Nortel Networks BCM200 manual Determining system capacity, Selecting a fiber expansion module FEM

Chapter 8 Installing a media bay module (MBM) 109

Selecting a fiber expansion module (FEM)

The FEM allows you to connect a maximum of six Norstar MBMs to a BCM system. Each FEM connection requires one DS30 bus, therefore, the BCM used for this purpose can only support one FEM module if you are converting a fully-configured Norstar system.

Note: The DIP switch settings you chose determine which FEM ports are available. If you enable all six FEM ports, the BCM system has no more DS30 resources available. Therefore, you cannot connect more MBMs to the system.

Determining system capacity

After you have selected the MBMs you require, you must ensure that the BCM system can support all the MBMs. System capacity is ultimately determined by the line requirements of each MBM.

The following sections describe the DS30 buses, which manage the DS30 buses, and how you fit your MBMs into the overall system planning:

•“Understanding DS30 numbers” on page 109

•“Setting offsets” on page 110

•“Determining bus requirements” on page 111

Understanding DS30 numbers

A DS30 bus is a block of virtual pathways on the media services card (MSC).

On a default system, six buses of DS30 channel blocks can be assigned to MBMs. The block to which the MBM is assigned determines the range of line (trunk) numbers or extension numbers (DNs) that can be allocated by the MBM to the equipment connected to that MBM. The other two blocks are permanently routed to the PEC digital signal processors (DSPs) to support internal BCM functions such as voice mail, VoIP trunks, IVR, and IP telephony functions. This configuration is called a 2/6 bus split.

You can change the DS30 allocation to a 3/5 split to accommodate increased IP telephony or VoIP trunk requirements. You do this by assigning bus 7 to the voice data sector. This choice should be made at system startup, but a default system can be changed through Element Manager to a 3/5 split after startup if IP requirements increase. You indicate the split you want when you configure the system.

Warning: If you change the bus split from 3/5 to 2/6 after your system is configured, you will lose all the data and optional application connections.

Figure 64 shows a model of how the MSC DS30 buses are a subgroup of the DS256 bus on the MSC. The diagram also shows the offset channels, which are a subgroup of the buses.

BCM200/400 4.0 Installation and Maintenance Guide