Computing Y10 EOY

Network

More than one computer system connected together allowing for communication and sharing of resources

LAN

Local area network - network that covers a small geographical area and is usually within the same building or site (e.g. office) and the network infrastructure is usually owned and managed by network owner.

WAN

Wide Area Network - network that covers a large geographical area (possibly a country or even the world). Often uses third party communication channels such as connections by the internet service providers

Client-server network

Network where clients make requests to server, server manages that request and responds. The client is completely dependent on the server to provide and manage information (server controls network security, backups and can be upgraded to manage higher demand)

Advantages of Client-server network

Controlled centrally (easy to backup data and update software), resources can be shared across network and more client can easily be added to the server

Disadvantages of Client-Server network

Traffic congestion can slow network down, if fault in server, whole network down, IT technicians may be required to maintain network and malware (e.g. viruses) can spread quickly

Peer-to-Peer network

Data shared directly between systems without central server, each computer is equally responsible for providing data

Advantages of Peer-to-Peer network

Simpler network to set up, not dependent on server and good for quickly sharing files between systems

Disadvantages of Peer-to-Peer network

No central device to manage security or backups (must be performed on individual systems), performance of computer will decrease with more devices connected to the network (especially if other machines are slow)

Data packets

When sending data across network, files are broken down into data packets because whole files are too large to transfer data so data packets allow data to be transferred across network quickly. Each packet is redirected by other routers across networks until destination (they sometimes might have to split to use alternative routes)

Network Topology

Layout of computer systems on a local network

Star Topology

Each computer is connected to a central device (usually a hub or switch) and transfers its data packets there. The central hub or switch looks at destination address and transfers packets to intended computer

Advantages of Star topology

Improved security (sent directly from and to hub and switch), new systems can be attached directly, system failures won’t cause complete network failure and fast transfer speeds

Disadvantages of Star topology

Extra hardware (hub or switch) is required to be purchased, installed and maintained and if central system fails than whole network will be unusable

Mesh topology

Each computer system is connected to every other computer network (full mesh) and partial mesh is where some nodes are connected to every other node. In this, data packets are transferred to destination address along quickest path

Advantages of Mesh topology

Alternative route can be taken if faulty cable/system, can withstand large amounts of data traffic and new systems can easily be added (no disruption)

Disadvantages of Mesh topology

Large amounts of cables are hard and expensive to install and maintain abd cavkes tgat are connected won’t ever need to communicate should be avoided

Bandwidth

Maximum amount of data that can be sent across a network at once

Factors that affect performance

Bandwidth, number of users at a time, number of data collisions, interference (e.g. thick walls), distance to travel/signal strength and amount of data to transfer

WAP (Wireless Access Point)

Provides a link between wireless and wired networks, creates local area network that allows Wi-fi enables devices to connect to a wired network. It may be built into the router or as a separate device

Router

Used to transfer data packets between networks. Receive data packets and use IP address in packet header to determine best route to transfer data. Data is transferred from router to router across internet toward destination. A router stores IP address of each computer connected to it on the network and used list called routing table to calculate shortest and quickest route to destination

Switch

Used to connect devices on a LAN, receives data packets from a connected node, reads the destination address in the packet header and forwards the data, directly, to its destination. It generates a list of MAC addresses of all devices connected to it when it receives data (must scan for matching destination address before sending)

Hub

Alternative to a switch but much slower ad less secure because it forwards a copy of received data to all connected nodes

NIC

Network interface card/controller - Internal piece of hardware that is required for the computer to connect to a network. It includes a MAC address which is used when sending data across a LAN. An ethernet cable is plugged into NIC to allow data to be exchanged between device and network. Typically embedded into the motherboard

Transmission Media

Communication channel along which data is transferred (e.g. ethernet, fibre optic, coaxial cables)

Ethernet

Used on LAN to transfer data between nodes and hardware

Fibre optic

Very fast but expensive - sent as pulses of light along WAN

Coaxial cables

Older type of transmission media - can be affected by electromagnetic interference hence not used so much anymore

The Internet

Global network of interconnected networks - servers provide services on the internet (web server responds to web browser’s request to display web page). Largely works on the client-server model

World Wide Web

Way of accessing information using protocols to view web pages

DNS Servers

Domain Name System server stores a list of domain names and a list of corresponding IP addresses where the website is stored (every web page has a domain name that is easy for humans to remember and type in)

Cycle of DNS

Domain name is typed into address bar, query is sent to local DNS for corresponding IP address of domain name, local DNS server checks if it hold IP address corresponding to name, if it does, it passes IP address to browser (access to website), if it doesn’t, query is passed onto another DNS server at a higher level until IP address is resolved and eventually found - then passed back for access to website

Cloud Storage

Stores data on remote servers accessed via the internet

Advantages of cloud storage

Accessible anywhere (with internet), allows collaboration of multiple users at once, large storage capacity and often free storage available

Disadvantages of cloud storage

Required internet to access data, data may be inaccessible if servers fail or are attacked, speed, portability and durability depend on internet quality

Wired connections

Use physical cables to connect and require an NIC to connect to network

Characteristics of Wired connections

Restricted movement, faster, more secure and NIC requires

Wireless connections

Requires WNIC (wireless NIC) and uses radio waves to carry signals

Characteristics of Wireless connections

Freedom of movement, slower, less secure and require WNIC

Ethernet

form of wired communication that is used to connect devices on a LAN

Advantages of Ethernet

Provides stable and reliable connection, offers higher speeds than wifi and is more secure

Disadvantages of Ethernet

Devices must be near to a connection point, can be difficult to install because it may have to run through walls and floor and cables can appear messy

Advantages of Wifi

Allows set up of LANs without wires, users can log in from anywhere within wifi network using any wifi device and wifi enables devices are now widely available

Disadvantages of wifi

signal strength weakens further away you are from router, wireless connection may not be as secure and wifi signal can be affected by weather conditions

Bluetooth

Form of wireless communication that enables different devices to connect. Allows two devices in small private network to share data

Advantages of bluetooth

Low cost to set up, uses little power compared to other types of wireless connection and you can set up bluetooth networks with other bluetooth enabled devices

Disadvantages of bluetooth

Short range, low level of security and low data transmission rate

Encryption

Process of disguising a message so that it cannot be understood by anyone but its intended recipient. Requires the use of a key and the key is only with destination holder and sender (turns plaintext into cipher-text)

Protocols

Set of rules that allow devices on a network to communicate with each other

TCP/IP

Transmission Control Protocol/Internet protocol - two separate protocols that are joined together (operate on different layers to allow computers to communicate across a network)

TCP

Allows packets to be sent and received by computer systems (breaks data into packets and reorders them back to original data at destination)

IP

Protocol in charge of routing and addressing data packets, ensures data packets are sent across networks to correct destination

HTTP

Hypertext Transfer Protocol - used to transfer web pages over the internet so that users can view them in a web browser.

FTP

File Transfer Protocol - used to transfer files across a network (commonly used to upload or download files to/from a web server)

SMTP

Simple Mail Transfer Protocol - used to send emails to a mail server and between mail servers

POP

Post office protocol - deletes email from email server once it has been downloaded to a device

IMAP

Internet Message Access Protocol - Syncs message with email server so it can be identified by different devices

IP addressing

When connected to a network each device is given a unique IP address. This address consists of four sets of up to three digits, each with a maximum value of 255, which are separated by dots. Can be static (makes it easy for network managers to know which device is on which network) However, dynamic addressing allows more devices to connect than there are available addresses - assigned any free address

MAC Addressing

A MAC address is a unique serial number assigned to each network interface controller (NIC). This allows a network to uniquely identify any device. A MAC address consists of a string of hexadecimal numbers (separated by colons)

IPv4

32-bit address in denary (allows over 4 billion unique addresses)

IPv6

8 16-bit segments of four hexadecimal values separated by colons

Standards

Standards are agreed ways of doing things that are decided by experts within standard developing organisations. Standards make hardware and software easier to use (e.g. ethernet, bluetooth, wifi, HTML and ASCII)

Why are standards used

They ensure compatibility and reliability, even if the products are made by different companies. Without standards, the tasks that are carried out online, such as browsing the world wide web, opening a file or connecting to devices, would be complicated because different systems and devices would be incompatible with each other.