ACF NCP stands for Advanced Communication Function - Network Control Program. It is the program that controls network communications in a standard SNA.
DLSW+ isan IP transport solution for SNA/NetBIOS between peering routers. In traditional SNA networks, ACF/VTAMsoftware on the host and ACF/NCP software on the FEPs together perform all routing of SNA traffic, ensuring thatthe traffic flows appropriately from source to destination. Because it does not have any ACF/NCP or ACF/VTAMfunctionality within it, DLSw+ routers cannot route traditional SNA traffic. Instead, DLSw+ simply encapsulates thetraffic in IP. Within the IP network the traffic is routed, but when converted back to SNA, it must continue to berouted by ACF/NCP or ACF/VTAM.Two issues that result from this fact have caused some IT organizations to continue to support FEPs in the data center.First, many SNA networks implement a design in which two FEPs running ACF/NCP can act as backup for oneanother. If one of the paths to one of the FEPs fails, the SNA traffic automatically can be sent through the other FEP.Known as duplicate Token Ring interface coupler (TIC) addressing, this feature has been the centerpiece of buildinghigh-availability SNA networks. DLSw+, although offering many high-availability features, cannot directly replacethis function. Therefore, SNA sessions can fail if one of the DLSw+ routers fails. Some IT organizations havecontinued to support FEPs in the data center primarily to provide this... Read More