Networking - The TCP/IP Five-Layer Model - Conclusion

The TCP/IP five-layer model provides a practical way of thinking about how the Internet protocol suite is organized. Like the OSI model, it divides network communication into layers, each with its own responsibilities.

In this model:

The Physical layer defines how bits move across a medium,
The Data Link layer groups bits into frames and handles local addressing and error detection,
The Network layer (Internet layer) routes packets between networks using logical addresses,
The Transport layer provides end to end conversations between processes, and
The Application layer offers the services users and programs actually see.

Although the OSI model has seven layers and the TCP/IP model has five, the ideas line up reasonably well:

The TCP/IP Physical and Data Link layers correspond roughly to the OSI Physical and Data Link layers,
The TCP/IP Network layer corresponds to the OSI Network layer,
The TCP/IP Transport layer corresponds to the OSI Transport layer, and
The TCP/IP Application layer combines the functions of the OSI Session, Presentation, and Application layers.

In practice, real network stacks implement these ideas in whatever way is most convenient. However, thinking in terms of layers makes it much easier to troubleshoot problems and to understand where particular protocols and devices fit into the picture.

Nah, I want to skip around:

Introduction
Physical (Layer 1)
Data Link (Layer 2)
Network (Layer 3)
Transport (Layer 4)
Application (Layer 5)
Conclusion