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Chapter 1

A computer network or data network is a telecommunications network which allows computers to exchange data. In computer networks, networked computing devices exchange data with each other using connections. The connections between nodes are established using either cable media or wireless media. The best-known computer network is the Internet.

Networks come in all sizes. They can range from simple networks consisting of two computers to networks connecting millions of devices. The Internet is the largest network in existence. In fact, the term Internet means a ‘network of networks’. The Internet is literally a collection of interconnected private and public networks.

All computers connected to a network that participate directly in network communication are classified as hosts. Hosts are also called end devices.

Servers (sunucular) are computers with software that enable them to provide information, like email or web pages, to other end devices on the network. Clients (istemciler) are computers with software installed that enable them to request and display the information obtained from the server.

Client and server software usually runs on separate computers, but it is also possible for one computer to carry out both roles at the same time. In small businesses and homes, many computers function as the servers and clients on the network. This type of network is called a peer-to-peer network.

The network infrastructure contains three categories of network components : Devices, Media and Services.

An end device is either the source or destination of a message transmitted over the network (Desktop computer, Laptop, Printer, IP Phone, Wireless Tablet, IP Camera etc. )

Intermediary devices connect the individual end devices to the network and can connect multiple individual networks to form an internetwork. These intermediary devices provide connectivity and ensure that data flows across the network (Router, Switch, Wireless Access Point, Firewall etc. )

Network Media :  Modern networks primarily use three types of media to interconnect devices and to provide the pathway over which data can be transmitted. These media are:

  • Metallic wires within cables - data is encoded into electrical impulses
  • Glass or plastic fibers (fiber optic cable) - data is encoded as pulses of light
  • Wireless transmission - data is encoded using wavelengths from the electromagnetic spectrum


 Network Representations














In addition to these representations, specialized terminology is used when discussing how each of these devices and media connect to each other. Important terms to remember are:

  • Network Interface Card - A NIC, or LAN adapter, provides the physical connection to the network at the PC or other end device. The media that are connecting the PC to the networking device, plug directly into the NIC.
  • Physical Port - A connector or outlet on a networking device where the media is connected to an end device or another networking device.
  • Interface - Specialized ports on a networking device that connect to individual networks. Because routers are used to interconnect networks, the ports on a router are referred to as network interfaces.

Topology diagrams are mandatory for anyone working with a network. They provide a visual map of how the network is connected. There are two types of topology diagrams:

  • Physical topology diagrams - Identify the physical location of intermediary devices and cable installation.
  • Logical topology diagrams - Identify devices, ports, and addressing scheme.