Mac: Track your Download speeds

This is a great app. Helps you to monitor the internet usage on your mac. Bandwidth+ is a simple app so only tracks the network usage on the Mac it is running on. If you are tethered to an iPhone then it will count the usage while tethered.
Best thing is it is FREE. You can download it from https://itunes.apple.com/in/app/bandwidth/id490461369?mt=12