Zhone Technologies 900, 800 Network and User Side Protocols, ACS-PRI/BRI Links to Two Carriers

Introduction ACS-PRI/BRI Card

6.1.3Network and User Side Protocols

In the example application shown in Figure 6-3,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 6-4shows how the application in Figure 6-3would 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.

Carrier A	Carrier B
ISDN Switch	ISDN Switch
Network Side	Network Side
23B+D	23B+D
User Side	User Side

ISDN PBX

Figure 6-4. ACS-PRI/BRI Links to Two Carriers

Figure 6-5shows how the system overcomes these disadvantages. Note that the configuration in Figure 6-5is identical to the one in Figure 6-3.

6-6 Server Cards