This chapter contains a brief outline of the features of the Cisco MGX 8250 switch. An illustration of the AC-powered version of the switch appears in Figure 2-1.
The MGX 8250 switch operates in two operational applications:
As a feeder, the MGX 8250 switch concentrates narrow-band and medium-band ATM, Frame Relay, and into a single, wide-band ATM feeder trunk to an BPX 8600-series switch.
As a stand-alonenode, the MGX 8250 switch concentrates narrow-band and medium-band ATM, Frame Relay, and voice into a single ATM line to at third-party switch. The MGX 8250 interface in this application is a UNI or an NNI.
The MGX 8250 switch can support a wide range of services over narrowband and mid-band user interfaces. It maps all the service traffic to and from ATM by using standardized interworking methods.
The supported interfaces for user-traffic are:
Frame Relay UNI on T3, E3, HSSI, T1, and E1 lines
ATM UNI and FUNI and optional inverse multiplexing for ATM (IMA)
Frame Relay to ATM network interworking and service interworking
Circuit emulation services
The optional Service Resource Module-3T3 (MGX-SRM-3T3/B) can support up to 80 T1 interfaces over its three T3 lines and provide 1:N redundancy for the T1 and E1 cards.
The modular, software-based system architecture enables the switch to support new features through downloadable software upgrades or new hardware modules.
The MGX 8250 backplane supports a minimum of 1.2 Gbps of non-blocking switching up to 45 Gbps. Individual line rates range from DS0 through OC-12.
The MGX 8250 switch converts all user information into 53-byte ATM cells by using the appropriate ATM Adaptation Layer (AAL) for transport over the ATM backbone network. The individual service modules segment and reassemble (SAR) cells to eliminate system bottlenecks. The following list shows the applicable AAL for each service:
Circuit emulation services uses AAL1.
Frame Relay-to-ATM network interworking uses AAL5 and Frame Relay Service Specific Convergence Sub-layer (FR-SSCS).
Frame Relay-to-ATM service interworking uses both transparent and translation modes to map Frame Relay to native ATM AAL5.
The MGX 8250 enclosure contains up to 24 service modules (I/O cards) and 4 optional Service Redundancy Modules (SRMs) provide redundancy. It resides in either in a 19-inch or a 23-inch rack. The closed, 19-inch Cisco-built rack also has an optional seismic anchor. The system can accept power from either a DC or an AC source.
Table 2-1: Power Supply Options
Model
Description
MGX-DC
MGX 8250 DC PEM and MBX-CAB-AC/DC
MGX-AC1-1
NR AC system for MGX 8250: AC shelf, 1 feed, 1 PS, MGX-CAB-AC/DC
MGX-AC2-2
Red AC pwr, red AC feed, AC shel, 2 PS, 2 MGX-CAB-AC/DC
The MGX 8250 switch supports two types of card sets: the corecards (or core modules) and service modules. The Processor Switching Module (PXM) and optional Service Resource Module (SRM) are core cards. The service modules provide the interface to the transport technologies of the CPE—Frame Relay, ATM, and so on. A card set consists of a front card with its attached daughter card and a back card (or line module). The front card contains the processing intelligence and, on the daughter card, the firmware that distinguishes the interface (OC-3, T3, E3, and so on). The back card is a simple card that provides the electrical interface for one or more lines of a particular type. The MGX 8250 front and back cards are the:
The downloadable firmware on each card determines the functionality, and you can upgrade functionality by downloading new firmware through a TFTP application on a workstation or a PC.
The current status and configuration parameters of the MGX 8250 modules reside in a Management Information Base (MIB). The firmware on each card updates the MIB as changes in status and configuration occur.
