On Mon, 2009-02-02 at 11:13 -0500, M. Ranganathan wrote:
> Scott Lawrence wrote:
> > On Mon, 2009-02-02 at 10:23 -0500, M. Ranganathan wrote:
> >   
> >> On Mon, Feb 2, 2009 at 10:07 AM, Scott Lawrence
> >> <[email protected]> wrote:
> >>     
> >>> On Sun, 2009-02-01 at 19:08 -0500, M. Ranganathan wrote:
> >>>       
> >>>> Hello
> >>>>
> >>>> I am working on XCF-3252
> >>>>
> >>>> http://track.sipfoundry.org/browse/XCF-3252
> >>>>
> >>>> This issue is talking about the admin user INVITING a third party but
> >>>> I have problems with the conference owner INVITing a third party. I
> >>>> fixed some things but other problems remain.
> >>>>
> >>>> Here is the scenario that is causing problems :
> >>>>
> >>>> I have an alias for an extension that I wish to INVITE to a conference
> >>>> ( say 204 ). I can dial this extension fine with a phone. Then (after
> >>>> fixing some other problems) I am trying to INVITE 402 using third
> >>>> party call control. For this, I need to send INVITE to 402 but I get
> >>>> NOT FOUND from the Proxy Server.
> >>>>
> >>>>
> >>>> Hypothesis: I think this might have something to do with the
> >>>> sipx-userforward=false parameter but I am not sure.  Attached is a
> >>>> trace for the successful call as well as a failed call to that
> >>>> extension.
> >>>>         
> >>> Your hypothesis is correct.
> >>>
> >>> This is a significant problem with the semantics of our 'user-forward'
> >>> attribute...
> >>>
> >>> The meaning of that attribute is really "do not apply any contacts to
> >>> this message derived from the "alias" database.  The attribute was
> >>> created to allow services that really want to address the users
> >>> registered phones to exclude other forwarding targets.  By including
> >>> this attribute, you are instructing the call not to use those targets,
> >>> but in your configuration the "phone number" is an alias for the user
> >>> (whose real AOR is 'us...@...').
> >>>
> >>> Since we don't have any way to distinguish the purpose for which an
> >>> alias was added, we can't tell the difference between what you were
> >>> doing and a forwarding entry added by the user that sends calls to
> >>> his/her cell phone or administrative assistant or whatever.
> >>>
> >>> In fact, we use aliases for a number of different purposes, and the
> >>> 'user-forward' is big non-discriminatory hammer - it just disables all
> >>> of them.  This just came up recently in some other context, but I can't
> >>> seem to find where I wrote about it last.
> >>>
> >>> So... if you remove that attribute from the invite you generate, then
> >>> users configured with extensions as aliases will work again, but your
> >>> INVITE may also find its way to other places you don't want it to.  At
> >>> the moment, that's the choice you face.
> >>>
> >>> I think that the real solution to this is to implement a different and
> >>> more discriminating filtering capability in the redirect server - one
> >>> that labels the source of each contact with some semantic tag and then
> >>> allows each request to specify either a set of tags to be used or a set
> >>> to be ignored.  This is going to take some significant work to figure
> >>> out all the scenarios we need to support, but the result would replace
> >>> both the 'user-forward' and 'sipX-noroute' attributes we're using now.
> >>>
> >>>       
> >> As you state above, the reason why that parameter was put there was on
> >> the INVITE request URI so that one could avoid being forwarded
> >> inadvertently. I am also reading that we may not have the time to fix
> >> this right at the moment (we can try but it can take some time and
> >> hence may not be do-able for this release?). So what is the conclusion
> >> ?
> >>
> >> There are three choices:
> >>
> >> Sipxconfig Change the help text so the extension cannot be entered
> >> there so people must use the entire address u...@sipx-domain to dial
> >> and we clearly state that aliases will not work. Is this an acceptable
> >> solution for the moment.
> >>
> >> The second choice would be to just disable the "INVITE third party to
> >> conference" feature (presumably, not acceptable as we want this
> >> feature).
> >>
> >> Or we simply allow forwarding and live with the expected consequences
> >> of doing so as you state above.
> >>
> >> Any ideas on which direction is best? I would vote for #1 as I would
> >> not want for my secretary to attend conferences ( especially because I
> >> do not have one :-)  ).
> >>     
> >
> > My general rule is "the call must go through", so I'd choose to allow
> > alias-based forwarding.  This may result in some interesting failure
> > modes, but they are failure modes that a human can figure out ("oh...
> > you wanted Bob but he has his phone forwarded to me today") as opposed
> > to the current "it broke" situation.
> >
> >
> >   
> Another option would be a checkbox in the sipxconfig screen that 
> indicates whether or not call forwarding is allowable on the INVITE. 
> This way, if a user selects it he is aware that the call may be 
> forwarded on the INVITE

Non-starter, I'm afraid - you're a developer on the project, and _you_
didn't understand the implications.


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