Scenario
In the case of primary path failure due to single
failure, the IAD is provisioned to automatically use the alternative path.Description
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1 | Call Termination with Primary Path Failure |
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- The IAD registers with AS1 through -3.
- Subscriber is pre-assigned (based on Application Server subscriber data configuration) to AS1, thus 10 has preset routing for the subscriber to AS1.
- From the register, AS1 is informed that the subscriber is reached by -3.
- The -3 goes down and AS1 can not terminate the call to the subscriber until the subscriber re-registers.
- The subscriber identifies that the -3 is down only when it sends traffic (invite, refresh register etc).
- IAD chooses an alternate IP address based on the DNS resolution and opens up a new path to the AS (paths should ideally be geo redundant).
- When AS1 receives the terminating call it learns -3 is unavailable and utilizes -5 path. Hence IAD receives call despite failure of primary path.