usefor-article-13 May 2004

6.18.  User-Agent

   The User-Agent-header contains information about the user agent
   (typically a newsreader) generating the article, for statistical
   purposes and tracing of standards violations to specific software
   needing correction. Although not one of the mandatory headers,
   posting agents SHOULD normally include it. It is also intended that
   this header be suitable for use in Email.

      header              =/ User-Agent-header
      User-Agent-header   = "User-Agent" ":" SP User-Agent-content
                     *( ";" extension-parameter )
      User-Agent-content  = product *( CFWS product )
      product             = [CFWS] token [CFWS] [ "/" product-version ]
      product-version     = [CFWS] token [CFWS]

   This header MAY contain multiple product-tokens identifying the agent
   and any subproducts which form a significant part of the posting
   agent, listed in order of their significance for identifying the
   application. Product-tokens should be short and to the point - they
   MUST NOT be used for information beyond the canonical name of the
   product and its version.  Injecting agents MAY include product
   information for themselves (such as "INN/1.7.2"), but relaying and
   serving agents MUST NOT generate or modify this header to list
   themselves.

        NOTE: Minor variations from [RFC 2616] which describes a similar
        facility for the HTTP protocol:

        1. "{" and "}" are allowed in a token (product and product-
 version) in Netnews,

        2. Comments are permitted wherever whitespace is allowed.

        NOTE: This header supersedes the role performed redundantly by
        experimental headers such as X-Newsreader, X-Mailer, X-Posting-
        Agent, X-Http-User-Agent, and other headers previously used on
        Usenet and in Email for this purpose. Use of these experimental
        headers SHOULD be discontinued in favor of the single, standard
        User-Agent-header.

--- ../usefor-article-12/User-Agent.out          November 2003
+++ ../usefor-article-13/User-Agent.out          May 2004