usefor-article-09 February 2003

5.6.2.  Adding a path-identity to the Path-header

   When an injecting, relaying or serving agent receives an article, it
   MUST prepend its own path-identity followed by a path-delimiter to
   the beginning of the Path-content. In addition, it SHOULD then add
   CRLF and WSP if it would otherwise result in a line longer than 79
   characters.

   The path-identity added MUST be unique to that agent. To this end it
   SHOULD be one of:

   1. A fully qualified domain name (FQDN) associated (by the Internet
      DNS service [RFC 1034]) with an A record, which SHOULD identify
      the actual machine prepending this path-identity. Ideally, this
      FQDN should also be "mailable" (see below).

   2. A fully qualified domain name (FQDN) associated (by the Internet
      DNS service) with an MX record, which MUST be "mailable".

   3. An arbitrary name believed to be unique and registered at least
      with all sites immediately downstream from the given site.

   4. An encoding of an IP address - <IPv4address> or <IPv6address> [RFC
      2373] (the requirement to be able to use an <IPv6address> is the
      reason for including ':' as an allowed character within a path-
      identity).
   The FQDN of an agent is "mailable" if the administrators of that
   agent can be reached by email using both of the forms "usenet@<FQDN>"
   and "news@<FQDN>", in conformity with [RFC 2142].

   Of the above options, nos. 1 to 3 are much to be preferred, unless
   there are strong technical reasons dictating otherwise. In
   particular, the injecting agent's path-identity MUST, as a special
   case, be an FQDN as in option 1 or option 2, and MUST be mailable.
   Additionally, in the case of an injecting agent offering its services
   to the general public, its administrators MUST also be reachable
   using the form "abuse@<FQDN>" UNLESS a more specific complaints
   address has been specified in a Complaints-To-header (6.20).

   The injecting agent's path-identity MUST be followed by the special
   path-delimiter '%' which serves to separate the pre-injection and
   post-injection regions of the Path-content (see 5.6.3).

   In the case of a relaying or serving agent, the path-delimiter is
   chosen as follows.  When such an agent receives an article, it MUST
   establish the identity of the source and compare it with the leftmost
   path-identity of the Path-content. If it matches, a '/' should be
   used as the path-delimiter when prepending the agent's own path-
   identity.  If it does not match then the agent should prepend two
   entries to the Path-content; firstly the true established path-
   identity of the source followed by a '?'  path-delimiter, and then,
   to the left of that, the agent's own path-identity followed by a '/'
   path-delimiter as usual.  This prepending of two entries SHOULD NOT
   be done if the provided and established identities match.

   Any method of establishing the identity of the source may be used
   (but see 5.6.5 below), with the consideration that, in the event of
   problems, the agent concerned may be called upon to justify it.

        NOTE: The use of the '%' path-delimiter marks the position of
        the injecting agent in the chain. In normal circumstances there
        should therefore be only one '%' path-delimiter present, and
        injecting agents MAY choose to reject proto-articles with a '%'
        already in them. If, for whatever reason, more than one '%' is
        found, then the path-identity in front of the leftmost '%' is to
        be regarded as the true injecting agent.

--- ../usefor-article-08/Adding_a_path-identity_to_the_Path-header.out          August 2002
+++ ../usefor-article-09/Adding_a_path-identity_to_the_Path-header.out          February 2003
@@ -24,7 +24,6 @@
       2373] (the requirement to be able to use an <IPv6address> is the
       reason for including ':' as an allowed character within a path-
       identity).
-
    The FQDN of an agent is "mailable" if the administrators of that
    agent can be reached by email using both of the forms "usenet@<FQDN>"
    and "news@<FQDN>", in conformity with [RFC 2142].