[cisco-voip] What controls bearer-cap?

[Robert Kulagowski]

I'm generating a PRI for internal use (it's connected to the PRI
modules of a Polycom HDX 4002).  I also have a PRI to the telco; I'm
trying to get the router to act as a tandem switch.

Here's the q931 on the router:
000298: Aug 17 15:28:02.987: ISDN Se0/3/0:15 Q931: RX <- SETUP pd = 8
callref = 0x0001
	Sending Complete
	Bearer Capability i = 0x8890
		Standard = CCITT
		Transfer Capability = Unrestricted Digital
		Transfer Mode = Circuit
		Transfer Rate = 64 kbit/s
	Channel ID i = 0xA98381
		Exclusive, Channel 1
	Called Party Number i = 0x80, '13122455128'
		Plan:Unknown, Type:Unknown
000299: Aug 17 15:28:02.991: ISDN Se0/3/0:15 Q931: Received SETUP
callref = 0x8001 callID = 0x0003 switch = primary-net5 interface =
Network
000300: Aug 17 15:28:03.003: ISDN Se0/3/0:15 Q931: TX -> CALL_PROC pd
= 8  callref = 0x8001
	Channel ID i = 0xA98381
		Exclusive, Channel 1
000301: Aug 17 15:28:03.011: ISDN Se0/1/0:23 Q931: Applying typeplan
for sw-type 0xD is 0x0 0x0, Calling num
000302: Aug 17 15:28:03.011: ISDN Se0/1/0:23 Q931: Sending SETUP
callref = 0x0082 callID = 0x8003 switch = primary-ni interface = User
000303: Aug 17 15:28:03.011: ISDN Se0/1/0:23 Q931: TX -> SETUP pd = 8
callref = 0x0082
	Bearer Capability i = 0x8090A2
		Standard = CCITT
		Transfer Capability = Speech
		Transfer Mode = Circuit
		Transfer Rate = 64 kbit/s
	Channel ID i = 0xA98397
		Exclusive, Channel 23
	Calling Party Number i = 0x0080, N/A
		Plan:Unknown, Type:Unknown
	Called Party Number i = 0x80, '13122455128'
		Plan:Unknown, Type:Unknown
000304: Aug 17 15:28:03.123: ISDN Se0/1/0:23 Q931: RX <- CALL_PROC pd
= 8  callref = 0x8082
	Channel ID i = 0xA98397
		Exclusive, Channel 23
000305: Aug 17 15:28:03.475: ISDN Se0/1/0:23 Q931: RX <- ALERTING pd =
8  callref = 0x8082
	Progress Ind i = 0x8088 - In-band info or appropriate now available
000306: Aug 17 15:28:03.487: ISDN Se0/3/0:15 Q931: TX -> ALERTING pd =
8  callref = 0x8001
	Progress Ind i = 0x8188 - In-band info or appropriate now available
000307: Aug 17 15:28:03.675: ISDN Se0/1/0:23 Q931: RX <- CONNECT pd =
8  callref = 0x8082
000308: Aug 17 15:28:03.675: %ISDN-6-CONNECT: Interface Serial0/1/0:22
is now connected to 13122455128 N/A
000309: Aug 17 15:28:03.679: ISDN Se0/1/0:23 Q931: TX -> CONNECT_ACK
pd = 8  callref = 0x0082
000310: Aug 17 15:28:03.683: %ISDN-6-CONNECT: Interface Serial0/3/0:0
is now connected to N/A N/A
000311: Aug 17 15:28:03.683: ISDN Se0/3/0:15 Q931: TX -> CONNECT pd =
8  callref = 0x8001
000312: Aug 17 15:28:03.707: ISDN Se0/3/0:15 Q931: RX <- CONNECT_ACK
pd = 8  callref = 0x0001
000313: Aug 17 15:28:17.403: ISDN Se0/3/0:15 Q931: RX <- DISCONNECT pd
= 8  callref = 0x0001
	Cause i = 0x8090 - Normal call clearing
000314: Aug 17 15:28:17.403: %ISDN-6-DISCONNECT: Interface
Serial0/3/0:0  disconnected from unknown , call lasted 13 seconds
000315: Aug 17 15:28:17.403: ISDN Se0/3/0:15 Q931: TX -> RELEASE pd =
8  callref = 0x8001
000316: Aug 17 15:28:17.427: ISDN Se0/3/0:15 Q931: RX <- RELEASE_COMP
pd = 8  callref = 0x0001
000317: Aug 17 15:28:17.439: %ISDN-6-DISCONNECT: Interface
Serial0/1/0:22  disconnected from 13122455128 , call lasted 13 seconds
000318: Aug 17 15:28:17.439: ISDN Se0/1/0:23 Q931: TX -> DISCONNECT pd
= 8  callref = 0x0082
	Cause i = 0x8090 - Normal call clearing
000319: Aug 17 15:28:17.475: ISDN Se0/1/0:23 Q931: RX <- RELEASE pd =
8  callref = 0x8082
000320: Aug 17 15:28:17.475: ISDN Se0/1/0:23 Q931: TX -> RELEASE_COMP
pd = 8  callref = 0x0082


Note that the incoming PRI call from the Polycom is 0x8890, which is
fine.  However, on the outbound call leg from the router to the telco,
the 2851 has made the bearer cap speech, (0x8090A2), and that's
causing the issue.  The Codian 3241 on the receiving end of the call
(which is directly connected to the PSTN) sees the incoming call from
the 2851 as bearer cap speech and tries to process it as a 64K audio
call rather than starting the bonding process.

Polycom HDX #1 -> PRI module -> crossover PRI -> 2851 router (0/3/0)
-> 0/1/0 -> PSTN

PSTN -> Codian 3241 H.320 gateway -> H.323 -> Polycom HDX #2