# Strange application bandwidth limit



## Arran (Dec 31, 2011)

Hello

I host a very busy (peaks about 350 players each day) game server which uses up around 70-80mbps of the 100mbit connection, Windows Server 2008 R2 Standard. However for some unknown reason when the usage is high it drops down and gets stuck at around 30mbps causing severe lag.

We've checked to see if its the ISP but it doesn't seem to be as other game servers hosted on the same server aren't suffering from lag and I was able to get the network usage to spike by forcing some players to stream a sound file. Then we thought it may be the game server software since its a mod (Multi Theft Auto: San Andreas), its got plenty of bugs.

The mod developers have even added test code to the mod so we can more easily reproduce the bug and we thought it may be down to the networking platform they used called RakNet but using 2 Linux servers as tests they were able to use 100mbps without any sign of the bug which rules out the software.

So we're left with the operating system. I've disabled QoS, firewall, any services I could disable and even changed NIC settings but everything we've tried is not the cause of the problem. This is a real problem because it prevents us getting more players as well as causing problems during events where players are close together and thus making the bug happen.

This is an image of what the network usage looks like every time when the bug happens: http://cit2.net/arran/pics/nub3.png As you can see its high which is normal until suddenly it falls to around 30% and gets stuck there until the game server stops sending out loads of bandwidth (players disconnecting because of the unplayable lag)

So if anyone has any ideas at all, anything I could just try to fix this problem, please let me know.


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## Rockn (Jul 29, 2001)

Watch what happens to your memory usage prior to the slow down. I had an instructor that told me about this bandwidth throttling issue, but can't recall the fix off of the top of my head.


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## Arran (Dec 31, 2011)

Interesting, the memory usage of the application rose fairly rapidly at about 3000K a second until I ended the bug.

Like it goes from 300,000 to 400,000 in 30 seconds and then as soon as I end the bug, it drops down to normal after 5 seconds.


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