks November 2005

        +------------+                                  +------------+
        |  IP        |                                  |  IP        |
        |  End Host  |                                  |  End Host  |
        +-----+------+                                  +------------+
              |                                                ^
              +------------>+---------------+                  |
                            +  IP           |                  |
              +-------------+  Encapsulator |                  |
      SI-Data |             +------+--------+                  |
      +-------+-------+            |MPEG-2 TS Logical Channel  |
      |  MPEG-2       |            |                           |
      |  SI Tables    |            |                           |
      +-------+-------+   ->+------+--------+                  |
              |          -->|  MPEG-2       |                . . .
              +------------>+  Multiplexor  |                  |
      MPEG-2 TS             +------+--------+                  |
      Logical Channel              |MPEG-2 TS Mux              |
                                   |                           |
                 Other    ->+------+--------+                  |
                 MPEG-2  -->+  MPEG-2       |                  |
                 TS     --->+  Multiplexor  |                  |
                       ---->+------+--------+                  |
                                   |MPEG-2 TS Mux              |
                                   |                           |
                            +------+--------+           +------+-----+
                            |Physical Layer |           |  MPEG-2    |
                            |Modulator      +---------->+  Receiver  |
                            +---------------+  MPEG-2   +------------+
                                               TS Mux
           Figure 3: An example configuration for a unidirectional
                     Service for IP transport over MPEG-2

3.4. IP Datagram Transmission

 Packet data for transmission over an MPEG-2 Transport Multiplex is
 passed to an Encapsulator, sometimes known as a Gateway.  This
 receives Protocol Data Units, PDUs, such as Ethernet frames or IP
 packets, and formats each into a Sub-Network Data Unit, SNDU, by
 adding an encapsulation header and trailer (see Section 4).  The
 SNDUs are subsequently fragmented into a series of TS Packets.
 To receive IP packets over an MPEG-2 TS Multiplex, a Receiver needs
 to identify the specific TS Multiplex (physical link) and also the TS
 Logical Channel (the PID value of a logical link).  It is common for
 a number of MPEG-2 TS Logical Channels to carry SNDUs; therefore, a
 Receiver must filter (accept) IP packets sent with a number of PID
 values, and must independently reassemble each SNDU.

Montpetit, et al. Informational [Page 13] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 A Receiver that simultaneously receives from several TS Logical
 Channels must filter other unwanted TS Logical Channels by employing,
 for example, specific hardware support.  Packets for one IP flow
 (i.e., a specific combination of IP source and destination addresses)
 must be sent using the same PID.  It should not be assumed that all
 IP packets are carried on a single PID, as in some cable modem
 implementations, and multiple PIDs must be allowed in the
 architecture.  Many current hardware filters limit the maximum number
 of active PIDs (e.g., 32), although if needed, future systems may
 reasonably be expected to support more.
 In some cases, Receivers may need to select TS Logical Channels from
 a number of simultaneously active TS Multiplexes.  To do this, they
 need multiple physical receive interfaces (e.g., radio frequency (RF)
 front-ends and demodulators).  Some applications also envisage the
 concurrent reception of IP Packets over other media that may not
 necessarily use MPEG-2 transmission.
 Bidirectional (duplex) transmission can be provided using an MPEG-2
 Transmission Network by using one of a number of alternate return
 channel schemes [ETSI-RC].  Duplex IP paths may also be supported
 using non-MPEG-2 return links (e.g., in Scenarios B-D of section
 3.1).  One example of such an application is that of UniDirectional
 Link Routing, UDLR [RFC3077].

3.5. Motivation

 The network layer protocols to be supported by this architecture
 include:
 (i)    IPv4 Unicast packets, destined for a single end host
 (ii)   IPv4 Broadcast packets, sent to all end systems in an IP
        network
 (iii)  IPv4 Multicast packets
 (iv)   IPv6 Unicast packets, destined for a single end host
 (v)    IPv6 Multicast packets
 (vi)   Packets with compressed IPv4 / IPv6 packet headers (e.g.,
        [RFC2507, RFC3095])
 (vii)  Bridged Ethernet frames
 (viii) Other network protocol packets (MPLS, potential new protocols)

Montpetit, et al. Informational [Page 14] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 The architecture will provide:
 (i)    Guidance on which MPEG-2 features are pre-requisites for the
        IP service, and identification of any optional fields that
        impact performance/correct operation.
 (ii)   Standards to provide an efficient and flexible encapsulation
        scheme that may be easily implemented in an Encapsulator or
        Receiver.  The payload encapsulation requires a type field for
        the SNDU to indicate the type of packet and a mechanism to
        signal which encapsulation is used on a certain PID.
 (iii)  Standards to associate a particular IP address with a Network
        Point of Attachment (NPA) that could or may not be a MAC
        Address.  This process resembles the IPv4 Address Resolution
        Protocol, ARP, or IPv6 Neighbor Discovery, ND, protocol
        [IPDVB-AR].  In addition, the standard will be compatible with
        IPv6 autoconfiguration.
 (iv)   Standards to associate an MPEG-2 TS interface with one or more
        specific TS Logical Channels (PID, TS Multiplex).  Bindings
        are required for both unicast transmission, and multicast
        reception.  In the case of IPv4, this must also support
        network broadcast.  To make the schemes robust to loss and
        state changes within the MPEG-2 transmission network, a soft-
        state approach may prove desirable.
 (v)    Standards to associate the capabilities of an MPEG-2 TS
        Logical Channel with IP flows.  This includes mapping of QoS
        functions, such as IP QoS/DSCP and RSVP, to underlying MPEG-2
        TS QoS, multi-homing and mobility.  This capability could be
        associated by the AR standard proposed above.
 (vi)   Guidance on Security for IP transmission over MPEG-2.  The
        framework must permit use of IPsec and clearly identify any
        security issues concerning the specified protocols.  The
        security issues need to consider two cases: unidirectional
        transfer (in which communication is only from the sending IP
        end host to the receiving IP end host) and bidirectional
        transfer.  Consideration should also be given to security of
        the TS Multiplex: the need for closed user groups and the use
        of MPEG-2 TS encryption.
 (vii)  Management of the IP transmission, including standardized SNMP
        MIBs and error reporting procedures.  The need for and scope
        of this is to be determined.

Montpetit, et al. Informational [Page 15] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 The specified architecture and techniques should be suited to a range
 of systems employing the MPEG-2 TS, and may also suit other
 (sub)networks offering similar transfer capabilities.
 The following section, 4, describes encapsulation issues.  Sections 5
 and 6 describe address resolution issues for unicast and multicast,
 respectively.

4. Encapsulation Protocol Requirements

 This section identifies requirements and provides examples of
 mechanisms that may be used to perform the encapsulation of IPv4/v6
 unicast and multicast packets over MPEG-2 Transmission Networks.
 A network device, known as an Encapsulator receives PDUs (e.g., IP
 Packets or Ethernet frames) and formats these into Subnetwork Data
 Units, SNDUs.  An encapsulation (or convergence) protocol transports
 each SNDU over the MPEG-2 TS service and provides the appropriate
 mechanisms to deliver the encapsulated PDU to the Receiver IP
 interface.
 In forming an SNDU, the encapsulation protocol typically adds header
 fields that carry protocol control information, such as the length of
 SNDU, Receiver address, multiplexing information, payload type,
 sequence numbers, etc.  The SNDU payload is typically followed by a
 trailer, which carries an Integrity Check (e.g., Cyclic Redundancy
 Check, CRC).  Some protocols also add additional control information
 and/or padding to or after the trailer (figure 4).
             +--------+-------------------------+-----------------+
             | Header |             PDU         | Integrity Check |
             +--------+-------------------------+-----------------+
             <--------------------- SNDU ------------------------->
      Figure 4: Encapsulation of a subnetwork PDU (e.g., IPv4 or IPv6
                packet) to form an MPEG-2 Payload Unit.
 Examples of existing encapsulation/convergence protocols include ATM
 AAL5 [ITU-AAL5] and MPEG-2 MPE [ETSI-DAT].
 When required, an SNDU may be fragmented across a number of TS
 Packets (figure 5).

Montpetit, et al. Informational [Page 16] RFC 4259 IP Transport over MPEG-2 Networks November 2005

                 +-----------------------------------------+
                 |Encap Header|SubNetwork Data Unit (SNDU) |
                 +-----------------------------------------+
                /         /                          \      \
               /         /                            \      \
              /         /                              \      \
      +------+----------+  +------+----------+   +------+----------+
      |MPEG-2| MPEG-2   |..|MPEG-2| MPEG-2   |...|MPEG-2| MPEG-2   |
      |Header| Payload  |  |Header| Payload  |   |Header| Payload  |
      +------+----------+  +------+----------+   +------+----------+
       Figure 5: Encapsulation of a PDU (e.g., IP packet) into a
                 Series of MPEG-2 TS Packets.  Each TS Packet carries
                 a header with a common Packet ID (PID) value denoting
                 the MPEG-2 TS Logical Channel.
 The DVB family of standards currently defines a mechanism for
 transporting an IP packet, or Ethernet frame using the Multi-Protocol
 Encapsulation (MPE) [ETSI-DAT].  An equivalent scheme is also
 supported in ATSC [ATSC-DAT, ATSC-DATG].  It allows transmission of
 IP packets or (by using LLC) Ethernet frames by encapsulation within
 a Table Section (with the format used by the control plane associated
 with the MPEG-2 transmission).  The MPE specification includes a set
 of optional header components and requires decoding of the control
 headers.  This processing is suboptimal for Internet traffic, since
 it incurs significant receiver processing overhead and some extra
 link overhead [CLC99].
 The existing standards carry heritage from legacy implementations.
 These have reflected the limitations of technology at the time of
 their deployment (e.g., design decisions driven by audio/video
 considerations rather than IP networking requirements).  IPv6, MPLS,
 and other network-layer protocols are not natively supported.
 Together, these justify the development of a new encapsulation that
 will be truly IP-centric.  Carrying IP packets over a TS Logical
 Channel involves several convergence protocol functions.  This
 section briefly describes these functions and highlights the
 requirements for a new encapsulation.

4.1. Payload Unit Delimitation

 MPEG-2 indicates the start of a Payload Unit (PU) in a new TS Packet
 with a "payload_unit_start_indicator" (PUSI) [ISO-MPEG] carried in
 the 4B TS Packet header.  The PUSI is a 1 bit flag that has normative
 meaning [ISO-MPEG] for TS Packets that carry PES Packets or PSI/SI
 data.

Montpetit, et al. Informational [Page 17] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 When the payload of a TS Packet contains PES data, a PUSI value of
 '1' indicates the TS Packet payload starts with the first byte of a
 PES Packet.  A value of '0' indicates that no PES Packet starts in
 the TS Packet.  If the PUSI is set to '1', then one, and only one,
 PES Packet starts in the TS Packet.
 When the payload of the TS Packet contains PSI data, a PUSI value of
 '1' indicates the first byte of the TS Packet payload carries a
 Payload Pointer (PP) that indicates the position of the first byte of
 the Payload Unit (Table Section) being carried; if the TS Packet does
 not carry the first byte of a Table Section, the PUSI is set to '0',
 indicating that no Payload Pointer is present.
 Using this PUSI bit, the start of the first Payload Unit in a TS
 Packet is exactly known by the Receiver, unless that TS Packet has
 been corrupted or lost in the transmission.  In which case, the
 payload is discarded until the next TS Packet is received with a PUSI
 value of '1'.
 The encapsulation should allow packing of more than one SNDU into the
 same TS Packet and should not limit the number of SNDUs that can be
 sent in a TS Packet.  In addition, it should allow an IP Encapsulator
 to insert padding when there is an incomplete TS Packet payload.  A
 mechanism needs to be identified to differentiate this padding from
 the case where another encapsulated SNDU follows.
 A combination of the PUSI and a Length Indicator (see below) allows
 an efficient MPEG-2 convergence protocol to receive accurate
 delineation of packed SNDUs.  The MPEG-2 standard [ISO-MPEG] does not
 specify how private data should use the PUSI bit.

4.2. Length Indicator

 Most services using MPEG-2 include a length field in the Payload Unit
 header to allow the Receiver to identify the end of a Payload Unit
 (e.g., PES Packet, Section, or an SNDU).
 When parts of more than two Payload Units are carried in the same TS
 Packet, only the start of the first is indicated by the Payload
 Pointer.  Placement of a Length Indicator in the encapsulation header
 allows a Receiver to determine the number of bytes until the start of
 the next encapsulated SNDU.  This placement also provides the
 opportunity for the Receiver to pre-allocate an appropriate-sized
 memory buffer to receive the reassembled SNDU.
 A Length Indicator is required, and should be carried in the
 encapsulation header.  This should support SNDUs of at least the MTU
 size offered by Ethernet (currently 1500 bytes).  Although the IPv4

Montpetit, et al. Informational [Page 18] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 and IPv6 packet format permits an IP packet of size up to 64 KB, such
 packets are seldom seen on the current Internet.  Since high speed
 links are often limited by the packet forwarding rate of routers,
 there has been a tendency for Internet core routers to support MTU
 values larger than 1500 bytes.  A value of 16 KB is not uncommon in
 the core of the current Internet.  This would seem a suitable maximum
 size for an MPEG-2 transmission network.

4.3. Next Level Protocol Type

 Any IETF-defined encapsulation protocol should identify the payload
 type being transported (e.g., to differentiate IPv4, IPv6, etc).
 Most protocols use a type field to identify a specific process at the
 next higher layer that is the originator or the recipient of the
 payload (SNDU).  This method is used by IPv4, IPv6, and also by the
 original Ethernet protocol (DIX).  OSI uses the concept of a
 'Selector' for this, (e.g., in the IEEE 802/ISO 8802 standards for
 CSMA/CD [LLC]; although in this case, a SNAP (subnetwork access
 protocol) header is also required for IP packets.
 A Next Level Protocol Type field is also required if compression
 (e.g., Robust Header Compression [RFC3095]) is supported.  No
 compression method has currently been defined that is directly
 applicable to this architecture, however the ROHC framework defines a
 number of header compression techniques that may yield considerable
 improvement in throughput on links that have a limited capacity.
 Since many MPEG-2 Transmission Networks are wireless, the ROHC
 framework will be directly applicable for many applications.  The
 benefit of ROHC is greatest for smaller SNDUs but does imply the need
 for additional processing at the Receiver to expand the received
 compressed packets.  The selected type field should contain
 sufficient code points to support this technique.
 It is thus a requirement to include a Next Level Protocol Type field
 in the encapsulation header.  Such a field should specify values for
 at least IPv4, IPv6, and must allow for other values (e.g., MAC-level
 bridging).

4.4. L2 Subnet Addressing

 In MPEG-2, the PID carried in the TS Packet header is used to
 identify individual services with the help of SI tables.  This was
 primarily intended as a unidirectional (simplex) broadcast system.  A
 TS Packet stream carries either tables or one PES Packet stream
 (i.e., compressed video or audio).  Individual Receivers are not
 addressable at this level.

Montpetit, et al. Informational [Page 19] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 IPv4 and IPv6 allocate addresses to end hosts and intermediate
 systems (routers).  Each system (or interface) is identified by a
 globally assigned address.  ISO uses the concept of a hierarchically
 structured Network Service Access Point (NSAP) address to identify an
 end host user process in an Internet environment.
 Within a local network, a completely different set of addresses for
 the Network Point of Attachment (NPA) is used; frequently these NPA
 addresses are referred to as Medium Access Control, MAC-level
 addresses.  In the Internet they are also called hardware addresses.
 Whereas network layer addresses are used for routing, NPA addresses
 are primarily used for Receiver identification.
 Receivers may use the NPA of a received SNDU to reject unwanted
 unicast packets within the (software) interface driver at the
 Receiver, but must also perform forwarding checks based on the IP
 address.  IP multicast and broadcast may also filter using the NPA,
 but Receivers must also filter unwanted packets at the network layer
 based on source and destination IP addresses.  This does not imply
 that each IP address must map to a unique NPA (more than one IP
 address may map to the same NPA).  If a separate NPA address is not
 required, the IP address is sufficient for both functions.
 If it is required to address an individual Receiver in an MPEG-2
 transport system, this can be achieved either at the network level
 (IP address) or via a hardware-level NPA address (MAC-address).  If
 both addresses are used, they must be mapped in either a static or a
 dynamic way (e.g., by an address resolution process).  A similar
 requirement may also exist to identify the PID and TS multiplex on
 which services are carried.
 Using an NPA address in an MPEG-2 TS may enhance security, in that a
 particular PDU may be targeted for a particular Receiver by
 specifying the corresponding Receiver NPA address.  However, this is
 only a weak form of security, since the NPA filtering is often
 reconfigurable (frequently performed in software), and may be
 modified by a user to allow reception of specified (or all) packets,
 similar to promiscuous mode operation in Ethernet.  If security is
 required, it should be applied at another place (e.g., link
 encryption, authentication of address resolution, IPsec, transport
 level security and/or application level security).
 There are also cases where the use of an NPA is required (e.g., where
 a system operates as a router) and, if present, this should be
 carried in an encapsulation header where it may be used by Receivers
 as a pre-filter to discard unwanted SNDUs.  The addresses allocated
 do not need to conform to the IEEE MAC address format.  There are
 many cases where an NPA is not required, and network layer filtering

Montpetit, et al. Informational [Page 20] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 may be used.  Therefore, a new encapsulation protocol should support
 an optional NPA.

4.5. Integrity Check

 For the IP service, the probability of undetected packet error should
 be small (or negligible) [RFC3819].  Therefore, there is a need for a
 strong integrity check (e.g., Cyclic Redundancy Check or CRC) to
 verify correctness of a received PDU [RFC3819].  Such checks should
 be sufficient to detect incorrect operation of the encapsulator and
 Receiver (including reassembly errors following loss/corruption of TS
 Packets), in addition to protecting from loss and/or corruption by
 the transmission network (e.g., multiplexors and links).
 Mechanisms exist in MPEG-2 Transmission Networks that may assist in
 detecting loss (e.g., the 4-bit continuity counter included in the
 MPEG-2 TS Packet header).
 An encapsulation must provide a strong integrity check for each IP
 packet.  The requirements for usage of a link CRC are provided in
 [RFC3819].  To ease hardware implementation, this check should be
 carried in a trailer following the SNDU.  A CRC-32 is sufficient for
 operation with up to a 12 KB payload, and may still provide adequate
 protection for larger payloads.

4.6. Identification of Scope.

 The MPE section header contains information that could be used by the
 Receiver to identify the scope of the (MAC) address carried as an
 NPA, and to prevent TS Packets intended for one scope from being
 received by another.  Similar functionality may be achieved by
 ensuring that only IP packets that do not have overlapping scope are
 sent on the same TS Logical Channel.  In some cases, this may imply
 the use of multiple TS Logical Channels.

4.7. Extension Headers

 The evolution of the Internet service may require additional
 functions in the future.  A flexible protocol should therefore
 provide a way to introduce new features when required, without having
 to provide additional out-of-band configuration.
 IPv6 introduced the concept of extension headers that carry extra
 information necessary/desirable for certain subnetworks.  The DOCSIS
 cable specification also allows a MAC header to carry extension
 headers to build operator-specific services.  Thus, it is a
 requirement for the new encapsulation to allow extension headers.

Montpetit, et al. Informational [Page 21] RFC 4259 IP Transport over MPEG-2 Networks November 2005

4.8. Summary of Requirements for Encapsulation

 The main requirements for an IP-centric encapsulation include:
  1. support of IPv4 and IPv6 packets
  2. support for Ethernet encapsulated packets
  3. flexibility to support other IP formats and protocols (e.g.,

ROHC, MPLS)

  1. easy implementation using either hardware or software

processing

  1. low overhead/managed overhead
  2. a fully specified algorithm that allows a sender to pack

multiple packets per SNDU and to easily locate packet

         fragments
       - extensibility
       - compatibility with legacy deployments
       - ability to allow link encryption, when required
       - capability to support a full network architecture including
         data, control, and management planes

5. Address Resolution Functions

 Address Resolution (AR) provides a mechanism that associates layer 2
 (L2) information with the IP address of a system [IPDVB-AR].  Many L2
 technologies employ unicast AR at the sender: an IP system wishing to
 send an IP packet encapsulates it and places it into an L2 frame.  It
 then identifies the appropriate L3 adjacency (e.g., next hop router,
 end host) and determines the appropriate L2 adjacency (e.g., MAC
 address in Ethernet) to which the frame should be sent so that the
 packet gets across the L2 link.
 The L2 addresses discovered using AR are normally recorded in a data
 structure known as the arp/neighbor cache.  The results of previous
 AR requests are usually cached.  Further AR protocol exchanges may be
 required as communication proceeds to update or re-initialize the
 client cache state contents (i.e., purge/refresh the contents).  For
 stability, and to allow network topology changes and client faults,
 the cache contents are normally "soft state"; that is, they are aged
 with respect to time and old entries are removed.
 In some cases (e.g., ATM, X.25, MPEG-2 and many more), AR involves
 finding other information than the MAC address.  This includes
 identifying other parameters required for L2 transmission, such as
 channel IDs (VCs in X.25, VCIs in ATM, or PIDs in MPEG-2 TS).

Montpetit, et al. Informational [Page 22] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 Address resolution has different purposes for unicast and multicast.
 Multicast address resolution is not required for many L2 networks,
 but is required where MPEG-2 transmission networks carry IP multicast
 packets using more than one TS Logical Channel.

5.1. Address Resolution for MPEG-2

 There are three elements to the L2 information required to perform AR
 before an IP packet is sent over an MPEG-2 TS.  These are:
    (i)   A Receiver ID (e.g., a 6B MAC/NPA address).
    (ii)  A PID or index to find a PID.
    (iii) Tuner information (e.g., Transmit Frequency of the
          physical layer of a satellite/broadcast link
 Elements (ii) and (iii) need to be de-referenced when the MPEG-2
 Transmission Network includes (re)multiplexors that renumber the PID
 values of the TS Logical Channels that they process.  In MPEG-2
 [ISO-MPEG], this dereferencing is via indexes to the information
 (i.e., the Program Map Table, PMT, which is itself indexed via the
 Program Association Table, PAT).  (Note that PIDs are not intended to
 be end-to-end identifiers.)  However, although remultiplexing is
 common in broadcast TV networks (scenarios A and B), many private
 networks do not need to employ multiplexors that renumber PIDs (see
 Section 3.3).
 The third element (iii) allows an AR client to resolve to a different
 MPEG TS Multiplex.  This is used when there are several channels that
 may be used for communication (i.e., multiple outbound/inbound
 links).  In a mesh system, this could be used to determine
 connectivity.  This AR information is used in two ways at a Receiver:
 (i)  AR resolves an IP unicast or IPv4 broadcast address to the (MPEG
      TS Multiplex, PID, MAC/NPA address).  This allows the Receiver
      to set L2 filters to let traffic pass to the IP layer.  This is
      used for unicast, and IPv4 subnet broadcast.
 (ii) AR resolves an IP multicast address to the (MPEG TS Multiplex,
      PID, MAC/NPA address), and allows the Receiver to set L2 filters
      enabling traffic to pass to the IP layer.  A Receiver in an
      MPEG-2 TS Transmission Network needs to resolve the PID value
      and the tuning (if present) associated with a TS Logical Channel
      and (at least for unicast) the destination Receiver NPA address.
 A star topology MPEG-2 TS transmission network is illustrated below,
 with two Receivers receiving a forward broadcast channel sent by a
 Hub.  (A mesh system has some additional cases.)  The forward
 broadcast channel consists of a "TS Multiplex" (a single physical

Montpetit, et al. Informational [Page 23] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 bearer) allowing communication with the terminals.  These communicate
 using a set of return channels.
        Forward broadcast
        MPEG-2 TS         \
           ----------------X       /-----\
                          /       /       \
                                 | Receiver|
                      /----------+    A    |
                     /            \       /
         /-----\    /              \-----/
        /       \  /
       |   Hub   |/
       |         +\                /-----\
        \       /  \              /       \
         \-----/    \            | Receiver|
                     \-----------+    B    |
                                  \       /
                                   \-----/
     Figure 6: MPEG-2 Transmission Network with 2 Receivers
 There are three possibilities for unicast AR:
 (1) A system at a Receiver, A, needs to resolve an address of a
     system that is at the Hub;
 (2) A system at a Receiver, A, needs to resolve an address that is at
     another Receiver, B;
 (3) A host at the Hub needs to resolve an address that is at a
     Receiver.  The sender (encapsulation gateway), uses AR to provide
     the MPEG TS Multiplex, PID, MAC/NPA address for sending unicast,
     IPv4 subnet broadcast and multicast packets.
 If the Hub is an IP router, then case (1) and (2) are the same:  The
 host at the Receiver does not know the difference.  In these cases,
 the address to be determined is the L2 address of the device at the
 Hub to which the IP packet should be forwarded, which then relays the
 IP packet back to the forward (broadcast) MPEG-2 channel after AR
 (case 3).
 If the Hub is an L2 bridge, then case 2 still has to relay the IP
 packet back to the outbound MPEG-2 channel.  The AR protocol needs to
 resolve the specific Receiver L2 MAC address of B, but needs to send
 this on an L2 channel to the Hub.  This requires Receivers to be
 informed of the L2 address of other Receivers.

Montpetit, et al. Informational [Page 24] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 An end host connected to the Hub needs to use the AR protocol to
 resolve the Receiver terminal MAC/NPA address.  This requires the AR
 server at the Hub to be informed of the L2 addresses of other
 Receivers.

5.2. Scenarios for MPEG AR

 An AR protocol may transmit AR information in three distinct ways:
    (i)   An MPEG-2 signalling table transmitted at the MPEG-2 level
          (e.g., within the control plane using a Table);
    (ii)  An MPEG-2 signalling table transmitted at the IP level (no
          implementations of this are known);
    (iii) An address resolution protocol transported over IP (as in ND
          for IPv6)
 There are three distinct cases in which AR may be used:
 (i)   Multiple TS-Muxes and the use of re-multiplexors, e.g., Digital
       Terrestrial, Satellite TV broadcast multiplexes.  Many such
       systems employ remultiplexors that modify the PID values
       associated with TS Logical Channels as they pass through the
       MPEG-2 transmission network (as in Scenario A of Section 3.1).
 (ii)  Tuner configuration(s) that are fixed or controlled by some
       other process.  In these systems, the PID value associated with
       a TS Logical Channel may be known by the Sender.
 (iii) A service run over one TS Mux (i.e., uses only one PID, for
       example DOCSIS and some current DVB-RCS multicast systems).  In
       these systems, the PID value of a TS Logical Channel may be
       known by the Sender.

5.2.1. Table-Based AR over MPEG-2

 In current deployments of MPEG-2 networks, information about the set
 of MPEG-2 TS Logical Channels carried over a TS Multiplex is usually
 distributed via tables (service information, SI) sent using channels
 assigned a specific (well-known) set of PIDs.  This was originally
 designed for audio/video distribution to STBs.  This design requires
 access to the control plane by processing the SI table information
 (carried in MPEG-2 section format [ISO-DSMCC]).  The scheme reflects
 the complexity of delivering and coordinating the various TS Logical
 Channels associated with a multimedia TV program.

Montpetit, et al. Informational [Page 25] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 One possible requirement to provide TS multiplex and PID information
 for IP services is to integrate additional information into the
 existing MPEG-2 tables, or to define additional tables specific to
 the IP service.  The DVB INT and the A/92 Specification from ATSC
 [ATSC-A92] are examples of the realization of such a solution.

5.2.2. Table-Based AR over IP

 AR information could be carried over a TS data channel (e.g., using
 an IP protocol similar to the Service Announcement Protocol, SAP).
 Implementing this independently of the SI tables would ease
 implementation, by allowing it to operate on systems where IP
 processing is performed in a software driver.  It may also allow the
 technique to be more easily adapted to other similar delivery
 networks.  It also is advantageous for networks that use the MPEG-2
 TS, but do not necessarily support audio/video services and therefore
 do not need to provide interoperability with TV equipment (e.g.,
 links used solely for connecting IP (sub)networks).

5.2.3. Query/Response AR over IP

 A query/response protocol may be used at the IP level (similar to, or
 based on IPv6 Neighbor Advertisements of the ND protocol).  The AR
 protocol may operate over an MPEG-2 TS Logical Channel using a
 previously agreed PID (e.g., configured, or communicated using a SI
 table).  In this case, the AR could be performed by the target system
 itself (as in ARP and ND).  This has good soft-state properties, and
 is very tolerant to failures.  To find an address, a system sends a
 "query" to the network, and the "target" (or its proxy) replies.

5.3. Unicast Address Scoping

 In some cases, an MPEG-2 Transmission Network may support multiple IP
 networks.  When this is the case, it is important to recognize the
 context (scope) within which an address is resolved, to prevent
 packets from one addressed scope from leaking into other scopes.
 An example of overlapping IP address assignments is the use of
 private unicast addresses (e.g., in IPv4, 10/8 prefix; 172.16/12
 prefix; 192.168/16 prefix).  These should be confined to the area to
 which they are addressed.
 There is also a requirement for multicast address scoping (Section
 6.2).

Montpetit, et al. Informational [Page 26] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 IP packets with these addresses must not be allowed to travel outside
 their intended scope, and may cause unexpected behaviour if allowed
 to do so.  In addition, overlapping address assignments can arise
 when using level 2 NPA addresses:
 (i)    The NPA address must be unique within the TS Logical Channel.
        Universal IEEE MAC addresses used in Ethernet LANs are
        globally unique.  If the NPA addresses are not globally
        unique, the same NPA address may be re-used by Receivers in
        different addressed areas.
 (ii)   The NPA broadcast address (all 1s MAC address).  Traffic with
        this address should be confined to one addressed area.
 Reception of unicast packets destined for another addressed area may
 lead to an increase in the rate of received packets by systems
 connected via the network.  IP end hosts normally filter received
 unicast IP packets based on their assigned IP address.  Reception of
 the additional network traffic may contribute to processing load but
 should not lead to unexpected protocol behaviour.  However, it does
 introduce a potential Denial of Service (DoS) opportunity.
 When the Receiver acts as an IP router, the receipt of such an IP
 packet may lead to unexpected protocol behaviour.  This also provides
 a security vulnerability since arbitrary packets may be passed to the
 IP layer.

5.4. AR Authentication

 In many AR designs, authentication has been overlooked because of the
 wired nature of most existing IP networks, which makes it easy to
 control hosts that are physically connected [RFC3819].  With wireless
 connections, this is changing: unauthorized hosts actually can claim
 L2 resources.  The address resolution client (i.e., Receiver) may
 also need to verify the integrity and authenticity of the AR
 information that it receives.  There are trust relationships both
 ways: clients need to know they have a valid server and that the
 resolution is valid.  Servers should perform authorisation before
 they allow an L2 address to be used.
 The MPEG-2 Transmission Network may also require access control to
 prevent unauthorized use of the TS Multiplex; however, this is an
 orthogonal issue to address resolution.

Montpetit, et al. Informational [Page 27] RFC 4259 IP Transport over MPEG-2 Networks November 2005

5.5. Requirements for Unicast AR over MPEG-2

 The requirement for AR over MPEG-2 networks include:
 (i)    Use of a table-based approach to promote AR scaling.  This
        requires definition of the frequency of update and volume of
        AR traffic generated.
 (ii)   Mechanisms to install AR information at the server
        (unsolicited registration).
 (iii)  Mechanisms to verify AR information held at the server
        (solicited responses).  Appropriate timer values need to be
        defined.
 (iv)   An ability to purge client AR information (after IP network
        renumbering, etc.).
 (v)    Support of IP subnetwork scoping.
 (vi)   Appropriate security associations to authenticate the sender.

6. Multicast Support

 This section addresses specific issues concerning IPv4 and IPv6
 multicast [RFC1112] over MPEG-2 Transmission Networks.  The primary
 goal of multicast support will be efficient filtering of IP multicast
 packets by the Receiver, and the mapping of IPv4 and IPv6 multicast
 addresses [RFC3171] to the associated PID value and TS Multiplex.
 The design should permit a large number of active multicast groups,
 and should minimize the processing load at the Receiver when
 filtering and forwarding IP multicast packets.  For example, schemes
 that may be easily implemented in hardware would be beneficial, since
 these may relieve drivers and operating systems from discarding
 unwanted multicast traffic [RFC3819].
 Multicast mechanisms are used at more than one protocol level.  The
 upstream router feeding the MPEG-2 Encapsulator may forward multicast
 traffic on the MPEG-2 TS Multiplex using a static or dynamic set of
 groups.  When static forwarding is used, the set of IP multicast
 groups may also be configured or set using SNMP, Telnet, etc.  A
 Receiver normally uses either an IP group management protocol (IGMP
 [RFC3376] for IPv4 or MLD [RFC2710][RFC3810] for IPv6) or a multicast
 routing protocol to establish tables that it uses to dynamically
 enable local forwarding of received groups.  In a dynamic case, this

Montpetit, et al. Informational [Page 28] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 group membership information is fed back to the sender to enable it
 to start sending new groups and (if required) to update the tables
 that it produces for multicast AR.
 Appropriate procedures need to identify the correct action when the
 same multicast group is available on more than one TS Logical
 Channel.  This could arise when different end hosts act as senders to
 contribute IP packets with the same IP group destination address.
 The correct behaviour for SSM [RFC3569] addresses must also be
 considered.  It may also arise when a sender duplicates the same IP
 group over several TS Logical Channels (or even different TS
 Multiplexes), and in this case a Receiver may potentially receive
 more than one copy of the same packet.  At the IP level, the
 host/router may be unaware of this duplication.

6.1. Multicast AR Functions

 The functions required for multicast AR may be summarized as:
 (i)  The Sender needs to know the L2 mapping of a multicast group.
 (ii) The Receiver needs to know the L2 mapping of a multicast group.
 In the Internet, multicast AR is normally a mapping function rather
 than a one-to-one association using a protocol.  In Ethernet, the
 sender maps an IP address to an L2 MAC address, and the Receiver uses
 the same mapping to determine the L2 address to set an L2
 hardware/software filter entry.
 A typical sequence of actions for the dynamic case is:
    L3) Populate the IP L3 membership tables at the Receiver.
    L3) Receivers send/forward IP L3 membership tables to the Hub
    L3) Dynamic/static forwarding at hub/upstream router of IP L3
        groups
    L2) Populate the IP AR tables at the encapsulator gateway
        (i.e., Map IP L3 mcast groups to L2 PIDs)
    L2) Distribute the AR information to Receivers
    L2) Set Receiver L2 multicast filters for IP groups in the
        membership table.

Montpetit, et al. Informational [Page 29] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 To be flexible, AR must associate a TS Logical Channel (PID) not only
 with a group address, but possibly also a QoS class and other
 appropriate MPEG-2 TS attributes.  Explicit per group AR to
 individual L2 addresses is to be avoided.
         \
          |
      +---+----+   +---------+
      |  Tuner |---+TS Table | . . . .
      +---+----+   +---------+       .
          |                        - .
      +--------+   +---------+       .
      | deMux  |---+PID Table|........
      +---+----+   +---------+       :
          |                        - :
      +--------+   +---------+   +------------+
      |MPE/ULE |---+AR Cache-|---+  L2 Table  |
      +---+----+   +---------+   +------------+
          |            |            |
      +---+----+   +---+-----+   +---+----+
      |  IP    |   |  AR     |   |IGMP/MLD|
      +---+----+   +---+-----+   +---+----+
          |            |            |
          *------------+------------+
     Figure 7: Receiver Processing Architecture

6.2. Multicast Address Scoping

 As in unicast, it is important to recognize the context (scope)
 within which a multicast IP address is resolved, to prevent packets
 from one addressed scope leaking into other scopes.
 Examples of overlapping IP multicast address assignments include:
 (i)    Local scope multicast addresses.  These are
        only valid within the local area (examples for IPv4
        include: 224.0.0/24; 224.0.1/24).  Similar cases
        exist for some IPv6 multicast addresses [RFC2375].
 (ii)   Scoped multicast addresses [RFC2365] [RFC 2375].  Forwarding
        of these addresses is controlled by the scope associated
        with the address.  The addresses are only valid with an
        addressed area (e.g. the 239/8 [RFC2365]).
 (iii)  Other non-IP protocols may also view sets of MAC multicast
        addresses as link-local, and may produce unexpected results
        if distributed across several private networks.

Montpetit, et al. Informational [Page 30] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 IP packets with these addresses must not be allowed to travel outside
 their intended scope (see Section 5.3).  Performing multicast AR at
 the IP level can enable providers to offer independently scoped
 addresses and would need to use multiple Multicast AR servers, one
 per multicast domain.

6.3. Requirements for Multicast over MPEG-2

 The requirements for supporting multicast include, but are not
 restricted to:
    (i)    Encapsulating multicast packets for transmission using an
           MPEG-2 TS.
    (ii)   Mapping IP multicast groups to the underlying MPEG-2 TS
           Logical Channel (PID) and the MPEG-2 TS Multiplex.
    (iii)  Providing AR information to allow a Receiver to locate an
           IP multicast flow within an MPEG-2 TS Multiplex.
    (iv)   Error Reporting.

7. Summary

 This document describes the architecture for a set of protocols to
 perform efficient and flexible support for IP network services over
 networks built upon the MPEG-2 Transport Stream (TS).  It also
 describes existing approaches.  The focus is on IP networking, the
 mechanisms that are used, and their applicability to supporting IP
 unicast and multicast services.
 The requirements for a new encapsulation of IPv4 and IPv6 packets is
 described, outlining the limitations of current methods and the need
 for a streamlined IP-centric approach.
 The architecture also describes MPEG-2 Address Resolution (AR)
 procedures to allow dynamic configuration of the sender and Receiver
 using an MPEG-2 transmission link/network.  These support IPv4 and
 IPv6 services in both the unicast and multicast modes.  Resolution
 protocols will support IP packet transmission using both the
 Multiprotocol Encapsulation (MPE), which is currently widely
 deployed, and also any IETF-defined encapsulation (e.g., ULE
 [IPDVB-ULE]).

Montpetit, et al. Informational [Page 31] RFC 4259 IP Transport over MPEG-2 Networks November 2005

8. Security Considerations

 When the MPEG-2 transmission network is not using a wireline network,
 the normal security issues relating to the use of wireless links for
 transport of Internet traffic should be considered [RFC3819].
 End-to-end security (including confidentiality, authentication,
 integrity and access control) is closely associated with the end user
 assets that are protected.  This close association cannot be ensured
 when providing security mechanisms only within a subnetwork (e.g., an
 MPEG-2 Transmission Network).  Several security mechanisms that can
 be used end-to-end have already been deployed in the general Internet
 and are enjoying increasing use.  Important examples include:
  1. Transport Layer Security (TLS), which is primarily used to

protect web commerce;

  1. Pretty Good Privacy (PGP) and S/MIME, primarily used to protect

and authenticate email and software distributions;

  1. Secure Shell (SSH), used to secure remote access and file

transfer;

  1. IPsec, a general purpose encryption and authentication mechanism

above IP that can be used by any IP application.

 However, subnetwork security is also important [RFC3819] and should
 be encouraged, on the principle that it is better than the default
 situation, which all too often is no security at all.  Users of
 especially vulnerable subnets (such as radio/broadcast networks
 and/or shared media Internet access) often have control over, at
 most, one endpoint - usually a client - and therefore cannot enforce
 the use of end-to-end mechanisms.
 A related role for subnetwork security is to protect users against
 traffic analysis, i.e., identifying the communicating parties (by IP
 or MAC address) and determining their communication patterns, even
 when their actual contents are protected by strong end-to-end
 security mechanisms.  (This is important for networks such as
 broadcast/radio, where eavesdropping is easy.)
 Encryption performed at the Transport Stream (encrypting the payload
 of all TS-Packets with the same PID) encrypts/scrambles all parts of
 the SNDU, including the layer 2 MAC/NPA address.  Encryption at the
 section level in MPE may also optionally encrypt the layer 2 MAC/NPA
 address in addition to the PDU data [ETSI-DAT].  In both cases,
 encryption of the MAC/NPA address requires a Receiver to decrypt all
 encrypted data, before it can then filter the PDUs with the set of

Montpetit, et al. Informational [Page 32] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 MAC/NPA addresses that it wishes to receive.  This method also has
 the drawback that all Receivers must share a common encryption key.
 Encryption of the MPE MAC address is therefore not permitted in some
 systems (e.g., [ETSI-DVBRCS]).
 Where it is possible for an attacker to inject traffic into the
 subnetwork control plane, subnetwork security can additionally
 protect the subnetwork assets.  This threat must specifically be
 considered for the protocols used for subnetwork control functions
 (e.g., address resolution, management, configuration).  Possible
 threats include theft of service and denial of service; shared media
 subnets tend to be especially vulnerable to such attacks [RFC3819].
 Appropriate security functions must therefore be provided for IPDVB
 control protocols [RFC3819], particularly when the control functions
 are provided above the IP-layer using IP-based protocols.  Internet
 level security mechanisms (e.g., IPsec) can mitigate such threats.
 In general, End-to-End security is recommended for users of any
 communication path, especially when it includes a wireless/radio or
 broadcast link, where a range of security techniques already exist.
 Specification of security mechanisms at the application layer, or
 within the MPEG-2 transmission network, are the concerns of
 organisations beyond the IETF.  The complexity of any such security
 mechanisms should be considered carefully so that it will not unduly
 impact IP operations.

8.1. Link Encryption

 Link level encryption of IP traffic is commonly used in
 broadcast/radio links to supplement End-to-End security (e.g.,
 provided by TLS, SSH, Open PGP, S/MIME, IPsec).  The encryption and
 key exchange methods vary significantly, depending on the intended
 application.  For example, DVB-S/DVB-RCS operated by Access Network
 Operators may wish to provide their customers (Internet Service
 Providers, ISP) with security services.  Common security services
 are: terminal authentication and data confidentiality (for unicast
 and multicast) between an encapsulation gateway and Receivers.  A
 common objective is to provide the same level of privacy as
 terrestrial links.  An ISP may also wish to provide end-to-end
 security services to the end-users (based on well-known mechanisms
 such as IPsec).
 Therefore, it is important to understand that both security solutions
 (Access Network Operators to ISP and ISP to end-users) may coexist.

Montpetit, et al. Informational [Page 33] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 MPE supports optional link encryption [ETSI-DAT].  A pair of bits
 within the MPE protocol header indicate whether encryption
 (scrambling) is used.  For encrypted PDUs, the header bits indicate
 which of a pair of previously selected encryption keys is to be used.
 It is recommended that any new encapsulation defined by the IETF
 allows Transport Stream encryption and also supports optional link
 level encryption/authentication of the SNDU payload.  In ULE
 [IPDVB-ULE], this may be provided in a flexible way using Extension
 Headers.  This requires definition of a mandatory header extension,
 but has the advantage that it decouples specification of the security
 functions from the encapsulation functions.  This method also
 supports encryption of the NPA/MAC addresses.

9. IANA Considerations

 A set of protocols that meet these requirements will require the IANA
 to make assignments.  This document in itself, however, does not
 require any IANA involvement.

10. Acknowledgements

 The authors wish to thank Isabel Amonou, Torsten Jaekel, Pierre
 Loyer, Luoma Juha-Pekka, and Rod Walsh for their detailed inputs.  We
 also wish to acknowledge the input provided by the members of the
 IETF ipdvb WG.

11. References

11.1. Normative References

 [ISO-MPEG]     ISO/IEC DIS 13818-1:2000, "Information Technology;
                Generic Coding of Moving Pictures and Associated Audio
                Information Systems", International Standards
                Organisation (ISO).
 [ETSI-DAT]     EN 301 192, "Digital Video Broadcasting (DVB); DVB
                Specifications for Data Broadcasting", European
                Telecommunications Standards Institute (ETSI).

11.2. Informative References

 [ATSC]         A/53C, "ATSC Digital Television Standard", Advanced
                Television Systems Committee (ATSC), Doc. A/53C, 2004.
 [ATSC-DAT]     A/90, "ATSC Data Broadcast Standard", Advanced
                Television Systems Committee (ATSC), Doc. A/090, 2000.

Montpetit, et al. Informational [Page 34] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 [ATSC-DATG]    A/91, "Recommended Practice: Implementation Guidelines
                for the ATSC Data Broadcast Standard", Advanced
                Television Systems Committee (ATSC), Doc. A/91, 2001.
 [ATSC-A92]     A/92, "Delivery of IP Multicast Sessions over ATSC
                Data Broadcast", Advanced Television Systems Committee
                (ATSC), Doc. A/92, 2002.
 [ATSC-G]       A/54A, "Guide to the use of the ATSC Digital
                Television Standard", Advanced Television Systems
                Committee (ATSC), Doc. A/54A, 2003.
 [ATSC-PSIP-TC] A/65B, "Program and System Information Protocol for
                Terrestrial Broadcast and Cable", Advanced Television
                Systems Committee (ATSC), Doc. A/65B, 2003.
 [ATSC-S]       A/80, "Modulation and Coding Requirements for Digital
                TV (DTV) Applications over Satellite", Advanced
                Television Systems Committee (ATSC), Doc. A/80, 1999.
 [CLC99]        Clausen, H., Linder, H., and Collini-Nocker, B.,
                "Internet over Broadcast Satellites", IEEE Commun.
                Mag. 1999, pp.146-151.
 [ETSI-BSM]     TS 102 292, "Satellite Earth Stations and Systems
                (SES); Broadband Satellite Multimedia Services and
                Architectures; Functional Architecture for IP
                Interworking with BSM networks", European
                Telecommunications Standards Institute (ETSI).
 [ETSI-DVBC]    EN 300 800, "Digital Video Broadcasting (DVB); DVB
                interaction channel for Cable TV distribution systems
                (CATV)", European Telecommunications Standards
                Institute (ETSI).
 [ETSI-DVBRCS]  EN 301 790, "Digital Video Broadcasting (DVB);
                Interaction channel for satellite distribution
                systems", European Telecommunications Standards
                Institute (ETSI).
 [ETSI-DVBS]    EN 301 421,"Digital Video Broadcasting (DVB);
                Modulation and Coding for DBS satellite systems at
                11/12 GHz", European Telecommunications Standards
                Institute (ETSI).

Montpetit, et al. Informational [Page 35] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 [ETSI-DVBS2]   EN 302 207, "Second generation framing structure,
                channel coding and modulation systems for
                Broadcasting, Interactive Services,News Gathering and
                Other Broadband Satellite Applications", European
                Telecommunications Standards Institute (ETSI).
 [ETSI-DVBT]    EN 300 744, "Digital Video Broadcasting (DVB); Framing
                structure, channel coding and modulation for digital
                terrestrial television (DVB-T)", European
                Telecommunications Standards Institute (ETSI).
 [ETSI-IPDC]    "IP Datacast Specification", DVB Interim Specification
                CNMS 1026 v1.0.0,(Work in Progress), April 2004.
 [ETSI-MHP]     TS 101 812, "Digital Video Broadcasting (DVB);
                Multimedia Home Platform (MHP) Specification", v1.2.1,
                European Telecommunications Standards Institute
                (ETSI), June 2002.
 [ETSI-RC]      ETS 300 802, "Digital Video Broadcasting (DVB);
                Network-independent protocols for DVB interactive
                services", European Telecommunications Standards
                Institute (ETSI).
 [ETSI-SI]      EN 300 468, "Digital Video Broadcasting (DVB);
                Specification for Service Information (SI) in DVB
                systems", European Telecommunications Standards
                Institute (ETSI).
 [IPDVB-ULE]    Fairhurst, G. and B. Collini-Nocker, "Unidirectional
                Lightweight Encapsulation (ULE) for transmission of IP
                datagrams over an MPEG-2 Transport Stream", Work in
                Progress, June 2005.
 [IPDVB-AR]     Fairhurst, G. and M-J. Montpetit, "Address Resolution
                for IP datagrams over MPEG-2 networks", Work in
                Progress, 2005.
 [ISO-AUD]      ISO/IEC 13818-3:1995, "Information technology; Generic
                coding of moving pictures and associated audio
                information; Part 3: Audio", International Standards
                Organisation (ISO).
 [ISO-DSMCC]    ISO/IEC IS 13818-6, "Information technology; Generic
                coding of moving pictures and associated audio
                information; Part 6:  Extensions for DSM-CC",
                International Standards Organisation (ISO).

Montpetit, et al. Informational [Page 36] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 [ISO-VID]      ISO/IEC DIS 13818-2:1998, "Information technology;
                Generic coding of moving pictures and associated audio
                information; Video", International Standards
                Organisation (ISO).
 [ITU-AAL5]     ITU-T I.363.5, "B-ISDN ATM Adaptation Layer
                Specification Type AAL5", International Standards
                Organisation (ISO), 1996.
 [LLC]          ISO/IEC 8802.2, "Information technology;
                Telecommunications and information exchange between
                systems; Local and metropolitan area networks;
                Specific requirements; Part 2: Logical Link Control",
                International Standards Organisation (ISO), 1998.
 [MMUSIC-IMG]   Nomura, Y., Walsh, R., Luoma, J-P., Ott, J., and H.
                Schulzrinne, "Requirements for Internet Media Guides",
                Work in Progress, June 2004.
 [OPEN-CABLE]   "Open Cable Application Platform Specification; OCAP
                2.0 Profile", OC-SP-OCAP2.0-I01-020419, Cable Labs,
                April 2002.
 [RFC1112]      Deering, S., "Host extensions for IP multicasting",
                STD 5, RFC 1112, August 1989.
 [RFC2365]      Meyer, D., "Administratively Scoped IP Multicast", BCP
                23, RFC 2365, July 1998.
 [RFC2375]      Hinden, R. and S. Deering, "IPv6 Multicast Address
                Assignments", RFC 2375, July 1998.
 [RFC2710]      Deering, S., Fenner, W., and B. Haberman, "Multicast
                Listener Discovery (MLD) for IPv6", RFC 2710, October
                1999.
 [RFC2507]      Degermark, M., Nordgren, B., and S. Pink, "IP Header
                Compression", RFC 2507, February 1999.
 [RFC3077]      Duros, E., Dabbous, W., Izumiyama, H., Fujii, N., and
                Y. Zhang, "A Link-Layer Tunneling Mechanism for
                Unidirectional Links", RFC 3077, March 2001.

Montpetit, et al. Informational [Page 37] RFC 4259 IP Transport over MPEG-2 Networks November 2005

 [RFC3095]      Bormann, C., Burmeister, C., Degermark, M., Fukushima,
                H., Hannu, H., Jonsson, L-E., Hakenberg, R., Koren,
                T., Le, K., Liu, Z., Martensson, A., Miyazaki, A.,
                Svanbro, K., Wiebke, T., Yoshimura, T., and H. Zheng,
                "RObust Header Compression (ROHC): Framework and four
                profiles: RTP, UDP, ESP, and uncompressed", RFC 3095,
                July 2001.
 [RFC3171]      Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper,
                "IANA Guidelines for IPv4 Multicast Address
                Assignments", BCP 51, RFC 3171, August 2001.
 [RFC3376]      Cain, B., Deering, S., Kouvelas, I., Fenner, B., and
                A. Thyagarajan, "Internet Group Management Protocol,
                Version 3", RFC 3376, October 2002.
 [RFC3569]      Bhattacharyya, S., "An Overview of Source-Specific
                Multicast (SSM)", RFC 3569, July 2003.
 [RFC3810]      Vida, R. and L. Costa, "Multicast Listener Discovery
                Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
 [RFC3819]      Karn, P., Bormann, C., Fairhurst, G., Grossman, D.,
                Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J.,
                and L. Wood, "Advice for Internet Subnetwork
                Designers", BCP 89, RFC 3819, July 2004 .

Montpetit, et al. Informational [Page 38] RFC 4259 IP Transport over MPEG-2 Networks November 2005

Appendix A: MPEG-2 Encapsulation Mechanisms

 Transmitting packet data over an MPEG-2 transmission network requires
 that individual PDUs (e.g., IPv4, IPv6 packets, or bridged Ethernet
 Frames) are encapsulated using a convergence protocol.  The following
 encapsulations are currently standardized for MPEG-2 transmission
 networks:
   (i)  Multi-Protocol Encapsulation (MPE).
          The MPE specification of DVB [ETSI-DAT] uses private
          Sections for the transport of IP packets and uses
          encapsulation that is similar to the IEEE LAN/MAN standards
          [LLC].  Data packets are encapsulated in datagram sections
          that are compliant with the DSMCC section format for private
          data.  Some Receivers may exploit section processing
          hardware to perform a first-level filtering of the packets
          that arrive at the Receiver.
          This encapsulation makes use of a MAC-level Network Point of
          Attachment address.  The address format conforms to the
          ISO/IEEE standards for LAN/MAN [LLC].  The 48-bit MAC
          address field contains the MAC address of the destination;
          it is distributed over six 8-bit fields, labelled
          MAC_address_1 to MAC_address_6.  The MAC_address_1 field
          contains the most significant byte of the MAC address, while
          MAC_address_6 contains the least significant byte.  How many
          of these bytes are significant is optional and defined by
          the value of the broadcast descriptor table [ETSI-DAT] sent
          separately over another MPEG-2 TS within the TS multiplex.
          MPE is currently a widely deployed scheme.  Due to
          Investments in existing systems, usage is likely to continue
          in current and future MPEG-2 Transmission Networks.  ATSC
          provides a scheme similar to MPE [ATSC-DAT] with some small
          differences.
   (ii) Data Piping.
          The Data Piping profile [ETSI-DAT] is a minimum overhead,
          simple and flexible profile that makes no assumptions
          concerning the format of the data being sent.  In this
          profile, the Receiver is intended to provide PID filtering,
          packet reassembly according to [ETSI-SI], error detection,
          and optional Conditional Access (link encryption).

Montpetit, et al. Informational [Page 39] RFC 4259 IP Transport over MPEG-2 Networks November 2005

          The specification allows the user data stream to be
          unstructured or organized into packets.  The specific
          structure is transparent to the Receiver.  It may conform to
          any protocol, e.g., IP, Ethernet, NFS, FDDI, MPEG-2 PES,
          etc.
   (iii)  Data Streaming.
          The data broadcast specification profile [ETSI-DAT] for PES
          tunnels (Data Streaming) supports unicast and multicast data
          services that require a stream-oriented delivery of data
          packets.  This encapsulation maps an IP packet into a single
          PES Packet payload.
          Two different types of PES headers can be selected via the
          stream_id values [ISO-MPEG].  The private_stream_2 value
          permits the use of the short PES header with limited
          overhead, while the private_stream_1 value makes available
          the scrambling control and the timing and clock reference
          features of the PES layer.

Montpetit, et al. Informational [Page 40] RFC 4259 IP Transport over MPEG-2 Networks November 2005

Authors' Addresses

 Marie J. Montpetit
 Motorola Connected Home Solutions
 45 Hayden Avenue 4th Floor
 Lexington MA 02130
 USA
 EMail: mmontpetit@motorola.com
 Godred Fairhurst
 Department of Engineering
 University of Aberdeen
 Aberdeen, AB24 3UE
 UK
 EMail: gorry@erg.abdn.ac.uk
 Web: http://www.erg.abdn.ac.uk/users/gorry
 Horst D. Clausen
 TIC Systems
 Lawrence, Kansas
 EMail: h.d.clausen@ieee.org
 Bernhard Collini-Nocker
 Department of Scientific Computing
 University of Salzburg
 Jakob Haringer Str. 2
 5020 Salzburg
 Austria
 EMail: bnocker@cosy.sbg.ac.at
 Web: http://www.network-research.org
 Hilmar Linder
 Department of Scientific Computing
 University of Salzburg
 Jakob Haringer Str. 2
 5020 Salzburg
 Austria
 EMail: hlinder@cosy.sbg.ac.at
 Web: http://www.network-research.org

Montpetit, et al. Informational [Page 41] RFC 4259 IP Transport over MPEG-2 Networks November 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Montpetit, et al. Informational [Page 42]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4259.txt · Last modified: 2005/11/17 19:16 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki