German ISDN Voice

Answered Question
Mar 25th, 2008
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I have a 2821 router in Germany configured as a H323 gateway and is attached to an ISDN PRI line. The E1 PRI line is configured with primary-net5 ISDN switch type.


The problem is that about 5 inbound calls from the German ISDN network arrive with one digit short in the 'called number' field and more specifically the missing digit is the last digit in the number which makes it unique and routable to a specific destination. As a workaround I put in a dial peer that has a wildcard to catch these calls and send them to office main number, but unfortunately some of these calls that come in with the last digit missing are fax machines.


Does anyone currently have Cisco voice routers in place in any part of Germany? What ISDN switching type are you using? Have you ever encountered inbound calls with the most significant digit missing?


Any advice is appreciated. Thank you.

Correct Answer by paolo bevilacqua about 9 years 3 months ago

Ahhh the post from iptuser makes me realize that you may be very well just need "isdn overlpa-receiving", as germany has a variable-length dialplan. Proof of that, would be setups with the missing digit comes without "Sending complete IE" and is followed within 1 or 2 seconds by an info IE with the last digit.


Not having catch that before makes me bonk head on the keyboard.... sorry.


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paolo bevilacqua Tue, 03/25/2008 - 08:18
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Which exact IOS are you running ? Whta is the missing digit, example, your number including area code is 0123456, what do do you receive ?


jdsalminen Tue, 03/25/2008 - 08:42
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My IOS is 12.3(14)T7. A sample of a failed number is


Called Party Number i = 0xC1, '11101'


All the direct inward dial numbers are at least six digits like '111012'.

paolo bevilacqua Tue, 03/25/2008 - 08:51
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That is be the first time I hear of such a problem, on the other handle Is not that I can know all the bugs. Taking an isdn q921 raw debug would show all what is sent, but I suggest you try to upgrade first to 12.4(3j).

jdsalminen Tue, 03/25/2008 - 09:23
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Thank you for your advice so far. Is there any particular reason why you suggest upgrading to 12.4 IOS?

s5rch Tue, 03/25/2008 - 09:05
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Im not sure if this will work but you can try it before upgrading the IOS.


1.Have you performed a Q931 debug and you know for sure the LEC is sending the proper amount of digits? If you not sure a Q931 debug will show you. If they are not sending the proper amount of digits then I would call them and get the issue correct via the LEC (carrier).


2. If they are sending you the proper amount of digits and its the router cutting the digit off. I would add "forward-digit all" or "forward-digit 6" (or forward-digit X (x representing the number of digits you need to see)to all of your incoming dial-peers.

jdsalminen Tue, 03/25/2008 - 09:26
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I have several q931 debug sessions. In each session there are many inbound calls that work properly, but then sporadically there are these calls with 5 digits instead of 6.


When I contacted the local phone company they said that Cisco routers do not work very well with German ISDN. I don't know of any other company that is using Cisco IP Telephony in Germany so I couldn't verify that claim.


On a side note I have the same routers and software in several other western European countries and I have never encountered this issue elsewhere.

paolo bevilacqua Tue, 03/25/2008 - 09:29
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Can you send "show controllers e1" ?


Cisco routers work with ISDN all over the world since 1992 circa, and the claim from telco is a blatant attempt to shift responsibility.


Anyway to be on the safe side you should upgrade first to the stable mainline image that I've suggested before.

jdsalminen Tue, 03/25/2008 - 09:32
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I can post the E1 controller output, but each time I look it is clean; no clock slips, etc.


Another piece of troubleshooting info I have is that the only inbounds that are ever affected are those that originate within Germany. Calls from outside of Germany always work which leads to my frustration because I cannot reproduce the problem since I am not in Germany.

paolo bevilacqua Tue, 03/25/2008 - 09:41
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I think the router is OK and the problem is in telco, of course they will never ever admit that.

There is only one solution, have them come onside with their analyzer and you have people make calls to prove that sometime one digits is lost.

However to be on the safe side I would upgrade IOS before.

iptuser55 Tue, 03/25/2008 - 12:36
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You amy wish to check if they have advertised any of the numbers. In Europe- Italy, Luxembourg, Austria and Germany they do not have fixed DDI numbers. You could have a DDI with +3912341291 for the switchboard and +391234129112 for a DN. Both are correct. to resolve it you may need a TP in the gatway to pick out the exact digit such /$291$ so to pick out the exact switchboard number and then maybe translate it to a dummy number on the swb, all other numbers goes through- +3912341291123, +3912341291324 ?

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paolo bevilacqua Tue, 03/25/2008 - 13:15
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Ahhh the post from iptuser makes me realize that you may be very well just need "isdn overlpa-receiving", as germany has a variable-length dialplan. Proof of that, would be setups with the missing digit comes without "Sending complete IE" and is followed within 1 or 2 seconds by an info IE with the last digit.


Not having catch that before makes me bonk head on the keyboard.... sorry.


jdsalminen Tue, 03/25/2008 - 13:41
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Thanks again for the input.


I was investigating a lead I received from another engineer. He mentioned using PRIMARY-QSIG switching type instead of PRIMARY-NET5.


Any advice about QSIG vs NET5?

paolo bevilacqua Tue, 03/25/2008 - 14:26
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No, please keep primary-net5 and just add "isdn overlap-receiving". Let us know!

paolo bevilacqua Wed, 03/26/2008 - 08:01
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It is indeed an overlap call, see below the digit 9 sent via info IE. Please send output of "show run int se0/3/0:15" to verify the command "isdn overlap-receiving" is present.


Note after you have it you need to remove whatever translation you had put as workaround.


Mar 26 07:51:50.368 CET: ISDN Se0/3/0:15 Q931: RX <- SETUP pd = 8 callref = 0x0227

Bearer Capability i = 0x9090A3

Standard = CCITT

Transfer Capability = 3.1kHz Audio

Transfer Mode = Circuit

Transfer Rate = 64 kbit/s

Channel ID i = 0xA18383

Preferred, Channel 3

Progress Ind i = 0x8083 - Origination address is non-ISDN

Calling Party Number i = 0x2183, 'XXXXXXX'

Plan:ISDN, Type:National

Called Party Number i = 0xC1, '523033'

Plan:ISDN, Type:Subscriber(local)

Mar 26 07:51:50.372 CET: ISDN Se0/3/0:15 Q931: TX -> SETUP_ACK pd = 8 callref = 0x8227

Channel ID i = 0xA98383

Exclusive, Channel 3

Mar 26 07:51:50.416 CET: ISDN Se0/3/0:15 Q931: RX <- INFORMATION pd = 8 callref = 0x0227

Called Party Number i = 0xC1, '9'

Plan:ISDN, Type:Subscriber(local)

jdsalminen Wed, 03/26/2008 - 08:12
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Ah, I do see the second iteration of 'Called Party Number' with the missing digit.


Here is my serial config.


interface Serial0/3/0:15

no ip address

encapsulation hdlc

isdn switch-type primary-net5

isdn overlap-receiving

isdn incoming-voice voice

no cdp enable

jdsalminen Wed, 03/26/2008 - 08:15
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In conjunction with overlap receiving here is my dial peers. Note that I created a new dial-peer at 1003 to catch all. The originals I left in place, but shutdown.


dial-peer voice 1001 voip

shutdown

destination-pattern 52303.

progress_ind setup enable 3

voice-class h323 1

session target ipv4:10.8.101.10

dtmf-relay h245-signal h245-alphanumeric

codec g711ulaw

no vad

!

dial-peer voice 1002 voip

shutdown

destination-pattern 52303..

progress_ind setup enable 3

voice-class h323 1

session target ipv4:10.8.101.10

dtmf-relay h245-signal h245-alphanumeric

codec g711ulaw

no vad

!

dial-peer voice 1003 voip

destination-pattern 52303T

progress_ind setup enable 3

voice-class h323 1

session target ipv4:10.8.101.10

dtmf-relay h245-signal h245-alphanumeric

codec g711ulaw

paolo bevilacqua Wed, 03/26/2008 - 08:22
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I think DP 1002 is more correct.

jdsalminen Wed, 03/26/2008 - 08:26
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I believe this long standing issue has finally been solved. I am noticing this a few seconds after the 6th digit is received 'Sending Complete'. Thereafter the call appears to be routed directly to the recipient.

paolo bevilacqua Wed, 03/26/2008 - 08:28
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Good, please remember to rate useful posts, I've rate the one above that made the solution to come back to my mind.

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