Лекция: Classification of Networks

Networking allows two or more computer systems to exchange information and share resources and peripherals. Networks are classified according to geographical area. They can be divided into PANs(Personal Area Networks) which typically include a laptop, a mobile phone and a PDA; LANs usually placed in the same building; MANs (Metropolitan Area Networks) which cover a campus or a city; WANs (Wide Area Networks) which have no geographical limit and may connect computers or LANs on opposite sides of the world. They are usually linked through telephone lines, fibre-optic cables or satellites. The main transmission paths within a WAN are high-speed lines called backbones. Wireless WANs use mobile telephone networks. The largest WAN in existence is the Internet.

LANs can be built with two main types of architecture: peer-to-peer, where the two computers have the same capabilities, or client-server, where one computer acts as the server containing the main hard disk and controlling the other workstations or nodes, all the devices linked in the network (e.g. printers, computers, etc.). Computers in a LAN need to use the same network protocol (the language, or set of rules) to communicate with each other. Networks use different protocols. For instance, the Internet uses TCP/IP. Ethernet is one of the most common protocols for LANs.

A router, a device that forwards data packets, is needed to link a LAN to another network, e.g. to the Net. Most networks are linked with cables or wires but new Wi-Fi, wireless fidelity, technologies allow the creation of WLANs, where cables or wires are replaced by radio waves. To build a WLAN you need access points, radio-based receiver-transmitters that are connected to the wired LAN, and wireless adapters installed in your computer to link it to the network.

Hotspots are WLANs available for public use in places like airports and hotels, but sometimes the service is also available outdoors (e.g. university campuses, squares, etc.).

1. LANs link computers and other devices that are placed far apart.

2. In a client-server architecture, all the workstations have the same capabilities.

3. The word protocol refers to the shape of the network.

4. Routers are used to link two computers.

5. Access points don’t need to be connected to a wired LAN.

6. Wireless adapters are optional when you are using a WLAN.

7. Hotspots can only be found inside a building.

8. The Internet is an example of a LAN.

9. Wireless WANs use fibre and cable as linking devices.

Ex. 2.Use the words in the box to complete the sentences.

1. All the PCs on a … are connected to one …, which is a powerful PC with a large hard disk that can be shared by everyone. 2. The style of … networking permits each user to share resources such as printers. 3. The star is a topology for a computer network in which one computer occupies the central part and the remaining … are linked solely to it. 4. At present Wi-Fi systems transmit data at much more than 100 times the rate of a dialup modem, making it an ideal technology for linking computers to one another and to the Net in a …. 5. All of the fibre-optic … of the United States, Canada and Latin America cross Panama. 6. A …. joins multiple computers (or other network devices) together to form a single network segment, where all computers can communicate directly with each other.

Ex. 3.Read these descriptions of different physical topologies of communication networks.