security wireless network

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2010-03-14T10:50:00.000-07:00

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2010-03-10T08:39:00.001-08:00

about my hobies-bodybilding-8 things you must do to bild maximum muscle continue

2010-03-07T05:32:00.000-08:00

3.Increase your water intake.

Water is an absolutely critical component to the muscle-building process and to overall body health in general. Failing to keep yourself properly hydrated throughout the day will have a negative impact on literally every single process within your entire body!
Most people know that they should be drinking "plenty" of water every day, but how many actually do?
If you really paid close attention to your water intake you'd probably be surprised at how little you actually consume.
What makes proper water intake so amazingly important?
Well for starters, it’s the most abundant element in your body. It is ranked only 2nd to oxygen as being essential to life.
Your body can survive for weeks without food, but without water you'd be dead in just a few days.
Roughly 80% of your body is made up of water; the brain is 85% water and lean muscle tissue is 70% water.
Research has shown that being even slightly dehydrated can decrease strength and physical performance significantly. In fact, merely a 3-4% drop in your body's water levels will lead to a 10-20% decrease in muscle contractions.
Not only will water increase your strength, but it also plays a large role in preventing injuries in the gym. Highly intensive training over a long period of time can put unwanted stress on your joints and connective tissue, and water helps to fight against this stress by lubricating the joints and forming a protective "cushion" around them.
So, just how much water is enough?
To find out how many ounces of water you should be consuming every day, multiply your bodyweight by 0.6. So if you weigh 150 pounds, you should be consuming around 90 ounces of water every day.
150 x 0.6 = 90
I know it sounds like a lot, but if you plan your day out properly it shouldn't be a problem. Keep a water bottle with you at all times and sip from it periodically. Keep water in the places where you spend most of your time: in your car, at work, on your nightstand etc.
Another good method to ensure that you drink enough water is to pre-fill a few 16 ounce bottles at the beginning of the day. This way you can have a visual representation of where your water consumption is at any point in the day.
For the first few days you'll probably find yourself running to the bathroom quite frequently, but your body will soon adapt to the increased water volume and this will no longer be a problem.

4.Keep a detailed record of every workout that you perform.

This muscle-building technique should form the underlying basis for your entire workout plan. When it comes to structuring a proper approach in the gym, this is the most important overall factor, bar none.
Everyone is so obsessed with all of the specific principles in the gym (such as exercise selection, rep ranges, which days to spend in the gym, how many sets to perform etc.) that they fail to see the big picture.
Regardless of what type of approach you are taking in the gym, the underlying factor for success is progression.
Our bodies build muscle because of an adaptive response to the environment. When you go to the gym, you break down your muscle fibers by training with weights. Your body senses this as a potential threat to its survival and will react accordingly by rebuilding the damaged fibers larger and stronger in order to protect against any possible future threat.
Therefore, in order to make continual gains in muscle size and strength, you must focus on progressing in the gym from week to week in order to consistently increase the stress level.
Progression can take 2 main forms:
a) Increasing the amount of weight lifted on a specific exercise. b) Increasing the number of reps performed with a given weight on a given exercise.
If you’re able to improve on at least one of the above factors each week in the gym, your body will be given continual incentive to grow larger and stronger.
If you neglect these factors and enter the gym without a concrete plan in mind, you’ll be ignoring the very foundation of the entire muscle growth process, and your gains will surely stagnate.

5.Be prepared to train HARD!
If you think that building muscle is going to be a walk in the park and that you can simply enter the gym, “go through the motions” and then go home, you are sadly mistaken.
The reality is that if you want to experience any appreciable gains in muscle size and strength, you’re going to have to be prepared to train hard. This is one of the key factors separating those who make modest gains from those who make outstanding gains.
Most people just plain don’t train hard enough!
As soon as the exercise starts to get difficult their spotter jumps in and begins needlessly assisting them, or they simply put the weight down altogether.
BIG mistake!
The gym is a war zone, and if you want to be victorious, you must be willing to endure the battle.
Intense weightlifting is perceived as a threat to your survival, and the body responds to this by increasing the size and strength of the muscles to battle against the threat. Therefore, in order to see the most dramatic response in size and strength, you must push your body as hard as you safely can.
This can be achieved by performing all sets in the gym to the point of concentric muscular failure…
Concentric Muscular Failure: The point at which no further positive repetitions can be performed using proper form despite your greatest efforts.
This is very challenging and will require a lot of mental toughness on your part. I’m not going to sit here and feed you a pack of lies by saying that training for muscle size is an easy task. It’s not!

6.Avoid overtraining by limiting your overall workout volume and by providing your body with sufficient recovery time in between workouts

This is one of the most common and most deadly mistakes that almost all beginners run into. They naturally assume that the more overall work they perform in the gym, the greater their results will be.
Heck, when I was a beginner myself I thought the same thing.
Who can blame us for thinking that?
In almost all aspects of life this basic logic holds true. If you want to perform well on a school test, you need to maximize your studying time. If you want to improve your skills in a specific sport, you need to practice as much as possible.
When it comes to training for muscular size and strength, you can take this basic logic and toss it right out the window, down the street and around the corner!
The key thing to realize is that your muscles will NOT grow larger and stronger if they are stressed beyond the point of recovery. Remember, training with weights is merely an activity that sets the wheels in motion; it “sparks” the muscle growth process and “tells” your body to start building new muscle tissue… But the actual growth process takes place away from the gym while you’re eating and resting.
If you disturb the recovery process, your muscles cannot rebuild themselves.
Overtraining is your number one enemy! Your goal in the gym is to perform the minimum amount of work necessary in order to yield an adaptive response from the body, and not a THING more.
You can avoid overtraining in the following ways…

1) Limit the number of sets that you perform during each workout – You should perform a total of 5-7 sets for large muscle groups (chest, back and thighs) and 2-4 total sets for small muscle groups (shoulders, biceps, triceps, calves and abs). And remember, this is total sets per WORKOUT, not per exercise.
2) Limit the amount of time spent in the gym – Each workout should not last for any more than 1 hour. This time frame comes into play beginning with your first muscle-building set and ends with your final muscle-building set.
3) Limit your training frequency for each muscle group – Each specific muscle group should only be directly stimulated once per week in order to allow for full recovery time. If you’ve been following the “more is better” mentality then you may find it hard to let go of, but believe me, as long as you train hard, you do NOT need to train often or with very many sets and exercises.
In fact, performing too much work in the gym may actually cause your muscles to become smaller and weaker.

7.Stop placing so much of your emphasis on dietary supplements
A supplement is just that… a supplement.
It is there to supplement your diet by filling in the missing gaps and by providing you with greater amounts of specific nutrients that will slightly speed up your progress. Supplements are NOT there to do the work for you and will only play a small role in your overall success in the gym.
Stop falling for the multi-million dollar ads that talk about the latest “revolutionary discovery” that will allow you to build 25 pounds of muscle while you lie on the couch.
As advanced as we’ve become as a society, the basic rules of hard work and dedication still apply. If you want to change your physique, then hard training in the gym and a consistent diet plan is the only true way to get there.
Now, this doesn’t mean that I’m AGAINST the use of supplements; I’m merely against the over-use and over-emphasis of supplements. There are a few good, solid, effective products out there that I do recommend, but only as a small part of your overall approach.

8.Understand that application and consistency is EVERYTHING

You can have the most effective workout schedule possible, the most intelligent diet approach available and the most intimate understanding of muscle growth from every possible angle, but without the inner drive and motivation to succeed you will get nowhere, and very fast.
Just as the famous saying goes…
“Knowing is NOT enough. You must APPLY!”
Those who make the greatest gains in muscular size and strength are the ones who are able to continually and systematically implement the proper techniques on a consistent basis.
Building muscle is a result of the cumulative effect of small steps.
Sure, performing 1 extra rep on your bench press will not make a huge difference to your overall results, and neither will consuming a single meal. However, over the long haul, all of those extra reps you perform and all of those single meals you consume will decide your overall success.
If you work hard and complete all of your muscle-building tasks in a consistent fashion, all of those individual steps will equate to massive gains in overall size and strength.
It is those who are willing to persevere that will succeed.
It is those who are willing to rise above laziness that will end up with the most impressive results.
I mean let's face it, everyone wants to be strong and muscular. If this is the case, why isn't everyone strong and muscular? It's because only certain people have the proper drive and motivation that it takes to get there.
______________________________________________________________________________________________

about my hobies-bodybilding-8 things you must do to bild maximum muscle

2010-03-06T13:29:00.000-08:00

1.Provide your body with a surplus of calories by ensuring that your caloric intake exceeds your caloric expenditure.
In order to build muscle, you must consume more calories than you burn!
This is a basic biological law of muscle growth, and if you fail to consume an adequate number of calories per day you will NOT build muscle, plain and simple.
The work that you perform in the gym is simply the “spark” that sets the muscle growth process into motion. However, the REAL magic takes place when you are out of the gym, resting and eating. This is when your body will use the nutrients that you consume to begin repairing your damaged muscles and increasing their size and strength in preparation for your next workout.
If you don’t provide your body with the raw materials needed to facilitate growth, this process simply cannot take place.
In order to provide your body with the calories necessary to fuel muscle growth and to keep your body in an anabolic, muscle-building state at all times, you should be consuming anywhere from 17-20x your bodyweight in calories every single day. So if you weigh 150 pounds…
150 x 17 = 2550
150 x 20 = 3000
…ThenYou should adjust this number based on…

a) Your Metabolic Rate – Are you naturally thin and have a hard time gaining weight? Or do you seem to put on body fat just by looking at food? Depending on your overall body type you can adjust the number higher or lower.

b) Your Activity Level – Do you play sports or work a physically strenuous job? If so, you’ll need to consume more calories in order to compensate. If you’re fairly sedentary and aren’t very physically active (besides your weight workouts of course), then you probably won’t need as many calories as someone who is more active.

c) Your Goals – Are you aiming to bulk up and build as much overall body mass as you possibly can? If so, you’ll obviously want to consume as many calories as you reasonably can. Are you simply trying to build a little bit of extra muscle and look better overall? If so, then a slight caloric increase is all you’ll need. Based on these 3 factors above you can decide where to place yourself on the caloric range.
Do NOT overlook this aspect of the muscle growth process!
Most trainees are so concerned with their workouts that they highly underestimate the importance of proper nutrition. If anything, nutrition is even MORE important than what you accomplish in the gym.
If you fail to eat properly by not providing your body with an adequate number of calories each day, building muscle will be physically impossible. you should be consuming anywhere from 2550-3000 daily in order to build muscle.

2.Consume the right types of calories from the proper food sources.

The 3 main food groups that you should be concerned with are…
a.High Quality Protein – Protein builds and repairs muscle tissue and is the most important nutrient for those trying to increase their lean mass. Stick to high quality, easily absorbed sources such as lean red meat, poultry, fish, eggs, skim milk, cottage cheese, peanuts/natural peanut butter and whey.
b.High Fiber, Low Glycemic Carbohydrates – Carbohydrates aid in the absorption of protein, provide your muscles and brain with energy throughout the day and also help to maintain an optimal hormonal environment within the body.
Stick to slow-release, low-glycemic sources that will provide you with a steady stream of sugars throughout the day such as oatmeal, yams, certain fruits, brown rice and whole wheat products.
c.healthy Unsaturated Fats – Not all fats will make you fat, and essential fatty acids fit that profile. EFA’s are highly beneficial to the muscle growth process by increasing testosterone levels, improving the metabolism and volumizing the muscle cells. Some good sources of EFA’s include fatty fish, nuts, seeds, avocados and liquids like flaxseed and olive oil.

more tips next day

Putting a Networked PC in Your Home Theater

2010-03-04T15:29:00.000-08:00

sources: that is, devices such as tape decks, AM/FM receivers, phono players,
CD units, DVD players, and other consumer electronics devices that provide
the inputs of the content you listen to and watch through your entertainment
system.
When you think about adding your networked PC or PCs to your entertainment
mix, the PC becomes just another high-quality source device attached
to your A/V system — albeit wirelessly. To connect your PC to your entertainment
system, you must have some special audio/video cards and corresponding
software to enable your PC to “speak stereo.” When the PC is configured
like this, you effectively have a home theater PC (or HTPC, as the cool kids
refer to them). In fact, if you do it right, you can create an HTPC that funnels
audio and video into your system at a higher-quality level than many moderately
priced, stand-alone source components. HTPC can be that good.
You can either buy a ready-to-go HTPC right off the shelf or build one yourself.
We don’t recommend that you build an HTPC unless you have a fair amount
of knowledge about PCs. If that’s the case, have at it. Another obvious point:
It’s much easier to buy a ready-to-go version of an HTPC off the shelf.
What you expect from your home theater PC is quite different from what
David Bowie might expect from his HTPC. Regardless of your needs, however,
a home theater PC should be able to store music and video files, play CDs
and DVDs, let you play video games on the big screen, and tune in to online
music and video content. Thus, it needs ample hard drive space and the
appropriate software (see the following section). Also, your HTPC acts as a
DVR (see the nearby sidebar, “Checking out PC DVRs,” for the lowdown on
PC-based DVRs). In addition, an HTPC can
Store audio (music) files: Now you can easily play your MP3s anywhere
on your wireless network.
Store video clips: Keeping your digital home video tapes handy is quite
the crowd pleaser — you can have your own America’s Funniest Home
Videos show.
Play CDs and DVDs: The ability to play DVDs is essential in a home
theater environment.
Act as a DVR (digital video recorder): This optional (but almost essential,
we think) function uses the HTPC’s hard drive to record television
shows like a TiVo (www.tivo.com).
Let you play video games on the big screen: With the right hardware,
PCs are sometimes even better than gaming consoles (which we cover
in Chapter 11).
Tune in to online music and video content: Grab the good stuff off the
Internet (yes, and pay for it), and then enjoy it on the big screen with
good audio equipment.
Provide a high-quality, progressive video signal to your TV video display:
This is behind-the-curtain stuff. Simply, an HTPC uses special hardware
to display your PC’s video content on a TV. Sure, PCs have built-in
video systems, but most are designed to be displayed only on PC monitors,
not on TVs. To get the highest possible video quality on your bigscreen
HDTV, you need a special video card that can produce a highdefinition,
progressive-scan video signal. (This investment also gives
you better performance on your PC’s monitor, which is never bad.)
Decode and send HDTV content to your high-definition TV display:
HTPCs can provide a cheap way to decode over-the-air HDTV signals
and send them to your home entertainment center’s display. You just
need the right hardware (an HDTV-capable video card and a TV tuner
card). If you have HDTV, this is a cool optional feature of HTPC.
For example, the HP z560 Digital Entertainment Center (www.hp.com, $1,799)
is a full-fledged digital media center PC with onboard 802.11g functionality
and includes Microsoft’s Windows XP Media Center Edition or Windows Vista

A better way: WPA

2010-03-04T15:28:00.000-08:00

What’s better about WPA?
More random encryption techniques: WPA has basically been designed
as an answer for all the current weaknesses of WEP, with significantly
increased encryption techniques. One of WEP’s fatal flaws is that because
its encryption isn’t sufficiently random, an observer can more easily find
patterns and break the encryption. WPA’s encryption techniques are
more random — and thus harder to break.
Automatic key changes: WPA also has a huge security advantage in the
fact that it automatically changes the key (although you, as a user, get to
keep using the same password to access the system). So, by the time a
bad guy has figured out your key, your system has already moved on to
a new one.
It’s possible to use an 802.1x system, as described in the sidebar “802.1x:
The corporate solution,” later in this chapter, to provide automatic
key changes for WEP systems. This is not something you would find in
anyone’s home network, but some businesses use it, and it does indeed
minimize the effect of WEP’s fixed keys.
More user friendly: WPA is easier for consumers to use because there’s
no hexadecimal stuff to deal with — just a plain text password. The idea
is to make WPA much easier to deal with than WEP, which takes a bit of
effort to get up and running (depending on how good your access point’s
configuration software is).
The type of WPA (and WPA2) we’re talking about here is often called WPA
Personal or WPA PSK (preshared key). The more complex (and not suitable
for the home) version of WPA/WPA2 that is often used by businesses is WPA
Enterprise. We talk about WPA Enterprise in the sidebar titled “802.1x: The
corporate solution.”

Installing the AP

2010-03-04T15:17:00.000-08:00

If you’re connecting your first computer with your ISP, the ISP should have
supplied you with all the information we list in the preceding section except
for the physical address of the network card (which isn’t needed if you aren’t
already connected).
Before you install your wireless gear, buy a 100-foot Ethernet cable. If you’re
installing your AP at a distance farther than that from your router or Internetsharing
PC, get a longer cable. Trust us: This advice comes with having done
this a lot. You need a wired backup to your system to test devices and debug
problems. To do that (unless you want to keep moving your gear around,
which we don’t recommend), you need a long cable. Or two. Anyone with a
home network should have extra cables, just like you have electrical extension
cords around the house. You can get good-quality 100-foot CAT-5e/6
patch cables online at places like Deep Surplus (www.deepsurplus.com) or
a host of other online retailers for around $15.
When you’re ready to do the AP installation, follow these steps:
1. Gather the necessary information for installing the AP (see the preceding
bulleted list) by following these steps:
In Windows XP:
a. Choose Start➪Programs➪Accessories➪Command Prompt.
This step brings up the command prompt window, which is a DOS
screen.
b. Type IPCONFIG /ALL and then press Enter.
The information scrolls down the screen. Use the scroll bar to slide
up to the top and write down the networking information we list
earlier in this chapter (physical address, IP address, default gateway,
subnet mask, DNS servers) and whether DHCP is enabled. You
use this information to configure the AP in Step 4.
In Windows Vista:
a. Choose Start➪Network➪Network and Sharing Center.
The Network and Sharing Center appears, which gives you access
to all network adapters and their properties.
From the Network and Sharing Center, click the View Status link.
A pop-up status window appears with all the information you need.
2. Run the setup software that accompanies the AP or device containing
your AP, like a wireless or Internet gateway.
The software probably starts when you insert its CD-ROM into the CD
drive. In many cases, this software detects your Internet settings, which
makes it much easier to configure the AP for Internet sharing and to configure
the first computer on the network. For example, Figure 6-1 shows
the Linksys Wireless-G Setup Wizard that accompanies the Linksys
WAP54G Wireless-G Access Point, which is a wireless gateway from
Linksys, a division of Cisco Systems, Inc.
If your computer is using Windows Vista, you will see a lot of security
dialog box pop-ups. The enhanced security in Vista asks for your permission
every time the installation software tries to do anything. As long
as you have administration rights on your user account, you can keep
saying yes to these security pop-ups and move through your AP setup.
Be sure to look at the top left of the pop-up window so you know when
you are saying yes to a security warning and when you are saying yes to
the install. Even though Vista dims the rest of the screen when a security
warning pops up, it is confusing with the number of pop-ups you can run
into. Just read the top left of the window and you will always know what
you are working in.
3. When you’re prompted by the setup software to connect the AP unplug the network cable that connects the broadband
modem to your computer’s Ethernet port and plug this cable into the
Ethernet port that’s marked WAN or Modem on your network’s cable
or DSL router or Internet gateway.
If you’re using an Internet or wireless gateway, run a CAT-5e/6 cable from
one of its Ethernet ports to the computer on which you’re running the
setup software. (CAT-5e/6 cable is a standard Ethernet cable or patch
cord with what look like oversized phone jacks on each end. You can
pick one up at any computer store or Radio Shack.)
If you’re using a separate AP and router (in other words, if your AP is not
your router), you need to connect a CAT-5e/6 cable between the AP and
one of the router’s Ethernet ports. Then connect another cable from
another one of the router’s Ethernet ports to the computer on which
you’re running the setup software.
Most new APs try to obtain an IP address automatically and configure
themselves for you by choosing the channel and setting default parameters
for everything else. In most cases, you need to manually
configure the security and some of the other information you
collected in Step 1 (so have that information handy).
4. Record the following access point parameters:
• Service set identifier (SSID)
• Channel — if you’re using an 802.11n draft 2 AP, this should be set
to Auto
• WEP key or WPA2 passphrase (see Chapter 9 for more details on
this subject), if your system doesn’t use WPS
• Router pin, if your system does use WPS (again, see Chapter 9 for
more details on Wi-Fi Protected Setup)
• Admin username and password

The BSSID

2010-03-04T15:15:00.000-08:00

BSSs throughout the network. The major advantage of the BSSID is
overlapping network.
In an infrastructure BSS, the BSSID is the MAC address of the wireless
networks brought into existence. To maximize the probability of creating a
unique address, 46 random bits are generated for the BSSID. The
Universal/Local bit for the new BSSID is set to 1, indicating a local address, and
BSSID, they would need to generate an identical random 46 bits.
broadcast BSSID. Frames that
broadcasts are used only when mobile stations try to locate a network by
sending probe requests. In order for probe frames to detect the existence of a
network, they must not be filtered by the BSSID filter. Probe frames are the only
Each BSS is assigned a BSSID, a 48-bit binary identifier that distinguishes it
filtering. Several distinct 802.11 networks may overlap physically, and there is
no reason for one network to receive link-layer broadcasts from a physically
interface in the access point creating the BSS. IBSSs must create BSSIDs for
the Individual/Group bit is set to 0. For two distinct IBSSs to create the same
One BSSID is reserved. The all-1s BSSID is the
use the broadcast BSSID pass through any BSSID filtering in the MAC. BSSID
frames allowed to use the broadcast BSSID.

Abbreviations

2010-03-04T15:07:00.000-08:00

μs microseconds
2G second generation (cellular)
3G third generation (cellular)
AC access category
ACK acknowledgement
ADC analog-to-digital converter
ADDBA add block acknowledgement
ADDTS add traffic stream
AGC automatic gain control
AID association identifier
AIFS arbitration inter-frame space
A-MPDU aggregate MAC protocol data unit
A-MSDU aggregate MAC service data unit
AoA angle of arrival
AoD angle of departure
AP access point
APSD automatic power save delivery
A-PSDU aggregate PHY service data unit
AS angular spectrum
ASEL antenna selection
AWGN additive white Gaussian noise
BA block acknowledgement
BAR block acknowledgement request
BCC binary convolution code
BF beamforming
BICM bit interleaved coded modulation
bps bits-per-second
BPSCS coded bits per single carrier for each spatial stream
BPSK binary phase shift keying
BSS basic service set
BSSID BSS identifier
BW bandwidth
CBPS coded bits per symbol
CBPSS coded bits per spatial stream
CBW channel bandwidth
CCA clear channel assessment
CCDF complementary cumulative distribution function
CCK complementary code keying
CFP contention free period
CP contention period
CRC cyclic redundancy code
CS carrier sense
CSD cyclic shift diversity
CSI channel state information
CSMA carrier sense multiple access
CSMA/CA carrier sense multiple access with collision avoidance
CSMA/CD carrier sense multiple access with collision detection
CTS clear to send
CW contention window
DA destination address
DAC digital-to-analog converter
dB decibels
dBc decibels relative to carrier
dBi decibels isotropic relative to an antenna
dBm decibel of measured power referenced to one milliwatt
DBPS data bits per OFDM symbol
dBr dB (relative)
DC direct current
DCF distributed coordination function
DELBA delete block acknowledgement
DIFS DCF inter-frame space
DLS direct link session
DS distribution system
DSL digital subscriber line
DSSS direct sequence spread spectrum
DTIM delivery traffic indication message
DVD digital versatile disc
EDCA enhanced distributed channel access
EIFS extended inter-frame space
ERP enhanced rate PHY
ESS extended service set
ETSI European Telecommunications Standards Institute
EVM error vector magnitude
EWC Enhanced Wireless Consortium
FCC Federal Communications Commission
FCS frame check sequence
FEC forward error correction
FFT fast Fourier transform
FHSS frequency hopped spread spectrum
FS free space
FTP file transfer protocol
GF Greenfield
GF-HT-STF Greenfield High Throughput Short Training field
GHz gigahertz
GI guard interval
GIF graphics interchange format
GPS global positioning system
HC hybrid coordinator
HCCA HCF controlled channel access
HCF hybrid coordination function
HEMM HCCA, EDCA mixed mode
HT high throughput
HTC high throughput control
HT-DATA High Throughput Data field
HT-LTF High Throughput Long Training field
HTSG High Throughput Study Group
HT-SIG High Throughput Signal field
HT-STF High Throughput Short Training field
HTTP hypertext transfer protocol
Hz Hertz
IBSS independent basic service set
IC integrated circuit
IDFT inverse discrete Fourier transform
IEEE Institute of Electrical and Electronic Engineers
IFFT inverse fast Fourier transform
IFS inter-frame space
IP Internet Protocol
IPv6 Internet Protocol version 6
IR infrared
ISI inter-symbol interference
ISM industrial, scientific, and medical
JPEG Joint Photographic Experts Group
kHz kilohertz
km/h kilometers per hour
LAN local area networking
LDPC low density parity check
LLC logical link control
L-LTF Non-HT (Legacy) Long Training field
LNA low noise amplifier
LOS line-of-sight
LSB least significant bit
L-SIG Non-HT (Legacy) Signal field
L-STF Non-HT (Legacy) Short Training field
LTF Long Training field
m meters
MAC medium access control
MAI MRQ or ASEL indication
MAN metropolitan area networking
Mbps megabit per second
MCS modulation and coding scheme
MF mixed format
MFB MCS feedback
MFSI MCS feedback sequence indication
MHz megahertz
MIB management information base
MIMO multiple-input multiple-output
ML maximum likelihood
MMPDU MAC management protocol data unit
MMSE minimum mean-square-error
MPDU MAC protocol data unit
MPEG Moving Picture Experts Group
MRC maximal-ratio combining
MRQ MCS request
Msample/s mega-samples per second
MSB most significant bit
MSDU MAC service data unit
MSE mean-square-error
MSFI MCS feedback sequence identifier
MSI MCS request sequence identifier
NAV network allocation vector
NDP null data packet
NF noise figure
NLOS non-line-of-sight
nsec nanosecond
OBO output back-off
OBSS overlapping BSS
OFDM orthogonal frequency division multiplexing
OSI open systems interconnection
PA power amplifier
PAR project authorization request
PAS power angular spectrum
PC point coordinator
PCF point coordination function
PCO phased coexistence operation
PDU protocol data unit
PER packet error rate
PHY physical layer
PIFS PCF inter-frame space
PLCP physical layer convergence procedure
PPDU PLCP protocol data unit
ppm parts per million
PSD power spectral density
PSDU PLCP service data unit
PSMP power-save multi-poll
PSMP-DTT PSMP downlink transmission time
PSMP-UTT PSMP uplink transmission time
QAM quadrature amplitude modulation
QoS quality of service
QPSK quadrature phase shift keying
R code rate
RA receiver address
RD reverse direction
RDG reverse direction grant
RF radio frequency
RIFS reduced inter-frame space
RMS root-mean-square
RSSI received signal strength indication
RTS request to send
Rx receive
SA source address
SAP service access point
SCP secure copy protocol
SDM spatial division multiplexing
SDU service data unit
SE spatial expansion
SIFS short inter-frame space
SIG Signal field
SIMO single-input, multiple-output
SISO single-input, single-output
SMTP simple mail transfer protocol
SNR signal-to-noise ratio
SOHO small-office, home-office
SS spatial stream
SSC starting sequence control
SSID service set identifier
SSN starting sequence number
STA station
STBC space-time block coding
STF Short Training field
STS space-time stream
SVD singular value decomposition
SYM symbol
TA transmitter address
TBTT target beacon transmission time
TC traffic category
TCLAS traffic classification
TCM trellis coded modulation
TCP transmission control protocol
TDD time division duplexing
TGn Task Group n
TGy Task Group y
TID traffic identifier
TIFF tagged image file format
TRQ training request
TS traffic stream
TSID traffic stream identifier
TSPEC traffic specification
TV television
Tx transmit
TxBF transmit beamforming
TXOP transmit opportunity
TXTIME transmit time
UDP user datagram protocol
USA United States of America
VoIP voice over IP
VPN virtual private network
WEP wired equivalent privacy
WFA Wi-Fi Alliance
WLAN wireless local area network
WM wireless medium
WNG SC Wireless Next Generation Standing Committee
WWiSE world wide spectral efficiency
XOR exclusive-or
ZF zero-forcing
ZIP ZIP file format

Installing Wireless Access Points in Windows

2010-03-03T13:57:00.000-08:00

We talk about both types of WPA2 in much greater detail in Chapter 9.
WPA2 Enterprise is, frankly, overkill for the home environment and much
more difficult to set up. We recommend that you use WPA2 Personal
instead — it gets you 99 percent of the way there in terms of security
and is much easier to set up and configure.
WEP keys: You should always use some security on your wireless network,
and if your network cannot support WPA, you should use, at minimum,
Wired Equivalent Privacy (WEP) encryption. Only a determined
hacker with the proper equipment and software can crack the key. If you
don’t use WEP or some other form of security, any nosy neighbor with a
laptop, wireless PC Card, and range-extender antenna may be able to see
and access your wireless home network. Whenever you use encryption,
all wireless stations in your house attached to the wireless home network
must use the same key. Sometimes the AP manufacturer assigns a
default WEP key. Always assign a new key to avoid a security breach.
Read Chapter 9 for great background info on WEP and WPA2.
WPS: Wi-Fi Protected Security works with WPA2 and makes it considerably
easier to set up WPA2 security on your network by automating the
process. As we discuss in Chapter 9, you can implement WPS in two
ways:
• PIN code: You can turn on WPA2 by simply entering a PIN code
printed on your Wi-Fi hardware (usually on a label).
• Pushbutton: You can press a button on your Wi-Fi router (a physical
button or a virtual button on a screen on the router). When the
button is pushed, your devices can automatically connect to the
router and automatically configure WPA2 in 2 minutes. Simply push
the button(s) and let things set themselves up with no further
intervention.
Username and password: Configuration software may require that you
enter a password to make changes to the AP setup. The manufacturer
may provide a default username and password (see the user documentation).
Use the default password when you first open the configuration
pages, and then immediately change the password to avoid a security
breach. (Note: This isn’t the same as the WPA2 shared key, which is also
called a password by some user interfaces.) Make sure that you use a
password you can remember and that you don’t have to write down.
Writing down a password is the same as putting a sign on the equipment
that says “Here’s how you hack into me.” If you ever lose the password,
you can always reset a device to its factory configuration and get back
to the point where you took it out of the box.
MAC address: The Media Access Control (MAC) address is the physical
address of the radio in the AP. This number is printed on a label attached
to the device. You may need to know this value for troubleshooting, so
write it down. The AP’s Ethernet (RJ-45) connection to the wired network
also has a MAC address that’s different from the MAC address of the AP’s
radio.
Dynamic or static wide area network (WAN) IP address: If your network
is connected to the Internet, it must have an IP address assigned
by your ISP. Most often, your ISP dynamically assigns this address. Your
router or Internet gateway should be configured to accept an IP address
dynamically assigned by a DHCP server. It’s possible, but unlikely, that
your ISP will require a set (static) IP address.
Local IP address: In addition to a physical address (the MAC address),
the AP also has its own network (IP) address. You need to know this IP
address to access the configuration pages by using a Web browser. Refer
to the product documentation to determine this IP address. In most cases,
the IP address is 192.168.xxx.xxx, where xxx is between 1 and 254. It’s also
possible that an AP could choose a default IP that’s in use by your cable
or DSL router (or a computer that got its IP from the cable or DSL
router’s DHCP server). Either way, if an IP conflict arises, you may have
to keep the AP and cable or DSL routers on separate networks while
configuring the AP
Subnet mask: In most cases, this value is set at the factory to
255.255.255.0. If you’re using an IP addressing scheme of the type
described in the preceding paragraph, 255.255.255.0 is the correct
number to use. This number, together with the IP address, establishes
the subnet on which this AP will reside. Network devices with addresses
on the same subnet can communicate directly without the aid of a
router. You really don’t need to understand how the numbering scheme
works except to know that the AP and all the wireless devices that will
access your wireless network must have the same subnet mask.
PPPoE: Many DSL ISPs still use Point-to-Point Protocol over Ethernet
(PPPoE). The values you need to record are the username (or user ID)
and password. The DSL provider uses PPPoE as a means of identifying and
authorizing users.

Planning Security

2010-03-03T11:26:00.000-08:00

Unless you work for the government or handle sensitive data on your computer,
you probably aren’t overly concerned about the privacy of the information
stored on your home network. Usually it’s not an issue anyway because
someone would have to break into your house to access your network. But if
you have a wireless network, the radio signals transmitted by your network
don’t automatically stop at the outside walls of your house. In fact, a neighbor
or even someone driving by on the street in front of your house can use
a computer and a wireless networking adapter to grab information right off
your computer, including deleting your files, inserting viruses, and using your
computer to send spam — unless you take steps to protect your network.
The original security technology for Wi-Fi equipment was Wired Equivalent
Privacy (WEP). Perhaps the most well-publicized aspect of Wi-Fi wireless networking
is the fact that the WEP security feature of Wi-Fi networks can be
hacked (broken into electronically). Hackers have successfully retrieved
secret WEP keys used to encrypt data on Wi-Fi networks. With these keys,
the hacker can decrypt the packets of data transmitted over a wireless network.
Since 2003, the Wi-Fi Alliance has been certifying and promoting a
replacement security technology for WEP: Wi-Fi Protected Access (WPA and
the newer but closely related WPA2). WPA/WPA2 is based on an IEEE standard
effort known as 802.11i (so many 802.11s huh?). This technology, which
makes cracking a network’s encryption key much more difficult, is standard
in most Wi-Fi access points and network adapters available now. As discussed
earlier in this chapter, in the section “Certification and Standards Support,”
look for Wi-Fi Alliance certifications for WPA equipment.
Any Wi-Fi gear that you buy should support the latest security certification —
WPA2. Don’t accept any less and don’t forget to turn on your network’s
security.
See Chapter 9 for a full discussion of how to set up basic security for your
wireless home network.
Other useful security features to look for when buying an AP include
Network Address Translation (NAT), which we discuss earlier in this
chapter
Virtual Private Network (VPN) pass-through that allows wireless network
users secure access to corporate networks
Monitoring software that logs and alerts you to computers from the
Internet attempting to access your network
Logging and blocking utilities that enable you to log content transmitted
over the network as well as to block access to given Web sites

Choosing Wireless Home Networking Equipment

2010-03-03T11:21:00.000-08:00

Access Point Selection

• WPA/WPA2 Enterprise: This business-oriented variant of WPA
provides the ability to use a special 802.1x or RADIUS server
(explained in Chapter 9) to manage users on the network. For
the vast majority of wireless home networkers, this capability is
overkill, but it doesn’t hurt to have it (any WPA/WPA2 Enterprise
certified system also supports WPA/WPA2 Personal).
Other certifications: The Wi-Fi Alliance provides a number of other specialized
certifications that not all Wi-Fi certified gear will have earned,
like the following:
• WMM: Wi-Fi Multimedia certification can be found on a growing
number of audio/video and voice Wi-Fi equipment (these items
are discussed in Chapters 12 and 13, respectively). WMM certified
equipment can provide on your wireless LAN some Quality of
Service (QoS), which can give your voice, video, or audio data
priority over other data being sent across your network. We talk
about WMM where appropriate in Chapters 12 and 13.
• WPS: Wi-Fi Protected Setup certification is increasingly common on
new equipment, but still rather new as we write this. WPS, which
we discuss in detail in Chapter 9, is a user-friendly front end to
WPA2 Personal, and allows you to set up network security simply
by pushing buttons (or entering preassigned PIN codes) on your
AP/router and network clients.
• EAP: Extensible Authentication Protocol is part of the WPA
Enterprise/802.1x system used in business wireless LANs — EAP
provides the mechanism for authenticating users (or confirming
that they are who they say they are). A number of different EAP
types can be used with WPA Enterprise — each type can be certified
by the Wi-Fi Alliance. You don’t need to worry about this
unless you’re building a WPA Enterprise security system for your
network.

Servers,Gateways, Routers, and Switches
DHCP servers
To create an easy-to-use home network, your network should have a Dynamic
Host Configuration Protocol (DHCP) server. A DHCP server dynamically assigns
an IP address to each computer or other device on your network. This function
relieves you from having to keep track of all the devices on the network and
assign addresses to each one manually.
Network addresses are necessary for the computers and other devices on
your network to communicate. Because most networks now use a set of protocols
(Transmission Control Protocol/Internet Protocol, or TCP/IP) with
network addresses (Internet Protocol, or IP, addresses), we refer to network
addresses as IP addresses in this book. In fact, the Internet uses the TCP/IP
protocols, and every computer connected to the Internet must be identified
by an IP address.

NAT and broadband routers

A wireless router is a wireless AP that enables multiple computers to share
the same IP address on the Internet. This fact would seem to be a contradiction
because every computer on the Internet needs its own IP address.
The magic that makes an Internet gateway possible is Network Address
Translation (NAT). Most access points you buy now are wireless gateways.
Vendors sometimes call these wireless routers wireless broadband routers or
perhaps wireless cable/DSL routers. What you’re looking for is the word router
somewhere in the name or description of the device itself. Stand-alone access
points (without the router functionality) usually are called just an access
point, so sometimes it’s easier to look for something not called that!
In addition to providing NAT services, the wireless routers used in home
networks also provide the DHCP service. The router communicates with
each computer or other device on your home network via private IP
addresses — the IP addresses assigned by the DHCP server. (See the section
“DHCP servers,” earlier in this chapter.) However, the router uses a single IP
address — the one assigned by your ISP’s DHCP server — in packets of data
intended for the Internet.

Switches

Wireless routers, available from nearly any manufacturer, include from one to
eight Ethernet ports with which you can connect computers or other devices
via Ethernet cables. These routers are not only wireless APs but are also wired
switches that efficiently enable all the computers on your network to communicate
either wirelessly or over Ethernet cables.
Make sure that the switch ports support at least 100BaseT Ethernet — this is
the 100 Mbps variant of Ethernet. You should also ensure that the switch
supports the full-duplex variant of 100BaseT — meaning that it supports 100
Mbps of data in both directions at the same time. If you’re looking for the ultimate
in performance, you should strongly consider paying a bit more for a
router that supports Gigabit Ethernet (1000BaseT)

Planning Security

2010-03-03T11:19:00.000-08:00

Any network can be attacked by a persistent hacker, but a well-defended network
discourages most hackers sufficiently to keep your data safe. However,
it’s easier for a hacker to gain access through the air to a wireless network
than to gain physical access to a wired network, making wireless networks,
and even home networks, more vulnerable to attack. Because a Wi-Fi signal
is a radio signal, it keeps going and going and going, like ripples in a pond,
in a weaker and weaker form until it hits something solid enough to stop it.
Anyone with a portable PC, wireless network adapter, and an external antenna
in a van driving by your house, or even a neighbor with this equipment, has a
reasonable chance of accessing your wireless network. (Such skullduggery is
known as war driving.) So, you must plan for security. We give you all the
down-and-dirty details in Chapter 9, but here are some key things to keep
in mind:

Internet security: Any Internet connection — especially always-on broadband
connections, but dial-up connections, too — can be vulnerable to
attacks arriving from the Internet. To keep your PCs safe from the bad
folks (who may be thousands of miles away), you should turn on any firewall
features available in your AP or router. Some fancier APs or routers
include a highly effective kind of firewall (a stateful packet inspection [SPI]
firewall), but even just the basic firewall provided by any NAT router can
be quite effective. You should also consider installing antivirus software
as well as personal firewall software on each PC or Mac on your network
for an extra level of protection.
Airlink security: This is a special need of a wireless home network. Wired
networks can be made secure by what’s known as physical security. That
is, you literally lock your doors and windows, and no one can plug into
your wired network. In the wireless world, physical security is impossible
(you can’t wrangle those radio waves and keep them in the house), so
you need to implement airlink security. You can’t keep the radio waves
from getting out of the house, but you can make it hard for someone to
do anything with them (like read the data they contain). Similarly, you
can use airlink security to keep others from getting onto your access
point and freeloading on your Internet connection. The primary means
of providing airlink security — and advances are on the way — is called
WPA2 (Wi-Fi Protected Access). You absolutely should use WPA2

Choosing a wireless technology

2010-03-03T11:13:00.002-08:00

After you know what you’re networking and what will be on your wireless network,
you have to decide how to network wirelessly. As we discuss extensively
in Chapter 2, four main variants of wireless networking technologies
exist: 802.11a, 802.11b, 802.11g and 802.11n (draft standard).
Collectively, all these technologies are usually referred to as Wi-Fi, which isn’t
a generic term, but, rather, refers to a certification of interoperability. The
folks at the Wi-Fi Alliance (www.wi-fi.org) do extensive testing of new wireless
gear to make sure that it works seamlessly with wireless equipment from different
manufacturers. When it works, it gets the Wi-Fi logo on the box, so you
can rest assured that it works in your network.

Wi-Fi certified gear works together — as long as it’s of a compatible type. That
means that any 802.11b, 802.11g, or 802.11n Wi-Fi certified gear works with
any other equipment of that type; similarly, any 802.11a Wi-Fi certified gear
works with any other 802.11a and 5 GHz capable 802.11n gear that has been
certified. (Note that not all 802.11n gear is 5 GHz capable — if a particular
piece of equipment supports this, it will say so and will also be 802.11a certified.)
802.11b and g gear does not work with 802.11a gear, even if it has all
been certified because they work on different radio frequencies and cannot
communicate with each other.
The discussion of wireless technology quickly degenerates into a sea of
acronyms and technospeak. If you need a refresher on this alphabet soup —
or to begin from square one — Chapter 2 is a primer on jargon, abbreviations,
and other nuts-and-bolts issues.
For home users, the three most important practical differences between
802.11a, 802.11b, 802.11g, and 802.11n networks are speed, price, and
compatibility.

802.11b is an older standard that is no longer used these days. You would
be hard pressed to find any 802.11b in your network, and only if you have
been buying legacy equipment at flea markets or electronic junk yards.
802.11g equipment has been the standard in use for a few years. Thanks
to its proliferation, it’s inexpensive but at least four times faster than
802.11b.
802.11a can still be found in some special-use corporate environments,
but it’s no longer used in the home. It is as fast as 802.11g, costs much
more, and has a shorter range.
802.11n is five times faster than 802.11a and 802.11g and is 22 times
faster than 802.11b.
802.11a and 802.11b are not compatible.
802.11a and 802.11g are not compatible.
802.11b and 802.11g are compatible.
802.11n is compatible with all other standards but at the cost of its
higher speed — when you add 802.11a, b, or g gear to an 802.11n network,
you slow down the ultimate throughput or speed of that network.
The 802.11n standard is compatible with all other standards, but not all 802.11n
equipment supports both the 2.4 GHz (802.11b and g) and 5 GHz (802.11a) frequencies
— many support only 2.4 GHz. An AP that includes 802.11n should
work with any other device as well (though not always at the higher 248 Mbps
speed of 802.11n). Thus, you don’t have to look for a multimode AP.
If your primary reason for networking the computers in your house is to
enable Internet sharing, 802.11g is more than fast enough because your
Internet connection probably won’t exceed the 54 Mbps of the 802.11g connection
any time soon — unless you’re one of the lucky few who lives where
fiber-optic Internet services (such as Verizon’s FiOS service) are installed.
Despite the fact that most Internet services are slower than 802.11g, we don’t
recommend that you buy only 802.11g gear. 802.11g is being superseded by
802.11n with full 802.11g compatibility. In fact, you would save only a few
bucks by buying 802.11g gear new. The speed, range, and compatibility of
802.11n are more than worth the increased price tag.
802.11g is the minimum standard around which you should build your network.
If you want to hedge your bets, look for an 802.11n AP that can handle all Wi-
Fi technology standards. Apple, Belkin, NETGEAR, D-Link, and several other
leading manufacturers of wireless home networking equipment already offer
802.11n wireless devices.

Choosing wired or wireless

2010-03-03T11:13:00.001-08:00

After you know what you’re networking, you need to choose how to network
it. By that, we mean that you have to decide what to connect to your home’s
network with wires and what you should use wireless networking for. At first
glance, this decision may seem obvious. You would expect us to always recommend
using wireless because this book talks about wireless networks;
however, using both wired and wireless connections can sometimes make
the most sense.
Wireless network devices and wired network devices can be used on the same
network. Both talk to the network and to each other by using a protocol
known as Ethernet. (You should be getting used to that term by now if you
have been reading from the beginning of the book. If not, read through
Chapters 1 and 2 for more information about networking technology.)
The obvious and primary benefit of connecting to a network wirelessly is that
you eliminate wires running all over the place. But, if two devices are sitting
on the same desk or table — or are within a few feet of each other — connecting
them wirelessly may be pointless. You can get Ethernet cables for $5 or
less; an equivalent wireless capability for two devices may top $100 when
everything is said and done. Keep in mind, however, that your computer
must have a wired network adapter installed to be able to make a wired connection
to the network. Fortunately, wired network adapters are dirt cheap
these days. Virtually all new computers come with one installed as a standard
feature (at no additional charge).

Wi-Fi versus Bluetooth

2010-03-03T11:07:00.000-08:00

Wi-Fi and Bluetooth are designed to coexist in the network, and although
they certainly have overlapping applications, each has its distinct zones
of advantage.
The biggest differences between Wi-Fi and Bluetooth are
Distance: Bluetooth is lower powered, which means that its signal can
go only short distances (up to 10 meters, or a bit more than 30 feet).
802.11 technologies can cover your home, and in some cases more,
depending on the antenna you use. Some Bluetooth devices operate
under a high-powered scheme (called Class 1 Bluetooth devices), which
can reach up to 100 meters. Most home Bluetooth devices don’t have
this kind of range, mainly because they’re designed to be battery powered,
and the shorter Class 2 range of 10 meters provides a better tradeoff
between battery life and range.
Speed: The latest versions of Wi-Fi can carry data at rates in the hundreds
of megabits per second; the fastest existing Bluetooth implementations
have a maximum data rate of 3 Mbps. So think of Wi-Fi as a networking
technology that can handle high-speed transfers of the biggest files, and
Bluetooth as something designed for lower speed connections (such as
carrying voice or audio signals) or for the transfer or synchronization of
smaller chunks of data (such as transferring pictures from a camera
phone to a PC).
Application: Bluetooth is designed as a replacement for cables: that is, to
get rid of that huge tangle of cables that link your mouse, printer, monitor,
scanner, and other devices on your desk and around your home. In fact,
the first Bluetooth device was a Bluetooth headset, which eliminated that
annoying cable to the telephone that got in the way of typing. Many new
cars are also outfitted with Bluetooth so that you can use your cell phone
in your car, with your car’s stereo speakers and an onboard microphone
serving as your hands-free capability. Pretty neat, huh?
Wi-Fi (802.11a/b/g/n) and Bluetooth are similar in certain respects: They both
enable wireless communication between electronic devices, but they are
more complementary than direct competitors. Wi-Fi technology is most often
used to create a wireless network of personal computers that can be located
anywhere in a home or business. Bluetooth devices usually communicate
with other Bluetooth devices in relatively close proximity.
The easiest way to distinguish Wi-Fi from Bluetooth is to focus on what each
one replaces:
Wi-Fi is wireless Ethernet: Wi-Fi is a wireless version of the Ethernet
communication protocol and is intended to replace networking cable
that would otherwise be run through walls and ceilings to connect
computers in multiple rooms or even on multiple floors of a building.
Bluetooth replaces peripheral cables: Bluetooth wireless technology
operates at short distances — usually about 10 meters — and most
often replaces cables that connect peripheral devices such as a printer,
keyboard, mouse, or personal digital assistant (PDA) to your computer.
Bluetooth replaces IrDA: Bluetooth can also be used to replace another
wireless technology — Infrared Data Association (IrDA) wireless technology
— that’s already found in most laptop computers, PDAs, and even
many printers. Although IR signals are secure and aren’t bothered with
radio frequency (RF) interference, IrDA’s usefulness is hindered by
infrared’s requirement for line-of-sight proximity of devices. Just like the
way your TV’s remote control must be pointed directly at your TV to
work, the infrared ports on two PDAs must be lined up to trade data,
and your laptop has to be “pointing” at the printer to print over the
infrared connection. Because Bluetooth uses radio waves rather than
light waves, line-of-sight proximity isn’t required.
Like Wi-Fi, Bluetooth can offer wireless access to LANs, including Internet
access. Bluetooth devices can potentially access the Public Switched Telephone
Network (PSTN: you know, the phone system) and mobile telephone networks.
Bluetooth is able to thrive alongside Wi-Fi by making possible such innovative
solutions as a hands-free mobile phone headset, print-to-fax, and automatic
PDA, laptop, and cell phone/address book synchronization.

Understanding Wi-Fi channels

2010-03-03T11:04:00.000-08:00

Now for a little talk about frequency bands used
by the various Wi-Fi standards. In 1985, the FCC
made changes to the radio spectrum regulation
and assigned three bands designated as the
industrial, scientific, and medical (ISM) bands.
These frequency bands are
902 MHz–928 MHz: A 26 MHz bandwidth
2.4 GHz–2.4835 GHz: An 83.5 MHz bandwidth
5.15–5.35 GHz and 5.725 GHz–5.825 GHz: A
300 MHz bandwidth
The FCC also opened some additional frequencies,
known as Unlicensed National Information
Infrastructure (U-NII), in the lower reaches of
the five GHz frequencies.
The purpose of the FCC change was to encourage
the development and use of wireless networking
technology. The new regulation
permits a user to operate, within certain guidelines,
radio equipment that transmits a signal
within each of these three ISM bands without
obtaining an FCC license.
Wireless networks use radio waves to send
data around the network. 802.11a uses part of
the U-NII frequencies, and IEEE 802.11b and g
use the ISM 2.4 GHz band. 802.11n can use
either band, though not all 802.11n systems do
(many use only the 2.4 GHz band).
An important concept when talking about frequencies
is the idea of overlapping and
nonoverlapping channels. As we discuss in
Chapter 18, signals from other APs can cause
interference and poor performance of your
wireless network. This happens specifically
when the APs’ signals are transmitting on the
same (or sometimes nearby) channels. Recall
that the standards call for a number of channels
within a specified frequency range.
The frequency range of 802.11g, for example, is
between 2.4 GHz and 2.4835 GHz, and it’s broken
up into fourteen equal-sized channels. (Only
eleven can be used in the United States — any
equipment sold for use here allows you to
access only these eleven channels.) The problem
is that these channels are defined in such a
way that many of the channels overlap with one
another — and with 802.11g, there are only
three nonoverlapping channels. Thus, you
wouldn’t want to have channels 10 and 11 operating
side by side because you would get signal
degradation. You want noninterfering, nonoverlapping
channels. So you find that people tend
to use Channels 1, 6, and 11, or something similar.
802.11a doesn’t have this problem because
its eight channels, in the 5 GHz frequency band,
don’t overlap; therefore, you can use contiguous
channels. As with 802.11b and g, however,
you don’t want to be on the same channel.

Wireless Networking Fundamentals

2010-03-03T11:02:00.000-08:00

Transmission Control Protocol/Internet Protocol (TCP/IP) is the most common
protocol for transmitting packets around a network. Every computer on a
TCP/IP network must have its own IP address, which is a 32-bit numeric
address that’s written as four groups of numbers separated by periods
(for example, 192.168.1.100). Each number of these four sets of numbers is
known as an octet, which can have a value from 0 to 255. The Internet transmits
packets by using the TCP/IP protocol. When you use the Internet, the
Internet service provider (ISP) — such as AOL, EarthLink, or your cable or
DSL provider — assigns a unique TCP/IP number to your computer. For the
period that your computer is connected, your computer “leases” this unique
address and uses it like a postal address to send and receive information
over the Internet to and from other computers.
A router with the Network Address Translation (NAT) feature also helps to
protect the data on your computers from intruders. The NAT feature acts as
a protection because it hides the real network addresses of networked computers
from computers outside the network. Many WAN routers also have
additional security features that more actively prevent intruders from gaining
unauthorized access to your network through the Internet. This type of protection
is sometimes described generically as a firewall. Good firewall software
usually offers a suite of tools that not only block unauthorized access
but also help you to detect and monitor suspicious computer activity. In
addition, these tools provide you with ways to safely permit computers on
your network to access the Internet.

Internet gateways

These days, you can get a device that really does it all: a wireless Internet gateway.
These devices combine all the features of an access point, a router, and
a broadband modem (typically, cable or DSL, but this could also be a fiberoptic
connection such as Verizon’s FiOS or even another wireless connection).
Some wireless Internet gateways even include a print server (which
enables you to connect a printer directly to the gateway and use it from any
networked PC), a dial-up modem, and even some Ethernet ports for computers
and devices that connect to your network with wires.
For example, the Motorola Netopia MiAVo Series Gateways (www.netopia.com)
include a built-in DSL modem, a router, a wireless access point, and other networking
features such as a firewall and an easy-to-use graphical user interface
(GUI) for configuring and setting up the gateway.
Not many of these devices are on the market; you can’t buy many of them offthe-
shelf, but you can get them directly from your broadband service provider.
The term gateway gets used a lot by different folks with different ideas about
what such a device is. Although our definition is the most common (and, in
our opinion, correct), you may see some vendors selling devices that they
call Internet gateways that don’t have all the functions we describe.

Network infrastructure

2010-03-03T10:58:00.000-08:00

Workstations must be electronically interconnected to communicate. The
equipment over which the network traffic (electronic signals) travels
between computers on the network is the network infrastructure.

Network hubs

In a typical office network, a strand of wiring similar to phone cable is run
from each computer to a central location, such as a phone closet, where each
wire is connected to a network hub. The network hub, similar conceptually
to the hub of a wheel, receives signals transmitted by each computer on the
network and sends the signals out to all other computers on the network.
Figure 2-1 illustrates a network with a star-shaped topology (the physical
design of a network). Other network topologies include ring and bus. Home
networks typically use a star topology because it’s the simplest to install and
troubleshoot.

Bridges

A network bridge provides a pathway for network traffic between networks or
segments of networks. A device that connects a wireless network segment to
a wired network segment is a type of network bridge. In larger networks, network
bridges are sometimes used to connect networks on different floors in
the same building or in different buildings. In a wireless home network, the
device that manages the wireless network, the access point, often acts as a
bridge between a wireless segment of the network and a wired segment.
Hubs and switches
Networks transmit data in bundles called packets. Along with the raw information
being transmitted, each packet also contains the network address of
the computer that sent it and the network address of the recipient computer.
Network hubs send packets indiscriminately to all ports of all computers connected
to the hub — which is why you don’t see them much any longer.
A special type of hub called a switched hub examines each packet, determines
the addressee and port, and forwards the packet only to the computer and
port to which it is addressed. Most often, switched hubs are just called
switches. A switch reads the addressee information in each packet and sends
the packet directly to the segment of the network to which the addressee is
connected. Packets that aren’t addressed to a particular network segment are
never transmitted over that segment, and the switch acts as a filter to eliminate
unnecessary network traffic. Switches make more efficient use of the
available transmission bandwidth than standard hubs, and therefore offer
higher aggregate throughput to the devices on the switched network.

Routers

Over a large network and on the Internet, a router is analogous to a superefficient
postal service — it reads the addressee information in each data packet
and communicates with other routers over the network or Internet to determine
the best route for each packet to take. In the home, a home or broadband
router uses a capability called Network Address Translation (NAT) to enable all
the computers on a home network to share a single Internet address on the
cable or DSL network. The home router sits between your broadband modem
and all the computers and networked devices in your house, and directs traffic
to and from devices both within the network and out on the Internet.
So, the local area network in your home connects to the wide area network,
which takes signals out of the home and on to the Internet.

Signal Loss for Obstacle Types

2010-03-01T03:31:00.001-08:00

Appendix E. Signal Loss for Obstacle Types

Obstruction	Additional Loss (dB)	Effective Range
Open space	0	100%
Window (nonmetallic tint)	3	70%
Window (metallic tint)	5–8	50%
Light wall (drywall)	5–8	50%
Medium wall (wood)	10	30%
Heavy wall (15 cm solid core)	15–20	15%
Very heavy wall (30 cm solid core)	20–25	10%
Floor/ceiling (solid core)	15–20	15%
Floor/ceiling (heavy solid core)	20–25	10%

Appendix B. 802.11 Wireless Equipment

2010-03-01T03:29:00.000-08:00

Table B.1. 802.11b Client Adapters
Card Name	Interface Type(s)	Power	Antenna Connector	Chipset
1stWave Wavemaxxpro	PCMCIA	100 mW	None	Prism
Actiontec HWC01170-01	PCMCIA	—	None	Prism 3
3com AirConnect	PCMCIA	30 mW	Dual Lucent	Prism 2.5
AddtronCard	PCMCIA	30 mw	None	IntersilPrism
Belkin F5d6020	PCMCIA	50 mW	None	Prism 2
Belkin F5d6020 Ver.2	PCMCIA 16	50 mW	Yes	Atmel AT76C50A
Buffalo Technology	PCMCIA	30 mw	—	IntersilPrism w/Aironet MAC controller
Demarc ReliaWave 200mW	PCMCIA	200 mW	RP-MMCX	Prism 2.5
Demarc ReliaWave 100mW	PCMCIA	100 mW	RP-MMCX	Prism 2.5
smartBridges airCard	Wireless PCMCIA	50 mW	Yes
Deliberant WEC-100	Ethernet client/bridge	100 mW	No	Prism 2.5
Dell TrueMobile 1150	PCMCIA/MiniPCI	30 mW	Same as Orinoco	Hermes
DlinkDwl520	PCI	32 mW	Reverse SMA	IntersilPrism 2.5
DlinkDwl520plus	PCI	32 mW	Reverse SMA	TI ncx100
DlinkDwl650Plus	CardBus	—	—	TI Chipset
DlinkDwl660	PCI	—	—	TI Chipset
Engenius	See entry for Senao	—	—	—
FarallonSkyLink PC-Card	N/A	—	Unknown	IntersilPrism
IBM High Rate Wireless LAN Card	PCMCIA/ISA (with adapter)	30 mW	Lucent proprietary connector	Hermes
InTalkNokiaCard	PCMCIA/ISA	—	—	—
Intel2011Card	PCMCIA/PCI	30 mW	None	IntersilPrism
LinksysCard WPC11	16-bit PCMCIA	95 mW	No	IntersilPrism
Linksys WPC11	PCMCIA 16	16 mW	No	Prism 2.0
Linksys WPC11 v2.5	PCMCIA 16	40 mW	No	Prism 2.5
Linksys WPC11 v3.0	PCMCIA 16	40 mW	No	Prism 3.0
Linksys WMP11	PCI	35 mW	Reverse SMA connector	Prism 2.5
LinksysWET11	Ethernet bridge/client	80 mW	Reverse SMA connector	Prism
Lucent / Orinoco Gold (Agere)	PCMCIA	30 mW	MC Card	Hermes
Lucent / Orinoco Silver (Agere)	PCMCIA	30 mW	MC Card	Hermes
Lucent WaveACCESS PC24E-H-ET-L	PCMCIA	6 mW	Same as Lucent wireless card	Hermes
NetGate 2511CD PLUS EXT2	PCMCIA	200 mW	2x MMCX external antenna jacks	Prism 2.5
NetGate 2511CD PLUS	PCMCIA	200 mW	No	Prism 2.5
NetGate 2511MP PLUS	Mini PCI	150 mW	2x MMCX antenna jacks	Prism 2.5
NetGear MA101	USB1.1	30 mW	SMA Mod	Atmel AT76C50A
NetGear MA301	PCI	—	—	—
NetGear MA311GE	PCI	—	Yes	IntersilPrism 2.5
Netgear MA401	PCMCIA	59 mW	None	Linux
NetWaveCard	—	—	—	—
Nortel Emobility 4121	PCMCIA	100 mW	None	SymbolSpectru
Nortel Emobility 4123	PCI	100 mW	Dual MMCX	SymbolSpectru
Proxim RangeLan-DS 8434-05	16-bit PCMCIA	30 mW	Reverse MMCX	IntersilPrism 2
Proxim RangeLan-DS 8433-05	16-bit PCMCIA	30 mW	Unknown (SSM-?)	IntersilPrism 2
SamsungCard	PCMCIA/ISA	—	—	IntersilPrism
Senao/Engenius L-2511 Plus EXT2	PCMCIA Type II 16-bit	250 mW max	Dual female MMCX	Prism 2.5
Senao/Engenius NL-2511 Plus	PCMCIA Type II 16-bit	250 mW max	Internal diversity antenna	Prism 2.5
SMC2602W	PCI	—	—	IntersilPrism
SMC 2532W-B 200mW	PCMCIA	200 mW	RP-MMCX-?	Prism 2.5
SMC2632W	PCMCIA	50 mW	None	IntersilPrism
Sony PCWA-C100	16-bit PCMCIA	—	MC-Card	Hermes
Symbol Spectrum 24	Compact Flash Type 1	100 mW	None	—
SymbolWireless Networked 4111	PCMCIA	100 mW	Dual MMCX	IntersilPrism 2
SymbolWireless Networked 4121	PCMCIA	100 mW	—	—
SymbolWireless Networked 4123	PCI	100 mW	Dual MMCX	IntersilPrism 2
ToshibaWireless	PCMCIA	30 mW	MC-Card (Radiall)	—
Trendware TEW-201PC	PCMCIA	—	—	—
Trendware TEW-221PC	PCMCIA	—	Yes	ADMTek ADM8211
Trendware TEW-301PC	PCMCIA	—	None	—
U.S. Robotics 2410	PCMCIA	30 mW	None	Prism 2
U.S. Robotics 2415	PCI	30 mW	None	Prism 2
Wave2Net by Ambicom (WL1100B, etc.)	PCMCIA/PCI	50 mW	None	Prism 2
YdiCard	PCMCIA	—	—	—
XircomSwe	Springboard	30 mW	None	—
ZoomAirCard	PCMCIA/ISA	—	—	—
ZoomAirCard	PCMCIA/PCI	25 mW	4105 with PCI Bridge Card (Elan with TI1440 chip)
ZcomaxCards xi325H/xi626	PCMCIA/PCI	100 mW xi325H1 is the 200mW version		Prism 2
ZcomaxCards xi325HP	PCMCIA	200 mW	—	IPrism 2.5

Table B.2. 802.11a Client Adapters
Manufacturer/Model	Bus Type	Transmit Power	External Antenna Connector	Chipset
Proxim	Cardbus	40 mW /200 mW	None	Atheros AR5000
Intel	Cardbus	40 mW /200 mW	—	Atheros AR5000
SMC2735	Cardbus	40 mW /200 mW	None	Atheros AR5000
NetGear	Cardbus	—	—	—

Table B.3. Prism-Based Cards
Manufacturer/ Model	Bus Type	Connector	Rx	Tx
Addtron	PCMCIA	—	–76 dBm	>13 dBm
Addtron	PCMCIA	—	—	—
Allnet	PCI	SMA	—	—
Asanté	PCMCIA	—	—	13 dBm
Asus	Compact Flash	None	—	12–15 dBm
Belkin	PCMCIA	—	—	13–20 dBm (50 mW max)
Belkin	PCI	Reverse SMA	—	—
Compaq	PCMCIA	None	—	20 mW typ. / 100 mW max
Compaq	PCI	Reverse threaded SMA	—	20 dBm max
CellVision	—	—	—	—
Demarc	PCMCIA	Diversity RP-MMCX	-91 dB	100 mW or 20 dBm
Demarc	PCMCIA	Diversity RP-MMCX	–91 dB	200 mW or 23 dBm
D-Link	PCI	Reverse SMA	—	—
D-Link	PCMCIA	Yes, with nice switch	—	—
D-Link	PCMCIA	Hackable	–78 or –84 dBm	14 or 17 dBm
D-Link	Compact Flash	Lid snaps off/has socket	–80 to –88 dBm	14 or 18 dBm
Linksys	PCMCIA	—	—	14 dBm
Linksys	PCI	RP-SMA	—	16 dBm
Musenki	PCI	Reverse SMC	–87 dBm	18 dBm
Musenki	PCMCIA	Dual MMCX	–89 dBm	23 dBm (200 mW)
Proxim	PCMCIA	Dual reverse MMCX	–83 dBm	13 dBm
Proxim	PCMCIA	Single unknown connector (SSMB?)	–83 dBm	13 dBm
SMC	PCMCIA	Dual (RP?)-MMCX	–89 dBm	200 mW max (23 dBm)
SMC	PCMCIA	Hackable	–76 dBm	50 mW max (17 dBm)
SMC	PCI	Unknown but strange solder pads on PCI card	–76 dBm	50 mW max (17 dBm)
Teletronics	PCMCIA	Dual reverse MMCX	–83 dBm	15 dBm
Zcomax	PCMCIA	Dual reverse MMCX	–83 dBm	13 dBm
Zcomax	PCMCIA	None	–83 dBm	13 dBm
Zcomax	PCMCIA	Dual MMCX (probably reverse)	—	—
Zcomax	PCMCIA	Dual reverse MMCX	–85 dBm	15 dBm
Zcomax	PCMCIA	Dual reverse MMCX	–83 dBm	100 mW
Zcomax	PCMCIA	Dual reverse MMCX	—	180 mW
ZoomAir	PCMCIA	RP-SMA	—	14 dBm

Appendix A. Decibel–Watts Conversion Table

2010-03-01T03:28:00.001-08:00

(dBm)	(mW)	(dBm)	(mW)	(dBm)	(mW)	(dBm)	(W)	(dBm)	(W)	(dBm)	(W)
-50.0	0.00001	-7.4	0.185	-2.7	0.535	23.0	0.200	36.9	4.90	45.1	32.0
-43.0	0.00005	-7.2	0.190	-2.0	0.635	24.0	0.250	37.0	5.00	45.2	33.0
-40.0	0.00010	-7.1	0.195	-1.3	0.735	24.8	0.300	37.2	5.20	45.3	34.0
-38.2	0.00015	-7.0	0.200	-0.8	0.835	25.4	0.350	37.3	5.40	45.4	35.0
-37.0	0.00020	-6.9	0.205	-0.3	0.935	26.0	0.400	37.5	5.60	45.6	36.0
-36.0	0.00025	-6.8	0.210	0.0	1.000	26.5	0.450	37.6	5.80	45.7	37.0
-33.0	0.00050	-6.7	0.215	3.0	2.000	27.0	0.500	37.8	6.00	45.8	38.0
-31.2	0.00075	-6.6	0.220	4.8	3.000	27.4	0.550	37.9	6.20	45.9	39.0
-30.0	0.00100	-6.5	0.225	6.0	4.000	27.8	0.600	38.1	6.40	46.0	40.0
-29.0	0.00125	-6.4	0.230	7.0	5.000	28.1	0.650	38.2	6.60	46.1	41.0
-28.2	0.00150	-6.3	0.235	7.8	6.000	28.5	0.700	38.3	6.80	46.2	42.0
-27.6	0.00175	-6.2	0.240	8.5	7.000	28.8	0.750	38.5	7.00	46.3	43.0
-27.0	0.00200	-6.1	0.245	9.0	8.000	29.0	0.800	38.6	7.20	46.4	44.0
-26.5	0.00225	-6.0	0.250	9.5	9.000	29.3	0.850	38.7	7.40	46.5	45.0
-26.0	0.00250	-5.9	0.255	10.0	10.00	29.5	0.900	38.8	7.60	46.6	46.0
-25.6	0.00275	-5.9	0.260	10.4	11.00	29.8	0.950	38.9	7.80	46.7	47.0
-25.2	0.00300	-5.8	0.265	10.8	12.00	30.0	1.000	39.0	8.00	46.8	48.0
-24.9	0.00325	-5.7	0.270	11.1	13.00	30.2	1.050	39.1	8.20	46.9	49.0
-24.6	0.00350	-5.6	0.275	11.5	14.00	30.4	1.100	39.2	8.40	47.0	50.0
-24.3	0.00375	-5.5	0.280	11.8	15.00	30.6	1.150	39.3	8.60	47.4	55.0
-24.0	0.00400	-5.5	0.285	12.0	16.00	30.8	1.200	39.4	8.80	47.8	60.0
-23.7	0.00425	-5.4	0.290	12.3	17.00	31.0	1.250	39.5	9.00	48.1	65.0
-23.5	0.00450	-5.3	0.295	12.6	18.00	31.1	1.300	39.6	9.20	48.5	70.0
-23.2	0.00475	-5.2	0.300	12.8	19.00	31.3	1.350	39.7	9.40	48.8	75.0
-23.0	0.00500	-5.2	0.305	13.0	20.00	31.5	1.400	39.8	9.60	49.0	80.0
-22.8	0.00525	-5.1	0.310	13.2	21.00	31.6	1.450	39.9	9.80	49.3	85.0
-22.6	0.00550	-5.0	0.315	13.4	22.00	31.8	1.500	40.0	10.00	49.5	90.0
-22.4	0.00575	-4.9	0.320	13.6	23.00	31.9	1.550	40.2	10.50	49.8	95.0
-22.2	0.00600	-4.9	0.325	13.8	24.00	32.0	1.600	40.4	11.00	50.0	100.0
-22.0	0.00625	-4.8	0.330	14.0	25.00	32.2	1.650	40.6	11.50	51.0	125.0
-21.9	0.00650	-4.7	0.335	14.1	26.00	32.3	1.700	40.8	12.00	51.8	150.0
-21.7	0.00675	-4.7	0.340	14.3	27.00	32.4	1.750	41.0	12.50	52.4	175.0
-21.5	0.00700	-4.6	0.345	14.5	28.00	32.6	1.800	41.1	13.00	53.0	200.0
-21.4	0.00725	-4.6	0.350	14.6	29.00	32.7	1.850	41.3	13.50	53.5	225.0
-21.2	0.00750	-4.5	0.355	14.8	30.00	32.8	1.900	41.5	14.00	54.0	250.0
-21.1	0.00775	-4.4	0.360	14.9	31.00	32.9	1.950	41.6	14.50	54.4	275.0
-21.0	0.00800	-4.4	0.365	15.0	31.50	33.0	2.000	41.8	15.00	54.8	300.0
-20.8	0.00825	-4.3	0.370	15.1	32.00	33.1	2.050	41.9	15.50	55.1	325.0
-20.7	0.00850	-4.3	0.375	15.4	35.00	33.2	2.100	42.0	16.00	55.4	350.0
-20.6	0.00875	-4.2	0.380	16.0	40.00	33.3	2.150	42.2	16.50	55.7	375.0
-20.5	0.00900	-4.1	0.385	16.5	45.00	33.4	2.200	42.3	17.00	56.0	400.0
-20.3	0.00925	-4.1	0.390	17.0	50.00	33.5	2.250	42.4	17.50	56.3	425.0
-20.2	0.00950	-4.0	0.395	17.4	55.00	33.6	2.300	42.6	18.00	56.5	450.0
-20.1	0.00975	-4.0	0.400	17.8	60.00	33.7	2.350	42.7	18.50	56.8	475.0
-20.0	0.0100	-3.9	0.405	18.1	65.00	33.8	2.400	42.8	19.00	57.0	500.0
-17.0	0.0200	-3.9	0.410	18.5	70.00	33.9	2.450	42.9	19.50	57.4	550.0
-15.2	0.0300	-3.8	0.415	18.8	75.00	34.0	2.500	43.0	20.00	57.8	600.0
-14.0	0.0400	-3.8	0.420	19.0	80.00	34.1	2.600	43.1	20.50	58.1	650.0
-13.0	0.0500	-3.7	0.425	19.3	85.00	34.3	2.700	43.2	21.00	58.5	700.0
-12.2	0.0600	-3.7	0.430	19.5	90.00	34.5	2.800	43.3	21.50	58.8	750.0
-11.5	0.0700	-3.6	0.435	19.8	95.00	34.6	2.900	43.4	22.00	59.0	800.0
-11.0	0.0800	-3.6	0.440	20.0	100.0	34.8	3.000	43.5	22.50	59.3	850.0
-10.5	0.0900	-3.5	0.445	20.2	105.0	34.9	3.100	43.6	23.00	59.5	900.0
-10.0	0.1000	-3.5	0.450	20.4	110.0	35.1	3.200	43.7	23.50	59.8	950.0
-9.8	0.1050	-3.4	0.455	20.6	115.0	35.2	3.300	43.8	24.00	60.0	1000.0
-9.6	0.1100	-3.4	0.460	20.8	120.0	35.3	3.400	43.9	24.50	61.8	1500.0
-9.4	0.1150	-3.3	0.465	21.0	125.0	35.4	3.500	44.0	25.00	63.0	2000.0
-9.2	0.1200	-3.3	0.470	21.1	130.0	35.6	3.600	44.1	25.50	64.0	2500.0
-9.0	0.1250	-3.2	0.475	21.3	135.0	35.7	3.700	44.1	26.00	64.8	3000.0
-8.9	0.1300	-3.2	0.480	21.5	140.0	35.8	3.800	44.2	26.50	65.4	3500.0
-8.7	0.1350	-3.1	0.485	21.6	145.0	35.9	3.900	44.3	27.00	66.0	4000.0
-8.5	0.1400	-3.1	0.490	21.8	150.0	36.0	4.000	44.4	27.50	66.5	4500.0
-8.4	0.1450	-3.1	0.495	21.9	155.0	36.1	4.100	44.5	28.00	67.0	5000.0
-8.2	0.1500	-3.0	0.500	22.0	160.0	36.2	4.200	44.5	28.50	67.4	5500.0
-8.1	0.1550	-3.0	0.505	22.2	165.0	36.3	4.300	44.6	29.00	67.8	6000.0
-8.0	0.1600	-2.9	0.510	22.3	170.0	36.4	4.400	44.7	29.50	68.1	6500.0
-7.8	0.1650	-2.9	0.515	22.4	175.0	36.5	4.500	44.8	30.00	68.5	7000.0
-7.7	0.1700	-2.8	0.520	22.6	180.0	36.6	4.600	44.8	30.50	68.8	7500.0
-7.6	0.1750	-2.8	0.525	22.7	185.0	36.7	4.700	44.9	31.00	69.0	8000.0
-7.4	0.1800	-2.8	0.530	22.8	190.0	36.8	4.800	45.0	31.50	70.0	10000.0

Counterintelligence: Wireless IDS Systems

2010-03-01T03:27:00.002-08:00

"Assess opponents conditions, observe what they do, and you can find out their plans and measures. "

Intrusion detection systems (IDSs) are divided into two major categories: signature-based and knowledge-based.

Signature-based IDSs are the most common and easy to implement, but they are also the easiest to bypass and lack the capability to detect novel attacks. These IDSs compare events on the network to signs of known attacks called attack signatures. If a hacking tool is modified to alter some part of its attack signature, the attack is likely to go unmentioned. Besides, the attack signatures database has to be well secured and frequently updated.

Knowledge-based IDSs monitor the network, collect statistics about standard network behavior, detect possible deviations, and flag them as suspicious. For these reasons, knowledge-based IDSs are also called behavior-based or statistical. Proper network baselining is essential for efficient statistical IDS operations. Although knowledge-based IDSs are not easily fooled, their main problems are false positives and difficulties detecting some covert channel communications. The possibility of false-alarm generation is particularly worrisome on wireless networks due to the unreliable nature of the Layer 1 medium. Also, attacks launched at the early stage of the baselining period can severely interfere with the IDS learning process, making deployment of a knowledge-based IDS on a production network a somewhat risky task. What if the "normal" behavior of the network is already altered by a cracker at the moment of IDS deployment?

We believe that a proper wireless IDS should belong to both categories simultaneously. Few wireless attack tools have specific attack signatures, as discussed in this chapter. The signatures that do exist can be matched against the database of known attack traces to trigger the alarm. However, many wireless attacks do not generate specific signatures, but instead cause a deviation from the standard network operation on lower network layers. This deviation can be as subtle as few wireless frames coming out of sequence or as straightforward as tripled bandwidth consumption on the WLAN. Detecting wireless network behavior abnormalities is not an easy task, because no two wireless networks are the same. A similar principle applies to the wired LANs, but wired networks do not suffer from radio interference, signal refraction, reflection, and scattering issues. They do not have roaming users and stretch CAT 5 cables out of the office window to give access to the potential attackers on streets. Thus, the key to efficient intrusion detection on WLANs is detailed network baselining over a significant time period.

Only by collecting a large number of statistics about the particular WLAN behavior is it possible to determine what constitutes abnormal behavior and what doesn't, and to distinguish connectivity problems, user errors, and malicious attacks. Multiple 802.1x/LEAP authentication requests might constitute a brute-forcing attempt. At the same time, it could be a user guessing his or her forgotten password, or a badly written supplicant application that attempts to log in until the correct password is entered. An increased number of beacon frames per second might signal a DoS attack or rogue access point presence, but it could also be a faulty or misconfigured access point. Higher layer IDS alarm-triggering events, such as a large number of fragmented packets or abundant TCP SYN requests, can indicate a possible portscan or DoS attack, but might also be a result of a Layer 1 connectivity problem on a WLAN. Fire up your Ethereal or similar protocol analyzer on a wireless interface and subject the network to a high level of RF interference; you will see all kinds of damaged and incomplete packets identified as various obscure protocols by your sniffer (Banyan Vines, anyone?). It is not surprising that some of these malformed packets can accidentally trigger an IDS alarm. After some investigation, the "evil cracker" can turn out to be a Bluetooth dongle or microwave oven creating RF interference in the network area.

Guarding the Airwaves: Deploying Higher-Layer Wireless VPNs

2010-03-01T03:27:00.001-08:00

"For an invincible defence, conseal your form."

"Formlessness means being so subtle and secret that no one can spy on you."

A virtual private network (VPN) is a way to use a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. Because 802.11 LANs use unlicensed frequency bands and can be easily accessible to outsiders either accidentally or with malicious intent, wireless networking provides an important area for VPN deployment and maintenance. Whereas the deployment of wired VPNs is usually restricted to specific cases of telecommuters and remote branch offices, the wireless world is entirely different, and deploying a VPN can be applicable to any wireless link if a high level of security is needed. This includes connections between hosts on a WLAN as well as point-to-point links between wireless bridges. Of course, when 802.11i is finally out and widely implemented, the need for wireless VPN deployment will decrease, but not disappear. As reviewed in the Attack chapters, even before the final draft is released, 802.11i standard implementations already have a handful of security problems. We are quite confident that new attacks against the novel standard will appear and spread as time passes. Besides, in a highly secure environment, one cannot completely rely on a single safeguard, or a single network layer safeguard. Also, there would be security-conscious network managers who prefer to trust tested and tried defense mechanisms, such as IPSec. In the case of point-to-point wireless links it is easier and more economical to deploy a network-to-network VPN than 802.11i-based defenses, including the RADIUS server and user credentials database, while using 802.11i with PSK and no 802.1x is not a good security solution for a high throughput network-to-network link. Either way, wireless VPNs are here to stay and surely deserve a place of their own in this book.

A VPN is the opposite of an expensive system of owned or leased lines that can be used by only one organization. The goal of a VPN is to provide the organization with the same capabilities at a much lower cost. Compare it to point-to-point bridged wireless connectivity solutions, which can also substitute expensive leased lines. VPN and wireless technologies do not compete, but complement each other.

A VPN works by using the shared public infrastructure, while maintaining privacy through security procedures and tunneling protocols such as the Layer Two Tunneling Protocol (L2TP). In effect, the protocols, by encrypting data at the sending end and decrypting it at the receiving end, send the data through a "tunnel" that cannot be entered by data that is not properly encrypted. An additional level of security involves encrypting not only the data, but also the originating and receiving network addresses.^[1] A WLAN can be compared to a shared public network infrastructure or, in some cases (hot spots, community nodes), is a shared public network infrastructure.

^[1] www.whatis.com definition

Let's examine the term VPN more closely and try to explain each component in detail, so readers who never encountered VPNs in the real world will have a clear understanding of what we imply here.

The virtual part of the term entails mutually exclusive and peaceful coexistence of two separate networks within single network segments, be it coexistence of IP, IPX, and DDP on the same LAN, or IP, IPSec, and L2TP traffic going through the Internet cloud. The private part acknowledges that the interaction and the underlying network are only understandable to the endpoints of the channel and not to anyone else. Later, you will see that it applies to both secrecy and authenticity of transmitted data. The final network part is pretty much self-explanatory and is a generally accepted definition. Any number of devices that have some common way of communicating with each other, irrespective of their geographic location, constitute a network.

It is a common misconception that a VPN must encrypt the bypassing data, but that is not necessarily true. The VPN is said to comply with three criteria: confidentiality, integrity, and availability. You have to note that no VPN is resistant to DoS or DDoS attacks and cannot guarantee availability on the physical layer due to its virtual nature and reliance on the underlying protocols. Two of the most important VPN features, especially in the wireless communication where you have limited control over the signal spread, are integrity and, most important, confidentiality of the passing data. Take a real-life situation when someone has managed to bypass the WEP encryption and connect to a WLAN. In the non-VPN scenario, he or she will be able to sniff the data and interfere with network operation. However, if the packets are authenticated, man-in-the-middle attacks are nearly impossible to perform, while the data can still be intercepted. Addition of an encryption element to the VPN mitigates the threat presented by data interception.

Therefore, we tend to see VPNs not as strict isolation of communication, but rather a communication that runs in a more controlled environment with exclusively defined groups of permitted participants.

Hash Functions, Their Performance, and HMACs

2010-03-01T03:15:00.000-08:00

Other widely used hash functions include 128-bit MD5 from RSA Data Security, Inc., which is a very fast and commonly implemented hash. MD5 is traditionally used to encrypt Linux user passwords (hashes start with the "$1$" character), authenticate routing protocols like RIPv2 and OSPF, create checksums of binaries in RPMs, and verify the integrity of Free/OpenBSD ports files. The specifications of MD5 are available in RFC 1321. Host intrusion detection tools like Tripwire (http://www.tripwire.com) use MD5 to take snapshots of a system's files and preserve them in a database (which must be encrypted) to determine if any of the system's files were modified by crackers. A poor man's Tripwire is the md5sum command available on many UNIX-like systems. A predecessor of MD5, MD4 is very fast, but it was broken in October 1995. Unfortunately, MS-CHAP still uses MD4 hashes even in its second version, and protocols such as 802.1x EAP-LEAP that rely on MS-CHAP can be vulnerable to attacks against MD4. Since 1995, there have been serious doubts about the security of MD5 and other 128-bit cryptographic hash ciphers, and the use of at least 160-bit hashes is recommended. You can check the security of your MD5 hashes using the MD5Crack tool, available for download from http://www.checksum.org/download/MD5Crack (this is the compiled Windows version of the tool; UNIX source code can be downloaded from http://www.packetstormsecurity.org).

Apart from SHA-1 and higher, there are other reasonably secure cryptographic hash ciphers to use, including HAVAL (variable-length hash values), RIPEMD, and Tiger. RIPEMD from the EU project Race Integrity Primitives Evaluation (RIPE) consists of two parallel MD5 processes running for five rounds and producing a 160-bit hash. RIPEMD is considered as secure as SHA-1 and is used by Nessus in conjunction with Twofish. Tiger was designed by the Serpent development team and is optimized to run on 64-bit chips, on which it is approximately 2.8 times faster than RIPEMD and 2.5 times faster than SHA-1. Tiger produces a 192-bit hash, although less-secure 128- and 160-bit variants of this cipher do exist.

Common block symmetric ciphers can also be used as the one-way hashes with few exceptions (e.g., Blowfish). In fact, being able to implement a symmetric cipher as a cryptographic hash was one of the conditions an AES candidate had to meet. Knowing how cryptographic hashes work, it is easy to see that there is nothing supernatural about using a block symmetric cipher in such a role: Supply a constant, use the input data to generate subkeys, and run. However, there is no reason to use AES or MARS, and so on, as a one-way hash when well-designed specific cryptographic hash algorithms like SHA exist.

Cryptographic hash ciphers are designed to quickly process large quantities of data; for example, to hash data and append hashes to packet headers on the fly as the packets are sent over the network. The processing rate of cryptographic hash ciphers in MB/sec is generally comparable to the processing rate of stream ciphers such as RC4 and is 1.5 to 2 times above the processing rate of AES. Obviously, there is a performance penalty for using more secure, larger hashes, and MD5 would have a higher data throughput than Tiger (on 32-bit CPUs) or SHA-1.

Cryptographic hashes are fine to sustain data integrity via data fingerprinting or to identify users against databases of hashed passwords. However, by themselves they do not authenticate the data itself; the attacker can alter the original data before hashing takes place. One possible solution for this problem is using a HMAC, also called a keyed message digest. A HMAC is nothing more than a cryptographic hash and shared secret key combined. Thus, the data gets encrypted before it is hashed, and the attacker would have to break the symmetric cipher key after generating the original message from the hash or break the symmetric cipher key if he or she has access to data before hashing takes place. An example of message authentication code specifically designed for improving wireless security is Michael (MIC).

MIC: Weaker But Faster

The main problem encountered in the design of MIC was developing a HMAC that would run on legacy hardware without imposing significant penalties on network throughput and latency. The client hosts can offload the HMAC computation to the sufficiently powerful laptop or even PDA CPU, even though it is still undesirable! What if a company decides to design and manufacture a tiny 802.11-enabled mobile phone? Besides, many access points do not boast high processing power. Yet, the AP or a wireless bridge should be able to verify both integrity and authenticity of the bypassing packets. Recall the structure of SHA with its 80 iteration rounds and imagine generating such a hash for every packet sent over the wireless network. Would a common access point or a PDA be able to implement that process without significant resource exhaustion? Not very likely!

Thus, an entirely new algorithm called MIC was designed by Niels Ferguson to provide packet integrity checking and forgery detection on TKIP-enabled WLANs. It was designed as a third attempt, after two previous designs called Mickey and Michelle. MIC is a trade-off between security and resource consumption and implementation capability. It runs on older wireless access points and client hardware without imposing a significant performance penalty, but the security level it provides is only 20 bits. As you should understand by now, in modern cryptographic terms this is not a lot.

Before discussing the trade-off and its practical outcome possibilities, learning how MIC works is helpful. The MIC secret key consists of 64 bits and is represented as an 8-byte sequence k₀...k₇. This sequence is converted to two 32-bit little-Endian words, K₀ and K₁. Throughout the MIC design, all conversions between bytes and 32-bit words use the Little-Endian conventions, because the cipher is expected to run on Little-Endian CPUs. In fact, the majority of access points now manufactured use older Intel line chips such as i386 or i486.

MIC operates on the data field, as well as source and destination address fields of the wireless frame. The integrity of IVs is not protected and the data field is not interpreted. Before the cipher runs, the frame is padded at the end with a single byte (value 0x5a), followed by 4 to 7 zero bytes. The number of zero bytes is selected to ensure that the overall length of the padded frame is always a multiple of four. The padding is never transmitted with the frame; it is used only to simplify the computation over the final block. After the padding, the frame is converted into a sequence of 32-bit words M₀...M_N-1, where N = [(n+5)/4]. By design, M_N-1 = 0 and M_N-2 != 0.

The MIC value is computed starting with the key value and applying a block function b for every message word. The cipher loop runs a total of N times (i includes 0 to N-1 values), where N is the number of 32-bit words making up the padded frame. The algorithm produces two words (l,r), which are converted into a sequence of eight Little-Endian octets, the MIC value:



Input: Key (K₀, K₁) and padded frame (represented as 32-bit words) M₀...M_N Output: MIC

 value (V₀, V₁)



MIC <= ((K ₀, K₁) , (M₀,...,M_N))

   (l,r) <=(K₀, K₁)

   for i = 0 to N-1 do

         l <= l ^= M_i

         (l,r) <= b(l,r)

return (l,r)

The MIC value is appended to the frame as data to be sent.

The block function b used by MIC is a tiny Feistel algorithm that employs alternating additions and XORing. The <<<>>> indicates right rotation of 32-bit values, and XSWAP is a function that exchanges the position of the two least significant bytes with the position of the two most significant bytes in a word:

Input: (l,r)

Output: (l,r)

b(L,R) 35



r <= r ^= (l <<< 17)

l <= (l + r) mod 2³²

r <= r ^= XSWAP(l)

l <= (l + r) mod 2³²

r <= r ^= (l <<< 3)

l <= (l + r) mod 2³²

r <= r ^= (l >>> 2)

l <= (l + r) mod 2³²

return (l, r)

As you can see, the cipher is neither sophisticated nor strong. It was estimated that an attacker has one chance in a million of sneaking in a frame with a compromised payload but correct MIC. One might argue that significant damage can be done by inserting a single modified frame after 1 million frames sent. However, the old WEP ICV (CRC-32) is still used as well, and has to be faked together with MIC. Thus, such attacks are neither easy nor have a high probability of success. Nevertheless, to mitigate their success the so-called TKIP countermeasures were introduced. When more than a single forgery attempt in a second has been detected, the host deletes the groupwise or pairwise key (depending on whenever a unicast or multicast frame was affected), deassociates, and waits for a minute before the reassociation. Thus, the possibility of an evil Joe Cracker sending a few million modified frames to sneak in a few of them undetected is eliminated.

However, the same Joe Cracker might turn desperate and try to send forged frames to trigger the countermeasures and cause a DoS attack, employing not a bug, but a feature. The possibility of such DoS attacks introduced by a new security feature was widely argued. The best example of such discussion is a thread at the Cryptography mail list (http://www.mail-archive.com/cryptography@wasabisystems.com/msg03070.html is the first message in a thread). In this thread Niels Ferguson, the creator of MIC, answers questions considering the possibility of a DoS attack abusing MIC countermeasures. Despite the hullabaloo around the likelihood of this DoS attack and the countermeasures' imperfections, such an attack might not be as realistic and easy to launch as many would think. Remember that the TSC will drop all out-of-sequence frames; the attacker thus has to send a frame with a "future," yet unused, IV. However, recall that the IV is actively used by the TKIP per-packet key generation function. If the IV is changed, the frame will not be decrypted correctly. Because the CRC-32 is still there, it would not give a proper value, leading to the forged frame being eventually dropped. Thus, the attacker has to sniff out valid frames, delete them to prevent them from reaching the receiver, corrupt the MIC, recalculate the CRC-32 to reflect the changes in MIC, and only then forward the "MIC-of-Death" frames to the target (desirably every 59 seconds). Although possible, it is by no means an easy task.

Because the final 802.11i release-compatible hardware will have to be optimized for running AES, using a CBC-MAC HMAC implementing AES as a one-way hash would be more practical and secure than employing some form of MIC or a well-known message digest like SHA. It will also remove all possible problems with MIC just discussed. Thus, in some specific cases, it could be preferable to use symmetric block ciphers for data integrity preservation as well as for data encryption and message authentication.

security wireless network

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about my hobies-bodybilding-8 things you must do to bild maximum muscle

Putting a Networked PC in Your Home Theater

A better way: WPA

Installing the AP

The BSSID

Abbreviations

Installing Wireless Access Points in Windows

Planning Security

Choosing Wireless Home Networking Equipment

Planning Security

Choosing a wireless technology

Choosing wired or wireless

Wi-Fi versus Bluetooth

Understanding Wi-Fi channels

Wireless Networking Fundamentals

Network infrastructure

Signal Loss for Obstacle Types

Appendix E. Signal Loss for Obstacle Types

Appendix B. 802.11 Wireless Equipment

Table B.1. 802.11b Client Adapters

Table B.2. 802.11a Client Adapters

Table B.3. Prism-Based Cards

Appendix A. Decibel–Watts Conversion Table

Counterintelligence: Wireless IDS Systems

Guarding the Airwaves: Deploying Higher-Layer Wireless VPNs

Hash Functions, Their Performance, and HMACs

MIC: Weaker But Faster