INTERNET-DRAFT                               Charles H. Lindsey
Usenet Format Working Group                  University of Manchester
                                             July 2001

6.6. Distribution

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   = ALPHA 1*distribution-rest
      distribution-rest   = ALPHA / "+" / "-" / "_"

        NOTE: The use of ALPHA in the syntax ensures that distribution
        names are always in US-ASCII.

   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.

Diffs to previous draft

--- {draft-04}	Wed Jul 11 21:55:32 2001
+++ {draft-05}	Wed Jul 11 21:55:33 2001
@@ -11,8 +11,11 @@
                           = *FWS distribution-name *FWS
       negative-distribution
                           = *FWS "!" distribution-name *FWS
-      distribution-name   = letter 1*distribution-rest
-      distribution-rest   = letter / "+" / "-" / "_"
+      distribution-name   = ALPHA 1*distribution-rest
+      distribution-rest   = ALPHA / "+" / "-" / "_"
+
+        NOTE: The use of ALPHA in the syntax ensures that distribution
+        names are always in US-ASCII.
 
    Articles MUST NOT be passed between relaying agents or to serving
    agents unless the sending agent has been configured to supply and the
@@ -25,6 +28,8 @@
    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
@@ -46,8 +51,6 @@
         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