Standards-Based Conversion To Atm; Mgx 8850 Enclosure And Power; Mgx 8850 Cards - Cisco MGX 8850 Installation And Configuration Manual

Standards-Based Conversion to ATM

The MGX 8850 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.
•
Frame Forwarding uses AAL5.

MGX 8850 Enclosure and Power

The MGX 8850 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.

MGX 8850 Cards

The MGX 8850 switch supports two types of card sets: the core cards (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 8850 front and back cards are the:
•
Processor Switching Module (PXM1)
This front card controls the switch and supports external interfaces for user-access and trunking
or UNI ports. The back cards consist of a user interface card (PXM-UI) and a broadband network
module (see subsequent list items).
•
Processor Switch Module User Interface (PXM1-UI)
The PXM1-UI is the user interface card that has various types of ports to let you access and
control the switch.
•
Broadband Network Module (MGX-SMFIR-1-622 and MGX-SMFLR-1-622)
The SMFIR-1-622 is a broadband network module for the PXM and provides a SONET
OC12/STM4 ATM interface at 622 Mbps.
•
Broadband Network Module (MGX-MMF-4-155)
The MMF-4-155 is a broadband network module for the PXM and provides 4 SONET
OC3/STM1 ATM interfaces at 155 Mbps.
•
Broadband Network Module (MGX-BNC-2T3)
The MGX-BNC-2T3 is a broadband network module for the PXM and provides 2 T3 ATM
interfaces.
Standards-Based Conversion to ATM
Introducing the MGX 8850 Switch 2-3