Lower Layer Guidelines for Robust RTP/UDP/IP Header Compression
RFC 3409

Document Type RFC - Informational (December 2002; No errata)
Last updated 2013-03-02
Replaces draft-ietf-rohc-lower-layer-guidelines
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IESG IESG state RFC 3409 (Informational)
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Responsible AD Allison Mankin
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Network Working Group                                         K. Svanbro
Request for Comments: 3409                                      Ericsson
Category: Informational                                    December 2002

    Lower Layer Guidelines for Robust RTP/UDP/IP Header Compression

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 (2002).  All Rights Reserved.

Abstract

   This document describes lower layer guidelines for robust header
   compression (ROHC) and the requirements ROHC puts on lower layers.
   The purpose of this document is to support the incorporation of
   robust header compression algorithms, as specified in the ROHC
   working group, into different systems such as those specified by
   Third Generation Partnership Project (3GPP), 3GPP Project 2 (3GPP2),
   European Technical Standards Institute (ETSI), etc.  This document
   covers only lower layer guidelines for compression of RTP/UDP/IP and
   UDP/IP headers as specified in [RFC3095].  Both general guidelines
   and guidelines specific for cellular systems are discussed in this
   document.

Table of Contents

   1.  Introduction.................................................. 2
   2.  General guidelines............................................ 2
         2.1.  Error detection....................................... 2
         2.2.  Inferred header field information..................... 3
         2.3.  Handling of header size variation..................... 3
         2.4.  Negotiation of header compression parameters.......... 5
         2.5.  Demultiplexing of flows onto logical channels......... 5
         2.6.  Packet type identification............................ 5
         2.7.  Packet duplication.................................... 6
         2.8.  Packet reordering..................................... 6
         2.9.  Feedback packets...................................... 6
   3.  Cellular system specific guidelines........................... 7
         3.1.  Handover procedures................................... 7
         3.2.  Unequal error detection (UED)......................... 8
         3.3.  Unequal error protection (UEP)........................ 9

Svanbro                      Informational                      [Page 1]
RFC 3409         Lower Layer Guidelines for Robust HC      December 2002

   4.  IANA Considerations........................................... 9
   5.  Security Considerations....................................... 9
   6.  References.................................................... 9
   7.  Author's Address..............................................10
   8.  Full Copyright Statement......................................11

1.  Introduction

   Almost all header compression algorithms [RFC1144, RFC2507, RFC2508]
   rely on some functionality from the underlying link layer.  Headers
   (compressed or not) are expected to be delivered without any residual
   bit errors.  IP length fields are inferred from link layer length
   fields.  Packet type identification may be separated from the header
   compression scheme and performed at the underlying link layer.
   [RFC2509], for example, elaborates on how to incorporate IP header
   compression [RFC2507] in PPP [RFC1661].

   It is important to be aware of such assumptions on required
   functionality from underlying layers when incorporating a header
   compression scheme into a system.  The functionality required by a
   specific header compression scheme from lower layers may also be
   needed if incorporation of a header compression scheme is to be
   prepared without knowing the exact details of the final scheme.

   This document describes lower layer guidelines for robust RTP/UDP/IP
   header compression [RFC3095] as specified by the ROHC working group.
   [RFC3095] will from this point be referenced to as ROHC.  These
   guidelines should simplify incorporation of the robust header
   compression algorithms into cellular systems like those standardized
   by 3GPP, 3GPP2, ETSI, etc, and also into specific link layer
   protocols such as PPP.  The document should also enable preparation
   of this incorporation without requiring detailed knowledge about the
   final header compression scheme.  Relevant standardization groups
   standardizing link layers should, aided by this document, include
   required functionality in "their" link layers to support robust
   header compression.

   Hence, this document clarifies the requirements ROHC put on lower
   layers, while the requirements on ROHC may be found in [RFC3096].

2.  General guidelines
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