2-2
Cisco MGX 8950 Hardware Installation Guide
Release 2.1, Part Number 78-11273-01 Rev. B0, March 2002
Chapter2 Product Overview
MGX 8950 Chassis and Power
MGX 8950 Chassis and Power
The MGX 8950 chassis is a high capacity ATMbackbone switch that can hold up to twelve ATMservice
modules, two Processor Modules (PXM45/Bs) and four Switching Modules (XM-60s). The switch can
be mounted in either a 19-inch or a 23-inch rack with industry standard EIA/Retma mounting hole
patterns. The system can accept power from either a –48 VDC (–42 + –56 VDC) DC source or an
optional 220 VAC (180–254 VAC) source.
MGX 8950 Backplane
The MGX 8950 backplane provides up to 240 Gbps of switching capacity,using four dedicated switch
modules (XM-60s), each containing 60 Gbps of cross-bar switching fabric.
APS Assembly (Optional)
An optional feature for the MGX 8950 is the Automatic Protection Switching (APS) assembly.The APS
assembly consists of two optical AXSM back cards, an active card and a standby card, which are
connected using an APS connector (Part No. MGX-APS-CON-8950). The APS assembly can then be
installed in the card cage. See Chapter 4, “Enclosure and Card Installation,” for installation procedures.
APS provides 1+1 and 1:1 redundancy protection. Forinformation on APS configuration, refer to Cisco
MGX 8850 and MGX 8950 Switch Software Configuration Guide, Release 2.1
An APS connector is needed for OC48 capacity AXSM cards (AXSM-1-2488/B). It is not needed for
OC192 capacity AXSM cards.
MGX 8950 Card Sets
The MGX 8950 switch supports two types of card sets: the core cards and service modules.
The Processor Module (PXM45/B) and the Switching Module (XM-60s) are the core modules.
The service modules provide either ATM trunking or an ATM UNI interface. The AXSMs have serial
link connections to the XM-60 switch modules, providing a data rate of up to 2.488Gbps per modules.
The MGX 8950 switch receives network clocking from the PXM-UI-S3 card. The clock distribution
logic in the modules of the MGX 8950 nulls any trace and buffer delays, which ensures that all cards
have their clocks in sync and in phase. The two PXM45/B back cards are the PXM-UI-S3
(user interface, network clocking) in the upper shelf, and the PXM-HD (hard drive) in the lower shelf.
The switch fabric of the MGX 8950 switch consists of four single height switch cards (XM-60s), which
reside in slots 9, 10, 25, and 26 of the MGX 8950 chassis. All four XM-60’s should be installed to
provide scalable bandwidth sharing. Each XM-60 provides 60 Gbps of cross point switching. The
XM-60 card contains four switch ASICs, and each XM-60 has four serial links to each AXSM slot (one
serial link per switch ASIC). The upper two XM60s have one serial link to each PXM slot. The switch
scheduling hardwareoptimizes switching throughput by adjusting to various traffic flows. A single point
of failure in the switch fabric does not block traffic flow in asystem with multiple switch modules.
Duringnormal operations, all installed XM-60 switch modules can participate in cell switching to enable
maximum hardware usage and reliability. The XM-60s do not have corresponding back cards.