VoIP numbering system
While the prospect of being able to take your phone number with you when you travel is attractive, this feature of VoIP also raises some challenges. For example, emergency services rely on what's called the Integrated Public Number Database (IPND) to locate callers based on their phone number. If that number no longer relates to a physical location, emergency calls can be compromised.

With this in mind, the Australian Communications and Media Authority (ACMA) has introduced a new location-independent numbering range and is encouraging VoIP service providers to use it. Under the system, any numbers that don't relate to a particular physical location will start with the prefix 0550. This will alert both emergency services and other callers to the fact that they are calling or being called from a VoIP service.

The system is currently voluntary for VoIP providers, however ACMA says it will be monitoring usage closely to ensure compliance.