
Implementation Notes for All Dial Services
114062 Rev. A 3-11
You can use Floating B if your network integrates a dial backup application that
uses ISDN B channels with network devices that send protocol traffic such as
SDLC or X.25. This type of application requires the following interfaces:
• One synchronous interface for SDLC, X.25 traffic
• One synchronous interface for the primary link to the backbone network
• One ISDN B channel for the dial backup link
Using 2B + D service without configuring floating B, the AN provides only one
synchronous interface, so you cannot integrate the dial service with other network
applications. However, by configuring floating B, you can configure two
synchronous interfaces, one Ethernet link, and one B channel. The router software
maps whichever B channel is in use to a single SCC.
To implement floating B operation, select Dialup - Floating B as the Port
Application Mode (refer to Chapter 7). This ensures that the router makes the
necessary adjustments for the use of only one B channel.
PRI Service on the ASN, BLN, and BCN
The Access Stack Node (ASN), Backbone Link Node (BLN), and Backbone
Concentrator Node (BCN) support the PRI standard for ISDN using the following
modules:
• 120 ohm Single Port MCE1-II Net Module (ASN only)
• Single or Dual Port MCT1 Link Module (BLN and BCN only)
• 120 ohm Single or Dual Port MCE1-II Link Module (BLN and BCN only)
• QMCT1 Link Module (BLN and BCN only)
The integrated ISDN PRI functionality allows you to connect directly to the ISDN
network, rather than connect via a terminal adapter. PRI becomes a cost-effective
solution when the number of BRI channels required for an application exceeds the
cost of a single PRI line. The cost savings depends on each country’s tariffs.
The PRI implementation supports all three dial services. Later chapters in this
book describe how to configure each service to connect to an ISDN network.
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