CUCM to CVP calls. CTI-RP vs Route Pattern

Question

CVP 9 or above
CUCM 9 or above
Requirement:
1. Consultive Warm Transfer - The agents to be able to transfer calls to a a different department by dialing an internal number and wait in the queue until answered.
2. Internal - Back-office people to dial internal IT-Helpdesk or HR
I see the above call flows as same, i.e. a Call Originating from CUCM to CVP .... correct me please?
I have tested both and they both work exactly the same way, i.e. using a CTI-RP associated to PGUSER, ICM answers it sends correlation id to CUCM and CUCM sends this to CVP ...AND... using a simple route patters instead point to CUCM-CVP SIP trunk. Functionally they behave same way - ICM/CVP answers and queues call until answered.
But the documentation confuses me, below snippet from CVP Config Guide
"... Calls Originated by Unified CM
Internal Help Desk calls: For these calls, the Unified Communication Manager (CM) phone user calls a CTI Route Point
Consultative Warm Transfer: For these calls, a Unified CM agent places the caller on hold and dials in to Unified ICME to reach a second agent .... "
And then on the same doc, there a Note
(*1) Note For warm transfers, the call from Agent 1 to Agent 2 does not typically use a SIP Trunk, but you must configure the CTI Route Point for that dialed number on the Unified CM server and associate that number with your peripheral gateway user (PGUSER)
(*2) And then again on the same doc under 'Unified ICME Warm Consult Transfer/Conference to Unified CVP' chapter/section it mentiones doing this using a Route Patter 'Create a route pattern and assign the route list to the route pattern'
So the confusion is
1. Why treat these call flows as Internal and Warm Transfer - they are calls from CUCM to CVP for the same end result - queue the call and transfer to an agent?
2. Route pattern or CTI-RP, what diff it makes? They both behave the same way, so is there a diff from reporting point of view that a call to CTI-RP are treated as Transferred rather than new calls or what?
3. Also if you compare (*1) & (*2) above, they both talk about Warm Transfer and *1 says 'must use CTI-RP' and *2 says use a Route Pattern?
Please assist.
Thanks & Regards,
Kartik

Answer 1

Kartik,
The Route Pattern that is mentioned is used for connecting a call leg through CVP to a local VXML Gateway for media playback. The CTI Route Point is entirely different from the Route Pattern/Route List setup. Here's the basic call flow:
Internal caller dials DN
DN hits CTI RP in CUCM. CTI RP sends call to ICM.
ICM matches DN to Call Type to Script, executes Script.
At some point, Script has either Send To VRU or a Run Ext. Script node.
ICM sends CUCM Network VRU label back to CUCM.
CUCM routes label using Route Pattern and Route List. The CSS of the internal caller determines how this is modified, i.e. which prefix digits to add for determining VXML gateway to route to.
Call is sent to CVP through SIP trunk
CVP receives call, tells ICM it has the call.
CVP starts new call leg to VXML gateway with digit string to match bootstrap dial-peer.
VXML Gateway receives call, initiates bootstrap TCL and VXML magic.
Yes, this is basically the same call flow for a fresh internal call to a queue, or an internal warm transfer to a queue. The CTI Route Point is needed in both cases. The Route Pattern/Route List combo is needed in both cases.
When you start looking at reporting, yes of course the two call scenarios are different. One is a transfer, the other isn't. The transferred call will have a more complex call history if you look at it in the TCDR.
From the standpoint of call legs, you will use less legs if you do a direct (one-step) transfer instead of a warm transfer. It is also simpler to maintain the call context in that case. In a warm transfer scenario, the agent is putting a caller on hold, then starting a new call, and joining the two calls together. The new call is coming from the agent, not the original caller. In a direct transfer, CVP just takes back the original call, potentially does more queuing, then sends the original caller to a new agent target.
-Jameson