Isdn Configuration; Introduction To Isdn - 3Com MSR 50 Series Configuration Manual

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Introduction to ISDN

ISDN C
ONFIGURATION
When configuring ISDN, go to these sections for information you are interested in:
"Introduction to ISDN" on page 421
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"Configuring ISDN" on page 422
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"Displaying and Maintaining ISDN" on page 434
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"ISDN Configuration Example" on page 434
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"Troubleshooting" on page 441
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Derived from integrated digital network (IDN), integrated services digital network
(ISDN), provides end-to-end digital connectivity and supports an extensive ranges
of services, covering both voice and non-voice services.
ISDN furnishes a finite set of standard multi-purpose user-network interfaces
(UNIs). In ITU-T I.412 recommendation, two types of UNIs are specified: basic rate
interface (BRI) with bandwidth of 2B + D and primary rate interface (PRI) with
Bandwidth of 30B + D or 23B + D. Where,
B channel is a user channel, used to transmit such user information as voice
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and data with a transmission rate of 64 kbit/s.
D channel is a control channel, which transmits the public channel signaling.
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These signals are used to control the calls on the B channel of the same
interface. The rate of D channel is 16 kbit/s (BRI) or 64 kbit/s (PRI). The ITU-T
Q.921 is a data link layer protocol of D channel. It defines the rule for Layer 2
information interchange via D channel from the user to a network interface
and supports the access of a layer 3 entity. The ITU-T Q.931 is a network layer
protocol of D channel. It provides a measure for creating, maintaining and
terminating network connection between communication application entities.
Call control (CC) is a further encapsulation of Q.931, which forwards the
message from the network side to CC for CC to perform information
interchange with higher layer applications such as DCC.
Figure 121 ISDN D channel protocol stack
Layer 3
Q.931
Layer 2
Q.921 LAPD
Layer 1 BRI
The ISDN protocols proposed by ITU-T provides different services in different areas,
forming the ISDN protocols that are suitable for different regions, such as NTT
CC
PRI