The world's practice of creating systems has led to the need to develop standards for every complex of food organizations edge systems. In 1977, the ISO Computing and Information Processing Committee produced a description of the reference model for intercommunication between OSI critical systems, which was called the 7-tier model. At this time, the model has become more widely known, and the fragments form the basis both for the analysis of existing ones and for the development of new systems and standards.
Images of equals in all or private warehouses are present in any payment system and interact on a strict hierarchical basis, then. Be that as it may, any rank serves the higher tier and is profited by the servants of the lower tier.
Due to standardization, the 7-line model, whether 2 devices based on the standard, can interact, regardless of the integrity of the design, functional purpose and internal interfaces. Such mutualism becomes possible for different models ta classy EOM. The IEEE Standardization Committee has decided to consider the physical medium as level 0.
Riven 1 – Physical
Provides an interface between the device and the transmission medium. The bit sequence is physically transmitted through subscriber channels. Channel control is limited to seeing the beginning and end of the frame, shaping the received signal, and analyzing the code sequence. Physical standards include Recommendation X.21, which defines the electrical, mechanical, functional and procedural characteristics necessary for the physical connection of ducts.
Riven 2 – Channel
Forms data transmitted by level 1, so called. Frames and their sequences help control access to the transmission medium, detect and correct errors. The physical and channel levels determine the characteristics of the channels and the method of frame transmission. The protocols of the 2nd level follow the recommendations of X.25 ICKT and, in the final version, define the procedure for managing channels: duplex, half-duplex, simplex.
Riven 3 – Merezhevy
Implements routing functions so that peer frames, called packets, can be transmitted through a number of channels in one or several layers. Please note that it is included in the middle address packet. The main objectives of the measurement protocol are the laying of a set of logical channels (up to 4096) in the skin physical channel, increasing the effectiveness of the physical channel. The merezhevy rhubarb can be used for processing of amuses. The standard for the transmission protocol is in accordance with ICCT Recommendation X.25/3.
Riven 4 – Transportny
To work for transport service providers and contractors in closed communication systems. The protocol combines all functions of switching, routing and information selection because This will ensure that the packages between these processes are thoroughly cleaned. An important role for the transport level is played by the window mechanism, which gives the sender the right to transfer (up to 8) blocks of data to the recipient without confirmation. After the transfer is completed, the supporter confirms the removal of data blocks or notifies about the deletion of them. The procedure for displaying this function is called the window mechanism. Transport protocol standard ECMA-72. Complete procedures of 5 classes.
Riven 5 – Session
Ensures the exchange of data blocks between application level objects. As a result, the protocol is being modified great number functions: 10 with the organization of transfer and 3 with synchronization of interaction procedures. The ECMA-75 standard defines 4 service classes: A–D.
River 6 – Predstavnytskyi
Effective interpretation of data. The appearance of symbols, page format, and graphic coding are analyzed.
When the terminal is connected to the screen, other functions are implemented:
Cleaning the screen is indicated on the screen with the most important fields for additional measures, etc.
The European Association of Virologists EOM has developed 4 interconnections of the ECMA-86 standard (basic principles for the 6th level of exchange protocols). One ECMA-84 standard (virtual terminal protocol). І one ECAM-88 standard (basic class virtual terminal protocol).
Riven 7 – Applied
Implements all functions that can be assigned to the lower level. Where ISO considers the following protocols:
FTAM – file transfer and transfer
JTM – transfer and processing to order
VTSP - virtual terminal service
FTAM is based on the principle of a virtual file repository, which provides a standard, independent EOM-specific method for describing the structure of files and their characteristics.
JTM – is based on remotely entered and displayed information that is used by the user external buildings various EOMs.
VTSP-applications for ensuring the interaction of clients installed at terminals with application processes located in various EOMs.
Basic EMBOS - this model, adopted by ISO for description sacred principles Interaction of information systems EMBOS is recognized by all international organizations as the basis for the standardization of information measurement protocols.
In the EMBOS, the information flow is viewed as a set of functions that are divided into groups called equals. The division on a level allows you to make changes to the methods of implementing one level without changing the costs of other levels, which will significantly simplify and make it cheaper to modernize the processes in the world of technological development.
EMBOS take revenge on these equals. Below are their numbers and the names of the functions.
7th riven - Application: includes the characteristics of applied processes; These processes can be connected to complete tasks and exchange data with each other. In other words, on which level data is identified and compiled into blocks that facilitate transmission along the border. Rhubarb includes, for example, features for the interaction of application programs, such as receiving and storing packages from mailboxes.
6th rhubarb - Presentation: the functions of data presentation (coding, formatting, structure) are implemented. For example, all types of data transfers are converted from EBCDIC code to ASCII.
5th raven - Session: purposes for organizing and synchronizing the dialogue conducted by monitoring objects (stations). On this level, the type of connection (duplex or semi-duplex), the beginning and completion of the task, the sequence and mode of exchange of inputs and outputs of mutual partners are determined.
4th raven - Transport: applications for managing cross-cutting channels of data transmission; whose level will ensure the connections between the terminal points (instead of the next intermediate level, which will ensure the transmission of data through the interconnecting components of the network). The functions of the transport level include multiplexing and demultiplexing (folding and disassembling of packages), identifying and removing errors in data transmission, implementing the specified level of services (for example, the obtained speed and reliability of transmission ). In the transport world, packages are called segments.
3rd raven - merezheviy (Network): on which level there is control over the transmission of packets through interconnecting nodes and networks, control of intrusion on the network in order to avoid overflows that negatively affect the work of the network, routing packages, then. The implementation of routes through which packets are transmitted is important. Routing is reduced to the assignment of logical channels. A logical channel is a virtual connection between two or more objects of the middle level, which allows the exchange of data between these objects. The concept of a logical channel is the existence of any physical connection between the points that communicate. This is introduced for abstraction from the physical implementation of the function.
2nd rhubarb - channel (Link, lanka data): provides services for the exchange of data between logical objects of the front-line level and defines functions associated with the formation and transfer of frames, detection and correction of problems that arise on the offensive, physical level i. Frame called a channel level package, the fragments of the forward level package can be composed of one or more frames. In LOM, the functions of the channel level are divided into two sub-levels: Keruvanya with access to the canal(MAC - Medium Access Control) logical channel control ( LLC - Logical Link Control). The LLC level includes some of the functions of the channel level, not related to the characteristics of the transmission middle. On older MACs, access to the transmission channel is available.
1st rhubarb - physical: provides mechanical, electrical, functional and procedural means for establishing, maintaining and distributing logical connections between logical channel level objects; implements the functions of transmitting bits of data through physical media. The most physical process involves supplying information such as electrical and optical signals, reshaping signals, and selecting parameters of physical transmission media.
In specific situations, there may be a need for the implementation of some of these functions, and therefore at least some of them. Thus, for simple (undamaged) scrap, there is no need for measures and transport systems.
Transmission of data through uninstalled networks takes place during the hour of interruption Encapsulation/decapsulation portion of data. Thus, the information that arrived at the transport level is divided into segments, which remove the headings and are transmitted to the transport level. At the middle level, a segment can be divided into parts (packets), since the border does not support the transfer of segments throughout. The packet will be provided with its own edge header (this ensures that the packet's segments are encapsulated). When transferring intermediate nodes between nodes, it may be necessary to divide packets into frames (that is, encapsulate packets per frame). At the primary node, the segments are decapsulated and the output is updated.
Ticket No. 9
1. Methods for accessing local computational networks
The local computing network includes one to tens, up to hundreds of computers, which share a data transmission middle ground for all nodes. One of the typical transmission media in the scrap is a section (segment) of a coaxial cable. Before this, nodes (data stations) are connected through the equipment that completes the data channel, which can be computers and peripheral equipment that is shared between the nodes. The fragments of the middle of data transmission are hidden, and the data on the edge exchanges between the nodes appear asynchronously, which raises the problem of a consistent middle between many nodes, in other words, the problem of ensuring access to the edge.
Access to the limit is called the interaction of a network node with a transmission middle for the exchange of information with other nodes. Controlling access to the middle ground - establishing a sequence in which nodes will increase the importance of access to the data transmission middle ground. Of great importance is the right to initiate song actions that are dynamically provided to an object, such as a data station information measures.
Access methods can be either random or deterministic. The main method of vicious access that is being studied is the method multiple access with control of unrelated and detected conflicts(MDKN/OK). Anglomovna's name for the method is Carrier Sense Multiple Access/Collision Detection (CSMA/CD). This method is based on the control of a non-current data transmission line (on the basis of the presence of electrical connections in the line) and the elimination of conflicts that arise through a one-hour test of the transmission of two or more stations. The solution is determined by the way of transferring the conflicting nodes and repeating tests of the accumulation of the skin line from these nodes through the epithelial section of the hour.
MDKN/OK is a decentralized broadcasting method. All nodes have equal access rights to the limit. The nodes that generate data for transmission through the fence control the data line station. Since the line is free, there are no electrical connections in it. Vuzol, who would like to publish the program, having appeared at the perfect moment of the hour t 1 day of Kolivan, who will bury the free line, then. takes away the renewed importance of the vicinity line. Whether there is another station that wants to print the program at the time of the hour t 2 > t 1, when electrical faults in the line are detected, transfer is delayed until t + t d, de t d- Trimming.
The distinction between heavy and non-legal MDCN/OK depends on how it is defined t d. In the first phase, the channel burying sample is taken immediately after release, which is permissible in case of weak pressure. However, there is a high likelihood that a number of stations will compete for access as soon as possible, and therefore, conflicts will become more frequent. That's why you should call vikoryists the non-aggressive MDKN/OK, who has a problem t dє of a fall size.
When the network is running, the skin station analyzes the address part of the frames that are transmitted along the network in order to identify and receive frames assigned to it.
Small 4.1. Algorithms for access using the MDCN/OK method
In Fig. 4.1 presents the algorithms for receiving and transmitting in one of the nodes at MDKN/OK.
Conflicts (shut up) will start to sound when two or more nodes “at the same time” try to grab the line. The concept of “single-hour response” in connection with the terminating fluidity of the signal broadening along the line is specified as the increase in the response rate at an hour is no more than or less than by an amount of 2 d called shut the window, de d- hour of passage of signals along the line between the nodes that are in conflict. If some nodes have started transmitting at the shutdown window, then overlaying the signals of these nodes one on one will result in a wider range of data creation. This is the result of conflict and conflict. This can be done either by equalizing the transmission of data that is transmitted to the line (uncreated) and received from it (created), or by the appearance of a constant storage voltage in the line. It remains clear that the Manchester code, which is used for filing data, does not have a permanent warehouse, which appears when it is solved. Having identified a conflict, the university can inform about its partner in the conflict by saying additional signal congestion, after which the stations at fault will try to connect to the line at any hour t d. Obviously, what is important t d they may be different for stations that have a conflict; that t d- Vipadkova value. This mathematical analysis is due to the growing trend in the world of increasing the number of recent samples of buried lines that are going to continue.
Between deterministic access methods and the extent of data transfer, priority is given to token access methods. Marker methods are geared towards transmission to one of the network nodes using a special information object called a marker.
There is a low variety of marker access methods. For example, in relay method the transfer of the marker is based on the order of the draft; at the way intercom(quantized transmission) the server receives data from stations and transmits new data to one station that is ready before transmission. In peer-to-peer rings, token access is widely suspended, which is clocked as a token circulates around the ring and is picked up by stations to transmit their data.
2. Integrated automated systems. EPD technology
Comprehensive design automation introduces fundamental changes in design technology, starting from the preparation of output data, submission of developmental information materials, methods of evaluation and evaluation to final operations , so that before the preparation and reproduction of design and cost documentation.
A significant portion of the region’s design institutes are already implementing the development of programs to automate key stages of the design process. The complexity of design automation is still being perfected, and stable methods and procedures for such design have not yet been developed. However, as a transition between established private programs and complex automation of the design process, there are technological lines of computer-aided design (TLP), which are being developed in a number of scientific and advanced institutes of our country. They are behind the cordon. TLP unites a number of highly efficient groups (teams) of automated design. The main objectives of TLP are to improve the efficiency of design and cost documentation and the productivity of designers.
At the hour of development of TLP projects, you can withdraw the singing complex project robots. In this case, the structure of the TLP consists of two subsystems: what is designed and what is ensured. The subsystems that are being designed directly take part in the design development processes, and to ensure that they are engaged in the technological preparation of automated design processes (Fig. II.7)
The organization, management and planning of the design process in TLP is carried out with the help of separate technological maps, of which there are three types: technological design maps (TKP), new technological maps (ITK) and organization and technological maps (VTK). The main one with the developed flow technology is design on the TLP and TCP (Table II.3), which is formed in the process of analyzing all operations that follow on the technological line, from the designated terms of design and labor spending at the skin stage.
The basis for organizing the design process is VTK (Table A.4), which is intended to provide information about the availability of software and the flow of design operations, in order to establish analyzes of the design process.
The Chamber of Commerce and Industry is a complex of technical features that include a calculation system, organizational technology, and communication systems.
One of the first in our region was the technological line of designing frames for civil vehicles based on the II-04-KORT series (orthogonal frame).
EPD technologies (Electronic Product Definition - electronic description of the product). Vidpov, to the EPD all of the іnormatsky, is to be up to one virob, structure to the type, recognized as the same technology vibration processes (priestly vidpov. EPD technology ensures the development and support of the electronic information model throughout life cycle viruses (including marketing, conceptual and operational design, technological preparation, production, operation, repair and disposal)
Ticket No. 10
Riznovidi CAD
The classification of CAD is carried out on a low level, for example, according to the addition, purpose, scale (complexity of the tasks involved), the nature of the basic subsystem - the CAD core.
For extras The most representative and widely followed CAD groups are:
- CAD for zastosuvannya at galuzakh zagalnogo mashinobuduvannya. They are often called machine-made CAD or MCAD (Mechanical CAD) systems;
- CAD for radio electronics: ECAD (Electronic CAD) or EDA (Electronic Design Automation) systems;
- CAD in the field of architecture and everyday life.
In addition, there is a large number of specialized CAD systems that can be found in certain groups, which represent an independent group of classifications. Applications of such systems include CAD systems for great integrated circuits (GIC); CAD of lethal devices; CAD for electrical machines.
For everyone's sake separate CAD and CAD subsystems to ensure different aspects (strategies) of design. Thus, the MCAD warehouse offers more CAE/CAD/CAM systems.
Beyond the scale are divided into different software and methodological complexes (PMK) CAD, for example: a complex for analyzing the value of mechanical components similar to the method of terminal elements (MCE) or a complex for analyzing electronic circuits; PMK systems; systems with unique architectures, both software and hardware, are secured.
Depending on the nature of the basic subsystem, there are the following types of CAD systems:
1. CAD based on the computer graphics and geometric modeling subsystem. These are CAD-oriented additions, the main procedure of design and construction, i.e. the importance of spatial forms and the mutual expansion of objects. For this group of systems, there is a large majority of CAD systems in the machine industry, which require the arrangement of graphics cores.
Nowadays, unified graphics cores are widely used, which are mostly combined into one CAD system (Parasolid core from EDS Urographies and ACIS from Intergraph).
2. CAD with DBMS. The stench is directly applied to the additions, in which a great deal of data is re-equipped for the rather awkward mathematical calculations. Such CAD systems are important in technical and economical applications, for example, when designing business plans, but also when designing objects, such as control panels in automation systems.
3. CAD based on the specific application package. In fact, there is an autonomous development of PMCs, for example, simulation modeling of manufacturing processes, development of the value of MCPs, synthesis and analysis of systems automatic servicing etc. Often CAD systems are located before CAD systems. Examples include logical design programs based on VHDL language and mathematical packages such as MathCAD.
4. Complex (integrated) CAD systems, which consist of a combination of advanced subsystems. Typical applications of complex CAD systems are CAE/CAD/CAM systems in machine-made CAD systems. Thus, CAD BIS includes a DBMS and subsystems for designing components, fundamental, logical and functional diagrams, topologies of crystals, tests to verify the identity of the cells To control such folding systems, special system cores are required.
Lesson No. 14 “Digitalization and integration between connections”
1. Stages of technology development for TCS
In today's computerized systems, almost all of the “functional” stuffing is written into a program that runs the microprocessor. In this case, it is practically impossible to assign functions to certain electronic elements.
The sequence of commands that the computer executes for a given program should be represented as an algorithm, which takes the form of vertically arranged functional modules. Such an image effectively predicts and allows for processes of transformation of information that have lost their origins, in current ways to quickly connect with the analogy of the everyday concept of “architecture”.
Another example of the use of new analogies with the galusia of everyday life is the expression “ TKS technologies", which involves the sense not of the existence of stationary objects and the larynx of the sexual functions of the connection, but of the choice of the individual interconnected functional elements of the framework, both these and other " architecture."
Specific boundary technologies (industrial boundary technologies) actually define the rules for which measures are carried out during a given (current control system) time, resources and subsequent flows are spent on these technologies mogi koristuvachs (subscribers) should make a connection with the singers (as a rule, they respect) My mind is flooding with dovkillya.
It should be noted that, in principle, the developers do not care what technologies are implemented in the framework. Koristuvachy need the result of the activity of the measure in the form of services, which is expected from the great (respected) minds and for the payment of resources (or in exchange for the resources that are seen). Because of the interrelationship between the services, acceptable external minds and resources that are combined (described by external functional characteristics), it is also possible to national characteristics).
The result of the unraveling of the processing and exchange of information has been the emergence of information networks that can be implemented by all means information processes processing and transmission of information.
Information network(ІВ) – this is folding and distributed in space technical system, which is a functionally related set of software and technical means of processing and information exchange and which consists of territorially distributed information nodes (processing subsystems information) and channels for transmitting information that connect these nodes.
The formalized functional architecture of IV can be presented in the form of a three-stage conceptual model.
The first level (internal) describes the functions and rules of interconnection when transmitting various types of information between territorially remote subscriber systems through physical communication (transmission) and implementation channels there are transport barrier(Previously, similar functions were carried out by the first interconnection).
The other level (intermediate) determines the functions and rules for exchanging information to the speed of interconnection of application processes of different subscriber systems and is implemented telecommunications network what is one
infrastructure for the exchange of various types of information on the back of a proprietary information network (previously, similar functions were linked to various secondary networks).
The third level (external) consists of a set of application processes located at geographically distant subscriber systems, which store information and store and replace it with processing. The third level, in addition to the first and other functions of information processing, creates a new look information measures.
2. Standard model of interconnection between critical systems
The information process of interaction between clients in the IS begins and ends at the same time and includes a number of invested stages, one of which is the implementation of a telecommunications measure for the interaction language in the interests of mutual interaction of information processes in order to implement local processing of formalized information with the highest level of application.
The process of interconnection may also involve representations in the form of a sequence of diverse and, as a rule, rich functional transformations of information in various boundary elements with one digital ї forms in another and from one type of physical (electrical) signals in another.
For different telecommunication networks, created at different times by different transmitters, the grouping of functional connections is created differently. There are also a number of stages and functions of the process interconnected, which are often seen to be combined within the framework of one or another functional architecture of IV (TCS) in the vicinity of out or balls. Nina is a low number of different architectures that have become de facto and de jure internationally accepted standards.
The example of the most knowledgeable and detailed architecture of Semirevneva standard model of interconnection of critical systems(EMBOS),
certified by the International Standards Organization. This architecture is focused on describing the implementation of the interconnection function during the interaction of IP, which will combine the functions of local information processing in geographically distributed nodes. B (that is why we call this architecture TCS architecture, and not IV architecture).
In the English code indicated by the EMBOS, it is indicated that this model belongs to this model. Interconnection of critical systems(OS) (OSI – Open System Interconnection) to MOS (ISO – International Standards Organization) in sight
It should be noted that in Russian literature the abbreviation EMBOS is often deciphered as a standard model of interaction, not the interconnection of critical systems, which is still an inaccurate translation of the word
"Interconnection".
The main Russian standard, which defines the principles of architecture for the interconnection of critical systems, is GOST 28906-91 “Information processing systems. Interconnections between critical systems. Basic reference model." This standard for preparation using the method of direct curing of standards MOS 7498-84, MOS 7498-84 Add. 1 and it completely confirms it. For similar reasons
The understanding of the “vidkrostostosti” systems of the intended vanity of the pidrim of the viddovydniy standard are mutually mutual, I am not aware of the specific real realization (programmable) bunches, the vicoristovy.
3. Connection |
Transportna |
4. Physical middle |
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Small 1. The main elements of the EMBOS and their relationship with the architecture of IV
The basis of the EMBOS consists of several elements presented in Fig. 1, therefore, with some components of applied processes, called applied logical objects (hereinafter referred to as logical objects), implement processes of interconnection of critical systems behind the installation of components through the VOS core, in such a way There is a set of mutually interacting real closed systems at once the physical medium for the VOS, intended for the transmission of information between them. As a physical medium for the BOS, digital channels of transmission of various physical natures appear.
The reference model within the framework of the VOS with the option of interconnection from the installed connection (with direct or switched virtual channels) is also transferred to the option of interconnection without the installation of connection, which indicates the datagram mode and the robotic network with packet switching (without vicor virtual channels). In general, the great diversity and complexity of the functions of interconnection have led to the need for a new hierarchical division into groups (balls, ranks) within the framework of a closed system and the creation of a rich arch texture of telecommunication networks.
Rivne organization EMBOS
Even if the rich organization of specialized systems is obviously supernumerary and ineffective for specific minds, it will also significantly simplify the work of closed systems (solar corroboration) intended for work in different minds and are composed of impersonal elements that are destined to condense the functions of the neighboring equals, being fragmented and independent. virobniks.
With the highest nutrition about those who may draw cordons between the levels
And for as long as there have been rivals, the EMBOS investigators have been spiraling into song principles of distribution on equal terms, the main points are:
many rivals are not guilty of being too great; draw a cordon between the lines of traces at that place, where the description of the services
In the simplest way, the number of operations through the cordon is minimal and there is already a standard interface;
create parallel tracks to identify specific functions that are involved in the implementation of their processes or technical solutions;
Next, formulate equals with functions that are easily localized, so as to ensure the possibility of updating them independently of the functions of the equals;
for the skin level, create interfaces with only the upper and lower levels;
It is possible to establish subdivisions between the subdivisions for those who require specific types of services (the ability to bypass subdivisions may be transferred).
Based on the established principles, the EMBOS stated that these equals should take precautions against the beast:
7 rhubarb - application layer;
6 rіven - presentation of data or presentation layer; 5 rhubarb - session layer;
4 level – transport layer;
3 rhubarb – hemstone (network layer);
2 riven - data links or channel (data link layer); 1 rhubarb - physical layer.
The description of the EMBOS is based on a number of formalizations, which are outlined below with short explanations:
A protocol is a set of rules for the interaction of equal logical objects (various subcritical systems).
Cross-level interface- A set of rules for the interaction of logical objects of peer-levels when providing N-services to objects of (N +1)-levels.
The main functions of all levels are:
select protocol; installation and expansion of connections;
multiplexing and splitting connections; transfer of normal (normal) data; transfer of term (by-drawing) data (with priority);
managing the flow of data (back-up, speed and size of the data flow); segmenting (folding) or blocking (deblocking) data; organization of data sequence (numbering); zakhist vid pomilok (correction, identification and discarding and/or repetition);
routing (addressing and distribution of data flows).
The importance of these functions and the large number of parameters of neighboring countries is accompanied by noticeable signs of real edge technologies that are closely followed by EMVOS.
Often organized in a hierarchical manner, a set of protocols from different levels of specific edge technologies is called a protocol stack.
It is important for a quick assessment of the results of this N-service and task parameters of service capacity, the main points are:
transmission delay parameters; information creation parameters; information consumption parameters; incorrect addressing parameters;
Security settings against unauthorized access.
In general, these parameters are considered neutral (average or marginal). There is an important relationship between these parameters and protocol parameters, available resources and minds that are respected, and the main tasks in assessing the value of edge technologies.
The values of the luminosity parameters of the lower levels merge with the values of the luminosity parameters of the upper levels. Finally, the values of the capacity parameters of the upper-tier services indicate the capacity of the service (QoS – Quality of Service), which allows for a limited connection on behalf of specific edge services.
Reference model for interconnection of critical systems (OSI – Open System Interconnection)
Protocols
Applied |
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Predstavnytskyi |
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Sessions |
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Transport |
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Rhubarb Lanka |
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danikh (channel) |
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Physical |
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Transmission medium (cable copper, optical, radio)
Physical rhubarb
The physical layer is to the right of the transmission of bits by physical communication channels, such as coaxial cable, twisted pair,
fiber optic cable or digital territorial channel. This level includes the characteristics of the physical media of data transmission, such as transmission, flexibility, support and others. On this level, the characteristics of electrical signals are determined that transmit discrete information, for example, the speed of the front pulses, the voltage or current of the transmitted signal, the type of encoding, the speed of signal transmission. Moreover, here the types of roses and the meaning of skin contact are standardized.
The functions of the physical level are implemented in all devices connected to the limit. On the side of the computer, the functions of the physical level are connected to the edge adapter and the serial port.
An example for the physical level protocol may be the l0-Base-T specification Ethernet technologies, which means that the cable is unshielded, unshielded, twisted pair of category 3 with a 100 Ohm pin, RJ-45 connector, maximum physical segment length of 100 meters, Manchester code for data representation in the cable, as well as other characteristics the middle of electrical signals.
Channel rhubarb
Physically, the beats are simply overpowered. In this case, it is not guaranteed that in any network, in which the connection lines are alternated (divided) by several pairs of computers that interact, the physical transmission center may be occupied. One of the reasons for setting the Data Link layer is to check the availability of the transmission middle. Other tasks of the channel level include the implementation of mechanisms for detecting and correcting damage. And therefore, on the channel level, sets are grouped, called frames. The channel rhubarb ensures the correctness of the transfer of the skin frame by placing a special sequence of bits on the beginning and end of the skin frame for its viewing, and also calculates the checksum, processing all the bytes of the frame in the same way and providing additional control well, up to the frame. If the frame arrives at intervals, it again calculates the checksum of the data being removed and equalizes the result with the checksum from the frame. Once the stench is avoided, the frame is considered correct and accepted. If the control amounts are not met, then a settlement is recorded. The channel can detect errors and correct them by retransmitting bad frames. It is necessary to note that the function of correcting data is not obligatory for the channel level, which is present in some protocols of this level, for example, Ethernet and frame relay.
U Channel level protocols, which are analyzed in local networks, lay down the unique structure of connections between computers and methods of their addressing. If the channel stream ensures the delivery of a frame between two nodes of a local network, it must work only in conjunction with the specific topology of connections, the very same topology, for which there will be splits. Such typical topologies, which are supported by channel-level protocols of local edges, include the field bus, ring and mirror, as well as the structures derived from them beyond the bridges and switches. Applications of channel-level protocols Ethernet protocols, Token Ring, FDDI, l00VG-AnyLAN.
U local network protocols of the channel level are vicorized by computers,
bridges, switches and routers. In computers, channel level functions are implemented by a combination of edge adapters and drivers.
U In global networks, which rarely have a regular topology, the channel network often ensures the exchange of information between two vessel computers connected by an individual communication line. Examples of protocols"point-to-point" (as such protocols are often called) can be widely expanded by the PPP and LAP-B protocols. In such situations, for delivery, information between the terminal nodes through the border is determined by means of the border level. This is how the X.25 network is organized. However, in global measures, the functions of the channel level are clearly visible, and it is important to see that fragments of the same protocol are connected to the functions of the channel level. Examples of this approach include ATM and frame relay technology protocols.
U The channel line is even tighter and has completed a set of functions that are sent between the nodes of the boundary. In some cases, channel level protocols are self-sufficient transport mechanisms and can allow work on top of them without application level protocols or add-ons, without obtaining the functions of the boundary and transport levels. For example, the main implementation of the SNMP network protocol is directly on top of Ethernet, although this protocol typically operates on top of the IP network protocol and the UDP transport protocol. Naturally, such an implementation will be limited - it will not be suitable for warehouse networks of different technologies, for example, Ethernet and X.25, and a thread for such a network.
V which all segments have static Ethernet, but between the segments there is no loop-like ligaments. And the axis of a two-segment Ethernet network, connected by a bridge, the implementation of SNMP over the channel level will be entirely practical.
It is not enough to ensure clear transport between any of the topologies and technology functions of the channel level, so in the OSI model the main task is placed on two levels of the level – the middle and the transport.
Merezhevyi rhubarb
The network layer serves to create a unified transport system that unites a number of networks, and the networks can use completely different principles of transmission between end nodes and a complete structure 'languages. The functions of the control level are varied. Let's take a closer look at the integration of local measures.
Channel level protocols of local networks ensure the delivery of data between any nodes of the network with a similar standard topology, such as the topology of a hierarchical mirror. This is an even tighter interconnection that allows for borders with an expanded structure, for example, borders that combine a number of borders into a single border, and high-quality borders that have excess connections Izh vuzla. It would be possible to compose the protocols of the channel level to support loop-shaped over-excess connections, and the principle of the distribution of connections between levels could be brought to a different decision. In order to, on the one hand, preserve the simplicity of transfer procedures for standard topologies, and on the other hand, allow the replacement of sufficient topologies, an additional hemline is introduced.
On the middle level, the term “merge” itself is given specific meanings. In this
At the same time, we understand the totality of computers connected to each other in one standard typical topology and vicorist to transmit data using one of the link-level protocols, values for Yes topologies.
In the middle of the network, the delivery of data is ensured by a separate channel level, and the axis of data delivery between the layers is carried out by the network channel, which encourages the possibility of choosing the correct route for transmitting information in that case, if the structure The connections between warehouse lines have a character that is different from that adopted in channel protocols equal. Routes connect to each other using special devices called routers. A router is a device that collects information about the topology of inter-edge connections and on its platform forwards inter-edge packets until they are accepted. In order to transmit a message from a dispatcher who is in one dimension, to a person who is in another dimension, you need to create a number of transit transfers between the boundaries, or hops (as hop - stripok), immediately choosing an alternative route. Thus, a route is the sequence of routers through which the packet passes.
The problem of choosing the shortest route is called routing, and it is solved by one of the main tasks of the intermediate level. This problem is complicated by the fact that the shortest route is never the shortest. Often the criterion when choosing a route is the hour of transmission for this route; there to lie down throughput capacity connection channels and traffic intensity, which can change over time. Some routing algorithms need to be adjusted until the setting changes, while others make decisions based on the average indicators over the last three hours. The choice of route may be based on other criteria, such as transmission reliability.
At the same time, the functions of the mesh level are broader, the lower functions of the transfer are related to connections with a non-standard structure, which we looked at from the butt of a number of local meshes. The fence line also relies on the use of various technologies, simplified addressing of large fences and the creation of reliable and flexible barriers to the route of unnecessary traffic between the fences.
The distribution of the intermediate level is usually called packages. At the hour of organizing the delivery of packages on the border level, the concept of “measurement number” is introduced. In this type of owner's address, the older part is the number of the network and the younger part is the number of the node in this network. All nodes of the same border are responsible for the same senior part of the address, so the term “margin” on the border level can be given a different, formal meaning: a border is a set of nodes whose addresses are located in the same number of the fence.
At a basic level, there are two types of protocols. The first type – routed protocols – implements the passing of packets through a fence. The protocols themselves deserve to be respected, if we talk about the protocols of the border level. However, another type of protocol is often brought to the edge level, which is called routing information exchange protocols or simply routing protocols. Using these additional protocols, routers collect information about the topology of cross-border connections. Middleware protocols are implemented by software modules of the operating system, as well as by software and hardware of routers.
On the border level, another type of protocol is used, which is responsible for mapping the address of the node that is used on the border level to the local address of the border. Such protocols are often called Address Resolution Protocol, ARP. Some of them are brought to a moderate level, and to the channel one, although fine classifications do not change their essence.
Applications of edge layer protocols include the TCP/IP IP stack cross-border protocol and the IPX stack cross-border packet exchange protocol
Transport rhubarb
On the way from the dispatcher to the delivery, the packages may be damaged or destroyed. I want to run programs vlasni koshti processing of favors, and those that are important for the best results of the mother’s right to reliable connections. The Transport layer ensures that the add-ons and upper layers of the stack - application and session - transfer data with the same level of reliability as they require. The OSI model defines five classes of service that are provided by the transport layer. These types of services are divided into the type of services that are expected: terminology, the possibility of renewing a broken connection, the availability of multiplexing methods for connecting multiple application protocols through the ny transport protocol, and the main thing is to create before identifying and correcting transfer issues, such as problems, waste and duplication of packages.
The choice of service class of the transport level is determined, on the one hand, by the fact that the measure of reliability is determined by the very additives and protocols of the lower transport levels, and on the other hand, this choice lies in In addition, how reliable is the data transport system at the border, What will be ensured by the ravines, which are laid out below the transport ones - the edges, the channels and the physical ones. So, for example, since the density of communication transmission channels is very high and the probability of receiving payments not detected by the protocols of the lower levels is small, then it is reasonable to speed up one of the lighter services of the transport level, not heavy in number by means of reconciliation, reconciliation and other methods of increasing reliability. Since the transport means of the lower regions are already unreliable, then it will be necessary to turn to the most advanced transport service, which will use the maximum of possibilities for identifying and reducing benefits, - with additional help new establishment of logical connection, delivery control, control of control sums and cyclical numbering of packages, setting delivery timeouts, etc.
As a rule, all protocols, starting from the transport level and above, are implemented programmatically end nodes of the fence – components of their edge operating systems. As an example of transport protocols, you can use the TCP and UDP protocols of the TCP/IP stack and the SPX protocol of the Novell stack.
The protocols of the lower four levels are referred to as a border transport or a transport subsystem, since they are faced with the task of transporting from a given level in storage lines with a sufficient topology and know technology. The other three upper levels revolve around the delivery of application services on the basis of the explicit transport subsystem.
Session rhubarb
The Session layer provides dialogue management: it records which side is active and provides synchronization methods. Remains allow you to insert control points into further transmissions, so that each view can be rotated to the remaining one. control point, and not start everything from scratch. In fact, these add-ons rely on session tier, and they are rarely implemented as separate protocols, but the functions of this tier are often combined with the functions of the application tier and implemented in one protocol.
Representative rhubarb
The Presentation layer is located to the right of the form of information that is transmitted gradually, without changing in any way. For the tier, the information that is transmitted by the application tier of one system is then understood by the application tier of another system. As an additional feature of this layer, application layer protocols can add syntactic meaning to the data or meaning in character codes, such as ASCII and EBCDIC codes. On this level, encryption and decryption of data can be considered, so that the confidentiality of data exchange is ensured for all application services. An example of such a protocol is Secure Socket Layer (SSL), which ensures the secret exchange of information for application layer protocols of the TCP/IP stack.
Applied rhubarb
Application layer is really just a set of different protocols, with the help of some neat barriers to deny access to resources that are shared, such as files, printers or hypertext Web sites, and also organize your sleepy robot, for example, for the additional protocol of electronic mail. The unit of data that the applied rhubarb operates on is called a message.
It is clear that the diversity of applied services is very large. Let's look at how we would like some of the most advanced implementations of file services: NCP in the Novell NetWare operating system, SMB in Microsoft
Windows NT, NFS, FTP and TFTP, which are included in the TCP/IP stack.
The greater diversity of electrical communication services is characterized by the diversity of services provided by communication operators. Even greater may be the overflow of telecommunication systems that are being used to provide these services. Most telecommunications systems can be used as open systems, or systems that can be added to new clients and systems at any time. Let’s look at one more basic function for telecommunications:
The term “closed system” refers to a system that can interact with any other system, which is representative of the capabilities of a closed system.
What criteria are used to formulate these “benefits of a closed system”? In order to see the vast growth of private implementations that are not currently competing in the market of telecommunication systems, it was necessary to establish a standard or a basic model of an open system (OSI - Open Systems Interconnection) and 1983 r. Yak Etalonno model of the member organized ZI standard (ISO - International) Standards Organization) is hardened by Semirivnev Model, in the Yaki Process, Scho Realize the system, rodbits on the mutual PIDPOGROTE I. The rank with a lower number gives services to its neighbor of the upper rank and competes with its neighbor of the lower rank. The highest (7) rank receives less services, and the lowest (1) receives them.
Riven 0 connected with the physical medium - the transmission of the signal and although it does not formally enter into the OSI model circuit, it will be recognized by many devices as a necessary classification of the system. This range characterizes the middle of the broadened signal that connects the end devices of the telecommunication system: cables, radio lines, optical lines, etc. This rhubarb doesn’t describe anything, except to tell you about the center. This is also not included in the model, although it is important for the classification of a telecommunication system.
Riven 1- Physical. Characterizes the physical aspects of transmission along a link line: voltages, frequencies, the nature of the transmission medium, etc. This range of models characterizes transmission protocols that ensure support for communication and reception and transmission of information flow. The mercy-free nature of the transfer is not required.
Riven 2- duct. The model of this level involves the formation of data blocks (frames and information packets) and access control to the expansion center. In this case, it is necessary to ensure the safe transfer of blocks of data through the wider media, which was established on the first level. This model is responsible for the beginning and end of the frame in the bit pototsi. On this level, methods of forming data that are transmitted by physical level, frames or sequences, including procedures for verifying the presence of benefits and their correction are described. When describing a telecommunication system, its peers operate with such elements as bit sequences, encoding methods, markers. Here we are responsible for describing the mechanisms responsible for the correct transmission of data (packets) on the sections between the directly connected elements of the boundary. Due to its complexity, the channel network is divided into two divisions: MAC (Medium Access Control) - Controlling access to the middle and LLC (Logical Link Control) - Controlling the logical link (channel). The MAC level controls access to the system and telecommunications network. The LLC tier, which operates above the MAC tier, provides methods for obtaining and removing information.
Riven 3- Merezheviy. This same model describes routing along with data flows. The third tier explores the possibilities that tier 2 hopes to ensure the connection of two points along the line. Merezha can have a richly linear connection, or without completely working margins that influence routing, then. the designated way, which is the next step to overpower the tribute. For proper routing of information, edge addresses are added to data packets. The standards of the regulatory level define the rules for specifying the address and the methods of the robotic system for processing address information. The main function of a telecommunications installation is the selection of information from the device, its processing into packets and the correct transmission to the destination point. Є two principles in different ways robots of the border level. The first is the method of virtual channels. Because the communication channel is established at the time of call (beginning of the session communication), information is transferred to it, and upon completion of the transmission the channel is closed (decreased). The transmission of packets is carried out by saving the output sequence, as packets are sent through different physical routes, then. The virtual channel is dynamically redirected. Whose packages of data include the address of the destination point, because It is determined by the time the connection is installed.
The other is the datagram method. Datagrams are independent and include all necessary information sent to them. While the first method provides the next level (Rank 4) with a reliable data transmission channel, a high-quality response (delivery) and correctly delivers packages to the destination point, the other method requires the next level to work on the orders and verify delivery to the required addressee.
Riven 4- Transport. This model regulates the transfer of packets between processes that are compiled on the computers of the network, ensuring interaction between remote processes. The transport network supports the uninterrupted transmission of data between two interconnected one-to-one processes. On this level, rules are established for monitoring on a cross-sectional basis the flow of data that follows the route designated by the third level: the correctness of the transfer of data blocks, the correctness of delivery to the required point of destination, their completeness, savings, the order of directing indicates algorithms for collecting information from blocks (packets) It's a great look. The transport system is the entrance to all other systems, regardless of the details of the data transmission problem, ensuring a standard interaction with the reception and transmission of information, regardless of the specific technical implementation this transfer.
Riven 5- Sessions. The most important aspect of the model is a description of the rules for promoting dialogue between remote processes. On which level the interaction between the servers is coordinated: improving connections, renewing abnormally terminated sessions. On some computers, names are converted into numeric addresses, and so on. In this case, the transfer is determined not by the technical parameters of telecommunication devices, but by measurement processes.
Riven 6- The rhubarb of the given data (or the representative rhubarb). This line is right with the syntax and semantics of the information that is transmitted, then. Here a mutual understanding between the two computers is established, which is determined by how they imagine and understand after the transmitted information is removed. Here, for example, there are problems such as the recoding of textual information and images, compression and decompression, support for edge file systems (NFS), abstract data structures, etc.
Riven 7- Applied. We will provide an interface between the system and the network, making all services accessible to people. On this level, five application services are implemented: file transfer, remote terminal access, electronic transmission, advisor service and networking. At this level, the model refers to the methods of presenting the transmitted and acquired information.
The main idea of the OSI model is that the cutaneous model describes a group of mutually related commands, as a result of which the complex underlying command transmission is dissected more easily in the analysis of the command.
Necessary lands for the connection of rivals are called protocols. The data transfer protocol ensures the visibility of information that allows you to solve problems such as:
1. Synchronization of information flows;
2. Initialization;
3. Blocking;
4. Addressing;
5. The appearance of pardons;
6. Numbering of blocks;
7. Data flow management;
8. Methods of renewal;
9. Allowed access.
The protocols of several rivalries produce descriptions of only a part of their orders, and not all of them.
Thus, a reference model for the interaction of critical systems is a great tool for parallel development of standards. It means the concept of encouraging the interaction of standards among themselves and can serve as a basis for standardization in various areas of transmission, saving and processing of information.
Calculation measures that make it possible to cover a whole range of telecommunication services, oriented towards mass communications, are of the greatest interest to the representatives of Galuzia. Because of the hugeness. With this in mind, let us look at the basic principles of the theory of computational measures.
ISO 7498 standard
Tsey standard The third heading is “Information and computing systems – Interaction between critical systems – Reference model”. Call it short: “Reference model of interaction between critical systems.” The publication of this standard in 1983 brought a lot of work to the table of many leading telecommunications companies and organizations that standardize.
The main idea behind this document is to develop a process of information interaction between peer systems with clearly defined functions.
The advantages of a shared organization of mutual cooperation lie in the fact that such an organization will ensure the independent development of the same standards, the modularity of the development of equipment and software for information and computing systems, and thereby technological progress in this country.
Compliant to ISO 7498, these levels of information interaction are visible:
- Riven programs
- Riven Vistavi
- Rhubarb session
- Transport rhubarb
- Merezhevyi rhubarb
- Channel rhubarb
- Physical rhubarb
Information interaction between two or more systems, in this way, is the totality of information interaction between level subsystems, and the skin of the local information system interacts only with The subordinate ball of the distant system.
Protocol is called a set of algorithms (rules) for the interaction of objects of the same peer group.
Interface is called a set of rules that define the interaction with the object of this level.
The process of placing fragmented data blocks of one level into data blocks of another level is called encapsulation.
Hierarchy of regions, protocols and stacks
The set of protocols required to organize the interaction of nodes at the edge is organized in a hierarchy, called stacks of communication protocols.
Communication protocols can be configured both in software and in hardware. Lower-level protocols are most often implemented by a combination of software and hardware, while upper-level protocols rely solely on software.
The software module that implements the singing protocol is most often called a protocol. This type of relationship between the protocol - a formally defined procedure and the protocol - software module that defines this procedure, is similar to the relationship between the algorithm for solving a particular task and the program that is responsible for that task.
The same algorithm can be programmed with different levels of efficiency. Similarly, the protocol can be modified by a number of software implementation features. Following from this, with updated protocols, it is necessary to take into account not only the logic of their work, but also the intelligence of software solutions. In addition, the effectiveness of the interaction of devices is influenced by the strength of the totality of protocols, which form a stack, together with the rational division of functions between protocols of different types. The interface between them is also very well designed.
Protocols are organized by computers and other network devices, such as hubs, bridges, switches, routers, etc. bud. In this case, the connection between computers and computers is not directly connected, but through various communication devices. It is important to install the necessary components in the new system in order to implement a different set of protocols.
Similar models TCP/IP
Internet rhubarb
All this meant the choice of a boundary model with packet switching, which is based on an inter-margin line that does not allow connection. This tier, which is called the Internet tier or the cross-cutting tier, is the basis of all architecture. This goal lies in the guaranteed ability for the skin host to strengthen the packages to any extent, which will inevitably collapse to the point of destination (for example, at any other time). The smells may not arrive as they were sent. If it is necessary to complete the order of administration, the upper levels must be finished. Please note that the word “Internet” is used here by most people, regardless of those who are close to the Internet.
Here you can draw an analogy with the postal system. People can throw a handful of international sheets to the postal screen in one country, and fortunately, most of them will be delivered to the correct addresses in other countries. It is certain that the leaves will have to pass through a number of international postal gateways, which will result in a prison for correspondents. The skin edge (or the skin edge) may have its own brands, its own envelope sizes and delivery rules, which are unknown to the postal service.
Intermediate rhubarb means the official packet format and protocol, called IP (Internet Protocol). The purpose of the cross-border protocol is to deliver IP packets to destination points. The main aspects here are the choice of the package route and avoidance of blockage of transport arteries. Therefore, it can be confirmed that the intermediate level of the TCP/IP model is functionally close to the intermediate level of the OSI model. This similarity is shown in Fig.
Transport rhubarb
The TCP/IP model, which grows over the intermarginal level of the TCP/IP model, is called transport. It is designed so that peer entities on receiving and transmitting hosts can support communications, similar to the transport layer of the OSI model. On this level two detailed protocols can be described. The first, TCP (Transmission Control Protocol), is a reliable protocol installed that allows you to deliver a byte stream from one machine to another machine on the same network without problems. It splits the input stream of bytes at the edge of the notification and transmits them to the inter-boundary level. At this point, the host TCP process selects the output stream from being rejected. In addition, TCP maintains flow kernels to ensure that the sender does not overwhelm the recipient with information.
Another protocol of this level, UDP (User Data Protocol), is an unreliable protocol without establishing a connection that does not provide consistent flow control TCP protocol, and such that it exerts its power. It is also widely used in one-time client-server queries and add-ons, where efficiency is important for accuracy, for example, when transferring movies and videos. The interaction of the IP, TCP and UDP protocols is shown in Fig. 1.18. Since the creation of the IP protocol, this protocol has been implemented in many other ways.
Applied rhubarb
The TCP/IP model does not have a session level or a data level. These countries simply did not have consumption, so the stench was not included in the model. The proof of the work with the OSI model proves the correctness of this point: most additions are not required.
Rotates over the transport plain applied rhubarb. It is necessary to abolish all high level protocols. The older protocols include the virtual terminal protocol (TELNET), the file transfer protocol (FTP), and the email protocol (SMTP), as shown in the diagram. The virtual terminal protocol allows clients to register on to a remote server ta pratsyuvati na nyomu. The File Transfer Protocol provides an efficient way to move information from machine to machine. Electronic mail was initially a type of file transfer, but later a special protocol was developed for it. Over the years, many other protocols have been added, such as DNS (Domain Name Service), which allows you to convert host names to network addresses, NNTP (Network News Transfer Protocol), HTTP, a protocol that is used for Creation of pages on the World Wide Web, and many others.
Host-merzhevyi rhubarb
The standard TCP/IP model does not describe what is below the boundary level. It is also clear that the host connects to the network using an additional protocol that allows it to pass IP packets through the network. This protocol is not specified and can be changed from host to host and from network to network. In books and articles devoted to the TCP/IP model, this is rarely discussed.