[cisco-voip] "Random" Call drops

[William Roy]

We are seeing random call drops on calls made from an CUCM site via the PSTN to another site where the phones are connected to a Siemens PABX. The CUCM is 6.1.1-200-3 and the calls are being made via a 3845 - h323 gateway connected to an E1 telco service with switchtype primary-net5. The random call drops  have not been reported to any other external numbers which go via the same E1, only to this specific site with the Siemens Pabx. The problem may also have started when the CUCM phone system was reconfigured to append a carrier access code to external numbers to swap the service provider for cheaper rates. We are currently seeing if sending calls via the default carrier fixes the issue. I managed to capture a debug isdn q931 of a call dropping. The Cisco gateway is receiving the following disconnect code: "   Cause i = 0x80FF - Interworking error; unspecified". Looking up the cause code - the point of origin 0x80 means that this was from the router, why would the router receive a disconnect from itself?


464020: Jan  6 13:15:12.130 WST: ISDN Se0/0/0:15 Q931: TX -> SETUP pd = 8  callref = 0x415B
        Sending Complete
        Bearer Capability i = 0x8090A3
                Standard = CCITT
                Transfer Capability = Speech
                Transfer Mode = Circuit
                Transfer Rate = 64 kbit/s
        Channel ID i = 0xA98387
                Exclusive, Channel 7
        Calling Party Number i = 0x0081, '35525'
                Plan:Unknown, Type:Unknown
        Called Party Number i = 0x80, '18875093114171'
                Plan:Unknown, Type:Unknown
464021: Jan  6 13:15:12.214 WST: ISDN Se0/0/0:15 Q931: RX <- CALL_PROC pd = 8  callref = 0xC15B
        Channel ID i = 0xA98387
                Exclusive, Channel 7
464022: Jan  6 13:15:13.974 WST: ISDN Se0/0/0:15 Q931: RX <- ALERTING pd = 8  callref = 0xC15B
        Progress Ind i = 0x8488 - In-band info or appropriate now available
        Progress Ind i = 0x8082 - Destination address is non-ISDN
464025: Jan  6 13:15:19.114 WST: ISDN Se0/0/0:15 Q931: TX -> ALERTING pd = 8  callref = 0xB0D2
        Progress Ind i = 0x8188 - In-band info or appropriate now available
464026: Jan  6 13:15:22.830 WST: ISDN Se0/0/0:15 Q931: RX <- CONNECT pd = 8  callref = 0xC15B
464027: Jan  6 13:15:22.834 WST: %ISDN-6-CONNECT: Interface Serial0/0/0:6 is now connected to 18875093114171 N/A

464028: Jan  6 13:15:22.834 WST: ISDN Se0/0/0:15 Q931: TX -> CONNECT_ACK pd = 8  callref = 0x415B

464063: Jan  6 13:16:34.953 WST: ISDN Se0/0/0:15 Q931: RX <- DISCONNECT pd = 8  callref = 0xC15B
        Cause i = 0x80FF - Interworking error; unspecified
464065: Jan  6 13:16:34.953 WST: %ISDN-6-DISCONNECT: Interface Serial0/0/0:6  disconnected from 18875093114171 , call lasted 72 seconds

464066: Jan  6 13:16:34.953 WST: ISDN Se0/0/0:15 Q931: TX -> RELEASE pd = 8  callref = 0x415B
464067: Jan  6 13:16:34.973 WST: ISDN Se0/0/0:15 Q931: RX <- RELEASE_COMP pd = 8  callref = 0xC15B


Regards,

Wil

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