In a computer network in general there are devices, media, and services that are bound by rules that work together to send messages. We use the word message as a term that includes web pages, e-mail, instant messages, telephone calls, and other forms of communication made possible on the Internet. In this paper, we will learn about the types of messages, devices, media, and services that enable the communication of these messages. We’ll also learn about the rules or protocols that bind these computer network elements together.

In the picture above can be seen 4 elements of a computer network, namely:

  • Rules (rules)
  • Medium (medium)
  • Messages (messages)
  • Device (device)

Computer networks can be described graphically and in the following figure, icons that represent computer network devices will be shown. On the left side of the image below are shown some of the common devices that are the origin of messages that are part of our communication. These devices consist of various types of computers (PC and laptop icons will be shown), servers, and IP phones. In a local area network this device is usually connected to a LAN media (wired or wireless).

The right side of the image above shows devices called intermediate devices, which are used to route and manage messages on a network. In addition, other network symbols are also shown. A brief explanation of the intermediate device is as follows:

  • Switch – a common device used to interconnect Local Area Networks (LAN).
  • Firewall – provides security for the network.
  • Router – helps route messages as they travel across the network.
  • Wireless Router – a special type of router often found in home networks.
  • Cloud – used to summarize a group of network devices, details of which may not be important to discuss.
  • Serial Link – a form of WAN interconnection, represented by a lightning bolt in the form of a line.

For a network to work, devices must be interconnected. Can be a wired network connection (wired) or wireless (wireless). In a cable connection, the medium can be copper which carries electrical signals, or optical fiber which carries light signals. In a wireless connection, the medium is Earth’s atmosphere, or space, and a microwave signal. Copper media includes cables such as twisted pair telephone cables, coaxial cables, or the cable most commonly known as Category 5 Unshielded Twisted Pair (UTP) cable. Optical fibers, thin strands of glass or plastic that carry light signals, are another form of network medium. Wireless media include a home wireless connection between a wireless router and a computer with a wireless network card, a terrestrial wireless connection between two stations on the ground, or communication between a device on the ground and a satellite. In its journey on the Internet, messages will go through various media.


Humans often attempt to send and receive messages using computer applications; This application requires the service provided by the network. These services include the World Wide Web, e-mail, instant messaging, and IP Telephony. Devices connected by media to provide services must be governed by rules or protocols. In the following table, some of the common services and protocols that are directly related to the services listed are shown.

tcp ip

Protocols are the rules on which network devices are used to communicate with each other. The industry standard in the field of computer networking today is a set of protocols called TCP/IP (Transmission Control Protocol/Internet Protocol). TCP/IP is used in home and business networks, as well as the main protocol of the Internet. The TCP/IP protocol that determines the format, addressing and routing mechanisms that ensure our messages are delivered to the correct recipients.

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