JP2017142675A - Transfer device and program for content delivery network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce processing load of a transfer device in a content delivery network that delivers content by dividing the content into one or more objects.SOLUTION: A transfer device comprises retaining means for retaining objects, and processing means configured to, in response to reception of a request packet requesting a plurality of objects, sequentially perform first search processing for determining if the plurality of objects are retained by the retaining means in order of search ranking of the plurality of objects. When the number of objects, of the plurality of objects, determined to be not retained by the retaining means reaches a first predetermined number, the processing means terminates the first search processing.SELECTED DRAWING: Figure 8

Description

  The present disclosure relates to a transfer device and a program for a content distribution network that performs routing based on a name related to content.

  A network that distributes content based on a name indicating the content has been proposed. 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 CCN, a server device that publishes content divides the content into one or more objects called chunks, and a client device acquires content in units of the divided objects. In addition, a communication device that has transferred an object in the CCN (hereinafter referred to as a transfer device) can store the object. When the transfer device receives an interest packet (request packet) requesting an object held by the own device from the client device, the transfer device holds the interest packet without transferring it to the server device. The object can be transmitted to the client device that has transmitted the interest packet.

  Below, an example of operation | movement of a transfer apparatus is demonstrated. The transfer apparatus manages CS (Contents Store), FIB (Forward Information Base), and PIT (PIT: Pending Interest Table). The CS is information indicating an object held by the own device. The FIB is information indicating a relationship between an interest packet and an interface to which the interest packet is to be transferred. The PIT is information indicating the relationship between the object requested by the transferred interest packet and the interface that has received the transferred interest packet.

  When receiving the interest packet, the transfer device searches the CS and determines whether or not the object requested by the interest packet is held. If it is held, the object held by the own device is transmitted to the client device that is the transmission source of the interest packet. On the other hand, if the received interest packet does not hold the requested object, the PIT is searched, the interest packet requesting the same object as the interest packet is already transferred, and the object waiting to be received is received. It is determined whether it is in a state. In the state of waiting for reception, the received interest packet is not transferred, and the PIT is updated so that the reception interface of the interest packet is associated with the object requested by the interest packet. On the other hand, if the received interest packet is not waiting for the requested object, the interest packet is transferred from the interface determined based on the FIB and the PIT is updated. Further, when receiving the object, the transfer apparatus determines the transfer destination interface of the object based on the PIT, and deletes the information related to the object from the PIT. The transfer device updates the CS when the received and transferred object is saved.

  For example, in CCN, the maximum size of an object is 64 KB. Therefore, in the CCN, the client device needs to transmit a large number of interest packets in order to acquire the entire content. Further, when the transfer device receives the interest packet, it searches for each CS. Further, if the transfer device finds that the object requested by the interest packet is not held as a result of searching for the CS, the transfer device searches for the PIT. It is necessary to search one by one. Therefore, the network bandwidth is compressed by a large number of interest packets transmitted by the client device, and the processing load on the transfer device increases.

  The present invention suppresses processing load on a transfer device in a content distribution network that divides content into one or more objects and distributes the content.

  According to one aspect of the present invention, a transfer device of a content distribution network that divides and distributes content into one or more objects receives the holding means that holds the objects and the request packet that requests a plurality of objects. Processing means for sequentially performing a first search process for determining whether or not a plurality of objects are held by the holding means in accordance with a search order of the plurality of objects, wherein the processing means includes: The first search process is terminated when the number of objects determined not to be held by the holding means among a plurality of objects reaches a first predetermined number.

  According to the present invention, the processing load on the transfer device can be suppressed.

The block diagram of the content delivery network by one Embodiment. The figure which shows the interest packet which a transfer apparatus receives in one Embodiment. The flowchart of the CS search process in the transfer apparatus by one Embodiment. The figure which shows the interest packet which the transfer apparatus transfers in one Embodiment. The figure which shows PIT of the transfer apparatus by one Embodiment. The figure which shows PIT of the transfer apparatus by one Embodiment. The figure which shows the interest packet which the transfer apparatus transfers in one Embodiment. The block diagram of the transfer apparatus by one Embodiment.

  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 embodiment>
FIG. 1 is a configuration diagram of a content distribution system according to the present embodiment. A content distribution network composed of a plurality of transfer devices 2 is connected to a server device 3 that publishes content and a client device 1 that acquires content. Here, when acquiring content, the client device 1 transmits a request packet (hereinafter referred to as an interest packet) including an object name to be acquired. Conventionally, the client apparatus 1 transmits only one object name in one interest packet. Accordingly, when acquiring all of the content divided into 10 objects, the client device 1 transmits 10 interest packets, and the transfer device 2 of the content distribution network transmits 10 interest packets. Each had to be processed separately.

  In the present embodiment, the client apparatus 1 can include a plurality of object names having a common prefix in the object name in one interest packet. For example, content whose content name is “/ a / b / c / d / name1” is divided into 10 objects, and the object names of these objects are “/ a / b / c / d / name1 /”. 1 "to" / a / b / c / d / name 1/10 ". In this case, the client apparatus 1 transmits an interest packet including 10 object names from “/ a / b / c / d / name1 / 1” to “/ a / b / c / d / name1 / 10”. can do. Normally, the object number (the last number of the object name) corresponds to the time order of the objects. That is, “/ a / b / c / d / name1 / 1” is the first object in time, and “/ a / b / c / d / name1 / 10” is the last object in time.

  FIG. 2 shows an interest packet transmitted by the client device 1 in this case. The interest packet in this embodiment includes a common name field and an object name field. As shown in FIG. 2, in the common name field, the longest prefix name common to the object names of the objects to be acquired (in this example, 10) is set. In the object name field, a part (hereinafter referred to as an individual name) excluding the common name field of the object name of the object to be acquired is listed.

  In the present embodiment, a search order is set for a plurality of objects in the object name field. In this example, it is assumed that the order of storage positions of individual names in the object name field, that is, the order of arrangement corresponds to the search order. Therefore, “/ a / b / c / d / name1 / 1” is the object to be searched first (hereinafter simply referred to as the first object), and “/ a / b / c / d / name1”. / 10 "is the 10th, that is, the last object. Normally, the client device 1 arranges individual names in the object name field in the time order of the objects, so that the search order also corresponds to the time order of the objects. Note that when the sequence of individual names in the object name field is different from the time order of the individual names, the search order may be determined based on the time order of the individual names.

  Next, CS search processing performed by the transfer apparatus 2 that has received the interest packet shown in FIG. 2 will be described with reference to FIG. In S10, the transfer device 2 initializes an index i indicating the search order to 1. In S11, the transfer device 2 determines whether or not the i-th object is held by searching for CS. If so, the transfer device 2 transmits the i-th object to the client device 1 that is the source of the interest packet in S12. Thereafter, in S13, the transfer apparatus 2 determines whether the object is the last object in the object name field of the interest packet. If it is not the last object, i is incremented by 1 in S14 and the processing is repeated from S11. On the other hand, if it is the last object in S13, the transfer device 2 ends the process. In this case, since the transfer device 2 holds all the objects requested by the interest packet, the received interest packet is discarded without being transferred to another device.

  On the other hand, if the transfer device 2 does not hold the i-th object in S11, the transfer device 2 ends the CS search process without determining whether or not the subsequent object is held, The PIT search process is started. The PIT search process in the present embodiment is the same as the conventional one. Therefore, if the transfer apparatus 2 does not hold the i-th and subsequent objects, the transfer apparatus 2 determines whether there is an entry in the PIT for each of the i-th and subsequent objects. Forward interest packets containing missing objects. In addition, for objects having entries in the PIT among the i-th and subsequent objects, the PIT is updated so that the interface that received the interest packet is associated with the object.

  For example, the transfer device 2 holds “/ a / b / c / d / name1 / 1” and “/ a / b / c / d / name1 / 2”, but “/ a / b / c”. Assume that / d / name1 / 3 "was not held. Further, it is assumed that there is no entry in the PIT, that is, there is no object waiting for reception. In this case, “/ a / b / c / d / name1 / 1” is transmitted to the client apparatus 1 in the first S12 of the process of FIG. 3, and “/ a / b / c / d” is transmitted in the second S12. / Name1 / 2 "is transmitted to the client apparatus 1. However, since the transfer device 2 does not hold “/ a / b / c / d / name 1/3”, the determination at S11 for the third time is “No”. Further, since there is no entry in the PIT, the transfer apparatus 2 performs the processing from “/ a / b / c / d / name1 / 3” to “/ a / b / c / d / name1 / 10” shown in FIG. Transfer interest packets requesting 8 objects. Note that the transfer destination is determined based on the common name field and the FIB.

  Usually, the client device 1 acquires a plurality of objects belonging to one content in the order of time. Therefore, there is a high possibility that objects that are close in time for the same content are held in the same transfer device 2, but different content or objects that are separated in time are held in the same transfer device 2 even if they are the same content. The possibility that it has been reduced. For example, in the above example, it is unlikely that the transfer apparatus 2 that does not hold “/ a / b / c / d / name1 / 3” holds the subsequent objects. Therefore, in the present embodiment, when an object that is not held is found, the CS search process for the subsequent objects is stopped. As a result, it is possible to reduce the time required to search for content that is not held, and thus to reduce the processing load on the transfer apparatus 2.

  In the processing of FIG. 3, the held content is transmitted to the client device 1 each time. However, the object is not transmitted until an object that is not retained is found, and the content is retained. When no object is found, the previous objects may be collectively transmitted to the client device 1. Further, in this embodiment, when even one object that is not held is found, the CS search process is immediately terminated. However, when a predetermined number of objects that are not held are found, the CS search process is terminated. It can also be. Furthermore, the CS search process may be terminated when a predetermined number of objects that are not held continue. In the present embodiment, the client device 1 has acquired all the objects of one content with one interest packet, but requests all the objects of one content, each of which requires a plurality of objects. It is also possible to obtain a plurality of interest packets.

<Second embodiment>
Subsequently, the present embodiment will be described focusing on differences from the first embodiment. First, the CS search process in this embodiment is the same as that in the first embodiment. That is, it follows the flowchart of FIG. Furthermore, in the present embodiment, the PIT search process is the same as the CS search process. That is, the PIT search is performed according to the search order for the remaining objects after the CS search process ends. When an object having no entry is found, the PIT search process for the subsequent objects is stopped, and the interest packet including the subsequent objects is transferred.

  For example, as in the first embodiment, it is assumed that the transfer apparatus 2 receives the interest packet shown in FIG. 2 at the interface # 3 (IF # 3) and the PIT at that time is as shown in FIG. Further, as in the first embodiment, the transfer device 2 holds “/ a / b / c / d / name1 / 1” and “/ a / b / c / d / name1 / 2”. , "/ A / b / c / d / name1 / 3" is not held. In this case, “/ a / b / c / d / name1 / 3” to “/ a / b / c / d / name1 / 10” are PIT search targets. The PIT has entries of “/ a / b / c / d / name1 / 3” and “/ a / b / c / d / name1 / 4”, but “/ a / b / c / Since there is no entry of “d / name 1/5”, the transfer apparatus 2 performs “/ a / b / c / d / name 1/5” to “/ a / b / c / d / name1” as shown in FIG. Transfers interest packets requesting / 10 ". FIG. 6 shows the updated PIT. In FIG. 7, the entries “/ a / b / c / d / name 1/9” and “/ a / b / c / d / name 1/10” are duplicated. Can be merged.

  In the present embodiment, as in the CS search process, when an object having no entry is found in the PIT search process, the subsequent PIT search process is stopped. Therefore, it is possible to suppress the search process for an object that is highly likely not to have an entry in the PIT, thereby reducing the processing load of the transfer apparatus 2. In the present embodiment, when a predetermined number of objects having no entry reaches a predetermined number, the PIT search process after that is stopped, or when a predetermined number of objects having no entry continue, the subsequent PIT search process is performed. It can be set as the structure to cancel.

  FIG. 8 is a configuration diagram of the transfer device 2 according to the present embodiment. The holding unit 21 holds CS, PIT, and FIB. Furthermore, the holding unit 21 holds a part of the object transferred in the past. The interface unit 23 includes a plurality of interfaces. The processing unit 22 performs the above-described CS and PIT search processing, and transmits an object to the client device 1 and transfers an interest packet.

  The transfer device 2 according to the present invention can be realized by a program that causes a computer to operate as the transfer device 2. These computer programs can be stored in a computer-readable storage medium or distributed via a network.

  21: Holding unit, 22: Processing unit, 23: Interface unit

Claims (9)

A transfer device of a content distribution network that distributes content into one or more objects and distributes the content,
Holding means for holding the object;
Processing means that, upon receiving a request packet requesting a plurality of objects, performs first search processing for determining whether or not the plurality of objects are held by the holding means in order according to the search order of the plurality of objects. When,
With
The transfer device, wherein the processing means ends the first search process when the number of objects determined not to be held by the holding means among the plurality of objects reaches a first predetermined number.   The transfer device according to claim 1, wherein the processing unit transmits an object determined to be held in the holding unit to a transmission source device of the request packet. The holding means holds reception waiting information indicating an object waiting for reception;
The processing means receives the reception of each of the plurality of objects that are determined not to be held by the holding means and the objects that are not determined to be held by the holding means. 3. The transfer apparatus according to claim 1, wherein it is determined whether or not waiting for reception based on the waiting information, and a request packet for requesting an object determined not to be waiting for reception is transferred. The holding means holds reception waiting information indicating an object waiting for reception;
The processing unit is waiting to receive an object that is determined not to be held by the holding unit and an object that has not been determined to be held by the holding unit among the plurality of objects. A second search process for determining whether or not the data is waiting for reception according to the search order, and the second search process is terminated when the number of objects determined not to be waiting for reception reaches a second predetermined number. The transfer apparatus according to claim 1 or 2, wherein   Upon completion of the second search process, the processing means transfers a request packet requesting an object that is determined not to be waiting for reception and an object that has not been determined whether or not waiting for reception. The transfer device according to claim 4.   The transfer device according to claim 1, wherein the search order corresponds to a time order of the plurality of objects in content corresponding to the plurality of objects.   The transfer device according to claim 1, wherein the search order corresponds to an order of storage positions in the request packet of information indicating the plurality of objects.   The transfer apparatus according to claim 1, wherein the first predetermined number is one.   A program that causes a computer to function as the transfer device according to claim 1.

Images