This chapter covers
- What networking models are and why we need them
- The OSI model
- The TCP/IP model and its layers
- How each layer plays a role in moving data across a network
- Data encapsulation and de-encapsulation
In the previous chapter, we looked at Ethernet; specifically, we looked at the types of physical connections defined by the Ethernet standard. Ethernet also defines rules for how devices can communicate over those connections. However, Ethernet alone isn’t sufficient for two computers to communicate over a network (e.g., for a PC to retrieve a web page from a server over the internet). Communicating over a network is a complex process, and it requires a variety of protocols, each of which performs specific functions and, when brought together, enables network communications.
In this chapter, we will look at a couple of models that define the various functions required to enable computers to communicate over a network: the Open Systems Interconnection (OSI) model and the TCP/IP model (named after two key protocols of the model: Transmission Control Protocol and Internet Protocol). TCP/IP is the model currently used by modern networks all over the world.