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ICT - Lecture - Computer-Networks, Slides of Information and Communications Technology (ICT)

National University of Science and Technology (NUST)Information and Communications Technology (ICT)

An introduction to computer networks, including definitions of key terms, types of networks, network topologies, and protocols. It also covers the ownership and management of the internet, packet switching, open systems, and network addresses. how data is transferred between devices on a network and how network software translates hostnames into IP addresses. It also discusses the domain name system and its use in translating hostnames into IP addresses.

Typology: Slides

2021/2022

Available from 12/04/2022

razaroghani
razaroghani 🇵🇰

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15-1
Networking
•Computer network A collection of
computing devices that are connected in
various ways in order to communicate and
share resources
Usually, the connections between
computers in a network are made using
physical wires or cables
However, some connections are wireless,
using radio waves or infrared signals
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Networking

  • (^) C omputer network A collection of computing devices that are connected in various ways in order to communicate and share resources Usually, the connections between computers in a network are made using physical wires or cables However, some connections are wireless , using radio waves or infrared signals

Networking

  • (^) The generic term node or host refers to any device on a network
  • (^) Data transfer rate The speed with which data is moved from one place on a network to another
  • (^) Data transfer rate is a key issue in computer networks

Networking

  • (^) File server A computer that stores and manages files for multiple users on a network
  • (^) Web server A computer dedicated to responding to requests (from the browser client) for web pages

Types of Networks

  • (^) Local-area network (LAN) A network that connects a relatively small number of machines in a relatively close geographical area

Types of Networks

  • (^) A bus technology called Ethernet has become the industry standard for local-area networks Figure 15.2 Various network topologies

Types of Networks

  • (^) Wide-area network (WAN) A network that connects two or more local-area networks over a potentially large geographic distance Often one particular node on a LAN is set up to serve as a gateway to handle all communication going between that LAN and other networks Communication between networks is called internetworking The Internet, as we know it today, is essentially the ultimate wide-area network, spanning the entire globe

So, who owns the Internet?

Well, nobody does. No single person or company owns the Internet or even controls it entirely. As a wide-area network, it is made up of many smaller networks. These smaller networks are often owned and managed by a person or organization. The Internet, then, is really defined by how connections can be made between these networks.

Types of Networks

Figure 15.1 Local-area networks connected across a distance to create a wide-area network

Internet Connections

  • (^) There are various technologies available that you can use to connect a home computer to the Internet - (^) A phone modem converts computer data into an analog audio signal for transfer over a telephone line, and then a modem at the destination converts it back again into data - (^) A digital subscriber line (DSL) uses regular copper phone lines to transfer digital data to and from the phone company’s central office - (^) A cable modem uses the same line that your cable TV signals come in on to transfer the data back and forth

Internet Connections

  • (^) Broadband A connection in which transfer speeds are faster than 128 bits per second - (^) DSL connections and cable modems are broadband connections - (^) The speed for downloads (getting data from the Internet to your home computer) may not be the same as uploads (sending data from your home computer to the Internet)

Open Systems

  • (^) Proprietary system A system that uses technologies kept private by a particular commercial vendor One system couldn’t communicate with another, leading to the need for
  • (^) Interoperability The ability of software and hardware on multiple machines and from multiple commercial vendors to communicate Leading to
  • (^) Open systems Systems based on a common model of network architecture and a suite of protocols used in its implementation

Open Systems

  • (^) The International Organization for Standardization (ISO) established the Open Systems Interconnection (OSI) Reference Model
  • (^) Each layer deals with a particular aspect of network communication Figure 15.5 The layers of the OSI Reference Model

TCP/IP

  • (^) TCP stands for Transmission Control Protocol TCP software breaks messages into packets, hands them off to the IP software for delivery, and then orders and reassembles the packets at their destination
  • (^) IP stands for Internet Protocol IP software deals with the routing of packets through the maze of interconnected networks to their final destination

TCP/IP (cont.)

  • (^) UDP stands for User Datagram Protocol
    • (^) It is an alternative to TCP
    • (^) The main difference is that TCP is highly reliable, at the cost of decreased performance, while UDP is less reliable, but generally faster