A Study on Mobile Commerce AAA Mechanism for Wireless LAN *

Transcription

1 A Study on Mobile Commerce AAA Mechanism for Wireless LAN * Gwanyeon Kim 1, Chinu Lee 1, Sehyun Park 1 **, Ohyoung Song 1, and Byungho Jung 2 1 School of Electrical and Electronic Engineering, Chung-Ang University Seoul Korea {cityhero,alelee}@ms.cau.ac.kr {shpark,song}@cau.ac.kr 2 Electrics and Telecommunications Research Institute cbh@etri.re.kr Abstract. Wireless LAN is rapidly becoming a crucial component in the next generation mobile communication. In spite of this success, user s privacy and access control like the authentication problems along with the Accounting and the Billing problems are arising. Especially in the accounting field, the research for the packet accounting based on IP is insufficient so that several ISP s adopted a fixed sum system for the accounting. This paper presents a packet accounting model compatible with the International Standards for mobile commerce and the verification results. 1 Introduction IMT-2000, 3G mobile communication, is suffering difficulty in the market entry due to the expensive hand-held device, the service rate and the delayed commercial service. Therefore the IMT-2000 service providers are attempting to cooperate with the wireless LAN service providers for the market entry and the profitability. In the wireless LAN, user s privacy and access control like the authentication problems along with the Accounting and the Billing problems are arising. Also, the authentication, the access control and the accounting process, and the interoperability with the next generation mobile communication are very complicate to implement. Consequently, this paper presents a packet-based accounting model for mobile commerce compatible with the International Standards and the simulation results of this accounting model. The proposed model is applied in the wireless LAN that is consisted of the IEEE b[1] networks, and to guarantee the compatibility and * This research was supported by the Chung-Ang University Research Grants in ** The corresponding author. C.-W. Chung et al. (Eds.): HSI 2003, LNCS 2713, pp , Springer-Verlag Berlin Heidelberg 2003

2 720 Gwanyeon Kim et al. the interoperability, we develop Diameter-based packet accounting model. We used IAPP (Inter Access Point Protocol)[2] and the prepaid accounting system for the effective accounting and to improve the mobility. The next section, we examine the AAA model for the public wireless LAN. 2 AAA Protocol for the Wireless LAN 2.1 Radius Protocol The best-known and most widely deployed AAA Protocol is RADIUS (Remote Access Dial-In User Service)[3][7]. It was developed in the mid-1990s by Livingston Enterprises (since acquired by Lucent) to provide authentication and accounting services to their NAS (Network Access Server) device. 2.2 Diameter Protocol RADIUS continues to enjoy widespread support among ISP and enterprise network managers. However, was originally engineered for small network devices supporting just a few end-users requiring simple server-based authentication. Dial providers must now provide AAA services for hundreds users accessing network services over a variety of technologies. Therefore, the IETF has undertaken an effort to develop a next-generation AAA protocol which is Diameter Protocol [4][7]. 3 AAA Protocol for Wireless LAN in Mobile Environment It must be researched and developed comprehensive and systematic AAA model that supports the roaming and the various charging system to apply wireless LAN over the Mobile Commerce. Therefore, in this paper, we provides Diameter-based AAA model for wireless LAN. The following section is about the accounting system with improved mobility over the wireless LAN system. 3.1 Extended IAPP for Mobility Support For the special quality of electric wave, the radius of AP (Access Point) is about 100 to 300 meters. For that reason, handover between APs occur frequently. Therefore, the authentication process between AP and AAA server happens for each handover and a new accounting session is created. Because of the authentication and the accounting process, the network traffics are increased and the user s connection is interrupted and the efficiency of server is decreased. Therefore, the cost of service is increased. Applying the proposed extended IAPP, the AP does not request an authentication process to an authentication server and uses the authentication and accounting information of the previous AP while handover occurs. Therefore, the mobile terminal receives the service immediately.

3 A Study on Mobile Commerce AAA Mechanism for Wireless LAN 721 So, these characteristics guarantee the mobility between domains and between networks. Fig. 1 shows the extended IAPP protocol. MN Old AP Old AAA Server New AP AAA Server 1 EAPOL.Start Authentication EAP Packet Transfer 2 EAP-Success (AP IP, Token) Accounting Session (Session.ID ) D ata Exchange EVENT : H andoff (oap -> nap) 3 E A P O L.S tart (O ld A P IP, T o ken ) IAPP-Move.Request (Token) IAPP-Move.Response (ConText) EAP-Success 4 Accounting Session (Sub_Session.ID ) 5 6 Data Exchange Fig. 1. Extend IAPP Protocol 3.2 Diameter-Based Packet Accounting Model The packet-based accounting model proposed in this paper is divided in prepaid and postpaid accounting systems. The postpaid accounting model is out of the subject and we will not handle in this paper. The billing server sends the number of available packet computed previously to AAA server. So the transaction is decreased between the billing server and AAA server. Also, the accounting policy and the service fee table must be discussed previously due to the user s roaming between the different service providers. Fig. 2 illustrates the proposed accounting system. Foreign D om ain Home Domain AP FAAA HAAA DB MN B illin g Server Fig. 2. Proposed AAA Architecture The following paragraphs explain the prepaid accounting procedures in five cases. (1) Case 1: Prepaid User Authentication AAA server must sends the accounting information to user and the authentication must set to Full service of Limited service according to accounting information. (2) Case 2: Balance Notification, Warning, Expiration

4 722 Gwanyeon Kim et al. The HAAA renews the user s balance in the real time based on the amount of data sent and received by the user and notifies it to the user. When the balance reaches some fixed limits in advance, the HAAA gives a warning message so that the user can make provisions for termination of the service. Finally, in the case that the balance is expired, the status is switched from Full Service to Limited Service. A balance notification, warning, expiration procedure is shown in Fig. 3. MN AP FAAA H AAA (1 ) S e s s io n In itia l (2 ) (UID, UsedPacket) (3 ) (4 ) Balance Notification (6 ) Balance Notification (UID, AvailablePacket) (5 ) (7 ) (UID, UsedPacket) Balance w arning (8 ) Balance w arning (UID, AvailablePacket, (9 ) W arningtext) (10) (UID, UsedPacket) Balance Expiration (Lim ited Service) (12) Balance Expiration (U ID, AvailablePacket=0, Service=LIM ITED) (11) Fig. 3. Balance Notification, Warning, Expiration Procedure (3) Case 3: Balance Recharge If the user recharges his or her balance, the Billing Server calculates the number of packets corresponding to the recharged balance and transmits it to the AAA server. The AAA server renews the number of packets and adds the remaining ones to the newly recharged ones. The balance recharging procedure is depicted as shown in Fig. 4. MN AP FAAA H AAA Billing Server (1 ) EVENT : Bala n c e R e c ha rg e Balance Recharge (Full Service) (4 ) Balance Recharge (UID, AvailablePacket= oavailablepacket+navailablepacket) Balance Recharge (2 ) (UID, navailablepacket) (3 ) (5 ) (UID, UsedPacket) Fig. 4. Balance Recharge Procedure (4) Case 4: Rate Change The rates vary according to QoS levels and time of day used. The Billing Server converts the remaining number of packet into money and computes the number of packets again in accordance with the new list of charges and transmits it so that the user can get the service continuously. The rate change procedure is shown in Fig. 5.

5 A Study on Mobile Commerce AAA Mechanism for Wireless LAN 723 H AAA Billing Server (1 ) R a te C h a n g e Rate Change Request (2 ) (3 ) Balance Packet Request (UID, AvailablePacket) Balance Packet Response (UID, AvailablePacket) (4 ) Fig. 5. Rate Change Event (5) Case 5: Roaming This case is similar to the rate change procedure of the previous case (Case 4) and is that the Rate Table is changed according to the global roaming. 4 Performance Evaluation Let s assume that a1, a2, a3, a4 represent a wireless LAN section, a private line section, an Ethernet section, a fast private line section respectively on the basis of network bandwidth and that the transmission delay of each section is defined in terms of a4 as follows: a1 = 14 * a4, a2 = 100 * a4 and a3 = 10 * a4. We change renewal times per minute with respect to the Rate Table (rate_n) from 1 to 60 and fix the value of other parameters. Since 60 times of per minute and the same times of balance notification per minute occur subsequently, 2 times of transaction per second take place from the MN to the Billing Server. Thus, the transmission delay can be expressed in the following form. 60sec * 2 times * (a1+a2+a3+a4) (1) In the proposed model, on the other hand, transaction times from the MN to the AAA server are the same with above but transaction to the Billing Server is proportional to the number of times of the rate change. Therefore, the transmission delay in the proposed model can be written as follows: 60sec * 2 times *(a1+a2+a3) +2 times *rate_n*a4 (2) We can get the difference (120-2*rate_n)*a4 from two equations above. Thus, this shows the higher performance improvement in the small rate_n and the results of two models are the same if rate_n=60. Table 1 compares the existing scheme (Case 1) with the proposed scheme (Case 2), and a graph for the performance analysis of case 1 and 2 is depicted as shown in Fig. 6. Table 1. Delay Relation Compare Table rate_n

6 724 Gwanyeon Kim et al. Case a a a a a4 Case a a a a a a Fig. 6. Performance Graph ra te _n Case 1 Case 2 5 Conclusions In this paper we presented AAA protocol to provide based wireless LAN, authentication, privilege and accounting services also, technologies to support the mobility. Finally, we proposed and verified a packet-based accounting model that satisfies the requirements for the prepaid/postpaid accounting service, and supports the mobility for the global roaming as well. The proposed prepaid packet-based accounting model provides real time accounting service and management of the balance. Also, authentication method for prepaid user is applied in this model. References [1] " Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications", ISO/IEC [2] David Bagby et. al., "Draft Recommended Practice for Multi-Vendor Access Point Interoperability via an Inter-Access Point Protocol across Distribution Systems Supporting IEEE Operation", internet draft, January 2003 [3] Rigney et. al., "Remote Authentication Dial In User Service", IETF, RFC2865, April 1997 [4] Pat R. Calhoun et. al., "Diameter Base Protocol", IETF Internet Draft, December 2002 [5] Perkins. C, "IP Mobility Support for IPV4 revised", IETF, RFC3220, January 2002 [6] Mick Seaman et. al., "Port-Based network Access Control", IEEE, June 2001 [7] Metz. C, "AAA protocol: Authentication, Authorization, and Accounting for the Internet", IEEE computing, IEEE, Vol3 Issue 6, Nov/Dec 1999, Page(s): 75-79