Frame Relay Nni Dna Cug Preferential

The attribute 'preferential', if set to yes indicates that this CUG is the SIMPLE CUG (as defined in ITU X.36 [10/96]), in which case it will be used during the call establishment phase if the DTE has not explicitly specified a CUG index in the call request packet. If set to no, then this CUG is not the SIMPLE CUG, but an instance of the SELECTABLE CUG. The attribute 'preferential' is set to no by CAS when a CUG instance is created. If only one CUG instance exists under a DNA, and if this CUG's attributes 'incCalls' and 'outCall' are both set to allowed, then this CUG instance can be changed to a SIMPLE CUG by setting the attribute 'preferential' to yes. If more than one CUG instances exist under a DNA, none of the CUGs can be set by the user as 'preferential'. Essentially, the attribute 'preferential' distinguishes a SIMPLE CUG from a SELECTABLE CUG. In the case of a FRUNI DNA with a single CUG instance, the CUG can be a SIMPLE CUG (preferential = yes) or the only instance of a SELECTABLE CUG (preferential = no).