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Prepaid Extensions for AAA Services

Edip Demirbilek, 27.01.2011

Motivation

Enterprise Networks Case: EDUROAM Purpose: Authentication, Authorization and Accounting (AAA Model) Standart Protocol: RADIUS

New Demand: Prepaid Capabilities Case: Wireless Networks in Airports Problem: Introducing a new Protocol is an Expensive Task

Ideal Solution: Use Existing Infrastructure with Add On’s Ideal Solution: Use Existing Infrastructure with Add-On’s Seminar Topic: Prepaid Extensions for Radius

January 27, 2011| Edip Demirbilek | Prepaid Extensions for AAA Services Slide 2 (26)

Overview

AAA Model Radius ProtocolRadius Protocol Prepaid System Prepaid Extensions for Radiusp

• Features and Example Flows


AAA Model

Following questions serve the basic functionality of AAA.Who are you?Who are you?What services am I allowed to give you?What did you do with my services while you were using them?y y y g

AAA: Authentication, Authorization, Accounting


Overview




Radius in Network


Properties of RADIUS

UDP-based connectionless protocol Supports the authentication-authorization-accounting modelSupports the authentication authorization accounting model Uses a hop-by-hop security model Supported Authentication Methodspp

• Password Authentication Protocol ( PAP) • Challenge-Handshake Authentication Protocol (CHAP) • Extensible Authentication Protocol (EAP)• Extensible Authentication Protocol (EAP)

Provides over 50 attribute/value pairs with the ability to create vendor-specific pairsp p


A Radius Session


Radius Data Packet Format

Data DescriptionCode 8-bit request/reply type:

1 A R t1 = Access-Request2 = Access-Accept3 = Access-Reject4 = Accounting Request4 = Accounting-Request5 = Accounting-Response11 = Access-Challenge

Id 8 bi bId 8-bit message sequence numberLength 16-bit message lengthAuthenticator 16 octet binary vectorAuthenticator 16 octet binary vectorAttributes Arbitrary numbers of information pairs


Attribute-Value Pair Format

Data DescriptionAttribute 8-bit value-pair code, listed in the

di ti fildictionary fileLength 8-bit integer from 2-255.Value 0 - 253 octet information item.Value 0 253 octet information item.


Overview




Prepaid Service

Mobile subscribers count over the years in OECD countries 96.1 mobile subscribers per 100 inhabitants in 200796.1 mobile subscribers per 100 inhabitants in 2007 Italy had the highest penetration rate with 151 subscribers per

100 inhabitant.

1 200

Mobile (Postpaid) Mobile (prepaid) Mobile (3G)Mobile subscribers (millions)

8001 000

200400600

0200

1997 1999 2001 2003 2005 2007


Prepaid Service

Today, 72 percent of the worlds 4.6 billion mobile subscribers March 2010use pre-paid services

28% Prepaid

72%

Prepaid

Postpaid

Charging ModelsVolume-based charging (e.g., 2 Cents/KiloByte).g g ( g , y )Duration-based charging (e.g., 3 Cents/minute).Resource-based charging (e.g., 3 videos for 1 Euros)g g ( g )Event-based charging (e.g., 7 Cents/ring tone or SMS or MMS).


Charging Network Complexity


Overview




Prepaid Extension to Radius Service

First draft of Prepaid extensions for Radius protocol released in August 2003.

Current draft with number 18 which has been released at the end of October 2010.

Enable service providers to perform accounting and charging in real time• Make sure subscriber has sufficient credit before consuming the serviceMake sure subscriber has sufficient credit before consuming the service• Make sure service delivery interrupted when subscriber credit exhausted

Does not address prepaid service subscription or billing


Architectural Model

End User initiates the connection with the Service Access Device to get Service.

Prepaid Client (PPC) in Service Access Device establish the connection with an AAA Server.

PPC meters the consumption of the service cooperating with Prepaid Server (PPS).


Supported Features

Services and Quotas


Simple Flow Duration-basedVolume-based

[allocates 5MB quota]

[allocates another 7MB]

PPAC: Prepaid Accounting Capability Attribute, VQ: Volume Quota, QID: QuotaIdPPAQ: Prepaid Accounting Operation Attribute, VTH: Volume-Threshold,


Supported Features

Resource Pools• Service-A rated 1 €/MB Service-B rated 0 1€/MinService A rated 1 €/MB, Service B rated 0.1€/Min• 5 Euro worth of resources allocated to each service (5 MB and 50 Min)

P bl If Q t A ti i l th Q t B• Problem: If Quota-A consumption is slower than Quota-B

0 50 100 min

Service-AService-B

0 50 100 min

• Solution: Assign both Quotas to the same resource pool

Service-AService-B


Resource Pool Multiple servicesResource pools

[allocates 5MBPoolr = 50 Units [allocates 5MB quota]

Poolr = 50 Units

[allocates 50 min quota]

Poolr = 50 + 50 = 100 Units 100 Units

C d 85[reimburses user

account]

Consumed 85 Units

SID: Service Id, DQ: Duration Quota Reimburse 15

Units


Supported Features

Tariff Switching• Traffic before 18:00 is rated at rate r1 and traffic after 18:00 isTraffic before 18:00 is rated at rate r1 and traffic after 18:00 is

rated at rate r2.• If the PPS needs to signal a tariff switch time it will send a PTS

attribute that indicates the point in time when the switch will occur. This indication represents the number of seconds from current time (TariffSwitchInterval TSI)current time (TariffSwitchInterval TSI).


Prepaid tariff switchingDuration-based Volume-basedTariff switching

[allocates 20MB quota]

[reimburses user account]

PTS: Prepaid Tariff SwitchingTSI: Tariff Switch IntervalVUATS: Volume Used After Tariff Switch


Supported Features

Support for Roaming Dynamic TerminationDynamic Termination Multiple Tariff Switches One Time Events

• One Time Charging• Resource Consumption Query• Balance Check• Balance Check• Refund• Price Enquiry


Summary

AAA Model: Authentication, Authorization, Accounting Radius Protocol and Use CaseRadius Protocol and Use Case Prepaid System in Charging Network Prepaid Extensions for Radiusp Radius vs Diameter?


References T. S. D. Szilagyi, A. Sood, Radius A Remote Authentication Dial-in User Service, 2009. HP, HP-UX AAA Server A.06.00 Administration and Authentication Guide: HP-UX 11.0,

11i v1 HP 200311i v1, HP, 2003. OECD, Information and Communications Technologies, OECD Communications Outlook

2009, Oecd technical report, 2009. J Hassell Radius O’Reilly 2002 p 206J. Hassell, Radius, O Reilly, 2002, p. 206. E. P. Release, Pre-paid subscribers in charge, http://www.ericsson.com/news/1395590,

2010. A. Lior, P. Yegani, K. Chowdhury, H. Tschofenig and A. Pashalidis, Network WorkingA. Lior, P. Yegani, K. Chowdhury, H. Tschofenig and A. Pashalidis, Network Working

Group, Internet-Draft, http://tools.ietf.org/html/draft-lior-radiusprepaid-extensions-17, 2009

Eduroam. A technical Overview http://www.eduroamus.org/technical_overview http://schools-wikipedia.org/wp/c/Circle.htm


Convergent Charging

Prepaid Postpaid

Convergent Charging

Prepaid Postpaid

Fixed Telephony Broadband TV Mobile

Telephony

January 27, 2011| Edip Demirbilek | Prepaid Extensions for AAA Services Additional Slide 1 (2)

Additional References http://en.wikipedia.org/wiki/Convergent_charging http://www.ericsson.com/ericsson/corpinfo/publications/review/2009_01/files/Charging.pdf

htt // i hi http://www.iconarchive.com http://www.iconspedia.com

January 27, 2011| Edip Demirbilek | Prepaid Extensions for AAA Services Additional Slide 2 (2)

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