Subject: [NEXTEL-1] Brave new world of WLAN analyzers

From: [email-masked]
Date: Tue, 02 Sep 2003 04:34:10 -0400

Brave new world of WLAN analyzers
By Kevin Tolly
Network World, 09/01/03

As wireless LAN use has surged in corporations, it is no surprise that WLAN
analyzers have sprung up all around us. What is surprising, though, is how
radically different some of them can be from their wired brethren - and from each
other. One could argue that the term "wireless LAN analyzer" is being used today
to refer to products so fundamentally different that they shouldn't be compared at
all.

As is so often the case, it is not an issue of better or worse but just of
different products, with different heritages, designed for different jobs. Most
familiar will be the new wireless versions of well-known wireline LAN analyzers
such as those from Finisar and Sniffer Technologies. Thanks to the network
transport independence of the network driver interface specification used as the
basic, low-level network application interface with all recent Microsoft operating
systems, many wired Ethernet analyzers can become "wireless" with relative ease.

Because ultimately the WLAN delivers protocols and packets recognized by
upper-layer decode and monitoring engines of existing analyzers, there is a huge
amount of reusable code. In fact, most network analyzers were (correctly) built in
a layered fashion so that new network interfaces could be introduced without
causing redevelopment of the core analyzer functions.
Thus, one typically can find a wireless version of one's favorite wired LAN
analyzer and start picking up "the air" quite rapidly.
The formula: Standard analyzer plus wireless network interface card plus
additional 802.11 decodes equal a WLAN analyzer.
Other vendors, for example, an Agilent Technologies or an AirMagnet, take a
different approach. While the formula has similar elements, the "mix" is
different, and thus the resultant product is also different.

With them, the formula is deliberately skewed to understanding and unraveling the
characteristics, behavior and potential problems inherent to radio frequency
transmission and the IEEE 802.11b/a/g wireless protocols in particular. Around
this core, traditional LAN analyzer functions (such as decodes and statistics) are
built.

While the two product classes overlap in some areas, the latter, by design, offers
significantly more wireless-specific information. For starters, "expert analysis"
of WLAN events is of particular value. Few of us "mainstream" TCP/IP, Ethernet
data networking types have had the time (or inclination) to learn the arcane
details of the 802.11b protocol. Yes, it is "like" Ethernet but it is not
Ethernet.

So just getting decodes referencing "associations" and "beacon" frames doesn't
help most of us. We need to know what it means to be seeing said frames. Some of
the wireless-centric analyzers offer up this type of expert advice.
Perhaps it will be superfluous three years hence, but for now it is very valuable.

Monitoring performance thresholds and detecting trends related to weak signals,
transmissions errors or low-rate associations and alerting the network staff to
the presence of such conditions is a virtual necessity given the way that wireless
networks can change on a daily, if not hourly, basis.

These types of functions are those that you'd want from either flavor of WLAN
analyzer.
Add to this some WLAN analyzers that even claim intrusion-detection system
capabilities and one thing is clear: With WLANs we've entered a brave new world of
net analysis.

http://www.nwfusion.com/columnists/2003/0901tolly.html

WLAN analyzers

 http://www.nwfusion.com/reviews/2003/0414rev.html

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