SQL Server Magazine

Communication networks consist of two types of traffic—data and voice. Many companies still maintain a dedicated voice network and a separate data network but are beginning to see the value (e.g., lower cost, flat-rate pricing) of Voice over IP (VoIP)­based data networks. VoIP is a technology that lets you make telephone calls and send faxes over an IP data network as if you were using a traditional Public Switched Telephone Network (PSTN). This capability lets companies reduce telephone and fax costs; converge data, voice, fax, and video services; and build new network infrastructures for advanced e-commerce applications (e.g., Web call centers).

VoIP has gained support from standards organizations, such as the International Telecommunications Union (ITU) and Internet Engineering Task Force (IETF), and communication vendors. Today, you can find VoIP products on the market and build VoIP-enabled networks. Before you implement VoIP in your enterprise, become familiar with its applications, underlying technologies, and H.323 and other VoIP standards, and explore several VoIP deployment considerations.

VoIP Applications
Voice communications play a fundamental role in daily life. In the near term, PSTNs will remain an important vehicle of voice delivery. VoIP, however, provides a competitive alternative to PSTNs by reproducing telephone capabilities at a significantly lower cost. VoIP is applicable to almost any type of voice communication, from simple interperson or interoffice calls to complicated teleconferences. The following examples of VoIP applications are possibilities that might work for your enterprise.

Telephone and PC communication. You can enable voice communication between traditional telephones on a PSTN and PCs in an IP network by connecting the IP network to the PSTN with an IP-PSTN gateway, as Figure 1 shows. The gateway interprets protocols and voice information for the two networks. With this configuration, a PC user can use a PC-based telephone to call a gateway close to the final call destination. The phone charge is based on the distance between the gateway and the destination.

Internet users can even receive telephone calls directly on their PCs. For example, many Internet users are dial-up users who have only one telephone line. When a user is accessing the Internet, the phone line is busy, so the user can't receive phone calls. However, VoIP software, such as eRing Solutions' itRings!, lets an Internet PC receive a call from a person who uses a traditional telephone. The PC user uses a microphone and speakers to talk and listen to the caller. When the PSTN user calls the Internet user, the PSTN user calls an itRings! gateway, then enters the Internet user's phone number. The itRings! gateway linking the PSTN and Internet establishes communication between the PSTN and Internet users.

Interoffice trunking. To handle intraoffice and interoffice voice communications, your company might have its own PBXs distributed throughout different locations and branch offices. Traditionally, you lease lines, called tie trunks in telecommunications terminology, from telecom carriers to interconnect PBXs. To reduce costs and consolidate network facilities, you can use your IP network to link these PBXs. In Figure 2, IP-PSTN gateways connect the PBX at each of two locations to the IP data network. In this way, voice and data share the same network. The IP-PSTN gateway can often compress a voice call (e.g., from 64Kbps to 8Kbps), which reduces the bandwidth requirement on the data network. The IP-PSTN gateway implementation is either a dedicated device or an integral part of a PBX. If a PBX incorporates the IP-PSTN gateway functionality, it's often called an IP PBX or iPBX device.

Remote access for mobile users. Many companies provide mobile users with remote access to the company's intranet through dial-up and VPN services. From their remote computers, mobile users can often access corporate data resources but not corporate voicemail and fax services. To make phone calls and use fax services, these users need additional analog lines. If the company's voice and fax systems are IP-enabled, however, mobile users can access voice and fax services from the same computer that they use for remote data access. Mobile users can dial their ISP's local Point of Presence (POP) and use the Internet to submit and retrieve voice messages.

Multimedia applications. VoIP multimedia applications, such as Microsoft NetMeeting and Microsoft Exchange 2000 Conferencing Server, enable workers in different locations to use their networked PCs to collaborate through realtime conferencing, whiteboard, and screen-sharing. These applications let users talk with one another from their PCs over an IP network, which saves travel time and expense and improves work efficiency.

E-commerce. Customers often browse a vendor's Web site for information. Sometimes they might not find the information they seek or might have questions about the information they find. To serve customers better, an e-commerce Web site can provide an interactive mechanism that lets customers talk to a live customer service agent in a call center. This voice-enabled e-commerce Web site integrates the Internet, PBX, and call center into one system.

When a customer has a question, he or she can click a Speak to an Agent button on the vendor's Web site. The customer then fills out and submits a short form that provides the vendor with contact information and details about what information the customer is seeking. The Web site directs the form to the proper customer service agent in the call center and establishes a voice channel between the customer's PC and the agent's telephone set in the PBX-based call center. During conversation, the agent can push Web pages to the customer's screen and guide the customer to the correct information. Avaya's Electronic Interactive Voice Response (e-IVR) and Cisco Systems' Cisco Customer Interaction Suite enable voice interaction between customers and agents at e-commerce Web sites.

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