CCNA Cisco Certified Network Associate Study Guide - FTP Server

Integrated Services Digital Network (ISDN) 509
going to connect to. If you don’t know which switch your provider is using
at their central office, simply call them to find out.
TABLE 10.1 ISDN Switch Types
Switch Type Keyword
AT&T basic rate switch Basic-5ess
Nortel DMS-100 basic rate switch Basic-dms100
National ISDN-1 switch Basic-ni1
AT&T 4ESS (ISDN PRI only) Primary-4ess
AT&T 5ESS (ISDN PRI only) Primary-5ess
Nortel DMS-100 (ISDN PRI only) Primary-dms100
Basic Rate Interface (BRI)
ISDN Basic Rate Interface (BRI, also known as 2B+1D) service provides two
B channels and one D channel. The BRI B-channel service operates at
64Kbps and carries data, while the BRI D-channel service operates at
16Kbps and usually carries control and signaling information.
The D-channel signaling protocol spans the OSI reference model’s Physical,
Data Link, and Network layers. The D channel carries signaling information
to set up and control calls. The D channel can also be used for other
functions like an alarm system for a building, or anything that doesn’t need
much bandwidth, since it is only a whopping 16k. D channels work with
LAPD at the Data Link layer.
When configuring ISDN BRI, you will need to obtain SPIDs (Service Profile
Identifiers), and you should have one SPID for each B channel. SPIDs can
be thought of as the telephone number of each B channel. The ISDN device
gives the SPID to the ISDN switch, which then allows the device to access the
network for BRI or PRI service. Without a SPID, many ISDN switches don’t
allow an ISDN device to place a call on the network.
To set up a BRI call, four events must take place:
1. The D channel between the router and the local ISDN switch comes up.