On the other hand, both companies rely on partners to fill out certain telephony or UC needs. For the time being, for example, IBM doesn't plan to build call routing and switching capabilities into Sametime, Wainhouse noted in a report at the beginning of the year.
One big difference, of course, is that Sametime supports multiple operating systems and LDPA directories, while OCS runs only on Windows Server.
Asked if IBM is trying to make Sametime into an enterprise PBX, Marshak said no. "Our customers do not want us to do that." But, he added, if customers change their minds "we have every ability to do so."
Kelly agrees, noting Sametime Unified Telephony is based on Siemens Enterprise Communications' OpenScape unified technology platform, which includes most of the logic of a PBX. "So if IBM wanted to unwrap some of the layers, it wouldn't be a difficult stretch of the imagination to say they could compete head to head with Microsoft."
However, Rob Helm, research director at Directions on Microsoft, cautions that buyers haven't decided yet whether they want software-based communications suites running on commodity hardware from companies like IBM and Microsoft, or appliance-based solutions from companies like Cisco and Alcatel-Lucent.
"IBM has an army of professional services to back it up, which makes it one of the tougher competitors (for Microsoft) in the enterprise," he said.
On the other hand, Cisco's integrated platform "in some ways makes it even tougher."