VOICE of the future?
- By J.B. Miles
- Sep 11, 2002
Communications' EXTender PBX Gateway II, at $8,995, has 24 ports and is compatible with most PBX systems.
IP gateways are a cost-effective way to find out whether VOIP will fly at your organization
IPCS' 1&2 Port Gateways uses an Ethernet port and supports several voice coding systems. Price ranges from $500 to $799.
Depending on who's talking, Internet telephony is either a genuine technological revolution or a nonessential fad.
Early experiments with Internet phone calls were far from impressive. You downloaded voice software into your PC, hooked up a microphone and, theoretically at least, were up and running with voice over the Internet. But sound quality was poor, reception was spotty and only the most devoted computer geeks used it much.
Nevertheless, the newest approaches to voice over IP have dealt with these early limitations well enough that VOIP is now beginning to compete with traditional circuit-switched telephony in many organizations.
VOIP holds significant potential benefits for any organization interested in voice and data integration. To start with, it can greatly reduce duplication of voice and data lines, because both voice and data can travel over data lines as well as the public network.
VOIP also can let you keep your legacy telephone gear because some IP private branch exchanges and most IP gateways work with analog phones.
Finally, VOIP technology can greatly reduce the cost of long-distance calls because calls stay local'the Internet covers the long distances.
Inexpensive IP gateways that attach to intranets also can save organizations bundles of money. For example, User A in New York wants to initiate a point-to-point call to a cohort across town or across the state. User A could dial a single number from his office phone. That number would connect with an IP gateway server on his LAN, which in turn would digitize the call, compress it and forward it over a WAN to User B.Leapfrog, anyone?
In this case, the call saved the organization money by bypassing both the local phone company and a long-distance provider; it took place entirely within the organization's intranet.
In many cases, intranet-based IP voice calling also bypasses the services of an Internet provider, avoiding even the monthly charges.
Industry representatives claim that bypassing traditional long-distance services saves up to 80 percent of an organization's communication costs in high-traffic, long-distance situations. A technology overview from E-tel Corp., an IP phone and gateway manufacturer in Warwick, R.I., claims that under the right conditions, a VOIP system can pay for itself in less than six months.
But as with any other emerging technology, there are a few problems in paradise. VOIP is beset by a muddle of different standards, nomenclature and hardware that makes it difficult for interested buyers to know where to begin.
IP PBXs represent a fairly new class of office-based telephone switches for IP voice. Like IP gateways, IP phones also convert analog voice to data, but many of them require attachment to computers, and many others work mainly with proprietary voice server or PBX systems such as Nortel Networks' Meridian 1.
If you require a comprehensive approach to VOIP, and your budget allows it, check out enterprise VOIP systems that use equipment ranging from carrier-class servers to IP PBXs to other types of phone systems.
When in doubt, go with an IP gateway, such as the products included in the accompanying chart.
At its simplest, an IP gateway is a standalone piece of network equipment placed between the Internet or an intranet and an analog telephone set.
It translates analog voice data to digital packets and compresses them, letting a standard phone set make VOIP calls.
The gateways in this guide range from inexpensive products with two or four analog ports to Mockingbird Networks' $24,000 Nuvo 200, a highly scalable gateway'24 to 240 ports'with a full range of compression standards capable of forming the foundation of an enterprisewide IP voice system.
One of the problems VOIP has that circuit-switched public networks do not is low bandwidth. The result is packet congestion on high-traffic Internet networks.
Voice packet delays or losses show as gaps in conversation or a clipped-speech effect that is unacceptable for business communication.Please knock
IP gateway builders have turned to a variety of standards, compression techniques and voice coding algorithms that greatly improve the quality of Internet voice transmissions.
The main VOIP specification is the International Telecommunications Union's H.323, which defines how voice, data and video traffic move over IP networks. It uses the Real-Time Transport Protocol and Real-Time Control Protocol (RTP/RTC) for managing audio and video signals.
One of the most important things about H.323 is that it ensures that VOIP gateways and other IP telephony gear give greater priority to time-sensitive voice and video traffic than to other data types, reducing transmission delays.
Subsets of the H.323 specification include voice coding systems, or codecs, such as G.711, G.723.1 and G.729. Each of the codecs provides different levels of compression that can be applied as network traffic increases and available bandwidth shrinks. J.B. Miles of Pahoa, Hawaii, writes about communications and computers. E-mail him at firstname.lastname@example.org.