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Extension Formats for Unidirectional Lightweight Encapsulation (ULE) and the Generic Stream Encapsulation (GSE)
RFC 5163

Network Working Group                                       G. Fairhurst
Request for Comments: 5163                        University of Aberdeen
Category: Standards Track                              B. Collini-Nocker
                                                  University of Salzburg
                                                              April 2008

 Extension Formats for Unidirectional Lightweight Encapsulation (ULE)
              and the Generic Stream Encapsulation (GSE)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This document describes a set of Extension Headers for the
   Unidirectional Lightweight Encapsulation (ULE), RFC 4326.

   The Extension Header formats specified in this document define
   extensions appropriate to both ULE and the Generic Stream
   Encapsulation (GSE) for the second-generation framing structure
   defined by the Digital Video Broadcasting (DVB) family of
   specifications.

Table of Contents

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................3
   3. Description of the Method .......................................4
      3.1. MPEG-2 TS-Concat Extension .................................5
      3.2. PDU-Concat Extension .......................................8
      3.3. TimeStamp Extension .......................................12
   4. IANA Considerations ............................................13
   5. Acknowledgments ................................................13
   6. Security Considerations ........................................14
   7. References .....................................................14
      7.1. Normative References ......................................14
      7.2. Informative References ....................................14
   Appendix A. The Second-Generation DVB Transmission
      Specifications .................................................16

Fairhurst & Collini-Nocker  Standards Track                     [Page 1]
RFC 5163      Extension Formats for the ULE Encapsulation     April 2008

1.  Introduction

   This document describes three Extension Headers that may be used with
   both the Unidirectional Lightweight Encapsulation (ULE) [RFC4326] 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
   in the first instance for DVB-S2 [ETSI-S2].  The requirements for the
   Generic Stream are described in [S2-REQ].  The important
   characteristics of this encapsulation are described in the appendix
   of this document.  GSE maintains a design philosophy that presents a
   network interface that is common to that presented by ULE and uses a
   similar construction for SubNetwork Data Units (SNDUs).

   The first Extension Header defines a method that allows one or more
   TS Packets [ISO-MPEG2] 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 a receiver that is not configured to
   receive the NPA address associated with an SNDU, allowing this
   receiver to 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

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