S 2.473 Selection of PBX service providers

Initiation responsibility: IT Security Officer, Head of IT

Implementation responsibility: Administrator, Head of IT, PBX System Manager

In almost all cases, it must be possible for the users to call other persons whose PBX end devices are not connected to their own PBX system. Examples of this include:

To be able to call persons who are not connected to the organisation's own PBX system (for example, calls to end devices at other locations of the organisation, mobile phones and external communication partners), the PBX system must be connected to the PSTN (Public Switched Telephone Network) via a subscriber line (also referred to as "last mile"). For this purpose, a PBX service provider must be commissioned.

The PBX service provider provides the physical connection between the organisation's PBX system and the PSTN and also takes care of the connection to the PSTN. IP system connections are an exception, where exclusively internet connections are used and the connection to the PSTN is the sole responsibility of the PBX service provider. As the external PBX connections are transmitted via the PBX service provider, the selection of the provider, the services provided, and the number of connections that can be used simultaneously is important.

The following requirements can be taken into account for the selection:

• Connection type
  
  Is the PBX system to be connected to the PSTN with one or multiple basic or S2m primary rate ISDN lines? Is IP system connection possible?
• Location networking
  
  How are the PBX systems of different locations connected?
• Reference installations and/or customers
  
  Does the PBX service provider have experience with organisations whose requirements correspond to the own requirements?
• Size and quality of the service team
  
  How quickly can the technicians be on site? What is the response time guaranteed by the provider?
• Hardware
  
  Is additional hardware required at the customer? Can this be purchased or leased? What outsourcing and service contracts are available?
• Capacity
  
  Is the provider verifiably able to provide the required number of outgoing lines?
• Redundant lines
  
  Is redundant connection of the PBX system to the PSTN via several physically independent lines and routes possible in case of high protection requirements in terms of availability?

In addition to the security aspects, contractual and financial aspects should also be taken into account:

• Contract terms
  
  What is the minimum term of the contract? What are the notice periods? Is it possible to switch to a different provider at a later point in time without any problems?
• Flexibility and availability
  
  Has the PBX service provider regularly introduced new products, service ideas, and tariffs in the past? Is the customer given the option to successively introduce individual products or services?
• Tariff models
  
  Are there tariff models that match the organisation's usage behaviour, such as fixed tariffs (flat rates) or staggered prices? Are there special tariff options for cheap international phone calls if frequent calls to communication partners abroad are to be made? What is the billing increment used for charging calls (charged by second or by minute)?

All services agreed to must be specified clearly and concisely in writing.

Review questions:

• Are all agreements with PBX service providers specified in writing?