When I open a TCP connection to a serial interface on a Lantronix server it takes about 9 seconds. Is there any way to speed this up?

Slow TCP connections are often caused by a host initiating a connection with a packet with the ECN flag set. Most current Lantronix products are using TCP stacks that do not support the ECN flag.

ECN stands for Explicit Congestion Notification, a relatively new option for TCP connections. Here is a Wikipedia article about ECN:
https://en.wikipedia.org/wiki/Explicit_Congestion_Notification

At this time, in general it is best practice to disable ECN unless it is known that all hosts on the network either support ECN or can respond to a packet with the ECN flag set to let the remote host know they don't support ECN.

Recent releases of Microsoft Windows Server enable ECN for TCP by default. Here's a link to Microsoft article on disabling ECN in Windows Server:

https://social.technet.microsoft.com/wiki/contents/articles/20204.how-to-enable-and-disable-explicit-congestion-notification-in-windows.aspxan

If you have some other operating system that enables ECN for TCP by default, see the documentation for that operating system to find out how to disable it.

Over time, Lantronix devices that do not support the ECN flag will be updated to recognize and respond to it, appropriately.  

[Originally Published On: 03/09/2017 12:55 PM]