JP6081322B2 - Communication device for storing transferred content - Google Patents

Description

  The present disclosure relates to a cache technology for content in a communication apparatus that has transferred content in a content distribution system.

  A network that routes content distribution request messages and distributes content based on the content name is proposed without the client device acquiring the content being aware of which server device stores the content to be acquired Has been. Patent Document 1 and Non-Patent Document 1 disclose a content-centric network (CCN) which is one of such networks.

JP 2009-277234 A

V. Jacobson, et al. , "Networking Named Content", in Proceedings of ACM CoNEXT 2009, December 2009

  In a content-centric network, a server device that publishes content divides the content into one or more segments, and a client device acquires content in segment units. In a content-centric network, a communication device (hereinafter referred to as an intermediate device) that has transferred a segment to a client device can store the segment. When the distribution request message of a certain segment is received from the client device, the segment held by the own device can be transmitted to the client device that is the transmission source of the distribution request message without transferring the distribution request message to the server device.

  There is an upper limit on the storage capacity that the intermediate device can use to hold segments, and when the total capacity of the segments already held reaches the upper limit, the intermediate device will receive a new segment for transfer. It is necessary to determine a segment that is not held by the intermediate apparatus from among the already held segment and the newly received segment. However, Patent Document 1 does not describe anything about this determination method. Further, in Non-Patent Document 1, the intermediate device discards the segment having the longest period from the time it is used for distribution to the determination time, and holds the newly transferred segment. .

  The method of Non-Patent Document 1 deletes the segment that is least likely to be requested in the delivery request message, that is, the possibility that the held segment is specified in the delivery request message (hereinafter referred to as hit rate). It is something to raise. However, in the content distribution system, it is desirable to select the segments held in the intermediate device so as to increase the use efficiency of the bandwidth in the network and shorten the time required for the client device to acquire the content. However, even if the selection is made by the hit rate in the intermediate device, it is not possible to increase the use efficiency of the bandwidth in the network and shorten the time required for the client device to acquire the content.

  The present invention relates to a communication apparatus and program for selecting a segment to be effectively held in a content distribution system in which content is divided into one or more segments and distributed, and the communication apparatus can hold the received segment for subsequent distribution. Is to provide.

  According to one aspect of the present invention, there is provided a communication device of a content distribution system that divides content into one or more segments for distribution, a holding unit that holds the segments, and a distribution request that indicates segments of the content that are not held When the message is received, the received distribution request message is transferred according to a predetermined criterion, and when the segment is received as a response to the transfer of the distribution request message, the received segment is directed to the transmission source of the distribution request message. And determining whether there is a free capacity for holding the received segment in the holding means, and if there is no free capacity, the received segment and the holding means hold it. Segments that are not to be held by the holding means according to the segment discard order A determination unit configured to determine, in response to the transfer of the distribution request message after the distribution request message indicating the segment is transferred to the determination of the discard order of the segment. It is characterized by using a round trip time until a segment is received.

  A segment to be effectively retained can be selected.

Explanatory drawing of a content centric network. 1 is a schematic configuration diagram of an intermediate device according to an embodiment. FIG. The figure which shows the data which the intermediate | middle apparatus by one Embodiment hold | maintains.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the following drawings, components that are not necessary for describing the embodiment are omitted from the drawings. Moreover, the following embodiment is an illustration and does not limit this invention to the content of embodiment.

  First, the outline of the content-centric network will be described with reference to FIG. A user who wants to publish content stores the content in the server device 1. The server device 1 divides the held public content into one or more segments, and notifies the other device of the content name held. The intermediate devices 21 and 22 responsible for content transfer create a routing table based on the content name from the content name notified by the server device 1. For example, it is assumed that the content desired to be acquired by the user of the client device 31 is held in the server device 1. At this time, when the user of the client device 31 inputs a content name to be acquired to the client device 31, the client device 31 transmits an interest packet (distribution request message) including the input content name to the intermediate device 21. . Since the client device 31 has not received any segment of the content corresponding to the input content name, the client device 31 includes the segment number “01” in the interest packet.

  The intermediate device 21 recognizes from the routing table that the server device 1 holds content corresponding to the content name included in the interest packet received from the client device 31, and sends this interest packet to the server device 1. Forward. The server device 1 that has received the interest packet from the client device 31 transmits the first segment of the content specified by the received interest packet to the intermediate device 21, and the intermediate device 21 has received from the server device 1. The segment is transmitted to the client device 31. At this time, the intermediate device 21 stores the transferred segment.

  The client device 31 transfers the interest packet including the input content name to the intermediate device 21 while incrementing the segment number by one, and the server device 1 receives the content name input from the server device 1 as described above. Receive the remaining segments. The last segment includes information indicating that it is the last segment, and the client device 31 recognizes that all segments of the content have been received based on this information. Further, since the intermediate device 21 is involved in the transfer of all the content requested by the client device 31, it holds all segments of the content.

  Thereafter, for example, when the client device 32 transmits an interest packet (the segment number includes “01”) for the same content acquired by the client device 31 to the intermediate device 22, the intermediate device 22 reads the routing table. The interest packet is transferred to the intermediate device 21 based on the above. Since the intermediate device 21 holds the segment of the content number 1 indicated by the received interest packet, the intermediate device 21 does not transfer the received interest packet to the server device 1 and does not transfer the content of the content held by itself. The segment of number 1 is transmitted to the intermediate device 22, and the intermediate device 22 transmits the received content to the client device 32. At this time, the intermediate device 22 stores the transferred content segment. Thereafter, the remaining segments are processed in the same manner, so that the intermediate device 22 also holds all the segments of the content by distributing the content to the client device 32. Thereafter, when the client device 33 requests acquisition of the same content that the client devices 31 and 32 have acquired, the client device 33 receives the content held by the intermediate device 22.

  FIG. 2 is a configuration diagram of the intermediate device 21 according to an embodiment. The configuration of the intermediate device 22 is the same as that of the intermediate device 21. When the communication unit 211 has a plurality of communication interfaces and receives a distribution request message indicating a segment of content from another device (client device or other intermediate device), the determination unit 212 receives the distribution request message. It is determined whether the holding unit 210 holds the segment to be shown. Here, when the holding unit 210 holds the segment, the communication unit 211 reads the segment from the holding unit 210 and transmits the segment to the transmission source device.

  On the other hand, when the holding unit 210 does not hold the segment, the received delivery request message is transferred to the server device 1 based on the routing table 213. At this time, the communication unit 211 stores, in the unprocessed table of the holding unit 210, a value indicating the segment specified in the distribution request message for the transferred distribution request message, an interface for transmitting a response to the distribution request message, Information indicating the transfer time of the delivery request message is added. FIG. 3B is an example of an unprocessed table. In FIG. 3B, the distribution request message requesting the second and third segments of the content named “Name2” is transferred to the server device 1 at time ta and tb, respectively, and the distribution request It is shown that when a segment is received from the server apparatus 1 as a response to the message, the received segment is output to the interface IF1 in order to distribute the received segment to the apparatus that has transmitted the distribution request message.

  Note that when the distribution request message specifying the same segment as the distribution request message transferred to the server device 1 is received as a response to the already transferred distribution request message before receiving the segment, the communication unit 211 holds Information related to the delivery request message received later is added to the unprocessed table of the unit 210, but transfer to the server device 1 is not performed. In this case, since the delivery request message is not transferred, the transfer time field of the unprocessed table is left with a null value or a value indicating that no transfer is performed. Further, a plurality of values can be set in the transfer destination interface, and a distribution request message specifying the same segment as the distribution request message transferred to the server apparatus 1 is used as a response to the already transferred distribution request message. When the segment is received before the segment is received, the transfer destination interface for the delivery request message received later can be added to the entry for the segment in the unprocessed table. Specifically, in the state of FIG. 3B, when a distribution request message requesting the second segment of “Name2” is received and the transfer destination interface for this distribution request message is IF2, “Name2” It may be a form in which IF2 is added to the transfer destination interface of the entry corresponding to the second segment.

  When the communication unit 211 receives a segment as a response to the distribution request message transferred to the server device 1, the communication unit 211 transfers the segment according to the unprocessed table and deletes the entry of the unprocessed table related to the transferred segment. Further, the determination unit 212 determines whether or not the holding unit 210 has a free capacity for holding the segment. If there is a free capacity, the determination unit 212 causes the holding unit 210 to hold the segment. Further, information about the newly held segment is added to the management table for managing the segment held by the holding unit 210.

  FIG. 3A is an example of a management table. As shown in FIG. 3A, the management table includes information indicating the name of the held segment and the round trip time of the segment. Note that the management table includes, for example, information (not shown) indicating the storage position of the segment. Here, the round trip time is the difference between the transfer time of the distribution request message in the unprocessed table and the time when the segment is received as a response to the distribution request message.

  The determination unit 212 calculates the discard order from the segments already held in the holding unit 210 and the newly received segments when the holding unit 210 does not have free space for holding the newly received segment for transfer. And decide to discard the one with the highest disposal order. That is, when the segment with the highest discard order is already held in the holding unit 210, the communication unit 211 deletes the segment with the highest discard order from the holding unit 210 and holds the newly received segment. 210. When the segment with the highest discard order is a newly received segment, the communication unit 211 discards the received segment after transfer.

  In this embodiment, the discard order is calculated based on the round trip time of each segment. It should be noted that the higher the discard order, the shorter the round trip time. Based on the case where a client device acquires a segment from an intermediate device, the amount of change in the acquisition time when the intermediate device does not hold the segment is the round trip time of the segment at the intermediate device. Will be equal. Therefore, even if a segment with a short round trip time is deleted, the influence on the time required to acquire the segment in the client device is small.

  Furthermore, the long round trip time of a segment means that the distance from the intermediate device to the intermediate device or the server device that stores the segment next is long, and this means that it goes through many transmission sections. It means that there is a high possibility. Therefore, when a segment having a long round trip time is deleted, if a delivery request message indicating the segment is received later, a large amount of network resources are consumed by forwarding the delivery request message and receiving the subsequent segment. Become. Therefore, the network usage efficiency can be improved by deleting the segment with the short round trip time first.

  The discard order can be calculated in consideration of the segment request frequency in addition to the round trip time of each segment. In this case, the lower the land trip time, the higher the discard order, and the smaller the content request frequency, the higher the discard order. For example, the discard order can be calculated based on a value obtained by multiplying the round trip time and the content request frequency. Note that the request frequency can be the average number of requests in the past predetermined period, the cumulative number of requests since the segment is held, or the number of requests in each predetermined period. Further, weighting can be performed with a weighting coefficient that decreases as the time from the present time to the time requested in the past increases. Since the request frequency of the newly received segment is 0 or a small value, when using the request frequency, the newly received segment can always be saved as a target for calculating the discard order. Furthermore, the request frequency of the newly received segment can be a predetermined value other than 0, for example, a value based on the request frequency of the already held segment, for example, an average value, a minimum value, or a maximum value.

  The intermediate device 21 according to the present invention can be realized by a program that causes a computer to operate as the intermediate device 21. These computer programs can be stored in a computer-readable storage medium or distributed via a network.

Claims (6)

A communication device of a content distribution system that distributes content into one or more segments,
Holding means for holding the segment;
When a distribution request message indicating a segment of content that is not held is received, the received distribution request message is transferred according to a predetermined criterion, and when the segment is received as a response to the transfer of the distribution request message, the received A communication means for transferring a segment toward a transmission source of the delivery request message;
It is determined whether there is a free capacity for holding the received segment in the holding means, and when there is no free capacity, the received segment and the discard order of the segments held in the holding means are used. Determination means for determining a segment not to be held by the holding means;
With
The determination means uses a round trip time from when a distribution request message indicating the segment is transferred to when the segment is received as a response to the transfer of the distribution request message for determining the discard order of the segment. A communication device characterized by:   The communication apparatus according to claim 1, wherein the discard order increases as the round trip time decreases.   The communication device according to claim 1, wherein the determination unit further uses a reception request message reception frequency indicating the segment for determining the discard order of the segment.   The communication apparatus according to claim 3, wherein the discard order increases as the round trip time decreases and increases as the reception frequency decreases.   5. The determination unit according to claim 1, wherein the determination unit causes the holding unit to hold the received segment when there is a free capacity for holding the received segment in the holding unit. Item 1. The communication device according to item 1.   A program for causing a computer to function as the communication device according to claim 1.

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