Networking & Cellular
E09 Wi-Fi Topology — Study Guide
This guide covers Wi-Fi Topology as part of Networking & Cellular. Start with the vocabulary, then try to answer each question before revealing the answer. Connect these facts to a real network or cellular connection and practice the subject in the arcade when you are ready.
Key facts
Which organization sets the 802.xx standards?
IEEE
802.15 covers…
Wireless PAN
Bluetooth (formerly 802.15.1) is now maintained by…
Bluetooth SIG
The FCC regulates radio frequencies from…
9 kHz to 3000 GHz
FCC spectrum auctions grant broadcast rights for how long?
10 years
Which band type allows higher power, longer range, and requires licensed operators?
Licensed
Which is an example of a LICENSED band user?
Cell phone networks
Which is NOT listed as an ISM band?
3.7 GHz
433 MHz and 13.56 MHz are…
ISM bands
A specified amount of an RF band set aside for a specific set of devices is a…
Channel
How many channels are in the 2.4 GHz range?
14
2.4 GHz channels are ___ MHz wide and offset by ___ MHz.
22; 5
Channel 14 is offset by…
12 MHz
Which 2.4 GHz channels have no overlap?
1, 6, 11, and 14
In the U.S., which 2.4 GHz channels are authorized?
1–11
Channel 14 is only available in…
Japan
5 GHz channels are how wide (base)?
20 MHz
Total 5 GHz bandwidth in the U.S.?
580 MHz in 3 non-contiguous chunks
5 GHz sub-bands are labeled…
UNII 1, UNII 2, UNII 2 extended, UNII 3
Which band has almost 1200 MHz of contiguous bandwidth?
6 GHz
6 GHz Wi-Fi is currently denoted as…
Wi-Fi 6E
Combining 2+ adjacent channels for more bandwidth is…
Channel bonding
Max bonded bandwidth at 2.4 GHz?
40 MHz
Max bonded bandwidth at 5 and 6 GHz?
160 MHz
2.4 GHz bonding requires channels how far apart?
Two channels apart (e.g., 1 & 3)
Two or more transmitters on the SAME channel causes…
Co-channel interference
Devices on OVERLAPPING channels cause…
Adjacent channel interference
Adjacent channel interference predominantly affects which band?
2.4 GHz
Which spread spectrum is harder to intercept unless the pattern is known, but only 1–2 Mbps?
FHSS
DSSS allows up to ___ throughput.
11 Mbps
Which collision method does 802.3 (wired) use?
CSMA/CD
Which collision method does 802.11 (wireless) use?
CSMA/CA
Why does 802.11 use avoidance instead of detection?
Wireless devices cannot sense a collision
CSMA/CD and CSMA/CA operate at which layer, in which duplex?
Layer 2; half-duplex only
After a collision in CSMA/CD, what alerts all devices to stop transmitting?
A jam signal
Collision detection is a reactive process.
True
In CSMA/CA a sender may send ____ and wait for ____ before transmitting.
RTS; CTS
Which access scheme assigns each user a code?
CDMA
Which multiplexing turns signals from multiple frequencies into a single signal?
FDM
Which multiplexing divides the time frame into slots per message?
TDM
Which multiplexing uses ORTHOGONAL sub-carriers to nearly eliminate interference?
OFDM
'Orthogonal' means signals are…
perpendicular to each other
OFDM max throughput listed?
Up to 10 Gbps
Using multiple antennas timed for constructive interference to boost signal is…
Beamforming
Which uses channel bonding + beamforming with multiple antennas — 802.11n+, up to 8 streams?
MIMO
Which allows multiple SIMULTANEOUS transmissions to different users?
MU-MIMO
Which are the four WLAN components listed?
Clients, Access Point, Distribution Systems, Wireless Gateway
APs know clients by their…
MAC address
An Access Point is essentially a wireless…
Hub
Which connects two or more APs by converting between 802.11 and 802.3?
Distribution System (DS)
Which expands coverage with WIRELESS links between APs — no wires but shorter reach?
WDS (Wireless Distribution System)
A wireless gateway typically combines…
Router, AP, Firewall, Modem
The two kinds of wireless gateways?
Residential and Enterprise
What are the three basic 802.11 topologies?
IBSS, BSS, ESS
The area around an AP where clients can communicate (a 'cell') is the…
BSA (Basic Service Area)
The BSSID is…
the MAC of the AP
The SSID is…
the human-readable version of the BSSID (not unique)
The ESSID is…
the SSID of the entire ESS
Which topology has devices directly connected with no AP (ad-hoc/peer-to-peer)?
IBSS
Which topology: one AP connects clients, cheap, but no outside connection?
BSS
Which topology joins two or more BSSs through a DS, all using the same SSID?
ESS
Order the client connection process to an AP.
Discovery → Authentication → Association
Client State 2 is…
Authenticated, Unassociated
Client State 3 is…
Authenticated, Associated
An AP that does NOT transmit a beacon frame has a…
Hidden SSID
During open authentication, the AP performs…
MAC filtering
After association, the AP assigns the client a unique…
Association ID (AID)
A client can be associated with multiple APs at the same time.
False
Captive portal user agreements generally contain an acceptable use policy and…
authorization to monitor/record your data
Intentionally slowing someone's connection to push an upgrade is…
Bandwidth throttling
Captive portals intercept and monitor data, negating the security of…
HTTPS
Which hotel-network attack is mentioned as a captive portal risk?
Dark Hotel
The four wireless addresses mnemonic is…
SATA/RADA
Which wireless address is the device that HAS data to send?
Source Address (SA)
Which wireless address is the device physically transmitting?
Transmitter Address (TA)
If two devices are on separate APs of an ESS, how many of the 4 addresses differ?
All four
All four wireless addresses are which kind of address?
MAC (Layer 2)
For management frames between client and AP, the To DS/From DS bits are…
both off
What are the four 802.11 frame types?
Management, Control, Data, Extension
Which frame type helps devices join or leave an AP?
Management
Which frame type is for high-throughput/experimental standards, not normal use?
Extension
Which management frame is broadcast at regular intervals with SSID and supported rates?
Beacon
The broadcast MAC address used by beacons and probe requests?
ff:ff:ff:ff:ff:ff
Which frame does a client broadcast on all frequencies to find networks?
Probe Request
Moving between APs at an airport for better signal uses…
Reassociation Request/Response
If a client is deauthenticated, it is also…
disassociated
Which frame terminates association and gets NO reply?
Disassociation
Which control frame happens for EVERY data frame?
ACK
Which control frame lets the AP assess the RF environment to optimize MU-MIMO?
Beamforming Report Poll
Which data frame carries control info without data (power-save entry/wake)?
Null Data / QoS Null Data
Which data frame adds QoS to optimize overall speed?
QoS Data
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