Recently, I had occasion to try to remedy an intermittent internet connection in Turkey… It ended up being more challenging than I had anticipated. There was a LAN with a remotely-located (around 100 meters away) proxy server, and it worked intermittently. A ping to the proxy server showed no problems, unless there was congestion on the network. A ping flood would show between 5 to 10 percent packet loss, which increased with the size of the packet.
Having established that the route to the proxy server was at fault, I investigated and learned that the cable from the switch to the proxy server was probably over 100 meters, and that at least a segment of that cable ran parallel with a high voltage power line.
Thinking about the old days of dial-up, and the necessity of reducing the connection speed depending on the line quality, I had the idea of trying to reduce the link speed from 100 Mb/s to 10 Mb/s. It shouldn’t have negatively impacted the internet connection, since it was only a 6 megabit ADSL connection. The problem was that the link speed was auto-negotiated by the switch at both ends, and there was no way to force the link speed slower than 100!
Linksys WRT54GL (loaded with Tomato firmware) to the rescue! Under advanced settings was an option to manually force the link speed down to 10. I installed the router in between the switches, and the problem was gone immediately!