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Wireless Networking
Some Important Differences between Wired LANS and
Wireless LANS:
While Wireless LANs use the same networking protocols as Wired LANS,
they use specialized physical and datalink protocols.
Wireless LANS integrate into existing networks through access points,
which provide a bridging function.
Wireless LANS let you stay connected as you "roam" from one coverage
area to another.
Wireless LANs have unique security considerations, including
encryption.
Wireless LANS have specific interoperability/compatibility
requirements.
Wireless LANs require different hardware than Wired LANS.
Wireless LANs offer unique performance factors that differ from Wired
LANs.
What a Wireless LAN Does A Wireless LAN allows workers more productivity, mobility, flexibility
and internal/external links to work and home environments. Things advantages
have never possible before today's new technology.
Selecting a Wireless LAN
Before purchasing wireless LAN equipment, ensure that the Wireless LAN can
configure with your particular setup. Wireless connects through your PC and
personal wireless LAN card fast and easily.
The performance of different Wireless LANs may vary widely, depending on
many factors. The throughput of two Wireless LANs advertising the same bit
rate may vary. Therefore, if you intend to cover a large geographical range,
test as many physical locations and combinations of your home, office or
area for range.
Most Wireless LANs are designed to work well in many configurations, but
some Wireless LANs, or some environments, may need to be carefully checked
for wireless configuration. Determine the limitations of your hardware. For
best results, use a high rate wireless LAN solution with connections of up
to 11 Mbit/s. This solution allows mobile operators, network operators and
ISPs to offer tailored and location-based wireless LAN services in enabled
access areas including areas such as airports, hotels, business campuses,
and convention centers.
Things to Consider when Deciding on a Wireless LAN
Wireless LANs exhibit somewhat lower performance levels than 10BaseT
Ethernet products. Although prices are continuously dropping, wireless
components may come at a premium for some users. Another issue is that
interference from other radio sources and even nearby LANs can become a
problem and may lead to lower data speeds or service disruption.
Almost any application that works over a wired LAN should work over a
wireless LAN. The only thing you may want to do differently is to consider
the size of applications and the speed of the network. If a user is
operating on a 1-Mbps network and is loading a 5-Mbyte application from a
file server, the application could take over a minute to load. It is usually
better for users to have copies of frequently used applications, utilities
and data files on their own hard drives rather than on file servers.
In many wireless LAN applications, users should be able maintain a
continuous connection as they roam from one physical area to another. They
must be able to move from the coverage of one access point to another.
Nearly all wireless LAN vendors support this kind of roaming through a
process by which the mobile nodes automatically register with the new access
point. Consider into the equation for your network planning how your
infrastructure network is divided into subnets. If one access point is on
one subnet and another access point is on another subnet, traffic will have
to cross a router, something that most wireless LAN vendors currently do not
support. The two possible solutions are to this scenario are:
Connect all access points back to one subnet, which might require extra
cabling.
Use Mobile IP if your network protocol is IP.
Wireless LAN Hardware
Requirements & Configuration:
Typical Wireless LAN hardware includes the following:
A PC Card, type 2 format, either with integral
antenna. This is becoming the norm, or a Card with a tethered antenna/RF
module.
An ISA Card with external antenna connected by
cable.
Handheld terminals with integrated radios for
vertical market applications such as warehousing.
Access points that are stand-alone devices.
A Client LAN adaptor.
There are two integral parts to a wireless LAN: an
access point and a client LAN adapter.
The access point is a device that connects to the
wired LAN and translates between the cabled Ethernet LAN and the radio link.
It contains a 10Base-T port that connects to the LAN's hub or switch,
communications and encryption software, and a radio transceiver. The client
LAN adapter is typically a PC Card that fits into a portable device,
although many vendors also offer ISA and PCI cards. The notebook, personal
access device, or specialized device such as an inventory scanner or medical
monitor sees the PC Card as an Ethernet adapter. The client adapter has a
small integrated antenna.
The client adapter uses its radio transceiver to find an access point and
negotiate a connection speed appropriate to the signal quality. If you want
your wireless LAN to cover more than a few thousand square feet, you'll need
more than one access point. Exact coverage depends on the building's
construction and layout, but plan for a connection radius of several hundred
feet in clear view and perhaps 50 to 60 feet going through walls, floors,
and ceilings. As the user moves, the radio connection transfers to another
access point, a process called "roaming". Maximum connection speeds are up
to 11 Mbps; A radio LAN is generally rated at 10 Mbps.
PC Cards A
PC or LAN Card (also known as a PCMCIA card) is a credit card-size memory or
I/O device that fits into a personal computer, usually a notebook or laptop
computer. The most common example of a PC Card is the 28.8 Kbps modem for
notebook computers. There are 16-binary bit and 32-bit (CardBus) varieties
of PC Cards. Another type of PC card is the ZV Card.
A card is used as an interface to connect to a PC.
Most cards are in Pcmcia ISA and PCI versions. Other vendors offer an
ISA-to-Pcmcia bridge to allow you to plug a Pcmcia card in a desktop.
Planning on establishing point-to-point links? Then you will need the card
to offer a connector for an external antenna. LAN cards are often plugged
into routers.
Routers
A router is a device or software in a computer, that determines the next
network point to which a packet should be forwarded toward its destination.
The router is connected to at least two networks and decides which way to
send each information packet based on its current understanding of the state
of the networks it is connected to. A router is located at any gateway
(where one network meets another), including each Internet
point-of-presence. A router is often included as part of a network switch.
A router may create or maintain a table of the available routes and their
conditions and use this information along with distance and cost algorithms
to determine the best route for a given packet. Typically, a packet may
travel through a number of network points with routers before arriving at
its destination. Routing is a function associated with network layer in the
standard model of network programming, the Open Systems Interconnection (OSI)
model. A layer-3 switch is a switch that can perform routing functions.
Access Points or "residential gateways"
Some vendors offer an Access Point or "residential gateways". An Access
Point is a bridge that allows you to connect the wireless network to an
Ethernet backbone, whereas the Residential Gateway connects it to an ISP. An
Access Point allows the Wireless LAN to be a natural extension of a wired
network. They are deployed in a cellular fashion, and provide extended
security, management and roaming. NOTE: These two kinds of products are
usually not fully interchangeable.
Wireless Bridges
A Wireless Bridge is connected to one of the LAN sections and redirects the
traffic over the air to the correct destination. There are many products on
the market, they can be slightly expensive but are very flexible,
transparent and optimized for the task.
Drivers
A driver is a program that interacts with a particular device or special
kind of software. The driver contains the special knowledge of the device or
special software interface that programs using the driver. In personal
computers, a driver is often packaged as a dynamic link library file.
Installation and Deployment
of Your Wireless LAN:
Each Wireless LAN implementation may offer different
wireless parameters. Having those parameters in mind will allow tuning of
the PC card for specific environments and configurations. Keep in mind that
most products communicate only with products from the same vendor.
Because corporate customers require an established unique standard, most of
the vendors have joined the IEEE in an effort to create a standard for radio
LANs. However, with Ethernet and the technology being brand new, some
products may not communicate with other products. Check carefully with your
vendor before purchasing equipment.
Installation
A good rule of thumb is to research as much as you can about wireless before
installation and implementation. Most Wireless LAN vendors offer products
with an Ethernet interface.
Wireless LAN is easy to install. A wireless LAN simplifies many of the
installation and configuration issues that cause problems for network
managers. Since only the access points require cabling, network managers are
freed from the task of connecting cables for end users. Moving, adding, and
changing cables becomes unnecessary. Finally, the portability of a wireless
LAN lets network managers pre-configure and troubleshoot entire networks
before installing them at remote locations. Once configured, a wireless LAN
can be moved from place to place with little or no extra modification. A
wireless LAN system does requires a driver and software to interface to the
hardware. Ensure that the driver knows about the specific hardware details
and the specific operating system ways. Compile your driver to specify the
details about it to your system.
Deploying your Wireless LAN
From a network administrator point of view, Wireless LANs are shared. If on
a cable you know who is there, anybody and anything can use the radio band.
Otherwise, you must specify network identifiers. Networks using different
network identifiers still share the bandwidth, but are logically separate
and don't interfere with each other.
To try to separate everyone out there, most products define a network
identifier. This is a number or character string which is used to identify
all the users wanting to be on the same logical network.
Distinct channels (i.e., frequencies, or hopping patterns) are necessary.
Users on distinct channels use a different part of the bandwidth in order to
not interfere with each other. If you want to install multiple independent
networks in the same area, this is the way to go.
The Wireless LAN has only a limited range, so you may reach only devices
within that range. This is usually why you should define some cells where
everybody is in range. If you want those cells to communicate or a node to
move across cells, you should install an access point in each of those and
configure those with the same network identifier (and also add an Ethernet
segment between the access points).
Reliability, Security, and Coverage:
Reliability
Most Wireless LANs protocols include mechanisms to improve the reliability
of the packet transmissions to be at the same level or even better than
Ethernet. If you are using a protocol such as TCP, you will be fully
protected against any loss or corruption of data over the air. Copying a
file across wireless cannot result in corruption of the file.
Wireless Area Coverage
The propagation of wireless transmissions is influenced by many factors.
Walls and floors tend to decrease and reflect the signal, and background
noise makes it more difficult to extract. Therefore, the channel quality of
the transmission may vary.
Depending on the quality of reception, the error rate will vary, or the
system may switch to a more robust and slower mode. Thus, the actual
throughput will vary from excellent to average, or, occasionally, less.
Because of the way wireless transmissions are affected by the environment,
it is quite difficult to predict the exact reception parameters of the
system, and to define the exact range at any given time. Approximations are
helpful and, at best, optimistic.
Security
Because they use radio waves or infrared, wireless LANs are usually
perceived as a security problem. Network identifiers usually provide
protection against casual users intercepting data.
Network administrators ensure security by using encryption. You may want to
increase the security of your system. Some Wireless LANs offer encryption
which is designed for those concerned users and target security equivalent
to a having an Ethernet cable. Some systems offer even tighter encryption
packages. Each packet transmitted over the network is individually
encrypted. This encryption is totally transparent to the higher layer and
the user just needs to set the same encryption key in the access point and
all nodes of the network. The ultimate encryption is IPsec or SSL. Ask your
administrator about these options.
NOTE: There is not any one unique standard like Ethernet with a
guaranteed compatibility between all devices, but many proprietary standards
are sold by each independent vendor and can be incompatible between
themselves.
Benefits
Wireless LANs are very appealing. One advantage is relocation - moving or
relocating as networks grow or if you move your residence or business. You
do not have to leave behind your investment in networks when geographical
changes occur. Because there's no wiring, you can take your system with you.
When you move or relocate, you can set up the system and save money on
installation. Wireless LANs are typically easier to set up than wired LANs
because users don't have to deal with making connections among cables.
A handheld device that integrates voice-over-IP communications, a bar-code
laser scanner, embedded client software, and a wireless LAN radio card, can
tap into a company's inventory database to check on a product while talking
with the customer. Clarity is generally good to excellent, although there
are variations according to range and areas of roaming.
Mobility for communications is a significant plus. Whenever away from your
phone or PC, you still retain your connection to the network. Note that
mobility is limited by the range of the Wireless LAN. To extend the range,
you must cover the area with access points, which very often include
roaming. If you want to move across IP subnets, then consider Mobile IP.
Wireless SOHO or Residential LANs:
Setting up a powerful Home or SO/HO LAN is not very
costly and can be done in a reasonable amount of time. When you build a
residential LAN, you can even use your old 386, if you still have it.
You may not need a server for your home network, if your computers can
communicate with one another on an equal basis in a peer-to-peer network.
While the peer-to-peer network services offered by Windows aren't
particularly sophisticated, they're more than enough for the basic job of
the network: sharing files, printers, and other peripherals. Otherwise, a
server will be a requirement.
Depending on which operating system(s) you have, different network options
and certain advantages are available.
If you have a PC purchased in 1995 or later, your system probably came with
Windows 95. This may be convenient, but can produce occasional program and
system crashes. Windows 98 is advisable.
If you have a PC with less than 16MB of RAM, or a 486 processor that's
slower than 100 MHz, Windows 95 will probably overtax the system. If you
must run Windows software, run Windows 98 .
If you have a 150-MHz or faster Pentium with at least 48MB of RAM (64MB is
better), use Microsoft's Windows NT 4.0 Workstation. It's slower than
Windows 95 or Windows 98, and requires a more powerful machine, but NT
Workstation runs most Windows-based software and crashes a lot less often
than Windows 95 or 98. Another advantage is that NT lets you set up separate
file-storage accounts. Even though each user is using the same PC, unless
each user has access privileges, they won't be able to share data.
The two best home wiring options are thin Ethernet (also called 10Base2) and
unshielded twisted-pair cabling (also called UTP or 10BaseT). Your choice
will depend on how much you're willing to spend and how your So/Ho is set
up.
Thin Ethernet
Thin Ethernet cable looks very much like the wire used for cable TV. It's
rugged but stiff, making it a challenge to run the cable through walls, but
it's inexpensive and requires the least hardware to connect. The cable is
run from one computer to each additional computer, until you get to the last
computer, where you add a cap called a terminator. Thin Ethernet runs at
only 10 mbps, much slower than UTP. Depending on your home's setup and the
number of machines you're connecting, it may be inconvenient to run cable in
a line through every room.
Thin Ethernet requires a BNC connector, a little metal cylinder with two
nubs near the outside edge. You can buy standard lengths of cable that
already have connectors, or you can buy the connectors at any good computer
store and crimp or twist them on using a special tool.
UTP
UTP cable looks like telephone cord and is more flexible than thin Ethernet.
If you're willing to buy more expensive adapter cards and a hub. UTP can run
at as fast as 100 mbps, much faster than thin Ethernet.
In a UTP network, the wires run out from a central hub (a box to which all
the computers are connected, and through which data is routed) like the
spokes of a wheel. A UTP network may work better for your home than thin
Ethernet, but setting up a hub requires some rudimentary understanding of
setup. Many users opt for the simplicity of the thin Ethernet system.
With UTP, you'll need an RJ-45 connector, which looks sort of like the
connector on a telephone cord. Again, standard lengths usually come with the
connector in place, or you can buy a crimping tool for about $5 and install
the connectors yourself.
If you go with UTP, you'll also need to purchase a basic 10BaseT hub for
about $60 (for a simple eight-port model); any computer store should be able
to sell you one. Make sure you get one that has several more ports (or
connections) than you have computers because you don't want to have to buy a
new hub when you decide to add to your network.
Safety Precautions
Whichever system you choose, check your local building codes to make sure
the cable is approved for your location. In a fire, some cables can emit
toxic fumes as they burn. If you're using twisted-pair cable in a home,
always choose cable labeled as Multi-purpose Plenum (MPP), and make sure
that it's installed properly.
After you select and install your cabling system, the next step is adding
network interface cards) and connectors. A NIC is the piece of hardware that
physically connects the cables to your computers.
The brand of card isn't important, but make sure each one works with your
operating system. An absolutely safe bet for matching your OS is to check
the box to see whether the card is compatible with the Novell NE2000 card.
The NE2000 is a time-honored design that works with all of the operating
systems for IBM-PC-compatible computers.
Network cards come in two basic flavors, ISA and PCI. Most computers can use
ISA cards, which are a little slower and less sophisticated. ISA cards are
designed for a standard 16-bit slot. PCI cards work in newer Pentiums, are a
faster and more advanced, and fit in a PCI slot. PCI cards are a bit more
expensive but probably worth the cost if your computer can use them.
Make sure that the card you choose also has the correct cable connector, UTP
or thin Ethernet. Many cards come with both kinds, enabling you to change
your cabling system later without buying new cards.
At your local computer superstore, you should find basic 10-mbps Ethernet
network interface cards for about $25. The cheapest cards require you to run
an installation program to set them up. Avoid cards that aren't
plug-and-play and don't have installation software.
Configuring a Home Wireless LAN Or Wireless SO/HO LAN
Once your cables are in place, you need to configure your NIC to select an
Iaddress and an interrupt request (IRQ) number. An I/O port address is where
the network card transfers information to and from the network. The IRQ
number is a label assigned to each I/O device (such as a printer, mouse, or
modem) attached to your computer.
Write down all the settings you make for your network cards and keep them in
a safe place. You may need to refer to some of the settings when configuring
other network software.
First, boot up one of the computers in the network. If you bought a
plug-and-play card and are running an operating system like Windows 95 or 98
that knows how to take advantage of it, the card should set itself up
automatically. The OS will recognize your card and set up the IRQ and I/O
address correctly.
If your operating system doesn't recognize a newly installed network card,
you'll need to help it out. In Windows 95 or 98, you can use the Add New
Hardware icon on the Control Panel; in other operating systems, the
procedure may be different. The Add New Hardware program will walk you
through locating and configuring your card's I/O and IRQ addresses.
If your operating system still doesn't recognize the card, or if the card
doesn't work correctly, you may need to configure it through DOS. Consult
the documentation that came with your card to find out how to do this.
To make sure your card is installed correctly, double-click the System icon
in the Control Panel. When the System Properties dialog box appears, click
the Device Manager tab; then double-click Network Adapters. If there's a red
mark over the icon beside your card's name, you need to try reinstalling the
card. If there's no red mark, your card is ready to go.
The whole setup process should take about an hour from the time you break
the shrink wrap on your network cards. Once the hardware and software are
running, you'll be able to set up your computers to share files and
printers.
Cost Considerations for Wireless LANs:
Although costs are continually decreasing, setting up
a residential or So/Ho Wireless LAN is not generally very costly. Setting up
A Wireless Business LAN may come at a premium. Nevertheless, for both
setups, if you are sharing multiple PCs and files it is a worthwhile
wireless benefit.
Some of the Business LAN wireless accessories will range from about $200 to
$800 for network cards, with access points costing $1,000 or more. Wireless
bridges that link wired LANs can together range from $2,000 to as high as
$10,000 per node, depending on performance and the size of the network.
Adapters cost around $300.
For a Residential LAN or SO/Ho wireless LAN, you can expect to pay around
$100 per PC Card and $300 per access point. These will be adequate enough to
allow users to share access to the Internet.
On an average, wireless subscribers should expect to pay about $30 to $50 a
month based on the amount of voice communication they use, or data they
transmit.
A
PC or LAN Card (also known as a PCMCIA card) is a credit card-size memory or
I/O device that fits into a personal computer, usually a notebook or laptop
computer. The most common example of a PC Card is the 28.8 Kbps modem for
notebook computers. There are 16-binary bit and 32-bit (CardBus) varieties
of PC Cards. Another type of PC card is the ZV Card.