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802.11T puts WLANs to the test
Written by Microsoft SQL Server Specialist   
Tuesday, 14 March 2006

Buyers of Wi-Fi equipment and systems must be assured that all products have the performance and stability to carry mission-critical applications and data. However, testing of Wi-Fi, or 802.11, devices and systems for performance and stability is a challenge for the industry because of the complexity of the 802.11 protocol. That is compounded by the inherent mobility of the wireless devices and the prevalence of radio frequency interference.

In July 2004, the IEEE formed the IEEE 802.11T Task Group to develop a test specification document, "Recommended Practice for the Evaluation of 802.11 Wireless Performance," expected to be completed in January 2008. By forming the task group, the IEEE has acknowledged the need to provide users with an objective means of evaluating functionality and performance of 802.11 products.

The 802.11T document defines test metrics in the context of use cases. The three principal-use cases are data, latency sensitive and streaming media.

Data

Data applications do not impose critical requirements on a network and include Web downloads, file transfers, file sharing, e-mail and others. Data-oriented traffic is typically transmitted using low priority. Performance test metrics important for data use include throughput vs. range, access-point capacity and access-point throughput per client.

Latency sensitive

Latency-sensitive applications are time-critical, such as VoIP over Wi-Fi. QoS requirements for these applications include limits on voice quality (latency, jitter and packet loss) vs. range, voice quality vs. network load, and voice quality vs. call load and Basic Service Set (BSS).

BSS is a single access-point network, similar to a single cell in the cellular environment. BSS transition is the process of a mobile station roaming from one access point to another.

Streaming media

Streaming-media applications include real-time audio/video streaming, stored content streaming and multicast high-definition television streaming. These applications require the most stringent QoS, including bandwidth and latency guarantees. Performance metrics include video quality (throughput, latency, jitter) vs. range and video quality vs. network load.

The metrics are classified as primary and secondary. Primary metrics directly affect the user experience, such as voice quality. Secondary metrics affect the primary metrics; for example latency, jitter and packet loss affect voice quality.

 

Last Updated ( Wednesday, 22 March 2006 )
 
Linux Management Tool
Written by Systems Integration Specialist   
Tuesday, 14 March 2006

Using sophisticated management tools make Linux management faster and more efficient.

So what tools are enterprises actually using? Not surprisingly, the most common tools came from the distro vendors, tools such as Novell SuSE's YaST (Yet another Setup Tool), YOU (YaST Online Update), and Yellowdog Updater Modified (YUM); Red Hat's RHN (Red Hat Network) and RPM (Red Hat Package Manager); and Debian's APT (Advanced Packaging Tool). All of these tools provide varying sophistication for monitoring, patch management, configuration management, recovery and provisioning. Smaller sites were especially dependent on these tools, and often found no need for anything more sophisticated.

A number of sites chose specialized tools from niche vendors (both open source and proprietary). These included Nagios or Groundwork Monitor for monitoring; Velocity Software's Esalps (for z/VM and Linux on z/Series) for performance management; Symantec/Veritas for backup; and Levanta Intrepid M or Opsware Server Automation System for provisioning and patch management. This best-of-breed approach allowed these companies to focus on their most important issues, and they often filled in the less critical gaps with their own scripts and in-house tools.

Several very large enterprises used tools from major framework vendors, such as IBM's Tivoli, HP's OpenView, and CA's Unicenter. These tools make it substantially easier to manage very large heterogeneous environments, without a dramatic expansion of skills, by allowing enterprises to manage Linux with the same skills and methodologies as Windows, Solaris, AIX, z/OS, and others.

Probably most surprising was that some sites were using Microsoft tools to manage Linux. Yes, you read that correctly - Microsoft tools can make Linux management easier. To its credit, Microsoft has made this easier through partnerships and programs like its Dynamic Systems Initiative - a commitment from Microsoft and its partners to deliver self-managing dynamic systems. Tools like Quest's Vintela suite and Centeris' Likewise can snap into native Microsoft management systems like System Management Server, Microsoft Operations Manager and the Microsoft Management Console, extending the familiar and functional Microsoft tools into other environments, including Linux. This allows enterprises to leverage their investment in native Windows tools to make them a very effective management platform for diverse networks.

The integration of Linux management into existing management tools is compelling because, despite the inroads that Linux is making, most enterprises will continue to have many non-Linux servers. As our research reported, no single operating system is the best or only choice for every implementation, application, or enterprise. Inevitably, there will continue to be mix of Linux, Windows, Unix, mainframe and even Mac. There will always be a place for highly functional best-of-breed solutions. However, being able to deploy a new operating environment, while re-using your existing management tools, will most likely reduce the cost of any new implementation.

Last Updated ( Wednesday, 22 March 2006 )
 

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