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rfc:rfc2476

Network Working Group R. Gellens Request for Comments: 2476 QUALCOMM Category: Standards Track J. Klensin

                                                                  MCI
                                                        December 1998
                         Message Submission

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1998).  All Rights Reserved.

Table of Contents

  1.  Abstract . . . . . . . . . . . . . . . . . . . . . . . . . .  2
  2.  Document Information  . . . . . . . . . . . . . . . . . . .   3
    2.1.  Definitions of Terms Used in this Memo . . . . . . . . .  3
    2.2.  Conventions Used in this Document . . . . . . . . . . .   4
  3.  Message Submission . . . . . . . . . . . . . . . . . . . . .  4
    3.1.  Submission Identification . . . . . . . . . . . . . . .   4
    3.2.  Message Rejection and Bouncing . . . . . . . . . . . . .  4
    3.3.  Authorized Submission . . . . . . . . . . . . . . . . .   5
    3.4.  Enhanced Status Codes  . . . . . . . . . . . . . . . . .  6
  4.  Mandatory Actions . . . . . . . . . . . . . . . . . . . . .   6
    4.1.  General Submission Rejection Code  . . . . . . . . . . .  6
    4.2.  Ensure All Domains are Fully-Qualified  . . . . . . . .   6
  5.  Recommended Actions  . . . . . . . . . . . . . . . . . . . .  7
    5.1.  Enforce Address Syntax  . . . . . . . . . . . . . . . .   7
    5.2.  Log Errors . . . . . . . . . . . . . . . . . . . . . . .  7
  6.  Optional Actions  . . . . . . . . . . . . . . . . . . . . .   7
    6.1.  Enforce Submission Rights  . . . . . . . . . . . . . . .  7
    6.2.  Require Authentication  . . . . . . . . . . . . . . . .   8
    6.3.  Enforce Permissions  . . . . . . . . . . . . . . . . . .  8
    6.4.  Check Message Data  . . . . . . . . . . . . . . . . . .   8
  7.  Interaction with SMTP Extensions . . . . . . . . . . . . . .  8
  8.  Message Modifications . . . . . . . . . . . . . . . . . . .   9
    8.1.  Add 'Sender' . . . . . . . . . . . . . . . . . . . . . .  9
    8.2.  Add 'Date'  . . . . . . . . . . . . . . . . . . . . . .  10
    8.3.  Add 'Message-ID' . . . . . . . . . . . . . . . . . . . . 10

Gellens & Klensin Standards Track [Page 1] RFC 2476 Message Submission December 1998

    8.4.  Transfer Encode . . . . . . . . . . . . . . . . . . . .  10
    8.5.  Sign the Message . . . . . . . . . . . . . . . . . . . . 10
    8.6.  Encrypt the Message . . . . . . . . . . . . . . . . . .  10
    8.7.  Resolve Aliases  . . . . . . . . . . . . . . . . . . . . 10
    8.8.  Header Rewriting  . . . . . . . . . . . . . . . . . . .  10
  9.  Security Considerations  . . . . . . . . . . . . . . . . . . 11
 10.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . .  11
 11.  References . . . . . . . . . . . . . . . . . . . . . . . . . 12
 12.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14
 13.  Full Copyright Statement  . . . . . . . . . . . . . . . . .  15

1. Abstract

 SMTP was defined as a message *transfer* protocol, that is, a means
 to route (if needed) and deliver finished (complete) messages.
 Message Transfer Agents (MTAs) are not supposed to alter the message
 text, except to add 'Received', 'Return-Path', and other header
 fields as required by [SMTP-MTA].
 However, SMTP is now also widely used as a message *submission*
 protocol, that is, a means for message user agents (MUAs) to
 introduce new messages into the MTA routing network.  The process
 which accepts message submissions from MUAs is termed a Message
 Submission Agent (MSA).
 Messages being submitted are in some cases finished (complete)
 messages, and in other cases are unfinished (incomplete) in some
 aspect or other.  Unfinished messages need to be completed to ensure
 they conform to [MESSAGE-FORMAT], and later requirements.  For
 example, the message may lack a proper 'Date' header field, and
 domains might not be fully qualified.  In some cases, the MUA may be
 unable to generate finished messages (for example, it might not know
 its time zone).  Even when submitted messages are complete, local
 site policy may dictate that the message text be examined or modified
 in some way.  Such completions or modifications have been shown to
 cause harm when performed by downstream MTAs -- that is, MTAs after
 the first-hop submission MTA -- and are in general considered to be
 outside the province of standardized MTA functionality.
 Separating messages into submissions and transfers allows developers
 and network administrators to more easily:
  • Implement security policies and guard against unauthorized mail

relaying or injection of unsolicited bulk mail

  • Implement authenticated submission, including off-site submission

by authorized users such as travelers

Gellens & Klensin Standards Track [Page 2] RFC 2476 Message Submission December 1998

  • Separate the relevant software code differences, thereby making

each code base more straightforward and allowing for different

     programs for relay and submission
  • Detect configuration problems with a site's mail clients
  • Provide a basis for adding enhanced submission services in the

future

 This memo describes a low cost, deterministic means for messages to
 be identified as submissions, and specifies what actions are to be
 taken by a submission server.
 Public comments should be sent to the IETF Submit mailing list,
 <ietf-submit@imc.org>.  To subscribe, send a message containing
 SUBSCRIBE to <ietf-submit-request@imc.org>.  Private comments may be
 sent to the authors.

2. Document Information

2.1. Definitions of Terms Used in this Memo

 Fully-Qualified
 Containing or consisting of a domain which can be globally resolved
 using the global Domain Name Service; that is, not a local alias or
 partial specification.
 Message Submission Agent (MSA)
 A process which conforms to this specification, which acts as a
 submission server to accept messages from MUAs, and either delivers
 them or acts as an SMTP client to relay them to an MTA.
 Message Transfer Agent (MTA)
 A process which conforms to [SMTP-MTA], which acts as an SMTP server
 to accept messages from an MSA or another MTA, and either delivers
 them or acts as an SMTP client to relay them to another MTA.
 Message User Agent (MUA)
 A process which acts (usually on behalf of a user) to compose and
 submit new messages, and process delivered messages.  In the split-
 MUA model, POP or IMAP is used to access delivered messages.

Gellens & Klensin Standards Track [Page 3] RFC 2476 Message Submission December 1998

2.2. Conventions Used in this Document

 In examples, "C:" is used to indicate lines sent by the client, and
 "S:" indicates those sent by the server.  Line breaks within a
 command example are for editorial purposes only.
 Examples use the 'example.net' domain.
 The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
 in this document are to be interpreted as defined in [KEYWORDS].

3. Message Submission

3.1. Submission Identification

 Port 587 is reserved for email message submission as specified in
 this document.  Messages received on this port are defined to be
 submissions.  The protocol used is ESMTP [SMTP-MTA, ESMTP], with
 additional restrictions as specified here.
 While most email clients and servers can be configured to use port
 587 instead of 25, there are cases where this is not possible or
 convenient.  A site MAY choose to use port 25 for message submission,
 by designating some hosts to be MSAs and others to be MTAs.

3.2. Message Rejection and Bouncing

 MTAs and MSAs MAY implement message rejection rules that rely in part
 on whether the message is a submission or a relay.
 For example, some sites might configure their MTA to reject all RCPT
 TOs for messages that do not reference local users, and configure
 their MSA to reject all message submissions that do not come from
 authorized users, based on IP address, or authenticated identity.
 NOTE:  It is better to reject a message than to risk sending one that
 is damaged.  This is especially true for problems that are
 correctable by the MUA, for example, an invalid 'From' field.
 If an MSA is not able to determine a return path to the submitting
 user, from a valid MAIL FROM, a valid source IP address, or based on
 authenticated identity, then the MSA SHOULD immediately reject the
 message.  A message can be immediately rejected by returning a 550
 code to the MAIL FROM command.

Gellens & Klensin Standards Track [Page 4] RFC 2476 Message Submission December 1998

 Note that a null return path, that is, MAIL FROM:<>, is permitted
 and MUST be accepted. (MUAs need to generate null return-path
 messages for a variety of reasons, including disposition
 notifications.)
 Except in the case where the MSA is unable to determine a valid
 return path for the message being submitted, text in this
 specification which instructs an MSA to issue a rejection code MAY be
 complied with by accepting the message and subsequently generating a
 bounce message. (That is, if the MSA is going to reject a message for
 any reason except being unable to determine a return path, it can
 optionally do an immediate rejection or accept the message and then
 mail a bounce.)
 NOTE:  In the normal case of message submission, immediately
 rejecting the message is preferred, as it gives the user and MUA
 direct feedback.  To properly handle delayed bounces the client MUA
 must maintain a queue of messages it has submitted, and match bounces
 to them.

3.3. Authorized Submission

 Numerous methods have been used to ensure that only authorized users
 are able to submit messages.  These methods include authenticated
 SMTP, IP address restrictions, secure IP, and prior POP
 authentication.
 Authenticated SMTP [SMTP-AUTH] has been proposed.  It allows the MSA
 to determine an authorization identity for the message submission,
 which is not tied to other protocols.
 IP address restrictions are very widely implemented, but do not allow
 for travellers and similar situations, and can be spoofed.
 Secure IP [IPSEC] can also be used, and provides additional benefits
 of protection against eavesdropping and traffic analysis.
 Requiring a POP [POP3] authentication (from the same IP address)
 within some amount of time (for example, 20 minutes) prior to the
 start of a message submission session has also been used, but this
 does impose restrictions on clients as well as servers which may
 cause difficulties.  Specifically, the client must do a POP
 authentication before an SMTP submission session, and not all clients
 are capable and configured for this.  Also, the MSA must coordinate
 with the POP server, which may be difficult.  There is also a window
 during which an unauthorized user can submit messages and appear to
 be a prior authorized user.

Gellens & Klensin Standards Track [Page 5] RFC 2476 Message Submission December 1998

3.4. Enhanced Status Codes

 This memo suggests several enhanced status codes [SMTP-CODES] for
 submission-specific rejections.  The specific codes used are:
  5.6.0  Bad content.  The content of the header or text is
         improper.
  5.6.2  Bad domain or address.  Invalid or improper domain or address
         in MAIL FROM, RCPT TO, or DATA.
  5.7.1  Not allowed.  The address in MAIL FROM appears to have
         insufficient submission rights, or is invalid, or is not
         authorized with the authentication used; the address in a
         RCPT TO command is inconsistent with the permissions given to
         the user; the message data is rejected based on the
         submitting user.
  5.7.0  Site policy.  The message appears to violate site policy in
         some way.

4. Mandatory Actions

 An MSA MUST do all of the following:

4.1. General Submission Rejection Code

 Unless covered by a more precise response code, response code 554 is
 to be used to reject a MAIL FROM, RCPT TO, or DATA command that
 contains something improper.  Enhanced status code 5.6.0 is to be
 used if no other code is more specific.

4.2. Ensure All Domains are Fully-Qualified

 The MSA MUST ensure that all domains in the envelope are fully-
 qualified.
 If the MSA examines or alters the message text in way, except to add
 trace header fields [SMTP-MTA], it MUST ensure that all domains in
 address header fields are fully-qualified.
 Reply code 554 is to be used to reject a MAIL FROM, RCPT TO, or DATA
 command which contains improper domain references.
 NOTE:  A frequent local convention is to accept single-level domains
 (for example, 'sales') and then to expand the reference by adding the
 remaining portion of the domain name (for example, to

Gellens & Klensin Standards Track [Page 6] RFC 2476 Message Submission December 1998

 'sales.example.net').  Local conventions that permit single-level
 domains SHOULD reject, rather than expand, incomplete multi-level
 domains, since such expansion is particularly risky.

5. Recommended Actions

 The MSA SHOULD do all of the following:

5.1. Enforce Address Syntax

 An MSA SHOULD reject messages with illegal syntax in a sender or
 recipient envelope address.
 If the MSA examines or alters the message text in way, except to add
 trace header fields, it SHOULD reject messages with illegal address
 syntax in address header fields.
 Reply code 501 is to be used to reject a MAIL FROM or RCPT TO command
 that contains a detectably improper address.
 When addresses are resolved after submission of the message body,
 reply code 554 with enhanced status code 5.6.2 is to be used after
 end-of-data, if the message contains invalid addresses in the header.

5.2. Log Errors

 The MSA SHOULD log message errors, especially apparent
 misconfigurations of client software.
 Note:  It can be very helpful to notify the administrator when
 problems are detected with local mail clients.  This is another
 advantage of distinguishing submission from relay: system
 administrators might be interested in local configuration problems,
 but not in client problems at other sites.

6. Optional Actions

 The MSA MAY do any of the following:

6.1. Enforce Submission Rights

 The MSA MAY issue an error response to the MAIL FROM command if the
 address in MAIL FROM appears to have insufficient submission rights,
 or is not authorized with the authentication used (if the session has
 been authenticated).
 Reply code 550 with enhanced status code 5.7.1 is used for this
 purpose.

Gellens & Klensin Standards Track [Page 7] RFC 2476 Message Submission December 1998

6.2. Require Authentication

 The MSA MAY issue an error response to the MAIL FROM command if the
 session has not been authenticated.
 Section 3.3 discusses authentication mechanisms.
 Reply code 530 [SMTP-AUTH] is used for this purpose.

6.3. Enforce Permissions

 The MSA MAY issue an error response to the RCPT TO command if
 inconsistent with the permissions given to the user (if the session
 has been authenticated).
 Reply code 550 with enhanced status code 5.7.1 is used for this
 purpose.

6.4. Check Message Data

 The MSA MAY issue an error response to the DATA command or send a
 failure result after end-of-data if the submitted message is
 syntactically invalid, or seems inconsistent with permissions given
 to the user (if known), or violates site policy in some way.
 Reply code 554 is used for syntactic problems in the data.  Reply
 code 501 is used if the command itself is not syntactically valid.
 Reply code 550 with enhanced status code 5.7.1 is used to reject
 based on the submitting user.  Reply code 550 with enhanced status
 code 5.7.0 is used if the message violates site policy.

7. Interaction with SMTP Extensions

 The following table lists the current standards-track and
 Experimental SMTP extensions.  Listed are the RFC, name, an
 indication as to the use of the extension on the submit port, and a
 reference:
 RFC   Name             Submission  Reference
 ----  ---------------  ----------  ------------------
 2197  Pipelining         SHOULD    [PIPELINING]
 2034  Error Codes        SHOULD    [CODES-EXTENSION]
 1985  ETRN              MUST NOT   [ETRN]
 1893  Extended Codes     SHOULD    [SMTP-CODES]
 1891  DSN                SHOULD    [DSN]
 1870  Size                MAY      [SIZE]
 1846  521               MUST NOT   [521REPLY]
 1845  Checkpoint          MAY      [Checkpoint]

Gellens & Klensin Standards Track [Page 8] RFC 2476 Message Submission December 1998

 1830  Binary              MAY      [CHUNKING]
 1652  8-bit MIME         SHOULD    [8BITMIME]
 ----  Authentication     ------    [SMTP-AUTH]
 Future SMTP extensions should explicitly specify if they are valid on
 the Submission port.
 Some SMTP extensions are especially useful for message submission:
 Extended Status Codes [SMTP-CODES], SHOULD be supported and used
 according to [CODES-EXTENSION].  This permits the MSA to notify the
 client of specific configuration or other problems in more detail
 than the response codes listed in this memo.  Because some rejections
 are related to a site's security policy, care should be used not to
 expose more detail than is needed to correct the problem.
 [PIPELINING] SHOULD be supported by the MSA.
 [SMTP-AUTH] allows the MSA to validate the authority and determine
 the identity of the submitting user.
 Any references to the DATA command in this memo also refer to any
 substitutes for DATA, such as the BDAT command used with [CHUNKING].

8. Message Modifications

 Sites MAY modify submissions to ensure compliance with standards and
 site policy.  This section describes a number of such modifications
 that are often considered useful.
 NOTE:  As a matter of guidance for local decisions to implement
 message modification, a paramount rule is to limit such actions to
 remedies for specific problems that have clear solutions.  This is
 especially true with address elements.  For example, indiscriminately
 appending a domain to an address or element which lacks one typically
 results in more broken addresses.  An unqualified address must be
 verified to be a valid local part in the domain before the domain can
 be safely added.

8.1. Add 'Sender'

 The MSA MAY add or replace the 'Sender' field, if the identity of the
 sender is known and this is not given in the 'From' field.
 The MSA MUST ensure that any address it places in a 'Sender' field is
 in fact a valid mail address.

Gellens & Klensin Standards Track [Page 9] RFC 2476 Message Submission December 1998

8.2. Add 'Date'

 The MSA MAY add a 'Date' field to the submitted message, if it lacks
 it, or correct the 'Date' field if it does not conform to [MESSAGE-
 FORMAT] syntax.

8.3. Add 'Message-ID'

 The MSA MAY add or replace the 'Message-ID' field, if it lacks it, or
 it is not valid syntax (as defined by [MESSAGE-FORMAT]).

8.4. Transfer Encode

 The MSA MAY apply transfer encoding to the message according to MIME
 conventions, if needed and not harmful to the MIME type.

8.5. Sign the Message

 The MSA MAY (digitally) sign or otherwise add authentication
 information to the message.

8.6. Encrypt the Message

 The MSA MAY encrypt the message for transport to reflect
 organizational policies.
 NOTE:  To be useful, the addition of a signature and/or encryption by
 the MSA generally implies that the connection between the MUA and MSA
 must itself be secured in some other way, e.g., by operating inside
 of a secure environment, by securing the submission connection at the
 transport layer, or by using an [SMTP-AUTH] mechanism that provides
 for session integrity.

8.7. Resolve Aliases

 The MSA MAY resolve aliases (CNAME records) for domain names, in the
 envelope and optionally in address fields of the header, subject to
 local policy.
 NOTE:  Unconditionally resolving aliases could be harmful.  For
 example, if www.example.net and ftp.example.net are both aliases for
 mail.example.net, rewriting them could lose useful information.

8.8. Header Rewriting

 The MSA MAY rewrite local parts and/or domains, in the envelope and
 optionally in address fields of the header, according to local
 policy.  For example, a site may prefer to rewrite 'JRU' as '

Gellens & Klensin Standards Track [Page 10] RFC 2476 Message Submission December 1998

 J.Random.User' in order to hide logon names, and/or to rewrite '
 squeeky.sales.example.net' as 'zyx.example.net' to hide machine names
 and make it easier to move users.
 However, only addresses, local-parts, or domains which match specific
 local MSA configuration settings should be altered.  It would be very
 dangerous for the MSA to apply data-independent rewriting rules, such
 as always deleting the first element of a domain name.  So, for
 example, a rule which strips the left-most element of the domain if
 the complete domain matches '*.foo.example.net' would be acceptable.

9. Security Considerations

 Separation of submission and relay of messages can allow a site to
 implement different policies for the two types of services, including
 requiring use of additional security mechanisms for one or both.  It
 can do this in a way which is simpler, both technically and
 administratively.  This increases the likelihood that policies will
 be applied correctly.
 Separation also can aid in tracking and preventing unsolicited bulk
 email.
 For example, a site could configure its MSA to require authentication
 before accepting a message, and could configure its MTA to reject all
 RCPT TOs for non-local users.  This can be an important element in a
 site's total email security policy.
 If a site fails to require any form of authorization for message
 submissions (see section 3.3 for discussion), it is allowing open use
 of its resources and name; unsolicited bulk email can be injected
 using its facilities.

10. Acknowledgments

 This updated memo has been revised in part based on comments and
 discussions which took place on and off the IETF-Submit mailing list.
 The help of those who took the time to review the draft and make
 suggestions is appreciated, especially that of Dave Crocker, Ned
 Freed, Keith Moore, John Myers, and Chris Newman.
 Special thanks to Harald Alvestrand, who got this effort started.

Gellens & Klensin Standards Track [Page 11] RFC 2476 Message Submission December 1998

11. References

 [521REPLY]        Durand, A. and F. Dupont, "SMTP 521 Reply Code",
                   RFC 1846, September 1995.
 [8BITMIME]        Klensin, J., Freed, N., Rose, M., Stefferud, E. and
                   D.  Crocker, "SMTP Service Extension for 8bit-
                   MIMEtransport", RFC 1652, July 1994.
 [ABNF]            Crocker, D., Ed. and P. Overell, "Augmented BNF for
                   Syntax Specifications: ABNF", RFC 2234, November
                   1997.
 [CHECKPOINT]      Crocker, D., Freed, N. and A. Cargille, "SMTP
                   Service Extension for Checkpoint/Restart", RFC
                   1845, September 1995.
 [CHUNKING]        Vaudreuil, G., "SMTP Service Extensions for
                   Transmission of Large and Binary MIME Messages",
                   RFC 1830, August 1995.
 [CODES-EXTENSION] Freed, N., "SMTP Service Extension for Returning
                   Enhanced Error Codes", RFC 2034, October 1996.
 [DSN]             Moore, K., "SMTP Service Extension for Delivery
                   Status Notifications", RFC 1891, January 1996.
 [ESMTP]           Klensin, J., Freed, N., Rose, M., Stefferud, E. and
                   D. Crocker, "SMTP Service Extensions", STD 10, RFC
                   1869, November 1995.
 [ETRN]            De Winter, J., "SMTP Service Extension for Remote
                   Message Queue Starting", RFC 1985, August 1996.
 [HEADERS]         Palme, J., "Common Internet Message Headers", RFC
                   2076, February 1997.
 [IPSEC]           Atkinson, R., "Security Architecture for the
                   Internet Protocol", RFC 1825, August 1995.
 [KEYWORDS]        Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.

Gellens & Klensin Standards Track [Page 12] RFC 2476 Message Submission December 1998

 [MESSAGE-FORMAT]  Crocker, D., "Standard for the format of ARPA
                   Internet text messages", STD 11, RFC 822, August
                   1982;
                   Braden, R., Editor, "Requirements for Internet
                   Hosts -- Application and Support", STD 3, RFC 1123,
                   October 1989.
 [PIPELINING]      Freed, N., "SMTP Service Extension for Command
                   Pipelining", RFC 2197, September 1997.
 [POP3]            Myers, J. and M. Rose, "Post Office Protocol --
                   Version 3", STD 53, RFC 1939, May 1996.
 [SIZE]            Klensin, J., Freed, N. and K. Moore, "SMTP Service
                   Extension for Message Size Declaration", STD 10,
                   RFC 1870, November 1995.
 [SMTP-AUTH]       Myers, J., "SMTP Service Extension for
                   Authentication", Work in Progress.
 [SMTP-CODES]      Vaudreuil, G., "Enhanced Mail System Status Codes",
                   RFC 1893, January 1996.
 [SMTP-MTA]        Postel, J., "Simple Mail Transfer Protocol", STD
                   10, RFC 821, August 1982.
                   Partridge, C., "Mail Routing and the Domain
                   System", STD 14, RFC 974, January 1986.
                   Braden, R., Editor, "Requirements for Internet
                   Hosts -- Application and Support", STD 3, RFC 1123,
                   October 1989.

Gellens & Klensin Standards Track [Page 13] RFC 2476 Message Submission December 1998

12. Authors' Addresses

 Randall Gellens
 QUALCOMM Incorporated
 6455 Lusk Blvd.
 San Diego, CA  92121-2779
 U.S.A.
 Phone: +1 619 651 5115
 Fax:   +1 619 651 5334
 EMail: Randy@Qualcomm.Com
 John C. Klensin
 MCI Telecommunications
 800 Boylston St, 7th floor
 Boston, MA 02199
 USA
 Phone: +1 617 960 1011
 EMail: klensin@mci.net

Gellens & Klensin Standards Track [Page 14] RFC 2476 Message Submission December 1998

13. Full Copyright Statement

 Copyright (C) The Internet Society (1998).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Gellens & Klensin Standards Track [Page 15]

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