Comparação Chamada à Cobrar x Chamada Normal - ISDN CISCO

???-2651xm-voz#show version
Cisco IOS Software, C2600 Software (C2600-ADVENTERPRISEK9_IVS-M), Version 12.4(25b), RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Wed 12-Aug-09 10:59 by prod_rel_team

ROM: System Bootstrap, Version 12.2(8r) [cmong 8r], RELEASE SOFTWARE (fc1)
???-2651xm-voz uptime is 11 weeks, 1 day, 23 hours, 3 minutes
System returned to ROM by power-on
System restarted at 20:09:12 brz Tue Jun 22 2010
System image file is "flash:c2600-adventerprisek9_ivs-mz.124-25b.bin"


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Cisco 2651XM (MPC860P) processor (revision 2.0) with 125741K/5331K bytes of memory.
Processor board ID JAE07490D4T
M860 processor: part number 5, mask 2
2 FastEthernet interfaces
31 Serial interfaces
1 Channelized E1/PRI port
1 ATM/Voice AIM
2 Voice FXO interfaces
32K bytes of NVRAM.
32768K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

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Usei o debug isdn q931

Primeiro a ligação normal:

Sep  9 20:18:51.248: ISDN Se0/0:15 Q931: RX <- SETUP pd = 8  callref = 0x15B4
        Sending Complete
        Bearer Capability i = 0x8090A3
                Standard = CCITT
                Transfer Capability = Speech
                Transfer Mode = Circuit
                Transfer Rate = 64 kbit/s
        Channel ID i = 0xA18398
                Preferred, Channel 24

        Calling Party Number i = 0x2183, '4599112233'
                Plan:ISDN, Type:National
        Called Party Number i = 0xC1, '9123'
                Plan:ISDN, Type:Subscriber(local)
Sep  9 20:18:51.296: ISDN Se0/0:15 Q931: TX -> CALL_PROC pd = 8  callref = 0x95B4
        Channel ID i = 0xA98398
                Exclusive, Channel 24
Sep  9 20:18:51.332: ISDN Se0/0:15 Q931: TX -> ALERTING pd = 8  callref = 0x95B4
???-2651xm-voz#
Sep  9 20:18:57.394: ISDN Se0/0:15 Q931: RX <- DISCONNECT pd = 8  callref = 0x15B4
        Cause i = 0x8290 - Normal call clearing
Sep  9 20:18:57.402: ISDN Se0/0:15 Q931: TX -> RELEASE pd = 8  callref = 0x95B4
Sep  9 20:18:57.551: ISDN Se0/0:15 Q931: RX <- RELEASE_COMP pd = 8  callref = 0x15B4
???-2651xm-voz#


Depois a ligação à cobrar:

Sep  9 20:19:39.797: ISDN Se0/0:15 Q931: RX <- SETUP pd = 8  callref = 0x16D4
        Sending Complete
        Bearer Capability i = 0x8090A3
                Standard = CCITT
                Transfer Capability = Speech
                Transfer Mode = Circuit
                Transfer Rate = 64 kbit/s
        Channel ID i = 0xA18399
                Preferred, Channel 25
        UNRECOGNIZED VARIABLE (0x4A)  i = 0x81
        Calling Party Number i = 0x2183, '4599112233'
                Plan:ISDN, Type:National
        Called Party Number i = 0xC1, '9123'
                Plan:ISDN, Type:Subscriber(local)
Sep  9 20:19:39.845: ISDN Se0/0:15 Q931: TX -> CALL_PROC pd = 8  callref = 0x96D4
        Channel ID i = 0xA98399
                Exclusive, Channel 25
???-2651xm-voz#
Sep  9 20:19:39.881: ISDN Se0/0:15 Q931: TX -> ALERTING pd = 8  callref = 0x96D4
???-2651xm-voz#
Sep  9 20:19:45.282: ISDN Se0/0:15 Q931: RX <- DISCONNECT pd = 8  callref = 0x16D4
        Cause i = 0x8290 - Normal call clearing
Sep  9 20:19:45.294: ISDN Se0/0:15 Q931: TX -> RELEASE pd = 8  callref = 0x96D4
Sep  9 20:19:45.466: ISDN Se0/0:15 Q931: RX <- RELEASE_COMP pd = 8  callref = 0x16D4
???-2651xm-voz#


Testei várias vezes e a mesma característica se repetiu em todas as tentativas.

Conclusão:
A variável que diferencia uma ligação a cobrar de uma ligação normal é a seguinte:
        UNRECOGNIZED VARIABLE (0x4A)  i = 0x81