JP2017204785A - Communication device, communication system, and packet transfer method of communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of packet loss.SOLUTION: A communication device includes: a change unit for changing destination information on a packet to destination information destined to a second device if the stored amount of a buffer capable of temporarily storing packets including destination information destined to a first device exceeds a prescribed value; and a management unit for storing packets in the buffer if the stored amount in the buffer is within the prescribed range when the packets which are transferred to the second device on the basis of the changed destination information and of which the destination information is changed to the first device are received from the second device.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication device, a communication system, and a packet transfer method for the communication device.

As one of communication facilities (communication devices) forming a network, there is a relay device (also called a concentrator) that relays packets transmitted and received between terminals (hosts). Examples of the relay device include a router, a layer 3 switch, a layer 2 switch, and a switching HUB.

  A communication amount (bandwidth) that can be communicated to the relay device in consideration of the limit of the processing performance of the relay device may be determined in advance. Alternatively, the communication amount (bandwidth) may be limited for the purpose of guaranteeing communication of other communications.

  With a rapid increase in communication volume in recent years, there may be a case where packets (data) having a communication volume exceeding the assumption from neighboring apparatuses reach the relay apparatus. In this case, a packet loss (packet loss) occurs due to an overflow of the buffer due to an excess of the allowable amount of packets that can be received by the relay device. Due to the occurrence of packet loss, communication between devices (hosts) at both ends of the packet transfer path becomes abnormal. As a method for starting the packet loss, for example, it is conceivable to replace the relay device with a high-performance one. Alternatively, it is conceivable to add a detour to the destination host.

JP 2007-325178 A JP 2003-78555 A

  However, there is a possibility that enormous costs may be incurred when replacing relay devices or adding detours.

  An object of this invention is to provide the technique which can avoid a packet loss, without replacement | exchange or expansion of communication equipment.

  One embodiment of the present invention is a communication device. The communication device includes: a changing unit that changes the destination information of the packet for the second device when a storage amount of a buffer capable of temporarily storing the packet including the destination information for the first device exceeds a predetermined value; When the packet transferred to the second device based on the changed destination information and the destination information is changed for the first device is received from the second device, the storage amount of the buffer is within a predetermined range. And a management unit that stores the packet in the buffer.

  According to one embodiment of the present invention, packet loss can be avoided without replacing or adding communication facilities.

FIG. 1 is an explanatory diagram of a reference example compared with the embodiment. FIG. 2 shows a configuration example of a communication system according to the embodiment. FIG. 3 shows a hardware configuration example of the relay apparatus. FIG. 4 is a block diagram showing the functions of the relay device 10 operating as the relay device 3a, and shows the operation during packet detour processing. FIG. 5 is a flowchart illustrating an example of packet detour processing. FIG. 6 is a diagram illustrating a data structure example of the detour destination management area. FIG. 7 shows an example of the data structure of the order management area. FIG. 8 is a diagram illustrating the operation of the relay device 3b (3c) during the packet restoration process. FIG. 9 is a flowchart illustrating an example of packet restoration processing. FIG. 10 is a diagram illustrating an operation at the time of the detour packet restoration process of the relay device 3a. FIG. 11 is a flowchart illustrating an example of packet return processing. FIG. 12 is a flowchart illustrating an example of packet return processing. FIG. 13 is an explanatory diagram of a packet transfer example when the relay apparatuses 2 and 3 are layer 2 switches (or switching HUBs). FIG. 14 is an explanatory diagram of a packet transfer example when the relay apparatuses 2 and 3 are routers (or layer 3 switches). FIG. 15 shows a packet transfer procedure when there is one detour destination. FIG. 16 shows a packet transfer procedure when there is one detour destination. FIG. 17 shows a packet transfer procedure when there is one detour destination. FIG. 18 shows a packet transfer procedure when there is one detour destination. FIG. 19 shows a packet transfer procedure when there are two detour destinations. FIG. 20 shows a packet transfer procedure when there are two detour destinations.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configuration of the embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment.

[Reference example]
FIG. 1 is an explanatory diagram of a reference example compared with the embodiment. The network system according to the reference example is formed as follows. That is, as shown in FIG. 1A, the network system includes a plurality of terminal devices 1 and a relay device 2 as a plurality of communication facilities. In the reference example, three terminal devices 1a, 1b, and 1c and six relay devices 2a to 2f are illustrated.

  The terminal device 1a is connected to the relay device 2a, the terminal device 1b is connected to the relay device 2e, and the terminal device 1c is connected to the relay device 2f. Assume that a packet is transferred from each of the terminal device 1b and the terminal device 1c to the terminal device 1a with a communication amount of 8 Mbps.

  In this case, a total of 16 Mbps packets arrive at the relay device 2c that relays packets from the relay device 2e and the relay device 2f. The relay device 2c has a buffer memory for temporarily storing packets to be transferred to the terminal device 1a, that is, to the relay device 2a. The storage amount of the buffer memory is limited to a range that does not exceed the bandwidth (10 Mbps in this example) considering the performance of the relay device 2c and the communication of other traffic. That is, when the storage amount (packet accumulation amount) of the buffer memory exceeds a predetermined value, the packet is not stored in the buffer memory and the packet is discarded.

  For example, if the capability (bandwidth) of the relay device 2c to transmit a packet to the relay device 2a accommodating the terminal device 1a is 10 Mbps, the excess 6 Mbps packets are discarded without being stored in the buffer memory. As a result, packet loss occurs. The communication between the terminal device 1a and the terminal device 1b and the communication between the terminal device 1a and the terminal device 1c become abnormal due to the packet loss.

  In order to avoid packet loss, as shown in FIG. 1B, it is conceivable to increase the bandwidth by replacing the relay device 2c with a high-performance relay device 2g. Alternatively, as shown in FIG. 1C, it is conceivable to increase the bandwidth by adding a detour via the relay device 2h between the relay device 2c and the terminal device 1a.

However, the replacement (replacement) of the relay device and the addition of a detour cause a great cost. In the embodiment, a communication device, a communication system, and a packet transfer method that can avoid a communication error due to packet loss and eventually packet loss without replacement with a high-performance relay device 2g or addition of a detour will be described.

Embodiment
<Network configuration>
FIG. 2 shows a configuration example of a communication system according to the embodiment. As for the network configuration, the arrangement and connection relationship between the network of the reference example shown in FIG. However, in the embodiment, a relay device 3a, a relay device 3b, and a relay device 3c are provided instead of the relay device 2c, the relay device 2b, and the relay device 2d. When the relay device 3a, the relay device 3b, and the relay device 3c are not distinguished, they are expressed as “relay device 3”.

  The relay device is an example of a “communication device”. The communication device is a concept including not only a relay device but also a terminal device. The configuration of the embodiment can be applied not only to a relay device that relays a packet, but also when a terminal device that generates and transmits a packet has two or more communication paths. The relay device 3a is an example of a “communication device”. The terminal device 1a is an example of a “first device”. The relay device 3b is an example of a “second device”. The relay device 3c is an example of a “third device”.

  Similarly to the relay device 2c, the relay device 3a according to the embodiment temporarily stores a packet transmitted to the relay device 2a on the communication path to the destination terminal device 1a (hereinafter also referred to as “buffer”). Have The buffer is used to adjust the packet transmission rate so that the amount of packets transmitted to the relay device 2a does not exceed a prescribed amount. By using the buffer, an overflow of the buffer in the relay apparatus 2a can be avoided, and a communication abnormality due to a packet loss can be avoided.

  Unlike the relay device 2c, the relay device 3a according to the embodiment does not discard a packet when the amount of packets stored in the buffer (an example of “amount of buffer storage”) exceeds a predetermined value. Instead of discarding, the relay device 3a bypasses and transmits a packet corresponding to the excess to the relay device 3b different from the original transfer destination of the packet (relay device 2a).

  The relay device 3b retains the packet that is detoured in the relay device 3b as necessary, and then transmits this packet back to the relay device 3a. When the packet is received by the relay device 3a, if the storage amount of the buffer memory falls within a predetermined range (for example, does not exceed the predetermined value), the relay device 3a transmits the packet received from the relay device 3b to the buffer memory. And transmitted to the relay device 2a.

When the packet amount exceeds the predetermined value, the relay device 3a transmits the packet received from the relay device 3b to another relay device 3c as a detour destination different from the relay device 3b. The relay device 3c retains the packet as necessary, and then sends back the detoured packet to the relay device 3a. The relay device 3a sends the packet from the relay device 3c to the relay device 2a.

  Thus, in the embodiment, when the storage amount of the buffer exceeds a predetermined value, the packet is not stored in the buffer, and the relay device 3a → the relay device 3b → the relay device 3a (→ the relay device 3c → the relay). The packet transfer is controlled so that the packet passes through the route (detour) of the device 3a). As a result, the packet delay time is increased, and packet loss due to buffer overflow, packet discarding for avoiding or eliminating overflow, that is, packet loss, is prevented. In the example of FIG. 2, the case where the number of relay apparatuses 3 that return a packet to the relay apparatus 3 a is two is illustrated, but the number of such relay apparatuses may be one or three or more.

<Hardware configuration of relay device>
FIG. 3 shows a hardware configuration example of the relay apparatus 10 that can be used as the relay apparatus 2 and the relay apparatus 3. The relay device 10 is connected to a central processing unit (CPU) 11, one or more memories 12 connected to the CPU 11, a switch 13 connected to the CPU 11, a memory 14 included in the switch 13, and the switch 13. PHY 15 and a plurality of ports 16 connected to PHY 15.

  The CPU 11 is an example of “processor”, “control unit”, and “control device”, and each of the memory 12 and the memory 14 is an example of “storage device”, “memory”, “storage unit”, and “storage medium”. It is.

  The memory 12 and the memory 14 include a main storage device and an auxiliary storage device. The main storage device is used as a program development area, a work area for the CPU 11, a data and program storage area, a buffer area, and a buffer area. The main storage device is formed by, for example, a random access memory (RAM) or a combination of a RAM and a read only memory (ROM).

Auxiliary storage devices include, for example, hard disk drives (HDD), Solid State Drives (
SSD), Flash memory, Electrically Erasable Programmable Read-Only Memory
It is formed of a non-volatile storage medium such as (EEPROM). The auxiliary storage device is used as a storage area for data and programs.

  For example, an operating system (OS) is installed in the memory 12 and stores setting data on the OS. However, the memory 12 can store programs other than the OS and data other than the OS setting data.

  The memory 14 is used as a buffer memory for buffering (temporarily storing) frames (packets). In addition, the memory 14 stores a table storing destination information corresponding to packet transmission source information. The table includes a MAC learning table used for transferring a MAC frame, a routing table used for transferring an IP packet, an ARP table indicating a correspondence relationship between an IP address and a MAC address, and the like. The IP address is an example of a “network address”, and the MAC address is an example of a “physical address”.

The switch 13 performs frame (packet) transfer (switching) using a table. That is, the switch 13 uses the table stored in the memory 14 to determine an output destination that matches the destination of the packet received from the PHY 15 and sends the packet to the port 16 corresponding to the output destination. The switch 13 also performs QoS (service quality) processing (processing according to traffic priority), MAC (Media Access Control) layer processing, and the like. The QoS information is handled as information indicating the priority order for the packet.

  The PHY 15 performs physical layer processing such as encoding. The PHY 15 and the switch 13 are formed by an integrated circuit such as an LSI, for example. Each port 16 is a physical interface for inputting / outputting data to / from the outside. A physical link (cable) connected to the network is connected to each port 16.

  The CPU 11 performs processing or operation as the relay device 2 (relay device 3) by executing a program stored in the memory 12. In the embodiment, there are a case where the relay device 2 and the relay device 3 are layer 3 switches or routers, and a case where the relay device 2 and the relay device 3 are layer 2 switches or switching HUBs.

  When the relay device 2 and the relay device 3 are layer 3 switches or routers, the CPU 11 executes software processing such as IP layer routing and redundancy. On the other hand, when the relay device 2 and the relay device 3 are layer 2 switches or HUBs, the CPU 11 executes routing of the MAC layer (layer 2) and software processing.

  When the CPU 11 in the relay device 10 executes the program, the relay device 10 can operate as the relay device 3a, the relay device 3b, and the relay device 3c. The relay device 3a performs at least packet detour processing, packet restoration processing, and detour packet return processing.

<Configuration and operation example of relay device>
FIG. 4 is a block diagram showing the functions of the relay device 10 operating as the relay device 3a, and shows the operation during packet detour processing. FIG. 5 is a flowchart illustrating an example of packet detour processing.

In FIG. 4, the relay device 3a includes a packet reception unit 21, a packet reception processing unit 22, a priority determination unit 23, a high priority buffer region 24, a low priority buffer region 25, a transmission control unit 26, a MAC A learning table 27. The relay device 3 a includes a packet transmission unit 28, a control processing unit 29, a header restoration unit 30, an ARP (Address Resolution Protocol) table 31, and a packet transmission unit 37. further,
The relay device 3 a includes a header restoration unit 30, a sequence management unit 32, a detour destination management region 33, a sequence management region 34, a detour transmission control unit 35, a header conversion unit 36, and a packet transmission unit 37. .

  The packet receiver 21 receives a packet that arrives at each port 16. The packet reception processing unit 22 performs packet reception processing such as whether the packet is addressed to its own device. The priority order determination unit 23 refers to the QoS data in the packet and determines the priority order of the packet.

The high priority buffer area 24 is a buffer area (buffer memory) for temporarily storing packets determined to have a priority of “high priority”. The low priority buffer area 25 is a buffer area (buffer memory) that temporarily stores packets determined to have a priority of “low priority” (packets other than high priority). The capacities of the high priority buffer area 24 and the low priority buffer area 25 are determined in consideration of the bandwidth of each port 16. In the high priority buffer area 24 and the low priority buffer area 25, a predetermined value that is an upper limit of the packet storage amount is set in advance. The transmission control unit 26 refers to the MAC learning table 27 to determine the packet transmission destination (output destination port 16). For example, the packet transmission unit is provided for port 16 and transmits a packet. FIG. 4 illustrates a packet transmission unit 28 corresponding to the port 16 that transmits a packet to the relay device 2a and a packet transmission unit 37 corresponding to the port 16 that transmits a packet to the relay device 3b. Note that a temporary storage area for adjusting the transmission rate according to the bandwidth of the port 16 (link) can be provided for the packet transmitter 28, and the transmission timing can be adjusted so as not to exceed the bandwidth. The control processing unit 29 performs control and processing based on the control packet.

  The header restoring unit 30 performs processing for returning the destination MAC address in the header of the packet returned from the detour destination to the original MAC address. The ARP table 31 stores information indicating the correspondence between the IP address and the MAC address obtained as a result of the ARP process. The order management unit 32 manages the order of packets to be diverted to the detour destination.

  The detour destination management area 33 stores information indicating a detour destination. FIG. 6 is a diagram illustrating a data structure example of the detour destination management area 33. As shown in FIG. 6, the detour destination management area 33 stores a table formed by one or more records prepared for each interface (port) serving as a detour destination. An adjacent device connected to each port serving as a detour destination is an example of “a plurality of second device candidates”. For example, the relay device 3b and the relay device 3c are examples of “a plurality of second device candidates”.

  The record includes identification information of a detour destination interface (port), a transmission rate, a reception rate, and the number of detour packets related to the detour destination port. The transmission rate indicates the amount of packet transmission per unit time, and the reception rate indicates the amount of packet reception per unit time. The number of bypass packets indicates the number of packets transmitted to the bypass destination port.

  The order management area 34 stores information indicating the order of packets transmitted to the detour destination. FIG. 7 shows an example of the data structure of the order management area 34. The order management area 34 stores a table formed by a set of records for storing identification information of bypass packets. Information (header information) stored in the packet header is used as packet identification information. In the example of FIG. 7, the packet illustrates a combination of a destination MAC address, a source MAC address, an Ether type, a protocol, a destination IP address, a source IP address, and a VLAN identifier (VLANID). However, the combination of header information that forms packet identification information can be selected as appropriate. Further, each record stores identification information of an interface (detour interface) selected as a packet detour destination and a time stamp (record storage time).

  The detour transmission control unit 35 specifies a detour destination of the packet. The header conversion unit 36 performs conversion processing of the destination MAC address included in the header of the packet. The packet transmission unit 37 transmits a packet to a detour destination.

For example, the packet reception unit 21, the packet transmission unit 28, the packet transmission unit 37, and the packet reception processing unit 22 are functions that the port 16 and the PHY 15 illustrated in FIG. 3 have. The priority determination unit 23, the transmission control unit 26, the header restoration unit 30, the order management unit 32, the bypass transmission control unit 35, and the header conversion unit 36 are functions obtained by the CPU 11 executing a program. In other words, the CPU 11 operates as each of these units. However, at least a part of each part described as the function of the CPU 11 may be performed by the switch 13.

The high priority buffer area 24, the low priority buffer area 25, the MAC learning table 27, and the ARP table 31 are created on the memory 14. However, it may be created on the memory 12. Each of the detour destination management area 33 and the order management area 34 can be created on at least one of the memory 12 and the memory 14. In addition, information shown in an operation example and a processing example described below is stored in the memory 12 or the memory 14.

  The low priority buffer area 25 is an example of a “buffer capable of temporarily storing packets including destination information for the first device”. However, it is not an essential requirement that the buffer is associated with priority or priority. The high priority buffer area 24 may be treated as a “buffer”. The header conversion unit 36 is an example of a “change unit”. The order management unit 32 is an example of a “management unit” or “determination unit”. The header restoration unit 30 is an example of a “rewriting unit”. The order management area 34 is an example of a “storage unit”.

<< Packet detour processing >>
Hereinafter, the packet detouring process will be described with reference to FIGS. In 001 of FIG. 5, the packet receiver 21 receives the packet (FIG. 4 (1)). The received packet is passed to the reception processing unit 22.

The reception processing unit 22 refers to the packet header and confirms the destination of the packet (002,
FIG. 4 (2)). The confirmation is performed, for example, by determining whether the destination address included in the header is the address of the own device (relay device 3a). If the destination of the packet is its own device (Y in 002), the packet is treated as a control packet and passed to the control processing unit 29. The control processing unit 29 performs processing and control based on the control-like packet (003).

  If the packet is not addressed to the own device (N in 002), the packet is passed to the priority order determination unit 23. The priority determination unit 23 distributes packets according to the packet priority (QoS) (003, FIG. 4 (3)).

Here, setting of high priority and low priority of the packet is performed in advance. The priority order can be set in various units such as traffic, service, network (for example, VLAN), and user. For example, a VoIP (Voice over Internet Protocol) packet may be set with high priority, and a UDP (User Datagram Protocol) packet may be set with low priority. The determination of the priority is performed based on, for example, packet header information.

If it is determined in 004 that the packet is a high priority packet, the packet is stored in the high priority buffer area 24 (005, FIG. 4 (4)). High priority buffer area 2
4 is preferentially read by the transmission control unit 26 (FIG. 4 (5)).

  The transmission control unit 26 specifies a transmission interface (port 16) corresponding to the destination MAC address (DstMAC) included in the packet header from the MAC learning table 27 (FIG. 4 (6)), and transmits the packet to the packet transmission unit 28. Send to. The packet transmitter 28 transmits a packet from the identified port 16 to another device (009).

  If it is determined in 004 that the packet is a low priority packet, the packet is passed to the order management unit 32 (FIG. 4 (7)). The order management unit 32 refers to the order management area 34 (FIG. 7) and confirms that there is no record including the same identification information as the identification information of the received packet (006). If there is a record, the process proceeds to 012. If there is no record, the process proceeds to 007.

  In 007, the order management unit 32 determines whether there is a free area in the low priority buffer area 25. This determination is made by determining whether the packet storage amount in the low priority buffer area 25 is a predetermined value or exceeds a predetermined value. When the storage amount is a predetermined value or exceeds, it is determined that there is no free area, and otherwise, it is determined that there is a free area.

If it is determined that there is an empty area (Y in 007), the packet is stored in the low priority buffer area 25 (008, FIG. 4 (9)). In this case, the packet is read from the low priority buffer area 25 at a timing according to the low priority by the transmission control unit 26, and the port 16 corresponding to the destination is specified using the MAC learning table 27 ((6 in FIG. 4). )). Then, the packet transmission unit 28 transmits the specified port 16 (009).

  When it is determined that there is no free area in the low priority buffer area 25 (N in 007), the order management unit 32 determines whether there is a packet detour destination (010). The process of 010 is performed as follows, for example.

  The order management unit 32 refers to the order management area 34 (FIG. 7) (FIG. 4 (8)). The order management unit 32 determines whether there is a record in the order management area 34 that includes the same information as the header information of the received packet.

  At this time, if there is a corresponding record, the order management unit 32 determines whether or not the information indicating the detour interface in the corresponding record indicates the reception port of the received packet. When the detour interface does not indicate a reception port (the detour interface and the reception port are different), the order management unit 32 determines to transmit a packet to the detour destination port indicated by the detour interface in the record. . Thereafter, the process proceeds to 012 (Y in 010 (there is a detour destination)). This maintains the packet order.

  Whether the bypass interface and the reception port are different is determined to determine whether the packet has arrived from the original communication path or whether the bypassed packet has returned.

  When the record including the same information as the header information of the received packet is not stored in the order management area 34, the order management unit 32 refers to the detour destination management area 33 (FIG. 6) (FIG. 4 ( 10)). The order management unit 32 selects a port having the lowest total value of the transmission rate and the reception rate from one or more ports 16 registered as bypass ports.

  The order management unit 32 determines whether at least one of the transmission rate, reception rate, and number of bypass packets of the selected port exceeds the threshold value. If not exceeding, the order management unit 32 determines the corresponding port as a bypass port and advances the process to 012 (Y in 010 (there is a bypass destination)). On the other hand, when at least one of the transmission rate, the reception rate, and the number of bypass packets exceeds, it is determined that the bypass using the selected port is not possible. This is to avoid an increase in traffic due to detours. When detouring is impossible (N of 010 (no detour destination)), the packet is discarded (011).

  As described above, in the embodiment, among the ports different from the port corresponding to the destination, a port whose traffic (transmission rate, reception rate) is small and whose transmission rate, reception rate, and number of packets do not exceed the threshold is a detour destination. Selected as the port. However, the method of selecting a detour destination may be other than the above.

  In 012, the order management unit 32 increments the “number of bypass packets” in the corresponding record (the record corresponding to the port determined in 010) in the bypass destination management area 33 by 1 (increment).

In 013, the order management unit 32 adds information (destination MAC / IP address, transmission source MAC / IP address, protocol, detour destination port, storage time, etc.) of the packet to be transferred to the detour destination to the order management area 34. (FIG. 4 (11)). The packet is sent to the bypass transmission control unit 35 (FIG. 4 (12)).

  In 014, the bypass transmission control unit 35 performs a header conversion process using the header conversion unit 36. By the header conversion process, a preset detour destination MAC address (a MAC address of an adjacent device connected via the detour destination port) is converted into a destination MAC address (DstMAC) in the header of the packet (FIG. 4). (13)).

  In 015, the bypass transmission control unit 35 refers to the MAC learning table 27 based on the converted destination MAC address, and identifies the bypass destination port 16 as the output destination port corresponding to the converted destination MAC address. (FIG. 4 (14)). The packet transmission unit 37 transfers the packet from the detour destination port 16 specified by the detour transmission control unit 35 to the adjacent device. In the embodiment, the relay device 3b and the relay device 3c are adjacent devices beyond the detour destination port.

<< Packet restoration process >>
Next, the packet restoration process will be described with reference to FIGS. FIG. 8 is a diagram showing the operation of the relay device 3b (3c) during the packet restoration process, and FIG. 9 is a flowchart showing an example of the packet restoration process.

  As shown in FIG. 8, the relay device 3b (3c) also has the same function as the relay device 3a by executing the program. Hereinafter, the description will be made on the assumption that the relay device 3b is a detour destination device. In 101 of FIG. 9, the packet receiving unit 21 of the relay device 3b receives the packet (FIG. 8 (1)). The packet is transferred to the reception processing unit 22 (FIG. 8 (2)).

  In 102, the reception processing unit 22 confirms the destination. If the destination MAC address and the IP address of the received packet are both addressed to the own device (relay device 3b) by the confirmation, the packet is sent to the control processing unit 29 as a control packet. The control processing unit 29 performs processing based on the packet (103, FIG. 8 (3)).

  In 103, when the destination MAC address of the received packet is addressed to the own device and the IP address is other than the own device, the packet is transferred to the header restoring unit 30 (FIG. 8 (4)), and the process proceeds to 106. Otherwise, for example, normal packet transfer processing is performed (105).

  In 106, the header restoration unit 30 refers to the ARP table 31 (FIG. 8 (5)). The correspondence relationship between the IP address and the MAC address is stored in the ARP table 31, and the header restoring unit 30 reads the MAC address corresponding to the destination IP address of the packet from the ARP table 31, and the destination MAC of the packet header. Set to address. As a result, the header of the packet detoured from the relay device 3a is restored. The packet is passed to the priority determination unit 23.

  In 107, the priority determination unit 23 determines the priority of the packet. If the packet is “high priority”, the packet is stored in the high priority buffer area 24 (108). However, since the priority order of the bypassed packet is “low priority”, the processing proceeds to 109 (FIG. 8 (7)).

  In 109, the order management unit 32 refers to the order management area 34 and checks whether there is a record corresponding to the received packet. If there is a record (109 Y), the packet is stored in the low priority buffer area 25 (111).

  If there is no record (N of 109), the order management unit 32 determines whether or not there is a free space in the low priority buffer area 25 (110). If there is a free space, the packet is stored in the low priority buffer area 25. If there is no room, the packet is discarded (112).

The packet stored in the low priority buffer area 25 is subjected to processing similar to the packet transmission processing (009) described with reference to FIGS. 4 and 5 (113, FIGS. 8 (10) and (1)).
1)). The details are the same as those already described, and a description thereof will be omitted. In this way, the packet received by the detour relay device 3b is sent back to the detour source relay device 3a.

<< Rerouting packet return processing >>
Next, the bypass packet return process will be described with reference to FIGS. FIG. 10 is a diagram showing the operation of the relay device 3a during the detour packet restoration process, and FIG. 11 is a flowchart showing an example of the packet restoration process.

  The processing from 001 to 006 in FIG. 11 is the same as the processing shown in FIG. In 006, the order management unit 32 advances the process to 301 when there is a record corresponding to the received packet in the order management area 34.

  In 301, the order management unit 32 deletes the record having the oldest storage time from the order management area 34. In 302, the order management unit 32 specifies a record including information on the detour destination port that matches the reception port of the packet from the detour destination management area 33, and decrements (subtracts 1) the number of detour packets in the record. .

  Thereafter, processing similar to each processing of 007, 008, 009 shown in FIG. 4 is performed. Description of these processes is omitted. In 303, the order management unit determines whether the number of consecutive detours is greater than zero. The continuous detour count is the number of times that a packet returned from a certain device can be transferred to another detour destination. The number of consecutive detours can be set in advance by a device configuration file or the like. If the number of consecutive detours is greater than 0, the process proceeds to 304; otherwise, the process proceeds to 011 and the packet is discarded.

  At 304, the number of consecutive detours is decremented. Thereafter, processing similar to 010 to 015 described in the packet detour processing is executed. Description is omitted. The packet returned from the detour destination by the detour packet return processing is transmitted from the port 16 connected to the relay apparatus 2a corresponding to the original destination (terminal apparatus 1a). If the number of consecutive detours is not zero, the process is transferred again to another detour destination, and a process for increasing the delay time is performed.

<Packet transfer example>
<< For Layer 2 Switch >>
FIG. 13 is an explanatory diagram of a packet transfer example when the relay apparatuses 2 and 3 are layer 2 switches (or switching HUBs). The packet in this example is a MAC frame.

In FIG. 13, the terminal device 1c (having the MAC address “AA”) transmits a packet addressed to the terminal device 1a (having the MAC address “FF”). In the header of the packet, the source MAC address (SrcMAC) “AA”, the destination MAC address (DstMAC)
“FF”, source IP address (SrcIP) “1.0.0.1”, and destination IP address (DstIP) “1.0.0.2” are included. The destination MAC address “FF” is an example of “destination information for the first device”. Note that the “˜address information for a device” is a concept including an address of the device itself and an address of a device on a path to the device.

  The packet is received by the switch A, which is a layer 2 switch that operates as the relay device 2f. The switch A transfers the packet to the switch B based on the destination MAC address. The switch B is a layer 2 switch that operates as the relay device 3a.

  In the switch B, it is determined whether or not there is an empty area in the low priority buffer area 32. That there is no free area (the queue is depleted) means that there is no free bandwidth in the route corresponding to the destination MAC address. In this case, the switch B (relay device 3a) is in a state of performing packet detour processing and detour packet return processing. That is, the switch B performs a packet bypass process on the packet received from the switch A (relay apparatus 2f), and performs a bypass packet return process on the packet returned from the switch D (relay apparatus 3b).

  In the example of FIG. 13, the switch B determines a detour destination for the packet received from the port “1”. As a bypass destination, the port “2” connected to the switch D (layer 2 switch operating as the relay device 3b) is determined. At this time, the switch B converts the MAC address “DA” of the switch D corresponding to the port “2” that is the detour destination port into the destination MAC address of the packet (header conversion). As a result, the packet is transferred to the detour destination switch D. The destination MAC address “DA” is an example of “destination information for the second device”.

  In the switch D, since the destination MAC address of the packet is the own device and the destination IP address is the IP address of the other device, the destination MAC address of the packet is returned to the original MAC address “FF” using the ARP table 31. (Header recovery). As a result, the packet is returned to the switch B. The destination MAC address “DA” and the destination IP address “1.0.0.2” are examples of “destination information indicating a predetermined value”.

  In the switch B, the already-described detour packet return processing is executed, and the packet is transferred to the switch C (a layer 2 switch operating as the relay device 2a). Thereby, the packet is transferred through the original communication path. The switch C sends the packet to the terminal device 1a according to the destination MAC address.

<< For router >>
FIG. 14 is an explanatory diagram of a packet transfer example when the relay apparatuses 2 and 3 are routers (or layer 3 switches). The packet in this example is an IP packet. The router transfers the packet according to the destination IP address included in the packet header.

  In FIG. 14, the terminal device 1c (IP address “1.0.0.1”) transmits a packet addressed to the terminal device 1a (IP address “1.0.0.2”). The packet header includes a source MAC address “AA”, a destination MAC address (DstMAC) “BA”, a source IP address (SrcIP) “1.0.0.1”, and a destination IP address (DstIP) “1. 0.0.2 "is included. When the packet is transferred based on the IP address, the MAC address of the next hop is set as the destination MAC address. The next hop of the terminal device 1c is the router a. The router a operates as the relay device 2f.

The router a forwards the packet from the terminal device 1c to the router b based on the destination IP address. The router b operates as the relay device 3a. The reception processing unit of the router b determines whether or not there is a free area in the queue (buffer) corresponding to the destination MAC address of the packet. When it is determined that there is no free area, the router b enters a state in which packet detour processing and detour packet return processing are performed. That is, the router b performs a packet bypass process on the packet received from the router a (relay device 2f), and performs a bypass packet return process on the packet returned from the router d. The router b rewrites the destination MAC address of the packet with “DA” of the router d and transmits it to the router d. The MAC address “DA” is an example of “destination information for the second device”.

  The router d operates as the relay device 3b. The router d performs packet transfer based on the destination IP address when the destination MAC address of the packet transferred from the router b is addressed to the own device and the destination IP address is another device. At this time, in the routing table of the router d, since the destination IP address “1.0.0.2” is ahead of the router b, the destination MAC address is rewritten to “CB” corresponding to the router b, and the router b Forwarded to As a result, the packet is folded. The MAC address “CB” is an example of “destination information for the first device”.

  The router b performs detour packet return processing, forwards the packet to the router c (operates as the relay device 2a) based on the destination IP address, and the router c forwards the packet to the terminal device 1a based on the destination IP address. Forward to.

<Example of packet transfer procedure 1: one detour destination>
15 to 18 show a packet transfer procedure example 1, that is, a procedure in the case of transmitting eight packets destined for the terminal device 1a from each of the terminal device 1b and the terminal device 1c. In FIG. 15, the relay device 3a is a port # 1 that receives a packet from the terminal device 1b, a port # 2 that receives a packet from the terminal device 1c, and a port # 3 that transmits a packet toward the terminal device 1a. Including.

  The port 16 includes a packet transmitting unit and a receiving unit, and each transmitting unit and each receiving unit is assigned a memory area (an area of the memory 14) that can store four fixed-size packets. Assume. Priority control (priority order) is not considered.

In the procedure 1 of FIG. 15, a packet group (referred to as traffic 1) from the terminal device 1b and a packet group (referred to as traffic 2) from the terminal device 1c are transmitted. In the procedure 2, the packet “1” of the traffic 1 is received at the port # 1. Further, the packet “1” of the traffic 1 is received at the port # 1.

  Each receiving unit receives one packet at one timing and sends one packet to the next. The transmitter also sends one packet next. Therefore, in the procedure 3, each packet “1” is transferred to the port # 3 from each receiving unit of the port # 1 and the port # 2. In addition, the receiving units of the port # 1 and the port # 2 receive the packet “2”, respectively.

  In the procedure 4, the transmission unit of the port # 3 transmits the packet “1” of the traffic 1 to the terminal device 1a, and receives the packet “2” from the port # 1 and the port # 2. In addition, the receiving units of the port # 1 and the port # 2 receive the packet “3”, respectively.

  In procedure 5, the transmission unit of port # 3 transmits the packet “2” of traffic 1 to the terminal device 1a. On the other hand, the transmission unit of port # 3 receives packet “3” from port # 1 and port # 2. As a result, the memory area (an example of a buffer) of the transmission unit of port # 3 becomes a predetermined value (upper limit: 4). Further, the reception units of the port # 1 and the port # 2 receive the packet “4”, respectively.

In the procedure 6 shown in FIG. 16, the packet “4” of the traffic 1 can be stored in the memory area of the transmission unit of the port # 3, but the packet “4” of the traffic 2 exceeds the predetermined value of four. Therefore, it cannot be stored in the memory area of the transmission unit. Therefore, the packet “4” of the traffic 2 is sent to the transmission unit of the port # 4 that is the detour destination port.

  As shown in the procedure 7, the transmission unit of the port # 4 transmits the packet “4” of the traffic 2 to the detour destination relay device 3b at the next timing. Received by the relay device 3b. The relay device 3b has a memory area (buffer) capable of retaining a maximum of two packets.

  Therefore, as illustrated in the procedure 8 which is the next timing, the relay device 3b holds the packets “4” and “5” of the traffic 2 at the next timing. In step 9, which is the next timing, the relay device 3b returns (sends back) the packet “4” of the traffic 2 to the relay device 3a, and the packet “4” is received by the reception unit of the port # 4.

  In step 10 (FIG. 17), which is the next timing, the packet received by the receiving unit of port # 4 is transferred to the transmitting unit of port # 3 connected to the original transmission destination at the next timing. In the procedure 10, the packet “4” of the traffic 2 is held in the transmission unit of the port # 3.

  In this way, packets that cannot be stored in the memory area of the transmission unit of port # 3 (exceeding the predetermined value of 4) are transmitted from the transmission unit of port # 4 → the relay device 3b → the reception unit of port # 4 → port It is transferred via the route of the # 3 transmission unit. As a result, a delay time corresponding to four packets is given to a packet that cannot be stored in the memory area of port # 3. Thereafter, a similar operation is performed after the procedure 11, and finally, all the packets related to the traffics 1 and 2 reach the terminal device 1a, and no packet loss occurs.

<Packet transfer procedure example 2: When there are two detour destinations>
19 and 20 show a packet transfer procedure example 2, that is, a packet transfer procedure when there are two detour destinations. In the packet transfer procedure example 2, 16 packets (traffic 1 and 2) destined for the terminal device 1a are transmitted from the terminal device 1b and the terminal device 1c, respectively (see procedure 1 in FIG. 19). In the relay device 3a, the port # 4 and the port # 5 are used as detour destination ports of the port # 3.

  The upper limit (predetermined value) of packets that can be held in port # 3 is the same as in packet transfer procedure example 1. The number of packets transferred at one timing is one. This is also the same as the packet transfer procedure example 1. After the procedure 2, the packet transfer is performed through the relay device 3b as the detour destination as in the packet transfer procedure example 2 (see FIG. 19, procedure 6, and procedure 12). Steps 2 to 5 and 7 to 11 are omitted.

  As illustrated in step 17 of FIG. 20 (steps 13 to 16 are omitted), when the number of packets in the transmission unit of port # 4 is a predetermined value (four), it is the second detour destination. The packet is transferred to the transmission unit of port # 5. The packet is transferred from the transmission unit of port # 5 to the relay device 3c.

  In the example of FIG. 20, the relay device 3c can retain (hold) two packets, and wraps the packet back to the reception unit of port # 5 of the relay device 3a (see step 21 and steps 18 to 20 are omitted). ). Eventually, the packets of traffic 1 and 2 (16 packets each) arrive at the terminal device 1a without packet loss (see procedure 35 in FIG. 20).

<Effect>
According to the embodiment, even when the amount of packets stored in the low priority buffer area 25 exceeds a predetermined value in the relay device 3a, the packets are not discarded, and at least one detour destination relay device (for example, the relay device 3b). Is then returned to the relay device 3a. At this time, if there is an empty area in the low priority buffer area 25 (an example of “the amount of storage is within a predetermined range”), the packet can be stored in the low priority buffer area 25 and transferred to the terminal device 1a. can do. According to the configuration of such an embodiment, the overflow of the low priority buffer area 25 in the relay device 3a can be avoided.

  Therefore, packet loss can be avoided and communication abnormality due to packet loss can be avoided. The configuration of the embodiment has an effect of reducing the occurrence frequency of packet loss in a scene where a large amount of traffic occurs in a short time. For this reason, the effect equivalent to expanding the network capacity can be obtained in a short time.

  The configuration of the embodiment can be realized by updating the firmware of the existing network device or adding a storage device without changing the physical network configuration. In other words, it is not necessary to replace the relay device or add a detour. For this reason, it is not necessary to install new equipment or to lay lines such as optical fibers. For this reason, there exists an advantage which can suppress introduction cost cheaply.

  Also, in the embodiment, the possibility of packet loss can be suppressed by enabling continuous detouring and increasing the delay time. In the embodiment, by using the order management area 34, it can be guaranteed that each packet belonging to the same traffic (packet flow) is transferred to the same detour destination. Further, by using the order management area 34, it is possible to determine whether or not the packet is returned from the detour destination. In this way, the configuration is simplified.

  In the embodiment, information on a plurality of detour destination ports can be prepared in the detour destination management area 33, and a packet can be transferred to a detour destination with a small traffic. Further, the detour destination relay device 3b (3c) can return the packet from the detour source to the original state (the state before the header conversion) by the header restoration process using the ARP table 31. In the embodiment, the buffer is provided in the priority unit, but the unit in which the buffer is provided can be set as appropriate. For example, the transmission (output) port unit, the reception (input) port unit, the destination unit, etc. Either may be sufficient. In short, when the capacity of a buffer capable of temporarily storing packets having destination information for the first device exceeds a predetermined value, the bucket is sent to the second device without being stored in the buffer. It ’s fine. The configurations of the embodiments described above can be combined as appropriate.

DESCRIPTION OF SYMBOLS 1 ... Terminal device 2, 3 ... Relay device 11 ... CPU
12, 14 ... Memory 13 ... Switch 32 ... Order management unit 36 ... Header conversion unit

Claims (8)

A changing unit that changes the destination information of the packet to the second device when the storage amount of the buffer capable of temporarily storing the packet including the destination information for the first device exceeds a predetermined value;
When the packet transferred to the second device based on the changed destination information and the destination information is changed for the first device is received from the second device, the storage amount of the buffer is within a predetermined range. If there is, a management unit for storing the packet in the buffer;
Including a communication device. When the packet transferred to the second device and whose destination information is changed for the first device is received from the second device, and the storage amount of the buffer is out of a predetermined range, the changing unit Changes the destination information of the packet for a third device different from the second device,
The management unit stores the buffer when the packet is transferred from the third device to the third device based on the changed destination information and the destination information is changed for the first device. The communication device according to claim 1, wherein the packet is stored in the buffer if the amount is within a predetermined range. A storage unit for storing identification information of a packet whose destination information is changed from the first device to the second device;
The said management part determines changing the destination information of the packet which has the identification information same as the identification information memorize | stored in the said memory | storage part from the said 1st apparatus direction toward the said 2nd apparatus. The communication device described. The said management part determines the packet by which identification information is memorize | stored in the said memory | storage part among the packets received from the said 2nd apparatus as a packet transferred to the said 2nd apparatus by the change of destination information. The communication apparatus as described in. A decision unit configured to determine a candidate having a small communication amount as the second device from the plurality of second device candidates based on information indicating a communication amount corresponding to each of the plurality of second device candidates; The communication apparatus according to any one of claims 1 to 4. A first device;
A second device;
A communication device connected to the first device and the second device;
The communication device
A changing unit that changes the destination information of the packet to the second device when a storage amount of a buffer capable of temporarily storing the packet including the destination information for the first device exceeds a predetermined value;
When the packet transferred to the second device based on the changed destination information and the destination information is changed for the first device is received from the second device, the storage amount of the buffer is within a predetermined range. And a management unit for storing the packet in the buffer,
The second device is a communication system in which when the destination information of the packet received from the communication device indicates a predetermined value, the destination information of the packet is changed for the first device and transferred to the communication device. The second device corresponds to the network address of the first device using an address resolution protocol when the destination information includes the physical address of the second device and the network address of the first device as the predetermined value. The communication system according to claim 6, further comprising: a rewriting unit that obtains a physical address of the first device to perform and rewrites the physical address of the second device included in the destination information of the packet with the physical address of the first device. The communication device
When the storage capacity of the buffer that can temporarily store the packet including the destination information for the first device exceeds a predetermined value, the destination information of the packet is changed for the second device,
When the packet transferred to the second device based on the changed destination information and the destination information is changed for the first device is received from the second device, the storage amount of the buffer is within a predetermined range. If present, store the packet in the buffer;
A packet transfer method for a communication apparatus.

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