1.4 WiFi and Wired networks Flashcards
What is a computer network?
A computer network is two or more computing devices connected together in order to share resources.
What is a network enabled device?
A device is said to be ‘network enabled’ when it is capable of joining a network.
What is a LAN?
A Local Area Network is a network that has two or more network-enabled devices connected within a fairly close geographical area.
Where may a LAN be used?
5
- Home
- Business Office
- Hospital
- Library
- School
What are some advantages of a LAN? (6)
- Users can log on from any workstation and still access all of their files
- Peripherals (printers etc.) can be shared between many users - reducing costs
- Resources and files shared by users - collaboration on projects
- Backups can be done centrally
- Software can be installed centrally
- Data transmitted quickly between networked computers
What are some disadvantages of a LAN? (6)
- Network failure (if server fails, no one can access files)
- Slow service if lots of users are logged on
- Viruses and malware could easily spread around the network
- Expensive to set up and keep running
- Requires specialist staff
- Security if users forget to log out
What are 6 measures to improve security of a LAN?
- Strong passwords that are changed every month
- Different access rights for different users (students , teachers etc.)
- Audit log (records who saved, deleted and changed records and files)
- Backups done at least once a day
- Encryption of data travelling around the netwok (especailly for hubs and wifi)
- Users should not be able to install software
What is a WAN?
A wide area network (WAN) connects two or more local area networks (LAN) that are in different geographical locations.
What can be used to connect offices close together?
A ‘leased line’ from a telecom company can be used to connect offices in different towns.
Why do companies normally hire a WAN from a major telecom company?
It is very expensive and complicated to set up and maintain.
What are four ways long distance communication by a WAN can be achieved?
- Fibre optic lines, including laying undersea cables
- Satellite communication links
- Leased telephone lines
- Microwave links
What are 3 advantages of WANs?
- Allow LANs to connect to one another
- Allows workers to collaborate over a wide ares, even across continents
- Allows files and data to be shared between LANs
What are 2 disadvantages of WANs?
- Can be expensive to hire a WAN service from the telecom operator
- If a WAN fails, it is beyond the control of the company to fix, because it is owned by a number of external suppliers
What is bandwidth measured in?
Bits per second (Kbps, Mbps or Gbps)
What is bandwidth?
How much data can be transferred over a connection in a given time
What is the contention ratio?
The ratio of users compared to available bandwidth
How might a business achieve a fast and reliable internet connection?
Paying a telecom company extra money for a low contention ratio connection
Compare the speeds of the two main categories of ethernet cables?
Cat-6 is faster than Cat-5
Compare the costs of the two main categories of ethernet cables?
Cat-6 is more expensive per metre than Cat-5
How do fibre optic cables transder data?
Fibre optic tables transfer data using light which is reflected along the inside of a cable
What is a disadvantage of fibre optic cable?
It is more expensive than ethernet copper cable
What is a backbone?
- A backbone joins together a number of LANs in the same building or as part of a WAN
- The backbone is expected to carry heavy data traffic.
How is Wi-Fi divided?
- There are two frequency bands (2.4GHz and 5Ghz)
* These bands are furhter divided into seperate channels
Why is using seperate channels a good idea?
• It reduces the interference caused by nearby devices