[Asterisk-Dev] MWI From tag in SIP message

[Olle E. Johansson]

Kevin P. Fleming wrote:
> Olle E. Johansson wrote:
> 
>> I would say that the core problem is that we send NOTIFY messages
>> WITHOUT a preceeding SUBSCRIBE for notifications, so there's no
>> transaction to match. The NOTIFY has nothing to do with the actuall call
>> to voicemail, but should be related to a subscription... Well, it works
>> anyway with a lot of phones and ignoring it is ok and propably a correct
>> way of handling it.
> 
> 
> Agreed, although we will need to always continue to support the 'push'
> method of MWI as well, since most phones do seem to support it properly.

Agreed. Most of these phones do not subscribe anyway, so there would be
no way to notify them without breaking the standard. Think they also
missed this part of the RFCs :-)

What we need to do, and it's on my to-fix-list for chan_sip, is to make
sure that phones that actually do subscribe get NOTIFY messages with a
reference to the SUBSCRIBE (Call-ID) and that we expire the subscriptions.

/O