Computer networks, connections and protocols

standalone computers

computers that are not connected to the netwrok

advantages of networking

-users can share files

-users can share peripherals: printers and other connections to other networks eg The Network

-users can access files from any computer in the network

-communication with other people

-servers can control security, software updates and backup of data

LAN (local area network)

-covers small geographical area

-all the hardware for a LAN is owned by the organisation using it

-are wired with UTP cable, fibre optic or wireless using Wi-fi

WAN (wide area network)

-covers a large geographical area, connecting LANs together

-Infrastructure between the LANs is leased from telecommunication companies who own and manage it

-WANs are connected with telephone lines, fibre optic cables or satellite links

disadvantages of networking

-increased security risks to data

-malware and viruses spread very easily between computers

-if a server fails, the computers connected to it may not work

-the computers may run more slowly if there is a lot of data travelling on the network

what is a network?

-a network is a group of 2 or more computers or devices that are linked together

-they can use cables such as Ethernet cables

-they can use wireless technology such as Wi-fi

-they allow us to share files or resources between devices or computers

factors that affect the performance of networks

-bandwidth

-number of users

-transmission media

error rate

latency

bandwidth

the amount of data that can be sent and received successfully in a given time

-this is not measure of how fast data travels but how much data can be sent on the transmission media

-measured in bits per second, often called bit rate

the number of users

-too many users or devices on the same network can cause the network to slow down if there is insufficient bandwidth for the data

transmission media

-wired connections have a higher bandwidth than wireless connections

-fibre optic cables have a higher bandwidth than copper cables

error rate

-less reliable connections increase the number of errors that occur when data is transferred

-this means the data has to be resent until it is 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

latency

-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 to appropiately segment traffic on a network

hardware such as switches and transmission media may not operate at the same speed

cclient server model

-a server controls access and security to one shared file store

-a server manages access to the Internet

a server manages printing jobs

a server provides email services

a server runs a backup of data

a client makes requests to the server for data and connections

client-server model advantages

-easier to manage security files

-easier to take backup of all shared data

-easier to install software updates to all computers

fclient server model disadvantages

-can be expensive to setup and maintain

requires IT specialists to maintain

the server is a single point of failure

users will lose access if the server fails

peer-to-peer model

-a peer is a computer on a network and is equal to all other peers

peers serve their own files to each other

each peer is responsible for its own security

each peer is responsible for its own backup

peers usually have their own printers

you can send print jobs to another peer to process, but that peer would need to be switched on to be able to communicate with the connected printer

peer to peer models advantages

very easy to maintain

specialist staff are not required

no dependency on a single computer

cheaper to set up

no expensive hardware required

peer to peer model disadvanatges

the network is less secure

users will need to manage their own backups

can be difficult to maintain a well ordered file store

data packets

files are broken down into smaller parts called data packets because whole files are too large to transfer as 1 unit so data packets allow data to be transferred across a network quickly. each packet of data is redirected by routers across networks until it arrives at its destination

-when all packets have arrive at the destination address the data is reassembled

wireless access point

provides link between wireless and wired networks. It creates a wireless local area network that allows Wifi-enabled devices to connect to a wired network

-may be a seperate device or built into another device such as a router

router

used to transfer data packets between networks

-receive data packets and use IP address in the packet header to determine best route to transmit data

-data is transferred from router to router across the Internet towards destination

-stores IP adress of each computer connected to it on the network and uses a list called routing table to calculate the quickest and shortest route to transfer data

switch

used to connect devices together in LAN

receives data packets from connected node, reads destination address in the packet header and forwards data directly to its destination

a switch will generate a list of the MAC addresses of all devices connected to it when it receives data and must scan for a matching destination address before sending

hub

-an alternative to a switch but slower and less secure as it forwards a copy of received data to all connected nodes

network interface controller/card

internal piece of hardware that is required for the computer to connect to a network

-the card includes a MAC address which is used when sending data across a LAN

-typically embedded in the motherboard

-an ethernet cable is plugged into the network card to allow data to be exchanged between device and a network

3 common types of transmission media include

-ethernet

-fibre optic cables

-coaxial cables

ethernet cables

used typically on a LAN to transfer data between nodes and hardware such as switches

fibre optic cables

very fast but more expensive and fragile cables typically used to send data quickly along a WAN. Data is sent as pulses of light

coaxial cables

older slower copper cables that are not used as much in modern times as they can be affected by electromagnetic interference

Internet

-global network of interconnected networks

the world wide web( WWW) is not the same as the internet. It is a way of accessing information, using protocols such as HTTPS to web pages

-servers provide services on the internet, such as a web server which responds to the web server (client) request to display a web page. the web server processes the client request to prepare the web page and return it so the web browser can display it to the user

-a website must be hosted (stored) on a web store so that it can be accessed by others using the Internet

-a unique domain name must be registered with a domain registrar-this is a company that checks the name is valid and not already taken

DNS server

Domain Name System stores a list of domain names and a list of corresponding IP addresses where the website is stored

-the first thing to understand is that every web page has a domain names and list of corresponding IP addresses where the website is stored

-the first thing to understand is that every web page has a domain name that is easy for humans to remebe