Digital protocol - PRI feature

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Digital protocol - PRI feature

Type of feature

The Primary Rate Interface (PRI) digital protocol is a licensed feature. You must have RTU licenses to use this feature.

About the PRI digital protocol feature

PRI is an ISDN configuration that functions like an enhanced T1 circuit. ISDN is an international telecommunications standard for voice, video, and data transmission over digital lines. The system supports AT&T PRI, National ISDN, ETSI, and Nortel PRI. With PRI, the system can communicate with any PBXs or switches that support the above mentioned protocols.

PRI is desirable for customers who need faster call-setup times, special signaling, or access to the information elements that are available with PRI. Such information elements as ANI, DNIS, redirecting number, and service type are available for incoming PRI calls. Outbound calls can provide information elements like outbound ANI and service type.

The Avaya IR system supports non-facility associated signaling (NFAS) across both spans on a single digital telephony card.

Hardware requirements

At least one digital telephony card must be installed and operational.

Software requirements

The PRI digital protocol feature requires the NMS package (AVnms) software.

Application development considerations

The following considerations apply to application development for PRI:

IVR Designer. The Answer Call and Disconnect nodes and the Make_Call and Call_Bridge external functions are supported by PRI. The Call Transfer node is not supported by the PRI protocol.
TAS. Several capabilities are available to implement the PRI feature in TAS applications. The tic instruction is used for basic control of incoming and outgoing calls on the PRI. The tic(`C') instruction provides additional return code information over the T1 implementation. For more information, see TAS script instructions.
IRAPI. The irCall() , irAnswer() , irDial() , and irDisconnect() functions provide the basic call control capabilities for T1 interfaces. The irSetIE() and irGetIE() can be used to set and get information elements available only with PRI.

Using this feature

Switch integration for the PRI feature is done using the Digital Interfaces screen in Web Administration. You must select ISDN-Primary Rate Interface T1 or ISDN-Primary Rate Interface E1 from the Digital Interfaces screen, and configure digital interfaces as follows:

Configure T1 cards with Non-Facility Associated Signaling (NFAS) or without NFAS. When a T1 card is administered with NFAS, the first trunk on the card carries the D-channel for both trunks on the card. The second trunk on the card is administered to have no D-channel. Thus, with NFAS, the card has 1 D-channel and 47 B-channels (23 B-channels from the first trunk and 24 B-channels from the second trunk).

When a T1 card is administered without NFAS, both trunks must be administered to have a D-channel. Without NFAS, each trunk has one D-channel, the 24th channel of the trunk, and 23 B-channels.

The D-channel cannot be used to run applications. It carries messages between the switch and the system. These messages are used to control the state of calls on all the other PRI channels. The B-channels (bearer channels) provide two-way audio channels to run applications. Therefore, on a PRI trunk that has a D-channel, the first 23 channels (B-channels) on that card can be used to run applications. The 24th channel (D-channel) is reserved for call control.

For E1 PRI, channel 0 is reserved for framing and channel 16 is reserved for the D channel, the remaining 30 channels are B-channels. Each E1 PRI trunk has its own D-channel. NFAS configurations are not supported for E1 PRI.

For more information

For more information on PRI digital protocols, see:

For more information on related features, see: