What types of queues are implemented on the Cisco 7200 series to support ATM traffic?
The Cisco 7200 series router implements both hardware and software queues. The ATM port adapter uses hardware queues located on the ATM port adapter itself, and also on the network processing engine (NPE) or network services engine (NSE). The PA-A3 and PA-A6 ATM port adapters have a separate receive buffer and transmit buffer for segmentation and reassembly (SAR) processing located on the port adapter. A direct memory access (DMA) transfer occurs between the hardware buffers on the port adapter and the private interface pool located on the NPE or NSE. The software queue is one or more Layer 3 queues, whose implementation is dependent upon the type of ATM port adapter. The PA-A3 and PA-A6 ATM port adapters activate their Layer 3 queues when congestion builds on the router and the transmit ring is full. Packets awaiting transmission enqueue to the Layer 3 queue until they can be placed onto the transmit ring of the outbound port adapter. For the PA-A3 and PA-A6 ATM port adapters, the Lay
