WO2014007247A1

WO2014007247A1 - Network device, packet processing method and program, and network system

Info

Publication number: WO2014007247A1
Application number: PCT/JP2013/068133
Authority: WO
Inventors: 賢輔松島
Original assignee: 日本電気株式会社
Priority date: 2012-07-03
Filing date: 2013-07-02
Publication date: 2014-01-09

Abstract

When a received packet is a packet segmented according to a predetermined communication protocol, a segmented packet identifier, which is a common value for a group of packets obtained by the segmentation, is extracted from the packet, and it is also determined whether the packet includes a higher protocol element, which is a header element in a communication protocol higher than the predetermined communication protocol. When it is determined that the packet includes a higher protocol element, the higher protocol element is recorded in association with the segmented packet identifier. When it is determined that the packet does not include a higher protocol element, a higher protocol element stored in association with the segmented packet identifier is acquired. The packet is processed on the basis of the header element included in the packet and the higher protocol element.

Description

Network device, packet processing method and program, and network system

The present invention relates to a network device, a packet processing method and program, and a network system.

An OpenFlow network including a plurality of OFS (OpenFlow Switch) and OFC (OpenFlow Controller) has been proposed.
Each OFS processes a packet based on header elements such as L4 information (L4: Layer 4) and tunnel protocol header information. Specifically, the OFS stores a flow table that associates a header element match condition with a process for a packet that matches the match condition, and executes a process according to the flow table for the received packet. To do.
The OFC defines a flow table and sets the flow table in each OFS.

Note that Patent Document 1 discloses a technology of a relay device that handles divided packets.

JP 2005-101690 A

By the way, in an IP (Internet Protocol) network, MTU (Maximum Transfer Unit) which is the maximum packet length that can be transferred is defined. When the packet length exceeds the MTU, a network device such as OFS divides the packet into a plurality of packets for transmission. At this time, IP header information is added to each of the divided packets, but L4 information, tunnel protocol header information, and the like, which are protocols higher than IP, are included only in the first packet among the divided packets. It will be.

Therefore, when a packet is divided, a header element necessary for comparison with a match condition of the flow table may not be included in a packet received by a network device such as OFS, and the network device performs an appropriate flow (processing). There is a problem that it cannot be identified.

An object of the present invention is to provide a network device, a packet processing method and program, and a network system that solve the above-described problems.

The present invention has been made to solve the above-described problems, and determines whether a reception unit that receives a packet and whether the packet received by the reception unit is divided according to a predetermined communication protocol. When the division determination unit and the division determination unit determine that the packet received by the reception unit is a divided packet, a divided packet identifier that becomes a common value in a group of packets divided from the packet And when the division determination unit determines that the packet received by the reception unit is a divided packet, a header element of a communication protocol higher than the predetermined communication protocol in the packet An element determination unit that determines whether or not a higher-level protocol element is included, and the element determination unit includes When it is determined that a protocol element is included, an element recording unit that records the higher-level protocol element in the element storage unit in association with the fragment packet identifier extracted by the identifier extraction unit, and the element determination unit includes the reception unit An element acquisition unit that acquires an upper protocol element stored in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit, There is provided a network device comprising: a header element included in a packet received by a receiving unit; and a packet processing unit that processes the packet based on a higher-level protocol element acquired by the element acquiring unit.

Further, the present invention receives a packet, determines whether or not the received packet is divided according to a predetermined communication protocol, and determines that the received packet is a divided packet. When the packet is extracted from the packet, a divided packet identifier that is a common value in the group of divided packets, and when the received packet is determined to be a divided packet, It is determined whether or not an upper protocol element that is a header element of a communication protocol higher than a predetermined communication protocol is included, and when it is determined that the received packet includes an upper protocol element, the upper protocol element Is recorded in association with the extracted fragmented packet identifier, and the received packet includes an upper protocol element. If it is determined that the received packet is not associated with the extracted fragmented packet identifier, the higher protocol element stored in association with the extracted fragmented packet identifier is acquired, and based on the header element included in the received packet and the acquired upper protocol element And a packet processing method characterized by processing the packet.

In addition, the present invention provides a network device including a receiving unit that receives a packet, a division determining unit that determines whether a packet received by the receiving unit is divided according to a predetermined communication protocol, and the division determining unit An identifier extracting unit that extracts a divided packet identifier that is a common value in a group of divided packets from the packet when it is determined that the packet received by the receiving unit is a divided packet; If the determination unit determines that the packet received by the reception unit is a divided packet, whether or not the packet includes an upper protocol element that is a header element of a communication protocol higher than the predetermined communication protocol An element determination unit that determines whether the upper-layer protocol element is included in the packet received by the reception unit. An element recording unit that records the higher level protocol element in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit, and the element determination unit adds the higher level protocol element to the packet received by the reception unit. Is included in the packet received by the receiving unit and the element acquiring unit that acquires the upper protocol element stored in the element storage unit in association with the fragmented packet identifier extracted by the identifier extracting unit. A program for causing a packet processing unit to process the packet based on the header element and the higher-level protocol element acquired by the element acquisition unit is also provided.

Further, the present invention provides a receiving unit that receives a packet, a division determination unit that determines whether or not a packet received by the reception unit is divided according to a predetermined communication protocol, and the division determination unit, An identifier extraction unit that extracts a divided packet identifier that is a common value in a group of divided packets when the received unit determines that the received packet is a divided packet; and the division determination When the unit determines that the packet received by the receiving unit is a divided packet, whether or not the packet includes an upper protocol element that is a header element of a communication protocol higher than the predetermined communication protocol When the element determination unit and the element determination unit determine that the packet received by the reception unit includes an upper protocol element. An element recording unit that records the higher level protocol element in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit, and the element determination unit includes a higher level protocol element in the packet received by the reception unit. An element acquisition unit for acquiring a higher-level protocol element stored in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit, and a header element included in the packet received by the reception unit There is also provided a network system comprising a plurality of network devices including a packet processing unit that processes the packet based on a higher-order protocol element acquired by the element acquisition unit.

According to the present invention, the network device can specify the flow to be applied to the divided packets.

It is the schematic which shows the structure of the OpenFlow network by one Embodiment of this invention. It is a figure which shows the data structure of the divided | segmented packet. It is a figure which shows the specific example of a header element. Similarly, it is a figure which shows the specific example of a header element. It is a schematic block diagram which shows the structure of OFS by one Embodiment of this invention. 3 is a flowchart illustrating an operation of an OFS according to an embodiment of the present invention. It is a schematic block diagram which shows the basic composition of the network device by this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a configuration of an OpenFlow network 1 according to an embodiment of the present invention.
The OpenFlow network 1 (network system) includes a plurality of OFS 10 (network devices) and an OFC 20. A plurality of terminals 30 are connected to each OFS 10. The terminal 30 is a device that can communicate via a network such as a mobile phone, a smartphone, a tablet terminal, a PC (Personal Computer), or a server.

Each OFS 10 stores a flow table associating a header element match condition with a process for a packet that matches the match condition, and executes a process according to the flow table for the received packet.
Specifically, the OFS 10 searches the flow table designated by the OFC 20 for a match condition that matches the header element of the received packet, and executes a transfer process corresponding to the searched match condition.
Examples of header elements required for comparison with match conditions are:
L4 header information such as destination IP address and destination UDP port number (UDP: User Datagram Protocol) Header information.
The OFC 20 defines a flow table and sets the flow table in each OFS 10.

Here, the packet division will be described.
FIG. 2 is a diagram illustrating a data structure of a divided packet.
When the packet length of the IP packet transmitted from the terminal 30 to the OpenFlow network 1 exceeds the MTU (Maximum Transfer Unit) of the OpenFlow network 1, the terminal 30 excludes the IP header from the IP packet (FIG. 2A). The IP payload (FIG. 2B) is divided into a plurality (FIG. 2C). Then, the terminal 30 divides the IP packet by attaching an IP header to each of the divided IP payloads (FIG. 2D).
A common value is assigned to the group of divided packets in the ID field of the IP header attached to the divided IP payload. The information of the IP header is a value common to the group of divided packets (divided packet identifier).

In the IP packet before division, the header of the protocol higher than IP is stored in the head part of the IP payload. Therefore, the header element (upper protocol element) of the protocol higher than the IP used for comparison with the match condition in the OFS 10 is included in the head packet.
In the example shown in FIG. 2, the case where the packet is divided into three has been described.

3A and 3B are diagrams illustrating specific examples of header elements.
FIG. 3A is a diagram illustrating an example of information included in an IP header of a divided packet.
As shown in FIG. 3A, the IP header of the divided packet includes an ID, a protocol, a transmission source IP address, a transmission destination IP address, and an index number of the information. In the example shown in FIG. 3A, TCP (Transmission Control Protocol), UDP, and ICMP (Internet Control Message Protocol) are listed as protocols, but other protocols may be used.

FIG. 3B is a diagram illustrating an example of upper protocol elements included in the IP payload.
As shown in FIG. 3B, the upper protocol elements include LPL information for identifying APL (Application) / tunnel information, the source port number, the destination port number, the tunnel information, and the tunnel information of the tunnel packet information. Index number. In FIG. 3B, GTP / GRE is used as the port number and TEID / GRE-Key is used as the tunnel information. However, other port numbers, tunnel information, or APL information may be used.

FIG. 4 is a schematic block diagram showing the configuration of the OFS 10 according to an embodiment of the present invention.
The OFS 10 includes a reception unit 101, a packet buffer unit 102, a division determination unit 103, an identifier extraction unit 104, an element determination unit 105, an element storage unit 106, an element recording unit 107, an element acquisition unit 108, a flow table storage unit 109, and a search unit. 110 and a packet processing unit 111.

The receiving unit 101 receives a packet by performing a PHY (Physical Layer) process and a MAC (Media Access Control) process on a signal received from the terminal 30 or another OFS 10.
The packet buffer unit 102 temporarily stores the packet received by the receiving unit 101.
The division determination unit 103 determines whether or not the packet stored in the packet buffer unit 102 is a divided packet.
When the packet stored in the packet buffer unit 102 is a divided packet, the identifier extraction unit 104 extracts a divided packet identifier from the header of the packet.

When the packet stored in the packet buffer unit 102 is a divided packet, the element determination unit 105 determines whether or not the upper protocol element is included in the packet.
The element storage unit 106 stores the fragmented packet identifier and the upper protocol element of the packet having the fragmented packet identifier in association with each other.
When the packet stored in the packet buffer unit 102 includes an upper protocol element, the element recording unit 107 associates the divided packet identifier of the packet with the upper protocol element and records it in the element storage unit 106.
When the packet stored in the packet buffer unit 102 does not include an upper protocol element, the element acquisition unit 108 acquires the upper protocol element associated with the divided packet identifier of the packet from the element storage unit 106.

The flow table storage unit 109 stores a flow table in which match conditions are associated with processing for packets that match the match conditions.
The search unit 110 searches the flow table stored in the flow table storage unit 109 for a matching condition that matches the upper protocol element included in the packet. Further, the search unit 110 searches the flow table stored in the flow table storage unit 109 for a matching condition that matches the upper protocol element acquired by the element acquisition unit 108.
The packet processing unit 111 executes a process corresponding to the match condition searched by the search unit 110 on the buffer stored in the packet buffer unit 102.

FIG. 5 is a flowchart showing the operation of the OFS 10 according to an embodiment of the present invention.
When receiving the packet, the receiving unit 101 of the OFS 10 records the packet in the packet buffer unit 102 (step S1).
Next, the division determination unit 103 analyzes the header information of the packet recorded in the packet buffer unit 102 (step S2). Then, the division determination unit 103 determines whether or not the packet includes a divided packet identifier from the packet analysis result (step S3).

When the division determination unit 103 determines that the packet does not include a divided packet identifier (step S3: NO), the search unit 110 extracts the upper protocol element of the packet from the analysis result of the packet in step S2, The upper protocol element is set in the device internal header (step S4). The device internal header is header information used only within the OFS 10 for searching for a flow in the OFS 10.

Next, the search unit 110 searches the flow table stored in the flow table storage unit 109 for a matching condition that matches the internal header of the apparatus (step S5).
Then, the packet processing unit 111 extracts the corresponding packet from the packet buffer unit 102, and executes a process corresponding to the matching condition searched by the search unit 110 on the packet (step S6).
In the present embodiment, “retrieving” a packet from the packet buffer unit 102 means reading a packet stored in the packet buffer unit 102 and deleting the packet from the packet buffer unit 102.
Thereby, OFS10 can process the packet which is not a division | segmentation packet appropriately.

On the other hand, when the division determination unit 103 determines in step S3 that the packet includes a divided packet identifier (step S3: YES), the identifier extraction unit 104 determines the packet from the analysis result of the packet in step S2. A divided packet identifier is extracted (step S7).
Next, the element determination unit 105 determines whether or not a higher-order protocol element is included in the packet from the analysis result of the packet (step S8).

When the element determination unit 105 determines that the upper protocol element is included in the packet (step S8: YES), the element recording unit 107 extracts the upper protocol element of the packet from the analysis result of the packet in step S2. (Step S9).
Next, the element recording unit 107 associates the segment packet identifier extracted in step S7 with the higher-level protocol element extracted in step S9 and records it in the element storage unit 106 (step S10).

Next, the search unit 110 sets the upper protocol element extracted by the element recording unit 107 in step S9 in the apparatus internal header (step S4).
Next, the search unit 110 searches the flow table stored in the flow table storage unit 109 for a matching condition that matches the internal header of the apparatus (step S5).
Then, the packet processing unit 111 extracts the corresponding packet from the packet buffer unit 102, and executes a process corresponding to the matching condition searched by the search unit 110 on the packet (step S6).
As a result, the OFS 10 can appropriately process the head packet among the divided packets.

On the other hand, when the element determination unit 105 determines in step S8 that the upper protocol element is not included in the packet (step S8: NO), the element acquisition unit 108 is associated with the divided packet identifier extracted in step S7. It is determined whether or not the higher-order protocol element is recorded in the element storage unit 106 (step S11).
When the element acquisition unit 108 determines that the upper protocol element is recorded in the element storage unit 106 (step S11: YES), the element acquisition unit 108 acquires the upper protocol element from the element storage unit 106 (step S12).

Next, the search unit 110 sets the upper protocol element acquired by the element acquisition unit 108 in step S12 in the device internal header (step S4). Then, the search unit 110 searches the flow table stored in the flow table storage unit 109 for a match condition that matches the device internal header (step S5).
Then, the packet processing unit 111 extracts the corresponding packet from the packet buffer unit 102, and executes a process corresponding to the matching condition searched by the search unit 110 on the packet (step S6).
Thereby, OFS10 can process appropriately packets other than the head packet among the divided packets.

If the element acquisition unit 108 determines in step S11 that the upper protocol element is not recorded in the element storage unit 106 (step S11: NO), the upper protocol element is stored in the element storage in association with the divided packet identifier of the packet. Until the packet is recorded in the unit 106, the packet remains in the packet buffer unit 102, and the packet is not processed.

As described above, when the OFS 10 performs a process on the first packet among the divided packets, the upper protocol element is recorded in the element storage unit 106 in association with the divided packet identifier. Therefore, even when an intermediate packet or a final packet is received prior to the head packet, these packets remain in the packet buffer unit 102 until the head packet is processed.
Thereafter, the OFS 10 performs processing according to the upper protocol element newly stored in the element storage unit 106. The packet stored in the packet buffer unit 102 until the first packet is processed is also analyzed and processed when step S2 is performed again.
Therefore, according to the present embodiment, all the divided packets can be appropriately processed regardless of the reception order of the divided packets.

As described above, according to the present embodiment, the OFS 10 stores the upper protocol element included in the packet having the upper protocol element in association with the divided packet identifier common to the divided packet. When the OFS 10 receives a packet that does not have an upper protocol element, the OFS 10 acquires the upper protocol element associated with the divided packet identifier and processes the packet. Thereby, the OFS 10 can specify processing to be performed for the divided packets.

In a related technique, when a miss occurs (a suitable flow (processing) is not found) in the packet flow search in OFS in the OpenFlow network, the received packet is transferred to the OFC, and the route is resolved in the OFC. There is. On the other hand, according to the present embodiment, since no miss occurs in the packet flow search for the divided packet, the transfer of the received packet from the OFS 10 to the OFC 20 can be suppressed, and the processing load on the OFC 20 can be reduced.

Further, according to the present embodiment, as described above, no miss occurs in the packet flow search with respect to the divided packet, so that the packet is not discarded. Thereby, it is possible to suppress the retransmission of the packet by the application of the terminal 30 due to the discarding of the packet, it is possible to reduce the traffic load, and it is possible to prevent the erroneous charging at the time of metered charging.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to
For example, in the present embodiment, the case where the upper protocol element is used for the search of the flow (processing) to be applied has been described. However, the present invention is not limited to this. APL information may be used.

In the present embodiment, the case where the network apparatus according to the present invention is applied to the OFS 10 has been described. However, the present invention is not limited to this, and the present invention may be applied to a network apparatus that operates with a protocol other than OpenFlow.

In the present embodiment, the case where the upper protocol element is included in the top packet has been described. However, the present invention is not limited to this, and even if the upper protocol element is included in the intermediate packet or the final packet, the present embodiment is performed by the same processing. The same effect can be obtained.

<Basic configuration>
FIG. 6 is a schematic block diagram showing the basic configuration of the network device according to the present invention.
In the embodiment described above, the OFS 10 shown in FIG. 4 has been described as an embodiment of the network device according to the present invention. The basic configuration of the network device according to the present invention is as shown in FIG.
That is, the network device according to the present invention includes the reception unit 101, the division determination unit 103, the identifier extraction unit 104, the element determination unit 105, the element recording unit 107, the element acquisition unit 108, and the packet processing unit 111 as basic components.

The receiving unit 101 receives a packet.
The division determination unit 103 determines whether or not the packet received by the reception unit 101 is divided according to a predetermined communication protocol.
The identifier extraction unit 104, when the division determination unit 103 determines that the packet received by the reception unit 101 is a divided packet, a divided packet that becomes a common value in the group of divided packets from the packet Extract the identifier.
The element determination unit 105, when the division determination unit 103 determines that the packet received by the reception unit 101 is a divided packet, is an upper layer that is a header element of a communication protocol higher than a predetermined communication protocol. Determine whether protocol elements are included.
When the element determination unit 105 determines that the upper protocol element is included in the packet received by the reception unit 101, the element recording unit 107 associates the upper protocol element with the divided packet identifier extracted by the identifier extraction unit 104. To the element storage unit 106.
The element acquisition unit 108 associates the element storage unit 106 with the divided packet identifier extracted by the identifier extraction unit 104 when the element determination unit 105 determines that the upper protocol element is not included in the packet received by the reception unit 101. Get the upper protocol element stored by.
The packet processing unit 111 processes the packet based on the header element included in the packet received by the receiving unit 101 and the upper protocol element acquired by the element acquiring unit 108.

Thereby, the network device can specify the flow to be performed for the divided packets.

The above-mentioned OFS 10 has a computer system inside. The operation of each processing unit described above is stored in a computer-readable recording medium in the form of a program, and the above processing is performed by the computer reading and executing this program.
Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.
Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

The program may be for realizing a part of the functions described above.
Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

This application claims priority based on Japanese Patent Application No. 2012-149233 filed on Jul. 3, 2012, the entire disclosure of which is incorporated herein.

According to the present invention, it is possible to specify a flow to be applied to a divided packet in a network device that handles a packet that also uses a protocol higher than a predetermined communication protocol.

1 ... OpenFlow network 10 ... OFS
20 ... OFC
DESCRIPTION OF SYMBOLS 30 ... Terminal 101 ... Reception part 102 ... Packet buffer part 103 ... Division determination part 104 ... Identifier extraction part 105 ... Element determination part 106 ... Element storage part 107 ... Element recording part 108 ... Element acquisition part 109 ... Flow table storage part 110 ... Search unit 111 ... packet processing unit

Claims

A receiver for receiving the packet;
A division determination unit for determining whether or not the packet received by the reception unit is divided according to a predetermined communication protocol;
When the division determination unit determines that the packet received by the reception unit is a divided packet, an identifier extraction that extracts, from the packet, a divided packet identifier that has a common value in the group of divided packets And
When the division determination unit determines that the packet received by the reception unit is a divided packet, the packet includes an upper protocol element that is a header element of a communication protocol higher than the predetermined communication protocol. An element determination unit for determining whether or not
When the element determination unit determines that the upper protocol element is included in the packet received by the reception unit, the upper protocol element is recorded in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit. An element recording unit to
When the element determination unit determines that the upper protocol element is not included in the packet received by the reception unit, the upper protocol element stored in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit An element acquisition unit for acquiring
A network apparatus comprising: a packet processing unit that processes a packet based on a header element included in a packet received by the reception unit and a higher-level protocol element acquired by the element acquisition unit.
The element acquisition unit, when there is no upper protocol element associated with the fragment packet identifier in the element storage unit, after the element recording unit records the upper protocol element in the element storage unit in association with the fragment packet identifier The network device according to claim 1, wherein an upper protocol element corresponding to the packet received by the receiving unit is acquired.
The packet processing unit processes a packet received by the receiving unit according to a processing rule that associates a process applied to a packet with the higher-level protocol element for specifying a packet to which the process is applied. The network device according to claim 1 or 2.
Receive the packet,
Determining whether the received packet is divided according to a predetermined communication protocol;
When it is determined that the received packet is a divided packet, a divided packet identifier that is a common value in the group of divided packets is extracted from the packet,
When it is determined that the received packet is a divided packet, it is determined whether or not the packet includes an upper protocol element that is a header element of a communication protocol higher than the predetermined communication protocol;
If it is determined that the received packet includes an upper protocol element, the upper protocol element is recorded in association with the extracted fragmented packet identifier;
If it is determined that the received packet does not include an upper protocol element, obtain the upper protocol element stored in association with the extracted fragmented packet identifier;
A packet processing method, comprising: processing the packet based on a header element included in the received packet and the acquired upper protocol element.
If an upper protocol element associated with the fragment packet identifier is not stored, an upper protocol element corresponding to the received packet is obtained after an upper protocol element is recorded in association with the fragment packet identifier. The packet processing method according to claim 4, wherein:
Network equipment,
A receiver for receiving packets,
A division determination unit that determines whether the packet received by the reception unit is divided according to a predetermined communication protocol;
When the division determination unit determines that the packet received by the reception unit is a divided packet, an identifier extraction that extracts, from the packet, a divided packet identifier that has a common value in the group of divided packets Part,
When the division determination unit determines that the packet received by the reception unit is a divided packet, the packet includes an upper protocol element that is a header element of a communication protocol higher than the predetermined communication protocol. An element determination unit for determining whether or not
When the element determination unit determines that the upper protocol element is included in the packet received by the reception unit, the upper protocol element is recorded in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit. An element recording section,
When the element determination unit determines that the upper protocol element is not included in the packet received by the reception unit, the upper protocol element stored in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit An element acquisition unit to acquire
A program for functioning as a packet processing unit that processes a packet based on a header element included in a packet received by the receiving unit and an upper protocol element acquired by the element acquiring unit.
The element acquisition unit, when there is no upper protocol element associated with the fragment packet identifier in the element storage unit, after the element recording unit records the upper protocol element in the element storage unit in association with the fragment packet identifier The program according to claim 6, wherein an upper protocol element corresponding to the packet received by the receiving unit is acquired.
A receiver for receiving the packet;
A division determination unit for determining whether or not the packet received by the reception unit is divided according to a predetermined communication protocol;
When the division determination unit determines that the packet received by the reception unit is a divided packet, an identifier extraction that extracts, from the packet, a divided packet identifier that has a common value in the group of divided packets And
When the division determination unit determines that the packet received by the reception unit is a divided packet, the packet includes an upper protocol element that is a header element of a communication protocol higher than the predetermined communication protocol. An element determination unit for determining whether or not
When the element determination unit determines that the upper protocol element is included in the packet received by the reception unit, the upper protocol element is recorded in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit. An element recording unit to
When the element determination unit determines that the upper protocol element is not included in the packet received by the reception unit, the upper protocol element stored in the element storage unit in association with the divided packet identifier extracted by the identifier extraction unit An element acquisition unit for acquiring
A network system comprising: a plurality of network devices including: a header element included in a packet received by the receiving unit; and a packet processing unit that processes the packet based on a higher-level protocol element acquired by the element acquiring unit.
The element acquisition unit, when there is no upper protocol element associated with the fragment packet identifier in the element storage unit, after the element recording unit records the upper protocol element in the element storage unit in association with the fragment packet identifier The network system according to claim 8, wherein an upper protocol element corresponding to the packet received by the receiving unit is acquired.