6.1.1. Features of BRI

BRI offers advantages or access to features not available on PRI. For example, many ISDN PBX Primary Rate products are designed as terminal equipment (TE) for connection to the central office, and cannot provide network-side access to other terminal equipment. The BRI/SC or BRI/2 board can be used to connect to a PBX.

Both the BRI/SC and the BRI/2 boards provide access to ISDN Layer 3 Supplemental Services. These services can be divided into two categories:

Hold and Retrieve allows the application to place calls on hold, to retrieve held calls and to respond to requests to hold or retrieve held calls using the following Global Call functions: gc_HoldCall( ), gc_RetrieveCall( ), gc_HoldAck( ), gc_HoldRej( ), gc_RetrieveAck( ), and gc_RetrieveRej( ). Refer to the function descriptions in Chapter 2, Applying Global Call Functions to ISDN Applications, for more information.

Messaging allows the application to access other supplemental services, such as Called/Calling Party Identification, Message Waiting and Call Transfer. The services are invoked by formatting information elements (IEs) and sending them as non-call related Facility Messages (SndMsg_Facility) to the PBX or network. See the gc_SndMsg( ), gc_SndNonCallMsg( ), and gc_SetInfoElem( ) functions for information on sending Facility Messages. See the gc_GetCallInfo( ) and gc_GetNonCallMsg( ) functions for information on retrieving Facility Messages. Also refer to Appendix C, "BRI Supplemental Services".

In addition to the features described above, BRI/2 boards provide the following fax and data communications features:

• Fax features - BRI/2 boards support Global Call DSP-based Group 3 Fax. Key features of DSP Fax include:
• Four channels of voice and fax per board
• Maximum of 16 fax channels per system (4 BRI/2 boards in one system)
• Software-based fax modem
• Compatibility with ITU-T Group 3 (T.4, T.30), ETSI NET/30

  
  Note: For more information on using DSP Fax with the BRI/2, see the Fax Software Reference for Windows.

  
  
• Data features - BRI/2 boards provide link layer access, across the B channel, which allows for reliable transfer of data across an ISDN network. The BRI/2 boards offer Network Device Interface Specification (NDIS) compatibility. NDIS is a Microsoft® standard that allows for multiple network adapters and multiple protocols to coexist. NDIS permits the high-level protocol components to be independent of the BRI/2 by providing a standard interface. This means that the BRI/2 may be used by applications that use the standard networking APIs that are part of the Windows operating system. NDIS supports Remote Access Service (RAS) and Point-to-Point Protocol (PPP):
• Remote Access Service (RAS) - RAS is enabled via NDIS and allows users to interact with the service selections provided by the specified dial-up networking setup.
• Point-to-Point Protocol (PPP) - PPP is a method of exchanging data packets between two computers. PPP can carry different network layer protocols over the same link. When the PPP connection sequence is successfully completed, the remote client and RAS server can begin to transfer data using any supported protocol. PPP Multilink provides the ability to aggregate two or more physical connections to form one larger logical connection, improving bandwidth and throughput for remote connections.

The BRI/SC boards provide a different set of ISDN features. Advantages and features specific to BRI/SC boards include the following:

• Data Link Layer Access - the BRI/SC products have data link layer access (also known as LAPD Layer 2). This feature provides for the reliable transfer of data across the physical link (physically connected devices), and sends blocks of frames with the necessary synchronization, error control, and flow control. Layer 2 access is particularly useful if you want to use a Global Call ISDN board to connect to a switch using a Layer 3 protocol that is not provided in the firmware.
• Point-to-Multipoint Configuration - this feature allows BRI/SC protocols to support multiple TEs to be connected to a line that is configured to be a network. Up to eight TEs may be connected with a maximum of two active, non-held calls at a time. An unlimited number of calls may exist in a held state, but these calls cannot be retrieved if both B channels are already in use by other calls.
• Tone Generation - this feature allows BRI/SC protocols, under a network configuration, to generate and play tones on any B channel with the use of the on-board DSP chip. These tones can be requested and configured by the application or they can be generated by the firmware.

Note: Global Call does not provide functions for tone management. The ISDN call control library functions cc_ToneRedefine( ), cc_PlayTone( ), and cc_StopTone( ) are appropriate in this context. However, the use of the ISDN call control library is not officially supported and the ISDN Software Reference, in which these functions are documented, may not be included in the documentation for future system releases.

• Multiple D Channel Configuration - this feature allows the D channel of each line to be configured at any time, and as many times as needed. The application can configure and reconfigure the protocol for each station interface, allowing you to run different protocols on different stations simultaneously. The application can also change between User side and Network side, assign and change the Service Profile Identifier (SPID), and change other attributes such as the generation of in-band tones. See the gc_SetDChanCfg( ) function description in Chapter 2, Applying Global Call Functions to ISDN Applications, for more information.
• 5ESS Custom Messaging - the 5ESS protocol has a custom messaging feature, which allows the application to send requests to drop calls and to redirect the state of calls. See the gc_SndMsg( ) function description in Chapter 2, Applying Global Call Functions to ISDN Applications, for more information.

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