I have proxies set up via Squid. The proxies usually works great, but last couple months they've been very slow from time to time. It's not consistent.
I really don't know where to start.
Which steps should I follow to troubleshoot?
Maybe the problem are the proxies. I tell you this because I used before Squid proxies and I had only problems with their proxies. Now, I use proxies from Proxy-N-Vpn.com and they are working perfect.