This document describes a common scenario of delay seen in fetching a first prompt which is generally a welcome wav file in cvp comprehensive call flow
Cisco recommends that you have knowledge of these topics:
- Cisco Unified Contact Center Enterprise (UCCE)
- Cisco Unified Customer Voice Portal (CVP)
- Cisco IOS and VXML Gateways
The information in this document is based on these software versions:
- Cisco Unified Customer Voice Portal (CVP) Release 11.X
- Cisco IOS Gateway with Cisco IOS software train 15.4(x)M acting as ingress gateway
- VXML Gateway running on the same ingress gateway
When the Customer calls in they experience a silence of 2 seconds after which IVR prompt starts playing. Analyis of CVP and VXML gateway logs explained here reveal that the delay experienced is because CVP takes more than 2 seconds to respond to the HTTP ping and HTTP NEW_CALL request generated from the VXML gateway.
VXML gateway creates HTTP PING message destined for the CVP call server at "16:11:31.292"
16:11:31.292: //199995//HTTPC:/httpc_write_stream: Client write buffer fd(0):
GET /cvp/VBServlet?MSG_TYPE=PING&CALL_DNIS=77777777771319&CALL_ANI=sip:xxx-xxx-xxxx@X.X.X.X:5060&ERROR_CODE=0&RECOVERY_VXML=flash:recovery.vxml&CLIENT_TYPE=IOS&CALL_ID=C350CF8000010000000003BD9663630E&CALL_LEGID=C350CF8000010000000003BD9663630E-1448554499804567@X.X.X.X&CALL_UUI=&VERSION=CVP_10_5_1_0_0_0_189 HTTP/1.1
CVP respond's back to the PING at "16:11:32.452" where the time difference is more than 1 second
16:11:32.452: processing server rsp msg: msg(212BBA48)URL: http://X.X.X.X:8000/cvp/VBServlet?MSG_TYPE=PING&CALL_DNIS=77777777771319&CALL_ANI=sip:4692551000@X.X.X.X:5060
This repsonse triggers VXML gateway to now generate a HTTP NEW CALL request which is at "16:11:33.064"
16:11:33.064: //199995//HTTPC:/httpc_write_stream: Client write buffer fd(0):
GET /cvp/VBServlet?MSG_TYPE=CALL_NEW&CALL_DNIS=77777777771319&CALL_UUI=&CALL_ANI=sip:xxx-xxx-xxxx@X.X.X.X:5060&RECOVERY_VXML=flash:recovery.vxml&CLIENT_TYPE=IOS&CALL_ID=C350CF8000010000000003BD9663630E&ERROR_CODE=0 HTTP/1.1
CVP responds back to this request at "16:11:34.112" where the time difference is again 1 second or more
16:11:34.112: processing server rsp msg: msg(212BBC48)URL: http://X.X.X.X:8000/cvp/VBServlet?MSG_TYPE=CALL_NEW&CALL_DNIS=77777777771319&CALL_UUI=&CALL_ANI=sip:xxx-xxx-xxxx@X.X.X.X:5060&RECOVERY_VXML=flash:recovery.vxml
This exchange of HTTP ping , HTTP NEW Call request and response from CVP cosumes more than 2 seeconds which is experienced by the caller as silence.
The reason CVP server has a delay in response is due to the tomcat process where it takes some time for it to establish a TCP connection and segments packets to 590 bytes each. To fix this condition on the VXML gateway configure the command "ip tcp mss 1500"
Note: This is issue is tracked under the defect "CSCuq07550 - CVP 10.0 tomcat delays when VxML gateway in a different subnet"