Computing - 5 Fundamentals of Computer Networks - 4 Protocols and Layers

Protocol

set of rules governing the exchange or transmission of data between devices

HTML stands for...

Hypertext Markup Language

HTTP

used for accessing and receiving web pages via the Internet

HTTPS

like HTTP, but encrypts web pages for security

Websites that may use HTTPS [3]:

- banks
- online shops
- social networks

FTP stands for...

File Transfer Protocol

File Transfer Protocol

used for sending or retrieving files from an FTP server

Email protocols [3]:

- SMTP
- POP
- IMAP

SMTP stands for...

Simple Mail Transfer Protocol

Simple Mail Transfer Protocol

protocol used to send an email to a mail server

Mail server

server that manages the storage and transfer of e-mail messages

POP stands for...

Post-Office Protocol

IMAP stands for...

Internet Message Access Protocol

Mail relay

device in which email is stored and forwarded from, and sends the email to its final destination

Post-Office Protocol

accesses emails by downloading them from the mail server

Internet Message Access Protocol

accesses emails by viewing and leaving them on a server so they may be viewed by multiple devices

SMTP process [3]:

- email software sends data to company or individual's mail server
- mail server relays message through servers called mail relays
- email arrives at destination mail server

TCP stands for...

Transmission Control Protocol

Transmission Control Protocol

breaks up and reassembles data packets, checking them for errors and resending lost messages

IP stands for...

Internet Protocol

Internet Protocol

routes packets from one IP address to another

Protocol stack

layers of protocols that build and rely on each other

Layers in the protocol stack [4]:

- application layer
- transport layer
- Internet layer
- link layer

Application layer

applications such as email clients and web browsers create data to send in this layer

Protocols operating in the application layer [3]:

- SMTP
- HTTP
- FTP

Transport layer

splits data into packets and numbers them, then reassembles them at the other end

Protocols operating in the transport layer [2]:

- TCP
- UDP

Internet layer

responsible for addressing, routing, and packaging data packets using routers

How do routers function on the Internet layer?

give the data a new IP address and route it to next router on way to destination

Protocols operating in the Internet layer [1]:

- IP

Link layer

handles all the physical details of interfacing and gives data source and destination MAC addresses

Hardware operating in the link layer [3]:

- NICs
- cables and Wi-Fi
- OS's device drivers

Advantages of layers [2]:

- layers are modular, allowing the functionality of one to change without affecting that of another
- different hardware and software operates on different layers, allowing interoperability between manufacturers

UDP stands for...

User Datagram Protocol

User Datagram Protocol

maintains an open data connection to send a stream of packets without checking they are received correctly

When might UDP be used?

when resending packets isn't worth it (e.g. when gaming online)

TCP vs. UDP [2]

- TCP error-checks and resends lost packets
- UDP does no error-checking and sends packets in a stream