JP2000358072A - Traffic observing device, system and method for transferring datagram - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a stable datagram communication network which never falls into a congestion collapsing state by providing a preference value inserting function, etc., for writing a preference value calculated by a preference value calculating function in the header of a datagram to be transmitted. SOLUTION: A traffic observing device 8 is formed of a traffic observing function 8a, a preference value calculating function 8b and a preference value inserting function 8c. Through the use of data obtained by the function 8a, this device 8 evaluates an impact (load) to the network of the traffic of a user to digitize it to realize writing of it into the header of the datagram. Then, a preference value to be written by the function 8c of the device 8 is retained in a field for writing a preference value in the header part of the datagram to be transferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a traffic observation device, a datagram transfer system, and a datagram transfer method for providing a best-effort data communication service in a public network providing high-speed computer-to-computer communication.

[0002]

2. Description of the Related Art Data units whose delivery is not guaranteed by the network, such as Internet Protocol (IP) packets used in the Internet, are called datagrams. A network that realizes a data communication service by transferring such a datagram is called a datagram transfer network. In such a datagram transfer network, a datagram transfer device in the network (for example, a device called a router in the Internet) corresponds to a datagram having an arbitrary size to a destination address described in its header. By relaying the data, a data communication service is realized. Further, in the datagram transfer device, when datagrams exceeding its own processing capacity arrive in a concentrated manner in a very short period of time (this is called a congestion state), the arrived datagram is appropriately discarded. For this reason, the datagram forwarding network provides a best-effort data communication service that the network aims to deliver each datagram to its destination and transfers as much of the capabilities of the forwarding devices in the network as possible. Will be done.

FIG. 19 is a block diagram showing a general configuration of a datagram transfer device constituting a datagram transfer system as described above. This datagram transfer device has a plurality of input interface units (hereinafter referred to as "input interface units"). , An input I / F unit) and a plurality of output interface units (hereinafter, referred to as output I / F units) 2 are connected to one backplane switch unit 3. This backplane switch unit 3 is connected to any input I / F
It has the ability to transfer datagrams from the unit 1 to any output I / F unit 2 without contention internally.

FIG. 20 shows an input I / F unit 1 shown in FIG.
Is shown in detail. The input I / F unit 1 includes a line I / F unit 1a, a transfer destination table 1b, a transfer processing unit 1c, and a datagram transfer unit 1d. In the input I / F unit 1, when a datagram from an input link is received in the line I / F unit 1a, the transfer processing unit 1c refers to the transfer destination table 1b and determines a desired output I / F from the destination address. / F unit 2 is determined, and the datagram is sent to an appropriate datagram transfer unit 1d in order to transfer the datagram received via the backplane switch unit 3 to a desired output I / F unit 2.

FIG. 21 shows the output I / F unit 2 in FIG.
Is shown in detail. The output I / F unit 2 includes a datagram receiving unit 2a, a buffer memory 2b, a buffer write control unit 2c, a buffer read control unit 2d, and a line I / F.
It is composed of an F section 2e. And this output I / F
In the unit 2, the datagram received by the datagram receiving unit 2a from the backplane switch unit 3 is written into the buffer memory 2b in accordance with the processing method of the buffer write control unit 2c, and waits until an output link becomes available. . That is, as shown in the flowchart of FIG.
The input I / F unit 1 is selected in a predetermined order (usually ascending I / F numbers, etc.) (step S1), and the presence or absence of a datagram arriving therefrom is checked (step S2). If it has arrived, it is written into a free area of the buffer memory 2b (step S3). If there is an unprocessed input I / F unit 1 (step S4), the processing from step S1 is repeated. finish. The processing for these input I / F units 1 is n times faster when the number of input I / F units 1 is n with respect to the processing unit time (normally, the time for transmitting one datagram) on the output link. Must be done in On the other hand, the buffer read control unit 2
When the line I / F 2e becomes empty, d transfers the datagram from the buffer memory 2b to the line I / F unit 2e in the order of writing. Then, this datagram is transmitted to the output link by the line I / F unit 2e.

In the conventional datagram transfer device, as a processing method of the buffer write control unit 2c in the output I / F unit 2, as long as there is a free space in the buffer memory 2b,
A method is employed in which datagrams are written in the order of arrival. A method combining this processing method and a method of reading data in the order of writing in the buffer read control unit 2d is called a first-in first-out (FIFO) method because a datagram that arrives first is output first.

When datagrams arrive during a period when there is no free space in the buffer memory 2b, all of them are usually discarded. In particular, in the Internet, it is possible to avoid a situation in which the buffer memory 2b is used up and to use many datagrams. By preventing a situation in which a link is discarded at once, it is possible to increase the link use efficiency. for that reason,
In a router used on the Internet, as a buffer writing method, random early detection (RED) in which datagrams are discarded in advance at an appropriate probability in accordance with the amount of buffer memory used, even if there is free space in the buffer memory. ) Method is adopted.

FIG. 23 shows a write processing procedure based on the RED method. This is done by selecting the input I / F unit 1 in a predetermined order (step S1) and checking for the presence or absence of a datagram arriving therefrom (step S1).
2), an approximate value of the used amount of the buffer memory 2b is obtained (step S5), a probability based on this approximate value is obtained (step S6), and a transfer determination is made (step S7);
Based on the result of this determination, if the transfer is not to be performed, a procedure is taken to discard the buffer memory 2b even if there is a free space.

As described above, in the conventional datagram transfer apparatus, focusing on the method of writing to the buffer memory 2b, the order of arrival of datagrams in the case of the FIFO method is different from that in the case of the RED method. 2b
Although the packets are discarded at an appropriate probability in accordance with the amount of data used, datagrams are basically written in the buffer memory 2b in the order of arrival. If there is no free space in the buffer memory 2b at the time of writing, the datagram is discarded. Also, the decision whether to transfer or discard the datagram is made not by the information on the datagram itself but by the output I / O. This is performed based on the information in the F unit 2, that is, the usage status of the buffer memory 2b, for example, when there is no free space in the buffer memory or when the free space in the buffer memory is less than 10%.

[0010]

However, in the conventional datagram transfer system using such a method, the datagram transfer device performs the datagram transfer processing only on the information obtained by the output I / F unit 2. Only in the order of arrival of datagrams, and by sending more datagrams than other users in a short period of time,
Although the transmitted datagram is discarded more frequently, it becomes possible to acquire more network resources than other users as a whole. When many users send out such many datagrams in order to acquire more network resources, each datagram transfer device in the network falls into a congestion state, and the transmitted datagrams are transmitted. Many will be discarded. As a result, the number of datagrams arriving at the final destination without being discarded sharply decreases, and the problem that the effective data transfer capability of the entire network is reduced, that is, the network is congested and collapsed. there were.

The present invention solves the above-mentioned problem, and a buffer write control section in an output I / F section of a datagram transfer device transmits information (preference value) obtained by evaluating a network for transmission of a datagram. By using and performing preferential transfer processing of datagrams in a method other than the order of arrival, it is possible to suppress the user from sending more datagrams than necessary in order to acquire more network resources, thereby causing a congestion collapse state An object of the present invention is to provide a traffic observation device, a datagram transfer system, and a datagram transfer method that can realize a stable datagram communication network that does not fall.

[0012]

In order to achieve the above object, a traffic observation apparatus according to the present invention is provided such that a user transmits or receives data from a network before or after a predetermined period of time. A traffic observation function that observes and retains traffic information related to the datagram
A preference value calculation function of quantifying a network evaluation regarding the transmission of a user datagram from the traffic information obtained by the traffic observation function, and calculating the preference as a preference; The preference value calculated by the preference value calculation function is written in the header of the transmitted datagram.

[0013] In the datagram transfer system according to the second aspect of the present invention, the datagram transfer device receiving the datagram transmitted from the user terminal transmits the datagram to the transfer destination address described in the header of the datagram. A traffic observing means which evaluates the impact of a user's traffic on a network based on traffic information related to the datagram, and writes a numerical result of the evaluation as a preference value in the header to a datagram transfer system for relaying the datagram. Is provided.

According to a third aspect of the present invention, in addition to the traffic observing means of the second aspect, the datagram transfer system performs priority transfer processing of the datagram according to the preference value described in the header of the datagram. Means are provided.

Further, the datagram transfer system according to the invention of claim 4 transfers the datagram to the datagram transfer device from any input interface unit to any output interface unit without conflict. A plane switch unit is provided, and the output interface unit obtains the preference value from the header of the received datagram, and selects datagrams to be transferred within a range that does not cause a congestion state, in order of the preference value being smaller. Then, a buffer write control unit for writing the data into the buffer memory preferentially is provided.

In the datagram transfer system according to a fifth aspect of the present invention, the traffic information is a datagram size or a time interval between datagrams transmitted continuously.

In the datagram transfer system according to the present invention, the traffic observation means uses a datagram size field present in a datagram header as the preference value. .

In the datagram transfer system according to the present invention, the traffic observation means may calculate a reciprocal of a difference between a transmission time of the immediately preceding datagram and a current time as a preference value. It was made.

The datagram transfer system according to the invention of claim 8 causes the traffic observation means to calculate an average rate by a sliding window method as a preference value from the size of the datagram and the interval between successive datagrams. It is like that.

The datagram transfer system according to a ninth aspect of the present invention causes the traffic observation means to calculate an average rate during an observation period as a preference value from the size of the datagram and a continuous datagram interval. It was done.

Further, the datagram transfer system according to the tenth aspect of the present invention causes the traffic observing means to calculate a difference between the number of datagrams transmitted by the user and the number of received datagrams as a preference value. It was made.

Further, in the datagram transfer system according to the eleventh aspect of the present invention, in the buffer write control unit,
The preference value of the received datagram is obtained by the preference value extraction function, the preference value is used as a key, the sorting is performed by the preference comparison function, the datagrams are ordered in ascending preference value order, and According to the order, the buffer write control function is caused to perform a write process to the buffer memory.

According to a twelfth aspect of the present invention, in the datagram transfer system, the output interface unit has a class-specific buffer memory unit having a plurality of priorities, and the buffer write control unit controls the priority according to a preference value. A plurality of classes having a ranking are selected, and the datagram is written.

According to a thirteenth aspect of the present invention, in the datagram transfer system, the processing for acquiring the preference value is performed at intervals of a variable interval which can be changed according to the arrival rate of the datagram or a fixed interval which is always fixed. It is something to do.

Further, in the datagram transfer system according to the invention of claim 14, the buffer write control unit includes:
A transfer determination is performed before writing the datagram to the buffer memory, and when it is determined that the transfer is not performed,
Even if there is an empty area in the buffer memory, discarding is performed, and when it is determined that transfer is performed, writing processing to the buffer memory is performed.

The datagram transfer system according to a fifteenth aspect of the present invention provides the datagram transfer system, wherein:
The sum of the preference values of processed datagrams already written in the buffer memory is calculated, a probability calculation based on the calculation result is performed, and the datagram is discarded according to the probability. is there.

Further, in the datagram transfer system according to the invention of claim 16, the buffer write control unit includes:
After the datagrams are ordered in ascending order of preference values, a probability is calculated based on the estimated value of the buffer memory usage according to the ordering, and the datagram is discarded according to the obtained probability. It is like that.

Further, in the datagram transfer method according to the seventeenth aspect of the present invention, when a user sends a datagram, the datagram is evaluated for its impact on the network, and this evaluation is performed. The reflected preference value is calculated, the calculation result is written in the header of the datagram, and priority transfer processing of the datagram is performed according to the preference value.

The datagram transfer system according to the invention of claim 18 transfers the datagram to the datagram transfer device from any of the input interface units to any of the output interface units without conflict. A plane switch unit, the output interface unit calculates a threshold value at an appropriate timing, obtains the preference value from a header of a received datagram, and writes the threshold value and the preference value before writing to a buffer. A transfer determination is performed using the value. If it is determined that the transfer is not to be performed, the buffer is discarded even if there is an empty area in the buffer memory. Is provided.

Further, in the datagram transfer system according to the invention of claim 19, in the transfer determination in the buffer write control unit, a comparison is made between a preference value of the received datagram and the threshold value,
If the preference value is larger than the threshold value, the datagram is discarded, and if the preference value is smaller, the data is written to the buffer memory.

The datagram transfer system according to the twentieth aspect of the present invention is the datagram transfer system, wherein in the transfer determination in the buffer write control unit, a function which receives a difference between a preference value of the received datagram and each of the threshold value as an input. , The probability is calculated, and the datagram is discarded according to the obtained probability.

Also, in the datagram transfer system according to the invention of claim 21, the buffer write control unit includes:
Arrival of a datagram in a predetermined range, a time at which any one of the events of transfer and discard occurs, and a preference value storage function for storing the preference value, and using these preference values, The threshold value is calculated.

Also, in the datagram transfer system according to the present invention, in the transfer determination in the buffer write control unit, the threshold value, the preference value of the received datagram, and the used amount of the buffer, or The probability is calculated by a function that receives the estimated value as an input, and the datagram is discarded according to the obtained probability.

In the datagram transfer system according to the twenty-third aspect of the present invention, in the calculation of the probability used for the transfer determination in the buffer write control unit, a value determined by a buffer usage amount or an approximate value thereof and the threshold value may be used. All datagrams having a preference value larger than the product of the above are discarded, and even if not, datagrams having a preference value equal to or higher than the threshold value are discarded with a higher probability as the preference value is larger and the buffer is used. A function that generates a probability value that discards a datagram having a larger preference value with a larger amount or an approximate value thereof is more preferentially used.

According to a twenty-fourth aspect of the present invention, in the datagram transfer method according to the thirteenth aspect of the present invention, in the threshold value calculation method used in the transfer determination, a preference value of the received datagram is randomly sampled at an appropriate probability, and When a certain number of samples are collected, the median of those samples is set to a threshold value.

Further, in the datagram transfer system according to the twenty-fifth aspect of the present invention, in the threshold value calculation method used for the transfer determination, a preference value of the received datagram is randomly sampled at an appropriate probability, and When a certain number of samples are collected, the average value of the samples is set to a threshold value.

In the datagram transfer system according to the twenty-sixth aspect, in the threshold value calculation method used for the transfer determination, a preference value of the datagram determined to be transferred is randomly sampled at an appropriate probability. Then, when a certain number of samples are collected, the average value of those samples is set as a threshold value.

[0038]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. The selective datagram transfer method using the preference value executed in the datagram transfer system of the present invention is executed by combining the following two points. 1. The network evaluates the impact (load) of the datagram on the network when the user sends the datagram, calculates a preference value as a value reflecting the impact, and uses the result as the header of the datagram. To be given. Here, a small preference value is given to those having a small impact on the network. 2.
In the datagram transfer device in the network, priority transfer processing of the datagram is performed according to the preference value, not the arrival order of the datagram. More specifically, the control is performed such that the smaller the preference value, which means the smaller the impact on the network, the higher the probability of transfer with priority.

FIG. 1 is a block diagram showing a datagram transfer system for executing the above-mentioned datagram transfer method. In this example, a general connection state between a network and a user terminal and an apparatus for realizing the present invention are shown. Specifically, the position where the traffic observation device is introduced is specifically shown. According to this, the datagram transmitted from the user terminal 4 via the line terminating device 5 and the access network 6 is transferred to the input I / F unit 1 as shown in FIG. According to the destination table 1b, relaying is performed to the terminal indicated by the destination address. A traffic observation device 8 as traffic observation means is connected between a line terminating device 7 for terminating the access network and the first datagram transfer device D in the network.

FIG. 2 shows the configuration of the traffic observation device 8, which is composed of a traffic observation function 8a, a preference value calculation function 8b and a preference value insertion function 8c, of which the traffic observation function 8a
Between the time before the predetermined period and the present,
This is a function of observing and holding traffic information related to datagrams transmitted or received in the user network, for example, the size of datagrams and the time interval of continuously transmitted datagrams. The preference value calculation function 8b is a function of calculating a preference value using a calculation formula determined from information held by the traffic observation function 8a. The preference value insertion function 8c is a function to write the value calculated by the preference value calculation function 8b into the datagram that has arrived, in the header of the datagram. That is, in such a traffic observation device 8, the traffic observation function 8a
Using the data obtained by the above, the preference value calculation function 8b evaluates the impact (load) of the user's traffic on the network, quantifies it, and writes it into the datagram header. The preference value written by the preference value insertion function 8c of the traffic observation device 8 is as shown in FIG.
As shown in (1), the preference value in the header portion of the datagram to be transmitted is stored in a field for writing. The value of this field is not changed during the transfer in the datagram transfer network, and each datagram transfer device D
The network realizes a function of transmitting an evaluation result performed in the traffic observation device 8.

FIG. 4 shows the buffer write control unit 2 in the output I / F unit 2 of the datagram transfer device D of the present invention.
This shows the configuration of c, which is composed of a preference value retrieval function 2c1, a preference value comparison function 2c2, and a write control function 2c3. Among these, the preference value retrieval function 2c1 retrieves and holds the preference value from the header of the arriving datagram, and the preference value comparison function 2c2 compares the stored preference values and receives A control procedure is provided such that a smaller preference value is given priority to a given datagram. Further, the write control function 2c3 uses the result of the preference value comparison function 2c2 to select datagrams to be transferred within a range that does not cause a congestion state in ascending order of preference values, and as shown in FIG. Control is performed to write data into the buffer memory 2b, and control is performed to discard unselected datagrams.

FIG. 5 is a flowchart showing a write processing method by the write control function 2c3 according to the present invention. This is different from the conventional FIFO method, in which a list of preference values of an arriving datagram is first acquired by the preference value retrieval function 2c1 (step S11). Next, sorting is performed using this value as a key by the preference value comparison function 2c2 (step S12), and the datagrams are ordered in ascending order of preference values (step S13). And
In accordance with the order, the writing control function 2c3 performs a writing process to the buffer memory 2b (step S1).
4) If there is an unprocessed datagram (step S15), the processing from step S13 is executed, and if not, the processing is terminated.

In the present invention, the datagram is not processed in the order of arrival in the datagram transfer device D, but the datagram having the smaller preference value existing in the header is transferred preferentially. This preference value is provided by the network by observing the user's traffic, so that even if a user sends many datagrams in a short period of time, a large traffic observing device is required for those datagrams. The reference value is added, and the datagram transfer device D discards the datagram with a higher probability than a datagram having a lower reference value. Therefore, sending many datagrams in a short period of time causes more datagrams to be discarded, but eventually makes it impossible to acquire more network resources. As a result, it is possible to suppress the user from sending unnecessary datagrams for the purpose of acquiring many network resources, and it is possible to reduce the risk of the datagram transfer network falling into a congestion collapse state.

The selective datagram transfer method using the above-mentioned preference value comprises two functional elements, that is, the evaluation of user traffic by the network, its numerical conversion, and priority transfer processing by ordering based on the numerical values. Are implemented as the processing method of the preference value calculation function 8b in the traffic observation device 8 and the buffer write control unit 2c in the datagram transfer device D, respectively. In the following, embodiments of these two will be described.

As described above, the buffer write control unit 2
In c, first, a list of preference values of the arriving datagram is acquired by the preference value retrieval function 2c1, and sorting is performed using this preference value as a key as a preference comparison function, and the datagram is processed. Order in ascending order of reference values,
Further, the writing process to the buffer memory 2b is performed according to the order. Then, the process of acquiring the preference value is performed every appropriate period T. If this period T is lengthened, the number of datagrams arriving during the period and to be sorted increases, so that the priority order can be compared among many datagrams, and the effect of the present invention increases.
The transfer processing is performed after arrival, and the delay time until transmission to the output link increases. In this period T, an optimum value is selected in consideration of this point. Although the period may be always fixed, the period may be adaptively changed according to the arrival rate of the datagram.

As shown in FIG. 6, in addition to the processing procedure of FIG. 5, before writing a datagram to the buffer memory 2b, a transfer judgment is separately performed (step S1).
6) If the transfer is not performed based on the determination result (step S17), it is also possible to take a processing procedure of discarding even if there is an empty area in the buffer memory 2b. One more specific example is shown in FIG. The sum of the preference values of the datagrams that have already been processed and written into the buffer memory is calculated (step S18).
A probability based on the probability is obtained (step S19), and discarding can be performed according to the probability. In this case, a datagram to be processed later, that is, a datagram having a larger preference value, will be discarded with a higher probability, and the effect of the present invention will be greater than in the case of FIG. 5 where this processing is not performed. Further, the write processing method according to the present invention uses the above-mentioned RE used in an Internet router.
A combination with the D method is also possible. FIG. 8 is a flowchart showing a write processing procedure using this RED method. According to this, first, a list of preference values is obtained (step S11), and sorting is performed (step S12). According to the ordering of the obtained datagrams (step S13), the transfer processing procedure of the RED method is performed. Will be That is, the used amount of the buffer memory 2b is roughly estimated (step S20), a probability based on the estimated value is obtained (step S21), and a transfer decision is made (step S17). 2b is written or discarded.

In the examples shown in FIGS. 6 to 8, it is necessary to appropriately set the period T for performing the process of acquiring the preference value. On the other hand, in the example shown in FIG. 9, the datagrams arriving at the same time are not processed one at a time as described above, but are processed one by one in order. Is not performed. That is, the input I / F unit 1 is selected in a predetermined order (step S31), and the presence or absence of a datagram arriving therefrom is checked (step S3).
2) Subsequently, a preference value is acquired by a preference value extraction function 2c1 as shown in FIG. 10 (step S33), and this preference value is stored in a preference value storage function 2c4. Further, in the threshold calculation function 2c5, a threshold value is calculated at an appropriate timing (step S34),
A comparison is made between the preference value and the threshold value of the arriving datagram (step S35). If the preference value is larger than the threshold value, the datagram is discarded. A write process is performed (step S14). In this example, there is no need to change the order in which datagrams are selected, so that there is a feature that improvement from the conventional method is relatively simple. When comparing the preference value and the threshold value, the probability is calculated using a function having the input of the difference between the preference value and the threshold value (step S).
35) It is also possible to adopt a method of discarding the datagram according to the probability (step S17).

As a method for selectively discarding datagrams by comparing the preference value with a threshold value calculated at an appropriate timing, the buffer usage is measured, and the datagram is determined according to the buffer usage. In addition to the RED method in which the datagram is calculated and the datagram is stochastically discarded, it is also possible to adopt a method in which the probability of discarding data having a larger preference value than the calculated threshold value is higher. . According to this method, it is possible to selectively block datagrams of a user who transmits datagrams more than necessary in order to use more network resources. That is, the discard probability B employed here is obtained by Expression (1).

[0049]

(Equation 1)

Here, m = Qtarget / Qcurr
ent, Qtarget is a fixed parameter, Qcur
rent is the current buffer usage, V is the threshold value, and p is the preference value of the arriving datagram.
This function has the following properties: That is, V <p
For <(m + 1) V, the drop probability increases with an increase in p,
When k is increased, the discard probability rapidly increases around (m + 1) V. Since datagrams having a value near (m + 1) V are discarded with a high probability, a TCP flow that does not transmit datagrams more than necessary, which is often used, lowers the datagram transmission speed up to this value. Let it. Therefore T
CP flow is (m + 1) V around threshold value V
It is stabilized in the following range.

Nevertheless, datagrams having a value larger than (m + 1) V can be estimated as flows other than TCP, and it can be determined that these datagrams are being transmitted to the network more than necessary. By discarding all datagrams having such a value, it is possible to block flows other than TCP that attempt to transmit datagrams more than necessary in order to acquire such more resources.

Here, the value of m is adaptively determined from a change in the buffer usage. A qualitative description of the formula for calculating m is as follows. If the total input rate from all flows is less than the link rate, the buffer usage will be 0 and m will be infinite, at which time the input datagram will not be discarded. On the other hand, at the time of congestion, the buffer usage increases, and m decreases in accordance with the increase of the usage. Therefore, datagrams having larger preference values are discarded in order. Thereby, rate suppression can be promoted in order from a flow having a high input rate.

The algorithm of such a datagram selective discard method is as follows. Where rand
(0, 1) indicates a uniform random number of [0, 1]. On receiving packet, if (V! = 0 && Qcurrent! = 0) ｛m = Qtarget / Qcurrent; if ((m + 1) * V <p) ｛dropPkt (); // Discard return;｝ else if (V <p ) ｛If (pow ((pV) / (m * V), k)> rand (0,1)) ｛dropPkt (); // discard return;｝｝｝

Now, regarding the blocking of flows (unresponsible flow) that do not reduce the input rate during congestion, the allocation to each flow is performed under the condition that 19 TCP flows and 1 CBR flow are mixed in one link. The simulation of the band evaluation is as follows. When the input rate of the CBR flow is Rcbr,
FIG. 11 shows the results of measuring the allocated bandwidth obtained in each flow for 100 seconds. Here, the input rate of the CBR flow is plotted on the horizontal axis, and the allocated bandwidth of each flow obtained at that time is plotted on the vertical axis. Since 20 flows are multiplexed, the fair allocated bandwidth is 1M
bps. Therefore, when the input rate of the CBR is smaller than 1 Mbps, the CBR packet is not discarded. If the CBR inputs packets at an input rate greater than 1 Mbps, the blocking mechanism will work and packets from the CBR will begin to be selectively dropped.

Further, the packets of the CBR flow start to be discarded when the input rate value is around 2 Mbps, and the value discarded in this way is larger than the fairly allocated bandwidth of 1 Mbps.
This is because the variance of the distribution of the input rate of the TCP is large and the parameter m of the equation (1) is large, so that the discarded packet label value becomes about 2 Mbps. This is due to the fact that a large bandwidth is allocated to a flow with a low burst characteristic between traffic with a low burst characteristic and traffic with a high burst characteristic.

Datagram transfer device D according to the present invention
The buffer write control unit 2c has a function of storing a time at which any event such as arrival, transfer, or discard of a datagram in a predetermined range occurs, and a preference value thereof. Further, the threshold value is calculated as a value as shown below using the respective values. 1. 1. Average value / median / average + variance / average + standard deviation / moving average / mode of distribution for the past n packets transferred 2. Average value / median / average + variance / average + standard deviation / moving average / mode of distribution for the past n packets that have arrived 3. Average value / median / average + variance / average + standard deviation / moving average / mode of distribution for the past n packets discarded Average value of packets transferred within the past t seconds /
4. Median / mean + variance / mean + standard deviation / moving average / mode of distribution Average value for packets arriving within the past t seconds /
5. median / mean + variance / mean + standard deviation / moving average / mode of distribution Average value of packets discarded within the past t seconds /
6. Median / mean + variance / mean + standard deviation / moving average / mode of distribution Average value / median / average + variance / average + standard deviation / for the past n packets transferred within the past t seconds
7. Mode of moving average / distribution Average / median / average + variance / average + standard deviation / for the past n packets arriving within the past t seconds
8. Mode of moving average / distribution Average / median / average + variance / average + standard deviation / for the past n packets discarded within the past t seconds
Mode of moving average / distribution

As another method of calculating the threshold value, a method of observing the preference value of the arriving datagram and statistically calculating it from the distribution as shown in the following (a) and (b) can be adopted. It is. (A) Randomly N from arrival datagram with probability Pa
Select a and extract preference values. (B) Order the extracted Na preference values, and use the median as a new threshold value.

The threshold value depends on the preference value distribution of the arriving datagram, and the threshold value changes the datagram transfer situation, which prompts the user to change the datagram selection method. The preference value distribution of the arriving datagram will change. The method of changing the threshold value requires that these changes reach an appropriate value in a stable state in as short a time as possible.

According to this method, the update time of the threshold value can be adjusted by the number Na of datagrams to be extracted, whereby the time until the threshold value is reached can be controlled. The threshold value update time when a datagram arrives at the link speed is approximately (Na / Pa) × pktsize / linkrat
e. Here, pktsize is a datagram length [bit], and linkrate is a multiplex link speed [bit / s].

Now, the rate observation distribution of the TCP flow and the median distribution observed by the label sampling are evaluated by simulation as follows. FIG.
2 is 20 TCP 1 on link with FIFO queue
The label distribution of the TCP flow and the median distribution observed when Na = 100 and Pa = 0.1 in the case of multiplexing for 00s are shown. Here, the label of the TCP is literature, Ion Stoica, ScottShenke
r, Jui Zhang, “Core-Statele
ss Fair Queuing: Achieving
Approximately Fair Bandw
id Allocations in High S
speed Network "SIGCOM98,19
98 rate observation method (time constant k = 400 m
s). The propagation delay of the link is set to 60 ms.

FIG. 13 shows the result of similarly evaluating the observed median and evaluating the average value of the median when the link propagation delay is changed. The average input rate of the flow can be estimated using such a median.

Next, FIG. 14 shows a buffer memory 2b having a plurality of class-specific buffer memory sections in the output I / F section 2. Each of these class-specific buffer memory units has a priority, and reading is performed by the buffer read control unit 2d according to the priority. The buffer write control unit 2c selects a class-specific buffer memory unit having a plurality of priorities according to the order given by the preference value comparison function, and writes the datagram there. Specifically, the following processing is performed in the buffer write control unit 2c. That is, consider the case where there are n queues with priorities and numbers from 1 to n are assigned, and the smaller the number, the higher the priority. Also, the value that the preference value can take is divided into n sections, and numbers 1 to n are assigned in ascending preference order. Further, the datagram having the preference value of the section i is allocated to the queue of i.
By performing the above processing in the buffer write control unit, a datagram having a smaller preference value is allocated to a buffer memory having a higher priority, and the effect of the present invention can be realized.

In the present invention, the size field of the datagram present in the header of a normal datagram (for example, IP) can be used as a preference value. On the other hand, in the example shown below, the value calculated by the traffic observation device 8 by the traffic observation is basically inserted into a special field of the header of the datagram. However, in this example, no special field is required for the format of the datagram. However, since the size of the datagram is not the value attached by the network but the value assigned by the user terminal, the traffic observation device 8 uses the datagram A test is performed to determine whether the size value and the actual size are correct. If the size is not correct, the datagram is discarded.

Further, other calculation functions of the preference value and
Then, the transmission time of the previous datagram, the current time,
Use the reciprocal of the difference between
Can be. In this case, the current time is t,
Let the size of the datagram be M, and
The sending time of the taggram is t_i, The size of the datagram
M_i, Α is a constant for adjusting the degree of influence, α
(M / M_i) ｛1 / (tt) _i)｝ Use the value expressed by the formula
I have. This value determines the instantaneous user traffic speed.
This value means that the larger this value is,
It is possible to determine that the impact is large.

Further, as another function of calculating the preference value, an average rate (sliding window method) calculated from the size of the datagram and the interval between successive datagrams can be used. In this case,
Assuming that the size of the datagrams i or earlier from the present is M _i , the arrival time is t _i , the number of datagrams going back is n, and the constant for adjusting the degree of influence is α _i (n and α _i are preset. Value), the average rate VK is α _i M _i , (T _i −T _{i + 1} )
Is obtained as a ratio of the sum of 0 to n.

Since the value VK is an average rate viewed over a longer time interval than the case where the reciprocal of the datagram transfer interval is used, the impact on the network can be similarly evaluated.

As another function of calculating the preference value, the average rate of the observation period calculated from the size of the datagram and the interval between successive datagrams can be used. That is, assuming that the observation period is TA, a value obtained by dividing the sum of the sizes of the datagrams arriving during the observation period TA by the observation period TA is used. It is also possible to use the sum of the datagram sizes themselves, and to divide the sum by the maximum value of the sum determined by the physical link speed of the access network to obtain a normalized value. is there.

As another function of calculating the preference value, the difference between the number of datagrams transmitted by the user and the number of received datagrams can be used. Normally, when the datagram transfer network is used properly, the delivery of the datagram is not guaranteed. Therefore, the user terminal transmits an ACK data packet for notifying the transmitting user terminal of the correct reception to the correctly received datagram. Send. Therefore, when the datagram communication network is used by using such an appropriate method, the number of transmitted datagrams and the number of received datagrams are substantially equal. On the other hand, when the user adopts the method as the object of the present invention, many datagrams are discarded in the network and ACK data packets corresponding thereto are not transmitted, so that the number of transmitted datagrams and the number of received datagrams are reduced. Is thought to be able to greatly open. Therefore, if this difference is used as the preference value, the one that is performing the proper use method is transferred with higher priority, and the effect of the present invention can be obtained.

In the embodiment relating to the method of calculating the threshold value, it is also possible to employ a method in which the average value of the preference values of the arriving datagrams is sampled randomly, not the median (median value), but the average value thereof. It is. That is, the arrival datagram is randomly sampled with a probability Pa, and its preference value is extracted and stored. Then, when the number of stored preference values becomes Na, the average value thereof is set as a threshold value.

When the median of the sampled and stored Na preference values is used as the threshold value, the threshold value becomes extremely large or small depending on the distribution state of the sample. For example, in a situation where extremely high-rate flows exist, the higher-rate flows are more likely to become samples, and therefore account for a larger percentage of the entire sample, resulting in extremely large threshold values. There is. On the other hand, when the average value is used, all samples are treated equivalently, so that the threshold value can be prevented from becoming an extreme value depending on the distribution state of the samples. As described above, the effect of suppressing a user trying to send more datagrams than necessary in order to acquire more network resources can be largely obtained in a more general situation.

Here, as an example of simulating a situation in which a user is sending out more datagrams than necessary in order to acquire more network resources, consider an unresponsive UDP flow with a constant transmission rate. For example, 20
It is assumed that a UDP flow having an unresponsible constant transmission rate of 15 Mbps flows first on a Mbps link, and then 19 TCP flows flow. In this case, in the method using the median as the threshold value, the median value of the sample is the reference value sampled from the unresponsive flow, and the threshold value is 15 Mbps. Then unres
The rate of the ponsive flow does not decrease, and the rate of the TCP flow does not increase due to the influence.

On the other hand, in the method in which the average value is used as the threshold value, if any datagram of the TCP flow arrives, the preference values thereof are sampled, and the threshold value, which is the average value thereof, also decreases, and unresponsible. Flow datagrams are more likely to be discarded. As a result, if the datagram of the TCP flow is transmitted without being discarded, the TCP
The flow rate is increased, making it easier to sample. Then, the datagram of the low-rate TCP flow is sampled, and the threshold value is further reduced. This repetition lowers the threshold value and unrequires more than using the median.
The transfer rate of a sponsive flow can be suppressed.

FIG. 15 shows the evaluation results (throughput and threshold value of each flow) of the method using the median as a threshold value in the above situation, and the evaluation results (throughput and threshold value of each flow) using the average value as the threshold value. ) Is shown in FIG. As shown in FIG. 15, when the median is set to the threshold value, the threshold value is set to a high value, and the unresponsi
ve flow (UDP flow) does not decrease, and T
It can be seen that the rate of the CP flow does not increase due to the influence. On the other hand, as shown in FIG. 16, when the average value is set to the threshold value, the threshold value decreases as compared with the case shown in FIG. 15, and as a result, the transfer rate of the unresponsive flow (UDP flow) decreases, while T
It can be seen that the rate of the CP flow is increasing. FIG.
From FIG. 5 and FIG. 16, the effect of setting the average value to the threshold value can be confirmed. In this evaluation, the function that generates the probability of discarding uses the equation (1).
Buffer size is 64 kbytes, Qtarget = 3
2Kbyte, k = 2, propagation delay of multiple links is 40m
sec, and Na = 100 and Pa = 0.1.
In FIGS. 15 and 16, 1 is used for easy understanding.
Although only two of the nine TCP flows are shown in the figure, the remaining TCP flows, not shown, are shown in FIG.
It has a rate similar to that of a book TCP float.

Further, as shown in FIG. 17, the target to be sampled may be a datagram to be transferred instead of an incoming datagram. That is, the output I / F
In the section 2, the input I / F section 1 is selected (step S3).
1) The presence or absence of a datagram arriving there is checked (step S32). If there is a datagram arriving, the threshold value calculated at an appropriate timing described later and the program of the arrived datagram are checked. Calculate the discard probability determined by a function that receives the reference value and the buffer usage amount or the approximate value thereof (step S40),
The datagram is discarded according to the calculation result (step S41). Then, only the datagram to be transferred without being discarded is randomly sampled with the probability Pa, its preference value is extracted (step S42), and the extracted preference value is stored (step S43).
When the number of stored preference values becomes Na, the average value of those preference values is set as a threshold value (step S44).

With this method, discarded datagrams are not subject to sampling, thus reducing the percentage of high rate unresponsive flow preference values in the overall sample. Therefore, the effect of further reducing the threshold value in the situation as in the above-described embodiment is obtained, and the unrespo
It is possible to suppress the transfer rate of the nive flow. FIG. 18 shows an evaluation result using a similar model.
As shown in FIG. 18, the unresponsive flow and the TCP flow have the same rate,
The effect of randomly sampling the transfer datagram and setting the average value as the threshold value can be confirmed. Note that in FIG. 18 as well as FIGS. 15 and 16, of the 19 TCP flows,
Although only two lines are shown, the remaining TCP flows not shown have the same rate as the two TCP flows shown.

A datagram having a threshold value, a preference value, and a buffer usage amount or an approximate value thereof as an input and having a preference value larger than the product of the threshold value and a value determined by the buffer usage amount is defined as: All datagrams with a preference value equal to or higher than the threshold value are discarded with a higher probability if the preference value is larger than the threshold value.Also, the higher the buffer usage or the approximate value, the higher the priority. Equation (2) is also conceivable as an embodiment of a function for generating a probability value for discarding a datagram having a large preference value.

[0077]

(Equation 2)

Here, in equation (2), m = Qtar
get / Qcurrent uses the same as in equation (1). The basic property in the case of using this equation (2) is the same as that of equation (1). The difference is that in equation (2), Qcur
If rent = Qtarget, all datagrams with a preference value greater than V are discarded and Qcu
When rent is equal to or larger than Qtarget (at this time, m <
1) To discard datagrams slightly smaller than V (mV <p).

The algorithm for selectively discarding such a datagram is as follows. Where rand
(0, 1) indicates a uniform random number of [0, 1]. On receiving packet, if (V! = 0 && Qcurrent! = 0) ｛m = Qtarget / Qccurent; if (m * V <p) ｛dropPkt (); // discard return;｝ else if (V <p) ｛if ( pow ((pV) / ((m-1) * V), k)> rand (0,1)) ｛dropPkt (); // discard return;｝｝｝

[0080]

As described above, according to the present invention, by using a datagram transfer apparatus for realizing a datagram transfer / discard method, a user can obtain more network resources than necessary in order to acquire many network resources. It is possible to suppress the transmission and thereby achieve an effect of realizing a stable datagram communication network that does not fall into the congestion collapse state.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a datagram transfer system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing details of a traffic observation device in FIG. 1;

FIG. 3 is an explanatory diagram showing a header field of a datagram according to the present invention.

FIG. 4 is a block diagram showing a buffer write control unit in the output interface unit according to the present invention.

FIG. 5 is a flowchart showing a writing procedure to a buffer memory by a writing control function according to the present invention.

FIG. 6 is a flowchart showing another writing procedure to the buffer memory by the writing control function according to the present invention.

FIG. 7 is a flowchart showing another writing procedure to the buffer memory by the writing control function according to the present invention.

FIG. 8 is a flowchart showing another writing procedure to the buffer memory by the writing control function according to the present invention.

FIG. 9 is a flowchart showing another writing procedure to the buffer memory by the writing control function according to the present invention.

FIG. 10 is a block diagram showing another example of the buffer write control unit in the output interface unit according to the present invention.

FIG. 11 shows an over-input CB according to the embodiment of the present invention.
It is a characteristic view which shows the cutoff characteristic of R flow.

FIG. 12 is a characteristic diagram showing label value distribution characteristics of TCP according to the embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a distribution state of observed median values according to the embodiment of the present invention.

FIG. 14 is a block diagram showing another example of the output interface unit according to the present invention.

FIG. 15 is a diagram illustrating an example of an evaluation result when a median is set to a threshold value.

FIG. 16 is a diagram illustrating an example of an evaluation result when an average value is set as a threshold value.

FIG. 17 is a flowchart showing another writing procedure to the buffer memory by the writing control function according to the present invention.

FIG. 18 is a diagram showing an example of an evaluation result when the flow shown in FIG. 17 is used.

FIG. 19 is a block diagram illustrating a basic configuration of a datagram transfer device according to the related art and the present invention.

20 is a block diagram showing a conventional example of an input interface unit in FIG.

FIG. 21 is a block diagram showing a conventional example of an output interface unit in FIG.

FIG. 22 is a flowchart showing a datagram transfer procedure according to a conventional first-in first-out method.

FIG. 23 is a flowchart showing a datagram transfer procedure according to a conventional random early detection method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input I / F part (input interface part), 2 ... Output I / F part (output interface part), 2c ... Buffer write control part, 2c4 ... Preference value storage function, 3
... Backplane switch section, 8... Traffic observation device, 8a... Traffic observation function, 8b... Preference value calculation function, 8c.

Claims (26)

[Claims] 1. A traffic observation function for observing and holding traffic information relating to a datagram transmitted or received from a network by a user between a time before a predetermined period and the present, and a traffic observation function A preference value calculation function for quantifying the evaluation of the network with respect to the transmission of the datagram of the user from the obtained traffic information and calculating it as a preference value, and a preference value calculated by the preference value calculation function, A traffic observation device having a function of inserting a preference value into a header of a transmitted datagram. 2. A datagram transfer system, wherein a datagram transfer device receiving a datagram transmitted from a user terminal relays the datagram toward a transfer destination address described in a header of the datagram. A datagram transfer system comprising a traffic observing means for evaluating an impact on a network based on traffic information on a datagram and writing a result of digitizing the result as a preference value in the header. 3. The datagram transfer system according to claim 2, further comprising means for performing priority transfer processing of the datagram according to the preference value described in a header of the datagram. 4. The datagram transfer device includes a backplane switch unit that transfers the datagram from any input interface unit to any output interface unit without conflict, and the output interface unit receives the datagram. Buffer write control that obtains the preference value from the header of the datagram obtained, selects datagrams to be transferred within a range that does not cause a congestion state, and sequentially writes the datagrams in a buffer memory in order of decreasing preference values. 3. The datagram transfer system according to claim 2, further comprising a unit. 5. The datagram transfer system according to claim 2, wherein said traffic information is a datagram size or a time interval of datagrams transmitted continuously. 6. The datagram transfer system according to claim 2, wherein said traffic observing means uses a datagram size field present in a datagram header as said preference value. 7. A value obtained by the traffic observing means on the basis of the reciprocal of a difference between the transmission time of the immediately preceding datagram and the current time and the size of the datagram transmitted and received at each of these times. The datagram transfer system according to claim 2, wherein is calculated as a preference value. 8. The traffic observation means calculates an average rate obtained by a sliding window method from the size of the datagram and the time interval between successive datagrams as a preference value. Datagram transfer system. 9. The data according to claim 2, wherein said traffic observing means calculates, as a preference value, an average rate of an observation period obtained from a size of said datagram and a time interval between successive datagrams. Gram transfer system. 10. The datagram transfer system according to claim 2, wherein said traffic observing means calculates a difference between the number of datagrams transmitted by the user and the number of received datagrams as a preference value. . 11. The buffer write control unit obtains a preference value of a received datagram by a preference value extraction function, performs sorting by a preference value comparison function using the preference value as a key, and 5. The datagram transfer system according to claim 4, wherein the datagrams are sequenced in ascending order of preference values, and the buffer write control unit performs a write process to the buffer memory according to the sequence. 12. The output interface unit has a class-specific buffer memory unit having a plurality of priorities, and the buffer write control unit selects a plurality of classes having the priorities according to a preference value, The datagram transfer system according to claim 4, wherein datagram writing is performed. 13. The processing for acquiring a preference value,
The datagram transfer system according to claim 11, wherein the transfer is performed at intervals of a variable interval that can be changed according to the arrival rate of the datagram or a fixed interval that is always fixed. 14. The buffer write control unit performs a transfer determination before writing a datagram to the buffer memory, and if it determines not to transfer the datagram, discards the datagram even if there is a free space in the buffer memory. 12. The datagram transfer system according to claim 11, wherein when it is determined that the transfer is performed, the writing process to the buffer memory is performed. 15. The buffer write control unit calculates a sum of preference values of processed datagrams already written in the buffer memory, performs a probability calculation based on the calculation result, and performs data calculation in accordance with the probability. The datagram transfer system according to claim 11, wherein the datagram is discarded. 16. The buffer writing control unit, after ordering datagrams in ascending order of preference values, obtains a probability based on the usage of the buffer memory according to the ordering, and determines the probability based on the obtained probability. 12. The datagram transfer system according to claim 11, wherein the datagram is discarded by using the datagram. 17. When a user sends a datagram, the user evaluates the impact of the datagram on the network, calculates a preference value reflecting the evaluation, and calculates the calculation result. A datagram transfer method, wherein the datagram is written in a header of the datagram and priority transfer processing of the datagram is performed according to the preference value. 18. The datagram transfer device includes a backplane switch unit that transfers the datagram from any one of the input interface units to any one of the output interface units without conflict, and the output interface unit includes: A threshold value is calculated at an appropriate timing, and when a datagram is received, the preference value is obtained from a header of the received datagram, and the datagram is obtained using the threshold value and the preference value. A buffer that performs the transfer determination before writing to the buffer, discards any free space in the buffer memory if it is determined not to transfer, and writes to the buffer memory if it determines to transfer. 3. The data according to claim 2, further comprising a write control unit. Lamb transfer system. 19. The method according to claim 19, wherein in the transfer determination before writing to the buffer, the threshold value is compared with a preference value of a received datagram, and if the preference value is larger than the threshold value, the datagram is discarded. The datagram transfer system according to claim 18, wherein: 20. In the transfer judgment before writing to the buffer, the threshold value is compared with a preference value of a received datagram, and a probability is calculated by a function using a difference between these values as an input. 2. The datagram is discarded according to the obtained probability.
9. The datagram transfer system according to item 8. 21. The buffer write control unit has a preference value storage function of storing a time when any one of an event of arrival, transfer, and discard of a datagram in a predetermined range occurs and the preference value. 21. The datagram transfer system according to claim 19, wherein the threshold value is calculated using these preference values. 22. In the transfer judgment before writing to the buffer, a probability is calculated by a function that receives the threshold value, a preference value of a received datagram, and a used amount of the buffer, or an approximate value thereof. 19. The datagram transfer system according to claim 18, wherein the datagram is discarded according to the obtained probability. 23. In the calculation of the probability used for the transfer decision before writing in the buffer, all datagrams having a preference value larger than a product of the threshold value and a value determined by the used amount of the buffer or the approximate value thereof are discarded. Even if not, datagrams having a preference value equal to or higher than the threshold value are discarded with a higher probability as the preference value is larger, and more preferentially as the buffer usage amount or the estimated value is larger. 23. The datagram transfer system according to claim 22, wherein a function for generating a probability value characterized by discarding a datagram having a large preference value is used. 24. The method of calculating a threshold value used for the transfer determination, wherein a preference value of an arriving datagram is randomly sampled with an appropriate probability,
24. The datagram transfer system according to claim 23, further comprising a function of storing a fixed number of preference values, and setting a median of the sampled preference values as a threshold value at an appropriate timing. 25. The method of calculating a threshold value used for the transfer determination, wherein a preference value of an arriving datagram is randomly sampled with an appropriate probability,
24. The datagram transmission system according to claim 23, further comprising a function of storing a fixed number of preference values, and setting an average value of the sampled preference values as a threshold value at an appropriate timing. 26. The method of calculating a threshold value used in the transfer determination, wherein a function of randomly sampling a preference value of a datagram determined to be transferred with an appropriate probability and storing a fixed number of preference values is provided. 24. The datagram transfer system according to claim 23, further comprising setting an average value of the sampled preference values as a threshold value at an appropriate timing.