KR20180106293A - Communication apparatus for calculating an rto value according to an actual rtt value and communication control method thereof - Google Patents

Abstract

The present specification provided a communication apparatus and a communication control method, capable of improving the communication success rate and efficiency of CoAP communication. The communication apparatus according to the present specification includes: a transmitting unit which retransmits a packet by including information about a retransmission number when the packet is retransmitted according to CoAP; an RTT calculating unit for calculating RTT using ACK including the information about the retransmission number of a received packet; an RTO calculating unit for calculating RTO using the RTT calculated by the RTT calculating unit; and a control unit for controlling the retransmission time of the transmitting unit using the RTO calculated by the RTO calculating unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus and a communication control method for calculating an RTO value according to an actual RTT value,

The present invention relates to a communication apparatus and a communication control method, and more particularly, to a communication apparatus and a communication control method for calculating an RTO value according to an actual RTT value.

The congestion control scheme of the Constrained Application Protocol ('CoAP'), a low-power communication protocol, uses a dynamic timeout (RTO) setting technique based on a round trip time (RTT).

The CoAP communication sets a timeout value for congestion control in advance and finds a proper timeout value by doubling the timeout value when packet retransmission occurs. In this case, however, if the initial setting is set too low, retransmission may occur for all packets.

In addition, the CoCoA scheme can improve dynamic timeout, but it has a drawback that the accuracy of timeout calculation for retransmission packets is relatively weak.

Therefore, a method of setting the RTO value using the RTT value indicating the degree of congestion in the congestion situation where the actual packet is retransmitted is needed.

Korean Registered Patent No. 10-1466712

The present specification aims to provide a communication apparatus and a communication control method for improving the efficiency of CoAP communication and the communication success rate.

The solutions described herein are not limited to those mentioned above, and other solutions not mentioned may be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a communication apparatus including a transmission unit for retransmitting a packet according to a CoAP, An RTT calculating unit for calculating an RTT using an ACK including retransmission count information of a received packet; An RTO calculating unit for calculating an RTO using the RTT calculated by the RTT calculating unit; And a control unit for controlling the retransmission time of the transmission unit using the RTO calculated by the RTO calculation unit.

When the ACK for the packet received according to the CoAP is transmitted, the transmitter may include the retransmission count information included in the received packet in the ACK and transmit the ACK.

The transmission unit may transmit information on the number of re-transmissions in the option field.

The communication apparatus according to the present invention may further include a storage unit storing a preset minimum RTO. At this time, the RTO calculating unit may calculate the minimum RTO value as the current RTO value when the RTO value calculated using the calculated RTT is less than or equal to the minimum RTO.

A communication control method according to the present invention for solving the above-mentioned problems is a control method of a communication apparatus for transmitting and receiving packets according to CoAP, the method comprising the steps of: (a) when a transmitting unit retransmits a packet, Re-transmitting; (b) calculating an RTT using an ACK including retransmission count information of a packet received by the RTT calculating unit; (c) calculating an RTO using the RTT calculated in the step (b); And (d) controlling the retransmission time of the transmission unit using the RTO calculated in the step (c).

In the step (a), the transmitting unit may transmit the information about the number of retransmissions in the option field.

According to an embodiment of the present invention, the step (a) may further include storing a preset minimum RTO in the storage unit. In this case, in the step (c), the RTO calculating unit may calculate the RTO value as a current RTO value when the RTO value calculated using the calculated RTT is less than or equal to the minimum RTO .

The communication control method according to the present invention can be implemented in the form of a computer program recorded in a computer-readable recording medium so as to perform each step of the communication control method in the computer.

The communication device and the communication control method according to the present invention increase the communication performance compared to the existing communication performance based on the measured correct packet round-trip time.

The effects described in the present specification are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a block diagram schematically illustrating a configuration of a communication apparatus according to the present specification.
FIG. 2 is a comparative reference diagram of the transmission section according to the prior art and the present specification. FIG.
3 is an exemplary diagram of a packet in which retransmission count information is described.
4 is an exemplary diagram in which the minimum RTO is set according to the present specification;
5 is a flowchart of a communication control method according to an embodiment of the present invention.
6 is a flowchart of a communication control method according to another embodiment of the present invention.
7 to 10 are experimental results of the communication apparatus and the communication control method according to the present specification.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto.

Means that a particular feature, region, integer, step, operation, element and / or component is specified and that other specific features, regions, integers, steps, operations, elements, components, and / It does not exclude the existence or addition of a group.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

The communication apparatus and the communication control method according to the present invention copes with a congestion situation of a communication network by calculating an RTO through a correctly measured RTT. The CoAP communication uses the message ID to match the request / response packet. When the packet retransmission occurs, the same packet as the first packet is transmitted. Therefore, when the retransmission occurs, the measurement accuracy of the round trip time of the packet drops. In the present invention, retransmission information is added to a packet using an option field usable as additional information in the CoAP communication standard in order to accurately measure the packet round trip time. If the request packet includes the packet retransmission number information, the response packet also includes the same number of retransmission times. Finally, by comparing the message ID and the retransmission number, the accurate round trip time of the packet can be measured even if retransmission occurs.

Hereinafter, a communication apparatus and a communication control method according to the present specification will be described with reference to the drawings.

1 is a block diagram schematically illustrating a configuration of a communication apparatus according to the present specification.

Referring to FIG. 1, a communication apparatus 100 according to the present invention may include a transmission unit 110, an RTT calculation unit 120, an RTO calculation unit 130, and a control unit 140.

When the transmitter 110 retransmits the packet according to the CoAP, the transmitter 110 may include information on the number of retransmissions and retransmit the packet.

The RTT calculating unit 120 may calculate the RTT using the ACK including the number of retransmissions of the received packet.

The RTO calculating unit 130 may calculate the RTO using the RTT calculated by the RTT calculating unit 120. [

The control unit 140 may control the retransmission time of the transmission unit 110 using the RTO calculated by the RTO calculation unit 130. [

FIG. 2 is a comparative reference diagram of the transmission section according to the prior art and the present specification. FIG.

2 (a) shows a conventional CoAP transmission process, and FIG. 2 (b) shows a transmission process of the transmission unit 110 according to the present invention. Referring to FIG. 2 (a), in the conventional CoAP transmission process, the ACK is ACK for the first retransmission but is recognized as ACK for the second retransmission. On the other hand, referring to (b) of FIG. 2, information on the number of re-transmissions is included in each retransmission. The ACK also contains information on the number of retransmissions to distinguish the ACK for the second retransmission. Therefore, accurate RTT calculation is possible.

To this end, when the ACK for the packet received according to the CoAP is transmitted, the transmitter may include the retransmission count information included in the received packet in the ACK and transmit the ACK.

Meanwhile, the transmission unit may transmit information on the number of re-transmissions in the option field.

3 is an exemplary diagram of a packet in which retransmission count information is described.

3 (a) is a structural diagram of the CoAP specification. FIG. 3B is an example of a CoAP packet in which information on the number of times of retransmission according to the present invention is applied to the option. Referring to FIG. 3, it can be seen that it is possible to record the number of retransmission information in a packet without invoking additional development overhead or standard protocol by utilizing the CoAP specification.

The RTO calculating unit 130 can calculate the RTO through the dynamic congestion control scheme proposed by the IETF.

For example, the strong estimator can set the RTO based on the actual RTT in the absence of packet retransmission. As another example, the Weak estimator can set the RTO based on the RTT computed in the context of packet retransmission.

The RTO setup using the strong estimator is done through the following procedure.

≪ Formula 1 >

RTT _x = (1-a) * RTT _x + a * RTT _xnew

Equation 1 is a formula for calculating the average of RTTs. The weighting factor is 0.25 according to CoCoA. The weighting factor of RTT _xt and RTT _xnew is RTT _x and RTT xnew, respectively.

&Quot; (2) "

_{RTTVAR x = (1-b)} * RTTVAR x + b * RTT x -RTT xnew

Equation 2 is a formula for obtaining RTTVAR, which is a variable for setting an RTO, and the value is updated by applying RTTs and weights collected immediately before to RTTVAR.

&Quot; (3) "

RTO _x = RTT _x + k * RTTVAR _x

Equation (3) is the calculation process of the RTO for the current packet and it is obtained by applying the weight K to RTT and RTTVAR. This?, K is 4, CoCoA specification can be used.

≪ Equation 4 &

RTO _p = 0.5 * RTO _x + 0.5 * RTO _xpre

Equation 4 is the RTO _p RTO finally obtained can be determined by using the average of _x and RTO before the RTO RTO _prev obtained by Equation 3.

On the other hand, if the RTO is set based on the actual RTT, the RTO value will increase in the congested state, and the RTO value will be gradually decreased when the congestion state is not established. Let's assume that the RTO value becomes smaller gradually. The smaller the RTO value, the higher the probability that the transmitter will retransmit. Therefore, if a small RTO value is set unnecessarily due to a measurement error of the RTT value, unnecessary retransmission can be performed. Therefore, it is necessary to prevent the RTO value from becoming unnecessarily small

To this end, the communication apparatus according to the present invention may further include a storage unit 150 storing a preset minimum RTO. At this time, the RTO calculating unit 130 may calculate the minimum RTO value as the current RTO value when the RTO value calculated using the calculated RTT is less than or equal to the minimum RTO. Thus, it is possible to prevent the RTO from being set below the minimum RTO.

4 is an exemplary diagram in which the minimum RTO is set according to the present specification;

4A is a top view of the communication in the conventional RTT-based RTO setting, and FIG. 4B is a communication example in which the minimum RTO is set according to the present specification. If the RTT value is small when the network is stable, unnecessary retransmission may occur if RTO is set within the error range as shown in (a). On the other hand, as shown in (b), the RTO minimum value is guaranteed to prevent the RTO from being set within the error range.

Hereinafter, a control method of a communication apparatus in which a communication apparatus according to the present specification transmits and receives a packet according to a CoAP will be described. However, in the description of the communication control method according to the present specification, the repetitive description of the communication device 100 described above will be omitted.

5 is a flowchart of a communication control method according to an embodiment of the present invention.

Referring to FIG. 5, when the transmitter 110 retransmits a packet in step (a), it may retransmit the packet including information on the number of retransmissions. In the next step (b), the RTT calculating unit 120 may calculate the RTT using the ACK including the retransmission count information of the received packet. In the next step (c), the RTO calculating unit 130 may calculate the RTO using the RTT calculated in the step (b). In step (d), the controller 140 may control the retransmission time of the transmitter using the RTO calculated in step (c).

6 is a flowchart of a communication control method according to another embodiment of the present invention.

Referring to FIG. 6, it can be seen that the step of storing the minimum RTO preset in the storage unit before the step (a) in the flowchart of FIG. 5 is further included. The step (c) may further include calculating the RTO value as a current RTO value when the RTO calculating unit calculates the RTO value using the calculated RTT and the calculated RTO value is equal to or smaller than the minimum RTO value .

The above-described communication control method may be implemented in the form of a computer program written in a computer-readable recording medium so as to perform each step in the computer.

Meanwhile, as an experimental environment for verifying the performance of the communication device and the communication control method according to the present invention, a server and client software are implemented using a CoAP open source as shown in FIG. The server used raspberry pie and the client used a regular PC. In order to measure the communication performance, congestion network situation was created by sending 10 request packets per each client while increasing the number of CoAP packet transmission clients from 25 to 100. As a result of measurement of packet throughput per packet time, the existing CoAP and CoCoA The packet throughput is 150% and 50%, respectively. Also,

In order to measure the communication success rate, it was confirmed that the success rate of the proposed technique is higher than that of the existing CoAP and CoCoA as shown in FIG.

To better verify the efficiency of the proposed scheme, we plotted the data in the 100 client environments that evaluated the most congested networks as shown in Figure 6). The X-axis of the drawing is the number of attempted work, the left Y-axis is the set RTO value, and the right Y-axis shows the overall work execution rate in%. At this time, the proposed scheme achieves the fastest task execution rate of 100%, thereby proving the efficiency of the present invention.

10, when the CoAP, CoCOA, CoCoA-E, and the proposed scheme are used in 100 client situations, the RTO value of the retransmission packet and the execution time required until the task execution rate becomes 100% This is a graph comparing the number of times. The blue dot indicates the RTO value when a retransmission packet is generated. The communication apparatus and the communication control method according to the present invention (d) show that the RTO value generated by the retransmission is the smallest and the task execution is completed the fastest, thereby proving the superiority of the proposed technique.

The embodiments and the accompanying drawings described in the present specification are merely illustrative of some of the technical ideas included in the present invention. Accordingly, the embodiments disclosed herein are for the purpose of describing rather than limiting the technical spirit of the present invention, and it is apparent that the scope of the technical idea of the present invention is not limited by these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100: communication device
110:
120: RTT calculation unit
130: RTO calculation unit
140:
150:

Claims (8)

A retransmission unit for retransmitting a packet according to the CoAP, the retransmission including information on the number of retransmissions;
An RTT calculating unit for calculating an RTT using an ACK including retransmission count information of a received packet;
An RTO calculating unit for calculating an RTO using the RTT calculated by the RTT calculating unit; And
And a control unit for controlling the retransmission time of the transmission unit using the RTO calculated by the RTO calculation unit. The method according to claim 1,
Wherein the transmission unit comprises:
Wherein when the ACK for a packet received according to the CoAP is transmitted, the ACK includes information on the number of retransmission included in the received packet. The method according to claim 1,
Wherein the transmission unit describes the information on the number of re-transmissions in the option field. The method according to claim 1,
And a storage unit for storing a preset minimum RTO,
Wherein the RTO calculating unit calculates the minimum RTO value as the current RTO value when the RTO value calculated using the calculated RTT is less than the minimum RTO. A control method of a communication apparatus for transmitting and receiving packets according to a CoAP,
(a) when the transmitting unit retransmits the packet, retransmitting the packet including information on the number of retransmissions;
(b) calculating an RTT using an ACK including retransmission count information of a packet received by the RTT calculating unit;
(c) calculating an RTO using the RTT calculated in the step (b); And
(d) controlling the retransmission time of the transmission unit using the RTO calculated in the step (c) by the control unit. The method of claim 5,
Wherein the step (a) includes the step of transmitting the information on the number of retransmissions of the transmitting part in the option field. The method of claim 5,
Storing the preset minimum RTO in the storage unit before the step (a)
Wherein the step (c) comprises calculating the RTO value as a current RTO value when the RTO calculating unit calculates the RTO value using the calculated RTT and the calculated RTO value is equal to or less than the minimum RTO value, The communication control method comprising: A computer program recorded on a computer-readable recording medium, the computer program being written in the computer to perform the steps of the communication control method according to any one of claims 5 to 7.

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