It might be ED servers, it might be the ISP, your friend's connection or the internet in general, but it wasn't that for me.
I was getting a lot of matchmaker disconnection issues recently, both in open and solo. It would disconnect me after random amounts of time and send me back to the main menu. Observing the data rate in-game in ED, the Tx rate was okay, but the Rx rate would drop to zero, indicating a disconnect was imminent. What was frustrating was that the game seemed to immediately reconnect to the server at the main menu without problem. I also found that whenever I tried to communicate in-game to a friend, it was nearly always unsuccessful.
I tried changing port settings without any success, and was starting to get annoyed. I then noticed that when I used the windows troubleshooter (right click on the wireless adaptor symbol at the bottom right on Windows 10), it was finding problems and would reset the card. I think the diagnostics was saying the card was transmitting data okay, but had problems receiving it. The signal strength to the router was strong, so this seemed a bit strange. The game would be fine for a while, and then the problems would come back. I did not experience any problems with downloading files or using a web browser.
I eventually tried to replace the card with a wireless dongle to see if that made a difference. I had trouble getting that set up (I'm no good with a router it seems), so I went back to the original card. Everything started working properly again. I eventually guessed that my problem with the original card was due to one of its antennas not being screwed in tight enough into the card connector, and this was causing an intermittent problem. My fault, because the antennas can only be fitted after the card is installed into the slot, and I was the one who fitted the card originally.