It is easy to let the iPBXs, IP phones, wireless IP access devices, and the other Internet gadgetry obscure a more direct and inexpensive path to voice-over-Internet protocol (VoIP). As a practical matter, you can keep your existing phone gear, purchase a VoIP gateway, and take advantage of VoIP's toll bypass benefits. The industry may have moved beyond its money-saving proposition, but if you're finally now taking the VoIP message seriously, the VoIP gateway can be a comfort. They are easy to install and administrate, and the bottom line benefits show up immediately in lower telecom costs.

These stand-alone, low-maintenance appliances hang off your PBX's station or trunk ports. They convert analog voice to digital, then transmit the signal via a 10BaseT port as IP packets to your private data network or the public Internet. A companion VoIP gateway at a remote site performs the opposite translation, turning voice packets back to a voice signal for your phone system or directly connected phone. For businesses with high enough intra-company call volume, the savings in long distance toll charges will typically pay for the equipment in under a year.

Although there are other standards, most of the gateways we've written about (and this feature's roundup is no exception) conform to H.323. Originally designed for videoconferencing, H.323 was expropriated by the telephony world and defines how endpoints (for example, IP phones) communicate with each other. Among the many substandards in the H.323 omnibus, there are ones defining codecs for audio compression (G.711, G.723, G.729) and call signaling for setting up and breaking down connections between end points (H.225).

Once the H.323 gateways are in place and saving your organization long distance toll charges, you're halfway to the goal that originally seized your technological imagination: VoIP at the desktop. An H.323 gateway lets you extend your telephony network by plugging hard IP phones or soft IP clients (like NetMeeting) into the local area network (LAN). You gain the pleasures (and cost savings) of instant installation and fret-free moves-adds-changes (MACs). And, you can make this daring move without purchasing a new IP PBX.

Talk to the Guy That Owns One

As we pointed out in last month's ATM-Frame Relay feature, domestic carriers receive enormous revenues (around $12 billion last year) from businesses paying for nuts-and-bolts leased lines - T-1, fractional T-2, or 56Kbps - between the main office and remote sites. So it should, in theory, be easy to find a company that has moved its voice traffic from the phone network to an overbuilt data network.

To help me in my VoIP quest, I contacted Multi-Tech (Mounds View, MN - 800-328-9717), whose MultiVOIP gateway we found to be one of the easiest to configure. The company put me in touch with Metal-matic, an old economy company that makes steel tubing for the auto industry. Jeff Hoffmann, the IT director, told me the Metal-matic wide area network consists of a single point-to-point T-1 linking the outfit's Minneapolis headquarters to a satellite manufacturing plant.

The main PBX rests at Metal-matic HQ. Jeff linked a MultiVOIP to eight of the PBX analog ports and to the LAN. At the satellite office, he installed a companion MultiVOIP. Because MultiVOIP supports FXS signaling (as do most gateways), Hoffmann attached analog phones directly to it. The analog phones at the PBX-less remote office could now be reached from any extension at the main office. To call manufacturing, staffers at HQ enter a special access code, which causes the gateway to route the call over the T-1 to the remote gateway. The directly connected analog phone rings and the toll saving starts.

My next VoIP gateway led me to a Canadian long distance reseller, Multi-Sync Communications. Multi-Sync provides flat-rate calling in the Toronto metropolitan area to its business subscribers. Businesses call a local number and connect to one of Multi-Synch's colocated switches. An access code is required to enter the Multi-Sync private network. Once in, the call is routed over leased lines to the destination switch and the called party's phone. With flat rates, you can talk as long as you want.

To maintain its rate structure for connections between cities in different area codes, Multi-Sync installed VoIP gateways (from Multi-Tech) to send calls through the free public Internet, as well as over permanent virtual circuits rented from service providers. Multi-Sync's subscribers place calls without knowing their voice is travelling as IP packets. Toll avoidance for this long distance reseller gets translated into an unlimited fixed-fee calling rate for its subscribers.

A Gateway Expert Speaks

To learn more about how a VoIP network is used in practice, I spoke to Thomas Liu, president of Voipack (San Jose, CA - 408-452-7916), a VoIP consulting firm and gateway vendor. He's helped a number of companies establish VoIP networks and had some practical insights into how they should be set up.

Liu recommends sending intra-company outbound calls over the gateway's FXS jack (linked to your phone system's trunk port) and accepting inbound calls on the gateway's FXO jack (linked to the phone system's station-side port). To dial out, callers enter a single-digit access code (i.e., "8") to seize a "trunk," receiving dialtone from the local gateway. They then enter an additional two- or three-digit access code, which has been mapped into the IP addresses of remote gateways.

When the remote gateway is signaled, it returns a second dialtone to the caller. The caller appears to the remote phone system as another local extension because the call is routed to the phone system's station port. To reach another extension or check voice mail, these VoIP interlopers enter the three- or four-digit extension numbers of the phone system's dialing plan.

Liu notes that a VoIP network also lets businesses convert long distance call to local ones when the call is to an area code at which a remote gateway resides. How? After the intra-company caller is inside the remote phone system, he can go "off Net," entering the traditional "9" to place a local call over the POTS network. Businesses effectively pay local charges for long distance service (see The Mother of All VoIP Networks).

Beyond Saving Money

While toll avoidance is worthy, there's more to a VoIP gateway than saving a few bucks. H.323-compliant gateways can accept calls from any H.323 endpoint, either a softie, like NetMeeting, or hard IP phones. An obvious application is to install an H.323 client application on your road warriors' laptops. For communicating in the field - checking voicemail, talking to someone at the office, or making long distance calls - they place a local call to your ISP. After they bring up their H.323 client, and connect to the H.323 gateway at the home office, they'll have access to all the services of the main PBX, wherever they may be.