Since I did the following Ive never had a connection timed out issue -
Ping the your service provide (you'll need to find their IP address usualy in your routers settings) with packets of data slowly decreasing the size until you don't get a 'needs defragmenting' message passed back. - you need to do this on a PC connected to your network using a DOS prompt.
GENERAL GUIDELINES FOR MTU TESTING
Use the following command at the Operating System prompt:
- ping -f -l 1024 <IP Address>
Explanation of parameters: The switch "- f" (minus sign followed by lowercase F) indicates do not fragment. The second switch "-l" (minus sign followed by lowercase L) is for size, and the number following it indicates the packet size you will be sending. Some operating systems and TCP/IP stacks allow additional parameters, for example, "-n <number>", which indicates how many times the ping is sent. (above is pinging a packet size of 1024)
If this PING passes successfully you will get a reply from the IP address specified. If the packet was too large you will get.the message:
"Packet needs to be fragmented but DF set"
You should reduce the packet size until you are successfully connecting. Then, use this successful size when specifying an MTU value on the PS3 / and the your router.
Example mine was trying to send 1500 MTU (value) to BT and when I 'pinged' BT the largest they would accept without fragmentation was 1472 MTU (value). Problem with fragmentation is that although putting fragmented files back together is ok for surfing the net etc. it's not quick enough to put back together for gaming online. (thats how I understand it ).