AUTOMATION OF HIGH SPEED COMPUTER NETWORK CONTROL

ABSTRACT

It is known, that questions of management of the traffic in high-speed computer networks are solved on MAC - a sublevel of model of interaction of local area networks which reports, as a rule, are realized by means of program automatic devices. Thus existing reports, responding a principle of construction of the open systems, suppose the certain opportunities of updating. The same opportunities are incorporated to the structures of formats of the frame of data and the operating frame. All this allows in the certain limits, without essential change of the standard to modify separate reports. Using this feature of the organization of reports, below is offered one of the mechanisms increasing of efficiency reports FDDI.

АННОТАЦИЯ

Как известно, вопросы управления трафиком в высокоскоростных вычислительных сетях решаются на МАС - подуровне модели взаимодействия локальных сетей, протоколы которого, как правило, реализуются с помощью программных автоматов. При этом существующие отчеты, отвечающие принципу построения открытых систем, допускают определенные возможности модификации. Те же возможности заложены в структуры форматов фрейма данных и операционного фрейма. Все это позволяет в определенных пределах, без существенного изменения стандарта модифицировать отдельные отчеты. Используя эту особенность организации отчетов, ниже предлагается один из механизмов повышения эффективности отчетов FDDI.

Keywords: method of access, the frame, a format of the frame, a marker.

Ключевые слова: способ доступа, кадр, формат кадра, маркер.

1. INTRODUCTION

Transfer of the information to networks FDDI between logic objects of a MAC-sublevel of various stations it should be carried out in the form of the frame which formats with the instruction of fields are resulted in figure 1.

Figure 1. a) Format of the frame of  FDDI data b) Format of the frame of a marker

PMB - the preamble in the frame serves for an establishment of original synchronization of the receiver and should consist, at least, of 16 symbols Ш (idling). In a status of relaying of station can dynamically change length of a preamble according to concrete requirements of synchronization. Each station should accept normally the frame with a preamble from 12 and more symbols I. [1]

The field NO is an initial field of any frame (data and a marker) and has two symbolical structure (IK).

Field UК defines type of the frame, length of fields AO and AP, and also operating functions of the frame, which format is represented on figure.2, and coding of field UK for various types of the frame of data and marker is resulted in table 1.

Figure 2. Format of field UK, where: C - bats of a class of the frame; L - bats of length of the address; FF - bats of a format; ZZZZ - bats of management

Table1.

Field АP, AO are coded similarly to fields of frame UDS in local computer networks SHSD and KMD, and also can be either short, or long.

2. HIGH SPEED TRAFIC CONTROL

The field information (INFO) has parallel length which is limited by the maximal common length of the frame of 900 symbols, including four symbols of a preamble. The order of transfer of a field INFO is defined by logic objects UDS or ULZ, or the dispatcher of stations, and should not change during the transfer.

The field CSS - control sequence of the frame serves for detection of errors of transfer of the frame and supervises fields: UK, AP, AO, INFO also is calculated on the basis of a standard forming polynomial of 32-nd station.

The field KO - the final terminator consists of two symbols ТТ, in the frame of data - from one symbol T.

Field СК - a status of the frame consists of three and more symbols R or S, and can come to an end T. The format of field СК is shown on figure.3. Three first symbolical positions Е, A and C fields СК are obligatory for each frame of data. [2]

Figure 3. Format of field СК: E-bats « the error » is found out; A-bats « address is authenticated »; С-bats « frame is copied »; R-a symbol « a logic zero »; S-a symbol « logic unit »

The station which is giving out in a ring the frame of data, installs symbol R in these positions. The station which has found out a mistake in the frame of data, identified АF as own address or copied the frame, establishes in positions E, A and C symbol S.

Essential additional services are services and primitives, allowing on the basis of the certain temporary parities to operate priority transfers.

Thus the important role is played by the dispatcher-subscriber of such system who cooperating with logic object of a MAC-sublevel and through it with dispatchers of other user's systems operates job of all network and in some limits adjusts character of loading and the traffic in a network. With this purpose it is expanded, in comparison with standard ISO 8802-5, a set of services and primitives, sold by them (table 2.)[3]

Primitives service as render a LLC-sublevel, and the dispatcher of user's system. In the first case they participate in management of the logic channel, in the second - allow to ajust (reconfigure) management of access to passing environment.

Table2

Set of services and primitives, sold by them

The set of parameters of primitives are expanded in appropriate way. So, for example, primitive UDS_DATA the inquiry contains following parameters: Value_UK(1); Value_AP(1); SBD(1); Class service(1); Divider(1);…; Value_UK(I); Value_AP(I); SBD(I); Class service(I); Divider(I); Class marker. .[4] As it is specified above, the opportunity of updating is incorporated and in structure of a field of management the frame in which for this procedure reserves bats for developers and the future standardization.

In a network the mode of normal work and a mode of restoration of work of a ring are stipulated, by means of the last actually and adjustment of parameters of functioning of network FDDI is carried out.

The analysis of process of restoration of work of a ring to show, that with some additions and changes in work of the dispatcher of user's system it is possible to organize management of the dataflow in a network [2].The block diagram of algorithm management of the dataflow is shown  on figure.4 [5]

At the certain divergence of the established size TTRT from user's system desirable the dispatcher initiates a mode of adjustment of a network. With this purpose he makes active procedure of adjustment of a ring, forming inquiry about initialization of the report with the instruction of desirable parameters of management.

Having entered logic object MAC - a sublevel the given inquiry by means of transmitter MAC - a sublevel according to the report of restoration of a ring is passed following user's system [6]. The inquiry about initialization of the report, having acted on corresponding user's system is processed by receiver MAC - a sublevel. Then repeats standard procedure of restoration the work of a ring.

3. CONCLUSION

Thus, the mode of reorganization of a ring depending on its status and intensity of streams can be realized. Considering a standard mode of restoration of work of a ring it is possible to read some delay of initialization connected with rivalry of user's systems, for an establishment of time TTRT. To increase efficiency of a mode of restoration the work of a ring it is possible due to formation on the basis of the reserved fields of management of the frame.

References:

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