Network protocols: The Foundation of Digital Communication - IMAP, POP3, SMTP, RDP and VNC

In our previous blog post on network protocols we covered the definition of a protocol, why they are important and began explaining some common protocols; TCP/IP and UDP. These are important network protocols as most other protocols rely on TCP/IP or UDP to perform their role. Our second blog post on the subject of network protocols covered some additional network protocols and their reliance on either TCP/IP or UDP (or both). In this blog post, we continue to discuss network protocols that rely on either TCP/IP, UDP, or both.


The Internet Message Access Protocol (IMAP) is a protocol for email retrieval. By using IMAP, your emails are not automatically downloaded by default, until you click on an email to open them. Similarly, attachments are not downloaded automatically to make IMAP work faster. Emails will continue to be stored on the server, even after downloading. Deletion on the servers occurs when you delete the email. You may have encountered IMAP when using an email client such as Microsoft Outlook or Thunderbird where you have to specify an incoming mail server. That could be either IMAP or POP, or you can choose, depending on the server configuration. IMAP uses the TCP protocol to ensure a reliable email retrieval process.


The Post Office Protocol version 3 (POP3) is similar to IMAP. POP3 enables email clients to fetch emails from a mail server. One of the main differences with IMAP is that POP3 downloads email messages to the client and then deletes them from the server. That means that once they are downloaded, the emails are only accessible from the device they are downloaded to. Whether you should choose IMAP or POP is dependent on your email account provider, if they have an IMAP server or a POP server (or both), and your personal preferences. A server with limited storage space, for example, may not provide you with a choice and may force you to use POP3. Like IMAP, POP uses TCP for email retrieval.


SMTP or Simple Mail Transfer Protocol is a protocol for sending out email messages from an email client such as Microsoft Outlook and Thunderbird to an email server or when forwarding emails from one email server to another. What is the difference between IMAP and POP and SMTP? SMTP is a protocol that uses a push mechanism, emails are pushed out of the server to the next mail server until the server of the email client is reached. The email client then pulls the emails from its server with the help of either IMAP or POP. SMTP uses the TCP protocol to ensure that the integrity of the email messages stays intact.


Remote Desktop Protocol (RDP) is a proprietary protocol from Microsoft. The protocol enables users to remotely connect to another computer. One of the computers runs the RDP client software, the other runs the RDP server software. Most Windows OS versions have both the server and the client installed. You will use the Remote Desktop Protocol when you use Remote Desktop Connection (RDC), which is a Windows application that uses RDP to remotely access another computer. When the connection is successful, you have access to the desktop of the other computer. You can run programs or change settings. RDP is often used by support technicians for remotely diagnosing and repairing systems. Systems administrators use RDP for system maintenance. There are alternatives to RDC such as TeamViewer, AnyDesk, RemotePC, and Chrome Remote Desktop. Many of these applications still rely on Microsoft’s Remote Desktop Protocol to establish the remote connection, but users who prefer an alternative interface to RDC have a variety of options now. RDP uses both TCP and UDP. The user can configure their preference for either protocol. To establish the connection, RDP usually uses TCP. UDP is used after the connection has been established.


Virtual Network Computing (VNC) is an alternative protocol to RDP. Similar to RDP, VNC is a client-server protocol that enables remote access to another device. There are a few differences. VNC is platform-independent. The protocol is open-source and available for all operating systems. VNC utilizes the remote frame buffer protocol (RFB). RFB is insecure by default. Using VNC with tunnelling technologies such as VPN or SSH is therefore recommended. You can use software applications for remotely accessing other devices that securely use VNC. Whether you should use VNC or RDP depends on the purpose of your remote connection and your personal preferences. VNC can be used with both TCP and UDP, depending on the application that uses VNC to establish the remote connection. Often you can configure the client application to either use TCP or UDP.

Do you want to get practical skills to work in cybersecurity or advance your career? Enrol in MCSI Bootcamps!