Many peer-to-peer networks become client/server networks by adding NOSs to create servers. However, both peer-to-peer traffic and client/server traffic can exist in the same network. When two clients are communicating directly, it is peer-to-peer communication. When a client requests services from a NOS, it is client/server communication.

As networks grow, the increased traffic may create performance problems. Devices, such as switches and routers relieve network congestion by isolating traffic to logical groupings of network devices. The choice of whether to switch or route is dependent on the functionality required by the network. A switch is used for performance boosts and is more efficient than a router. A router is used to provide connectivity to other networks and for specialized security functions, such as Internet firewalls.

We then traced the path and format of data as it travels across local and remote boundaries. We explained how a new frame is built to cross each type of link, carrying packets from source to destination. We saw how applications communicate through software ports, including client application port to network application port. Most important, we saw that the same basic concepts and processes are used to carry data across workgroups and LANs, over wide area links, and across the worldwide Internet.