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Introducing the MGX 8220 Shelf

Introducing the MGX 8220 Shelf

This chapter describes the features and functions of Release 4.1 of the Cisco MGX 8220 edge concentrator. (See Figure 1-1.)


Figure 1-1: MGX 8220 Shelf

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:

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.

Aggregation of Traffic into ATM Networks

Each MGX 8220 shelf connects to the BPX switch across:

  or

Thus, the MGX 8220 shelf supports aggregation of traffic up to 80 T1 or E1 access ports or up to 1240 64-Kbps subscribers, onto a single T3, E3, or OC-3c trunk, using only a single port on the
BPX switch.

The MGX 8220 shelf should normally be collocated with the BPX switch. Figure 1-2 shows how the
MGX 8220 shelf usage is envisioned in Release 4.1.


Figure 1-2: MGX 8220/BPX Switch Relationship

For remote locations with limited bandwidth needs, the MGX 8220 shelf can be remotely located from the BPX switch using IMA trunk machines as shown in Figure 1-3.


Figure 1-3: Remote MGX 8220 Configuration

The following subsections provide an overview of the MGX 8220 shelf, the Release 4.1 cards, and management capabilities. In-depth details are provided in subsequent chapters.

MGX 8220 Shelf

Physically, the MGX 8220 shelf consists of cards in a 19 inch rack mountable shelf.

The shelf can be powered either from a -48V DC source or from a 220-240V AC source. The DC version includes DC power entry modules that can be mounted in the shelf. The AC version requires an external rack mounted, AC Power Module. Both versions require a rack mounted cooling assembly. Multiple MGX 8220 shelves can be mounted in the same rack sharing power and cooling assemblies.

The MGX 8220 shelf contains 16 slots where each slot can accommodate a front card and a back card. The front row is used for function modules, cards that perform more complex functions within the unit (for example, frame relay to ATM conversion). The back row is used for line modules, cards that provide interfaces to one or more transmission lines connected to the MGX 8220 shelf
(for example, the trunk line to the BPX switch or an RS-232 line to a control terminal).

MGX 8220 Cards

Unless a service module uses the SRM 3T3 distribution bus, MGX 8220 cards are installed as a pair consisting of a front card (function module) and a matching back card (line module) in the same slot, except for the SRM-T1E1 card which only has a front card. Communication between slots is achieved through buses in the shelf backplane.

Release 4.1 consists of the following module pairs:

The ASC and the BNM modules must always be present in an MGX 8220 shelf and are referred to as the core modules. The MGX 8220 shelf supports redundant core modules where one ASC/BNM set is an active set and a second ASC/BNM is a standby set. In the event of a malfunction, the standby set automatically takes over as the active set. The SRM is optional. If present, it is part of the core card set, with switchover to the standby upon a malfunction of the active BNM or ASC.

MGX 8220 Management

The functions and operation of the MGX 8220 shelf are achieved through downloaded firmware. The firmware controls the overall operation of the shelf and responds to configuration and other The MGX 8220 shelf has a command repertoire of over 60 user commands which are used to configure and display the various operational parameters of the shelf.

The current status and configuration parameters of the MGX 8220 modules are maintained in a Management Information Base (MIB) which is updated by the firmware as changes in status and configuration occur. The MIB can be interrogated using SNMP commands.

Most of the functions of the MGX 8220 shelf Release 4.1 can be effected through the graphical user interface provided in StrataView Plus Release 9.1.

The ASC module includes three ports for user input of management commands. A further means of management access is provided in-band over the ATM trunk.

The maintenance port is a simple RS-232 port for direct connection to an alpha-numeric terminal into which the user can type commands through a Command Line Interface (CLI).

The control port (SLIP protocol only), the LAN (Ethernet) port and the in-band ATM connection all support the CLI (via Telnet), TFTP and SNMP protocols for communicating with the MGX 8220 shelf.

New in Release 4.1

This section provides a very brief description of the new MGX 8220 shelf features that have been added since Release 4.0:


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Posted: Mon Jan 15 16:43:20 PST 2001
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