XMPP vs SIMPLE: The race for messaging standards

There's a race on for the future of the enterprise messaging system. The contestants are backing competing protocols for IM and presence awareness. Which standard takes home the prize may depend less on technical merits than on brute force. At the head of the competition are SIMPLE (Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions) and the open-source, XML-based XMPP (eXtensible Messaging and Presence Protocol). Both are currently being developed by the Internet Engineering Task Force (IETF).

SIMPLE backers extol the broad media possibilities of a SIP-based signaling protocol with natural affinities for voice, video, and conferencing. XMPP proponents, on the other hand, tout an XML-based data transport technology that is built to manage IM and presence.

As it now stands, real-time communications in the enterprise is in its infancy. The long-term goal is to develop a single protocol that not only unifies real-time messaging with the tracking and notification of worker presence and availability but also allows for those functions to be performed across corporate boundaries and on a vast range of devices.

Beyond basic IM system interoperability, a common protocol for IM and presence holds the key for unlocking valuable state awareness from the tethers of a stand-alone system. The challenge of stitching availability awareness into a variety of systems -- both within and between enterprises -- is piquing the interest of heavy hitters. IBM Corp. and Microsoft Corp. have stepped up to the plate to declare standards compliance, regardless of whether the market or the protocols themselves are ready.

"It is very important here at this (early) stage of enterprise IM (for vendors) to say, 'We are compliant with these standards.' It is more important to say it than to do it," says Robert Mahowald, research manager at IDC in Framingham, Mass.

The favoured SIMPLE

SIMPLE is a set of extensions to the established SIP protocol that initiate, set up, and manage a range of media sessions, including voice and video. SIMPLE extensions define SIP signaling methods to handle the transport of data and presence.

SIMPLE's designers set out to develop a system that represented the communications state as broadly as possible, supporting presence not just for PC messaging applications but also for devices such as phones and PDAs, says Jonathan Rosenberg, chief scientist at Parsippany, N.J.-based Dynamicsoft Inc. and co-author of SIP and SIMPLE.

"We realized a long time ago that presence and IM (are) just another facet of communications, and that is what SIP is all about. IM is just like voice and video; it is another aspect of real-time, person-to-person communications," Rosenberg says.

SIMPLE's capability of unifying voice, video, and data messaging appealed greatly to Microsoft Corp., according to Ed Simnett, lead product manager of RTC (Real Time Communications) Server at the Redmond, Wash.-based software giant.

According to observers, one potential problem with SIMPLE is that it is a paging protocol meant to perform signaling but not to carry anything else. "(SIMPLE) can carry a brief conversation, which is great for single-session IM traffic and SMS traffic, but it is not very good for doing the heavy load to carry things like data signals or video signals on top," IDC's Mahowald says. "There is where you have to deviate from the standard to create your own extensions."

Because of the inherent limitations of SIP and because many SIMPLE extensions are still under construction, the existing implementations of the protocol from Microsoft and IBM have included proprietary extensions. Furthermore, SIMPLE is missing core IM-related functionality such as contact lists and group chat capabilities, according to observers.

Another potential pitfall with SIMPLE is that SIP uses both TCP and UDP (User Datagram Protocol) as transport layers. TCP includes congestion control, whereas UDP does not, thereby opening the door for packet loss during times of network congestion. According to dynamicsoft's Rosenberg, the IETF will address these issues as the standard evolves.

In addition, presence awareness might be problematic with SIMPLE, according to IDC's Mahowald. "I think when (Microsoft's) RTC rolls out later this year, it will be slightly less ambitious and more problematic than Microsoft thinks. But they will work it out. They will adopt the standard to do what they want it to do and still win the war of compliance."


Meanwhile, proponents of XMPP contend that an XML-based data-transport technology is better suited than a signaling technology to handle IM and presence. According to its designers, one major benefit of XMPP is that it can be extended across disparate applications and systems because of its XML base.

Bell South, for example, is using XMPP as a building block for constructing real-time, digital call-center applications, says Dale Malik, director of application development strategy at Bell South in Atlanta. "XMPP is a very robust communications protocol -- not just for IM. ... The fact that it is using XML as its messaging structure allows us to tie into other applications for ourselves for internal apps or offering services to enterprises," he says.

Industry observers claim that another strength of XMPP is that all messages go through a server, which allows the server to log and audit messages.

"That is a really big deal for a lot of our customers, particularly in the financial services space, which have (Securities Exchange Commission) regulations for how long they keep messages. It is an absolute rock-solid (customer) requirement that there be a single place that messages go through," says Joe Hildebrand, chief architect at Denver-based Jabber, a developer of an XMPP-based commercial messaging platform.

Jabber's extensibility and XML foundation is a considerable technical advantage over SIMPLE, according to IDC's Mahowald.

"Vendors, carriers, and users don't have to make much in the way of modifications to XMPP. It is highly extensible as opposed to (SIP/SIMPLE), which requires some fairly specific changes be made to it" to make it work for IM and presence, Mahowald says.

Countering Jabber's conclusions, dynamicsoft's Rosenberg says that the peer-to-peer capability of SIMPLE is actually a benefit because it avoids putting a heavy load on the servers. The initial message connection goes through servers, and then after that, all the data carried within the message goes directly between clients.

"You can support a lot more users with a particular hardware configuration because much less message traffic is passing though on the server," Rosenberg says.

Predicting the race's outcome

Despite the standards' respective technical merits, the race for supremacy may actually be decided by industry might. Following the lead of IBM and Microsoft, messaging giants Novell Inc. and Sun Microsystems Inc. have recently thrown their weight behind SIMPLE.

With its open-source genesis, XMPP is backed by considerable grassroots support. In addition, the protocol recently snagged some big-name backers, including Hewlett-Packard Co., Intel Corp.'s Wireless Computing Group, Sony Corp., and Hitachi Ltd. HP's ongoing interest in XMPP could be significant. HP has ported XMPP-based Jabber to both Windows and the HP-UX operating system and has recently inked a deal to resell Jabber as part of its professional services.

Although the Palo Alto, Calif.-based company is keeping the door open for Microsoft's RTC when it ships, HP is actively embracing XMPP because it supports multiple platforms and is scalable, reliable, and available today, says Michael Dang, manager of enterprise IM services at HP.

By providing a means for getting technology to market, HP could give XMPP the exposure and reach it needs to achieve success. "When a really large integrator like HP gets behind you, the possibilities are much greater to get the technology out there. That is the big war right there. That is what Microsoft is going to be able to do when it ships RTC this summer, paired with Windows Server 2003. They will get it out there on more desktops, and it is that kind of dispersion that creates a default winner," Mahowald says.

Although SIMPLE has gained momentum from the big vendors, XMPP counts tens of thousands of real-world deployments and a large, active open-source community that continues to develop the system, says Peter Saint-Andre, executive director of the Jabber Software Foundation at Denver-based Jabber. "Jabber really is the Linux of IM. There is a whole army of people out there with pitchforks implementing it. People who think there is not (momentum) have not heard the army."

But, according to industry analysts, SIMPLE has yet to hit the ground with large-scale, real-world deployments.

Whatever the outcome of the race between XMPP and SIMPLE, the landscape of IM standards may look considerably different several years down the road, analysts say. What ends up prevailing may be a hybrid or morphed version of SIMPLE that is better suited for IM and presence, IDC's Mahowald says. Rob Batchelder, president of Relevance, a consultancy based in Trumbull, Conn., agrees. The eventual standard, he predicts, will likely be a mixture of XMPP and some of IETF's work on SIMPLE.

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