[En-Nut-Discussion] TCP Retransmissions too fast by PC

[Brett Abbott]

Hi

Over a slow and performance variable network link like GPRS, we are 
finding that the PC/Boradband Internet side of the link often gets too 
impatient and will often send a retranmission of  a TCP packet.  At the 
ethernut end, this often appears as a duplicate packet received shortly 
after it has sent the ACK.  It copes ok but isnt ideal.

Does anyone know of how we might better train the VB .NET application to 
instruct/override the TCP socket to wait longer for an ACK before 
re-sending a packet?  Cant seem to find a way to override the Automatic 
RTTO setting.

Typical timings on the ethenut side are:
1. Receive TCP packet
2. Send ACK 120ms later
3. Receive resent TCP packet 80ms after that.

Propagation delay varies between 200ms and 4 seconds depending on the 
radio sleep state.

Many Thanks
Brett

-- 
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Brett Abbott, Managing Director, Digital Telemetry Limited
Email: Brett.Abbott at digital-telemetry.com
PO Box 24 036 Manners Street, Wellington, New Zealand
Phone +64 (4) 5666-860  Mobile +64 (21) 656-144
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