[asterisk-dev] On PRIs, blocked channels, congestiona and telco technicians

[Edwin Groothuis]

It has been discussed before here, unfortunately without result or
outcome.

The issue? After about two months of operation, all 31 channels of
our PRI bcome, according to our telco, in a "blocked" state. What
that precisely means I am not really sure of, but all my SETUP PDUs
are answered with a RELEASE COMPLETE PDU:

> Protocol Discriminator: Q.931 (8)  len=42
> Call Ref: len= 2 (reference 3/0x3) (Originator)
> Message type: SETUP (5)
> [04 03 80 90 a3]
> Bearer Capability (len= 5) [ Ext: 1  Q.931 Std: 0  Info transfer capability: Speech (0)
>                              Ext: 1  Trans mode/rate: 64kbps, circuit-mode (16)
>                              Ext: 1  User information layer 1: A-Law (35)
> [18 04 e9 80 83 9f]
> Channel ID (len= 6) [ Ext: 1  IntID: Explicit  PRI  Spare: 0  Exclusive  Dchan: 0
>                        ChanSel: Reserved
>                       Ext: 1  DS1 Identifier: 0  
>                       Ext: 1  Coding: 0  Number Specified  Channel Type: 3
>                       Ext: 1  Channel: 31 ]
> [6c 0c 00 80 30 32 38 38 31 35 39 30 39 36]
> Calling Number (len=14) [ Ext: 0  TON: Unknown Number Type (0)  NPI: Unknown Number Plan (0)
>                           Presentation: Presentation permitted, user number not screened (0)  '0288159096' ]
> [70 09 80 39 35 34 30 33 32 33 36]
> Called Number (len=11) [ Ext: 1  TON: Unknown Number Type (0)  NPI: Unknown Number Plan (0)  '95403236' ]
> [a1] 
> Sending Complete (len= 1)


< Protocol Discriminator: Q.931 (8)  len=9
< Call Ref: len= 2 (reference 3/0x3) (Terminator)
< Message type: RELEASE COMPLETE (90)
< [08 02 82 a2]
< Cause (len= 4) [ Ext: 1  Coding: CCITT (ITU) standard (0)  Spare: 0  Location: Public network serving the local user (2)
<                  Ext: 1  Cause: Circuit/channel congestion (34), class = Network Congestion (resource unavailable) (2) ]


Tomorrow I will be talking to a telco technician about this problem
and hopefully I can get the right data out of him to explain what
exactly happens and why their exchanges decide that a channel is
blocked.


If somebody has a good question I can ask that technician which
could give me the right hint on where I could look for it in the
asterisk code, this is your chance...


Edwin

-- 
Edwin Groothuis      |            Personal website: http://www.mavetju.org
edwin at mavetju.org    |              Weblog: http://www.mavetju.org/weblog/