Two B-Channel Transfer (TBCT)

Overview:

Feature F-1638 Release Link Trunk utilizes the Two-Bearer Channel Transfer technique for ISDN NI2 to off load two b-channels which are bridged or looped on the IMG. If there are two calls active on the IMG and they are bridged or looped together the resources on the IMG are being used inefficiently. With this feature the IMG has the ability to send specific facility messages back to the Stored Program Control Switch (SPCS) on the PBX or TDM switch and tell the PBX/TDM switch to connect these two calls together so they are no longer active on the IMG. This would effectively open up two b-channels on the IMG that were initially being utilized. Below is information on how TCBT is utilized and configured on the IMG.

Feature F-0858 Explicit Call Transfer Support is also now supported on the IMG. All functionality for ECT is the same as that for TBCT. Explicit Call Transfer is supported in E1 where TCBT is supported for T1. ECT is configured and operates the same as TCBT.

 

Call Flow Diagram: (ISDN to SIP)

cf_tbct_isdn_to_sip.png

 

Note: Prior to Software 10.5.3 SP3 the TBCT feature was supported being initiated from the TDM side. In 10.5.3 SP3 TBCT was updated to support a call initiating from the SIP side as well. See call flow below.

Call Flow Diagram: (SIP to ISDN)

cf_tbct_sip__to_isdn.png

 

Diagram:

Below is diagram explaining how TBCT would operate in an ISDN to SIP network.

 

  1. Two calls are in progress. The SIP side sends a REFER message to the IMG telling the IMG to connect the two calls together.

    dg_f1638_2bct_step1.png




     

  2. After the call is bridged in the IMG, the SIP leg is no longer connected. Call A and Call B are now routed through IMG as shown below.

    dg_f1638_2bct_step2.png






     

  3. With F-1638 Two Bearer Channel Transfer “Enabled”, the IMG will recognize that the call does not need to be routed through it. The bridged call is using resources on the IMG that could be used for other functions. The IMG would then send a request to the SPCS/Switch B (Stored Program Control Switch) that the two independent calls be bridged together as shown below.

    dg_f1638_2bct_step3.png



     

  4. At this point, the call is being routed through Switch B and the IMG has released the call thereby freeing resources on both the IMG and the SPCS.
     

 

Configuration:

 

Initial Configuration:

The procedure below explains how to configure the IMG for TBCT. Verify the following entities are configured before proceeding:

 

Configure these initial objects before proceeding to the procedure below.

 

Feature Configuration:

 

  1. Right click on the Physical IMG node and select New Signaling. A Signaling object will get created. This is a placeholder for multiple signaling objects. No configuration is needed here. For more information, see Signaling.

  2. Right Click on the Signaling object created and select New ISDN.  An ISDN D Channels object will get created.  This is a placeholder for multiple signaling objects. No configuration is needed here. For more information see ISDN Signaling.

  3. Right Click on ISDN D Channels object and select New ISDN D Channel. Select which Interface and Channel to configure the D-Channel on. See Configuring ISDN Signaling or ISDN D Channel for more information on configuring this object and other ISDN configuration.

  4. Right Click on Dialogic IMG EMS and select New Routing Configuration. The routing configuration object will appear. This object is a placeholder object and no configuration is accomplished within this object. See Routing Configuration for more information.

  5. Right Click on Routing Configuration and select New Channel Groups. The channel group object will appear. This object is a placeholder object and no configuration is accomplished within this object. See Channel Groups for more information.

  6. Right Click on the Channel Groups object just created and select New Channel Group. Enter a name for the channel group and select ISDN as the signaling type. By selecting ISDN, the Channel Transfer field can now be enabled or disabled.

  7. To enable the Two Bearer Channel Transfer feature, select ‘enable’ from the drop down menu in the ‘Channel Transfer’ field. See screen capture below. For more information on Channel Group pane see Channel Group.

    sc_f1638_channel_transfer_en.png

     

  8. Once the Two Bearer Channel Transfer has been enabled, complete the ISDN Channel group by configuring the D-Channel created earlier into the ISDN Channel Group. Right Click on Ch_Grp_ISDN_2BCT – ID:0  and select New ISDN Group. See ISDN Group for more information on configuring this object.

  9. At this point the feature has been enabled and can now be added to a Route Table, Route List, or Translation Table.

  10. Below is screen capture of tree within ClientView once the above procedure has been configured

    sc_tree_f1638_cv_pane.png

 

Additional Information:

 

Related Topics:

Channel Group