# The method for determining the order of transmission of messages

(57) Abstract:

The invention relates to computer technology and is intended for use in a local area network with bus topology to control the transmission of data packets through a common channel. The technical result is to increase the efficiency of the operation of the local computer network by taking into account the priority of the packet from the network when they collide. The technical result is achieved in that in the method of determining the order of transmission of messages in a computer network, each station area network control channel occupancy and start transmission if the channel is free, with each packet starts transmission on the network assign an initial priority for each station measures the time conflict-free transmission and the measured results to determine the current priority by the formula: Pt= Pp+ k Tiwhere Ptthe current priority of the packet; Pp- the original priority of the packet; k is the ratio of the weight of the temporary parameter; Tithe time conflict-free transmission of the i-th station of the participants of the conflict on the basis of which establish the sequence of the packet, and in the case of repeat CLASS="ptx2">

The invention relates to computer technology and is intended for use in a local area network with bus topology to control the transmission of data packets through a common channel.

There is a method of determining the order of transmission of messages in a computer network, namely, that at each station computer network control channel occupancy, measure the interval T. 1 private transfer from its beginning to the termination of the transmission if a collision is detected and the interval T. 2 from the date of termination own transmission until the channel release, and the beginning of retransmissions is determined by the formula

,

where

K is the load factor of the channel, and if before the expiry of the interval Tvthe channel becomes busy, move the beginning of the re-transmission interval T+T*vwhere T is time employment channel, T*v=Tv-v, wherevthe time from the release channel to his employment.

The disadvantage of this method is that when the destruction of the conflict between stations on the network is not taken into account the priority of the transmitted their packets.

The closest in technical essence and the response is that at each station computer network control channel occupancy and begin the transfer, if the channel is free, measure the duration of the program from its beginning until the termination of transmission if a collision is detected, the interval from the start of the first collision to the end of the second collision or before the first pause, the interval from the start of the second collision, or from the end of the first pause until the end of the third collision, or before the second pause, and so on, compare the duration of your transfer with other measured intervals and on the basis of the results obtained establish the sequence of transmission.

The disadvantage of this method, taken as a prototype, is that when resolving conflicts between stations is not taken into account the priority of the transmitted their packets, which significantly reduces the efficiency of the functioning of local area network (LAN) from the point of view of the criterion in respect of which is assigned a priority of the packets of information. This is due primarily to the fact that the efficient functioning of the LAN when resolving conflicts between stations is determined not only by time, conflict resolution, but also the order of priority of service stations participating in the conflict. The conflict in LAN always bring to the delay of the th degree of significance (different initial priority). The degree of importance of the message is determined mainly by the contribution of a given message, in the implementation of the targets fixed by LAN. Therefore, the same transmission delay of messages with varying degrees of significance leads to different LAN damage. The greater the degree of significance of delayed messages, the greater the damage inflicted on a LAN. Maximum reducing damage to the LAN, and thus increase the efficiency of its functioning. In known as the prototype of the message even with the highest degree of importance may be placed in the last place in the queue when the conflict, resulting in the target problem to be solved LAN, will suffer the maximum damage.

The purpose of the invention is the increase of efficiency of functioning of the local area network by taking into account the priority of the packet from the network when they collide.

This objective is achieved in that in the method of determining the order of transmission of the message, namely, that at each station computer network control channel occupancy and start transmission if the channel is free, in addition to each packet before transmission to the network when the current my priority transmission at each station participating in the conflict and compare current priority stations, then determine the order of their service, and in the case of a retransmission packet as its initial priority use the current priority.

Comparative analysis of the prototype shows that the inventive method is characterized by the presence of new operations:

assigning an initial priority packets;

measurement interval conflict-free transmission;

the calculation of the current packet priority stations participating in the conflict;

a comparison of the current priority packets;

the current priority as the original in the case of a retransmission of the packet that meets the criteria of novelty of technical solutions.

In scientific and technical literature not found a way described by a set of new features. This allows to conclude that the technical solutions according to the criterion of "significant differences".

The positive effect achieved by implementation of the proposed method is to improve the efficiency of the LAN.

In Fig. 1 shows a diagram of States and transitions for a given method and the following notation is used: REQ - original state, AO zero active is rendered timing diagrams of the processes in collisions of two (a) and three (b) transmission. They show the time intervals : THE first measured interval, the duration of the conflict-free transmission And the per - second measured interval, the duration of the conflict-free transmission B, TC - third of the measured interval, the duration of the conflict-free transmission C, tf- interval forced collision.

In Fig. 3 shows a timing diagram of the operation of the network after the collision of three transmission. It is marked: A B C is the collision of three gears (no details); A, B, C - successful transfer stations; A, B, and C, X - a successful transfer of new active stations; X, tPt- pause between transmissions (i = 1, 2, 3); TP2 - pause between gears C and X; TXA- the waiting time for access to the shared channel stations X.

In a local area network using multiple access with carrier detection and collision detection (MDCN/OS) all stations connected to the same shared resource through which are transmitted the data packet, which contains the destination address and the priority of the data packet. Station continuously listen to the common channel and the appearance of a data packet checks its destination address. If the packet's destination address matches the address of the station, the latter takes this packet all passive station (not having ready to transmit a data packet). They either expect a data packet from its upper levels, or even its form. They also listen to the shared channel and determine its state ("Free", "Successful transfer", "Collision") and, if necessary, can take them addressed data packets. When in the station ready to transmit a data packet, it enters the state of A2 (transition 1 in Fig. 1).

The station, located in the state REF and A2 form the time interval TP2 whenever the disappearance of the carrier in the General channel. For these stations, the overall channel is considered free immediately, but after the expiration of the said interval TP2, if at the time of its formation has not appeared bearing a new transfer. If during the formation of TP2 appears carrying a new transfer, the formation of TP2 is terminated, and the total channel for this station is considered to be continuously employed. TP2 is the minimum allowable interval between transmission in the General channel, necessary to ensure that the end of one transmission is not merged with the beginning of another.

Station, caught in the active state A2, waiting for the General release channel (if it is busy) and immediately goes into a state of PD (transition 2), i.e., starts the transmission (if the common channel is free). Able Predeco and if it is successful, it continues to transmit the entire data packet and then returns to its original state (transition 3). Thus, in the absence of collisions, the operation of the process control data transfer in LAN does not differ from the prototype.

If the state of the PD will be at least two stations, each of them will find other transfer (i.e., detects a collision of transmission). Then the station detects transmission (i.e., continues for a given tf) and then stops its transmission.

At the station participating in clashes during the process of collision measure the time intervals TA and TB (when m = 2, m is the number of stations participating in the collision, Fig. 2, a) or TA, TB, TC (when m = 3, Fig.2,b), etc. to obtain the necessary transmission control information (the same as in the prototype).

Although in Fig. 2 shows the cases m = 2 and m = 3, the proposed method is not limited to these examples. Similarly, measure four or more intervals in the case of m > 3.

After measuring the duration of all transmissions of a single collision process, i.e. after the end of the collision process, the stations participating in the collision, which is in the state of AP, begin the formation of two innno at each of these stations expect the current priority transmission as:

PT= PP+ K Ti(i = 1...m),

where

PTthe current priority of the packet;

PP- the original priority of the packet;

k is the ratio of the weight of the temporary parameter;

Tithe time of successful transmission of the i-th station of the participants of the conflict.

In the General case, the original priority of the packet is determined not only temporal, but also other parameters of LAN operation.

After calculating the current priorities of their packages compare and set the queue in ascending order of priorities, for example PtaPtbPtc.

After defining your place in the queue station, won first place, a status in the AO, and all the rest (not the first) station move in condition A1 (transition 6). JSC station continues to set the interval TP and A1 interval TP. After TP this station of JSC enters a state of PD, i.e., starts transmission. If the first transmission is not started after TP station from A1 enters a state of PD, i.e., the start of transmission. In the case m = 1 this station is only one, so it successfully transmits its packet. In the case of m = 2 will be followed by repeated collision.

If the first transmission of nachinau in the General channel, they increase their place in the queue according to certain priorities, and the new first station enters the state of the AO. After the disappearance in the General channel of the carrier once the first station in the AO again generates TP and other stations (A1) form TP and so on, as already described, until all stations in order not move from A1 AO and then in PD, i.e., until all the participants of the collision does not transmit their data packets.

If at this time there will be a new active station X, then it goes into a state of A2 and is awaiting the release of the shared channel. But since tpiTP2(i= 1,2,3), the total channel for her busy as long as all members of the collision does not transmit their packets. Then in the General channel appears pause TP2 (Fig. 3), indicating that all participants in the clashes have transferred their packages, and therefore, the station X enters the state of DD (starts transmission).

If two stations begin transmitting at exactly the same time and the packets sent by them, have the same initial priority, it may be that Pthe= PTV. Then in the queue can be two first or two second) station. This will lead to the re-collision, to new dimensions, etc.. Then because of the different delays in the=PTVand will be followed by two successful transmission. Perhaps another solution. As soon as the station detect the equality Pthe=PTVthey then move to its original state and cease trying to transfer this package.

With increasing load increases and the number m of participants in the collision. Accordingly, the number of calculated current priorities also increases, and the probability of their occurrence equality and other special cases also increases, which could affect the performance of the LAN. This can easily be fixed for example, if m = M, where M is the maximum number of participants in the collision, which apparatus can cope, then all m members of the encounter are transferred to the initial state as well as in the prototype after the specified maximum number of failed transmission attempts. In other words, part of the input load is reset, but the rest are serviced efficiently and effectively, i.e., eliminates the possible deterioration LAN when overloaded.

For the implementation of the proposed method, each station must have a standard means to determine the status of the shared channel (free, successful transmission, a collision), for creation, storage, transmission and reception (such which are or may be in standard or other LAN using MDCN/OS).

In addition, the necessary equipment for the implementation of the operations of the measurement of time intervals TA, TB, TC ... and for the implementation of the introduction of new operations calculation and assignment of the current and the initial priority packages, compare them, and to store its sequence number in the transmission queue.

Thus, in the proposed method, when the conflict takes into account the priority of the message of the stations participating in the conflict that allows the average to reduce damage to LAN conflict.

Technical and economic effect from the implementation of the proposed method is to improve the efficiency of the LAN from the point of view of the criterion in respect of which is assigned a priority of the message.

The proposed method of determining the order of message passing can be implemented is described below the device.

Device for determining the order of transmission of the message (see Fig. 4) contains units of account 1.1-1.(With the number of transmitting stations); the unit of analysis priority 2; element OR NOT 3; a synchronization unit 4; delay element 5; the first 10.1-10.With a group of control inputs of the device; group outputs 11.1-11.With internal communication 12-16 device.

The synchronization unit 4 (see Fig. 5) contains a divider 17 and the clock 18.

The unit of account 1 (see Fig. 6) contains the first 19, second 22 and third 27 registers; the multiplier 20; the adder 21, the first 23 and second 31 delay elements; counter 24; the first 25, the second 28 and third 39 group elements; group element OR 26; item NO 29; the first 30 and second 34 elements; a decoder 32; trigger 33.

The unit of analysis priority 2 (see Fig. 7) contains a matrix of triggers 35.11-35. MS; group of items And 36.21-36. MS; group delay components 37.21-37.MS; group of items OR 38.1-38.With.

In accordance with the above description of the method, the device for determining the order of transmission of the messages is as follows.

Before you begin the triggers 33, 35.11-35.MS, the counter 24, the registers 19, 22, 27 are set in the initial (zero) condition (inputs installation to its original state conditional not shown).

After that, the group of inputs of the second group of information inputs 7 devices in each unit of account 2 enters code corresponding to the weight coefficient K of the temporary parameter, which is stored in the first register 19 of each unit packet of the corresponding station via group element OR 26 in the third register 27 is recorded initial priority of the corresponding service information. Simultaneously with the beginning of a successful transmission of the i-th station at the entrance 9ireceives a pulse, which sets the trigger 33 in one state and the potential of a single level with its single output opens the item And 34 for the passage of clock pulses from generator 18 clock unit 4 synchronization communication device 12 to the counting input of the counter 24. The counter 24 performs the counting of clock pulses and displays their values on the first group of inputs of the multiplier 20, the second group of inputs which enters code ratio weight temporal parameter. The result of the multiplication is supplied to the first group of inputs of the adder 21, a second group of inputs which receives the code of the initial priority of the register 27. The sum of these values at the output of the adder 21 shows a code corresponding to the current priority of the packet in a given time.

The divider 17 synchronization unit 4 is a counter, which provides an account of a certain number of clock pulses from generator 18, after which it offline is set to the initial state and its output pulse appears poll. The pulse survey on the communication device 13 comes in all the same pulse survey is supplied to the control input group item And 39, resulting value of the adder 21 is recorded in the register 22. The response time of the element, And 30 is selected somewhat larger than the response time of the group element And 39. Therefore, in the register 22 will be written to the current priority of the packet, and register 27 will be installed in its original state. In addition, the pulse survey is delayed in the delay element 31 at the time So 31 and its output is fed to the control input group item And 25. In the current priority of the packet from the register 22 via group elements AND 25, OR 26 is supplied to the register 27. The pulse survey from the output of the delay element 31 is supplied to delay element 23, which is delayed by time T. 23, and then sets the register 22 in the initial state. After this cycle unit of account 1 is repeated again with a new pulse survey on the communication device 13. For proper operation of the unit of account 1, the following inequalities:

T. 31>T. 27.0.+T. 30

T. 23>T. 27.1+T. 25+T. 26,

where T. 31 - delay time of the delay element 31;

T. 23 - delay time of the delay element 23;

T. 27.0 - the time of installation to its original state register 27;

T. 27.1 - time information is recorded in the register 27;

T. 30 - trip delay element AND 30;

T. 25 - time is of each polling cycle in the register 27 of the corresponding unit of account 1 stores the current priority of the packet corresponding station.

When a conflict is detected between stations (after successful packet station party to the conflict) on the response input device receives a return pulse, which confirms the zero state triggers 35 unit of analysis priority 2 (in subsequent installs them in the zero state). The return pulse is delayed in the delay element 5 on the response time of the unit of analysis of priorities 2 and then link 14 is supplied to each unit of account 1. When the control input group element And 28 with connection 14, the pulse survey opens it, resulting from the outputs of the element And 28 code displays the current priority of the packet, which is detectable in the decoder 32 and the group of links 15 arrives at the inputs of delay elements 37 of the corresponding column block analysis priorities 2. Moreover, the delay elements of the delay 37 unit of analysis priority 2 is determined from the relation: t3ij=jit*+t*where t*the trigger fires matrix analysis priority 2, the total time delay elements OR 38, OR 3 and item And 36. Due to such delay values increasing from left to right and from top to bottom in the unit of analysis priority 2, the origin Taiwan is a single output potential appears, which passes through the corresponding element OR 38 and appears on one of the outputs 11 of the device. This potential suggests that at this point in time it is necessary to maintain the priority and to the corresponding output of which is allowing potential. Zero potential from the output of the element OR NOT 3 is fed to the third inputs of elements And 36 unit of analysis priority 2, which prevents the transition to a single state of all the other triggers of the unit of analysis priorities 2.

With the simultaneous appearance of signals on adjacent delay elements 37 of any line unit of analysis priority 2 faster in one state would move the trigger with the lowest sequence number due to lower his eponymous delay. Prohibiting potential from the zero output of the trigger closes the element And 36 adjacent the trigger number, the result is a potential of only one of the outputs of the device corresponding to the station, which at this point in time given the right classes share.

Thus, the proposed device provides means for determining the order of transmission of messages.

1. The way opredelennosti channel, wherein the start message packets, each of which prior to transmission on the network assign an initial priority, measure the time conflict-free transmission at each station, calculate the current priority of the transmission at each station participating in the conflict and compare current priority stations, and then determine the order of their service.

2. The method according to p. 1, characterized in that in the case of a retransmission packet as its initial priority use the current priority.

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