Research And Design Of ENUM Server

ENUM (tElephone NUmber Mapping) is a protocol defined by the telephone number mapping working group under IETF (Internet Engineering Task Force). Aiming at providing a global network infrastructure service, the protocol provides facilities to resolve E.164 telephone numbers into other resources or services on Internet so that users can use telephone, fax, e-mail and other telecommunication services through a phone number. Because ENUM is one of the computer network resource addressing technologies, research and promotion of ENUM technologies are of significance in the development of future Internet applications, especially in the VOIP-based fusion between PSTN and Internet.On the basis of comprehensive review of related technologies of DNS and ENUM, the author designs the structure of ENUM Server, divides and defines three subsystem functions and implements all subsystems of the ENUM Server in the LAN environment. The main work is as follows:First, the author analyzes in detail the structure of ENUM Server, the application of ENUM services and the security issues involved, then divides ENUM server structure into three independent functional subsystems, that is ENUM search subsystem, ENUM registration subsystem and ENUM update subsystem, and analyses the functions and demands of each subsystem. The ENUM search subsystem provides the communication interface for users and completes the analysis and inquiry of ENUM service. When local ENUM server can not provide enum request, it will request remote ENUM servers by the recursive method. Meanwhile, this subsystem also provides ENUM client numbers verification to improve the security of DNS system. For the ENUM registration subsystem, its structure and various registration programme are analyzed. For the ENUM update subsystem, the author analyzes the purposes and functions that update subsystem is designed as a bridge between ENUM registration subsystem and ENUM search subsystem, and the structure of ENUM update subsystem. Second, on the basis of analysis of ENUM server structure and all subsystems, each subsystem is designed and implemented in details. For the ENUM search subsystem, the following three issues are mainly addressed. (1) Building, sending and resolving the enum messages by using the resolver and name server library routines of BIND and DNS; (2) Analyzing the NAPTR records according ENUM protocol to find out URIs; (3) Using the regular expression in the Regexp field of NAPTR records to prevent illegal users from accessing enum information. For the ENUM registration subsystem, the basic functions needed in registration are implemented, and an update signal is sent to ENUM update subsystem after setting enum services. For the ENUM update subsystem, its main task is to receive update signal sent by ENUM registration subsystem, to verify the update user right and then to update the ENUM DNS zone files from ENUM service table.In the end, a test is made for ENUM server under LAN environment, and the e-mail services application process is presented as an example of the application of ENUM services.