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As a result, emergency calls cannot be made via VoIP either. “The emergency-call problem with VoIP stems from the fact that it is not possible to localize exactly where a call comes from. The data packets are divided and sent via different routers and gateways. They are only put together again at the recipient, meaning that it is not possible to determine clearly where they come from,” explains Philipp Bohn, analyst at Berlecon Research http://www.berlecon.de, in a conversation with pressetext.
As soon as a VoIP device goes online, it registers with the provider’s server and tells it the IP address. The device can thus be located on the Internet. However, since this is usually a dynamic IP, no fixed geographic position can be assigned to the device. The VoIP provider only has the data that was supplied when the connection was activated – in most cases this is the billing address. In many cases, this information will not be sufficient.
The emergency-call function is offered, for example, by the VoIP provider Sipgate http://www.sipgate.de. The numbers 110 and 112 can be reached via a Sipgate connection and are activated for the stored address. However, at the same time Sipgate points out that customers must keep their personal data continually up to date. This is because flawless emergency-call functionality can only be guaranteed if the name and address provided are correct at the time an emergency call is placed. If the data are not correct, the caller must at least be able to state their location. So-called gasping calls are not possible in connection with nomadic use. Help would be sent to the wrong address.
A further possibility is for the location determina-tion currently implemented in mobile communications to be transferred to the VoIP sector as well. However, this would require additional hardware equipment for the devices. Researchers at Frankfurt University of Applied Sciences have developed an emergency-call mo-del that determines the correct location on the basis of the Session Initiation Protocol (SIP). “A SIP telephone must always first register with its home SIP server in order to communicate the current Internet address,” explains researcher Ulrich Trick from the Department of Computer Science and Engineer-ing. With the aid of these signals, the physical network addresses can be read out and assigned to the user, from which in turn the DSL entry port used can be clearly deduced.
At present, many VoIP operators still do not offer an emergency-call function. Anyone who wants to be on the safe side must ensure that, in addition to VoIP access, they still have an additional telephone connection through which even a gasping emergency call can be placed successfully – in other words, a landline connection or a mobile telephone. “In companies that use VoIP exclusively, the emergency-call facility is implemented via a backup connection through the conventional telephone network,” reports Bohn, who is confident that “there will be corresponding solutions in the next two years. “The VoIP providers are already working intensively on this,” the analyst concludes.