1. Design Goals

   This profile is intended to provide a range of functional
   capabilities for message routing based on one of two mechanisms.  The
   most complete service should use the ENUM address resolution service
   to determine the VPIM directory, and then use LDAP to retrieve the
   VPIM-specific email address that will be used for message routing.

   The more basic send-and-pray message service uses only the ENUM
   service and MX records to route the message to the intended
   recipient's domain.  The intelligence to further route the message to
   the intended recipient is placed within the message routing system of
   the recipient's domain.

   The basic mechanism may be used even when there is a VPIM directory
   service available.  The basic service is useful when LDAP queries are
   not available, such as may be the case for disconnected mobile
   terminals or because of firewall or information security policies.

   The basic mechanism should facilitate the routing of VPIM messages to
   a suitable internal destination with a minimum of configuration.  It
   is an important goal to avoid any content-processing to determine the
   nature of the message and its internal destination.  At a minimum, it
   should be possible to establish a simple mail forwarding rule that

   sends all inbound VPIM messages to a designated system, while
   facilitating the routing of FAX, SMS, or other telephone-addressed
   messages to other potentially different systems.

   It is a goal that the mechanisms outlined in this document be
   extensible for all store-and-forward, telephone-number addressed
   messaging services.

   It is a goal that the VPIM directory discovery and VPIM directory
   query steps occur within the timing constraints for user interfaces
   in PSTN networks.  95% of the time, that constraint can be a two-
   second response.