How do I use ffmpeg with live streaming from an IP camera

Question

My question is very basic because I am a newbie to all these technologies.

I have an IP camera connected to my internal network.

http://192.168.1.20/videostream.cgi?user=admin&pwd=

...gives a live streaming view in Firefox or Internet Explorer.

Now I want to record the live stream into a video.

The parameters to be supplied are begin_time, end_time, format of video etc.

How do I accomplish this?

I appreciate any guidance.