The speed at which you can download is largely dependent on the speed at which the other end can upload. Most people share no, or very few, files. Consequently, those people who do share files are very popular - there is usually a high demand and you will almost certainly be sharing their upload bandwidth with a number of other people.

Or you might be trying to download from a modem user.

There is a small possibility of a communications problem...

The speed of download is negotiated between the two clients up to any other maximum limits that have been imposed. There's no point in a T1 user sending to a modem user at full bandwidth - the modem user can't accept it all. So the receiving end sends out a message each time it receives a chunk of information. The sending end learns not to send data faster than the receiver can cope with them (based on the acknowledgement messages from the receiver).

If the acknowledgments get lost (dropped packets) this can screw up the whole process - the two ends have to re-negotiate and find out where they were - this can really slow down the communications rate.

Poor communication (dropped packets) can happen for lots of reasons. Most sites will experience the problem from time to time. If a site is persistently bad then the local connection may have a fault.

Long latency (high ping times) should not cause a problem - It will slow down the initial negotiation but shouldn't impact on the transfer rate.

Firewalls should either block or not block packets. A firewall should make no difference to transfer speed.

Mark