Why does Skype connect to an unlimited amount of IP address at start up?

Well it connects to about 300 random IP addresses at start up, to random UDP and TCP ports, plus more as you use it. But every time you start it up it connects to another 300 random different IP addresses at start up. I can see this thanks to a useful program called Little Snitch. These are not my contacts, when I select a contact from the list it prompts me to accept their IP address connection which can only be done after the initial set up.