What is the NTC OC-3?
The NTC is a service interface module that concentrates the data traffic from all Cisco 6200 subscriber ports and connects the node to a single trunk line from the service-providing ATM network. This full-duplex channel unit carries data both downstream (to the subscriber) and upstream (from the subscriber). In Release 1, the trunk is a full-duplex OC-3c fiber optic channel. One OC-3c channel terminates at a single NTC. The OC3 NTC is available in both single-mode and multimode versions. Multimode fiber is LED-driven and is designed for distances up to 2 kilometers (1.2 miles). Longer distances (up to 15 kilometers or 9.2 miles) require laser-driven single-mode fiber. In the downstream direction, the OC3 NTC accepts ATM cells at the OC-3c rate (155.52 Mbps) and adapts these cells to the Cisco 6200 internal bus. The OC3 NTC also transmits upstream data back to the service provider via ATM on the OC-3c physical layer. The Cisco 6200 uses a fixed mapping of permanent virtual channels (PVC
