Wifi 802.11x WLAN Basics

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WLAN – 802.11x
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topics covered:


-wifi types
-standards and ranges
-spread spectrum
-antenna types
-CA vs CD
-SSID and MAC authentication
-WEP, WPA, WPA2
-WLAN facts:

lilly pad network – free example: hotels have free wifi
hot spots – credentials neeeds example truck stops.
Ad hock – PC to PC wlan connection
AP to pc is infractructure connection
ESS is multiple access point (AP)
BSS is basic 1 Access point only
cells is what is called the coverage area
Example below:

 

 

3 Services WLAN:

1. Independent Basic Service Set (IBSS)

– no AP
– AD hoc only

2. Basic Service Set (BSS)

-1 AP only

3. Extended Service Set (ESS)

– multiple AP
– large area coverage
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Wireless 802.11x standards
—————————————
802.11 IEEE

802.11a – 25 MBps – 54 MBps, indoor range 100 feet 5 Ghz 

802.11b – 6.5 MBps – 11 MBps, 100 feet indoor range, 2.4 Ghz

802.11g – 25 MBps – 54 MBps, indoor 100 feet, 2.4 Ghz comapt with  802.11b

802.11n – 200 MBps – 540 MBps indoor 160 feet, 2.4 Ghz or 5 Ghz

wifi issues of inerferrence:

– microave ovens or microaves

– Wirless phones on 2.4 Ghz channel

– Solid objects walls etc…

Talking about Spread Spectrum Types:

FHSS-Frequent Happening Spread Spectrum – sender/reveiver agree on frequency range.

DSSS-Direct Sequence Spread Spectrum-Spread signal over entire range at once (11b, 11g, 11n)

OFDM-Orthogonal Frequency Division Multiplexing- Splits signal and sends the signal fragments over different frequencies at the same time at once.

———————————————————
Why all the talk about Spread Spectrum?
———————————————————

– Increases resistance to noise
– allows sharing of frequency band
– more difficult to intercept
————————————————————-
Types of Antennas
————————————————————

Type 1 : Yagi antenna :

– signal in single direction
– must be aligned correctly
– called directional antenna
– p2p direction
Type 2: Omni –
– sends signal all directions hence name OMNI
– omni directional
– Point to multipoint

——————————————————————
CSMA/CA  wifi
——————————————————————-

Carrier Sense Multiple Access with Collission Avoidance!
– Listens first
– if channel idle (random timer)hosts listen again.
– if channel is busy host cannot transmit

Wifi facts:

– no jam signal used
– half-duplex only  – no full-duplex used in wifi
——————————————————————-
SSID
——————————————————————

– 32 character max
– case sensitive
– if disable broadcast, must be statically configured
– wifi allow mac addresses only can be set

—————————————————————
WEP–WPA–WPA2
————————————————————–

– WEP 1st came
– WPA evolved from WEP
– WPA2 evolved from WPA

WEP:
-Wired Equivalent Privacy
– clear text key
– static keys
-one way auth -client doesnt authenticate
-Authentication (open-shared key)
WPA
– no friendly to older devices.
-Wifi protection authentication
– 2 way authentication
– TKIP with preshared key
WPA2 – not on exam
-802.11i
-wpa2 complex

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3 Responses to “Wifi 802.11x WLAN Basics”

  1. thanks it worked ;)))

    That’s rally nice………..keep it up!

  2. A pal encoraged me to look at this site, great post, fascinating read… keep up the good work!

    • hey thanks man. I am back on the band wagon. I am studying for my ccnp and hope to start posting again my ccnp stuff
      but it is all fun and hope I can improve on my stuff…stuff that you can use to help…
      thanks man cheers!
      -robert
      ps. if you ever neen anyquestions or configs just email me at robert (at) itdaddy (dot) net and I can send you what I have or point you to some good stuff to learn this cool stuff.

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