Subject: RE: [Sip] RE: [rohc] New I-D on compression of SIP

From: "Price, Richard" <[email-masked]>
Date: Fri, 20 Jul 2001 14:55:58 +0100

Hi,

Apologies to members of the SIP mailing list who haven't received
my previous emails on the subject. The scheme in question is
EPIC (Efficient Protocol-Independent Compression) which is a
programmable compression scheme with a very high level of efficiency.

There is also a "learning" version of EPIC that does not need to be
programmed - we used this to obtain the results for SIP compression.

The new EPIC draft is being published today - we will post a copy on
our website and provide the link shortly.

Regards,

Richard P

-----Original Message-----
From: Romeo Zwart [mailto:[email-masked]]
Sent: Friday, July 20, 2001 2:11 PM
To: Price, Richard
Subject: RE: [Sip] RE: [rohc] New I-D on compression of SIP

Hi Richard,

Thanks for this info, results look impressive. I am a bit confused
when you say "our own SIP compression scheme". So that's not SCRIBE
or ROGER, is it? Has that scheme been documented anywhere?

Romeo

At 02:21 PM 7/20/2001, you wrote:
>Hi,
>
>We chose the "Successful Simple SIP to SIP" call flow from
>Section 3.1.1 of <draft-ietf-sip-call-flows-05.txt> to
>benchmark our own SIP compression scheme.
>
>Initially the "dictionary" of previously received messages
>is empty, but new messages can be compressed relative to all
>previously received messages. This illustrates nicely how the
>compression ratio goes up with a more comprehensive dictionary.
>
>The results for our scheme are as follows:
>
>Message Size    Compressed Size         Compression Ratio
>
>         423                     152                             2.78
>         189                     6                               31.50
>         205                     16                              12.81
>         420                     28                              15.00
>         195                     4                               48.75
>         214                     8                               26.75
>         198                     2                               99.00
>
>If anyone has an alternative set of SIP messages, we could provide
>compression ratios for these also.
>
>Regards,
>
>Richard P

---

From: Romeo Zwart <[email-masked]>
Date: Fri, 20 Jul 2001 17:02:32 +0200

Richard,

I think your draft is already in the IETF repository. I've glanced
over it just now, so maybe I missed some of the fine print, but
here's one comment.

The compression results of your protocol seem impresssive. However,
an immediate drawback of using a 'programmed' protocol like this,
is that this is a rather inflexible approach. E.g. compression
of new extensions popping up will not be supported until new
versions of the en/decoders have been distributed to all involved
nodes (network and endpoints). I think that is a practical problem
in many scenarios.

Romeo

> >Message Size    Compressed Size         Compression Ratio

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