VoIP Implementation Considerations

By Larry Hettick
Network World 2009

Today we hear about some practical tips from our longtime colleague William (Bill) Flanagan who heads up Flanagan Consulting. Flanagan has a comprehensive understanding of voice and data technologies, products, markets and customers derived from more than two decades of telecom experience. In a recent online discussion group, Flanagan wrote, "Our team has been surveying sites where the existing analog PBXs are scheduled for replacement by VoIP installations. In most cases not much can be saved; most sites need lots of preparation before completing the changeover."

He continued by highlighting some key business case considerations for those looking to install VoIP:

• Cable lengths: Noting that many campuses are made from multiple buildings spread as far as 3 miles, Flanagan observes that while telco standard copper lines present no analog lines "where a local loop of up to 18,000 feet is standard . . . [but] copper cables for Ethernet. . . are limited to just over 300 feet."

• Space for remote switches: In "analog days", connections between house wiring and distribution cables were often made in "uncontrolled environments like boiler rooms, external electrical boxes, attics and basements -- not acceptable for active electronics." Flanagan warns: "Don't forget to plan for a space with power and climate control for the switch.”

• Phone power: Analog phones are frequently powered by a battery at the PBX. Flanagan observes: "Best practice now is for the local switch to inject power into the CAT6 wire to each IP phone. Then, only the switch needs local power."

• Backup power: What happens if a remote building served by VoIP loses power? Flanagan advises, "Best to plan for how long you want backup to last when each phone could be drawing up to 15W in addition to the switch's own drain."

• Lightning and surge protection: With LAN switches and electronic phones in a building, IT managers . . . "must consider the building's lightning protection. Bring back the surge protectors."

• Privacy: Flanagan correctly notes that "a clever hacker can tap an IP phone from just about anywhere over the network."His advice: "Security deserves attention to avoid vulnerabilities and to balance risks against protections."