I've been ssh'ing into a specific server from my home office via Wifi and Time Warner Cable internet for years with no problem.
In recent months, I started having problems, where I'd be unable to ssh in to that server (I'd get ssh login time outs) for periods of several minutes, then for no apparent reason everything would work normally. I can't detect any pattern to when it works and when it doesn't; just seems like it's a few minutes working, a few minutes not working. Also, sometimes after ssh'ing in successfully my connection would just freeze at random times, even when I'm just idle on the command line.
Clues: 1. When I get the ssh time outs with this particular server from my computer, I immediately try ssh'ing into a different server and never have problems. 2. Likewise, when I get the ssh time outs, I try to ssh into the same server with my phone on the same Wifi network, and ALSO get time outs. 3. If, at the same time as the time outs are happening, I ssh into the same server on my phone via 4G, I get in with no problems.
This suggests the problems is something to do with my Wifi router or Time Warner connection and how they interact with the specific server I'm trying to get into.
That's as much as I've been able to figure out. What are the next things I should check to figure out this mystery?