[lwip-users] question about TCP retransmission

[yueyue papa]

Hi All,

 

IwIP is used on the GPRS network. There is a small TCP data exchanged in TCP stream: about 100~300 bytes.

 

We hope to get the faster interaction speed, but as normal state the GPRS environement is not so stable that the tcp retransmitt may happen. But based on the observer the TCP behaviour, I guess the TCP retransmitting is not as quick as possible.

 

Which paramters or code could be changed let TCP retransmit as quick as possible? I am struggling it for long time, but unable to find the suitable method.

 

My methods

 

1> change the TCP_TMR_INTERVAL, TCP_FAST_INTERVAL or TCP_SLOW_INTERVAL to a small value.

2> change Ack solution

     (pcb->flags & TF_ACK_DELAY && pcb->rcv_wnd >= TCP_WND/2

==>

    (pcb->flags & TF_ACK_DELAY && pcb->rcv_wnd >= TCP_WND/8

 

I uanble to see the valid result.

 

How could I increase the TCP retransmit as quick as possible.  The normal interact between server will be 1.4s ~ 2.5s. Some time the receive will be long than 20s, event to 50s. The interact is success, but it is extremely slow.

 

I used raw API to quick the speed, but nothing got.

 

Thank you for suggestion.

 

Lee