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Versions: 00 01 draft-ietf-ipdvb-ule-ext

Internet Engineering Task Force                         Gorry Fairhurst
Internet Draft                                   University of Aberdeen
Document: draft-fairhurst-ipdvb-ule-ext-00.txt



Category: Draft                                               June 2006


   Extension Formats for the ULE Encapsulation
   to support the Generic Stream Encapsulation (GSE)


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
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
   Drafts. Internet-Drafts are draft documents valid for a maximum of
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   documents at any time. It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html
   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.



Abstract

   This document describes a set of Extension Headers. For the
   Unidirectional Lightweight Encapsulation (ULE).

   The Extension Header formats defined in this document provide new
   extensions that are common extensions to both ULE and the Generic
   Stream Encapsulation (GSE) defined by the second generation framing
   structure DVB-S2 standard (Channel coding and modulation systems for
   Broadcasting, Interactive Services, News Gathering and other
   broadband satellite applications).










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   Table of Contents

   1. Introduction

   2. Conventions used in this document

   3. Description of method

   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 a set of Header Extensions for ULE [RFC4236]
   over the MPEG-2 Transport-Stream. The methods are also applicable to
   a link that uses the physical layer specified by DVB-S2 [ETSI-S2] in
   the Generic Mode (also known as the Generic Stream (GS)). The
   Generic Stream Encapsulation (GSE) [GSE] is currently a work item of
   the DVB-TM. The requirements for the Generic Stream are defined in
   [S2-REQ], [S2-REQ-RCS], and [ID-S2-REQ]. GSE maintains a design
   philosophy that presents a similar network interface to that of ULE
   and uses a similar construction for SNDUs. The important
   characteristics of this encapsulation are described in an Appendix
   to this document.

   The approaches seek to define well-founded methods that may be used
   with both ULE and GSE. This will present the same network layer
   interface over both physical layers.

   One method allows one or more TS-Packets [ISO-MPEG] to be sent
   within a ULE SNDU. In GSE this method may be used to provide then
   control plane information including the transmission of MPEG-2
   Program Specific Information (PSI) for the Multiplex.

   A second method 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.

   Future versions of this document are expected to provide
   recommendations on the interface between the Generic Stream
   Encapsulation (GSE) and the Internet Protocol Stack.

   The appendix is also expected to be enhanced to include a summary of
   key design issues and considerations based on the GSE Specification
   defined by the DVB-TM (e.g. [ID-S2-REQ]).












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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 the Generic
   Mode of DVB-S2.

   GS: Generic Stream.

   GSE: Generic Stream Encapsulation.

   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-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: Programme 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 in a



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

   Stream: A logical flow from an Encapsulator to a set of Receivers.
   The addresses at the MAC/NPA level and IP level need to be unique
   within a specific stream (i.e. denoted by a common S.2 ISI value).

   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 Lightweight 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 less than 1536 Decimal indicates an
   Extension Header.  This section describes a set of two extension
   formats for the ULE encapsulation.


3.1 MPEG-2 TS-Concat Extension

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

   The extension is used to communicate 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. A Receiver MUST silently
   discard any data, if present, between the last complete encapsulated
   MPEG-2 TS Packet and the size denoted in the Length field of the
   SNDU fragment base header.

   A value of D=1 indicates there is no NPA/MAC address in use. A value
   D=0 is also permitted, as defined in ULE.

   The extension may be used to communicate 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
   and clock references over the ULE framing.


       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 = 0xtbd          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   TS-Packet 1                                 |
      =                                                               =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   TS-Packet 2 (if Length > 2*188)             |
      =                                                               =
      |                              etc.                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             (CRC-32)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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







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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 = 0xtbd-concat          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Receiver Destination NPA Address  (6B)             |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      |                   TS-Packet 1                                 |
      =                                                               =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   TS-Packet 2 (if Length > 2*188)             |
      =                                                               =
      |                              etc.                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             (CRC-32)                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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


3.2 PDU-Concat Extension

   The PDU-Concat Extension is specified by an IANA assigned H-Type
   value of <tbd>. 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 is set
   to the combined length of all PDUs to be encapsulated, including
   each set of encapsulation headers.

   Each PDU is prefixed by its length in bytes (shown as PDU-Length in
   the following diagrams) and a 16-bit ULE Type field. The most
   significant bit of the first byte MUST must be set to zero. The
   length of each PDU MUST be less than 32 768 bytes. The Type field
   (shown as PDU-Type in the following figures) may be any ULE-
   specified Type.

   The Receiver processes this Extension Header by extracting each PDU
   in turn. The Receiver first verifies the Length of each PDU, and
   ensures the sum of the Lengths of all processed PDUs is less than
   the Length specified in the SNDU base header. A Receiver MUST
   silently discard any data, if present, after the last complete
   encapsulated PDU.








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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|           Length  (15b)     |  Type = 0xtbd-concat          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|        PDU-Length  (15b)    |           PDU-Type            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      =                        PDU-1                                  =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|        PDU-Length  (15b)    |           PDU-Type            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      =                        PDU-2                                  =
      |                                                               |

                                 More PDUs as required

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

       Figure 3: SNDU Format for a PDU-Concat Payload (D=1)


   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.

   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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       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 = 0xtbd-concat          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Receiver Destination NPA Address  (6B)             |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               ||0|           Length  (15b)    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Frag-Type            |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      =                        PDU-1                                  =
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|           Length  (15b)     |          Frag-Type            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      =                        PDU-2                                  =
      |                                                               |

                                 More PDUs as required

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

       Figure 4: SNDU Format for a PDU-Concat Payload (D=1)


4. Summary

   This document defines a set of Next_Header options for the
   Unidirectional Lightweight Encapsulation (ULE).


5. IANA Considerations

   This document will require 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 <tbd>.

   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 <tbd>.

6. Acknowledgments

   The author gratefully acknowledges the inputs, comments and
   assistance offered by the members of the DVB-GBS ad hoc group on S2


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   encapsulation, in particular contributions on networking aspects
   from Axel Jahn, Ulrik De Bie, and Bernhard Collini-Nocker..


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.


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
   Lightweight 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).


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   [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-Eval] "Procedure for Comparative Evaluation of IP/DVB-S2
   Encapsulation Protocol over Generic Streams", Technical Note, Work
   in Progress, DVB TM-GBS.

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

   [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


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 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 Internet Society (2006).  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.


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

   DOCUMENT HISTORY

   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


   [END of RFC EDITOR NOTE]






















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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.




























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