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Re: [lwip-users] ip fragmentation - can i disable?


From: Jonathan Larmour
Subject: Re: [lwip-users] ip fragmentation - can i disable?
Date: Thu, 06 Mar 2008 11:54:46 +0000
User-agent: Thunderbird 1.5.0.12 (X11/20070530)

Piero 74 wrote:
> Hi all
> 
> can i disable ip fragmentation if i'm sure that my board will receive
> from pc application only packet with size < 1500 bytes (MTU) ???

That would be IP reassembly, which is the opposite of IP fragmentation. IP
fragmentation is breaking up large packets before sending them; IP
reassembly is putting fragmented received packets back together.

If your PC is going to be directly connected via an ethernet LAN, then yes
as long as the size is less than 1500 bytes that should be ok. Arguably
this may not be future-proof as there is some movement towards jumbo frames
for gigabit ethernet. But if you have control over the network environment,
that won't be a problem for you.

> if fragmentation is on, what is the better setting for
> IP_FRAG_USES_STATIC_BUF? i understood that for memory usage is better
> set this option to 0, IS IT RIGHT?

Usually yes.

Jifl
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