A networking model organizes the functions required for data to travel from a source to a destination. It divides those functions into layers, allowing multiple protocols to fulfill each layer’s role. section 4.0 section 4.1
Use the models as a practical framework for understanding network communication:
- TCP/IP is used by modern networks and commonly appears as five layers: Physical, Data Link, Network, Transport, and Application. section 4.4
- OSI has seven layers and strongly influences networking terminology, although it is not used as the modern networking model. section 4.4
- Layers separate responsibilities: Data Link handles hop-to-hop delivery, Network handles end-to-end delivery, and Transport addresses the destination application through port numbers. section 4.4
Wired or wireless delivery
An email application can perform its role without knowing whether lower layers send the message through Ethernet over cable or Wi-Fi over radio waves. section 4.1
