Chapter 6 CONE

Wireless Networking Notes

Chapter 6 Overview

This module covers wireless networking, including characteristics of wireless transmissions, $802.11$ standards, Wi-Fi network planning, security, and troubleshooting.

Introduction

• Wireless networks are common in homes, offices, and specialized environments like IoT.
• Wireless signals use the air as a medium, working with wired technologies.
• The module focuses on setting up, managing, securing, and troubleshooting local wireless networks.

On the Job: Real-World Example

• A service manager from Dalton Computer Services, Inc. shares an experience of installing a wireless AP in an old home in Dalton, Georgia.
• Signal strength was unexpectedly low in the living room due to chicken wire within the plaster wall blocking the signal.
• A second AP was installed to resolve the issue.
• Moral: Be aware of the impact walls can have on wireless signals, particularly in older homes.

Characteristics of Wireless Transmissions

• Wireless signals travel through the air via electromagnetic waves.
• The wireless spectrum, or airwaves, is the frequency range used for data and voice communication, as defined by the FCC.
• The spectrum spans frequencies from $9 \, kHz$ to $300 \, GHz$.
• Some frequency bands are subdivided into channels, while others use a fixed frequency.

Wireless Technologies and Frequency Ranges

• RFID: $125$ kHz–$134.2 \, kHz$ (lowest)
• NFC: $13.56 \, MHz$ (fixed frequency)
• Z-Wave: $90.842 \, MHz$ (fixed frequency)
• Cellular: $824 \, MHz$–$896 \, MHz$ (800 band) & $1850 \, MHz$–$1990 \, MHz$ (1900 band)
• Wi-Fi (802.11b/g/n/ax): $2.4 \, GHz$–$2.4835 \, GHz$ (11 or 14 channels)
• ZigBee: $2.4 \, GHz$–$2.4835 \, GHz$ (16 channels)
• Bluetooth: $2.4 \, GHz$–$2.4835 \, GHz$ (79 channels)
• Wi-Fi (802.11a/n/ac/ax): $5.1 \, GHz$–$5.8 \, GHz$ (24 channels)
• Wi-Fi (802.11ax Wi-Fi 6E): $5.925 \, GHz$–$7.125 \, GHz$
• IR: $300 \, GHz$–$300,000 \, GHz$

Wireless Technologies Explained

• RFID (Radio Frequency Identification): Uses electromagnetic fields to store data on a tag with an antenna. Tags can store $1$–$8 \, KB$ of data that transmits to a reader. Commonly used for inventory management and contactless payments.
• NFC (Near-Field Communication): A form of RFID for short-distance wireless data transfer (usually under $10 \, cm$). Uses a fixed frequency of $13.56 \, MHz$. Used for ticketing, cashless payments, loyalty programs, ID, data sharing, and PC logon.
• Z-Wave: Smart home protocol for managing wireless connections and controlling devices. A hub receives commands and relays them to devices, identified by a 1-byte Node ID. Networks have a 4-byte Network ID to prevent interference. Offers a range of up to $100 \, m$ per hop, tolerating up to four hops.
• ZigBee: Low-powered wireless tech based on $802.15.4$ standard. Ideal for ISM sensors. Used in IoT for building automation, HVAC control, AMR, and fleet management. Employs 128-bit AES encryption for security.
• Bluetooth: Defined by IEEE $802.15.1$. Operates in the $2.4 \, GHz$ to $2.4835 \, GHz$ band, hopping frequencies up to $1600$ hops/sec to reduce interference. Requires close proximity for connection.
• ANT1: Ad-hoc wireless protocol around $2.4 \, GHz$. Used to gather and track data from sensors in heart rate monitors, GPS devices, and activity trackers. Can sync data from multiple devices, unlike Bluetooth.
• IR (Infrared): Used in IoT for data collection via sensors and in remote controls. Requires a nearly unobstructed Line of Sight (LOS). Security can be increased due to its LOS limitation.

The Wireless Spectrum

• Wi-Fi, Bluetooth, ZigBee, ANT1, and some satellite signals share frequencies around $2.4 \, GHz$.

Regulation of the Airwaves

• The FCC controls the use of the wireless spectrum in the U.S., granting exclusive rights for specific frequencies.
• The ITU sets standards for international telecommunications, including wireless frequency allocations.
• Some bands require licenses, while others like Wi-Fi bands and CB radio are available for public use without a license, provided they meet signal transmission strength restrictions.

Channel Management

• Bands are subdivided into channels, which are further subdivided into narrowband channels.

Techniques to Avoid Interference

• FHSS (Frequency Hopping Spread Spectrum): Transmits short data bursts on different frequencies within the band. Cheaper and better in crowded, indoor environments.
• DSSS (Direct Sequence Spread Spectrum): Divides data into small chunks (chips) spread over all available frequencies within wide channels. Uses a unique chipping code for each device. More efficient bandwidth usage and higher throughput.

Wireless Standards and Channel Usage

• Wi-Fi: Uses DSSS. The FCC defines 11 channels in the $2.4 \, GHz$ band and 24 channels in the $5 \, GHz$ band. Each channel is $20 \, MHz$ wide.
• Bluetooth: Uses FHSS with 79 channels.
• ZigBee: Uses DSSS and 16 channels.

Collision Avoidance

• Technologies have procedures to handle collisions.
• Bluetooth devices back off when they sense a collision with a Wi-Fi channel.
• Wi-Fi uses a “listen before transmit” strategy to find a silent channel.

Antennas

• Antennas transmit and receive wireless signals.
• Two antennas must be tuned to the same frequency to communicate.
• Specifications determine power output, frequency, and radiation pattern.

Radiation Patterns and Antenna Types

• Directional Antenna: Issues signals in a single direction, for point-to-point links.
• Omnidirectional Antenna: Issues signals equally in all directions.

Considerations for Antenna Use

• Range: The geographical area the antenna can reach.
• Wireless technology can be used to connect two different parts of a LAN or two separate LANs.
• Point-to-point links can apply more energy for greater transmission distance.
• Attenuation, or signal loss, over the antenna cable typically necessitates placing a network access point in close vicinity to the antenna.

EIRP and RSSI

• EIRP (Effective Isotropic Radiated Power): Measures the gain or loss of an access point, in dBm.
• Formula: $EIRP = \text{transmission power (dBm)} - \text{cable loss (dB)} + \text{antenna gain (dBi)}$
• RSSI (Received Signal Strength Indicator): Measures signal power on the receiver’s end, in dBm. Closer to 0 is better (shown as negative numbers).

RSSI Levels

• -30 dBm: Excellent (very close to the AP)
• -50 dBm: Good (reliable data delivery)
• -70 dBm: Acceptable (minimum for reliable data delivery)
• -80 dBm: Not good (basic connectivity)
• -90 dBm: Unusable (difficulty establishing a connection)

Signal Propagation

• Propagation: The way a wave travels from one point to another.
• LOS (Line of Sight): Straight-line propagation for clearest signal reception.

Phenomena Affecting Wireless Signals

• Attenuation: Signals weaken as they move away from the source.
• Fading: Signal energy gradually fades due to obstacles.
• Interference: Electromagnetic waves interfere with wireless communications, measured by the SNR (signal-to-noise ratio).
• Refraction: Wave direction, speed, and wavelength are altered when traveling through different media.
• Reflection: Wave bounces back toward its source off large, flat surfaces.
• Scattering: Signal is diffused in multiple directions by objects with small surface dimensions compared to the signal’s wavelength.
• Diffraction: Signal splits into secondary waves when encountering an obstruction.
• Multipath Signals: Signals travel through different paths, causing multiple instances of the same signal to arrive at different times, potentially leading to data errors.

WLAN Standards: IEEE 802.11

• WLANs support TCP/IP higher-layer OSI protocols.
• Wi-Fi refers to the IEEE $802.11$ standards.
• Key standards: $802.11b$, $802.11a$, $802.11g$, $802.11n$, $802.11ac$, $802.11ax$.

802.11 Standards Detailed

• 802.11b: Released in 1999, it separates the $2.4 \, GHz$ band into $22 \, MHz$ channels. Dubbed Wi-Fi 1.
• 802.11a: Released after 802.11b, uses higher frequencies and bandwidth. Called Wi-Fi 2.
• 802.11g: Designed to be affordable as 802.11b, increasing throughput, compatible with the $2.4 \, GHz$ band and 802.11b networks, called Wi-Fi 3.
• 802.11n: Released in 2009, known as Wi-Fi 4, utilizes both the $2.4 \, GHz$ and $5 \, GHz$ bands, with a maximum throughput of $600 \, Mbps$. Backwards compatible with earlier standards.
• 802.11ac: Approved in 2014. Operates on the $5 \, GHz$ band. Named Wi-Fi 5. Approaches Gigabit Ethernet capabilities.
• 802.11ax: Current standard (Wi-Fi 6), operates in both $2.4 \, GHz$ and $5 \, GHz$, and increases data speeds and transmission distances. Can support higher speeds for more network clients. Builds on improvements of $802.11ax$, Wi-Fi 6E will use the unlicensed $6 \, GHz$ frequency range.

Technical Details of 802.11 Standards

Notes on Actual Geographic Range

• The geographic range of any wireless technology depends on the power of the antenna, physical barriers between sending and receiving nodes, interference in the environment, and how well it saturates its range with a strong, fast signal.

802.11 Innovations

• All 802.11 standards use half-duplex signaling.

Key Innovations for Improved Performance

• Channel Bonding:Combines two adjacent $20 \, MHz$ channels to make a $40 \, MHz$ channel.
• MIMO (Multiple Input-Multiple Output): Uses multiple antennas on the access point and client device to process data. Improves signal quality, range, and signal capacity.
• MU-MIMO (Multiuser MIMO): Allows multiple antennas to service multiple clients simultaneously.
• OFDMA (Orthogonal Frequency Division Multiple Access): Supports efficient multi-user functionality. Subdivides each channel into smaller frequency allocations for each client.
• Frame Aggregation: Combines multiple data frames into one larger frame to reduce overhead, using A-MSDU (Aggregated Mac Service Data Unit) or A-MPDU (Aggregated Mac Protocol Data Unit).

Access Method: CSMA/CA

• 802.11 networks use CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) to access a shared medium.

CSMA/CA Process

1. A node checks for existing wireless transmissions.
2. If no activity is detected, the node waits a brief, random amount of time and then sends its transmission.
3. The destination node receives the transmission and issues an ACK (acknowledgment) packet to the source.
4. If the source does not receive acknowledgment, it assumes the transmission did not arrive properly and restarts the process.

RTS/CTS Protocol

• Optional RTS/CTS (Request to Send/Clear to Send) can be used to reserve the medium for one node’s use.

Association and Wireless Topologies

• Association: Packet exchanges between an access point and a computer.

Scanning Types

• Active Scanning: Clients take the initiative, transmitting a probe frame on all available channels.
• Passive Scanning: APs take the initiative, issuing a beacon frame containing information that wireless nodes need to associate.

Wireless Topologies

• IBSS (Independent Basic Service Set): Network has a small number of nodes closely positioned that transmit directly to each other without an intervening connectivity device, using an ad hoc topology
• BSS (Basic Service Set): Network that has a group of nodes sharing an access point, using an infrastructure topology.
• ESS (Extended Service Set): Network that has several access points working as peer devices on the same network, forming a mesh topology. Clients share an ESSID (extended service set identifier). AP devices cooperate to allow for more fault-tolerant network access to clients across a larger geographical range. Typically managed via a wireless LAN controller.

Wireless Controllers

• Centralized wireless management is made possible by protocols like Cisco’s LWAPP and CAPWAP.
• Controllers provide centralized authentication, load balancing, and channel management.
• Wireless controllers can also detect the presence of unauthorized APs, called rogue access points.

Roaming

• Within an ESS, a client can associate with any AP that uses the same ESSID, allowing users to roam without losing network service.

IEEE 802.11 Frames

• Frame types: management frames, control frames, and data frames

Key Parts of the 802.11 Data Frame

• Frame Control
• Duration
• Address 1-4
• Sequence Control
• Data
• Frame Check Sequence (FCS)

Implementing a Wi-Fi Network

Factors Affecting Wireless Network Design

• Network environment, number and expectations of users, and networked devices that need to be supported.

SOHO Networks

• Typically requires one central AP and range extenders. Often referred to as a wireless router or SOHO router, combines switching, routing, or other network function.

IoT in Home Networks

• Internet of Things (IoT) constitutes any device that can be connected to the Internet, from sensors to computers to wearable devices.
• Home area networks (HAN) consist of connected devices within a home.

Smart Home Devices

• Smart thermostat: Adjust settings based on schedules, activity, weather & voice commands.
• Smart doorbell: Monitors entryways. May communicate with visitors remotely with video, play prerecorded messages, or use AI to identify frequent visitors.
• Security camera: Wireless devices with rechargeable batteries that can be installed anywhere for remote monitoring.
• Smart refrigerator: Detects items stored, alerts users when items are low or expired using RFID tracking and interior cameras.

Considerations for Access Point Installation

• Distance: Consider typical client distance and restrictions for 802.11 standards.
• Type and number of obstacles: Consider potential interference from obstacles in three-story buildings/bunkers.
• Coverage: Place the AP in a high spot.
• Interference: Do not position the AP near cordless phones, fluorescent lights, or microwave ovens.

Corporate Networks

• Larger wireless networks need a systematic approach for access point placement, conducting a site survey.
• A site survey assesses client requirements, facility characteristics, and coverage areas.

Site Survey Activities

• Study building blueprints: This will help to identify potential obstacles, clarify distances on each floor, and anticipate wireless demand.
• Consider wireless bridge: A wireless bridge could connect two networks or two remote portions of a network.
• Determine whether the floors require multiple APs: Visually confirm and test locations, test wireless access from farthest corners, factor in materials, & how the wireless portions will integrate with the wired portions.
• Ensure seamless connectivity: All APs must belong to the same ESS and share an ESSID.

Key items for using and mainitaining wireless survey tools

• Study and inspect building blueprints to locate potential obstacles.
• Consider demands of wireless bridges, such as throughput.
• Survey floors and locations that require multiple APs.
• Measure signal coverage and strength of other WLANs.
• Stress-test access-point locations.
• Complete the job efficiently with wireless survey tools, including NetSpot, VisiWave, iBwave Wi-Fi Suite, and inSSIDer by MetaGeek.

Configure Wi-Fi Connectivity Devices

• Access points provide wireless connectivity and vary in features, such as supported wireless standards, antenna strength, and support for voice signals/security measures.

Configurations

• Administrator password
• SSID (and determine whether it’s broadcast)
• Set up the security and credentials needed for association
• If DHCP or related options are used, ensure there are no designation problems

Resetting a SOHO Router

1. Disconnect data cables and unplug the power cable.
2. Depress the reset button while plugging the power cable back in.
3. Hold the button for at least 30 seconds.
4. Release the button.

Configure Wi-Fi Clients

Two-Part Processes

• Onboarding: Users or network technicians install an agent on a user’s device so the device can have trusted network access with specific permissions.
• Offboarding: Procedure involves removing the device permissions. Needs a remote wipe feature to clear info, permissions, and apps without physical access to a stolen device.

Policies

• Used in BYOD environments to maintain network safety.

Linux Wireless Interface

• There are a few, basic steps to completing this approach:

1. Verify that your wireless NIC is installed and within range of a working AP.
2. Open Terminal iwconfig.
3. See output regarding wireless adapter, and verify connection.
4. For further information enter the command "man iwconfig"

Wi-Fi Network Security

Authentication and Encryption

• Authentication: Allows a wireless client to log into the network using the proper password for the SSID or by providing user credentials that might be processed by an authentication server.
• Encryption algorithms: Scramble data transmitted in format that cannot be interpreted if the signal is intercepted, to ensure information privacy.

Options for Secure Wireless Networks

• WEP
• WPA
• WPA2

WEP (Wired Equivalent Privacy)

• Allows for optional encryption, but is outdated.

Offers Two Forms of Authentication (Neither of Which Are Secure)

• OSA (Open System Authentication): Uses no code. No encrypted data can be sent.
• SKA (Shared Key Authentication): All wireless access clients use the same key, which can then encrypt transmissions. The key can be cracked, comprising client security on the network.

WPA (Wi-Fi Protected Access)

• Replaces WEP with dynamic key assignment.
• 802.11i incorporates TKIP (Temporal Key Integrity Protocol): Improves security for legacy devices through message integrity, key distribution, and en encryption using RC4 (Rivest Cipher 4).
  Note: Intended more for assessing and checking WEP than as a sophisticated encryption protocol.

WPA2 (Wi-Fi Protected Access, Version 2)

• Uses stronger technologies and can be enabled on consumer-grade APs, most notably CCMP (Counter Mode with CBC Message Authentication Code Protocol).

Security Measures from CCMP

• AES (Advanced Encryption Standard): provides data confidentiality data transformation for encryption.
• Message integrity: CBC-MAC ensures packets are coming from the declared source, doing so using AES.

Additional notes

1. Wi-Fi Alliance released WPA3 in 2018. Some features include disabling legacy protocols, more advanced methods of encryption/authentication, and better protection of data. Intended to close some loopholes present in WPA2 by researchers looking for WPA3 flaws.

Personal and Enterprise Configurations

Key Differences

• Options for WPA-Personal and WPA-Enterprise can be set in wireless routers and some access points (APs).
  • WPA-Personal and WPA2-Personal are also known as *Pre-Shared Key, or WPA-PSK, and WPA2-PSK - which are the default key configurations on home wireless networks. Need to enter a passphrase to authenticate an encryption key.
  • The most secure Wi-Fi communication is made possible with a combination of a RADIUS authentication with WPA and WPA2, known as WPA-Enterprise and WPA2-Enterprise respectively.
• RADIUS (Remote Authentication Dial-In User Service): Central authentication for wireless, mobile, & remote users. A RADIUS server works in cooperation with authentication via EAP. Features of EAP include: User ID, Password and biometric scanning authentication.
  • 802.1X allows EAPoL traffic over wired/wireless client until the client has authenticated via the server - and is dubbed EAPoL, or “EAP over LAN.”
  • PNAC (port-based network access control, or port-based authentication): allows for EAP traffic on switched devices

Key Adaptions of EAP (extensible authentication protocol) include EAP-TLS, PEAP, and EAP-Fast.

• EAP-TLS- This implementation of EAP is also is similar to HTTPS and utilizes TLS encryption when securing HTTP settings.EAP-TLS uses PKI (public-key infrastructure) certificates. It exchanges public keys and authenticates both the supplicant and the server through mutual authentication. EAP-TLS also requires a CA (Certificate Authority) is to help manage the certificates as needed, though they can be a challenge to set up. However, those certificates provide more authentication.
• PEAP (Protected EAP): Creates an encrypted TLS tunnel between the supplicant and the server before proceeding to the usual EAP process. Then EAP is used for the inner method - and another method is what occurs inside the protected tunnel. Some common inner methods include EAP-MSCHAPv2.
• EAP-FAST (EAP-Flexible Authentication via Secure Tunneling): It functions and was developed by, and is similar to PEAP It utilizes PACs (Protected Access Credentials). Its website cookies store on a user’s computer to track their activities. When added, a PAC is stored on the supplicant devices for faster establishment of the TLS tunnel via future sessions.

Other Security Configurations

**AP and antenna placement- Optimal positioning of a router enables ideal signal management across an area.*

• Geofencing: A more sophisticated security technique that detects a Wi-Fi client’s geographical position and activates resources or access according to that location.
• *Guest network: Many establishments create an isolated guest network through their Wi-Fi router AP, set with separate SSID and passphrases. Gives guests access to Internet service without granting access to the LAN.
• *Wireless client isolation: Similar to an isolated guest network but simple.. It imposes firewall rules to restrict that client’s ability only with the default gateway.
• *Captive portal: The first page a new browser sees when connecting to the guest network, usually requiring agreement with a set of terms for access. Reminds users of a lack of authentication/data encryption measures for an open network, as well as data transmitting and legal issues.

Key items of note here, include the limitations of Captive Portals, particularly using custom DNS servers and the need to reach nonsecure web pages so that the captive portal can load successfully.

• *IoT access considerations

Security Threats to Wi-Fi Networks

• Wireless transmissions are particularly susceptible to eavesdropping.
• Key aspects of threat awareness, include: • War driving • War chalking • Evil twin • WPA attack • WPS attack
  • Note that physical Contact is required to collect data from a magnetic strip, but the RFID chip can transmit data to a skimmer several inches away.
    • Always examine payment terminals for physical signs of tampering.

Other physical threats include:

• Theives who swiping theft with RFID near victim pockets for information from enclosed RFID credit cards, in a tactic termed “electronic pickpocketing.”
• EMV: Europay, Mastercard, and Visa- contain a different chip kind that generates individual transactions for the best safety and security.

Check Wireless Security Settings (Win 10)

1. Open the Network and Sharing Center.
2. Select Wireless Properties.
3. Review the Connection and Security settings

Troubleshooting Wi-Fi Networks

Wi-Fi Network Tools

• An application that is made to scan for the wireless signals within a certain area, and can even discover all the wireless nodes. These can be used to quickly find any transmitting access points in that said area. This can then ensure all access points from nodes are broadcasting at a safe and secured rate.

  • Spectrum analyzer: a hardware device that can assess wireless signals by frequency-scanning.
  • Wi-Fi analyzer: A software application that can manage the Wi-Fi availability , optimization, and wireless signal settings or help identify Wi-Fi security threats.
    -Wireless network testing include Identify APs & Nodes, Measure signal, Indicate effects, Interpret location data, Ensure the right association and transmission/exchange between nodes, Measure data, and Analyze information of each channel.

When properly set up, channels will exist at the start, core, and limit channel bandwidths.
It is better to program a channel in order to make sure the channel does not conflict or overlap with other channels.

Avoid Pitfalls

When Unable To Connect to an AP: Key Areas of Focus

• Wrong SSID
• Encryption Protocol Mismatch
• Incorrect passphrase
• Static Chanel Utilization
• Long AP Association Time
• Mismatched RF Standards
• Mismatched 802.11 b/a/g/n/ac/ax Protocols.

Addressing Slow Connection Speeds

• Factors that affect and slow down connection speeds in the workplace or in more public areas are:*:

• Insufficient coverage

• RF Attenuation/Loss

• Interference- EMI is often the sole cause for slower connectivity

• Channel Overlap- Causing interference between transmission rates.
  Wireless Standard

• Simultaneous wired and wireless connectivity - create transmission conflicts

• Problems with firmware updates

• Incorrect Antenna Type- Make sure the type is omnidirectional as needed

• Mismatched polarization. Radio waves radiate from an antenna in all directions, in many different axis (Vertical and Horizontal). Ensure that the set up, for example, is vertically polarized where needed. Otherwise, the connection between AP may be less performant.

• Client Saturation (Overcapacity). There are limits to devices for an active network, ensure the usage of available devices does not outweigh the APs capabilities.

• Customer Dissociation