TCP (Transmission Control Protocol) is a protocol created and developed by the US Department of Defense. TCP, which serves for the smoothness of the basic communication between computers, also authenticates in addition to ensuring data integrity in data exchange.

The reason for the creation of TCP also prevents the loss of communication between computers. Today, data exchange of protocols such as HTTP, HTTPS, POP3, SSH, SMTP, SNMP, TELNET, and FTP is TCP.

TCP is a connection-oriented protocol, which means that the connection is established and maintained until the application programs at both ends have finished exchanging messages.

It determines how the application data is divided into packets that networks can deliver, sends packets to the network layer and accepts packets from these layers, manages flow control, and manages the retransmission of dropped or corrupted ones as it is intended to provide error-free data transmission packets and acknowledges all incoming packets.

In the Open Systems Interconnection (OSI) communication model, TCP encompasses parts of Layer 4, the transport layer, and parts of Layer 5, the session layer.

When a web server sends an HTML file to a client or another server, it uses the hypertext transfer protocol (HTTP) to do so. The HTTP program layer asks the TCP layer to establish the connection and send the file. The TCP stack splits the file into data packets, enumerates it, and then transmits it to the individual IP layer for distribution.

Packets can be sent over multiple routes, although each packet in the transmission has the same source and destination IP address. The TCP program layer on the client computer waits until all packets arrive, then acknowledges their received and requests retransmissions of those that do not receive due to missing packet numbers. The TCP layer then combines the packets into a file and delivers the file to the receiving application.

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Ethernet connection can be defined as a type of connection that is used to establish a network connection between computers. The method that will support the formation of a network between two computers is called Ethernet.

The card required to connect these computers to each other is called the Ethernet card. In order to understand better what is Ethernet, it is necessary to first learn what local area network means.

In fact, the local area network, known as LAN, is a network of two or more computers, in the same case, devices such as printers and fax machines, in a not too distant area.

The main purpose of using the Local Area Network is to use a fast data flow between computers in the same network frame and peripheral devices simultaneously, that is, in a binary way. One of the most used LAN technologies today is the Ethernet connection.

Of course, there are other manufactured technologies besides Ethernet. For example; Like Token Ring and FDDI. However, Ethernet is more preferred because it is cheaper and easier in terms of the operating system.

It explains how devices that you can qualify as network devices will design and transmit their data packets. Therefore, those in other network domains can recognize it.

When you look at it, it has the ability to work in the same way on both LAN and WAN networks. Power can also be transferred over this technological development, which is very simple to assign. In this way, it becomes easier to establish a network connection between computers.

The Ethernet consists of two transmission units known as packets and frames. The framework does not have a packet containing only the transmitted data payload.

Same time; the sender and receiver, the physical media access control addresses, including error correction information for determining transmission problems.

In addition, ethernet cables connect network devices with cables that operate at different speeds to devices or modems that are appropriately called routers.

The Ethernet card divides the data to be transmitted into packets and sends it to the network cable connected to the card output. Data packets transmitted in a local network system contain the receiver's MAC address, the sender's MAC address, the transmitted data, and the CRC code. CRC code is the code that checks whether the data sent is corrupted or not.

Before sending the packet, the cable is checked and if the cable is empty, the data is sent. Packaged data is sent to the opposite computer, received and decoded by the ethernet card of the receiving computer, and the CRC code is checked. If the CRC code is the same, the data is accepted. Data is taken from the packet and processed by the computer. If the CRC is not the same, it is understood that the data is corrupted and the data is not accepted.

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Wi-Fi stands for wireless fidelity and means wireless connection area. As can be understood from the definition of wifi, it is a wifi signal area and you can access the internet wirelessly with tablets, phones, smartwatches, audio players, televisions, game consoles, and similar devices in this area.

Wi-Fi technology is the same as the working principle of transistor radios. In order for the Wi-Fi connection to be established, if a device that emits the signal at one end is at the other end, another device that can receive these signals and convert them to data is required.

Let's consider how the wireless internet connection takes place in an average home: Devices such as routers, phones, or computers have hardware that can transmit the signal wirelessly.

Router or modem creates a network by spreading the connection provided by your internet service provider at a frequency that your home devices can understand. Communication between devices that have Wi-Fi hardware such as a computer or smartphone and are allowed to access this connection is through the signal exchange, enabling wireless data exchange.

The key invention for Wi-Fi technology is a set of local area network standards referred to as IEEE 802.11. Based in the USA, these standards announced by the Institute of Electrical and Electronics Engineers, an international non-governmental organization, in 1997, were further developed in the following years and the speed and capacity of the connection were increased.

The standardization performed by the IECC on this issue is very important. Before 1999, when Wi-Fi technology started to be marketed, there were technologies that can provide a wireless connection between devices, but since there is no standard, incompatibility between these technologies created various difficulties in use.

The development of a technical standard has enabled different technology manufacturers to use this technology effectively and widely, and many products with Wi-Fi capability to enter the consumer market.

Wi-Fi technology works by means of radio signals. Bandwidth refers to the range of radio frequency that enables wireless data transmission. The specified range for the wireless network connection is between 2.4 GHz and 5 GHz.

Wi-Fi radio waves are generally at either 2.4 GHz or 5 GHz frequency. The biggest difference between the two frequencies is that a device with a frequency of 5 GHz can emit a signal to half the area of

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Access Point is the common name of devices that connect multiple computers, mobile devices, smartphones, and all devices that can access the Internet.

Access Points are generally used to convert wired connections to wireless connections. In addition to the ability of APs to convert wired internet to wireless wifi internet, it can also be used as a signal repeater.

Repeater mode in Access Points is generally preferred indoors to provide internet access to endpoints or by users who do not want to experience cable pollution.

APs are produced for indoor and outdoor environmental conditions. Outdoor Access Points are produced with a special working principle in order to ensure signal continuity in bad weather conditions, and their durability is higher than indoor products.

Access Points can undertake multiple functions. They convert the wired internet connection received via modem or switch into a wireless internet connection. In short, it provides a wireless network connection in an environment where there is no wireless network connection.

If you make the correct settings, the access points have the ability to strengthen the wireless network signal. It strengthens the current network signal and presents it to the environment. In this way, the wireless network connection is strengthened and the domain expands.

The setup logic of the Access Point device is very similar to the ADSL modem setup. First of all, you need to establish a connection with an Ethernet cable between the ADSL modem that provides your internet connection and the access point device.

In cases where the signal strength of the ADSL modem is weak, the access point device is activated and expands the internet connection. In environments where signal strength may be low such as factories, schools, homes, and workplaces, we connect the modem and the access point device with an ethernet cable.

We plug the access point device into the socket. We plug the cable coming from the power adapter into the access point device and turn the device on by pressing the power button.

When these processes are implemented completely, the signal strength starts to spread from the access point device. Encryption is extremely important to encrypt the internet network in order to control the reliability of the internet connection and to prevent easy access to the interface of the access point device.

Just as we connect to the interface of a normal modem, we can connect to the interface of the access point. The first thing required for this is a computer. First, we connect the computer and the access point device with an ethernet cable. In order to access the interface of the access point, we use the IP number if available in the manual or any of the IP addresses such as 192.168.1.1 or 192.168.2.1.

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The most important point to be considered when wiring is that the data reaches the destination smoothly. However, depending on the technology used, the maximum distances that the cable can transmit the data without any problem are limited. The repeater is activated at distances that the cable cannot reach.

The repeater is used to strengthen data packets that may not reach its recipient. Data packets lose power while trying to reach remote computers.

A repeater works in the physical layer. Its job is to recreate the signal over the same network before the signal is too weak or distorted to extend the length at which the signal can be transmitted over the same network.

It empowers the repeater data packets to keep them on their way. When the repeater receives a signal, it returns it to its original power and state. Some hubs already act as repeaters in UTP cables.

In token ring systems, there is no need for a repeater as each station strengthens the incoming data and leaves it on the road again. 185 meters when using thin coax in coaxial cable,

When using thick coax can be a maximum cable length of 500 meters.

If the target station is further than these distances, the repeater should be activated. Up to 4 repeaters can be used in a row.

A typical router is usually strong enough to provide a Wi-Fi signal in a small house or apartment, but may not be strong enough to serve a large home. This causes dead spots in the house with no signal.

It is important to place a repeater in the correct location where the signal is strong. A location between the router and the weakest reception area is ideal. Then, following the instructions that came with the repeater, log into the Wi-Fi repeater on your computer and enter the login and password for your Wi-Fi network. The repeater connects to the Wi-Fi network and increases the signal strength from where it is located outwards.

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Hubs do not know which computers are connected to it and do not perform a network operation of the source or target computer. For this, they are defined as stupid devices according to Switches.

If data is sent to a computer on the network, the Hubs send this data to all computers, and the computer that will receive the data checks whether the data was sent to it or not, if it was sent to it, it receives the data. Therefore, hubs do not send anything directly to the computer but help to send. If the target computer accepts, it is thrown into the computer. Hubs are one of the central devices in a star topology. Topology refers to the physical and logical structure of a network.

The connection types of the components that make up the network, the devices to be used, the wiring standards, the selection of the communication protocol, and the applicability of these protocols to the network structure are also within the scope of the topology. They work with plug and play logic.

Another difference is that it is both uncomplicated and cheap. Being cheap is one of the reasons why the hub is preferred. The hub allows computers to communicate on the network. Each computer is connected to the Hub with an Ethernet cable, and information sent from one computer to another passes through the hub. The hub cannot determine the source or destination to which the information it receives is intended to be sent, so it sends the information to all computers connected to it, including the computer that sent the information.

Hub is the central coupling device that connects computers together. There are Active and Passive Hubs. Passive types connect computers but do not process signals.

The Networking Hub sends data to all computers connected to it. If it is the only computer that needs to receive the data, it also keeps them busy as it sends data to other computers connected to it. Therefore, Hubs are weaker in performance than Switches. As many computers as the number of ports can be connected.

Switches, on the other hand, are devices that find a separate path to each data transmission channel with the encryption method. It only sends data to the desired computers. Whichever device is connected to its ports, it prepares a separate path for all of them. It is the same as the hub as the task. but in terms of performance and speed, it is faster than a hub.

The switch looks at which address the incoming data will go to, establishes a connection between the sender and the receiver, and transmits it without the knowledge of other computers and without engaging them.

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Bridges are network devices used to connect two or more independent networks using the same protocol. It examines the data that is placed between two independent networks and wanted to be transferred to both sides. If the data address matches an address on the computer network, it allows data to pass to that network; otherwise, it does not allow data to pass through the network.

Bridges generally do what repeaters do. But their main difference is that a repeater amplifies the message coming to it and sends it directly, without looking at the destination. The networking bridges will not send this packet if the packet cannot reach its destination. In addition, bridges connect different networks from each other and allow them to communicate between them.

We can list the properties of bridges as follows.

Bridges need to be understood very well in order to understand the Routing and Switching processes. Usually, bridges resemble devices with two ports, but there are also bridges with three or more ports.

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The switch is one of the network hardware that allows PCs and other network equipment to be integrated with each other. OSI works in layer 2 of the seven-layer model and also in layer 3, as new switches are capable of IP routing.

Each of the network switches can exchange data independently of the others. When a data packet reaches one of the ports, the network key records the sender's Mac address and the sent port in the address table.

It tries to detect the port to which the target MAC address is connected by examining the existing records in the MAC address table. If no record is found, the data packet is sent to all ports except the incoming port. If the mac address is known, then the data packet is only sent to the destination port. If the sender's and receiver's MAC addresses are the same, the packet is deleted.

Basic network switches, such as those used in consumer routers, do not require any special configuration beyond plugging in cables and power.

Compared to these unmanaged switches, high-end devices used in corporate networks support a range of advanced features designed to be controlled by a professional administrator. Popular features of managed switches include SNMP monitoring, link aggregation, and QoS support.

Traditionally managed switches are created to be controlled from Unix-style command-line interfaces. A newer category of managed switches called smart switches that target entry-level and mid-level corporate networks to support web-based interfaces similar to a home router.

Switches connect devices (such as computers, printers, wireless access points) on a network and allow them to communicate by exchanging data packets. Switches can be software-based virtual devices as well as hardware devices that manage physical networks.

Switches make up the majority of network devices in modern data networks. They provide wired connections to desktop computers, wireless access points, industrial machines, and some IoT devices such as card entry systems.

They connect the computers that host virtual machines (VMs) in data centers, as well as physical servers and most of the storage infrastructure. They carry large amounts of traffic on their telecommunications provider networks.

A network switch operates on the network layer L2 of the OSI model. In a local area network (LAN) using Ethernet, a network switch determines where each incoming message frame is sent by examining the physical device address or MAC address. The switches hold tables that match each MAC address and the port from which the MAC address is obtained.

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The internet is one of the 20th century's greatest inventions and communication tools. It allows people around the world to email each other in a matter of seconds and allows you to read content posted on the website, among other functions.

In fact, most people have never come face to face with or didn't want to, the technology that allows the internet to exist. We are all used to seeing the familiar parts of the internet that it brings to our homes and offices, web pages, email messages, and downloaded files that make the internet a dynamic tool. But none of this could happen without an internet device that many people have probably never seen before. Without a router, there is no virtual world we call the Internet.

Most of the work done to send messages from one computer to another is done by the router. Because the router is an important device that enables messages to reach the correct address by traveling within the networks.

The router is the only device that sees messages sent by any computer in one of the networks of the company in which it is installed. In other words, the router sees which computer in the company the data packet originates from and which computer it is addressed to.

It controls the traffic of all connected computers and in this way ensures that the data reaches the correct address. The traffic line that provides data communication between computers does not interfere with each other thanks to the router. This is a different answer to the question of where to use the router.

Since modern modems are often equipped with a built-in router, the distinction between router and modem is often blurred in people's minds.

However, those who remember the early days of the internet know that routers and modems have different functions. The modem expression is derived by combining the word modulator with a letter at the beginning of the word demodulator.

It is possible for a computer to connect to the internet, that is, to the public network, that is to be online, with a modem. Also, a modem is a device that connects computers to computers in remote locations over the public network.

Thanks to the modem, the audio signals coming from the telephone box are converted into data that the computer can understand. Likewise, it converts the data coming from the computer into audio signals and transfers it to the general network.

The modem is a must-have device for connecting to the internet and building a large network. Router, on the other hand, is hardware for connecting multiple computers to the same network.

The router can connect the existing internet connection to home, office, etc. It is a device that shares it with other devices in the spaces. The router creates a network by emitting a wireless signal so that devices with wireless connectivity can connect to the internet via itself. You can also connect your devices to a router with ethernet ports directly by cable.

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Network systems is a computer technology that enables computers in a local or a wide area to communicate with each other.

This technology is divided into some definitions according to the area it covers and the type of physical connection. These are LAN (Local Area Network), MAN (Metropolitan Area Network), and WAN (Wide Area Network).

Local Area Network (LAN)

It is a type of private network consisting of a group of computers and network devices within a small geographic area. Often an office is used to describe a network of computers located several buildings away from each other. The criterion here is that the computers are close to each other in general, rather than how many computers the network consists of. Home, office, school, hospital networks can be examples of local area networks.

Twisted (ethernet) or coaxial cables are generally used in local area networks. Since the distance is short, the speed is high and the noise ratio is lower.

Metropolitan Area Network (MAN)

MAN is a type of network that covers more areas than LANs and less than WANs. It is a type of network that connects networks that are usually hosted in the same cities but in different geographic regions. Networks covered by Internet Service Providers (ISPs) in a city can be an example of a MAN.

Due to their location in different geographical areas, their speed will be lower than LAN.

Wide Area Network (WAN)

It defines a network created by connecting many LANs to each other via the Internet over a wide geography. Internet service providers perform the task of connecting multiple Local Area Networks. The local area networks mentioned here can be in many different parts of the world. Optical cables or satellites can be used for transmission.

To compare,

WAN covers a much larger area than LAN and MAN. It is more difficult to design and maintain than LAN. Since it can send information to much more distant geographic locations, its speed is slower than LAN and MAN and its error probability is higher.

LAN has exclusive use. It is faster than others and less likely to fail. It is easier to install, maintain, and manage.

MAN sits in the middle of the LAN and the WAN in terms of coverage and speed.

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