A Classification of IMS Critics, Part 2

I see three more groups of people generally expressing reservations, if not more, against IMS.

#2 The non-IMS VoIP Suppliers

Telco suppliers which initially decided to implement VoIP using a non-IMS technology (e.g. H.323, Softswitch architecture, IETF SIP architecture) more and more face pressing questions from existing or potential customers about IMS compliance.

While some of them have plans to evolve towards IMS, others do not and need to find a way to get away with this strategy.

An approach for them is to relativize the existence of IMS as a coherent standard. They start to tell their customers about the existence of multiple "IMS flavors", and with a little bit of imagination their own solution can be considered as one of these IMS flavors.

Another approach is simply to attack IMS, this standardization monster, far too complex and expensive for VoIP.

And actually they have a point here. I am not sure that IMS brings a lot of value for money if an operator only intends to use it for VoIP. IMS starts to be valuable if you want to use it as a framework for multiple services, including but not limited to voice.

On the other hand, the non-IMS VoIP solutions are usually optimized to support voice, and will have great difficulties to evolve and support much more than that.

#3 IETF SIP People

IETF SIP people tend to think that IMS betrays the original spirit of SIP, defined in the IETF as an end-to-end protocol localizing intelligence and control at the edges of the network. IMS specifications are full of operator control mechanisms and tend to shift the intelligence balance from the edges to the network. IMS pushed for a set of SIP extensions that deal with charging, bundling of signalling and QoS, control of user identities from the network... a whole set of hair rising ideas when you believe into the free for all Internet.

Critics coming from IETF SIP people are the most interesting, as their vision of a SIP world is what the IMS application layer must aim at in order to be innovative and competitive.

On the other hand, my criticism to them is that they are shooting at the wrong target. Their attacks are more aimed at the classical telco mindset and what this mindset might be tempted to do with IMS, than the IMS technology as such. Used with the right attitude, IMS does not have too be so bad, and there might even be some valuable concepts in it that improve on the IETF ones.

To be frank, IETF people have excuses. You just have to rapidly browse through an IMS specification and an IETF RFC to see that there is a huge cultural gap between the two communities. I can understand that for IETF people, reading an IMS specification is just good to go to sleep. Moreover, it is true that some companies in 3GPP or TISPAN sometimes push very strange ideas, which definitely betray the SIP philosophy. However, these ideas rarely fly, even within the 3GPP community, which is generally very IETF-minded.

#4 Opportunists

Any hype calls for kill-the-hype people, and so did the IMS hype.

Anti-IMS opportunists rely on the belief that it is too late to avert the telco decline, and they consider IMS as the last pitiful gasp of the industry. They ride on the "Internet is cool, Telco is shit" wave, that a lot of people in the industry are deeply convinced of.

They use any good or bad argument to support their point, but usually very bad ones. Why would they take the time to read technical documents or speak with technicians when their role is to capture deeper philosophical problems?

A risk is that by repeating over and over to an already tormented industry that it cannot think "modern" and "right", these people actually deliver self-fulfilling prophecies.

Christophe