Course12:Advanced - The PSTN Simulation

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Some of the lessons use a simulated PSTN on the IP800. Her is how it works.



The PSTN simulation is a special configuration file that can be installed on your IP811. It emulates part of the worldwide PSTN numbering plan. A number of ISDN lines are provided which simulate real trunk lines for various lessons. Also, some VoIP terminals (e.g. IP phones or analogue interfaces on the IP411RIGHT) can be registered and calls can be placed between these interfaces.

Some lessons where ISDN trunks are not required, will use your IPVA1 as PSTN simulation. The configuration is identical to the one of the IP811, therefore for the remainder of this book we will use the IP811 as reference gateway.

Distinctions of National Numbering Plans

A national numbering plan defines how phone numbers in this country are composed (number format) and what digits you have to dial to call a phone number in the same country, but in different area/zone, or a phone number in another country.

The following components usually make up a phone number you have to dial to call a subscriber in the same country:
  • National Prefix - is usually dialled before the Area Code and gives ability to reach subscribers in other cities or regions. In some countries National Prefix must be dialled always or does not exists at all, especially in countries without Area Codes. E.g. in Germany the National Prefix is 0. So if you want to call any number not in your area, you have to dial first 0
  • Area Code - is usually assigned to a geographical area like a city or town and region around it, and can be of fixed or variable length. Also Area Codes are used for mobile numbers and identifies a GSM provider, like T-Mobile or Vodafone. If you call from one area to another you usually have to dial the National Prefix followed by Area Code. In some countries there are only a few zones defined or even no Area Codes defined. The Area Code may be mandatory for any call , even for calls within the same area. Also, the length of Area Codes may vary. In Germany, the area code is optional and the length is variable
  • Subscriber Number - usually follows the Area Code (if any) and can be of fixed or variable length. The subscriber number may or may not be sufficiant to call subscribers in the same area. E.g. within the same Area in Germany, Subscriber Number can be dialled directly, without National Prefix and Area Code. In other countries, any call may need to have the national prefix, the area code and the subscriber number
Please note that many countries have a fixed or closed numbering plan. This means that the total length of area code and subscriber number is fix. It is not possible to dial longer numbers, that is, extra digits will be discarded. However, in some countries - as is the case in Germany - there is a variable or open numbering plan. Extra digits appended to the destinations subscriber number will be presented to the destination if this is a DDI trunk. This way, many more extensions within the destination PXB can be addressed than would be possible with a fixed numbering plan. For example, innovaphone officially has subscriber number 73009 with 1 digit extension (73009x). In a country with a fixed numbering plan (like Switzerland), callers would be able to address extensions 0 to 9 only. However, as Germany has a variable numbering plan, callers can directly address longer extensions such 532.

An international phone number formatted according to E.123 starts with "+"-Sign followed by the country code. While calling to international phone numbers(e.g. +49 7031 730090), following must be considered:
  • International Prefix - in most countries a mandatory digit sequence, that must be dialled to call to foreign countries. If you want to call an E.123 formatted phone number from PSTN, you have to replace the "+"-Sign with the International Prefix. E.g. in Germany the International Prefix is 00, therefore to call a number +44 1 23456789 (in Zurich/Switzerland) you have to dial 00 44 1 23456789.
  • Country Code - identifies a specific country and may vary in length. The Country Code is usually optional to dial for calls within the same country (German country code is 49).

www.png has an overview of the world wide numbering plans.

Numbering Plan

The numbering plan of the PSTN-Simulation mimics part of the world-wide E.164 PSTN numbering plan. There are the German and the Austrian numbering plans partially implemented.

In the German numbering plan three geographic Area Codes are implemented: Sindelfingen (Area Code 7031), Hannover (Area Code 511) and Stuttgart (Area Code 711).

  • In Sindelfingen we have placed a Point-to-Point Trunk Line implemented on BRI2 and BRI3 (Subscriber Number 73009) as well a Point-to-Multipoint Trunk Line implemented on BRI1 (MSNs 4455661, 7755666, 3322888 and 6655441).
  • In Hannover a Point-to-Multipoint Trunk Line on BRI4 is implemented with single MSN 987. Additionally a SIP-trunk using the DDI 2222 exists.
  • Stuttgart provides access to a SIP-provider using two trunk lines (12345 and 6789). Furthermore the Stuttgart area has a gateway connection to the Community PBX (advanced course only) which can be reached via +49 711 5 for faxserver application tests. Vice versa the PSTN-Simulation can be accessed from the community PBX using 5<userno>, where <userno> is the number the trainee got dynamically assigned.

Additionally to geographic Area Codes in German numbering plan, there two non-geographic special Area Codes implemented: one for Vodafone mobile phones(Area Code 151) and one for value-added services(Area Code 900).

To call from Hannover to MSN 4455661 in Sindelfingen you have to dial National Prefix 0 followed by the Area Code for Sindelfingen 7031 and a Subscriber Number 4455661: 0 7031 4455661. Keep in mind to dial also a PBX Trunk Line Prefix (in case you have one an the Trunk Line Object in the PBX), to get out of the PBX to the Trunk Line.

To call from Point-to-Point Trunk to Point-to-Multipoint in Sindelfingen (a call within the same Area) you can omit the National Prefix 0 and Area Code of Sindelfingen 7031 and dial the subscriber number directly: 4455661.

To call a number in Austria you have to dial the International Prefix 00 followed by the Country Code of Austria 43, some Austrian national number. E.g. to call an Austrian mobile number +43650876, you have to dial 00 43 650876.

screenshot.png PSTN Simulation Description file


The screenshot.png simulated PSTN provides a number of ISDN and VoIP interfaces:
  • BRI1: Point to Multipoint trunk line
    Country 49 (Germany)
    Area code: 7031 (Sindelfingen)
    MSN1: 4455661
    MSN2: 7755666
    MSN3: 3322888
    MSN4: 6655441
  • BRI2, BRI3: Point to Point 2-BRI trunk line bundle
    Country 49 (Germany)
    Area code: 7031 (Sindelfingen)
    Trunk base number: 73009
  • BRI4: ISDN Phone Subscriber Line (with ISDN power enabled, suitable for an ISDN phone)
    Country 49 (Germany)
    Area code: 511 (Hannover)
    Subscriber number: 987
  • VoIP Phone Subscriber Line (to register a VoIP terminal)
    Country 49 (Germany)
    Area code: 511 (Hannover)
    Subscriber number: 271
    Registration name: Triton (SIP or H.323)
  • VoIP Phone Subscriber Line (to register a VoIP terminal)
    Country 43 (Austria)
    Area code: 650 (Vodafone)
    Subscriber number: 876
    Registration name: Handy4 (SIP or H.323)
Also, there are a number of virtual destinations that can be called for test purposes and provide announcements without any endpoint registered on them:
  • Mobile phones
    Country 49 (Germany)
    Area code: 151 (Vodafone)
    Subscriber numbers: 234, 567, 753
  • German Hotline
    Country 49 (Germany)
    Area code: 900 (Value Added Services)
    Subscriber numbers: 999
  • Austrian Hotline
    Country 43 (Germany)
    Area code: 900 (Value Added Services)
    Subscriber numbers: 999


To use the PSTN simulation, the config file must be installed on your IP811.

Turning on CLNS on BRI2/3

The point to point trunk line bundle provided on BRI2 and BRI3 can be re-configured so that it supports CLIP no screening.

If required, this must be done by the trainee on the IP811 (although the box title says DO NOT TOUCH!).

To enable CLNS on this trunk line bundle, follow these steps:

  • Open the IP811 user interface
  • Go to Gateway / Interfaces of your IP811. You will see the screenshot.png interfaces and their interface mappings
  • Open the screenshot.png interface mappings for BRI2
  • Within the CGPN In mappings, there is a line like empty ! -> 0 empty
  • In the leftmost column, select Unknown from the dropdown
The mappings should now look like these screenshot.png fixed mappings.

  • Save the settings and do the same modification on the interface mappings for BRI3
Your trunk line bundle now supports CLNS for CGPNs with subscriber, national or international type of number.
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