KR101962346B1 - Method for measuring path latency based on sdn - Google Patents

Abstract

A path delay measurement method in an SDN (Software Defined Network) environment is disclosed. The path delay measurement method includes the steps of: (a) generating a flow entry in response to a flow rule installation command for transmission of a first packet received from a controller, each of a plurality of switches included on a path, ) Wherein the controller is configured to send identification information for identifying the first packet to a first switch on the path among the plurality of switches, identification information for identifying a destination switch on the path among the plurality of switches, (C) transmitting the first message to the destination switch and receiving the second message from the destination switch, and (d) transmitting the first message to the destination switch, ) Calculates a RTT (Round Trip Time) using the time at which the first switch transmits the first message and the time at which the second message is received, A step for calculating a route from the delay time period RTT, and the (c) step and the (d) step is performed based on the interval of the path delay measuring repeatedly the number of times of the path delay measurements.

Description

[0001] METHOD FOR MEASURING PATH LATENCY BASED ON SDN [0002]

The present invention relates to a software defined network (SDN), and more particularly, to a method for measuring a path delay time of a network for traffic engineering in an SDN-based network platform.

Software Defined Networking (SDN) is a networking architecture that allows a single control over the entire network by separating the transmission plane (or data plane, data plane) and control plane of the networking equipment and centralizing the control plane. , There is an advantage in that it gives flexibility and programmability to networks that are difficult to apply new research that is dependent on existing manufacturers. The control plane of the centralized switch is called the SDN controller, and the switch and the SDN controller can communicate with each other through the SBI (Southbound Interface). As an initial study of SDN, OpenFlow is mainly used as a de facto standard SBI protocol. This technology is a technology that brings revolutionary development to the existing closed network environment and operates as the base technology of next generation networking technology such as IoT, 5G and NFV Orchestration.

The path delay time is a delay time consumed in transmitting and receiving data packets between specific nodes on the network (computer network) from one side to the other side, and an index such as RTT (Round Trip Time) is mainly utilized. This inter-path delay time is a basis for various network optimization and modeling techniques because it can predict the time taken for a specific packet to be transmitted to the transmission / reception terminal. Based on the RTT, it is possible to estimate congestion, physical distance, and transmission speed between specific transmitting and receiving hosts. In particular, it is a dynamic network monitoring method that dynamically reflects traffic changes in a measurement situation can do.

As a method for measuring the inter-path delay time in the conventional SDN, a method of measuring a delay time based on the measured RTT by generating a probe packet other than a standard protocol and a method of periodically transmitting And a method of measuring the delay time using a link layer discovery protocol (LLDP). However, according to these methods, there is a problem that additional packets need to be defined and transmitted in addition to the standard protocol. In addition, the delay time calculation using LLDP requires a correction process to improve the accuracy, and the corrected delay time also has a problem in that it is different from the delay time in the physical link.

That is, in the case of the method using the LLDP, when the first switch of the path receives the PacketOut message, the corresponding switch transmits the probe message attached to the PackOut message on the path, and the flow rule for transmitting the probe packet to the controller through the FlowMod message When the probe packet reaches the last switch installed, the packet is sent to the controller. At this time, correction for the delay time is performed through experiments or modeling, which means that a large change in the correction value occurs even if the traffic is slightly changed on the network. Further, as the configuration of the switch and the configuration of the network topology change, there is a problem that it is difficult to actually utilize the correction value since the correction value must be re-measured or recalculated.

As described above, delay measurement of a network is a necessary element of network management in that congestion between hosts, physical distance, transmission speed, and the like can be estimated and the basis of traffic and fault identification is provided. However, there are standard techniques for bandwidth and loss in active SDN, but there is no definite specification for delay measurement technique. In particular, related studies for measuring delay in the SDN environment have problems such as poor accuracy of the delay measurement because the controller consumes excessive resources or performs a correction process. In the present invention, a path latency table inside the switch is designed to overcome such a problem. Based on this, we propose a method to measure the accurate path delay time through the inter-switch BFD protocol and transmit the measured result to the controller.

Korea Patent Publication No. 2015-0100027 Korean Patent Publication No. 2016-0098321 United States Patent Publication No. 2010-0149992 U.S. Patent No. 9,602,374

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a path delay measurement method capable of acquiring measurement values without generating additional traffic between a controller and a switch, .

A path delay measurement method according to an embodiment of the present invention includes the steps of: (a) receiving, in response to a flow rule installation command for transmission of a first packet received from a controller, each of a plurality of switches included on a path, (B) identifying, by the controller, identification information for identifying the first packet to a first switch on the path among the plurality of switches, identification information for identifying a destination switch on the path among the plurality of switches, (C) transmitting the first message to the destination switch, receiving the second message from the destination switch, receiving the second message from the destination switch, (D) using the time at which the first switch transmits the first message and the time at which the second message was received, and calculating a path delay time from the RTT, wherein the step (c) and the step (d) are repeatedly performed by the number of times of the path delay measurement based on the interval of the path delay measurement, .

In addition, the path delay measurement method according to another embodiment of the present invention includes the steps of: (a) determining whether a first one of a plurality of switches included on a path includes a flow rule setup command for transmitting a BFD packet received from a controller (B) identifying, by the first switch, identification information for identifying the BFD packet from the controller, identification information for identifying a destination switch on the path among the plurality of switches, (C) receiving, by the first switch, an echo request message from the destination switch and an echo reply message from the destination switch, And (d) a time at which the first switch transmits the echo request message and a time at which the echo reply message is received Calculating a round trip time (RTT) using the angle, and calculating a path delay time from the RTT, wherein the step (c) and the step (d) Is repeatedly performed as many times as the path delay measurement.

According to the path delay measurement method of the embodiment of the present invention, more accurate path delay time can be obtained without performing a separate correction process.

In addition, according to the present invention, additional packets for obtaining the path delay value are not consumed, thereby reducing the bottleneck of the control channel between the controller and the switch.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more fully understand the drawings recited in the detailed description of the present invention, a detailed description of each drawing is provided.
1 illustrates an SDN system according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining a path delay time measurement method performed on the SDN system shown in FIG.
3 shows a transmission / reception process of an inter-switch BFD echo mode.
FIG. 4 shows a LLDP-based link delay collection process.

It is to be understood that the specific structural or functional description of embodiments of the present invention disclosed herein is for illustrative purposes only and is not intended to limit the scope of the inventive concept But may be embodied in many different forms and is not limited to the embodiments set forth herein.

The embodiments according to the concept of the present invention can make various changes and can take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms disclosed, but includes all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example, without departing from the scope of the right according to the concept of the present invention, the first element may be referred to as a second element, The component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like are used to specify that there are features, numbers, steps, operations, elements, parts or combinations thereof described herein, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings attached hereto.

1 illustrates an SDN system according to an embodiment of the present invention.

Referring to FIG. 1, an SDN system, which may be referred to as a path delay time measurement system, may include a controller and a plurality of network devices A, B, and C. FIG. 1 is an exemplary system assuming a situation in which the path delay between network device C and network device A is measured.

Software Defined Networking (SDN) separates the control plane and the data plane from the network and provides programmability and flexibility. SDN allows the free deployment of new protocols and networking services away from existing fixed functionality and limited accessibility, and enables more effective network management than a traditional distributed environment through a centralized SDN controller.

A controller may refer to an SDN controller and may refer to a functional entity that controls an associated component (e.g., a switch, a router, etc.) to control the flow of traffic. Further, the controller is not limited by the physical implementation form or the location of the implementation. For example, the controller may refer to a controller functional entity defined in OpenFlow, Internet Engineering Task Force (IETF), European Telecommunication Standards Institute (ETSI) and / or International Telecommunication Union Telecommunication (ITU-T) .

Each of the plurality of network devices A, B, and C may refer to a functional element that forwards or switches or routes traffic or packets, such as a switch or a router. For example, a plurality of network devices may be a switch, a router, a switching element, a routing element, or a forwarding element defined in OpenFlow, IETF, ETSI and / or ITU- ) And the like. It is apparent that the number of the plurality of network devices A, B, and C shown in FIG. 1 does not limit the scope of the present invention. In addition, each of the plurality of network devices A, B, and C may include storage space (memory or storage unit, etc.) for storing and managing the path delay table to be described later.

In the SDN environment shown in FIG. 1, the controller may set a transmission rule for transmitting a BFD packet on a path to be measured, and set session information on a switch for measuring a delay. The measurement of the inter-switch path delay is performed without intervention of the controller based on the session information, and the measured delay value can be transmitted again to the controller. A concrete method of measuring the path delay will be described later.

FIG. 2 is a flowchart for explaining a path delay time measurement method performed on the SDN system shown in FIG.

In order to measure the path delay time, a step of installing a flow rule for packet transmission is first performed (S100). Specifically, the controller may establish a flow rule for transmitting a BFD (Bidirectional Forwarding Detection) packet to at least one switch included in a path for measuring a delay time. For example, the controller may transmit a flow rule change command, a flow rule add command or a flow rule install command for installing a flow rule for transmitting a BFD packet to each of at least one switches included in the path, Each can establish a flow rule by adding a flow entry (or flow table entry) to its own flow table in response. Since the BFD protocol communicates with the UDP (User Datagram Protocol), there is no need to install a separate flow rule if there is a flow rule matching IP (Internet Protocol) or UDP already on the switch on the transmission path to be measured. If not, install additional flow rules for this on the path. The flow table maintained by each of the switches is composed of a match field for distinguishing a flow and an action field for processing the flow.

Thereafter, a session information setting step for measuring a delay time is performed (S200). In the present invention, in order to prevent the controller 100 from intervening each time a delay time is measured, a memory for storing information related to measurement may be separately allocated to the switch. Each switch can manage a predetermined table that can be named a path latency table using the allocated memory. At this time, since delay measurement for various paths can be performed in one switch, an identifier for identifying delay measurement packets arriving on different paths is needed. To do this, use the BFD cookie value. The path delay table can consist of a set of latency entries consisting of such cookies as SID representing the destination switch address, Interval as the measurement interval, CountOut as the measurement count, and Latency field for storing the measurement value. That is, the path delay table includes identification information (e.g., BFD Cookie) for identifying a BFD packet (or identifying a path for which a delay is measured or delay is to be measured), identification information for identifying a destination switch on the path , The address of the destination switch, etc.), information about the interval to measure the delay, and information about the number of times the delay is to be measured. The information included in the path delay table may be included in the session information transmitted from the controller to the first switch among the plurality of switches included in the path on which the delay is to be measured. An exemplary path delay table is shown in Table 1 below.

BFD Cookie SID Intermal CountOut Latency 0x0000 A 900 5 NULL ...

Suppose that in the SDN shown in FIG. 1, the delay for the path from switch C to switch B to switch A as the final destination is measured five times at intervals of 900 ms. At this time, the controller adds the latency entry having the 0x0000 cookie and the destination as the switch A in the path delay table of the switch C as the first switch in the path as shown in Table 1.

For example, the controller may transmit session information, which is information about a path for which path delay is to be measured, to a first one of a plurality of switches included in the path. The first switch may add an entry to the path delay table maintained by the first switch in response to receipt of the session information. The session information may be named measurement path information, path measurement information, etc., and may include information (e.g., BFD Cookie) identifying a packet (e.g., a BFD packet), information identifying a final destination switch Or the address of the final destination switch of the path), the interval of the path delay measurement, and the information on the number of path delay measurement times.

Thereafter, a path delay measurement step is performed (S300). The path delay measurement step may be performed without controller intervention. When an entry is added to the path delay table, the switch can measure a delay on the path by a specified number of times by setting a timer with an interval of the corresponding entry as an interval. At this time, the delay measurement can be performed using the echo mode of the BFD. BFD is a standard protocol for confirming the availability of forwarding links established by the IETF, allowing to check the transmission / reception status of periodic packets. 3, when a BFD session is established between the switches, the transmission switch (switch C) transmits a control message (packet or echo message) to the port where the BFD is set To the receiving switch (switch A). When the echo mode is used, the switch A directly retransmits the control message (packet or echo message) transmitted by the switch C. Since the difference between the time at which the transmission switch transmits the control message and the time at which the control message is received becomes the RTT (Round Trip Time) between the transmission switch and the reception switch, the switch C divides the RTT in half, Can be obtained. At this time, the echo message transmitted by the switch C may be referred to as an echo request message, and the echo message transmitted by the switch A may be referred to as an echo response message.

Since the number of path delay measurements included in the entry may be two or more, the switch C may determine a value obtained by averaging a plurality of measured values according to the number of path delay measurements as a final delay time. According to an embodiment, all of the plurality of measured values may be transmitted to the controller.

Thereafter, a step of transmitting the measured delay value is performed (S400). The process of transmitting the measured delay value to the controller also has no standard protocol defined in the existing SDN environment. In the present invention, a delay value is collected using a link layer discovery protocol (LLDP) packet (or message) used in a topology discovery process that the controller periodically generates so as not to further generate control traffic . In the SDN environment, the LLDP protocol uses the SDN controller periodically to check the configuration of the topology such as switches and links in the network. When used in parallel with the topology discovery process, the LLDP protocol consumes no additional packets to receive the path delay measurement value from the switch There is an advantage of not doing so.

Referring to FIG. 4 illustrating a LLDP-based link delay collection process, a controller may include a LLDP in a PacketOut message transmitted periodically and transmit the packet to a switch. At this time, the LLDP message may include the switch and port information to be transmitted. When the controller wants to collect the path delay value, the controller adds the System Capabilities TLV option when sending the LLDP packet to the switch and sends out the BFD Cookie value corresponding to the Path latency entry of the delay value to be acquired. That is, the controller may send an LLDP packet to the first switch in the path, which includes the path where the path delay is measured or identification information (e.g., BFD Cookie) to identify the BFD packet.

Upon receiving the PacketOut message and confirming that the packet is LLDP, the switch C receiving the LLDP packet checks whether the System Capabilities TLV option (or identification information for identifying the path or the BFD packet, for example, whether or not the BFD cookie exists) And confirms and records the corresponding path delay value and transmits through the output port defined in the PacketOut message. The LLDP packet transmitted from the switch C can be transmitted to the control via the at least one switch.

When the switch B, which is an adjacent switch, receives the LLDP, the flow entry for the packet does not cooperate with its own flow table. Therefore, the LLDP packet received from the switch C through the table miss processing operation is included in the PacketIn message, Lt; / RTI > Finally, the LLDP packet is forwarded to the controller. The controller is able to obtain the path delay time in the LLDP packet when processing the received PacketIn message.

The present invention proposes a technique for measuring the delay on a particular network path in an SDN environment and for the controller to perform active measurements based on the BFD echo mode without intervening in individual delay measurements. In addition, we tried to design a control channel that can mitigate the bottleneck of the control channel between the controller and the switch by collecting the measured result by adding it to the control traffic between the existing controller and the switch instead of the separate control traffic.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (10)

A path delay measurement method in an SDN (Software Defined Network) environment,
(a) generating a flow entry in response to a flow rule installation instruction for transmission of a BFD packet (Bidirectional Forwarding Detection) received from a controller, each of a plurality of switches included on a path;
(b) the controller is operable to provide identification information for identifying the BFD packet to a first switch on the path among the plurality of switches, identification information for identifying a destination switch on the path among the plurality of switches, And session information including the number of path delay measurements;
(c) the first switch sending an echo request message to the destination switch and receiving an echo reply message from the destination switch;
(d) calculating a round trip time (RTT) using the time at which the first switch transmits the echo request message and the time at which the echo reply message was received, and calculating a path delay time from the RTT;
(e) transmitting, by the controller, a Link Layer Discovery Protocol (LLDP) packet including identification information for identifying the BFD packet to the first switch;
(f) generating a modified LLDP packet by including the measured path delay time of the path corresponding to the identification information for identifying the BFD packet in the LLDP packet by the first switch, and transmitting the modified LLDP packet to the second Transmitting to a switch; And
(g) the controller receiving the modified LLDP packet from the second switch,
Wherein the step (c) and the step (d) are repeatedly performed by the number of times of the path delay measurement based on the interval of the path delay measurement,
Wherein the step (c) is performed in an echo mode of the BFD,
Path delay measurement method.
The method according to claim 1,
The identification information for identifying the BFD packet is a BFD cookie value,
Path delay measurement method.
delete delete delete delete delete A path delay measurement method in an SDN (Software Defined Network) environment,
(a) generating a flow entry in response to a flow rule installation instruction for transmission of a BFD packet received from a controller, the first one of the plurality of switches included on a path;
(b) the first switch comprises identification information for identifying the BFD packet from the controller, identification information for identifying a destination switch on the path among the plurality of switches, an interval of the path delay measurement, Receiving session information including the session information;
(c) the first switch sending an echo request message to the destination switch and receiving an echo reply message from the destination switch;
(d) calculating a round trip time (RTT) using the time at which the first switch transmits the echo request message and the time at which the echo reply message was received, and calculating a path delay time from the RTT;
(e) receiving, from the controller, a Link Layer Discovery Protocol (LLDP) packet including identification information for identifying the BFD packet by the first switch;
(f) generating a modified LLDP packet by including the measured path delay time of the path corresponding to the identification information for identifying the BFD packet in the LLDP packet by the first switch, and transmitting the modified LLDP packet to the second Transmitting to a switch; And
(g) the second switch sending the modified LLDP packet to the controller,
Wherein the step (c) and the step (d) are repeatedly performed by the number of times of the path delay measurement based on the interval of the path delay measurement,
Wherein the step (c) is performed in an echo mode of the BFD,
Path delay measurement method.
delete 9. The method of claim 8,
The identification information for identifying the BFD packet is a BFD cookie,
Wherein the identification information for identifying the destination switch is an address of the destination switch,
Path delay measurement method.

Images