Subject: WG Review: Revised Charter for Robust Header Compression (rohc)

From: The IESG <[email-masked]>
Date: Wed, 09 Jan 2002 13:02:41 -0500

A revised charter has been received for the Robust Header Compression (rohc)
Working Group, and is provided here for informational purposes.

The current charter can be accessed at: 

	http://www.ietf.org/html.charters/rohc-charter.html

New/Proposed Description of Working Group:

Note: Erik Nordmark ([email-masked]) is serving as a Technical
Advisor to the 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.

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