Tony's ramblings on Open Source Software, Life and Photography

Finding Packet Loss

Finding Packet loss on a large wide network or within your ISP's network can be difficult. Generally the cause of packet loss is bad hardware or lines at a specific location, or an oversaturated network. Since most pathways on the internet will require 10 hops or more, figuring out which hop is troublesome can be difficult.

Traceroute may help, but if the packet loss is intermittent then you may think the loss is happening further down the line than it is.

Ping is nice, but you'd have to ping each hop repeatedly, starting at the closest and working your way out.

The tool for the job is My traceroute (mtr). It will ping a specified number of times to every hop on the path, and if the path changes - as sometimes they will - it will ping all of the other routers and list them out as alternates.

My default mtr will give you an interactive constantly updating display of the results. You may want to generate a report you can email to your ISP when you complain about the problem however, and there's a few switches that allow you to do that.

  -c X   Sends X pings and then stops
  -r     Generate a report and quit

So the command you would use might look like:

mtr -c 100 -r 74.125.228.17

The report will show loss percentage, average ping time, best and worst times.