[Asterisk-Users] any ISDN/PRI signaling experts out there?

[Paul Belanger]

See comments inline!

Damon Estep wrote:
> I have officially engaged in a pissing contest with the local Telco over
> PRI calling name delivery.

Welcome to my world, I deal with theses guys daily!  Errgiant arn't
they.  We have a saying around work 'The telco is always wrong!'.

> The telco publishes their calling name delivery over PRI feature as
> being bellcore gr-1367-core compliant.
> 
> The gr-1367-core spec states that the calling name is to be included as
> a facility IE in the setup message, or sent in a subsequent facility IE
> message with an indicator in the setup message that the CNAM will
> follow.
> 
> Extensive testing and ISDN/PRI protocol analysis shows that the facility
> IE they are sending out with the CNAM in it comes only after we have
> sent back PROGRESS and ALERTING in response to the SETUP. If we block
> the PROGRESS and ALERTING and sit and WAIT for the FACILITY we never get
> it, the call will time out, so we know they are actually waiting for the
> call to progress before sending the facility IE CNAM.

This sounds a little fishy, Orgination Number is usually transmitted in
the SETUP message.  Your are almost correct in your messaging:

Network                  User(Switch)
Setup
                         CALL PROCEEDING
                         ALERTING
                         CALL CONNECT
CALL CONNECT ACKNOWLEDGE
....

There is about a 4sec timeout allow after SETUP is initially sent, if
CALL PROCEEDING is not transmitted by that time, the Network side will
terminiate the call.

> As far as I can tell the GR-1367-CORE spec does not define a maximum
> delay in sending the facility IE or whether it is acceptable to wait for
> PROGRESS and ALERT before sending it.
> 
> The setup is; Telco PRI Lucent 5ESS <> Lucent MAX TNT <> Asterisk

Here is an ISDN trace from a Dialogic board attached to a 5ESS switch
with framing/coding ESF/B8ZS:

SETUP(0x05)
  1:           BEARER CAPABILITY(0x04)
  2:           IE Length(0x03)
  3:  1------- Extension Bit
      -00----- Coding Standard
      ---00000 Info. Transfer Cap.
  4:  1------- Extension Bit
      -00----- Transfer Mode
      ---10000 Info. Transfer Rate
  5:  1------- Extension Bit
      -01----- Layer 1 Indent
      ---00010 User Info. Layer 1
  1:           CHANNEL ID(0x18)
  2:           IE Length(0x03)
  3:  1------- Extension Bit
      -0------ Interface ID Present
      --1----- Interface Type
      ---0---- Spare
      ----1--- Preferred/Exclusive
      -----0-- D-Channel Indicator
      ------01 Info. Channel Sel.
3.2:  1------- Extension Bit
      -00----- Coding Standard
      ---0---- Number Map
      ----0011 Channel/Map Element
  4:  1------- Extension Bit
      -0000001 Channel Number/Slot Map
  1:           CALLING PARTY NUM(0x6c)
  2:           IE Length(0x0b)
  3:  1------- Extension Bit
      -010---- Type Of Number
      ----0001 Numbering Plan ID
      949459xxxx  Number Digit(s)    <-- Here is the ANI
  1:           CALLED PARTY NUM(0x70)
  2:           IE Length(0x04)
  3:  1------- Extension Bit
      -100---- Type of Number
      ----0001 Numbering plan ID
      200  Number Digit(s)           <-- Here is the DNIS

Notice my comments on where ANI and DNIS arrive in the SETUP message.

> The MAX TNT responds to the Facility IE with ISDN error 98, invalid
> message for call state.

This is an actual CAUSE CODE from Q.931:

Cause No. 98 – Message not compatible

This cause indicates that the message received is not compatible with
the call state or the message type is non-existent or not implemented.

In short it is a protocol error.  Check out
http://www.telos-systems.com/?/techtalk/cause.htm for a complete lists
of causes and there meaning.

> The SIP INVITE from the TNT to Asterisk contains no Caller Name
> information.
> 
> It seems really odd to me that a Lucent TNT can not translate the caller
> ID Name info delivered by a Lucent 5ESS switch.
> 
> On the same setup, if I connect another PRI device to it that emulates
> switch side signaling and includes the CNAM as a Display IE in the
> setup, the SIP invite is properly formatted and * receives the calling
> party name.
> 
> Does anyone here have enough experience with ISDN PRI signaling to
> comment with some level of authority on this?

Can you set a ISDN trace from your telco to your switch?  I would be
curious to see what it looks like.

Again, it looks like your telco's problem.  Your best to ask them to
through a ThunderBird (T-Bird) on your circuit at your demarc and ask
them if they see the CallerID, chances are they don't

> Damon

/PB