The Computer Journal Advance Access published online on May 20, 2009
The Computer Journal, doi:10.1093/comjnl/bxp042
Distributed Hash Table-Based Interrogating-Call Session Control Function Network in the Internet Protocol Multimedia Subsystem for Efficient Query Services
Department of Computer Science and Information Engineering, National Cheng Kung University, Tainan, Taiwan 701, R.O.C.
* Corresponding author: huangcm{at}locust.csie.ncku.edu.tw
Received 15 October 2008; revised 31 January 2009
Internet protocol multimedia subsystem (IMS) is an overlaid infrastructure above the packet-switched domain of the universal mobile telecommunication system core network. IMS enables and enhances real-time multimedia mobile services. IMS signaling and media are separated in IMS. For media session negotiation, two basic procedures in IMS are (i) IMS registration procedure and (ii) IMS incoming call setup procedure. IMS signaling needs to traverse a set of call session control functions (CSCFs), which are proxy-CSCF, interrogating-CSCF (I-CSCF) and serving-CSCF (S-CSCF). However, we observe that I-CSCFs need to query the home subscriber server (HSS) to obtain the name of S-CSCF for each subscriber's request in both the basic procedures. It results in a certain load occuring in the HSS and a certain procedure delay also occurs. Therefore, we employ the distributed hash table (DHT) into IMS to form a DHT-based I-CSCF network. Each I-CSCF in the DHT-based I-CSCF network can share and relieve HSS's load. As a result, the incoming call setup procedure can be speeded up. We also propose two maintaining procedures to maintain the DHT-based I-CSCF network for I-CSCFs join and leave scenarios. We propose one maintaining mechanism to guarantee the proposed system to be able to work well in the failure scenario of I-CSCF. According to the performance evaluation results, the load of HSS is reduced and shared among I-CSCFs in the home network and the signaling delay cost of the incoming call setup procedure is less than that of existent systems even if failure occurs and then is removed.
Key Words: Chord Chord ring call session control function distributed hash table IP multimedia subsystem incoming call setup registration session initiation protocol