Instant messaging, voice, video, and other real-time communications will be supported by a server product and a developer kit coming in the third quarter of 2003, Microsoft has announced. Real-Time Communications Server (formerly code-named Greenwich), based on the Session Initiation Protocol (SIP), will eventually replace Exchange as Microsoft's enterprise real-time communications product, while the kit will help developers add SIP routing to applications such as help desk systems. However, many technical and licensing questions remain on both the product and the kit.

The announcement that Greenwich will be a product, rather than a free add-on to Windows Server, will be welcome to companies such as Cisco and Lotus that have SIP products and might find it difficult to compete with a no-cost offering from Microsoft.

Server Supports Enterprise Real-Time Communications

Real-Time Communications Server (RTC) 2003 will provide server-side support for SIP, which Microsoft already supports in Windows XP and its Windows Messenger real-time communications client. (Windows Messenger also supports the separate protocols used by Exchange instant messaging and the public .NET Messenger service). SIP is a standard for setting up and ending real-time communications sessions, such as instant messaging (IM), voice calls, videoconferences, and application sharing. SIP enables users to locate one another on the network, start communication sessions, and end sessions. SIP itself does not manage data exchanged during sessions or provide features such as IM or video streaming. Other protocols such as SIP Instant Messaging and Presence Leveraging Extensions, or SIMPLE, provide these functions on top of SIP.

RTC Server will be an enterprise product for SIP-based, point-to-point real-time communications. Tasks performed by the product will include the following:

Session routing (proxy). RTC Server will act as a SIP proxy, routing SIP sessions sent to a published user address to the actual network location of the user. For example, a caller could initiate an IM session to a user's e-mail address (such as rhelm@directionson.com); RTC Server would then route that session to the computer where the user was currently located (such as asterix.dom.com).

Registration and location. RTC Server will act as a SIP registrar and location server: it will enable users to register their current network locations and allow SIP proxies (including the SIP proxy in RTC Server) to look up user locations when routing sessions.

Authentication and access control. RTC Server will authenticate users via Active Directory and will enforce organization policies (such as blocking IM sessions from the Internet except those targeted at customer service operators).

IM and presence. RTC Server will implement SIMPLE, enabling users to register not only their network location but also presence status (e.g., online, away, busy), to determine the presence status of others, and to exchange text messages.

RTC Server will support only two-party, point-to-point communications sessions, not multiparty sessions such as conference calls, broadcast video conferencing, or text chat.

Kit Supports SIP-Based Applications

Complementing RTC Server will be an SDK for developers. The most notable component of the kit will be a stripped-down SIP proxy which developers may redistribute with applications. With this proxy, developers will be able to create applications that perform SIP session routing, such as help desk applications that route incoming voice calls to the least-loaded operator.

However, the kit will not deliver other parts of RTC Server, such as the support for registration, authentication, and IM. Developers will have to create these functions themselves in their applications or rely on SIP infrastructure from Microsoft or other vendors.

Many Licensing, Technical Unknowns

Both RTC Server and the redistributable proxy will run exclusively on Windows Server 2003. RTC Server will also require Active Directory.

Microsoft has not announced pricing for RTC Server. In particular, it has not indicated whether customers using Exchange IM (included with Exchange 2000) and Exchange 2000 Conferencing Server (a separate product) will be able to migrate their licenses to RTC Server. The SDK will be available to developers with MSDN Universal subscriptions, but the company has not yet decided which other levels of MSDN subscription will get the SDK.

Finally, relatively little technical information has been published on RTC Server or the SDK, and RTC Server has not yet had a public beta test, so the capabilities of each could change.

For background on the business case for RTC Server, see "'Greenwich' to Support Windows IM, Real-Time Communications" on page 6 of the Nov. 2002 Update.

For an update on Microsoft's real-time communications business strategy, see "Acquisition Moves Collaboration Strategy Forward" on page 22 of the Mar. 2003 Update.

For a roadmap to Microsoft's real-time communications clients and public services, see "Instant Messaging Split to Continue" on page 22 of the Apr. 2003 Update.