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

Edwin Groothuis edwin at mavetju.org
Thu May 29 09:20:43 CDT 2008


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/



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