rpoa - Recognized Private Operating Agency is a ITU-T specified
facility which allows the user to specify--at call setup time--the next
transit network the call should use. The rpoa can override all
routing decisions.
If Dna subscribes to preselectRpoa as indicated by the previously
described attribute, (preselectRpoa set to yes) then this attribute
contains preselected rpoa. If the preselectRpoa attribute is set to no,
then this attribute can be left at its default.
This preselected rpoa will be used for all outgoing call request
packets using this Dna if an rpoa is not explicitly specified in the
call request. The rpoa represents the dnic of the directly connected
network through which the call will be routed in the presence of the
rpoa.