The Design And Implementation Of ISIP And SIP Protocol Inter-working Software

ISUP is one important protocol that is responsible for voice call control in Signaling SystemNo.7protocol stack. It has been widely applied in circuit-switched domain of existingcommunication networks. SIP, originated from Internet, is an IP-based call control protocol, whichis able to provide end-to-end session initiation, update, and release functionalities and betterextensibility. With the advancement of IP transformation trend of communication network, how tosupport interworking between traditional circuit-switched domain networks and next generationIP-based networks becomes a problem that requires immediate solutions. Realization ofinterworking functionality between ISUP and SIP protocols can help tradictional networkssmoothly migrate to Next Generation Network and IP Multimedia Subsystem, maximizingexisting network resources usage and protecting operators’ previous investments.With the introduction of ISUP and SIP protocols and their respective charateristics, study ofrelevant IETF and ITU-T standards, and consideration of the role Alcatel-Lucent3G-MSC playsin customer (operator) networks, this article makes requirement analysis for ISUP and SIPinterworking functionality on3G-MSC. Based on existing3G-MSC software architecture, thedesign covers where the protocol interworking sub-module is put, the definition of the generalmiddle format, and interface to existing call processing modules. The protocol interworkingsub-module is implemented using C language. At last, according to composed testing plan and testcases, the ISUP and SIP protocol interworking software is verified, testing results are analyzed.Those detected software bugs have been fixed and verified further.The general middle format, introduced by this article, does not depend on any specificprotocol. It provides convenience for future extension to support other protocol interworkingfunctionalities, and can be suggestion and reference to other communication products when theydevelop protocol interworking functionalities. After functional testing and call load testing in lab,the software passed network entrance testing of AT&T mobility, and has been in use in customernetworks. Feedback from customer proves that this software is designed properly, functioned asrequested, running with stability and reliability, meeting the anticipated objectives.