28236-DSH-001-B_15 Datasheet, PDF (69/443 Pages) M/A-COM Technology Solutions, Inc. – ATM ServiceSAR Plus with xBR Traffic Management

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3.0 Host Interface
3.1 Overview
The CN8236 segments and reassembles user data packets at 200 Mbps simplex,
and over 155 Mbps full duplex. The actual segmentation and reassembly
processes execute without run-time host control. However, the ATM host system
supplies the data for transmission and buffers for received data. In addition to this
control, the host processes status returned from the SAR. To take advantage of the
CN8236’s high throughput, the host must process control and status information
at a comparable rate.
APPLICATION EXAMPLE
An Ethernet Switch uses a CN8236-based subsystem as an uplink to an
OC-3 ATM backbone. Under worst case conditions, Ethernet packets
(64 octets) map into two ATM cells. At OC-3 rates, the CN8236 converts
176.6 K packets/second (Kpps) to cells in each direction. Therefore, the
host must process control and status information for a total of 353.2 Kpps.
This packet rate equates to a packet service time of 2.83 µs/packet.
In cases such as the example above, the service rate places extraordinary
performance requirements on the host system. High throughput systems require
large numbers of processing cycles and efficient use of system buses.
The CN8236 provides a flexible, high-performance, host interface
architecture. With this interface, the CN8236 facilitates a scalable, distributed
host system. The interface also minimizes the impact of an ATM port on the host
system’s PCI bus.
28236-DSH-001-B
Mindspeed Technologies™
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