Re: [lwip-users] How to force dup ACK

[yueyue papa]

>From the wireshark,

item 13, is a 1460 data resend,

but in terminal log, we confirmed the data is get, and ACK is also
send to remote.

So I think we just lost ACK.

The problem is easy to meet in  larger TSS 1460, but with 512 TSS , I
could see the send/receive is very stable.

But smaller TSS give a lower performance.

If I increase the TSS, the resend cause the complete flow is low and not stable.

I tried to make duplicate ACK sent to remote, so as to solve my current problem.

I make resend ACK in different code, but still could not see the
duplicate ACK in the server, so I think my changing is not correct.

Kieran, could you guild me to add code for force send duplicate ACK

THANKS.

On Thu, Apr 15, 2010 at 5:49 PM, yueyue papa <address@hidden> wrote:
> Kieran,
>
> thank you to review.
>
>
>
> On Thu, Apr 15, 2010 at 5:44 PM, Kieran Mansley <address@hidden> wrote:
>> On Thu, 2010-04-15 at 15:32 +0800, yueyue papa wrote:
>>> Hi All,
>>>
>>> I use lwIP in GPRS environment.  Wireshark is setup in the server.  I
>>> find these information:
>>>
>>> lwip  device  <--------------------> server (Wireshark running there)
>>>
>>> if  TSS = 512, the TCP stream is working very stable.
>>>
>>> if TSS = 1024, 1460, there is always TCP ACK lost in server. The
>>> resend is always happen.
>>>
>>> The resend cause the performance down.
>>
>> Are you sure it is ACKs that are being lost rather than packets with
>> payload?  Could you post an example wireshark capture to show this?
>>
>>> Is there a solution I could configure lwIP make duplicate ACK send, so
>>> as to decrease the ACK lost possibility?
>>
>> Not that I know of.
>>
>> Kieran
>>
>>
>>
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>