The default arrangement of IP Office lines in an IP Office Server Edition and IP Office Select network is for each server to have a line to the primary server and, if present, a line to the secondary server. In return, the primary and secondary servers have lines to each expansion system. This is referred to as a 'double-star' configuration.
Data Routing vs IP Office Routing
The IP Office Server Edition network relies on the customer's data network which routes the traffic of the IP Office lines. However, the routes between sites within that data network may not necessarily match the configured IP Office lines. This can cause scenarios where when failover occur resilience features are not accessible to users.
Unable to access failover servers:
The use of resilience features assumes that there is still a data network between sites even if the server at that site is in failover. If the cause of failover at a user's home server site also affects the data network, resilience features at the failover server are still invoked. However, users at the home site are isolated from the failover server and so receive no support.
For example:
Data Network Failure:
The expansion server at site B host Avaya IP phones and is configured to failover to the primary server at site A. Suppose the data connection between the two sites fails for some reason.
Site A cannot see the server at site B and so starts failover support for site B.
At site B, the result depends on whether the data network failure is affect traffic with the site and or traffic to other sites.
If the IP phones can still see the server at site B, they continue operating with it. However, the users will not be able to access services provided from site A such as voicemail and Avaya one-X® Portal for IP Office.
If the IP phones cannot see the server at site B, they try to failover to site A. However, the lack of data network between sites prohibits that.
Network Blocked:
There are scenarios where users can become network blocked. For example, if an IP phone is not able to see its home server it will attempt to reregister with its failover server. However, if the failover server is able to see the home server, it will not support failover of the phone.
Data Network Resilience
Resilience of the data network should be considered in conjunction with IP Office resilience. For example:
Ensuring that the data network routes between sites are such that traffic has alternate routes.
Ensuring that the data network equipment is supported by UPS and similar backup power supply options.
