Frozen connections

[Don Lewis]

On  3 Mar, Eugene Grosbein wrote:
> H!
> 
> I'm experiencing strange problems with HTTP connections between
> two machines connected using 100Mbit ethernet switch.
> Client is Windows 2000 SP4 (named kost),
> server is FreeBSD 4.9/Apache 1.3.27 (named www).

> ---------------------------------------------------------------------------
> Packet 90
> TIME:   12:06:51.278337 (0.279509)
> LINK:   00:90:27:AB:08:88 -> 00:90:27:35:05:1B type=IP
>   IP:   www -> kost hlen=20 TOS=00 dgramlen=41 id=64CE
>         MF/DF=0/1 frag=0 TTL=64 proto=TCP cksum=A7ED
>  TCP:   port http -> 2134 seq=1179931920 ack=1524903532
>         hlen=20 (data=1) UAPRSF=010000 wnd=58400 cksum=FC43 urg=0
> DATA:   t
> ---------------------------------------------------------------------------
> Packet 91
> TIME:   12:06:51.278615 (0.000278)
> LINK:   00:90:27:35:05:1B -> 00:90:27:AB:08:88 type=IP
>   IP:   kost -> www hlen=20 TOS=00 dgramlen=40 id=10E6
>         MF/DF=0/1 frag=0 TTL=128 proto=TCP cksum=BBD6
>  TCP:   port 2134 -> http seq=1524903532 ack=1179931920
>         hlen=20 (data=0) UAPRSF=010000 wnd=0 cksum=5466 urg=0
> DATA:   <No data>
> 
> As you see, last pair of packets repeats many times
> and transfer is stalled here. What's wrong and who is guilty?

It looks like the client is the guilty party.  The server is sending
1-byte long window probes, and the client is responding with an ACK
packet that is advertising a receive window of 0.

I'd be suspicious of the application software on the client.  Can you
try a different web browser, or even fetch the same URL using something
like telnet?