RU2526755C1 - Method for multi-dimensional dynamic routing in message batch transmission communication network - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method includes, based on results of monitoring quality of links that are part of communication nodes, calculating target link functions which take into account the probability and time of delivering a message, then based on the target link functions, forming one-dimensional transmission routes and a multi-dimensional transmission route and calculating target functions thereof, when forming one-dimensional transmission routes, performing optimisation of the target function of said transmission routes, when forming a multi-dimensional transmission route, performing optimisation of the target function of said transmission route, first selecting the one-dimensional transmission route with the highest value of the target function, then the one-dimensional transmission route with the next lower value of the target function until the multi-dimensional transmission route enables transmission of all message packets at a given time and with a given probability of delivering the message, wherein the values of the target functions of links that are part of communication nodes are transmitted to adjacent communication nodes, which then transmit the values of the target functions to other adjacent communication nodes, except the nodes from which the values of the target functions were received.

EFFECT: high reliability, robustness and throughput of a communication network, easy implementation of the method.

5 cl

Description

The invention relates to the field of network information technology and can be used for multidimensional dynamic routing in a communication network with packet messaging.

In many existing and promising communication networks, messaging is carried out in small blocks or packets. Packets transmit at the same time, each in its own transmission route, which significantly reduces the time it takes to complete the message.

A one-dimensional transmission route is a set of series-connected communication channels in a point-to-point connection between a communication node that is a message source and a communication node - a recipient of messages. A plurality of parallel connected independent one-dimensional transmission routes through which packets constituting the message are transmitted is called a multi-dimensional message transmission route. When forming a multidimensional route, one-dimensional routes of the best quality are used, therefore, a multidimensional message transmission route ensures that the message is delivered to the recipient at a given time with the greatest probability. The quality of the one-dimensional transmission route is determined by the quality of the communication channels included in the one-dimensional transmission route. The main characteristic of the quality of a communication channel is its throughput, which depends on the bandwidth of the communication channel and the signal-to-noise ratio in the communication channel. The bandwidth, as a rule, is a constant value selected when designing a given communication channel, while the signal-to-noise ratio can change during the operation of the communication channel depending on external and internal distortions and interference. A universal characteristic of a communication channel is an objective function that takes into account the quality of the communication channel through the probability and time of message delivery. The initial formation of one-dimensional routes is carried out according to well-known dynamic routing protocols, for example, according to the Dijkstra protocol, the metric of which is set by the objective function of communication channels. In the process of operation of the communication network, additional iterative correction of one-dimensional routes is performed, taking into account changes in the quality of communication channels. To form a multidimensional message transmission route, it is necessary to constantly monitor the quality of the communication network channels, which leads to an increase in the traffic of official routing information. The transmission of overhead information and the change of packet transmission routes are performed when the network state changes to a critical threshold value. This reduces the amount of overhead routing information and the number of calculations when choosing transmission routes. The communication network node evaluates the quality of incoming communication channels by the frequency and time of packet delivery and exchanges this information only with neighboring nodes, which also reduces the amount of overhead routing information.

The proposed method with a minimum expenditure of network resources generates multidimensional message transmission routes and reduces the amount of service routing information about the quality of channels, which improves the reliability, survivability and performance of the communication network.

A known method of multidimensional dynamic routing in a communication network with packet messaging, according to which in each of the communication nodes carry out quality control of the communication channels included in the communication node. The quality control results of communication channels are transmitted to communication nodes of a communication network. If the quality of communication channels decreases below the maximum permissible value, one-dimensional transmission routes containing low-quality communication channels are excluded, and message packets that must be transmitted along these one-dimensional transmission routes are sent for transmission along other one-dimensional transmission routes of better quality. When restoring the quality of communication channels to the value necessary for transmitting message packets with a given probability, one-dimensional transmission routes containing these communication channels are restored, and message packets transmitted earlier on other one-dimensional transmission routes are sent for transmission along the restored one-dimensional transmission routes (Mizin I .A., Urinson LS, Khrameshin GK Messaging in networks with message switching. M., Radio and communication, 1977, 328 p.).

The disadvantage of this method is to reduce the reliability, survivability and performance of the communication network in case of failure of the channels and communication nodes due to the fact that one-dimensional transmission routes are not ordered by quality, depending on the quality of the constituent communication channels.

Also known is a method of multidimensional dynamic routing in a communication network with packet messaging, according to which the quality of the communication channels included in the communication node is monitored in each of the communication nodes. The quality control results of communication channels are transmitted to communication nodes of a communication network. Depending on the quality of the communication channels, the throughput of the communication channels is estimated, then the throughput of the one-dimensional routes is determined depending on the throughput of the communication channels included in this one-dimensional route. Next, a multidimensional message transmission route is formed, first, the multidimensional route includes the one-dimensional transmission routes with the highest bandwidth, then the one-dimensional transmission routes with the lower, but the next largest bandwidth, and so on, until the bandwidth of the multidimensional transmission route provides sending a message at a given time, and then transmitting the message along this multidimensional transmission route (V.V. Kvashennikov, A.K. Shabanov. Adaptive routing method in a communication network and 20.10.2011. Bulletin. №29) with multidimensional routes messaging. RF patent №2431945. Publ..

The disadvantage of this method is to reduce the performance of the communication network due to the fact that the formation of a multidimensional route does not take into account the probabilities of message delivery along the components of one-dimensional routes, and also because it is necessary to transmit large traffic overhead information on the quality of communication channels to network nodes communication.

Closest to the proposed method (prototype) is a method of multidimensional dynamic routing in a communication network with packet messaging, which consists in the fact that the nodes of the communication monitor the quality of incoming communication channels. The quality control results of communication channels are transmitted to other communication nodes and, depending on the quality of communication channels, form one-dimensional transmission routes. Next, from a one-dimensional transmission route, a multidimensional message transmission route is formed, including first one-dimensional transmission routes with better quality communication channels, then one-dimensional transmission routes with a lower but next highest quality communication channel, and so on until the quality of the multi-dimensional transmission route will not ensure the transmission of the entire message. Then, the probability of bringing the message along the multidimensional transmission route is estimated, and if the probability of bringing the message along the multidimensional transmission route of less than a specified value is redistributed, the packets are distributed along the one-dimensional transmission routes and then the message is transmitted along the multidimensional transmission route (V.V. Kvashennikov, E.N. Soldatenko. Method dynamic routing in a communication network with multidimensional routes and packet messaging. Patent of the Russian Federation No. 2457628 Prior. 06/14/2011, publ. 27.07.2012, Bull. No. 21).

The disadvantage of this method is to reduce the reliability, survivability and performance of the communication network due to the fact that the formation of multidimensional routes does not take into account the target functions of communication channels and one-dimensional routes for packet delivery, as well as the fact that it is necessary to transmit large traffic overhead information quality of communication channels to communication nodes.

The purpose of the invention is to increase the reliability, survivability and performance of the communication network, as well as reducing the complexity of the method due to the fact that when forming a multidimensional message transmission route, its objective function is optimized, taking into account the probability and time of bringing the message along the route, as well as due to the correction of the routing table only with a decrease in the probability-time characteristics of bringing the message below predetermined threshold values.

To achieve the goal, a method for multidimensional dynamic routing in a communication network with packet messaging is proposed, which consists in the quality control of incoming communication channels in communication nodes. The quality control results of communication channels are transmitted to other communication nodes and, depending on the quality of communication channels, form one-dimensional transmission routes. Then, from a one-dimensional transmission route, a multidimensional message transmission route is formed, including first one-dimensional transmission routes with better quality channels, then one-dimensional transmission routes with lower, but the next highest quality communication channels, and so on, until the quality of the multidimensional transmission route will provide a message. Then, the probability of bringing the message along the multidimensional transmission route is estimated, and if the probability of bringing the message along the multidimensional transmission route of less than a given value is redistributed, the packets are redistributed along the one-dimensional transmission routes and then the message is transmitted along the multidimensional transmission route. What is new is that, based on the quality control results of the communication channels included in the communication nodes, the target functions of the communication channels are calculated, which take into account the probability and time of message delivery. Then one-dimensional routes and a multi-dimensional transmission route are formed and their objective functions are calculated. When forming one-dimensional transmission routes, the objective function of these transmission routes is optimized; when forming a multi-dimensional transmission route, the objective function of this transmission route is optimized, first selecting one-dimensional transmission routes with the highest value of the objective function, then one-dimensional transmission routes with a smaller, but the next largest value of the target functions and so on, until a multidimensional transmission route ensures the transmission of message packets at a given time and with a given faith tnostyu of message delivery. In this case, the values of the objective functions included in the communication nodes of the communication channels are transmitted to adjacent communication nodes, which then transmit the values of the objective function to other adjacent communication nodes, excluding the communication nodes from which the values of the objective function were obtained. Moreover, the quality of communication channels is determined by the frequency of bringing message packets, taking into account the time of bringing message packets through communication channels. The target function of one-dimensional transmission routes is determined on the basis of the objective function of independent series-connected communication channels from the communication node that is the source of the message to the communication node that is the recipient of the message, while the total number of series-connected communication channels is limited by the maximum allowable time and predetermined probability bringing messages. Moreover, the objective function of the multidimensional transmission route is calculated for independent parallel-connected one-dimensional message transmission routes, which are ordered by the value of the objective function, starting from one-dimensional transmission routes of message-free messages with the highest value of the objective function and ending with the one-dimensional transmission route occupied by sending messages with the lowest value of the target functions. In this case, the initial formation of one-dimensional routes for delivering messages from the communication node, which is the source of the message, to the communication node, which is the recipient of the message, is performed according to the Dijkstra routing protocol, the metric of which is the value of the target function of the communication channels, taking into account the trial operation of the communication network for a given time.

The proposed method of multidimensional dynamic routing in a communication network with packet messaging is implemented as follows.

Communication nodes of a communication network carry out continuous quality control of incoming communication channels. The quality of communication channels is determined by the results of the reception of message packets, taking into account the time of bringing the message packets through the communication channels.

Upon receipt of a message packet, the communication node that is the recipient of the packet calculates a checksum of the packet. If the calculated checksum and the received checksum of the packet coincide with a probability sufficiently close to 1, it is assumed that the packet was received correctly, and the frequency of the correct reception of packets or the probability of bringing the message packet P equal to the ratio of the number of correctly received packets m to the total number of transmitted packets is estimated packages n

$$P=\frac{m}{n}.\left(\mathrm{one}\right)$$

Then evaluate the time of bringing the packet T equal to the length of the message packet L divided by the transmission rate in the communication channel ν

$$T=\frac{L}{\nu }.\left(2\right)$$

For the communication channel, depending on the probability-time requirements for bringing the message, P _ass is determined - the specified probability of bringing the packet and T _ass - the specified time of bringing the packet in the communication channel.

The specified probability of bringing the message should be close enough to 1, for example, P _ass is 0.99. The specified time to bring the packet in the communication channel depends on the urgency and importance of the message. For real-time systems, the delivery time of a packet in a communication channel is usually fractions of a second or less.

The main task of a communication network is to bring a message to a specified address with a given probability at a given time. Therefore, the objective function of the communication network depends on bringing the message at a specified time to the specified address. We define the target functions of communication channels, one-dimensional routes, and a multi-dimensional message transmission route.

The objective function of the communication channel is determined by the expression

$$F_{\mathrm{to}\mathrm{from}}=P\cdot \left(\mathrm{one}+\sin g\left(P-P_{s\mathrm{but}d}\right)\right)\cdot \left(\mathrm{one}+sign\left(T_{s\mathrm{but}d}-T\right)\right)/\mathrm{four,}\left(3\right)$$

where P is the probability of bringing the packet in the communication channel,

P _ass - the given probability of bringing the packet in the communication channel,

T is the time of bringing the packet in the communication channel,

T _ass - the specified time to bring the packet in the communication channel,

sign (x) - sign of the argument sign (x) = 1 if x≥0, otherwise -1.

The objective function of the communication channel can take values in the range from 0 to 1. If the probability of bringing the packet to less than a given value or the time to bring the packet to more than a predetermined time, the objective function of the communication channel will be zero, otherwise the objective function is equal to the probability of bringing the packet.

A one-dimensional package delivery route consists of series-connected independent communication channels with target functions _Fcc1 , _Fcc2 , ..., _Fcst . The objective function of the one-dimensional reduction route by the probability multiplication theorem is written as

$$F_{\mathrm{about}m}={\displaystyle \prod _{i=\mathrm{one}}^m{F}_{\mathrm{to}\mathrm{from}i}}.\left(\mathrm{four}\right)$$

A multidimensional message delivery route consists of parallel connected independent one-dimensional routes with the target functions F _ohm1 , F _ohm2 , ..., F _ohm . A message is sent along a multidimensional route if at least k packets are brought in, and the remaining no more than nk redundant packets out of a total of n packets are not brought. The objective function of the multidimensional route of message delivery will be in the form of a multibinomial distribution

$$F_{mm}={\displaystyle \sum _{i=0}^{n-k}{C}_n^i{\displaystyle \prod _{j=\mathrm{one}}^{n-i}{F}_{\mathrm{about}mj}{\displaystyle \prod _{j=n-i}^n\left(\mathrm{one}-F_{\mathrm{about}mj}\right)}}}.\left(5\right)$$

Addressing in the communication network is carried out using routing tables of communication nodes containing a list of all one-dimensional routes for bringing message packets from this communication node to the message recipient. The routing table of the communication nodes for each one-dimensional transmission route contains the following fields:

1) the address of the communication node-recipient of the message packet;

2) the sequence of addresses of the intermediate communication nodes during the transition from a given communication node to the communication node receiving the packet;

3) the metric of the one-dimensional transmission route, determined by the value of its objective function;

4) a timer for the release of the communication channel to the first communication node on the way to the communication node - the recipient of the packet.

In the communication node, the current state of the communication channel connected to the first communication node on the way to the target node - the recipient of the packet: is it busy or free. Timer shows the time of release of the communication channel, if it is busy.

The initial filling of the routing table is performed when the network is put into operation or when the operating modes of the communication network change, accompanied by a significant change in the state of the communication network. In other cases, an additional iterative correction of routing tables is performed, which requires significantly less computation and transmission of less routing information over the communication channels. At the beginning of the operation of the communication network, to determine the quality of the communication channels, the pilot operation of the communication network for some time is necessary. After determining the quality of the communication channels and calculating using the formula (3) the values of the objective function of the communication channels, one-dimensional packet transmission routes are formed and the routing table of the communication network node is filled.

The formation of one-dimensional routes is performed according to one of the known dynamic routing protocols, for example, according to the Dijkstra routing protocol. As a metric of the routing protocol, we choose the value of the objective function of the communication channels. Dijkstra's routing protocol is a search procedure on a graph of a communications network based on the shortest path principle. The communication network appears as a directed weighted graph with vertices {α ₁ , α ₂ , ..., α _n }, in which the objective function l _{ij of} the communication channel corresponding to this arc is taken as the metric of the arc {α _i , α _i }. The Dijkstra routing protocol solves the problem of minimizing the objective function of a one-dimensional route and is unimprovable in the order of the number of operations.

Denote the matrix of objective functions of communication channels L = {l _ij }. The Dijkstra routing protocol acts on the matrix L = {l _ij } (Mizin I.A., Urinson L.S., Khrameshin G.K. Messaging in networks with message switching. M., Radio and communication, 1977. 328 p. ) Upon completion of the algorithm, the first row of the resulting matrix will contain the metrics of optimal one-dimensional routes from the first communication node to all other communication nodes of the communication network. During the operation of the Dijkstra protocol, they receive optimal one-dimensional routes from the first node to all other communication nodes of the communication network. Then the optimal one-dimensional transmission routes are recorded in the first row of the routing table and excluded from the communication network. For the resulting communication network, the Dijkstra protocol is repeated, and the newly calculated optimal one-dimensional transmission routes are already written to the second row of the routing table and are also excluded from the communication network. The Dijkstra protocol is repeated until all possible one-dimensional routes are ordered in the routing table of the communication node, ordered by the value of the probability-time metric. The first line of the routing table will have one-dimensional routes with the maximum possible metric, the second line will have routes with the maximum possible metric after excluding from the communication network the routes of the first line of the routing table and so on.

One-dimensional transmission routes in the routing table of the communication node are ordered by the value of the objective function, taking into account the busyness of the transmission routes, that is, according to points 3 and 4 of the routing table of the communication node. The formula for the transmission rate of the communication channel, taking into account its employment, is written in the form

$${\nu }_{\mathrm{one}}=\frac{N}{T_t+T},\left(6\right)$$

where N is the length of the message packet,

T _t - timer time to release the communication channel,

T is the transmission time of the packet in the communication channel.

A routing table containing one-dimensional transmission routes ordered by the value of the objective function is used to form a multidimensional message transmission route.

To form multidimensional routes, first choose one-dimensional transmission routes free of message transmission with the largest objective function, then one-dimensional routes with a smaller, next largest objective function, and end with one-dimensional transmission routes busy with message transmission with the smallest objective function, until until all message packets are distributed along one-dimensional routes. The number of one-dimensional transmission routes selected for the formation of a multi-dimensional transmission route depends on the length of the message, that is, the number of packets in the message. The last one-dimensional transmission routes used to form a multidimensional transmission route should have an objective function of at least a value that provides a given probability and time to bring the message packet. Otherwise, the transmission of the entire message with the specified probability-time characteristics becomes impossible.

During network operation, the quality of communication channels may change. Following the quality of the communication channels, the value of the objective function of the communication channels will also change, which leads to the need to correct the routing table. An overly frequent correction of routing tables of communication nodes can lead to non-optimal route determination. On the other hand, the insufficient frequency of changing routing tables of communication nodes will lead to the fact that the state of the communication network will not be quickly monitored and the probability-time characteristics of message delivery may decrease. The most appropriate correction of routing tables is carried out at time intervals, the duration of which is tied to the duration of the quasi-stationary states of communication channels, which is determined by the conditions of signal transmission and ripple load channels. If, after some time (usually 3-5 minutes), the probability-time characteristics of the communication channels deviate from the initial state by more than a threshold value, it is advisable to correct the routing tables of the communication nodes. The threshold value for the probability and time of delivery depends on the importance and urgency of the messages and can be, for example, 0.01 for probability and 0.5 s for the time of message delivery.

The iterative correction of the routing table of the communication node will consist in the fact that after changing the state of the network, the target functions of the communication channels are recalculated, and based on them, new target functions for the previously constructed one-dimensional packet delivery routes are determined. Then, sorting of one-dimensional routes for bringing packets from a given node to a node of a message recipient by the value of the objective function is performed. The routes with the largest objective function are written in the first row of the routing table, routes with the smaller, next largest objective function, and so on. The new routing table is used to form a multidimensional transmission route for the next message.

With a more significant change in the state of the communication network, the Dijkstra procedure should be repeated again to form the routing table. The iterative table correction does not create new routes, but only interchanges previously constructed routes of the routing table depending on the change in their objective function. The criterion for using the Dijkstra procedure can, for example, be the maximum permissible number of permutations of the rows of the routing table. For example, if the number of permutations is more than 2-3, the Dijkstra procedure should be used.

In the communication node, the current state of the communication channel connected to the first communication node on the way to the target node - the recipient of the packet: is it busy or free. Timer shows the time of release of the communication channel, if it is busy. One-dimensional transmission routes in the routing table of a communication node are ordered by transmission speed, taking into account the busyness of transmission routes.

The transmission of the packet is accompanied by service information about the address of the node that is the recipient of the packet, which allows each communication node of a one-dimensional transmission route, having received the message packet, to determine the further transmission route of the packet according to the routing table of the communication node. The number of one-dimensional transmission routes in a multidimensional transmission route depends on the length of the message, that is, the number of packets in the message. The formation of a multidimensional route is completed when all message packets are distributed between one-dimensional transmission routes.

When forming one-dimensional transmission routes, the loading of communication channels should also be taken into account. With equal objective function of the communication channels, less loaded communication channels are first selected, and then more loaded communication channels. With an unequal objective function, first select communication channels for which the objective function, taking into account their load, will be greater, then select communication channels with a lower objective function, taking into account their load.

In the present invention, due to the formation of a multidimensional message transmission route on the basis of one-dimensional packet transmission routes, the probability of which is of maximum importance, the greatest probability of message transmission is ensured. When the state of the communication network changes, its dynamic reconfiguration is performed. Communication channels of poor quality or with a loss of communication are excluded from the messaging process, and unloaded communication channels of the best quality are selected. This allows you to bring messages with a given probability and at a specified time to the recipient of the message. At the same time, they increase the reliability, survivability and network performance in case of failure of individual communication channels. Ordering one-dimensional transmission routes in the routing table of the communication node by the objective function can significantly reduce the number of operations in the formation of multidimensional message transmission routes and reduce the complexity of the method.

Achievable technical result of the method of multidimensional dynamic routing in a communication network with packet messaging is to increase the reliability of survivability and performance of the communication network, as well as reducing the complexity of the method.

Claims (5)

1. The method of multidimensional dynamic routing in a communication network with packet messaging, which means that the quality of incoming communication channels is monitored in the communication nodes, the quality control results of the communication channels are transmitted to other communication nodes and, depending on the quality of the communication channels, form one-dimensional transmission routes , then from one-dimensional transmission routes a multidimensional message transmission route is formed, including first one-dimensional transmission routes with better quality channels, then one-dimensional route transmission with a lower but next highest quality communication channel, and so on, until the quality of the multidimensional transmission route ensures the transmission of the entire message, then assess the probability of bringing the message along the multidimensional transmission route and when the probability of bringing the message along the multidimensional transmission route is less than a specified value redistribute packets along one-dimensional transmission routes and then transmit a message along a multi-dimensional transmission route, characterized in that according to the results of quality control The channels of communication channels that are connected to the communication nodes calculate the target functions of the communication channels, which take into account the probability and time of message delivery, then form one-dimensional routes and a multidimensional transmission route and calculate their target functions, when forming one-dimensional transmission routes, they optimize the target function of these transmission routes, when forming multidimensional of the transmission route, the objective function of this transmission route is optimized by first selecting the one-dimensional transmission routes with the highest value of the target function ii, then one-dimensional transmission routes with a smaller, but the next largest value of the objective function, and so on until the multidimensional transmission route ensures the transmission of message packets at a given time and with a given probability of message delivery, while the values of the target functions included in the communication nodes communication channels are transmitted to adjacent communication nodes, which then transmit the values of the objective function to other adjacent communication nodes, excluding the nodes from which the values of the objective function were obtained. 2. The method according to claim 1, characterized in that the quality of the communication channels is determined by the frequency of bringing the message packets taking into account the time of bringing the message packets through the communication channels. 3. The method according to claim 1, characterized in that the objective function of the one-dimensional transmission routes is determined on the basis of the objective function of independent series-connected communication channels from the communication node that is the source of the message to the communication node that is the recipient of the message, while the total number is sequential connected communication channels is limited by the maximum permissible time and the given probability of bringing the message. 4. The method according to claim 1, characterized in that the objective function of the multidimensional transmission route is calculated for independent parallel-connected one-dimensional message transmission routes that are ordered by the value of the objective function, starting from one-dimensional transmission routes of message-free messages with the highest value of the objective function and ending with one-dimensional transmission route, busy sending messages with the smallest value of the objective function. 5. The method according to claim 1, characterized in that the initial formation of one-dimensional routes for delivering messages from the communication node that is the source of the message to the communication node that is the recipient of the message is performed according to the Dijkstra routing protocol, the metric of which is the value of the objective function of the communication channels with taking into account the trial operation of the communication network for a given time.