DNS Re-query over TCP

The Oracle® Enterprise Session Border Controller DNS supports the truncated (TC) header bit in DNS responses as defined in RFC 2181 and a re-query over TCP.

DNS queries start on UDP ports with the limit of 512 bytes. Longer responses require that the result not be cached and that the truncated (TC) header bit is set. After receiving a DNS response with the TC header set, the Oracle® Enterprise Session Border Controller will initiate a re-query to the DNS server over TCP. The option dns-tcp-for-truncated-response in realm-config can be set to no to disable this behavior.