1.3 Computer Networks Flashcards
LAN features
-Small geographical area on a single site
-owned by the organisation that uses it,
-wired or wireless
-eg. in schools
WAN features
-Group of LANs
-large geographical area
-external company managed
-eg. internet
4 factors that affect the performance of a network
Bandwidth, latency, error rate, transmission media
Interference
Additional energy in a network that causes a signal to be disrupted
Bottleneck
Data that is delayed in transmission through an overloaded section of a network
Bandwidth
The rate at which data can be transmitted around a network. The more bandwidth a network has, the higher the performance ability.
Latency
The measure of any delay that it takes to transmit a data packet from one destination to another in a network. Can be caused by interference, type of cable and bottlenecks.
Error rate
The number of errors that occur in the transmission of data packets around a network
Transmission media
The type of cables used in a network. Fibre-optic cables are faster and more reliable.
Number of devices connected
As more devices connect, available bandwidth is used up which can slow down network performance.
Client-server network
Managed by a server, the devices connected to the server are clients. Files and software are stored centrally on the server. Clients send requests to the server.
Server
Powerful computer which provides services or resources required by any of the clients
Client
Computer which requests the services or resources provided by the server
Client-server pros
Reliable and always on, everything is managed and controlled centrally: back-ups, updates, files
Client-server cons
Expensive, server dependant, could become overloaded
Peer-to-peer networks
All devices are equal and connect directly, files are individually stored and can be shared, associated with illegal file sharing
Peer-to-peer pros
Easy to maintain, no server dependence
Peer-to-peer cons
Bad security, disorganised, bad performance, difficult to back up
Hardware needed for a LAN
WAP, NIC, routers, servers, transmission media
NIC
Internal piece of hardware that allows a device to connect to a network, built into the motherboard. For wired and wireless.
Switches
Connect devices on a LAN. Receive data from one device and transmit it to another on the network with the correct MAC address.
Routers
Transmit data between networks, decide best route for the data. Link, manage and coordinate all devices in the network.
WAP
Switch that allows devices to connect wirelessly, can’t direct messages to particular devices
Two types of transmission media
Cable (wired) or microwaves (wireless)
Hub
Links the computers and sends every message to every computer on the network
MAC address
A unique identifier for a device on the network
Protocols
The rules that govern how data is transmitted on a network and make it possible for different devices to be compatible
SSID
Gives a wireless network a name
Internet
Worldwide collection of inter-connected networks.
TCP/IP
A set of protocols that allow computers to communicate with each other in a network. Allows digital devices to be compatible.
IP address
A numeric public address for digital devices to be identified on the network
DNS
Servers that translate between IP addresses and domain names/ URLs
Hosting
When a business uses its servers to store files of another organisation
Cloud storage
Saving data in an off-site storage system maintained by a third party. Clients can access data storage, software and processing power remotely over the internet.
Cloud pros
- users can access from any connected device
- easy to increase how much storage is available
- no expensive hardware
- automatic back ups and updates
Cloud cons
- need internet connection
- dependant on host
- data is vulnerable to hackers
- unclear who has ownership over data
Star topology
All devices are connected to a central switch or server that controls the network. The central switch allows many devices to access the server simultaneously. Can be wired or wireless.
Star topology pros
- if a device fails, the rest of the network is unaffected
- easy to add more devices
- high security
Star topology cons
- dependant in the central switch working
- if wired, many cables are needed
Mesh topology
No central device, all nodes are involved in the transmission of messages.
Mesh topology pros
- no single point of failure, alternative routes are available
- easier to set up
- doesn’t need a central computer (cheaper)
Mesh topology disadvantages
- can be slower
- cabling all computers can be expensive
Ethernet
A family of networking protocols widely used in LANs
Plaintext
The original message to be encrypted
Wired
- very high bandwidth
- hard to set up
- expensive
- good security
- no interference
- not very mobile
Wireless
- lower bandwidth
- easy installation
- cheaper
- poor security
- possible interference
- very mobile
Cipher text
The encrypted message
Encryption
The process of converting plaintext into cipher text so it can’t be understood. To secure data across network connections.
Key
A sequence of letters, numbers and other characters used to encrypt or decrypt
Encryption algorithm
The method for encrypting the plaintext
IP address format
IPv4 and IPv6
Network standard
Specifies the way that computers access a network, the speeds and the types of physical cable or the wireless technology used. Allow hardwares/softwares to interact across different manufacturers.
HTTP
Used for accessing and receiving web pages on the internet. The protocol requests the web server to transmit the requested web page to the users browser.
FTP
File transfer protocol: provides the rules that must be followed when files are being transmitted between computers
SMTP
Simple mail transfer protocol: sending email messages until it reaches its destination
POP
Post Office Protocol: used by a client to retrieve emails from a mail server
IMAP
Internet Message Access Protocol: messages can be read and stored on the message server
Layering advantages
- reduces the complexity of the problem
- easier to fix problems and improve systems
- modules can be modified/ developed independently
Packet switching
Breaks data down into packets which are sent separately across the network
Circuit switching
The whole data is transmitted through a dedicated communication channel
