The Avaya S3500 Message Server family consists of two major elements: the Message Application Server (MAS) and the Message Storage Server (MSS). Sometimes known as the front end and the back end, each Modular Messaging system consists of one or more MAS front ends and a single MSS back end. Multiple MASs are deployed based on the number of messaging sessions/ports required or to enhance system resiliency by providing duplication of services. The Message Application Server is essentially an IP Gateway, providing the Messaging Application software layer (features) and IP Gateway functions (switch integration interface to IP messaging, i.e., transport). All Message Application Server data is transient; both customer data and messages are stored on the Message Store Server. The Message Storage Server stores the customer configuration database and message database.
The Message Application Server and Message Storage Server communicate over an IP link, which is designed to be separate from the customer's LAN/WAN infrastructure. In the event of an IP link failure between the MAS and MSS, the Message Application Server is sustainable and can continue to store up to 5,000 hours of messages per Modular Messaging system. During operation in a sustainable mode, the MAS "pings" the MSS every 30 seconds so that the message store reconciliation begins within 30 seconds of service resumption. With Modular Messaging, during an MSS or link outage, subscribers can access messages on the MAS (recent messages only) while in an off-line mode.
