Good day Masters. After getting some suggestions from our co-pdsl mates regarding on a best router. Since I don't have any budget replacing my present router (Linksys BEFSR41). I've researched about the same Problem I have. And I found this one: http://www.allaboutjake.com/network/linksys/mtu/ after reading the article I quickly change the MTU of my router from 1492 to 1362 and observed it from 10am up to now, and the problem doesn't persist anymore. I hope this will be the solution for my problem. I will update this thread as soon as any changes occurs.
