Four-Nines Reliability

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Many organizations excel in their WLAN design, but don't give enough thought to a wireless network's management, maintenance, monitoring and troubleshooting, all of which are as much a part of the deployment process as the implementation itself. It is very important to implement a cohesive network management strategy, and that industry standard tools, platforms and applications be used to manage the wired and wireless infrastructure seamlessly.

To ensure that a network management platform incorporates all of a WLAN's components requires that adequate planning and staff training be put in place prior to deployment. Although a WLAN's components support the standard network protocols, TCP/IP, NetBEUI, and IPX, and they can be managed with existing network management tools, often additional tools are needed to ensure the network management platform is monitoring the wireless network fully, and keeping track of performance and problems.

First, think about how you're going to manage the access points. The process of configuring and upgrading the large number of APs serving the average enterprise WLAN needs to be automated. Some AP vendors, including Proxim, design their systems with this in mind. Others, including Agere and Symbol, provide management software to accomplish that goal. In some cases, you may find it valuable to turn to third-party systems, such as Wavelink's Mobile Manager, for added functionality or to integrate APs from multiple vendors under a single management framework.

If the WLAN can't be managed remotely, whenever there is an upgrade, a "bug" fix, or a firmware change, a labor-intensive effort is required to physically disconnect and individually program each access point and then reinstall each unit in its original location. But if these same tasks can be done remotely, the access points need never be removed.

Annual site re-surveys can help to guarantee a high level of system performance and RF coverage. An organization's facilities and inventory layouts can change over time, so performing an annual site survey is invaluable. For example, a warehouse's inventory during tough economic times is a very different RF environment than during boom times. A university campus RF environment will evolve as the school year changes over to a summer classes.

Wireless Network Management Systems

Network-accessible data and mission-critical applications are essential to the operations of most organizations. They all rely on the availability of their network. The introduction of wireless into the networking environment adds additional complexities to the already complicated world of network management. You should implement a network management system that can meet the following goals:

• Improve network availability (up time) and service.

• Centralize control of network components.

• Reduce complexity.

• Reduce operational and maintenance costs.

A network management system can effectively reduce the cost and complexity of a network's maintenance by providing a set of integrated tools that allows a network manager or support staff to quickly isolate and diagnose network issues. The ability to analyze and correct network problems from a central location is critical to the management of both network and personnel resources.

In fact, network management is so critical that the general requirements of a network management system have been defined by the International Organization for Standardization (but commonly known as the "ISO") and categorized as part of the OSI specification for systems management. These general requirements are known as "The Open Systems Interconnect (OSI) Management Functional Areas," and are used as a base line for the key functional areas of network management on any system. The acronym FCAPS is used to represent the key elements of the ISO definition:

• Fault management

• Configuration management

• Accounting management

• Performance management

• Security management

Fault management: This encompasses the activities of detection, isolation, and correction of abnormal network operation. Fault management provides the means to receive and present fault indication, determine the cause of a network fault, isolate the fault, and perform a corrective action.

Configuration management: Activities include the configuration, maintenance, and updating of network components. Configuration management also includes notification to network users of pending and performed configuration changes.

Accounting management: The ability to track network usage to detect inefficient network use, or the abuse of network privileges or usage patterns, is included in accounting management, a key component for planning network growth.

Performance management: Activities include the monitoring and maintenance of acceptable network performance, and the collection and analysis of statistics critical to network performance. Tools are used to recognize current or impending performance issues that can cause problems for network users.

Security management: This encompasses controlling and monitoring the access to the network and associated network management information, including the control of passwords and user authorization, and collecting and analyzing security or access logs.

The goal of a network management system is to provide the above functionality in a concise manner that views the entire network as one homogeneous entity.

Network management systems rely on defined standards to interface with network devices for monitoring and controlling their configuration, performance and functionality. The Simple Network Management Protocol (SNMP) is the basis for most modern network management, since it provides multi-vendor network management systems with the ability to manage network devices from a central location. SNMP includes standard protocols, databases, and procedures to monitor and manage devices connected to the network. Nearly all vendors of network-based components, computers, bridges, routers, switches, etc., offer SNMP. Basic SNMP components are:

• A management station or console, which is the user interface component of the network management system. It provides the applications to configure, monitor, analyze, and control the various components that comprise the network.

• A management agent program that resides on a given network device that responds to requests from the management console or generates events (traps) based on configured parameters.

• The management information base (MIB), which is the management database for a given network component. There is a standard definition of a MIB for every device that is supported by SNMP. The management station monitors and updates the values in the MIB, via the agent. SNMP provides three main functions, GET, SET, TRAP, which retrieve, set device values and receive notification of network events.

• A proxy agent that supports devices that do not have an SNMP implementation available. The proxy is an SNMP management agent that services requests from the management console, on behalf of one or a number of non-SNMP devices.

• Remote Network Monitoring (RMON) is a specification that was developed to provide a standard interface between a management station and remote monitoring agents or probes. Remote monitoring agents are used to gather network statistical information in order to diagnose network faults and performance issues. RMON defines additional MIBs that collect this performance information.

Standard Wireless Network Management Platforms

Network management platforms can provide the management and maintenance features needed to manage a network system that provides both wired and wireless connectivity. Although they share standard elements and mechanisms, wired and wireless networks have significant differences. In addition to the conventional wired network, wireless networks have the following unique issues:

Secondary hierarchy: The wireless network environment is hierarchical, with mobile units attached or associated to a given access point. Standard network management products that are designed for wired networks cannot represent this critically important tiered topology network structure, since they represent the wireless network as a "Flat Topology."

Roaming: The wireless network environment supports dynamic cell connection or roaming, which is the process of changing the network connection of a mobile device from one access point to another. This is a unique component within the wireless environment.

Persistence of mobile computing devices. In an environment that is comprised of handheld computers, the ability to manage networked devices also becomes a factor. Unlike desktop systems or other network components that operate continuously on a daily basis, handheld computers are turned on and off frequently throughout the day, making it difficult to monitor these devices.

SNMP agents. The ability of devices utilizing wired and wireless networks to "host" an SNMP agent is another differentiating factor that impacts network management functionality. Desktop or laptop systems have adequate amounts of memory and processor power to support an SNMP agent operating as a background task handling requests from the network management station. However, on handheld terminals, many of which still run DOS, memory space and processor speed are highly limited resources, making it difficult to provide agents for these devices.

The unique features associated with wireless networks need to be addressed in order to provide a complete network management solution. Also wireless network management software is needed to continuously monitor all of the access points in the WLAN and alert the IT staff if anything strange is going on.

Due to the continually changing wireless network environment, established network management systems have not incorporated the necessary support for unique issues associated with wireless networks. Instead, they rely on the wireless vendors or third parties to provide "management applications" that can be incorporated into their enterprise network management system to manage the wireless component of the system.

A number of vendors offer wireless network management systems (WNMS), including NetMotion Wireless's NetMotion Mobility and Wavelink Corp.'s Wavelink Mobile Manager. However, let's look at Symbol's SpectrumSoft WNMS to demonstrate how a WNMS is specifically designed to solve network management issues associated with mobile computing devices in a wireless network. First off, the SpectrumSoft WNMS is seamlessly integrated into the corporate enterprise network management platform. This provides the ease of working in a single management environment and avoids the additional expense of purchasing, training, and maintaining a new management tool.

Since the SpectrumSoft WNMS is constructed using an Open Systems architecture, it utilizes proven network management standards (SNMP, MIB-2) to provide a comprehensive solution to the unique aspects of wireless networks: roaming, cell association, random connectivity, and power management.

The graphical user interface provides an intuitive tool for navigating, examining, and managing the wireless network. The products feature set provides the functionality as defined by the ISO FCAPS network management requirements, including the unique areas associated with wireless networks and mobile computing environments.

SpectrumSoft WNMS's modular design and the use of standard interfaces provide an easy integration path into a variety of enterprise network management platforms, including CA Unicenter, Cabletron Spectrum, Tivoli TME 10, IBM NetView, and SunNet Manager/Solstice. Also, a management console for SpectrumSoft WNMS has been created for wireless networks that do not require the extensive functionality provided in the above-mentioned platforms.

Monitoring and Troubleshooting

It is necessary to constantly monitor access point settings to ensure that they not only remain in compliance with the organization's current security policies, but also perform to specification. If a WNMS isn't an option, then get some monitoring and troubleshooting tools. Find software that allows the IT staff to set the performance and security thresholds at any value they wish and change them at any time. Also, be sure the software can produce detailed WLAN performance reports, so the IT staff can review the reports and fine-tune the network. You may also want to consider whether you need a software package that offers auto-repair features, which automatically return the access points to their proper settings.

Network management staff also can benefit from specialized tools, such as handheld WLAN analyzers that provide the mobility technicians and engineers need to manage a wireless network environment. If you have a protocol analyzer for your Ethernet network, you'll also need a version for your WLAN. Capable products are available from Network Instruments, Sniffer Technologies and WildPackets.

Another handy tool is a spectrum analyzer, which can troubleshoot RF problems. High-end spectrum analyzers, which may cost $20,000 or more, are available from Agilent and Tektronix. Lower-priced systems designed specifically for WLANs are available for less than $3,000 from Avcom-Ramsey. Most of these products put a ton of power into the hands of IT staffers.

Note 

Sometimes if the WLAN isn't an enterprise-size network, it makes good business sense to buy a lower-end spectrum analyzer. After all, it's not likely to be a tool you use every day, and you may not need all the advanced features of a high-end unit. But over-economizing is a bad idea when managing a large WLAN. So take the time to thoroughly understand the management issues and then select products from reputable vendors. Cutting corners may save you a few dollars today, but the cost of reduced productivity or stolen secrets will be a price you may be forced to pay in the future.

A WLAN analyzer can help throughout the life of a WLAN with site surveys, deployment, troubleshooting, and auditing. Post-installation connectivity problems between end-user computing devices and access points can be analyzed. Traffic and signal distribution problems can be found, analyzed and corrected. WLAN analyzers can be used to sniff out rogue equipment, as well as to discover devices with inappropriate settings that could open the WLAN to unauthorized users

Some WLAN analyzers are designed for laptops and others for the smaller handheld or PDA device. The analyzer software that's designed for a handheld device is used less for protocol analysis than for WLAN-specific features, such as surveying radio channels for signal strength and device populations. The range, though, is similar to laptop-based WLAN analyzers, except that a handheld device is much easier to wave in the air while looking for a signal.

The readers may wonder if a PDA is the right form factor for advanced troubleshooting. As with many applications, sometimes a PDA can be as much a limitation as a benefit. For example, the larger screen and higher resolution of a laptop computer make high-layer protocol analysis much more convenient. Furthermore, PDA-based systems are prone to occasional system lockups that necessitate a reboot.

But when considering an analyzer remember that these products stress the capabilities of the underlying hardware and software platforms on which they operate. The painful truth is that handheld analyzers don't replace other tools; they supplement them.

Because it's a relatively new market, comparing products isn't easy. One product might offer superior Physical Layer spectrum analysis while another might have the best expert system, letting people in the field quickly identify problems-two different tools for two different problems.

Note 

Don't expect these tools to be a substitute for understanding WLANs. They're just tools.

To choose the right handheld WLAN analyzer, consider its intended use. Which layers of the network stack do you want to analyze and who will do it? If you aim to equip your Tier 1 field technicians, perhaps the same folks who handle your wiring infrastructure, you should match the device to those workers' knowledge and experience with RF and WLANs. In many cases, this means choosing a tool that captures and analyzes WLAN traffic and provides practical expert analysis in real time. These techs also could benefit from having a tool that helps them perform site surveys, troubleshoot connection and performance problems, and identify and locate rogue devices and network attacks or intrusions.

If your needs are advanced, consider a more specialized tool. As RF-based communications systems grow, both in scope and usage, there is a greater need for precise tools that detect Physical Layer abnormalities. Remember, these are unlicensed airwaves, so the sources of interference are many. The tool of choice for serious RF engineers is the spectrum analyzer. Sometimes, a spectrum analysis tool is the only systematic way of identifying the source of WLAN performance problems, including those that may be caused by cordless phones or other unlicensed radio devices. While you can easily spend $20,000 on a capable spectrum analyzer, Berkeley Varitronics Systems' analyzer can be carried in your hand, at a dramatically lower price (less than $4000). Using a spectrum analyzer requires significant RF training, but for enterprise WLANs that must meet four-nines availability, this is a cost you may need to absorb.

Although most enterprise IT professionals appreciate the long-term business value of wireless LANs, use of this technology remains low enough to mask underlying design and management problems. The most popular applications-email and web access-don't place extraordinary demands on a WLAN's infrastructure. For this reason, buying expensive wireless troubleshooting tools to fix what isn't broken may seem like a low priority. However, if you anticipate your organization will support more wireless data services, you will eventually need specialized tools that will satisfy field technicians and WLAN designers alike.

When considering the purchase of a costly analysis tool, look for a product that can, at a minimum:

• Perform a thorough security assessment of the network.

• Provide a good site survey analysis.

• Offer simple installation and ease of use.

• Perform detailed protocol analysis.

Management Tools

Even if the project's budget can't swing a costly WNMS, the deployment team still needs to determine how to manage the access points. Although today's access points are highly reliable when supported with clean power, they still require maintenance. As previously mentioned, some AP vendors, like Proxim, design their systems with automated and/or remote management of APs in mind. Agere, Symbol and other vendors, however, provide management software to accomplish that goal.

There are also third-party tools that, while not as robust as the more costly WNMSs, can help centralized network management departments identify and solve problems before system failure. The attributes to look for when purchasing these solutions include:

• The ability to control everything from a central location-a network administrator should be able to configure and monitor infrastructure, change access point settings, and firmware upgrades from one terminal.

• System design flexibility-the management tool should support access point hardware from a variety of vendors.

• Easy upgrades-management tools that cannot change with the times are a poor investment.

• Easy integration with existing network infrastructure-it is always good when a product can integrate with a legacy system. The management tool must also be able to integrate seamlessly with other network management software that may already be in use for an existing wired network.

• The software-must be user friendly, easy to navigate, and provide intuitive help when needed.

• The ability to automatically implement changes over large groups of access points-this feature helps to eliminate the chance for human error and ensures uniform implementation of any necessary changes.

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