netzwerkprotokolle

Network Protocols

In short: Sets of rules that determine how devices in a network communicate with each other — format, order and meaning of the messages exchanged.

In more detail: Without a shared protocol, devices from different manufacturers couldn’t talk to each other. Protocols are usually organised in layers (see OSI model): a protocol like HTTP at the application level builds on a transport protocol like TCP, which in turn sits on top of IP.

In Depth

Network protocols can be roughly classified by their task: addressing protocols (IP, ARP) clarify who is who; transport protocols (TCP, UDP) govern how reliably and in which order data flows; application protocols (HTTP, SMTP, SSH) define the concrete, purpose-specific communication between two programs. In addition there are control and diagnostic protocols such as ICMP, which don’t transport actual payload but status and error information about the network itself.

A protocol is considered “open” (a standard, e.g. specified by the IETF) if anyone may implement it without licence fees or vendor lock-in — which is why devices from completely different manufacturers can communicate smoothly with each other on the internet. New protocol versions often have to remain backwards compatible (e.g. modern web servers still support HTTP/1.1 alongside HTTP/2 and HTTP/3), so that older devices aren’t suddenly excluded.

See also: OSI model, Network services