Protocol Examples (Cambridge (CIE) A Level Computer Science): Revision Note

Standard protocols

• A protocol is a set of rules that govern communication on a network

• There are protocols for different purposes, such as:

  • HTTP & HTTPS

  • FTP

  • POP3, IMAP & SMTP

  • BitTorrent

HTTP & HTTPS

• Hypertext Transfer Protocol (HTTP) allows communication between clients and servers for website viewing

• HTTP allows clients to receive data from the server (fetching a webpage) and send data to the server (submitting a form, uploading a file)

• HTTPS works in the same way as HTTP but with an added layer of security

• All data sent and received using HTTPS is encrypted

• HTTPS is used to protect sensitive information such as passwords, financial information and personal data

FTP

• File Transfer Protocol (FTP) allows sending and receiving files between computers

• Uploading and downloading files to/from a web server is often completed using FTP

• FTP offers greater efficiency and support for bulk transfers and large files such as resuming interrupted transfers

• FTP clients are software applications that use the FTP protocol to make the process easier for users

POP3, IMAP & SMTP

• A family of protocols that handle sending and receiving of email across the internet (WAN)

SMTP

• SMTP is a push protocol: it is used for sending (uploading) emails

• In the diagram above, SMTP is used to transfer the senders email to their email providers server and SMTP is used to transfer the email to the recipients email server

POP3

• POP3 is a pull protocol: it is used for receiving (downloading) emails from a mail server

• Once the email has been retrieved it is removed from the server

IMAP

• IMAP is also a pull protocol used for receiving (downloading) emails from a mail server

• Once the email has been retrieved, a copy is retained on the mail server

BitTorrent

• BitTorrent is a protocol for peer-to-peer file sharing over a network

• It allows files to be shared between thousands of users who are connected together over the internet

• Users share files directly with each other: the users' computers act as peers

• No web server or central device is used, and all users are of equal status

• This makes it efficient for sharing large files, as no single server has to supply the whole file to everyone

• While BitTorrent is a legal technology, it is sometimes used for sharing copyrighted content illegally, so ethical and legal use is important