How to Troubleshoot Slow Network in Ubuntu?

Hello,
I am posting this just want to get some general idea where can we check based on a slow network issue in Ubuntu.
For me, I may do the following :
1.use 'ethtool' to check speed & duplex issue;
2. ifconfig ==>check network interface, mtu
3. iftop ==> list all coection with its bandwidth use
4. traceroute ==> check routeufeff

I will be really appreciated if more troubleshoot method can be raised!
ps. If a webpage simply timedout, what troubleshoot process should I follow?
Thank you guys so much!!!