IP phones and VoIP apps commonly support notifying users about new voicemail messages and faxes. For example, upon receiving a new voicemail, Yealink T46G plays an alert tone, the LED indicator slowly flashes red, and a prompt, such as “1 New Voice Mail,” pops up on the screen. To inform phones/apps of mailbox changes for accounts, such as a new voicemail, PortaSwitch sends them notifications (SIP NOTIFY requests) using the Message Waiting Indication (MWI).
Starting from MR112, the MWI service is automatically accessible on all processing nodes in the system. Since the notification processing is now spread evenly across the nodes, this eliminates delays and ensures scalability as your customer base grows, as it allows you to enhance processing speed with each new node you add.
Additionally, to reduce the load in the system, there is an option to send MWI notifications only to the phones/apps that are currently subscribed to the MWI (e.g., if a user of Yealink T46G explicitly enabled the MWI option for their account via the phone’s web UI). Thus, by avoiding sending unnecessary notifications to registered but not subscribed phones/apps (for instance, those that do not handle MWI at all), you can reduce the total load on PortaSIP servers.
Limitation
Notifications about mailbox changes will not be sent in the standalone mode (when the main site in site-redundant PortaSwitch goes down).
Configuration
If you update your system to MR112 or a later version
For backward compatibility, if you update your system to MR112 or a later version, the old behavior is preserved by default – PortaSwitch will send the mailbox changes to all registered IP phones regardless of their subscription status.
To send the mailbox changes only to subscribed IP phones, log in to the Configuration server web interface and set the MediaServer.mwi_backward_compatibility option to “N” (No).
With the MediaServer.mwi_backward_compatibility option set to “N” (No), PortaSwitch fully complies with RFC 3842 "A Message Summary and Message Waiting Indication Event Package for the SIP"
If you install MR113 or a later version
If you install MR113 or a later version from scratch, no configuration changes are required. PortaSwitch will send the notifications about the mailbox changes only to IP phones that are currently subscribed to these notifications. On the Configuration server web interface, the MediaServer.mwi_backward_compatibility option is set to “N” (No) by default.
For backward compatibility (for instance, if your customers use old IP phone models that do not support MWI subscription), you can set the MediaServer.mwi_backward_compatibility option to “Y” (Yes). In this case, the notifications will be sent to all registered phones.
