A Resource object can be associated with a Transport object,
or a Message object, or both. It is intended to describe generic
characteristics of the transport mechanism. When there is a
Resource object associated with both, the Message's resources
take precedence. The Transport's resources provide "default"
values when none are supplied for a Message. The NULL value for
these attributes only really makes sense for the Message resource
object, and means "go look at the Transport's resource object".