Postel’s prescription definition
Postel’s prescription, which some people call Postel’s law or the robustness principle, is a rule for designing network communication protocols. The main idea behind Postel’s law is that systems should be careful about what they send, making sure the data is correct and follows the rules — but flexible about what they receive.
The principle advises systems to accept data that doesn’t fully follow the rules — as long as it can be understood. The premise is that sending data carefully but accepting it more flexibly helps keep communication smooth, reliable, and safe between different systems.
Postel’s prescription history
Jon Postel, a computer scientist and a key player in the early days of the internet, was the mind behind Postel's prescription. He introduced the principle in the 1980s during the development of the TCP (Transmission Control Protocol).
Postel wanted to make sure different systems could communicate well, so he created a principle that kept it strict and flexible at the same time. It helped create reliable network protocols, playing a big role in the internet's success.
Real-world examples of Postel’s law in action
- Email protocols. Email servers often follow Postel's law by accepting and processing emails that don’t perfectly follow email format standards. This way, messages keep coming through even if they have some formatting issues.
- Web browsers. Web browsers are designed to interpret and display web pages even if the HTML or CSS code is not flawless. This flexibility ensures users can still view websites that may have a coding error every now and then.
- DNS servers. DNS servers often accept and handle queries even if they don't follow the rules perfectly. This helps ensure that domain names are resolved correctly, even if they have small errors.
