[Users] Networkproblem: VE stops sending ACKs

[Konstantin Seiler]

On Saturday 02 December 2006 01:43, Konstantin Seiler wrote:
> I've got a strange networkingproblem around here - the VE suddenly stops to
> send ACKs.

Hi!
I finally found something related to that problem. It seems to be a problem 
with TCPRCVBUF in the VEs config. For a check I multiplied the values by 10 
and the download went fine. 
(By the way, what are considered proper values - the defaults caused the 
trouble)

So I interpret the situation as a Bug of OpenVZ: The VE doesn't take TCPRCVBUF 
into account when setting the TCP-Window-Size and the propagated window is 
too big for the available buffer.
If a packet gets lost now, the connection is doomed to die: The sender keeps 
sending packets and eventually the buffer is full. When the retransmission of 
the lost packet finally arrives, it is discarded because of the full buffer 
and the connection is in a deadlock. 
The retransmission can't be accepted because of the full buffer and the buffer 
can't be emptied, because a packet is missing.

Cheers,
Konstantin