Bay Networks 6300 Supplement Manual page 31

Book A
Remote Annex 6300 Supplement to the Remote Annex Administrator's Guide for UNIX
The BRI B channels operate at transmission rates of 64Kbps or 56Kbps.
These channels usually carry data, voice, and video traffic, although some
telephone companies also use B channels to carry signals normally
carried by the D channel. Some companies handle signaling accounts for
the lower B channel transmission rate (56Kbps vs. 64Kbps).
A BRI D channel operates at 16Kbps. It sets up and tears down calls, and
handles other connection management signaling between the user's
equipment and the ISDN-capable switch at the local telephone company.
The D channel also manages transmission and reception of packet data
over an X.25 network.
Primary Rate Interface
The ISDN PRI service provides greater B channel capacity and higher-
speed D channel operation than BRI service. PRI is provided over
dedicated trunk lines such as T1 and E1. Businesses and other institutions
use PRI service to connect their communications resources to ISDN:
• Private Branch Exchange (PBX) switches.
• Local Area Networks (Loans).
• Wide Area Networks (WANs).
• Video conferences equipment.
In the United States, Canada, and Japan, PRI service is provided over T1
trunk lines. A single T1 line supports 23 B channels (for voice, data and
video) and 1 D channel (for call set up, tear down, and connection
management). All B and D channels operate at 64Kbps and provide
1.544Mbps of total bandwidth. This flavor of PRI service is referred to
as 23B+D.
Chapter 1 Introduction to the Remote Annex 6300
A-3