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VoIP at the Branch Office
The branch office is probably the best place to begin implementing VoIP. Branch offices typically are small and do not generate overwhelming amounts of traffic. These sites are most likely to benefit from the toll-bypass capabilities of VoIP as a replacement for long-distance services. And, if these sites do not have a dedicated PBX, you can offer users some advanced call-management features in exchange for using them as guinea pigs.

However, these criteria may not reflect your branch-office environment(s). If you house several hundred users in a particularly large remote office, chances are good that you will experience infrastructure problems. Similarly, if the remote office already has a PBX, then there is little need to introduce new equipment, unless the existing gear is at the end of its life cycle. Or, if you route your long-distance calls over a fixed-cost dedicated circuit, you might not save much money on long-distance charges back to HQ.

This last issue is perhaps the most interesting, as it is frequently touted by vendors. Though you can place many more G.723 or G.729 calls over a T1 line than you can with voice, you cannot with G.711, which uses a full 64 Kbps of bandwidth in each direction. Furthermore, many voice-compression products grant you the benefits of G.723 and G.729 with your equipment.

The real cost benefit of using VoIP as a long-haul alternative comes in the ability to use the Internet for connectivity between offices, as opposed to paying per-minute usage rates on the PSTN or competing with a private WAN infrastructure. In this scenario, it is highly feasible to buy guaranteed services from an ISP, and then route VoIP calls over that connection, instead of paying long-distance toll charges or buying a dedicated network of your own. Providing VoIP services to a field office also affords you the option of integrating these users into your corporate dialing plan, voicemail system and other services, for less than the cost of a traditional PBX.