Networks Flashcards
What is a network
When several computers are connected together, to share files / software / an internet connection, peripherals and processing power.
what is it called when a computer is not connected to a network
Stand Alone
What is a wide area network
the internet is an inter-connected network of networks. it is an example of a wide area network
-covers a large geographical area
-the infrastructure is owned by the organisation
What is a Local Area Network (LAN)
-A network that covers a small geographical area
-Typical the infrastructure is owned by the organisation
What is the backbone
A backbone or core network is a part of a computer network which interconnects networks, providing a path for the exchange of information between different LANs or subnetworks.
what is a IP (internet protocol) address
All devices connected to a network have an IP address
-Uses IPv4 which could hold 4.3billion addresses
-this was ok when the internet first started
-IPv6 is looking to solve this
What happens when you type a url into a browser
The request is sent a DNS (Domain Name System) Server to look-up the IP address of the server that is hosting the website
What is an internet registry ?
allows individuals to register domain names (website addresses) and adds them to the DNS index
What is a Switch
A device that connects computers together on a LAN. A switch onl forwards traffic to the intended recipient
what is a hub
A device that connects computers together on a LAN. A hub forwards traffic to all connected computers
What is a gateway?
When two types of networks join, e.g. LAN to WAN
What is a WAP?
Wireless access point so that WIFI devices can connect to a network
What is a router
-Acts as WAP, a hub and a gateway in a house
-a node on a WAN that forwards network traffic along the most appropriate route
What is a bridge
Join two LANs together
what is a NIC
Network interface card- traditionally a NIC was separate card to connect an ethernet cable
What is circuit switching
involves creating a complete dedicated physical connection between two endpoints
once used for the telephone networks but is not practical for the billions of devices that connect to the internet today
What is package switching
When data is split into equal sized “packets” and transferred over a network. Each packet can take it’s own independent route
if one packet arrives corrupt, that single packet can be re-sent rather than the whole file
What is latency
the amount of time it takes for a packet to reach its destination
what is badwidth
the amount data that can be transferred within a set time period. E.g. per second
What is a router
A router forwards packets from one network to another. Routers look at the destination IP address of a packet and forward on the most appropriate link. Each transfer is called a hop
What is a packet made up of
each packet is kept small
Header - sender’s IP / Recipient’s IP, protocol, packet number and hop count
Payload - data
Trailer - error checking. A check sum is a value that is sent with the payload. when some maths is done, if the answer is the same the sent checksum then we assume that the data is not corrupt
What are protocells
Are a series of rules that computers follow when communicating
What is HTTP
Hyper Text Transfer Protocol - is for transmitting and receiving small files e.g. HTML, CSS, JS, JPGS
What is FTP
File Transfer Protocol - is more appropriate for transferring large files
what is HTTPS
Encrypted version of http
What is SMTP
Simple Mail Transfer Protocol for sending Emails
What is TCP and UDP
Requires packets to be ordered, received no errors and are confirmed by recipients. UDP packets are just received, any corrupt packets are just delt with and there is no conformation
What is TCP/IP Stack
There are 4 layers to the TCP / IP stack which is used to transfer packets over a network
What is the application layer
The software that wants to transmit data to another computer uses the application layer to select an appropriate protocol
What is the transport layer
Uses TCP to split data into packets and numbers them. Adds the port number to the header according to the protocol.
When a device receives a packet, this is when it is re-ordered, checked for errors and acknowledged
what is the internet layer
The IP address of the sender and recipient are added to the header of each packet.
What is the link layer
The IP address of the sender and recipient are added to the header of each packet
what are the 4 layers of the tcp stack
application layer, transport layer, internet layer & link layer
What is a firewall
A firewall can be hardware or software
It prevents unauthorised network from incoming and outgoing through the firewall
A computer has a number of ports, lots of different kinds of network traffic arrives at certain ports. E.g. port 80 is HTTP traffic
the firewall listens to these ports and inspects traffic
What is packet filtering
A firewall technique is where the IP address of each packet is inspected to check if its “allowed”
if the packet is allowed, the port is opened for the duration of the transfer and closed again after.
What are proxy servers and VPN’s
A proxy server is a computer in another location that forwards on web requests on your behalf. Responses (Files / streaming Video) are sent to proxy, who forward it on to you - This hides your true location and make your computer anonmous on a network
A VPN also encrypts data
What are the features of a proxy server
-Anonymise location
-Filter content (handy in a school / collage)
-Log all web requests with your user ID
-Keep a cache of frequently visited websites
What should the proxy server do if website update occurs
If an update occurs to a website, the proxy server should check the Data/time of cached vs homepage so that a stale website isn’t sent to the requesting computer
What is malware
A general term for software written by someone with malicious intent, such as to corrupt data / collect personal information covertly
What is a virus
Malicious software that corrupts files on your computer. Requires a human to help spread
What is spyware
When software sends a key log and files to attacker
What is a Trojan
malware disguised as legitimate software. Users open unwittingly thinking they’re installing reputable software
What is a worm
Same as a virus, but can spread over a network
What is Phishing
Attackers send emails impersonating companies trying to et victims to click a link to website clone and enter personal data
What is buffer overflow
Buffer overflow occurs when a program accidently writes data to a location too small to handle it
- As a result, the overflowed data (written to location #3 below) may end up in a neighbouring instruction space
- Malware can deliberately cause and manipulate overflow data which may then be read as malicious ‘instruction’
What is SQL injection
A malicious user can enter SQL commands via online database forms to change the processing
