VoIP and ENUM

One hot topic at the VON Sessions was the IMS. There are two camps fighting each other fiercely. Everybody reading my blog and also everybody present at my Industry Perspective presentation on Wednesday knows which side I belong to.

But during the discussions I had to shift my position slightly. It is not IMS per se which is bad, it is how you implement it. You may implement IMS also on the Internet (if you want to), and you may implement a plain RFC3261 compliant SIP server in a walled garden.

So the camps are really the Internet vs. the Walled Gardens, the IMS is only used as an example, of course because it may help you to make the walls higher.

To make this point clear I use a picture from a presentation Jay Batson gave recently:


Title: What is good for operators may not be good for nations.

In my presentation I deleted operators (service providers) and replaced it by manufacturers. Alistair Woodman from Cisco proved this correct the next day in his Industry Perspective when he said: "We manufacturers like complicated protocols and also different protocols: the more the better, we make a lot of money out of Interworking Units".

The picture clearly shows in a nutshell the issue. There is only a minor mistake on this picture: the word IMS should not be placed on the person, it should be places on the gun.

The correct analogy is: the gun is the IMS, the person is the service provider and the manufacturer is the manufacturer.

A gun per se is not bad, it is always the person pulling the trigger. It could be a policeman or a criminal. You can also not blame gun manufactures for simply producing and selling guns. (You may blame them for lobbying and supporting the NRA ;-)

So one may not blame IMS per se, one may only blame a service provider trying to implement IMS in a walled garden, but this can also be done with an OpenSER (an even better gun?).

See also the presentation from Adrian Georgescu on Building Scalable SIP networks using IMS-in-a-Box and P"P networks.

Keep It Simple, Stupid.

So since we now have demystified IMS a bit, we may concentrate on the two real questions from a service providers point of view:

1. should he implement his voice and multi-media services using IMS or something else?

2. should he implement his voice and multi-media services in a walled garden or on the Internet?

Question 1: IMS or not?

This is up to him. A service provider should always look what he gets for his money and what he will get in return from his subscribers. My personal opinion here is that this will not work out for IMS based products, at least not for the fully monty standard bodies and manufacturers are promising at the moment, and also not now. Every service provider should keep in mind that he now has to compete with the virtual service providers on the Internet, and they do not need to wait until the promised applications are available in IMS in the distant future. They can implement it now. If the SP does not get his investments back, this is stranded costs, as I also pointed out in my presentation.

One operator seems to have got this message -KPN. KPN is approaching IMS very carefully and will only implement two functions, the S-CSCF (basically a simple SIP-proxy) and the only real asset IMS has: the HSS. Eventually a P-CSCF for their mobile part as an outbound proxy.

I suggest that all operators should look at the excellent KPN presenation Colin Pons gave at the break-out panel: IMS: Walled In or Open very carefully. See also Martin Geddes commenting on this in KPN: a viable IMS vision and here.

Question 2: Walled garden or not?

Here we have to distinguish between three sub-options:

a) Is the SP reachable from other SP's on the public Internet, via bilateral peering agreements or via so-called federations. This is a SP decision and is currently discussed all over the place, in all standards bodies (e.g. SPEERMINT), in national bodies dealing with IP Interconnect and in a number of conferences. I will come back on this in one of my next posts on ENUM.

b) Are the application servers also within the walled garden or are they available via the public Internet? Can anybody provide an third-party service or only for selected third-parties, or something in between. This is an issue not so much discussed yet, but very important for innovation speed and global availability of services.

c) Does the user has access to the SP from the public Internet or is he bundled in via the access? This issue is currently the hottest in the net-neutrality discussion, because this works only if the SP disables the end-user to use the services he provides also over the Internet access.

KPN seems to have here also a very open approach:

The KPN Strategy is: "Making the Internet even more significant for our consumers"

and to concentrate on identity management, presence, location, user preferences and profile mediation, service and personal mobility.

KPN: "Preserve the E2E principle"

The KPN design principles and guidelines state: "No service intelligence shall reside in the IMS core elements"

So I strobgly recommend that operators, carriers and service providers may reconsider their plans of using IMS: the full monty, not all of it, or none of IMS.

This may be of course a problem for the IMS manufacturers, but also for new-entrant VoIP providers hoping that the telcos binge-drink the IMS and fall over.

My two cents for SP:

1. Do not use IMS now, wait until it gets ready and even then do not use all of it.
2. Do not implement the end-user access and the applications in a walled garden.
3. for interconnect, use all options available now, but finally you MUST find a way to peer with ALL other service providers via IP. Do not rely on the PSTN as default.

and finally:

4. Do not believe too much in conspiracy theories like all incumbent telcos and regulators are bad. They are all cooking only with water. Leave the conspiracy theories to the "Da Vince Code" (also a big flop, BTW)