Configuring a T1 CSU/DSU

1. Click Configure CSU/DSU on the SystemWAN InterfacesConfigure PPP/Frame Relay screen. The Configure CSU/DSU screen appears.

Figure 31 SystemWAN InterfacesConfigure PPPCSU/DSU screen



2. Set the Clock Source. This field sets where the timing is being determined, from the gateway (Internal) or from the T-1 service provider (Loop). The clock source is usually set to Loop when connected to a live T-1 service. Internal clocking is used for local or test applications only.
3. Set the Line Build Out (dB) value. The line build out value is a power level that is set based on the distance from the CSU/DSU to the T-1 service provider's gateway. If the CSU/DSU card is close by, the gateway requires less power and the line build out value is lower; if the card is far away, the gateway requires more power and the line build out value is higher. This setting is determined by the T-1 service provider. Valid options are:
• 0.0
• -7.5
• -15.0
• -22.5
4. Set the Line Coding value. This field sets the method of encoding binary digits on the line. The line coding value is supplied by the T-1 service provider. Valid options are AMI and B8ZS.
5. Select the HDLC Polarity. This field determines whether or not the user data is inverted. This field must be synchronized with the AMI line coding; otherwise, you might violate the AMI specification. Both the local and the remote CSU/DSU must terminate the T-1 data circuit with the same setting: either both using Normal or both using Inverted. Valid options are Normal and Inverted.
6. Set the Line Framing value. This field determines the low-level protocol between the T-1 service provider and the gateway. It determines how the data is encapsulated and it handles the signaling for alarms and loopbacks. The newer ESF framing uses out-of-band signaling, while the older SF framing uses in-band signaling. The line framing value is supplied by the T-1 service provider. Valid options are SF and ESF.
7. Select the Performance Report Message setting. The Performance Report Message parameter is a part of the ANSI T-1 specification. It generates messages that state how many errors there are per second. This value is used with ESF framing only. When using SF framing, this parameter has no effect but should be set to None to avoid any confusion. The Performance Report Message value is supplied by the T-1 service provider and are None and ANSI.
8. Enable Fractional T-1. A T-1 service consists of up to 24 channels. Typically, you purchase the number of necessary channels from the service provider, and you can add additional channels (up to 24) as growth requires. When you add a fractional T-1 channel, you must enable it through this parameter and restart the system. Valid options for each of the 24 DS-0 channels are On (checked) and Off (unchecked).