Overview of ISDN BRI
ISDN is most commonly used to provide low-cost connectivity between sites that cannot justify the cost of a dedicated high-speed leased line. However, ISDN connections provide more bandwidth than asynchronous dial-up connections can, as well as quicker call completion---approximately 1 second instead of 45 seconds.
PortMaster products support manual dial-on-demand and automatic ISDN connections that use the BRI port and the PPP protocol. BRI supports two 64Kbps B channels for data and one 16Kbps D channel for signaling. ISDN ports are available as either a U or S/T interface.
ISDN ports are easier to configure than asynchronous or synchronous ports. Because the ISDN U interface has the NT1 device integrated in the port, no modem, CSU/DSU, or external terminal adapter is required.
For the ISDN S/T interface, a PortMaster requires an external terminal adapter to connect from the PortMaster synchronous port to the ISDN link. For terminal adapters that do not have automatic dialing or for administrators who want to manually connect with the terminal adapter, the PortMaster supports automatic location table scripting.
ISDN BRI ports can provide the same services that an asynchronous port provides, except for direct network hardwired connections. The PortMaster automatically detects whether the port is providing asynchronous or synchronous, 56Kbps or 64Kbps.
ISDN BRI connections can be initiated as needed, or they can remain active continuously. A dial-out location must be specified in the location table (Configure==>Locations) for dial-out connections, and a dial-in user must be specified in the user table (Configure==>Users) or in RADIUS for dial-in connections.