The Skype protocol
is a proprietary
Internet telephony network based on peer-to-peer
architecture, used by Skype
. The protocol's specifications have not been made publicly available by Skype and official applications using the protocol are closed-source
The Skype network is not interoperable
with most other VoIP networks without proper licensing from Skype. Digium
, the main sponsor of Asterisk PBX
released a driver
licensed by Skype dubbed 'Skype for Asterisk' to interface as a client to the Skype network, however this still remains closed source. Numerous attempts to study and/or reverse engineer
the protocol have been undertaken to reveal the protocol, investigate security or to allow unofficial clients.
Skype was the first peer-to-peer
IP telephony network, requiring minimal centralized infrastructure. The Skype user directory is decentralized and distributed among the clients, or nodes
, in the network.
The network contains three types of entities: supernodes
, ordinary nodes, and the login server. Each client maintains a host cache
with the IP address
and port numbers of reachable supernodes.
Any client with good bandwidth, no firewall, and adequate processing power can become a supernode. Supernodes relay communications for clients behind firewalls
and Symmetric NAT
. This puts an extra burden on those who connect to the Internet... Read More