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3.5 fundamentals of computer networks (keeping a network secure …
3.5 fundamentals of computer networks
networks
two or more devices that are connected. they are able to communicate and share resources.
disadvantages
costs money to set up, manage, maintain a network
users need support - forget passwords
users can occasionally break tings
benefits
files are shared easily
software can be installed and shared centrally
backing up is easier - as data is installed centrally
data can be sent to remote areas that are connected to the network
saves money as hardware and peripheral resources can be shared across networks
risks
virus can spread across devices
risks of hacking
if centralised server stops working then no one can access network resources or computers
networks can control:
network access and privileges (passwords can be shared across devices)
installation of software's can be done across networks
ant-virus software updated across networks
remote access can be used
Types
PAN
LAN
WAN
wireless
advantages
can use internet as long as in range of Wireless access point (WAP)
files and resources can be shared without needing a cable
allows inexpensive LAN to be set up without cables
easy to connect new computers (compared to a wired network)
disadvantages
data transfers are normally slower
wireless connections can be obstructed by physical barrier (e.g walls)
wireless networks are generally less secure and easier to hack (compared to cable)
risks
unauthorised users can use the wireless connection to hack the network and to plant a virus. - can also flood network with useless traffic: denial of service attack
confidentiality - if data is not encrypted then an intruder can access data/ info
stealing bandwidth - when someone uses your wireless to connect to the internet and download data, they are using your data allowance to do this.
topologies
bus
star
network protocols
Common network protocols
FTP
used to transfer computer files between a client and a server
file Transfer Protocol
wifi - a type of trademark
Allows devices to transfer data wirelessly using a WIFI adapter and a wireless access point (WAP) to a wireless local area network (WLAN)
wireless devices connect to WAP and the WAP will broadcast a SSID (servers identifier - name) that the users can see. this will be encrypted
HTTP
HTTPS
encrypts the data
HyperText Transfer Protocol Secure)
accesses and receives web pages from HTML files on internet. the protocol makes a request to wed server to tramsit web page to users browser
HyperText Transfer Protocol
ethernet
a family related protocol.
divides data into frames containing source and destination MAC addresses and error testing.
TCP
TCP/IP
IP identifies location of the device on the internet and routes the packets from source to destination via routers
Internet Protocol
defines how messages are broken into packets and reassemble at destination. also detectes errors and resends 'lost ' protocols
transmission control Protocol
UDP
This allows applications to send messages (datagrams) to another host on an IP network. the connection remains open during the communication so is faster. used for time sensitive data (e.g video streaming, VoIP)
User Datagram Protocol
email Protocols
SMPT
Simple Mail Transfer Protocol
used to send emails from one server to another.
it will go to your emails provider email server. sent onwards to destinations email server
IMAP
Inter Message Access Protocol
messages are stored on email server
IMAP is used to send and retrieve emails
advantages
multiple devices can connect to an IMAP email account at same time
devices will be up to date at same time
definition
set of rules that define / allow two devices to communicate
keeping a network secure
encryption
firewall
authentication
password / username
user access levls
failed attempt logout
MAC address filtering
cable methods
ethernet
Electrical signal communication via inner conduct of the wires
Medium noise contamination
Less affected by external magnetic interference
Medium band width
Middle expense out of two
fibre optic
Optical signal communication via the glass fibres.
Very low noise contamination
Not affected by external magnetic interference
High bandwidth
Most expensive
coaxile
Electrical signal communication via the wires
High noise contamination
Can be affected be external magnetic interference
Low bandwidth
cheapest