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January 2007 SIP Magazine
Volume 2 / Number 1
SIP Magazine January 2007 Issue

SIMPLE in the Enterprise

By Richard “Zippy” Grigonis, Feature Articles



If and when IM (Instant Messaging) and presence eventually become an IETF standard, the SIMPLE protocol will undoubtedly be the principal component, thanks in part to its ability to integrate IM/presence with voice, video, data-sharing, and other elements of conferencing and real-time collaboration. Every major telecom software and hardware vendor now has support for SIP/SIMPLE, or soon will.

SIP is a control protocol for initiating, modifying and terminating IP sessions such as multimedia conferences and IP telephony calls. Its functions thus parallel those of SS7 in the PSTN (Public Switched Telephone Network). SIP simply makes communication possible. SIP works with other IETF (Internet Engineering Task Force) protocols to actually achieve communications. Given its humble beginnings, SIP wasn’t originally designed to centrally concentrate all call intelligence, or provide network usage information for billing purposes, or handle all facets of security, or support overlapping dialing, or completely replace the PSTN (the original NNI, or network-to-network interface approach, presumes a closed network like an SS7 network). This is why SIP has undergone some extensions in recent years and/or relies on other protocols (e.g. XCON for centralized conferencing), which in turn is why SIP is popping up everywhere.

SIP can deal with multimedia multi-party sessions; the use of SIP for two-party multimedia telephony was first suggested by Scott Petrack of eDial (later Divisional CEO of Alcatel), because two-party audio-only calls seemed to him to be a trivial limiting case of collaboration. The varied nature of multimedia suggests conferencing and collaboration applications, and for conferencing and collaboration to be truly effective, IM (instant messaging) and presence-awareness (or “availability”) signaling must be supplied either by adding additional signaling extensions to SIP, or else developing something different, such as the IETF’s XMPP (Extensible Messaging and Presence Protocol) suite, found in the Jabber IM system.

In the case of SIP, an IETF working group extended SIP functions and came up with SIMPLE (SIP for Instant Messaging and Presence Leveraging Extensions) — Jonathan Rosenberg, formerly of dynamicsoft, now of Cisco, co-author of the original SIP specification, is also the principal figure in SIMPLE’s development.

Don’t let SIMPLE’s name fool you. As the Wikipedia says, “Despite its name, SIMPLE is not simple. It is defined by about 30 documents or more than 1000 pages (7 times more than HTTP 1.1, 15 times more than SMTP and IRC).”

Even so, SIP/SIMPLE definitely overshadows competing protocols. Most non-SIP IM protocols are relegated to solely handling text communications. This compels their users to resort to other approaches when using voice and video — namely, SIP. The SIP extensions in SIMPLE are a comprehensive standards family for events, presence and IM, so non-SIP IM will probably fade over time, since most public and enterprise services are deploying SIMPLE or migrating to it. Major IT companies such as Microsoft and IBM support SIMPLE and SIP/SIMPLE is the official 3G wireless multimedia protocol and a cornerstone of IMS (IP Multimedia Subsystem), a universal service architecture for the worlds of both wireline and wireless.

Microsoft Windows Messenger soon adopted SIMPLE, as did the Microsoft Office Live Communications Server (LCS), starting in 2003. In 2005, some improvements were made. Microsoft Office Communicator 2005 provides integrated communications capabilities that include IM, extendable presence with Microsoft Exchange Server calendar information, PC based voice/video, and VoIP telephony. Live Communications Server enables users to determine the status of other users (e.g., away, buys, idle, do not disturb) and whether they are offline or unavailable. Microsoft Office Communicator 2005 can display offline presence details even if a user is not logged in — you just right-click on the user name, and the system will tell you whether the person in question can be reached via other forms of communication such as email or a telephone. The platform can also serve as the presence engine for team sites and portals, thus making available presence and IM access from within Windows SharePoint Services and SharePoint Portal Server sites. Live Communications Server 2005 (with Service Pack 1) allows security enhanced IM and presence information to travel between public IM service providers so that enterprises can collaborate with business partners just like co-workers, while keeping sensitive business information encrypted and logged. This can be taken to its most sophisticated incarnation, federation, which enables an organization to establish trusted relationships with other organizations, allowing users to initiate and share IM sessions and subscribe to user presence across organizational and network boundaries without a VPN connection.

SIMPLE’s use will continue on into Microsoft’s successor platform, Microsoft Office Communications Server 2007 (OCS), currently in beta, to be released in the second quarter of 2007. (“Live” was nixed from the product’s name to avoid confusion with Microsoft’s hosted Office Live and Windows Live.) Deployed with Microsoft Exchange Server 2007, the business-oriented OCS will help make Microsoft into a major player in the unified communications market. OCS will also integrate its functionality into Microsoft’s Office products — particularly the 2007 Microsoft Office applications. Clicking on a fellow worker’s name in Office Outlook 2007, Office Word 2007, or the Office Communicator client will initiate a call. A revision to the desktop Office Communicator software offers VoIP capabilities along with various telephony capabilities (users can enjoy such features as call hold, call forward, and call transfer), web conferencing (previously offered via hosting in Live Meeting), incremental chat, corporate instant messaging and richer presence capabilities. Microsoft has also forged alliances with partners to help facilitate the development of sophisticated unified communications platforms, such as the Innovative Communications Alliance (ICA) with Nortel. This will be a user-centric software-based approach enabling a user to maintain a single identity across email, voice mail, VoIP, call processing, IM and video, as well as embedding communications functionality into the Microsoft Office system and thirdparty software applications.

Microsoft is considering adding support for the XMPP protocol, but their commitment to SIP and SIMPLE is such that you shouldn’t expect anything any time soon. IBM’s Sametime IM and web conferencing platform supports both XMPP and SIP/SIMPLE. IBM Sametime is interoperable with AIM, and IBM recently announced upcoming interoperability among Sametime, Google Talk and Yahoo IM networks. A feature in the new Lotus Sametime 7.5 is location awareness, which informs you not just if your chat partner is available, but whether he or she is at a desk, in a home office, working in a hotel room, or elsewhere. The person can leave a detailed message, such as “I’m in a meeting with a vendor”.



SIMPLE and XMPP have been positioned as competing technologies. XMPP is basically a data transport protocol for streaming XML elements — called “stanzas” — between any two network endpoints. Message and presence stanzas are both defined as core data elements in XMPP and are generally used to exchange instant messages and presence information between IM users. XML is extensible and applications can use the general semantics of these stanza types for other purposes, but XMPP focuses on IM and presence. SIMPLE, on the other hand, is more general in nature, making it suitable for not just presence and IM, but voice, video, push-to-talk and other types of communications. SIP has even been used to add voice to XMPP-based IM systems.

There are ways for SIMPLE and XMPP can work together, however. SIMPLE is basically a paging protocol meant to perform signaling via SIP methods but not actually carry anything else. For SIP/SIMPLE, the signaling occurs using basic SIP methods and the media data (e.g. voice and video) is exchanged using dedicated data transport mechanisms such as RTP (Real-Time Transport Protocol). Since SIP can rely on various media types and media transports, it can use XMPP as just another one of these media transports, a peer to RTP. SIP can then be used to set up and manage XMPP IM sessions.

Even so, XMPP is still slowly gaining in popularity. Sun’s Java System Instant Messaging offers presence by using XMPP in an integration of Sun’s Messaging, Portal and Calendar servers. In January 2006 Google made Google Talk into an open federation product so that you can now chat with users on other XMPP services. Shortly thereafter, Jive Software released its XMPP-based Wildfire 3.1 enterprise IM server, that allows for communication with users on proprietary IM networks, such as AOL.

SIMPLE still has an edge, however, and will continue to worm its way into everyday business and consumer applications.

Richard Grigonis is Executive Editor of TMC’s IP Communications Group.



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