[SOLVED] udp and packet loss

[danni.coy]

I have just updated to the latest SDK - now the UDP network test seems to be running a lot faster 50MBs as opposed to 5MBs per second after I have changed the buffer sizes down from 1024 to 900. What is really concerning me is that we are now getting ~10% packet loss which wasn't there before.

 

Update - changing the values back to 1024 makes the packet loss go away but the throughput drops back down to 5 MBs. The changes I have made is a text replace of 1024 for 900 in server.usc and client.usc - Am I doing this wrong?

[frustum]

Try to play with send/recv buffers size. Moreover the network driver quality is very important.

[danni.coy]

so better quality network cards may aleviate the problem?

[ulf.schroeter]

so better quality network cards may aleviate the problem?

 

Hi Danni, this is hard to predict as consistent network performance without spikes seems to be quite challenging and is influenced by OS, drivers, network cards (and their over-complex parameters) and also used network switches

 

We spend weeks to track down network frame synchronization issues in the field of real-time visual simulation with multiple render PC's connected via LAN for synchronized, fixed frame-rate (30/60 Hz), vsynced rendering...wireshark and hrping were our best friends.

 

In most cases occational highly increased delivery delay times of only some network data packets send at a constant rate were the key problem (UDP packet losses never were an issue).

 

When you have to fight for every millisecond as in real-time visual simulation than one might be tempted to spend some dollars/euros on specialized network cards with own co-processor and optimized driver stack for low-latency network packet processing.

 

Key player in this field is the killer 2100 network card (some review edit: just saw that they used UNIGINE Heaven for workload-stressing)     

 

Though these products claim highly reduced ping times for online gaming etc. the real benefit in practice is often questioned (as ping times are primarily dominated by the internet transmission and not the local network card).

 

Nevertheless in case of LAN-based multi-nodes PC rendering clusters they might improve network performance. Saving some milliseconds in case of 60 Hz fixed-frame-rate rendering with 16 ms frame time budget can make a big difference. Also they might avoid network packet delay jittering/spikes due to their dedicated co-processor and driver stack by-passing standard (non-real-time) windows subsystems.

 

You could buy 2 cards and do some testing on your own. These cards also seem to have much better tools for tuning and network performance monitoring.