Of all the "pieces" of a business-level VoIP system, gateways may be the least understood. If you're in charge of setting up VoIP on your organization's network, selecting the right gateway is a crucial part of the process.
But before you make a decision, you first need to understand what this component does, how it works, and some of the options that are available. Let's look at the role VoIP gateways play and discuss some of the factors you need to take into consideration to choose the right one.
The role of the VoIP gateway
As most IT professionals know, a gateway is a device that provides a connecting point from one network to another. Gateways often act as transition points between networks that use different protocols — performing the translation tasks necessary for devices on either side to communicate with one another.
In the case of VoIP, a gateway is necessary to allow calls to go between the VoIP network and the public switched telephone network (PSTN). Without the gateway, users on a VoIP network can't make or receive calls to and from "outsiders" with traditional phone lines.
VoIP gateways are also necessary to translate between systems using different VoIP protocols (for example, between a SIP network and one that uses H.323). There are also VoIP-to-GSM and VoIP-to-CDMA gateways that route VoIP calls directly to Global System for Mobile communication (GSM) or Code-Division Multiple Access (CDMA) mobile numbers without going through the PSTN network (and thus in some cases incurring additional charges).
Hardware vs. software gateways
Like other gateway products such as routers and firewalls, we can divide VoIP gateways into two categories: software-only gateways and so-called "hardware" gateways. I say "so-called" because, of course, every gateway consists of both software and hardware.
The distinction is between gateway software that runs on a standard network operating system (such as Windows or Linux) and a gateway product sold as an "appliance" with the software preinstalled on the hardware's (often proprietary) OS. Even if the gateway appliance runs on a more general OS, that OS almost always serves only one purpose — running the gateway software — and you can't install other applications on it.
There are advantages and disadvantages to both types of gateways. Here are some advantages of the software gateway:
- It's less expensive to buy a software program only, and you may be able to install it on equipment that you already have. You may even be able to run the gateway software on a server running other services or applications, but there are security issues with doing so.
- It's usually easier to upgrade the hardware that a software-only gateway runs on, since it tends to be a standard PC running a standard OS. That means you can relatively easily add more RAM or a faster processor if you find you need it. Appliances may or may not be upgradeable and may require that you use special non-standard (and more expensive) components if you do upgrade them.
- Because it runs on a standard OS, you may be able to more easily monitor and manage the software gateway machine using the same network administration tools that you use for other PCs on the network.
On the other hand, gateway appliances offer some real benefits. Here are some advantages of gateway appliances:
- Appliances are often sold as "turn-key" solutions; you don't have to spend time installing the software — and troubleshooting problems that occur during installation. If the OS is proprietary, the same vendor will likely support the hardware, OS, and gateway software.
- Because the appliance is dedicated to a single task (VoIP gateway), you can optimize it for the best possible performance of that task. There won't be other OS services running on it that slow it down.
- If the appliance runs on a proprietary OS, it's likely to be more easy to secure than a PC running a standard network OS. Even if it runs on a standard OS, the vendor will have already removed unnecessary services and locked it down to make it more secure.
Factors to consider
Whether to go with a software gateway or a dedicated gateway appliance is a matter of personal preference and management priorities. Once you've made the decision, there are a number of other factors to consider when deciding exactly which gateway program or device to purchase.
This is especially true when buying a gateway appliance. An appliance's specs may be more rigid than a software program that you can install on hardware of varying cost and/or features.
Here are some factors to consider:
- Call load: It's important to make sure the gateway you select can handle the volume of VoIP calls that will need to go through it. Calculate the number of expected incoming and outgoing calls that users will make simultaneously at peak times — and then add 20 to 25 percent for future growth.
- VoIP protocol support: The two most popular VoIP call signaling protocols are the Session Initiation Protocol (SIP) and H.323. Your gateway must support the protocol used by your network's VoIP system.
- Compatibility: You need to ensure that the ports on the gateway are compatible with those on your private branch exchange (PBX) equipment.
- Cost: VoIP gateways cover a large price range, depending on type, brand, features, and capacity. You want the best VoIP gateway solution that fits your budget and meets your needs.
Some VoIP gateways have built-in extras such as advanced routing and firewalls. You can also get wireless VoIP gateways that, in addition to providing a voice gateway, serve as a wireless access point.
Examples of VoIP gateways
Many companies offer VoIP gateways. Here are a few examples:
- Motorola: With several different product lines, Motorola provides traditional, advanced, and wireless VoIP gateways designed to work with broadband Internet connections.
- Mediatrix: This company provides gateway products that can connect to traditional PBX systems as well as IP PBX, with both analog and digital gateways.
- NovaTec: This German company is one of the few that make VoIP-to-GSM gateways.
- Hypermedia: This company offers the CDMA Gateway Series for connecting IP PBX devices with CMDA cellular networks.
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Deb Shinder is a technology consultant, trainer, and writer who has authored a number of books on computer operating systems, networking, and security. She currently specializes in security issues and Microsoft products, and she has received Microsoft's Most Valuable Professional (MVP) status in Windows Server Security.
Debra Littlejohn Shinder, MCSE, MVP is a technology consultant, trainer, and writer who has authored a number of books on computer operating systems, networking, and security. Deb is a tech editor, developmental editor, and contributor to over 20 additional books on subjects such as the Windows 2000 and Windows 2003 MCSE exams, CompTIA Security+ exam, and TruSecure's ICSA certification.