Cisco Systems OL-12397-13 VM Implementation for Centrex Subscribers

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Cisco BTS 10200 Softswitch SIP Feature and Provisioning Guide, Release 5.0

OL-12397-13

Chapter2 SIP Subscribers

Cisco BTS 10200 Softswitch-Based Features

Whenever a change in VM status occurs for a subscriber (for example, when a VM message is deposited

for the subscriber, or when all such messages have been retrieved), the VM server sends an update to the

BTS 10200. If the subscriber is on a SIP phone, the BTS 10200 sends an unsolicited SIP Notify message

to convey the MWI status to the phone. The number in the Notify message Request URL (which is the

assigned subscriber number) identifies the subscriber.

When the BTS 10200 is congested by a flood of registrations (which might occur, for example, when

power is restored to a region after an outage), it can automatically suppress the MWI indication to the

registering phones, so that registration throughput is not adversely affected.

The BTS 10200 implements the draft-ietf-sipping-MWI-01.txt with the following caveat: It supports

receiving unsolicited NOTIFYs from a VM system; however, it does not support subscribing to these

notifications. Further, the BTS10200 does not support subscriptions for MWI. It sends unsolicited

NOTIFYs for MWI to SIP subscribers. No subscription is expected from the SIP phones for the purpose

of receiving this notification.

The notification of MWI by the BTS 10200 is enabled by default (VMWI=Y in the Subscriber table).

You can disable it by setting VMWI=N.

Tip For MGCP subscribers, the BTS 10200 sends the MGCP RQNT message to turn on MWI on the analog

phone. This activates the MWI indicator on the subscriber phone. The indicator can be visual (a lamp,

an envelope, or another icon on a display) or it can be auditory, such as a stutter dial tone that is provided

when the user next goes off-hook.

For information on setting the MWI and VMWI parameters in the Subscriber table, see the “Message

Waiting Indicator (MWI)—Audible and Visual” section in the CiscoBTS 10200 Softswitch Network and

Feature Descriptions document.

To retrieve a VM message, subscribers dial the pilot number for the VM server. The BTS 10200 routes

the call to the SIP trunk for VM, based on the provisioned dial plan for the subscriber and the route,

destination, and trunk-group entries.

Once the VM message is retrieved, the VM server sends a Notify message to the BTS 10200 to turn off

the MWI indicator.

When subscribers call into a VM server, this feature allows for calling back the person who left the

voice-mail message. The feature requires that a Softswitch trunk for the VM server be provisioned in the

Cisco BTS 10200 Softswitch with the relevant routes, destination, and dial plans in order to admit

VM-originated calls into the BTS 10200.

VM Implementation for Centrex Subscribers

For calls received on SIP VM trunks from the VM server, a subscriber is provisioned and associated as

the main sub-ID for each trunk. The subscriber information represents properties of a specific Centrex

group and does not represent any particular subscriber. No AOR is provisioned for this subscriber. This

information is used for call processing.