Many ISPs block the use of P2P (Peer-to-Peer) software/networks as they can cause slow down the broadband connections for most other users when the ISPs networks are under heavy P2P use, its said that where there are no P2P blocks in place its roughly 5% of customers that use 99% of all available bandwidth through downloading large files on Bit-Torrent networks, so to ensure the networks stay fast for everyone an ISP may block the use of P2P/Bit-Torrent during peak hours or at anytime but how much is dependant on network load (Virgin Media uses such a method)
There is a website called Glasnost
which allows you to check if your ISP are applying P2P blocks on your connection.
Glasnost tests work by measuring and comparing the performance of different application flows between your host and our measurement servers. The tests can detect traffic shaping in both upstream and downstream directions separately. The tests can also detect whether application flows are shaped based on their port numbers or their packets' payload. For more details on how Glasnost tests work, please read our NSDI 2010 paper.
The goal of our Glasnost project is to make access networks, such as residential cable, DSL, and cellular broadband networks, more transparent to their customers.
ISPs are increasingly deploying a variety of middleboxes (e.g., firewalls, traffic shapers, censors, and redirectors) to monitor and to manipulate the performance of user applications. Most ISPs do not reveal the details of their network deployments to their customers. We believe that this knowledge is important to help users make a more informed choice of their ISP. Further, such knowledge is also useful for researchers designing protocols and systems that run on top of these networks.
To improve network transparency, we are building online tools that are easy to use and publishing them on this web page. Currently, there are two tools you could use to test your ISP. We will release more tools as we develop them in the future.
to test your connection