Re: [lwip-users] How to make tcp segment out as much as possible

[yueyue papa]

send part (lwIP), --->  server is windows based.

I find the lwIP only send 2 tcp segment and wait for ACK.  I use TCP_NODELAY.



On Thu, Apr 15, 2010 at 6:10 PM, Kieran Mansley <address@hidden> wrote:
> On Thu, 2010-04-15 at 17:54 +0800, yueyue papa wrote:
>> I give enough windows size e.g. 16k,  and use TCP_NODELAY.
>>
>> Why I could only see 2 TCP segments out, and wait the remote ACK and
>> then goes on.
>>
>> Is it possible to see all TCP segment out as much as possible?
>
> In which direction (lwIP is sending or receiving) are you seeing
> problems?
>
> When you set TCP_WND you are configuring how much space the stack will
> advertise to allow the other end to send to lwIP.  This does not affect
> how much space lwIP has to send to the other end: this is controlled by
> the other end.  It should be very easy to work out from a packet capture
> what the receive windows are in both directions, and so whether the
> receive windows are limiting the rate of sending.
>
> Sending in TCP is controlled by a number of things, the most important
> being: (i) the receiver's window, which is what you can control with
> TCP_WND; (ii) the congestion window which is not a configurable value.
> These are separate mechanisms, but the amount that lwIP can send is
> limited to whichever value is currently smallest.
>
> The congestion window will initially start off small, but will grow if
> there is no loss.  When there is loss it will reduce drastically to try
> and limit the rate of sending as TCP assumes loss is due to congestion.
> This algorithm tries to find the maximum rate it can send at without
> seeing loss.
>
> Kieran
>
>
>
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