Thursday, January 29, 2015

Proving Telco Problems

Why are Voice carriers always able to get by telling you whatever they want, without ever having to prove anything to you???  Doesn't anyone think that is just not right?  Well, its ok.  I can prove things for them.  So I have a DID number that I cant call into.  I mean, the customer internal phone doesn't ring anymore when you call its external DID number.  A little frustrating for the customer for sure.  We looked into the Cisco CUCM and the translation pattern looks ok.  Lets debug on the voice gateway, to make sure the call is getting that far.  I mean, it has to come into the gateway to get to the customer CUCM, right?
So I get on the Cisco router (the voice gateway), and I do a "debug isdn q931".  That turns on debugging for incoming/outgoing calls on the PRI.  Lets make a test call into one we know works.  Ive changed the numbers for customer privacy.

003768: *Jan  6 20:07:25.958: ISDN Se0/0/1:23 Q931: RX <- SETUP pd = 8  callref = 0x406C 
Bearer Capability i = 0x8090A2 
Standard = CCITT 
Transfer Capability = Speech  
Transfer Mode = Circuit 
Transfer Rate = 64 kbit/s 
Channel ID i = 0xA98385 
Exclusive, Channel 5 
Facility i = 0x9F8B0100A11702011C020100800F4A4343454F20202020202020202020 
Protocol Profile =  Networking Extensions 
Component = Invoke component 
Invoke Id = 28 
Operation = CallingName 
Name Presentation Allowed Extended
Name = XYZ Company           
Display i = 'XYZ Company ' 
Calling Party Number i = 0x2180, '2055558511' 
Plan:ISDN, Type:National 
Called Party Number i = 0xC1, '3337546' 
Plan:ISDN, Type:Subscriber(local)
003769: *Jan  6 20:07:26.146: ISDN Se0/0/1:23 Q931: TX -> CALL_PROC pd = 8  callref = 0xC06C 
Channel ID i = 0xA98385 
Exclusive, Channel 5

Yeah, looks like we see that call coming in from the Telco.  Now lets try the number we question, that the Telco says is fine:

Oh look, nothing.  Well, Im no genius, but if my voice gateway doesnt see it, it must not be getting to it.  Which means its a Telco issue.

1 comment:

  1. Great post Shane! And the command "debug isdn q931" is a command that gets used a lot if you have a VoIP system and a PRI with DID's. We use it here all the time.


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