[prev in list] [next in list] [prev in thread] [next in thread] 

List:       olpc-devel
Subject:    OLPC "iperf hang" notes
From:       wmb () firmworks ! com (Mitch Bradley)
Date:       2007-02-28 19:35:32
Message-ID: 45E61FC4.3020100 () firmworks ! com
[Download RAW message or body]



David Miller wrote:
>
> Looks like the retransmits on the sender side are being
> dropped at the device.
>
>   
Quite possibly.

I decoded the packets in the USB trace.  There is a lot of packet 
reordering going on - the sequence numbers don't increase monotonically.

Subtracting out the first sequence number and dividing by the constant 
fixed length of the outgoing packets, the sequence is:

0 1  4  6  2  3  7  5  8  9  11  13  10 14 12  15  16  18  20  17  21  
19  22  23  *  25 *  27  28  29  30

The ACKs work as expected, i.e. when the sequence fills in, the ACKs 
catch up.

"*" shows a sequence number that never showed up - packets "24" and "26" 
were not transmitted.  The ACK sequence stalled after "23", reflecting 
the fact that 24 never arrived.

I killed the process 12 seconds after progress stalled (i.e. after point 
"30').  There were no retransmissions during that time.

[prev in list] [next in list] [prev in thread] [next in thread]