The Request for Comments, better known by its acronym, RFC, are a series of publications of the internet engineering working group that describe various aspects of the operation of the internet and other computer networks, such as protocols and procedures.

Each RFC defines a monograph or memorandum that engineers or experts in the field have sent to the Internet Engineering Task Force (IETF) organization, the most important technical collaboration consortium on the internet, so that it can be valued by the rest of the community.

RFCs cover a wide range of standards, and TCP/IP is just one of these. They are freely available on the IETF's website, which can be found at www.ietf.org/rfc.html. Each RFC has a number; IPv4 is documented by RFC 791, and other relevant RFCs will be mentioned as we progress throughout this book.

The most important IPs are defined by RFC, such as the IP protocol that's detailed in RFC 791, FTP in RFC 959, or HTTP in RFC 2616.

You can use this service to search by RFC number or keyword. This can be found here: https://www.rfc-editor.org/search/rfc_search.php.

In the following screenshot, we can see the result of searching for RFC number 2616 for the HTTP protocol: