The document discusses optimization of authentication, authorization, and accounting (AAA) systems in mobile networks. It presents models to estimate AAA signaling rates under different conditions. A basic model accounts for user mobility between network areas. An optimization framework aims to minimize signaling load and unreported usage while meeting capacity limits. AAA systems could enable new applications like wireless mesh backhaul billing and multi-operator optical network accounting. Open research questions include planning for multiple services, improving reliability optimization, and investigating new AAA applications.

1. Design and Optimization of Authentication, Authorization, and Accounting (AAA) Systems in Mobile Telecommunications Networks Said Zaghloul Technical University Carolo Wilhelmina of Braunschweig, Germany PhD Defense 27.04.2010 Braunschweig, Germany

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3. Background: Evolution Trends Evolution of Service Requirements Evolution of Cellular Systems

4. Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, 2009-2014

5. Background: How an all-IP Network Looks Like ? RNC CAS DPI Rating Server Billing Server AAA Internet Acronyms RNC: Radio Network Controller AGW: Access Gateway CAS: Content Adapt. Server DPI: Deep Packet Inspection IMS: IP Multimedia Subsystem PCRF: Policy & Charging Rules Function CSCF: Call Session Control Function AS: Application Server HSS: Home Subscriber Subsystem Users Database AS AS Radio Access Network PCRF HSS AS CSCF AGW IP Transport Network 3 rd Parties IMS Network Authentication & Billing WiFi Access Car-2-X Services Service/Content Aggregation Network Transport Billing Provider Location Info. Broker Content Provider Wireless Access Subscribers Operator Centric Revenue Streams Adapted from Eliot Weinman, Harnessing the Mobile Internet, Yankee Group

6. Background: The AAA Systems Role (1) RNC CAS P-GW Rating Server Billing Server AAA Internet Users Database AS AS Radio Access Network PCRF HSS AS CSCF AGW IP Transport Network 3 rd Parties IMS Network Authentication & Billing WiFi Access Car-2-X Services AAA systems are central elements that enable service offerings in emerging cellular networks.

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9. Thesis Contribution and Scope

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12. Planning: Models and Analytical Tools Probability and stochastic analysis Probability and stochastic analysis Probability and stochastic analysis Renewal theoretic concepts Renewal theoretic concepts Transient Markov chains theory Analytical Tools Fixed Model Basic Model Distributed Model Control Plane Planning Analytical Toolbox

14. Planning: Fixed Model (1): Mean Interims Interim Interval Signaling Rate     Authentication/ Authorization   Accounting Interim    Reauth Authorization Lifetime   Interim Interval Session Time ( S ) Accounting Start Accounting Stop A message can be transmitted f times Accepted session with probability ( ) Retransmissions Factor Proportion of Received Accepts Let k be the number of transmissions, p be the packet loss probability, and N be the maximum number of retransmissions.

15. Planning: Fixed Model (2): Mean Interims f J (2) is the service session duration (R.V.) is the accounting interim interval (const.) E[S] /  T Error (E[S]/  T , Model) > 3 < 5% 2-3 30% - 5% 1-2 72% - 30% 0.5 219% 0  T 2  T 3  T 4  T 5  T f S (s) f J (j) 0 1 2 3 4 5

20. Planning – Basic Model (4) t Session Start  T ACR (Stop) Case 3 Handoff Event Handoff Event ACR (Stop) Case 2 Handoff Event ACR (Stop) Case 1  T  T  T  T Case 1 no handoffs S H F  T  T  T Case 2 one handoff S H O H T  T  T  T Case 3 multiple handoffs S H Tr H T H Tr H O Accounting Starts and Authentications Accounting Stop Accounting Interims Session Duration

21. Planning – Basic Model (5) Recall that Break by E [ K ] Combine using E [ K ], p 0 Get E [ I ]

23. Planning – Distributed Model (1)

24. Planning – Distributed Model (2) 15 27 21 9 8 26 20 14 1 2 6 0 7 13 19 25 . . . 12 18 24 32 5 Areas 6 Areas We overlay the a transient Markov chain model to describe the mobility pattern between areas or AGW regions.

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28. The Optimization Mechanisms: Delay (3) RNC: Radio Network Controller PCRF: Policy and Charging Rules Function AAA: Authentication, Authorization, and Accounting Signal to Noise Ratio TIME Current Cell Candidate Cell Hysteresis Margin Handoff D 1 D 2 Trg2 Trg1 Handoff Prediction Proactive QoS Authorization Service Delay Estimates RNC PCRF AAA AAA PCRF

30. Optimization Mechanisms: Reliability (2) Load almost independent of the interim interval AAA Server Capacity Limit Potential Loss Min Loss Max Load Max Loss Min Load AAA Load Loss Upper Bound Optimization Region 0 0.5 1 1.5 Interim Interval/Mean Session Duration (  T /E s ) AAA Signaling Load (message/sec)

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35. Proposed New Applications for AAA Systems Gateway Router 1 AAA RNC RNC Goal: Allow mesh operators to bill cellular operators for backhaul services Wireless Mesh Operator 2 AAA PCE SW Source Domain AAA PCE SW SW Transit Domain AAA SW SW Goal: AAA for multi operator layer 2 optical networking Dest Domain B PCE