Block diagram of the network. Logical, structural diagram of the network

Contact network (CN) - complex engineering structure, having a significant length and a periodic structure, designed for continuous power supply of rolling stock through a sliding contact.

Analysis of tram rolling stock (FS) downtime on the line in a number of large cities shows that quite common cause downtime on the line becomes a failure contact network. Thus, according to the Novosibirsk Department of Transport, up to 7.5% of substation downtime in time terms occurred on the line due to the failure of the compressor station. In this regard, assessing the technical condition of the compressor station from the standpoint of reliability is one of the most important tasks.

When analyzing CS failures in Novosibirsk, failures that arose as a result of extraneous interactions, such as breakage of suspensions due to oversized loads, damage to supporting structures, were identified and excluded vehicles, wire annealing as a result of accidents at substations, damage to pendants by faulty pantographs. During the preliminary analysis of the statistical material, it was revealed that the main part (79.8% of the total number of failures) consists of the following failures: breakage of the contact wire, breakage of the wire from the clamp, breakage of the flexible crossbar, damage to the intersections.

An analysis of statistical material and data from operational services shows that the catenary system is not an equally reliable system, which indicates the need for further improvement of the structures and components of the tram catenary system, in particular intersections. Nai large quantity failures occur when the pantograph passes through special parts and points of suspension and fixation of the contact wire, i.e., as a result of unsatisfactory interaction caused by improper adjustment and installation of the suspension, as well as malfunctions of the pantograph.

It should be noted that up to 27.3% of all failures of tram pantographs on the line occur as a result of cuts and increased wear of contact inserts, which, as is known, is largely caused by a violation of the contact suspension parameters, such as: zigzag values, height of the contact wire above the level rail heads, slopes and rises of contact wire, arson.

In addition, from the graphs shown in Fig. 4.10, there is a clear dependence of the amount of damage on climatic conditions. Thus, the maximum intensity of failures of the “flexible cross member breakage” type occurs in May and September with the largest daily temperature difference, and for failures of the “gearbox breakage and gearbox breakage” type, the maximum intensity occurs in June, characterized by the highest temperatures.

Rice. 4.10.

Since the CS is a complex electrical object, its reliability as a whole is determined by the reliability of its constituent elements. Therefore, when analyzing the reliability of the CS it is necessary:

• determine the influence of the type of suspension and the quality of its maintenance on the reliability of the CS;
• identify elements that have reduced reliability compared to others;
• determine climatic factors affecting the reliability of elements.

The main requirement for the CS as an element of the system Maintenance and repair - constant compliance of the main parameters with the required level of reliability, operating conditions and intensity of use. Such compliance can be achieved if the actual reliability indicators of the CS, as well as the parameters of the maintenance and repair system, are formed on the basis of objective information about the technical condition of the CS.

The technical condition of the compressor station can be determined based on the results of measuring and evaluating a large number of input, internal and output parameters. In practice, to determine the technical condition, it is enough to identify a set of direct and indirect diagnostic signs and parameters that reflect the most likely malfunctions associated with a decrease in performance and the occurrence of failures.

The block-functional decomposition of the CS is shown in Fig. 4.11. Vertical decomposition leads to the construction of a hierarchy of connections between its constituent components. This hierarchy has four levels: sectional, which includes a section of the contact network; system, including supporting, load-bearing, fixing, linear current-carrying, support devices, devices for compensating for thermal expansion, interfaces and special parts; the subsystem level includes individual assembly units; the fourth level - elemental - includes non-separable parts. This decomposition predetermines the form of subordination of diagnostic goals and algorithms. Horizontal decomposition of the CS makes it possible to distinguish individual components according to the basic principle of the physical process, functional purpose or principle of technical execution.

Rice. 4.11.

As an example of the relationship between elements of the CS in Fig. 4.12 shows diagrams for idle (A) and chain (b) pendants.

When diagnosing each of these systems, among several used physical methods diagnostics can be identified as dominant, allowing sufficient degree reliability to determine the technical condition of the compressor station.

During operation, the CS may be in the following basic states:

It is serviceable and efficient, and therefore the parameters Z, which characterize the state of its elements and assemblies, are within the nominal tolerance range:

Rice. 4.12.

Faulty, but operational, which is due to the parameters of the main elements and assemblies being outside the tolerance range, but not exceeding the limit values:

It is faulty and inoperable, therefore, the parameters of the main elements and components are outside the tolerances:

The limits of the specified tolerances for existing types of catenary suspensions are given in regulatory documents. However, it should be noted that existing tolerances mainly reflect the state of the suspension through its geometric dimensions in a static state, i.e., in the absence of rolling stock. In mode normal functioning Throughout its entire length, the CS is in interaction with the current collectors of the PS, and therefore should also be assessed by indicators characterizing the interaction, taking into account reliability, durability and quality, i.e., contact stability.

The given level of operational reliability of the compressor station is supported by the implementation of a system of repairs and adjustments defined by regulatory and technical documentation. Existing system maintenance and repair, aimed at maintaining the performance of the compressor station, includes control the most important parameters contact suspension and their adjustment. However, control measurements show that the technical equipment of individual operations is insufficient and unproductive. In addition, it is planned to monitor the parameters of the CS in a static state, which, given the existing connections, makes it even more difficult to objectively assess its condition. Consequently, complete and reliable information can only be obtained through a comprehensive diagnosis of all parameters of the CS throughout its entire duration in the operating mode.

At this stage, for the selected LAN configuration option:

• 1. develop a LAN architecture;
• 2. develop a block diagram of the LAN, select LAN components;
• 3. We will draw up a LAN specification.

The local area network design methodology consists of the steps shown in Figure 3.

Figure 3 - Aircraft design stages

The LAN architecture design methodology consists of the stages shown in Figure 4.

Figure 4 - LAN architecture design stage

For this financial company we chose network topology"Star". Since its advantages are:

• - failure of one workstation does not affect the operation of the entire network as a whole;
• -good network scalability;
• -Easy search for faults and breaks in the network;
• -high network performance (subject to proper design);
• - flexible administration options.

To create this LAN, a peer-to-peer architecture was chosen, which has a number of advantages:

• - ease of installation and configuration;
• -independence of individual machines from a dedicated server;
• -the ability for the user to control their own resources;
• - comparatively cheap to purchase and operate;
• -no need for additional software other than the operating system;
• -no need to have a separate person as a dedicated network administrator.

For this course project, the standard topology was chosen 100Base-TX(using two pairs of conductors of Category 5 cable or shielded twisted pair STP Type 1).

The 100Base-TX standard supports shielded cable twisted pairs with an impedance of 150 Ohms. This cable is not as widely available as UTP cable and is typically found in buildings equipped with a Token Ring network. Shielded twisted pair cables are routed according to the ANSI TP-PMD specification for shielded twisted pair cables and use a nine-pin D-type connector. The DB-9 connector uses pins 1, 2 and 5, 9. If the NIC does not have a DB-9 connector, 9, then an RJ 45 Category 5 plug must be connected to the ends of the STP cable.

Let's choose software .

Windows XP Professional Edition was designed for businesses and entrepreneurs and contains features such as remote access to the computer desktop, file encryption (using the Encrypting File System), central access rights management and support for multiprocessor systems. Therefore, for the company I am developing, I am using this particular operating system, which will be installed on workstations.

Since one of the requirements for the designed LAN is connection to the Internet, you must select modem.

Modems can be internal or external. Internal modems are made in the form of an expansion card, inserted into a special expansion slot on motherboard computer. The external modem is designed as a separate device, i.e. in a separate case and with its own power supply. For our network we will choose an external ADSL modem Acorp Sprinter@ADSL USB.

Our LAN architecture uses switch. Switches monitor network traffic and manage its movement by analyzing the destination addresses of each packet. The switch knows which devices are connected to its ports and routes packets only to the necessary ports. This makes it possible to simultaneously work with several ports, thereby expanding the bandwidth. For our network we will choose the ASUS GigaX 1024/1024X 24x10/100Base-TX switch. Unmanaged. 19".

Also, guided by the security requirements of the developed LAN, we will select the necessary antivirus software. As an antivirus, we will choose ESET NOD32 (license for 1 user, 1 year) BOX.

Antivirus functions: computer network security architecture

• *Email protection.
• *Checking Internet traffic. The program provides antivirus scan Internet traffic arriving via the HTTP protocol in real time and regardless of the browser used.
• *Scanning file system. Any separate files, directories and disks.
• *Preventing information leaks. The program protects your computer from Trojans and all types keyloggers, preventing the transfer of confidential data to attackers.
• *Reversal of malicious changes in the system.
• *Minimal impact on computer operation.
• *Automatic update. When new updates are detected, the program downloads and installs them on the computer.

Structural scheme The LAN is shown in Figure 5.

1 - director; 2 - secretary; 3, 4, 5 - accounting; 6, 7 - System Administrator; 8 - electronics engineer; 9, 10, 11 - managers; 12 - security; 13 - network printer; 14 - switch; 15 - modem.

Figure 5 - Block diagram of a LAN for a financial company

Table 8 - LAN specification

Based on the diagram of information flows, the division of these flows, and the diagram of information flows taking into account servers, also knowing the location of buildings and their dimensions, we will draw up a block diagram corporate network(IN THE APPENDIX) and provides a brief description of it.

Organization of communication with branches.

In this section, it is necessary to describe the type of communication with branches issued by the teacher in the following sections: theoretical description of the given method, equipment that allows you to organize this connection on the receiving and transmitting sides.

Distribution of workstation addresses taking into account the structural diagram.

IN this section it is necessary to divide the network into several subnets based on the network structure diagram. Determine IP addresses for subnets (for servers and PCs), mask and broadcast addresses. Use a classless model to distribute addresses.

Selection of network protocols.

Choose network protocols which will be used in the developed network and what functions will be performed based on these protocols.

Selecting active and passive equipment for a corporate network.

Types of cables used.

The most commonly used means of communication are twisted pair, radio channel and fiber optic lines. When choosing a cable type, take into account the following indicators:

1. Cost of installation and maintenance;

2. Information transfer speed;

3. Restrictions on the distance of information transmission (without additional amplifiers-repeaters (repeaters));

4. Security of data transmission.

The main challenge is to simultaneously ensure these indicators, e.g. highest speed data transmission is limited to the maximum possible data transmission distance, which still ensures the required level of data protection. Lightweight and easy to expand cable system affect its cost and security of data transmission.

Selecting cable types for the network.

To select the cable type, and therefore the type network technology and, accordingly, the equipment, you need to know what the load will be on this communication channel. The length of this channel and the environmental conditions in which this channel will be located.

Let's calculate the load on communication channels. This requires data from the tables in the first chapter, as well as a block diagram of the network.

Selecting switches.

Switches are:
1. A multiport device that provides high-speed packet switching between ports.
2. In a packet switching network, a device that routes packets, usually to one of the nodes in the backbone network. This device is also called a data switch.

A switch provides each device (server, PC, or hub) connected to one of its ports with the entire network bandwidth. This improves performance and reduces network response time by reducing the number of users per segment. Like dual-speed hubs, the latest switches are often designed to support 10 or 100 Mbps, depending on the maximum speed connected device. If they are equipped with automatic baud rate detection, they can adjust themselves to the optimal speed - no manual configuration changes are required. How does a switch work? Unlike hubs, which broadcast all packets received on any of the ports, switches transmit packets only to the target device (addressee), since they know the MAC (Media Access Control) address of each connected device (similar to the postman at a postal address determines where the letter should be delivered). As a result, traffic decreases and overall traffic increases. throughput, and these two factors are critical given the growing network bandwidth requirements of today's complex business applications.

Switching is gaining popularity as a simple, low-cost method of increasing the available network bandwidth. Modern switches often support features such as traffic prioritization (which is especially important when transmitting voice or video over the network), network management functions, and multicast control.

To select switches, you first need to calculate the minimum number of ports for each of them. It is necessary to provide spare ports on each switch so that if one of the used ones fails, you can quickly fix the problem and use one of the backup ports. This approach makes sense for ports for UTP cables. This is not relevant for optical ports, since they rarely fail.

The number of ports is calculated using the following formula:

where: N – required number of ports; N k – number of occupied ports.

And it is rounded up depending on the standard number of ports on the switches.

Next you can proceed to select specific models switches. If possible, we will take switches and network cards from the same manufacturer. This will avoid conflicts and also simplify network setup.

Selecting network adapters.

Network interface cards (NIC, Network Interface Card) are installed on desktop and laptop PCs. They are used to interact with other devices on the local network. There is a whole range of network cards for various PCs that have specific performance requirements. They are characterized by data transfer speed and methods of connecting to the network.

If we consider simply the method of receiving and transmitting data on PCs connected to the network, then modern network cards (network adapters) play an active role in improving performance, prioritizing critical traffic (transmitted/received information) and monitoring traffic on the network. In addition, they support features such as remote activation from a central workstation or remote configuration changes, which significantly saves administrators time and effort in ever-growing networks.

Selecting the configuration of servers and workstations.

The main requirement for servers is reliability. To increase reliability, we will choose machines with a RAID controller. It can work in two modes: “mirror” and “ fast mode" We will be interested in the first mode. In this mode, the data recorded on HDD simultaneously recorded on another second similar hard drive (duplicated). Also, servers require a larger number random access memory(it is not possible to find out how much memory is required, since we do not know the actual sizes of the databases and the volumes stored on hard drives information). Also, the server processes requests (database servers) of the user, therefore you need to choose the brand and frequency of the processor better (more) than on workstations.

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To organize data transmission over power networks, the transmitted information undergoes the same transformations as when transmitting data over telephone network common use. That is, the transmitted information at the transmitting end is subject to encoding, digital-to-analog conversion and modulation, and at the receiving end - demodulation, analog-to-digital conversion and decoding.

Since each subscriber of a data transmission system is both a source and a recipient of information, it is necessary to organize the transmitting and receiving parts of the system on each PC. It is convenient to organize this by using one internal and external interface for the transmitter and receiver. Thus, the generalized block diagram of a data transmission system on one PC will look like this (Fig. 3.1).

Figure 3.1 - Generalized diagram of the data transmission system

From Fig. 3.1 it is clear that transmitted information V digital form enters the data transmission device through the internal interface. The internal interface serves to separate from the entire stream of data that is transmitted via the internal PC data bus those that are intended for transmission to the communication line. The allocation process occurs in accordance with the address information transmitted on the address bus. It follows from this that the internal interface ensures that only the data that needs to be transmitted over the communication line enters the transmitting device. In the same way, the data received by the receiver is transmitted through the internal interface to the PC for further processing.

Front end serves to coordinate the data transmission and reception device with the communication line. It performs the functions of separating signals by direction, adapting signals to the transmission medium, decoupling voltage, matching resistance in the line and linear path, and selecting only the useful signal.

The processes of encoding, decoding, digital-to-analog and analog-to-digital conversion, as well as modulation and demodulation are performed by a microprocessor system. This system includes a read-only memory (ROM) that contains software that performs certain functions of the microprocessor system. It also includes random access memory (RAM) and reprogrammable read-only memory (PROM). RAM is used to store intermediate calculation results and key data. Temporary algorithms for the operation of the microprocessor system are recorded in the EEPROM. All transformations to which the signal undergoes are performed in the microprocessor (MP) itself. The microprocessor used is subject to special requirements. Since when implementing encoding and decoding algorithms the main mathematical operation is floating-point multiplication, when using classical MPs the complexity of writing programs and their execution time sharply increases. Today, digital signal processors, also called DSP controllers, are widely used in digital signal processing. The main advantage of these DSP controllers is the ability to perform single-cycle multiplications, additions, and the presence of specific commands, such as binary inversion. The use of such a DSP controller sharply reduces the requirements for its performance, which has a positive effect on the price of the system. Using in microprocessor system, along with a conventional microprocessor, DSP controller, you can redistribute the functions performed. So the MP organizes data exchange via the data bus from the PC, generating and receiving address information via the address bus, that is, it performs the functions of an internal interface. Since the speed of the DSP controller is much higher than the MP, it performs the functions of encoding, decoding, digital-to-analog and analog-to-digital conversion, as well as modulation and demodulation.

The external interface is organized by several devices, each performing its own function. An adaptive equalizer is used to adapt the signal to the communication line. An echo canceller is used to separate signals by direction. Connection device that performs following functions: cuts off the industrial frequency and passes only a useful high-frequency signal, serves as a barrier device for high voltage, serves as a matching element between the high-frequency cable and the linear path, since the characteristic impedance of the cable is not equal to the characteristic impedance of the linear path.

Thus, the general block diagram of the data transmission system over the power network has the following form (Fig. 3.2), where, UP is the connection device, SHA is the address bus, SD is the data bus.

Figure 3.2 - Block diagram of the information transmission system over power grids

Based on this diagram, we can give a block diagram of the transmitter (Fig. 3.3).

The functioning of the MP is carried out according to an algorithm recorded in ROM and PROM. The data that is analyzed by the microprocessor is stored in RAM. After performing all the necessary operations on the data, the RAM is cleared in order to accept other data. The principle of operation of the encoder depends on the encoding method, which is selected from the condition of obtaining a minimum probability of error and maximum noise immunity. Modulation should ensure that the spectrum of the useful signal is transferred to the frequency region where it will be least susceptible to interference. The data transmission speed and maximum noise immunity also depend on the modulation method. Therefore, the main parameters of the data transmission system as a whole depend on the choice of modulation type.

Figure 3.3 - Block diagram of the transmitter

Since data transmission is carried out in four frequency ranges, which are located quite close to each other, it becomes necessary to limit the spectra of transmitted signals within the frequency range. The limitation is made to ensure that signals transmitted in one frequency range do not affect signals transmitted in another frequency range. To limit the spectra, bandpass filters are used, each tuned to its own resonant frequency.

The processes occurring in the microprocessor and DSP controller are controlled using drivers that are supplied with the microprocessor and DSP controller from the manufacturer.