MGC list You must specify at least one, and up to four, MGCs in the list. The first MGC on the list is the primary MGC. If the Branch Gateway cannot connect with, or loses its connection with, the primary MGC, it attempts to connect with the other MGCs on the list.

Standard Local Survivability (SLS) SLS consists of a module built into the Branch Gateway to provide partial backup MGC functionality in the event that the connection with the primary MGC is lost. This feature allows a local Branch Gateway to provide a degree of MGC functionality when no link is available to an external MGC. Alternatively, it can be configured on an individual Branch Gateway using the CLI.

Enhanced Local Survivability (ELS) ELS is available for the Branch Gateway using a local S8300 or S85XX functioning in LSP mode. If the ECC stops serving the Branch Gateway, the S8300 takes over the service.

Auto fallback to primary MGC This feature provides a means by which a Branch Gateway being serviced by its LSP can return to its primary MGC automatically when the connection is restored between the Branch Gateway and the MGC. By migrating the Branch Gateway to the MGC automatically, a fragmented network can be made whole faster, without the need for human intervention. Auto fallback is configured via the CM. For details, see the Administrator Guide for Avaya Aura® Communication Manager.

Connection preservation This feature enables the Branch Gateway to preserve the bearer paths of stable calls if the Branch Gateway migrates to another MGC (including an LSP), including migration back from an LSP to the primary MGC. A call for which the talk path between parties in the call has been established is considered stable. A call consisting of a user listening to announcements or music is not considered stable and is not preserved. Any change of state in the call prevents the call from being preserved. For example, putting a call on hold during MGC migration will cause the call to be dropped. Special features, such as conference and transfer, are not available on preserved calls. Connection preservation preserves all types of bearer connections except BRI. PRI trunk connections are also preserved. For details, see the Administering Network Connectivity on Avaya Aura® Communication Manager, 555-233-504.

Modem dial-backup This feature can be used to provide redundant WAN connectivity between a Branch Gateway and its primary MGC using a serial modem. This connection uses a virtual interface called the Dialer interface. This feature recognizes that even if the Branch Gateway is configured for survivability via SLS or ELS, the best solution is to maintain the gateway’s connection with its primary MGC whenever possible.