DNS ALG Message Throttling

You can limit DNS ALG-bound throughput by using the dns-alg-constraints configuration element. Message throttling is performed on request messages, and since DNS-ALG is transaction stateful, the responses are automatically throttled. Once a dns-alg-constraints element is configured, it can be referenced by a DNS configuration object. This allows users to create constraint profiles and apply them to multiple DNS configuration objects.

When any of the constraints are exceeded, the DNS server’s status changes to Constraints Exceeded and requests are rejected with a 503 error message. The server, via the ALG, remains in that state until the time-to-resume parameter period ends. When this period ends, the Oracle Communications Session Border Controller re-examines the server’s traffic with respect to the current burst or sustain window and the state is determined again, along with the decision to readmit traffic.