Plexus 9000 Planning and Engineering Guide
Switch Fabric Front Module
Section 130-120-300
Issue 2, April 23, 2004
5-97
5.7.3.3
Serial In, Parallel Out (SIPO) Interface
Each switch fabric module features twenty-four 622 Mb/s, OC12 capable,
ATM ports providing a total usable bandwidth of 15 Gb/s. The twenty-
four ports are used as follows:
•
1 for the working SP/TMG module
•
1 for the protection SP/TMG module (The protection SP can
send/receive traffic even when it is in the protection state.)
•
22 for the IO Modules
The SFs run in lockstep. The IOM sends the serial ATM signal to both the
working and protection SF.
5.7.3.4
ATM Switch Element (ASX)
The ATM Switch Element provides the switching function for an ATM
switch. It is used in conjunction with the ATM Crossbar Element to
provide a larger multi-stage, high-performance, nonblocking, lossless,
self-routing switch fabric.
Data for each port is clocked into an input processor in the ASX, passed to
internal cell buffers, and then routed to the appropriate output processor in
the ASX. The internal queue processor, routing and arbitration circuit,
and backpressure generation circuit control the movement of data into and
out of the cell buffer memory. Control and status are communicated
through an internal microprocessor.
On the left of the block diagram, the ASX is called the expander and it
increases the number of paths available for switching the data. The ASX
on the right is called the concentrator and it concentrates data from the
ATM Crossbar Element
.
5.7.3.5
ATM Crossbar Element (ACE)
The center of a switch fabric is the ATM Crossbar Element that functions
as crossbar allowing construction of non-blocking, lossless switch fabrics.
The ACE is functionally similar to the ASX, but without the internal cell
buffer because a hand-shake protocol between the ASX and the ACE
ensures that the ACE does not need to store data.
5.7.3.6
ATM Port Controller (APC)
The ATM port controller interfaces to the SAR on the SW/FAB module
and is responsible for inter-module messaging. During initialization the
ATM connections to the IOMs are established.