11.4.1. What is it?
Internet telephony, or more common, Voice over IP (VoIP) or
digital telephony allows parties to exchange voice data flows over
the network. The big difference is that the data flows over a
general purpose network, the Internet, contrary to conventional
telephony, that uses a dedicated network of voice transmission
lines. The two networks can be connected, however, under special
circumstances, but for now this is certainly not a standard. In
other words: it is very likely that you will not be able to call
people who are using a conventional telephone. If it is possible at
all, it is likely that you will need to pay for a subscription.
While there are currently various applications available for
free download, both free and proprietary, there are some major
drawbacks to telephony over the Internet. Most noticably, the
system is unreliable, it can be slow or there can be a lot of noise
on the connection, and it can thus certainly not be used to replace
conventional telephony - think about emergency calls. While some
providers take their precautions, there is no guarantee that you
can reach the party that you want to call.
Most applications currently do not use encryption, so be aware
that it is potentially easy for someone to eavesdrop on your
conversations. If security is a concern for you, read the
documentation that comes with your VoIP client. Additionally, if
you are using a firewall, it should be configured to allow incoming
connections from anywhere, so using VoIP also includes taking risks
on the level of site security.