RE: [lwip-users] Jumbo frame questions

[Bill Auerbach]

Hi Simon,

 

I updated and retested – so it’s the latest as of yesterday.  I can’t say if it’s an lwIP issue or not.  The problem exists only when lwIP is configured for jumbo frames, the connection is to the PC configured for large frames, but the network cannot support large frames.  WinXP works in this configuration but the lwIP device connected does not.  I can change the Frame Size to 1512 and both the PC and lwIP device work.

 

Could it be that the netif MTU has to be adjusted – it’s set to the frame size – 28 (for headers).

 

Thanks,

 

Bill Auerbach

 

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From: address@hidden [mailto:address@hidden On Behalf Of Goldschmidt Simon
Sent: Thursday, January 31, 2008 12:09 PM
To: Mailing list for lwIP users
Subject: RE: [lwip-users] Jumbo frame questions

 

Bill

 

Which version of lwIP are you using? I think there has been a change in CVS recently that fits your problem (remote mss not used for sending). Could you try to use the v1.3.0 release candidate?

 

Simon

 

 

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Von: address@hidden [mailto:address@hidden Im Auftrag von Bill Auerbach
Gesendet: Donnerstag, 31. Januar 2008 16:54
An: 'Mailing list for lwIP users'
Betreff: [lwip-users] Jumbo frame questions

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