1. IP Front End User Guide
  2. Introduction to IPFE
  3. Failure and Recovery Scenarios
  4. External Connectivity Failure and Recovery

External Connectivity Failure and Recovery

If external connectivity to the IPFE, say IPFE-A1, fails:
  • Connections to IPFE-A1 and TSA1 fail.
  • IPFE-A2 does not take over TSA1 since it sees IPFE-A1 as available. That is, internal connections still work.
  • Clients with failed connections to TSA1 must send traffic to TSA2.
  • Clients attempting to create new connections to TSA1 fail.
  • IPFE-A2 and TSA2 carry all the traffic for all the clients.
When external connectivity is restored:
  • There are no existing connections for TSA1 to handle.
  • IPFE-A1 still retains control over TSA1.
  • Clients route new connections to TSA1 over time.
  • In the interim, there is a substantial imbalance between the two IPFEs as well as between the servers in the two TSAs. The IPFEs monitors the traffic for imbalances and distribute new connections to reduce the imbalance.