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

A Classification of IMS Critics, Part 1

I am usually very upset when I read articles or presentations that dismiss IMS as yet another stupid telco technology. It might be because I am an IMS dogmatic devout, but I prefer to think that this is because most of the time the writer does not know what he or she is speaking about, and has a personal or company agenda when performing this IMS bashing activity.

I have my own classification of IMS critics. In this first post on the subject I will speak about one of the most active anti-IMS groups, at least at the begining.

#1 The OSA/Parlay Gang

For those who do not know, OSA/Parlay has been for some time and for some people the future of telecommunications. The original idea was that the exposure of network capabilities to 3rd party service providers through a set of CORBA APIs would generate plenty of new services.

Though OSA/Parlay is still branded as a success by the Parlay group, I think that it did not work out as initially planned. First, the APIs did not expose so attractive capabilities (how many 3rd party service providers want to control voice calls?). Second, the APIs were far too complex and the usage of CORBA did not help making them simpler. Third, the architecture implying the clear separation between an application server implementing service logic and the OSA/Parlay gateway was far from optimal for an operator wishing to use OSA/Parlay to implement its own services.

Then came Parlay X, which is much better as it relies on the idea that network capabilities should be exposed through simple web services. This said, it is still not clear whether the Parlay X services are the best telco web services you can think of.

OSA/Parlay was already struggling for success when IMS came. While the IMS service architecture included an OSA/Parlay gateway from the begining, it rapidly appeared that IMS and OSA/Parlay were perceived more as alternatives than complements.

A problem was that the OSA/Parlay APIs were specified to apply to a pre-IMS circuit-switched network. On the other hand, SIP and IMS defined a new world that did not optimally map to the old one. Moreover, the IMS service architecture came with a "SIP Application Server" alternative, and it was rapidly clear that all initial IMS applications were implemented on a SIP AS rather than an OSA/Parlay AS.

More generally, OSA/Parlay makes sense when you need to provide an IT interface to a telco network making use of complex and specific telco protocols like SS7. SIP is far from being such a complex protocol, and therefore makes the need for a protocol-independent exposure layer less critical. More especially when this exposure layer is unable to provide access to most of SIP capabilities.

IMS therefore became a threat to companies implementing OSA/Parlay gateways (at least until they manage to adapt their products to it) and to individuals who spent years evangelizing the world about OSA/Parlay.

I think that some of these individuals want the failure of IMS as a way to legitimate their own mistakes, i.e. "OSA/Parlay was a good technology, but this was a good technology for a telco industry near to its demise. Demise for which IMS is certainly the main reason".

Typical arguments from the OSA/Parlay gang (sometimes conflicting):
- SIP is a complex protocol like SS7. Nobody can directly implement an application on SIP. You need a gateway.
- The success of IMS will be measured through its ability to support the same voice quality as circuit-switched.
- IMS is the new IN.
- IMS is widely opening the door to Internet companies so that they can kill telco operators.

As I wrote above, I think that as OSA/Parlay companies find new IMS-friendly products to sell and OSA/Parlay gurus re-invent themselves as IMS or SOA gurus, this gang is weakening in strength.

Christophe