Specifications

1-2 Cisco MGX 8220 Reference, Release 4.1
MGX 8220 System Overview
MGX 8220 System Overview
MGX 8220 shelf is designed on the philosophy that large scale deployment of narrowband and
medium-band services is best handled using an ATM infrastructure. In fact, support of these services
can, by themselves, cost justify an ATM infrastructure. The same infrastructure can then be used to
provide broadband services to customers when and where they are needed.
The MGX 8220 shelf is an adjunct shelf to the BPX switch. Architecturally it provides:
• A means for flexibly providing many narrowband and/or medium-band ATM and non-ATM
service interfaces without consuming BPX switch slots.
• Conversion of non-ATM traffic streams to and from ATM traffic streams using Adaptation Layer
standards.
• A means for concentrating the traffic from the narrowband and/or medium-band interfaces onto
the broadband ATM ports of the BPX switch.
The MGX 8220 shelf can also be used as a stand-alone unit in which it can communicate with third
party devices over ATM UNI and NNI links provided there is inter-operability between the third
party devices and the MGX 8220 ATM port.
Service Interfaces
The MGX 8220 shelf is a flexible standards-based service access platform. The MGX 8220 shelf can
support a wide range of services over narrowband and mid-band user interfaces, mapping all the
service traffic to and from ATM, based upon standardized interworking methods. The aggregated
traffic is sent/received over an ATM interface to an ATM switch (BPX switch), using up only a single
port on the ATM switch.
The MGX 8220 shelf supports up to 80 channelized or non-channelized T1 and E1 interfaces on a
single shelf providing support for Frame Relay UNI and NNI; ATM UNI, NNI, and FUNI; Frame
Relay to ATM network interworking; Frame Relay to ATM service interworking, circuit emulation
services, and Frame Relay Access services for supporting IBM SNA networks. Using the Service
Resource Module (SRM), multiple T1 interfaces can be supported on physical T3 lines.
The MGX 8220 shelf also supports the use of Inverse Multiplexing for ATM (IMA) to provide ATM
trunking below T3/E3.
The system’s modular, software-based architecture enables it to support these and other additional
user services in the future, through downloadable software upgrades or new hardware modules.
Standards-Based Conversion to ATM
All user information received by the MGX 8220 shelf interfaces is converted into 53-byte ATM cells,
using standard ATM Adaptation Layers (AALs) for transport over the ATM backbone network. Cell
segmentation and reassembly (SAR) and other adaptation functions are distributed to each interface
module to eliminate system bottlenecks.
• For Circuit Emulation Services AAL1 is used.
• For Frame Relay (FR to ATM network interworking) AAL5 and FR-SSCS (Frame Relay Service
Specific Convergence Sublayer) are used.
• For Frame Relay to ATM service interworking, both transparent and translation modes are
supported to map FR to native ATM AAL5.
• For Frame Forwarding AAL5 is used.