networks

what is malware

software designed to disrupt, damage or gain unauthorised access to computer system

eg of malware

viruses, worms, trojan horses, ransomware, spyware

how to protect against malware

• firewall

• spam filter

• anti-virus

• anti-spyware

• anti-spam

• OS and security software updates

• training staff to be cautious

• regularly backing files

what is phishing

sending emails pretending to be from reputable companies in order to get someone to reveal personal info

how to protect against phishing

• firewall

• spam filter

• anti-virus

• anti-spyware

• anti-spam

• OS and security software updates

• training staff to be cautious

what is a brute force attack

trial and error method of attempting passwords

how to protect against brute force attack

• lock account after certain number of password attempts with progressive delays

• train staff to use strong passwords

• challenge responses eg. CAPTCHA

what is a denial of service attack

flooding a server with useless traffic causing server to become overloaded and unavailable

how to protect against DOS attack

• strong firewall

• packet filters on routers

• configuring web server

• auditing, logging, monitoring systems

what is data interception and theft

unauthorised act of stealing computer-based information from unknowing victim with intention of obtaining confidential info

how to protect against data interception and theft

• encryption

• using viral networks

• penetration testing

what is SQL injection

technique used to view/change data in database by inserting additional code into a text input box

how to protect against SQL injection

• validation on input boxes

• parameter queries

• setting database permissions

• penetration testing

what are the advantages of networking

• can share files and peripherals

• users can access files from any computer on network

• servers can control security, software updates and data backups

• communicating with others

what are the disadvantages of networks

• increased security risks to data

• malware/viruses spread more easily

• if server fails computers connected it may not works

• computer runs slowly if lots of data travelling on network

LAN

• small geographical area on one site

• all hardware is owned by organisation using it

• wired with UTP cable, fibre optic or wireless using WiFi

WAN

• large geographical area connecting LANs

• infrastructure between LANs leased from telecommunication companies who own/manage it

• connected with telephone lines, fibre optic cables, satellite links

what factors affect network performance

bandwidth, number of users, transmission media, error rate, latency

what is bandwidth

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

• not a measure of speed but how much data sent

• measured in bits per second (bit rate)

how does number of users affect network performance

• too many users/devices on same network can cause network to slow down

• bandwidth shared by more people

how does transmission media affect network performance

• wired connections have higher bandwidth than wireless

• fibre optic cables have higher bandwidth than copper cables

what is error rate

errors occurring when data is transferred so has to be resent

what affects error rate

less reliable connections

signal quality of wireless connections

what affects signal quality

• range of devices from wireless access point

• signal quality of copper cables determined by grade of material used

• length of cable

what is latency

delay from transmitting data to receiving it

what causes latency

• hardware and transmission media not operating at same speed

• bottlenecks in infrastructure

• ie. not uses switches to appropriately segment traffic on network

what are the features of client-server model

server:

• controls access and security to shared file store

• manages access to internet

• manages printing jobs

• provides emails services

• runs data backups

client:

• makes requests to server for data and connections

what is a peer in peer-to-peer network

computer

• equal to all other peers

• serve own files to each other

what are the features of peer-to-peer model

• each peer responsible for security and backup

• each peer has own printer

• can send print jobs to another peer to process but said peer would need to be switch on to communicate w/ printer

what does a network interface controller do

connects device to wired/wireless connection

how does NIC work

uses protocols for communication

what does a wireless access point do

allows wireless-enabled devices to access device

advantage of wireless connections

dont need to install cables

disadvantages of wireless connections

less bandwidth than wired network

increased security risk

how does a switch work

uses NIC address on device to route traffic

what does a router do

sends data between networks

connects LAN to WAN

how does a router work

uses IP address on device to route traffic to other routers

what does a unshielded twisted pair (UTP) copper cable do

make connections between desktop computers and switch

what are advantages of copper cable

cheap

flexible

easy to install

what does a fibre optic cable do

connect long distance cables and WANs

what are the advantages of fibre optic cables

higher bandwidth than copper

less interference

what is the internet

global network of networks

what is the domain name service

multiple domain name servers

what does the domain name service (DNS) do

convert web addresses into IP addresses for routers

what is hosting

websites being stored on servers

what are the advantages of hosted solutions (???)

provide 24/7 access

multiple users

greater security

what is cloud storage

server that store data/programs remotely that can be accessed/used via the internet

what does cloud storage do

provide access to anything anywhere

automatic backup

collaboration of documents

what is the order of requests (???)

client → web server → web page → file server → file storage

what is a star network topology

all devices connected to central switch

• most popular wired type of network

advantage of star network topology

if single cable breaks only that computer affected

disadvantage of star network topology

if switch fails all fails

what is a full mesh network topology

each device connected to every other device

advantage of full mesh network topology

if break in connection you can route traffic via another router

disadvantage of full mesh network topology

more cabling

switch hardware required - expensive for large network

what is partial mesh network topology

multiple routes exist between different devices

• not every device connected to each other

advantages of partial mesh network topology

compromise solution

less hardware needed than full mesh

what is a ethernet

standard of networking technologies

what is ethernet used for

communicating on wired LAN

what are the features of ethernet

many protocols

what are the advantages of ethernet

reliable, error free, fast communication

features of data transmission by ethernet (???)

preamble of bits uses to synchronise transmission

start frame deliminator to signify start of data part of frame

source/destination MAC address

actual data

error checking info

disadvantages of ethernet

users location limited by need of physical cable connection

needs lots of cables, connections, ports, physical hardware - expensive

advantages of wifi

• users can move around freely

• easier to set up

• cheaper

• convenient to use

• can handle large amount of users

• transferring info to social media easier

disadvantages of wifi

• speed slower than wired networks

• relies on signal strength to wireless access point

• signal can be obstructed

• less secure than wired

advantages of bluetooth

ideal for connection personal devices

v low power consumption

disadvantages of bluetooth

v short range

what is encryption

scrambling data into cipher text using master key created from SSID of network and the password

data decrypted by receiver using same master key so key not transmitted

what protocols used for wireless encryption

• WEP

• WPA

• WPA2

• handshaking protocol to ensure receiver has valid master key before transmission

what is mac addressing used for

to route frames on a LAN

unique to every network interface card

how are mac addresses formatted

12 characters of numbers and letters

every pair of characters separated by a colon

what is ip addressing used for

routing packets on WAN

what is IPv4 address

• 32 bits in size

• four numbers separated by .

• each number between 0-255

what is IPv6 address

128 bits in size

eight groups of four hexadecimal digits separated by colons

why is IPv6 replacing IPv4

unique static address running out

why does a router have a unique WAN and LAN IP address

allows LAN device to have same IP address as another device on LAN

what are standards

specifications for hardware allowing manufacturers/producers to create products and services which are compatible with each other

examples of standards

ASCII/Unicode

HTML

what is a protocol

set of rules allowing two devices to communicate

what is TCP

Transmission Control Protocol

• provides error free transmission between two routers

• part of TCP/IP protocol stack

what is IP

Internet Protocol

• routes packets across WAN

• part of TCP/IP protocol stack

what is HTTP

Hypertext Transfer Protocol

• client-server method of requesting/delivering HTML web pages

what is HTTPS

Hypertext Transfer Protocol Secure

• encryption and authentication for requesting/delivering HTML web pages

• used when sensitive info being transferred

what is FTP

File Transfer Protocol

• send files between computers, usually on WAN

what is POP

Post Office Protocol

• retrieves emails from mail server

• removes it from server and transfers to your device

what is SMTP

Simple Mail Transfer Protocol

• sends email to email server

what is IMAP

Internet Message Access Protocol

• used by mail clients to manage remote mails boxes and retrieve mail from mail server

what is the point of layering

• divide complex task of networking into smaller, simpler tasks

• hardware and/or software for each layer has defined responsibility

• each layer provides server to layer above it

advantages of layering

• reduces complexity of problem into manageable sub problems

• devices can be manufactured to operate at particular layer

• products from different vendors work together

what happens in TCP/IP protocol stack

• set of networking protocols consisting of four layers working together

• all incoming/outgoing data packets pass up and down through various layers when communicate on network

what happens in application layer

uses appropriate protocol relating to whatever application being used to transmit data

ie. HTTP for web browser

what happens in transport layer

• uses TCP protocol

• establishes end-to-end connection

• once connection made it splits data to be transmitted into packets

• to each packet it adds its sequence, total number of packets and the port number the packet should use

what happens in network layer

• uses IP protocol

• to each packet it adds source IP address and destination IP address

• all routers operate at this layer

what happens in link layer

• represents actual physical connection between various network nodes

• adds source MAC address and destination MAC address