A RFC (Request for Comments) is a pure technical document published by the Internet Engineering Task Force (IETF). Request for Comments (RFCs) are mainly used to develop a "standard" network protocol, a function of a network protocol or any feature which is related with network communication.
Some RFCs are informational and others are published Internet standards. The final version of the RFC becomes the standard and is published with a number. No further comments or changes are permitted for the final version. Changes are permitted only via subsequent RFCs that supersede the previous RFCs.
At the early stages of network communication, each vendor had their own proprietary network communication protocols. Different network protocols for the same purpose were a serious problem in heterogeneous network environments, consisting of devices and Operating Systems from different vendors.
"Standard" network protocols are not considered as proprietary. Any vendor can develop application software or drivers based on defined RFC standard. Hence RFC provides a strong base for cross platform network communication.
All the standard network protocols (like, HTTP, FTP, SMTP, TCP, UDP, IP etc) are defined as RFCs. Individuals may join the IETF working groups to help draft and develop networking standards or network protocols.
More than 7000 RFCs are available now. To search an RFC by its number or title, please visit following links.