Subject: RE: [Sip] INFO

From: "Brian Stucker" <[email-masked]>
Date: Sun, 9 Sep 2007 23:43:18 -0500

> -----Original Message-----
> From: Eric Burger [mailto:[email-masked]] 
> Sent: Thursday, August 30, 2007 5:03 PM
> To: Peili Xu
> Cc: sip
> Subject: Re: [Sip] INFO
> 
> Saying, "OK for interworking" does not really say anything.  
> If I come up with a really broken method for interworking, 
> saying that it is for interworking does not make it correct.
> 
> The problem is, how do the endpoints know they will be able 
> to communicate?
> For the ISUP/Q.sig/DPNSS/mumble case, the endpoints know they 
> will be able to interoperate because they know a'priori: they 
> are configured to work.
> However, this means that the devices must be in the same 
> administrative domain and configured properly.

...or all of your UAs come from the same vendor or set of vendors that
have agreed previously to support said mechanism, or you buy one of
Hadriel's magic boxes to fix it for you.

I realize the same could be said for any protocol scheme, but it's a
very real fact in the case of how INFO works today, especially for DTMF.
There's really only a few widely deployed schemes running around out
there for DTMF via INFO. If we're complaining about using INFO for DTMF
because of negotiation issues, I think that's a very solvable problem
without deprecating INFO.

> 
> Said in a different manner, INFO works fine for 
> non-inter-network use.  

It works fine for inter-network use as well depending upon what you are
trying to use it for. Take for instance trying to figure out if a
session is still alive by periodically sending an INFO to the other
endpoint. I know we have a session timer mechanism defined, but many
endpoints don't support it (yet). Even getting back an error response,
depending upon the response code, may mean that the session is still
alive (success). The point of the usage wasn't to convey anything, and
so no negotiation was necessary. SIP was all you needed.

> It would be hard for the IETF to say, 
> "Here is a non-IETF use.  We will not use it.  You cannot use 
> it with anyone else.  You cannot use it between 
> manufacturers, unless you get them to agree to this use."  
> That is a bit more of what we call the toxic waste warning 
> that accompanies 3GPP specifications...
> 
> 

You could say this for a lot of things. For instance, point me to the
IETF use of SIP to do call forwarding.

You can't use SIP between manufacturers unless you get them to agree to
implement it correctly either. I'm not really sure what your point was
here unless you are against people writing down a common way of using a
protocol amongst themselves.

:)

Regards,
Brian

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