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Versions: (draft-fairhurst-ipdvb-ule-ext) 00 01 02 03 04 05 06 07 RFC 5163

Internet Engineering Task Force                         Gorry Fairhurst
Internet Draft                                   University of Aberdeen
Expires July 2007                                     B. Collini-Nocker
                                                 University of Salzburg


Category: WG Draft intended for PS                           March 2007


       Extension Formats for Unidirectional Link Encapsulation (ULE)
              and the Generic Stream Encapsulation (GSE)
                     draft-ietf-ipdvb-ule-ext-01.txt

Status of this Draft

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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Abstract

   This document describes a set of Extension Headers for the
   Unidirectional Link Encapsulation (ULE) [RFC4236].

   The Extension Header formats defined in this document define new
   extensions that are common extensions to both ULE and the Generic
   Stream Encapsulation (GSE) [GSE] defined by the second generation
   framing structure DVB-S2 standard [S2].












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Table of Contents

   1. Introduction

   2. Conventions used in this document

   3. Description of method
       3.1 MPEG-2 TS-Concat Extension
       3.2 PDU-Concat Extension
       3.3 TimeStamp Extension

   4. Summary

   5. IANA Considerations

   6. Acknowledgments

   7. Security Considerations

   8. References
       8.1 Normative References
       8.2 Informative References

   9. Authors' Addresses

   10. IPR Notices
       10.1 Intellectual Property Statement
       10.2 Disclaimer of Validity


   11. Copyright Statement
       11.1 Intellectual Property Statement
       11.2 Disclaimer of Validity

   Appendix A:



















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1. Introduction

   This document describes two new Header Extensions that may be used
   with both Unidirectional Link Encapsulation, ULE, [RFC4236] and the
   Generic Stream Encapsulation (GSE) [GSE]. ULE is defined for links
   that employ the MPEG-2 Transport Stream, and supports a wide variety
   of physical-layer bearers [RFC4259].

   GSE has been designed for the Generic Mode (also known as the
   Generic Stream (GS)), offered by second-generation DVB physical
   layers, and specifically for DVB-S2 [ETSI-S2]. The requirements for
   the Generic Stream are defined in [S2-REQ], [S2-REQ-RCS], and [ID-
   S2-REQ]. The important characteristics of this encapsulation are
   described in an Appendix to this document. GSE maintains a design
   philosophy that presents a common network interface to that of ULE
   and uses a similar construction for Subnetwork Data Unit (SNDUs).

   One extension header defines a method that allows one or more TS-
   Packets [ISO-MPEG] to be sent within a ULE SNDU. This method may be
   used to provide control plane information including the transmission
   of MPEG-2 Program Specific Information (PSI) for the Multiplex. In
   GSE, there is no native support for transport stream packets and
   this method is therefore suitable for providing an MPEG-2 control
   plane.

   A second extension header allows one or more PDUs to be sent within
   the same ULE SNDU. This method is designed for cases where a large
   number of small PDUs are directed to the same Network Point of
   Attachment (NPA) address. The method may improve transmission
   efficiency (by removing duplicated MAC layer overhead). It can also
   reduce processing overhead for receivers that are not addressed by
   the NPA, since these receivers may then skip several PDUs in one
   operation. The method is defined as a generic extension header and
   may be used for IPv4 or IPv6 packets. If and when a compression
   format is defined for ULE or Ethernet, the method may also be used
   in combination with this method.

   A third extension header provides an optional timestamp value for an
   SNDU. Examples of the use of this timestamp option include
   monitoring and benchmarking of ULE and GSE links. Receivers that do
   not wish to decode (or do not support) the timestamp extension may
   discard the extension and process the remaining PDU or extension
   headers.

   The appendix includes a summary of key design issues and
   considerations based on the GSE Specification defined by the DVB
   Technical Module [GSE].







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2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   RFC 2119 [RFC2119].

   b: bit. For example, one byte consists of 8b.

   B: Byte. Groups of bytes are represented in Internet byte order.

   BBFrame payload [ETSI-S2]: The data field part of a Baseband frame
   that may be used for the communication of data. Typical BBFrames
   range in size from 3072 to 58192 bits according to the choice of
   modulation format and FEC in use.

   DVB: Digital Video Broadcast. A framework and set of
   associated standards published by the European Telecommunications
   Standards Institute (ETSI) for the transmission of video, audio, and
   data.

   Encapsulator: A network device that receives PDUs and formats these
   into Payload Units (known here as SNDUs) for output in DVB-S or the
   Generic Mode of DVB-S2.

   GS: Generic Stream [S2].

   GSE: Generic Stream Encapsulation [GSE].

   MAC: Medium Access Control [IEEE-802.3]. A link layer protocol
   defined by the IEEE 802.3 standard (or by Ethernet v2).

   MPEG-2: A set of standards specified by the Motion Picture Experts
   Group (MPEG), and standardized by the International Standards
   Organisation (ISO/IEC 113818-1) [ISO-MPEG], and ITU-T (in H.220).

   Next-Header: A Type value indicating an Extension Header [RFC4236].

   NPA: Network Point of Attachment [RFC4236]. In this document, refers
   to a destination address (resembling an IEEE MAC address) within the
   DVB-S/S2 transmission network that is used to identify individual
   Receivers or groups of Receivers.

   PDU: Protocol Data Unit [RFC4259]. Examples of a PDU include
   Ethernet frames, IPv4 or IPv6 datagrams, and other network packets.

   PSI: Program Specific Information [ISO-MPEG].

   SI Table: Service Information Table [ISO-MPEG]. In this document,
   this term describes a table that is been defined by another
   standards body to convey information about the services carried on a
   DVB carrier.


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   SNDU: Subnetwork Data Unit [RFC4259]. In this document this is an
   encapsulated PDU sent using ULE or GSE.

   Stream: A logical flow from an Encapsulator to a set of Receivers. .

   TS: Transport Stream [ISO-MPEG], a method of transmission at the
   MPEG-2 level using TS Packets; it represents layer 2 of the ISO/OSI
   reference model.

   ULE: Unidirectional Link Encapsulation (ULE) [RFC4236]. A scheme
   that encapsulates PDUs, into SNDUs that are sent in a series of TS
   Packets using a single TS Logical Channel. The encapsulation format
   defined by this document shares the same extension format, and basic
   processing rules and uses a common IANA Registry.








































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3. Description of the Method

   In ULE, a Type field value that is less than 1536 Decimal indicates
   an Extension Header.  This section describes a set of two extension
   formats for the ULE encapsulation. The GSE specification is defined
   in [GSE] and follows these formats, but as in other  SNDU formats,
   GSE does not include a per-SNDU CRC and utilises a different SNDU
   length calculation [GSE].


3.1 MPEG-2 TS-Concat Extension

   >>> IANA Action required, please replace < #NH-TS-CAT> with assigned
   value from the Next-Header Registry>>>

   The MPEG-2 TS-Concat Extension Header is specified by an IANA
   assigned H-Type value of <#NH-TS-CAT>. This is a Mandatory Next-
   Header Extension.

   The extension is used to transport 1 or more MPEG-2 TS Packets
   within a ULE SNDU. The number of TS Packets carried in a specific
   SNDU is determined from the size specified by the remainder of the
   Payload following the MPEG-2 TS Extension. The number of TS packets
   contained in the SNDU is therefore (Length-N-10+D*6) / 188, where N
   is the number of bytes associated with Extension Headers that
   precede the MPEG-2 TS-Concat Extension (zero if there are none). A
   Receiver MUST check that the payload length is correct prior to
   processing it. Any mismatch (remainder from the division) MUST
   result in discard of all encapsulated PDUs and SHOULD be recorded as
   TS-concat size mismatch error.

   A value D=0 indicates the presence of a NPA address. In that case
   the correct payload length for ULE is (Length-10) / 188, whereas in
   case of GSE the correct payload length is (Length-6) / 188.

   >>> IANA Action required, please replace < #NH-TS-CAT> with assigned
   value from the Next-Header Registry>>>

















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       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|           Length  (15b)     |  Type = 0x <#NH-TS-CAT>       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Receiver Destination NPA Address  (6B)             |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      |                   TS-Packet 1                                 |
      =                                                               =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   TS-Packet 2 (if Length > 2*188)             |
      =                                                               =
      |                              etc.                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             (CRC-32)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1: ULE/SNDU Format for a TS-Packet Payload (D=0)


   >>> IANA Action required, please replace <#NH-TS-CAT> with assigned
   value from the Next-Header Registry>>>


       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|           Length  (15b)     |  Type =0x <#NH-TS-CAT>        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Receiver Destination NPA Address  (6B)             |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      |                   TS-Packet 1                                 |
      =                                                               =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   TS-Packet 2 (if Length > 2*188)             |
      =                                                               =
      |                              etc.                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Figure 2: GSE/SNDU Format for a TS-Packet Payload (D=0)


   Note that fragmented GSE SNDUs are protected by a CRC-32 carried in
   the final fragment, and that non-fragmented GSE SNDUs are protected
   by a CRC-32 in the final bytes of the GS DataField.

   A value of D=1, is also permitted and indicates the absence of a NPA
   address, as defined in ULE. A similar format is supported in GSE.

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   >>> IANA Action required, please replace <#NH-TS-CAT> with assigned
   value from the Next-Header Registry>>>


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|           Length  (15b)     |  Type = 0x<#NH-TS-CAT>        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   TS-Packet 1                                 |
      =                                                               =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   TS-Packet 2 (if Length > 2*188)             |
      =                                                               =
      |                              etc.                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             (CRC-32)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 3: ULE/SNDU Format for a TS-Packet Payload (D=1)



   The extension may be used to transport one or more MPEG-2 TS Packets
   of arbitrary content, interpreted according to [ISO-MPEG]. One
   expected use is for the transmission of MPEG-2 SI/PSI signalling.

   The use of this format to transfer MPEG-2 clock references (e.g. a
   Network Clock Reference, NCR, SI Table) over ULE/GSE framing raises
   timing considerations at the encapsulation gateway, including the
   need to update/modify the timing information prior to transmission
   by the physical layer. These issues are not considered here, but it
   is noted that the operation may be simplified by ensuring that all
   SNDUs that carry this Extension Header are placed before other data
   within the GSE DataField [GSE].
















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3.2 PDU-Concat Extension

   >>> IANA Action required, please replace <#NH-PDU-CAT> with assigned
   value from the Next-Header Registry>>>

   The PDU-Concat Extension is specified by an IANA assigned H-Type
   value of <#NH-PDU-CAT> This is a Mandatory Next-Header Extension.
   It enables a sequence of (usually short) PDUs to be sent within a
   single SNDU payload.

   The base header contains the Length of the entire SNDU. This carries
   the value of the combined length of all PDUs to be encapsulated,
   including each set of encapsulation headers. The base header also
   caries a 16-bit ULE Type field. Although any Type value specified in
   the ULE Next-Header Registry may be assigned to the encapsulated
   PDU, all PDUs included in the SNDU payload MUST have a common ULE
   Type (i.e. all concatenated PDUs passed by the network layer must be
   associated with the same Type value). This simplifies the receiver
   design, and reduces the transmission overhead for common use cases.

   Each PDU is prefixed by its length in bytes (shown as PDU-Length in
   the following diagrams). Encapsulated PDUs are of arbitrary length
   (in bytes) and are not necessarily aligned to 16-bit or 32-bit
   boundaries within the SNDU (as shown in the figure). The most
   significant bit of the first byte MUST be set to zero. The length of
   each PDU MUST be less than 32 758 bytes, but will generally be much
   smaller.

   When the SNDU header indicates the presence of an SNDU Destination
   Address field (i.e. D=0), a Network Point of Attachment, NPA, field
   directly follows the fourth byte of the SNDU header. NPA destination
   addresses are 6 Byte numbers, normally expressed in hexadecimal,
   used to identify the Receiver(s) in a transmission network that
   should process a received SNDU.  When present the Receiver MUST
   associate the same specified MAC/NPA address with all PDUs within
   the SNDU Payload. This MAC/NPA address MUST also be forwarded with
   each PDU, if required by the forwarding interface.











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   >>> IANA Action required, please replace <#NH-PDU-CAT> with assigned
   value from the Next-Header Registry in the next two figures>>>


       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|           Length  (15b)     |  Type = 0x<#NH-PDU-CAT>       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Receiver Destination NPA Address  (6B)             |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |        CONCAT-PDU-Type        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|      PDU-Length-1  (15b)    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      =                        PDU-1                                  =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|      PDU-Length-2  (15b)    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      =                        PDU-2                                  =
      |                                                               |

                                 More PDUs as required

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             (CRC-32)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 4: ULE/SNDU Format for a PDU-Concat Payload (D=0)

       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|           Length  (15b)     |  Type = 0x<#NH-PDU-CAT>       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Receiver Destination NPA Address  (6B)             |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |        CONCAT-PDU-Type        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|      PDU-Length-1  (15b)    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      =                        PDU-1                                  =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|      PDU-Length-2  (15b)    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      =                        PDU-2                                  =
      |                                                               |

                                 More PDUs as required

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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       Figure 5: GSE/SNDU Format for a PDU-Concat Payload (D=0)

   A value of D=1 indicates there is no NPA/MAC address in use. This
   field MUST be carried (i.e. D=0) for IP unicast packets destined to
   routers that are sent using shared links (i.e., where the same link
   connects multiple Receivers). A sender MAY omit this field (D=1) for
   a set of packets delivered to a Receiver or group of receivers that
   are able to utilise a discriminator field (e.g. the IPv4/IPv6
   destination address, or a bridged MAC destination address), which in
   combination with the PID value, could be interpreted as a Link-Level
   address. A similar format is supported in GSE.


       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|           Length  (15b)     |  Type = 0x<#NH-PDU-CAT>       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         CONCAT-PDU-Type       |0|      PDU-Length-1  (15b)    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      =                        PDU-1                                  =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|      PDU-Length-2  (15b)    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      =                        PDU-2                                  =
      |                                                               |

                                 More PDUs as required

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             (CRC-32)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 6: ULE/SNDU Format for a PDU-Concat Payload (D=1)



   The Receiver processes this Extension Header by verifying that it
   supports the specified CONCAT-PDU Type (unsupported Types MUST be
   discarded but the receiver SHOULD record a PDU-Type error).  It then
   extracts each encapsulated PDU in turn. The Receiver MUST verify the
   Length of each PDU. It MUST also ensure the sum of the Lengths of
   all processed PDUs is less than the Length specified in the SNDU
   base header. A Receiver MUST discard the whole SNDU if the sizes do
   not match and this event SHOULD be recorded as a PDU-concat size
   mismatch error.







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   3.3 Timestamp Extension

   The timestamp extension header permits an Encapsulator to add a
   timestamp field to an SNDU. This is designed to support monitoring
   and measurement of ULE performance over a link to indicate the
   quality of an operational ULE link. This may be useful for GSE links
   (where significant complexity exists in the scheduling provided by
   the lower layers). This extension may be (optionally) checked at the
   Receiver.

   Possible uses of this extension include:

   * Validation of in-sequence ordering per Logical Channel,
   * Measurement of one-way delay (when synchronised with the sender)
   * Measurement of PDU Jitter introduced by the link,
   * PDU loss (with additional information from the sender).


   >>> IANA please insert a value for the H-Type from the Optional part
   of the Next-Header Registry, and replace <NH-TStamp> in the sentence
   below, and the figure following <<<

   The Timestamp Extension Header is specified by the IANA-assigned H-
   Type of <NH-TStamp>. This extension is an Optional Extension Header
   ([RFC4326], Section 5).

    0               7               15              23              31
    +---------------+---------------+---------------+---------------+
    |     0x03      | <NH-TStamp>   |       time stamp HI           |
    +---------------+---------------+---------------+---------------+
    |         time stamp LO         |            Type               |
    +---------------+---------------+---------------+---------------+

         Figure 7 The format of the 32-bit Timestamp Extension Header

   Figure 7 shows the format of this extension with a HLEN value of 3
   indicating a timestamp of length 4B with a Type field (there is no
   implied byte-alignment).

   The extension carries a 32-bit value (time stamp HI plus time stamp
   LO). The specified resolution is 1 microsecond. The value therefore
   indicates the number of 1 microsecond ticks past the hour in
   Universal Time when the timestamp option was inserted, right-
   justified to the 32-bit field. Systems unable to insert timestamps
   at the specified resolution may use an arbitrary (and varying) value
   to pad the unused least-significant bits.

   The last two bytes carry a 16-bit Type field that indicates the type
   of payload carried in the SNDU, or the presence of a further Next-
   Header ([RFC4326], Section 4.4).

   This is an Optional Extension Header. Receivers that do not
   implement, or do not wish to process, the Timestamp Extension MAY

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   skip this extension and continue to process the remainder of the
   SNDU, forwarding the encapsulated PDU.


4. Summary

   This document defines a set of Next_Header Extensions for the
   Unidirectional Link Encapsulation (ULE).



5. IANA Considerations

   This document requires IANA involvement for the assignment of two
   new Next-Header Type values from the IANA ULE Next-Header Registry.
   These options are defined for specific use cases envisaged by GSE,
   but are compatible with ULE.

   The TS-Concat Extension is a Mandatory next-type extension header,
   specified in section 3.1 of this document. The value of this next-
   header is defined by an IANA assigned H-Type value of <#NH-TS-CAT>.

   The PDU-Concat Extension is a Mandatory next-type extension header
   specified in section 3.2 of this document. The value of this next-
   header is defined by an IANA assigned H-Type value of <#NH-PDU-CAT>.

   The Timestamp Extension is an Optional next-type extension header
   specified in section 3.3 of this document. The value of this next-
   header is defined by an IANA assigned H-Type value of <#NH-TStamp>.
   This documents defines format for a HLEN value of 0x3.


6. Acknowledgments

   The author gratefully acknowledges the inputs, comments and
   assistance offered by the members of the DVB-GBS ad hoc group on S2
   encapsulation, in particular contributions on transmission aspects
   from Rita Rinaldo, Axel Jahn, and Ulrik De Bie.


7. Security Considerations

   No specific security issues are raised within this document.

   Additional security control fields may be provided as a part of a
   link encryption Extension Header, e.g. to associate a PFU with one
   of a set of Security Association (SA) parameters. As a part of the
   encryption process, it may also be desirable to authenticate
   some/all of the headers. The method of encryption and the way in
   which keys are exchanged is beyond the scope of this specification,
   as also are the definition of the SA format and that of the related
   encryption keys.


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8. References


8.1 Normative References

   [RFC2119] Bradner, S., "Key Words for Use in RFCs to Indicate
   Requirement Levels", BCP 14, RFC 2119, 1997.

   [RFC4236] Fairhurst, G. and B. Collini-Nocker, "Unidirectional
   Link Encapsulation (ULE) for transmission of IP datagrams over an
   MPEG-2 Transport Stream", RFC 4236, December 2006.


8.2 Informative References

   [ETSI-DAT] EN 301 192, "Specifications for Data Broadcasting",
   European Telecommunications Standards Institute (ETSI).

   [ETSI-S2] EN 302 307, "Digital Video Broadcasting (DVB); Second
   generation framing structure, channel coding and modulation systems
   for Broadcasting, Interactive Services, News Gathering and other
   broadband satellite applications", European Telecommunication
   Standards Institute (ETSI).

   [GSE] "Generic Stream Encapsulation", Work in Progress, DVB
   Technical Module (GBS Group), 2006.

   [ID-S2-REQ] "Requirements for transmission of IP datagrams over DVB-
   S2", Internet Draft <draft-cantillo-ipdvb-s2encaps-01.rxr>, Work in
   Progress.

   [ISO-MPEG] ISO/IEC DIS 13818-1:2000, "Information Technology;
   Generic Coding of Moving Pictures and Associated Audio Information
   Systems", International Standards Organisation (ISO).

   [RFC4259] Montpetit, M.-J., Fairhurst, G., Clausen, H., Collini-
   Nocker, B., and H. Linder, "A Framework for Transmission of IP
   Datagrams over MPEG-2 Networks", RFC 4259, November 2006.

   [S2] EN 302 307, "Digital Video Broadcasting (DVB); Second
   generation framing structure, channel coding and modulation systems
   for Broadcasting, Interactive Services, News Gathering and other
   broadband satellite applications", European Telecommunication
   Standards Institute (ETSI).

   [S2-REQ] GBS0339, "Functional and performance requirements for
   IP/S2", DVB-TM (GBS WG).


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   [S2-REQ-RCS] "Requirements for S2", Document 529r1, DVB Technical
   Module (RCS WG).



9. Authors' Addresses

   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

   Bernhard Collini-Nocker
   Department of Computer Sciences
   University of Salzburg
   Jakob Haringer Str. 2
   5020 Salzburg
   Austria

   EMail: bnocker@cosy.sbg.ac.at
   Web: http://www.cosy.sbg.ac.at/

10. IPR Notices

10.1 Intellectual Property Statement

   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.




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10.2 Disclaimer of Validity

   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, THE
   IETF TRUST 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.


11. Copyright Statement


   Copyright (C) The IETF Trust (2007).

   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.




APPENDIX: DVB-S.2

   PDUs, (Ethernet Frames, IP datagrams or other network layer packets)
   are encapsulated to form a Subnetwork Data Unit (SNDU) [RFC4236]
   associated with a specific Stream at the link layer. The SNDU is
   transmitted over an DVB-S2 link by placing it either in a single
   BBFrame, or if required, an SNDU may be fragmented into a series of
   BBFrames [ID-S2-REQ]. A mode also permits an SNDU to be fragmented
   with the remaining fragments sent in a later BBFrame(s), while
   preserving the original order of each SNDU sent to a specific
   MAC/NPA address over a Stream. Where there is sufficient space, the
   method permits a BBFrame to carry more than one SNDU (or part there
   of), sometimes known as Packing. All parts comprising an SNDU are
   assigned to the same Stream.

   In ULE and MPE [ETSI-DAT], each SNDU carries a 32-bit CRC field in
   the last four bytes of the SNDU. The purpose of this CRC is to
   protect the SNDU (header, and payload) from undetected reassembly
   errors and errors introduced by unexpected software / hardware
   operation. This also serves to verify the delineation (framing) of
   PDUs and may detect the presence of uncorrected errors from the
   physical link

   When an SNDU is sent over a DVB-S2 subnetwork using GSE, the
   Integrity protection is provided by a CRC at the baseband frame
   level, using a CRC in the final bytes of the DataField.

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   [RFC EDITOR NOTE:
   This section must be deleted prior to publication]

   DOCUMENT HISTORY

   Individual Draft 00
   This draft complements a study item in the DVB-GBS in this area to
   define a Generic Stream Encapsulation (GSE).  Comments relating to
   this document will be gratefully received by the author(s) and may
   also be sent to ip-dvb mailing list at: ip-dvb@erg.abdn.ac.uk

   Individual Draft 01
   Co-Author Added.
   This draft updates the language and format.
   This draft fixes problems with the concatenation mode, and defines a
   new header format that restricts the use of the Type field so that
   all concatenated PDUs MUST have the same Type.

   Future versions of this draft may define additional Extension
   Headers, proposals and ideas are welcome via the IETF ipdvb mailing
   list. Possible extensions include those for encapsulation FEC, Link
   parameter negotiation (e.g. for header compression), and support for
   ATM/ULE.

   Working Group Draft 00

   Fixed editorial mistakes from Christian Praehauser and ID style for
   WG adoption.

   Working Group Draft 01

   Corrected contact info for Bernhard.
   Added TimeStamp Options
   Corrected NITS in draft

   [END of RFC EDITOR NOTE]

















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