[Planetlab-users] TCPDUMP response side traffic lost

[Hecker W]

Hi Sapan,

Please let me know if you understand the problem well now. Or you need
anything from us. Thanks.

-Zhichun

On Tue, Jul 15, 2008 at 5:07 PM, Hecker W <heckerme at gmail.com> wrote:
> Thanks Sapan. I just saw your message today.
>
> The silence period I mentioned is not only for the TCP handshakes but
> also for the payload packets.
>
> I did some tests on the machine you mention in another email
> (plantlab-7 and echo). I have put the traces I produced by downloading
> files in different size from my university online at
> http://mot.cs.northwestern.edu/Planetlab/.
>
> You can take a look at the traces to see the problem.  I have tried
> different files with different sizes on the planetlab-7 and echo. .
> For the traces captured on echo.cs.princeton.edu, the incoming traffic
> always have loses. For the
> traces of planetlab-7, in some cases I can get full traces even with
> SYN/ACK. But in other cases it repeated the behavior I mentioned. I
> notice after the stabilization period, there are no noticeable packet
> loss even when the downloading speed is high, so it seems not due to
> the disk bottleneck.
>
> Here are the traces and corresponding file sizes
> TRACE           FILESIZE
> testfull*pcap   4572765
> testsmall*pcap  25376
> testtiny*pcap   2219
>
> For planetlab-7 node
> testfull2.pcap, testsmall1.pcap have obvious packet loss at the
> initial silence period.
>
> Thanks,
> -Zhichun
>
>
> On Mon, Jul 14, 2008 at 2:42 PM, Sapan Bhatia <sapanb at cs.princeton.edu> wrote:
>>
>> Hi Zhichun,
>>
>> I can't reproduce this problem. I tried some simple tests (wget a
>> small file, wget a big file) but I could capture all incoming packets.
>>
>> Is the initial period of silence that you've encountered restricted to
>> the TCP handshake? If that's the case, then it's expected - and you
>> need to do something special to be able to see it. But you should not
>> be missing any payload packets because of this.
>>
>> If not, then could you give me a test case to work with?
>>
>> Sapan
>>
>> On Thu, Jul 10, 2008 at 9:47 PM, Hecker W <heckerme at gmail.com> wrote:
>> > I need to issue HTTP requests from Planetlab nodes and
>> > to dump the whole TCP connection traces. I found it worked
>> > on the FC4 version. But for the FC8 version, after the initial
>> > SYN packet sent out, I cannot capture the server response
>> > traffic until 0.6 second later. All the packets responded from
>> > web servers are lost within this 0.6 second time window. After that
>> > I can get all the traffic from both side.  I tried the big web objects to
>> > make
>> > sure its downloading time is longer than 1 seconds, and find this problem is
>> > persistent.
>> >
>> > I am not sure whether it is due to the new version of Planetlab needs
>> > 0.6 seconds to recognize that the new connection is issued so that it begin
>> > to
>> > allow TCPDUMP to see the packets?
>> >
>> > I guess it is not expected behavior, doesn't it? I did not use any raw
>> > socket API.
>> >
>> > The problem is similar to the problem mentioned by Greg in the previous
>> > post.
>> >
>> > If anyone needs the pcap trace to see the problem please reply the post. I
>> > will make it available online.
>> >
>> > Thanks
>> > -Zhichun
>> >
>> >
>> >
>> >
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