Wireless Home Networking - Index of

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Part IV: Using a Wireless Network
� VoIP phone: You can also find phones that handle all the telephone
adapter’s functionality internally; these are called VoIP phones (or,
commonly, SIP phones if they support the SIP protocol). Dual-mode
VoIP phones can work as both VoIP phones and as standard POTS
phones (which can be handy when you’re making local phone calls).
� Softphone: You don’t need a phone to make VoIP calls — your PC or Mac
(when equipped with speakers and microphones or a headset) can be a
full-fledged VoIP phone as well. In fact, that’s how the whole VoIP phenomenon
started back in the late 1990s, with people making free PCto-PC
phone calls over the Internet. The software program used on computers
for VoIP calls is called a softphone client (software phone). You can
even find softphones on phones — smartphones may have softphone
software to allow users to place international calls, for instance, over the
cellular broadband data connection.
Understanding VoIP services
Like traditional telephony services (POTS and cell phone service), VoIP
requires you to have a service provider. The service provider provides two
main functions:
� A gateway between the VoIP network and the PSTN: Your VoIP service
provider provides the software and hardware (within their network) to
move calls between the VoIP network and the PSTN (POTS phones and
cell phones). This functionality gives your VoIP phone the capability to
make calls anywhere in the world, to any phone. This gateway service is
part of a paid subscription service, but typically the monthly and/or percall
costs are lower than they are for POTS or cell phone service.
� Directory services: Your VoIP service provider also provides directory
services, which gives your VoIP phone a “phone number” and lets
people find and call you. Traditional phone services use a global standard
for numbering, but VoIP doesn’t (yet), so your service provider
runs a service that associates your broadband connection’s IP address
to your identity. This service can be part of a for-pay monthly service,
or it can be free for PC-to-PC VoIP services. Note that many leading VoIP
providers, such as Vonage, let you transfer your landline phone number
to their directory service; this essentially tells all other service providers
that when that number is dialed, they should send the call to the Vonage
network for call completion.