Hi hsb
I've checked and they are indeed retransmission packets and not duplicates. I tried a different GPRS operator and repeated the same test set-up. Guess what, no retransmissions!
I know every network is unique and each is never like the other. I'm suppose to give a report on captures I did but I just don't know what is happening to this GPRS network nor can I provide any explanation. I couldn't even verify the server captures and compared them to the client captures as everything from IP to port to packet sequence number were different in both. I know IP and port can be masked etc, but at least packet sequence number is still intact. The second GPRS network I tested didn't have this problem, I could easily traced packets based on the sequence number as they were not changed.
Overall performance: it takes approximately twice the amount of time to download a file for the first GPRS network compares to the second GPRS network,
the extra time is due to this 'unexplained retransmissions'.
Any ideas? I tried googling for GPRS mailing list/forum but found none. At this point any theory/suggestion is most welcome.
Thanks
Hansang Bae <hbae@xxxxxxxxxx> wrote:
On 12:35 AM 3/7/2006, fonte fonte wrote:
>I did a capture on USB interface using GPRS dial up (FTP download). It looked like almost every single packet was retransmitted (server-to-client direction). I repeated the test 3 times, result was still the same.
>
>I would like some opinions/theories on the capture I had. Any suggestion or any website recommended? I'm facing dead end.
Are you sure they are not just duplicated packets (i.e. you captured at two points).
Check the IP Identification field. Do you see two packets with the same IP
ID?
This can happen when you have "virtual" adapters like VPNs etc. I imagine you're running into the same thing with your GPRS/USB interface.
hsb
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