The Architecture of a Novel Tool for Network Management Using GSM/GPRS Mobile Devices

Transcription

1 The Architecture of a Novel Tool for Network Management Using GSM/GPRS Mobile Devices Vieira Junior, A.C. Computer Science Department Catholic University of Petrópolis (UCP) Rio de Janeiro - Brazil [email protected] Anido, M.L. Computing Center (NCE) Federal University of Rio de Janeiro (UFRJ) Rio de Janeiro Brazil [email protected] Abstract Computer network management is a highly demanding task because network managers have to deal with urgent requests to solve network problems Unfortunately, a network manager may be situated in a location where there is no internet-connected computer to perform remote network management tasks. To solve this problem, this paper describes the architecture of a novel tool for network management using GSM/GPRS mobile devices. The paper starts by presenting some general concepts about network management and GPRS technology. Then it focuses on the description of architecture for the development of applications for network management. The paper also describes implementation details of a network management tool, particularly the interface for mobile devices. At the end, it shows results by depicting the screen of several mobile devices, which provide network management information. Keywords network management; SNMP; GPRS; I. INTRODUCTION AND PREVIOUS WORK Network management is a hard task. It requires the coordination of several issues, such as different hardware, software and communication environments. A Network Management System (NMS) is a set of software and hardware tools for the monitoring and management of a network [7] [8]. Sometimes, we think that Wide Area Networks (WANs) are harder to manage than Local Area Networks. Modern LANs are so complex that the difficulty of managing them is similar to, or even bigger than, the difficulty of managing a WAN. Nowadays, almost every IT department settles Service Level Agreements (SLAs) with their users, which requires additional resources in network monitoring systems. Network monitoring has many disciplines, such as installation, integration, and the coordination of hardware, software and human resources for the monitoring, test, configuration, analysis and evaluation. The final goal is to control the network in real-time, knowing its resources, its performance, and then comparing this information with the user requirements. All these tasks should be executed within an acceptable budget. The increasing demand for applications and services that allow the development of new business, stimulate companies to increase the investment on network infrastructure services and telecommunication systems. These systems have had their complexity increased, interconnecting equipments of different manufacturers, which generally use different technologies. Accordingly, the increasing use of SLAs has demanded sophisticated monitoring and management systems. IP based network management protocols appeared in the 80 s with the development of the Host Monitoring Protocol (HMP), High-Load Entity Management System (HEMS) and Simple Gateway Monitoring Protocol (SGMP) [1]. These protocols evolved towards the Simple Network Management Protocol (SNMP) [1] [25]. The Internet Engineering Task Force (IETF) Application MIB Working Group is responsible for the definition of a set of managed objects that provides information about configuration, faults, performance, accountability and security. These managed objects offer the necessary information to define the quality of service and reliability of a network infrastructure. The basic parameters of SLAs are established by this information. Technology development in the mobile communications area has been growing substantially in recent years. The success of Global Systems for Mobile (GSM) [2] technology is a fact and the continuous growth of the Internet creates opportunities for the mobile cell companies to offer new data services, mostly Internet and Intranet access for mobile users. Currently, two technologies have appeared as big players in the wireless arena. One is the result of the development and migration of LAN technologies, standardized by the IEEE as or Wireless Fidelity (Wi-Fi) [3]. The other is General Packet Systems Radio (GPRS) [4] [5]. GPRS was created to fulfill the needs for transmitting data packets over cellular telephony. Other technologies like Code Division Multiple Access - 1 x Radio Transmission Technology (CDMA - 1xRTT) [22] and movements toward standardization with Universal Mobile Telecommunications Systems (UMTS) [6] make it clear that a big market for wireless access is coming. Nikolaou and Zervos [23] have made an excellent analysis about wireless convergence, presenting a case study, which uses GSM and Wireless LANs. However, their paper does not address the problem of network management using mobile /04/$ IEEE. 539

2 devices. In [24] Jacques presents his work about an implementation of a web-based management system using standard computers, but without GSM/GPRS connectivity. This work is centered on mobile devices with GSM/GPRS connectivity to provide network management facilities, despite having more limitations than standard computers. How to circumvent such limitations is one of the topics of this paper. II. GPRS: AN OVERVIEW The GPRS (General Packet Radio System) technology has been standardized by the ETSI (European Telecommunications Standards Institute) [9] and is one of the main data services available for mobile cellular networks. It is a service that provides data access using packet switching over GSM and TDMA (Time Division Multiple Access) networks. One of the greatest advantages when compared with CSD (Circuit Switched Data), is the moderate use of network resources, which only occurs when there is traffic activity. GPRS is a step towards third generation (3G) cellular systems. The use of GPRS allows mobile cell companies to change their networks, enabling IP data services. The packet switching capability that already exists in GSM networks is extended with GPRS, using Packet Data on Signaling- Channel Services (DSS). This technique allows transfer rates up to 171,2 Kbps, when all the eight (8) timeslots are used together. This rate is more than twice the speed of dial-up connections and more than 10 times the speed of the CSD services offered by the cellular mobile systems. GPRS was designed to coexist with the GSM Public Land Mobile Networks (PLMN) and could be gradually implemented over existent GSM networks. GPRS is the main convergence technology for GSM and TDMA (IS-136) networks, because it is available on both systems, allowing traffic between different network providers and a smooth transition into 3G networks. The use of the Internet Protocol (IP) and packet switching on mobile networks allows the deployment of Internet/Intranet applications over mobile cell networks. The three main characteristics of GPRS are: the system is always on-line; it is an evolution of the current systems and is part of 3G systems. The always on-line feature, traffic-based billed system is changing the way mobile devices are used. This feature is not unique of GPRS, but it is the first time it is available for mobile services and will continue in the next generations of mobile services. This feature provides real-time access using a WAP (Wireless Application Protocol) [10] browser or a proprietary application on the mobile device. The possibility of evolving GSM into GSM/GPRS with a software upgrade on the Base Stations System (BSS) is a very interesting point. The major part of the costs of the installation of mobile cellular infrastructure is in the Base Station Controller (BSC) and the Base Transceiver Station (BTS). With a software update and a small hardware investment, new value-based services could be offered to customers. One such service is that GSM networks could support GPRS by adding two new elements beyond the software upgrade and some specific hardware like the Packet Control Unit (PCU), which makes the traffic separation between packet switching traffic and circuit switching traffic. The PCU is installed on the BSC (figure 1). The new elements are the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN). The first one is responsible for the management of mobile devices, packet routing between the mobile devices and available networks, user authentication, cryptography and data compression. The second one is an interconnection point between the SGNS and the packet switching networks. The GGSN has a tunneling capacity, implemented by the GPRS Tunneling Protocol (GTP). This feature allows a secure communication channel between the GPRS mobile device and the packet switching network connected with the GPRS network. Figure 1. GPRS System Architecture mobile-based network management, which is the subject addressed by this paper. III. AN ARCHITECTURE FOR MANAGING AND MONITORING NETWORKS USING MOBILE DEVICES With the possibility of data traffic between mobile devices and packet switching networks, using GPRS, we can design an architecture that can be used for the development of a /04/$ IEEE. 540

3 Network Monitoring System. Network managers can use this NMS to remotely monitor and/or manage networks. A global view of such architecture is presented by figure 2. Figure 2. An architecture for managing and monitoring networks using mobile devices An NMS was developed using this architecture and comprises seven (7) modules, which are: NMS Core This is the main module and it is responsible for keeping information about network element records, interfaces, data link, users, user groups, administrators, user authentication, private MIB elements and general NMS configuration. Another responsibility of this module is to process and analyze all the events collected from other modules of the application. These processes occur every minute or two and several events, such as trap from module Trap Receiver, generate alarms, which are sent to the network administrator. Polling Unit It is responsible for the synchronous verification of the state of managed elements. It collects information about the state of network elements and stores them in a database. If an element (device) cannot be reached, the Polling Unit triggers an alarm. Trap Receiver It is responsible for trap processing. Traps received from network elements are processed by the snmptrapd daemon and are forward to the trap receiver. After receiving a trap, the trap receiver searches a dictionary, which contains the most important traps, devices and interfaces used for network monitoring and management. Storing a trap event on a trap database is preceded by its search and, if necessary, the trap can be converted into an SMS and sent to the SMS Gateway. SMS Gateway This module receives notifications that have to be sent to the wireless GSM/GPRS module. After sending the notification, the SMS Gateway records a notification timestamp on a database. SLA It is responsible for recording the Service Level Agreements that have to be performed. When a violation occurs, the SLA module records that event on a table to be processed by the NMS Core Module. Statistics It maintains data about network elements and generates graphics. It also feeds the SLA module with statistical data. Interface This module provides access using WAP / WML, HTML, HDML, I-mode TM or MML interfaces. Figure 3 shows an application of the architecture in a managed network connected to a GSM/GPRS network. One of the major differences, when compared with the usual monitoring and managing system, is the capability of sending SMS messages directly to the GSM network across its own SMS Gateway, thus being independent of the SMS gateway mobile service provider. It also allows the network administrator to access the managed elements of the network with a mobile device, using a suitable interface for the current device /04/$ IEEE. 541

4 When an event, such as a link down event, on a router occurs, a SNMP trap notifies this event. The Trap Receiver module processes the trap and if it is an important event, the trap is converted into an SMS message and is sent to the network administrator. The Polling Unit module uses a similar procedure when an element cannot be reached. Both modules will record their operations on a database for logging proposes. After receiving the SMS message, the network administrator can access the elements via the Interface module. One limitation of the current GPRS Phase 2+ standard is that it is not possible to connect the mobile station to the wireless module directly, as shown in figure 3. To circumvent this problem we used one or more dedicated Internet connections with a virtual private network (VPN) between the mobile service provider and the managed network or a dedicated connection (point-to-point, not using the Internet). This circuit is the weakest link on the chain. If it fails, the administrator cannot access the managed elements. Nonetheless, even in this scenario, is possible to make the NMS open a call using the Circuit Switch Data (CSD) to the mobile service provider and configure a temporary VPN connection. The performance will diminish, but the administrator will have access to the network elements. IV. A NETWORK MANAGEMENT TOOL BASED ON THE PROPOSED ARCHITECTURE The development of software for mobile devices has two basic approaches for the Human-Machine Interface, which is the terminal based approach and the browser-based approach. Using the first one, we install the software on the mobile device by downloading it. Of course, the operating system of the mobile device should support the software. Using the browser-based approach, one can use a browser compatible device, using one of the many technologies available, such as WAP / WML, I-mode and DTML. Using the latter approach most of the software runs on the server and the user interface is sent to the browser. The major advantage of the browser s approach is the high portability of the application because there are many mobile devices that support browsers as standard applications. Figure 3. Network Monitoring and Managing using GPRS One of the requirements of this particular application is that it should be used with all browsers that are compatible with WAP / WML, HTML, HDML or I-Mode. Another requirement of the application is to use Open Source development tools, thus reducing the cost of licenses, no matter the benefits a proprietary solution would bring. The NMS was developed using the PHP [11] programming language which allows direct access to the managed elements via a SNMP API. Using the NET-SNMP 1 [12] package, it is possible to use the basic SNMP commands (SNMPGET, SNMPSET, SNMPWALK) inside a PHP application. The application runs on a Linux Red Hat 9 Server [17], with an Apache HTTP Server [18] and an SMS gateway [19]. The database used to store the network elements, interfaces, service provider contacts, users, notifications and messages was the MySQL [13] database. The interface with the mobile devices was developed using a framework known as HawHaw - HTML and WML Hybrid Adapted Web server [14]. This framework uses PHP and has an adaptation layer for the different technologies used in mobile devices. The modem used by the SMS Gateway is a mobile cell phone from Siemens model S45 [15] with a serial cable for the Linux Server. The statistics module was 1 NET-SNMP is a set of tools for Simple Network Management Protocol (SNMP). This package is based on the SNMP implementation of the University of Carnegie Mellon. It implements a SNMP agent, a library and tools for using SET e GET commands and trap management /04/$ IEEE. 542

5 implemented using RRDTool [20] and to convert GIF/PNG to WBMP, we used ImageMagik [21]. Figures 4, 5 and 6 illustrate the different interfaces available to access the information about network devices. To validate our system we used a Siemens mobile cell phone, a Palm V, as illustrated by figure 4. A SmartPhone 2003 emulator from Microsoft [16] and OpenWave Emulator, as illustrated by figure 5 and 6. Figure 5. SmartPhone 2003 emulator accessing the NMS Figure 4. Accessing the NMS through different mobile devices Figure 6. OpenWave emulator accessing the NMS /04/$ IEEE. 543

6 V. CONCLUSIONS This paper addressed the architecture of a novel tool for network management using GSM/GPRS mobile devices, focusing on its block diagram and the corresponding functions. It also presented the approach that was used to develop software for mobile devices. One of the major difficulties for the development of this tool was the Human-Machine Interface, because the displays of mobile devices have limited resolution to display the monitoring information. On cell phones, this problem is worse and we have to deal with a small and inappropriate keyboard. Nevertheless, the existence and availability (always on-line) of a GPRS application is a great resource for a network administrator. Most of the simple problems of networks can be easily solved remotely, anytime, anywhere. New functionalities are under development. These new modules will allow VLAN control, Routing Protocol configuration and other services. The development of templates for the monitoring/managing of Database Servers, Proxy Servers, Web Servers, and Mail Servers is also being considered. We use this tool to monitor and manage the network elements of the Catholic University of Petropolis (UCP), which had enough complexity for our test case. REFERENCES [1]. Stallings, William - SNMP, SNMPv2, SNMPv3 and RMON 1 and 2 Addison-Wesley, 3rd edition, [2]. Redl, Siegmund M., Weber, Matthias K., Oliphant, Malcon W. An Introduction to GSM Artech House Publishers, [3]. Wi-Fi Alliance, May [4]. Bates, Regis J. GPRS General Packet Radio Service McGraw Hill, [5]. B. Ghribi and L. Logrippo, "Understanding GPRS: the GSM packet radio service," Computer Networks, vol. 34, pp , [6]. UMTS FORUM - May [7]. Subramanian, Mani - Network Management: Principles and Practice - Addison-Wesley, [8]. Hegering, Heinz-Gerd, Sebastian Abeck, Bernhard Neumair Integrated Management of Networked Systems: Concepts, Architectures, and Their Operational Application (Networking) - Morgan Kaufmann, [9]. ETSI - European Telecommunications Standards Institute May [10]. Wireless Application Protocol (WAP), May [11]. PHP, The Hypertext Preprocessor, May [12]. NET-SNMP, The NET-SNMP Project, May [13]. MySQL, The MySQL Database, May [14]. HAWHAW, The HTML and WML hybrid adapted Web server, May [15]. Siemens S45 Mobile Phone, May [16]. SmartPhone 2003 Emulator, fault.mspx, Sep [17]. Red Hat, May [18]. Apache HTTP Server Project, May [19]. SMSLink A client/server gateway to SMS protocol, May [20]. RRDTool Round Robin Database Tool - May [21]. ImageMagik /ImageMagick.html, May [22]. Ames, Phillip - The Evolution of Third-Generation Cellular Standards, Wireless Communications and Computing Group, Intel Technology Journal, [23]. Nikolaou, Nikos A., Zervos, Nicholas A. - Wireless Convergence Architecture: A Case Study Using GSM and Wireless LAN, Mobile Networks and Applications 7, , 2002 [24]. Sauvé, Jacques P. Web Manager A Web-based Network Management Application, IEEE-LANMOS, , [25]. Rose, Marshall T. The Simple Book An Introduction to Network Management. Second Ed. Prentice Hall Inc, /04/$ IEEE. 544