Voice over IP (VoIP)—the use of IP for voice communications—is quickly becoming the technology that businesses are using to connect their telephone systems. One important reason for this trend is that most business phone manufacturers are freezing further development of the Time Division Multiplexing (TDM) technology that traditional phone systems use. (TDM is a method of separating a signal into many small segments at the sending end, transmitting the pieces separately, and reassembling them at the receiving end.) Manufacturers such as Avaya, Mitel Networks, NEC, Nortel Networks, and Siemens are creating migration strategies to help their customers move from TDM to VoIP. At the same time, these manufacturers aren't significantly upgrading their traditional TDM architectures, thus increasing demand for VoIP by companies that want new or upgraded service.

For any business with significant telephony needs, VoIP systems can offer a multitude of advantages. When you're deciding whether to implement VoIP, you should keep in mind not only the advantages but also the considerations associated with VoIP. You should also be aware of the various types of VoIP solutions available.

VoIP Advantages
VoIP can offer many advantages to companies that rely on the phone to interact with their customers. The advantages include the following:

  • When companies implement a VoIP system, they can use Automatic Number Identification. ANI provides the receiver of a call with the phone number of the person who is calling. Companies can use ANI to route calls to multiple call centers. For example, a company might use ANI to identify calls from its largest customers so that it can route those calls directly to the top salespeople while routing all other calls to an Interactive Voice Response (IVR) system.
  • A VoIP system can facilitate video over IP. Videoconferencing has been a hard sell through traditional broadband methods, but it's a more viable option with VoIP.
  • VoIP can simplify wiring in new construction. Theoretically, one wiring network can handle both voice and data, thus expediting the wiring of a new phone system.
  • When used with a private network, VoIP systems can significantly reduce the costs associated with employees placing calls between offices and with the internal routing of outside calls that enter the private network.
  • VoIP can reduce costs associated with moving and reprogramming employees' phones when they move to a new office or cubicle. The cost to move and reprogram a TDM phone can run from $70 to $100. VoIP phones eliminate those charges—typically, employees can simply unplug their VoIP phones from their old location and plug them in at their new location.

VoIP Considerations
To ensure a successful VoIP system implementation, you need to keep in mind several considerations. First and foremost, VoIP isn't a telephony cure-all. Routing voice communication over the public Internet through an ordinary ISP usually isn't a workable business solution. When you route calls over the Internet, problems such as latency and jitter often seriously degrade call quality. For companies that rely on customers calling in, routing calls over the Internet is far from ready for prime time.

Instead of using the Internet, many companies set up private networks in which they own the bandwidth. These companies can prioritize voice traffic over data traffic, which lets the VoIP system transmit voice packets effectively, with no perceptible degradation in quality.

Another important consideration is Quality of Service. QoS ensures that voice packets receive priority over data traffic on a business's network. Bandwidth providers are beginning to take QoS seriously as it applies to VoIP. Carriers are starting to implement various kinds of QoS options. You pay more for these options, but the carriers then guarantee transit times. These carriers structure their networks so that the networks route voice packets ahead of data traffic, which results in an asynchronous kind of communication.

Conventional 10Base-T and 100Mb networking hubs aren't qualified to provide the QoS capability that's necessary to guarantee that the voice and video will always sound good and look good, no matter what happens with the data traffic on the network. If you have such hubs and you want to implement a VoIP system, you must replace the hubs with Ethernet switches that ensure the voice packets get priority over data and video traffic on the network. I recommend that you also use routers whose algorithms favor voice traffic over data traffic.

Because voice packets are so sensitive to delays, I also recommend that you use a VoIP system that provides low-latency queuing. Low-latency queuing treats voice data preferentially by letting voice packets be sent before any other types of packets.

Voice packets can consume a lot of bandwidth, so another consideration is call-admission control and provisioning. For example, when you use G.729A as the coder-decoder (codec) and compressed Real Time Protocol (RTP) as the packet mechanism, you need to plan for 12,000 bits per second (bps) per simultaneous phone call over a WAN. (For information about VoIP codecs and packet mechanisms, see "Valuable VoIP," July 2001, http://www.winnetmag.com, InstantDoc ID 21130.) Admission control is possible only if you provision the system with enough bandwidth to handle simultaneous calls. For example, you might configure the system to handle five simultaneous calls at 12,000bps, which totals 60,000bps. If someone were to place a sixth call between the two sites, the call-admission control system would cause a dialed overflow through the network. In this respect, the call-admission control system acts like a PBX. If two PBXs were to have a tied line with five circuits in it and someone placed a sixth call, the PBXs would create a dialed overflow as well. Without a call-admission control system, the sixth call would cause all six calls in that circuit (not just the sixth call) to degrade and begin to sound bad.

VoIP Solutions
A variety of VoIP products are available—far too many to cover them all here. So, let's look at a few of the more interesting products on the market. These products fall into three broad categories: complete systems, hardware (e.g., VoIP-enabled phones, VoIP gateways), and software (e.g., applications, softswitches).

Complete systems. Several manufacturers produce complete VoIP systems. Perhaps the largest is Cisco Systems, which according to some analysts has more than 50 percent of the VoIP market. Cisco's integrated systems incorporate IP telephony, conferencing, a contact center, and messaging to create a complete customized IP communications system for a business.

CommWorks, a 3Com subsidiary that's dedicated to IP-based networking solutions, also produces complete VoIP systems. CommWorks' platform is based on common hardware that lets the company deliver multiple services, regardless of the transport medium (i.e., wired, wireless, narrowband, or broadband) or the type of traffic (i.e., voice, data, fax, or video).

Hardware. VoIP hardware vendors include such companies as 3Com, Cisco, Polycom, and SMC Networks. 3Com produces a full line of VoIP-enabled phones. For example, the 3Com NBX 2102-IR infrared (IR)­enabled business phone features 18 programmable buttons, a full-duplex speakerphone, IR port, and 10/100Mbps switched Ethernet connectivity. 3Com also produces call processors that you can set up for VoIP. The 3Com SuperStack 3 NBX and 3Com NBX 100 call processors combine call-processing capabilities, telephony applications, and multisite IP connectivity options. You can use the 3Com NBX 100 with as many as 200 phones and the 3Com SuperStack 3 NBX with as many as 1500 phones.

In addition to offering complete VoIP systems, Cisco offers VoIP hardware products, including VoIP-enabled phones. For example, Cisco introduced the Cisco IP Phone 7905G in late 2002 as part of its Cisco 7900 Series IP Phones. The 7905G supports inline power, which lets the phone receive power over the LAN and gives the network administrator centralized power control. Cisco also produces high-end individual user phones, such as the Cisco IP Phone 7960G, which has an LCD display and six programmable buttons for lines, and the Cisco IP Conference Station, a VoIP-enabled conference room speakerphone.

Polycom produces a full range of voice- and video-communication hardware products, including VoIP-enabled phones. Polycom's IP phones are compatible with Cisco's and 3Com's VoIP hardware. For example, Polycom's SoundStation IP 3000 3Com NBX conference-room speakerphone is specifically designed for use with the 3Com SuperStack 3 NBX and 3Com NBX 100.

VoIP gateways are a specialty of SMC Networks. This vendor manufactures the SMCVIP04 four-port VoIP gateway and the SMCVIP08 eight-port VoIP gateway, which feature voice compression mechanisms designed to limit the amount of bandwidth required in the IP network. Standards-based protocols support the gateways' voice quality and call-control routing.

Software. Some VoIP hardware vendors offer optional software. For example, 3Com offers the 3Com NBX IP Site software for the 3Com SuperStack 3 NBX or 3Com NBX 100. This software lets remote employees be part of the IP network. Similarly, Siemens offers the HiPath 5000 enterprise softswitch for its traditional PBX platforms. (A softswitch is software that provides call-control functionality. For more information about softswitches, go to the International Softswitch Consortium—ISC—Web site at http://www.softswitch.org or the MobileIN.com Web site at http://www.mobilein.com/what_is_softswitch.htm.) The HiPath 5000 supports PBX features offered on Siemens' PBX platforms, interoperates with such platforms, and shares applications (e.g., multimedia contact centers and unified messaging) with as many as 2000 users across 64 nodes.

Some vendors provide VoIP software only. For example, for systems in which billing is a concern, LogiSense offers Hawk-i. This VoIP billing software lets network service providers incorporate usage-based billing in their businesses. Service providers can bill customers either before or after they make their calls. Another example is TeleSym. This vendor offers SymPhone Client, a client software program that gives VoIP capability to laptop PCs and Pocket PC 2002 devices. NetIQ's Vivinet series of programs monitor call and network quality, provide detailed diagnostics, and can lessen the skills required for VoIP troubleshooting, both before and after deployment of a VoIP-enabled network.

Go Fast or Go Slow
If you decide to implement a VoIP solution, you might want to take the plunge and quickly change your entire system all at once. Alternatively, you can test the waters by slowly integrating VoIP into an existing PBX. For example, one company used a mixture of IP phones and TDM phones for about 18 months before converting the entire system. The company built a connection through a VoIP gateway to the existing PBX, and the PBX supported calling-name and calling-number displays. When someone called from the PBX, his or her calling name and calling number appeared on the receiving IP phone, and vice versa. So, go fast or go slow—it's up to you.


Contact the Vendors
3Com
408-326-5000 or 800-638-3226
http://www.3com.com

Cisco Systems
408-526-4000 or 800-553-6387
http://www.cisco.com

CommWorks
847-262-5000 or 866-266-6967
http://www.commworks.com

LogiSense
519-249-0508
http://www.logisense.com

NetIQ
408-856-3000
http://www.netiq.com

Polycom
408-526-9000 or 800-765-9266
http://www.polycom.com

Siemens
212-258-4335 or (49) (89) 636-00
http://www.siemens.com

SMC Networks
949-679-8000 or 800-762-4968
http://www.smc.com

TeleSym
425-467-9485
http://www.telesym.com