Secure and Fast Mobility Schemes for IP Multimedia Subsystem (IMS)

Abstract

This is the era of modern mobile technology that provides users to access different networks at any time and any where according to their situations and requirements. User Equipments (UEs) are designed to switch between different Access Networks (ANs) e.g. from WiMax to 3G or from Wifi to LTE. IP Multimedia Subsystem (IMS) promises a framework that provides services to all types of ANs. In 2020, 5G is promised to be on scene, and IMS is a candidate to provide its features to this as well. One of the features of IMS is to provide Quality of Service (QoS) to users. Due to mobility of user, UE handovers from one AN to another. This handover requires disconnection from current AN and then connection to a new. This leads to de-registration of UE in IMS and registration in IMS again after handover. In LTE-femtocell heterogeneous networks, handovers tend to occur more due to the decrease in the size of cells. Registration phase in IMS handles user’s registration along with its authentication and authorization. This phase establishes IPSec Security Associations (SAs) between UE and entry point of IMS i.e. Proxy-Call Session Control Function (P-CSCF). If a UE handovers to new AN while having a session with a Corresponding Node (CN) then it has to undergo long process of registration, authentication authorization and establishment of IPSec SAsin IMS before resuming its session with CN. Meanwhile user of UE experiences delay in media disruption time and packet loss. The servers of IMS along with UE suffer the communication overhead. In other words QoS gets affected due to handover of UE to new AN. As one of the promises of IMS is to provide good QoS to users then there is a strong need to minimize media disruption time , loss of packets and communication overhead. This thesis proposes a complete framework for mobility issues in IMS that resulted from UE’s handover to new AN. It proposes two schemes for providing solution to the problems of sub phases of registration in IMS after handover. The first scheme caters with UE’s registration with new IP address and P-CSCF, UE’s authentication, UE’s authorization and transfer of IPSec SAs to new P-CSCF in a secure manner. Second scheme deals with the establishment of new IPSec SAs between UE and new P-CSCF after handover with reduced number of messages and within SIP capabilities. We give solution for these issues by avoiding de-registration before Abstract Shireen Tahira 56-FBAS/PHDCS/F09 iii handover. Our scheme FIM (Fast IMS Mobility) sends a proposed subsequent request from UE instead of conventional request to IMS servers that does not undergo the long phase of registration. Instead it gives a solution to do only necessary things needed after handover Proposed scheme caters registration with new IP address of UE and P-CSCF that takes care of authentication and authorization as well. FIM also transfers IPSec SAs from old server to new. For the establishment of new IPSec SAs, second proposed scheme EMSA (Efficient Mechanism for Security Associations) uses proposed subsequent request and response. It establishes IPSec SAs between UE and IMS after negotiating necessary parameters. Both schemes use already running protocols of IMS. The overhead of new protocol integration is avoided. We analyzed the media disruption time, number of commands and packet loss of proposed scheme FIM theoretically as well as on a test bed developed by using an open IMS core (i.e. FOKUS) and compared the results with existing schemes. Transmission delay, processing delay and queuing delay of the establishment of IPSec SAs for our proposed scheme EMSA are also calculated theoretically and the results are compared with the old schemes. On the developed testbed we compared the delay and packet loss of EMSA with IMS scheme. Overall our proposed schemes FIM and EMSA outperform than existing schemes in terms of minimizing number of messages, media disruption time, packet loss and signaling delay.