JP6226691B2 - Link quality measuring apparatus and flow entry aggregation method and program - Google Patents

Description

  The present invention relates to a link quality measuring apparatus, and a flow entry aggregation method and program thereof, and more particularly, to a link quality measuring apparatus capable of reducing the number of flow entries of a test packet registered in each switch on a network, and its flow entry aggregation method and Regarding the program.

  Non-Patent Document 1 discloses an architecture called SDN (Software Defined Network) for centrally controlling network devices with software. Non-Patent Document 2 describes the flow matching conditions and processing for OpenFlow, which is a typical technology for realizing SDN, in units of “flows” defined by combining MAC addresses, IP addresses, and port numbers. A technique for controlling a communication path by setting a method as a flow entry in a controller or a switch is disclosed.

  However, the OpenFlow network operation monitoring method has not yet been fully studied. In the OpenFlow switch (hereinafter referred to as a switch), a method of remotely monitoring statistical information (MIB: Management Information Base) held by the network device itself can be used as in the case of a conventional network device. However, frequent MIB queries to the switch increase the processing load on the switch, making it difficult to constantly monitor communication quality. There are also issues where some quality metrics related to packet delay are not defined in the MIB.

  In Patent Document 1, in an OpenFlow network, a communication path is set so as to comprehensively pass through all links on the network, and then a test packet is sent from one measuring terminal and returned from each switch. A technique for monitoring the communication quality (loss rate, average delay, etc.) of each link by observing the behavior of the incoming test packet has been proposed.

  Patent Document 2 discloses a technique for reducing the number of flow entries by aggregating a plurality of flow entries into one in order to reduce the number of flow entries of test packets registered in each switch on the network. Yes. At this time, if a plurality of entries having different destination addresses (port numbers) are aggregated, the identification of each entry is impaired. Therefore, in Patent Document 2, an identification concept of “group” is newly introduced, and the destination address and port are collected by aggregation. When the identification by numbers is impaired, the entries are classified into different groups, and the identification of each flow entry is secured by a combination of the group identifier Gx and the destination address.

Japanese Patent Application No. 2013-064413 Japanese Patent Application No. 2013-202316

Open Networking Foundation (URL) http://www.openflow.org/ "Latest Trends in OpenFlow Technology for Next-Generation Networks 2013" Impress R & D Internet Media Research Institute N. Varris, and J. Manner, "Performance of a Software Switch," in Proc.of HPSR 2011, July 2011. A. Bianco, R. Birke, L. Giraudo, and M. Palacin, "OpenFlow Switching: Data Plane Performance," in Proc. Of ICC, page 1-5, IEEE 2010.

  In the conventional active measurement technology for the OpenFlow network, as disclosed in Patent Document 1, for each switch, (almost) the same number of flow entries as the test packet flow passing through the switch are registered. For this reason, as the monitoring target network becomes larger, the number of flow entries registered in each switch also increases.

  However, as discussed in Non-Patent Document 3, since there is generally an upper limit on the number of flow entries that can be registered in each switch, a new flow entry (other than the test packet flow) is assigned to the switch. Will cause a problem that cannot be added. Further, as discussed in Non-Patent Document 4, there arises a problem that the packet processing performance decreases as the number of registered flow entries increases. For this reason, it is necessary to minimize the number of flow entries for test packets registered in each switch as much as possible.

  Patent Document 2 proposes an approximation algorithm that minimizes the number of flow entries registered in each switch in a measurement system. However, the obtained solution is an approximate solution and is not necessarily an optimal solution.

  An object of the present invention is to solve the problems of the prior art and to reduce the number of flow entries of test packets registered in each switch on the network to the optimal solution of the minimum value, and a flow entry aggregation method thereof, To provide a program.

  In order to achieve the above object, the present invention provides a link quality measuring apparatus for relaying a test packet sent from a measuring terminal according to a flow entry registered in each switch on the network, and a flow entry aggregation method and program thereof Is characterized by the following measures.

  (1) In the link quality measurement device of the present invention, in at least one of the switches, flow entries relating to a plurality of test flows passing through one outgoing link are aggregated into one, and the aggregated flow entry is unique. The switch in which the identifier is associated with the outgoing link and the flow entries are aggregated transfers the test packet in which the identifier is described to the corresponding outgoing link based on the flow entry.

  (2) In the link quality measuring apparatus of the present invention, a switch in which other links through which a plurality of test flows of a link in which the flow entries of all the test flows that pass through are aggregated into one are passed in common are output links Then, the flow entries of the plurality of test flows are aggregated.

  (3) The flow entry aggregation method of the present invention sets an objective function for minimizing the maximum number of flow entries registered in each switch in the network, and sets the number of flow entries for each switch to each outgoing link of the switch. Define a binary variable that defines the total number of test flows passing through, with the aggregated link set to “1” and the non-aggregated link set to “0”, and the number of test flows for each switch as the number of incoming test flows. The number of test flows for the aggregated link is set to “1”, and the total number of binary variables corresponding to the links through which each test flow passes can be added to the test packet (number of identifiers). The link to be aggregated is determined by solving an integer programming problem that includes a constraint condition equal to (number).

According to the present invention, the following effects are achieved.
(1) With SDN such as OpenFlow, when measuring the communication quality of all links with one measuring terminal, each switch can control packets with a small number of flow entries and measure the communication quality. Become.

  (2) By registering with the number of flow entries minimized, the matching search processing time and memory size used are reduced, and by increasing the number of entries for normal data transfer, the original purpose of data transfer is reduced. Can be used effectively for control.

It is the block diagram which showed the structure of the principal part of the link quality measuring device system with which this invention is applied. It is a figure for demonstrating the aggregation method of a flow entry (before aggregation). It is a figure (after aggregation) for demonstrating the aggregation method of a flow entry. It is a figure for demonstrating the inclusion relation of a communication path. It is a figure for demonstrating the method of additional aggregation. It is a figure for demonstrating Formula (3) and (4).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of a link quality measuring apparatus to which the present invention is applied, and is composed of a link quality measuring unit 10 and an SDN network 20. Here, the case where the SDN is OpenFlow will be described as an example, and illustrations of components unnecessary for the description of the present invention are omitted.

  The link quality measurement unit 10 includes a server device 1 and a measurement terminal 2, and the server device 1 includes a measurement route calculation unit 101, a flow entry aggregation unit 102, and a communication route setting unit 103. The network 20 includes an OpenFlow controller 201, a plurality of OpenFlow switches (corresponding to routers), and a plurality of hosts. The controller 201 and each switch communicate with each other using the OpenFlow protocol, each switch is connected by SDN, and data (packet) transfer is performed between each switch and the host.

  The server device 1 and the measurement terminal 2 may be configured by mounting an application (program) for realizing each function on a general-purpose computer or server, or a part of the application is implemented in hardware or ROM. It may be configured as a dedicated machine or a single machine.

  In the server device 1, the measurement path calculation unit 101 calculates a test packet communication path by, for example, the method disclosed in Patent Document 1 and acquires a group of test packet communication paths. As will be described in detail later, the flow entry aggregating unit 102 aggregates the flow entries of test packets registered in each switch according to the calculation result of the communication path and passing through the switch to reduce the number of flow entries. . The communication path setting unit 103 registers the aggregated flow entry from the controller 201 to each switch.

  In the measurement terminal 2, the measurement execution unit 104 transmits and receives a test packet, and executes measurement processing such as estimating communication quality of each link from observation data. In this embodiment, it is assumed that the topology information indicating the connection relationship between physical network devices and the management information (for example, MAC address) of each switch are known, and these information are stored in the server device 1 in advance.

  First, the measurement path calculation unit 101 sets the shortest tree with the measurement terminal 2 as the root so that all the links are covered, with the interfaces of the switches as vertices and the links between the interfaces as edges. calculate. Next, a packet transfer rule (flow entry) is set to each switch so that each test packet is transferred to each switch along the calculated shortest path, and then returned to the measuring terminal 2 by returning at a predetermined interface. Set.

  FIG. 2 is a diagram schematically showing an example of the flow entry set by the measurement route calculation unit 101. Here, the description will be given focusing on the forward flow entry registered in the switch SW8.

  A destination port number (DstPort) is assigned as identification information to each test flow sent from the measurement terminal 2 and relayed through each switch SW and link to each destination switch (interface). In FIG. 2, the flow entry of switch SW8 has five transfer rules indicating that each test flow of DstPort = 1, 2, 3, 4, and 7 is transferred to link l7. Of the eight test flows input to the switch SW8, five test flows with DstPort = 1, 2, 3, 4, and 7 are transferred to the link l7.

  In the example shown in the figure, each test flow with DstPort = 5, 6 is transferred to the link l5, and the test flow with DstPort = 8 is returned to the measuring terminal 2, so entries relating to these test flows are also registered in the flow entry. However, the illustration is omitted here.

  The flow entry aggregating unit 102 aggregates the flow entries for the forward path (until the designated switch is reached) and the backward path (until the measurement terminal 2 is reached) in each switch SW.

  Among these, for the return flow entry, the destination IP address of the test packet returned at the interface of the destination switch is rewritten to the IP address of the measuring terminal 2, so that, for example, “the destination IP address is the IP address of the measuring terminal 2. If only one flow entry such as “transfer to the link on the upstream side (measurement terminal side) if it is the same” is set in each switch, the flow entries for the return path registered in each switch can be integrated into one.

  For example, in the case of the switch SW7 in FIG. 2, it is only necessary to set one flow entry that “all packets for which the IP address of the measuring terminal 2 is set as the destination IP address is forwarded to the link l7”. All test flows input from l2 and l4 for the return path can be processed.

  This is because, in Patent Document 1 on which the present invention is premised, the communication path of the test packet is calculated based on the shortest tree rooted at the measurement terminal 2, so that it is located upstream from the interface (link) of each switch SW. This is because only one communication path to the measurement terminal 2 is determined.

  On the other hand, in the aggregation of forward flow entries in each switch SW, a plurality of test packets transferred from the upstream link to the downstream link are grouped, and the same identifier is set in a new header field (for example, source port number). It is realized by. Since a common transfer rule is applied to the aggregated flow entry set, the flow entry must originally be applied with the same transfer rule. That is, a set of a plurality of test flows output from the same interface (link) of the same switch is an aggregation target.

  In this embodiment, the flow entry of the loopback test packet set in each switch SW is classified as a forward flow entry. Here, the reason why it is not counted as a return flow entry is that the current OpenFlow switch implementation rewrites the header of the test packet input from the upstream link to the switch for the outbound route, and returns it to the return route interface. This is because a set can be set as one entry, and if it is counted as a forward flow entry, it is counted redundantly in the calculation of the number of flow entries registered in each switch.

  That is, the inbound flow entry means only a flow entry for transferring a test packet from the downstream switch SW to the measuring terminal, while the outbound flow entry is a test for the downstream switch SW. Both a flow entry for transferring a packet and a flow entry for returning a test packet at the interface are included.

  FIG. 3 is a diagram schematically showing the state of each flow entry after being aggregated by the flow entry aggregating unit 102.

  Since each test flow with DstPort = 1, 2, 3, 4, and 7 is transferred to the same link l7, the switch SW8 does not need to uniquely identify each flow. Therefore, the flow entry aggregating unit 102 aggregates the five flow entries that have been uniquely identified by the destination port number (DstPort) into one, and sets the source port number as a unique identifier common to each entry. By separately assigning (SrcPort = 100) and associating this with link l7, a transfer rule is additionally introduced in which all test packets in which SrcPort = 100 is described are forwarded to link l7.

  For example, since the SrcPort = 100 is described in the header field of the test packet transmitted in the aggregated flow, each switch SW includes the SrcPort number and the flow entry described in the test packet. If the switch is SW8, all test packets in which SrcPort = 100 is described are transferred to the link l7.

  As discussed in Non-Patent Documents 3 and 4, the number of flow entries registered in each switch is affected by the packet transfer processing performance of the switch and the maximum number of flow entries that can be registered other than the test packet flow. The Therefore, in this embodiment, the optimal combination of the flow entries to be aggregated (which switch is aggregated by which switch) is formulated as follows so that the number of flow entries registered in one switch is minimized. Calculate by solving an integer programming problem.

  It is assumed that topology information indicating a connection relationship between physical network devices (hereinafter referred to as switches) and management information (MAC address, IF port number) of each switch are known. Further, the present invention aims to reduce the number of flow entries by aggregating the flow entries registered in each switch SW. However, for the sake of convenience, “test flows are aggregated” for a plurality of test flows in which the flow entries are aggregated. Is sometimes used.

  It is assumed that the flow entry information set in each switch is given as an initial state by the measurement path calculation unit 101. Given a monitored network consisting of switch SWi (i = 1,…, N) and link lj (j = 1 to L), and assuming that the number of flow entries in switch SWi is Fi, the objective function is It is expressed by This means that the maximum value of the number of flow entries registered in each switch SW is minimized.

  Next, the topology of the interface (link) unit is considered. When the number of flows of test packets that pass through the link lj (only the forward path) is fj, the flow entry number Fi of the switch SWi is expressed by the following equation (2). Here, ljεSWi represents that the link lj is connected as an upstream link (incoming link) of the switch SWi, and can be determined by topology information representing a connection relationship between physical switches.

  Note that the shortest tree calculated by the above equation (1) is configured in units of interfaces and is represented as different vertices even when belonging to the same switch. For this reason, it is necessary to use physical topology information that is not the shortest tree for the calculation of the following equation (2). For example, since two links of l4 and l5 are input to SW5 in FIGS. 2 and 3, the calculation is performed by the sum of the test flows passing through both links.

Further, the flow number f _j (j = 1, 2,... L) of the test packet passing through each link satisfies the relational expression expressed by the following expression (3) based on the topology information for each interface. Symbol R in Expression (3) is a path matrix expressing connection information between links (topology information in units of interfaces). If there is a connection relationship between the links li and lj, “1”, and if there is no connection relationship, “1”. The element (i, j) has a value of “0”.

For example, in FIG. 6, the number of test flows f ₁ passing through the input link l1 on the upstream side of the switch SW2 is obtained as the sum of the number of test flows f ₂ and f ₃ of the two downstream output links l2 and l3. Only the element (1, 2) and the element (1, 3) corresponding to the outgoing links l2, l3 are calculated as the following expression (4) using the path matrix R of “1”.

  Note that the addition of “1” to each element in the second term on the right side of Equations (3) and (4) indicates that one test flow that is folded back at the interface is added. In addition, equation (3) means that the number of outbound test flows at the upstream interface is calculated based on the sum of the number of test flows at the downstream switch, so the aggregation rule at the downstream switch is applied to the upstream switch. Is also applied.

  Furthermore, if the binary function bj indicating whether or not to aggregate the test flows that pass through each link lj is defined by the following equation (5), the number of test flows fj when the flow entries are aggregated is It can be expressed in 6). Therefore, if the test flow entries passing through the link lj are aggregated, fj = 1 is assumed to be calculated, and if not aggregated, fj remains.

  Here, since a common identifier common to the new header field is set for the aggregated flow entries, the once-aggregated flow entries cannot be re-aggregated using the same header field. In other words, when aggregation is performed using one type of header field, a flow entry aggregated once cannot be re-aggregated with a different flow on the communication path. For this reason, bj is restricted by the following equation (7).

Here, rj means the shortest path between the link li and the measuring terminal, and r _j ⊂r _k in the above equation (7) is the communication path (outward path) r _j of the test packet. It is meant to be encompassed in the communications path r _k. For example, in the topology of FIG. 4, communication such as r ₈ ⊂r ₇ ⊂r ₃ ⊂r ₁ , r ₈ ⊂r ₇ ⊂r ₂ , r ₈ ⊂r ₇ ⊂r ₄ , r ₈ ⊂r ₅ ⊂r ₆ Since there is an inclusion relation of the route, from the first inclusion relation (r ₈ ⊂r ₇ ⊂r ₃ ⊂r ₁ ), at most _{one of} b _8, b _7, b _3, b ₁ is “1”. Is applied (the same restriction is applied from other inclusion relationships). If the number of header fields that can be set for aggregation is M, the above equation (7) is generalized by the following equation (8).

  The above equations (1)-(8) are expressed by integer programming problems. The optimal solution (max {F1, F2,… , FN} and bj (j = 1, 2,..., L)) at that time can be calculated.

  After the above optimization calculation is completed, all test flows passing through the link are aggregated for each link lj for which bj = 1. Specifically, a new unique identifier is set in the test packet header field of the target flow, and as described with reference to FIGS. 2 and 3, the transfer rule using the new field is set in the switch. To replace the existing flow entry.

  Note that the above aggregation is performed not only on the switch to which the link is connected downstream but also on each switch located upstream due to the restrictions of the above equations (3) and (4). For example, in FIG. 5, when the aggregation at the link l3 is calculated as the optimal solution (b3 = 1), a rule such as SrcPort number = 100 is added to the flow entry corresponding to the communication paths r1 and r3 passing through the link l3. Are integrated into one flow entry, and the setting is set for all switches (SW8, SW7) through which the communication paths r1, r3 pass in common.

  That is, according to this embodiment, not only the switch SW7 having the link l3 calculated as the optimum solution as the outgoing link, but also the flow entries of the switch SW8 through which the communication paths r1 and r3 pass in common on the upstream side are aggregated. Is done.

  According to the present embodiment, in SDN such as OpenFlow, the communication quality of all links can be measured with one measuring terminal while keeping the number of flow entries of each switch small. In addition, by minimizing and registering the number of flow entries, the matching search processing time can be reduced and the memory size used can be reduced, and the number of entries for normal data transfer can be increased. Quality measurement that prioritizes certain data transfer becomes possible.

  DESCRIPTION OF SYMBOLS 1 ... Server apparatus, 2 ... Measurement terminal, 10 ... Link quality measurement part, 20 ... Network, 101 ... Measurement route calculation part, 102 ... Flow entry aggregation part, 103 ... Communication path setting part, 201 ... OpenFlow controller

Claims (7)

In the link quality measurement device that relays the test packet sent from the measurement terminal according to the flow entry registered in each switch on the network,
In at least one of each switch, flow entries relating to a plurality of test flows passing through one outgoing link are aggregated into one,
In the aggregated flow entry, a unique identifier is associated with the outgoing link,
The link quality measuring apparatus, wherein the switch into which the flow entries are aggregated transfers the test packet in which the identifier is described to a corresponding outgoing link based on the flow entry.   In switches where multiple test flows of a link in which all the flow entries of all the test flows that pass through are aggregated into one link are used as the outgoing link, the flow entries of the plurality of test flows are aggregated. The link quality measuring apparatus according to claim 1, wherein Means for calculating a measurement path of the test packet;
Means for aggregating the flow entries in at least one of the switches corresponding to the measurement path;
Means for registering each aggregated flow entry with a corresponding switch,
The means for aggregating is
Set an objective function that minimizes the maximum number of flow entries registered in each switch,
Let the number of flow entries for each switch be the sum of the number of test flows that pass through each outgoing link for that switch,
Define a binary variable with “1” for the link with aggregation and “0” for the link without aggregation.
Obtain the number of incoming test flows for each switch based on the total number of test flows for each outgoing link, set the number of test flows for aggregated links to "1", and support the links through which each test flow passes The link quality according to claim 1 or 2, wherein a link to be aggregated is determined by solving an integer programming problem including a constraint condition that a sum of binary variables equal to a number of fields that can be added to a test packet. Measuring device.   4. The link quality measuring apparatus according to claim 3, wherein the number of test flows for each incoming link of each switch is obtained as a sum of the number of test flows for each outgoing link + 1.   5. The link quality measuring apparatus according to claim 1, wherein each switch aggregates the flow entries for the return path test packets whose destination address is the address of the measuring terminal. A method in which a computer aggregates the entry flow of test packets registered in each switch on a network,
Set an objective function that minimizes the maximum number of flow entries registered in each switch,
Let the number of flow entries for each switch be the sum of the number of test flows that pass through each outgoing link for that switch,
Define a binary variable with “1” for the link with aggregation and “0” for the link without aggregation.
Obtain the number of incoming test flows for each switch based on the total number of test flows for each outgoing link, set the number of test flows for aggregated links to "1", and support the links through which each test flow passes A flow entry aggregation method for a link quality measurement apparatus, comprising: solving an integer programming problem including a constraint that a sum of binary variables equal to a number of fields that can be added to a test packet is determined. A program that causes a computer to aggregate flow entries of test packets registered in each switch on the network,
Set an objective function that minimizes the maximum number of flow entries registered in each switch,
Let the number of flow entries for each switch be the sum of the number of test flows that pass through each outgoing link for that switch,
Define a binary variable with “1” for the link with aggregation and “0” for the link without aggregation.
Obtain the number of incoming test flows for each switch based on the total number of test flows for each outgoing link, set the number of test flows for aggregated links to "1", and support the links through which each test flow passes Link quality measurement device flow entry aggregation that causes the computer to determine the link to be aggregated by solving the integer programming problem that includes the constraint that the sum of the binary variables equal to the number of fields that can be added to the test packet program.