Re: [lwip-users] What is MEMP_NUM_TCP_SEG?

[Kieran Mansley]

On 15 Mar 2011, at 18:43, Chen wrote:
> 
> "lwip_sanity_check: WARNING: MEMP_NUM_TCP_SEG should be at least as big as 
> TCP_SND_QUEUELEN"
> 
> When I search the lwip 1.3.2 source, I only found three occuracies of this 
> MEMP_NUM_TCP_SEG, and none of them has real meaning.
> 
> So what is MEMP_NUM_TCP_SEG for?

It's the number of TCP segments you can allocate if you're using the internal 
memory pools.  The reason the send queue length should be less than this is 
that otherwise you won't be able to fill the send queue as there can never be 
enough TCP segments.  It also, and more importantly, means that all the TCP 
segments can be allocated and used in the send queue, leaving none for handling 
received packets such as ACKs that would allow you to process the send queue, 
leading to deadlock.

Kieran