ESS Design and Planning
68 Avaya Enterprise Survivable Servers (ESS) Users Guide
● Administrative value: The value of the Main server(s) is always the highest ranking value
on an IPSI’s priority list. The value for the Main server cannot be administered. However,
the value of each ESS server is administrable. For information on administration see
Administering ESS
on page 122.
● ESS server capacity: When used as an ESS server, the S8500 Media Servers matches
the capacity of the S8700 series media server used as a Main server.
● S8500 ESS server: When the S8500 Media Server is used as an ESS server, the S8500
Media Server can support a duplicated network with the addition of a dual NIC card. The
dual NIC card is not supported if the S8500 Media Server is used as the Main server.
Trunking considerations
ISDN PRI Non Facility Associated Signaling
Customers can have up to 479 B channels with one D channel. In North America a backup D
channel is offered. The backup D channel is located on channel 24 of a second DS1 interface.
While both DS1 interfaces are connected to the same Central Office, only one is used for
signaling at a time.
In the event of a failover, if a different ESS server controls the primary and the backup D
channels, each ESS server will think the D channel it does not control is out of service and will
try to bring the D channel that it controls into service. The Service Provider will only use one of
the D channels for signaling. When the D channel is not in service, the associated B channels of
the DS1 will be out of service.
Guidelines
1. Whenever possible place both D-channels in one Port Network.
2. If it is not possible to place both D-channels in one Port Network, place the D-channels
within Port Networks where:
- The Port Network has an IPSI
- The Port Networks are most likely to failover to the same ESS server
3. After failover, if the D-channels are being serviced by two different ESS servers:
- Perform the get forced-takeover ipserver-interface command if the
network conditions allow bringing both Port Networks under the same ESS server.
- Busy out one D-channel to prevent thrashing with the Central Office if network
fragmentation will not allow one ESS server to provide service to the Port Networks
containing both D-channels. On the SAT of the server, use the busyout port X
(where X is the location of the port) to busy-out the D-channel.
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