1. Introduction - 1 p.
2. Statement of the problem - 2 pages.
3. Analysis of methods for solving the problem - 2 pages.
4. Basic OSI Model - 4 p.
5. Network devices and means of communication - 7 p.
6. Computer network topology - 10 pages.
7. Types of networking - 16 pages.
8. Network operating systems - 18 pages.
9. Technical solution - 25 pages.
10.Literature - 28 pages.
Introduction.
Today there are more than 130 million computers in the world, and more than 80% of them are united in various information and computer networks from small local area networks in offices to global networks such as the Internet. The worldwide trend towards connecting computers in a network is due to a number of important reasons, such as the acceleration of the transmission of information messages, the ability to quickly exchange information between users, receiving and transmitting messages (faxes, E-Mail letters, etc.) without leaving the workplace, the ability to instantly receive any information from anywhere in the world, as well as the exchange of information between computers of different manufacturers running under different software.
Such huge potential opportunities that the computer network carries and the new potential rise that the information complex is experiencing, as well as a significant acceleration of the production process, do not give us the right not to accept this for development and not to apply them in practice.
Therefore, it is necessary to develop a fundamental solution to the issue of organizing an ICS (information and computer network) on the basis of an already existing computer park and software complex that meets modern scientific and technical requirements, taking into account the increasing needs and the possibility of further gradual development of the network in connection with the emergence of new technical and software solutions.
Formulation of the problem.
At the current stage of the development of the association, a situation has developed when:
1. The association has a large number of computers operating separately from all other computers and not having the ability to flexibly exchange information with other computers.
2. It is impossible to create a public database, the accumulation of information with the existing volumes and various methods of processing and storing information.
3. Existing LANs combine a small number of computers and work only on specific and narrow tasks.
4. The accumulated software and information support is not used in full and does not have a common storage standard.
5. With the available connectivity to global computer networks such as the Internet, it is necessary to connect to the information channel of not one group of users, but all users using grouping.
Analysis of methods for solving this problem.
To solve this problem, it was proposed to create a unified information network (UIS) of the enterprise. The enterprise's EIS must perform the following functions:
1. Creation of a single information space that is capable of embracing and applying for all users information created at different times and under different types of data storage and processing, parallelization and control of work performance and data processing on them.
2. Increasing the reliability of information and the reliability of its storage by creating a computing system resistant to failures and loss of information, as well as creating data archives that can be used, but at the moment there is no need for them.
3. Providing an effective system for accumulating, storing and searching for technological, technical, economic and financial and economic information on current work and what was done some time ago (archive information) by creating a global database.
4. Processing of documents and building on the basis of this operating system of analysis, forecasting and assessment of the situation in order to make the best decision and develop global reports.
5. Provide transparent access to information for an authorized user in accordance with his rights and privileges.
In this work, in practice, the solution of the 1st point "Tasks" - Creation of a single information space - is considered by considering and choosing the best of the existing methods or their combination.
Consider our IVS. Simplifying the task, we can say that this is a local area network (LAN).
What is a LAN? A LAN is understood as the joint connection of several separate computer workstations (workstations) to a single data transmission channel. Thanks to computer networks, we got the opportunity to use programs and databases simultaneously by several users.
The concept of a local area network - LAN (English LAN - Lokal Area Network) refers to geographically limited (geographically or production) hardware and software implementations in which several computer systems are connected to each other using appropriate means of communication. Thanks to this connection, the user can interact with other workstations connected to this LAN.
In industrial practice, LANs play a very important role. Through a LAN, the system integrates personal computers located at many remote workplaces that share equipment, software and information. Workplaces of employees are no longer isolated and are combined into a single system. Consider the benefits obtained by networking personal computers in the form of an intra-industrial computer network.
Sharing resources.
Sharing resources allows for conservative use of resources, such as managing peripheral devices such as laser printers from all attached workstations.
Data sharing .
Data sharing provides the ability to access and manage databases from peripheral workstations that need information.
Separation of software.
Software separation allows for the simultaneous use of centralized, previously installed software.
Sharing processor resources .
By dividing processor resources, it is possible to use computing power for data processing by other systems in the network. The provided opportunity lies in the fact that the available resources are not "pounced on" instantly, but only through a special processor available to each workstation.
Multiplayer mode.
The multi-user properties of the system facilitate the simultaneous use of centralized application software previously installed and managed, for example, if a user of the system is working on another job, the current work being performed is pushed into the background.
All LANs work in one standard adopted for computer networks - in the Open Systems Interconnection (OSI) standard.
Basic OSI (Open System Interconnection) Model
In order to interact, people use a common language. If they cannot speak to each other directly, they use appropriate messaging aids.
The stages shown above are required when a message is passed from sender to receiver.
In order to set in motion the process of data transmission, machines were used with the same data coding and connected to one another. For a unified presentation of data in communication lines through which information is transmitted, the International Organization for Standardization (ISO - International Standards Organization) has been formed.
ISO is designed to develop a model for an international communication protocol within which international standards can be developed. For a visual explanation, we will divide it into seven levels.
The International Organization for Standardization (ISO) has developed a basic model for open systems interconnection (OSI). This model is the international standard for data transmission.
The model contains seven distinct levels:
Level 1 : physical- bit protocols of information transfer;
Level 2 : channel- staffing, management of access to the environment;
Level 3 : network- routing, data flow control;
Level 4 : transport- ensuring the interaction of remote processes;
Level 5 : session- support for dialogue between remote processes;
Level 6 : submission data - interpretation of transmitted data;
Level 7 : applied- user data management.
The main idea of this model is that each level is assigned a specific role, including the transport environment. This breaks down the overall data transfer task into individual, easily visible tasks. The necessary agreements for communication of the same level with the above and below are called a protocol.
Since users need efficient management, a computer network system is presented as an integrated structure that coordinates the interaction of users' tasks.
Given the above, the following tier model can be derived with administrative functions performed in the user application layer.
The individual layers of the base model extend downward from the data source (from layer 7 to layer 1) and upward from the data sink (from layer 1 to layer 7). User data is passed to the lower layer along with the layer-specific header until the last layer is reached.
At the receiving side, the incoming data is analyzed and, as required, is transmitted further to a higher level, until the information is transferred to the user application level.
Level 1. Physical.
The physical layer defines the electrical, mechanical, functional, and procedural parameters for physical communication in systems. Physical connectivity and unbreakable availability is a core Layer 1 function. Physical layer standards include CCITT Recommendations V.24, EIA RS232 and X.21. The ISDN standard (Integrated Services Digital Network) will play a decisive role for data transmission functions in the future. A three-core copper wire (shielded twisted pair), a coaxial cable, a fiber-optic conductor and a radio relay line are used as the data transmission medium.
Level 2. Channel.
The link layer forms the so-called "frames" of the sequence of frames from the data transmitted by the 1st layer. At this level, access control to the transmission medium used by several computers, synchronization, error detection and correction are carried out.
Level 3. Network.
The network layer establishes communication in a computer network between two subscribers. The connection is made thanks to routing functions that require the presence of a network address in the packet. The network layer must also provide error handling, multiplexing, and data flow control. The best known standard related to this layer is CCITT Recommendation X.25 (for public packet switched networks).
Level 4. Transport.
The transport layer supports the continuous transfer of data between two user processes interacting with each other. Quality of transportation, error-free transmission, independence of computer networks, end-to-end transportation service, cost minimization and communication addressing guarantee uninterrupted and error-free data transmission.
Level 5. Session.
The session layer coordinates the reception, transmission and issue of one communication session. Coordination requires monitoring of operating parameters, data flow control of intermediate storage devices and interactive monitoring, which guarantees the transfer of the available data. In addition, the session layer additionally contains the functions of password management, calculating the payment for the use of network resources, managing the dialogue, synchronizing and canceling communication in the transmission session after a failure due to errors in the lower layers.
Level 6. Data views.
The data presentation layer is for data interpretation; as well as data preparation for the user application level. At this level, data is converted from frames used to transfer data to a screen format or a format for printing devices of the end system.
Level 7. Applied.
At the application level, it is necessary to make the processed information available to users. The system and user application software can handle this.
For the transfer of information via communication lines, the data is converted into a string of successive bits (binary coding using two states: "0" and "1").
Transmitted alphanumeric characters are represented using bit patterns. Bit patterns are located in a specific code table containing 4-, 5-, 6-, 7- or 8-bit codes.
The number of characters represented in the course depends on the number of bits used in the code: a four-bit code can represent a maximum of 16 values, 5-bit code - 32 values, 6-bit code - 64 values, 7-bit - 128 values, and 8-bit code - 256 alphanumeric characters.
When transferring information between the same computing systems and different types of computers, the following codes are used:
At the international level, the transmission of symbolic information is carried out using 7-bit coding, which allows you to encode upper and lower case letters of the English alphabet, as well as some special characters.
National and special characters cannot be represented using a 7-bit code. The most commonly used 8-bit code is used to represent national characters.
For correct and therefore complete and error-free transmission of data, agreed and established rules must be adhered to. All of them are specified in the data transfer protocol.
The data transfer protocol requires the following information:
Synchronization
Synchronization is understood as a mechanism for recognizing the beginning of a data block and its end.
Initialization
Initialization is understood as the establishment of a connection between interacting partners.
Blocking
Blocking is understood as the division of the transmitted information into data blocks of a strictly defined maximum length (including the identification marks of the beginning of the block and its end).
Addressing
Addressing provides identification of the various data equipment in use that communicate with each other during interaction.
Error detection
By error detection is meant the setting of the parity bits and hence the computation of the check bits.
Block numbering
The current block numbering allows you to identify erroneously transmitted or lost information.
Data flow control
Data flow control is used to distribute and synchronize information flows. So, for example, if there is not enough space in the buffer of the data device or the data is not processed quickly enough in peripheral devices (for example, printers), messages and / or requests accumulate.
Recovery methods
After the interruption of the data transfer process, recovery methods are used to return to a certain position for retransmission of information.
Access authorization
The allocation, control and management of data access restrictions is the responsibility of the access authorization point (eg, "send only" or "receive only").
Network devices and means of communication.
Twisted pair, coaxial cable and fiber-optic lines are most often used as communication means. When choosing the type of cable, the following indicators are taken into account:
installation and maintenance costs,
information transfer rate,
Limitations on the distance of information transmission (without additional repeater amplifiers (repeaters)),
security of data transmission.
The main problem lies in the simultaneous provision of these indicators, for example, the highest data transfer rate is limited by the maximum possible data transmission distance, at which the required level of data protection is still provided. The ease of scalability and ease of expansion of the cabling system affects its cost.
Twisted pair.
The cheapest cable connection is a twisted two-wire wiring connection, often referred to as a "twisted pair". It allows you to transfer information at a speed of up to 10 Mbit / s, it can be easily expanded, but it is noise-immune. The cable length cannot exceed 1000 m at a transmission rate of 1 Mbps. The advantages are low cost and hassle-free installation. To increase the noise immunity of information, a shielded twisted pair is often used, i.e. twisted pair, enclosed in a shielding, like the shield of a coaxial cable. This increases the cost of a twisted pair cable and brings it closer to that of a coaxial cable.
Coaxial cable.
Coaxial cable has an average price, good noise immunity and is used for communication over long distances (several kilometers). The information transfer rate is from 1 to 10 Mbit / s, and in some cases it can reach 50 Mbit / s. Coaxial cable is used for basic and broadband data transmission.
Broadband coaxial cable.
Broadband coaxial cable is immune to interference, easy to build, but expensive. The information transfer rate is 500 Mbit / s. When transmitting information in the base frequency band over a distance of more than 1.5 km, an amplifier, or a so-called repeater (repeater), is required. Therefore, the total distance during information transmission increases to 10 km. For computer networks with a bus or tree topology, the coaxial cable must have a terminating resistor (terminator) at the end.
Ethernet cable.
The Ethernet cable is also a 50 ohm coaxial cable. It is also called thick Ethernet or yellow cable. It uses a 15-pin standard connection. Due to its noise immunity, it is an expensive alternative to conventional coaxial cables. The maximum available distance without a repeater does not exceed 500 m, and the total distance of the Ethernet network is about 3000 m. The Ethernet cable, due to its trunk topology, uses only one terminating resistor at the end.
Сheapernеt cable.
Cheapernet cable, or thin Ethernet as it is often called, is cheaper than Ethernet. It is also a 50-ohm coaxial cable with a data transfer rate of ten million bits / s.
Repeaters are also required when connecting the segments of a Cearenet cable. Computing networks with Cheapernet-cable are low cost and minimal costs for expansion. The network cards are connected using widely used small bayonet connectors (CP-50). Additional shielding is not required. The cable connects to the PC using T-connectors.
The distance between two workstations without repeaters can be a maximum of 300 m, and the total distance for the network on the Cheapernet cable is about 1000 m. The Cheapernet transceiver is located on the network board both for galvanic isolation between the adapters and for amplifying the external signal
Fiber optic lines.
The most expensive are optical conductors, also called fiberglass cables. The speed of information dissemination through them reaches several gigabits per second. The permissible distance is more than 50 km. There is practically no external influence of interference. This is currently the most expensive LAN connection. They are used where electromagnetic interference fields occur or information transmission is required over very long distances without the use of repeaters. They have anti-jamming properties, since the branching technique in fiber optic cables is very complex. The optocouplers are connected in JIBC using a star connection.
The figures for the three typical transmission media are shown in the table.
| Indicators | Data transmission medium | ||
| Coaxial cable | Fiber optic cable | ||
| Price | Low | Relatively high | High |
| Build-up | Very simple | Problematic | Simple |
| Eavesdropping protection | Insignificant | Good | High |
| Indicators | Data transmission medium | ||
| Two-core cable - twisted pair | Coaxial cable | Fiber optic cable | |
| Grounding problems | Not | Possible | Not |
| Susceptibility to interference | Exists | Exists | Missing |
There are a number of principles for constructing a LAN based on the above components. Such principles are also called topologies.
Computer network topology.
Star topology.
The concept of a star network topology comes from mainframe computers, in which the host receives and processes all data from peripheral devices as the active processing node. This principle is applied in data transmission systems such as RELCOM e-mail. All information between two peripheral workstations passes through the central node of the computer network.
Star topology
The network bandwidth is determined by the processing power of the node and is guaranteed for each workstation. Collisions (collisions) of data do not occur.
The cable connection is fairly straightforward as each workstation is connected to a node. Cabling costs are high, especially when the central site is not geographically located at the center of the topology.
When expanding computer networks, the previously made cable connections cannot be used: a separate cable must be laid to the new workplace from the center of the network.
The star topology is the fastest of all computer network topologies, because data transmission between workstations passes through the central site (with good performance) on separate lines that are used only by these workstations. The frequency of requests for information transfer from one station to another is low compared to that achieved in other topologies.
The performance of a computer network primarily depends on the capacity of the central file server. It can be a bottleneck in a computer network. In the event of a failure of the central unit, the operation of the entire network is disrupted.
Central control unit - the file server is used to implement the optimal protection mechanism against unauthorized access to information. The entire computer network can be controlled from its center.
Ring topology.
In a ring network topology, workstations are connected to one another in a circle, i.e. workstation 1 with workstation 2, workstation 3
Ring topology
with workstation 4, etc. The last workstation is linked to the first. The communication link is closed in a ring.
Routing cables from one workstation to another can be quite difficult and expensive, especially if the workstations are geographically located far from the ring (for example, in a line).
Messages circulate regularly in a circle. The workstation sends information to a specific end address, having previously received a request from the ring. Message forwarding is very efficient as most messages can be sent “on the road” over the cable system one after the other. It is very easy to make a circular request to all stations. The duration of information transmission increases in proportion to the number of workstations included in the computer network.
The main problem with a ring topology is that each workstation must actively participate in the transfer of information, and if at least one of them fails, the entire network is paralyzed. Faults in cable connections are easily localized.
Connecting a new workstation requires a short and urgent disconnection of the network, since the ring must be open during installation. There is no limit to the length of a computer network, since it is ultimately determined solely by the distance between two workstations.
Logic ring circuit structure
A special form of ring topology is the logical ring network. It is physically mounted as a star topology junction. Individual stars are switched on with the help of special switches (English hub-hub), which in Russian is also sometimes called a “hub”. Depending on the number of workstations and the length of the cable, active or passive concentrators are used between workstations. Active hubs additionally contain an amplifier for connecting 4 to 16 workstations. The passive hub is a purely branching device (for a maximum of three workstations). A single workstation in a logical ring is controlled in the same way as in a conventional ring. Each workstation is assigned an address corresponding to it, at which control is transferred (from the oldest to the youngest and from the youngest to the oldest). The disconnection occurs only for the downstream (closest) node of the computer network, so only in rare cases the operation of the entire network can be disrupted.
Bus topology.
With a bus topology, the information transmission medium is represented in the form of a communication path available for all workstations to which they all must be connected. All workstations can directly contact any workstation on the network.
Bus topology
Workstations at any time, without interrupting the work of the entire computer network, can be connected to it or disconnected. The functioning of a computer network does not depend on the state of an individual workstation.
Typically, a thin cable or Cheapernet cable with a tee connector is often used for an Ethernet bus network. Switching off and especially connecting to such a network requires breaking the bus, which causes disruption of the circulating flow of information and the system freezing.
New technologies offer passive plug boxes through which workstations can be turned off and / or turned on while the network is running.
Due to the fact that workstations can be turned on without interrupting network processes and communication environment, it is very easy to listen to information, i.e. fork information from the communication environment.
In a LAN with direct (non-modulated) transmission of information, there can always be only one station transmitting information. To prevent collisions, in most cases, a temporary separation method is used, according to which an exclusive right to use the data transmission channel is granted for each connected workstation at certain points in time. Therefore, the requirements for the bandwidth of the computer network under increased load are reduced, for example, when new workstations are introduced. Workstations are connected to the bus by means of TAP devices (Terminal Access Point). TAP is a special type of coaxial cable connection. The needle-shaped probe is inserted through the outer sheath of the outer conductor and the dielectric layer to and attached to the inner conductor.
In a modulated broadband LAN, the various workstations receive, as needed, the frequency on which these workstations can send and receive information. The transmitted data is modulated at the respective carrier frequencies, i. E. modems for modulation and demodulation are located between the information transmission medium and the workstations, respectively. Broadband communication technology allows a rather large amount of information to be transported simultaneously in a communication environment. For the further development of discrete data transportation, it does not matter what the initial information is supplied to the modem (analog or digital), since it will still be converted in the future.
The characteristics of the topologies of computer networks are given in the table.
| Characteristics | Topology | ||
| Star | Ring | Tire | |
| Expansion cost | Insignificant | Average | Average |
| Subscribers joining | Passive | Active | Passive |
| Failure protection | Insignificant | Insignificant | High |
| Characteristics | Topology | ||
| Star | Ring | Tire | |
| System dimensions | Any | Any | Limited |
| Eavesdropping protection | Good | Good | Insignificant |
| Connection cost | Insignificant | Insignificant | High |
| System behavior at high loads | Good | Satisfactory | Bad |
| Ability to work in real time | Very good | Good | Bad |
| Cable routing | Good | Satisfactory | Good |
| Service | Very good | The average | The average |
LAN tree structure.
Along with the well-known topologies of computer networks, ring, star and bus, in practice, a combined structure is also used, for example, a tree-like structure. It is formed mainly in the form of combinations of the above-named topologies of computer networks. The base of a computer network tree is located at the point (root) at which communication lines of information are collected (tree branches).
Computing networks with a tree structure are used where it is impossible to directly apply the basic network structures in their pure form. To connect a large number of workstations, according to adapter cards, network amplifiers and / or switches are used. A switch that has both the functions of an amplifier is called an active hub.
In practice, two types of them are used, providing connection of eight or sixteen lines, respectively.
A device to which a maximum of three stations can be connected is called a passive hub. A passive hub is usually used as a splitter. It doesn't need an amplifier. A prerequisite for connecting a passive hub is that the maximum possible distance to the workstation should not exceed several tens of meters.
Types of building networks by methods of transferring information.
Local token ring network
This standard was developed by IBM. Unshielded or shielded twisted pair (UPT or SPT) or fiber is used as the transmission medium. The data transfer rate is 4 Mbps or 16 Mbps. The Token Ring method is used as a method for controlling the access of stations to the transmission medium. The main points of this method:
¨ devices are connected to the network using ring topology;
¨ all devices connected to the network can transfer data only after receiving permission to transfer (token);
¨ at any given time, only one station in the network has this right.
Types of packages.
There are three main types of packets used in the IBM Token Ring:
¨ package control / data (Data / Command Frame);
¨ marker (Token);
¨ reset package (Abort).
Management / Data package... With the help of such a package,
transmission of data or commands to control the operation of the network.
Marker. A station can start transmitting data only after receiving such a packet. There can be only one marker in one ring and, accordingly, only one station with the right to transmit data.
Reset package. Sending such a packet is called the termination of any transmissions.
The network can connect computers in a star or ring topology.
Arknet local network.
Arknet (Attached Resource Computer NETWork) is a simple, inexpensive, reliable and flexible enough LAN architecture. Developed by Datapoint Corporation in 1977. Subsequently, the Arcnet license was acquired by Standard Microsistem Corporation, which became the main developer and manufacturer of equipment for Arcnet networks. Twisted pair, coaxial cable (RG-62) with a characteristic impedance of 93 Ohm and fiber-optic cable are used as the transmission medium. The data transfer rate is 2.5 Mbps. When connecting devices in Arcnet, bus and star topologies are used. The method of controlling the stations' access to the transmission medium is the Token Bus. This method provides the following rules:
¨ All devices connected to the network can transmit data
¨ only after receiving permission to transfer (marker);
¨ At any given time, only one station in the network has this right;
¨ Data transmitted by one station is available to all stations on the network.
Basic principles of work.
The transfer of each byte to Arcnet is performed by a special message ISU (Information Symbol Unit), consisting of three service start / stop bits and eight data bits. At the beginning of each packet, the initial separator AB (Allegt Burst) is transmitted, which consists of six service bits. The leading delimiter acts as a preamble for the packet.
Arcnet defines 5 packet types:
1. ITT package(Information To Transmit) - an invitation to transfer. This message transfers control from one network node to another. The station that received this packet gets the right to transmit data.
2. FBE package(Free Buffe? Inquiries) - a request for readiness to receive data. This packet checks the readiness of the node to receive data.
3. Data package. This message is used to transfer data.
4. ACK package ( ACKnowledgments) - acknowledgment of receipt. Confirmation of readiness to receive data or confirmation of receipt of a data packet without errors, i.e. in response to FBE and data packet.
5. NAK package(Negative AcKnowledgments) - not ready to receive. Unavailability of the node to receive data (response to FBE) or received a packet with an error.
There are two topologies that can be used in an Arknet network: star and bus.
Ethernet LAN
The Ethernet specification was introduced in the late seventies by Xerox Corporation. Later, Digital Equipment Corporation (DEC) and Intel Corporation joined this project. In 1982, the Ethernet specification version 2.0 was published. Based on Ethernet, the IEEE Institute developed the IEEE 802.3 standard. The differences between them are minor.
Basic principles of work.
At the logical level in Ethernet, the bus topology is applied:
¨ all devices connected to the network are equal, i.e. any station can start transmission at any time (if the transmission medium is free);
¨ data transmitted by one station is available to all stations on the network.
Network operating systems for local area networks.
The main direction of development of modern Network Operation System (NOS) is the transfer of computing operations to workstations, the creation of systems with distributed data processing. This is primarily due to the growth of computing capabilities of personal computers and the increasingly active introduction of powerful multitasking operating systems: OS / 2, Windows NT, Windows 95. In addition, the introduction of object-oriented technologies (OLE, DCE, IDAPI) makes it possible to simplify the organization of distributed processing data. In such a situation, the main task of NOS is to combine unequal workstation operating systems and provide a transport layer for a wide range of tasks: database processing, messaging, management of distributed network resources (directogu / name service).
In modern NOS, there are three main approaches to organizing network resource management.
The first is Bindery Tables. Used in network operating systems NetWare 28b and NetWare v3.1x. Such a table is found on every file server on the network. It contains information about users, groups, their access rights to network resources (data, services, etc.). This organization of work is convenient if there is only one server in the network. In this case, it is required to define and control only one information base. With the expansion of the network, the addition of new servers, the volume of tasks for managing network resources increases dramatically. The system administrator is forced to define and control the work of users on each server in the network. Network subscribers, in turn, must know exactly where certain network resources are located, and in order to gain access to these resources, they must register on the selected server. Of course, for information systems consisting of a large number of servers, such an organization of work is not suitable.
The second approach is used by LANServer and LANMahager - Domain Structure. All network resources and users are combined into groups. A domain can be viewed as an analogue of object tables (bindery), only here such a table is common for several servers, while server resources are shared for the entire domain. Therefore, in order to gain access to the network, the user only needs to connect to the domain (register), after which all resources of the domain, resources of all servers and devices that are part of the domain become available to him. However, using this approach, problems also arise when building an information system with a large number of users, servers and, accordingly, domains. For example, networks for an enterprise or a large branched organization. Here these problems are already associated with the organization of interaction and management of several domains, although in content they are the same as in the first case.
The third approach, Directory Name Services (DNS), avoids these drawbacks. All network resources: network printing, data storage, users, servers, etc. are considered as separate branches or directories of the information system. DNS definition tables are found on each server. This, firstly, increases the reliability and survivability of the system, and secondly, it simplifies the user's access to network resources. By registering on one server, all network resources become available to the user. Managing such a system is also easier than using domains, since there is one table that defines all network resources, while with a domain organization it is necessary to define resources, users, and their access rights for each domain separately.
Currently, according to IDC, the following network operating systems are the most common:
¨ NetWare v2.x and v3.x, Nowell Inc. 65%
¨ LAN Server, IBM Conform. 14%
¨ LAN Manager, Microsoft Corp. 3%
¨ VINES, Banuan Systems Inc. 2%
Let us consider in more detail the capabilities of these and some other network operating systems and the requirements they place on the software and hardware of network devices.
NetWare 3.11, Nowell Inc.
Distinctive features:
¨ the most efficient file system among modern NOS;
¨ widest selection of hardware
¨ Minimum hard disk space: 9 MB.
¨ The amount of RAM (RAM) on the server: 4 MB - 4 GB.
¨ Minimum volume of the client's OP (Workstation): 640 KB.
¨ Operating system: Nowell's own development
¨ Protocols: IPX / SРХ.
¨ Multiprocessing: no.
¨ Number of users: 250.
¨ Maximum file size: 4GB.
¨ Data encryption: no.
¨ UPS monitor: yes.
¨ ТТS: yes.
¨ Management of distributed network resources: bindegu tables on the server.
¨ Failover system: disk duplication, disk mirroring, SFT II, SFT III, tape drive support, bindery table and data backup.
¨ Block suballocations: none.
¨ Client file system: DOS, Windows, Mac (optional), OS / 2 (optional), UNIX (optional), Windows NT.
LAN Server, IBM Conform.
Distinctive features:
¨ the use of domain network organization simplifies management and access to network resources;
¨ provides full interaction with hierarchical systems (SNA architecture).
A holistic operating system with a wide range of services. It works on the basis of OS / 2, so the server can be nondedicated. Provides interaction with hierarchical systems, supports internetworking.
LAN Server is available in two versions: Entry and Advanced. Advanced, unlike Entry, supports a High Performance File System (HPFS). It includes Fail Tolerances and Local Security systems.
Servers and users are combined into domains. The servers in the domain operate as a single logical system. All domain resources are available to the user after registering in the domain. Several domains can operate in one cable system. When used on an OS / 2 workstation, the resources of these stations are available to users of other workstations, but only one at a given time. The administrator can control the network operation only from a workstation on which the OS / 2 operating system is installed. LAN Server supports remote loading of DOS, OS / 2 and Windows workstations (Remote Interface Procedure Load - RIPL).
The disadvantages include:
¨ complex procedure for installing NOS;
¨ limited number of supported network adapter drivers.
Main characteristics and requirements for hardware.
¨ Central processor: 38b and higher.
¨ Minimum hard disk space: 4.6 MB for the client (requestor) / 7.2 MB for the server.
¨ The minimum amount of RAM on the server: 1.3 MB - 16 MB.
¨ The minimum size of the client's operating system: 4.2 MB for OS / 2, 640 KB for DOS.
¨ Operating system: OS / 2 2.x.
¨ Protocols: NetBIOS, ТСР / IP.
¨ Number of users: 1016.
¨ Maximum file size: 2 GB.
¨ Data encryption: no.
¨ UPS monitor: yes.
¨ ТТS: yes.
¨ Failover system: disk duplication, disk mirroring, tape drive support, domain table backup.
¨ Data Compression: None.
¨ Client file system: DOS, Windows, Mac (optional), OS / 2, UNIX, Windows NT (optional).
VINES 5.52, Banyan System Inc.
Distinctive features:
¨ the ability to interact with any other network operating system;
¨ Using the StreetTalk naming service allows you to create branched systems.
Prior to the advent of NetWare 4, VINES dominated the network operating system market for distributed networks, for enterprise networks. Tightly integrated with UNIX.
To organize interaction, the global name service - StreetTalk, is used, which is in many ways similar to NetWare Directory Services. Allows a user to connect anywhere on the network. StreetTalk is a database distributed across all servers on the network.
X.29 support allows a remote DOS workstation to connect to a local area network via an X.25 or ISDN network.
VINES is critical to the type of computer and hard drives. Therefore, when choosing your equipment, you must ensure that the hardware and the VINES network operating system are compatible.
Main characteristics and requirements for hardware.
¨ Central processing unit: 386 and higher.
¨ Minimum hard disk space: 80 MB.
¨ The amount of RAM on the server: 8 MB - 25 MB.
¨ The minimum size of the client's OP RS: b40 KB.
¨ Operating system: UNIX.
¨ Protocols: VINES IP, AFP, NetBIOS, ТСР / IP, IPX / SPX.
¨ Multiprocessing: yes - SMP (Symmetric MultiProcesing).
¨ Maximum file size; 2GB.
¨ Data encryption: no.
¨ UPS monitor: yes.
¨ ТТS: no.
¨ Management of distributed network resources: StreetTalk.
¨ Fault Tolerance System: Back up StreetTalk tables and data.
¨ Data compression: yes.
¨ Block suballocation: no.
¨ Client file system: DOS, Windows, Mac (optional), OS / 2, UNIX (optional), Windows NT (optional).
Windows NT Advanced Server 3.1, Microsoft Corp.
Distinctive features:
¨ simplicity of user interface
¨ availability of application development tools and support for progressive object-oriented technologies
All this has led to the fact that this operating system can become one of the most popular network operating systems.
The interface resembles the windowed interface of Windows 3.1, installation takes about 20 minutes. The modular design of the system makes it easy to make changes and port to other platforms. The subsystems are protected from unauthorized access and from their mutual influence (if one process freezes, this does not affect the work of the rest). There is support for remote stations - Remote Access Service (RAS), but remote job processing is not supported.
Windows NT places higher demands on computer performance than NetWare.
Main characteristics and requirements for hardware.
¨ Minimum hard disk space: 90 MB.
¨ The minimum amount of RAM on the server: 16 MB.
¨ The minimum volume of the client's OP RS; 12 MB for NT / 512 KB for DOS.
¨ Operating system: Windows NT.
¨ Protocols: NetBEUI, ТСР / IP, IPX / SPX, Appletalk, АsyncBEUI.
¨ Multiprocessing: supported.
¨ Number of users: unlimited.
¨ Maximum file size: unlimited.
¨ Data encryption: level C-2.
¨ UPS monitor: yes.
¨ ТТS: yes.
¨ Management of distributed network resources: domains.
¨ Failover system: disk duplication, disk mirroring, RAID 5, tape drive support, domain table and data backup.
¨ Data Compression: None.
¨ Block suballocation: no.
¨ Client file system: DOS, Windows, Mac, OS / 2, UNIX, Windows NT.
NetWare 4, Nowell Inc.
Distinctive feature:
¨ the use of a specialized network resource management system (NetWare Directory Services - NDS) allows you to build effective information systems with up to 1000 users. NDS defines all resources, services and network users. This information is distributed across all servers on the network.
Only one area (ROOL) is used to manage memory, so the RAM freed after the execution of any processes becomes immediately available to the operating system (unlike NetWare 3).
The new Data Storage Managment consists of three components to improve the efficiency of the file system:
1. Fragmentation of Blocks or Dividing Blocks of Data into Subblocks (Block Suballocation). If the size of the data block on the volume is 64 KB, and you want to write a file of 65 KB, then earlier it would be necessary to allocate 2 blocks of 4 KB each. At the same time, 6Z Kbytes in the second block cannot be used to store other data. In NetWare 4, the system will allocate one 64K block and two 512 Byte blocks in this situation. Each partially used block is divided into subblocks of 512 Bytes, free subblocks are available to the system when writing other files.
2. Packing Files (File Compression). The system automatically compresses and packs data that is not used for a long time, thus saving space on hard drives. When this data is accessed, the data is automatically decompressed.
3. Data Migration. The system automatically copies data that is not used for a long time to magnetic tape or other media, thus saving space on hard drives.
Built-in support for Packet-Burst Migration Protocol. This protocol allows multiple packets to be transmitted without waiting for an acknowledgment of receipt of each packet. Acknowledgment is sent after receiving the last packet in the series.
When transmitting through gateways and routers, the transmitted data is usually divided into segments of 512 bytes, which reduces: the data transfer rate by about 20%. NetWare 4 uses the Large Internet Packet (LIP) protocol to improve the efficiency of communication between networks, since in this case division into segments of 512 bytes is not required.
All system messages and interface use a special module. To switch to another language, it is enough to change this module or add a new one. It is possible to use several languages at the same time: one user, when working with the utilities, uses English, and the other at the same time uses German.
The management utilities support DOS, Windows and OS / 2 interface.
Main characteristics and requirements for hardware.
¨ Central processor: 38b and higher.
Minimum hard disk space: 12 MB to 60 MB.
The amount of RAM on the server: 8 MB - 4 GB.
The minimum volume of the client's operating system is 40 KB.
Operating system: Nowell's own development.
Protocols: IPX / SPX.
Multiprocessing: no.
Number of users: 1000.
Maximum file size: 4 GB.
Data encryption: C-2.
UPS monitor: yes.
ТТS: yes.
Distributed network resource management: NDS.
Fault Tolerance: Disk duplication, disk mirroring, SFT II, SFT III, tape drive support, NDS table backup.
Data compression: yes.
¨ Block suballocation: yes.
¨ Client file system: DOS, Windows, Mac (5), OS / 2, UNIX (optional), Windows NT.
Technical solution.
In view of the material considered, which provides a comparative consideration of the maximum number of all possible solutions based on existing technologies and world experience, as well as on existing and accepted worldwide standards for building a LAN, we can take the following concept as the basis for building a network as best meeting the set requirements and technically and economically complete.
Step 1. We have (see p-t 1) small networks (department, division, workshop) and stand-alone computers that are not connected to anyone (heads of departments and the administrative building). At the first stage, we will unite all computers in one building into one network, according to the methods and technologies considered specifically for each case. Each building (bundle) (see p-t 2) will have a dedicated server connected to the central server of the enterprise, but allowing simple computers to communicate only through itself. Since a number of computers have rather weak technical characteristics, it is rational to combine them in a network running the Nowell NetWare 4.02 or Windows 3.11 for WorkGroups OS, since they provide the ability to connect "clients" at the DOS level.
Step 2. At the second step, we need to combine the buildings into a single network (see p-t 3). To do this, we will take a powerful server with high performance and connect it via fiber-optic communication with all 6 chassis according to the "star" topology as the most protected from failures and complete network outages and having the maximum throughput. The network will be managed by Nowell NeWare 4.02 as an OS that makes it possible to connect any computers and work with all other OS (see p. 4). To increase the range of tasks to be solved, we will connect Sun Spark Station running under Unix OS and SQL Server Windows NT to the central server, connected under the control of mathematical bridges in the combined Unix / NetWare and Windows NT / NetWare environments, enabling mutual performance of servers and clients and servers on relation to each other.
Networking.
The unification of local networks of departments and "working groups", informationally related by functional interaction when solving their production problems, is carried out on the basis of the "client-server" principle, followed by the provision of a summary of the resulting technological and financial and economic information to the level of the AWS of the heads of the enterprise (and associations, in the future ) for making management decisions.
Program-structured organization of the network.
It is proposed to solve this problem by creating a corporate network of an enterprise based on the Nowell NetWare 4.02 operating system based on the Nowell NetWare 4.02 principle, operating under the control of several servers and supporting the main transport protocols (IPX / SPX and TCP / IP) depending on the protocol under which are operated by local local area networks and which have segments such as Ethernet.
Cable structure
The passive part of the cable structure of the enterprise's EIS contains:
¨ 6 backbone segments of fiber-optic communication cables FXOHBMUK-4GKW-57563-02;
¨ connecting cables F / O Patch Cable;
¨ switching panels F / O Patch Panel;
¨ shielded RF cables RG-58;
¨ cables "twisted pair" 10Base-T Level 5;
¨ switching panels TP Patch Panel;
¨ T-connector;
¨ end radio frequency terminators.
The use of fiber-optic communication lines is justified by the significant distance of production facilities and buildings from each other and a high level of industrial interference. RG-58 cables are used when connecting to a network of automated industrial installations, which also require protection of technological and other information processed at these AWPs and transmitted to other AWPs from various types of industrial interference. "Twisted pair" 10Base-T Level 5 is used to connect workstations of network users in places that do not require increased requirements for the protection of the information transmission medium from interference.
The active part of the EIS cable structure is represented by the following equipment:
¨ CMMR-1440 Multi-Media Repeater;
¨ switching concentrators 10Base-T UTPC-1220 Concentrator;
¨ switching concentrators 10Base-T UTPC-6100 Concentrator.
Hardware and software organization
The EIS shown in the figure contains 3 database servers (file servers), 2 of which are represented by IBM PC / AT486DX computers, the third one - Pentium 120/40 / 4.2G, operating under Novell NetWare network operating system and Unix server based on Sun Sparkstation. Servers, in addition to their direct purpose of processing and storing information, solve the problem of routing and transporting information, on the one hand, reducing traffic on the main information highway and on the other, providing transparent access to information from other servers.
The servers currently serve about 60 workstations processing various types of technological information, as well as over 40 workstations in the administrative and management and financial and economic divisions of the enterprise.
The following network adapter cards are used as network hardware for servers and workstations:
Network streams - IEEE 802.2, IEEE 802.3 CSMA / CD.
Transport protocols - IPX / SPX - for NetWare servers, TCP / IP -
with their rights and privileges.
For hardware and software integration of NetWare and Unix network environments, use a software bridge based on the combined transport protocol IPX / IP, with a possible transition to the network integrated Unix / Ware operating system in the future.
Along with the NetWare 3.11 network operating system, for groups of clients that are functionally interconnected in solving production problems, the network environment Artisoft LANtastic 6.0 and Windows for Workgroup 3.11 are used, which provide transparent access to users of these peer-to-peer networks to each other's information. At the same time, users of LANtastic 6.0 and Windows for Workgroup 3.11 are clients of NetWare servers, having access to their resources and information on hard drives in accordance with their rights and privileges.
Thus, we got a really working corporate network that has a lot of originally working nodes and principles for solving a problem that today in the world is one of the most interesting and advanced in the world in the field of information technology. This network will give an opportunity in the future to move to new more powerful software and hardware communications and communications that will be developed in the world, since the entire network is implemented on the basis of ISO and fully complies with world standards.
Literature.
· D. Wetting “Nowell NetWare for the User”
· S. I. Kazakov "Fundamentals of network technologies"
· “Nowell NetWare 4.02 for Lan Managers” Nowell Corp.
B.G. Golovanov "Introduction to programming in Nowell NetWare"
Federal Agency for Education State Educational Institution of Higher Professional Education Nizhny Novgorod State University named after N.I. Lobachevsky Faculty of Computational Mathematics and Cybernetics Department of Informatics and Automation of Scientific Research Textbook for the course COMPUTER SYSTEMS, NETWORKS AND TELECOMMUNICATIONS Section INFORMATION AND COMPUTING NETWORKS Part 1 Nizhny Novgorod 2008 Computer networks. Tutorial. Part 1 // Nizhniy Novgorod, Nizhny Novgorod State University, 2008. The textbook contains material on the course "Computing systems, networks and telecommunications" section "Information and computing networks". The first part of the manual contains basic information on the basics of networking technologies. General issues related to the organization of computer networks, the OSI model, and the principles of data transmission are considered. Compiled by: Art. teacher of the department. IANI f-that VMK, Ph.D. Kumagina E.A. 2 Contents 1. GENERAL PRINCIPLES OF ORGANIZING COMPUTER NETWORKS ......... 4 1.1. BACKGROUND OF DEVELOPMENT AND EVOLUTION OF COMPUTER NETWORKS ............................... 4 1.2. CONCEPT OF A COMPUTER NETWORK ............................................... ................................... 5 1.3. AIRCRAFT COMPONENTS ................................................ .................................................. .......... 5 1.4. SINGLE-TO-PER LAN AND LAN WITH DEDICATED SERVERS ......................................... 7 1.5 ... LAN TOPOLOGY ................................................ .................................................. ........... 8 2. OPEN SYSTEMS AND PROBLEMS OF STANDARDIZATION ....................... 11 2.1. NETWORK ARCHITECTURE LEVELS ............................................... .................................... 11 2.2. SOURCES OF NETWORK STANDARDS ............................................... ............................... 13 2.3. OPEN SYSTEM NETWORKS ............................................... ............................................... 14 2.4. OSI MODEL ................................................ .................................................. ................ 14 3. COMMUNICATION LINES ............................. .................................................. ................................ 20 3.1. COMMUNICATION LINE CHARACTERISTICS ............................................... .................................... 21 3.2. CABLES ................ .................................................. .................................................. ...... 23 4. METHODS OF PHYSICAL CODING ...................................... .................. 26 4.1. ANALOG MODULATION ................................................ ............................................ 26 4.2. DIGITAL CODING ................................................ ............................................. 27 4.3. LOGICAL CODING ................................................ ......................................... 29 4.4. DISCRETE MODULATION OF ANALOG SIGNALS. .................................................. 30 5. METHODS OF DUCT LEVEL DATA TRANSMISSION .............................. 31 5.1. ASYNCHRONOUS AND SYNCHRONOUS DATA TRANSMISSION ............................................. ........ 31 5.2. CHANNELS AND PACKETS SWITCHING .............................................. ............................... 32 5.3. PRINCIPLES OF MULTIPLEXING ................................................ ........................... 36 5.4. DETECTION AND CORRECTION OF ERRORS .............................................. ............................ 37 6. REFERENCES .................. .................................................. ............................................. 38 3 1. General principles of computer networks organization 1.1. Preconditions for the development and evolution of computer networks The CS concept is a logical result of the evolution of computer technology and telecommunications. 50s. The first computers were quite bulky. They were not intended for interactive work, but worked in batch mode. The programmer stuffed the text of the program on punched cards, took them to the computing center, and the next day received the printed result. This approach made the most of the processor's working time. Mainframes are not missing. Now they are used, since one super-powerful computer is easier to maintain and maintain, even a few less powerful ones. 60s. A new way of organizing the computational process has appeared. Interactive multi-terminal time sharing systems began to develop. There is only one processor, several terminals are connected to it. The response time of the system was short enough that the user did not notice the parallel work with other users. Access to shared files and peripherals was provided. It looks very much like a LAN, but such a system has a centralized nature of data processing. Now this principle is used, for example, by ATM networks. At this time, there was a need to unite computers located at a great distance from each other. It began with solving the problem of connecting the terminal to a computer hundreds of kilometers away. This was done via telephone lines using modems. Such systems allowed users to gain remote access to shared resources of powerful computers. Then computer-to-computer communications were implemented. Computers were able to exchange data in an automatic mode, and this is already the basic mechanism in the Armed Forces. So, using this mechanism, the services of file exchange, e-mail, database synchronization, etc. were implemented. 70s. There was a technological breakthrough in the field of computer production - large integrated circuits appeared. The first mini computers appeared. Their cost has been steadily decreasing, and now even small divisions of enterprises have the opportunity to have computers. Now one enterprise had many disparate computers. There was a need to exchange data between closely spaced computers. This is how the first LANs were formed. The software and interface devices necessary for the interaction of computers were developed. The difference from modern LANs is that a variety of non-standard devices with their own ways of presenting data on the line and with their own cables were used for connections. These devices could only connect the types of computers for which they were designed. 80s. Widespread use of personal computers. They have become ideal elements for building networks. On the one hand, they were powerful enough to run network software, but on the other hand, they were not powerful enough to solve complex problems. Standard technologies for connecting computers to the Ethernet, Arcnet, Token Ring network have been approved. 4 Modern trends in the development of aircraft Instead of a passive cable, more complex communication equipment (switches, routers) is used. The use of large computers (mainframes). Transfer of a new type of information (voice, video). Changes in protocols and operating systems are needed so that there are no delays in the transfer of information. Delays in file or mail transfer are not so critical. The emergence of new wireless communication methods. The merger of networks (local and global) and technologies (computer networks, telephone networks, television networks) thanks to the emergence of IP technologies. 1.2. The concept of a computer network A computer network is a collection of computers connected by communication lines. Network nodes are end or intermediate devices with a network address. These are workstations or servers (computers with a network interface), peripheral devices (printer, plotter, scanner), network telecommunication devices (shared modem) and routers. Communication lines are formed by cables, network adapters and other communication devices. All network equipment operates under the control of system and application software. Computing networks enable users to share resources, programs, and data across all computers. The concept of local area network - LAN (English LAN - Lokal Area Network) refers to geographically limited (geographically or production) hardware and software implementations in which several computer systems are connected to each other using appropriate means of communication. Thanks to this connection, the user can interact with other workstations connected to this LAN. Local networks can be combined into larger networks - CAN (Campus Area Network). This is a network located in nearby buildings. Larger networks are metropolitan area networks (MAN) and global area networks (GAN). Local networks are characterized by a higher data transfer rate of 10 Mbit / s and the fact that a special cable system is usually laid for them. In global networks, already laid communication lines are used and the transmission rates in them are significantly lower. 1.3. Aircraft components 1. Hardware platform Computers. From personal computers to supercomputers. The set of computers must correspond to the class of problems solved by the network. Communication equipment. Although computers are central to the processing of information on a network, communication equipment plays an important role as well. These are cable systems, repeaters, bridges, switches, routers, modular hubs. They affect both the characteristics of the network and its cost. 2. Network software platform Operating systems. The efficiency of the network depends on what concepts of management of local and distributed resources form the basis of the network operating system. (Novell NetWare, Windows NT) Network applications. The topmost layer of network tools is various network applications: network databases, mail systems, team automation systems, etc. Table 1. Aircraft components Subject area applications (accounting, computer-aided design, process control, etc.) System services (www, e-mail, file, software platform multimedia, IP-telephony, e-commerce) DBMS Network operating systems Transport system Hardware platform Computers Question: when do you need a network? The introduction of a network at an enterprise should ultimately increase the efficiency of its work, which will be reflected in an increase in profits. Aircraft play a very important role in industrial practice. By means of a LAN, the system integrates personal computers located at many remote workplaces that share equipment, software and information. Workplaces of employees are no longer isolated and are combined into a single system. Let us consider the advantages obtained by network interconnection of personal computers in comparison with stand-alone computers or multicomputer systems. 1. Ability to share data and devices. This provides quick access to extensive corporate information, which allows you to make fast and quality decisions. Sharing resources allows them to be used economically, for example, to control peripheral devices such as laser printers from all attached workstations. Shared resources include disk space, printers, modems, fax modems. The separation of software tools allows the simultaneous use of centralized, previously installed software tools. Although the operation of such an application will slow down somewhat (it takes time to transfer data over the network), this approach will facilitate the administration and maintenance of the application. By dividing processor resources, it is possible to use computing power for data processing by other systems in the network. The provided opportunity lies in the fact that the available resources are not immediately "pounced" on, but only through a special processor available to each workstation. 2. Improving communications. This is an improvement in the process of exchanging information between employees of the enterprise, customers, suppliers. Networks reduce the need for businesses to use other forms of information transfer (telephone or mail). New technologies make it possible to transmit not only computer data, but also video information. There is no need to talk about e-mail programs, chats, schedulers. 3. High resiliency. This is the ability of the system to perform its functions in the event of failure of individual hardware elements and incomplete data availability. The basis for this is the redundancy of the processing units. If a node fails, its tasks are reassigned to other nodes. Data sets can be duplicated on the OVC of several computers on the network, so that if one of them fails, the data continues to be available. 4. Ability to perform parallel computations. This can achieve performance in a multi-node system that exceeds that of a single processor. 1.4. Peer-to-Peer and Dedicated Server LANs There are two approaches to organizing networking software. LANs are divided into two radically different classes: peer-to-peer (single-level) networks and hierarchical (multi-level) networks. When working in a network, a computer can provide its resources to network users (server), and can access network resources (client). Peer-to-peer networks A peer-to-peer network is a network of peer-to-peer computers (equal access rights to each other's resources). Network management functions are transferred in turn from one station to another. As a rule, workstations have access to disks of other stations. It is advisable to use peer-to-peer networks if there is an intensive data exchange between stations. In peer-to-peer networks, all computers have equal access rights to each other's resources. Each user can, at will, declare any resource of his computer shared, after which other users can exploit it. In such networks, the same operating system is installed on all computers, which provides all computers on the network with potentially equal opportunities. In peer-to-peer networks, functional asymmetry can also arise: some users do not want to share their resources with others, and in this case their computers act as clients. The administrator has assigned only the functions of organizing the sharing of resources to other computers, which means that they are servers. In the third case, when the local user does not object to the use of his resources and himself does not exclude the possibility of accessing other computers, the OS installed on his computer must include both the server and client parts. Unlike networks with dedicated servers, in peer-to-peer networks there is no OS specialization depending on the prevailing 7 functional orientation - client or server. All variations are implemented by means of configuring the same OS version. The advantage of a peer-to-peer network is ease of maintenance (these are the functions of a system administrator). However, these networks are mainly used to unite small groups of users that do not impose large requirements on the amount of stored information, its security from unauthorized access and access speed. Hierarchical networks With increased requirements for these characteristics, two-rank networks (hierarchical, with a dedicated server) are more suitable, where the server better solves the problem of serving users with its resources, since its hardware and network operating system are specially designed for this purpose. The type of server is determined by the set of tasks for which it is intended: file server - storing data and controlling access to them; print server - managing the printer and access to it; security services server - ensuring the functioning of the resource protection system, storing information about devices, and For users, the application server - executes the computing parts of client-server applications; the mail server - is responsible for the functioning of e-mail. 1.5. LAN Topology Topology (topos - place, logos - teaching) is a branch of mathematics that studies how to connect different entities. With regard to computer networks, these are methods of connecting network elements. A LAN topology is a configuration of a graph, the vertices of which are computers or other equipment, and the arcs are physical connections between them. The configuration of the physical links is determined by the electrical connections. It can differ from the configuration of the logical links, which are determined by the data transmission routes by setting up the communication equipment. The choice of this or that topology affects the composition of the equipment, the methods of network management, and the possibilities of expanding the network. A passive topology is one in which the devices do not regenerate the signal transmitted by the source. An example is bus and star topologies. In the active topology, the devices regenerate the signal not intended for them and transmit it further. An example of an active topology is a ring. a b c Fig. 1 Basic topologies 8 Common bus In a network with a bus topology (Fig. 1, a), all devices are united by a single transmission medium. All workstations can directly contact any workstation on the network. The transmitted information can be spread in both directions. The bandwidth of the communication channel is divided between all the nodes of the network. Workstations at any time, without interrupting the work of the entire computing network, can be connected to it or disconnected. The functioning of the computing network does not depend on the state of the individual workstation. Due to the fact that workstations can be turned on without interrupting network processes and communication environment, it is very easy to listen to information, i.e. fork information from the communication environment. Pros: low cost and ease of wiring, no additional equipment required. Cons: poor reliability and performance. A defective cable or connector paralyzes the entire network. Star The concept of a network topology in the form of a star (Fig. 1b) came from the field of mainframes, in which the host receives and processes all data from peripheral devices as an active data processing node. All information between two peripheral workstations passes through the central node of the computer network. The network bandwidth is determined by the processing power of the node and is guaranteed for each workstation. The cable connection is fairly straightforward as each workstation is connected to a node. Cabling costs are high, especially when the central site is not geographically located at the center of the topology. When expanding computer networks to a new workplace, it is necessary to lay a separate cable from the center of the network. The star topology is the fastest of all computer network topologies, since data transfer between workstations passes through the central node (with good performance) on separate lines used only by these workstations. The frequency of requests for information transfer from one station to another is low compared to that achieved in other topologies. The performance of a computer network primarily depends on the capacity of the central node. It can be a bottleneck in a computer network. In the event of a failure of the central unit, the operation of the entire network is disrupted. The central control unit can implement an optimal protection mechanism against unauthorized access to information. The entire computer network can be controlled from its center. Pros: higher bandwidth, ease of connecting new nodes, higher protection from eavesdropping. Cons: dependence of efficiency on the state of the center, high cable consumption, higher cost. 9 Ring In a ring network topology (Fig. 1, c), workstations are connected to one another in a circle, i.e. workstation 1 with workstation 2, workstation 3 with workstation 4, etc. The last workstation is linked to the first. The communication link is closed in a ring. Currently, instead of pairing, a central device is used, inside which a ring topology is implemented. This device can be active and regenerate the signal, or it can be just a switch. Routing cables from one workstation to another can be quite difficult and costly, especially if the workstations are geographically located far from the ring (for example, in a line). Messages circulate regularly in a circle. The workstation sends information to a specific end address, having previously received a request from the ring. Message forwarding is very efficient as most messages can be sent “on the road” over the cable system one after the other. It is very easy to make a circular request to all stations. The duration of information transmission increases in proportion to the number of workstations included in the computer network. The main problem with a ring topology is that each workstation must actively participate in the transfer of information, and if at least one of them fails, the entire network is paralyzed. Faults in cable connections are easily localized. Connecting a new workstation requires a short and urgent disconnection of the network, since the ring must be open during installation. There is no limitation on the length of the computer network, since it is ultimately determined solely by the distance between two workstations. Cons: low fault tolerance, network disruption to add nodes. Table 2. Characteristics of computer network topologies Topology Characteristic Bus Star Ring Extension cost Medium Negligible Medium Subscriber attachment - Passive Passive Active goods Protection against failures High Negligible Negligible System size Limited Any Any Protection against negligible Good Good listening System behavior when Poor Good Satisfy high load Possibility to work in Poor Very good Good in real time Cable routing Good Satisfactory Satisfactory 10
1. Introduction - 1 p.
2. Statement of the problem - 2 pages.
3. Analysis of methods for solving the problem - 2 pages.
4. Basic OSI Model - 4 p.
5. Network devices and means of communication - 7 p.
6. Computer network topology - 10 pages.
7. Types of networking - 16 pages.
8. Network operating systems - 18 pages.
9. Technical solution - 25 pages.
10.Literature - 28 pages.
Introduction.
Today there are more than 130 million computers in the world, and more than 80% of them are united in various information and computer networks from small local area networks in offices to global networks such as the Internet. The worldwide trend towards connecting computers in a network is due to a number of important reasons, such as the acceleration of the transmission of information messages, the ability to quickly exchange information between users, receiving and transmitting messages (faxes, E-Mail letters, etc.) without leaving the workplace, the ability to instantly receive any information from anywhere in the world, as well as the exchange of information between computers of different manufacturers running under different software.
Such huge potential opportunities that the computer network carries and the new potential rise that the information complex is experiencing, as well as a significant acceleration of the production process, do not give us the right not to accept this for development and not to apply them in practice.
Therefore, it is necessary to develop a fundamental solution to the issue of organizing an ICS (information and computer network) on the basis of an already existing computer park and software complex that meets modern scientific and technical requirements, taking into account the increasing needs and the possibility of further gradual development of the network in connection with the emergence of new technical and software solutions.
Formulation of the problem.
At the current stage of the development of the association, a situation has developed when:
1. The association has a large number of computers operating separately from all other computers and not having the ability to flexibly exchange information with other computers.
2. It is impossible to create a public database, the accumulation of information with the existing volumes and various methods of processing and storing information.
3. Existing LANs combine a small number of computers and work only on specific and narrow tasks.
4. The accumulated software and information support is not used in full and does not have a common storage standard.
5. With the available connectivity to global computer networks such as the Internet, it is necessary to connect to the information channel of not one group of users, but all users using grouping.
Analysis of methods for solving this problem.
To solve this problem, it was proposed to create a unified information network (UIS) of the enterprise. The enterprise's EIS must perform the following functions:
1. Creation of a single information space that is capable of embracing and applying for all users information created at different times and under different types of data storage and processing, parallelization and control of work performance and data processing on them.
2. Increasing the reliability of information and the reliability of its storage by creating a computing system resistant to failures and loss of information, as well as creating data archives that can be used, but at the moment there is no need for them.
3. Providing an effective system for accumulating, storing and searching for technological, technical, economic and financial and economic information on current work and what was done some time ago (archive information) by creating a global database.
4. Processing of documents and building on the basis of this operating system of analysis, forecasting and assessment of the situation in order to make the best decision and develop global reports.
5. Provide transparent access to information for an authorized user in accordance with his rights and privileges.
In this work, in practice, the solution of the 1st point "Tasks" - Creation of a single information space - is considered by considering and choosing the best of the existing methods or their combination.
Consider our IVS. Simplifying the task, we can say that this is a local area network (LAN).
What is a LAN? A LAN is understood as the joint connection of several separate computer workstations (workstations) to a single data transmission channel. Thanks to computer networks, we got the opportunity to use programs and databases simultaneously by several users.
The concept of a local area network - LAN (English LAN - Lokal Area Network) refers to geographically limited (geographically or production) hardware and software implementations in which several computer systems are connected to each other using appropriate means of communication. Thanks to this connection, the user can interact with other workstations connected to this LAN.
In industrial practice, LANs play a very important role. Through a LAN, the system integrates personal computers located at many remote workplaces that share equipment, software and information. Workplaces of employees are no longer isolated and are combined into a single system. Consider the benefits obtained by networking personal computers in the form of an intra-industrial computer network.
Sharing resources.
Sharing resources allows for conservative use of resources, such as managing peripheral devices such as laser printers from all attached workstations.
Data sharing .
Data sharing provides the ability to access and manage databases from peripheral workstations that need information.
Separation of software.
Software separation allows for the simultaneous use of centralized, previously installed software.
Sharing processor resources .
By dividing processor resources, it is possible to use computing power for data processing by other systems in the network. The provided opportunity lies in the fact that the available resources are not "pounced on" instantly, but only through a special processor available to each workstation.
Multiplayer mode.
The multi-user properties of the system facilitate the simultaneous use of centralized application software previously installed and managed, for example, if a user of the system is working on another job, the current work being performed is pushed into the background.
All LANs work in one standard adopted for computer networks - in the Open Systems Interconnection (OSI) standard.
Basic OSI (Open System Interconnection) Model
In order to interact, people use a common language. If they cannot speak to each other directly, they use appropriate messaging aids.
The stages shown above are required when a message is passed from sender to receiver.
In order to set in motion the process of data transmission, machines were used with the same data coding and connected to one another. For a unified presentation of data in communication lines through which information is transmitted, the International Organization for Standardization (ISO - International Standards Organization) has been formed.
ISO is designed to develop a model for an international communication protocol within which international standards can be developed. For a visual explanation, we will divide it into seven levels.
The International Organization for Standardization (ISO) has developed a basic model for open systems interconnection (OSI). This model is the international standard for data transmission.
The model contains seven distinct levels:
Level 1 : physical- bit protocols of information transfer;
Level 2 : channel- staffing, management of access to the environment;
Level 3 : network- routing, data flow control;
Level 4 : transport- ensuring the interaction of remote processes;
Level 5 : session- support for dialogue between remote processes;
Level 6 : submission data - interpretation of transmitted data;
Level 7 : applied- user data management.
The main idea of this model is that each level is assigned a specific role, including the transport environment. This breaks down the overall data transfer task into individual, easily visible tasks. The necessary agreements for communication of the same level with the above and below are called a protocol.
Since users need efficient management, a computer network system is presented as an integrated structure that coordinates the interaction of users' tasks.
Given the above, the following tier model can be derived with administrative functions performed in the user application layer.
The individual layers of the base model extend downward from the data source (from layer 7 to layer 1) and upward from the data sink (from layer 1 to layer 7). User data is passed to the lower layer along with the layer-specific header until the last layer is reached.
The structure of the information and computer network . To create large-scale data processing systems, computing centers (CC) and computers serving individual enterprises and organizations are combined by means of data transmission means into the information and computing networks of the IVS, where the following designations are adopted: DB - data bank; Main computer - main computer; VTsKP - computing center for collective use; PC - personal computer; АС - network administrator; UMPD - remote PDT - data teleprocessing processor; UK - switching node; CC - switching center; MTD - multiplexer PD; TVM - terminal computer; multiplexer PD.
In the most general case, ICS includes three classes of logical modules:
- modules for processing user data, providing the subscriber with access to various computing resources. These modules allow realizing the main target function of the ICS - processing user data;
- terminal modules providing the user with access to processing modules;
- interaction modules and connections providing local or remote interaction of terminal modules with data processing modules, as well as terminal modules with each other.
The listed logical modules correspond to certain physical objects in the IVS. So, the data processing modules correspond to the main computers of the network, which actually create the information and computing resources of the ICS. End points or AP implement terminal modules, and switching centers (switching computers) correspond to interaction modules.
IVS are subdivided into four interconnected objects:
- basic data transmission network;
- computer network;
- terminal network;
- network administrator.
Computer network - a set of computers, united by the basic network of PD. The computer network includes main computers (GVM), data banks (DB), computer centers for collective use (VCKP), as well as terminal computers (TVM). The main task of the TVM is to interface the terminals with the basic PD network. This function can also be performed by PDTs (data teleprocessing processors) and UMPD (remote PD multiplexers). In addition, terminals can even be connected to a host computer.
Terminal network - set of terminals and terminal networks of PD. A terminal is understood as a device with the help of which subscribers carry out data input / output. Intelligent terminals (PC) and AP (subscriber points) can be used as terminals. To connect terminals to a computer network, besides, of course, communication channels, terminal computers (TVM), UMPD (remote PD multiplexers), PTD (teleprocessing data processors) are used.
Administrative system provides control of the state of the IVS and control of its operation in changing conditions. This system includes specialized computers, terminal equipment and software, with the help of which:
- turns on or off the entire network or its components;
- the operability of the network is monitored;
- the mode of operation of the network and its components is established;
- the volume of services provided to network subscribers is established, etc.
The gateway elements of the ICS ensure the compatibility of both the basic PD network and the entire ICS with other external networks. External IVS protocols may differ from existing protocols. Therefore, gateways, if necessary, ensure the conversion and coordination of interfaces, formats, addressing methods, etc. Gateways are implemented on specialized computers.
IVS can be conditionally divided into two classes:
- territorial, i.e. having a large service area;
- local - located, as a rule, within one building.
The main characteristics of information and computer networks . The main characteristics of ICS are: operational capabilities, performance, message delivery time, data processing cost.
Let's consider these characteristics in more detail.
Operational characteristics (capabilities) of the network - list of basic data processing steps. The main computers, which are part of the network, provide users with all traditional types of services (programming automation tools, access to application packages, databases, etc.). Along with this, the IVS can provide the following additional services:
- remote input of tasks - execution of tasks from any terminals on any computers in batch or dialog modes;
- transfer of files between computers of the network;
- access to remote files;
- protection of data and resources from unauthorized access;
- transfer of text and, possibly, voice messages between terminals;
- issuance of certificates about information and software resources of the network;
- organization of distributed databases located on several computers;
- organization of distributed problem solving on several computers.
Network performance - represents the total performance of the host computers. In this case, usually the performance of the main computer means the nominal performance of their processors.
The delivery time of messages is defined as the average time from the moment the message is sent to the network until the moment the message is received by the addressee.
The price of data processing is formed taking into account the cost of funds used for input / output, transmission and processing of data. This cost depends on the amount of used resources of the ICS, as well as the mode of data transmission and processing.
The main parameters of the IVS depend not only on the hardware and software used, but also, to a large extent, on the load created by the users.
