802.11 wi-fi handbook, Chapter 9 Wireless Lans in the network(1).pdf

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CHAPTER 9
Wireless LANs
in the Enterprise
175
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802.11 (Wi-Fi) Networking Handbook
A
s discussed in Chapter 1, early forms of wireless LANs have been available
since the mid-1980s. Standardized and interoperable WLANs have been
shipping since 1997, and Wi-Fi products have been available since 1999. Despite
this and the more than $1 billion spent worldwide annually on 802.11 products at this
writing, WLAN deployments in the enterprise are still in their earliest days. Today, to
the extent that WLANs are found in the enterprise, they tend to be limited deployments
in places like conference rooms, cafeterias, and, naturally, the senior executive floors.
Indeed, WLAN proliferation into vertical markets like retail, manufacturing, and
warehousing greatly exceeds enterprise adoption. As evidenced by the sheer number
of low-cost, easy-to-install Wi-Fi products available at computer retailers and catalogers,
proliferation of wireless into residences and small offices is growing rapidly—in fact,
far more quickly than into enterprises. Today’s enterprise deployments are almost
experimental in nature, as enterprise IS (information services) professionals, managers,
and staff gain familiarity with WLANs and come to understand how they can best
integrate Wi-Fi into an overall enterprise information infrastructure.
In this chapter, we define enterprise WLAN deployments, making, at the functional
level, a distinction between enterprise deployments and small office/home office
(SOHO) deployments. We discuss the approach an enterprise typically takes when
deploying a WLAN. We also outline the steps enterprise IS professionals should take
to maximize the likelihood of a successful initial deployment, including a physical
assessment of the facilities in which wireless is to be deployed (the site survey) and the
capacity planning needed to provide the enterprise-level performance demanded by
users. Given that in the enterprise an existing wired LAN already exists, we discuss
how IS professionals best can integrate Wi-Fi into this overall infrastructure, where
wireless adds a vital mobility element to a network and where it might be a replacement
or alternative to more traditional wires. We also discuss how you can best leverage
existing network management tools and practices from the wired world to most
expediently bring a similar level of management to the WLAN.
A theme throughout this chapter is that 802.11 equipment should be considered a
highly integrated network element, rather than simply tacked onto a LAN, whether the
network is in the home office or resides within a large enterprise.
WHAT IS THE ENTERPRISE?
First and foremost, the
Enterprise
is, of course, a series of starships, all captained by
dashing leaders and crewed by a pan-galactic collection of Federation officers. Having
said that, a definition of the enterprise as it relates to WLAN deployments is probably
more germane to this book. Like the
Enterprise,
many enterprises are large, consisting
of, at minimum, hundreds of individuals, all of whom are users of the organization’s
information infrastructure in some fashion. While many of these users may be located
in a single headquarters building or campus, the enterprise is typically geographically
distributed, with users scattered across a region, a continent, or even around the world.
Chapter 9:
Wireless LANs in the Enterprise
177
The fact that a user may be working out of a spare bedroom thousands of miles from
the enterprise headquarters makes that user no less an enterprise user—indeed, it is
these sorts of users who often most challenge IS professionals.
NOTE
The average 802.11 sale to enterprises consists of three to five access points, because most
enterprises worldwide are small businesses rather than the more widely publicized large corporations.
Certainly, large commercial entities around the world are considered to be enterprise-
level organizations. The more expansive definition is one that includes any large
organization with a common purpose where individuals are engaged in specific,
complementary tasks—including managing the enterprise information infrastructure.
By this definition, larger governmental entities on the city, county, state, and provincial
level as well as on the national level are “enterprises.” Similarly, school systems, whether
public or private, are enterprise organizations.
Stated another way, an enterprise is any organization that reaches the size at which
it requires a dedicated staff of one or more IS professionals. The charter of this staff, no
matter how small, is to make certain that the information infrastructure meets the needs
of the organization and enables it to meet its goals—ideally, better than competitive
organizations. And to remain
competitive,
leveraging new technologies to its advantage
is a requirement for any organization, whether in the private or public sector. Wireless
LANs are an excellent example—perhaps the best example available today—of an
information technology that can have dramatic impact on the efficiency and effectiveness
of an organization. Not surprisingly, IS professionals around the world are increasingly
being charged with installing Wi-Fi, often on a trial basis with small pilot programs but
with a mind toward a ubiquitous enterprise-wide deployment.
A SOHO Wi-Fi deployment presents few of the challenges associated with an
enterprise deployment. As discussed in Chapters 5 and 6, the range of Wi-Fi devices,
varying from a low of 60 feet to over hundreds of feet, is more than sufficient to cover
even the largest of homes and small offices—even at the highest possible data rates.
Indeed, if a home is so large as to require more than a single access point to achieve full
physical coverage, it’s likely that the owner has the wherewithal to hire an IS professional
to manage the installation. The number of users in a SOHO environment tends to be
fairly limited. While it’s true that users of a SOHO LAN use the LAN to access other
local computers, it is far more typical for users on a smaller LAN to access data from
across the WAN, which can be cable, DSL, or even dial-up. This sets their performance
expectations at fairly modest levels.
The enterprise is, of course, a completely different story. Typical corporate,
governmental, and educational facilities, by their multistory nature alone, require
more than a single access point to cover the entire building. In campus settings, the
requirement can even be extended to include not just complete and reliable in-building
coverage, but also WLAN availability between buildings. This opens up a whole host
of challenges not found in SOHO deployments including
roaming
and
channel reuse
that
will be discussed further in this chapter.
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802.11 (Wi-Fi) Networking Handbook
In larger enterprises, users have come to expect a level of network performance that
is consistent with a wired network, one that is often switched, providing dedicated
bandwidth that is typically rated at 100Mbps—and occasionally faster. Given this level
of expectation, the IS professional’s challenge is to provide the freedom and flexibility of
wireless with performance and security that approximates that of the wired network.
In short, an enterprise is a relatively large organization with a common goal. The
organization is typically in some form of competition with organizations with similar
goals and, as such, employs information technology (among other tools) to gain
competitive advantage. As such, the deployment of Wi-Fi in an enterprise presents
challenges not found in other sorts of deployments and substantial consequences when
things don’t go quite as planned.
WI-FI DEPLOYMENT IN THE ENTERPRISE
Like any large project, the first step is to set goals and then formulate a plan to meet
those goals. Although the specific goals of an enterprise’s Wi-Fi deployment will vary,
there is a constant: to deploy a Wi-Fi network in designated areas that provides reliable
coverage and delivers the expected level of performance without compromising corporate
security. Although this sounds simple, as the saying goes, “The devil is in the details.”
Designating Areas
Rare are the cases in which a large enterprise chooses to deploy a Wi-Fi network across
the whole organization in one fell swoop from initial deployment. There are a few
reasons for this. Obviously, finding the budget for what can be a significant financial
undertaking can be quite difficult. Responsible financial planners tend to take more
of a “show me” approach, requesting first that a pilot program be run to assess the
expense and resource drains of the project, the veracity of the budget estimates, and
the return on investment.
Additionally, IS professionals recognize that Wi-Fi has a learning curve (as is typical
with any new technology), and running a limited deployment provides valuable
on-the-job training. Finally, as was discussed in Chapter 6, Wi-Fi is a technology
undergoing rapid change, and organizations have concerns, unfounded or not, that
the product they deploy will lock them into a soon-to-be-obsolete technology.
The great majority of enterprises instead initially opt for a limited WLAN deployment.
There are different criteria by which these deployments can be limited, as described in
the following sections.
Limiting Deployment to Only Where It’s Needed Most
This strategy is based on the assumption that when laptop users are in their base area,
such as an office, cubicle, or desk, they access the network via a wired connection,
either by plugging directly into an Ethernet jack or through a docking station. Therefore,
the Wi-Fi deployment is limited to places people tend to congregate
away from their
Chapter 9:
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179
desks,
in areas like conference rooms and smaller meeting rooms, cafeterias, classrooms,
auditoriums, lobbies, and other similar public areas. For many enterprise organizations,
this strategy meets the “80-20 rule”—it deploys WLANs in the 20 percent of places
where 80 percent of it will be demanded.
What this strategy doesn’t take into account is the fact that people are unpredictable
and the places where they meet to collaborate are not always where the building’s
architect envisioned. Information is exchanged (and required from the network) in
a variety of places: leaning up against a coworker’s cubicle, in the smoking “lounge”
outside, in the hallway. . .wherever.
This unpredictability continues to increase as enterprises more commonly issue
laptops (as opposed to desktop computers) and as more than data is being transferred.
Also, the growing popularity of personal digital assistants (PDAs) and devices such as
bar code scanners and 802.11 handheld phones, and the associated demand for them
to be just as connected as a laptop, drives demand for a more ubiquitous wireless
infrastructure, because people use PDAs and similar devices in more places than they
would a full laptop.
Similarly, as organizations begin to use the Wi-Fi infrastructure to provide local
voice support, the user expectation is that coverage will be as complete as for their
cellular telephone—only more reliable. For other organizations, deploying Wi-Fi
“only” in the classrooms and auditoriums is tantamount to a full deployment. If a
limited deployment in kindergarten through twelfth-grade schools, colleges, and
universities is desired, another means of limiting the deployment is necessary—leading
us to the next strategy.
Limiting Deployment to One Building at a Time
In campus environments, particularly those campuses where different buildings or
groups of buildings have differing charters, it’s common for Wi-Fi to be rolled out on
a building-by-building basis. This is a very typical model in a university where, for
example, the business school deploys WLANs in its building and then supplies Wi-Fi
client adapters to (or mandates their purchase by) all students who use that facility.
Often, the financial structure of a university plays a role in the choice of this strategy.
Using the business school example again, the business school may have the budget
autonomy to fund an initiative to deploy Wi-Fi without the involvement of the university’s
central organization, and may be able to rely on outside sources of funds such as alumni
associations and local business partnerships.
Sometimes, a single-building deployment is accomplished even without the
involvement of the central IS organization, although this is more common, not
surprisingly, in an engineering school than in a business school. The central drawback
to this approach is that all but a few students and even some faculty spend their academic
days in more than a single building or group of buildings. This is all the more true of
new matriculates—the very ones who are receiving the first client adapters.
Experience has shown that once WLANs are deployed in a single building, the
expectation is set that it should be similarly deployed across campus, in classrooms,

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