usefor-article-03 February 2000
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6.6. Distribution
The Distribution header is an inheritable header (see 4.2.2.2) which
specifies geographical or organizational limits to an article's
propagation.
Distribution-content= distribution *( dist-delim distribution )
dist-delim = ","
distribution = positive-distribution /
negative-distribution
positive-distribution
= *FWS distribution-name *FWS
negative-distribution
= *FWS "!" distribution-name *FWS
distribution-name = letter 1*distribution-rest
distribution-rest = letter / "+" / "-" / "_"
Articles MUST NOT be passed between relaying agents or to serving
agents unless the sending agent has been configured to supply and the
receiving agent to receive BOTH of
(a) at least one of the newsgroups in the article's Newsgroups
header, and
(b) at least one of the positive-distributions (if any) in the
article's Distribution header and none of the negative-
distributions.
Additionally, reading agents MAY be configured so that unwanted
distributions do not get displayed.
NOTE: Although it would seem redundant to filter out unwanted
distributions at both ends of a relaying link (and it is clearly
more efficient to do so at the sending end), many sending sites
have been reluctant, historically speaking, to apply such
filters (except to ensure that distributions local to their own
site or cooperating subnet did not escape); moreover they tended
to configure their filters on an "all but those listed" basis,
so that new and hitherto unheard of distributions would not be
caught. Indeed many "hub" sites actually wanted to receive all
possible distributions so that they could feed on to their
clients in all possible geographical (or organizational)
regions.
Therefore, it is desirable to provide facilities for rejecting
unwanted distributions at the receiving end. Indeed, it may be
simpler to do so locally than to inform each sending site of
what is required, especially in the case of specialized
distributions (for example for control messages, such as cancels
from certain issuers) which might need to be added at short
notice. Tha possibility for reading agents to filter
distributions has been provided for the same reason.
Exceptionally, ALL relaying agents are deemed willing to supply or
accept the distribution "world", and NO relaying agent should supply
or accept the distribution "local". However, "world" SHOULD NEVER be
mentioned explicitly since it is the default when the Distribution
header is absent entirely. "All" MUST NOT be used as a
distribution-name. Distribution-names SHOULD contain at least three
characters, except when they are two-letter country names as in [ISO
3166]. Distribution-names are case-insensitive (i.e. "US", "Us" and
"us" all specify the same distribution).
NOTE: "Distribution: !us" can be used to cause an article to go
to the whole of "world" except for "us".
Posting agents SHOULD NOT provide a default Distribution header
without giving the poster an opportunity to override it. Followup
agents SHOULD initially supply the same Distribution header as found
in the precursor.
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#Diff to first older
--- ../s-o-1036/Distribution.out June 1994
+++ ../usefor-article-03/Distribution.out February 2000
@@ -1,83 +1,66 @@
-6.7. Distribution
-
-The Distribution header content specifies geographic or
-organizational limits on an article's propagation:
+6.6. Distribution
+ The Distribution header is an inheritable header (see 4.2.2.2) which
+ specifies geographical or organizational limits to an article's
+ propagation.
Distribution-content = distribution *( dist-delim distribution )
dist-delim = ","
- distribution = plain-component
-
-A distribution is syntactically identical to a one-component
-newsgroup name, and must satisfy the same rules and restric-
-tions. In the absence of Distribution, the default distri-
-bution is "world".
-
- NOTE: This syntax has the disadvantage of contain-
- ing no white space, making it impossible to con-
- tinue a Distribution header across several lines.
- Implementors of relayers and reading agents are
- warned that it is intended that the successor to
- this Draft will change the definition of dist
- delimiter to:
-
- dist-delim = "," [ space ]
-
- and are urged to fix their software to handle
- (i.e., ignore) white space following the commas.
-
-A relayer MUST not pass an article to another relayer unless
-configuration information specifies transmission to that
-other relayer of BOTH (a) at least one of the article's
-newsgroup(s), and (b) at least one of the article's distri-
-bution(s). In effect, the only role of distributions is to
-limit propagation, by preventing transmission of articles
-that would have been transmitted had the decision been based
-solely on newsgroups.
-
-A posting agent might wish to present a menu of possible
-distributions, or suggest a default, but normally SHOULD not
-supply a default without giving the poster a chance to over-
-ride it. A followup agent SHOULD initially supply the same
-Distribution header as found in the precursor, although the
-poster MAY alter this if appropriate.
-
-Despite the syntactic similarity and some historical confu-
-sion, distributions are NOT newsgroup names. The whole
-point of putting a distribution on an article is that it is
-DIFFERENT from the newsgroup(s). In general, a meaningful
-distribution corresponds to some sort of region of propaga-
-tion: a geographical area, an organization, or a cooperating
-subnet.
-
- NOTE: Distributions have historically suffered
- from the completely uncontrolled nature of their
- name space, the lack of feedback to posters on
-
-INTERNET DRAFT to be NEWS sec. 6.7
-
-
- incomplete propagation resulting from use of ran-
- dom trash in Distribution headers, and confusion
- with newsgroups (arising partly because many
- regions and organizations DO have internal news-
- groups with names resembling their internal dis-
- tributions). This has resulted in much garbage in
- Distribution headers, notably the pointless prac-
- tice of automatically supplying the first compo-
- nent of the newsgroup name as a distribution
- (which is MOST unlikely to restrict propagation!).
- Many sites have opted to maximize propagation of
- such ill-formed articles by essentially ignoring
- distributions. This unfortunately interferes with
- legitimate uses. The situation is bad enough that
- distributions must be considered largely useless
- except within cooperating subnets that make an
- organized effort to restrain propagation of their
- internal distributions.
-
- NOTE: The distributions "world" and "local" have
- no standard magic meaning (except that the former
- is the default distribution if none is given).
- Some pieces of software do assign such meanings to
- them.
+ distribution = positive-distribution /
+ negative-distribution
+ positive-distribution
+ = *FWS distribution-name *FWS
+ negative-distribution
+ = *FWS "!" distribution-name *FWS
+ distribution-name = letter 1*distribution-rest
+ distribution-rest = letter / "+" / "-" / "_"
+
+ Articles MUST NOT be passed between relaying agents or to serving
+ agents unless the sending agent has been configured to supply and the
+ receiving agent to receive BOTH of
+ (a) at least one of the newsgroups in the article's Newsgroups
+ header, and
+ (b) at least one of the positive-distributions (if any) in the
+ article's Distribution header and none of the negative-
+ distributions.
+ Additionally, reading agents MAY be configured so that unwanted
+ distributions do not get displayed.
+
+ NOTE: Although it would seem redundant to filter out unwanted
+ distributions at both ends of a relaying link (and it is clearly
+ more efficient to do so at the sending end), many sending sites
+ have been reluctant, historically speaking, to apply such
+ filters (except to ensure that distributions local to their own
+ site or cooperating subnet did not escape); moreover they tended
+ to configure their filters on an "all but those listed" basis,
+ so that new and hitherto unheard of distributions would not be
+ caught. Indeed many "hub" sites actually wanted to receive all
+ possible distributions so that they could feed on to their
+ clients in all possible geographical (or organizational)
+ regions.
+
+ Therefore, it is desirable to provide facilities for rejecting
+ unwanted distributions at the receiving end. Indeed, it may be
+ simpler to do so locally than to inform each sending site of
+ what is required, especially in the case of specialized
+ distributions (for example for control messages, such as cancels
+ from certain issuers) which might need to be added at short
+ notice. Tha possibility for reading agents to filter
+ distributions has been provided for the same reason.
+
+ Exceptionally, ALL relaying agents are deemed willing to supply or
+ accept the distribution "world", and NO relaying agent should supply
+ or accept the distribution "local". However, "world" SHOULD NEVER be
+ mentioned explicitly since it is the default when the Distribution
+ header is absent entirely. "All" MUST NOT be used as a
+ distribution-name. Distribution-names SHOULD contain at least three
+ characters, except when they are two-letter country names as in [ISO
+ 3166]. Distribution-names are case-insensitive (i.e. "US", "Us" and
+ "us" all specify the same distribution).
+ NOTE: "Distribution: !us" can be used to cause an article to go
+ to the whole of "world" except for "us".
+
+ Posting agents SHOULD NOT provide a default Distribution header
+ without giving the poster an opportunity to override it. Followup
+ agents SHOULD initially supply the same Distribution header as found
+ in the precursor.