wierd dsl performance with -CURRENT

Kenneth Culver culverk at yumyumyum.org
Wed Jul 9 14:31:59 PDT 2003


> > > Can you do a
> > > 'netstat -s -p tcp >> tcpstats' before and after the transfer?
> > >
> > > This should tell us if there were retransmits etc.  It could be a
> > > difference in minimum rtt values or a congestion issue that results in
> > > timeout for our stack but some other recovery mechanism with other stacks.
> > >
> >
> > Here is the output of the netstat before and after transferring "kern.flp"
> > for FreeBSD 5.1:
> >
> > tcp:
> [...]
> >         35600 packets received
>
> [...]
> >                 1220 out-of-order packets (1657153 bytes)
> >
> > This is after:
> >
> > tcp:
> [...]
> >         36688 packets received
> >                 1298 out-of-order packets (1770089 bytes)
>
> This is the only thing that is of any interest..
> and it could only really be if the etherent driver was re-ordering
> them..
>
> possibly FreeBSD 5  might react more to out-of-order packets..
>
> capture a download with tcpdump
> and save it (ascii version) to a file using the -ttt option to get
> relative timestamps..
>
> look of any large values in the timestamps and see if there is anything
> before that indicates a lost packet or a re-ordered one or something
> (or a retransmitted ack)
>
> The key is to find the gap in the arriving packets and figure out
> what caused it..
>
Alright, I'll have to do this later this evening, don't have time right
now. Thanks for the help though.

Ken


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