Installing Wireless Networks

Question 1

SSID

Answer 1

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

Question 2

Beacon Frame

Answer 2

• 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

Question 3

Fat AP

Answer 3

• contains procesing logic to function autonomously and handle clients without wireless controller

Question 4

Thin AP

Answer 4

Requires wireless controller to function

Question 5

Speed

Answer 5

• Data rate established at physical and data link layers

- Determined by wifi standards, bonded channels and things like MU-MIMO

Question 6

Throughput

Answer 6

• 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)

Question 7

RF attenuation

Answer 7

• 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

Question 8

RSSI

Answer 8

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

Question 9

SNR

Answer 9

Signal-to-noise Ratio

- Measured in DBm, but closer to zero is bad

Question 10

Wifi Analyzer

Answer 10

Measures RSSI and SNR

Question 11

Yagi

Answer 11

• Bar with fins omnidirectional antenna

- Useful for point to point wireles bridge connections

Question 12

Polarization

Answer 12

• Orientation of wave propagating from antenna
• Tx and Rx antennas should usually be the same
• Dual polarized can be configured in either orientation

Question 13

CCI

Answer 13

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

Question 14

ACI

Answer 14

Adjacent channel interference

- When APs use different, but overlapping channels, like 1 and 3

Question 15

WPA

Answer 15

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

Question 16

PSK

Answer 16

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

Question 17

PAKE

Answer 17

Password Authenticated Key Exchange

- Used by WPA 3 to authenticate

Question 18

Enterprise Authentication

Answer 18

• Uses EAP to autheticate against network directory
• 802.1x
• Alternative to personal authentication
• Uses Radius or TACAS

Question 19

Disassociation attack

Answer 19

• Sends spoofed frames to disassociate agenst with SSID

- Used for DDoS or to force agents to reconnect to rogue AP

Question 20

BSS

Answer 20

Basic Service Set

- AP mediating communications between client devices and bridge to cabled network segments

Question 21

ESS

Answer 21

Extended service set

- More than one BSS grouped together

Question 22

Site Survey

Answer 22

• First examine blueprints or floor plan
• Identify features that may produce RFI
• Each AP mounting needs network port and power

Question 23

Wireless Survey Tool

Answer 23

• 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

Question 24

ESA

Answer 24

Extended Service Area

• Created by installing multiple APs with same SSID and security configuration
• Clients can roam within it

Question 25

WDS

Answer 25

• 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

Question 26

Wireless LAN controller

Answer 26

• 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

Question 27

IBSS

Answer 27

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

Question 28

MBSS

Answer 28

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

Question 29

EIRP

Answer 29

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

Question 30

Overcapacity Issues

Answer 30

• 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