There are more differences in philosophy and approach than in ultimate functionality.

IBM Lotus Sametime and Microsoft Office Communications Server 2007 are the two most widely deployed premises-based enterprise unified communications systems – loosely defined for these purposes as a system that includes elements of presence, instant messaging, voice and/or voice conferencing, web conferencing, mobility, unified messaging, and/or videoconferencing, all integrated through a common user interface and experience. For the purposes of this article, we lump Microsoft Office Live Communications Server (LCS) and Microsoft Office Communications Server 2007 together for simplicity and refer to them collectively as Office Communications Server or OCS.

We estimate that there are approximately 20 million paid Lotus Sametime licenses, based on information from IBM Lotus, while Microsoft OCS/LCS has somewhere between 10 and 20 million clients deployed (we have no indicators from Microsoft regarding how many clients are deployed and how many are paid licenses).

To put these numbers in perspective, this installed base of roughly 30 - 40 million unified communications clients represents less than 5 percent of the addressable market. With so many more desktop, laptop and PDA clients still to be converted to unified communications, the stakes are high, and Microsoft and IBM Lotus both want a dominant share of this emerging market. These companies are regarded as fierce competitors in any market they enter. Both are well capitalized, and they are ramping up their development and sales/marketing teams in order to seek significant revenue in the unified communications market.

This article contrasts and compares the unified communications solutions these two giants offer.

Significant Functional Differences

Out of the box, there are a host of differences between OCS and Sametime; however, when one includes partner company integrated solutions, there is little that OCS can do that can’t be done with Sametime, and vice versa. There are some notable exceptions.

A major difference is that Sametime can be deployed on multiple operating systems, including Windows, whereas OCS will only play in a Windows Server environment. Furthermore, Sametime integrates with Outlook and other Microsoft Office applications, but OCS does not integrate with Lotus Notes.

On the other hand, OCS allows Office Communicator 2007’s IP voice and video to traverse both corporate firewalls and network address translation devices, letting remote users come in over the Internet, but Sametime’s IP voice and video are designed to work over the enterprise LAN/WAN.

Microsoft has developed software-based call routing and switching capability within OCS 2007 with the intent that it will ultimately supersede, or at least render less valuable, the PBX capabilities offered by most enterprise telephony vendors. Although IBM Lotus has publicly declared that Sametime will rely on third-party PBX vendors to provide telephony capabilities for Sametime, IBM has not publicly revealed the details of its pending Sametime Unified Telephony offering and architecture.

There are numerous other differences, large and small, but the biggest differences are found in the approaches these two giants bring to the unified communications market.