JP7469699B2 - Packet forwarding system and packet forwarding method - Google Patents

Description

The present invention relates to a packet forwarding system and a packet forwarding method.

The technology disclosed in Non-Patent Document 1 will be outlined with reference to FIG. 9. FIG. 9 is a block diagram showing a communication network system 100 in which the OpenFlow protocol operates. The communication network system 100 includes an OpenFlow controller 101, OpenFlow switches 110, 111, and 112, and a DHCP (Dynamic Host Configuration Protocol) server 120.

The OpenFlow switches 110 and 111 are connected, and each has already established a connection with the OpenFlow controller 101. The OpenFlow switch 111 is connected to the DHCP server 120. In this state, assume that the OpenFlow switch 112 is newly connected to the OpenFlow switch 110.

When connecting to the OpenFlow switch 110, the OpenFlow switch 112 uses a data transfer port, not a management port, to connect to the OpenFlow switch 110. A DHCP client is running in the OpenFlow switch 112, and the OpenFlow switch 112 is recognized by the OpenFlow controller 101 in the following procedure.

(1) OpenFlow switch 112 sends a DHCP message to OpenFlow switch 110. OpenFlow switches 110 and 111 forward the DHCP message sent by OpenFlow switch 112 to DHCP server 120.

(2) The DHCP server 120 sends the IP (Internet Protocol) address and port number of the OpenFlow controller 101 to the OpenFlow switch 112. The OpenFlow switches 110 and 111 forward the IP address and port number of the OpenFlow controller 101 sent by the DHCP server 120 to the OpenFlow switch 112.

(3) The OpenFlow agent running in the OpenFlow switch 112 retrieves the IP address and port number of the OpenFlow controller 101. The OpenFlow agent connects to the OpenFlow controller 101 based on the retrieved IP address and port number. The OpenFlow controller 101 detects the connection relationship between the OpenFlow switches 110, 111, and 112 using LLDP (Link Layer Discovery Protocol) or the like.

In this way, the newly connected OpenFlow switch 112 establishes a connection with the OpenFlow controller 101 by superimposing it on the data network without using the management ports and network. The OpenFlow controller 101 can detect the connection relationship between the OpenFlow switches 110, 111, and 112. This makes it possible to reduce the costs required for installing and managing the management ports and network.

S. Sharma et al., “In-Band Control, Queuing, and Failure Recovery Functionalities for OpenFlow”, IEEE Network, 30(1), pp.106-112, 2016

The technology disclosed in Non-Patent Document 1 requires that a DHCP client and an OpenFlow agent are running in the newly connected OpenFlow switch 112. Furthermore, the technology disclosed in Non-Patent Document 1 is premised on the OpenFlow switch 112 being equipped with a CPU (Central Processing Unit) and the like for running these.

Here, it is assumed that the device connected to the OpenFlow switch 110 is a modular communication device. Such modular communication devices may not have a port dedicated to management. Furthermore, due to size and cost considerations, they may not have a CPU for operating an OpenFlow agent or DHCP client. For this reason, such modular communication devices may not be able to connect to the OpenFlow controller 101.

In view of the above circumstances, the present invention aims to provide technology that enables a communication device that is unable to run an OpenFlow agent, a DHCP client, etc., to connect to a controller in a simple manner.

One aspect of the present invention is a packet forwarding system comprising a forwarding control device that controls the forwarding of packets, a forwarding device that forwards the packets based on forwarding rules defined by the forwarding control device, and a communication device that is newly connected to the forwarding device, wherein the communication device sends a control packet to the forwarding device, the forwarding device assigns physical port identification information that identifies the physical port that received the control packet and identification information of its own device to the control packet sent from the communication device, and forwards the control packet to the forwarding control device, and the forwarding control device obtains the identification information of the forwarding device and the physical port identification information assigned to the control packet.

One aspect of the present invention is a packet forwarding method in a packet forwarding system comprising a forwarding control device that controls the forwarding of packets, a forwarding device that forwards the packets based on forwarding rules defined by the forwarding control device, and a communication device that is newly connected to the forwarding device, in which the communication device sends a control packet to the forwarding device, and the forwarding device assigns physical port identification information that identifies the physical port that received the control packet and identification information of its own device to the control packet sent from the communication device, and forwards the control packet to the forwarding control device, and the forwarding control device obtains the identification information of the forwarding device and the physical port identification information assigned to the control packet.

According to this invention, even a communication device that cannot run an OpenFlow agent, a DHCP client, etc. can connect to a controller in a simple manner.

1 is a block diagram showing a configuration of a packet forwarding system according to a first embodiment. 1 is a block diagram showing a configuration of a packet forwarding system which is a specific example of a first embodiment. 10 is a sequence diagram showing the flow of a connection configuration collection process performed by the packet forwarding system according to the first embodiment. FIG. 4A and 4B are diagrams illustrating connection configuration information recorded by a transfer control device in the first embodiment. FIG. 11 is a block diagram showing a configuration of a packet forwarding system according to a second embodiment. FIG. 11 is a sequence diagram showing a part of the flow of a connection configuration collection process performed by the packet forwarding system according to the second embodiment. FIG. 13 is a block diagram showing a configuration of a packet forwarding system according to a third embodiment. FIG. 13 is a sequence diagram showing a partial flow of a connection configuration collection process performed by the packet forwarding system according to the third embodiment. FIG. 1 is a diagram for explaining the technique disclosed in Non-Patent Document 1.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(overview)
First, an overview of the packet transfer system of the present invention will be described.
In the packet forwarding system of the present invention, one or more forwarding devices are connected to a forwarding control device. The one or more forwarding devices have multiple ports, and spanning tree-like logical paths with the forwarding control device as the root are set in advance on the multiple ports. The spanning tree-like logical paths may be set in each forwarding device by the forwarding control device, or may be set in each forwarding device in response to an instruction from the forwarding control device.

When a new communications device is connected to one of the transfer devices, the communications device sends a control packet to the transfer control device through the logical path. The communications device sends control packets at regular intervals from the time it is powered on and started up, or sends control packets in response to instructions from outside (for example, the transfer control device). Note that since the logical path is configured in the shape of a spanning tree, no control packet loops occur. Control packets always reach the transfer control device through a port on the transfer device that corresponds to the root.

The forwarding device to which the communication device is connected receives the control packet through the logical path. The forwarding device to which the communication device is connected assigns to the control packet the identification information of the physical port that received the control packet and the identification information of the forwarding device (its own device), and forwards the control packet to the forwarding control device.

The transfer control device identifies the newly connected communication device based on information attached to the control packet transferred from the transfer device, and also identifies the transfer device to which the communication device is newly connected and its physical port. In this way, a spanning tree-shaped logical path is set for one or more transfer devices, so that the communication device can identify the newly connected transfer device and its physical port. This allows the newly connected communication device to connect to the transfer control device. Therefore, even a communication device that cannot operate an OpenFlow agent, a DHCP client, or the like can be connected to the controller in a simple manner.
An embodiment constituting the above-mentioned packet forwarding system will be described below.

First Embodiment
1 is a block diagram showing the configuration of a packet forwarding system 1 according to the first embodiment. The packet forwarding system 1 includes a forwarding control device 2, an OpenFlow switch 3, an autonomous forwarding device 4, and a communication device 5.

The transfer control device 2 controls the path of packets. The transfer control device 2 transmits information indicating the transfer rules defined in the transfer control device 2 (hereinafter referred to as "transfer rule information") to the OpenFlow switch 3. The transfer control device 2 is, for example, a controller in a Software Designed Network (SDN). In the following description, it is assumed that the transfer control device 2 is an OpenFlow controller.

The forwarding rule information is, for example, an OpenFlow flow entry. The forwarding rule information includes information for identifying the packet to be forwarded and information indicating the processing to be performed on the identified packet. The processing to be performed on the identified packet is, for example, a process of forwarding the packet to a specific route, a process of rewriting or deleting part of the packet's data, a process of discarding the packet, etc.

The transfer control device 2 receives a Packet-In message of the OpenFlow protocol sent by the OpenFlow switch 3. The transfer control device 2 sends a Packet-Out message of the OpenFlow protocol to the OpenFlow switch 3. The transfer control device 2 instructs the OpenFlow switch 3 and the autonomous transfer device 4 to set a logical path. The transfer control device 2 may also set a logical path for the OpenFlow switch 3 and the autonomous transfer device 4.

The OpenFlow switch 3 comprises an autonomous transfer device transceiver unit 31, a search logical path generation unit 32, a transfer rule memory unit 34, a transfer processing unit 35, a transfer control device transceiver unit 36 and an external transceiver unit 37.

The transfer control device transceiver unit 36 is a physical port that connects to the transfer control device 2. The transfer control device transceiver unit 36 connects to the transfer control device 2 via a physical line 7. The transfer control device transceiver unit 36 establishes a secure channel connection with the transfer control device 2, and transmits and receives data in accordance with the OpenFlow protocol.
The external transmission/reception unit 37 is a port that connects the OpenFlow switch 3 to another OpenFlow switch, a communication network such as the Internet, or the like. The communication device 5 may be directly connected to the external transmission/reception unit 37. The external transmission/reception unit 37 may be a single or multiple physical ports.

The autonomous transfer device transceiver unit 31 is a physical port that connects to the autonomous transfer device 4. In FIG. 1, the autonomous transfer device transceiver unit 31 is shown as being connected to the autonomous transfer device 4 via a physical line 6-n. When the OpenFlow switch 3 is connected to multiple autonomous transfer devices 4, it is provided with an autonomous transfer device transceiver unit 31 corresponding to each of the multiple autonomous transfer devices 4.

For ease of explanation, the autonomous transfer device transceiver unit 31, the transfer control device transceiver unit 36, and the external transceiver unit 37 are given different names, but they are all physical ports provided in the OpenFlow switch 3. The physical port to which the transfer control device 2 is connected becomes the transfer control device transceiver unit 36, the physical port to which the autonomous transfer device 4 is connected becomes the autonomous transfer device transceiver unit 31, and the other physical ports become the external transceiver unit 37.

The forwarding rule memory unit 34 stores the forwarding rule information that the forwarding control device 2 transmits to the OpenFlow switch 3. The forwarding rule information is written to the forwarding rule memory unit 34 as follows. The forwarding control device transceiver unit 36 receives the forwarding rule information from the forwarding control device 2. The forwarding control device transceiver unit 36 outputs the received forwarding rule information to the forwarding processing unit 35. The forwarding processing unit 35 writes the forwarding rule information output by the forwarding control device transceiver unit 36 to the forwarding rule memory unit 34.

In response to an instruction from the transfer control device 2, the search logical path generation unit 32 generates a logical path consisting of a spanning tree with the transfer processing unit 35 as a node. The spanning tree is configured such that the physical links between the transfer devices (for example, between the OpenFlow switch 3 and the autonomous transfer device 4) are the branches, and the transfer processing unit of the transfer device directly connected to the transfer control device is the root, but no loop occurs. Here, for example, a tag VLAN (Virtual Local Area Network) is applied to generate the logical path. The search logical path generation unit 32 associates a VLAN-ID (identifier) indicating the generated logical path with identification information (hereinafter referred to as "physical port identification information") that specifies the autonomous transfer device transmission/reception unit 31, and adds it to the transfer rule information stored in the transfer rule storage unit 34. The transfer rule information may have a rule for Packet-In of a control packet set in advance. For example, a rule for transferring a Packet-In message to the transfer control device 2 when a control packet is received may be set in advance in the transfer rule information.

The forwarding processing unit 35 selects an operation to be performed on the received packet based on the forwarding rule information stored in the forwarding rule memory unit 34, and performs the selected operation on the packet.

The autonomous forwarding device 4 is, for example, a device equivalent to a Layer 2 switch. The autonomous forwarding device 4 comprises physical ports 41-1 to 41-N, an autonomous search logical path generation unit 42, an autonomous forwarding processing unit 44, and an autonomous forwarding rule storage unit 45. Physical lines 6-1 to 6-N are connected to each of the physical ports 41-1 to 41-N. Note that N is an integer of 2 or more, and n is any integer from 1 to N. In FIG. 1, physical line 6-n refers to any one of the physical lines 6-1 to 6-N.

The autonomous forwarding rule storage unit 45 stores predetermined autonomous forwarding rule information. The autonomous forwarding rule information is information indicating the rules of forwarding processing performed by a general Layer 2 switch. For example, the autonomous forwarding rule information includes information for identifying a packet to be forwarded and information indicating processing for the identified packet. The processing for the identified packet is, for example, a process of forwarding the packet to physical ports 41-1 to 41-N to which a device having a destination MAC (Media Access Control) address is connected. For example, the autonomous forwarding rule information also includes the following information: In the logical path of the spanning tree, a packet received at a physical port connected to a node far from the root of the spanning tree (i.e., a child in the tree structure) and a packet received at a physical port corresponding to a leaf of the spanning tree are transmitted to a physical port connected to a node close to the root (i.e., a parent in the tree structure).

In response to an instruction from the transfer control device 2, the autonomous search logical path generation unit 42 permits the physical ports 41-1 to 41-N to connect to the communication device 5, with the OpenFlow switch 3 as the root. In other words, the autonomous search logical path generation unit 42 generates a logical path that constitutes a spanning tree with the physical ports 41-1 to 41-N to which the communication device 5 may be connected as leaves.

The autonomous search logical path generation unit 42 assigns to the generated logical path a VLAN-ID that is the same as the VLAN-ID that was assigned to the logical path by the search logical path generation unit 32 of the OpenFlow switch 3. The autonomous search logical path generation unit 42 writes to the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45, in association with identification information (hereinafter referred to as "physical port identification information") that identifies the physical ports 41-1 to 41-N to which the VLAN-ID was assigned and the assigned VLAN-ID.

The autonomous forwarding processing unit 44 selects the processing for the received packet based on the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45, and performs the selected processing on the packet. When the autonomous forwarding processing unit 44 captures a control packet transmitted by the communication device 5, it performs the following processing. Specifically, when the captured control packet does not have any additional information regarding other autonomous forwarding devices 4, the autonomous forwarding processing unit 44 adds additional information to the control packet, including the identification information of its own device that is stored in advance in an internal memory area, and the physical port identification information that received the control packet, and then forwards the control packet.

The communication device 5 is, for example, a modular communication device equipped with IP communication capabilities. Here, a modular communication device is a communication device with limited functionality, for example, one that does not have a dedicated management port and does not have a CPU on which an OpenFlow agent or DHCP client runs. Note that, for convenience of explanation, in FIG. 1, the communication device 5 is connected to the physical port 41-1 of the autonomous transfer device 4 via the physical line 6-1, but such a modular communication device may also be connected directly to the physical port 41-1 without using the physical line 6-1.

When the communication device 5 is powered on and starts up, it sends out a control packet including its own device identification information at regular intervals. The identification information of the own device is, for example, information such as a MAC address or an IP address.

Figure 2 is a block diagram showing the configuration of a packet forwarding system 1a, which is a specific example of the first embodiment. In Figure 2, the same components as those in Figure 1 are given the same reference numerals. The packet forwarding system 1a comprises a forwarding control device 2, an OpenFlow switch 3, autonomous forwarding devices 4a, 4b, and communication devices 5a, 5b. In the following description, when referring to each of the internal functional parts of the autonomous forwarding devices 4a, 4b, the reference numerals of the respective functional parts are indicated by adding "a" and "b".

The autonomous transfer device 4a has four physical ports 41a-1, 41a-2, and 41a-3. The autonomous transfer device 4b has four physical ports 41b-1, 41b-2, and 41b-3.

The physical port 41a-1 of the autonomous transfer device 4a and the autonomous transfer device transceiver unit 31 of the OpenFlow switch 3 are connected by a physical line 6a-1. The physical port 41a-3 of the autonomous transfer device 4a and the physical port 41b-1 of the autonomous transfer device 4b are connected by a physical line 6a-3. The communication device 5a is connected to the physical port 41b-2 of the autonomous transfer device 4b via the physical line 6b-2, and the communication device 5b is connected to the physical port 41a-2 of the autonomous transfer device 4a via the physical line 6a-2.

The search logical path generation unit 32 of the OpenFlow switch 3, the autonomous search logical path generation unit 42a of the autonomous transfer device 4a, and the autonomous search logical path generation unit 42a of the autonomous transfer device 4b generate the logical path 60 shown in Figure 2 in response to instructions from the transfer control device 2.

The search logical path generation unit 32 assigns any one of the available VLAN-IDs to the autonomous forwarding device transmitting/receiving unit 31. Here, for example, it is assumed that "1001" is assigned as the VLAN-ID. The search logical path generation unit 32 transmits the assigned VLAN-ID "1001" to the autonomous search logical path generation units 42a, 42b. The search logical path generation unit 32 writes the physical port identification information of the autonomous forwarding device transmitting/receiving unit 31 and the VLAN-ID "1001" in association with the forwarding rule information stored in the forwarding rule memory unit 34.

The autonomous search logical path generation units 42a and 42b receive the information of the VLAN-ID "1001" sent by the search logical path generation unit 32. The autonomous search logical path generation unit 42a associates the physical port identification information corresponding to each of the physical ports 41a-1, 41a-2, and 41a-3 with the VLAN-ID "1001" received from the search logical path generation unit 32 and writes it to the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45a. Similarly, the autonomous search logical path generation unit 42b associates the physical port identification information corresponding to each of the physical ports 41b-1, 41b-2, and 41b-3 with the VLAN-ID "1001" received from the search logical path generation unit 32 and writes it to the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45b. As a result, a logical path 60 corresponding to the VLAN-ID "1001" is generated.

(Connection Configuration Collection Process by Packet Forwarding System in First Embodiment)
Fig. 3 is a sequence diagram showing the flow of processing for collecting the connection configuration of the communication device 5a by the packet forwarding system 1a shown in Fig. 2. It is assumed that the communication device 5a is started up in a state where it is connected to the physical port 41b-2 of the autonomous forwarding device 4b. The communication device 5a sends out a control packet including its own device identification information to the physical line 6b-2 at regular intervals (step Sa1).

The physical port 41b-2 of the autonomous forwarding device 4b receives the control packet sent by the communication device 5a. The physical port 41b-2 outputs the received control packet to the autonomous forwarding processing unit 44b (step Sa2). The autonomous forwarding processing unit 44b captures the control packet output by the physical port 41b-2. The captured control packet has no additional information attached to it. Therefore, the autonomous forwarding processing unit 44b reads the identification information of the autonomous forwarding device 4b from the internal storage area. The autonomous forwarding processing unit 44b generates additional information including the read identification information of the autonomous forwarding device 4b and the physical port identification information of the physical port 41b-2 that captured the control packet. The autonomous forwarding processing unit 44b attaches the generated additional information to the control packet (step Sa3).

The autonomous forwarding processing unit 44b refers to the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45b, and forwards the control packet via the logical path 60 associated with the physical port 41b-2 that received the control packet (step Sa4). Specifically, forwarding is performed as follows. In the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45b, the physical port 41b-2 that received the control packet is associated with the VLAN-ID "1001". The autonomous forwarding processing unit 44b refers to the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45b, and detects the physical ports 41b-1, 41b-2, and 41b-3 that are associated with the VLAN-ID "1001".

The physical port 41b-2 that received the control packet is a port that corresponds to a leaf of the spanning tree. Therefore, the autonomous forwarding processing unit 44b refers to the autonomous forwarding rule information, assigns the VLAN-ID "1001" to the control packet, and forwards the control packet to the physical port 41b-1, which is the port closest to the root of the spanning tree.

The physical port 41b-1 sends out a control packet via the physical line 6a-3. The physical port 41a-3 of the autonomous forwarding device 4a receives the control packet via the physical line 6a-3 (step Sa5). The physical port 41a-3 outputs the received control packet to the autonomous forwarding processing unit 44a. The autonomous forwarding processing unit 44a captures the control packet output by the physical port 41a-3. The captured control packet has already been assigned additional information related to the autonomous forwarding device 4b. Therefore, the autonomous forwarding processing unit 44a does not assign additional information to control packets to which additional information has been assigned.

The autonomous forwarding processing unit 44a refers to the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45a, and forwards the control packet via the logical path 60 associated with the physical port 41a-3 that received the control packet (step Sa6). Specifically, forwarding is performed as follows. The control packet received by the autonomous forwarding processing unit 44a is assigned the VLAN-ID "1001". Therefore, the autonomous forwarding processing unit 44a refers to the autonomous forwarding rule information stored in the autonomous forwarding rule storage unit 45a, and detects the physical ports 41a-1, 41a-2, and 41a-3 associated with the VLAN-ID "1001".

The physical port 41a-3 that received the control packet is a port that corresponds to a leaf of the spanning tree. The autonomous forwarding processing unit 44a then refers to the autonomous forwarding rule information and forwards the control packet to the physical port 41a-1, which corresponds to the root of the spanning tree.

The physical port 41a-1 sends a control packet via the physical line 6a-1. The autonomous forwarding device transceiver unit 31 of the OpenFlow switch 3 receives the control packet via the physical line 6a-1 (step Sa7).

The autonomous forwarding device transceiver 31 of the OpenFlow switch 3 outputs the received control packet to the forwarding processing unit 35. The forwarding processing unit 35 references the forwarding rule information stored in the forwarding rule memory unit 34 and generates a Packet-In message including a control packet with the VLAN-ID "1001" removed from the control packet and the physical port identification information of the autonomous forwarding device transceiver 31 that received the control packet. The forwarding processing unit 35 transmits the generated Packet-In message to the forwarding control device 2 via the forwarding control device transceiver 36 (step Sa8). Note that the forwarding processing unit 35 does not need to remove the VLAN-ID when forwarding the control packet.

The transfer control device 2 receives the Packet-In message sent by the transfer control device transceiver 36 (step Sa9). The transfer control device 2 reads the identification information of the autonomous transfer device 4b included in the assigned information attached to the control packet included in the Packet-In message, the physical port identification information of the physical port 41b-2 that captured the control packet, and the identification information of the communication device 5a included in the control packet, and records the read information in an internal memory area (step Sa10).

For example, the transfer control device 2 generates a table having three items, "communication device," "destination device," and "destination port," as shown in Figure 4. The transfer control device 2 writes the information shown in the first row of Figure 4, i.e., the identification information of communication device 5a, the identification information of autonomous transfer device 4b, and the physical port identification information of physical port 41b-2, to the generated table.

The same processing as in the case of communication device 5a is performed in communication device 5b, and the information shown in the second row of the table shown in Figure 4 is recorded. As a result, by referring to the table shown in Figure 4, the transfer control device 2 can recognize that communication device 5a is connected to physical port 41b-2 of autonomous transfer device 4b, and that communication device 5b is connected to physical port 41a-2 of autonomous transfer device 4a.

In the configuration of the first embodiment described above, a spanning tree logical path 60 is generated with the OpenFlow switch 3 as the starting point and the physical ports 41a-2, 41b-2, and 41b-3 of the autonomous transfer devices 4a and 4b that allow connection to the communication devices 5a and 5b as leaves. The communication devices 5a and 5b connect to the physical ports 41a-2 and 41b-2 of the autonomous transfer devices 4a and 4b, and send a control packet including the identification information of the autonomous transfer devices 4a and 4b to the connected autonomous transfer devices 4a and 4b. When the communication devices 5a and 5b connect to the physical ports 41a-2 and 41b-2 of the autonomous transfer devices 4a and 4b and receive a control packet from the communication devices 5a and 5b, the autonomous transfer devices 4a and 4b assign physical port identification information that identifies the physical port 41a-2 and 41b-2 that received the control packet and the identification information of the autonomous transfer devices to the control packet, and send the control packet via the logical path 60. The OpenFlow switch 3 transfers the control packet received via the logical path 60 to the transfer control device 2. The transfer control device 2 receives the control packet and reads the identification information and physical port identification information of the autonomous transfer devices 4a, 4b attached to the received control packet, and the identification information of the communication devices 5a, 5b included in the control packet.

This allows the transfer control device 2 to identify the transfer device (e.g., autonomous transfer device 4a, 4b or OpenFlow switch 3) to which the communication device is newly connected and its physical port. As a result, the newly connected communication device can connect to the transfer control device 2. Therefore, even a communication device that cannot operate an OpenFlow agent or a DHCP client, etc., can be connected to the transfer control device 2 in a simple manner.

Second Embodiment
Fig. 5 is a block diagram showing the configuration of a packet forwarding system 1b according to the second embodiment. In Fig. 5, the same components as those in the packet forwarding systems 1 and 1a shown in Fig. 1 and Fig. 2 are denoted by the same reference numerals, and different components will be described below. The packet forwarding system 1b includes a forwarding control device 2b, an OpenFlow switch 3, autonomous forwarding devices 4a and 4b, and a communication device 5ab.

The transfer control device 2b has the following configuration in addition to the configuration of the transfer control device 2. The transfer control device 2b generates a control packet transmission instruction packet. The control packet transmission instruction packet is a packet that includes an instruction to send a control packet to a communication device newly connected to a transfer device such as the OpenFlow switch 3 or the autonomous transfer device 4a, 4b. The transfer control device 2b sends a Packet-Out message to the OpenFlow switch 3 that includes an instruction to send a control packet transmission instruction packet from the autonomous transfer device transceiver unit 31 of the OpenFlow switch 3 and the generated control packet transmission instruction packet.

The communication device 5ab is, for example, a modular communication device, similar to the communication devices 5, 5a, and 5b of the first embodiment. The communication device 5ab has a configuration that differs from the communication devices 5, 5a, and 5b in the following respects: When the communication device 5ab receives a control packet transmission instruction packet, it transmits a control packet including identification information of its own device.

(Connection Configuration Collection Process by Packet Forwarding System of Second Embodiment)
FIG. 6 is a sequence diagram showing a part of the flow of the process of collecting the connection configuration of the communication device 5ab by the packet forwarding system 1b shown in FIG.

The transfer control device 2b generates a control packet transmission instruction packet. The transfer control device 2b transmits a Packet-Out message to the OpenFlow switch 3, the Packet-Out message including an instruction to send a control packet transmission instruction packet from the autonomous transfer device transceiver unit 31 of the OpenFlow switch 3 and the generated control packet transmission instruction packet (step Sb1).

The transfer control device transceiver unit 36 of the OpenFlow switch 3 receives the Packet-Out message sent by the transfer control device 2b (step Sb2), and outputs the received Packet-Out message to the transfer processing unit 35. The transfer processing unit 35 imports the Packet-Out message output by the transfer control device transceiver unit 36.

The forwarding processing unit 35 sends out a control packet sending instruction packet from the physical port 31 in accordance with the instruction contained in the Packet-Out message to send a control packet sending instruction packet from the autonomous forwarding device transceiver unit 31 (step Sb2).

The autonomous forwarding device transceiver unit 31 sends a control packet transmission instruction packet via the physical line 6a-1. The physical port 41a-1 of the autonomous forwarding device 4a receives the control packet transmission instruction packet via the physical line 6a-1 (step Sb4). The physical port 41a-1 outputs the received control packet transmission instruction packet to the autonomous forwarding processing unit 44a.

The autonomous forwarding processing unit 44a sends out a control packet send instruction packet from a physical port other than the physical port that received the control packet send instruction packet (here, physical port 41a-1) (step Sb5). As a result, the control packet send instruction packet is sent to physical ports 41a-2 and 41a-3. No device is connected to physical port 41a-2. Therefore, the control packet send instruction packet is not sent out from physical port 41a-2.

The physical port 41a-3 sends a control packet transmission instruction packet via the physical line 6a-3. The physical port 41b-1 of the autonomous forwarding device 4b receives the control packet transmission instruction packet via the physical line 6a-3 (step Sb6). The physical port 41b-1 outputs the received control packet transmission instruction packet to the autonomous forwarding processing unit 44b.

The autonomous forwarding processing unit 44b sends out a control packet send instruction packet from a physical port other than the physical port that received the control packet send instruction packet (here, physical port 41b-1) (step Sb6). As a result, the control packet send instruction packet is sent to physical ports 41b-2 and 41b-3. No device is connected to physical port 41b-3. Therefore, the control packet send instruction packet is not sent out from physical port 41b-3.

The physical port 41b-2 sends a control packet transmission instruction packet via the physical line 6b-2. The communication device 5ab receives the control packet transmission instruction packet via the physical line 6b-2 (step Sb8). The communication device 5ab sends a control packet including its own device's identification information to the physical line 6b-2. Then, the processing of steps Sa2 to Sa10 shown in FIG. 3 is performed. As a result, the transfer control device 2b acquires the information shown in the first row of the table shown in FIG. 4, similar to the transfer control device 2 of the first embodiment.

In the second embodiment described above, the communication device 5ab does not send control packets at regular intervals, but sends a control packet when it receives a packet sending instruction packet. Therefore, the communication device 5ab does not need to be equipped with a clock or the like for sending control packets at regular intervals. In the case of the communication devices 5, 5a, and 5b of the first embodiment, there is a possibility that a large number of control packets will be sent due to a malfunction, but the communication device 5ab of the second embodiment sends a control packet at the timing when it receives a control packet sending instruction packet, so that it is possible to suppress the transmission of unnecessary control packets more than in the first embodiment.

In addition, the format of the control packet transmission instruction packet may be the same as that of the control packet. In this case, the communication device 5ab does not need to generate a new control packet, but only needs to send back the control packet transmission instruction packet that it received, thereby making it possible to further reduce the weight of the communication device 5ab's functions.

In the second embodiment, when the transfer control device 2b generates a control packet transmission instruction packet, the transfer control device 2b may generate the control packet transmission instruction packet including information indicating the format of the logical path 60. In this way, when the communication device 5ab receives the control packet transmission instruction packet, it can generate a control packet based on the information indicating the format of the logical path 60 included in the control packet transmission instruction packet.

For example, suppose that the OpenFlow switch 3 and the autonomous transfer devices 4a, 4b change the format of the logical path 60. The OpenFlow switch 3 transmits information about the changed format of the logical path 60 to the transfer control device 2b. This allows the transfer control device 2b to notify the communication device 5ab of the changed format of the logical path 60 by a control packet transmission instruction packet, so that the communication device 5ab can flexibly follow the change in the format of the logical path 60.

Here, the format of the logical path 60 is, for example, a VLAN-ID. In the above first and second embodiments, the communication devices 5, 5a, 5b, and 5ab are not shown as being configured to be assigned a VLAN-ID in advance, but the VLAN-ID "1001" of the logical path 60 can be preregistered in the communication devices 5, 5a, 5b, and 5ab. In this case, the autonomous forwarding processing unit 44a of the autonomous forwarding device 4b does not need to assign a VLAN-ID to the control packet captured via the physical port 41b-2. In such a configuration, for example, if the VLAN-ID is changed from "1001" to "1002", it becomes possible to notify the communication device 5ab of the change in the VLAN-ID by a control packet transmission instruction packet.

Third Embodiment
Fig. 7 is a block diagram showing the configuration of a packet forwarding system 1c according to the third embodiment. In Fig. 7, the same components as those in the packet forwarding systems 1, 1a, and 1b shown in Figs. 1, 2, and 5 are given the same reference numerals, and different components will be described below. The packet forwarding system 1c includes a forwarding control device 2c, OpenFlow switches 3 and 3c, an autonomous forwarding device 4a, and a communication device 5ab.

The OpenFlow switch 3c has the same internal configuration as the OpenFlow switch 3 shown in Fig. 1. Hereinafter, when referring to each of the functional units in the OpenFlow switch 3c that correspond to the functional units in the OpenFlow switch 3, the reference numeral of each functional unit will be denoted by adding the letter "c."

The OpenFlow switch 3c comprises a transfer control device transceiver unit 36c, a transfer processing unit 35c, a transfer rule memory unit 34c, a search logical path generation unit 32c, external transceivers 37c-1, 37c-2 and autonomous transfer device transceivers 31c-1, 31c-2.

The transfer control device transceiver unit 36c connects to the transfer control device 2c via a physical line 7c. The transfer control device transceiver unit 36c establishes a secure channel connection with the transfer control device 2c and transmits and receives data according to the OpenFlow protocol. The autonomous transfer device transceiver unit 31c-1 is connected to the physical port 41a-3 of the autonomous transfer device 4a via a physical line 6a-3. The communication device 5ab connects to the external transceiver unit 37c-2 via a physical line 6b-2.

The search logical path generating unit 32c of the OpenFlow switch 3c generates a logical path consisting of a spanning tree in response to an instruction from the transfer control device 2c. Note that the search logical path generating unit 32c is preset so that the OpenFlow switch 3c is not the starting point of the spanning tree.

As shown in FIG. 7, in the packet forwarding system 1c of the third embodiment, a logical path 60 similar to that of the first and second embodiments is generated. The VLAN-ID "1001" is used to generate the logical path 60. In this case, the search logical path generation unit 32c of the OpenFlow switch 3c writes the identification information of the autonomous forwarding device transceiver unit 31c-1 and the external transceivers 37c-1 and 37c-2, and the VLAN-ID "1001" in association with them to the forwarding rule information stored in the forwarding rule memory unit 34c.

The transfer control device 2c has the following configuration in addition to the configuration of the transfer control device 2b. When the OpenFlow switch 3c receives a control packet, the transfer control device 2c transmits to the OpenFlow switch 3c forwarding rule information including an instruction to forward the received control packet to the transfer control device 2b by a Packet-In message. The transfer control device transceiver unit 36c receives the forwarding rule information transmitted by the transfer control device 2c, and outputs the received forwarding rule information to the transfer processing unit 35c. The forwarding processing unit 35c writes the forwarding rule information output by the transfer control device transceiver unit 36c to the forwarding rule memory unit 34c.

(Connection Configuration Collection Process by Packet Forwarding System of Third Embodiment)
In the third embodiment, as in the second embodiment, the process of transmitting the control packet transmission instruction packet shown in FIG. 6 from the transfer control device 2c is started. In steps Sb1 to Sb5, the transfer control device 2c, the OpenFlow switch 3, and the autonomous transfer device 4a perform the same processes as in the second embodiment. In steps Sb6 and Sb7, the OpenFlow switch 3c performs the same processes instead of the autonomous transfer device 4b. In step Sb8, the communication device 5ab receives the control packet transmission instruction packet that the external transmission/reception unit 37c-1 of the OpenFlow switch 3c sends to the physical line 6b-2.

Figure 8 is a sequence diagram showing the flow of processing performed after communication device 5ab receives a control packet transmission instruction packet in the third embodiment. Communication device 5ab transmits a control packet including its own device identification information to physical line 6b-2 (step Sd1).

The external transmission/reception unit 37c-1 of the OpenFlow switch 3c receives the control packet sent by the communication device 5ab. The external transmission/reception unit 37c-1 outputs the received control packet to the forwarding processing unit 35c (step Sd2).

The forwarding processing unit 35c refers to the forwarding rule information stored in the forwarding rule memory unit 34c. The forwarding rule information stored in the forwarding rule memory unit 34c defines an instruction to forward the control packet to the forwarding control device 2c by a Packet-In message. The forwarding rule information includes information about the VLAN-ID "1001". However, it is assumed that the instruction to forward the control packet to the forwarding control device 2c by the Packet-In message is defined to take priority. In this case, the forwarding processing unit 35c does not forward the control packet via the logical path 60. The forwarding processing unit 35c transmits a Packet-In message including the control packet and physical port identification information specifying the received external transmitting/receiving unit 37c-1 to the forwarding control device 2c via the forwarding control device transmitting/receiving unit 36c (step Sd3).

The transfer control device 2c receives the Packet-In message sent by the transfer control device transceiver 36c (step Sd4). By referencing the sender information of the Packet-In message, the transfer control device 2c detects that the device that received the control packet is the OpenFlow switch 3c. The transfer control device 2c can obtain information on the physical port to which the communication device 5ab is connected from the physical port identification information of the external transceiver 37c-1 contained in the Packet-In message. The transfer control device 2c can obtain the identification information of the communication device 5ab by referencing the control packet contained in the Packet-In message.

Therefore, the transfer control device 2c can obtain from the Packet-In message a combination of three pieces of information recorded in a table having the items "Communication device," "Destination device," and "Destination port" shown in Figure 4. The transfer control device 2c records the obtained three pieces of information in a table in its internal memory area (step Sd5).

In the configuration of the third embodiment described above, the OpenFlow switch 3c is connected to the autonomous transfer device 4a, and the logical path 60 is generated in the physical ports of the OpenFlow switch 3c, that is, the external transmission/reception units 37c-1 and 37c-2 that allow connection to the communication device 5ab, and the OpenFlow switch 3c is further connected to the transfer control device 2c by a physical line 7c, which is a path other than the logical path 60. The communication device 5ab is connected to the OpenFlow switch 3c. When the OpenFlow switch 3c receives a control packet sent by the communication device 5ab, it sends the control packet to the transfer control device 2c via the physical line 7c based on the forwarding rule information stored in the forwarding rule storage unit 34c together with the physical port identification information that identifies the external transmission/reception unit 37c-1 that received the control packet.

As a result, even if communication device 5ab, which does not have a dedicated management port and does not have an OpenFlow agent or DHCP client running, is connected to OpenFlow switch 3c on which an OpenFlow agent is running, it is possible to detect the connection configuration between communication device 5ab and OpenFlow switch 3c. The OpenFlow switch 3c to which communication device 5ab is connected does not forward the control packet to a device upstream of the logical path 60, but instead sends it directly to the transfer control device 2c by a Packet-In message. As a result, the control packet is not forwarded to the autonomous transfer device 4a and OpenFlow switch 3 upstream of the logical path 60, and therefore the bandwidth utilization rate can be improved compared to the configuration of the second embodiment.

In the first to third embodiments, the starting point of the logical paths 60, 61, and 62 is the OpenFlow switch 3, but the starting point of the logical paths 60, 61, and 62 may be the transfer control devices 2, 2b, and 2c. In this case, the transfer of control packets from the OpenFlow switch 3 to the transfer control devices 2, 2b, and 2c is performed via the logical paths 60 and 61, that is, based on the VLAN-ID. The transfer of control packet transmission instruction packets from the transfer control devices 2b and 2c to the OpenFlow switch 3 is also performed based on the VLAN-ID.

In the above first to third embodiments, the logical paths 60, 61, and 62 are generated by the search logical path generation units 32 and 32c and the autonomous search logical path generation units 42a and 42b in response to instructions from the forwarding control devices 2, 2b, and 2c, but the generation of the logical paths does not need to be limited to this. For example, when the configuration is not complicated, the administrator of the packet forwarding systems 1a, 1b, and 1c may generate the logical paths 60, 61, and 62 so as to configure a spanning tree. In this case, the administrator adds information about the VLAN-ID to the forwarding rule information stored in the forwarding rule storage units 34 and 34c and the autonomous forwarding rule information stored in the autonomous forwarding rule storage units 45a and 45b.

A logical path may be set in each transfer device so that the transfer control devices 2, 2b, and 2c configure a spanning tree. When configured in this way, the OpenFlow switches 3 and 3c do not need to be equipped with the search logical path generator 32, and the autonomous transfer devices 4, 4a, and 4b do not need to be equipped with the autonomous search logical path generator 42. Instead, the transfer control devices 2, 2b, and 2c are equipped with a logical path generator for configuring a spanning tree.
In the above first to third embodiments, the control packet includes the identifiers of the communication devices 5, 5a, 5b, and 5ab, but the control packet does not need to include the identifiers of the communication devices 5, 5a, 5b, and 5ab. When configured in this way, the communication devices 5, 5a, 5b, and 5ab transmit control packets that do not include the identifiers of the communication devices 5, 5a, 5b, and 5ab at regular intervals from the time when the power is turned on and the devices start up, or in response to an instruction from outside (for example, a transfer control device).

In the above first to third embodiments, it is assumed that the OpenFlow protocol of SDN is operating in the transfer control devices 2, 2b, 2c and the OpenFlow switches 3, 3c, but an SDN communication protocol other than the OpenFlow protocol may also be operating.

In the above first to third embodiments, the packet forwarding systems 1, 1a, 1b, 1c are configured to include both an OpenFlow switch (e.g., OpenFlow switches 3, 3c) and an autonomous forwarding device (e.g., 4, 4a, 4b), but the packet forwarding systems 1, 1a, 1b, 1c may be configured to include either one of the forwarding devices. Taking FIG. 2 as an example of such a configuration, the packet forwarding system 1a includes either the OpenFlow switch 3 or the autonomous forwarding devices 4a, 4b. The packet forwarding system 1a then sets a spanning tree-like logical path with the forwarding control device 2 as the root to the forwarding device that includes it.

The transfer control devices 2, 2b, and 2c, the OpenFlow switches 3 and 3c, and the autonomous transfer devices 4, 4a, and 4b in the first to third embodiments described above may be realized by a computer. In that case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the function. Note that the "computer system" here includes hardware such as an OS and peripheral devices. In addition, the "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, the "computer-readable recording medium" may also include a medium that dynamically holds a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in that case. Furthermore, the above program may be for realizing part of the functions described above, or may be capable of realizing the functions described above in combination with a program already recorded in a computer system, or may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment and also includes designs that do not deviate from the gist of the present invention.

It can be applied to a communication network in which devices equipped with SDN communication protocols and devices that do not have SDN communication protocols are interconnected.

1...Packet forwarding system, 2...Forwarding control device, 3...OpenFlow switch, 4...Autonomous forwarding device, 5...Communication device, 31...Autonomous forwarding device transceiver, 32...Search logical path generation unit, 34...Forwarding rule storage unit, 35...Forwarding processing unit, 36...Forwarding control device transceiver, 37...External transceiver, 41-1 to 41-N...Physical port, 42...Autonomous search logical path generation unit, 44...Autonomous forwarding processing unit, 45...Autonomous forwarding rule storage unit

Claims (7)

A packet forwarding system comprising: a forwarding control device that controls forwarding of packets; a forwarding device that forwards the packets based on a forwarding rule defined by the forwarding control device; and a communication device that is newly connected to the forwarding device,
The communication device transmits a control packet to the forwarding device;
the transfer device assigns physical port identification information that identifies a physical port that received the control packet and identification information of the transfer device to the control packet sent from the communication device, and transfers the control packet to the transfer control device;
the transfer control device acquires the identification information of the transfer device and the physical port identification information assigned to the control packet;
Packet forwarding system. In the transfer device, a logical path of a spanning tree is generated, the logical path being a physical port included in the transfer device, the transfer processing unit of each transfer device being a node, the physical port that allows connection to the communication device being a leaf, and the transfer processing unit of the transfer device connected to the transfer control device being a root.
2. The packet forwarding system according to claim 1. Further comprising an autonomous forwarding device that is directly or indirectly connected to the forwarding device and forwards packets based on an autonomous forwarding rule;
the transfer device is connected to the autonomous transfer device, a logical path is generated on a physical port of the transfer device that allows a connection to a communication device, and the transfer device is connected to the transfer control device via a route other than the logical path,
The packet forwarding system according to claim 1, wherein when the forwarding device receives the control packet sent by the communication device, the forwarding device sends the control packet to the forwarding control device through a route other than a logical path based on forwarding rules defined by the forwarding control device. When the communication device is powered on while connected to the transfer device, the communication device transmits the control packet to the connected transfer device at a predetermined interval.
The packet forwarding system according to any one of claims 1 to 3. The transfer control device transmits a control packet transmission instruction packet via the transfer device,
Upon receiving the control packet transmission instruction packet, the communication device transmits the control packet.
The packet forwarding system according to any one of claims 1 to 4. The transfer control device includes:
the control packet transmission instruction packet includes information indicating a format of a logical path for transmitting the control packet transmission instruction packet,
The communication device includes:
upon receiving the control packet transmission instruction packet, generating the control packet according to information indicating a format of the logical path, which is included in the control packet transmission instruction packet, and transmitting the generated control packet to the logical path;
The packet forwarding system according to claim 5. A packet forwarding method in a packet forwarding system including a forwarding control device that controls forwarding of packets, a forwarding device that forwards the packets based on a forwarding rule defined by the forwarding control device, and a communication device that is newly connected to the forwarding device, comprising:
The communication device transmits a control packet to the forwarding device;
the transfer device assigns physical port identification information that identifies the physical port that received the control packet and identification information of its own device to the control packet sent from the communication device and transfers the control packet to the transfer control device;
the transfer control device acquires the identification information of the transfer device and the physical port identification information assigned to the control packet;
Packet forwarding method.

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