Summary

We summarize the chapter with the following points:

• The internet is the network of the networks.
• A computer network is a group of computers connected to each other in order to share resources.
• Usually, the resources can be data, network services, and peripheral devices.
• The fundamental requirement for designing a computer network is that there must be two or more computers:
  • A PAN is defined as a computer network that is used to connect and transmit data among devices located in a personal area, usually utilizing Bluetooth or Wi-Fi to interconnect devices
  • A LAN usually covers the floor of the building, several floors of the building, an entire building, or even a few buildings that are close to one another
  • A MAN represents a group of LANs interconnected within the geographical boundary of the town or city
  • A WAN is a computer network that covers a wide geographic area using dedicated telecommunication lines such as telephone lines, leased lines, or satellites
• The intranet is considered to be the private network of an organization where employees can access network services.
• The extranet can be thought of as an intranet with a controlled access.
• Physical topology presents ordering, arrangement, and placement of the physical parts of a computer network, such as computers, peripheral devices, cables for data transmission, and network equipment:
  • Bus is the physical topology in which computers, peripheral and network devices are connected through the bus that mainly consists of coaxial cable.
  • Ring is the physical topology in which computers, peripheral and network devices form a closed cycle that takes the shape of a ring network where each device is connected to each other.
  • Star is the physical topology in which computers and peripheral and network devices are connected independently with a central device.
  • Extended star is the physical topology in which computers, peripheral and network devices are connected into two or more star topology networks, and then the central components (that is switches) are interconnected over a bus.
  • Hierarchical is the physical topology that represents a combination of star and bus topologies.
  • Mesh is the physical topology in which each computer is connected with every computer to form the network.
• Logical topology represents the logical aspect of the computer network.
• In logical topology, it is the logical paths that are used to carry electric or light signals from one computer to another, or from one network node to another node.
• Clients are computers that request the resources in a computer network.
• Servers are network components that provide resources to clients. Servers too have an active role.
• A host is any device with an IP address that requests or provides networking resources to any other host or node on the network.
• A node is any device that can generate, receive, and transmit the networking resources on the computer network.
• A network interface is a component-like network card or LAN port on network equipment that enables clients, servers, peripheral devices, and network equipment to get connected and communicate with each other.
• Peripheral devices are printers, scanners, SAN, and any other peripheral device that provides resources to clients either through a LAN or as a shared device on a network.
• Applications and shared data are virtual network components that represent applications and files shared on the network that are usually provided by servers.
• Hubs and switches are acting as central components (in Ethernet communication technology) of the computer network to enable interconnection and communication between clients, servers, and peripheral devices.
• Routers are a computer network component that enables routing of the data (that is, packets) from an LAN to the internet, and vice versa.
• The computer network architecture represents the computer network design that allows the computer network components to communicate with one another:
  • Peer-to-peer is a computer network in which the participating computers do not play the predefined roles in the network, but instead they change roles from client to server and vice versa, based on the actual activity on the network.
  • Client/server is a computer network in which participating computers have a predefined role. That means that, in this computer network architecture, computers that access resources act as clients, while computers that provide resources act as servers.
• NOSs are software that are capable of managing, maintaining, and providing resources in the network.
• In metallic mediums, copper wires in twisted pairs and coaxial cables transmit electrical impulses.
• In glass mediums, fibre optic cable transmits pulses of light.
• In air mediums, waves and rays from the electromagnetic spectrum transmit signals in different frequencies.
• Twisted pairs is a cable that contains four twisted pairs of copper with a total of eight wires, each with a specified color.
• Coaxial is a copper cable presented in two forms: thin coaxial with the length up to 185 m, and thick coaxial with the length up to 500 m.
• Fibre optic is a cable made up of glass through which the light is transmitted:
  • Single mode utilizes only one light, and can reach the length from 40 km to 60 km
  • Multimode utilizes multiple lights, and can reach the length from 2 km to 3 km
• Infrared and Bluetooth are wireless technologies for transmission of data over short distances.
• Radio waves, or otherwise known as electromagnetic radiation, uses electromagnetic waves with the longer spectrum of wavelengths than infrared rays.
• Satellite technology uses a wide spectrum of wavelengths and frequencies.
• The converged networks, known also as triple play services networks, are networks that have the ability to transmit data, voice, and video, or any combination of these services over the same networks:
  • A convergent device is the multiplexer that, at its input, merges multiple communication signals into a single signal at its output
  • A converged service is a service that provides voice, data, and video signals in a single network, thus providing services for all modes of communication
• Cisco's three-layered hierarchical model helps define the enterprise networks by simplifying the process of designing a reliable, highly redundant, and scalable hierarchical internetworks:
  • Access layer, as the name indicates, is the layer in which network services are accessed.
  • Distribution layer is the middle layer that plays the role of the bridge by interconnecting the access layer and the core layer.
  • Core layer is a fast and highly redundant network that is managed by core switches and routers.
• We live in the IoT era in which the internet dictates the way we live and work.