And of course the other issue is those running their own SIP proxies, running their own SIP domain (or sub-domain) and that could (in the not too distant future) include residential end-users. Think it's that far fetched? Who thought we'd be running our own PIX boxes? Or remember when phones used to say "Property of Western Electric" on them?

I agree with you that the capability of hosting ones own SIP service will be commonplace. I am hoping that soon I can make much stronger staement than that :-). So LEAs need a monitoring capability like Carnivore as you mention in your blog.

So let us take the Carnivore scenario. It is collecting the full data. But when a court authorizes legal intercept there are all kinds of
restrictions; one of them is LEA can access only certain data. If they have call control information from the SP, then they can focus on the relevant data.

I suppose one can argue that why place this burden on the SP. I submit that we place additional responsibility on public carriers, be they communication oriented or transport or utility etc.

Hmmm. I'm quite interested the 'strong statement'.

In terms of a Carnivore-like capability for SIP, I think ultimately it will be the way things go, and it will be able to do more than SIP. There's still an issues if end-to-end encryption becomes general.

Rumors say the feds have managed to get back doors put into a lot of vendors products to address this, but that's a challenge for them to keep up with. Other rumors suggest every SSL type encryption scheme in use has already been cracked and that's why you don't hear much complaining about encryption from lae enforcement anymore.

One issue with application level gateways (ALGs) or SBCs, is that they fundamentally break a major benefit of SIP, that of separation of session establishment from session description. A SIP proxy isn;t supposed to know or care what the end-points are going to do, or how they're going to talk to each other. That's between the end-points. When a nifty new thing comes out, SIP proxies don't have to be updated to accommodate or support it. But a ALG that is handling media won't understand the nifty new thing unless it is upgraded or recoded.