1.3.1 - Networks and topologies

Local Area Network that connects devices within a small geographical area. Uses its own hardware to transmit data, maintained by a single organisation. eg. home networks, schools, work offices.

Wide Area Network connects multiple LAN’s together over a large geographical area. Uses third party or external hardware, eg. satellites and phone lines. eg. banking networks, the Internet.

Bandwidth, Number of devices connected, Latency, Error rate, Transmission media.

The bandwidth is the amount of data that can be transmitted across a network connection. The higher the bandwidth, the more data can be transferred simultaneously therefore increased network performance.

The more devices connected, the available bandwidth is used up, therefore less data is able to be sent and received, slowing down the network performance. mark scheme bits: more devices means Slower transmission of data as more data is being transmitted (at a time) so bandwidth will be split between all the devices this means that there is less bandwidth for each device so Devices have to wait longer before they can transmit // increased latency If the maximum bandwidth is used then devices cannot transmit, Central device/switch/router has to handle more requests and may run slower * More collisions (likely) so more data has to be retransmitted * Loss of more packets so more data has to be retransmitted

Latency is the time delay between data being sent and received at its destination. The bigger the delay, the more data packets on a network prone to collisions.

The error rate is the measure of how many data packets do not reach their destination. The higher the error rate, the less reliable the network connection.

Fibre optic cabling has a much higher bandwidth than copper cabling, therefore can transmit much more data simultaneously.

Wireless Access Points (WAP), Routers, Switches, Network Interface Card, Transmission Media.

It is a component of a LAN. It is a wireless transmitter which converts data into radio waves, allowing wireless devices to connect to a network.

Directs data packets from one router to another, across WAN’s like the Internet. Receives packets. Forwards packets along a network. Assigns IP addresses to nodes/devices in a network. tasks of a router: * Receive packets * Forward/sending/transmitting packets * Maintain a routing table // by description * Identify the most efficient path to the destination / correct IP / correct location * Assign IP addresses to nodes/devices * Converts packets from one protocol to another

Component of a LAN. Learns the MAC addresses of each individual device connected locally. Designed to connect devices on a LAN by receiving and forwarding relevant data packets to the recipient, using their MAC addresses. mark scheme bits: - Connects the devices together in the network // allows devices to communicate in the network - Receives data from (all) devices in the star topology - Record/register/store the address of devices connected to it in a table - Uses MAC address of devices - Direct data to destination - ff address not recorded transmit to all devices

Physical component required by all devices to connect to a network.

Provides a physical path for data transfer to connect wired networks together. eg. copper, twisted pair, fibre optic cabling.

A server is a powerful computer that provides services and resources required by the clients. A client is a computer that requests the resources from a server. eg. A file server would store and provide files per a clients requests. A mail server would filter spam, send and provide emails you want like to read or send. A web server will provide web pages at the request of the users browser on the client computer. A print server would queue printer jobs, and ensure each is completed correctly.

Central storage of files therefore can be accessed from any computer. Ensures a central database which avoids multiple copies of data and losing synchronisation. Central backups, meaning each individual doesn’t need to back up their own client computers. Security can be managed centrally, by installing anti-virus software. Software can be upgraded and installed centrally, without having to do it individually to each client.

Requires costly maintenance (+team) to manage network snd server. Too many client requests will degrade the server performance. If server goes down, or network connect is lost, it is lost for the whole network and all clients.

A network with NO central server. All nodes are equal and share resources eg. files. Typically used in smaller networks.

Very easy to set up and maintain. Very cheap to set up because there is no expensive hardware needed. No specialist knowledge needed to run the network.

Users will need to manage their own backups Users will need to manage their own software updates Network can be less secure.

A collection of INTERconnected NETworks. It is a WAN, that can be accessed by anyone.

The Domain Name Service is made up of multiple Domain Name Servers. The role of the DNS is to translate/convert a domain name/website address (URL: www.google.co.uk) into an IP address (172.217.14.195) so that the browser on the client machine can make the a request to the correct web server hosting the webpage. When the IP address is found, it is returned to the browser, however if it is not found at a local DNS, it is passed to the next server, and if it still cannot be found, it will return an error.

User enters URL of website into browser. URL sent to local DNS server and the server tries to find the matching IP address in its database. If the IP is not in the sever, it will send the request to other higher level servers until the IP address is found DNS returns the correct IP address to computer/device browser with webpage. An error is returned if IP address cannot be found.

An Internet/web hosting company, often an ISP (Internet Service Provider), will host websites, files and databases. The company allow you to be able to store files and make them available to you or others on connected computers. They maintain high bandwidth, so that performance does not slow down, and have strong connections and perform backups, so that the servers are accessible 24/7 for many users.