RE: [lwip-users] Significant overhead periodically during TCP receive transfers

[bill]

> That truly is weird.  If you can get a packet capture from just before
> the failure, I'd be happy to take a look.

I don't know if the text version I sent helped, but I know a lot more now.

What I see in the packet capture that causes the problem is that the PC
broadcasts an ARP "who has", 50uS later lwIP sends a response packet to the
PC. 4uS after that the PC sends 1460 bytes to lwIP, but the sequence number
is 13140 bytes *ahead* (9 * 1460) of the expect number.  It looks like the
PC has dropped 9 packets while it was doing its ARP query.  Unless WireShark
missed these packets (doubtful).

If I change the PC's ARP table to make the lwIP device static, this problem
disappears!

The only thing I see that I don't understand is when lwIP asks for the first
missed packet, a duplicate request of the same sequence is sent 17uS later.
I would expect that request to have a more reasonable time before asking for
the packet again.  Is there a timeout that I can check being set somewhere
on sending an ack for a missed packet?

Thank you,
Bill