Re: francois' comments and why RFC4474 not used in the field

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of Dean
> Willis
> Sent: Thursday, April 02, 2009 1:47 AM
>
> > If the peers can circumvent the SP and make their own business
> > agreement, then perhaps the SP wasn't actually providing a service.
> >
> 
> And they're afraid the other folks will find out? Hang 'em from the
> yardarm, Captain Bligh. Those fellows are pirates!

I don't think they hide them to avoid circumvention - at least not in the general case.  I've heard that argument a few times, but not often.  Providers already know who the origination and termination providers are (they're identified in the NPAC/LERG/etc.), but they just can't reasonably peer direct with everyone.  There's a demand/need for transit providers mostly because phone calls cost money, are nationally regulated, users/law-enforcement expect traceability, and there's a need for identity (ironically).  

Anytime money is involved, for example, it means you need a business relationship to handle billing arrangements, and providers clearly can't scale to have a business relationship with every other provider/domain/Enterprise on the planet.  Heck, even in the PSTN right now, SMS messages between very large mobile providers in the same country go through a middleman, purely because the middleman acts as the arbiter for billing.

I'm not saying some transits don't fear circumvention - IP transits feared it too when BGP first came out and advertised AS paths - I'm just saying it's not the only, or even a primary, reason for SDP changing in transits.  There are really a lot of reasons the media gets steered through transit providers.  The first one is probably: because that's what is being billed/paid-for.  You yourself, Dean, have said many times that one shouldn't bill on signaling, but rather bill on media.  So providers sort of do that - they bill on the signaling, but they open/close gates on the media to enforce that billing.  Then of course they also like to measure the QoS of the media (and sometimes make call routing decisions based on it even), monitor that there actually is media and that the call didn't j
 ust mysteriously fail, etc.

If phone calls were free for everyone, had no regulation, etc., then I would expect transit providers to not steer media. (I would in fact expect no transit providers period, ultimately)  If there's no value in something, then there's nothing to protect/monitor/troubleshoot/hide/arbitrate/provide-service-for. 

-hadriel
p.s. and not all transits do change SDP, and some only change SDP in certain circumstances (like for transcoding).

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