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March 2006
Volume 1 / Number 2
Simple & MSRP: An Interview with Robert Sparks

Erik Lagerway

SIMPLE — SIP for Instant Messaging using Presence Leveraging Extensions. Whew! That was a mouthful. SIMPLE is an architecture for developing rich presence and messaging enabled applications. In other words you can build a skookum Instant Messaging application using this technology. This is true but it’s also much more than that.

In an attempt to get an accurate understanding of the current state of SIMPLE, I interviewed Robert Sparks the President of SIPfoundry (news - alert) and a member of the board. Robert is currently VP of Research and Development at Estacado Systems, providing solutions in real-time IP communications. Prior to Estacado, Robert held the CTO position at Counterpath (formerly Xten) focusing on SIP-based voice, video, instant messaging, and presence communication software and currently serves on the Technical Advisory Board at Counterpath. Before that, Robert was a Principal Engineer at dynamicsoft, the company that pioneered commercial SIP solutions. Robert is a co-author of the core SIP specification, RFC3261, and several of its extensions. He co-chairs the IETF’s SIMPLE working group. Robert has focused on improving the level of interoperability of SIP implementations by coordinating the SIPIt and SIMPLEt interoperability events and by contributing to the SIP Forum Interoperability Test Framework. Robert is currently on the board of directors of the SIP Forum, and is an active contributor to the reSIProcate project. Robert has a BSc in Computer Science and a MSC in Mathematics from Texas A&M University. Robert addresses SIMPLE as an open standard and the fact that this is now essentially finished in the IETF (Internet Engineering Task Force) and is on its way to the IESG (Internet Engineering Steering Group). This means that SIMPLE is now so close to becoming an open standard it’s hard to think of a reason it would not do so. This 25-minute interview has been truncated in this article but you can listen to it in its entirety on the Web at:

EL: Robert, where are we with SIMPLE today, is it nearing a useful state?

RjS: Definitely. The good news is that SIMPLE is primarily a done deal from a standards perspective. We have long finished the core parts of the protocol. The Working Group still exists and is active. With a couple of exceptions most of our work now is simply taking the last crumbs of the meal. The exceptions are to do with some ongoing work in putting together the last of the framework that’s needed for a user of SIMPLE to be able to tell a service provider what their preferences are on how people can reach them. Which are the last parts of the mechanism that let XCAP (XML Control Access Protocol) work. The XCAP data formats are all well defined and the protocol for the most part is well-defined. The one corner that we are working out right now is the modification of partial documents in XCAP. For example, if you want to modify your buddy list or make small changes to the buddy list or presence state without resubmitting the entire list back to the server. This incremental change piece is still something that is still in flight. Fortunately it’s almost done, in two to five months we should have that over that wall to the IESG. The second price that is still in flight is messaging sessions based on MSRP (Message Session Relay Protocol) which is in the very final process of the IETF standardization process. The Working Group has approved the documents and we are reviewing feedback before submitting this to the IESG.

EL: What will partial updates for XCAP mean to the users?

RjS: The best way to look at that would be talk about a couple of use cases. We currently have the technology to reproduce a classic Instant Messenger not unlike Yahoo!, MSN, AOL and that has been in place for a while. The work that we are doing right now will allow the user to say additional things apart from the typical status messages like “At lunch” or “On the phone”. Imagine this… I have two people on my buddy list, Ben and Adam. I want to show Ben my entire and private Presence state, which could easily include “I am on the phone with X customer.” And I want Ben to be able to see that, all I want Adam to see is “I’m on the phone.” The work we are doing right now will easily allow users to put this rich presence to work for them in a standard way so that you are not locked into one client or the other.

EL: So this is really empowering Presence now, allowing the users to leverage the benefits of rich presence, not just basic status messages which are static for all.

RjS: Exactly.

EL: This is a path to localized Presence and very specific presence meant for specific purposes that everyone can use.

In the past we talked about MSRP, and the importance of MSRP if SIMPLE was to take off and actually get some traction in the market. MSRP is required in order to provide the conferencing aspect to IM using SIMPLE, correct?

RjS: Sure, but it’s not just that. It allows us to treat Instant Messaging the same way that SIP treats voice. So anything we can do with Voice we can now do with an IM text stream.

EL: So now have conferencing, three-way calling, transfer etc.

RjS: Right, it also provides a much more robust way to introduce into your text stream like pictures, audio, video etc. An example would be that if we were in an IM session and I had a picture I wanted to show you. I could do that and we could share that image dynamically without interrupting the Text session plus associating that image with the session when we were done.

EL: So we can transfer images back and forth now, what makes MSRP so much better for this?

RjS: MSRP allows us to break the file down into chunks and sending these chunks over in multiple streams.

(For the remainder of this interview please visit

Robert goes into detail about how MSRP works and what the implication sit will have in Firewall traversal for file transfer and more. Robert also talks about how MSRP abides by Fair Use policies and takes into consideration the fact that bandwidth is not limitless. We talked about MSRP relay servers and the function of these servers in a SIMPLE network and who the vendors most likely to include this technology would be. Robert also mentioned that there are a few companies working with MSRP but none have released product yet, sounds like there could be a great opportunity here for a nimble software start-up! Robert sends a message to those working on MSRP to bring your wares to the next SIPit event in Tokyo in April 2006, find out more and register at or e-mail Robert closes with his positive and strong comments on the adoption of SIP by providers of business class VoIP and hosted IP Centrex. And that makes a great segue to my next article where I will be talking about SIP and VoIP in the enterprise and the powerful communications features that are now being deployed for business users at the edge of the network.

Erik Lagerway is an independent consultant and contributing writer for various publications, a full bio can be found here ( Contact Erik via e-mail:
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