JP2016220102A - Communication device and packet relay method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the latency of packet transfer to thereby improve a communication network throughput.SOLUTION: A communication device 10 includes: a storage unit 12 which stores a reference table including a plurality of route entries for each destination node, with set validity periods; and a control unit 11 which, when relaying a packet destined to another station to an adjacent node, updates the validity periods for first to fourth entries defined below, corresponding to the destination and the transmission source of the packet. The storage unit 12 individually stores the second and the fourth entries in order that a search of the reference table becomes unnecessary. As to the second and the fourth entries, the control unit 11 updates the validity periods of the second and the fourth entries without searching the reference table.SELECTED DRAWING: Figure 2

Description

The present invention relates to a communication device and a packet relay method.
Specifically, the present invention relates to a technique for reducing packet transfer latency in a communication device used for a communication node that autonomously performs path control in a communication network.

As a communication network in which each communication node autonomously searches for a route, there is a communication network of a distance vector type routing protocol. The distance vector type routing protocol is an algorithm for determining a suitable route based on distance (distance) and vector (direction).
For example, AODV (Adhoc ON-Demand Distance Vector) is a typical example of a distance vector type routing protocol.

In AODV, each communication node holds a route entry for each destination node, and each communication node determines information to be written in its own route entry when receiving a route request (RREQ) and a route response (RREP). As a result, a path between predetermined communication nodes is established.
The route entry for each destination node held by each communication node includes a lifetime (Lifetime) that is updated to a predetermined setting value (recommended is 3 seconds) each time the route entry is used. (See Non-Patent Document 1).

RFC3561 2. Overview

In a conventional communication apparatus that implements AODV, when a packet addressed to another station is received, the valid period of the route entry is updated before the packet is transmitted, and the packet is transmitted after the update is completed. .
The reason is considered that if a packet is not relayed within the effective period of the route entry, the route entry becomes invalid and a new route search is required, so priority is given to securing the effective period of the route entry.

However, in the relay process including the update of the effective period between the reception and transmission of the packet, the packet transfer latency increases by the amount including the update of the effective period.
In particular, in the conventional communication device, the forward route corresponding to the packet destination and the next hop thereof, and the four route entries of the reverse route corresponding to the packet source and the next hop thereof are searched from the reference table, respectively. Since the effective period of the route entry is updated, the processing load for searching for the route entry is large.

  As a result, the processing time required for updating the valid period also becomes long, so that the throughput of data communication is lowered, and there is a problem that the communication speed of the entire network is deteriorated. This problem becomes more prominent as the number of communication nodes included in the communication network increases.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a communication apparatus and the like that can improve the throughput of a communication network by reducing packet transfer latency.

  (1) A communication apparatus according to an aspect of the present invention is a communication apparatus used for the communication node, which is located in the middle of a communication path in which communication nodes that autonomously perform path control in a communication network are arranged in series, A storage unit that stores a reference table including a plurality of route entries for each destination node for which a valid period is set, and when relaying a packet addressed to another station to an adjacent node, the following corresponding to the destination and source of the packet: A control unit that updates the validity period of each of the first to fourth entries defined in the first and fourth entries, and the storage unit includes the second and fourth entries so that a search for the reference table is not required. And the control unit does not search the reference table for the second and fourth entries, and the valid of the second and fourth entries. To update between.

First entry: Route entry of the forward route corresponding to the destination of the packet Second entry: Route entry of the next hop of the forward route corresponding to the destination of the packet Third entry: Route entry of the reverse route corresponding to the source of the packet 4 entries: Route entry of the next hop of the reverse route corresponding to the packet source

  (3) In the relay method according to one aspect of the present invention, a packet transmitted by a communication device used for the communication node located in the middle of a communication path in which communication nodes that autonomously perform path control in the communication network are arranged in series. In the relay method, a first step of storing a reference table including a plurality of route entries for each destination node for which a valid period is set; and when a packet addressed to another station is relayed to an adjacent node, the destination of the packet And a second step of updating the validity period of the first to fourth entries defined above corresponding to the transmission source, respectively, so that the search for the reference table is not required in the first step , Including the process of storing the second and fourth entries individually, and the second step includes a step of referring to the reference table for the second and fourth entries. Without search that includes a process of updating the validity period of the second and fourth entry.

  According to the present invention, it is possible to improve the throughput of a communication network by reducing packet transfer latency.

It is a figure which shows the connection form of the communication system which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of a communication apparatus. It is a block diagram which shows the internal structure of the control part of a communication apparatus. It is explanatory drawing which shows the memory structure of the conventional path | route entry. It is a flowchart which shows the update process of the conventional effective period. It is explanatory drawing which shows the forward path | route of an intermediate | middle communication node, a reverse path | route, the next hop of a forward path | route, and the next hop of a reverse path | route in the communication path | route where a some communication node is arranged in series. It is explanatory drawing which shows the memory structure of the path entry of this embodiment. It is a flowchart which shows the update process of the effective period of this embodiment. It is explanatory drawing which shows the modification of the memory structure of a path entry.

<Outline of Embodiment of the Present Invention>
Hereinafter, an outline of embodiments of the present invention will be listed and described.
(1) The communication device according to the present embodiment is a communication device used for the communication node, which is located in the middle of a communication path in which communication nodes that autonomously perform path control in a communication network are arranged in series, and has an effective period. A storage unit that stores a reference table including a plurality of route entries for each set destination node, and when relaying a packet addressed to another station to an adjacent node, the following is defined corresponding to the destination and source of the packet A control unit that updates the validity period of each of the first to fourth entries.

In the communication apparatus according to the present embodiment, the storage unit stores the second and fourth entries individually so that a search for the reference table is not required, and the control unit For the fourth entry and the fourth entry, the validity period of the second and fourth entries is updated without searching the reference table.
First entry: Route entry of the forward route corresponding to the destination of the packet Second entry: Route entry of the next hop of the forward route corresponding to the destination of the packet Third entry: Route entry of the reverse route corresponding to the source of the packet 4 entries: Route entry of the next hop of the reverse route corresponding to the packet source

According to the communication device of the present embodiment, the control unit updates the validity period of the second and fourth entries without performing a search on the reference table for the second and fourth entries. Compared with the conventional relay processing that searches all the fourth entries, the processing time for updating the valid period can be reduced by the amount that the second and fourth entries need not be searched.
For this reason, by employing the above communication device as a communication node, the packet transfer latency of the communication node is reduced and the throughput of the communication network is improved.

  (2) In the communication device of the present embodiment, the communication network includes one parent station and a plurality of child stations, and when relaying the packet for communication between the parent station and the child station, The storage unit individually stores a master station entry that is the route entry of the master station so that the destination node does not need to search the reference table. Regarding the first or third entry corresponding to the master station entry among the three entries, it is preferable that the validity period of the first or third entry is updated without performing a search on the reference table.

According to the communication apparatus of the present embodiment, the control unit does not search the reference table for the first or third entry corresponding to the master station entry among the first and third entries, and performs the first or third entry. Since the validity period of the third entry is updated, the validity period is updated by an amount that does not require the search for either the first or third entry, as compared with the conventional relay process that searches all the first to fourth entries. The processing time for can be reduced.
For this reason, by employing the above communication device as a communication node, the packet transfer latency of the communication node is reduced and the throughput of the communication network is improved.

  (3) The relay method of the present embodiment is a packet relay method performed by a communication device used for the communication node, which is located in the middle of a communication path in which communication nodes that autonomously perform path control in the communication network are arranged in series. A first step of storing a reference table including a plurality of route entries for each destination node for which a validity period is set; and when relaying a packet addressed to another station to an adjacent node, the destination and source of the packet A second step of updating each of the valid periods of the first to fourth entries defined above corresponding to.

  In the relay method of the present embodiment, the first step includes a process of storing the second and fourth entries individually so that a search for the reference table is not required, and the second step Includes a process for updating the validity period of the second and fourth entries without searching the reference table for the second and fourth entries.

According to the relay method of the present embodiment, the second step includes processing for updating the validity period of the second and fourth entries without searching the reference table for the second and fourth entries. Therefore, the processing time for updating the validity period can be reduced by the amount that the search for the second and fourth entries is unnecessary.
For this reason, by employing the above communication device as a communication node, the packet transfer latency of the communication node is reduced and the throughput of the communication network is improved.

<Details of Embodiment of the Present Invention>
Hereinafter, details of embodiments of the present invention will be described with reference to the drawings. In addition, you may combine arbitrarily at least one part of embodiment described below.
A PDU (Protocol Data Unit) used in layer 2 communication is often referred to as a “frame”, and a PDU used in layer 3 communication is often referred to as a “packet”. However, in the following description, “packet” and “frame” "Is used in the meaning of PDU.

[Connection form of communication system]
FIG. 1 is a diagram showing a connection form of a communication system according to an embodiment of the present invention.
As shown in FIG. 1, the communication system of the present embodiment includes a communication network NW including a plurality of communication nodes N0 to N6, and a management device 4 that communicates with one communication node N0 via a higher level network 3. Yes.

In the following description, when common items of the communication nodes N0 to N6 are described, “N” is used as a representative code of the communication nodes N0 to N6.
In the communication network NW of FIG. 1, each communication node N is connected to one or a plurality of adjacent nodes via a transmission path 5 so as to be communicable. The communication medium constituting the transmission path 5 may be a transmission line such as a one-core or two-core optical fiber or a metal line, or may be a wireless communication path using a wireless LAN or the like.

In the communication network NW of FIG. 1, the communication node N0 is the master station 1, and the communication nodes N1 to N6 are the slave stations 2. The communication nodes N1 to N6 of the slave station 2 have a ring topology (N1 → N2 → N3 → N6 → N5 → N4 → N1).
Further, one communication node N6 in the ring is connected to the communication node N0 of the master station 1 by the transmission path 5. Therefore, for example, the path from the communication node N1 to the communication node N0 can be made redundant into two paths of N1->N2->N3->N6-> N0 and N1->N4->N5->N6-> N0.

The communication node N0 of the master station 1 is communicably connected to an upper network 3 such as the Internet. The terminal device 6 is connected to the communication nodes N1 to N6 of the slave station 2 so that they can communicate with each other.
In FIG. 1, for simplification of illustration, only one slave station 2 (communication node N3) is connected to the terminal device 6, but in practice, all the slave stations 2 (communication nodes N1 to N6) are connected. Are communicably connected to the terminal device 6.

The management device 4 includes a computer device capable of IP communication such as a server computer or a personal computer. The management device 4 can communicate with a predetermined terminal device 6 by IP communication via the upper network 3 and the master station 1 and communication within the communication network NW.
The terminal device 6 includes a computer device capable of IP communication such as a personal computer. The terminal device 6 can communicate with the management device 4 by communication within the communication network NW and IP communication via the master station 1 and the upper network 3.

[Usage form of communication system]
The usage forms of the communication network NW in FIG.
Use form 1: Remote control for a plurality of power distribution devices such as high-voltage switches managed by an electric power company, and remote sensing for the power distribution equipment Use form 2: Remote control for a plurality of manufacturing machines installed in a factory, and production thereof Remote sensing for machines Usage 3: Remote monitoring of in-house computer equipment and shared equipment connected to this equipment

In the usage mode 1, the terminal device 6 functions as a control command relay device for the management device 4 to remotely control the operation of a power distribution device (not shown).
For example, when controlling a power distribution device connected to the terminal device 6 of the communication node N1, the management device 4 transmits a downlink frame including a control command for the power distribution device to the terminal device 6 of the communication node N1. . The terminal device 6 controls the operation of the power distribution device according to the control command included in the received downlink frame.

In the usage mode 1, the terminal device 6 functions as a relay device for transmitting sensing information related to power distribution equipment to the management device 4.
For example, when collecting sensing information of a power distribution device connected to the terminal device 6 of the communication node N1, the terminal device 6 transmits an upstream frame including sensing information measured by various sensors (such as a voltmeter) of the power distribution device. It transmits to the management apparatus 4. The management device 4 totals the sensing information included in the received upstream frame.

Similarly, in the usage mode 2, the terminal device 6 functions as a control command relay device for the management device 4 to remotely control the operation of the manufacturing machine (not shown).
For example, when controlling a manufacturing machine connected to the terminal device 6 of the communication node N1, the management device 4 transmits a downlink frame including a control command for the manufacturing machine to the terminal device 6 of the communication node N1. . The terminal device 6 controls the operation of the manufacturing machine according to the control command included in the received downstream frame.

In the usage mode 2, the terminal device 6 functions as a relay device for transmitting sensing information related to the manufacturing machine to the management device 4.
For example, when collecting sensing information of a manufacturing machine connected to the terminal device 6 of the communication node N1, the terminal device 6 transmits an upstream frame including sensing information measured by various sensors (for example, a speedometer) of the manufacturing machine. It transmits to the management apparatus 4. The management device 4 totals the sensing information included in the received upstream frame.

In usage mode 3, the terminal device 6 is composed of a personal computer such as a desktop personal computer or a notebook personal computer used by employees in the company.
The shared device is communicably connected to a personal computer and includes an OA device such as a printer, a copier, or a facsimile that is used with the computer.

For example, paying attention to the terminal device 6 of the communication node N1, the terminal device 6 displays information on the operation contents when there is a terminal operation (for example, Internet access to an unauthorized homepage) that violates a predetermined in-house rule. The included upstream frame is transmitted to the management apparatus 4.
Further, when paying attention to the shared device of the terminal device 6 of the communication node N1, the terminal device 6 has the operation contents when the operation of the shared device violates a predetermined internal rule (for example, printing of a predetermined number of sheets or more). An uplink frame including information is transmitted to the management apparatus 4.

As described above, the communication network NW according to the present embodiment is used as a communication network for an administrator who operates the management apparatus 4 to remotely monitor target devices (such as power distribution equipment and manufacturing machines) corresponding to each communication node N. can do.
In this case, the communication node N is installed close to the target device, and the topology becomes complicated as the number of target devices increases. For this reason, the topology of the communication network NW is not limited to the simple ring shape shown in FIG. 1, but may be a complex topology such as a form including a plurality of rings or a tree shape or a mesh shape.

Of the communication frames relayed by the communication node N, the data included in the upstream frame addressed to the management apparatus 4 is referred to as “monitoring data”. The monitoring data includes “sensing information” relating to the above-described power distribution equipment and manufacturing machines, “information indicating operation contents” for personal computers and shared devices, and the like.
Further, in the communication system of FIG. 1, a connection form in which one communication node N is associated with a plurality of terminal devices 6, or a connection form in which a plurality of power distribution facilities or manufacturing machines are associated with one terminal device 6. It may be.

[Configuration of communication device]
FIG. 2 is a block diagram illustrating an internal configuration of the communication device 10. The communication device 10 of FIG. 2 can be employed for all or part of the communication nodes N of the communication network NW of FIG.
As illustrated in FIG. 2, the communication device 10 according to the present embodiment includes a control unit 11, a storage unit 12, a communication unit 13, a power supply unit 14, and a clock unit 15. The storage unit 12 includes a nonvolatile memory 16 and a volatile memory 17.

The control unit 11 includes a CPU (Central Processing Unit). The control unit 11 is connected to the communication unit 13 and the memories 16 and 17 via the internal bus 18. The control unit 11 comprehensively controls each unit of the communication node N.
The nonvolatile memory 16 includes, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), a USB (Universal Serial Bus) memory, an SD memory card, and the like. The volatile memory 17 is composed of, for example, a DRAM (Dynamic Random Access Memory), an SRAM (Static Random Access Memory), or the like.

In the nonvolatile memory 16, a boot loader program, an OS (Operating System) program, an application program, and the like are installed. The application program includes a communication control program.
The volatile memory 17 stores a communication control program read from the nonvolatile memory 16 by the control unit 11 and is used as a working memory for the program.

The communication unit 13 is a communication interface having a communication function according to the path control protocol in the communication network NW and a communication function according to the communication protocol with the terminal device 6.
The control unit 11 executes communication control for the communication unit 13 in accordance with a communication control program stored in the volatile memory 17. The communication unit 13 transmits and receives IP packets (hereinafter simply referred to as “packets”) to and from adjacent nodes in accordance with instructions from the control unit 11.

For example, the control unit 11 performs packet transmission / reception with an adjacent node belonging to the communication network NW in accordance with a predetermined path control protocol (AODV, DYMO, etc.) adopted in the communication network NW. Specifically, the communication path is established and the packet is transferred using the established path.
In addition, the control unit 11 performs transmission / reception of a communication frame with the terminal device 6 according to a predetermined communication protocol adopted with the terminal device 6.

The power supply unit 14 includes an AC / DC converter therein. The power supply unit 14 converts an external power source composed of a commercial power source (for example, 100 V AC) into a predetermined DC voltage, and supplies the converted DC voltage to each unit in the communication node N.
The clock unit 15 includes a clock circuit that independently counts the local time. The clock unit 15 is operated by a standby power source (not shown) such as a coin-type lithium battery without receiving power supply from the power supply unit 14, and the local time is It is always output to the control unit 11.

[Communication node routing protocol]
The communication node N configuring the communication network NW relays the packet received from the adjacent node according to a predetermined route control protocol, and transfers the packet in the “bucket relay system” within the communication network NW.
Specifically, the communication network NW of the present embodiment employs a distance vector type routing protocol in which each communication node N searches for a route after a route request is generated.

Examples of the routing protocol include AODV (Adhoc ON-Demand Distance Vector) and DYMO (Dynamic MANET On-Demand). In this embodiment, AODV is assumed.
In AODV, all the communication nodes N (communication nodes N0 to N6 in FIG. 1) hold a “routing table (route table)” and use the routing table of their own node without including route information in the packet. Route control.

That is, AODV is an autonomous route control protocol, and is assumed to be a dynamic network in which the disappearance and appearance of the communication node N occur relatively frequently. Accordingly, the network path is not permanent, and a specific link is broken due to various failures, or a new communication node N appears and a new link appears.
In order to follow such a change in the network and each communication node autonomously establishes a route, a “route entry” having the following contents is defined for each end point (destination) in the routing table.

(Contents of route entry)
“Destination IP Address”: Destination IP Address
"Destination Sequence Number": Destination Sequence Number
“Destination Sequence Number Valid Flag”: Valid Destination Sequence Number flag
"Other flags": Other state and routing flags
(eg, valid, invalid, repairable, being repaired)

"Network Interface": Network Interface
“Hop Count”: Hop Count (number of hops needed to reach destination)
"Next Hop": Next Hop
"Precursor list": List of Precursors
“Validity Period”: Lifetime (expiration or deletion time of the route)

The “end point sequence number” is an index for indicating the newness of the route. A larger end point sequence number indicates a new route. Control message loops are prevented by not using the old sequence number path.
Further, when a path change such as a link disconnection occurs, the corresponding end point sequence number is incremented and diffused throughout the network by RERR. This notifies that a new change has occurred in the route of the network and prompts to invalidate the route.

The “valid period” represents a period during which the route entry is valid. The recommended value of the valid period is, for example, 3 seconds in AODV. The valid period is updated every time the route entry is used, and the route entry that is not used beyond the valid period from the last data communication becomes invalid.
Therefore, once the route entry becomes invalid because the valid period has been exceeded, the route entry cannot be used for packet relay unless the route entry is validated again by a new RREQ.

In AODV, the following five types are defined as route control messages. The communication node N exchanges these messages to maintain the route in an optimal state.
RREQ (Route Request) message RREP (Route Reply) message RERR (Route Error) message RREP-ACK (Route Reply Acknowledgment) message HELLO message

RREQ is a control message that is flooded when the source node requests a route search. RREP is a control message that the destination node transmits in unicast to the source node in response to RREQ. RERR is a control message that an intermediate node that has detected a link break notifies the source node.
RREP-ACK is a control message used for one-way link detection. HELLO is a control message for checking the survival status of adjacent nodes.

For example, in the communication network NW of FIG. 1, it is assumed that the communication node N3 makes a route request for route search with the communication node N5.
In this case, the source communication node N3 floods RREQ with the communication node N5 as the destination address. The communication nodes N2, N1, N4, and N6 that have received the RREQ also flood the same RREQ. As a result, the RREQ arrives at the communication node N5 through the clockwise and counterclockwise routes.

Each communication node N generates a reverse path (hereinafter referred to as “reverse path”) with respect to the transmission source address (IP address of the communication node N3) when transferring the RREQ.
The communication node N5 set as the destination returns a RREP addressed to the communication node N3 by unicast to the first RREQ (in the example of FIG. 1, RREQ relayed in the order of N3 → N6 → N5). The RREP is delivered to the communication node N3 that is the transmission source through the reverse path generated when the RREQ is transferred.

Each communication node N generates a forward path (hereinafter referred to as “forward path”) for the destination address when transferring the RREP. Thereby, a bidirectional path between the communication node N3 and the communication node N5 is established.
Thus, when the communication path between the communication node N3 and the communication node N5 is established, the communication node N3 starts transmitting data packets to the communication node N5.

[Configuration of communication device controller]
FIG. 3 is a block diagram showing an internal configuration of the control unit 11 of the communication apparatus 10 that can be employed as the communication node N of the communication network NW that conforms to AODV.
Assuming the above-described usage modes 1 to 3 regarding the communication network NW of the present embodiment, the more communication devices necessary for the communication network NW exist, the more terminal devices 6 are collection targets of sensing information and information indicating operation contents. The number of N increases.

Therefore, it is preferable that the communication device 10 employed in the communication node N can operate with low power consumption and can be manufactured at low cost in both hardware and software.
Therefore, in the communication apparatus 10 of the present embodiment, it is preferable to employ a control unit 11 composed of a single core CPU, for example, a real-time OS in which the control unit 11 executes a plurality of processes preemptively. In this case, the control unit 11 executes an application program capable of executing AODV communication control incorporated in the real-time OS.

However, the control unit 11 including a multi-core CPU may be employed, and a plurality of CPUs of the control unit 11 may execute a plurality of processes in parallel.
The CPU of the control unit 11 may have a built-in memory (not shown) such as a cache or a TCM (Tightly Coupled Memory) that can access the volatile memory 17 at a higher speed. Good.

As illustrated in FIG. 3, the control unit 11 includes a header determination unit 21, a protocol determination unit 22, an entry determination unit 23, and an AODV processing unit as functional units realized by executing an application program for AODV communication control. 24.
The AODV processing unit 24 is subdivided into a message processing unit 25, a packet relay unit 26, and a route search unit 27 as its internal functional units. Note that reference numeral 28 in FIG. 3 denotes a “search waiting queue” included in the volatile memory 17.

Packets received by the communication unit 13 or packets in the search waiting queue 28 are sequentially input to the header determination unit 21. The header determination unit 21 determines whether the packet is addressed to the own station or another station from the IP header of the input packet.
The header determination unit 21 sends a packet whose determination result is addressed to its own station to the protocol determination unit 22, and sends a packet whose determination result is addressed to another station to the entry determination unit 23.

The protocol determination unit 22 determines whether the packet is an AODV control message or another packet from the IP header of the input packet.
The protocol determination unit 22 sends a packet that is a control message having a determination result of AODV to the message processing unit 25 of the AODV processing unit 24. The protocol determination unit 22 sends a packet whose determination result is other (for example, a data packet addressed to the own station) to the general-purpose processing unit 29 that performs processing such as communication control with the management device 4 or the terminal device 6.

The entry determination unit 23 determines from the destination information in the IP header of the input packet whether the destination route entry is valid, invalid, or no entry.
The entry determination unit 23 sends a packet whose determination result is valid to the packet relay unit 26 of the AODV processing unit 24. The entry determination unit 23 sends a packet whose determination result is invalid or no entry to the route search unit 27 of the AODV processing unit 24.

The message processing unit 25 performs a predetermined process corresponding to the type of the control message of the packet on the input packet (AODV control message addressed to the own station).
For example, when the input control message is RREQ, the message processing unit 25 generates a reverse path for the transmission source. Further, the message processing unit 25 compares the RREQ information and the information held by itself with respect to the route information such as the sequence number and the hop count number, and updates the own route information when the RREQ information is newer. .

  If the input control message is RREP, the message processing unit 25 generates a forward path for the destination. Further, the message processing unit 25 compares the RREP information and the information held by itself with respect to the route information such as the sequence number and the hop count, and updates the route information when the RREP information is newer. .

The packet relay unit 26 performs packet relay processing on the input packet (a data packet addressed to another station and having a valid route entry or an AODV control message) based on the information of the corresponding route entry. .
Specifically, the relay processing performed by the packet relay unit 26 includes “packet transfer processing” and “validity period update processing”.

The packet forwarding process executed by the packet relay unit 26 controls the communication unit 13 to transmit the input packet addressed to the other station to the next-hop communication node N included in the currently valid route entry. It is processing to do.
The valid period update process executed by the packet relay unit 26 includes four paths (specifically, “forward path”, “reverse path”, “forward path The valid period of “next hop” and “next hop of reverse path”) is updated to a predetermined set value.

The route search unit 27 performs route search processing on the input packet (a data packet addressed to another station and the route entry is invalid or does not exist, or an AODV control message).
The route search process executed by the route search unit 27 includes a process of issuing an RREQ including a destination included in an input packet addressed to another station, a process of temporarily storing the issued RREQ in a search waiting queue, And processing for causing the communication unit 13 to transmit the issued RREQ.

[Conventional path entry memory configuration and period update processing]
FIG. 4 is an explanatory diagram showing a memory configuration of a conventional route entry.
As shown in FIG. 4, the conventional path entry memory configuration includes an entry table T <b> 1 that is a reference table assigned to a predetermined memory area of the volatile memory 17. The AODV processing unit 24 manages a plurality of route entries for each destination node using the entry table T1.

The entry table T1 includes a plurality of entry storage units #i (i = 1, 2, 3,... N) arranged in the row direction. Each entry storage unit #i is assigned a predetermined address Ai (i = 1, 2, 3... N).
Each entry storage unit #i describes information (hereinafter referred to as “entry information”) indicating the data contents of the route entry described above in the order of “destination”, “next hop”, “valid period”, and the like. For this purpose, a plurality of storage areas arranged in the column direction are provided.

The entry information in the entry storage unit #i is deleted from the entry storage unit #i when it is not used for a predetermined time exceeding the valid period. As a result, entry information corresponding to an old route that is not used is deleted from the entry table T1.
When the route search unit 27 finds a new route, it writes predetermined entry information in an empty entry storage unit #i or a newly generated entry storage unit #i. As a result, entry information corresponding to the newly discovered route is added to the entry table T1.

FIG. 5 is a flowchart showing a conventional valid period update process.
As shown in FIG. 5, conventional valid period update processing (hereinafter also simply referred to as “period update processing”) executed by the packet relay unit 26 includes “forward route update processing” and “next forward route”. Four update processes of “hop update process”, “reverse path update process”, and “reverse path next hop update process” are included.

When the packet relay unit 26 determines the relay destination (= packet transmission destination) from the received IP header of the packet addressed to the other station, the packet relay unit 26 executes the period update process shown in FIG. 5 before transmitting the packet to the relay destination.
That is, the packet relay unit 26 has a valid period for each of the forward route, the forward hop, the reverse route, and the reverse route hop corresponding to the source address and the destination address extracted from the IP header of the received packet. Update process is executed.

  Specifically, the packet relay unit 26 searches the entry table T1 in FIG. 4 for a route entry of the forward route corresponding to the destination address of the packet (step ST11), and determines the validity period of the hit route entry. The setting value is updated (step ST12). This is the forward route update process.

  The packet relay unit 26 searches for a route entry corresponding to the next hop included in the route entry of the forward route from the entry table T1 of FIG. 4 (step ST13), and sets the validity period of the hit route entry to the set value. (Step ST14). This is the update process for the next hop of the forward route.

  The packet relay unit 26 searches the entry table T1 in FIG. 4 for a reverse route entry corresponding to the packet source address (step ST15), and updates the valid period of the hit route entry to the set value. (Step ST16). This is the reverse path update process.

  The packet relay unit 26 searches the entry table T1 in FIG. 4 for a route entry corresponding to the next hop included in the route entry of the reverse route (step ST17), and sets the validity period of the hit route entry to the set value. (Step ST18). This is the update process for the next hop in the reverse path.

[Problems and solutions for period update processing]
As described above, when receiving a packet addressed to another station, the packet relay unit 26 updates the validity period of the route entry such as the forward route and the reverse route prior to transmission of the packet. Perform transmission.
The reason is that in the AODV communication standard, if a data packet is not relayed within the valid period of the route entry, the route entry becomes invalid and a new route search is required, so the valid period of the route entry is secured. This is thought to be due to the priority.

For this reason, in order to quickly transfer a packet addressed to another station, it is preferable to perform the period update process by the packet relay unit 26 in as short a time as possible.
However, in the conventional period update process of FIG. 5, all of “forward route”, “next hop of forward route”, “reverse route”, and “next hop of reverse route” are stored in the entry table T1. Which route entry is applicable is searched using the destination of the entry information as a key, and the valid period of the route entry hit by this search is updated.

As described above, in the conventional period update process, since all four route entries are searched, the process time of the period update process cannot be shortened. This is one of the causes for increasing the latency of the packet transfer process. It has become one.
As a result, for example, the throughput of session-type data communication is lowered, and there is a problem that the communication speed of the entire network may be deteriorated. This problem is significant in a communication network NW including a large number of communication nodes N as in the above-described usage modes 1 to 3.

  Therefore, in the communication device 10 according to the present embodiment, for example, in a communication network NW including a plurality of communication nodes N that autonomously performs route control in the network in accordance with AODV, the topology and communication adopted in the communication network NW. Considering the characteristics of the form, the search for the route entry at the time of relaying the packet can be omitted, and the processing time required for the period update process is reduced.

Specifically, for example, as illustrated in FIG. 6, a serial communication path in which a plurality (five in the illustrated example) of communication nodes Na to Ne are arranged in series is assumed.
A communication path including five communication nodes N1 to N5 included in the ring portion of the communication network NW in FIG. 1 also corresponds to a serial communication path. Therefore, the communication path in the serial form may be partially included in the communication network, or may be a path that forms part of a communication network having various topologies such as a tree, a star, and a mesh.

In the communication path of FIG. 6, it is assumed that the communication node Nc indicated by a double circle relays a data packet whose destination is the communication node Ne and whose transmission source is the communication node Na. In FIG. 6, “forward direction” means a direction in which a packet is transferred.
Since the communication node Nc is an intermediate node located in the middle of the serial communication path, the communication node Nc is connected only to the communication node Nd in the forward direction and is connected only to the communication node Nb in the reverse direction. Therefore, when the communication node Nc relays a forward packet, the next hop of the forward path is always the communication node Nd, and the next hop of the reverse path is always the communication node Nb.

Therefore, in the case of the communication node Nc located in the middle of the communication path in the serial form, there is no dynamic change in the next hop of the forward path and the next hop of the reverse path, and the path entry of the forward hop and the next hop of the reverse path Can be stored in a predetermined state.
For this reason, if the communication node Nc skips the search for the entry table T1 for each route entry of the next hop of the stored forward route and reverse route, the validity period is immediately updated to the set value. Useful for shortening the processing time of the period update process.

Next, it is assumed that a packet (for example, a packet including monitoring data) communicated between the master station 1 and the plurality of slave stations 2 is relayed.
In the following description, a route entry whose entry information destination is the IP address of the master station 1 is referred to as a “master station entry”, and a route entry whose entry information destination is not the IP address of the master station 1 is referred to as “children”. Station entry ".

Here, if the IP address of the master station 1 is fixed, a master station entry whose destination is the master station 1 can be stored in a state that is determined in advance for all the slave stations 2.
For this reason, if the communication node Nc omits the search for the entry table T1 for the stored master station entry and immediately replaces the valid period with the set value, it helps to shorten the processing time of the period update process. .

In FIG. 6, when the communication node Ne is the master station 1, the transmission destination address (DA) of the packet matches the IP address of the master station 1. Conversely, when the communication node Na is the master station 1, the source address (SA) of the packet matches the IP address of the master station 1.
Therefore, when the destination address (DA = Ne) of the packet matches the IP address of the master station 1, the communication node Nc does not search for the forward route entry (= parent station entry) and does not search for the reverse route. The route entry (= slave station entry) may be searched.

On the other hand, when the destination address (SA = Na) of the packet matches the IP address of the master station 1, the communication node Nc does not search for a route entry (= master station entry) in the reverse path, The route entry (= slave station entry) of the route may be searched.
As described above, for the forward route and the forward route entry, the search for the route entry in the direction corresponding to the master station entry may be omitted, and only the search for the route entry in the direction corresponding to the slave station entry may be executed.

[Memory configuration and period update processing of route entry according to this embodiment]
A specific example of the path entry memory configuration and the period update process according to the above-described solution will be described below. FIG. 7 is an explanatory diagram showing the memory configuration of the path entry of this embodiment.
As shown in FIG. 7, the memory configuration of the path entry of this embodiment includes an entry table T1 and a pointer table T2 assigned to a predetermined memory area of the volatile memory 17. The contents of the entry table T1 are the same as in FIG.

The pointer table T2 includes three address storage units (pointers) P1 to P3 arranged in the row direction. Address storage units P1 to P3 can store addresses Ai to Ai + 2 of entry storage units #i to # i + 2.
The address storage unit P1 is a pointer that designates the address of the entry storage unit of “next hop of forward route”. The address storage unit P2 is a pointer that designates the address of the entry storage unit of “next hop of reverse path”. The address storage unit P3 is a pointer that designates the address of the entry storage unit of “master station”.

Therefore, as shown in FIG. 7, by designating the address Ai in the address storage unit P1, it is specified that the route entry in the entry storage unit #i of the address Ai is the route entry of the next hop of the forward route. Can do.
Similarly, by writing the address Ai + 1 in the address storage unit P2, it is possible to specify that the route entry of the entry storage unit # i + 1 of the address Ai + 1 is the next hop route entry of the reverse route.

Further, by writing the address Ai + 2 in the address storage unit P3, it is possible to specify that the route entry of the entry storage unit # i + 2 of the address Ai + 2 is a master station entry.
Note that the address designation of the route entry by the pointers P1 to P3 may be manually set to the communication device 10 before connection to the network, or remotely set by a control frame transmitted from the management device 2 or the master station 1 or the like. You may decide to do it.

FIG. 8 is a flowchart showing the validity period update processing according to the present embodiment.
As shown in FIG. 8, the effective period update process (period update process) executed by the packet relay unit 26 includes a “first update process” accompanied by a search for a route entry and a search for a route entry. The “second update process” is not included.

When the packet relay unit 26 determines the relay destination (= packet transmission destination) from the IP header of the packet addressed to the other station, the packet relay unit 26 executes the period update process shown in FIG. 8 before transmitting the packet to the relay destination.
In the period update process of FIG. 8, the packet relay unit 26 first determines whether one of the source address and the destination address extracted from the IP header of the received packet contains the IP address of the master station 1 or not. (Step ST21).

The determination in step ST21 identifies whether the packet relayed by the own station is a packet for communication between the master station 1 and the slave station 2.
If the determination result in step ST21 is negative, the packet relay unit 26 performs a normal update process (step ST27) and ends the process. The normal update process is a period update process shown in FIG.

If the determination result in step ST21 is affirmative, the packet relay unit 26 searches the entry table T1 (FIG. 7) for a route entry (= child station entry) on the child station address side (step ST22). The search in step ST22 corresponds to a process of searching for a route entry in the direction corresponding to the slave station entry among the forward route and the reverse route in FIG.
Thereafter, the packet relay unit 26 updates the valid period of the hit slave station entry to the set value (step ST23).

Next, the packet relay unit 26 updates the valid period of the route entry of the address Ai designated by the next hop pointer P1 of the forward route to the set value (step ST24).
The packet relay unit 26 updates the validity period of the route entry of the address Ai + 1 designated by the next hop pointer P2 of the reverse route to the set value (step ST25).
The packet relay unit 26 updates the valid period of the route entry of the address Ai + 2 specified by the pointer P3 of the master station entry to the set value (step ST26).

The valid period update process in steps ST24 to ST26 is an update process for a route entry determined in advance by designation of the pointers P1 to P3, and no search is performed on the entry table T1. In other words, the route entry search is omitted in these update processes.
The packet relay part 26 will complete | finish a process, if the update process of the effective period of step ST24-ST26 is performed. Note that the order of the three processes of steps ST24 to ST26 can be arbitrarily changed.

[Effect of communication device]
According to the communication device 10 of the present embodiment, the packet relay unit 26 does not search the entry table T1 for the next hop of the forward route and the next hop of the reverse route, and validates the route entries. The period is updated (steps ST24 and ST25 in FIG. 8).
Therefore, compared to the conventional update process (FIG. 5) that searches all four types of route entries of the forward route, its next hop and reverse route, and its next hop, the route of the next hop of the forward route and the next hop of the reverse route. The processing time for updating the validity period can be reduced by the amount that does not require searching for entries.

  For this reason, by adopting the communication device 10 that performs the above update processing as the communication node N included in the serial communication path, the latency of packet transfer by the communication node N is reduced and the throughput of the communication network NW is improved. can do.

According to the communication device 10 of the present embodiment, the packet relay unit 26 does not search the entry table T1 for the route entry corresponding to the master station entry among the route entries of the forward route and the reverse route. The validity period of the route entry of the route or the reverse route is updated (step ST26 in FIG. 8).
Therefore, compared with the conventional update process (FIG. 5) that searches all four types of route entries of the forward route, its next hop, and the reverse route and its next hop, it searches for either the forward route or the reverse route route entry. The processing time for updating the effective period can be reduced by the amount that is unnecessary.

  For this reason, by adopting the communication device 10 that performs the update process as the communication node N included in the serial communication path, the packet transfer latency by the communication node N is reduced, and the throughput of the communication network is improved. .

[Modification of memory configuration of route entry]
In the above-described embodiment, the pointer table T2 (FIG. 7) for designating the addresses Ai to Ai + 2 of the entry table T1 is provided as means for storing a predetermined route entry so as not to be searched.
However, as shown in FIG. 9, it is not necessary to search for the next hop route entry of the forward route, the next hop route entry of the reverse route, and the master station entry by the individual storage unit allocated inside the volatile memory 17. As such, those route entries may be stored.

In other words, FIG. 9 is an explanatory diagram showing a modified example of the memory configuration of the path entry.
In the memory configuration of FIG. 9, an individual storage unit having three entry storage units B1 to B3 is allocated inside the entry table T1 of the volatile memory 17.
The entry storage unit B1 is a storage unit for storing the next hop route entry of the forward route. The entry storage unit B2 is a storage unit for storing the next hop route entry of the reverse route. The entry storage unit B3 is a storage unit for storing a master station entry.

  When the memory configuration of FIG. 9 is adopted, the packet relay unit 26 stores the route entries stored in the entry storage units B1 to B3 of the individual storage unit in the processing of steps ST24 to ST26 of the period update processing of FIG. It is sufficient to update the validity period of.

In the memory configuration of FIG. 9, the storage location of the individual storage unit may be the internal memory of the CPU of the control unit 11 instead of the volatile memory 17.
In this way, the effective period of each path entry stored in each of the entry storage units B1 to B3 can be updated more quickly than in the case where an individual storage unit is provided in the volatile memory 17.

[Other variations]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

In the above-described embodiment, the communication node (intermediate node) N provided in the middle of the serial communication path does not necessarily have two types of communication ports (non-branching), and communication having three or more communication ports. The device 10 may be used.
In this case, a program for executing the first operation mode for two ports and the second operation mode for multi-ports having three or more ports is incorporated in the communication device 10, and the period update process described above is performed in the first operation mode. (FIG. 8) may be executed, and the normal period update process (FIG. 5) may be executed in the second operation mode.

  In the above-described embodiment, AODV and DYMO are illustrated as distance vector type routing protocols, but the present invention is not limited to this. Modifications such as improvements and modifications to a part of the protocol and combination with a link state type protocol are also possible.

  In addition, in the communication network NW of the present embodiment in which each communication node N performs route control according to a distance vector type routing protocol, the type of metric that is a route selection criterion includes the number of hops, the distance between nodes, and the like. A predetermined parameter may be selected depending on the protocol to be performed.

  Furthermore, in the communication network NW according to the present embodiment, the route selection algorithm applied to each communication node N is not limited to an algorithm that selects a route with an optimal metric (for example, the minimum number of hops), but also a suitable one (other Other algorithms may be used, such as selecting the second most suitable one in consideration of constraints.

DESCRIPTION OF SYMBOLS 1 Master station 2 Slave station 3 Host network 4 Management apparatus 5 Transmission path 6 Terminal apparatus 10 Communication apparatus 11 Control part 12 Storage part 13 Communication part 14 Power supply part 15 Clock part 16 Non-volatile memory 17 Volatile memory 18 Internal bus 21 Header Determination unit 22 Protocol determination unit 23 Entry determination unit 24 AODV processing unit 25 Message processing unit 26 Packet relay unit 27 Route search unit 28 Search wait queue 29 General-purpose processing unit N0 to N6 Communication node NW Communication network T1 Entry table (reference table)
T2 pointer table

Claims (3)

A communication device used for the communication node, located in the middle of a communication path in which communication nodes performing autonomous path control in a communication network are arranged in series,
A storage unit for storing a reference table including a plurality of route entries for each destination node for which a validity period is set;
A controller that updates each of the validity periods of the first to fourth entries defined below corresponding to the destination and source of the packet when a packet addressed to another station is relayed to an adjacent node. ,
The storage unit individually stores the second and fourth entries so that a search for the reference table is not necessary.
The said control part is a communication apparatus which updates the said effective period of the said 2nd and 4th entry, without performing the search with respect to the said reference table about the said 2nd and 4th entry.
First entry: Route entry of the forward route corresponding to the destination of the packet Second entry: Route entry of the next hop of the forward route corresponding to the destination of the packet Third entry: Route entry of the reverse route corresponding to the source of the packet 4 entries: Route entry of the next hop of the reverse route corresponding to the packet source When the communication network includes one master station and a plurality of slave stations, and relays the packet for communication between the master station and the slave stations,
The storage unit individually stores a master station entry in which the destination node is the route entry of the master station so that a search for the reference table is unnecessary,
The control unit does not search the reference table for the first or third entry corresponding to the master station entry among the first and third entries, and stores the first or third entry. The communication apparatus according to claim 1, wherein the valid period is updated. A packet relay method performed by a communication device used for the communication node, located in the middle of a communication path in which communication nodes performing autonomous path control in a communication network are arranged in series,
A first step of storing a lookup table including a plurality of route entries for each destination node for which a validity period is set;
A second step of updating each of the validity periods of the first to fourth entries defined below corresponding to the destination and source of the packet when relaying a packet addressed to another station to an adjacent node,
The first step includes a process of individually storing the second and fourth entries so that a search for the reference table is not necessary.
The packet relaying method, wherein the second step includes a process of updating the validity period of the second and fourth entries without searching the reference table for the second and fourth entries.
First entry: Route entry of the forward route corresponding to the destination of the packet Second entry: Route entry of the next hop of the forward route corresponding to the destination of the packet Third entry: Route entry of the reverse route corresponding to the source of the packet 4 entries: Route entry of the next hop of the reverse route corresponding to the packet source

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