usefor-article-03 February 2000

6.16.  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 optional, posting agents SHOULD normally
   include this header.

      User-Agent-content  = product-token *( CFWS product-token )
      product-token       = value ["/" product-version]  ; see 4.1
      product-version     = value

   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 servers (such as INN/1.7.2), but serving and relaying
   agents MUST NOT generate or modify this header to list themselves.

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

 1. use of arbitrary text or octets from character sets other
    than US-ASCII in a product-token may require the use of a
    quoted-string,

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

 3. UTF-8 replaces ISO-8859-1 as charset assumption.

        NOTE: Comments should be restricted to information regarding the
        product named to their left such as platform information and
        should be concise. Use as an advertising medium (in the mundane
        sense) is discouraged.