[asterisk-dev] Dialog Subscriptions, Bug 6728 and snom dialog; purpose=call-completion

[Kevin P. Fleming]

Martin Koenig wrote:

> In specific cases of call forwarding via a function key, the dialog state
> subscriptions to specific hints get unsubscribed because the call completion
> mechanism subscribes to the same hint with a shorter expires time than the
> original subscription.
> 
> The original subscription is
> Event: dialog, Expires: 3600
> 
> The call-completion subscription is
> Event: dialog;purpose=call-completion, Expires: 60

Actually, call-completion is on its way for Asterisk 1.8, but that's not
really related to your issue :-)

If the RFC that describes the dialog event package says that these
should be considered distinct package names because of the parameter
added to the second one, then the parser in chan_sip should be improved
to treat them as such (and it's a bug if it treats them as the same
package).

If on the other hand the RFC says that the parameter does not change the
event package name, but is ancillary to the package name, then the phone
is at fault, because it is changing the subscription it already made for
the dialog event package, and it would be fully understandable for that
subscription to expire in 60 seconds. Then again, depending on the
Call-ID in the SIP request, it may be that we should be treating them as
independent subscriptions regardless of whether the event package name
matches or not.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kpfleming at digium.com
Check us out at www.digium.com & www.asterisk.org