Caching ENUM Responses

As DNS responses often lead to further DNS queries, a DNS server can send additional multiple records in a response to attempt to anticipate the need for additional queries. The Oracle® Enterprise Session Border Controller can locally cache additional NAPRT, SRV, and A records returned from an ENUM query to eliminate the need for unnecessary external DNS requests by enabling the cache addl records parameter. These cached records can then be accessed by internal ENUM and DNS agents.

The unprompted NAPTR, SRV, or A record returned to the Oracle® Enterprise Session Border Controller must include complete information to resolve a call to be added to the local DNS/ENUM cache, otherwise the Oracle® Enterprise Session Border Controller will preform an external query to fine the address it is looking to resolve.

Cached entries are per ENUM config. That means if one ENUM config has a number of cached entries, and an ENUM request is directed through a different ENUM config, the second configuration is not privy to what the first configuration has cached.

The Oracle® Enterprise Session Border Controller uses the shorter lifetime of the DNS response’s TTL or the server dns attribute’s transaction-timeout to determine when to purge a DNS record from the local cache.