Q:

Network simulator?

Do you know of software which is capable of emulating networking conditions such as constrained bandwidth, latency, closed ports, congestion, collision?
Platform-specific is fine, but I'd like to be able to emulate hundreds or thousands of nodes under varying network conditions.

A:

You could check out ns-2 or ns-3. ns-2 is a well-tested network simulator. ns-3 is the "replacement" by the same group of people.

A:

Fiddler can do constrained bandwidth and latency simulations.

