As the promise of converged technologies grows ever closer, we are seeing some small steps that could have some big implications. One of those is "presence", which refers to the ability to know whether other users are online or not. This sounds pretty cool until we realize the converse is true; others know whether we are online or not.
This technology and ability aren't really new. The "finger" service and protocol have been around since the mid- 1970s. It was a way to tell who was on a given host and what program they were executing. Of course, for security reasons, nearly everyone has disabled this service and blocked its ports. Today, presence is most often found in the Instant Messaging world, where services such as AOL's AIM, Microsoft's Messenger and Lotus' Sametime give friends, family and colleagues the ability to know whether someone is at their computer in addition to the quick text messaging. Predictably, a significant percentage of companies have blocked these services as well.
What is relatively new is the interest in merging instant messaging and IP Telephony. The IETF has a number of drafts and specifications in the works now, including the Common Presence and Instant Messaging (CPIM) and SIMPLE, which is the SIP for Instant Messaging and Presence Leveraging Extensions.
Given the recent push for interoperability, SIP will likely get a big boost in adoption and when IM and IP Telephony share a common signaling mechanism, enterprises are naturally going to want to integrate the two.
If presence is something that appeals to you, you can integrate your VOIP and IM today using products that support SIP already, such as Lotus' Sametime. If you are planning to deploy VOIP or IM, be sure to consider their support for the SIP protocol. And you will certainly want to consider the security implications of having an IP-based telephone with an instant messaging client on your network advertising its presence and your username to the world.
Thomas Alexander Lancaster IV is a consultant and author with over ten years experience in the networking industry, focused on Internet infrastructure.