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Diameter Signaling Router IP Front End (IPFE)
Release 8.2
E89005
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Application server failure and recovery

When an application server, say Server1, fails, the following occurs:
  • The connections from the client also fail.
  • Other connections through TSA1 to Server2 and Server3 survive.
  • Clients who were sending traffic to the failed application server must send traffic to their alternate TSA (TSA2).
  • IPFE-A1 routes new connection requests to the remaining application servers (Server2 and Server3). If all application servers in a target set fail, and IPFE-A1 receives a request for a new connection to TSA1, it optionally notifies the client the request cannot be fulfilled using either a TCP RST packet (for TCP connections) or a configurable ICMP message.
When Server1 recovers:
  • IPFE-A1 detects Server1's availability.
  • IPFE-A1 routes new connection requests to Server1.
  • Some imbalance across application servers in TSA1 exists after recovery. IPFE-A1 monitors for imbalances in traffic and distributes new connections to reduce the imbalance.