Wireless Networking Flashcards
Most common wireless standard
802.11 Wireless
WAP
Wireless Access Point
- interconnects wireless network nodes with wired networks
- operates like a hub and works at layer 1
link state
if device is connected
IBSS
Independent Basic Service Set
- two or more wireless nodes communicatingin an ad hoc mode
Infrastructure Mode
use one or more WAPs to connect the wireless network node centrally
WLAN
Wireless Local Area Network
BSS
Basic Service Set
- area serviced by a single WAP
ESS
Extended Service Set
- area serviced by added WAPs
BSSID
Basic Service Set Identifier
- same as MAC address for WAP
- in ad hoc, nodes generate random 48-bit string of numbers
SSID
Service Set Identifier
- 32-bit indentifier inserted into the header of each frame processed by a WAP
- WAPs advertise existence by sending out continuous SSID broadcasts
roaming
as clients move through different coverage areas, they will change WAP connections seamlessly
spread-spectrum
broadcasts data in small, discrete chunks over the different frequencies available within a certain frequency range
three different spread-spectrum broadcasting methods
DSSS - direct-sequence spread-spectrum
FHSS - frequency-hopping spread-spectrum
OFDM - orthogonal frequency-division multiplexing
Wi-Fi Channels
14 channels, 20-MHz each on 2.4 GHz
40 channels with automatic channel switching on 5 GHz
Collision detection on wired vs wireless
wired - CSMA/CD
wireless - CSMA/CA
collisions on wireless
each sending node detects the collision and responds by generating a random timeout period for itself called a backoff
DCF
Distributed Coordination Function
- method for collision avoidance on Wireless
- Defines backoffs
- requires receiving nodes send an ACK for every frame they process
goodput
the acutal number of useful bits per second on a wireless network
802.11b
- first standard
- 11 Mbps
- 300 ft
- 2.4 GHz
- DSSS spectrum
802.11a
- 54 Mbps
- 150 ft
- 5.0 GHz
- OFDM spectrum
802.11g
- 54 Mbps
- 300 ft
- 2.4 GHz
- OFDM spectrum
- backwards compatible with 802.11b
- if only g devices connected, runs in Native Mode 54 Mbps
- if b devices are connected, runs in Mixed Mode at 11 Mbps
802.11n
- 100+ Mbps
- 300 ft
- 2.4 Ghz
- OFDM (QAM) spectrum quadruple-amplitude modulated
- MIMO (requires multiple antennas)
- employs tranmit beamforming (helps get rid of deadspots)
- backwards compatible with b/g
- legacy mode - sends out separate packets just for legacy devices
- mixed mode - same as legacy, but wide bandwidth
- greenfield mode - n mode only
802.11g-ht
means it is connecting to a 802.11n WAP in mixed mode
802.11ac
- 1 Gbps
- 3000 ft
- 5.0 GHz
- OFDM (QAM) quadruple-amplitude modulated
- MU-MIMO (multi-user)
WPS
Wi-Fi Proctected Setup
- push button or PIN
- very susceptible to attack
802.11i
security standard that enables you to set up a network with a RADIUS server and passwords encrypted with Extensible Authentication Protocol (EAP)
RADIUS server
- stores usernames and passwords to store user’s rights on a network
supplicant
wireless client computer contacts a WAP, called a Network Access Server (NAS), requesting access to a network through a RADIUS server
EAP
- developed to create a single standard to allow to devices to authenticate
- not a protocol, but a PPP wrapper that EAP-compliant applications can use to accept one of many types of authentication
- used in wireless networks
EAP-PSK
Pre-shared Key
- most popular form of wireless authentication
- a shared secret code that stored on both wireless AP and client
- encrypted using AES
EAP-TLS
EAP with Transport Layer Security
- defines use of RADIUS server as well as mutual authenticaion
- requires certificates on both server and every client
EAP-TTLS
Tunneled TLS
- similar to EAP-TLS but only uses a single server-side certificate
- very common for more secure wireless networks
EAP-MS-CHAPv2
- uses a password function based on MS-CHAPv2 with the addition of an ecrypted TLS tunnel
- also called Protected EAP (PEAP)
EAP-MD5
- simple version of EAP that only uses MD5 hashes for transfer of authentication credentials
- weak, least used version
LEAP
Lightweight EAP
- Cisco
- combiation of MS-CHAP and RADIUS server
EAP-FAST
EAP Flexible Authenticaion vioa Secure Tunneling
- Cisco’s replacement for LEAP
- supported by all modern OSs
802.1X
- Ethernet version of EAP
- does not use PPP
- puts EAP inside an ethernet frame
- port based authenticaion
- combines RADIUS-style AAA with EAP
WEP
Wired Equivalent Privacy
- uses a 64 or 128 bit encryption algorithm to scramble data frames
- easily cracked
WPA
Wi-Fi Protected Access
- adpoted most of the 802.11i standard
- dynamic encryption key generation
- adds extra layer of secruity called TKIP (temporal key integrity protocol)
- easily cracked
CCMP
Counter Mode Block Chaining Message Authentication Code Protocol
WPA2
Wi-Fi Protected Access 2
- fully supports 802.11i
- most common is WPA2-PSK
- use long passphrases to prevent hacking
5 differences between SOHO and enterprise
robust device contruction centralized management VLAN pooling Power over Ethernet bringing personal wireless devices into the enterprise environment
Wireless Controller
A switch designed to handle a number of WAPs simultaneously
Difference between WAP thin and thick client
Thick - can access the device directly
Thin - can only be configued by a wireless controller
LWAPP
Lightweight Access Point Protocol
- standard protocol used for WAP configuration
VLAN pooling
randomly assign wireless clients to a VLAN
Power over Ethernet
802.3af
outputs up to 25.5 watts
site survery
will reveal any obstacles to creating the wireless network and will help determine the best possible location for your access points
Wi-Fi Analyzer
a device that looks for and documents all existing wireless networks in the area
High Device Density Environments
an area with a lot of wireless devices
Four things needed to configure a NIC for ad hoc mode?
SSID
IP Address
Channel
Sharing
Three types of antennas
Omnidirectional
Unidirectional
Patch
Omnidirectional Antenna
- radiates the signal outward in all directions
- straight wire omnidirectionals are called dipole antennas
gain
- the ratio of increase from a strenghtened antenna signal
- measured in dB
- typical WAP is 2 dB
- increasing the signal requires a bigger antenna (up to 11)
