Disabling Recursive DNS Queries for ENUM

By default, the Oracle® Enterprise Session Border Controller (E-SBC) requests DNS query with recursive searches. The Telecommunication Technology Committee's Standard JJ-90.31 specifies that ENUM DNS queries be performed iteratively. The E-SBC complies with this requirement when remote (server) recursive searches are disabled. You can disable recursive searches on a per enum-config basis.

Remote recursive DNS queries instruct DNS servers to query other servers on behalf of the requester to resolve the query. Alternatively, the DNS server can return a list of other DNS servers for the requester to query itself. RFC 1035 specifies that setting the Recursive Data (RD) bit in the DNS query to 1 requests a remote recursive DNS. Setting RD to 0 requests lists of other servers.

By default, the E-SBC sets the RD bit to 1. The user can disable this recursion by configuring the enum-config element's remote-recursion parameter to disabled.

This feature affects queries associated with the enum-config:

• Health queries
• CNAM subtype
• ENUM query

Changing this parameter's operational value does not invalidate any current DNS cache entry. The E-SBC uses the cached information until the cache is aged.