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Multi-Device vs PBX ISDN SetUp


asterisk_nicht_mehr
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I am wanting to understand how a Point to Mulitpoint ISDN configuration should be set up differently from a Point to Point ISDN configuration. I want to avoid mismatching the incoming calls to specific devices when it is a Point to Multi-Point ISDN phone line.

 

It seems to me that a Point to Point Configuration: where the provider gives a main number and an additional range of numbers which may be addressed (usually sequential) is fairly straight forward. Enter the Trunk--->assign the extention within the trunk and one is more or less finishted because the telalias can identifiy the inbound based on both assignments.

 

With a Basis rate configuration that is Point to Multipoint the provider usually gives a list of up to 20 numbers, which most of the time are not sequential, and usually are not logically related. Because they come in over the common ISDN trunk and the numbers are assigned by the provider I have had some small problems with the setup.

 

By chance I found that one must set a trunk for as many ISDN Channels as one has. Is that correct? 1 BRI = 2 SiP Gateway Trunks, so that with 2 BRIs one would require 4 SIP Gateway Trunks.

 

The telalias is then used to provide number assignment (MSN) to the extentions. Is that correct?

 

Otherwise, what is the best method for assigning these numbers when one has several aliases that must be linked to a limited number of extensions (physical telephones)?

 

It is my understanding that with a Point to Point Trunk setup one may arrange for Fall Over to the next Trunk. IS that also possible with a Point to Multi-Point Trunk setup?

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I am wanting to understand how a Point to Mulitpoint ISDN configuration should be set up differently from a Point to Point ISDN configuration. I want to avoid mismatching the incoming calls to specific devices when it is a Point to Multi-Point ISDN phone line.

 

It seems to me that a Point to Point Configuration: where the provider gives a main number and an additional range of numbers which may be addressed (usually sequential) is fairly straight forward. Enter the Trunk--->assign the extention within the trunk and one is more or less finishted because the telalias can identifiy the inbound based on both assignments.

 

With a Basis rate configuration that is Point to Multipoint the provider usually gives a list of up to 20 numbers, which most of the time are not sequential, and usually are not logically related. Because they come in over the common ISDN trunk and the numbers are assigned by the provider I have had some small problems with the setup.

 

By chance I found that one must set a trunk for as many ISDN Channels as one has. Is that correct? 1 BRI = 2 SiP Gateway Trunks, so that with 2 BRIs one would require 4 SIP Gateway Trunks.

 

The telalias is then used to provide number assignment (MSN) to the extentions. Is that correct?

 

Otherwise, what is the best method for assigning these numbers when one has several aliases that must be linked to a limited number of extensions (physical telephones)?

 

It is my understanding that with a Point to Point Trunk setup one may arrange for Fall Over to the next Trunk. IS that also possible with a Point to Multi-Point Trunk setup?

 

You can use the "Prefix" setting for outbound trunks. Then the PBX will just append the extension number to the prefix and uses that as the "ANI" (subscriber number, MSN).

 

Inbound you can use a expression to extract the extension. There is a example in http://wiki.pbxnsip.com/index.php/Inbound_Calls_on_Trunk where you can see how to extract the last few digits from a incoming number.

 

With this, you don't need to specify any alias. All you need to do is to configure your trunk correctly.

 

Failover is a topic that is not related to inbound traffic; and for outbound traffic it is not related to the caller-ID representation.

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You can use the "Prefix" setting for outbound trunks. Then the PBX will just append the extension number to the prefix and uses that as the "ANI" (subscriber number, MSN).

 

Inbound you can use a expression to extract the extension. There is a example in http://wiki.pbxnsip.com/index.php/Inbound_Calls_on_Trunk where you can see how to extract the last few digits from a incoming number.

 

With this, you don't need to specify any alias. All you need to do is to configure your trunk correctly.

 

Failover is a topic that is not related to inbound traffic; and for outbound traffic it is not related to the caller-ID representation.

 

 

Let me clarify my understanding of your instructions:

For a point to point ISDN Configuration (PBX exchange) I would normally freely associate to an extention (ISDN Point to Point) (2-5 digit City Code) + (6-7 Main trunk number) + (2-3 digit extension).

That I grasp.

 

For a Mulitipoint to Point (Multiple Line Exchange) I should set up the Lines with unique ANIs. That does not sound right to me. If I have one BRI that allows only 2 simultaneous calls over the ISDN line, then the outgoing line could be in use by a number of identified numbers. I need to associate the incoming call to the specific extension. It would seem to me that setting up the tel alias is quite enough to allow the call to be directed to the proper extension.

 

The point I think you were making was about another point than I was trying to clarify. I wanted to determine if it is normal to set up 2 Trunks for every BRI on an ISDN line, or is the system smart enough to use the Line B without being programmed. My question about falling over was framed to clarifiy if one ISDN is busy, will the second caller calling over the ISDN line get a busy if no 2nd Trunk is listed. I was having symptoms of such problems that led me to install a second trunk.

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Let me clarify my understanding of your instructions:

For a point to point ISDN Configuration (PBX exchange) I would normally freely associate to an extention (ISDN Point to Point) (2-5 digit City Code) + (6-7 Main trunk number) + (2-3 digit extension).

That I grasp.

 

For a Mulitipoint to Point (Multiple Line Exchange) I should set up the Lines with unique ANIs. That does not sound right to me. If I have one BRI that allows only 2 simultaneous calls over the ISDN line, then the outgoing line could be in use by a number of identified numbers. I need to associate the incoming call to the specific extension. It would seem to me that setting up the tel alias is quite enough to allow the call to be directed to the proper extension.

 

The point I think you were making was about another point than I was trying to clarify. I wanted to determine if it is normal to set up 2 Trunks for every BRI on an ISDN line, or is the system smart enough to use the Line B without being programmed. My question about falling over was framed to clarifiy if one ISDN is busy, will the second caller calling over the ISDN line get a busy if no 2nd Trunk is listed. I was having symptoms of such problems that led me to install a second trunk.

 

I have to admit I dont 100 % understand what you mean by "multipoint" and "point to point". I know that in ISDN a "line" can have different From/To identities (because the signalling is outside of the "line"). For example you can have ten MSN, but only two calls at the same time.

 

I would just set up one trunk for one BRI, and then have two CO-lines on that trunk. The CO-lines are not bound to specific MSN, so there should be no problem. The pbxnsip "trunk" can have more than one call as well, pretty much like the ISDN model.

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