Increased use of laptop computers and other wireless
access devices within an enterprise along with an increase in worker
mobility, have fuelled the demand for wireless networks in recent
years. Up until recently, wireless technology was plagued with
incompatibility issues and vendor-specific products. The technology was
slow, expensive, and reserved for mobile situations or hostile
environments where cabling was impractical or impossible. In recent
years, the maturing of industry standards has caused a leveling point.
This is thanks to industry-enforced compatibility standards and the
deployment of lightweight wireless networking hardware. All of these
factors have allowed wireless technology to come of age in the modern
networking hardware requires the use of technology that deals with
radio frequencies as well as data transmission. The most widely used
standard is 802.11 produced by the IEEE. This is a standard defining
all aspects of radio frequency wireless networking. There have been
several amendments to the 802.11 standard, the most recent being
networks use an AP to gain connectivity. In this type of network, the
AP acts like a hub, providing connectivity for the wireless computers.
It can connect the wireless LAN to a wired LAN, allowing wireless
computer access to LAN resources. This includes such resources as file
servers or existing internet connectivity. This type of wireless
network is said to run in infrastructure mode.
ad hoc or peer-to-peer wireless network is one in which a number of
computers each equipped with a wireless networking interface card, can
connect without the use of an AP. Each computer communicates with all
of the other wireless-enabled computers directly. This allows for the
sharing of files and printer services, but may not be able to access
wired LAN resources. The exception to this is if one of the computers
acts as a bridge or AP to the wired LAN using special software.
you might be familiar with in Windows Server 2003, Wireless Auto
Configuration will attempt to pair up configured preferred wireless
networks with the wireless networks that are broadcasting their network
name. If no such available networks exist that match a preferred
wireless network, Wireless Auto Configuration will then send a number
of probe requests to attempt to find a match. These are to try and
determine if the preferred networks in the ordered list are
non-broadcast networks. The end result of this total process should be
that broadcast networks are connected to before non-broadcast networks.
This even includes situations where a non-broadcast network is higher
in the preferred list than a broadcast network. A big downside of this
method, however, is that a Windows XP or Windows Server 2003 wireless
client has to advertise its list of preferred wireless networks when
sending probe requests. This leaves clients vulnerable while sending
these probe requests.
Server 2008 presents a better option. By configuring the wireless
networks as broadcast, the wireless network names will be included in
the Beacon frames sent by the wireless AP. If you set the wireless
network as non-broadcast, the Beacon frame contains a wireless network
name. This name is set to NULL, which results in Wireless Auto
Configuration attempting connection to the wireless networks in the
preferred network list order. This is regardless of whether they are
broadcast or non-broadcast. By explicitly marking wireless networks as
broadcast or non-broadcast, Windows Server 2008 wireless clients only
send probe requests for non-broadcast wireless networks. This reduces
wireless client side vulnerability and enhances security.
if a preferred wireless network could not be connected to and the
wireless client was configured in a way that prevented automatic
connections not in the preferred list by default, then Wireless Auto
Configuration would create a random wireless network name. Then it
would place the wireless network adapter in infrastructure mode. The
random wireless network does not have a security configuration, making
it possible for all kinds of malicious users to connect to the wireless
client, thereby using the random wireless network name.
computers running Windows Server 2008 that use updated wireless drivers
designed for Windows Vista, Wireless Auto Configuration will remove
this vulnerability by parking the wireless network adapter in a passive
listening mode. A parked wireless device
does not send probe request frames for a random wireless network name.
It also does not allow for any other names, so malicious users cannot
connect to the wireless client.
you are using a wireless network adapter driver that was designed for
Windows XP, computers running Windows Vista or Windows Server 2008 will
use the behavior of the Wireless Client Update for Windows XP with
Service Pack 2 (a random wireless network name with a security
Windows Server 2008 troubleshooting wireless connections is made much easier through the following features:
Network Diagnostics Framework
The Network Diagnostics Framework is an extensible architecture that
provides users with a means to recover from and troubleshoot problems
with network connections. In the case of a failed wireless connection,
Network Diagnostics Framework will give the user the option to identify
and correct the problem. Wireless support for the Network Diagnostics
Framework tries to discover the source of the failed connection and
will automatically fix the problem. Also based on your security
considerations, it can be made to prompt the user to make the
appropriate configuration change themselves.
a failed wireless connection attempt, the wireless components of
Windows Server 2008 now records detailed information about the
connection attempt in the Windows event log. Support professionals can
now access and use these records to perform troubleshooting tasks, and
attempt to resolve the problem quickly if the wireless diagnostics
either could not resolve the problem or when it could resolve the
problem, but the problem cannot be fixed by changing wireless client
settings. This will cut down on the time needed to resolve wireless
connection support problems. These can also be automatically collected
by network administrators using Microsoft Operations Manager, to be
analyzed for patterns and wireless infrastructure design changes.
can now gain access to in-depth information about the computer’s state
and wireless components in Windows, and their interaction when the
problem occurred. This can be done using information from wireless diagnostics tracing
in Windows Server 2008. To use wireless diagnostics tracing, you must
start tracing, reproduce the problem, stop tracing, and then collect
the tracing report. To view the tracing report, in the console tree of
the Reliability and Performance Monitor snap-in open Reports | System | Wireless Diagnostics.
Server 2003 and Windows XP do not have a command-line interface that
allows you to configure the wireless settings that are available from
the wireless dialog boxes in the Network Connections folder, or through
the Wireless Network (IEEE 802.11) Policies Group Policy settings.
Command-line configuration of wireless settings can help deployment of
wireless networks in the following situations:
script support for wireless settings without using Group Policy
Wireless Network (IEEE 802.11) Policies Group Policy settings only
apply in an Active Directory domain.
For an environment without Active Directory or a Group Policy
infrastructure, a script that automates the configuration of wireless
connections can be run either manually or automatically, such as part
of the login script.
Bootstrapping of a wireless client onto the protected organization’s wireless network.
A wireless client computer that is not a member of the domain cannot
connect to the organization’s protected wireless network. Furthermore,
computers are not able to join the domain until a successful connection
has occurred to the organization’s secure wireless network. A
command-line script provides a method to connect to the organization’s
secure wireless network to join the domain.
In Windows Server 2008, you can use Netsh commands in the netsh wlan context to do the following:
all wireless client settings in a named profile including general
settings (the types of wireless networks to access), 802.11 settings
(SSID, type of authentication, type of data encryption), and 802.1X
authentication settings (EAP types and their configuration).
Specify the list of allowed and denied wireless network names.
Specify the order of preferred wireless networks.
Display a wireless client’s configuration.
Remove the wireless configuration from a wireless client.
Migrate a wireless configuration setting between wireless clients.
applications are not network aware, resulting in customer confusion and
developer overhead. For example, an application cannot automatically
adjust its behavior based on the currently attached network and
conditions. Users might have to reconfigure application settings
depending on the network to which they are attached (their employer’s
private network, the user’s home network, the Internet). To
remove the configuration burden, application developers can use
low-level Windows APIs, data constructs, and perhaps even probing the
network themselves to determine the current network and adjust their
application’s behavior accordingly.
provide an operating system infrastructure to allow application
developers to more easily reconfigure application behavior based on the
currently attached network, the Network Awareness APIs in Windows
Server 2008 make network information available to applications and
enables them to easily and effectively adapt to these changing
environments. The Network Awareness APIs allow applications to obtain
up-to-date network information and location change notification.
take a look at how to deal with the variety of elements available with
Windows Server 2008 in regards to wireless network access and how they
will be applied to your exam.
Set Service Identifier (SSID)
Service Set Identifier (SSID) is a 32-character unique identifier
attached to the header of packets that are sent over a Wireless Local
Area Network (WLAN). The SSID acts as a password when a mobile device
tries to connect to the BSS. The SSID differentiates one WLAN from
another. This way all APs and all devices attempting to connect to a
specific WLAN must use the same SSID in order to succeed. No device
will be permitted to join the BSS unless it can provide the unique
SSID. SSID is not a security measure, because it can very easily be
sniffed due to being stored in plain text.
Windows Server 2008, an additional wireless network configuration
setting has been added that can indicate whether a wireless network is
broadcast or non-broadcast. This setting can be configured locally
through the “Manually connect to a wireless network” dialog box, the
properties of the wireless network, or through Group Policy. The
“Connect even if the network is not broadcasting” check box determines
whether the wireless network broadcasts or does not broadcast its SSID.
Once selected, Wireless Auto Configuration sends probe requests to
discover if the non-broadcast network is in range.
wireless networks are now openly marked as broadcast or non-broadcast.
Windows Server 2008-based wireless clients only send probe requests for
wireless networks that are configured for automatic connection and as
method allows Windows Server 2008-based wireless clients to detect
non-broadcast networks when they are in range. Therefore, even though
they are not broadcasting the name of their wireless network, they will
appear in the list of available wireless networks when they are in
range. The wireless client detects whether
the automatically connected, non-broadcast networks are in range based
on the probe request responses. Then Wireless Auto Configuration
attempts to connect to the wireless network in the preferred networks
list order. This is regardless of whether they are configured as
broadcast or non-broadcast. By only sending probe requests for
automatically connected, non-broadcast networks, Windows Server
2008-based wireless clients reduce the number of situations in which
they disclose their wireless network configuration.
can also configure manually connected, non-broadcast wireless networks.
In doing so, you can control exactly when to send probe requests.
Manually connected, non-broadcast wireless networks are always
displayed in the list of available networks, allowing users to initiate
connections as needed.
the improvements in non-broadcast network support in Windows Server
2008, Microsoft recommends against using non-broadcast wireless
Wi-Fi Protected Access (WPA)
Protected Access (WPA) was designed to provide a much higher level of
security for wireless users than existing WEP standards provide. The
WPA specification makes allowances both for network-based
authentication for corporate networks, and for a special home mode for
use in a SOHO or home-user environment. WPA is capable of
interoperating with WEP devices, although in cases of interoperability,
the default security for the entire wireless infrastructure reverts to
the WEP standard. WPA’s network-based authentication can make use of
existing authentication technologies such as RADIUS servers, so adding
the secure technology that WPA represents won’t disrupt existing
network infrastructures too much. Windows Server 2008 offers full
support and configuration for WPA through the Wireless Group Policy
to know your hardware. The installed wireless network adapter must be
able to support the wireless LAN or wireless security standards that
you require. For example, Windows Server supports configuration options
for the Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access 2
(WPA2) security standards. However, if the wireless network adapter
does not support WPA2, you cannot enable or configure WPA2 security
Wi-Fi Protected Access 2 (WPA2)
Server 2008 includes built-in support to configure WPA2 authentication
options with both the standard profile (locally configured preferred
wireless networks), and the domain profile with Group Policy settings.
WPA2 is a product certification available through the Wi-Fi Alliance
that certifies wireless equipment as being compatible with the IEEE
802.11i standard. WPA2 in Windows Server 2008 supports both
WPA2-Enterprise (IEEE 802.1X authentication) and WPA2-Personal
(pre-shared key authentication) modes of operation.
Windows Server 2008 also includes full support for WPA2 for an ad hoc mode wireless network including the Fast Roaming
settings. Fast roaming is an advanced capability of WPA2 wireless
networks that allow wireless clients to more quickly roam from one
wireless AP to another by using pre-authentication and pair wise master
key (PMK) caching in infrastructure mode. With Windows Server 2008, you
can configure this feature using the Wireless Group Policy settings.
Ad Hoc vs. Infrastructure Mode
set up an ad hoc wireless network, each wireless adapter must be
configured for ad hoc mode versus the alternative infrastructure mode.
In addition, all wireless adapters on the ad hoc network must use the
same SSID and the same channel number.
An ad hoc network tends to feature a small group of devices all in very close proximity to each other.
suffers as the number of devices grows, and a large ad hoc network
quickly becomes difficult to manage. Ad hoc networks cannot bridge to
wired LANs or to the Internet without installing a special-purpose
networks make sense when needing to build a small, all-wireless LAN
quickly and spend the minimum amount of money on equipment. Ad hoc
networks also work well as a temporary fallback mechanism if normally
available infrastructure mode gear (APs or routers) stop functioning.
installed wireless LANs today utilize infrastructure mode that requires
the use of one or more APs. With this configuration, the AP provides an
interface to a distribution system (e.g., Ethernet), which enables
wireless users to utilize corporate servers and Internet applications.
an optional feature, however, the 802.11 standard specifies ad-hoc
mode, which allows the radio network interface card (NIC) to operate in
what the standard refers to as an independent basic service set (IBSS)
network configuration. With an IBSS, APs are not required. User devices
communicate directly with each other in a peer-to-peer manner.
hoc mode allows users to form a wireless LAN with no assistance or
preparation. This allows clients to share documents such as
presentation charts and spreadsheets by switching their NICs to ad hoc
mode to form a small wireless LAN within their meeting room. Through ad
hoc mode, you can easily transfer the file from one laptop to another.
With any of these applications, there’s no need to install an AP and
ad hoc form of communications is especially useful in public-safety and
search-and-rescue applications. Medical teams require fast, effective
communications when attempting to find victims. They can’t afford the
time to run cabling and install networking hardware.
Before making the decision to use ad hoc mode, you should consider the following:
Cost Efficiency Without the need to purchase or install an AP, you’ll save a considerable amount of money when deploying ad hoc wireless LANs.
Rapid Setup Time
Ad hoc mode only requires the installation of radio NICs in the user
devices. As a result, the time to set up the wireless LAN is much less
than installing an infrastructure wireless LAN.
Better Performance Possible
The question of performance with ad hoc mode is very debatable.
Performance can be higher with ad hoc mode because there is no need for
packets to travel through an AP. This only applies to a small number of
users, however. If you have many users, then you will have better
performance by using multiple APs to separate users onto
non-overlapping channels. This will help to reduce medium access
contention and collisions. Also, because of a need for sleeping
stations to wake up during each beacon interval, performance can be
lower with ad hoc mode due to additional packet transmissions if you
implement power management.
Limited Network Access
There is no distribution system with ad hoc wireless LANs. Because of
this, users have limited effective access to the Internet and other
wired network services. Ad hoc is not a good solution for larger
enterprise wireless LANs where there’s a strong need to access
applications and servers on a wired network.
Difficult Network Management
Network management can become a nightmare with ad hoc networks, because
of the fluidity of the network topology and lack of centralized
devices. The lack of an AP makes it difficult for network managers to
monitor performance, perform security audits, and manage their network.
Effective network management with ad
hoc wireless LANs requires network management at the user device level.
This requires a significant amount of overhead packet transmission over
the wireless LAN. This again disqualifies ad hoc mode away from larger,
enterprise wireless LAN applications.
mode requires a wireless AP for wireless networking. To join the WLAN,
the AP and all wireless clients must be configured to use the same
SSID. The AP is then cabled to the wired network to allow wireless
clients access to, for example, Internet connections or printers.
Additional APs can be added to the WLAN to increase the reach of the
infrastructure and support any number of wireless clients.
to the alternative, ad hoc wireless networks, infrastructure mode
networks offer the advantage of scalability, centralized security
management, and improved reach.
The disadvantage of infrastructure wireless networks is simply the additional cost to purchase AP hardware.
Wireless Group Policy
technology makes it easier for mobile workers to connect to hotspots or
corporate LANS, by eliminating the need for manual configuration of the
network connection. Enterprises can better manage guest access on their
network and provide payment plans such as pay-per-use or monthly
Internet access to customers, but in order to do so a strict wireless
group, policy must be maintained to better control access.
network settings can be configured locally by users on client
computers, or centrally. To enhance the deployment and administration
of wireless networks, you need to take advantage of Group Policy. In
doing so, you can create, modify, and assign wireless network policies
for Active Directory clients and members of the wireless network. When
you use Group Policy to define wireless network policies, you can
configure wireless network connection settings, enable IEEE 802.1X
authentication for wireless network connections, and specify the
preferred wireless networks that clients can connect to. By default,
there are no Wireless Network (IEEE 802.11) policies.
To create a new policy:
Right-click Wireless Network (IEEE 802.11) Policies in the console tree of the Group Policy snap-in.
Click Create Wireless Network Policy.
Create Wireless Network Policy Wizard is started, from which you can
configure a name and description for the new wireless network policy.
You can create only a single wireless network policy for each Group
To modify the settings of a Wireless Network Policy, double-click its name in the details pane.
Locate the General tab for the Wireless Network Policy you wish to update.
Click on the General tab and configure the following:
- Name Specifies a friendly name for the wireless network policy.
- Description Provides a description for the wireless network policy.
- Check for Policy Changes Every...
Specifies a time period in minutes, after which wireless clients that
are domain members will check for changes in the wireless network
- Networks to Access Specifies the types of wireless networks with which the wireless client is allowed to create connections to. Select either Any available network (AP preferred), Access point (infrastructure) networks only, or Computer-to-computer (ad hoc) networks only.
Select the Windows to configure wireless network settings for clients check box if you wish to enable the Wireless Auto Configuration.
Click the Automatically connect to non-preferred networks check box if you wish to allow automatic connections to wireless networks that are not configured as preferred networks.
Click the Preferred tab of the Wireless Network Policy pane to configure these options:
- Networks Displays the list of preferred wireless networks.
- Add/Edit/Remove Creates, deletes, or modifies the settings of a preferred wireless network.
- Move Up/Move Down Moves preferred wireless network up or down in the Networks list.
Click on a Preferred Wireless Network to open up advanced configuration options.