Robust Header Compression (rohc)
--------------------------------

 Charter
 Last Modified: 2007-09-28

 Current Status: Active Working Group

 Chair(s):
     Carl Knutsson  <carl.knutsson@effnet.com>

 Transport Area Director(s):
     Magnus Westerlund  <magnus.westerlund@ericsson.com>
     Lars Eggert  <lars.eggert@nokia.com>

 Transport Area Advisor:
     Magnus Westerlund  <magnus.westerlund@ericsson.com>

 Technical Advisor(s):
     Erik Nordmark  <erik.nordmark@sun.com>
     Carsten Bormann  <cabo@tzi.org>

 Mailing Lists: 
     General Discussion:rohc@ietf.org
     To Subscribe:      rohc-request@ietf.org
     Archive:           http://www.ietf.org/mail-archive/web/rohc/index.html

Description of Working Group:

Due to limited bandwidth, IP/UDP/RTP/TCP packets sent over cellular
links benefit considerably from header compression. Existing header
compression schemes (RFC 1144, RFC 2508) do not perform well over
cellular links due to high error rates and long link roundtrip times,
particularly as topologies and traffic patterns become more
complex. In addition, existing schemes do not compress TCP options
such as SACK or Timestamps.

Another consequence of low bandwidth links is long session setup
delays when text-based signaling protocols, such as SIP and SDP, are
used. These delays can be significantly reduced by compressing not
only the headers, but also the signaling information.

The goal of ROHC is to develop generic header compression schemes that
perform well over links with high error rates and long roundtrip
times, as well as related signaling compression schemes. The schemes
must perform well for cellular links built using technologies such as
WCDMA, EDGE, and CDMA-2000. However, the schemes should also be
applicable to other future link technologies with high loss and long
roundtrip times. Ideally, it should be possible to compress over
unidirectional links.

Good performance includes both minimal loss propagation and minimal
added delay. In addition to generic TCP and UDP/RTP compression,
applications of particular interest are voice and low-bandwidth
video.

ROHC may develop multiple compression schemes, for example, some that
are particularly suited to specific link layer technologies. Schemes
in addition to those listed in the milestones below may be added in
consultation with the area directors.

A robust compression scheme must:

* assure that the result after decompression is semantically identical
  to the uncompressed original;

* perform well when the end-to-end path involves more than one
  cellular link;

* support IPv4 and IPv6.

* provide benefit in the presence of IPSEC.

Creating more thorough requirements documents will be the first task
of the WG for each of its specific areas of work, which are:

* 0-byte improvements to RTP header compression

* TCP header compression

* Signaling compression

* SCTP header compression

In addition, the WG will work on MIBs for its compression schemes, as
well as the sheperding of RFC3095 to draft standard.

The working group shall maintain connections with other
standardization organizations developing cellular technology for IP,
such as 3GPP and 3GPP-2, to ensure that its output fulfills their
requirements and will be put to good use.

In addition, the WG should develop a solid understanding of the impact
that specific error patterns have on the compression schemes, and
document guidelines to Layer 2 designers regarding what Layer 2
features work best to assist Layer 3 and Layer 4 header compression.
This work is in coordination with the PILC WG.

Some of the schemes developed in ROHC will be used in wider contexts
than just the specific link technologies discussed.  The working group
will ensure the applicability in particular of the TCP and signaling
compression schemes to the general Internet.  This includes
considering the applicability of the technologies under consideration
to open-source implementations.

Finally, working group documents will address interactions with IPSEC
and other security implications.

 Goals and Milestones:

   Done         Submit I-D on Requirements for IP/UDP/RTP header compression. 

   Done         Submit I-D of layer-2 design guidelines. 

   Done         Submit I-D(s) proposing IP/UDP/RTP header compression schemes. 

   Done         Submit I-D of Requirements for IP/TCP header compression. 

   Done         Requirements for IP/UDP/RTP header compression submitted to 
                IESG for publication as Informational. 

   Done         Resolve possibly multiple IP/UDP/RTP compression schemes into a 
                single scheme. 

   Done         Submit I-D on IP/TCP header compression scheme. 

   Done         IP/UDP/RTP header compression scheme submitted to IESG for 
                publication as Proposed Standard. 

   Done         Layer-2 design guidelines submitted to IESG for publication as 
                Informational. 

   Done         Initial draft on general signaling compression security 
                analysis. 

   Done         Requirements and assumptions for signaling compression 

   Done         Signaling compression scheme submitted to IESG for publication 
                as Proposed Standard, including security approach for SIP 
                compression usage. 

   Done         General signaling compression security analysis submitted to 
                IESG for publication as Informational. 

   Done         ROHC MIB submitted to IESG for publication as Proposed 
                Standard. 

   Done         ROHC IP-only profile submitted to IESG for publication as 
                Proposed Standard 

   Done         ROHC UDP Lite schemes submitted to IESG for publication as 
                Proposed Standard. 

   Done         Requirements for IP/TCP header compression submitted to IESG 
                for publication as Informational. 

   Done         Problem analysis ROHC-over-channels-that-can-reorder-packets 
                submitted to IESG for publication as Informational 

   Done         I-Ds of ROHC IP/UDP/RTP bis, framework and profiles separated. 

   Done         RFC 3095 Implementer's Guide submitted to IESG for publication 
                as Proposed Standard 

   Done         IP/TCP compression scheme submitted to IESG for publication as 
                Proposed Standard 

   Done         ROHC framework submitted to IESG for publication as Proposed 
                Standard 

   Done         SigComp for SIP submitted to IESG for publication as Proposed 
                Standard 

   Dec 2006       Revised ROHC IP/UDP/RTP profiles submitted to IESG for 
                publication as Proposed Standard 

   Done         SigComp Implementer's Guide submitted to IESG for publication 
                as Proposed Standard 

   Jan 2007       RObust Header Compression Protocol Number Registration 
                submitted to IESG for publication as Proposed Standard 

   Feb 2007       ROHC encapsulation profile(s) for IPHC/CRTP/eCRTP submitted to 
                IESG for publication as Proposed Standard 

   Mar 2007       IKE/IPsec extensions for HC-session Parameter Negotiation 
                submitted to IESG for publication as Proposed Standard 

   Mar 2007       Header Compression over IPsec (HCoIPsec) submitted to IESG for 
                publication as Informational 

   Jun 2007       Recharter of WG to develop additional profiles if needed, or 
                possible additional compression schemes. Consideration of 
                concluding the working group. 


 Internet-Drafts:

Posted Revised         I-D Title   <Filename>
------ ------- --------------------------------------------
Nov 2005 Oct 2008   <draft-ietf-rohc-hcoipsec-09.txt>
                Integration of Robust Header Compression (ROHC) over IPsec 
                Security Associations 

Sep 2006 Oct 2008   <draft-ietf-rohc-ikev2-extensions-hcoipsec-07.txt>
                IKEv2 Extensions to Support Robust Header Compression over 
                IPsec (ROHCoIPsec) 

Aug 2007 Oct 2008   <draft-ietf-rohc-ipsec-extensions-hcoipsec-03.txt>
                IPsec Extensions to Support Robust Header Compression over 
                IPsec (ROHCoIPsec) 

Aug 2008 Aug 2008   <draft-ietf-rohc-rfc4995bis-00.txt>
                The RObust Header Compression (ROHC) Framework 

 Request For Comments:

  RFC   Stat Published     Title
------- -- ----------- ------------------------------------
RFC3095 PS   Jul 2001    RObust Header Compression (ROHC) 

RFC3096 I    Jul 2001    Requirements for robust IP/UDP/RTP header compression 

RFC3242 PS   May 2002    A Link-Layer Assisted ROHC Profile for IP/UDP/RTP 

RFC3243 I    May 2002    Requirements and assumptions for ROHC 0-byte IP/UDP/RTP 
                       compression 

RFC3241 PS   May 2002    ROHC over PPP 

RFC3408 PS   Dec 2002    Zero-byte Support for Reliable Bidirectional Mode 
                       (R-mode) in Extended Link-Layer Assisted RObust Header 
                       Compression (ROHC) Profile 

RFC3409 I    Dec 2002    Lower Layer Guidelines for Robust RTP/UDP/IP Header 
                       Compression 

RFC3321 I    Jan 2003    SigComp - Extended Operations 

RFC3320 PS   Jan 2003    Signaling Compression 

RFC3322 I    Jan 2003    Signaling Compression Requirements & Assumptions 

RFC3759 I    Apr 2004    RObust Header Compression (ROHC):Terminology and Channel 
                       Mapping Examples 

RFC3816Standard  Jun 2004    Definitions of Managed Objects for Robus Header 
                       Compression 

RFC3843Standard  Jul 2004    RObust Header Compression (ROHC): A Compression Profile 
                       for IP 

RFC4019Standard  Apr 2005    RObust Header Compression (ROHC):Profiles for UDP-Lite 

RFC4077Standard  May 2005    A Negative Acknowledgement Mechanism for Signaling 
                       Compression 

RFC4163 I    Aug 2005    RObust Header Compression (ROHC): Requirements on TCP/IP 
                       Header Compression 

RFC4164Standard  Sep 2005    RObust Header Compression (ROHC):Context Replication for 
                       ROHC Profiles 

RFC4224 I    Jan 2006    RObust Header Compression (ROHC): ROHC over Channels 
                       that can Reorder Packets 

RFC4362Standard  Jan 2006    RObust Header Compression (ROHC): A Link-Layer Assisted 
                       Profile for IP/UDP/RTP 

RFC4413 I    Mar 2006    TCP/IP Field Behavior 

RFC4464 I    May 2006    Signaling Compression (SigComp) Users' Guide 

RFC4465 I    Jun 2006    Signaling Compression (SigComp) Torture Tests 

RFC4815 PS   Feb 2007    RObust Header Compression (ROHC): Corrections and 
                       Clarifications to RFC 3095 

RFC4896 PS   Jun 2007    Signaling Compression (SigComp) Corrections and 
                       Clarifications 

RFC4997 PS   Jul 2007    Formal Notation for RObust Header Compression (ROHC-FN) 

RFC4996 PS   Jul 2007    RObust Header Compression (ROHC): A Profile for TCP/IP 
                       (ROHC-TCP) 

RFC4995 PS   Jul 2007    The RObust Header Compression (ROHC) Framework 

RFC5049 PS   Dec 2007    Applying Signaling Compression (SigComp) to the Session 
                       Initiation Protocol (SIP) 

RFC5225 PS   Apr 2008    RObust Header Compression Version 2 (ROHCv2): Profiles 
                       for RTP, UDP, IP, ESP and UDP Lite