N10-009 Network Implementation Study Guide for the CompTIA Network+

Wireless Devices and Technologies

Wireless standards govern wireless device usage, frequencies, specifications, and frequency spectrums. Given a scenario, you will need to be able to identify, install, and configure the appropriate wireless standard and technology for a given scenario.

Channels

A channel is a smaller band or range of frequencies within a larger band through which signals can be sent. The 2.4 GHz frequency has 11 possible channels, and the 5 GHz frequency has 34 possible channels in the United States. How many channels are available for usage, however, depends on the 802.11 standard that is being used. The 2.4 GHz frequency has three non-overlapping channels while the 5 GHz frequency has 24 non-overlapping channels in the US. For example, 802.11b/g uses three 2.4 GHz channels: channels 1, 6, and 11. The graphic below depicts these three non-overlapping channels used on the 2.4 GHz frequency:

Retrieved from: https://commons.wikimedia.org/wiki/File:Wifi-channels.svg

Channel Width

The channel width, measured in megahertz (MHz), refers to the designated range of frequency each channel uses for transmission. The 2.4 GHz frequency typically uses 20 MHz, while 5 GHz uses 40 MHz, and 6 GHz uses 320 MHz.

Non-Overlapping Channels

Wireless channels are non-overlapping, meaning no two channels will share range values. This prevents interference and signal disturbance.

Regulatory Impacts

Wireless communications regulations, such as 802.11, provide requirements for all devices that use electromagnetic spectrum radio frequency signals, including bandwidth usage specifications. These regulations are designed to both standardize communications and protect the public from the potential negative impacts of exposure to radio frequencies. With the ever-increasing usage of wireless transmissions, these regulations are continually developing to meet the needs of the changing environment. These same regulations, however, can also be restrictive for emerging wireless technology, since new devices that use wireless communications must stay within the confines of the set regulations.

802.11h

The 802.11h specification is designed to address interference between devices on the 5 GHz frequency. 802.11h provides specifications regarding the ability of wireless transmissions to dynamically switch channels using dynamic frequency selection (DFS) and adjust transmission power using transmit power control (TPC).

Frequency Options

A wireless frequency is the range of radio waves, known as a band and measured in hertz (Hz), that a wireless device communicates through. Each frequency is split into separate groups, or channels, to prevent interference and traffic congestion. The range of a wireless signal is the distance a signal can travel and still transmit data effectively. However, the further a receiving device gets from the transmitting device, the more attenuated and distorted the signal may get.

2.4 GHz

The 2.4 GHz frequency is more capable of transmitting signals through solid objects, such as walls, and at a greater distance than 5 GHz, but it does so at lower speeds. Transmissions at this frequency are also more susceptible to interference from other electrical devices using the same frequency.

5 GHz

The 5 GHz frequency can transmit at higher speeds than the 2.4 GHz frequency and is less prone to interference and disturbance, but it does not have the same range capabilities and penetration power.

6 GHz

The 6 GHz frequency provides a larger bandwidth, decreasing interference and increasing data transmission speeds.

a—The 802.11a standard runs on the 5 GHz frequency, with 12 non-overlapping channels, at a max rate of 54 Mbps. 802.11a transmission can be sent using orthogonal frequency-division multiplexing (OFDM) and is less prone to interference issues encountered by wireless devices using the 2.4 GHz frequency.

b—The 802.11b standard, sent using direct-sequence spread spectrum (DSSS), runs on the 2.4 GHz frequency, with three non-overlapping channels, at a max rate of 11 Mbps. The 802.11b standard is more prone to interference due to the large number of electrical devices that also use the 2.4 GHz frequency, such as microwaves and Bluetooth devices.

g—The 802.11g standard runs on the 2.4 GHz frequency, with three non-overlapping channels, at a max rate of 54 Mbps. 802.11g can use DSSS for transmission, but it more commonly uses OFDM. 802.11g is backward compatible with the 802.11b standard.

n (Wi-Fi 4)—The 802.11n standard can run on both 2.4 GHz and 5 GHz, with a varying number of channels, at a max rate of 300 Mbps. 802.11n is capable of using DSSS, OFDM, and complementary code keying (CCK) and is backward compatible with 802.11a/b/g. The 802.11n standard also added the ability to use multiple antennas and receivers, known as multiple-input multiple-output (MIMO), as well as multiple antennas and receivers spread between multiple APs, known as multi-user MIMO (MU-MIMO), on four spatial streams for throughput.

ac (Wi-Fi 5)—The 802.11ac standard uses the 5 GHz frequency, with a varying number of channels, at a max rate of 1 Gbps using OFDM. 802.11ac provides eight MIMO spatial streams and MU-MIMO capabilities, as well as the ability to identify very high throughput (VHT) data frames. 802.11ac is backward compatible with 802.11a/n.

ax (Wi-Fi 6)—The 802.11ax standard can run on 2.4 GHz, 5 GHz, and 6 GHz with a varying number of channels, at a max speed of 3.3 Gbps or higher. 802.11ax uses orthogonal frequency-division multiple access (OFDMA) scheduling, which reduces transmission latency and overhead. 802.11ax is backward compatible with all of the other standards indicated above.

Band Steering

Band steering is used to direct Wi-Fi traffic to the most appropriate frequency for optimal performance. It relies on factors such as transmission distance and the capabilities of the connecting device.

Service Set Identifier (SSID)

An SSID, sometimes referred to as a network name, is a unique character-based identifier that is assigned to a wireless network. The SSID is also used to define the type of installation mode the wireless network is using, either the ad hoc or infrastructure mode.

Basic Service Set Identifier (BSSID)

A BSSID, also known as infrastructure mode, creates wireless networks via a wireless access point (AP). All devices connected to the wireless network must communicate through the AP and do not have direct access to other devices on the network, while all devices connected to the AP in the wireless network must be connected to the same SSID for access to the network. For example, consider two laptops using BSSID mode that are attempting to send data files to one another. In BSSID mode, the two laptops will not be able to connect directly to one another, but both have access to an AP. As such, both laptops can connect to the AP using the same SSID and establish communications.

Extended Service Set Identifier (ESSID)

An ESSID is created when more than one wireless network is configured to use the same SSID, allowing connected devices to move freely from AP to AP. For example, say there is a large office building that has multiple APs placed throughout the building. If all the APs are configured with the same SSID, once an initial connection is made using the SSID, the connection will transfer between any AP using the same SSID, no matter its location in the building.

Network Types

Wireless networks, like physical networks, can be connected in different ways or modes depending on the needs and requirements of the network.

Mesh Networks

A wireless mesh network is composed of multiple APs that communicate with one another to create a wireless network covering a larger geographical area. In a wireless mesh network, connected devices automatically switch between APs based on location and signal strength.

Ad Hoc

An ad hoc wireless network, also known as an independent basic service set (IBSS), is one in which two or more devices connect directly to one another rather than going through an AP. For devices to create this type of network, both devices must be in ad hoc mode.

Point-to-Point

A wireless point-to-point network is one in which two devices connect directly with one another without using an AP. A point-to-point connection is used to create connections over long distances and requires a line of sight to establish a connection.

Infrastructure

A wireless network in infrastructure mode, also known as BSSID, is one in which all communications, both wired and wireless, go through an AP to access the network. As a result, all devices appear to be physically connected to the network.

Encryption

A wireless encryption standard is a wireless security protocol that is used to create secure, authenticated connections to a wireless network. Wireless encryption standards vary depending on the type of encryption used and the authentication method used.

Wi-Fi Protected Access 2 (WPA2)

A WPA is a security standard developed by the Wi-Fi Alliance that specifies the use of the Temporal Key Integrity Protocol (TKIP) for encryption. WPA2-Personal increased the security of WPA by using a pre-shared key (PSK) with TKIP or the Advanced Encryption Standard-Counter Mode CBC-MAC Protocol (AES-CCMP). WPA/WPA2-Enterprise uses an authentication server to create the key, which can then be encrypted using either AES-CCMP or TKIP.

WPA3

WPA3 is the latest iteration of the WPA standard. WPA3 increases security by using the Simultaneous Authentication of Equals (SAE) protocol for key exchange, individual device data encryption, and higher 192-bit encryption standards in Personal mode.

Guest Networks

A guest network is a wireless configuration that creates a separate network for guest connections, keeping the guest network completely separate from the primary network. Guest network isolation only provides internet access and uses client isolation to separate connected devices.

Captive Portals

A captive portal is an AP connection method that directs clients to a predefined web page prior to AP access. Captive portals are commonly used in free Wi-Fi connection situations, such as in coffee shops or hotels. When the SSID for the free Wi-Fi is connected to, it automatically directs the client to a sign-in page or a terms and agreement page prior to allowing access to the Wi-Fi connection.

Authentication

Authentication for a wireless network refers to how a device is verified prior to being granted access to the network and its resources. Authentication is commonly achieved through the use of verifiable credentials, such as a username and a password.

Pre-Shared Key (PSK) vs. Enterprise

A network using a PSK for authentication is one that has a single passphrase for all connected devices. In contrast, a wireless network using enterprise authentication assigns unique credentials for each user.

Antennas

For wireless communications to occur, devices must be equipped with a wireless antenna that is used for both receiving and sending transmissions. Wireless antennas are divided into two primary categories: omnidirectional and directional.

Omnidirectional vs. directional

An omnidirectional antenna, also known as an omni or point-to-multipoint antenna, is able to send and receive data from any direction. Omni antennas are more versatile but have smaller ranges since all of the power has to be dispersed over an entire location. APs commonly use omni antennas to enable users to connect from any location within the range of the AP. An omni antenna, as illustrated below, disperses a signal evenly on the horizontal plane with the significant signal degradation (or signal attenuation) on the vertical plane, or directly above and below the antenna.

Retrieved from: https://commons.wikimedia.org/wiki/File:Omnidirectional_antenna_-_horizontal_and_vertical_radiation_patterns.png

A directional antenna, also known as a Yagi or point-to-point antenna, limits connection to a specified area. Directional antennas are more difficult to connect to but are able to provide a longer transmission range since all of the power of the antenna is focused on a single location. A directional antenna, illustrated below, provides the highest signal strength directly in front of the antenna, as indicated by the red lines, with degraded peripheral signal dispersed around the antenna, as indicated by the blue lines.

Retrieved from: https://upload.wikimedia.org/wikipedia/commons/a/ae/Patch_antenna_pattern.gif

Autonomous vs. Lightweight Access Point

An autonomous access point is one that can be used as a standalone device, allowing for individual management and configuration of the device. A lightweight access point is one that requires a connection to a WLAN controller for management and configuration. A lightweight access point is unable to function as an individual device.