[Freeciv-Dev] Re: Network bandwidth, and other things.

[Jason Dorje Short <vze49r5w@xxxxxxxxxxx>]

Christian Knoke wrote:

> What happens with TCP/IP, when a single packet got lost? I think, in the
> first place, _nothing_ happens. Neither of both endpoints of the connection
> gets aware of this (But I may be wrong here!). Only after another packet is
> sent in the same direction, or a specific amount of time passes, the
> receiver gets notified of this and resends the packet.
After each packet sent an "ACK" packet is sent in return.  If the ACK 
does not arrive in a reasonable timeframe (which is a very difficult 
subject in itself), the packet is resent.
So, this is not a problem.

> So: What happens when I try to move a unit (cursor key) and the packet gets
> lost? I wait a long time, getting nervous, losing needed time to fight the
> battle. That has actually happened to me. Finally, the TCP/IP layer gets
> aware that a packet is missing and resends it. Civserver answers, the unit 
> moves on the screen, the battle's lost. Shit happens.
> What can we do? Just send a ping every second (if nothing else is sent
> within a second). TCP/IP notices the packet loss when the ping arrives, and
> retransmit of the lost packet is initiated. This should keep the delay below
> 2 seconds. - - And now the flames, please :)
Flame flame :-)

Sending a ping every second will only slow things down.  Now not only 
will you have to wait for our lost packet above, but every time a ping 
is lost you'll have to wait then too (although a later packet may 
arrive, it will not be usable by the server until your.
I can imagine (but can't say definitively) why the above behavior might 
happen.  If you're on a slow (high-latency) connection, then the 
round-trip-time from client to server will be high.  In this case the 
packet will take longer to be sent.  And if the packet is lost multiple 
times (which is probably likely - packets usually aren't just dropped 
randomly but are dropped because somewhere a server's buffer is too big) 
then the wait will be extended.
jason