OSI Troubleshooting
Model overview

Internet Protocols
Internet protocols (IPs) can be used to communicate across any set of interconnected networks. They are equally applicable to local area network (LAN) and wide area network (WAN) communications. The Internet suite includes lower-layer specifications such as TCP and IP, and also specifications for common applications such as e-mail, terminal emulation, and file transfer. Figure shows the TCP/IP suite layers and their relationships to the OSI reference model.

The OSI reference model provides a common language for network engineers. When using a systematic approach to documentation and network architectures, the OSI model is pervasive in troubleshooting networks. The model allows troubleshooting to be performed in a structured fashion. Problems are typically described in terms of the related OSI model layer. A quick review of the OSI model can help clarify its role in the troubleshooting methodology.

Each layer is reasonably self-contained, so that the tasks assigned to each layer can be implemented independently. This enables the solutions offered by one layer to be updated without adversely affecting the other layers. The OSI model provides a logical framework and a common language used by network engineers to describe network scenarios. The Layer 1 through Layer 7 terminology is so common that most engineers do not have to think twice about it.