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Request for comment

Request for comment. One of a series, begun in 1969, of numbered Internet informational documents and standards widely followed by commercial software and freeware in the Internet and Unix communities. Few RFCs are standards but all Internet standards are recorded in RFCs. Perhaps the single most influential RFC has been RFC 822, the Internet electronic mail (email) format standard.

The RFCs issued by the Internet Engineering Task Force (IETF) and its predecessors are the most well-known series known as 'RFC', and is almost always what is meant by RFC without further qualification; however, other organizations have in the past also issued series called 'RFCs'.

The RFCs are unusual in that they are floated by technical experts acting on their own initiative and reviewed by the Internet at large, rather than formally promulgated through an institution such as ANSI. For this reason, they remain known as RFCs even once adopted as standards.

The RFC tradition of pragmatic, experience-driven, after-the-fact standard writing done by individuals or small working groups has important advantages over the more formal, committee-driven process typical of ANSI or ISO.

Emblematic of some of these advantages is the existence of a flourishing tradition of joke RFCs. Usually at least one a year is published, usually on April Fool's Day.

The RFCs are most remarkable for how well they work - they manage to have neither the ambiguities that are usually rife in informal specifications, nor the committee-perpetrated misfeatures that often haunt formal standards, and they define a network that has grown to truly worldwide proportions.

RFC 1, entitled "Host Software", was issued on April 7 1969 by Steve Crocker.

For more details about RFCs and the RFC process, see RFC 2026, "The Internet Standards Process, Revision 3"

A complete RFC index in text format is available from the IETF website, but because of its length, it is impractical to include it in the Wikipedia. The text of any particular RFC can be found by entering its number at

Here is the list of the most important RFCs:

RFC 0822 (Format of e-mail) RFC 0823 (The Internet gateway) RFC 0824 (CRONUS Virtual Local Network) RFC 0825 (RFC on RFCs)

RFC 0983 (ISO transport over TCP), RFC 0985 (Gateway Requirements), RFC 0987 (Mapping X.400 to RFC822)

RFC 1006 (ISO over TCP ver. 3), RFC 1009 (Gateway Requirements), RFC 1066 (Mib for TCP/IP)

RFC 1123 (Host Requirements), RFC 1149 (IP via Carrier Pigeon), RFC 1156 (Mib for TCP/IP)

RFC 1495 (Mapping X.400 to RFC822)

RFC 1521 (MIME)

RFC 1632 (Catalog of X.500 Implementations)

RFC 1718 (TAO of IETF)

RFC 1776 (The Address is the Message), RFC 1789 (Telephone over Internet), RFC 1792 (TCP/IPX Mib)

RFC 1809 (Flow Label in IPv6), RFC 1812 (IPv4 Routers), RFC 1876 (Location Information in DNS), RFC 1889 (Real-Time transport)

RFC 1918 ("Network 10"), RFC 1969 (PPP DES Encryption)

RFC 2026 (Internet Standards Rev. 3) RFC 2045 (MIME 1) RFC 2046 (MIME 2), RFC 2047 (MIME 3), RFC 2048 (MIME 4), RFC 2049 (MIME 5), RFC 2083 (PNG Format)

RFC 2116 (X.500 Implementations Catalog), RFC 2126 (ISO over TCP), RFC 2156 (Mapping X.400 to RFC822), RFC 2181 (Clarifications to DNS), RFC 2183 (Content-Disposition Header), RFC 2184 (Character Sets)

RFC 2223 (Instructions to RFC Authors), RFC 2231 (Character Sets)

RFC 2326 (Real Time Streaming), RFC 2327 (Session Description)

RFC 2401 (Security Architecture) RFC 2419 (PPP DES Encryption), RFC 2420 (PPP Triple-DES Encryption), RFC 2421 (Voice Mail), RFC 2440 (OpenPGP Message Format)

RFC 2525 (TCP Problems) RFC 2535 (DNS Security) RFC 2543 (Session Initiation) RFC 2549 (IP via Carrier Pigeon with QOS)

RFC 2644 (Changing Router Default Directed Broadcasts), RFC 2645 (On Demand Mail), RFC 2646 (Plain Text)

RFC 2747 (RSVP Crypto), RFC 2748 (COPS Protocol), RFC 2749 (COPS usage for RSVP)

RFC 2822 (e-mail format)

RFC 3008 (DNS Security) RFC 3023 (XML Media Types), RFC 3066 (Language Tags), RFC 3094 (Tekelec's Transport), RFC 3097 (RSVP Updated Message), RFC 3098 (Advertise Responsibly Using E-Mail)

RFC 3106 (ECML for E-Commerce), RFC 3114 (Company Security Classification with S/MIME), RFC 3115 (Mobile IP Extensions)

RFC 3261 (Session Initiation Protocol )

See also: FYI, Internet standard, BCP

partially based on FOLDOC

Table of contents
1 Links to IETF RFCs
2 External links

Links to IETF RFCs

Generic RFCs

Link-Level RFCs

Internetwork-Level RFCs

This is about using the flow label field in IPv6. This document is merely a suggestion and does not contain any standards in it. The current standard for flow labels in IPv6 is described in RFC 3595 here.

Host/Router Requirements RFCs

ISO Interoperation RFCs

Domain Name System RFCs

This covers the operation of secondary domain name servers.

X.500 RFCs

See also X.500

Network Management RFCs

E-Mail RFCs

This is an important early RFC from the IETF that specified the format of e-mail messages exchanged between computers on the Internet. Many additions have been made to it, but it remained a standard for many years until obsoleted by RFC 2822 (the number is not a coincidence: it was reserved for this use).

This standard specifies a syntax for text messages that are sent between computer users, within the framework of electronic mail messages. This standard is about text-only messages. The syntax for sending other types of messages, such as binary or structured data, is specified as an extension of this standard by the MIME document series: RFC 2045, RFC 2046, RFC 2049.

X.400 E-Mail RFCs


RFC 2047 specifies a standard way of encoding non US-ASCII characters into a string that identifies both the character set to use and the actual characters. The result of the encoding will be US-ASCII, and can be transmitted in Internet mail and decoded appropriately on the receiving end. This encoding is necessary in the first place because many characters in non-English languages can not be represented in 7-bit ASCII.

There are some mail clients that are not RFC 2047 Compliant, if you are using one of this clients you are strongly encuraged to change your mail client or to update it to a compliant version:

Eudora 4: Double quote characters are encoded with a Windows codpage and are eight-bit characters. Eudora's MIME headers indicate the MIME type but not 8-bit encoding. Suggest enabling "quoted printable" encoding.

April 1st RFCs

This is a humorous RFC by the IETF. It was written by D. Waitzman and released on April Fool's Day 1999; it is an April 1st RFC. It updates Waitzman's earlier RFC 1149 about the transmission of IP traffic via carrier pigeons.

Random Support RFCs

Random Application RFCs

This provides a way to register extensions of codes for language names in ISO 639. The current reviewer of new tags and maintainer of the registry is Michael Everson. An alternative for language codes is the Ethnologue.

See also Registry

Random RFCs

This is a memo and status report of the DARPA Internet Gateway. It deals with two areas: gateway procedures and message formats. Topics include information on the forwarding of internet datagrams, various protocols supported by the gateway, and specific gateway software. Unlike many other RFCs, it does not list any implementation specifics.

External links