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VoIP for the Telecommuter
Telecommuters are a tough group to support. They need data lines and separate voice circuits--both of which rack up huge costs. And there is little hope for seamlessly integrating them into a corporatewide call-management system because the most-advanced options usually are telco-provided Centrex services. But VoIP holds tremendous promise for telecommuters. By providing a single data circuit and H.323-compliant equipment, you can integrate them into your network easily, with access to the company operator (just by dialing "0"), the voicemail system and other telephony resources. You can even reduce toll charges by letting the telecommuter place H.323 calls to remote offices. Telecommuters can also forward calls to a regional office without sacrificing any features.

Unfortunately, there are many hurdles to overcome before implementing VoIP for telecommuters, mostly involving bandwidth and network management. Users will need enough bandwidth to move VoIP traffic while simultaneously prioritizing, fragmenting and queuing other data to protect voice quality. If VoIP traffic gets caught up in the middle of a big database query over a 56-Kbps circuit, all the little H.323 packets get beaten up, turning a smooth-flowing call into something that sounds like a transistor radio at the bottom of a gravel truck.

In addition, circuits for telecommuters must be "nailed-up" during business hours, or calls to the user's equipment may not be established. For example, some H.323 devices attempt to measure latency to a remote system before establishing the call. For some of these systems, even ISDN's short call-setup times are too long, and calls will be rejected. Even if you could disable this feature, the setup time could still cause problems: Callers may not hear any rings or just two or three rings before the recipient hears any; some callers will give up before the recipient ever knows he or she has a call.

H.323's firewall-hostile negotiation mechanisms mean remote users will need direct connections into the corporate network, bypassing the public firewalls. This may or may not be in accord with your security policies.

All of these issues--prioritization, full-time connectivity and inside connectivity--practically dictate the use of flat-rate ISDN or xDSL (Digital Subscriber Line). ISDN is better-suited to the task than xDSL, since it offers two distinct channels that allow you to implement ToS (type of service)-based routing at both ends of the connection. Voice traffic can go down one circuit, and everything else can be shunted down the other.

In our survey of network managers considering VoIP, telecommuter sites were the last locations they expected to get the service. Still, the superior integration that you can provide will make you an instant hero in the telecommuters' eyes, and if you can implement the infrastructure required, the payback can be immense.