SIP Subscription and Notification requests update connected SIP endpoints on state changes related to services that the endpoints consume. For example, when a new voice message arrives in a mailbox, Session Manager sends a SIP notification request to notify the related endpoints about the arrival of a new voice mail message.

For an endpoint to receive SIP notifications, it first needs to subscribe to the relevant subscription package. Each subscription package is related to a specific service that the network delivers to the endpoint. The SIP endpoints automatically establish all required subscriptions upon logging into the network.

When a subscription to an event package or service, is established, SIP subscription is assigned with a subscription expiration timer. The endpoint continues to receive notifications as long as the expiration timer does not expire. The endpoints automatically refresh any subscriptions before their expiration timer expires. A lower subscription expiration timer generates more SIP traffic related to subscription refresh events. Refreshing a subscription updates the state of the subscription.

Session Manager allows administration of the subscription expiration timer for each type of event package.