Zhone Technologies 800 - Manual (Page 72)

4-6 IMACS System Release 5.1.6 Server Cards
Model No. Running Head Introduction ACS-PRI/BRI Card
4.1.3 Network and User Side Protocols
In the example application shown in Figure 4-3, there is an important difference between the
two D channels terminating in the carrier switches and the D channel terminating in the user’s
PBX. The ISDN signaling protocol that runs on the D channel is not symmetrical. Signaling
messages are treated differently depending on whether the D channel is setup to run the
network side protocol or the user side protocol. All carrier switches run the network side
protocol, and all user devices connected directly to a network switch must run the user side
protocol. In general, network side applications cannot be connected to other network side
applications. Local routing, the exception to this rule, is explained in the next section.
Figure 4-4 shows how the application in Figure 4-3 would be set up if the user’s PBX was not
connected to the system.
The disadvantage of this configuration is that the PBX may not be able to support two D
channels, may not be able to handle the differences in D channel protocols between the two
carriers, and may not be able to route calls to the appropriate carrier.
Figure 4-4. ACS-PRI/BRI Links to Two Carriers
Figure 4-5 shows how the system overcomes these disadvantages. Note that the configuration
in Figure 4-5 is identical to the one in Figure 4-3.
Carrier A
ISDN Switch
Carrier B
ISDN Switch
User Side User Side
Network Side Network Side
23B+D 23B+D
ISDN PBX