Flashcards in Networks Deck (50):
What is a computer network?
A computer network is 2 or more computers connected for the purpose of sharing recources, either physically or wirelessly. To exchange infomation and data and share network recources.
What is a server?
a program or device used for a specific service which is more powerfil than other clients. E.g. internet server / file server
What is a client?
A less powerful device which is connected to the server and uses the services
What is a communication medium?
How your message is sent to the reciever.
Guided = cables
Unguided = wireless
What is a network adapter?
A network adapter is an internal hardware component that is used for communicating over a network with another computer. Wired or wireless.
What is a wireless access point / router?
A networking device that forwards data packets between computer networks. Allows internet connection to be shared towards users.
What are network recources?
Peripheral devices such as a printer that can be used by all users
What is a user?
Someone that uses a client to access recources on a network
What are protocols?
A set of rules that govens the communications between computers on a network
What is TCP?
Breaks down data into packets so that data gets there quicker and puts data back in order once it has arrived.
Detects errors and resends lost packets.
Transmission Control Protocol.
What is IP?
Identifies the location of a device on the Internet
Routes individual packets from source to destination via routers
What are mail protocols?
SMTP: Simple Mail Transfer Protocols
Used to send mail
POP3: Post Office Protocol 3
Used to recieve mail
What is HTTP?
Hypertext transfer protocol
Used to transmit HTML pages.
HTTPS is a sercure webpage
What is FTP?
File transfer protocol
Used to copy and send files over a network from one computer to another
What are the advantages of a computer network?
• Sharing resources such as software and other devices such as printers saves money.
• Site (software) licences are likely to be cheaper than buying several standalone licences.
• Files can easily be shared between users.
• Network users can communicate by email and instant messenger.
• Security is good - users cannot see other users' files unlike on stand-alone machines.
• Data is easy to backup as all the data is stored on the file server.
• Network Management is more affective
What are the disadvantages of a computer network?
• Purchasing the network cabling and file servers can be expensive.
• Managing a large network is complicated, requires training and a network manager usually needs to be employed.
• Relies on a server, if the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated.
• Viruses can spread to other computers throughout a computer network very quickly.
• There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, e.g. a firewall.
What is WAN?
Wide Area Network
Interconnects computers across a large geographical area i.e. company building located in different towns or cities
Uses the services of telecommunications companies i.e. BT, Virgin Media
What is LAN?
Local Area Network
Interconnects computers across a small geographical area i.e. a building or campus
Uses physical cables or wireless
What is PAN?
Personal Area Network
Interconnects devices centred around an individual person's workspace – typically within 10m
Uses wireless technology such as Bluetooth
MiFi - wireless devices that enable multiple users to share a single mobile broadband connection while they are on the go.
What is standalone?
A computer with no connection to a network or the outside world. No internet connection.
What is network topology?
Defines the way in which all network devices are interconnected to create a LAN
What are the three main topologies?
Which topology is most common?
What is bus topology?
Computers are connected to a single bakbone cable. The computers all share this cable to transmit to each other but only one computer can transmit at any one time. This is fine most of the time if the network is not too busy but if there is a lot of traffic then transmissions interfere with each other and computers have to retransmit.
What are the advantages of bus topology?
Easy and inexpensive to install - less cabling than in a star topology network
Easy to add new computers
What are the disadvantages of bus topology?
If the main cable fails then the whole network goes down
Cable failures are hard to isolate because it affects all of the components attached
Performance slows down as the amount of traffic increases
What is ring topology?
Computers are connected to adjacent computers in a ring.
Computers take it in turns to transmit, controlled by passing a token
around the ring. Computers can only transmit when they have the
What are the advantages of ring topology?
Not dependent on a central computer like
the star network
Token passing protocol is simple and
Consistent performance even when there
is a lot Of traffic
What are the disadvantages of ring topology?
A Single node or link failure and the
network is disrupted
What is star topology?
All of the computers have their own cable that connects
them to a central computer. The central computer controls
the network. This is usually a server, where shared
resources are stored.
What are the advantages of star topology?
If one cable fails only one station is
affected rather than the whole network
Consistent performance even when
network is heavily used
Easy to add new computers
More secure — messages from a computer
go directly to the centre
What are the disadvantages of star topology?
Can be costly to install because there is a
lot of cabling
Dependence on central computer, if it
fails whole network goes down
Network diagrams should include?
At least three PCs
One shared device i.e Printer
Servers i.e. Email, File, Internet
Router connecting to the Internet
Any topology specific devices labelled
Devices need a NIC
What are the network security aims?
Two basic goals:
Stop unauthorised people accessing resources
Ensure authorised people can access all the resources they need
What is authentication?
When the user is required to prove they are an authorised user.
Normally done with a username and password.
They are checked in the central database
What is encryption?
Protects data as it makes it difficult for others to read or alter it
Typically used for online shopping to keep payment details safe
Plaintext – original message
Ciphertext – encrypted message
Encryption – process of converting from plaintext to ciphertext
Decryption – the process of converting from ciphertext to plaintext
Key – a sequence of numbers used to encrypt/decrypt
Algorithm – the method used for encrypting
What is a firewall?
Designed to prevent unwanted traffic from gaining access to a LAN
Unauthorised users are blocked by the firewall
Certain ports can be closed to prevent specific types of packets from entering
What is MAC address filtering?
Generally used on a wireless network
A list of allowed MAC addresses can be set up under the MAC address filtering option
Only identifies permitted device
Doesn’t identify the individual user
What is the best security method?
In order to provide a high level of security a combination of the methods discussed would need to implemented
What are the layers in a TCP/IP prototcol stack
It consists of a number of different protocols across the four layers, that collectively allow data packets to be sent and received.
Advantages of using a layered approach?
A complex problem can be broken into smaller manageable pieces (decomposition) changes in one layer do not impact on other layers
It provides a universal standard for hardware and software manufacturers to follow
Each layer carries out distinct functions and therefore avoids repetition of tasks
What is the application layer?
Is where applications such as web browsers and email clients operate
Data being sent is encoded so that it will be understood by the recipient
An appropriate header is added, according to the protocol being used, before passing the data to the transport layer
What are the application layer protocols?
This provides a level of encryption to keep personal information secure, such as payment details
What is IMAP?
Internet Message Access Protocol
Similar to POP but messages do not have to be downloaded as they can be read and stored on the server.
This is better for users with multiple devices as they can be accessed from all devices.
What is the transport layer?
Sets up the communication between the hosts and agrees settings such as language and packet size
Divides data received from Application layer into packets of the correct size and adds packet information such as packet number and total number of packets
Checks that packets arrive safely (TCP) and sends acknowledgements when receiving data
What are the transport layer protocols?
Alternative to TCP but has no error checking or correction
Maintains an open connection between sender and receiver for the duration of the communication
Often used for online gaming and live broadcasting where speed is desirable and error correction is not necessary
What is the network layer?
Addresses and packages data for transmission
Attaches source and destination IP address which are used to route the packet across the Internet
What are the network layer prototcols?
What is the link layer?
Concerned with transmitting the data through the local network using the protocols of the specific network i.e. Ethernet
The MAC addresses of the sender and recipient are attached to the data allowing the packet to be directed to a specific device on a local network
This is where network hardware is located, such as the NIC, and the operating system device drivers