Installing Wireless Networks Flashcards
SSID
Service Set Identifier
- Up to 32 bytes in length and should use ASCII letters and digits
- ESSID is multiple APs connected to same distribution system and share security information
Beacon Frame
- Special managment frame broadcast by AP to advertise WLAN
- Contains SSID, supported date rates, and signaling and encryption and authentication requirements
- Interval of broadcast can be modified
Fat AP
- contains procesing logic to function autonomously and handle clients without wireless controller
Thin AP
Requires wireless controller to function
Speed
- Data rate established at physical and data link layers
- Determined by wifi standards, bonded channels and things like MU-MIMO
Throughput
- Amount of data that can be transferred at network layer
- Accounts for overhead lost with layers 1 and 2
- Goodput refers to data transfer at application layer (accounting for overhead from header fields and packet loss)
RF attenuation
- AKA free space path loss
- Weakening of signal over distance
- Signal weakens in inverse-square, doubling distance decreases signal strength by factor of 4
- Measured in decibels
RSSI
Received Signal Strength Indicator
- Strength of signal on client end
- dBm is measurement, with values closer to zero equalling better prformance
- RSSI must exceed minimum received sensitivity
SNR
Signal-to-noise Ratio
- Measured in DBm, but closer to zero is bad
Wifi Analyzer
Measures RSSI and SNR
Yagi
- Bar with fins omnidirectional antenna
- Useful for point to point wireles bridge connections
Polarization
- Orientation of wave propagating from antenna
- Tx and Rx antennas should usually be the same
- Dual polarized can be configured in either orientation
CCI
Co-Channel Interference
- Contention
- Multiple access points using same channel, reducing opportunities to transmit
- Referred to in percentage called channel utilization
- No more thatn 50% is preferred
ACI
Adjacent channel interference
- When APs use different, but overlapping channels, like 1 and 3
WPA
Wireless Protected Acces
- Designed to fix vulnerabiliteies in WEP
- Uses TKIP (Temporal Key Integrity Protocl) to mitigate those problems
- Not considred secure anymore, like WEP
PSK
Preshared Key
- Used in WPA2
- Uses passphrase to generate key that is used to encrypt communications
- Passphrase is hashed and referred to as PMK (pairwise master key)
- Can be vunerable to attacks taht try to crack passphrase. It should be at least 14 characters long
PAKE
Password Authenticated Key Exchange
- Used by WPA 3 to authenticate
Enterprise Authentication
- Uses EAP to autheticate against network directory
- 802.1x
- Alternative to personal authentication
- Uses Radius or TACAS
Disassociation attack
- Sends spoofed frames to disassociate agenst with SSID
- Used for DDoS or to force agents to reconnect to rogue AP
BSS
Basic Service Set
- AP mediating communications between client devices and bridge to cabled network segments
ESS
Extended service set
- More than one BSS grouped together
Site Survey
- First examine blueprints or floor plan
- Identify features that may produce RFI
- Each AP mounting needs network port and power
Wireless Survey Tool
- Used to record signal strength and supported data rate a various points in intended Basic Service Area
- Cisco Aironet, Metageek inSSIDer, Ekahu Site Survey
- Heat map can be generated to find areas of weak signal strength
- Neighboring APs should have non-overlapping channels
ESA
Extended Service Area
- Created by installing multiple APs with same SSID and security configuration
- Clients can roam within it
WDS
- Wireless Distribution System
- Using APs to cover areas where it is not possible to run cable
- APs must be put in WDS/Repeater mode
- One is configured as base station, while others are remote stations
- Base should be connected to cabled segment
- Can also be setup to bridge cabled segments
- In bridge modes APs only forward traffic and do not server wireless clients
Wireless LAN controller
- Dedicated hardware used to monitor and mange APs
- Software applications can also be used
- Can also aggregate client traffic and provide central switching and forwarding point for WLAN and wired LAN
- Can also assign clients to VLANs and manage PoE
IBSS
Independent Basic Service Set
- Allows ad hoc connections between devices
- suits a small workgroup of devices or connectivity to single device, like a printer
- Is not scalable
MBSS
Mesh Basic Service Set
- Part of WMN (Wireless Mesh Network)
- Mesh Stations can discover each other and forward between peers using routing protocol like Hybrid Wireless Mesh Protocol (HWMP)
- More scalable than ad hoc
- Increasingly popular and foundation of IoT networks
EIRP
Effective Isotropic Radiated Power
- Power at which an AP Transmits
- Must not exceed regulatory limits
- Increasing power is not usually effective at improving wireles coverage
- Roughlt 2/3rds of weakest client power
Overcapacity Issues
- Varies on wifi standard and type of network traffic
- Roughly 30 per AP is standard
- Wireless is a broadcast medium and all bandwidth shared between clietns
- Controllers will normally have reporting tools for these issues
- Traffic shapers can automatically throttle bandwidth to overactive nodes
