Release Trunk Transfer
Release Trunk Transfer releases the ingress trunk and removes Unified CVP and the gateway from the call control loop. These transfers have the following characteristics:
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They can be invoked by VXML Server (Standalone Call Flow Model) or using Unified ICM.
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Unified ICM Network Transfer using Unified CVP as the routing client does not work because Unified CVP can no longer control the call.
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They are blind, that is, if the transfer fails for any reason then Unified ICM does not recover control of the call. Router Requery is not supported.
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They cause the switch leg to terminate resulting in a Telephony Call Dispatcher (TCD) record being written to the database for the call even though the caller is still potentially talking to an agent. This behavior differs from other types of transfers in which the TCD record is not finalized until the caller hangs up.
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As the ingress trunk is released, you do not have to size gateways to include calls that have been transferred using Release Trunk Transfer. This behavior differs from other types of transfers in which gateway resources continue to be occupied until the caller hangs up.
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Because Unified CVP is no longer monitoring the call, you do not have to size Call Servers to include calls that have been transferred using Release Trunk Transfer. Additionally, Unified CVP Call Director port licenses are not required.
Following are the signaling methods available to trigger a release trunk transfer:
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Takeback-and-Transfer. See Takeback-and-Transfer
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Hookflash and Wink. See Hookflash and Wink
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Two B Channel Transfer. See Two B Channel Transfer
Takeback-and-Transfer
Takeback-and-Transfer (TNT), also known as Transfer Connect, is a transfer method where dual tone multifrequency (DTMF) tones are outpulsed to the PSTN by Unified CVP. TNT outpulses DTMF tones to the PSTN. A typical DTMF sequence is *8xxxx, where xxxx represents a new routing label for the PSTN. Upon detection of a TNT DTMF sequence, the PSTN drops the call leg to the Ingress Gateway port, and then reroutes the caller to a new PSTN location, such as a TDM ACD location. This method is offered by a few PSTN service providers.
Customers can use TNT, if they have an existing ACD site but no IVR and want to use Unified CVP as an IVR. Over time, customers may need to transition agents from the TDM ACD to Unified CCE and use Unified CVP as an IVR, queueing point, and transfer pivot point. Using Unified CVP as more than just an IVR eliminates the need for TNT services.
In Unified CVP deployments with Unified ICM, the DTMF routing label that is outpulsed can be a Unified ICM translation routing label to enable passing of call data to another Unified ICM peripheral, such as a TDM ACD. In this scenario, Unified CVP views the call as completed, and Unified CVP call control is ended. With TNT, if the transfer to the termination point fails, Unified CVP cannot reroute the call. Using some TNT services, you can reroute the callback to Unified CVP. However, Unified CVP treats this call as a new call.
Hookflash and Wink
Hookflash and wink are signaling methods that are associated with a TDM PBX or ACD. With the Hookflash feature, Unified CVP can transfer SIP calls using a hookflash followed by the DTMF destination. This feature allows for deployments in which a PBX is in the front-end of the Unified CVP Ingress Gateway, and in which the PBX provides non-VoIP connectivity to agents. Hookflash applies to analog trunks and wink applies to digital trunks (T1 or E1 channel), although both are similar in function. Both hookflash and wink send an on-hook or off-hook signal to the PBX or ACD, which responds with dial tone (or the PBX winks back on a digital trunk). This signaling causes the Voice Gateway to send a string of routing digits to the PBX or ACD. Upon collection of the routing digits, the PBX or ACD transfers the caller to the new termination point, which can be an ACD queue or service on that same PBX or ACD.
Customers can use hookflash and wink if they have an existing ACD but no IVR, and want to use Unified CVP as an IVR that is installed on the line side of their existing PRX or ACD. Over time, the customer may need to transition agents from the TDM ACD to Cisco Unified CCE and have the Voice Gateways connected to the PSTN instead of the line side of the PBX or ACD. In Unified CVP deployments with Unified ICM, the routing label can be a Unified ICM translation routing label. This label enables passing of call data to the ACD service (and subsequently to the agent in a popup message). With hookflash and wink, if the transfer to the termination point fails, Unified CVP cannot reroute the call. Some PBX or ACD models can reroute the callback to Unified CVP. However, Unified CVP treat this call as a new call.
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When PBXs and gateways have constrained support, hookflash transfer becomes difficult. If possible, avoid using the PBX for Unified ICM switching. Also, terminate all incoming calls on Unified CVP ingress gateways to allow Unified CVP to route calls to the PBX rather than on the ingress gateways. |
Following guidelines and notes apply for hookflash transfers:
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Cisco 1700 Series Gateways are not tested with hookflash transfers.
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Cisco 2800 and 3800 Series Gateways can support Analog FXO or Digital FXO (T1/CAS). This function is considered line-side hookflash to the PBX. However, E&M is not supported at this time. You can adjust the hookflash duration with the timing hookflash-out command in voice-port. This feature is useful if you have a PBX that has a nonconfigurable hookflash duration, and it gives you the ability to adjust the hookflash duration on the gateway side.
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Cisco 5x00 Series Gateways are tested with T1/CAS and the e&m-fgb dtmf dnis command. E&M is considered "trunk-side hookflash" to the PBX, and not all switches support trunk-side hookflash. Additionally, the hookflash duration on the Cisco 5x00 Series Gateways is 200 ms, and you must configure the PBX for the same duration. This option varies with switch type and a proof-of-concept with the switch used.
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In Deployment Model No. 1, Standalone Self-Service, a TCL script is required to produce the hookflash. A TCL script is provided with Unified CVP.
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For Digital FXO (T1 CAS) Trunks, configure Dialed Number Identification Service (DNIS) on the gateway, based on the T1/E1 channel on which the call arrives. The PBX is programmed to route DNIS calls over T1 trunks. Configure the DNIS of the gateway because the call arrives to the gateway on that trunk.
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For Digital FXO (T1 CAS) Trunks, configure Dialed Number Identification Service (DNIS) on the gateway, based on the T1/E1 channel on which the call arrives. The PBX is programmed to route DNIS calls over T1 trunks. Configure the DNIS of the gateway because the call arrives to the gateway on that trunk.
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The disadvantage to this approach is that the gateway trunk allocation must be predetermined. You must know the percentage of calls that arrive to a particular DNIS so that the trunk groups on the gateway can be allocated accordingly.
An alternate method, also known as converse on step, can be used on some PBXs where DTMF tones indicating DNIS and ANI are sent to the IVR. This method requires a single main Unified ICM routing script to input DNIS digits using a Get Data (GD) Microapplication and to invoke the correct subscript based on the collected DNIS digits. This method requires close coordination between Cisco, the PBX vendor, and the customer.
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For FGB E&M trunks in Cisco 5x100 Series Gateways, ANI and DNIS can be sent by using "*" as the delimiter, for example, *ANI*DNIS*. For configuration details, see ANI/DNIS Delimiter for CAS Calls on CT1, available at http://www.cisco.com/c/en/us/td/docs/ios/redirect/eol.html.
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Two B Channel Transfer
Two B Channel Transfer (TBCT) is an Integrated Services Digital Network (ISDN)-based release trunk signaling function that is offered by some public switched telephone network (PSTN) service providers. When a TBCT is invoked, the Ingress Gateway places the initial inbound call on hold briefly while a second call leg (ISDN B Channel) is used to call the termination point. When the termination point answers the call, the gateway sends ISDN signaling to the PSTN switch to request to complete the transfer, bridge the call through the PSTN switch, and remove the call from the Ingress Gateway. As with a TNT transfer, the termination point might be a TDM PBX or ACD connected to the PSTN.
This process may be necessary for a customer with an existing ACD site but no IVR, who wants to use Unified CVP initially as just an IVR. Over time, the customer might want to transition agents from the TDM ACD to Cisco Unified CCE and use Unified CVP as an IVR, queueing point, and transfer pivot point (which eliminates the need for TBCT services and using Unified CVP to perform reroute on transfer failure).