AudioCodes Mediant 500L - Message Waiting Indication

User's Manual 582 Document #: LTRT-10532
Mediant 500L Gateway & E-SBC
27.8 Message Waiting Indication
The device supports Message Waiting Indication (MWI) according to IETF RFC 3842. The
device also supports subscribing to an MWI server (using SIP SUBSCRIBE messages).
For FXS interfaces, the device can accept a SIP MWI NOTIFY message that indicates
waiting messages or cleared messages. Users are informed of these messages by a
stutter dial tone. You can define the stutter and confirmation tones in the CPT file. If the
MWI display is configured, the number of waiting messages is also displayed. If the MWI
lamp is configured, the phone’s lamp (on a phone that is equipped with an MWI lamp) is lit.
The device can subscribe to the MWI server per port (usually used on FXS) or per device
(used on FXO).
For more information on configuring IP-based voice mail, refer to the IP Voice Mail
CPE Configuration Guide.
To configure MWI, use the following parameters:
 EnableMWI
 MWIServerIP, or MWISubscribeIPGroupID and ProxySet
 EnableMWISubscription
 MWIExpirationTime
 SubscribeRetryTime
 SubscriptionMode
 VoiceMailInterface
 EnableVMURI
The device supports the following digital PSTN-based MWI features:
 ISDN BRI: The device supports MWI for its BRI phones, using the Euro ISDN BRI
variant. When this feature is activated and a voice mail message is recorded to the
mail box of a BRI extension, the softswitch sends a notification to the device. In turn,
the device notifies the BRI extension and a red light flashes on the BRI extension’s
phone. Once the voice message is retrieved, the MWI light on the BRI phone turns off.
This is configured by setting the VoiceMailInterface parameter to 8 (“ETSI”) and
enabled by the EnableMWI parameter.
 Euro-ISDN MWI: The device supports Euro-ISDN MWI for IP-to-Tel calls. The device
interworks SIP MWI NOTIFY messages to Euro-ISDN Facility information element (IE)
MWI messages. This is configured by setting the VoiceMailInterface parameter to 8.
 QSIG MWI: The device supports the interworking of QSIG MWI to IP (in addition to
interworking of SIP MWI NOTIFY to QSIG Facility MWI messages). This provides
interworking between an ISDN PBX with voice mail capabilities and a softswitch,
which requires information on the number of messages waiting for a specific user.
This support is configured using the TrunkGroupSettings_MWIInterrogationType
parameter (in the Trunk Group Settings table), which determines the device's handling
of MWI Interrogation messages. The process for sending the MWI status upon request
from a softswitch is as follows:
1. The softswitch sends a SIP SUBSCRIBE message to the device.
2. The device responds by sending an empty SIP NOTIFY to the softswitch, and
then sending an ISDN Setup message with Facility IE containing an MWI
Interrogation request to the PBX.
3. The PBX responds by sending to the device an ISDN Connect message
containing Facility IE with an MWI Interrogation result, which includes the number
of voice messages waiting for the specific user.