Slow internet speed is usually caused by internal PC OS problems or externally from your internet service provider. To increase speed internally by just removing viruses or breaking off updates or by removing cache or cookies is easy but it’s impossible if the internet server provider is down or has lots of load on the server. Usually the result of lots of sharing by DSL provider on a single server.
We use Domain Name Server (DNS) of our service provider which changes the website URL we use on browser and covert it to ip to make connection with our Internet ip to collect data for a website we want. To speed up our internet to maximum we can use a different DNS which has higher speed than a default DSL which could have a lots of load of their internet users or that may be slow. There are lots of free and open DNS which could be faster than our ISP like opendns.com or google public DNS.
Using DNS on windows is easier because it has more software than Mac. To tweak speed on Mac we can use Namebench which helps to find the fastest DNS available for our PC. It uses different benchmarks from browser history, tcpdump output and etc and gives recombination.
Namebench is open source and it’s free to use and gives lots of premium details of DNS test by checking ping time and other information that can be viewed graphically or in table. This helps to choose the fastest DNS available to get maximum speed from your ISP on MAC .