The Need for Network Protocols

Definition: A computer protocol consists of an agreed format for messages, expressed by a packet header, an optional message component, and a set of rules for the exchange of messages between computers.

We see the use of protocols in Computer Science in almost every activity:

• World Wide Web servers (Microsoft's IIS, and The Apache Software Foundation's apache) communicate with Web clients/browsers such as Firefox, Chrome, and Edge using the Hyper Text Transfer Protocol (HTTP),
• electronic mail and news articles are delivered and exchanged using the Simple Mail Transfer Protocol (SMTP) and the Network News Transfer Protocol (NNTP),
• some operating systems (such as Linux) display their windows and graphics using the X-Windows Protocol, Virtual Network Computing (VNC), and Remote Desktop Protocol (RDP) display systems, and
• computers share their local disks using the Network File Systems (NFS), samba/SMB, or the Windows-NT File System (NTFS) and Resilient File System (ReFS) protocols.

Most importantly the protocol messages must -

• happen in an agreed to order,
• travel from the sender to the correct receiver(s), and
• contain the correct, unambiguous, data (what arrives must be what was sent).

Equally important -

• time plays a critical role, and
• information will be lost and corrupted and protocols must account for this.