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RE: [lwip-users] Jumbo frame questions
From: |
Bill Auerbach |
Subject: |
RE: [lwip-users] Jumbo frame questions |
Date: |
Wed, 6 Feb 2008 14:54:59 -0500 |
Thanks,
Bill Auerbach
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On Behalf
> Of Kieran Mansley
> Sent: Tuesday, February 05, 2008 11:01 AM
> To: Mailing list for lwIP users
> Subject: RE: [lwip-users] Jumbo frame questions
>
> On Tue, 2008-02-05 at 15:47 +0000, Kieran Mansley wrote:
> > If that's correct, then you've got
> > a configuration error: all nodes on the same LAN are supposed to have
> > the same frame length and MTU, and it sounds like you've put the lwIP
> > node with an MTU of 9000 on a network with an MTU of 1500. That just
> > doesn't work I'm afraid.
>
> I've just had another look! If you use the LWIP_CALCULATE_EFF_SEND_MSS
> option and then set the MTU appropriately in your netif (the example
> ethernetif.c just always sets it to 1500 - I presume your changes to get
> jumbo frames working did something more sophisticated) you should be
> able to safely set TCP_MSS to 8960 (i.e. an MTU of 9000) and lwIP will
> downsize the MSS appropriately.
I do (or have left) this option enabled. My issue was setting MTU to the
packet size. I'm surprised I've gotten as far as I have. :)
> The bit that's probably missing in your port is the setting of netif-
> >mtu. This is normally configured using a tool like ifconfig on Linux,
> but how you do this on your target will depend heavily on the OS (if
> any) it's running.
I wasn't adjusting MTU (or MSS) for the headers. I am able to leave the
lwIP stack and it's controller set for Jumbo frames and it does communicate
on a network not supporting it. This was what I was after - and maybe it
works *only* with my router? lwIP was crashing this way because of the MTU.
Thank you for your help and replies. I didn't mean for you to expend so
much effort but it helped me. I can't explain the jumbo and non-jumbo mix
working.
Bill