[lwip-users] Jumbo frame questions

[Bill Auerbach]

Hello,

 

I made changes to support Jumbo Frames (9k).  Besides the driver changes, I used TCP_MSS of 9000.  All is good with about 100Mb/S speed increase.

 

I dropped back to a connection that doesn’t support jumbo frames and I have connection problems because of TCP_MSS not being e.g. 1512.

 

I cannot use something like: #define TCP_MSS (UseJumbo ? 9000 : 1512).

 

How can I adjust TCP_MSS when I’m on a “normal” network?  Or… what else do I need to look at for supporting Jumbo frames transparently?  Shouldn’t my lwIP side see the other end’s MSS on connection and downsize accordingly?

 

If this is a basic networking or TCP question and off topic, please let me know where to find what I need.

 

Thank you,

 

Bill Auerbach