This draft specifies a Per Domain Behavior that provides the ability 

   to Diffserv nodes located outside Diffserv domain(s), e.g., receiver 

   or other Diffserv enabled router to detect when the resources 

   provided by the Diffserv domain(s) are not available. This PDB is 

   used when the negotiated SLS is associated to throughput (or 

   bandwidth) and when the SLS agreed throughput bound is not 

   statically but loosely defined in order to allow a more efficient 

   utilization of the Diffserv domain(s) and a simpler network 

   management operation. This PDB can be applied in association with 

   either a single Diffserv domain or multiple neighboring Diffserv 

   domains. This specification is denoted as Resource Unavailability 

   (RU) PDB and it follows the guidelines given in RFC 3086.