Understanding PC Networking
PC networking, or simply a network, is a series of two or more computers connected to each other electronically to share resources, exchange files, or allow communication. The computers on a network are the nodes, and the servers are the devices that allocate the resources. Computers on a network can be linked together in various ways, the most common being through cables, Wi-Fi, satellites, telephone lines, or infrared light beams. Networks also differ in the communications protocols they used to organize network traffic. The two main types of networks include Local Area Networks (LAN) and Wide Area Networks (WAN or "internetwork"). Local area networks connect two or more computers and are confined to small areas whereas wide area networks connect two or more networks, have no geographical limitations, and can even encompass the globe. In fact, the largest wide area network is the Internet.
The first computer networks, though not personal computer networks, were established in the late 1950s through the military radar system. In 1965, the first wide area network was created by Thomas Marill and Lawrence Roberts via a telephone switch. From that point on, personal computer networks were established and became somewhat commonplace. It wasn't until 1996 when Ethernet's transmission speed capacity was increased tenfold (from 10 Mbit/s to 100 Mbit/s) that networks became widely used.
Computer networks can be established as wired (i.e., with cables) or wireless. They are also comprised of network interfaces (hardware that provides computers with the ability to accept a network cable connector and to process network information), repeaters (devices that cleans and regenerates a network signal), bridges (hardware that connects multiple network segments to form a single network), switches (devices that forward and filter between ports), routers (devices that forward packets of information between networks), hubs (repeaters with multiple ports), and firewalls (network devices that control the network's security).
Understanding the Open Systems Interconnection (OSI) model is essential in understanding how networks and their protocols function. Although the model is conceptual, the abstract layers it described allows for the visualization of the internal functions of a communication system. The OSI model groups similar functions into one of seven layers. Each layer is in a stack; it serves the layer above it and is served by the layer below it. The first three layers in the OSI model are media layers. The bottom layer – the physical layer – is a direct point-to-point data connection. The second layer is the data link that functions as a reliable direct point-to-point data connection. The third layer is the network layer, which addresses, routes, and delivers datagrams between points on a network. Above the media layers is where the host layers are stacked, the final four layers in the stack. The fourth layer is the transport layer, which primarily functions as reliable delivery of packets between points on a network. The fifth layer, the session layer, is for interhost communications and for managing sessions between applications. The sixth layer is the presentation layer where data is represented, encrypted and decrypted, and converts machine-dependent data to machine-independent data. The top layer of the entire stack, the application layer, functions as a network supplier to end-user applications.