INTERNET-DRAFT Charles H. Lindsey
Usenet Format Working Group University of Manchester
April 2001
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 Ought Not to 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.
[Previous Up Next]
See also previous draft (03): 6.6. Distribution
See also previous draft (02): 6.7.2 Definition
See also previous draft (02): 6.7.1.2 Planned Uses
See also previous draft (02): 6.7.1.1 New Semantics
See also previous draft (02): 6.7.1 Historical Note
See also previous draft (02): 6.7. Distribution
See also previous draft (son-of-1036): 6_7__Distribution
See also previous draft (rfc-1036): RFC1036_2_2_7__Distribution