The data transmission standard is

UDP is generally not used if reliable transmission of information is required. It makes sense to use UDP where the loss of a piece of information would not be critical to the application, such as in video games or video streaming. UDP is necessary when it is difficult or unreasonable to make a second request for some reason.

Data transfer

Data transmission is the process of carrying data in the form of signals from a point to a point or from a point to several points by means of telecommunications over a channel. Dictionaries mention the borrowing (1640s) by scholars of the Latin word datum, meaning "thing," "datum." Philosophy substantiates the connection of the concepts of information, knowledge, data, freedom, and gives examples. The height of a mountain predominantly acts as data. The parameter is measured with an altimeter, fill in the bases. The information obtained, taking a concrete form, decorates the book studied by the climber. An experienced mountaineer comes up with the best way to conquer the summit. Understanding the specifics of the process already becomes knowledge.

Immediately there is freedom of choice. The climber is free to decide, taking responsibility. There are groups that don't go back.

Types of data

Historically, information has been represented in many ways. Let's leave the hieroglyphs of papyrus to the historians and look at modern techniques. The greatest impact was made by the development of electricity. If man had learned to transmit thought, the symbolism would have been different…

Analog signal

The first attempts to measure analog quantities are the experiments of Volta, who measured voltage, current. Next came the resistance of a conductor, George Ohm, who was able to estimate the resistance of a conductor. Each time analog values were used. The representation of the characteristics of an object in the form of current, voltage gave a powerful impetus to the development of the modern world. An electron-beam kinescope with the brightness of pixels of three colors displays a fairly clear picture.

The reasons for the departure from the analog signal were revealed by World War II. The Green Hornet system could encrypt information perfectly. The 6-level signal is difficult to call digital, but a clear bias is emerging. Historically, let's call Schilling's 1832 experiments with the telegraph the first attempt to transmit a binary code. In an effort to reduce the number of wires connecting subscribers, the diplomat recalled the methods of binary numbering proposed by priests. The introduction of digital transmission, however, took mankind over a century and a half to complete.

Binary numeric code

Binary numbering is common knowledge. An analog quantity is represented by a discrete number, then coded. The resulting set of zeros and ones is usually broken down into words of 8 bits in length. For example, the first Windows operating systems were 16-bit, the graphics processor handled higher floating point numbers. Even longer words are used by specialized graphics card calculators. The specifics of the system determines the specific way the information is presented.

The OSI model is a reference model for the interaction of devices on a network

The OSI model is a model which allows different communication systems to communicate with each other according to generally accepted standards. It can be compared to English, which is the global, universal language of networks.

The model is based on the principle of dividing a communication system into seven separate layers. You can read more about it here.

If there is a failure in the transmission of information, the model helps to locate the problem on a particular layer more quickly and easily and to get the system back up and running much faster.

The OSI model is the reference standard but is now obsolete as modern protocols operate across multiple layers of the OSI model. The OSI model has been replaced by TCP/IP, which is the basis for most of the devices in the world today.

TCP/IP is the model on which the Internet works

Model TCP/IP helps to understand how the nodes on the Internet work and interact. Its name includes the two main protocols on which the Internet is built. TCP/IP stands for Transmission Control Protocol/Internet Protocol, or Transmission Control Protocol/Internet Protocol.

The model is used throughout the modern Internet, and new network protocols are being developed based on the TCP/IP model. For example, when you connect to the Selectel website, you use the IP, TCP and HTTPS protocols, which work within the framework of the mentioned model.

Next we look at the core protocols of the interconnect, transport, and application layers. These are the protocols we encounter most often when analyzing any problems on the network or on the server.

Why a port is needed and what the term "socket" means

Application layer applications, communicate also with the previous, transport layer, but they see its protocols as "black boxes". They can work with e.g. TCP or UDP to send and receive information, but they only understand the final address as IP and port, not how they work.

As stated earlier, an IP address is assigned to each endpoint by a gateway protocol. But the data exchange does not happen between the end devices, but between the applications installed on them. To gain access to a particular network application is not enough only the IP-address, so to identify applications also use ports. The combination of an IP address and a port is called a socket.

In addition to their own protocols, applications at the application level often have a fixed port number to address the network. The Internet Assigned Numbers Authority (IANA), which assigns ranges of IP addresses, is also responsible for assigning ports to network applications.

So e-mail applications that communicate by SMTP protocol use port 25, by POP3 protocol use port 110, browsers when working by HTTP use port 80, FTP-clients use port 21. Port is always written after IP and separated from it with a colon, it looks like this: 192.168.1.1:80.

What is DNS and what is it used for?

To avoid having to remember the numeric addresses of Internet servers was created DNS – Domain Name Service. DNS always listens on port 53 and converts the alphabetic names of network domains into numeric IP addresses and vice versa. DNS service allows you not to remember the IP – the computer itself sends a request "what is the IP of selectel.ru?" on port 53 DNS-server received from the Internet service provider.

DNS-server gives the computer the answer "IP for selectel.ru – XXX.XXX.XXX.XXX". Then, the computer establishes a connection to the web server of the received IP, which listens on port 80 for the HTTP protocol and on port 443 for HTTPS. In the browser, the port is not displayed in the address bar, but is used by default, but, in fact, the full address of the Selectel site looks like this: https://selectel.ru:443.

To ensure the correct operation of the protocols of different layers in the network models a special method is used – encapsulation. The essence of this method is to add the current level protocol header to the data received from the higher level protocol. The opposite process is called decapsulation. Both processes are performed on the sender and receiver computers alternately, this ensures that one side of the channel is not kept busy for long, leaving time for the information to be transmitted to the other computer.

Disk connection interfaces: SATA and NVMe

Interface is the set of ways the drive connects to the motherboard and how it communicates with the rest of the PC. This includes the types of physical connectors, data transfer protocols, and methods of data transfer.

Parallel IDE Connection Interface

A clear example of interface as applied to HDD disks is IDE (Integrated Drive Electronics), or ATA (Advanced Technology Attachment). Conventionally, this is a simple way to connect the hard drive to the motherboard via a 40 or 80 core loop.

We mentioned that the interface includes data transfer methods. For IDE there are a few such methods. For example, PIO (Programmed input/output), when data is transferred between devices through the processor, or DMA (Direct Memory Access), when the processor is not used to transfer data.

Information through the IDE interface is transmitted in parallel when each bit of data goes on its own signal line – over a physical channel. Therefore, the connection for the interface is via a 40- or 80-wire loop. Data is transmitted in portions equal to the number of channels.

The disadvantages are that the parallel channels influence each other, which leads to distorted messages. This problem has been solved in the SATA interface, which is a development of the parallel IDE interface.

SATA Serial Data Exchange Interface

SATA or Serial ATA (SATA) is a serial method of sending bits of information. It involves bits following one another, one bit at a time.

Your motherboard may have multiple SATA connectors. This allows multiple hard disks to be connected at the same time, something that was not possible with IDE.

PCIe and AHCI transfer protocols

Let us now look at the data transfer modes based on the interfaces discussed. Here we will focus on PCIe and AHCI.

PCIe

Peripheral Component Interconnect Express, or PCIe, is a serial I/O bus. Physically, it is a connection, an "adapter", in the form of a slot or connector to connect devices directly to the motherboard.

PCIe has a direct "communication channel" to the CPU and RAM, as well as independent receive and transmit channels, or lines.

A line is a kind of connection between devices in the form of four wires: two for transmitting, two for receiving data. They transmit data like on a two-lane highway: one way and the other way at the same time. This is called duplex mode. Two signal wires with opposite polarity allows you to fight interference.

PCIe data transfer speeds vary depending on the version and number of lines. For example, the theoretical speed of PCIe 3.0 is 986 MB/s with one line, and 1970 MB/s with two lines.

Note. The PCIe bus is designed to connect peripheral devices – not only hard drives, but also GPUs or network cards.

PCI Express is the way to connect to the motherboard and transfer data. It is what the NVMe protocol/interface uses.

AHCI

Despite the name, AHCI (Advanced Host Controller Interface) is not an interface in the literal sense. Rather, it is a mechanism or mode that enhances the SATA standard.

For example, AHCI has hot-swap drives without shutting down the server and a hardware NCQ command queuing algorithm that is achieved by optimizing the movement of the read head. Since the same head is not an issue for SSD disks, it is generally accepted that AHCI mode is more appropriate for HDD disks.

Types of standards

Legal standards (De jure) are adopted by organizations that have the authority to do so.

De facto standards are standards that are set by themselves, no one has accepted them. For example, there was a new technology that quickly developed and became popular. As happened with the TCP/IP protocol stack, which is now the backbone of the Internet.

Standards for networks

Many different standards are being adopted, but there are some of the most significant:

• The International Organization for Standardization (IOS) adopted a standard for the OSI reference model, describing how computer networks should be built.
• Institute of Electrical and Electronics Engineers (IEEE) adopting standards for data communications technology.
• The Internet Architecture Board (IAB) adopts standards for Internet protocols.
• W3C consortium accepts standards in the Web domain.

IEEE standards

The ieee Institute approves standards not only in computer networks, but also in other areas of electronics, electrical engineering. The Institute is divided into committees. The development of standards for computer networks is handled by a committee under No. 802.

Each No. is a family of standards. For example, 802.3 describes different variations of Ethernet technologies such as, Fast Ethernet, Gigabit Ethernet and 10 Gigabit Ethernet.

Internet Architecture Council

The council is divided into two parts. The Internet Research Task Force (IRTF) conducts forward-looking research on the Internet.

Part 2 of the Internet Engineering Task Force (IETF) produces standards for network protocols. The IETF produces RFC (Request for Comments) documents. These docks contain detailed descriptions of Internet protocols. If you use different protocols, then your device or software will not work on the Internet.

RFC Documents

Every RFC has a number and describes a protocol.

There are many RFCs to consult.

W3C (World Wide Web)

The W3C develops standards for the Web. The consortium documents, just like the RFCs formally, they are not called standards, they are called recommendations. But if you don't follow these recommendations, you won't be able to work with the web.

But there are more recommendations, which are freely available on the consortium's website .

4G mobile standards.

LTE is a standard for wireless data transmission and is also an evolution of the GSM/UMTS standards. The purpose of this new standard was to increase bandwidth and data transfer speeds using a new method of digital signal processing and modulation, which were developed at the turn of the millennium. Another goal was to simplify the architecture of IP-based networks, while reducing the data latency of the mobile network.

• High speed data transfer
• Improved quality of voice calls
• Better speed support when the subscriber moves around
• Low latency in data transmission.

1. 3G-4G Internet amplification kit № A1
2. 3G-4G Internet amplification kit № A20

LTE Advanced is a major enhancement to the LTE network standard. This technology has received a claimed speed of up to 1 Gbit/s for fixed subscribers and 300 Mbit/s for mobile subscribers.

This standard is a more improved version of the standard – LTE Advanced Pro. The possible data transfer rate is up to 3 Gbit/s. In addition, this standard has support for other new technologies directly related to the network 5G, which allows in the near future to support the LTE Advanced Pro standard, a network of a new fifth generation – 5G.

What communication standards do Russian operators support?

Cellular standards and operators in Russia are in the frequencies shown in the table below:

Russian operator.	Yota, Megafon, Beeline. MTS, Tele2	Yota, Megafon, MTS, Beeline	Yota, Megafon, MTS, Beeline, Tele2(SPb)	Yota, Megafon, MTS, Beeline, Tele2	Yota, Megafon, MTS, Beeline, Tele2
Standard of communication.	4G	2G,3G	2G,3G,4G	3G	4G
Frequency (MHz)	800	900	1800	2100	2600

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