A cache lookup mechanism for ENUM query

ENUM (E.164 Number Mapping) is widely used to provide automatic mappings between the telephone numbers and the VoIP (Voice over IP) URIs (Uniform Resource Identifiers). With ENUM, the subscribers dial the telephone number of the called party and the system automatically forwards the call through IP networks if the VoIP URI of the call is found. Typically, the ENUM query process is performed at the telephone gateway. Specifically, upon receipt of a call, the telephone gateway queries the ENUM server to retrieve the called party's VoIP URI If the URI is found, the call is forwarded through the IP networks. Otherwise the call is forwarded to the PSTN (Public Switched Telephone Network) through T1 or E1 interface. The latency of ENUM query is very large when the network or the ENUM server is heavy loaded. Base on the call logs, this paper proposes a cache lookup mechanism to reduce the latency of the ENUM query process. The paper discusses the performance of different cache algorithms.