Monday, March 12, 2007

BitTorrent and traffic shaping

One of the problems of moving house is getting new providers for all kinds of services. Choosing a new broadband provider is a worry, particularly if you were happy with your old ISP. Telewest (now Virgin Media) were pretty good in general, even despite the fact that they were too quick to disconnect my web space and to get rid of all my files the very second after mys subscription ran out. Now I am with BT, and while I have been quite happy with some features of their service (free wireless roaming hours, yay!), I have found to my surprise that they seem to cap BitTorrent transfers. I found to my dismay that I could not get a BitTorrent load exceeding 30 kbps.

How could BT do this? And why? Welcome to the weird and wonderful world of traffic shaping. Even the most conservative estimates tell us that BitTorrent traffic makes up for 30% of all bandwidth used in the world at any given time. At peak hours, some have estimated the figure to go as high as 55%. This is a large chunk of very expensive bandwidth. Some ISPs have decided to regulate this by applying traffic shaping rules that will provide caps on the bandwidth allocated to P2P traffic, particularly BitTorrent. One Quality of Service (QoS, talk about euphemisms!) software provider describes the traffic shaping done by their software like this:

QoS ClassProtocolsPriorityGuaranteedMaximum
VOIPSIP, H323, Skype, MSN MessengerHigh1Mbit/s
P2PeMule, EDonkey, KaZaA, Gnutella, BitTorrent, Direct ConnectLow 256Kbit/s
SHELLssh, telnetHigh
BULKftp, smtpLow

This assigns a 256 kbps to all P2P traffic, which is very low indeed.

Should ISPs get away with this? Trying to see their point of view, one could argue that ISPs are entitled to make sure they provide an adequate service to all their users at all times, and that a few people using a large percentage of bandwidth to download their next episode of Lost is not a particularly efficient way to allocate resources. However, ISPs make a big point in their advertisement about how fast they are, and how you can get 8 mbps, or even 16 mbps in their ultra-fast network. Who are they trying to entice with these offers of speed? P2P traffic of course! After all, you don't need 16 mbps to read the email from Auntie Rita. It is highly unlikely that people will use it to download cookie recipes either.

So, if I pay BT a premium price for their fast connection, I very much expect to get top download speed for whatever protocol I choose to use. It should also be pointed out yet again that BitTorrent is used to share legitimate content. I downlaoded both OpenOffice and Open SuSE Linux with the protocol. Also, we must not forget "legitimate" file-sharing. After all, content providers keep advertising that we will be able to download movies in the future. Will these also be affected? Probably not, as most of this traffic will be offered through proprietary systems, like iTunes, or through sanctioned broadband systems like Cache Logic's Velocix.

So, what to do? Should I just sit and take the slow BitTorrent bandwidth? No way! There's always a technological solution for every technological attempt to regulate technology. Armed with encouraging previous experiences that someone somewhere will have an answer, I was able to find out that the best solution is to turn on encrypted connections in the BitTorrent client (in my case Azureus). This will not cover all downloads as the sending client needs to have encryption turned on as well, but it will drastically improve download speeds (from 30 kbps for three torrent files to almost 200 kbps). Most moderns clients will have encryption turned on.

So, if you are moving house, check out the list of "Bad ISPs" (BT is not listed, funnily enough).

1 comment:

Anonymous said...

I agree entirely.

They should just charge people for the amount of traffic they use, rather than trying to charge a standard amount to everyone.