Docstoc

Wireless Networking

Document Sample
Wireless Networking Powered By Docstoc
					                                      George Niflis


Wireless Networking
What is wireless networking?

Technically, wireless networking refers to any data exchange between PCs and other
devices which doesn't involve cables. Connecting to a wireless hotspot in a cafe, sending
data from your PC to a handheld computer using an infrared link, or synching data
between your mobile phone and notebook via Bluetooth are all examples of wireless
networking.
In practice, however, wireless networking allows computers and peripherals to
communicate using radio frequency (RF) transmissions rather than over conventional
network cabling. Using wireless Ethernet adaptors, any device capable of being used on a
regular computer network can be accessed over a wireless connection for tasks ranging
from file and printer sharing to multimedia and Internet access.
Wireless Ethernet technology is generally outlined by a set of standards called IEEE
802.11, although other wireless technologies and protocols such as HomeRF and
Bluetooth also exist. A wireless network of this kind can offer you all the facilities of a
conventional PC network, such as Internet access and the ability to share files and
peripherals such as printers. It uses the same Ethernet standards for transmitting data, but
doesn't require every machine be connected by cable to a network hub. In the previous
examples, connecting in a cafe makes use of Wi-Fi wireless networks, while the others
don't.
This guide will focus on wireless networking at home or in a small business, using
equipment based on the 802.11 standard.

What is Wi-Fi?
Wi-Fi is a certification program established by the Wi-Fi Alliance
(www.wirelessethernet.org) to ensure the interoperability of wireless devices. Originally,
the term Wi-Fi was intended to be interchangeable with 802.11b, but more recently it has
broadened to cover any 802.11 network. Bear in mind that while all Wi-Fi devices
conform to the IEEE 802.11 standard, the reverse is not always true.




                                             16
                                       George Niflis



                                      Types of Wi-Fi
               Network    Maximum                              Wireless
               Protocol   Speed       Average Speed
                                                               Range
                                                               12m indoors,
               802.11a    54Mbps      27Mbps                   30m line-of-
                                                               sight outdoors
                                                               30m indoors,
               802.11b    11Mbps      4.5Mbps                  120m line-of-
                                                               sight outdoors
                                      7Mbps (in
                                                               30m indoors,
                                      compatibility mode),
               802.11g    54Mbps                               120m line-of-
                                      16Mbps (with other
                                                               sight outdoors
                                      802.11g devices)
               NB: Some manufacturers have developed proprietary
               technology that can double the data rate of wireless devices.
               These are not IEEE 802.11 compliant and will only work at
               these speeds with other compatible proprietary devices.


Wireless standards
The communication protocols for wireless networking are defined by the Institute of
Electrical and Electronics Engineers (IEEE) 802.11 standard, which incorporates the
802.11a, 802.11b and 802.11g protocols (although several other standards are in
progress). The most widely used of these is 802.11b (Wireless-B), which is more reliable
than the faster 802.11a (Wireless-A) standard. It is more cost-effective to produce and
operate as well. Wireless-G, or 802.11g, is a newer protocol that is becoming more
widely adopted by vendors as it is capable of speeds up to 54Mbps rather than the
11Mbps of 802.11b devices.
It is very rare to find devices that support all three standards, but Wireless-G is designed
to be backwards compatible with Wireless-B devices. Thus Wireless-B and Wireless-A
devices will not work with each other, and neither are they compatible with Wireless-G
devices.
It is worth noting that although the maximum speed provided by the IEEE standards is
54Mbps, some vendors (notably D-Link) have introduced proprietary protocols that
effectively double the 802.11b rate to 22Mbps and the 802.11g rate to 108Mbps. Once
again this is a theoretical throughput, with actual data rates being considerably lower. It is
also worth bearing in mind that all wireless network devices must support the proprietary
standard in order to function at these higher speeds.




                                             17
                                      George Niflis

How does wireless work?
Wireless technology utilizes the license-free radio frequency bands around the 2.4GHz
and/or 5GHz ranges. The 802.11b and 802.11g protocols use the 2.4GHz band whereas
802.11a uses the 5GHz band. The benefit of this frequency band is that it is longer-range,
although it can be susceptible to interference from other RF devices such as cordless
phones.
The 5GHz band used by 802.11a provides more bandwidth and less interference, but it
requires more expensive hardware, larger silicon chips and higher power consumption.
As a consequence, Wireless-B is by far the most popular standard, with the newer
Wireless-G closing in fast.




What is a WLAN?

A WLAN, or wireless local area network, is a computer network - or part thereof - that
incorporates wireless devices. A conventional LAN (local area network) - as used in a
home or small office network - incorporates two or more PCs connected to an Ethernet
hub using network cables. This conventional LAN setup can be extended to include
wireless devices using an access point. Although wireless networks can be completely
independent of conventional networks, a WLAN usually forms part of an existing wired
network.

What is an access point?
An access point is required to connect PCs with wireless cards to an existing LAN. An
access point is like a transceiver (transmitter-receiver) that translates between wireless
network traffic and wired network traffic, acting as a gateway between the two.



                                             18
                                         George Niflis

An access point resides on a LAN the same way a PC does -- via a network cable. It is
assigned its own IP address, and can be connected to by other PCs on the LAN. While the
IP address can be set manually, it is common to have one assigned automatically by a
DHCP server. This task is usually performed by a router where ADSL Internet
connection sharing is in place, or a domain server in more conventional IT networks.
As well as being located on the LAN, an access point is also the centre of a wireless
network. Wireless devices in the vicinity can connect to the access point via radio waves
and these transmissions are converted by the access point into IP traffic on the network.
Some access points are also capable of communicating with other access points using a
protocol called Ethernet over AP. These can be used to extend the range of a WLAN. In
recent years it is more common to find access points that have integrated routers and,
sometimes, broadband modems. An access point with a built-in router can be used as the
central hub of a LAN with WLAN capabilities. The router component allows the device
to connect to remote networks such as the Internet for maximum connectivity.

What is the range of wireless?
Although wireless transmission ranges vary greatly and lowering the bandwidth will increase the
coverage area, a standard 802.11b or 802.11g device will typically have a range of about 30m
indoors and up to 120m line-of-sight outdoors. Devices using the higher frequency 802.11a
protocol will have a range of about 12m indoors and 30m line-of-sight outdoors.

The main reason for the variance between indoors and line-of-sight coverage is that walls and
other objects do impede the wireless signal. Because wireless transmissions are actually low
frequency radio waves, they will pass through walls and other solid matter relatively easily. Bear
in mind, though, that as the distance increases, the throughput decreases. This is because lower
signal strength will result in dropped packets and result in a general decrease in network
efficiency.


Why does my business need wireless?

There are two main benefits to wireless networking: portability and flexibility. If you use
a notebook with a wireless connection, then you can access your network from anywhere
in your office. If you travel regularly, you'll be able to access the Internet wherever
there's a wireless hotspot (this includes many cafes, convention centres, airport lounges
and other locations). If your company network is set up to allow virtual private network
(VPN) connections, you'll be able to access it from any Internet-connected hotspot
(though this requires some configuration). Being able to easily relocate desktop PCs is a
strong reason to go wireless. If, for instance, your company premises expands, a wireless
network will allow you to move your PCs without the time and expense of having new
network cabling installed.




                                                19
                                       George Niflis



What else can I do with wireless?
There are also some multimedia devices that support wireless networking, including
digital cameras and hardware media players. These can be used to transfer video and
audio files to and from a network for purposes ranging from security and surveillance to
multi-room entertainment.

Are there any disadvantages to wireless networking?
While there are many benefits to wireless networking, there are also some disadvantages.
These fall into three categories: speed, cost and security.
Speeds for wireless networking depend on which standards you use, but are usually lower
and more variable than speeds on conventional network connections. Modern networking
gear allows speeds of up to 100Mbs, and even older networks will achieve 10Mbs. With
the exception of new systems, most wireless networks will be lucky to achieve even
10Mbs; their performance often varies according to the layout of the office.
For most businesses, 10Mbs is more than adequate. If, however, you often need to send
large files -- common in the graphic arts and architectural industries -- then a wired
connection may be more practical.
Cost is another reason why wireless may not suit your needs. While prices have dived
noticeably over the past two years, wireless networking gear remains expensive. For
instance: while you can buy a conventional Ethernet network card for less than $20, a
similar wireless card is likely to cost up to three to four times that amount at least. While
you will save money on cabling with wireless, that won't make up the cost difference.
Wireless networks also give rise to their own security concerns, since poorly secured
networks can be pried open by hackers. We will discuss how to protect against these
threats later.

What will happen to my existing network if I go wireless?
If you've no problems with your existing network, there's no need to abandon it because
you want to give some users wireless access. Since all the basic network transports are
identical -- only the medium used to move data is different -- wired and wireless users
can happily co-exist. Indeed, a notebook user may choose a wired connection when at
their desk, to utilise faster speeds, but opt for the portability of wireless during meetings.
The likely scenario for a completely wireless operation is if you're setting up a new
company or moving to a new site. In other situations, running both in tandem will
probably make more sense -- at least until your existing network hardware gives out.




                                              20
                                     George Niflis




What kind of hardware will I need?

The minimum requirement for a wireless network is a wireless adapter (or wireless NIC)
in each PC. These can take several forms. Many new notebooks have a wireless adapter
built-in. These often take advantage of the Intel Centrino's support for Wi-Fi standards.
Notebooks that don't have a wireless adapter can gain one in the form of a PC Card or
USB adapter. A PC card adapter is generally less obtrusive, but a USB adapter can more
easily be redeployed to desktop systems.
Desktop users can choose between the two. If you or your business is purchasing new
PCs, consider ones with built-in cards, as this will be cheaper than adding them later.
Whatever device you have, it's good practice to purchase 802.11g hardware if you can
afford it. This will offer higher speeds and remain compatible with older 802.11b
networks. Conversely, the rise of 802.11g means that 802.11b equipment is rapidly
becoming cheaper, which may remain an important consideration for many businesses.
PCs equipped with wireless adapters can communicate directly with each other via a
peer-to-peer network, but this is of limited use for most businesses. Assuming you
already have a network in place, the easiest way to get wireless access is to link a
wireless access point to your existing hub or router. Entry-level access points are
available from around $200.
Despite the name, the wireless access point connects to your network hub via
conventional cable and has its own IP address. Each PC with a wireless adapter can then
connect to the access point, which in turn provides access to network resources. Make
sure your access point can support the number of users you'll need.
If you want to minimise hardware, access points with built-in routers, DHCP servers (to
assign IP addresses to each machine on the network) and even DSL modems are
available. These combine the functions of several pieces of networking gear into one.
This integration can be useful, but such devices are more expensive.
For larger offices, multiple wireless access points can be connected, which is a useful
way of extending the range of devices beyond the 30-metre indoor limit. Note, however,
that other factors such as walls or other electronic devices may restrict the range, no
matter how many 'hopping points' you use. Microwaves, in particular, have been known
to cause problems.
Device management is simple for entry-level wireless access points, and configuration
can usually be done via a Web browser. With more complex equipment, such as access



                                            21
                                      George Niflis

points with integrated routers, network knowledge may be required for set up tasks. If
your system is complex, you may need to hire a consultant.
An important part of network configuration is sharing your Internet connection. Your ISP
should be able to provide you with details on how to make your broadband link
accessible to wireless clients. Some sell the hardware and services to do so, as a package.
Bear in mind that a wireless network in itself doesn't provide any form of Internet access.
You'll still need broadband from a service provider to connect to the Internet. Wireless
also doesn't offer any speed increase; if your broadband only runs at 512Kbs, then that's
the fastest speed you will be able to achieve.

Wireless game adaptor
                  Another recent addition to the wireless world is the game adaptor.
                  These devices are designed to connect to the standard Ethernet port of a
                  gaming console such as an Xbox or Playstation2. By converting the
                  network traffic to the 802.11b protocol, these adaptors allow driver-free
                  wireless gaming over a LAN or the Internet. By using two of these
                  adaptors in ad-hoc mode, local wireless network gaming is possible
                  between two consoles. Although they are intended for game consoles
                  and are more expensive than conventional wireless network cards
                  (about $210), there is no reason why these adaptors can't be used with
standard Ethernet cards in desktop and notebook PCs, either.


How can I make sure my wireless network is secure?

If you switch on a PC that has a wireless adapter and is running a relatively new
operating system, such as Windows XP, it will automatically look for available wireless
networks. While this makes connecting easy, it also makes it easy for anyone in the
vicinity to detect and access your network. While there's a small degree of security
inherent in a cabled network -- as an intruder must physically connect to the system -- a
wireless hacker could access your network while in a car outside your building, or in the
office next door. Even if your business data is secured by passwords, an unsecured
connection could allow anyone to surf on your network, possibly running up a large
download bill. For this reason, it's important to make sure your wireless connection is
secured.
The most widely deployed security solution for wireless networks is WEP (Wired
Equivalent Privacy), which encrypts data sent over the network. To gain access to a
WEP-protected network, users must know both the network name -- generally referred to
as an SSID -- and have a password for that network. By design, these are generally a
nightmare to remember, and are changed regularly.
WEP is a form of encryption that is similar to SSL (secure sockets layer), which is used
to secure Web browser sessions. The cryptological algorithm used by WEP is a very
strong 128bit password key encryption. Unfortunately, although it does veil the content
of data sent through the airwaves, the implementation of WEP lends itself to easy


                                            22
                                      George Niflis

decryption by anyone willing to dedicate a few hours of their time. Nonetheless,
protection via WEP is better than none, so make sure you enable it on your network.
An additional safety measure that can be taken is configuring all access points to restrict
connections to predefined MAC addresses. A MAC address is a hexadecimal number that
forms a unique hardware ID for every network card ever manufactured. A MAC address
can be determined by typing ipconfig /all into a DOS or command window, or by
viewing the network card hardware properties from the control panel. Configuring an
access point to only accept connections from specified MAC address will ensure that no
roaming wireless devices can browse your network. Bear in mind, however, that it won't
prevent them from intercepting your transmissions! Another recommended setting is to
disable any access points from broadcasting their network name or SSID wherever
possible.
A more advanced form of protection is WPA (Wi-Fi Protected Access), which provides
individual user authentication as well as more secure encryption. However, this is only
effective if support is built into the operating system -- which is the case, for instance,
with Windows XP but not with earlier releases of Windows. WPA is generally only
active on 802.11g networks. WPA will be built into 802.11i, the successor to 802.11g.
It's worth reinforcing that these security standards are specifically designed only to
protect the wireless component of your network, and that normal network security
protocols should also be in place. If you try to carefully protect your network from casual
intruders, but still allow connections with a guest log-in, you're going to run into trouble
eventually.


How do I configure a WLAN?
The first step in configuring a WLAN is to ensure that all wireless network cards have the
correct drivers installed. For an ad-hoc connection between computers (without an access
point), the computers need to be set to operate in ad-hoc mode using the wireless
configuration utility. In Windows XP, wireless configuration is automated by the Zero
Wireless Configuration service, but other operating systems will require the WNIC
configuration utility that came with the device.
Secondly, a name or SSID needs to be assigned to the WLAN. This is the station ID, and
it performs the same function in the wireless network that a workgroup name does on a
regular Windows LAN. For devices to communicate, they must connect to the same
SSID. Alternatively, the devices can be set to connect to any available wireless
connection. To enable data encryption, WEP should be turned on and a password entered.
In Windows XP, the password can be 5 orto 13 characters long or a hexadecimal string.
The process is similar when configuring a WLAN in "infrastructure" mode, which simply
means that an access point is incorporated, usually as a gateway to a LAN. Most access
points can be configured using any PC on the LAN they are connected to. This can be via
a Web interface or standard desktop application. The access point, like a WNIC, must be
assigned the same SSID or network name, along with the password for WEP encryption.



                                             23
                                      George Niflis



What are the operating system requirements?
As mentioned previously, wireless networking is integrated into Windows XP - both
Home and Professional versions. For other operating systems the only requirement is that
the WNIC used has compatible drivers and a configuration utility. If you plan to use a
USB wireless adaptor, make sure you have at least one USB port available and the latest
drivers installed for your motherboard and/or USB PCI card.

Ad-hoc Networking
Two or more PCs with wireless network cards can be configured to form what is referred
to as an ad-hoc wireless network. Simply set all the network cards to connect to the same
wireless workgroup name (SSID) and to use ad-hoc mode. In Windows XP this is done
using the network properties for the wireless network card. Other operating systems will
require the configuration utility that came with the card.

Infrastructure Networking
To connect one or more wireless PCs to an existing wired network, a wireless access
point is needed. Sometimes these devices combine a router and an ADSL modem,
making them ideal for Internet connection sharing. Simply plug the access point into the
Ethernet hub and configure it with the utility supplied by the vendor. Assign it a wireless
workgroup name (SSID) and use this name when configuring the wireless PCs to run in
infrastructure mode.


Connecting a WLAN to the Web
There are two ways that an Internet connection can be shared with a WLAN. In the first
instance, one computer must have dial-up or broadband access while the other(s) connect
via a proxy server or Network Address Translation (NAT) service, such as Windows
Internet Connection Sharing or ICS, running on the host computer.

                        What is Centrino?
                        Intel's Centrino technology is an umbrella term that encompasses
                        a range of integrated wireless, performance, efficiency and speed-
                        stepping technologies designed for notebook computers.
                       The wireless aspect of Centrino provides Wi-Fi certified
                       connectivity using any 802.11 protocol, as well as WEP, WPA
                       and the forthcoming AES security standards. If you are looking to
                       buy a new notebook computer and battery life is a priority, then
Centrino might offer some advantages over the mini-PCI or USB wireless adaptors
discussed earlier.
The other technique involves a router - which may or may not have an integrated access
point - that is wired up to a modem. In this case, the router performs the Internet



                                            24
                                       George Niflis

connection sharing. The latter method is preferred as it does not require any computer to
be booted-up and operational in order for the other(s) to have Internet access.

Boosting wireless signal
It is possible to buy specialised antennae that can boost the signal strength of a wireless
device. In most cases these are only available for access points as few WNIC devices
include a detachable antenna - which is required in order to fit a new one. Antennae range
from 5dBi to 9dBi in signal gain and are typically designed to work either as a directional
or omni-directional device. Directional antennae are usually used outdoors for long range
signal boosting between remote access points. Home and small offices normally use
omni-directional antennae, which provide an overall boost to network signal strength in a
WLAN environment.

Other wireless technologies
Bluetooth is a wireless protocol designed to connect computers to gadgets such as mobile
phones and PDAs. Although it is possible to connect two computers together via $60
Bluetooth adaptors - and Bluetooth access points are available - they can't compete with
the flexibility or throughput of a WLAN. The range of Bluetooth is only about 10m and
the data rate is a mere 723Kbps with a typical throughput of only 300Kbps, making it
virtually unusable except for small file transfers.
                                                              Another wireless option is to
                                                              use an Infrared protocol
                                                              known as IrDA (Infrared Data
                                                              Association). Many notebook
                                                              computers are equipped with
                                                              IrDA wireless adaptors, and
                                                              these allow simple file
                                                              transfers between nearby
                                                              computers as well as the
                                                              downloading of photos from
                                                              digital cameras. USB IrDA
                                                              adaptors are also available for
                                                              under $60 for use with
                                                              Windows XP/2000/ME/98SE
                                                              computers. Like Bluetooth,
                                                              this is a possible substitute for
wired peer-to-peer networking, but isn't really a valid alternative to a WLAN. The IrDA
protocol is rated at 4Mbps with a high-speed version called VFIR rated at 16Mbps.
HomeRF 2.0 is a competing wireless standard that is claimed to be up to 2.5 times faster
than 802.11b although it is rated at only 10Mbps. While access points, USB and PCI
adaptors are available for less than their 802.11 counterparts, the technology is not
compatible with any 802.11 device and is widely expected to be unsupported in the near
future.



                                              25
                                      George Niflis



What is the future of wireless?

In November 2003 Intel announced that wireless router technology was to be integrated
into desktop computers later in 2004, replacing the need for an access point to build a
WLAN. The chipset would not include the necessary Wi-Fi radio card, however, and
would require the PC to be permanently powered-up in order to function. Pre-empting
Intel's plans somewhat, Asus and MSI have already started shipping motherboards with
onboard wireless adaptors. While this doesn't replace the need for an access point, it is a
sign that wireless networking is becoming more accessible and mainstream.
The integrated Wireless adaptor in the new ASUS motherboards makes WLAN
configuration simple. Here's an example of an ASUS WLAN settings status box.
Probably the most anticipated development in wireless will be the ratification of the IEEE
802.11i and 802.11g standards. The major advantage of these new protocols is they
address the security flaws of the current wireless protocols. This security benefit of
802.11i is expected to be complemented by the increased bandwidth of 802.11g devices.




                                             26

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:10
posted:9/5/2011
language:English
pages:11