Signaling rate and performance for authentication, authorization, and accounting (AAA)) systems in all-IP cellular networks

Abstract

Authentication, Authorization, and Accounting (AAA) systems are one of the most significant architectural components of the current cellular networks and within the emerging IP Multimedia Subsystem (IMS) standard. Despite the operators' experience in AAA operations, very little is fundamentally known about the expected signaling rate towards the AAA system. In this paper, using stochastic and renewal theoretic techniques, we develop the first analytical model for the AAA signaling rate as a function of protocol parameters, users' access rates, session durations, and mobility. We provide model approximations and evaluate their accuracy under various operational conditions. Our results show that the AAA signaling rate is a monotonic non-linear function of the mobility rate and asymptotically converges to the AAA signaling rate in fixed networks. We also show that by adjusting the accounting interim and the authorization-lifetime intervals from half to full mean session duration, it is possible to define an AAA operational range for accounting messages that minimizes the signaling rate fluctuations due to likely perturbations in session and mobility statistics. The results also include the effect of the session dropping during handoffs and shows that is marginal in operational networks.

Optimal Accounting Policies for AAA Systems in Mobile Telecommunications Networks

“…For Static_Med and Static_Max policies, the interim settings are fixed to half and full mean session durations, respectively. For example, for two services of 5 and 15 minutes, the corresponding interim settings are [1,1], [2.5, 7.5], and [5,15] for the Static_Min, Static_Med, and Static_Max policies, respectively.…”

“…To account for statistical variability due to mobility, our method uses standard protocol attributes [3], [4] to categorize mobile service sessions into four distinct types relevant to their initiation and termination locations. The statistics of the four components are then used to estimate the load and loss by extending concepts of holding time, based on our past work [13], [14], [15]. Our optimization mechanism embraces the current AAA IETF standards, RADIUS, and its successor Diameter [1], [2] and does not require any modifications to the AAA protocols nor to the network access servers, and its implementation scope is limited to the AAA systems.…”