You are supplied with a router when you sign up for a Westnet service. A router is basically a small PC running an operating system. It also runs programs such as a firewall for security, a web-server for the set up of the router and a DHCP server to issue any connected devices with the information they need to contact the internet. Your router also manages every connect that comes from and towards it to make sure information is sent to the device that is waiting to receive it. It also watches for connections aimed at it that you may not have requested and then subsequently refuses them entry.
As you can see, a router is a very busy piece of equipment. At times, the connections that are set up from your device can stay open for long periods of time and open multiple connections to display one web page. This consumes a lot of the already small amount of memory and processor cycles that your router has. So as you push more data through your router it may reach a point where the memory simply runs out, the operating system freezes and your router stops working. Turning off and on the router (also known as power cycling) restores peace and calm to the router, clears the memory and any frozen processor cycles allowing data to flow again.