1.3.3 NETWORKS

Collection of interconnected devices which can communicate with eachother

Set of hard/software specifications allowing companies to create products/services compatible with each other

A set of rules that allows two devices to communicate

Transmission control protocol - provides/ gives error free transmission between two routers
Internet protocol - routes packets across WAN

TCP/IP - foundation of communication over internet

Hypertext transfer protocol - way for client and server to send, receive requests and deliver/ return web pages.
HTTPS - adds encryption

File transmission protocol - used for sending files

Simple mail transfer protocol - used to send emails between servers and clients

Post office protocol - retrieves emails from mail server and sends it to your device but removes it from server
INTERNET MESSAGE ACCESS PROTOCOL -same but keeps email on mail server

Divide complex tasks into smaller simpler ones which work together and have separate jobs

Makes complex tasks into more simpler tasks
Devices can be made to work at specific layers

Application , transport , internet , link

Selects the specific protocol to use of the application. HTTP/FTP/IMAP work here

Sets up communications between devices and agree on settings like language.
TCP works here

responsible for addressing, packaging, and routing the packets for transmission across the network
IP works here

Facilitates the transmission of the packets
Network hardware and connection ports are here

1)Application layer uses appropriate protocol of application.

2)transport layer splits data into packets, adds order sequence ,number of packets and port number to use to each packet

3) internet layer adds source and destination IP address to each packet. We now have socket being IP address + port

4)link layer adds MAC address of source and destination device

5)Packets are transmitted and arrives at the targeted device. Then it goes up the layers in reverse order and does the opposite

Stores index of domain names and their IP addresses.

1)User requests a URL via browser
2)Browser sends domain name to DNS
3)DNS maps domain name to IP address and returns it
4)Browser uses this to retrieve web page

1)DNS contacts higher authority TLD server which sends a copy of the ip address to it
2)DNS gives ip address to browser

A network that covers a small geographical area and all hardware is owned by the people

a network that covers a large geographical area. Infrastructure that connects LANS to make a WAN is owned by companies

Server controls access/security of shared file store and manages access to internet
Clients make requests to server for data and etc.

Pros:
Easier to manage file security and back up shared data
Easier to install updates to all computers
Cons:
Can be expensive
Needs IT specialist
Server single point of failure

Decentralised network model where peers communicate and share resources with each other directly

Pros:
Easy to maintain
Cheap and no expensive hardware
Cons:
Network less secure
Users need to manage their own back ups
Can lead to outdated files

Creates a temporary dedicated link of fixed bandwidth between source and destination that terminates when finished.
Provides great quality but leads to waste of bandwidth as no one else can use it.

Breaks streams of data into smaller ones sent independently and via least congested routes and can mean packets use different routes. Its more affordable and maximises bandwidth

Software which allows only certain types of traffic to go through and can block ports and types of traffic.
prevents unauthorised traffic from outside a LAN

Device placed between a network and a remote source and all traffic flows through it and checks if page is on its banned list

Turns normal text into unreadable and is encrypted with an algorithm and key

Transforms digital info from computer into analogue signals and can do the opposite

Routes data between devices on LAN or WAN

Fibre optic
Coaxial
Twisted copper

Allows wired and wireless communication between computers on LAN/WAN

Creates a WLAN for wireless wifi by connecting to a router

Connects multiple devices to one network. Broadcasts data to everyone else

Same as hub but inspects and routes data to exact/correct device making it much faster

Header: Contains source and destination IP address and TTL hops
Payload: The data
Trailer: Contains error checking parts and looks if data is corrupted or not

Used for when data travels between 2 networks which use different protocols. Translating them.

Nodes connected to a single back bone cable and contains terminators in both ends. One PC can transmit at a time.

Pros:
Inexpensive to set up
Devices can easily be added
Good for small networks
Cons:
Main cable point of failure
One PC can transmit at a time
Poor security

protocol and domain name