1.3 Computer networks, connections and protocols Flashcards
LAN
Local Area Network. Small geographic area. All the hardware for the LAN is owned by the organisation using it. Wired with UTP cable, fibre optic cable or wireless using routers and Wi-Fi access points.
WAN
Wide Area Network. Large geographical area. Infrastructure is hired from telecommunication companies who own and manage it. Connected with telephone lines, fibre optic cables or satellite links.
Client-server network
A client makes requests to the server for data and connections. A server controls access and security to one shared file store. A server manages access to the internet, shared printers and email services. A server runs a backup of data.
Peer-to-peer network
All computers are equal. Computers server their own files to each other. Each computer is responsible for its own security and backup. Computers usually have their own printers.
Wireless access point
A networking hardware device that allows a Wi-Fi device to connect to a wired network.
Router
A router sends data between networks. It is needed to connect a local area network to a wide area network. It uses the IP address on a device to route traffic to other routers.
Switch
A switch sends data between computers on a local area network. It uses the NIC address on a device to route traffic.
NIC
Network Interface Card/Controller. A computer hardware component that connects a computer to a computer network.
Transmission media
The physical media over which data transmitted, e.g. twisted copper cable, fibre optic etc.
The Internet
The Internet is a worldwide collection of interconnected computer networks. It is an example of a WAN, albeit the vary largest one which exists.
DNS
Domain Name System. The Internet’s equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses. This is necessary because, although domain names are easy for people to remember, computes or machines access websites based on IP addresses.
Hosting
Websites stored on dedicated servers. Reasons include: Websites need to be available 24/7. Accessed by thousands of users at a time. Strong protection from hackers. They need an IP address that doesn’t change.
The Cloud
Remote servers that store data that can be accessed over the internet. Advantages: Access anytime, anywhere and from any device. Automatic backup. Collaborate on files easily.
Web server
A program that uses HTTP (Hypertext Transfer Protocol) to serve the files that form Web pages to users, in response to their requests, which are forwarded by their computers’ HTTP clients. Dedicated computers and appliances may be referred to as Web servers as well.
Client
A client can be thought of as computing device which requests or is using the services from some remote/connected server.
Network topology
The physical or logical arrangement of connected devices on a network. e.g. Computers, switches, routers, printers, servers etc.
Star topology
Computers connected to a central switch. If one computer fails no others are affected. If the switch fails, all connections are affected.
Mesh topology
Switches (LAN) or routers (WAN) connected so there is more than route to the destination. e.g. The Internet. More resilient to faults but more cable needed.
Disadvantages of the cloud?
There is an ongoing monthly / yearly cost for hosting data and information. There are bandwidth problems and it all depends on speed of connection. The cloud relies completely on a stable internet connection. There is a lack of control because you are handing over data and information.
What is a full mesh topology?
A full mesh topology is when every device is connected to every other device. One of the advantages is if you get a break in any of the connections, you now haven’t got a problem because the traffic can travel via an alternative route. A disadvantage of a full mesh network is that there is a lot more cabling and switch hardware required which will add the cost and will be impractical, especially in a large network.
What is a partial mesh network?
Not every computer is connected to every other computer, but there are still multiple connections. We haven’t got a cable between every single computer, but we have got multiple paths to reach a destination. If you get a break in any of the connections, you still have other routes for the data to travel on. However there is a lot less hardware than a full mesh topology. Therefore lowers the cost and is more practical, which is good for large networks. There is still a lot more switch hardware required for a partial mesh topology than a star network topology.
Which network topology best describes The Internet?
Partial Mesh Network.
What are factors affecting the performance of a network?
Too many users - Too many users or devices on the same network can cause the network to slow down if there is insufficient bandwidth for each user.
Error rate - Less reliable connections increase the number of errors when data is transferred. This means the data has to be resent until it arrives correctly. The signal quality of wireless connections is dependant on the range of devices from the wireless access point and other environmental factors. The signal quality of copper cables is determined by the grade of material used which reduces interference. The length of the cable is also a factor.
Transmission media - Wired connections have a higher bandwidth than wireless connections. Fibre optical cables have a higher bandwidth than copper cables
Bandwidth - This is the amount of data that can be sent and received successfully in a given time. This is not a measure of how fast the data travels, but how much data can be sent on the transmission media. Bandwidth is measured in bits per second and is often called bit rate.
Latency - Latency is the delay from transmitting data to receiving it. Latency is caused by bottlenecks in the infrastructure of the network. For example, by not using switches appropriately segment traffic on a network. Hardware such as switches and transmission media, may not operate at the same speed.
