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Listen to the Computerworld TechCast: VoIP.

Voice over IP (VoIP) has exploded in popularity since the first PC-to-PC Internet phone-calling systems were introduced in 1995, as evidenced by the millions of households now subscribed to VoIP services. Audio quality, call reliability and telephony features of VoIP systems are finally maturing to be viable on enterprise networks as well, and only a few barriers remain to widespread corporate adoption of VoIP.

The Case for VoIP

Businesses can benefit from VoIP technology in several respects. One obvious advantage VoIP brings is avoidance of long-distance toll fees by routing calls through Internet connections. VoIP phones can call to (or be called from) any number in the world just like traditional or cell phones. While VoIP will not completely eliminate public telephone charges, geographically dispersed organizations especially can save much money here.

Linking VoIP call management systems with corporate e-mail, instant messaging and database systems also expands business communication capabilities. Using the presence awareness of an application such as Microsoft Office Communicator, VoIP calls to employees can automatically be generated from instant messages as needed according to their preferences. Similarly, incoming VoIP voice mails can automatically be converted into e-mail messages for faster access and response. The benefits of voice and data integration reach even further, increasing the flexibility of IT help desks, human resources and other intranet systems that manage employee information, as well as customer call centers.

To the extent their voice and data networks converge, enterprises implementing VoIP can reduce their IT support burden through consolidation. Compared to how virtual private networks have reduced mobile workers' need for remote access servers and modem pools in some corporate environments, VoIP systems can shrink the infrastructure and support costs associated with traditional telephony systems even more dramatically.

Enterprise VoIP Building Blocks

On an end-to-end enterprise VoIP network, an IP phone replaces the traditional digital phone handset and shares a similar physical appearance. An ordinary PC can also serve as an IP phone (a "soft phone") when VoIP software is installed. Enterprise IP phones typically connect directly to the LAN via Ethernet or sometimes Wi-Fi, while Universal Serial Bus phones exist as an alternative to soft phones. VoIP phones obtain an IP address, normally via Dynamic Host Configuration Protocol (DHCP), which allows them to make and receive calls.

Analog telephone adapters (ATA) allow ordinary telephones to interface with a VoIP-enabled network as an alternative to using an IP phone. ATAs normally feature RJ-11 ports for connecting the phone and corresponding RJ-45 Ethernet ports for connecting to the LAN.