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SIP/SIMPLE vs. XMPP – Why are there (at least) Two Competing UC Standards?

September 30, 2011

If the unified communications (UC) interoperability landscape isn’t confusing enough we find that, among the market leaders, the technology being used for instant messaging and presence (IM&P) is based on two completely incompatible standards: SIP and XMPP.  Yes, you read that right – these aren’t minor variations or subtle interpretations of a single standard; these are two completely different standards.  This isn’t “You say *tomayto*, I say *tomahto*”, this is: “You speak Chinese and I speak English”.

How did that come to be?  What does this mean for UC interoperability?

First, let’s take a look at the specific issue.

Is either SIP/SIMPLE or XMPP a single standard?

SIP and the IM&P extension, SIMPLE, was ratified in 2004 in a series of IETF RFCs (‘Request for Comments’ aka ‘standards track’ documents).  These documents were authored by various contributors, but the main contributors to the SIMPLE specs were dynamicsoft, Inc. (now owned by Cisco), Microsoft and Cisco.  There are as many interpretations of these standards as there are implementations: few, if any, are interoperable.

XMPP was ratified in 2004 in a series of IETF RFCs, sponsored mainly by Jabber Inc. (now owned by Cisco) and its open source program, the Jabber Software Foundation.  There are now many implementations of this standard (see below) and there are interoperability problems.

How two competing standards for the same concept were defined in the same standards body around the same time, and why the implementations diverge from the standards will be a topic for another day.

Who Builds on What Standard?

Since the late 1990s, IBM has been shipping its Sametime enterprise IM&P product and pretty much owned the market until other vendors saw the IM&P market start to merge with what we now call UC.  Sametime is based on a proprietary protocol owned by IBM and implemented only by IBM (i.e. it is neither SIP nor XMPP based).  There are SIP/Sametime and XMPP/Sametime gateways in the market shipped by a range of vendors.

Since 2002 Microsoft, like many other UC vendors in the Gartner Magic Quadrant for UC, has based its IM&P features on a set of standards known as SIP/SIMPLE.  Many vendors, including Microsoft, ship SIP/XMPP and SIP/Sametime gateways.

Since around 2002, Jabber Inc. (see above) gained market share for enterprise IM&P in the Government and Finance market sectors, based on XMPP.

Around 2006 Google launched their Google Talk service, based on XMPP.  Google isn’t usually considered an enterprise UC vendor, but they clearly have mindshare in the market.

Whereas Avaya had previously implemented its UC product line on SIP and SIMPLE; in early 2008 Avaya shipped its Intelligent Presence Server product based on XMPP after it acquired a license for the Jabber XCP implementation.  The reasons for this change in strategy are opaque, but the impact on interoperability is clear.

Cisco supported the SIP/SMPLE standard up to UCM 7.0.  However, in late 2008 Cisco acquired Jabber Inc., (see above) and started to ship XMPP based IM&P in UCM 8.0 (2010).  Once again, the reasons for this are opaque, but this added another dimension to the interoperability puzzle.

The Bottom Line for Interoperability

If you own or are considering purchasing any of the IM&P technologies mentioned above; and interoperability is important to you, your challenges will be many and various:

  • SIP implementations don’t interoperate with each other
  • XMPP implementations don’t interoperate with each other
  • Neither interoperates with the other.

So what are your options?

  1. No interoperability (some companies are happy just using IM&P to communicate internally)
  2. Implementing a series of gateways to implement bi-lateral interoperability, e.g. SIP to XMPP
  3. Evaluating a multi-lateral interoperability service such as NextPlane.

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