TCP/IP

What is TCP / IP ?

Transmission Control Protocol / internet protocol
Allows different devices to communicate

What are the 4 layers of sending data ?

Application
Transport
Network
Link

What does the application layer do ?

Selects and uses the correct protocol to transmit data
Interacts with user with application software - web browser

What does the transport layer do ?

Establishes a connection between sender and receiver. Then splits the message into packets with port number to identify the protocol

What does the network layer do ?

Provides the correct IP address for each packet source and destination
Routers work with in this layer to get packets to the correct destination

What does the link Layer do ?

Controls physical connections between hardware in a network
Adds MAC address to packets which identifies the hardware which the packet should be sent to
They MAC address will change with every hop

What is a socket address ?

When IP address is combined with a port number
Identifies which application on recipients devices a packet should be sent

What are the different protocols ?

FTP
SSH
HTTP
HTTPS
POP3
STMP

What does FTP do ?

Used for sending file between devices. Client can access FTP servers anonymously or not by using passwords and user names

What does SSH do ?

Used for remote access / management of computers
To remote access computer

What does HTTP / HTTPS ?

Web server holds web pages in text form which they deliver to clients
HTTPS does the same but only encrypted

What does POP 3 do ?

Used to retrieve emails from a server but gets removed from server once retrieved

What does STMP do ?

Used for sending emails between a client and server

What is the structure of an IP address ?

IP address is split into 2 parts : network identifier and host identifier
Each computer has the same network ID

What is a subnet ?

Networks that are divided into smaller networks

What is a subnet mask ?

Determines the network identifier of an IP address
More bits assigned to the network identifier = more different subnets
More bits assigned to the host ID = more devices able to connect to network

What is a public IP address ?

Anyone can view them. Routable

What is a private IP address ?

a non-routable IP address that can be used within a LAN

What is Dynamic Host Configuration Protocol ?

Assigns devices with IP addresses as they join the network
Uses a pool of available addresses

How does DHCP work ?

DHCP discover : broadcast to all requesting an IP addresses
DHCP offer : offers an address with lease time
DHCP request : broadcast confirm IP address
DHCP : acknowledge and assign

What is network address translation ?

Devices an the network that send packets to a server

How does NAT work ?

When a device on a private network needs to communicate with a device on the internet :
Its sends packets through the router which makes record of packets
Replaces private IP with its own public IP address and makes note
Once a response is revived its sent to routers public IP address it's forwarded to the correct IP address

What is port forwarding ?

Used when a client needs to communicate with a server that's connected to a private network

How does port forwarding work ?

Client sends packets to public IP address of the router belonging to servers private network
Packets sent by the client contains the port number of application running that client wants to access
Private network router forwards packet to server via NAT

What is the client server model ?

Client sends request messages to servers

What is an API ?

Set of protocols relating to how different applications communicate
Defines how interactions between the applications should be carried out

What is a web socket ?

Example of an API which operates in the application layer. Provides constant stream of info
Full duplex
Fast transmission of data by decreasing the size of packets headers

What is CRUD ?

Query online database
Create
Retrieve
Update
Delete

What is REST ?

A design methodology for online database applications that are queried with a web browser
Post
Get
Put
Delete

How does REST work ?

Client server request made by client on web
Web browser responds with request file
File contains java Script which loads API - uses rest to enable database
Client sends HTTP request to server
Database responds with XML or JSON
Client browser process JSON

What are advantages of JSON ?

Easier for humans to write

What are disadvantages of JSON ?

Only works with limited data types

What are advantages of XML ?

Any data type allowed = more flexible

What are disadvantages of JSON ?

Use of tags = difficult to follow

What is a thin client network ?

Majority of networks processing power belongs to servers
Provides services and resources include storage and processing

What are advantages of thin client networks ?

Easy to add new clients
Clients inexpensive
Greater centralised control as network updates security managed from servers

What are disadvantages of thin client networks ?

Requires powerful server = expensive
Expertises required to set up and maintain
High volume of traffic

What is a thick client network ?

Clients are powerful enough to provide there own processing power + storage
Eliminates requirement for a server

What are advantages of thick Client networks ?

Robust and reliable
Operates without continuous server connections
Better for running more powerful applications

What are disadvantages of a thick client network ?

Software needs to be stored on each computer
High specification computers needed
Integrity issues with distributed data