KR20120056728A - Opportunistic Fair Parallel Download Method and System Based on Priority of Connection Link - Google Patents

Abstract

PURPOSE: An opportunist parallel download method based on connection link priority and system thereof are provided to reduce content download time on a network by changing the establishment of a network connection method by selecting a priority group. CONSTITUTION: Plural reception apparatuses(123) respectively contacts with an action server and a network. The reception apparatuses receive content. A congestion controller(122) monitors network connection states of the reception apparatuses. The congestion controller selects the monitored reception apparatus from the priority groups. The congestion controller changes the establishment of a network connection method in the reception apparatus.

Description

Opportunistic Fair Parallel Download Method and System Based on Priority of Connection Link}

The present invention relates to a method and a system for downloading a content. By setting up a parallel connection to a plurality of servers and assigning different priorities according to a user's policy or the status of a connection link, the content download time is reduced and the server load is reduced through distribution. The present invention relates to an opportunistic parallel download method and system that can improve the reliability of the system.

In a Contents Distribution Network or Peer-to-Peer File Sharing Network, the replication and distribution of files is one of the most important issues. In other words, if the same content is distributed and stored in multiple servers, not only can the load of the server be distributed but also the service interruption due to the server's fault can be prevented, thereby improving the reliability of the system.

The parallel download protocol establishes a connection from one receiving node to multiple servers and downloads simultaneously. If the bottlenecks of each connection link are different, the download throughput is increased by increasing the number of connections established. Can be reduced. However, parallel download protocols cause performance problems when sharing the same bottlenecks, resulting in poor performance of other connection links.

Accordingly, an object of the present invention is to solve the above-described problem, and an object of the present invention is to reduce content download time on a network in which replicated content is distributed and stored in a plurality of servers, and to solve the problem of equity caused by parallel download. To provide an opportunistic parallel download method and system that can overcome.

In addition, in establishing a multipath TCP connection with multiple servers, an opportunistic parallel download method and system for downloading contents by assigning priorities to parallel connections based on a user's policy or the status of a connection link. To provide.

Opportunistic parallel download method that continuously monitors the connection status while the connection is established and downloads the content, and changes the priority assigned as the connection status changes to solve the problem of equity with other connections without degrading performance. To provide a system.

First, to summarize the features of the present invention, in accordance with an aspect of the present invention for achieving the object of the present invention, a parallel download method in the receiving terminal for parallel downloading of the content stored in a plurality of servers in parallel, Receiving devices connected to respective corresponding servers in a network to receive content; Monitoring a network connection state of the plurality of receiving devices; And changing a setting of a network connection scheme of the plurality of receiving devices by selecting from a plurality of priority groups.

The monitoring may include collecting respective packet reception amounts from the plurality of receiving devices, and the changing of the setting may be performed by comparing the respective packet reception amounts with a threshold for the corresponding reception apparatus. Determining any one of the plurality of priority groups, and setting a network connection method of a corresponding receiving device based on the determined network connection method of the priority group.

The plurality of priority groups may include: a general TCP group, which is a connection group between a server and a terminal that performs a process of retransmitting if there is no response during a retransmission timeout after the packet transmission of the server; And a TCP_LP group, which is a connection group between the server and the terminal performing retransmission according to an ECN (Early Congestion Notification) message after packet transmission of the server.

In addition, according to another aspect of the present invention, a parallel download apparatus of a receiving terminal for parallelly downloading contents distributed and stored in a plurality of servers includes: a plurality of receiving apparatuses connected to a network corresponding to each corresponding server to receive the contents; And a congestion control coordinator for monitoring a network connection state of the plurality of receiving apparatuses and selecting from a plurality of priority groups to change a setting of a network connection scheme of the plurality of receiving apparatuses.

The congestion control coordinator, the network monitoring unit for collecting each packet receiving amount from the plurality of receiving devices; A priority determining unit which determines one of the plurality of priority groups with respect to a corresponding receiving device by comparing each packet receiving amount with a threshold; And a setting unit configured to set a network connection method of the corresponding reception device as the network connection method of the determined priority group.

According to the parallel download method and system according to the present invention, the download time can be reduced when downloading content using a plurality of TCP connections compared to when using one TCP connection.

In addition, by changing the priority according to the state of the connection link, it is possible to solve the problem of equity without degrading performance.

1 is a view for explaining a content providing system according to an embodiment of the present invention.
FIG. 2 is a diagram for describing the congestion control coordinator of FIG. 1.
3 is a flowchart illustrating an operation of a congestion control coordinator according to an embodiment of the present invention.
4 is an example of one topology for performance testing.
5 is a graph of download completion time versus performance test results for a high number of prioritized links.
FIG. 6 is a graph normalizing the contribution of low priority links in percentages according to the number of high priority links.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

1 is a view for explaining a content providing system 100 according to an embodiment of the present invention. Referring to FIG. 1, the content providing system 100 according to an exemplary embodiment of the present invention may provide content (referred to as TCP) to a receiving terminal 120 from a plurality of servers 110 through a TCP / IP network. Text, images, video, etc.). In particular, the content providing system 100 according to an embodiment of the present invention, a content distribution network or a peer-to-peer according to a Transmission Control Protocol / Internet Protocol (TCP / IP) scheme. -Peer) In the file sharing network, the content is distributed and stored in a plurality of servers 110 to distribute the load of the server corresponding to the sender and to increase the reliability of the system, and to the receiving terminal 120 corresponding to the receiver if necessary. It is a system that can distribute content in parallel.

In the present invention, the receiving terminal 120 includes an execution unit 121 for supporting a parallel download function by starting an application program, the execution unit 121 is a plurality of receiving devices 123 provided in the transport layer In particular, the plurality of receivers 123 may be controlled by a congestion control coordinator 122 to determine a network connection method of the plurality of receivers 123. .

For example, the n receivers 123 correspond to the n servers 110 one by one, and are connected to the corresponding network to receive the contents, but the congestion control coordinator 122 receives the receivers 123. You can flexibly change the configuration of your network connection. That is, the congestion control coordinator 122 continuously monitors the network connection status of the receivers 123 and sets priority groups (eg, high priority fast general) according to the user's policy or network connection status. It is possible to flexibly change the network connection scheme of the receivers 123 by selecting among a TCP group / low priority TCP_LP group).

Accordingly, the execution unit 121 may generate and reproduce one file such as text, image, or video executable by a predetermined codec by collecting and synthesizing content blocks that are opportunistically parallel downloaded through the receiving devices 123. Will be.

According to the opportunistic parallel download technique of the present invention, the download time for downloading content can be reduced by using a plurality of TCP connection methods as compared to when using one general TCP network connection. By changing the priority, we can solve the equity issue that occurs when sharing bottlenecks without compromising performance.

Hereinafter, the configuration of the congestion control coordinator 122 of FIG. 2 and the flowchart of FIG. 3 will be described in more detail.

2, the congestion control coordinator 122 may include a network monitoring unit 210, a priority determining unit 220, and a setting unit 230. Each such component of the congestion control coordinator 122 may be implemented in hardware, software, or a combination thereof.

The network monitoring unit 210 continuously monitors network connection states of the receiving devices 123, for example, may collect respective packet reception amounts from the receiving devices 123 (S10). When the receiving device 123 receives the content, the packet receiving amount (eg, the number of bytes per second) may be different according to the network connection state, and the network monitoring unit 210 receives the packet from each receiving device 123. Information about quantities can be collected.

The priority determining unit 220 determines the priority of the network connection scheme of the receiving devices 123 based on the information on the packet receiving amount of the receiving devices 123 collected by the network monitoring unit 210. For example, the priority determiner 220 compares the packet receiving amount of each of the receiving devices 123 with a threshold value (S20), and then sets priority groups (eg, high priority, fast) for the corresponding receiving device. General TCP group / low priority slow TCP_LP group) can be determined (S30), accordingly, the setting unit 230 is a network connection method of the priority group determined by the priority determining unit 220 accordingly The network connection method of the receiving device is set (S40). The above operations of the network monitoring unit 210, the priority determining unit 220, and the setting unit 230 are repeatedly performed at step S50.

For example, the priority groups determined by the priority determiner 220 may be a fast general TCP group having a high priority, a slow TCP_LP group having a low priority, and the like. You may want to further refine your network connectivity to include more groups.

In the above example, the general TCP group is a group having a good network connection state. If there is no response for a predetermined retransmission timeout after the packet transmission of the server 110 according to the congestion control function of the general TCP, the server 110 ) Indicates a connection group between the server and the terminal that will retransmit the packet. In addition, in the congestion control function of the general TCP, the server 110 receives a predetermined number of response messages for a lost packet through a router (or an Ethernet switch) on the network for a packet transmitted from the server 110 to the terminal 120. For example, 3 times) if not received it has the function to retransmit the packet. At this time, if there is no response (response message) from the receiving terminal 120 during the predetermined retransmission timeout time as described above, the server 110 may retransmit the corresponding packet.

In the above example, the TCP_LP group is a LP (Low Priority) group having a poor network connection, and does not wait for the retransmission timeout time to eliminate the delay of waiting for the retransmission timeout time. A connection group between a server and a terminal that is retransmitted according to an Early Congestion Notification (ECN) message received by the server 110 through a router (or an Ethernet switch) on a network. The ECN message may be a message including a predetermined notification value for congestion in a predetermined TCP field of a predetermined response packet.

As described above, in the present invention, by changing the priority group according to the network connection state of the receiving devices 123 using the congestion control coordinator 122, it is possible to solve the equity problem that occurs when sharing the bottleneck without degrading performance. do. For example, the higher the number of groups (servers and receiving devices) communicating over a higher priority group of connections, the faster the download time but the lower the performance of other connections, resulting in lower fairness, and vice versa. The greater the number of groups that communicate via a priority group connection, the better the fairness but the lower the performance. In the present invention, the congestion control coordinator 122 can be used to determine the number of high priority groups to tune the performance and fairness of the parallel connection, and also the network state between the receiving terminal 120 and the server 110 By giving a high priority to the connection between the good and low latency server-receiving devices, and giving a low priority to the connection between the server-receiving device with poor connection status, performance can be improved without deterioration of equity.

4 is an example of one topology for performance testing. In the performance test as shown in FIG. 4, it is assumed that the receiving terminal (node) is connected to 8 servers to download contents through routers on the network, and all connection links between the 8 servers and the receiving terminal (node) pass through both routers. It is assumed to pass through one bottleneck.

5 is a graph of download completion time versus performance test results for a high number of prioritized links. In FIG. 5, the five graphs show the download completion time for the high priority link number of each background traffic. As shown in FIG. 5, the download time decreases as the number of high priority links (number of groups) increases. For example, in the case of a 0 cross TCP packet, when the number of high priority links is 1, when the number of high priority links is increased from 2.3 to 8, it is shortened to 1.45 seconds.

FIG. 6 is a graph normalizing the contribution of low priority links in percentages according to the number of high priority links. As shown in FIG. 6, when the number of high priority links is 0, the contribution of the low priority link is 100%, which means that the entire content is downloaded using the low priority link. If the number of links assigned is 8, the contribution of the low priority link is 0%, which means that the entire content is downloaded using the high priority link. You can increase the download performance by increasing the number of high-priority links, and the download performance is similar when the number of high-priority links is higher than 3, so select the appropriate number so that the number of high-priority links is not maximum. By securing the degree of contribution of the ranked links, the content download performance can be improved without compromising equity.

As described above, in the present invention, in a parallel download scheme in which one receiving node establishes a parallel connection to a plurality of servers and simultaneously downloads content in an environment in which content is distributed among multiple servers, throughput of the receiving node is improved. In addition to reducing the download time of the content, it is possible to solve the problem of overload through load balancing of the server. The problem of fairness may be caused by causing performance degradation of other connections using the same server. In the present invention, a method for mitigating a problem of equity caused by parallel download is used to set up a parallel connection using a congestion control coordinator. The priority is determined differently according to the policy or connection status, and the status of the connection link is continuously monitored and reflected to change the priority of the connection link to prevent performance degradation.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

Content Provision System (100)
Multiple servers 110
Receiving terminal 120
Congestion Control Tuner (122)
Network monitoring unit 210
Priority decision unit 220
Setting unit 230

Claims (6)

In the parallel download method in the receiving terminal for parallel downloading the content distributed in a plurality of servers,
A plurality of receiving devices connected to respective corresponding servers through a network to receive contents;
Monitoring a network connection state of the plurality of receiving devices; And
Changing a setting of a network connection method of the plurality of receiving devices by selecting from a plurality of priority groups
Parallel download method comprising a. The method of claim 1,
The monitoring may include collecting each packet received amount from the plurality of receiving devices,
Changing the setting,
Determining one of the plurality of priority groups for the corresponding receiving device by comparing the received packet amount with each threshold; and
Setting the network connection method of the corresponding receiving device with the network connection method of the determined priority group
Parallel download method comprising a. The method of claim 1,
The plurality of priority groups,
A normal TCP group, which is a connection group between a server and a terminal which performs a retransmission process if there is no response during the retransmission timeout after the packet transmission by the server; And
TCP_LP group, which is a connection group between a server and a terminal that performs a process of retransmitting a packet according to an ECN (Early Congestion Notification) message after transmitting the packet
Parallel download method comprising a. In the parallel download device of the receiving terminal for downloading the content distributed in a plurality of servers in parallel,
A plurality of receiving devices connected to a network corresponding to each corresponding server to receive contents; And
A congestion control coordinator for monitoring a network connection state of the plurality of receiving devices and changing a setting of a network connection method of the plurality of receiving devices by selecting from a plurality of priority groups.
Parallel download device comprising a. The method of claim 4, wherein
The congestion control coordinator,
A network monitoring unit collecting respective packet reception amounts from the plurality of receiving devices;
A priority determining unit which determines one of the plurality of priority groups with respect to a corresponding receiving device by comparing each packet receiving amount with a threshold; And
Setting unit for setting the network connection method of the receiving device to the network connection method of the determined priority group
Parallel download device comprising a. The method of claim 4, wherein
The plurality of priority groups,
A normal TCP group, which is a connection group between a server and a terminal which performs a retransmission process if there is no response during the retransmission timeout after the packet transmission by the server; And
TCP_LP group, which is a connection group between a server and a terminal that performs a process of retransmitting a packet according to an Early Congestion Notification (ECN) message.
Parallel download device comprising a.

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