___________________________________________*Copyright © 2005 by the Consortium for Computing Sciences in Colleges. Permission to copywithout fee all or part of this material is granted provided that the copies are not made ordistributed for direct commercial advantage, the CCSC copyright notice and the title of thepublication and its date appear, and notice is given that copying is by permission of theConsortium for Computing Sciences in Colleges. To copy otherwise, or to republish, requires afee and/or specific permission.151WLAN TRAFFIC GRAPHING APPLICATION USING SIMPLENETWORK MANAGEMENT PROTOCOL*Bhargavi Hiremagalur and Dulal C. KarDepartment of Computing and Mathematical Sciences, Texas A&M University-CorpusChristi, Corpus Christi, TX 78412, Tel: 361-825-2474e-mail: {bhiremagalur, dkar} @sci.tamucc.eduABSTRACTAs today’s world is making transition from being wired to becoming wireless,Wireless Local Area Networks (WLANs) are gaining importance. Like thewired networks, WLANs also need to be managed. One of the key things inmanaging a WLAN is to monitor the bandwidth usage. This is possible bymonitoring the network traffic at the wired and wireless interfaces of an accesspoint, a device that acts as a bridge between the wireless and wired networks.In this work, we present a Web-based graphing application that can be used tomonitor, collect, maintain, and visualize traffic data of the access pointsdeployed in a network. The application uses the Simple Network ManagementProtocol (SNMP) to communicate with the access points in a network. Thisapplication can be used by a network administrator to determine idle orunderutilized access points as well as congested or overloaded access pointsin a network. This information can be used by the administrator for relocatingthe idle access points or deploying additional access points at the overloadedsegments of a network for better load sharing. The application can also be usedfor educational purposes in a computer networking course.1. INTRODUCTIONIn the recent years, the market for wireless networks is growing fast and wirelessLocal Area Networks (WLAN) are replacing or extending wired network services. Unlikethe traditional LANs, the WLAN users can move about freely and access the networkfrom anywhere [3]. WLANs offer the services of wired networks with no expensivewiring. They have practical uses in warehouses, hospitals, factories, and universities toJCSC 20, 4 (April 2005)152name a few. A Wireless LAN comprises of two main components, the Wireless NetworkInterface Card (WNIC) and Access Point (AP). The wireless users connect to the networkwith WNICs via the access points. The access points act as a bridge between the wiredand wireless networks. The wireless users connect their mobile stations via the Radiointerface and the connection to the wired network is through some traditional interface(such as Ethernet) of an access point. IEEE has approved a family of standards forWLANs that include IEEE 802.11, IEEE 802.11a (also known as Wi-Fi-5), IEEE 802.11b(also known as Wi-Fi), and IEEE 803.11g. The lowest data rate of 1 Mbps is supportedby IEEE 802.11 standard, whereas the highest data rate of 54 Mbps is supported by IEEE802.11a or IEEE 802.11g standard [1]. There are APs available in the market that aretri-mode i.e., they support IEEE 802.11a/b/g standards. They have three interfaces,namely, the ‘Ethernet Interface’ which provides connectivity to a wired network, a 5 GHzinterface(Radio-0) for IEEE 802.11a standard, and a 2.4 GHz interface (Radio-1) for theIEEE 802.11 b/g standards (IEEE 802.11g is backward compatible with 802.11b). The number of wireless users is increasing by the day. It is important for thenetwork manager to know the usage at every access point in order to determine thenumber of access points to be installed at various locations in a network so that a hugeuser base, such as in an educational institution, can be supported efficiently. Bymonitoring the network traffic at the access points, the network manager can decide if anadditional access point is needed to share the load at a particular location or the existingaccess point can be relocated to some highly congested location on the network. There are some similar tools available on the Internet. One such tool is the MultiRouter Traffic Grapher (MRTG). This tool monitors traffic on a network and graphs it.It is an open source tool and is coded in C and Perl. However, it is not Web-based and isnot flexible enough to provide the bandwidth usage information for all interfaces of anetworking device for a given time period. For example, using MRTG, it is not easy toomonitor and visualize traffic for the Ethernet and Radio interfaces of an access point. Inthis work, a Web-based application has been developed using Simple NetworkManagement Protocol (SNMP). This application monitors network traffic at variousaccess points on both wired and wireless interfaces and graphs it to provide visualrepresentation to the user.The rest of the paper is organized as follows. Section two describes the SimpleNetwork Management Protocol (SNMP). Section three describes the system architecturebased on the popular client-server computation model. Section four explains its variousinterfaces to visualize traffic data. Section five and six highlight some advantages andlimitations of the application and suggests how the application can be used forinstructional as well as network planning purposes.2. SIMPLE NETWORK MANAGEMENT PROTOCOL (SNMP)SNMP is an application layer protocol in the TCP/IP protocol suite and facilitatesthe exchange of management information between network devices. SNMP helps networkmanagers to monitor the network performance and solve network problems [2]. AnSNMP managed network has three components, namely, Managed Device, Agent, andNetwork Management System (NMS) [2]. A managed device is a network node that hasCCSC: South Central Conference153an SNMP agent. A SNMP managed device maintains a Management Information Base(MIB), a collection of information which is organized hierarchically in a tree structure.An MIB is comprised of many managed objects, in which each object is identified by anobject identifier. MIBs are accessed using SNMP. These devices reside on a managednetwork, collect, and store management information. This information is made availableto the Network Management Systems (NMS) using SNMP [2]. An agent is a networkmanagement software component that