Maybe you've just changed your Router for a more advanced model and dumped that horrible old Thompson router?
We recently changed one of our clients over to a brand spanking new Draytek Vigor 2860n model. We can't sing its praises enough. But we noticed a problem. A great big elephant in the room problem that just wouldn't go away.
Once our all singing all dancing fantastic box was in and working wonderfully on the internal network, our internet had suffered a horrible performance hit. Not good.
We we began looking for a solution. We checked and double checked all our DNS, internal routing and ping diagnostics.
Pings came back from google within a timely 20ms. So something was pointing to our data packets. Well time to test.
Here's what you need to do on a Windows machine:
- Open a command prompt by pressing the win key + r and type in cmd into the run box
- Press OK to open a black window. The command prompt
- In the command prompt, we will begin testing drop outs on our packet size using the following command, ping google.co.uk -f -l xxxx where xxxx is the packet size we will send
- Our current MTU on the Vigor was set to its default rating of 1492, so we started at 1300 by entering ping google.co.uk -f -l 1492
- Ping responses came back successfully in just over 300ms
- We then began to increase our MTU towards our 1492 packet size limit
- In our tests, our packet limits were hit at 1480 with the error: Packet needs to be fragmented but DF set
- We got down to 1470 and found that we were no longer getting a packet error, but the return result was taking far too long.
- Our sweet spot was at 1438. A quick response time of around 280ms and all ping backs were successful
- We applied these MTU settings to our Vigor under WAN > Internet Access > WAN 1 > Details > MTU
- We had to restart our router to confirm and once done tested our internet
- Our connection had returned back to its normal speed and was a great improvement on what it was. Our client was happy again and so were we.
The method on a mac is very similar, but the command you have to use to ping with a specified packet size is as follows:
- ping -D -s xxxx google.co.uk where xxxx is the packet size to send