Ready for VoIP: Network Management Architectures: GL Communications

GL Communications, Inc., headquartered in Gaithersburg, Maryland, was founded in 1986, and since that time, has grown into a firm that supplies a broad range of telecommunications testing products and consulting services.

GL’s products fall into three broad technology areas: wireless, TDM, and VoIP. These solutions are primarily PC-based test and measurement products, with the key features of visualization, capture, and storage of high speed telecommunications signals in a portable platform.

The company has branch offices in Los Gatos, California, Bangalore, India, and Shanghai, China, and is positioned worldwide by a network of representatives and distributors.

Given their specialty in the telecommunications arena, they have compiled an impressive list of customers, including the key service providers in North America such as AT&T, Infonet, Intelsat, Sprint, and Teleglobe Canada; major manufacturers including 3Com, Cisco Systems, Ericsson, Motorola, Nokia, Nortel Networks, and Siemens; plus large enterprises including Boeing, General Dynamics, Lockheed Martin, Safeco Insurance, and Ticket Master.

GL provides a number of solutions for network-wide analysis of TDM, wireless, and VoIP networks, including probes, centralized monitoring solutions, analyzers, and simulators. The probes are deployed at strategic locations in the network to collect data, voice, protocol, statistical, and performance information, and then relay that information back to a centralized or distributed network management system, or NMS.

The NMS may be a client/server-based or web-based system, consisting of a database and various applications that control, collect and analyze the information that has been collected by the various probes. These solutions include the capabilities for monitoring, testing, and diagnostics for T1/E1 lines; monitoring and surveillance of Signaling System 7 (SS7), ISDN and wireless protocols; wireless, wireline, and VoIP voice-quality monitoring; plus packet and VoIP monitoring and surveillance.

For T1/E1, SS7, and ISDN networks, GL provides the T1E1 Analyzer Probes, which provide the basis for network-wide management of T1 and E1 lines, including line health and intrusive diagnostics. The information from the probes is stored in a central relational database, and then graphically viewed by the NetSurveyor network management and surveillance system. The call detail records display the Call ID, Probe Name, Disposition, Calling and Called Numbers, Start time, Duration, and Timeslot (see Figure 1). Each record can be expanded be expanded to show message trace information, including the Frame ID, Card, Timeslots, Length, Error Status, and a hexadecimal dump of the information (see Figure 2).

For packet and VoIP networks, an Ethernet probe called the PacketScan monitors packet flows in real time. These probes gather IP packet details, including Quality of Service (QoS) statistics such as the direction, payload, packet count, conversation Mean Opinion Score (MOS), packet loss, delay and jitter) and forward that information to the central database.

The PacketScanWeb network management system navigates through those records, filtering and summarizing the collected VoIP traffic. The VoIP traffic summary displays the Traffic Summary ID, Probe Name, Calling Number, Called Number, Start Time and Duration (see Figure 3). To navigate the call records, users can specify the index of the starting record to be displayed, and also filter the data based upon the start time and end time of the calls (see Figure 4). PacketScan supports SIP, MGCP, MEGACO/H.248 and H.323-based voice networks, plus H.263-based video.

For active wireless, wireline, and VoIP network voice quality testing, GL provides the Global Intrusive Network VQT system, which uses multiple nodes at various locations, accessing the networks under study. This system includes a regional command center that controls the probes, software that provides voice analysis, and a remote NetViewer application that remotely controls the entire system, displays real time statistics, and queries the results. The Voice Band Analyzer graphically displays the call statistics that are calculated (see Figure 5), and also provides real-time data that displays the Call ID, Direction, Probe Name, and Call Information, plus the call performance statistics such as noise level, clipping and echo (see Figure 6).

GL Communications also offers the PacketGen, a SIP bulk-call generator, the PacketH323 single call simulator, and the IPNetSim, an IP network simulator.

Further details on the GL Communications architecture and products can be found at Our next tutorial will continue our examination of vendors’ network management architectures.

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