Efficient Security Associations Establishment Using IPSec in IMS after Handover in NGMN

Next generation mobile networks allow smart phones to constantly switch and handover its networks to access internet for multimedia applications. To avail multimedia services, IP Multimedia Subsystem (IMS) is a 3gpp based framework for all types of networks. UE has to register with IMS where it first contacts to P-CSCF for establishing IPSec Security Associations (SA). During handover to a new network, de-registration from IMS is imposed that results in expiring IPSec SAs with old P-CSCF. UE has to establish new IPSec SAs with new P-CSCF that causes more signaling delay due to more number of messages. This paper presents a novel solution to establish SAs in IMS after handover where a flag is used to block de-registration until expiry. IPSec SAs are negotiated by reducing steps of re-authorization without appending new protocol in IMS. We tested our scheme on a test bed and compared the results with existing IMS re-authorization schemes. Our approach dominates the preliminaries in reducing transmission delay, processing delay and queuing delay as well as VHO delay and packet loss.