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When running Video Telephony Advantage (VTA), outbound calls fail from Cisco CallManager through H.323 gateways to PSTN

Core Issue

If a user has the Video Telephony (VT) Advantage client running on a PC and attempts an outbound call through an H.323 gateway, the call may fail. The user may see a release complete from the gateway similar to this:

Inbound H225 RELEASE_COMP message from 10.0.0.23 at 
timestamp 07/28/2004 11:44:42.077 RELEASE_COMP, pd =
8, callref = 0x81AC, Message Size = 65 bytes
Cause i = 0x80E4 - Invalid IE contents  User-User, i =
0x052580060008914A000201110000C0D408B0FE911DAC
0100000A00011806A00100130140B50000120C60010400010805080380E404

The IE field that is identified as invalid can consist of many different IEs that describe the features and capabilities of a given call. For instance, a single Setup message contains more than 15 different IEs, including these:

  • Called party number
  • Calling party number
  • Bearer capability
  • Transit network selection
  • Date and time

The bearer capability IE is important in addressing issues where the setup is released due to invalid contents. The bearer capability IE identifies which capabilities a call is requesting from the network, and it is responsible for conveying the actual call characteristics to the called device and negotiates between both devices. This IE must be present and valid in the Setup message or the call fails.

In this case, the bearer capability is i = 0x8890A2, which translates to this:

  • Information Transfer Capability: Unrestricted digital information
  • Transfer Mode: Circuit Mode
  • Information Transfer Rate: Multirate. 64 kbps base rate, Rate = 384 kbps, == 6 B channels
  • User Information Layer 1 Protocol: H.221 and H.242

The release is due to Cisco CallManager setting up a call with video capabilities that the called device is incapable of accepting.

Resolution

A workaround to this problem is to issue the bearer-cap speech command under the voice port. This command forces the calls to use audio only, allowing the calls to work. This bypasses the bearer capabilities mismatch.

Since this call is across an H.323 gateway to the Public Switched Telephone Network (PSTN), and video calls should never be required in this case, there should be no problem disabling video call capability.

Version history
Revision #:
1 of 1
Last update:
‎06-22-2009 03:37 PM
Updated by:
 
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