Public Wireless LANs
Many accessible venues, such as airports, coffee shops, hotels, and assemblage centers, action Wi-Fi
access to the Internet. This anatomy of arrangement is generally referred to as a accessible wireless LAN
(PWLAN). PWLANs acquiesce bodies who are abroad from their homes and offices to admission e-mail,
browse the Internet, and interface with accumulated applications. The abate accessible “hotspots” may
only accept a distinct admission point abutting anon to an ISP. Larger implementations usually have
numerous admission points, agnate to an action installation, and absorb user authentication
and announcement functions. In some cases, admission to the Internet is free. Other hotspots, abnormally those
offering civic roaming, allegation a fee for usage.
The accomplishing of a accessible wireless LAN is generally the best complex, as compared to other
networks, mainly because of the charge to adapt admission to the arrangement and to abutment a wide
variety of user interfaces. Figure H-6 illustrates the agreement of a PWLAN. Admission points
interconnect to an admission controller, which regulates admission to the Internet. A user, for
example, initially connects to an admission point and attempts to use their browser. The access
controller receives the browser’s URL appeal and, instead of abiding the requested page,
returns an HTML login page. The user enters their credentials, such as username and password,
and the ambassador again opens admission to the Internet for that user. If a user is not a subscriber, the
controller easily them off to a announcement arrangement to accumulated acquittal afore acceding admission to the
Internet.
Public Wireless LANs 841
Figure H-6 Typical Accessible Wireless LAN Configuration
When deploying PWLANs, accede the tips begin in Table H-4.
Table H-4 Accessible Wireless LAN Deployment Tips
Tip Justification Details
Offer an accessible user
interface
A PWLAN needs to serve a assorted population, and the connection
experience for users should be as accessible as application a adaptable phone. The
quandary is that PWLAN users do not use a frequently configured device.
As a result, adverse user accessory configurations are the base of most
problems, such as agitation abutting to the network. Be abiding the solution
interfaces with the widest accessible cardinal of users. This maximizes the
number of subscribers that the hotspot provider can attain. Best Wi-Fi
users today accept 802.11b applicant devices, but plan advanced for the larger
potential admeasurement of 802.11g and 802.11a and accede installing
access credibility that abutment 802.11b/g and 802.11a.
Implement user
authentication and billing
For authentication, arrange a ambassador that regulates admission to the
protected arrangement casework you are accouterment to users. Whether you should
purchase a abstracted admission ambassador or use a “smart” admission point that
provides hotspot casework depends on your specific requirements. If there
are lots of hotspots with alone a few users at anniversary one, again it makes sense
to use lower-end admission credibility in the accessories and a abstracted ambassador at a
central point to serve the assorted hotspots. If you accept abounding users at the
hotspot, again an admission point with congenital access-control appearance is
preferable because it localizes ascendancy and improves performance.
continues
Access Points
Switch
Access
Controller
Access Points
Internet
Billing
System
Tip Justification Details
Disable Layer 2 aegis It is not applied to apparatus Layer 2 aegis as allotment of a PWLAN,
because it is not achievable or alike accessible in best cases to manage
passwords and accommodate adequate levels of interoperability. As a result,
disable link-level encryption, such as WEP and WPA, and await on public
users to defended their own admission through the use of VPNs and
SSL-based websites and e-mail systems.
Broadcast SSIDs With PWLANs, you appetite abeyant users to acquisition the network. Thus, be
certain to accredit broadcasting of SSIDs from admission points. Also, accord the
SSID a apparent name that distinguishes your hotspot from others.
Include DHCP casework As users roam to altered hotspots, their applicant accessories charge an IP address
that corresponds to the bounded network. To accredit adrift with as few enduser
actions as necessary, authorize DHCP casework to automatically assign
IP addresses to visiting users. Best versions of Windows operating
systems by absence actuate DHCP, so users apparently will not accept to do
anything.
Focus on increasing
capacity
Many hotspots, such as those at airports and assemblage centers, accept lots
of users in almost baby areas. The accumulated throughput requirements
of these densely busy areas can be actual ambitious on individual
access points, abnormally those based on the almost low-bandwidth
802.11b. As a result, pay appropriate absorption to appropriately allocation the PWLAN.
To break this problem, accede agreement the admission credibility afterpiece together
and blurred their address power. This provides college accommodation in a given
area by segmenting users.
Enable broadcasting of
SSIDs
In PWLANs, you should ensure that beacons beatific by the admission point
broadcast the SSID of the network. This enables Microsoft Windows to
identify and affectation the wireless arrangement to the user. If the SSIDs are not
broadcasted, again the user will apprehend that the arrangement is present, and the
user will accept to manually configure the SSID in Windows.
Monitor for RF
interference
As with any wireless LAN, RF arrest can be an issue. So, pay
special absorption to the achievability of RF arrest back deploying
PWLANs. The best accepted arrest sources in a accessible ambience are
other wireless LANs, mainly because of abutting adjacency of unrelated
public hotspots and appointment barrio with wireless LANs.