Linux Unwired [Electronic resources] نسخه متنی

3.1 Hotspots

It would be pretty much impossible for any notebook user not to have
heard the term hotspot.
Wireless hotspots are popping up in many locations; coffee shops,
airports, hotels, conferences, restaurants, city parks, and libraries
are just a few places where you might find a hotspot.

You can easily build your own hotspot, and we cover this in detail in
Chapter 6. A
hotspot
requires at least one access point, a good antenna that covers the
needed area, a broadband Internet connection, and some form of access
control (if you want to restrict access).

Most hotspots are built around these four basic pieces. Some use DSL
as their broadband Internet connection, while many of the commercial
hotspots use a T1 line or other dedicated circuit. However, many
hotspots are simply in a house or apartment, particularly in dense
urban areas, and these connections are DSL, cable, or even simply
dial-up.

Before you leave for a trip, research online to find hotspots along
the way to your destination. To find both fee-based and free
hotspots,
consult the following web sites:

WiFinder

http://www.wifinder.com/search.php

HotSpotList

http://www.hotspotlist.com

T-Mobile Hotspots

http://www.t-mobile.com/hotspot

Wi-Fi Zone Finder

http://www.wi-fizone.org/zoneLocator.asp

JiWire

http://www.jiwire.com

3.1.1 Wireless Hotspot Providers

There are an
increasing
number of commercial hotspot providers, ranging from large companies,
such as T-Mobile and WayPort, to small operations in local coffee
shops, and wireless aggregators that allow you to access multiple
networks from different hotspot providers.

Nearly all of these providers restrict access to their
hotspots through a captive
portal. This form of access control intercepts
all TCP/IP traffic. To gain access through a captive portal, simply
open a web browser and attempt to navigate to any web page, such as
http://www.oreilly.com. Your
browser traffic is intercepted and redirected to the login screen of
the hotspot's portal software. Figure 3-1 shows a typical hotspot login screen.

Figure 3-1. Typical hotspot login to a captive portal

With commercial hotspot providers, you have a number of payment
choices for access. The large operators all offer monthly
subscriptions in addition to pay-as-you-go pricing. This is
convenient if you don't want to sign up with a
specific provider or if you don't travel enough to
justify the $20-40 per month that most monthly subscriptions cost.

If you travel frequently, you may want to sign up with one of the
wireless hotspot providers. Deciding which one to use is tricky. It
really depends on where you think you may spend the most time.
T-Mobile provides access in nearly all Starbucks coffee shops, as well as
Borders
bookstores, Kinko's copy centers,
and many airports. Surf and Sip has neatly taken up many of the
non-Starbucks coffee shops in major cities.
WayPort is a good
choice if you need hotel or airport access.

Associating with a
hotspot provider is easy. They all have
easy-to-identify SSIDs. You can also locate their hotspots ahead of
time using their web pages. Table 3-1 lists some
major hotspot providers, their SSIDs, and their web pages for locating
their hotspots.

3.1.2 Wireless Aggregators

With the rise in availability of commercial hotspot
providers comes a conundrum: which hotspot provider do you sign up
with? As you've seen, there are many providers, and
each of them has different coverage. If you're a
real road warrior, using several different hotspots could cost quite
a bit.

Wireless aggregators have come into the market to address this
problem. You sign up for an account with the aggregator, and through
its revenue-sharing agreements with different hotspot providers, you
are able to use many different hotspots while maintaining a single
account with one company.

That's the theory. In practice, roaming is still
very difficult, especially for non-Windows users.
Boingo (http://www.boingo.com), the largest
aggregator, requires the use of proprietary software on your
notebook, and as of this writing, that software is Windows-only.
There are reports of adventurous people running the Boingo software
using a Windows emulator like Wine, but we're not
going to attempt to cover that here. Unless the web-based captive
portal offers a roaming option, roaming with Boingo and Linux
isn't possible at this time.

Two other aggregators fall into the same category:
Trustive
(http://www.trustive.com/)
provides only a Windows client software package, and
iPass (http://www.ipass.com), while providing
clients for Windows, Windows CE/Pocket PC, Mac OS X, and Mac OS, does
not provide a Linux software client.

Fortunately, there is at least one roaming company that has gotten it
right: FatPort. FatPort's roaming customers
don't need any special software. Its locations and
partner locations all use captive portal software that requires only
a web browser.

Although FatPort is
based primarily in Canada, it has a wide range of partner agreements
with Surf and Sip, Boingo, and iPass. While not a complete coverage
of all roaming sites, this is an excellent option for the Linux user
who is constantly on the road. FatPort accounts range from hourly
rates to yearly subscriptions. Check out http://www.fatport.com for more details.

3.1.3 Open Hotspots

Just as the software world is split into proprietary and open source,
the hotspot world is populated with commercial hotspots (which
we've covered) and open
hotspots.
These open wireless networks span a
wide range of locations and philosophies:

Businesses providing free wireless access as an incentive to
customers. Hotels, coffee shops, restaurants, bookstores, and other
businesses are all using free wireless access as a way to bring in
customers and entice them to stay.

Public places serving up hotspots as a public service. Libraries,
city parks, town squares, city halls, and other publicly owned spaces
view free wireless access as a way of promoting their city, county,
or other locations, and attracting visitors.

Community wireless groups working with businesses, governments, and
private citizens placing hotspots in all sorts of locations,
including apartment buildings, parks, downtown areas, and any place
that would benefit from free wireless access. Many community groups
view this as a way to better their neighborhoods.

Open hotspots are a mixed bag. You may simply be associating with a
wireless router in someone's apartment, connected to
his DSL line. On the other hand, it may be a custom-built Linux-based
access point in a New York City park, installed by NYCWireless
(http://www.nycwireless.net),
with a T1 or DSL backhaul.

Access control is also going to vary. If you connect to
someone's home network with an SSID of
"default" or
"linksys," chances are you
won't find a captive portal or any other form of
access control in place. Many community and business that open
hotspots have some sort of access control in place, such as a web
page that asks you to agree to a Terms of Service (ToS) agreement
before you are allowed to use the network.

A good place to locate open hotspots is the
Personal Telco Project in Portland,
Oregon. Visit its Wireless Communities site at http://www.personaltelco.net/index.cgi/WirelessCommunities.
A second place to look for hotspots is WiFiMaps at http://www.wifimaps.com. This site, while
still in development, shows you hotspots all over the world.

3.1.4 Associating with Hotspots

To associate your Linux notebook with an open or commercial
hotspot, you have a couple of options. If
you know the SSID of the hotspot, simply set the SSID using
iwconfig:

$ iwconfig eth1 ESSID SurfandSip

Once you've done this, fire up your favorite web
browser, attempt to navigate to any web page, and you will be
redirected to the hotspot captive portal login, as shown in Figure 3-1.

If you've settled in a coffee shop that has an
unknown hotspot provider, the first thing you can try is:

$ iwconfig eth1 ESSID any

If there is a hotspot in range, your card should find and associate
with it. This can be tricky, especially if you're in
a densely populated urban area. For example, sitting in a coffee shop
in San Francisco, we were able to associate with four different
SSIDs. The signal strength from the coffee shop hotspot was not as
strong as a neighboring open hotspot located in
someone's apartment.

In these cases, you want to identify all of the access points in your
immediate area before you decide which one to associate with. There
are several methods of finding access points with Linux, and we cover
each one in turn.