Is my bandwidth being shaped ?

The other day I was running some tests because it seemed that my VPN traffic was being slowed down quite a lot. 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.... 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.