The 4 Layer Internet Model
- Application: Bi-directional reliable byte stream between two applications, using application-specific semantics
- Transport: Guarantees correct, in-order delivery of data end-to-end. Controls congestion.
- Network: Delivers datagrams end-to-end. Best-effort delivery - no guarantees. Must use the Internet Protocol (IP)
- Link: Delivers data over a single link between an end host and router, or between routers.
Reuse is a big advantage of layering. Each layer provieds a service to above.