Subject: ROCCO header compression, motivation and IPR

From: "Lars-Erik Jonsson" <[email-masked]>
Date: Wed, 22 Sep 1999 16:14:38 +0200

In June, a concept called "RObust Checksum-based header COmpression (ROCCO)"
was introduced in the internet draft "draft-jonsson-robust-hc". The work was
also presented in the AVT-group at the 45'th IETF meeting (Oslo, July -99).

When presented at the Oslo meeting, there were questions raised about the
IPR situation regarding this proposal. Ericsson has therefore made a
statement regarding ROCCO and IPR which can be found at the IETF IPR page:
http://www.ietf.org/ietf/IPR/ERICSSON-ROCCO
Questions regarding this statement should be directed to Tage Lovgren,
[email-masked]

So, over to the technical stuff!!!
In the future, cellular "telephones" will support more services than speech.
This could be achieved by implementing specialized solutions for each
service supported (as in todays systems) or by providing only ONE transport
service on top of which all kind of applications, including speech, could be
run. Because IP is already used in the fixed parts of the networks and
builds a well known platform for all communication, a cellular "phone"
providing an IP-stack, on top of which you can run all kind of applications
from which vendor you want, would be a desirable solution. However, it is
not a simple task to bring IP over the cellular air interface and some
manufacturers are still very sceptical to such solutions. Cellular systems
provide their users with a service that works almost everywhere and to a
price that can be accepted by most people. The secret behind this is an
efficient usage of the radio spectrum. To make IP-based solutions
economically feasible compared to the solutions of today, the spectrum usage
must still be (almost) as efficient as today.

One of the most important mechanisms needed for spectrum efficient radio
usage is then header compression. Today, header compression is performed
using any of the schemes defined in RFC1144 (Van Jacobson), RFC2507
(Degermark et.al.) or RFC2508 (Casner, Jacobson). For real-time data the
only candidate is RFC2508, also called CRTP. CRTP compresses the 40 octetes
of IPv4/UDP/RTP headers down to a minimum of 2 octets and works very well
over RELIABLE low-bandwidth links. However, as shown in the Internet-Draft
"draft-degermark-crtp-cellular", when used over error-prone links such as
cellular links, CRTP does NOT perform well. ROCCO on the other hand is
designed to be adaptable both to the characteristics of the channel over
which it is used and to the packet stream it compresses. It can therefore
both compress in an optimal way and at the same time avoid additional packet
losses due to header compression because of errors on the link. ROCCO and
CRTP have been implemented and evaluated in a testbed environment with
different voice-over-IP applications. The testbed results has shown that for
an IP-solution with ROCCO, the spectrum usage is almost as good as for
traditional solutions and demanding real-time services like IP-telephony
works well. With CRTP, the spectrum usage is worse but also, the quality of
the service is far below what could be accepted.

It is our conviction that cellular telephony will be a market of explosive
growth also in the future, and if the cellular terminals were based upon IP
we would get a much more flexible and open environment for all kinds of
applications. However, to make this happen it is important to provide
technical solutions that solves the problems which today makes specialized
solutions more attractive. ROCCO is one such mechanism NEEDED.

The ROCCO draft was updated lately and current version is:
draft-jonsson-robust-hc-01.ps,txt

/Lars-Erik Jonsson

--------------------------------------------------------------
Lars-Erik Jonsson, M.Sc.
Voice Processing and Radio Network Research
Ericsson Erisoft AB
Box 920, S-971 28 Luleå, Sweden
E-mail: [email-masked]
Phone: +46 920 20 21 07
Mobile: +46 70 365 20 58
Fax: +46 920 20 20 99
Home: +46 920 999 57