A day in the life of an application

Network Applications

Dominant model: bidirectional, reliable byte stream connection

• HTTP client server
• BitTorrent peer to peer
• Skype

Abstracts away entire network -- just a pipe between two programs

Common Models

Client Server Model

• The most common communication model used is a bidirectional, reliable stream of bytes.
• Client sends a request by writing to the connection, the server reads the request, processes it and writes it back to the client.

Peer to Peer Model

• BitTorrent also use reliable bidirectional data stream
• BitTorrent file describes info about the data file and tracker node
• A tracker is a node that keeps track of what clients are member of the swarm.
• To join a torrent, your client contacts the tracker

Skype

• Unlike the web, where there's a client and a server, in the Skype case you have two clients
• Rather than having a personal computer request something from a dedicated server, you have two clients requesting data from each other.
• NAT