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[Didier Barvaux <didier@xxxxxxxxxxx>]

Hi Ramya,

> Thanks Didier,
>                     That was wonderful piece of information :) It
> helped me a lot in understanding the concepts.

I'm glad to hear it :) If you got another question, do not hesitate.

Regards,
Didier Barvaux

 
> On Sat, May 15, 2010 at 4:25 PM, Didier Barvaux <didier@xxxxxxxxxxx>
> wrote:
> 
> > Hello Ramya,
> >
> > > Thanks,I got the output
> > > I could execute it succesfully using the ping application after
> > > which i got the output that has been attached.
> >
> > Congratulation! You just compressed your first packets with the ROHC
> > library :)
> >
> >
> > > In the last line of the output,it gives the size of the ROHC
> > > Packet,feedback,compressed header size and payload size,.
> > > I sent a packet with size 56 to which 8 bytes of header is
> > > added..In the output statistics the payload
> > > is being printed as 64 and the ROHC size is being printed as the
> > > payload plus the compressed header size..
> > > Is this right?
> >
> > According to the screenshot you sent, you compressed a 84-byte
> > ICMPv4 packet. See the trace "[rohc_comp.c:175 rohc_compress()]
> > size of IP packet = 84 bytes".
> >
> > Your 84-byte ICMPv4 packet is composed of a 20-byte IPv4 header, an
> > 8-byte ICMPv4 header and 56 bytes of ICMPv4 payload. The ROHC
> > library compresses the IPv4 header but not the ICMPv4 header and
> > the ICMPv4 payload.
> >
> > In the case of the last packet that I see on your screenshot (this
> > is the packet #164), the resulting ROHC packet is 67-byte long. It
> > is made of a 3-byte ROHC header (ie. the compressed equivalent of
> > the 20-byte uncompressed IPv4 header) and a 64-byte ROHC payload
> > (ie. the 8-byte ICMPv4 header and the 56-byte ICMPv4 payload
> > unchanged). See the trace "[rohc_comp.c:362 rohc_compress()] ROHC
> > size = 67 (feedback = 0, header = 3, payload = 64), output buffer =
> > 5120" in the screenshot.
> >
> > ROHC compression with the last packet results in a 85% gain for
> > header (20 bytes -> 3 bytes) and 20% gain for header+payload (84
> > bytes -> 67 bytes).
> >
> > I updated FAQ #639 "How to easily test the ROHC library ?"
> > (https://answers.launchpad.net/rohc/+faq/639) to explain the
> > rohctunnel traces the same way I did in this email. Let me know if
> > the explanations are sufficient.
> >
> > Regards,
> > Didier Barvaux
> >
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