Wireless Networking & Internet Flashcards
IEEE 802.11
A wireless ethernet networking standard.
Uses RF (Radio Frequency)
Uses spread spectrum radio waves.
Broadcasts/Receives one of two bands:
2.4GHz & 5GHz
WAP
Wireless Access Point:
Centrally connects wireless network nodes in the same way a hub connects wired Ethernet PCs.
Also act as switches & internet routers.
PoE
Power over Ethernet:
Ethernet cable that supplies power.
Supplied by a PoE-capable switch.
PoE Injector
Connects PoE-enabled network device to a non-PoE LAN switch port
Can extend a PoE connection up to 100m
CSMA/CA
Carrier Sense Multiple Access/Collision Avoidance:
Network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by beginning transmission only after the channel is sensed to be “idle”.
Collision Avoidance
A wireless node listens in on the wireless medium to see if another node is currently broadcasting data. Waits a random amount of time before retrying.
RTS/CTS
Request to Send/Clear to Send:
Transmitting node sends an RTS frame to the receiving node after it determines the wireless medium is clear to use.
Receiving node responds with CTS frame; tells sending node that it’s okay to transmit
Data is sent, then transmitting node waits for an ACK from the receiving node before sending the next data packet.
Ad Hoc Mode
Each wireless network node is in direct contact with every other node in a decentralized free-for-all (no need for WAP).
Good for small groups of PCs sharing files/printers.
Good for temporary networks (study groups/meetings)
IBSS
Independent Basic Service Set:
2 or more wireless nodes communicating in ad hoc mode.
Infrastructure Mode
Devices connect using an access point (ex: router).
Better for networks that need to share dedicated resources such as internet connections and centralized databases.
Good for SOHO (Small office/Home office)
BSS
Basic Service Set:
A single WAP servicing a given area.
WMN
Wireless Mesh Network:
Hybrid wireless topology, where most of the nodes connect in a mesh network (includes wired machines).
Nodes act like routers, forwarding traffic for other nodes, but without wires.
Wireless Speed & Range Issues
Speed decreases as distance increases.
Maximum throughput is only really achieved at 25ft or less.
Dead spots
Increasing Wireless Range
You can install multiple WAPs to permit “roaming” between one WAPs coverage area and another’s.
Replace WAP with one that has greater signal strength/range.
Signal boosters.
Wireless Repeaters/Extenders
Frequency Band (or just Band)
A contiguous range of frequencies that is usually divided up into discrete slices (channels).
802.11a
Frequency Band: 5GHz
Max Range: 150ft
Max Speed: 54Mbps
8 Available Channels
Less prone to interference than 802.11b & g
802.11b
Frequency Band: 2.4GHz
Max Range: 300ft
Max Speed: 11Mbps
14 Available Channels (11 for US)
3 Non-overlapping Channels
802.11g
Frequency Band: 2.4GHz
Max Range: 300ft
Max Speed: 54Mbps
14 Available Channels (11 for US)
Backwards compatibility: 802.11b
Improved security enhancements.
3 Non-overlapping Channels
802.11n
Frequency Band: 2.4 & 5GHz
Max Range: 300ft
Max Speed: 100+Mbps
MIMO to increase range & speed.
Backwards compatibility: 802.11b & g
Same as 802.11g but adds 5GHz band.
802.11ac
Frequency Band: 5GHz
Max Range: 300+ft
Max Speed: 1Gbps
MU-MIMO
Backwards compatibility: all previous
Tethering/Hotspots
Using your smartphone to tether.
Tethering: Using a cellular device to bridge cellular network and Wi-Fi
Infrared Wireless Networking
IrDA Protocol (Infrared Data Association)
Max Speed: 4Mbps
Max Range: 1 meter
Links are direct line-of-sight
Anything that breaks the beam can disrupt.
Point-to-point (ad hoc only)
Half-duplex
Bluetooth
Creates small wireless networks preconfigured to do specific jobs. (PAN: Personal Area Network)
802.15 Network Standard
Bluetooth Speeds (by generation)
1st Gen: 1Mbps
2nd Gen: 3Mbps
3rd Gen: 24Mbps
4th Gen: Reduces cost & power consumption
Improves speed & security.
IP Connectivity
5th Gen: Option to increase speed at cost of range
Better IoT support
Bluetooth Broadcasting Method
Uses a broadcasting method that switches between any of the 79 frequencies available in the 2.45GHz range.
Hops frequencies 1600 times per second (highly resistant to interference)