>From Herman Robak on Monday, 2005-11-07 at 00:46:33 +0100: > > Actually, for UDP traffic there are more options, most of them dirty hacks. > <http://en.wikipedia.org/wiki/UDP_hole_punching> > > One of them, STUN, even has an RFC <http://www.ietf.org/rfc/rfc3489.txt>
Skype uses a variant of STUN, according to this analysis: http://arxiv.org/pdf/cs.NI/0412017 7. CONCLUSION Skype is the first VoIP client based on peer-to-peer technology. We think that three factors are responsible for its increasing popularity. First, it provides better voice quality than MSN and Yahoo IM clients; second, it can work almost seamlessly behind NATs and firewalls; and third, it is extremely easy to install and use. We believe that Skype client uses its version of STUN [1] protocol to determine the type of NAT or firewall it is behind. The NAT and firewall traversal techniques of Skype are similar to many existing applications such as network games. It is by the random selection of sender and listener ports, the use of TCP as voice streaming protocol, and the peer-to-peer nature of the Skype network, that not only a SC traverses NATs and firewalls but it does so withhout any explicit NAT or firewall traversal server. Skype uses TCP for signaling. It uses wide band codecs and has probably licensed them from GlobalIPSound [10]. Skype communication is encrypted. The underlying search technique that Skype uses for user search is still not clear. Our guess is that it uses a combination of hashing and periodic controlled flooding to gain information about the online Skype users. Skype has a central login server which stores the login name and password of each user. Since Skype packets are encrypted, it is not possible to say with certainty what other information is stored on the login server. However, during our experiments we did not observe any subsequent exchange of information with the login server after a user logged onto the Skype network. Conrad -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
