Network Types and Topologies
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A computer network connects multiple computers together allowing sharing of resources. There are two main types: local area networks (LANs) covering a small area like a school, and wide area networks (WANs) spanning large geographical areas like the internet. Network topologies determine how devices are physically connected - a bus network uses one cable, a ring network forms a continuous loop, and a star network connects each device to a central hub/switch. Networks provide advantages like shared printing and internet access but also have costs and potential single points of failure.
Network Types and Topologies
- 1. Network Types and Topologies
- 3. What is a computer network? • To answer this question you must first understand what a network is. • Put simply a network is a number of things that are connected together in some way. You frequently use networks in everyday life. • For example a railway network and a road network. • A computer network is a number of computers linked together to allow the sharing of resources.
- 4. Two Main Types of Networks • Local Area Network (LAN) • A LAN covers a small area such as one site or building, eg a school or a college.
- 5. Two Main Types of Networks • Wide Area Network (WAN) • A WAN covers a large geographical area. Most WANs are made from several LANs connected together
- 6. Examples of LANs and WANs LAN • A school network is usually a LAN. • Your home network is a LAN WAN • The internet is a WAN. • A network of bank cash dispensers is a WAN.
- 7. Advantages of networks • Sharing devices such as printers saves money. • Site (software) licences are likely to be cheaper than buying several standalone licences. • Files can easily be shared between users. • Network users can communicate by email and instant messenger. • Security is good - users cannot see other users' files unlike on stand- alone machines. • Data is easy to backup as all the data is stored on the file server.
- 8. Disadvantages of networks • Purchasing the network cabling and file servers can be expensive. • Managing a large network is complicated, requires training and a network manager usually needs to be employed. • If the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated. • Viruses can spread to other computers throughout a computer network. • There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg a firewall.
- 9. Group Discussion • All 20 computers will be able to print to a single printer. Without the network you would need 20 printers, or each student would have to wait until the computer with the printer attached was free. • All 20 computers will be able to share an internet connection, giving all the students access to the internet. • Students can have their own space on the file server, improving security when compared to storing the files locally on each computer. • The file server can be backed up to tape every night keeping the students' documents safe. A school with 20 stand alone PCs is considering networking them together and adding a file server. Consider four possible benefits of doing this.
- 11. The Bus Network • In a bus network all the workstations, servers and printers are joined to one cable (the bus). At each end of the cable a terminator is fitted to stop signals reflecting back down the bus.
- 12. Advantages and Disadvantages The advantages of a bus network are: • it is easy to install • it is cheap to install, as it doesn't require much cable The disadvantages of a bus network are: • if the main cable fails or gets damaged the whole network will fail • as more workstations are connected the performance of the network will become slower because of data collisions • every workstation on the network "sees" all of the data on the network – this is a security risk
- 13. The Ring Network • In a ring network each device (workstation, server, printer) is connected to two other devices - this forms a ring for the signals to travel around. Each packet of data on the network travels in one direction and each device receives each packet in turn until the destination device receives it.
- 14. Advantages and Disadvantages The advantage of a ring network is: • This type of network can transfer data quickly, even if there are a large number of devices connected because the data only flows in one direction, so there won’t be any data collisions. The disadvantage of a ring network are: • However, the real disadvantage is that if the main cable fails or any device is faulty, then the whole network will fail.
- 15. The Star Network • In a star network each device on the network has its own cable that connects to a switch or hub. A hub sends every packet of data to every device, whereas a switch only sends a packet of data to the destination device. • This is the most common type of network topology used.
- 16. Advantages and Disadvantages The advantages of a star network are: • it is very reliable – if one cable or device fails then all the others will continue to work • it is high-performing as no data collisions can occur The disadvantages of a star network are: • it is expensive to install as this type of network uses the most cable (network cable is expensive) • extra hardware is required (hubs or switches) which adds to cost • if a hub or switch fails, all the devices connected to it will have no network connection