Incoming Fax doesn't work

[Support Albakom]

Hi,

we have an CUCM 8.5 connected via MGCP Gateway (Cisco 2911) to the PSTN. At the gateway there are 4 FXS ports configured with SCCP at the CUCM.

Now we have following. One fax machine in PSTN calls a fax machine which connected to one of the FXS ports.

This is the incoming debug isdn q931:

001674: Oct 12 14:11:03.578: ISDN BR0/2/1 Q931: RX <- SETUP pd = 8  callref = 0x01

        Bearer Capability i = 0x9090A3

                Standard = CCITT

                Transfer Capability = 3.1kHz Audio

                Transfer Mode = Circuit

                Transfer Rate = 64 kbit/s

        Channel ID i = 0x89

                Exclusive, B1

        Progress Ind i = 0x8583 - Origination address is non-ISDN

        Calling Party Number i = 0x2181, 'XXX206XXX'

                Plan:ISDN, Type:National

        Called Party Number i = 0xC1, '1234408'

                Plan:ISDN, Type:Subscriber(local)

001675: Oct 12 14:11:03.586: ISDN BR0/2/1 Q931: TX -> SETUP_ACK pd = 8  callref = 0x81

        Channel ID i = 0x89

                Exclusive, B1

001676: Oct 12 14:11:03.670: ISDN BR0/2/1 Q931: RX <- INFORMATION pd = 8  callref = 0x01

        Called Party Number i = 0xC1, '4'

                Plan:ISDN, Type:Subscriber(local)

001677: Oct 12 14:11:03.670: ISDN BR0/2/1 Q931: TX -> DISCONNECT pd = 8  callref = 0x81

        Cause i = 0x8081 - Unallocated/unassigned number

001678: Oct 12 14:11:03.718: ISDN BR0/2/1 Q931: RX <- INFORMATION pd = 8  callref = 0x01

        Called Party Number i = 0xC1, '4'

                Plan:ISDN, Type:Subscriber(local)

You see this call fails.

But now I called from another fax machine to the same number: It works:

Here is the debug isdn q931 output:

001699: Oct 12 14:13:06.881: ISDN BR0/2/0 Q931: RX <- SETUP pd = 8  callref = 0x01

        Bearer Capability i = 0x9090A3

                Standard = CCITT

                Transfer Capability = 3.1kHz Audio

                Transfer Mode = Circuit

                Transfer Rate = 64 kbit/s

        Channel ID i = 0x89

                Exclusive, B1

        Calling Party Number i = 0x2183, '5555555'

                Plan:ISDN, Type:National

        Called Party Number i = 0xC1, '123440844'

                Plan:ISDN, Type:Subscriber(local)

001700: Oct 12 14:13:06.889: ISDN BR0/2/0 Q931: TX -> CALL_PROC pd = 8  callref = 0x81

        Channel ID i = 0x89

                Exclusive, B1

001701: Oct 12 14:13:06.921: ISDN BR0/2/0 Q931: TX -> ALERTING pd = 8  callref = 0x81

        Progress Ind i = 0x8088 - In-band info or appropriate now available

001702: Oct 12 14:13:13.762: ISDN BR0/2/0 Q931: TX -> CONNECT pd = 8  callref = 0x81

001703: Oct 12 14:13:13.866: ISDN BR0/2/0 Q931: RX <- CONNECT_ACK pd = 8  callref = 0x01

Can somebody say why the first call fails?

[andypoore]

Hi

This maybe a simple CSS partition issue, can you dial the fax internally from a phone?

Sent from Cisco Technical Support iPad App

[acampbell]

Hi,

The 1st call is using over lap signalling from the PSTN.

Try adding this to your BRI interfaces

!

interface BRI 0/2/0

isdn overlap-receiving

isdn overlap-receiving T302 2000

!

!

interface BRI 0/2/1

isdn overlap-receiving

isdn overlap-receiving T302 2000

!

HTH

Alex

[andypoore]

Apologies didn't read the debug in it's entirety, Alex is probably right as the last two digits are sent after the call setup.

Sent from Cisco Technical Support iPad App

[acampbell]

Andy,

I had a look on my lab set up.

Not sure if ISDN BRI is going to support the OVERLAP signalling under MGCP.

You may need to change to H323.

HTH

Alex

[andypoore]

Hi Alex

Cisco have never been explicit on the matter, and this depends on which country this ISDN line is in, it looks suspiciously like it's not overlap sending of the digits from the Telco, but the T302 timing out before all the digits are received, I haven't used BRI in a long time but it's worth extending the timer via the command line and via the CUCM parameters, although again I'd have to check if changing it applies to both back hauled PRI and BRI.

Interested to see the results though.

Sent from Cisco Technical Support iPad App

[Support Albakom]

isdn overlap-receiving T302 is already set to 5000 at all BRI interfaces and seems that it doesn't influence any if gateway configured with MGCP. I cant configure as H323 because we have just changed to MGCP while great trouble with ISDN channels with H323-configuration and overlap dialing.

[acampbell]

Hi,

Clutching at straws here now re the overlap receiving.

You could check the following service parameter.

Service Parameters --> Call Manager --> (DEVICE PRI & MGCP SECTION) -->

Overlap Receiving Flag for PRI.

Check this is set to TRUE

Other than changing back to H323 I can not think of how else to resolve this

HTH

Alex