IMS Dirty Laundry

by Bruce Stewart

We've talked about the controversies surrounding IMS here on ETel before (see Lee Dryburgh's The IMS Debate for one interesting perspective). Brough Turner, one of the really smart guys out there in this field, has written up the notes from his recent talk about what he learned in porting his MyCaller ringback tones application from the Intelligent Network (IN) implementation to an "IMS" version. You may be surprised at what he found.

In Lessons Learned Implementing IMS, Brough really breaks down the details of where IMS is today, what it can offer, and some of the problems people will face in moving towards IMS. He presents a short and sweet executive summary of his findings, but the entire article is well worth a read.

For the impatient, here are the takeaways.

  1. It’s very early days for IMS. Today’s “IMS” networks are combinations of SIP infrastructure with 3GPP Release 4 softswitch-controlled voice service.

  2. IMS is about connection control, only. Only part of your application has to change. For MyCaller, ~90 percent of the software remains the same.

  3. IMS enables multimedia ringback, i.e. video! So there is significant new functionality, versus today’s audio-only ringback.

  4. Parallels with Intelligent Network are striking!

  5. Most application–specific data remains outside of IMS. In particular, operators do not want to add data fields to their Home Subscriber Server (HSS).

  6. Application–specific MRFs make sense. Operators tend to avoid sharing resources between diverse applications. And, for rich media, application–specific MRFs can be more cost-effective.

  7. Operators await 3GPP Release 7. At least anecdotally, several operators have suggested that 3GPP Release 7 is the first complete, stable, and consistent version they will fully deploy.

And for more good analysis of the state of IMS and a deeper look at the R4 vs. R7 issue, check out Dean Bubbley's response post, When is an IMS not an IMS?.

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