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rfc:rfc5538

Internet Engineering Task Force (IETF) F. Ellermann Request for Comments: 5538 xyzzy Category: Standards Track April 2010 ISSN: 2070-1721

                 The 'news' and 'nntp' URI Schemes

Abstract

 This memo specifies the 'news' and 'nntp' Uniform Resource Identifier
 (URI) schemes that were originally defined in RFC 1738.  The purpose
 of this document is to allow RFC 1738 to be made obsolete while
 keeping the information about these schemes on the Standards Track.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/5538.

Copyright Notice

 Copyright (c) 2010 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow

Ellermann Standards Track [Page 1] RFC 5538 'news' and 'nntp' URIs April 2010

 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.1.  'nntp' URIs  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.2.  'news' URIs  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.3.  Query Parts, Fragments, and Normalization  . . . . . . . .  5
 3.  Syntax of 'nntp' URIs  . . . . . . . . . . . . . . . . . . . .  5
 4.  Syntax of 'news' URIs  . . . . . . . . . . . . . . . . . . . .  6
 5.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  7
 6.  Internationalization Considerations  . . . . . . . . . . . . .  8
 7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
 8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   8.1.  'snews' URIs . . . . . . . . . . . . . . . . . . . . . . .  9
   8.2.  'news-message-ID' Access Type  . . . . . . . . . . . . . . 10
 9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   9.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
   9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
 Appendix A.  Collected ABNF  . . . . . . . . . . . . . . . . . . . 13
 Appendix B.  Detailed Example  . . . . . . . . . . . . . . . . . . 13

Ellermann Standards Track [Page 2] RFC 5538 'news' and 'nntp' URIs April 2010

1. Introduction

 The first definition for many URI schemes appears in [RFC1738].  This
 memo extracts the 'news' and 'nntp' URI schemes from it to allow that
 material to remain on the Standards Track if [RFC1738] is moved to
 "historic" status.  It belongs to a series of similar documents like
 [RFC4156], [RFC4157], [RFC4248], and [RFC4266], which are discussed
 on the <mailto:uri@w3.org> list.
 The definitions for the 'news' and 'nntp' URI schemes given here are
 updates from [RFC1738] based on modern usage of these schemes.  This
 memo intentionally limits its description of the 'news' URI scheme to
 essential features supposed to work with "any browser" and Network
 News Transfer Protocol (NNTP) server.
 [RFC3986] specifies how to define schemes for URIs; it also explains
 the term "Uniform Resource Locator" (URL).  The Network News Transfer
 Protocol (NNTP) is specified in [RFC3977].  The Netnews Article
 Format is defined in [RFC5536].
 The key word "MUST" in this memo is to be interpreted as described in
 [RFC2119].  UTF-8 is specified in [RFC3629].  The syntax uses the
 ABNF defined in [RFC5234].

2. Background

 The 'news' and 'nntp' URI schemes identify resources on an NNTP
 server, individual articles, individual newsgroups, or sets of
 newsgroups.
 User agents like Web browsers supporting these schemes use the NNTP
 protocol to access the corresponding resources.  The details of how
 they do this, e.g., employing a separate or integrated newsreader,
 depend on the implementation.  The default <port> associated with
 NNTP in [RFC3977] is 119.

2.1. 'nntp' URIs

 The 'nntp' URI scheme identifies articles in a newsgroup on a
 specific NNTP server.  In [RFC3986] terminology, this means that
 'nntp' URIs have a non-empty <authority> component; there is no
 default <host> as for the 'file' or 'news' URI schemes.
 Netnews is typically distributed among several news servers, using
 the same newsgroup names but local article numbers.  An article
 available as number 10 in group "example" on server
 "news.example.com" has most likely a different number on any other

Ellermann Standards Track [Page 3] RFC 5538 'news' and 'nntp' URIs April 2010

 server where the same article is still available.  Users allowed to
 read and post articles on "their" server may not be allowed to access
 articles on an "arbitrary" server specified in an 'nntp' URI.
 For these reasons, the use of the 'nntp' URI scheme is limited, and
 it is less widely supported by user agents than the similar 'news'
 URI scheme.

2.2. 'news' URIs

 The 'news' URI scheme identifies articles by their worldwide unique
 "Message-ID", independent of the server and the newsgroup.
 Newsreaders support access to articles by their "Message-ID", without
 the overhead of a URI scheme.  In simple cases, they do this directly
 as an NNTP client of a default or currently used server as configured
 by the user.  More general user agents use the 'news' URI scheme to
 distinguish "Message-IDs" from similar constructs such as other URI
 schemes in contexts such as a plain text message body.
 The 'news' URI scheme also allows the identification of newsgroups or
 sets of newsgroups independent of a specific server.  For Netnews, a
 group "example" has the same name on any server carrying this group,
 exotic cases involving gateways notwithstanding.  To distinguish
 "Message-IDs" and newsgroup names, the 'news' URI scheme relies on
 the "@" between local part (left-hand side) and domain part (right-
 hand side) of "Message-IDs".
 [RFC1738] offered only one wildcard for sets of newsgroups in 'news'
 URIs, a "*" used to refer to "all available newsgroups".  In common
 practice, this was extended to varying degrees by different user
 agents.  An NNTP extension known as <wildmat>, specified in [RFC2980]
 and now part of the base NNTP specification, allows pattern matching
 in the style of the [POSIX] "find" command.  For the purpose of this
 memo, this means that some additional special characters have to be
 allowed in 'news' URIs, some of them percent-encoded as required by
 the overall [RFC3986] URI syntax.  User agents and NNTP servers not
 yet compliant with [RFC3977] do not implement all parts of this new
 feature.
 Another commonly supported addition to the [RFC1738] syntax is the
 optional specification of a server at the beginning of 'news' URIs.
 This optional <authority> component follows the overall [RFC3986]
 syntax, preceded by a double slash "//" and terminated by the next
 slash "/", question mark "?", number sign "#", or the end of the URI.

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2.3. Query Parts, Fragments, and Normalization

 Fragments introduced by a number sign "#" are specified in [RFC3986];
 the semantics is independent of the URI scheme, and the resolution
 depends on the media type.
 This memo doesn't specify a query part introduced by a question mark
 "?" for the 'news' and 'nntp' URI schemes, but some implementations
 are known to use query parts instead of fragments internally to
 address parts of a composite media type [RFC2046] in Multipurpose
 Internet Mail Extensions (MIME).
 There are no special "." or ".." path segments in 'news' and 'nntp'
 URLs.  Please note that "." and ".." are not valid <newsgroup-name>s.
 URI producers have to percent-encode some characters as specified
 below (Section 4); otherwise, they MUST treat a "Message-ID" without
 angle brackets for 'news' URLs as is, i.e., case-sensitive.

3. Syntax of 'nntp' URIs

 An 'nntp' URI identifies an article by its number in a given
 newsgroup on a specified server, or it identifies the newsgroup
 without article number.
     nntpURL         = "nntp:" server "/" group [ "/" article-number ]
     server          = "//" authority               ; see RFC 3986
     group           = 1*( group-char / pct-encoded )
     article-number  = 1*16DIGIT                    ; see RFC 3977
     group-char      = ALPHA / DIGIT / "-" / "+" / "_" / "."
 In the form with an <article-number>, the URL corresponds roughly to
 the content of an <xref> header field as specified in [RFC5536],
 replacing its more general <article-locator> by the <article-number>
 used with the NNTP.
 A <newsgroup-name> as specified in [RFC5536] consists of dot-
 separated components.  Each component contains one or more letters,
 digits, "-" (hyphen-minus), "+", or "_" (underscore).  These
 characters can be directly used in a segment of a path in an
 [RFC3986] URI; no percent-encoding is necessary.  Example:
     nntp://news.server.example/example.group.this/12345
 A <wildmat-exact> newsgroup name as specified in [RFC3977] allows (in
 theory) any <UTF8-non-ascii> (see Section 6) and most printable
 US-ASCII characters, excluding "!", "*", ",", "?", "[", "\", and "]".
 However, [RFC5536] does not (yet) permit characters outside of

Ellermann Standards Track [Page 5] RFC 5538 'news' and 'nntp' URIs April 2010

 <group-char> and so, to keep the syntax simple, the additional
 characters are here covered by <pct-encoded> as defined in [RFC3986],
 since most of them have to be percent-encoded anyway (with a few
 exceptions, such as ":", ";", and "~").  Example:
     nntp://wild.server.example/example.group.n%2Fa/12345
 In the form without <article-number>, the URL identifies a single
 group on the specified server.  This is also possible with an
 equivalent 'news' URL, and the latter is better supported by user
 agents.  Example:
     nntp://news.server.example/example.group.this
     news://news.server.example/example.group.this

4. Syntax of 'news' URIs

 A 'news' URI identifies an article by its unique "Message-ID", or it
 identifies a set of newsgroups.  Additionally, it can specify a
 server; when the server is not specified, a configured default server
 for Netnews access is used.
     newsURL         = "news:" [ server "/" ] ( article / newsgroups )
     article         = msg-id-core                  ; see RFC 5536
 The form identifying an <article> is the <msg-id-core> from
 [RFC5536]; it is a "Message-ID" without angle brackets.  According to
 [RFC3986], characters that are in <gen-delims> (a subset of
 <reserved>), together with the character "%", MUST be percent-encoded
 (though it is not wrong to encode others).  Specifically, the
 characters allowed in <msg-id-core> that must be encoded are
     "/"  "?"  "#"  "[" "]" and "%"
 Note that an agent which seeks to interpret a 'news' URI needs to
 decode all percent-encoded characters before passing it on to an NNTP
 server to be acted upon.
 Please note that "%3E" (">") is not allowed; <msg-id-core> is
 otherwise identical to
         id-left "@" id-right
 as defined in [RFC5322].
 The form identifying <newsgroups> corresponds to the [RFC3977]
 <wildmat-pattern>, a newsgroup name with wildcards "*" and "?".  Any
 "?" has to be percent-encoded as "%3F" in this part of a URI.

Ellermann Standards Track [Page 6] RFC 5538 'news' and 'nntp' URIs April 2010

 Examples (the first two are equivalent):
     news://news.server.example/*
     news://news.server.example/
     news://wild.server.example/example.group.th%3Fse
     news:example.group.*
     news:example.group.this
 Without wildcards, this form of the URL identifies a single group if
 it is not empty.  User agents would typically try to present an
 overview of the articles available in this group, likely somehow
 limiting this overview to the newest unread articles up to a
 configured maximum.
 With wildcards, user agents could try to list matching group names on
 the specified or default server.  Some user agents support only a
 specific <group> without wildcards, or an optional single "*".
 As noted above (Section 2.2), the presence of an "@" in a 'news' URI
 disambiguates <article> and <newsgroups> for URI consumers.  The new
 <message-id> construct specified in [RFC3977] does not require an
 "@".  Since [RFC0822], the "Message-ID" syntax has been closely
 related to the syntax of mail addresses with an "@" separating left-
 hand side (local part of addresses, unique part of message
 identifiers) and right-hand side (domain part), and this memo sticks
 to the known [RFC1738] practice.

5. Acknowledgments

 Henry Spencer was the driving force to adopt MIME in Netnews; he
 registered the MIME 'message/external-body' access type
 'news-message-ID', discussed below (Section 8.2), in 1993 as recalled
 in "Son-of-1036" [RFC1849].
 "The 'news' URL scheme" [GILMAN], by Alfred S. Gilman (March 1998),
 introduced additions to the original [RFC1738] 'news' URI scheme.
 Some of these ideas are now widely supported and reflected by the
 revised 'news' URI scheme specified here.
 Thanks to Alfred Hoenes, Charles Lindsey, Clive Feather, Chris
 Newman, Ken Murchinson, Kjetil T. Homme, Lars Magne Ingebrigtsen,
 Martin Duerst, Matt Seitz, Nicolas Krebs, Paul Hoffman, Pasi Eronen,
 Roy T. Fielding, Russ Allbery, Stephane Bortzmeyer, and Tom Petch for
 their feedback, contributions, or encouragement.
 Bill Fenner's _xml2rfc validator_ and _ABNF checker_ were a great
 help in the creation of (not only) this memo.  The same goes for
 various great _IETF tools_ written by Henrik Levkowetz.

Ellermann Standards Track [Page 7] RFC 5538 'news' and 'nntp' URIs April 2010

6. Internationalization Considerations

 The URI schemes were updated to support percent-encoded UTF-8
 characters in NNTP newsgroup names as specified in [RFC3977] and
 [RFC3987].
 The Netnews Article Format in [RFC5536] does not yet allow UTF-8 in
 <newsgroup-name>s; therefore, well-known Unicode and UTF-8 security
 considerations are not listed below.  For an overview, see [UTR36]
 and [RFC3629].
 The work on Email Address Internationalization (EAI), started in
 [RFC4952], is not expected to change the syntax of a "Message-ID".

7. Security Considerations

 There are many security considerations for URI schemes discussed in
 [RFC3986].  The NNTP protocol may use passwords in the clear for
 authentication or offer no privacy, both of which are considered
 extremely unsafe in current practice.  Alternatives and further
 security considerations with respect to the NNTP are discussed in
 [RFC4642] and [RFC4643].
 The syntax for the 'news' and 'nntp' URI schemes contains the general
 <authority> construct with an optional <userinfo> defined in
 [RFC3986].  As noted in [RFC3986], the "user:password" form of a
 <userinfo> is deprecated.
 Articles on NNTP servers typically expire after some time.  After
 that time, corresponding 'news' and 'nntp' URLs may not work anymore
 depending on the server.  While a "Message-ID" is supposed to be
 worldwide unique forever, the NNTP protocol does not guarantee this.
 Under various conditions depending on the servers, the same
 "Message-ID" could be used for different articles, and attackers
 could try to distribute malicious content for known 'news' or 'nntp'
 URLs.
 If a URI does not match the generic syntax in [RFC3986], it is
 invalid, and broken URIs can cause havoc.  Compare [RFC5064] for
 similar security considerations.

8. IANA Considerations

 The IANA registry of URI schemes has been updated to point to this
 memo instead of [RFC1738] for the 'news' and 'nntp' URI schemes.

Ellermann Standards Track [Page 8] RFC 5538 'news' and 'nntp' URIs April 2010

8.1. 'snews' URIs

 This section contains the [RFC4395] template for the registration of
 the historical 'snews' scheme specified in [GILMAN].
 URI scheme name:   snews
 Status:            historical
 URI scheme syntax: Same as for 'news' (Section 4)
 URI scheme semantics:
                    Syntactically equivalent to 'news', but using NNTP
                    over SSL/TLS (SSL/TLS with security layer is
                    negotiated immediately after establishing the TCP
                    connection) with a default port of 563, registered
                    as "nntps"
 Encoding considerations:
                    Same as for 'news' (Section 6)
 Applications/protocols that use this URI scheme name:
                    For some user agents, 'snews' URLs trigger the use
                    of "nntps" instead of NNTP for their access on
                    Netnews
 Interoperability considerations:
                    This URI scheme was not widely deployed; its
                    further use is deprecated in favor of ordinary
                    'news' URLs in conjunction with NNTP servers
                    supporting [RFC4642]
 Security considerations:
                    See [RFC4642]; the use of a dedicated port for
                    secure variants of a protocol was discouraged in
                    [RFC2595]
 Contact:           <mailto:uri@w3.org> (URI mailing list)
 Change controller: IETF
 References:        RFC 5538, [RFC4642], [GILMAN]

Ellermann Standards Track [Page 9] RFC 5538 'news' and 'nntp' URIs April 2010

8.2. 'news-message-ID' Access Type

 The MIME 'news-message-ID' access type was erroneously listed as a
 subtype.  IANA has removed 'news-message-ID' from the application
 subtype registry, and has added it to the access types registry
 defined in [RFC4289].
 [RFC4289] requires an RFC (preferably on the Standards Track) for the
 access types registry.  To provide a definition meeting this
 requirement, the following paragraph is reproduced verbatim from
 [RFC1849]:
    NOTE: In the specific case where it is desired to essentially make
    another article PART of the current one, e.g., for annotation of
    the other article, MIME's "message/external-body" convention can
    be used to do so without actual inclusion.  "news-message-ID" was
    registered as a standard external-body access method, with a
    mandatory NAME parameter giving the message ID and an optional
    SITE parameter suggesting an NNTP site that might have the article
    available (if it is not available locally), by IANA 22 June 1993.
 Please note that 'news' URLs offer a very similar and (today) more
 common way to access articles by their Message-ID; compare [RFC2017].

9. References

9.1. Normative References

 [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3977]      Feather, C., "Network News Transfer Protocol (NNTP)",
                RFC 3977, October 2006.
 [RFC3986]      Berners-Lee, T., Fielding, R., and L. Masinter,
                "Uniform Resource Identifier (URI): Generic Syntax",
                STD 66, RFC 3986, January 2005.
 [RFC5234]      Crocker, D. and P. Overell, "Augmented BNF for Syntax
                Specifications: ABNF", STD 68, RFC 5234, January 2008.
 [RFC5536]      Murchison, K., Lindsey, C., and D. Kohn, "Netnews
                Article Format", RFC 5536, November 2009.

Ellermann Standards Track [Page 10] RFC 5538 'news' and 'nntp' URIs April 2010

9.2. Informative References

 [GILMAN]       Gilman, A., "The 'news' URL scheme", Work in Progress,
                March 1998.
 [POSIX]        Institute of Electrical and Electronics Engineers,
                "The Open Group Base Specifications Issue 6",
                IEEE Standard 1003.1, 2004 edition.
 [RFC0822]      Crocker, D., "Standard for the format of ARPA Internet
                text messages", STD 11, RFC 822, August 1982.
 [RFC1738]      Berners-Lee, T., Masinter, L., and M. McCahill,
                "Uniform Resource Locators (URL)", RFC 1738,
                December 1994.
 [RFC1849]      Spencer, H., ""Son of 1036": News Article Format and
                Transmission", RFC 1849, March 2010.
 [RFC2017]      Freed, N. and K. Moore, "Definition of the URL MIME
                External-Body Access-Type", RFC 2017, October 1996.
 [RFC2046]      Freed, N. and N. Borenstein, "Multipurpose Internet
                Mail Extensions (MIME) Part Two: Media Types",
                RFC 2046, November 1996.
 [RFC2595]      Newman, C., "Using TLS with IMAP, POP3 and ACAP",
                RFC 2595, June 1999.
 [RFC2980]      Barber, S., "Common NNTP Extensions", RFC 2980,
                October 2000.
 [RFC3629]      Yergeau, F., "UTF-8, a transformation format of ISO
                10646", STD 63, RFC 3629, November 2003.
 [RFC3987]      Duerst, M. and M. Suignard, "Internationalized
                Resource Identifiers (IRIs)", RFC 3987, January 2005.
 [RFC4156]      Hoffman, P., "The wais URI Scheme", RFC 4156,
                August 2005.
 [RFC4157]      Hoffman, P., "The prospero URI Scheme", RFC 4157,
                August 2005.
 [RFC4248]      Hoffman, P., "The telnet URI Scheme", RFC 4248,
                October 2005.

Ellermann Standards Track [Page 11] RFC 5538 'news' and 'nntp' URIs April 2010

 [RFC4266]      Hoffman, P., "The gopher URI Scheme", RFC 4266,
                November 2005.
 [RFC4289]      Freed, N. and J. Klensin, "Multipurpose Internet Mail
                Extensions (MIME) Part Four: Registration Procedures",
                BCP 13, RFC 4289, December 2005.
 [RFC4395]      Hansen, T., Hardie, T., and L. Masinter, "Guidelines
                and Registration Procedures for New URI Schemes",
                BCP 35, RFC 4395, February 2006.
 [RFC4642]      Murchison, K., Vinocur, J., and C. Newman, "Using
                Transport Layer Security (TLS) with Network News
                Transfer Protocol (NNTP)", RFC 4642, October 2006.
 [RFC4643]      Vinocur, J. and K. Murchison, "Network News Transfer
                Protocol (NNTP) Extension for Authentication",
                RFC 4643, October 2006.
 [RFC4952]      Klensin, J. and Y. Ko, "Overview and Framework for
                Internationalized Email", RFC 4952, July 2007.
 [RFC5064]      Duerst, M., "The Archived-At Message Header Field",
                RFC 5064, December 2007.
 [RFC5322]      Resnick, P., Ed., "Internet Message Format", RFC 5322,
                October 2008.
 [UTR36]        Davis, M. and M. Suignard, "Unicode Security
                Considerations", Unicode Technical Reports #36,
                August 2006.

Ellermann Standards Track [Page 12] RFC 5538 'news' and 'nntp' URIs April 2010

Appendix A. Collected ABNF

 In addition to the syntax given above, this appendix also lists the
 sources of terms used in comments and the prose:
     nntpURL         = "nntp:" server "/" group [ "/" article-number ]
     server          = "//" authority               ; see RFC 3986
     group           = 1*( group-char / pct-encoded )
     article-number  = 1*16DIGIT                    ; see RFC 3977
     group-char      = ALPHA / DIGIT / "-" / "+" / "_" / "."
     newsURL         = "news:" [ server "/" ] ( article / newsgroups )
     article         = msg-id-core                  ; see RFC 5536
     newsgroups      = *( group-char / pct-encoded / "*" )
     authority       = <see RFC 3986 Section 3.2>
     host            = <see RFC 3986 Section 3.2.2>
     pct-encoded     = <see RFC 3986 Section 2.1>
     port            = <see RFC 3986 Section 3.2.3>
     gen-delims      = <see RFC 3986 Section 2.2>
     msg-id-core     = <see RFC 5536 Section 3.1.3>
     reserved        = <see RFC 5536 Section 2.2>
     userinfo        = <see RFC 3986 Section 3.2.1>
     message-id      = <see RFC 3977 Section 9.8>
     UTF8-non-ascii  = <see RFC 3977 Section 9.8>
     wildmat         = <see RFC 3977 Section 4.1>
     wildmat-exact   = <see RFC 3977 Section 4.1>
     wildmat-pattern = <see RFC 3977 Section 4.1>
     ALPHA           = <see RFC 5234 Appendix B.1>
     DIGIT           = <see RFC 5234 Appendix B.1>
     article-locator = <see RFC 5536 Section 3.2.14>
     newsgroup-name  = <see RFC 5536 Section 3.1.4>
     xref            = <see RFC 5536 Section 3.2.14>

Appendix B. Detailed Example

 Here is an example of a mail to the <mailto:tools.discuss@ietf.org>
 list with "Message-ID" <p0624081dc30b8699bf9b@[10.20.30.108]>.
 <http://dir.gmane.org/gmane.ietf.tools> is one of the various list
 archives; it converts mail into Netnews articles.  The header of this
 article contains the following fields (among others):

Ellermann Standards Track [Page 13] RFC 5538 'news' and 'nntp' URIs April 2010

        Message-ID: <p0624081dc30b8699bf9b@[10.20.30.108]>
        Xref: news.gmane.org gmane.ietf.tools:742
        Archived-At: <http://permalink.gmane.org/gmane.ietf.tools/742>
 The "Xref" roughly indicates the 742nd article in newsgroup
 <news://news.gmane.org/gmane.ietf.tools> on this server.  An 'nntp'
 URL might be <nntp://news.gmane.org/gmane.ietf.tools/742>.  For
 details about the "Archived-At" URL, see [RFC5064].
 The list software and list subscribers reading the list elsewhere
 can't predict a server-specific article number 742 in this archive.
 If they know this server, they can however guess the corresponding
 <news://news.gmane.org/p0624081dc30b8699bf9b@%5B10.20.30.108%5D> URL.
 In theory, the list software could use the guessed 'news' URL in an
 "Archived-At" header field, but if a list tries this, it would likely
 use <http://mid.gmane.org/p0624081dc30b8699bf9b@%5B10.20.30.108%5D>.
 Using domain literals in a "Message-ID" could cause collisions.  A
 collision might force the mail2news gateway in this example to invent
 a new "Message-ID", and an attempt to guess the future URL on this
 server would then fail.

Author's Address

 Frank Ellermann
 xyzzy
 Hamburg, Germany
 EMail: hmdmhdfmhdjmzdtjmzdtzktdkztdjz@gmail.com
 URI:   http://purl.net/xyzzy/

Ellermann Standards Track [Page 14]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5538.txt · Last modified: 2010/04/29 02:24 by 127.0.0.1

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