Symptom

Calls in duration over 15 minutes involving CUBE and UCCE may be dropped. This is a deployment in which the CUBE forks media for recording at MediaSense.

Conditions

Make a call involving UCCE and CUBE. Leave the call up for 15 minutes. This roughly occurs 1 out of a 100 kiosk under traffic. It is difficult to determine the exact call rate failure as this is a very intermittent issue. The worst case we have observed is 1 call failure in the first 100 calls attempted. The reason for the call drop is that after 15 minutes CUCM attempts to refresh the session between CUCM and CUBE by sending a SIP re-INVITE message. Sometimes (rarely) CUBE ignores this re-INVITE message. Thus, CUCM concludes that the call/session is not really active and tears down the call by sending a BYE message to CUBE.

Workaround

There are two workarounds that can be configured to prevent this problem from occurring. 1) On CUBE configure voice service voip sip midcall-signaling passthru media-change And on each dial-peer configure no voice-class sip session refresh The midcall-signaling pass thru media-change cause CUBE to not forward mid call RE-INVITES that do not have a different SDP. If the SDP does not change then the RE-INVITE is not forwarded. The no voice-class sip session refresh keeps CUBE from refreshing any dialogs/call legs. With the above configuration no call drops have been observed. 2) Disable session refresh Re-INVITES on CUCM for the length of the call. This can be done by setting the session refresh timer and min SE timer fields on the service parameter, ccm service, admin web page. Set these values to twice the expected length of the longest call. For example, if a customer believes it is highly unlikely to ever experience a call duration greater than say 2 hours, set the refresh timer and min SE timer to 4 hours. Note, these timer values are specified in seconds. Thus, 14400 is the value to use for 4 hours. CUCM sends refresh re-INVITES 1/2 the value of the session timer per RFC 4028. Work around 1 is the recommend since it only involves configuration on the CUBE.

Further Problem Description