JP6516692B2 - Transfer device and program for content distribution network - Google Patents

Description

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

  There has been proposed a network that delivers content based on a name indicating the content. Patent Document 1 and Non-Patent Document 1 disclose Content Centric Networking (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 the client device acquires the content in units of the divided objects. Also, in the CCN, the communication device (hereinafter referred to as a transfer device) that has transferred the object can save the object. When the transfer device receives an interest packet (request packet) for requesting an object held by the own device from the client device, the transfer device holds the interest packet without transferring the interest packet to the server device. The object can be sent to the client device that sent the interest packet.

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

  When the transfer device receives an interest packet, it searches for CS and determines whether the interest packet holds the requested object. If it is held, the object held by the own device is transmitted to the client device of the transmission source of the interest packet. On the other hand, when the received interest packet does not hold the requested object, the PIT is searched, and the interest packet requesting the same object as the interest packet is already forwarded, and the reception of the object is awaited. Determine if it is a state. In the state of waiting for reception, the PIT is updated so as to associate the reception interface of the interest packet with the object requested by the interest packet without transferring the received interest packet. On the other hand, if the received interest packet is not waiting to receive the requested object, the interest packet is transferred from the interface determined based on the FIB, and the PIT is updated. Also, when receiving the object, the transfer device determines the transfer destination interface of the object based on PIT, and deletes the information on the object from PIT. Also, the transfer device updates the CS upon saving the received and transferred object.

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

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

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 includes holding means for holding an object and reception waiting information indicating an object waiting for reception . A processing unit that performs first search processing for determining whether or not the plurality of objects are held by the holding unit in accordance with the search order of the plurality of objects when receiving a request packet that requests a plurality of objects And the processing means ends the first search process when the number of objects among the plurality of objects determined not to be held by the holding means becomes a first predetermined number , Among the plurality of objects, an object determined not to be held by the holding means and the holding means The second search process of determining whether or not the object is not held is determined based on the reception waiting information for the object for which the determination of whether or not the object is not held is performed in order according to the search order. The second search process may end when the number of objects determined reaches a second predetermined number .

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

FIG. 1 is a block diagram of a content distribution network according to one embodiment. FIG. 5 is a diagram illustrating an interest packet received by a transfer device in one embodiment. 10 is a flowchart of CS search processing in the transfer device according to one embodiment. FIG. 4 is a diagram illustrating an interest packet transferred by a transfer device in one embodiment. FIG. 7 shows a PIT of a transfer device according to one embodiment. FIG. 7 shows a PIT of a transfer device according to one embodiment. FIG. 4 is a diagram illustrating an interest packet transferred by a transfer device 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 the description of the embodiment will be omitted from the drawings. Also, the following embodiments are exemplifications, and the present invention is not limited to the contents of the embodiments.

First Embodiment
FIG. 1 is a block diagram of a content delivery system according to the present embodiment. Connected to a content distribution network configured of a plurality of transfer devices 2 are a server device 3 for publishing content and a client device 1 for acquiring content. Here, when acquiring the content, the client apparatus 1 transmits a request packet (hereinafter, interest packet) including the object name to be acquired. Conventionally, the client device 1 transmits only one object name in one interest packet. Therefore, 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 device 1 can include, in one interest packet, a plurality of object names having a common prefix in the object name. For example, content whose content name is "/ a / b / c / d / name1" is divided into 10 objects, and object names of those objects are "/ a / b / c / d / name1 /". It is assumed to be 1 "to" / a / b / c / d / name1 / 10 ". In this case, the client device 1 transmits an interest packet including ten object names of "/ a / b / c / d / name1 / 1" to "/ a / b / c / d / name1 / 10" can do. Note that, usually, the object number (the last number of the object name) corresponds to the time sequence of the object. 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 the present embodiment includes a common name field and an object name field. As shown in FIG. 2, in the common name field, the longest name of the common prefix of the object names of the objects to be acquired (10 in this example) is set. Further, in the object name field, parts (hereinafter referred to as individual names) excluding the common name field of the object name of the object to be acquired are listed.

  Further, in the present embodiment, a search order is set for a plurality of objects in the object name field. In this example, the order of storage positions of the 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 referred to simply as the first object), and "/ a / b / c / d / name1" "/ 10" is the 10th, the last object. Usually, the client device 1 arranges the individual names in the object name field in the order of object time, so that the search order also corresponds to the object time order. If the order of the 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.

  Subsequently, a CS search process performed by the transfer device 2 which has received the interest packet shown in FIG. 2 will be described with reference to FIG. The transfer device 2 initializes the index i indicating the search order to 1 in S10. Then, in S11, the transfer device 2 determines whether or not the i-th object is held by searching CS. If it is held, the transfer device 2 transmits the i-th object to the client device 1 that is the source of the interest packet at S12. Thereafter, in S13, the transfer device 2 determines whether it is the last object in the object name field of the interest packet, and 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 the object is the last object in S13, the transfer device 2 ends the processing. 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 forwarded to other devices.

  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 objects are held. Start PIT search processing. The search process of PIT in this embodiment is the same as that of the prior art. Therefore, if the transfer device 2 does not hold the i-th and subsequent objects, the transfer device 2 determines whether or not there is an entry in the PIT for each of the i-th and subsequent objects. Forward interest packets that contain missing objects. In addition, for objects having an entry in the PIT among the i-th and subsequent objects, the PIT is updated so that the interface that has 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" It is assumed that / d / name1 / 3 "is not held. Further, it is assumed that there is no entry in 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" in the second S12. / Name1 / 2 "is sent to the client device 1. However, since the transfer device 2 does not hold “/ a / b / c / d / name1 / 3”, the third determination in S11 is “No”. Also, since there is no entry in the PIT, the transfer device 2 is shown in FIG. 4 as “/ a / b / c / d / name1 / 3” to “/ a / b / c / d / name1 / 10” Forward an interest packet that requires 8 objects. The transfer destination is determined based on the common name field and FIB.

  Usually, the client device 1 acquires a plurality of objects belonging to one content in order of time. Therefore, although it is highly likely that objects with the same content close in time are held in the same transfer device 2, different content or objects that are separated in time but the same content are held in the same transfer device 2 It is less likely to have been. For example, in the above example, it is unlikely that the transfer device 2 not holding "/ a / b / c / d / name1 / 3" holds the subsequent objects. Therefore, in the present embodiment, when an object not held is found, the CS search processing for the subsequent objects is stopped. As a result, it is possible to reduce the time for searching for content that is not held, and thus to reduce the processing load of the transfer device 2.

  In the process of FIG. 3, although the transmission of the held content to the client apparatus 1 was executed each time, the transmission of the object is not performed until the object which is not held is found. If no object is found, it may be in the form of collectively sending the object up to that point and transmitting it to the client device 1. Further, in the present embodiment, the configuration is such that the CS search processing is ended immediately when even one object not held is found, but the CS search processing is ended when a predetermined number of objects not held are found. It can also be done. Furthermore, the configuration may be such that the search processing of the CS ends when a predetermined number of non-held objects continue. Also, in the present embodiment, although the client device 1 acquires all objects of one content in one interest packet, it requests all objects of one content, and a plurality of objects each. It may be configured to be acquired by a plurality of interest packets.

Second Embodiment
Subsequently, the difference between the present embodiment and the first embodiment will be mainly described. First, CS search processing in the present embodiment is the same as in the first embodiment. That is, it follows the flow chart of FIG. Furthermore, in this embodiment, the PIT search process is the same as the CS search process. That is, for the remaining objects after the end of the CS search processing, PIT search is performed according to the search order. Then, when an object without an entry is found, the PIT search processing for the subsequent objects is stopped, and interest packets including the subsequent objects are transferred.

  For example, as in the first embodiment, it is assumed that the transfer device 2 receives an interest packet shown in FIG. 2 at interface # 3 (IF # 3), and the PIT at that time is that shown in FIG. Furthermore, 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” is a PIT search target. And PIT has the entries "/ a / b / c / d / name1 / 3" and "/ a / b / c / d / name1 / 4", but "/ a / b / c / Since there is no entry of d / name1 / 5 ", as shown in FIG. 7, the transfer device 2" / a / b / c / d / name1 / 5 "to" / a / b / c / d / name1 ". Forward interest packet requesting "10". FIG. 6 shows the updated PIT. In FIG. 7, the entries of "/ a / b / c / d / name1 / 9" and "/ a / b / c / d / name1 / 10" are duplicated, but this is a process after that Can be merged.

  In this embodiment, similarly to the CS search process, when an object without an entry is found in the PIT search process, the subsequent PIT search process is canceled. Therefore, it is possible to suppress the processing of searching for an object having a high possibility that there is no entry in the PIT, thereby suppressing the processing load of the transfer device 2. Also in the present embodiment, when the number of objects having no entry reaches a predetermined number, the search processing of the PIT after that is canceled, or if the number of objects having no entry continues a predetermined number, the search processing of the PIT thereafter is performed. It can be configured to cancel.

  FIG. 8 is a block diagram of the transfer device 2 according to the present embodiment. The holding unit 21 holds CS, PIT, and FIB. Further, 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 search processing of CS and PIT, and performs transmission of an object to the client device 1 and transfer of an interest packet.

  Furthermore, 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 are stored in a computer readable storage medium or can be distributed via a network.

  21: holding unit, 22: processing unit, 23: interface unit

Claims (7)

A transfer device of a content distribution network that divides content into one or more objects and distributes the content.
Holding means for holding an object and reception waiting information indicating an object waiting for reception ;
A processing unit that performs first search processing for determining whether or not the plurality of objects are held by the holding unit in accordance with the search order of the plurality of objects when receiving a request packet that requests a plurality of objects When,
Equipped with
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, and among the plurality of objects, Based on the reception waiting information, it is determined whether the object determined not to be held by the holding unit and the object for which the determination as to whether or not the holding unit is held is not received Performing a second search process in order according to the search order, and terminating the second search process when the number of objects determined not to be waiting for reception reaches a second predetermined number .   2. The transfer apparatus according to claim 1, wherein the processing means transmits the object determined to be held in the holding means to a device as a transmission source of the request packet. The processing means, when finishing the second search process, transfers a request packet for requesting an object determined not to be waiting for reception and an object for which it is not determined whether or not waiting for reception. The transfer apparatus according to claim 1 or 2 . The transfer apparatus according to any one of claims 1 to 3 , wherein the search order corresponds to the time order of the plurality of objects in the content corresponding to the plurality of objects. The transfer apparatus according to any one of claims 1 to 3 , wherein the search order corresponds to the order of storage positions in the request packet of the information indicating the plurality of objects. The transfer apparatus according to any one of claims 1 to 5 , wherein the first predetermined number is one. A program that causes a computer to function as the transfer device according to any one of claims 1 to 6 .

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