5. Provisioning

   While the BEEP Framework [2] is used, the attributes described are
   sufficient for the TCP mapping [3] of BEEP.  The attributes on the
   "tunnel" element may need to be extended to handle other transport
   layers.

   In a mapping where multiple underlying transport connections are
   used, once the "ok" element is passed, all channels are closed,
   including channel zero.  Thus, only the underlying transport
   connection initially established remains, and all other underlying
   transport connections for the session should be closed as well.

   If a transport security layer (such as TLS) has been negotiated over
   the session, the semantics for the TUNNEL profile are ill-defined.
   The TUNNEL profile MUST NOT be advertised in any greetings after
   transport security has been negotiated.

   An SRV identifier of "_tunnel" is reserved by IANA for use with this
   profile.  Hence, the "srv" attribute "_tunnel._tcp" MAY be used as a
   default for finding the appropriate address for tunneling into a
   particular domain.

   System port number 604 has been allocated by the IANA for TUNNEL.