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DAVJ277 1.3
J277 GCSE CS 1.3 Networks
| Question | Answer |
|---|---|
| What is a Local area network (LAN) | Network over a small geographic area. The infrastructure for the LAN is owned by the organisation using it. Wired with Ethernet cable or wifi using routers and Wi-Fi access points. |
| What is a Wide area network (WAN)? | A network over a large geographic area. Infrastructure is hired from third party who own and manage it. Connected with telephone lines, fibre optic cables or satellite links. |
| What factors affect the performance of a network? | Number of users/network traffic Error rate (caused by interference to signal). Interference to signal—eg. walls (for wifi) Distance data has to travel (wifi) - signal gets weaker if further away Type of transmission media used (for ethernet) Bandwidth available - this is divided by number of users. Number of data collisions |
| What could the affect be of more devices joining a wireless network? | Slower transmission of data More data is being transmitted at at time Bandwidth will be split between all the devices (sending data) … less bandwidth for each device 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) // higher error rate |
| What is a Client-server network? Consider the potential roles of the server | A client makes requests to the server for data and connections. A server holds the files—can be centrally accessed from any computer A server manages access to the internet, shared printers and email services. Sofware installation, backups, virus updates can be done centrally (by the server)—this can be 3 separate points CENTRAL IS THE KEY THING TO REMEMBER - HAVING A SERVER ALLOWS THINGS TO BE CENTRALISED. |
| What is a Peer-to-peer network? | All computers have equal status—no server controlling Each computer is responsible for its own security and backups. Computers usually have their own printer. Files are stored across network on any clients. |
| What hardware is used in a local area network (LAN) | Wireless access points. Network interface card to connect a computer to the wireless access point or switch. Switches to connect computers. Ethernet cables—(UTP/CAT5 cable or fibre optic cable). Router to connect to another network. E.g. to connect to the internet. |
| Describe the purpose of a router in a home network | Directs packets/data to destination Receives packets from the internet Forwards packets to other computers on the network Joins home network to the internet Has (public) IP address for LAN Designates (private) IP addresses to network nodes |
| What is the internet? | A worldwide collection of computer networks. |
| What is the Domain name system (DNS)? | The domain name system is used to look up the URL of a web site and return the IP address of the web server. |
| Why do we use the Domain name system? | People do not need to remember IP addresses Easily upgradable (eg IPv4 toIPv6) without all web addresses needing to be the same As long as you are connected to a DNS server you can have access to all the databases |
| How does the Domain Name System (DNS) work? | 1) URL/domain name is sent to the DNS 2) DNS servers have a database of URLS and matching IP addresses 3) DNS looks up the URL to find the IP address. If not found, searches other DNS or returns error if still not found 4) DNS sends back IP address to web browser 5)Browser uses IP address to retrieve webpage/connect to web server |
| What is hosting? | Hosting is the provision of storage space online on a web server. An internet host is a company that is able to store your files and make them available to you, or others from internet connected computers. This includes: Website pages, images and other media Online file hosting such as Onedrive and dropbox Video hosting services such as Youtube |
| What is cloud storage? | Data and software is stored on REMOTE computers (web servers). The servers are maintained by a third party. Instead of saving files to your local hard drive or other storage device it is saved to a remote storage facility using the internet (often automatically) and files are accessed via the internet (or via client on pc) |
| What are some advantages of cloud storage? | REMEMBER TO RELATE TO THE CONTEXT IF GIVEN Users can access their files from anywhere in the world with an internet connection. Users can access their files from any device with an internet connection Security is normally handled by a third party Easy to increase storage available |
| What are some disadvantages of cloud storage? | REMEMBER TO RELATE TO THE CONTEXT If you don’t have an internet connection you won’t be able to access your files You are reliant on a third party for security but you will be liable if the data protection act is broken Data may be vulnerable to hacking—you have no control over this. Reliant on a third party for back up |
| What is a star topology? | Computers connected to a central switch. If one computer fails no others are affected. If the switch/central point fails all connections are affected Exam tip - remember to label cable if you draw a star network. |
| What is a mesh topology? | Switches (LAN) or routers (WAN) connected to one another so there is more than one route to the destination. E.g. The Internet More resilient to faults but more cable needed. |
| What is Wi-Fi? | Wireless connection to a network. Requires a wireless access point or router. Data is sent on a specific frequency (number of waves per second). Each frequency is divided into channels. |
| Advantages and disadvantages of Wi-Fi over wired connections | + Can work anywhere in range with wifi enabled device. + No cabling. + Useful for hard to reach places. - Lower bandwidth. - Suffers from interference. - Less secure. |
| Compare Wi-Fi and Bluetooth | Bluetooth is for short range communication—WiFi larger range Bluetooth uses less battery power WiFi allows devices to connect to internet Bluetooth connects devices with Bluetooth adapter directly with each other . |
| What is Encryption? | Encoding readable data called plaintext into ciphertext. Ciphertext cannot be understood if intercepted Only the intended recipient can decode the data using a key. Protects communications from hackers. |
| What is a network protocol? | A set of rules/standards for how computers should communicate/how data is sent/ on a network |
| What is Ethernet? | Ethernet uses cables to transmit data between devices in a LAN Ethernet is a protocol ... within the TCP/IP stack ... it governs the connection of and transmission of data between devices within a LAN ... |
| Why is Ethernet a standard? | Ethernet is used by (mostly) by all manufacturers // Ethernet is used in many devices • To allow compatibility with other devices • Ethernet is a proven/reliable connection • Ethernet is low cost for purchase/installation/maintenance (compared to other wired connections) |
| What is TCP/IP Transmission Control Protocol Internet Protocol | TCP provides an error free transmission between two routers. IP routes packets across a wide area network. |
| What is HTTP? Hyper Text Transfer Protocol | The rules over which data is sent between your browser and the server of the website you are connected to. Used when the information on a web page is not sensitive or personal. |
| What is HTTPS? Hyper Text Transfer Protocol Secure | HTTPS is the secure version of HTTP, The 'S' at the end of HTTPS stands for 'Secure'. It means all communications between your browser and the website’s server are encrypted |
| What is FTP File Transfer Protocol | A protocol for transferring files between a client and server, usually on a wide area network. Typically used for uploading web pages and associated files to a web server for hosting. Unlike email there are no size limits Also more secure than email |
| What is POP Post Office Protocol | A protocol for receiving emails. Downloads email from the server to client then deletes the email (pops!) from the server. Recommended if you have limited space on your email server |
| What is IMAP? Internet Message Access Protocol | A protocol for retrieving email/ downloading a copy of email. Email remains on the server.(unlike POP) Recommended if you want to access your email from multiple devices. |
| What is SMTP? Simple Mail Transfer Protocol | The protocol for sending/transmitting email |
| Name the three network protocols for sending or receiving email | POP, IMAP (receiving) and SMTP (sending) |
| Network layers—what are they and why do we have them? | Layers are a division of network functionality Each layer is self-contained and contains a number of protocols Layers allow different developers to concentrate on one aspect of the network. A layer can be edited without affecting other layers. |
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