The other day I was running some tests because it seemed that my VPN traffic was being slowed down quite alot. One of the tests was plain FTP, that went at about 1mbyte/sec, then FTP via VPN, that seemed capped at around 200kbytes/sec. Some say "overhead because encryption", and I believed it, until I tested between two weak machines (VIA 2ghz) on a LAN:
- FTP: 10Mbytes/sec
- FTP/VPN: 6.5Mbytes/sec
obviously 200kbytes is a joke.
I of course suspected one of my ISPs (ADSL or dedicated server provider) of doing something uncool.. this lead me to discovering two things:
- Some ISPs openly cap VPN traffic like PlusNet. They actually have a whole timetable with various speed limits for various services ! You might have noticed P2P gets the lowest speed ever and youtube is way up there.... ..in short, the client's needs are not important, what is important is who's paying.. anyway.
- a cool tool called shaperprobe. This tool helps detect if there is any packet shaping happening on your network.
I soon after figured out where the issue was, my ISPs who say they don't throttle or shape etc are correct. : ] The issue was with this WAG54GS I hooked up temporarily that has this super cool option called "SPI Firewall", it's sole purpose is to slow down your VPN traffic, that's all it does.
In the end I learned that there are many bad ISPs nowadays that decide what's good for you, I am glad mine(s) don't, but how long will this last ? As they say, it's the consumer who decides, so if this matters to you, pick an ISP that doesn't shape their bandwidth.