Small businesses constitute the biggest sector of the market. A major question going forward is how quickly SMBs -- and especially the smaller players among them -- will adopt VoIP. The news to date has been mixed.

The segment clearly is being targeted by vendors. This week, Microsoft said that it will offer Packet8's VoIP system on its Response Point small-business phone platform. The two companies will jointly market the combined gear through their value-added reseller channels and promote it in other ways. Earlier this summer, Sotto Wireless said that it is selling a small office/home office (SOHO) product at Costco Wholesale Business Center stores in Washington state, California and Phoenix.

The Sotto and Packet8 news items, in and of themselves, are not earth-shattering. They do, however, point to the fact that VoIP is well on its way to becoming an everyday option for even very small businesses.

Indeed, the movement of small- and medium-sized businesses from legacy on-premise phone systems to VoIP is moving along nicely, according to a report released this week by Access Markets International.

The study, which looked at the telecommunications tendencies worldwide of companies with as many as 999 employees, said that the total on-premise market, including legacy and new gear, will hit the $6 billion mark this year. The study also said that the IP-PBX/converged network segment will grow from $2.77 billion two years ago to $4.32 billion in 2012.

The migration, which the analyst on the project labeled "encouraging," is being spurred by positive results from early implementations. The key to maintaining and accelerating the momentum, the report suggests, is to provide ways to further lower ROI time frames.

IP PBXes and the broader world of VoIP provides the underpinnings of unified communications (UC). Put another way, UC is the culmination of what starts with VoIP. The question is when and how smaller companies, with less expertise and manpower, will adopt this tool.