CNT 3004: Chapter 6: Wireless Networking

Passive scanning:

- Listens for signal. - Known as beacon frame. - Beacon is put out by the access point, along with AP's SSID.

Active scanning:

- Transmits special frame. - Known as a probe. - Client establishes connection to access point (AP) and detects / responds to probe.

802.11b WLAN Standards Table

802.11b: Frequency: 2.4 GHz. Max throughput: 11 Mbps. Range: 100m 802.11a: Frequency: 5 GHz. Max throughput: 54 Mbps. Range: 50m 802.11g: Frequency: 2.4 GHz. Max throughput: 54 Mbps. Range: 100m 802.11n: Frequency: 2.4 / 5 GHz. Max throughput: 600 Mbps. Range: Indoor=70m, Outdoor=250m. 802.11ac Wave 1 (3 data streams): Frequency: 5 GHz. Max throughput: 1.3 Gbps. Range: Indoor=70m, Outdoor=250m 802.11ac Wave 2 (4 data streams): Frequency: 5 GHz. Max throughput: 3.47 Gbps. Range: Indoor=70m, Outdoor=250m 802.11b Wave 3 (8 data streams): Frequency: 5 GHz. Max throughput: 6.93 Gbps. Range:Indoor=70m, Outdoor=250m

Infrastructure Wireless Topology:

A Wireless AP or AP accepts wireless signals from multiple nodes and retransmits them to the rest of the network.

ANT Protocol

Ad-hoc wireless protocol operating at about 2.4 GHz. Owned by Garmin, 2004.

Unidirectional Antenna

Also called YAGI Antenna Issues wireless signals along single direction.

802.11 MAC Services:

Appends 48-bit physical addresses to frame to identify source/destination. Same physical addressing scheme as other Ethernet networks. -Allows easy combination with other IEEE networks, but not same as wired ethernet.

Refraction:

As a wave travels through objects, the wave's direction, speed, and wavelength are altered / refracted.

Fading:

As signal runs into obstacles, energy gradually fades. Excessive fading causes dropped connections or slow data transmission.

Zigbee:

Based on 802.15.4 standard. A low-powered, battery-conserving wireless technology designed to handle small amounts of data. Ideal for industrial, scientific, medical sensors. Used in IOT for building automation, HVAC control, AMR, and fleet management.

ANT+

Based on ANT Protocol. Gathers and tracks information from sensors typically embedded in heart rate monitors, GPS, and other activity monitors. Can sync data from multiple devices for same activity. Examples are smartwatches, smartphones, etc.

Wireless USB:

Based on UWB (Ultra-wideband) radio platform. Certified W-USB products mimic wired USB 2.0 connections. -Similar speeds, security, etc. UWB radios transmit in range between 3.1 - 10.6 GHz.

Bluesnarfing:

Bluetooth security risk. Connection is used to download data without permission.

Bluejacking:

Bluetooth security risk. Connection used to send unsolicited data.

WPS Attack

Brute force attack towards cracking a PIN in order to access AP's settings.

Spectrum Analyzer:

Can assess quality of wireless signal.

Wireless Analyzer

Can evaluate Wi-Fi network availability, optimize Wi-Fi signal settings, and help identify Wi-Fi security threats.

CSMA / CA:

Carrier Sense Multiple Access/Collision Avoidance. Minimizes collision potential. Uses ACK packets to verify every transmission. Requires more overhead than 802.3. Real throughput less than theoretical max.

Lightweight Wireless Protocol:

Centralized wireless management made possible by lightweight wireless protocol. Example: - Cisco's LWAPP (Lightweight access protocol) -Cisco's CAPW (Control and Provisioning of Wireless Access Points).

Bluetooth Power Classes:

Class 1: Max power: 100 mW. Range: Up to 100 m. Purpose: Industrial. Class 2: Max power: 2.5 mW. Range: Up to 10 m. Purpose: Mobile devices. Class 3: Max power: 1 mW. Range: Up to 1 m. Purpose: Rarely used.

Frame Aggregation:

Combine multiple frames into one larger frame. Two techniques: -A-MSDU (Aggregated Mac Service Data Unit) -A-MPDU (Aggregated Mac Protocol Data Unit)

Scattering:

Diffusion in multiple different directions.

WPA

Dynamically assigns every transmission its own key.

Near-Field Communication (NFC)

Form of RFID that transfers data wirelessly over very short distances. Signal can be transmitted one-way by NFC or smart tag. -When employees need access to secure area. NFC tag collects power from smartphones or other devices by magnetic induction.

802.11 Data Frame:

Four address fields: - Source address, transmitter address, receiver address, destination address.

Basic Service Set (BSS)

Group of nodes sharing one AP.

Basic Service Set Identifier (BSSID)

Group of stations / notes that share the AP identifier.

Extended Service Set (ESS):

Groups of access points connected to same LAN. - Share ESSID (Extended Service Set Identifier) is what allows roaming.

War Driving:

Hacker searches for unprotected wireless networks by driving around with laptop configured to receive and capture wireless data transmissions.

War Chalking:

Hackers draw symbols with chalk on sidewalk / wall near vulnerable APs so other hackers know.

Sequence Control Field:

How a large packet is fragmented. Error checking and fragmentation are handled at MAC sublayer of Data Link Layer.

Bluetooth:

IEEE 802.15.1 specification. Operates in radio band of 2.4 - 2.4835 GHz. Hops between frequencies within that band to help reduce interference. (1600 hops per sec). Requires close proximity. Distance depends on bluetooth class.

Infrared (IR)

IR used primarily to collect data through sensors. Exists just below spectrum visible to human eye. IR sensors can collect: -Presence of liquid. -Variations in reflections from skin. -Proximity to device.

WPA Attack

Interception of network keys communicated betweens tations and Aps. AKA WPA cracking

Omnidirectional Antenna:

Issues, receives wireless signals with equal strength, clarity in all directions.

Multiple Input Multiple Output (MIMO)

Multiple APs and client antennas may issue signal to 1+ receivers. Increases range and network's throughput.

Wireless Networks (WLANS)

Networks that transmit signals through the air via radio frequency Uses the same layer 3 and higher protocols.

Multiuser MIMO (MU-MIMO)

Newer tech allows multiple antennas to service multiple clients simultaneously. Reduces congestion, gives faster data transmission. Available with WAVE 2 802.11ac products.

Wireless Devices:

Not designed to simultaneously transmit and receive. Cannot prevent collisions. Uses different access method than Ethernet.

Signal-to-Noise Ratio (SNR)

Proportion of noise to strength of signal.

Wireless Controllers:

Provides: - Centralized authentication for wireless clients. - Load balancing. - Channel management. - Detection of rogue APs.

Range:

Reachable geographic area.

Radiation Pattern

Relative strength over three dimensional area of all electromagnetic energy that antenna sends and receives.

WPA2

Replacement for WPA, stronger encryption. Most secure communication made possible by combining RADIUS server with WPA/WPA2. -Known as WPA/2-Enterprise WPA has been cracked.

RTS / CTS:

Request to Send / Clear to Send protocol. Ensures packets are not inhibited by other transmissions. Efficient for large transmission packets. Further decreases overall 802.11 efficiency.

Evil Twin:

Rogue AP planted in network's area to pose as authorized AP.

Scanning Types:

Scanning types survey surroundings for access point.

Mesh:

Several access points work as peer devices on the same network.

Reflection:

Signal bounces back towards its source.

Diffraction:

Signal splits into secondary waves.

Line of Sight (LOS)

Signal travels in straight line directly from transmitter to receiver. When obstacles are in a signal's way, signal may pass through or be absorbed.

Attenuation:

Signal weakens as it moves away from transmission antenna. Correcting signal attenuation: - Increase power of transmission. - Repeat signal from closer broadcast point called wireless range extender.

Ad Hoc Wireless Topology

Small number of nodes closely positioned transmit directly to each other.

Z-Wave:

Smart-home protocol that provides 2 basic functions: -Signaling to manage wireless connections. -Control to transmit data and commands between devices. Z-Wave Network controller: - AKA a hub. Receives commands from smartphone/pc and relays commands to smart devices. Range: up to 100 m per hop, 4 hops total.

Wireless Spectrum

The frequency range of electromagnetic waves used for data/voice communication. Spans frequency ranges or bands between 9 kHz and 300 GHz.

Propagation:

The way in which a wave travels from one point to another.

Channel Bonding:

Two adjacent 20-MHz channels bonded to make 40-MHz channel Doubles the bandwidth available in single 20-MHz channel

IEEE 802.11 Frames:

Types of overhead required to manage access to an 802.11 network. -ACKs, probes, beacons. 802.11 specifies MAC sublayer and frame type. Multiple frame groups: - Management frames: Association, reassociation. - Control frames: Medium access and data delivery. ACK and RTS/CTS frames. - Data frames: Carry data sent between stations.

Service Set Identifier (SSID):

Unique character string identifying access point - in beacon frame information. Configured in access point, better security, easier network management.. Each WLAN has a unique SSID, wireless devices can see SSIDs for all available networks.

Radio Frequency Identification (RFID):

Uses electromagnetic fields to store data on RFID tag. 3 general types: ARPT (Active Reader Passive Tag) PRAT (Passive Reader Active Tag) ARAT (Active Reader Active Tag) Commonly used for inventory management, credit cards, etc.

802.11 WLAN Standards

WLANs work at OSI Layers 1 and 2. Support TCP/IP higher-layer OSI protocols and operating systems. Most popular standard is WiFi. -Developed by IEEE 802.11 committee. LLC sublayer primarily concerned with multiplexing, flow, error control, reliability.

Frame Aggregation Frame Sizes

Wi-Fi Standard: - 802.11n A-MSDU: -7935 bytes. -A-MPDU: -65,535 byes. Wi-Fi Standard: -802.11ac A-MSDU: -11,454 bytes. A-MPDU -4,692,480 bytes

Channel Management

Wifi uses DSSS (11 channels = 2.4 GHz, 24 channels = 5 GHz). Bluetooth uses FHSS (79 channels - piconets), uses one to set channel and clock speed. ZigBee uses DSSS (16 channels - used for medical, industry, and scientific purposes) ANT+: Uses a fixed frequency for device monitoring. Not DSSS or FHSS.

Interference:

Wireless signals are more vulnerable to noise. No wireless conduit, shielding.

Multipath Signals:

Wireless signals follow different paths to destination. Advantages: -Better chance of reaching destination. Disadvantages: -Signal delay will result in data errors.

Antennas

Wireless signals originate from electrical current traveling along a conductor. Travels from transmitter to an antenna. Antenna emits signal as series of electromagnetic waves into atmosphere. Destination antenna accepts signal and receiver converts it back to current. 2 antennas must be tuned to the same frequency in order to use the same channel.