3Com MSR 50 Series Configuration Manual page 105

can be used to forward digital and analog information. The standardization efforts
that ITU-T made in provisioning the ISDN services make the implementation of
ISDN become possible. The provisions of the recommendations I.430, Q.921, and
Q.931 allow all the devices meeting ITU-T ISDN provisions of unbarring ISDN
network access.
The following is the provision standardizing the ISDN user-network interface.
ITU-T I.411 provides the referential ISDN user-network interface configuration as
shown in the following figure on the basis of function group (a set of functions
required for accessing an ISDN network) and reference point (a concept used to
differentiate function groups).
Figure 5 Referential ISDN user-network interface configuration
4 3
5
TE2
R
Function groups include:
Network terminal 1 (NT1) implements the functionality of the first layer in the
■
OSI reference model, such as subscriber-line transmission, loop test, D-channel
competition.
Network terminal 2 (NT2), also known as intelligent network terminal,
■
implements the functionality of layers 1 through 3.
Category-1 terminal equipment (TE1), also known as ISDN standard terminal, is
■
user equipment compliant with the ISDN interface provisions. Digital phone-set
is such an example.
Category-2 terminal equipment (TE2), also known as non-ISDN standard
■
terminal equipment, refers to the user equipment incompliant with the ISDN
interface provisions.
Terminal adapter (TA) implements the adaptation function so that TE2 can
■
access a standard ISDN interface.
Reference points include:
R reference point between a non-ISDN equipment and TA.
■
S reference point between a user terminal and NT2.
■
T reference point between NT1 and NT2.
■
U reference point between NT1 and line terminal.
■
Preparing for making configuration
Before making configuration, you should:
2
TE1 NT2
S
TA
S
ISDN BRI Interface
1
NT1
T U
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