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A voice-over-IP gateway can be loosely defined as a mechanism that takes circuit-switched voice from a traditional PBX, converts it to IP and transfers it across a LAN or WAN to another gateway where it is reconstituted back into a format that is understood by the receiving phone system.
Gateway functionality can be obtained through stand-alone boxes, modules or chassis cards for proprietary boxes; also expandable routers or software and expansion cards for Windows NT servers.
For example, Cisco is taking a modular approach with a voice-over-IP card that fits its 1750, 2600 and 3600 series routers. Suda Madabusi, product manager for the Cisco 1750, says all Cisco products can easily be equipped for voice. Cisco says voice packets can be guaranteed via quality-of-service policy implementation on a Cisco-switched network.
Lucent, Nortel Networks and Siemens offer similar strategies for providing voice-over-IP gateway capabilities in some form or another.
While gateways are the most popular voice-over-IP products on the market -- available from at least 30 vendors -- the key point here is that you have voice packets running over IP. However, the packets are not running on the Internet, and you're not gaining any of the features and capabilities you get by converging voice and data networks.
Until recently, IP PBXs have mainly been targeted at small or branch offices with 100 users or less, but Alcatel recently announced OmniPCX, a voice-over-IP system that incorporates gateway and call processing in a single device and can accommodate up to 50,000 users. Additionally, 3Com, Lucent and Cisco have all announced plans to provide the same type of product.
Cisco's Selsius products and 3Com's NBX series fit in this category because the goal of both is to provide the same services as OmniPCX on a large scale. However, while initial versions of these products are in trial stages, they have not been proven for high numbers of users. Alcatel is the first to stake that claim, and Cisco and 3Com will have products in the future that compete. 3Com now says its product is only for midsize businesses with less than 500 users.
The beauty of an IP PBX is being able to create a distributed system. For example, Nokia's IP Telephony Gateway and Shoreline Teleworks' ShoreGear IPBX allow you to distribute your phone system throughout an IP network, so geographically separated phones -- with features such as direct dial, call forwarding, conferencing and voice mail -- provide the appearance of being connected directly to the local PBX. Alcatel's, 3Com's, Lucent's and Cisco's IP PBXs do not offer these features.
Four ways to do VoIP
A do-it-yourselfer's guide to installing voice over IP on your enterprise network.
 
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Gateways: popular, but lack features
A voice-over-IP gateway can be loosely defined as a mechanism that takes circuit-switched voice from a traditional PBX, converts it to IP and transfers it across a LAN or WAN to another gateway where it is reconstituted back into a format that is understood by the receiving phone system.
Gateway functionality can be obtained through stand-alone boxes, modules or chassis cards for proprietary boxes; also expandable routers or software and expansion cards for Windows NT servers.
For example, Cisco is taking a modular approach with a voice-over-IP card that fits its 1750, 2600 and 3600 series routers. Suda Madabusi, product manager for the Cisco 1750, says all Cisco products can easily be equipped for voice. Cisco says voice packets can be guaranteed via quality-of-service policy implementation on a Cisco-switched network.
Lucent, Nortel Networks and Siemens offer similar strategies for providing voice-over-IP gateway capabilities in some form or another.
While gateways are the most popular voice-over-IP products on the market -- available from at least 30 vendors -- the key point here is that you have voice packets running over IP. However, the packets are not running on the Internet, and you're not gaining any of the features and capabilities you get by converging voice and data networks.
IP PBXs: great features, scalability lacking
IP PBXs, such as Altigen's AltiServe and Artisoft's TeleVantage, are great if you have the luxury of designing your system from the ground up. IP PBXs are complete phone systems, usually with IP phone options that include many of the IP telephony applications, such as managing your phone from your desktop PC, multiline call control and automatic call distribution. IP PBXs are usually NT servers with telephony software and voice cards. Disadvantages often include scalability and a dial tone that's dependent on NT, which doesn't offer the same uptime as a switched phone network.Until recently, IP PBXs have mainly been targeted at small or branch offices with 100 users or less, but Alcatel recently announced OmniPCX, a voice-over-IP system that incorporates gateway and call processing in a single device and can accommodate up to 50,000 users. Additionally, 3Com, Lucent and Cisco have all announced plans to provide the same type of product.
Cisco's Selsius products and 3Com's NBX series fit in this category because the goal of both is to provide the same services as OmniPCX on a large scale. However, while initial versions of these products are in trial stages, they have not been proven for high numbers of users. Alcatel is the first to stake that claim, and Cisco and 3Com will have products in the future that compete. 3Com now says its product is only for midsize businesses with less than 500 users.
The beauty of an IP PBX is being able to create a distributed system. For example, Nokia's IP Telephony Gateway and Shoreline Teleworks' ShoreGear IPBX allow you to distribute your phone system throughout an IP network, so geographically separated phones -- with features such as direct dial, call forwarding, conferencing and voice mail -- provide the appearance of being connected directly to the local PBX. Alcatel's, 3Com's, Lucent's and Cisco's IP PBXs do not offer these features.
