7 Wireless and SOHO Networks

Question 1

The 4 wireless technology groups:

Answer 1

802.11
Bluetooth
long-range fixed wireless
radio frequency

Question 2

What is SSID ?

Answer 2

service-set identifier (SSID) of the network. SSID is a fancy term for the wireless network’s name

Question 3

Three types of wireless modulation used today:

Answer 3

Frequency-hopping Spread spectrum (FHSS) accomplishes communication by hopping the transmission over a range of predefined frequencies. The changing, or hopping, is synchronized between both ends and appears to be a single transmission channel to both ends.

Direct-Sequence Spread Spectrum (DSSS) accomplishes communication by adding the data that is to be transmitted to a higher-speed transmission. The higher-speed
transmission contains redundant information to ensure data accuracy. Each packet can then be reconstructed in the event of a disruption.

Orthogonal Frequency Division Multiplexing (OFDM) accomplishes communication by breaking the data into subsignals and transmitting them simultaneously. These transmissions occur on different frequencies, or subbands.

Question 4

What is 802.11 ?

Answer 4

802.11 is a standard that was developed by the Institute of Electrical and Electronic Engineers (IEEE). It is the original wireless specification. Extensions of the 802.11 standard were given the same number with a letter suffix.

802.11 Provides up to 2Mbps transmission in the 2.4GHz band

802.11b Provides up to 11Mbps transmission in the 2.4GHz band

802.11a Provides up to 54Mbps transmission in the 5GHz band

802.11g Provides up to 54Mbps transmission in the 2.4GHz band

802.11n Provides up to 450Mbps transmission in the 2.4/5GHz band

802.11ac Provides up to 7 Gbps transmission in the 5GHz band

802.11ax Provides up to 10Gbps transmission in the 2.4/5/6GHz band

Question 5

What is 802.11a ?

Answer 5

The 802.11a standard provides WLAN bandwidth of up to 54 Mbps in the 5 GHz frequency spectrum. The 802.11a standard also uses a more efficient encoding system, orthogonal frequency division multiplexing (OFDM), rather than FHSS or DSSS.

Question 6

What is 802.11b ?

Answer 6

The 802.11b standard was ratified in 1999. 802.11b provides for bandwidths of up to 11 Mbps (with fallback rates of 5.5, 2, and 1 Mbps) in the 2.4 GHz range. The 802.11b standard uses DSSS for data encoding. You may occasionally still see 802.11b devices in use, but they are becoming rare.

Question 7

What is 802.11g ?

Answer 7

Ratified in 2003, the 802.11g standard provides for bandwidths of 54 Mbps in the 2.4 GHz frequency spectrum using OFDM or DSSS encoding. Because it operates in the same frequency and can use the same modulation as 802.11b, the two standards are compatible. Because of the backward compatibility and speed upgrades, 802.11g replaced 802.11b as the industry standard. Devices that can operate with both 802.11b and 802.11g standards are labeled as 802.11b/g. Both can be used on the same network. 802.11b devices are not capable of understanding OFDM transmissions; therefore, they are not able to tell when the 802.11g access point is free or busy. To counteract this problem, when an 802.11b device is associated with an 802.11g access point, the access point reverts back to DSSS modulation to provide backward compatibility. This means that all devices connected to that access point will run at a maximum of 11 Mbps.

Question 8

2.4 GHz wireless networking channels:

Answer 8

Within the 2.4 GHz wireless range, the Federal Communications Commission (FCC) has defined 14 different 22 MHz communication channels. Although 14 channels have been defined for use in the United States, you’re allowed to configure your wireless networking devices only to the first 11. When you install a wireless access point and wireless NICs, they will all auto-configure their channel. If you are experiencing interference, changing the channel might help. Two channels will not overlap if there are four channels between them. If you need to use three nonoverlapping channels, your only choices are 1, 6, and 11.

Question 9

What is 802.11n ?

Answer 9

802.11n was ratified in 2010. The standard claims to support bandwidth up to 600 Mbps, but in reality the typical throughput is about 300–450 Mbps. It works in both the 2.4 GHz and 5 GHz ranges. 802.11n achieves faster throughput in a couple of ways. Some of the enhancements include the use of wider 40 MHz channels, multiple-input multiple-output (MIMO), and channel bonding. 802.11n combines two channels to double (basically) the throughput. MIMO means using multiple antennas rather than a single antenna to communicate information. (802.11n devices can support up to eight antennas, or four streams, because each antenna only sends or receives.) Channel bonding also allows the device to communicate simultaneously at 2.4G Hz and 5 GHz and bond the data streams, which increases throughput. One big advantage of 802.11n is that it is backward compatible with 802.11a/b/g. This is because 802.11n is capable of simultaneously servicing 802.11b/g/n clients operating in the 2.4 GHz range as well as 802.11a/n clients operating in the 5 GHz range.

Question 10

What is 802.11ac ?

Answer 10

802.11ac (Wi-Fi 5) is a more powerful version of 802.11n. 802.11n introduced channel bonding and MIMO, and 802.11ac takes those concepts further. Instead of bonding two channels, 802.11ac can bond up to eight for a 160 MHz bandwidth. This results in a 333-percent speed increase. First 802.11ac doubles the MIMO capabilities of 802.11n to eight streams, resulting in another 100 percent speed increase. Second, it introduces multi-user MIMO (MU-MIMO) for up to four clients. MU-MIMO allows multiple users to use multiple antennae for communication simultaneously, whereas MIMO only allowed for one such connection at a time on a device. The theoretical maximum speed of 802.11ac is 6.9 Gbps, but most 802.11ac devices peak at about 1.3 Gbps. Common maximum throughput is just under Gigabit Ethernet speeds, at around 800 Mbps. You might see devices in the marketplace that claim to offer speeds over 2 Gbps, but the reality is that you’re unlikely to get those speeds.

The most important new feature of 802.11ac is beamforming, which can allow for range increases by sending the wireless signal in the specific direction of the client, as opposed to broadcasting it omnidirectionally. Beamforming helps overcome the fact that the range for a 5 GHz signal is inherently shorter than one for a 2.4 GHz signal. Not all 802.11ac routers support beamforming, however, so you might have some range limitations, depending on your hardware. And even if the router does support the technology, the maximum distance still won’t be any more than what you will get out of 802.11n.

Question 11

What is 802.11ax ?

Answer 11

released in 2019 (Wi-Fi 6). enhancements over
Wi-Fi 5:

Faster:
Much Faster. The theoretical maximum speed of Wi-Fi 6 goes from 6.9 Gbps to 9.6 Gbps at 50 feet or less.

Better Connection Management:
Wi-Fi 6 introduces a new modulation technique called Orthogonal Frequency Division Multiple Access (OFDMA), which is an enhancement over the previously used OFDM. While OFDM was fast, it had a limitation that it could only transmit to one recipient at a time. OFDMA can handle communications with several clients at once. MU-MIMO works for uplink connections, too, meaning the router can also simultaneously receive data from multiple clients at once. This lowers latency (time spent waiting) and allows for more simultaneous devices on one network.

Less Co-channel Interference:
In Wi-Fi 6, a feature called Basic Service Set (BSS) coloring adds a field to the wireless frame that distinguishes it from others, reducing the problems of co-channel interference. Specifically, the 802.11ax access point has the ability to change its color (and the color of associated clients) if it detects a conflict with another access point on the same channel.

Simultaneous Use of Frequencies:
Wi-Fi 6 can operate at the 2.4 GHz and 5 GHz
frequencies at the same time, which also increases performance. Improved Battery Life and Power Consumption for Connected Devices Finally, Wi-Fi 6 has improvements in the technology that allow for client devices to essentially “sleep” while not directly communicating with the access point. This improves battery life and reduces power consumption for client Wi-Fi devices.

Cons:

They likely will be more expensive than their Wi-Fi 5 counterparts for several years.

You won’t get total speed increases until all devices on the network use Wi-Fi 6, including network cards.

You might not get the full benefit of the technology unless you have a gigabit Internet connection. Otherwise, your Internet connection will definitely be the bottleneck to the internal network.

Question 12

802.11 standards:

Answer 12

Type / Frequency / Maximum throughput / Modulation / Indoor range / Outdoor range

802.11 2.4 GHz 2 Mbps FHSS/DSSS 20 meters 100 meters

802.11a 5 GHz 54 Mbps OFDM 35 meters 120 meters

802.11b 2.4 GHz 11 Mbps DSSS 40 meters 140 meters

802.11g 2.4 GHz 54 Mbps DSSS/OFDM 40 meters 140 meters

802.11n 5 GHz/2.4 GHz 600 Mbps OFDM/DSSS 70 meters 250 meters

802.11ac 5 GHz 6.9 Gbps OFDM 35 meters 140 meters

802.11ax 5 GHz/2.4 GHz 9.6 Gbps OFDMA 35 meters 140 meters

Question 13

Bluetooth major versions and features

Answer 13

Version Basic Rate (BR) / Enhanced Data / Rate (EDR) / High Speed (HS) / Low Energy (LE) / Slot Availability Masking (SAM)

1.x X
2.x X X
3.x X X X
4.x X X X X
5.x X X X X X

Basic Rate (BR): All Bluetooth devices since version 1.0 have supported a basic data transfer rate of 1.0 Mbps. After overhead, actual data transfer is actually 721 Kbps.

Enhanced Data Rate (EDR): Version 2.0 supported EDR, which delivered bit throughput of 3.0 Mbps. After overhead, it goes down to 2.1 Mbps. EDR consume more power than BR consumes.

High Speed (HS): With version 3.0 came the HS enhancement, which allowed Bluetooth to transmit over available 802.11 signals. This boosted the data transfer rate to 24 Mbps. Using HS requires considerably more power than EDR.

Low Energy (LE): Version 4.0 introduced a low energy mode, which sacrifices data transfer rate (270 Kbps) but maintains transmission distance while using less energy. Devices using LE will consume somewhere between 1 percent and 50 percent of power compared to a device operating in Classic mode. The primary intent was to make this compatible with IoT devices. Version 4.2 was the first to include specific features for IoT.

Slot Availability Masking (SAM): One potential issue with Bluetooth is interference on its communication channels—it uses the same unlicensed 2.4 GHz frequency that WiFi does—and SAM is designed to help reduce problems. SAM can detect and prevent interference by switching bands within that frequency spectrum to help maintain throughput.

Question 14

Bluetooth v5

Answer 14

Bluetooth v5 has several new features over its predecessor, v4.2. Along with introducing SAM, and better security, it is capable of doubling the throughput and achieving four times the maximum distance, up to about 240 meters (800 feet) outdoors with line-of-sight, when in LE mode. That drops to about 40 meters (133 feet) indoors. It can increase throughput at a shorter distance, or it can go up to longer distances at a lower data rate. Subsequent improvements on v5 (v5.1, v5.2, and v5.3) have added features such as Angle of Arrival (AoA) and Angle of Departure (AoD), used to locate and track devices, better caching, improved LE power control and LE audio, and enhanced encryption. All versions of Bluetooth are backward compatible with older versions. When using mixed versions, the maximum speed will be that of the older device.

Question 15

Bluetooth Network

Answer 15

One of the key features of Bluetooth networks is their temporary nature. Whenever two Bluetooth devices get close enough to each other, they can communicate directly with each other. This dynamically created network is called a piconet. Bluetooth-enabled devices can communicate with up to seven other devices in one piconet. One device will be the primary, and the others will be secondaries.
The primary controls communication between the devices. Multiple piconets can be combined together to form a scatternet, and it’s possible for a primary of one piconet to be a secondary in another. In a scatternet, one of the Bluetooth devices serves as a bridge between the piconets.

Question 16

Bluetooth Devices

Answer 16

Bluetooth devices have classically been computer and communications peripheral —keyboards, mice, headsets, and printers being common. Smartphones and other mobile devices support Bluetooth as well. With the newest versions, we may see more IoT devices with Bluetooth capabilities as well. One such device is a Bluetooth beacon, which is a small hardware transmitter that uses Bluetooth LE. It’s broadcast only and transmits its unique identifier to nearby Bluetooth-enabled devices, such as smartphones.

There are four classes of Bluetooth devices, which differ in their maximum transmission range and power usage:

Class Distance Power usage
1 100 meters 100 mW
2 10 meters 2.5 mW
3 1 meters 1 mW
4 0.5 meters 0.5 mW

Question 17

Long-Range Fixed Wireless

Answer 17

In situations where the distance is too far for Wi-Fi but high-speed wireless network connectivity is needed, long-range fixed wireless could be the solution. Examples could include networking from building to building in a city or on a campus, bringing Internet access to a remote residence on a lake or in the mountains where wires can’t be run, or providing Internet to boats and ships.

Long-range fixed wireless is a point-to-point technology that uses directional antennas to send and receive network signals. An antenna typically looks like a small satellite dish, usually only about 1 meter wide, and can usually send and receive signals for 10 to 20 kilometers. Different dishes will support different technologies. For example, some may support Wi-Fi 5 or 6, whereas others may support those plus cellular networking, too. As the technology is point-to-point, the sending and receiving devices must be pointed at each other—misalignment will cause network failure—and obstructions such as trees or other buildings will cause problems, too.

Question 18

Unlicensed and Licensed Frequencies

Answer 18

Wi-Fi operates on the unlicensed frequencies of 2.4 GHz and 5 GHz. In 2020, 6 GHz was opened up to Wi-Fi in the United States as well. Other unlicensed frequencies include 900 MHz and 1.8 GHz and are used by devices such as walkie-talkies and cordless telephones. Unlicensed frequencies are free to use. Since everyone can use them, they are more susceptible to interference from other signals or eavesdropping. The same concept applies to long-range fixed wireless. The difference is that here, the beams are directional, fairly narrow, and pointed at a specific receiver. For someone to eavesdrop, they would need to get within the range of the field, which could be challenging but is not impossible. Other frequencies are licensed frequencies, meaning that use of them is granted by a governmental body. If access is granted, then that company is the only one that can use the frequency within a certain geographical area.

Question 19

Power over Long-Range Fixed Wireless

Answer 19

In addition to network signals, power can be transmitted over long-range fixed wireless as well. A common name for the technology is wireless power transfer (WPT). The transmitting station generates the power and then transmits it via microwave or laser light toward the receiver. The receiving station gets the signal and converts it back to electricity. It’s the exact same principle used by other radio transmissions. A small-scale example of wireless power transfer is wireless charging pads for mobile devices. Efficiency is an issue with current WPT implementations. The amount of energy lost can vary; some commercial providers claim to have 70 percent efficiency, which is far lower than copper cables. WPT technology is currently regulated in the United States by the FCC.

Question 20

Radio Frequency Identification

Answer 20

Radio frequency identification (RFID) is a communications standard that uses radio waves to facilitate communication. There are three types of RFID, based on the frequency used. This also affects the maximum distance that the waves can travel:

Name / Frequency / Distance
Low frequency (LF) / 125–134 kHz / 10 centimeters
High frequency (HF) / 13.56 MHz / 30 centimeters
Ultra-high frequency (UHF) / 856–960 MHz / 100 meters

Question 21

Radio Frequency Identification (RFID) components

Answer 21

The primary purpose of RFID is to identify items. Those items can be inventory in a store or warehouse, people, or even fast-moving things, such as race cars. RFID is simplistic in networking terms. Its function is to identify items within a relatively short range. Two-way communication is pretty limited. An RFID system is made of three components:

Tag
Reader
Antenna

Question 22

What is an RFID tag ?

Answer 22

An RFID tag is fastened to the item that needs to be tracked. This can be temporary, such as an access badge an employee carries around, or it can be permanently affixed to an item. The RFID tag contains identifying information, such as an employee ID, product number, inventory number etc. There are passive RFID tags and active RFID tags. Passive tags do not have a power source and draw their power from radio waves emitted by the RFID reader. This works only across short distances, typically about 25 meters or less. An active tag has its own power source (often a small battery) and may have its own antenna as well. Because it has power to generate a signal, the range for active tags is about 100 meters.

Question 23

What is a RFID reader ?

Answer 23

The reader’s job is to read information from tags. Readers have a power source and antenna. Once they get within 100 meters of an active tag or 25 meters of a passive tag, they can detect its presence. Readers can be mobile, such as a handheld inventory tracker, or static. An example of a static reader is the security gates that line the entrances of many retail stores. The products in the store have an RFID tag, and if an active tag passes through the scanners, an alarm sounds to notify the store personnel that someone may be attempting to steal an item.

Question 24

What is an RFID antenna

Answer 24

An antenna boosts the distance an RFID signal can travel. Readers may have multiple antennae, depending on the model.

Question 25

What is Near-Field Communication ?

Answer 25

A subset of RFID is a very short distance technology known as near-field communication (NFC). NFC is designed to facilitate information sharing and, in particular, contactless payment. It transmits at 13.56 MHz, which is the same frequency as HF RFID. Used for mobile contactless payment. NFC uses radio frequency (RF) signals, and NFC devices can operate in three different modes:

NFC Card Emulation Mode: This lets the device act as a smartcard. This is useful for making payments at the site of a merchant that uses NFC.

NFC Reader/Writer Mode: This allows the device to read information stored in an NFC tag on a label or poster.

NFC Peer-to-Peer Mode: This allows for ad hoc data transfer between two NFC-enabled devices.

NFC works up to 10 cm from another compatible device.

Question 26

NFC Transfer rates:

Answer 26

Data rates are rather slow compared to other wireless methods, as NFC operates at
106 Kbps, 212 Kbps, and 424 Kbps. Tags currently hold up to about 8 KB of data, which is more than enough to store a URL, phone number, or other date and time or contact information. In peer-to-peer mode, NFC data is transmitted in the NFC Data Exchange Format (NDEF), using the Simple NDEF Exchange Protocol (SNEP). SNEP uses the Layer 2 Logical Link Control Protocol (LLCP), which is connection-based, to provide reliable data delivery. NFC uses two different coding mechanisms to send data. At the 106 Kbps speed, it uses a modified Miller coding (delay encoding) scheme, whereas at faster speeds it uses Manchester coding (phase encoding). Neither method is encrypted, so it is possible to hack NFC communications using man-in-the-middle or relay attacks. Because of the limited distance of the RF signals, though, hacking is pretty hard to do. The potential attacker would need to be within a meter or so to attempt it.

Question 27

DSL standards and approximate speeds

Answer 27

Standard / Download speed / Upload speed
ADSL Up to 8 Mbps Up to 1 Mbps
SDSL Up to 2.5 Mbps Up to 2.5 Mbps
HDSL Up to 42 Mbps Up to 8 Mbps
VDSL Up to 52 Mbps Up to 16 Mbps

Question 28

Common Internet connection types and speeds

Answer 28

Dial-up: $10–$20, Up to 56 Kbps, Plain old telephone service. A regular analog phone line

DSL: $20–$30, Up to 50 Mbps, Inexpensive broadband Internet access method with wide availability, using telephone lines.

Cable: $20–$30, Up to 100 Mbps, Inexpensive broadband Internet access method with wide availability, using cable television lines.

Fiber: $40–$50, Up to 1 Gbps, Incredibly fast and expensive.

Satellite: $30–$40 Up to 25 Mbps, Great for rural areas without cabled broadband methods. More expensive than DSL or cable.

Cellular: $30–$50, Up to 100 Mbps, with 5G LTE or 1 Gbps with mmWave Great range; supported by cell phone providers. Best for a very limited number of devices.

WISP: $40–$150, 6 Mbps to 50 Mbps, Fast connection for rural areas without cabled broadband methods.

Question 29

Common Ethernet standards

Answer 29

Standard / Cables used / Maximum speed / Maximum distance

10BaseT UTP Cat 3 and above 10 Mbps 100 meters (∼300 feet)

100BaseTX UTP Cat 5 and above 100 Mbps 100 meters

100BaseFX Multi-mode fiber 100 Mbps 2,000 meters

1000BaseT UTP Cat 5e and above 1 Gbps 100 meters

10GBaseT UTP Cat 6 and above 10 Gbps 55 meters (Cat 6) or 100 meters (Cat 6a, 7, an 8)

25GBaseT or 40 GBaseT UTP Cat 8 25 Gbps or 40 Gbps 30 meters

10GBaseSR Multi-mode fiber 10 Gbps 300 meters

10GBaseLR Single-mode fiber 10 Gbps 10 kilometers (6.2 miles)

10GBaseER Single-mode fiber 10 Gbps 40 kilometers (∼25 miles)

Question 30

Types of Firewalls

Answer 30

Network-Based Firewall:

A network-based firewall is what companies use to protect their private network from public networks. The defining characteristic of this type of firewall is that it’s designed to protect an entire network of computers instead of just one system. It’s generally a stand-alone hardware device with specialized software installed on it to protect your network.

Host-Based Firewalls:
In contrast to network-based firewalls, a host-based firewall is implemented on a single machine, so it protects only that one machine. This type of firewall is usually a software implementation because you don’t need any additional hardware in your personal computer to run it. All current Windows client operating systems come with Windows Defender Firewall (or just Windows Firewall), which is a great example of a host-based solution. Norton Security and many other security products come with software firewalls too. Host-based firewalls are generally not as secure as network firewalls, but for small businesses or home use, they’re an adequate, cheap solution.

Question 31

How do Firewalls Work ?

Answer 31

Firewalls are configured to allow only packets that pass specific security restrictions to get through them. They can also permit, deny, encrypt, decrypt, and proxy all traffic that flows through them, most commonly between the public and private parts of a network. The network administrator decides on and sets up the rules a firewall follows when deciding to forward data packets or reject them. The default configuration of a firewall is generally default deny, which means that all traffic is blocked unless specifically authorized by the administrator. While this is very secure, it’s also time consuming to configure the device to allow legitimate traffic to flow through it. The other option is default allow, which means all traffic is allowed through unless the administrator denies it. If you have a default allow firewall and don’t configure it, you might as well not have a firewall at all.

The basic method of configuring firewalls is to use an access control list (ACL). The ACL
is the set of rules that determines which traffic gets through the firewall and which traffic is blocked. ACLs are typically configured to block traffic by IP address, port number, domain name, or some combination of all three. Packets that meet the criteria in the ACL are passed through the firewall to their destination.

Question 32

Network Address Translation

Answer 32

Network Address Translation (NAT) is a very cool service that translates a private IP address on your internal network to a public IP address on the Internet. If you are using your wireless router to allow one or more clients to access the Internet but you have only one external public IP address, your router is using NAT. Most routers have NAT enabled by default, and there might not be any specific configuration options for it. That’s true in the case of the router we’ve been using as an example. You can enable or disable it on the Advanced Routing tab in Connectivity, but otherwise the only options you can configure are the internal IP addresses that the router hands out to clients.

Another type of NAT is called Dynamic Network Address Translation (DNAT), which
translates a group of private addresses to a pool of routable addresses. This is used to make a resource that’s on a private network available for consumption on public networks by appearing to give it a publicly available address. For example, if a web server were behind a NAT-enabled router and did not have its own public IP address, it would be inaccessible to the Internet. DNAT can make it accessible.