Request for Comments

(from Wikipedia, the free encyclopedia)

RFC index

A Request for Comments (RFC) document is one of a series of numbered Internet informational documents and standards very widely followed by both commercial software and freeware in the Internet and Unix communities. They are now published under the aegis of the Internet Society (ISOC, an open organization whose mission is developing the Internet for the benefit of people throughout the world) and its technical standards-setting bodies.

The basic communication protocols which the Internet uses to operate are all specified in RFCs, for instance. However, RFCs cover many topics in addition to standards, such as introductions to new research ideas and status memos about the Internet. While few RFCs are standards, almost all Internet standards are recorded in RFCs.

1 History and current organization
2 How to obtain RFCs
3 How RFCs are made (the RFC process)
4 History
5 List of commonly-used RFCs
6 See also
7 Links to IETF RFCs

7.1 Generic RFCs
7.2 Link-level RFCs
7.3 Internetwork-level RFCs
7.4 Host/router requirements RFCs
7.5 ISO interoperation RFCs
7.6 Domain Name System RFCs
7.7 X.500 RFCs
7.8 Network management RFCs
7.9 E-mail RFCs
7.10 X.400 E-mail RFCs
7.11 MIME RFCs
7.12 April 1st RFCs
7.13 Random support RFCs
7.14 Random application RFCs
7.15 Random RFCs

History and current organization

The RFC series of documents on networking began in as part of the original ARPA wide area networking ARPANETproject.

Today, it is the official publication channel for the Internet Engineering Task Force (IETF), the Internet Architecture Board (IAB), and the broader Internet community. RFCs are published by the RFC Editor, who is supported by the ISOC, but is under the general direction of the IAB.

Once published and issued a number, an RFC is never canceled or depublished; it is instead superseded by the publication of a new one. To determine which RFCs are actually active Internet standards and which ones have been superseded, one must consult the official list, Internet Standard 1 (STD 1), which itself is republished regularly as an RFC.

How to obtain RFCs

RFCs can be obtained on the Internet from the RFC Editor (, the IETF (rfc.html), or many other sites, principally using the Web, but also through anonymous FTP, gopher, and other Internet document-retrieval systems.

Every RFC is available as ASCII text and may be available in other formats, depending on the author. The definitive version of any standards-track specifications is always the ASCII version.

A complete RFC index in text format (iesg/1rfc_index) is available from the IETF website. Any published RFC can be directly found by inserting the number into the following URL:

rfc/rfc# (replace # with the RFC number).

How RFCs are made (the RFC process)

The RFCs are produced in a process that is different from that used in formal standards organizations such as ANSI. They can be floated by technical experts acting on their own initiative and reviewed by the Internet at large. Practically speaking, standards-track RFCs are usually produced by experts participating in working groups which first publish what the IETF calls Internet-Drafts; this facilitates initial rounds of review before documents become RFCs.

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.

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


RFC 1, entitled "Host Software", was written by Steve Crocker from the University of California, Los Angeles, and published on April 7, 1969.

The initial RFCs were apparently typewritten and circulated on hard copy among the ARPA researchers. Once ARPANET was fully functional by December 1969, subsequent RFCs were drafted and circulated over the network.

Douglas Engelbart's Augmentation Research Center at SRI was the first Network Information Center as well as one of the first two nodes on the network (the other was UCLA). The sociologist Thierry Bardini has pointed out that ARC personnel authored a large number of the early RFCs.

One advantage of the tradition of never depublishing obsolete RFCs is that they form a continuous historical record of the evolution of Internet standards. Lawyers will notice that this is roughly analogous to the tradition in common law countries (including the United States, where the Internet was born) of never depublishing case opinions, but instead overruling them with new ones.

List of commonly-used RFCs

RFC 768User Datagram Protocol
RFC 791Internet Protocol
RFC 792Control message
RFC 793Transmission Control Protocol
RFC 821Simple Mail Transfer Protocol, obsoleted by RFC 2821
RFC 822Format of e-mail, obsoleted by RFC 2822
RFC 826Address resolution protocol
RFC 894IP over Ethernet
RFC 951Bootstrap Protocol
RFC 959File Transfer Protocol
RFC 1034Domain Name System - concepts
RFC 1035DNS - implementation
RFC 1122Host Requirements I
RFC 1123Host Requirements II
RFC 1191Path MTU discovery
RFC 1256Router discovery
RFC 1323High performance TCP
RFC 1350Trivial File Transfer Protocol
RFC 1403BGP OSPF Interaction
RFC 1459Internet Relay Chat Protocol
RFC 1498Architectural discussion
RFC 1518CIDR address allocation
RFC 1519Classless inter-domain routing
RFC 1591Domain Name Structure
RFC 1661Point-to-Point Protocol
RFC 1738Uniform Resource Locators
RFC 1771A Border Gateway Protocol 4
RFC 1772BGP application
RFC 1789Telephone over Internet (obsoleted by current VoIP standards)
RFC 1812Requirements for IPv4Routers
RFC 1889Real-Time transport
RFC 1905Simple network management protocol
RFC 1907Simple network management protocol v2 Management information base
RFC 1918"Network 10"
RFC 1939Post Office Protocol version 3 (POP3)
RFC 2001TCP performance extensions
RFC 2026Internet Standards process
RFC 2046 
RFC 2047 
RFC 2048 
RFC 2049 
RFC 2060Internet Message Access Protocol version 4 (IMAP4), obsoleted by RFC 3501
RFC 2223Instructions to RFC Authors
RFC 2231Character Sets
RFC 2401Security Architecture
RFC 2453Routing Information Protocol
RFC 2525TCP Problems
RFC 2535DNS Security
RFC 2581TCP congestion control
RFC 2663Network address translation
RFC 2821Simple Mail Transfer Protocol
RFC 2822Format of e-mail
RFC 3010Network File System
RFC 3031MPLS architecture
RFC 3066Language Tags
RFC 3092Etymology of "Foo"
RFC 3098Advertise Responsibly Using E-Mail
RFC 3160Tao of IETF
RFC 3501IMAP4rev1

Links to IETF RFCs

Generic RFCs

Link-level RFCs

Internetwork-level RFCs

Host/router requirements RFCs

ISO interoperation RFCs

Domain Name System RFCs

This covers the operation of secondary domain name servers.

X.500 RFCs

Network management RFCs

E-mail RFCs

This is an important early RFC from the IETF that specified the protocol for transferring e-mail messages between computers on the Internet. Many additions have been made to it, but it remained a standard for many years until obsoleted by RFC 2821(the number is not a coincidence: it was reserved for this use).
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 the protocol for transferring e-mail messages between computers on the Internet.
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 2047, 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

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.

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.