MGX 8220 System Overview
MGX 8220 System Overview
The 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, 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 Cisco BPX® 8600 series wide-area 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.
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 a single port on the ATM switch.
Release 3.0 of the MGX 8220 shelf supports up to 40 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 and circuit emulation services. The MGX 8220 shelf Release 3.0 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 MGX 8220 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.
