Re: [Sipping] [RAI] Expert review of draft-sinnreich-sip-tools-03

[Adrian Georgescu <ag at ag-projects.com>]

On Oct 22, 2008, at 4:52 PM, Paul Kyzivat wrote:

> Adrian Georgescu wrote:
> > Hi Paul,
> > I believe Henry is heading into one direction only. The idea is to  
> > help developers implement the minimum necessary features in their  
> > User Agent and not biased towards a voice only application. The SIP  
> > end-points as describe by Henry would work with any service  
> > provider as long as they talk plain SIP. So 911 and voicemail and  
> > other services can be performed in the network as well, they are  
> > just another end-point.
>
> There is a huge difference between services implemented in the UA  
> and services implemented in the network. Take for example emergency  
> services. The typical implementation is simply for the UA to accept  
> the dial string (e.g. 911) and put it into an INVITE. The UA most  
> likely is treating this as any other call - not realizing it is an  
> emergency call.

I can easily make the SIP UA give more priority and to that call  
rather than re-engineering the whole Internet to do something like  
that, can't I?

> Hence it doesn't apply special processing to it, that is supposed to  
> be supplied, like refusing to disconnect the call on hangup. Also,  
> it doesn't play any part in determining its location - depending on  
> the network to be able to figure that out. The network may or may  
> not be able to determine that.

Do you mean a network can better figure out where I am rather than  
myself? I highly doubt that I wish to let the network dispatch the  
ambulance to where they think I am rather than where I am actually (by  
my local GPS or AGPS device). Is up to me to convey location  
information and not to the network.

> In any case, each SP has its own requirements for what a device that  
> connects to it must do to work with it. Perhaps it would be a useful  
> thing to create a common spec for a UA that can work with "most"  
> SPs. To do that it would probably be better to gather the specs from  
> the SPs than to look at a few phone adapters. But I think a lot of  
> SPs are not open to connection from devices they don't supply, so  
> there may not be a lot of value in such a spec.
> >
> If I were to develop a UA today, I think I would figure out who I  
> intend it to connect to,

A SIP URI is a SIP URI. Do you make a distinction when you send an  
email what type of server software or type of recipient is behind the  
destination email address? Your email client works the same every  
time. This is why you use email and skype today instead of SIP. They  
do not make this distinction.

Why is this tendency with SIP to make it more complicated than it  
actually is?

Is not a personal question, I am just wondering because I am young and  
I was not around when SIP was invented.

Adrian

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