Re: [lwip-users] TCP send queue and small windows

[Vlad]

This didn't help. I forgot to said that our lwip client is masqueraded by 
windows 2003 server (on linux masquerading i have seen the same effect). It's 
seems that some lwip-created packets just dropped by win2003 server tcp/ip 
stack.

this is connection scheme:

<my windows xp client|here is lwip-software> --- <linux with tcpdump connected 
by vpn to windows 2003 server> --- < windows 2003 server > -- internet --- 
<destination server with tcpdump>

this is tcpdump listing at linux:

12:02:52.163700 IP windows_xp_lwip_machine > remote_server: S 6531:6531(0) win 
20480 <mss 1460>
12:02:52.398417 IP remote_server > windows_xp_lwip_machine: S 
1174020218:1174020218(0) ack 6532 win 5840 <mss 1460>
12:02:52.818934 IP windows_xp_lwip_machine > remote_server: P 1:248(247) ack 1 
win 20480
12:02:53.069843 IP remote_server > windows_xp_lwip_machine: . ack 248 win 6432
12:02:53.120341 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:02:57.038349 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:03:06.257675 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:03:15.445718 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:03:24.633976 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:03:24.634256 IP windows_xp_lwip_machine > remote_server: R 1708:1708(0) ack 
1 win 20480

this is remote server tcpdump listing:

13:00:09.701308 IP windows_2003 > remote_server: S 6531:6531(0) win 20480 <mss 
1460>
13:00:09.701332 IP remote_server > windows_2003: S 1174020218:1174020218(0) 
ack 6532 win 5840 <mss 1460>
13:00:10.372385 IP windows_2003 > remote_server: P 1:248(247) ack 1 win 20480
13:00:10.372408 IP remote_server > windows_2003: . ack 248 win 6432
13:00:42.200931 IP windows_2003 > remote_server: R 1708:1708(0) ack 1 win 
20480

as you can see, this packets just lost:

12:02:53.120341 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:02:57.038349 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:03:06.257675 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:03:15.445718 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480
12:03:24.633976 IP windows_xp_lwip_machine > remote_server: P 248:1708(1460) 
ack 1 win 20480

they retransmitted many times but didn't go to remote_server (i changed 
tcp_rexmit timeout to 10 second for test).

any ideas?

On Thursday 22 March 2007 11:35, Kieran Mansley wrote:

> On Thu, 2007-03-22 at 11:27 +0200, Vlad wrote:
> > Hi!
> >
> > i've tried to reduce  TCP_SND_QUEUE even to:
> >
> > #define TCP_SND_QUEUELEN        TCP_SND_BUF/TCP_MSS
>
> Sorry, I should have been more explicit: decrease TCP_SND_BUF not
> TCP_SND_QUEUELEN.  The former is the max length in bytes, the latter is
> the max number of pbufs in the send queue (and must be at least 2 *
> TCP_SND_BUF/TCP_MSS for things to work well).
>
> Kieran
>
>
>
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