Revised terms

[Scott Michel <scottm@rush.aero.org>]

Ok, here's goes again. Note that we're avoiding ITU terms, because we're
the IETF, not the ITU. Also note that we want to *avoid* at all costs the
name "VIF", as this can be easily confused with prior-Deering-isms like
tunnelling. :-)

BDL	Bidirectional link. A link layer where transitive communcation
	occurs.

UDL	Unidirectional Link. A link layer where non-transitive communication
	occurs or BDL behaviour is not permitted.

UDLN	Unidirectional Link Network. A network composed of or containing UDLs.

IT	Ingress tap. An ingress tap is an interface attached to a sending
	host or router which inserts packets into a UDL.

ET	Egress tap. An egress tap is an interface attached to a host or
	router which receives packets from a UDL.

CLIF	"Complete loop" interface. A "complete loop" interface is an
	receiving host or router's interface distinct from the ET which
	allows communication to a sending host.

CIF	Composed interface. An composed interface is a composition of
	a ET and a CLIF to provide transitive communcation.


-scooter