TCP/IP SENT_SYNC to CLOSED Timeout Configuration

We’ve have a customer that would like to use our existing NS9750 NetOS63 based product, and maybe eventually a new NS9215 NetOS75 based product with TCP/IP over a radio link. If the units are connected via wires, they connect without any problem. When a radio link is used, the two NS9750 NetOS63 units cannot make a TCP/IP connection apparently because the roundtrip time over the radio is about 600 ms. In TCP parlance, one unit sends a SYN to start the connection and receives a SYN-ACK 600 ms later; by that time, it has timed out so it replies to the SYN-ACK with a RST to reset the connection. This repeats indefinitely and a connection is never made.

My question is, is there a way to adjust the timeout for the establishment of the TCP/IP connection (timeout from SYNC_SENT to CLOSED states) in either NetOS63 or NetOS75?


There is a non-standard tcp socket option (for use with setsockopt) that affects tcp transmission timeout. The option is TCP_REX_MAX. It is written up in the API reference guide. Try varying this value. The value is in milliseconds. You’ll need to do this for each socket for which yoou wan tto modify the value. Set it after creating the socket but before doing much else with the socket

Thanks for the suggestion. I tried it but it didn’t seem to solve the connection timeout on NetOS63. The NetOS75 version doesn’t exhibit the problem so I’m guessing the connection timeout is hardcoded in NetOS75 to something > 500 ms. Thanks again for the suggestion.

The other difference, which maybe more relavent is that starting with NET+OS V7.0 and going forward a different (completely different) stack was used as compared to the stack used in V6.3 and before. Thus I am not surprised that the behavior is different.