[ENet-discuss] Peer starving problem....

[David L. Koenig]

It sounds to me like the host is running out of outgoing bandwidth.  
Most DSL connections give you about 128Kbps outgoing, 768Kbps to 3Mbps 
incoming. 512k is 4 times the outgoing max. So, under the best 
conditions you can hope to have the packet go through to the/from the 
server in four seconds. That will never happen as enet is going to have 
to break up the packets into chunks of around 1500 bytes which is a 
standard MTU limit, so you lose some bytes to overhead.   It's so backed 
up with outgoing packets that it can't possibly send them all within the 
connection timeout limit. You want to try to limit your packet size to 
1500 including any overhead (UDP header overhead, enet overhead).

Exactly what sort of data is it that you're trying to send?  Why must 
the packet be so large?  Do you know the upload/download speed provided 
to your server?

-dave

Nono BEZMan wrote:
> Hi all,
>
> I have used enet for a while now, and we just came
> across this issue which we could not resolve:
>
> - Setup: we have one client talking to one server
> (enet_host_service every 20 ms) on a DSL connection.
>
> - Test1: client send packets of 512KB to server back
> to back, using only one peer. Everything goes fine.
>
> - Test2: client sends packets of 512KB on more than
> one peer (2-3 in general). All peers are disconnected
> after one minute or so, but one which goes on once it
> "killed" the other ones.
>
> We have also tried to send 4kB (or 2KB) packets with
> 50 peers at the same time.... at the end most "starved
> to disconnection", except for a few ones (like a
> dozen) which then went on happily forever. The bigger
> the packet, the less peer at the end of the fight.
> With 1K packets we ended up with ~20 peers, with 2KB
> about 12 peers and with 4KB we had ~6 peers still
> going at the end.
>
> We even tried to randomize the order in which the
> peers where serviced in send_outgoing_commands to no
> avail.
>
> It is very puzzling to me, as enet being UDP based, I
> do not see why peers starve to death after some point.
> Sending 512KB packets back to back (and maxing our
> upload connection at 50kKB) works fine until we add a
> second peer....
>
> We tried Enet 1.0 (latest CVS) as well as previous
> versions of Enet.
>
> Anybody would have any ideas/pointer on how to resolve
> that issue?
>
> Thank you,
>
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