User agents cannot exchange signaling messages when the SIP signaling path for a call between user agents is disconnected. Reasons for disconnection can be:
SIP element failure
Network unavailability
Non-functioning of one or more SIP elements, such as proxy or location server, if the user switches the network from WiFi to 4G and from 4G to WiFi
Failure of Session Manager
Using the SIP Resiliency feature, Avaya SBC preserves the call by using Session Manager to reconstruct the call between disconnected endpoints. Avaya recommends using the same domain names for signaling groups to support call reconstruction.
The SIP Resiliency feature is applicable for non Avaya Aura® Failover Group Domain Name (FGDN) segments, whereas for FGDN segments the Call Preservation feature of the previous release is applicable.
Note:
Avaya SBC does not require SIP Resiliency or call reconstruction for HA failovers. You can deploy Avaya SBC in HA mode to preserve active calls.
Avaya supports IPv6 addressing for Session Manager reconstructed calls.
Session Manager uses +
sign as a prefix in the From header user part for all the reconstructed calls. The +
in the From header user part causes URI group mismatch on Avaya SBC when the server flows are configured with URI groups. To avoid this, Avaya SBC must be able to configure URI groups with or without +
sign as a prefix.
