- When NSG receives INR from network, send back INF with calling
         party category information IE and calling number information IE.
         - Introduced a new global setting of "force-inr" for testing
         purpose. Stinga generated INR/INF packets are not acceptable by
         trillium stack since it misses call related information in the
         packets. If configure force-inr to true in freetdm.conf.xml, when
         NSG receives an incoming IAM, it'll send out INR packet regardless
         of incoming IAM's IEs, and keep waiting for INF response from the
         calling side.
         - T.39 timer is introduced in order to handle INR timeout. The
         default value of T.39 is 12 seconds and is configurable according
         to spec.
         - Only supports calling number IE and calling party category IE in
         current fix. The customer only needs the calling number IE right now.
         In ISUP spec, there are 6 optional IEs. NSG only supports calling
         party number and calling category information IE since the other
         IEs are not configurable in freetdm.conf.xml or included in IAM
         message.
         - In collect state, INR/INF implementation needs to work with existed
         SAM messages. If NSG sent out INR and wait for SAM, collect state
         check both INF received and enough dialed numbers received. If one
         of these conditions are not met, it'll stay in collect state and wait
         until either conditions met or timeout. After received INF and enough
         dailed number, state moves to dailing and proceed as regular calls.