Лекция: Network Topology
Topology refers to the shape of a network. There are three basic physical topologies.
• Star: there is a central device to which all the workstations are directly connected. This central position can be occupied by a server, or a hub, a connection point of the elements of a network that redistributes the data.
• Bus: every workstation is connected to a main cable called a bus.
• Ring: the workstations are connected to one another in a closed loop configuration. There are also mixed topologies like the tree, a group of stars connected to a central bus.
Ex.4.Which network topology type is described below?
1. All the devices are connected to a central station. 2. In this type of network there is a cable to which all the computers and peripherals are connected. 3. Two or more star networks connected together; the central computers are connected to a main bus. 4. All devices (computers, printers, etc.) are connected to one another forming a continuous loop.
Ex.5.A network administrator has set up a new network in a school. Which topology has she chosen?
We have decided to install computers in all the departments but we haven’t spent a lot of money on them. Actually, only the one in the staff room is really powerful (and expensive). They all have common access to the Net and share a laser printer. The teachers in this school have built up a general file of resources kept in the main computer to which all the others in the network have access.
Ex.6. Read the text and write a list of the advantages and disadvantages of wired and wireless networks.
Wired networks are linked by Ethernet cables, phone lines and high-speed fibre optic cables. Wireless networks, however, use electromagnetic waves, such as radio waves, to transmit data. These are the main types of wireless networks: satellites – for long distances; WiMAX – for connecting Wi-Fi hotspots; Wi-Fi – for medium-range distances; Bluetooth – for short distances; GSM – for mobile phones.
To set up at home wireless LAN you’ll need computers equipped with a wireless adapter or wireless card, a wireless access point (a wireless router) and a broadband internet connection. Wired LANs are more difficult to install, but they are cheaper, faster and more re liable. Wireless networks let you move, or roam, from one access point to another, but they are less secure and subject to interference.
Ex.7. Read the text and tell how to install a wired modem router. Use modal verbs.
A modem router is a device that connects your computer or home LAN to the Internet.
• Plug one end of the phone cord directly into a phone jack, and the other end into the ADSL port on the router.
• Plug one end of the Ethernet cable into your computer’s network port and the other end into an Ethernet port on the router.
• Turn on your computer. To set up, or configure, the router, you’ll need to input some parameters, for example your ISP’s name and phone number. NOTE: a router has various Ethernet ports, so you can connect various PCs to the router via Ethernet cables. If you already have a hub or switch connecting a LAN, you only need one cable to connect the hub to the router.
Ex.8. In pairs, do this network quiz. See which pair can finish first.
1. This network typically consists of two or more local area networks, covering a large geographical area.
|a) LAN||b) WAN||c) Intranet|
2. This type of network does not have a dedicated server; all the computers are independent.
|a) peer-to-peer||b) client-server||c) MAN|
3. On this topology, all devices are connected to the same circuit, forming a continuous loop.
|a) star||b) ring||c) bus|
4. The language used by computers to communicate with each other on the Internet is called
|a) Ethernet.||b) ADSL.||c) TCP/IP.|
5. Which cables are used to transfer information for the Internet over long distances at high speeds?
|a) telephone lines||b) Ethernet cables||c) fibre optic cables|
6. Which device allows several computers on a local network to share an internet connection?
|a) an ADSL port||b) a router||c) an Ethernet port|
7. Which device serves as a common connection point for devices in a wireless network?
|a) wireless access point||b) wired router||c) wireless adapter|
8. Bluetooth is a wireless technology that uses radio waves to transmit data over
|a) long distances.||b) medium-range distances.||c) short distanc- es (10 m or less).|
Ex.9.Match the questions (1-6) with the answers (a-f).
1. Why was the hacker arrested? 2. Is it OK to log on to my bank account using public computers in a cyber-safe? 3. How do I set up an internet connection at home? 4. Can I download software from your site? 5. How can I add video to instant messaging? 6. What do I need to do to sign up for a Yahoo! e-mail account?
a) Yes, but always remember to log off after you’ve ended your session; b) Yes, you can even try the programs out for a period before you buy them! c) Because he broke into a computer system and stole confidential data; d) Simply install this program and plug the webcam into your computer; e) You need to install the software for your router. Follow the instructions provided by your ISP, probably in the form of a .pdf file on a CD; f) You have to create a username and password and then give some personal details.
Ex.10. Listen to an extract from a lecture on networks and answer these questions.
1. What does LAN stand for? 2. Where are LANs usually located? 3. What is the difference between a wired LAN and a wireless LAN?
Ex. 11.Listen again and label the elements of this LAN.