[lwip-users] TCP performance in receiving

[Wei Bo-Er \(Jason\)]

Hi All,

 

I am using lwip 1.0.0 and meet a problem in TCP performance. I found that TCP performance much dependents on usage of connection.

A  connection which sends & receives packets alternately will get much higher perfoemance than the one which only receives packets.

This seems due to that tcp_ack will always set pcb->flag to TF_ACK_DELAY in tcp_receive. I guess doing so is for waiting to see if

there is any packet to be sent later and ack can also be sent in that packet. But as a connectionis is always in recving packets, each ack will

always delay about 250ms and then it can be sent. This will much reduce TCP performance.

 

I'm not sure what is best solution about this question. I just reduce TCP_FAST_INTERVAL from 250ms to 50ms. It really works and gets

about five times performance than before. But I'm afread this will also increase tcpip_thread loading in processing too much useless timeout

as there is no connection which is only in receiving packets. I'm not expert in TCP,so I think there may be someone can give me a better solution

than what I did.

 

 

Regards,

 

Bo-Er