JP6148546B2 - Packet transfer apparatus and program - Google Patents

Description

  The present invention relates to a transfer technique for received packets in a packet transfer apparatus having a plurality of interfaces.

  Open flow technology has attracted attention as a network control. In a network using OpenFlow technology, a flow is identified by a combination of a MAC address, an IP address, a port number, and the like, and quality (QoS) control and path control are performed for each flow. A packet transfer apparatus that transfers a packet in an OpenFlow network determines a flow identifier from header information of an input packet, and determines an interface to output the packet based on the determined flow identifier and a flow table. . For example, when the flow identifier is specified by a combination of a source and destination IP address and a source and destination port number, a value obtained by arranging these four values in a predetermined order is the flow identifier.

  Note that each entry in the flow table is a wild card, that is, it allows a part or all of the flow identifiers to have an arbitrary value, so that one flow identifier has a plurality of entries in the flow table. Can occur to match. For example, consider a case where a flow identifier is specified by a combination of a source and destination IP address and a source and destination port number, and the flow table shown in FIG. 5 is set in the packet transfer apparatus. Note that “*” in FIG. 5 is a wild card and indicates that the value of the corresponding position of the flow identifier may be an arbitrary value. The entry with the number 1 is a default route and is an entry that matches all the flow identifiers. Here, for example, when a packet with a transmission source IP address (X1, X2, X3, X4) and a transmission destination IP address (Y1, Y2, Y3, Y4) is received, Matches the four entries of table numbers 1, 100, 101 and 102. Each entry in the flow table is given a priority. When the flow identifier matches a plurality of entries, the output interface is determined according to the entry with the highest priority. For example, if the entry with the highest priority among the four entries with the numbers 1, 100, 101, and 102 is the entry with the number 102, this received packet is output to the interface IF # 3.

  As described above, in a flow table that allows wildcards, there may be a plurality of matching entries, and thus there is a problem that it takes time to search for matching entries and to determine priority. For this reason, Non-Patent Document 1 discloses a flow table that permits wild cards (hereinafter referred to as a wild card type table) and a flow table that indicates the relationship between a flow identifier and an output interface without using wild cards. (Hereinafter referred to as an exact match table) is disclosed. Specifically, when Non-Patent Document 1 receives a packet, first, the output interface is determined based on the exact match type table, and there is no entry in the complete match type table. Therefore, the output interface is determined based on the exact match type table. In the case where the output interface is not determined, the output interface is determined by the wild card type table, and the correspondence between the determined output interface and the flow identifier of the received packet is added to the exact match type table.

  With this configuration, when a packet belonging to a new flow arrives, a wildcard type table with a slow search speed is used. However, when an entry is added to the exact match type table, a perfect match with a fast search speed is complete. Since the output interface is determined by the type table, the overall search speed is increased.

N. Matsumoto, et al. , "LightFlow: Speeding Up GPU-based Flow Switching and Fatiguing Maintenance of Flow Table", HPSR 2012

  However, in the configuration described in Non-Patent Document 1, the output order of packets belonging to the same flow may be different from the input order. For example, as shown in FIG. 6, it is assumed that packets A, B, C, D and E belonging to the same flow are received in the order of description. It is assumed that the entry for the flow identifier of this flow does not exist in the complete match type table. Since the first determination unit cannot determine the output interface in the exact match type table, the first determination unit outputs the packet belonging to this flow to the second determination unit that determines the output interface based on the wild card type table. Here, until the second determining unit determines the output interface of the packet A first output to the second determining unit and the result is reflected in the complete match type table, the packets B and C are also the second determining unit. Is output.

  In this case, since the output interface of the subsequent packets D and E is determined by the complete match type table with a high search speed, the packets D and E are output before the packets B and C as shown in FIG. It may occur that packets belonging to the same flow are output in an order different from the input order.

  The present invention provides a packet transfer apparatus that outputs packets belonging to the same flow in the same order as the input order while preventing an increase in the time for determining an interface to output.

According to one aspect of the present invention, a packet transfer apparatus having a plurality of interfaces, which holds first information indicating a relationship between a flow identifier and an interface, and second information indicating a relationship between a flow identifier portion and an interface Means for determining the flow identifier of the first packet based on the received header information of the first packet; and an interface for outputting the first packet based on the flow identifier of the first packet and the first information. A first determination unit that determines and outputs the first packet from the determined interface; and when the first determination unit cannot determine an interface that outputs the first packet, the flow identifier of the first packet and the second An interface for outputting the first packet is determined based on the information, and the determined interface is determined. Second decision means for outputting the first packet from the source, and when the second decision means decides the interface for outputting the first packet, the flow identifier of the first packet and the second decision means decide Updating means for updating the relationship with the interface so as to be added to the first information, and the first determining means cannot determine an interface for outputting the first packet based on the first information. The second packet having the same flow identifier as the first packet received before the update unit updates the first information after receiving the first packet determines an interface to be output to the second determination unit. let not, after the second determining means is allowed to output to determine the interface that outputs the first packet, out of the relevant interface Characterized in that to.

  Packets belonging to the same flow can be output in the same order as the input order while preventing the time for determining the output interface from becoming long.

1 is a schematic configuration diagram of a packet transfer device according to an embodiment. FIG. The figure which shows the exact match type | mold table by one Embodiment. The figure which shows the wild card type table by one Embodiment. The figure which shows the waiting | standby packet table by one Embodiment. The figure which shows the wild card type table by one Embodiment. Explanatory drawing of a change of packet order.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the following drawings, components that are not necessary for the description of the embodiments are omitted from the drawings.

  FIG. 1 is a schematic configuration diagram of a packet transfer apparatus according to the present embodiment. The packet transfer apparatus 1 has a plurality of interfaces, and stores packets received by each interface in the buffer unit 10. The flow determination unit 11 determines the flow identifier of the flow to which the received packet belongs from the header information of the received packet, and stores the determined flow identifier 11 and the storage position of the received packet in the buffer unit 10 in the first determination unit 12. Output. In this embodiment, the flow identifier includes an interface to which a received packet is input, a source and destination MAC address, a source and destination IP address, a source and destination port number included in the header information of the received packet. A combination of The MAC address is a layer 2 address, and the IP address is a layer 3 address. However, the information used for the flow identifier may be a part of the information. Further, all or a part of the information and other values such as a VLAN (virtual local area network) identifier may be used.

  A holding unit (not shown) of the packet transfer apparatus holds a complete match type table 16 and a wild card type table 17. As described above, the wild card type table 17 includes an entry indicating the relationship between the flow identifier portion and the interface to be output, that is, information for determining an interface to be output by partial matching of the flow identifier. It is. Note that the partial match here includes a case where there is no match at all, that is, a default route is included. FIG. 3 shows an example of the wild card type table 17 of the present embodiment. In FIG. 3, the entry of number 1 is the default route. For example, when the interface # 5 receives a packet whose source IP address is (X1, X2, X3, X4) and whose destination IP address is (Y1, Y2, Y3, Y4), the received packet is , Numbers 1, 100 to 103 correspond to the five entries. For example, if the highest priority among the five entries is the entry with the number 102, this received packet is output from the interface IF # 3. The wild card type table 17 is set by the operator of the packet transfer apparatus or generated by signaling from another apparatus indicating the flow setting.

  On the other hand, the complete match type table 16 includes an entry indicating the relationship between the flow identifier and the interface to be output, that is, information for determining an interface to be output by the complete match of the flow identifier. FIG. 2 shows an example of the exact match type table 16 of the present embodiment. In the present embodiment, in order to speed up the search for matching entries, the relationship between the value of the flow identifier itself and the interface to be output is not shown, but the hash value by the hash function of the flow identifier and the interface The relationship is shown. That is, the exact match table 16 is a hash table. Since there is a probability that different flow identifiers have the same hash value, in this embodiment, the value of the flow identifier itself is also included in the exact match type table 16 and used for confirmation after the search. Furthermore, in this embodiment, the exact match type table 16 has a status field. This status field has three values “A”, “B”, and “C”.

  The value “A” indicates that the exact match table 16 has a correspondence relationship between the flow identifier and the interface, and therefore, the output interface of the packet belonging to the flow indicated by the flow identifier can be determined by the exact match table 16. ing. Further, the value “B” does not include the correspondence between the flow identifier and the interface in the exact match table 16, and therefore, the output interface of the packet belonging to the flow indicated by the flow identifier by the exact match table 16. Indicates that it cannot be determined. Further, the value “C” indicates that the correspondence between the flow identifier and the interface is not currently included in the exact match table 16, but the correspondence between the flow identifier and the interface is added to the exact match table 16. It shows that it is waiting. For example, in the exact match table 16 of FIG. 2, the value of the status field of the flow identifier whose hash values are H2 and H100 is “A”, and the interfaces IF # 2 and IF # 1 are output destinations. It is shown. On the other hand, the output destination is not shown for the flow identifiers whose state field values are “B” and “C” and whose hash values are H1 and H3. Note that the update of the complete match type table 16 such as addition and deletion of entries to the complete match type table 16 is performed by the table management unit 14 as described later.

  When receiving information such as a flow identifier from the flow determination unit 11, the first determination unit 12 determines the output interface of the received packet corresponding to the flow identifier from the state field of the complete match type table 16 using the complete match type table 16. Determine if you can. If it can be determined, that is, if the status field of the entry corresponding to the flow identifier is “A”, the first determination unit 12 determines the output interface of the received packet corresponding to the flow identifier by the exact match table 16. Then, output information indicating the determined output interface and the storage position of the received packet in the buffer unit 10 is output to the reading unit 15. On the other hand, when the status field of the entry corresponding to the flow identifier is “B”, the first determination unit 12 outputs the information such as the flow identifier received from the flow determination unit 11 to the second determination unit 13. To do. At this time, the first determination unit 12 notifies the table management unit 14 that the flow identifier whose status field is “B” has been received, and the table management unit 14 then determines the flow identifier of the exact match table 16. The value of the status field of the entry corresponding to is changed to “C”.

  When receiving information such as a flow identifier from the first determination unit 12, the second determination unit 13 determines an output interface of a received packet corresponding to the flow identifier using the wild card type table 17, and determines the determined output interface; Output information indicating the storage position of the received packet in the buffer unit 10 is output to the reading unit 15. At this time, the second determination unit 13 notifies the table management unit 14 of the relationship between the flow identifier and the determined output interface. The table management unit 14 adds the interface notified from the second determination unit 13 to the output interface field of the entry of the exact match table 16 corresponding to the flow identifier notified from the second determination unit 13, and The status field of the entry is changed from “C” to “A”. In addition, this update is notified to the first determination unit 12.

  When the status field of the entry in the exact match table 16 corresponding to the flow identifier received from the flow determination unit 11 is “C”, the first determination unit 12 receives the flow identifier and the buffer unit from the flow determination unit 11 The ten storage positions are stored as the standby packet table 18. FIG. 4 shows an example of the standby packet table 18. The standby packet table 18 indicates the storage position of the corresponding packet in the buffer unit 10 for each flow identifier together with the reception order. In the present embodiment, as in the exact match table 16, the hash value is used instead of the value of the flow identifier itself. For example, in FIG. 4, four packets belonging to the flow identifier whose hash value is H1 are received after the state field of the entry of the exact match type table 16 corresponding to the flow identifier becomes “C”. The received packet is at position P1 of the buffer unit 10, the second received packet is at position P4 of the buffer unit 10, the third received packet is at position P8 of the buffer unit 10, and the fourth received packet is buffered. It is shown that the part 10 is held at the position P20.

  When the table management unit 14 adds the output interface corresponding to the flow identifier to the exact match type table 16, the first determination unit 12 sets the output interface for the packet indicated in the entry corresponding to the flow identifier in the standby packet table. The output information including the storage position is output to the reading unit 15 in the order of reception. That is, when an output interface is added to the entry of the exact match type table 16 corresponding to the hash value H1 in FIG. 4, the first determination unit 12 outputs the output in the order of the storage positions P1, P4, P8, and P20. The interface is notified to the reading unit 15. The first determination unit 12 receives an output interface to be notified to the reading unit 15 from the table management unit 14 or the second determination unit 13. Alternatively, the first determination unit 12 may search and acquire the exact match table 16 after the exact match table 16 is updated by the table management unit 14. The reading unit 15 reads packets from the buffer unit 10 in the order of notification in accordance with the output information from the first determination unit 12 and the second determination unit 13, and outputs the read packets to the interface specified by the output information.

  As described above, when a packet belonging to a new flow arrives, only the first packet is subjected to the determination of the output interface by the second determination unit 13, and the second determination unit 13 Is held in the buffer unit 10 until an output interface is determined. At this time, a standby packet table 18 is created and held as information indicating the reception order. Then, when the second determination unit 13 determines the output interface, the packets held in the buffer unit 10 are read from the buffer unit 10 according to the reception order and transmitted to the determined output interface. Further, for the packets belonging to the flow after that, the first determination unit 12 determines the output interface. Accordingly, the output interface is determined only by the first packet of each flow by the second determination unit 13 having a low speed, and the first determination unit 12 having a high speed determines the output interface for the subsequent packets. As a result, the determination speed of the output interface as a whole can be shortened. Furthermore, it is possible to prevent the output order of packets of the same flow from being different from the input order. In the present embodiment, it is not necessary to synchronize the table search process by the first determination unit 12 and the table search process by the second determination unit 13, and a simple circuit configuration can be achieved. Further, until the second determination unit 13 determines the output interface, only the packets belonging to the flow for which the second determination unit 13 determines the output interface are held in the buffer unit 10, and other flows The packet to which it belongs is not affected.

  In the above embodiment, the state field is provided in the exact match type table 16, but the relationship between the flow identifier and the state field can be managed by a table different from the complete match type table 16. Further, in the above embodiment, the received packet is buffered at once in the buffer unit 10, and only the flow identifier and the storage location in the buffer unit 10 are notified to the first determination unit 12 and the second determination unit 13. However, an actual packet may be output to the first determination unit 12 or the second determination unit 13. Further, the exact match table 16 may indicate a relationship between an actual flow identifier and an output interface instead of a hash value.

Claims (6)

A packet transfer apparatus having a plurality of interfaces,
Holding means for holding first information indicating a relationship between a flow identifier and an interface, and second information indicating a relationship between a portion of the flow identifier and an interface;
Determining means for determining a flow identifier of the first packet based on the received header information of the first packet;
First determining means for determining an interface to output the first packet based on the flow identifier of the first packet and the first information, and outputting the first packet from the determined interface;
When the first determination unit cannot determine the interface that outputs the first packet, the interface that outputs the first packet is determined based on the flow identifier of the first packet and the second information. Second determining means for outputting the first packet;
When the second determining means determines the interface that outputs the first packet, the relation between the flow identifier of the first packet and the interface determined by the second determining means is updated to be added to the first information Updating means to
With
If the interface for outputting the first packet cannot be determined based on the first information, the first determining unit receives the first packet after the first packet is received until the updating unit updates the first information. For the second packet having the same flow identifier as that of one packet, the interface for outputting to the second determining means is not determined, and after the second determining means determines and outputs the interface for outputting the first packet, A packet transfer apparatus, characterized by being output from the interface. For the flow identifier, the holding means indicates that a first value indicating that the relationship between the flow identifier and the interface exists in the first information, and that the relationship between the flow identifier and the interface does not exist in the first information. A third value indicating at least a second value indicating, and a third value indicating that the relationship between the flow identifier and the interface does not exist in the first information but is waiting for addition; and
The first determining means determines an interface for outputting the received packet when the third information for the flow identifier of the first packet indicates the first value;
The second determining means determines an interface for outputting the received packet when the third information for the flow identifier of the first packet indicates the second value;
The update means updates the third information to the third value when the third information for the flow identifier of the first packet indicates the second value, and the second determination means sets the first information to the first value. The packet transfer apparatus according to claim 1, wherein when the interface that outputs a packet is determined, the third information is updated to the first value.   3. The packet transfer apparatus according to claim 2, wherein the first information is a hash table indicating a relationship between a hash value of a flow identifier and an interface, and the third information is included in the hash table. .   The first determination means creates fourth information indicating the reception order of the second packets when the interface for outputting the first packet cannot be determined by the first information, and the second determination means The interface according to any one of claims 1 to 3, wherein after the interface for outputting a packet is determined and output, the second packet is output from the interface in the same order as the reception order indicated by the fourth information. 2. The packet transfer apparatus according to item 1.   The fourth information is a hash table indicating a reception order of the second packet and a storage position in a buffer with respect to a hash value of a flow identifier of the second packet. The packet transfer apparatus described.   A program for causing a computer to function as the packet transfer apparatus according to claim 1.

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