Date: Friday, August 22, 2008 @ 14:50:29
Author: eagle
Revision: 4891
Resolution of #1416.
Introduce the concept of multiple injection, replacing reinjection. Allow
posting agents to add Injection-Date and require them to do so in the
multiple injection scenario. Prohibit injecting agents from changing
existing Injection-Date headers. Prohibit injecting agents from adding
Injection-Date if Date and Message-ID are present but Injection-Date is
missing. Better explanation of multiple injection and more
recommendations about how to do it properly.
Add an example of a header deprecated for netnews.
Modified:
docs/usefor/usepro.xml
Modified: docs/usefor/usepro.xml
===================================================================
--- docs/usefor/usepro.xml 2008-08-20 04:58:28 UTC (rev 4890)
+++ docs/usefor/usepro.xml 2008-08-22 21:50:29 UTC (rev 4891)
@@ -18,6 +18,8 @@
'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2822.xml'>
<!ENTITY rfc3629 PUBLIC ''
'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3629.xml'>
+ <!ENTITY rfc3798 PUBLIC ''
+ 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3798.xml'>
<!ENTITY rfc3977 PUBLIC ''
'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3977.xml'>
<!ENTITY rfc4234 PUBLIC ''
@@ -165,8 +167,9 @@
<t>"Injecting" an article is the processing of a proto-article by
an injecting agent. Normally this action is done once and only
- once for a given article. "Reinjecting" an article is passing an
- already-injected article to an injection agent.</t>
+ once for a given article. "Multiple injection" is passing the
+ same article to multiple injecting agents, either serially or in
+ parallel, by one or several posting agents.</t>
<t>A "gateway" is software which receives news articles and
converts them to messages of some other kind (such as <xref
@@ -519,10 +522,35 @@
<t>Posting agents SHOULD ensure that proto-articles they create
are valid according to <xref target="USEFOR" /> and any other
- applicable policies. They MUST NOT create any Injection-Date or
- Injection-Info header fields; these headers will be added by the
- injecting agent.</t>
+ applicable policies. They MUST NOT create any Injection-Info
+ header field; this header field may only be added by the injecting
+ agent.</t>
+ <t>If the proto-article already contains both Message-ID and Date
+ header fields, posting agents MAY add an Injection-Date header
+ field to that proto-article immediately before passing that
+ proto-article to an injection agent. They SHOULD do so if the
+ Date header field (representing the composition time of the
+ proto-article) is more than a day in the past at the time of
+ injection. They MUST do so if the proto-article is being
+ submitted to more than one injecting agent; see <xref
+ target="multi-injection" />.</t>
+
+ <t>The Injection-Date header field is new in this revision of the
+ Netnews protocol and is designed to allow the Date header field to
+ hold the composition date (as recommended in section 3.6.1 of
+ <xref target="RFC2822" />), even if the proto-article is not to be
+ injected for some time after its composition. However, note that
+ all implementations predating this specification ignore the
+ Injection-Date header field and use the Date header field in its
+ stead for rejecting articles older than their cutoff (see <xref
+ target="history" />), and injecting agents predating this
+ specification do not add an Injection-Date header. Articles with
+ a Date header field substantially in the past will still be
+ rejected by implementations predating this specification,
+ regardless of the Injection-Date header field, and hence may
+ suffer poorer propagation.</t>
+
<t>Contrary to <xref target="RFC2822" />, which implies that the
mailbox or mailboxes in the From header field should be that of
the poster or posters, a poster who does not, for whatever
@@ -544,48 +572,75 @@
agent.</t>
<t>A proto-article has the same format as a normal article
- except that the Injection-Date, Injection-Info, and Xref header
- fields MUST NOT be present; the Path header field MUST NOT
- contain a "POSTED" <diag-keyword>; and any of the following
- mandatory header fields MAY be omitted: Message-ID, Date, and
- Path. In all other respects, a proto-article MUST be a valid
- Netnews article. In particular, the header fields which may be
- omitted MUST NOT be present with invalid content.</t>
+ except that the Injection-Info and Xref header fields MUST NOT
+ be present; the Path header field MUST NOT contain a "POSTED"
+ <diag-keyword>; and any of the following mandatory header
+ fields MAY be omitted: Message-ID, Date, and Path. In all other
+ respects, a proto-article MUST be a valid Netnews article. In
+ particular, the header fields which may be omitted MUST NOT be
+ present with invalid content.</t>
<t>If a posting agent intends to offer the same proto-article to
- multiple injecting agents, the header fields Message-ID and Date
- MUST be present and identical in all copies of the
- proto-article.</t>
+ multiple injecting agents, the header fields Message-ID, Date,
+ and Injection-Date MUST be present and identical in all copies
+ of the proto-article. See <xref target="multi-injection" />.</t>
</section>
- <section anchor="reinjection" title="Reinjection of Articles">
- <t>A given article SHOULD be processed by an injecting agent
- once and only once. The Injection-Date or Injection-Info
- header fields are added by an injecting agent and are not
- permitted in a proto-article. Their presence (or the presence
- of other unstandardized or obsolete trace headers such as
- NNTP-Posting-Host, NNTP-Posting-Date, or X-Trace) indicates
- that the proto-article is instead an article and has already
- been processed by an injecting agent. A posting agent SHOULD
- normally reject such articles.</t>
+ <section anchor="multi-injection"
+ title="Multiple Injection of Articles">
+ <t>Under some circumstances (posting to multiple disjoint
+ networks, injecting agents with spotty connectivity, or for
+ redundancy, for example), a posting agent may wish to offer the
+ same article to multiple injecting agents. In this unusual
+ case, the goal is to not create multiple independent articles
+ but rather to inject the same article at multiple points and let
+ the normal duplicate suppression facility of Netnews (see <xref
+ target="history" />) ensure that any given agent accepts the
+ article only once, even if supposedly disjoint networks have
+ unexpected links.</t>
- <t>In the exceptional case that an article needs to be
- reinjected for some reason (such as transferring an article from
- one Netnews to another where those networks have no relaying
- agreement), the posting agent doing the reinjection MUST convert
- the article back into a proto-article before passing it to an
- injecting agent (such as by renaming the Injection-Info and
- Injection-Date header fields and removing any Xref header field)
- and MUST perform the date checks on the existing Injection-Date
- or Date header fields that would otherwise be done by the
- injecting agent.</t>
+ <t>Whenever possible, multiple injection SHOULD be done by
+ offering the same proto-article to multiple injecting agents.
+ The posting agent MUST supply the Message-ID, Date, and
+ Injection-Date header fields, and the proto-article as offered
+ to each injecting agent MUST be identical.</t>
- <t>Reinjecting articles may cause loops, loss of trace
- information, and other problems and should only be done with
- care and when there is no available alternative. A posting
- agent that does reinjection is a limited type of gateway and as
- such is subject to all of the requirements of an incoming
- gateway in addition to the requirements of a posting agent.</t>
+ <t>In some cases, offering the same proto-article to all
+ injecting agents may not be possible (such as when gatewaying,
+ after the fact, articles found on one Netnews network to
+ another, supposedly unconnected one). In this case, the posting
+ agent MUST convert the article back into a proto-article before
+ passing it to another injecting agent, but it MUST retain
+ unmodified the Message-ID, Date, and Injection-Date header
+ fields. It MUST NOT add an Injection-Date header field if it is
+ missing from the existing article. It MUST remove any Xref
+ header field and either rename or remove any Injection-Info
+ header field and other trace fields.
+ <list style="empty">
+ <t>NOTE: Multiple injection inherently risks duplicating
+ articles. Multiple injection after the fact, by converting
+ an article back to a proto-article and injecting it again,
+ additionally risks loops, loss of trace information,
+ unintended repeat injection into the same network, and other
+ problems. It should be done with care and only when there
+ is no alternative. The requirement to retain Message-ID,
+ Date, and Injection-Date header fields minimizes the
+ possibility of a loop and ensures that the newly injected
+ article is not treated as a new, separate article.</t>
+ </list>
+ </t>
+
+ <t>Multiple injection of an article listing one or more
+ moderated newsgroups in its Newsgroups header field SHOULD only
+ be done by a moderator and MUST only be done after the
+ proto-article has been approved for all moderated groups to
+ which it is to be posted and has an Approved header field (see
+ <xref target="moderator" />). Multiple injection of an
+ unapproved article intended for moderated newsgroups will
+ normally only result in the moderator receiving multiple copies,
+ and if the newsgroup status is not consistent across all
+ injecting agents, may result in duplication of the article or
+ other problems.</t>
</section>
<section anchor="followups" title="Followups">
@@ -710,23 +765,27 @@
<t>It MUST reject any proto-article that does not have the
proper mandatory header fields for a proto-article; that has
- Injection-Date, Injection-Info, or Xref header fields; that
- has a Path header field containing the "POSTED"
- <diag-keyword>; or that is not syntactically valid as
- defined by <xref target="USEFOR" />. It SHOULD reject any
- proto-article which contains a header field deprecated for
- Netnews. It MAY reject any proto-article that contains trace
- header fields indicating that it was already injected by an
- injecting agent that did not add Injection-Info or
- Injection-Date.</t>
+ Injection-Info or Xref header fields; that has a Path header
+ field containing the "POSTED" <diag-keyword>; or that is
+ not syntactically valid as defined by <xref target="USEFOR"
+ />. It SHOULD reject any proto-article which contains a
+ header field deprecated for Netnews (see, for example, <xref
+ target="RFC3798" />). It MAY reject any proto-article that
+ contains trace header fields (e.g., NNTP-Posting-Host)
+ indicating that it was already injected by an injecting agent
+ that did not add Injection-Info or Injection-Date.</t>
- <t>It SHOULD reject any article whose Date header field is
- more than 24 hours into the future (and MAY use a margin less
- than 24 hours). It SHOULD reject any article whose Date
- header appears to be stale (more than 72 hours into the past,
- for example, or too old to still be recorded in the database
- of a relaying agent the injecting agent will be using) since
- not all news servers support Injection-Date.</t>
+ <t>It SHOULD reject any article whose Injection-Date or Date
+ header field is more than 24 hours into the future (and MAY
+ use a margin less than 24 hours). It SHOULD reject any
+ article whose Injection-Date header field is too far in the
+ past (older than the cutoff interval of a relaying agent the
+ injecting agent is using, for example). It SHOULD similarly
+ reject any article whose Date header field is too far in the
+ past, since not all news servers support Injection-Date and
+ only the injecting agent can provide a useful error message to
+ the posting agent. In either case, this interval SHOULD NOT
+ be any shorter than 72 hours into the past.</t>
<t>It SHOULD reject any proto-article whose Newsgroups header
field does not contain at least one <newsgroup-name> for a
@@ -770,8 +829,14 @@
the source of the article and possibly other trace information
as described in Section 3.2.8 of <xref target="USEFOR" />.</t>
- <t>The injecting agent MUST then add an Injection-Date header
- field containing the current date and time.</t>
+ <t>If the proto-article already had an Injection-Date header
+ field, it MUST NOT be modified or replaced. If the
+ proto-article had both a Message-ID header field and a Date
+ header field, an Injection-Date header field MUST NOT be
+ added, since the proto-article may have been multiply injected
+ by a posting agent that predates this standard. Otherwise,
+ the injecting agent MUST add an Injection-Date header field
+ containing the current date and time.</t>
<t>Finally, the injecting agent forwards the article to one or
more relaying agents, and the injection process is
@@ -1068,8 +1133,7 @@
for reasons understood by the moderator (such as delays in the
moderation process) in which case they MAY substitute the
current date. Any Injection-Date, Injection-Info, or Xref
- header fields already present (though there should be none)
- MUST be removed.</t>
+ header fields already present MUST be removed.</t>
<t>Any Path header field MUST either be removed or truncated
to only those entries following its "POSTED"
@@ -2109,6 +2173,7 @@
&rfc1036;
&rfc2045;
&rfc2606;
+ &rfc3798;
&rfc3977;
<reference anchor="USEAGE">
<front>
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