# Chapter 5

A **local area network** (**LAN**) is a [computer network](https://en.wikipedia.org/wiki/Computer_network) that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a [wide area network](https://en.wikipedia.org/wiki/Wide_area_network) (WAN) not only covers a larger geographic distance, but also generally involves [leased telecommunication circuits](https://en.wikipedia.org/wiki/Leased_line).

[Ethernet](https://en.wikipedia.org/wiki/Ethernet) and [Wi-Fi](https://en.wikipedia.org/wiki/Wi-Fi) are the two most common technologies in use for local area networks. Historical network technologies include [ARCNET](https://en.wikipedia.org/wiki/ARCNET), [Token Ring](https://en.wikipedia.org/wiki/Token_Ring), and [AppleTalk](https://en.wikipedia.org/wiki/AppleTalk).

A **wireless LAN** (**WLAN**) is a [wireless computer network](https://en.wikipedia.org/wiki/Wireless_computer_network) that links two or more devices using [wireless communication](https://en.wikipedia.org/wiki/Wireless_communication) to form a [local area network](https://en.wikipedia.org/wiki/Local_area_network) (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a [gateway](https://en.wikipedia.org/wiki/Gateway_\(telecommunications\)), a WLAN can also provide a connection to the wider [Internet](https://en.wikipedia.org/wiki/Internet).

Most modern WLANs are based on [IEEE 802.11](https://en.wikipedia.org/wiki/IEEE_802.11) standards and are marketed under the [Wi-Fi](https://en.wikipedia.org/wiki/Wi-Fi) brand name.

Wireless LANs are popular for use in the home, due to their ease of installation and use. They are also popular in [commercial properties](https://en.wikipedia.org/wiki/Commercial_property) that offer wireless access to their employees and customers.



## Types of Ethernet cabling

There are three cable types commonly used for Ethernet cabling: coaxial, twisted pair, and fiber-optic cabling. In today’s LANs, the twisted pair cabling is the most popular type of cabling, but the fiber-optic cabling usage is increasing, especially in high performance networks. Coaxial cabling is generally used for cable Internet access. Let’s explain all three cable types in more detail.

#### Coaxial cabling

A coaxial cable has an inner conductor that runs down the middle of the cable. The conductor is surrounded by a layer of insulation which is then surrounded by another conducting shield, which makes this type of cabling resistant to outside interference. This type of cabling comes in two types – thinnet and thicknet. Both types have maximum transmission speed of 10 Mbps. Coaxial cabling was previously used in computer networks, but today are largely replaced by twisted-pair cabling (Photo credit: Wikipedia)

[![coaxial cable](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/coaxial_cable.jpg)](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/coaxial_cable.jpg)

#### Twisted-pair cabling

A twisted-pair cable has four pair of wires. These wires are twisted around each other to reduce crosstalk and outside interference. This type of cabling is common in current LANs.

Twisted-pair cabling can be used for telephone and network cabling. It comes in two versions, **UTP (Unshielded Twisted-Pair)** and **STP (Shielded Twisted-Pair)**. The difference between these two is that an STP cable has an additional layer of insulation that protects data from outside interferences.

Here you can see how a twisted pair cable looks like (Photo credit: Wikipedia):

[![UTP cable](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/UTP_cable.jpg)](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/UTP_cable.jpg)

A twisted-pair cable uses 8P8C connector, sometimes wrongly referred to as RJ45 connector (Photo credit: Wikipedia).

[![RJ45](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/RJ45.jpg)](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/RJ45.jpg)

#### Fiber-optic cabling

This type of cabling uses optical fibers to transmit data in the form of light signals. The cables have strands of glass surrounded by a cladding material (Photo credit: Wikipedia):

[![optical fiber cable](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/optical_fiber_cable.jpg)](https://603168-1953132-raikfcquaxqncofqfm.stackpathdns.com/wp-content/images/optical_fiber_cable.jpg)

This type of cabling can support greater cable lengths than any other cabling type (up to a couple of miles). The cables are also immune to electromagnetic interference. As you can see, this cabling method has many advantages over other methods but its main drawback is that it is more expensive.

There are two types of fiber-optic cables:

* **Single-mode fiber (SMF)** – uses only a single ray of light to carry data. Used for larger distances.
* **Multi-mode fiber (MMF)** – uses multiple rays of light to carry data. Less expensive than SMF.

Four types of connectors are commonly used:

* ST (Straight-tip connector)
* SC (Subscriber connector)
* FC (Fiber Channel)
* LC (Lucent Connector)

#### Baseband

Baseband transmissions typically use digital signaling over a single wire; the transmissions themselves take the form of either electrical pulses or light. The digital signal used in baseband transmission occupies the entire bandwidth of the network media to transmit a single data signal. Baseband communication is bidirectional, allowing computers to both send and receive data using a single cable. However, the sending and receiving cannot occur on the same wire at the same time.

Note: Ethernet and baseband

Ethernet networks use baseband transmissions; notice the word "base"—for example, 10BaseT or 10BaseFL.

Using baseband transmissions, it is possible to transmit multiple signals on a single cable by using a process known as _multiplexing_. Baseband uses Time-Division Multiplexing (TDM), which divides a single channel into time slots. The key thing about TDM is that it doesn't change how baseband transmission works, only the way data is placed on the cable.

#### Broadband

Whereas baseband uses digital signaling, broadband uses analog signals in the form of optical or electromagnetic waves over multiple transmission frequencies. For signals to be both sent and received, the transmission media must be split into two channels. Alternatively, two cables can be used: one to send and one to receive transmissions.

Multiple channels are created in a broadband system by using a multiplexing technique known as _Frequency-Division Multiplexing (FDM)_. FDM allows broadband media to accommodate traffic going in different directions on a single media at the same time.

### Wired Network Topologies <a href="#wired-network-topologies" id="wired-network-topologies"></a>

Each computer on the network is connected to the other computers with cable (or some other medium, such as wireless using radio frequency signals). The physical arrangement of the cables connecting computers on a network is called the **network topology**.

The three basic topologies used in computer networks have been as follows:

* **Bus—**&#x43;onnects each computer on a network directly to the next computer in a linear fashion. The network connection starts at the server and ends at the last computer in the network. (Obsolete.)
* **Star—**&#x43;onnects each computer on the network to a central access point.
* **Ring—**&#x43;onnects each computer to the others in a loop or ring. (Obsolete.)

The following table summarizes the relationships between network types and topologies.

| Network Cable Types and Topologies |                      |                      |              |
| ---------------------------------- | -------------------- | -------------------- | ------------ |
| Network Type                       | Standard             | Thin (RG-58) coaxial | Topology     |
| Ethernet                           | 10BASE-2             | Thin (RG-58) coaxial | Bus          |
| 10BASE-5                           | Thick coaxial        | Bus                  |              |
| 10BASE-T                           | Cat 3 UTP or better  | Star                 |              |
| Fast Ethernet                      | 100BASE-TX           | Cat 5 UTP or better  | Star         |
| Gigabit Ethernet                   | 1000BASE-TX          | Cat 5 UTP or better  | Star         |
| 1000BASE-TX                        | Cat 6a UTP or better | Star                 |              |
| Token-Ring                         | (All)                | UTP or STP           | Logical ring |

The **bus**, **star**, and **ring topologies** are discussed in the following sections. Wireless networking, which technically doesn’t have a physical topology as described here, does still employ two logical (virtual) topologies, which I discuss as well.\


Ethernet used RJ 45 for connector and protection&#x20;

In the 5th version of the bluetooth it used wifi 802.11 to transmit data , so the data transmission proses can be fast.

zigbee temperature humidity if it is the temperature sensor it can show us its temperature it can transmit in higher speed

In general terms, **throughput** is the rate of production or the rate at which something is processed.

When used in the context of [communication networks](https://en.wikipedia.org/wiki/Communication_networks), such as [Ethernet](https://en.wikipedia.org/wiki/Ethernet) or [packet radio](https://en.wikipedia.org/wiki/Packet_radio), throughput or **network throughput** is the rate of successful message delivery over a communication channel. The data these messages belong to may be delivered over a physical or logical link, or it can pass through a certain [network node](https://en.wikipedia.org/wiki/Network_node). Throughput is usually measured in [bits per second](https://en.wikipedia.org/wiki/Bits_per_second) (bit/s or bps), and sometimes in [data packets](https://en.wikipedia.org/wiki/Data_packets) per second (p/s or pps) or data packets per [time slot](https://en.wikipedia.org/wiki/Time-division_multiplexing).

The **system throughput** or **aggregate throughput** is the sum of the data rates that are delivered to all terminals in a network.[\[1\]](https://en.wikipedia.org/wiki/Throughput#cite_note-1) Throughput is essentially synonymous to [digital bandwidth consumption](https://en.wikipedia.org/wiki/Digital_bandwidth_consumption); it can be analyzed mathematically by applying the [queueing theory](https://en.wikipedia.org/wiki/Queueing_theory), where the load in packets per time unit is denoted as the arrival rate (λ), and the throughput, where the drop in packets per time unit, is denoted as the departure rate (μ).

The throughput of a communication system may be affected by various factors, including the limitations of underlying analog physical medium, available processing power of the system components, and [end-user](https://en.wikipedia.org/wiki/End-user) behavior. When various protocol overheads are taken into account, useful rate of the transferred data can be significantly lower than the maximum achievable throughput; the useful part is usually referred to as [goodput](https://en.wikipedia.org/wiki/Goodput).

throughput = 8 times of the received packet.

The higher the speed the higher the throughput we get&#x20;

Let's have a closer look at WEP, WPA, WPA2, and WPA3 wireless security protocols.

**WEP. Wired Equivalent Privacy**

* Security : Poor
* Configurable : Hard

**WEP** was developed for wireless networks and approved as a Wi-Fi security standard in September 1999. WEP was supposed to offer the same security level as wired networks, however there are a lot of well-known security issues in WEP, which is also easy to break and hard to configure.

Despite all the work that has been done to improve the WEP system it still is a highly vulnerable solution. Systems that rely on this protocol should be either upgraded or replaced in case security upgrade is not possible. WEP was officially abandoned by the Wi-Fi Alliance in 2004.

**WPA. Wi-Fi Protected Access**

* Security : Poor
* Configurable : More or less

For the time the 802.11i wireless security standard was in development, WPA was used as a temporary security enhancement for WEP. One year before WEP was officially abandoned, WPA was formally adopted. Most modern WPA applications use a pre-shared key (PSK), most often referred to as WPA Personal, and the Temporal Key Integrity Protocol or TKIP for encryption. WPA Enterprise uses an authentication server for keys and certificates generation.

WPA was a significant enhancement over WEP, but as the core components were made so they could be rolled out through firmware upgrades on WEP-enabled devices, they still relied onto exploited elements.

WPA, just like WEP, after being put through proof-of-concept and applied public demonstrations turned out to be pretty vulnerable to intrusion. The attacks that posed the most threat to the protocol were however not the direct ones, but those that were made on Wi-Fi Protected Setup (WPS) - auxiliary system developed to simplify the linking of devices to modern [access points](https://www.netspotapp.com/what-is-a-wireless-access-point.html).

WPA is a personal type and password are saved in the access point

**WPA2. Wi-Fi Protected Access version 2**

* Security • Good
* Configurable • Norm

The 802.11i wireless security standard based protocol was introduced in 2004. The most important improvement of WPA2 over WPA was the usage of the Advanced Encryption Standard (AES). AES is approved by the U.S. government for encrypting the information classified as top secret, so it must be good enough to protect home networks.

ADVANCED ENCRYPTION STANDARD IS APPROVED BY THE U.S. GOVERNMENT At this time the main [vulnerability to a WPA2](https://www.netspotapp.com/krack-wifi-vulnerability-wpa2.html) system is when the attacker already has access to a secured WiFi network and can gain access to certain keys to perform an attack on other devices on the network. This being said, the security suggestions for the known WPA2 vulnerabilities are mostly significant to the networks of enterprise levels, and not really relevant for small home networks.

Unfortunately, the possibility of attacks via the Wi-Fi Protected Setup (WPS), is still high in the current WPA2-capable access points, which is the issue with WPA too. And even though breaking into a WPA/WPA2 secured network through this hole will take anywhere around 2 to 14 hours it is still a real security issue and WPS should be disabled and it would be good if the access point firmware could be reset to a distribution not supporting WPS to entirely exclude this attack vector.

WPA2 is a industry type and  password are saved in the radius server

WEP 100% cracked , WPA , WPA2 ( dictionary , brute-force crack)

