[lwip-devel] How to understand TCP_SND_BUF

[narke]

Hi,

I found the value of TCP_SND_BUF was assigned directly to snd_buf
attribute when a new pcb was allocated.   Then I lost understanding
why this variable should be used.

It's different with snd_wnd,  which is dynamically changed after a new
value is advertised from the peer end.
It's also has nothing to do with memory space of sending pbufs, which
is determined by MEM_SIZE constant.

It will decreased after sent some data and increased while these data
are acknowledged.   Is this the only purpose?  I am wondering, if I am
going to send out some data, I will ask if the memory is enough to
hold it (MEM_SIZE) and if the peer is willing to receive such more
(snd_wnd), you see, there is no a role for snd_wnd.

Could someone please clarify this and tell me give me a guideline in
correctly setting the TCP_SND_BUF.

Thanks in advance.


-- 
Life is the only flaw in an otherwise perfect nonexistence
    -- Schopenhauer

narke
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