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Syed Shahzad Ali


  • The Switch is the entity that first receives the call from the network or  caller.
  • The VRU is the entity that plays audio and preforms prompt-and-collect  functions.

CUCM and/or ACDs can issue Route Requests and can therefore be considered as  Switch leg devices.


Unified ICM perceives calls that need IVR treatment as having two portions:

  • The Switch leg and
  • The VRU leg.

Unified CVP can participate in the Switch role or the VRU role, or both, from  the perspective of Unified ICM.

In a network deployment, multiple Unified CVP devices can also be deployed to  provide the Switch and VRU portions independently.

CVP's IVR Service functions as the VRU leg.

  • The VRU leg is the leg that talks to the VoiceXML Gateway(s).



Hi Syed,

Can you help me understand, how many VXML and Call server ports will be utilized for a single call. I'm very confused about usage of these ports.

At present, in my environment we have 4 CVP servers (v10.0.1) with 850 VXML ports and 900 call servers ports. We are seeing lot of calls coming in and VXML port utilization is approx. 30% say hardly during peak hours it would go to 250 VXML ports being used. However at the same time we are seeing 850+ call server ports being utilized. So the ratio of ports being used for vxml and call server port is like 1:3.

Also what happens if we max out the call server ports? Will the new call fail?

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