Asynchronous Transfer Mode (ATM) port adapters are available on Cisco 7200 series routers, on the second-generation Versatile Interface Processor (VIP2) in Cisco 7500 series routers, and in Cisco 7000 series routers with the 7000 Series Route Switch Processor (RSP7000) and 7000 Series Chassis Interface (RSP7000CI).The ATM port adapter provides a single SONET/SDH OC-3 full-duplex interface (either multimode or single-mode intermediate reach) and supports data rates of up to 155 Mbps bidirectionally. The ATM port adapter connects to a SONET/SDH multimode or SONET/STC-3C single-mode optical fiber cable (STS-3C or STM-1 physical layer) to connect the router to an external DSU (an ATM network). The ATM port adapter supports the following features: segmentation and Reassembly (SAR) of up to 512 buffers simultaneously, where each buffer represents a packet; up to 256 transmit buffers for simultaneous fragmentation; up to 2, 048 SAR virtual circuits (VCs); ATM adaptation layer (AAL) 5; operation, Administration, and Maintenance (OAM) cells.