Core Issue
When an IP phone calls the voice mail pilot number, the Cisco Unity voice mail port receives StationStartMediaTransmissionID, but does not transmit a Real-Time Transport Protocol (RTP) stream. Cisco Unity fails to create an RTP stream when the Skinny messages are split between packets due to fragmentation.
These are the error messages logged in the Event Viewer:
Event Type: Warning
Event Source: AvCs_MC
Event Category: None
Event ID: 101
Date: 10/13/2003
Time: 10:49:50 AM
User: N/A
Computer: UNITY
Description:
Assertion failed: dwCurrentPacketSize >= sizeof(UINT32) in File:
e:\views\skinny\un_Applications\Skinny\AvSkinnyTsp\Skinny.cpp at Line: 507
Event Type: Warning
Event Source: CiscoUnity_TSP
Event Category: None
Event ID: 117
Date: 10/13/2003
Time: 3:35:27 PM
User: N/A
Computer: UNITY
The environment where the problem was observed was in Cisco Unity 3.1(5), TSP 6.0(2)b, TSP7.0(3) and Cisco CallManager 3.3(3)sr1.
Resolution
This problem only occurs for specific Cisco CallManager operating systems to which the Cisco Unity is registered to. It also happens due to fragmentation.
These symptoms are observed in Cisco bug ID CSCec60226.
The workaround for this problem is to change this Cisco CallManager server registry entry to 1:
HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\EnablePMTUDiscovery
Make sure to reboot the Cisco CallManager after changing the registry entry. For more details, refer to Cisco bug ID CSCec60226 or CSCec58236.
