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What is RFC?

If you're new to RFC or want to systematically understand the RFC document system, this article will help you build a complete understanding framework.

One-Sentence Definition​

RFC (Request for Comments) is a technical standard document that defines how the Internet works.

From the HTTP protocol you use when accessing websites, to the SMTP protocol used for sending emails, to TLS encryption for network security, almost all underlying implementations of Internet technologies are defined by RFC documents.

Why "Request for Comments"?​

The full name RFC stands for "Request for Comments", and this name originated in 1969.

At that time, ARPANET, the predecessor of the Internet, had just been born, and a group of engineers needed to collaborate to develop network protocols. To encourage open discussion and improvement, they named the technical documents "Request for Comments", meaning "this is not the final version, criticism and suggestions are welcome".

But ironically: Over time, many RFCs have become unshakable Internet standards. For example:

  • RFC 791 defined the IPv4 protocol (published in 1981, still the main IP protocol worldwide)
  • RFC 2616 defined HTTP/1.1 (published in 1999, dominated the Web world for over a decade)
  • RFC 6749 defined OAuth 2.0 (published in 2012, now used by almost all third-party logins)

So, the name "Request for Comments" has been retained, but many RFCs are actually technical laws that must be followed.

Types of RFC​

RFC documents are divided into several categories with different importance and binding force:

1. Standards Track​

This is the most important RFC type, defining the core protocols and standards of the Internet.

Examples:

  • RFC 9110 - HTTP Semantics (2022, latest HTTP standard)
  • RFC 8446 - TLS 1.3 (2018, modern HTTPS encryption standard)

2. Best Current Practice (BCP)​

Not protocol definitions, but recommended technical practice methods.

Examples:

  • BCP 14 (RFC 2119) - Defines the meaning of keywords like "MUST", "SHOULD", "MAY"

3. Informational​

Provides technical information, historical background, or community perspectives, not mandatory.

4. Experimental​

Technologies still in the experimental stage, may succeed or fail.

How to Read RFC?​

RFC is a technical specification for engineers, not a popular science article. Reading RFC for the first time may feel very boring and difficult to understand.

Typical RFC Structure​

  1. Abstract: A paragraph explaining what this RFC does
  2. Status: Indicates whether it's standard/informational/experimental
  3. Table of Contents: Chapter index
  4. Body: Technical details (this is the main part)
  5. Security Considerations: Potential security risks
  6. References: Other RFCs or technical documents cited

Reading Tips​

  1. Start with abstract and introduction: Quickly determine if this RFC is relevant to your needs
  2. Focus on "MUST" and "MUST NOT": These are mandatory requirements
  3. Check examples: Many RFCs provide protocol interaction examples, more intuitive than text descriptions
  4. Compare with implementations: If there are open source implementations (like curl, nginx), understanding is faster combined with code

RFC and You​

If You're a Developer​

  • Implementing OAuth login? See RFC 6749
  • Processing JSON data? See RFC 8259
  • Building RESTful API? See RFC 9110 (HTTP Semantics)

If You're a System Administrator​

  • Configuring mail server? See RFC 5321 (SMTP)
  • Setting up DNS? See RFC 1035
  • Troubleshooting network issues? See RFC 791 (IP) and RFC 793 (TCP)

If You're a Security Engineer​

  • Understanding TLS? See RFC 8446
  • Researching JWT? See RFC 7519
  • Analyzing attack surface? See "Security Considerations" sections of related protocols

Where to Start?​

Entry-Level RFCs (Easy to read and practical)​

  1. RFC 3339 - Date and Time Format (short and concise, readable in 30 minutes)
  2. RFC 7519 - JWT (essential for modern Web development)
  3. RFC 2616 - HTTP/1.1 (although replaced, still the most classic HTTP introductory material)

Intermediate-Level RFCs (Requires some foundation)​

  1. RFC 793 - TCP Protocol (understanding the cornerstone of network communication)
  2. RFC 6749 - OAuth 2.0 (understanding modern authentication and authorization systems)
  3. RFC 8446 - TLS 1.3 (understanding network encryption)

Start Exploring​

This site has translated 137 RFC documents, covering multiple fields including Internet core protocols, Web technologies, security encryption, and more.

👉 View Complete RFC Document List - Browse all translated documents by category

Now, you can select an RFC of interest from the sidebar and start exploring the underlying world of Internet technology.

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