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New Member

GSM ISDN Data Calls terminating on BRI....

Hi, I'm trying to terminate a GSM ISDN Data call (v.110) on a BRI int in a 3620.

With 12.2(5) the following "debug isdn q931" indicated the ISDN call coming up with a bind to the dialler. The "debug ppp negotiation" (not included here) indicated no incoming LCP packets, just the router sending them to the GSM mobile device.

30w2d: ISDN BR0/0: RX <- SETUP pd = 8 callref = 0x4B

30w2d: Bearer Capability i = 0x8890214802BB

30w2d: Channel ID i = 0x89

30w2d: Progress Ind i = 0x8181 - Call not end-to-end ISDN, may have in-band info

30w2d: Calling Party Number i = 0x00, 0x80, '7610', Plan:Unknown, Type:Unknown

30w2d: Called Party Number i = 0x80, '5334', Plan:Unknown, Type:Unknown

30w2d: ISDN BR0/0: Event: Received a DATA call from 7610 on B1 at 64 Kb/s

30w2d: ISDN BR0/0: Event: Accepting the call id 0x3C

30w2d: %DIALER-6-BIND: Interface BR0/0:1 bound to profile Di1

30w2d: %LINK-3-UPDOWN: Interface BRI0/0:1, changed state to up

30w2d: ISDN BR0/0: TX -> CALL_PROC pd = 8 callref = 0xCB

30w2d: Channel ID i = 0x89

30w2d: ISDN BR0/0: TX -> CONNECT pd = 8 callref = 0xCB

30w2d: ISDN BR0/0: RX <- CONNECT_ACK pd = 8 callref = 0x4B

30w2d: %ISDN-6-CONNECT: Interface BRI0/0:1 is now connected to 7610

30w2d: ISDN BR0/0: RX <- DISCONNECT pd = 8 callref = 0x4B

30w2d: Cause i = 0x8190 - Normal call clearing

30w2d: %ISDN-6-DISCONNECT: Interface BRI0/0:1 disconnected from 7610 , call lasted 10 seconds

30w2d: %LINK-3-UPDOWN: Interface BRI0/0:1, changed state to down

30w2d: %DIALER-6-UNBIND: Interface BR0/0:1 unbound from profile Di1

30w2d: ISDN BR0/0: TX -> RELEASE pd = 8 callref = 0xCB

30w2d: Cause i = 0x8090 - Normal call clearing

30w2d: ISDN BR0/0: RX <- RELEASE_COMP pd = 8 callref = 0x4B

In reading what Cisco has on V.110 (BC & LCC) and advice from a GSM q931 expert, we suspected the rate adaptation to be the problem.

Cisco recommend use of the BRI int command "no isdn v110 padding" specifically for GSM data calls. This command is supported from 12.2(8).

After upgrading to 12.2(29) the following debug is seen. However the ISDN call will now not come up at all, indicating the router cannot support the bear capability.

00:03:30: ISDN BR0/0: RX <- SETUP pd = 8 callref = 0x7C

00:03:30: Bearer Capability i = 0x8890214802BB

00:03:30: Channel ID i = 0x89

00:03:30: Progress Ind i = 0x8181 - Call not end-to-end ISDN, may have in-band info

00:03:30: Calling Party Number i = 0x00, 0x80, '7610', Plan:Unknown, Type:Unknown

00:03:30: Called Party Number i = 0x80, '5334', Plan:Unknown, Type:Unknown

00:03:30: ISDN BR0/0: Event: Received a V.110 call from 7610 on B1 at 64 Kb/s

00:03:30: ISDN BR0/0: Event: Accepting the call id 0x2

00:03:30: ISDN BR0/0: TX -> CALL_PROC pd = 8 callref = 0xFC

00:03:30: Channel ID i = 0x89

00:03:30: ISDN BR0/0: TX -> DISCONNECT pd = 8 callref = 0xFC

00:03:30: Cause i = 0x80BA - Bearer capability not available

00:03:30: ISDN BR0/0: RX <- RELEASE pd = 8 callref = 0x7C

00:03:30: ISDN BR0/0: TX -> RELEASE_COMP pd = 8 callref = 0xFC

Any suggestions would be appreciated.

Regards

Alan

2 REPLIES
VIP Purple

Re: GSM ISDN Data Calls terminating on BRI....

Hello,

can you try and configure the BRI interface with the command 'isdn incoming-voice modem', and see if that makes a difference ?

Regards,

GP

New Member

Re: GSM ISDN Data Calls terminating on BRI....

Hi GP,

Thank you for the tip. When tried the bearer capability is still not available;

See Config and Debug A in attachment.

With further consideration of the comments (following paragraph) from the GSM q931 expert I mentioned before and points from this Cisco technote, I'm getting more doubtful.

"the Cisco ISDN2 line must support the LLC (9.6k V11O etc) detailed. The default setting for a fixed ISDN line is a LLC of 64kbits UDI, thus the fixed ISDN is only expecting receive 64kbit LLC calls, so when a call is received with the LLC set to a different value the fixed ISDN line is not able to support this particular LLC value, Where an fixed ISDN call receives an unknown LLC it will either fail to answer the call or answers the call which will be dropped after around 20 seconds."

http://www.cisco.com/en/US/tech/tk801/tk36/technologies_tech_note09186a00802b2527.shtml

Particularly from the technote;

- The only Cisco equipment that implements V.110 is digital internal modems (and only for ISDN connections).

-Note: Be aware that ISDN parses V.110 parameters in the bearer capability (BC) Information Element (IE) for PRI, but it does not parse them for BRI. For BRI, ISDN only supports V.110 parameters in low layer compatibility (LLC).

Further I have tried with internal digital modems, but a hardware compatibility error indicates the modems cannot be used with a BRI and gives a new code indicating a bearer cannot be supplied to the incoming call. (see debug B attached)

The GSM call includes the v110 parameters in the BC part, but the Cisco BRI needs them in a LLC part.

Unless there are other configuration options with the current hardware I see two options;

- Use PRI - (this solution's budget will not permit)

- Use an external TA (isdn modem) in to the aux port of the 3620. (an isdn modem that can set the call up from only the BC part)

Any further suggestions would be appreciated.

Regards

Alan

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