KR101552130B1 - Apparatus and methof for sla guranteed lsp setup in real time multimedia service of mpls network - Google Patents

Abstract

A method of a network entity for establishing a routing path list, the method comprising the steps of: identifying at least one link that does not satisfy at least one of a required maximum delay time and an available bandwidth among a plurality of links; Selecting a plurality of routing paths by Constraint Shortest Path First (CSPF) based on the remaining links except for the identified link; determining, for each of the plurality of selected routing paths, Generating a routing path list including at least one routing path based on a sum of delay times of the plurality of routing paths; To the LSP (Label Switched Path) , It is possible to implement an SLA considering a multimedia service in an MPLS network in an environment where a wired and wireless network is integrated into MPLS, and in particular, an SLA can be guaranteed in a next generation mobile communication system based on All IP.

Routing algorithm, MPLS, MCSPF, SLA, LSP.

Description

TECHNICAL FIELD [0001] The present invention relates to an apparatus and a method for establishing an SLP in a real-time multimedia service in an MPLS network,

 A Multimedia Constraint Shortest Path First (MCSPF) apparatus and method using a SLA parameter, which is a new traffic engineering (TE) service for ensuring SLA (Service Level Agreement) when a real-time multimedia service is used in an MPLS (Multiprotocol Label Switching) .

 In recent years, MPLS networks have been rapidly spreading in various wired and wireless networks because of their advantages of ensuring QoS (Quality of Service) and easily building a VPN (Virtual Private Network). Especially, it is used in IP based 3G mobile communication network centered on core network, and it is expected that diffusion will accelerate as it evolves into 4G network such as LTE (Long Term Evolution).

1 is a block diagram of a wired / wireless communication network using an MPLS network as a core network.

Referring to FIG. 1, the MPLS can be mainly used in core networks 100 of various wired / wireless networks, and can be used not only in wired communication and enterprise network but also in mobile communication 110, 120, 130, 140, Can be used as a core network for various network services satisfying the so-called triple play of convergence of broadcasting and communication.

In this way, MPLS is widely used in core networks because it provides various methods of guaranteeing QoS. In recent years, there has been a movement to discuss such QoS from the viewpoint of service level agreement (SLA) Is progressing actively.

SLA is a kind of protocol for managing various service quality of a service user's view rather than a position of a network manager, and can be explained broadly, specifically, throughput, response-time, delay ), And delay variation (jitter).

In order to guarantee the SLA, an active monitoring technique that transmits a probe packet having information for acquiring a specific parameter or a statistical data of a network management system (NMS) such as a management information base (MIB) Based passive monitoring technique is used.

However, SLA measurement in MPLS networks is mentioned at the broad definition level, and how to actually apply these SLAs to MPLS standards is not yet defined precisely.

Therefore, when providing real-time multimedia service, there is a need for a concrete method of measuring SLA using parameters of SLA and using measurement results in the control plane of MPLS standard. In addition, a new traffic engineering method considering the characteristics of the service is required in the process of generating LSP (Label Switched Path) to provide SLA of real-time multimedia.

As described above, the conventional traffic engineering technique uses a classical CSPF algorithm that calculates ER (Explicit Route) information based on available bandwidth information, but does not consider information of real time traffic such as delay time at all not.

This classical traffic engineering technique is designed to focus on the distribution of network load, so it has some limitations in terms of finding the ideal path from the QoS point of view.

In case of real-time application services that are sensitive to delay time including VoIP (Voice over IP), delay time for traffic engineering path as well as bandwidth guarantee must be guaranteed above a certain level.

If the CSPF mechanism is performed considering only the available bandwidth as in the existing path, the result obtained by the CSPF satisfies the available bandwidth, but it may cause the case that the maximum delay time required by the user is exceeded have.

In order to traffic engineering the real-time multimedia service, a new CSPF algorithm is required to compute and set the traffic engineering path in consideration of the delay engineering time, considering traffic bandwidth.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for setting an SLA-guaranteed LSP in a real-time multimedia service in an MPLS network.

Another object of the present invention is to define how an SLA is defined in the case of providing a real-time multimedia service in an MPLS network, and to obtain an SLA parameter using an active monitoring technique, The present invention provides an apparatus and method for generating an MPLS path that satisfies an SLA protocol of a real-time multimedia service at all times by applying it to a signaling protocol on an MPLS control plane.

Another object of the present invention is to provide a new method for generating an MPLS LSP that maintains an MPLS path that satisfies the SLA protocol of the real-time multimedia service at all times, a CSPF algorithm (MCSPF: Multimedia Constraint Shortest Path First The present invention also provides an apparatus and method for providing an SLA service structure in an MPLS network that provides routing from traffic engineering to actual SLA protocol validation for active monitoring.

According to a first aspect of the present invention, there is provided a method of a network entity for establishing a routing path list, the method comprising the steps of: Identifying a plurality of routing paths by CSPF (Constraint Shortest Path First) based on the remaining links excluding the identified link; Generating a routing path list including at least one routing path based on a sum of delay times of respective links constituting the corresponding routing path; One routing path among the routing paths included in the path list is called an LSP (Switched Path).

According to a second aspect of the present invention, there is provided an apparatus for configuring a routing path list, the apparatus comprising: at least one of a plurality of links that does not satisfy at least one of a maximum delay time and an available bandwidth, A plurality of routing paths are selected by the CSPF based on the remaining links excluding the identified link, and for each of the plurality of selected routing paths, a delay time of each link constituting the corresponding routing path And generates one routing path among the routing paths included in the routing path list by using the parameter for guaranteeing SLA (Service Level Agreement) as an LSP A Label Switched Path).

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The present invention has the advantage of enabling SLAs considering multimedia services in an MPLS network in an environment where wired and wireless networks are integrated into MPLS, and in particular, ensuring SLAs in a next generation mobile communication system based on All IP.

The present invention supports an SLA based on active monitoring, and has an advantage that it is possible to confirm whether an LSP generated by a traffic engineering method satisfies an actual SLA protocol. For LSPs that do not satisfy the SLA, there is an advantage of automatically generating a bypass route in conjunction with the MPLS signaling protocol.

The present invention introduces the MCSPF concept considering real-time multimedia, and has an advantage of enabling setting of a high-level QoS considering real-time multimedia as well as load distribution of the network. In particular, when a real-time multimedia service such as VoIP, which is sensitive to delay time, is set in the MPLS network, there is an advantage in that the constraint of the delay time can be solved through traffic engineering.

This system also supports SLA that takes into account jitter value, which has the advantage of dramatically improving the service quality related to echo etc. in VoIP.

The traffic engineering technique of the present invention enables a network configuration that satisfies the most important requirements of two QoSs, that is, bandwidth and delay time, in a network area to provide an infrastructure for ensuring end-to-end QoS There is an advantage of presenting the structure. Here, considering delay time, it is advantageous not only to consider the delay time on the link but also to check whether the delay time on the entire route is satisfied and to calculate the route considering the entire delay time.

The present invention can be easily implemented by expanding on the basis of existing traffic engineering techniques, and it is advantageous that interworking with other equipment can be secured by adding to the current traffic engineering standard.

An advantage of the present invention is to find an optimal path for a real-time multimedia service in an MPLS network and to confirm the path in an actual network to provide an optimal service path considering bandwidth, delay time, delay variation, and the like in a comprehensive manner.

The present invention provides a function to reset the SLA protocol when it is difficult to provide an optimal SLA service when the established SLA protocol is applied to an actual MPLS network, so that the network manager can find out the best SLA protocol There is an advantage to have.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, an apparatus and method for setting an SLA-guaranteed LSP in a real-time multimedia service in an MPLS network will be described.

In recent years, the MPLS network has been increasingly used as a wireless network and a user network in the existing wired and core networks. In accordance with the recent flow of wired / wireless integration and opening, IP-based mobile communication network.

Recently, as user-level service quality becomes more important, how to guarantee SLA (Service Level Agreement) is becoming an important issue.

In the present invention, a new CSPF algorithm called MCSPF (Multimedia Constraint Shortest Path First) using an SLA parameter of a real-time multimedia service and a MPLS LSP (Label Switched Path) We propose an active monitoring method to confirm that it meets the actual SLA protocol.

Through the method proposed in the present invention, SLA characteristics required by a multimedia user can be managed more effectively by linking traffic engineering and MPLS signaling, thereby realizing a real-time service quality such as VoIP in a wired / To improve and manage it.

The present invention can be largely divided into three parts. First, considering the characteristics of the real-time multimedia service, the operation of the MCSPF algorithm (FIG. 2, FIG. 4, FIG. 5, FIG. 6, The process of confirming the SLA protocol using the monitoring technique (FIG. 8), and the process of resetting the LSP by applying the active monitoring result (FIG. 9).

2 is a flowchart illustrating an operation of the MCSPF according to an exemplary embodiment of the present invention.

Referring to FIG. 2, in step 210, information such as a bandwidth and a delay time is set in the network interface of the MPLS equipment in order to drive the MCSPF algorithm (step 705 ). To set the bandwidth and delay time, refer to SLA parameters against each multimedia service as shown in <Table 1> for example.

CLASSofService DELAY THROUGHPUT JITTER QoSBandwidthPerAPP Priority
Traffic <80msec PacketLoss
<5% <35 msec MAX75% Real-Time
Traffic <80msec PacketLoss
<3% NoTarget 60% Priority
Traffic <80msec PacketLoss
<2% NoTarget 30% BestEffor
Traffic <100 msec NoTarget NoTarget 10%

Table 1 shows SLA parameters in the MPLS network.

Then, based on the information thus set, the MCSPF algorithm for the real-time multimedia service is applied to determine Explicit Route (ER) information for setting the MPLS LSP (Step 215). A detailed description of the MCSPF algorithm is given below. Thereafter, an LSP is set using the MPLS signaling protocol such as RSVP-TE or CR-LDP with the determined ER path (step 220).

Then, for active monitoring, values such as bandwidth, delay time and delay variation for a given LSP are derived (step 225). In order to confirm whether the set MPLS LSP satisfies the SLA protocol, a probe packet is transmitted to calculate parameters for a real-time multimedia service such as delay time and delay variation (step 230).

The probe packet is transmitted to the MPLS network in the form of a time stamp for calculating a desired SLA parameter, such as ICMP or UDP, and transmits the required number of times N, which is defined by the network manager, in order to obtain a delay variation.

If the calculated delay time and the delay variation value satisfy the SLA parameter (step 235), the MPLS LSP setting is finally completed (step 260)

If the calculated delay time and the delay variation value do not satisfy the SLA of the corresponding LSP (step 235), if there is an alternative path (step 240), the MPLS signaling protocol causes the corresponding LSP to be released (step 245) , The ER value is re-derived by applying the MCSPF algorithm except for the ER of the corresponding LSP (step 250). Thereafter, the LSP is set up using the MPLS signaling protocol such as RSVP-TE or CR-LDP with the newly derived ER path (step 220), and the subsequent process is performed.

If there is no other alternative path (step 240), the SLA value is renegotiated in a static or dynamic manner (step 255). In order to drive the MCSPF algorithm, which is an initial process, , Delay time, and the like (step 210).

Thereafter, the algorithm according to the present invention terminates.

FIG. 3 is a block diagram illustrating an overall structure of a MCSPF (Multimedia Constraint Shortest First) algorithm according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 3, FIG. 3 illustrates a network entity (e.g., router 310) in which the operation of FIG. 2 occurs. The operation sequence of the basic traffic engineering mechanism is similar to that of the existing method, but the MCSPF algorithm is clearly distinguished from the existing CSPF algorithm defined in the standard in that it is a parameter considering the parameters for the real-time multimedia service.

Extension of the existing MPLS call processing protocol (RSVP-TE or CR-LDP) 301, IGP-TE protocol (OSPF-TE or ISIS-TE) 303, CSPF 304, need. The explanation is as follows.

First, information such as bandwidth and delay time 305 is set in the network interface for applying traffic engineering (the delay time of the interface is variable or fixed as shown in Table 2 below, And use the information gained by the operator of the network by statistical methods.)

DelayComponent Fixed Variable CodecDelay 0 PacketizationDelay 0 Queuing / Buffering 0 SerializationDelay 0 NetworkDelay 0 De-jitterBufferDelay 0

Then, the set information is transmitted to the same protocol of the other communication equipment by the IGP-TE 303 such as OSPF-TE or ISIS-TE so that all traffic engineering databases can be shared within the same network area.

For the present invention, the IGP-TE protocol should be extended so as to additionally transmit information such as the maximum delay time, in addition to the information such as the available bandwidth defined in the current OSPF standard.

Next, the CSPF 304, which is the most important module, performs traffic engineering according to the algorithm described in the present invention based on the traffic engineering database (TE-LSDB) 306 generated in consideration of the delay time and the like And notifies the MPLS call processing protocol 301 such as RSVP-TE or CR-LDP.

Thereafter, the MPLS call processing protocol 301 makes a request to the CSPF module 304 to calculate the ER path. In this case, in addition to the existing bandwidth information, a request is made with information such as a maximum delay time.

The MPLS call processing protocol 301 receives the ER computed from the CSPF module 310 and then determines whether the available bandwidth and maximum delay time are not exceeded by the interface manager 302 Perform the procedure to confirm the number.

In order to implement the traffic engineering function proposed in the present invention, the following functions are required in the existing traffic engineering structure.

First, the definition of an additional message for transmitting the delay time information to the existing IGP-TE protocol (OSPF-TE, ISIS-TE) 303 and the function of processing the message are required. Next, the computation of the ER path through the improved CSPF algorithm is performed with the generated traffic engineering database.

Next, the call processing protocol performs call processing with the requested maximum delay time information in addition to the bandwidth in the resource reservation request, and the interface manager 302 confirms the information at each node. A statistical method or a function to dynamically set delay time and bandwidth information is performed for traffic engineering considering delay time on each interface. The functions required for this are as follows.

First, information such as bandwidth and delay time is set in a network interface for applying traffic engineering. The delay time of the interface is variable or fixed as shown in <Table 2>. However, most of the delay time can be determined as a fixed factor and the information obtained by the operator of the network is used statistically.

The set information is transmitted to the same protocol of the other communication equipment by the IGP-TE 303 such as OSPF-TE or ISIS-TE so that all traffic engineering databases can be shared within the same network area.

For the present invention, the IGP-TE protocol 303 is extended so as to additionally transmit information such as the maximum delay time, in addition to information such as the available bandwidth defined in the current OSPF standard. The CSPF 304, which is the most important module, generates an ER for traffic engineering according to the algorithm described in the present invention based on the traffic engineering database (TE-LSDB) 306 generated in consideration of the delay time and the like. Path, and notifies the call processing protocol 301 such as RSVP-TE or CR-LDP. As a result of the improved MCSPF algorithm for the real-time multimedia described above, an ER (Explicit Route) is obtained, and the LSP is set up using the signaling protocol in this path.

In the above-described block configuration, although not shown, the control unit may perform the functions of the blocks 301, 302, 303, 304, and 309 described above. In the present invention, these are separately constructed and described in order to describe each function separately.

Therefore, when the product is actually implemented, all of the functions of the blocks 301, 302, 303, 304, and 309 may be configured to be processed by the control unit, and only a part of the functions may be processed by the control unit It is possible.

4 is a flowchart illustrating an algorithm for obtaining an ER according to an embodiment of the present invention. This process corresponds to the step 215 of FIG. The CSPF graphs shown in FIGS. 5 and 6, which are prepared considering the available bandwidth or delay time, will be referred to for the CSPF algorithm described above.

Referring to FIG. 4, if the call processing protocol requires 100M of bandwidth and links i (50M) and l (60M) violate this condition, i and l links are once removed on the graph (see FIG. 5) (Step 405).

Then, in order to consider the delay time proposed in the present invention, the link that violates the maximum delay time is once again removed (refer to FIG. 6) (step 410). That is, 150 msec is requested as a requirement, and link e (220 msec), k (210 msec) that violates this is deleted. Thereafter, under these conditions, the CSPF path calculation process is performed (step 415).

If there is an ER list to be calculated (step 420), the sum of delay times in the ER list is calculated (step 425). In this case, rather than checking the maximum delay time on each link, the CSPF determines whether the sum of the delay times of the entire path exceeds the required maximum delay time for the ER path selected first.

If the sum of the delay times is smaller or larger than the maximum delay time (step 430), it is as follows

For example, as shown in Table 3 below, A-> D-> E-> C (total delay time: 60 msec) and A-> B-> E-> C msec) path is selected as possible ER list because it satisfies the condition (step 435), but the path A-> F-> G-> C (total delay time: 210 msec) exceeds the required maximum delay time, (Step 440).

ER PATH LINK SUN (DELAY) SELECTED PRIOIRTY A-> D-> E-> C a-> b-> c 10 + 20 + 30 = 60 msec YES One A-> B-> E-> C d-> j-> c 40 + 50 + 30 = 120 msec YES 2 A-> F-> G-> C f-> g-> h 60 + 70 + 80 = 210msec NO N / A

A-> D-> E-> C path with the sum of the delay times of fewer paths among the selected ERs has the highest priority and the A-> B-> E-> C path has the following priority And arranged in this order (step 445). Is selected as the final ER (step 450).

5 is a CSPF graph considering the available bandwidth according to an embodiment of the present invention.

Referring to FIG. 5, if the call processing protocol requires a bandwidth of 100M and links i (50M) and l (60M) violate this condition, i and l links are removed on the graph.

FIG. 6 is a CSPF graph considering the delay time according to an embodiment of the present invention.

Referring to FIG. 6, the link e (220 msec) and k (210 msec), which do not satisfy the requested maximum delay time, are also removed from the graph.

7 is a graph showing the final MCSPF according to an embodiment of the present invention.

Referring to FIG. 7, a possible path A-> D-> E-> C (LINK: a-> b-> c) (total delay time 60 msec) -> B-> E-> C (LINK: d-> j-> c) (total delay time: 120 msec) > C (LINK: f-> g-> h) (total delay time: 210 msec) The path is removed from the ER list beyond the required maximum delay time. Among the selected ERs, A-> D-> E-> C with the sum of the delay times of the fewer paths has the highest priority, and A-> B-> E-> C has the following priority .

FIG. 8 is a diagram illustrating a process of confirming a given SLA in an LSP through active monitoring on a set LSP according to an embodiment of the present invention.

Referring to FIG. 8, once the LSP is generated, the probe packet is transmitted to the generated LSP. The probe packet is transmitted as an ICMP or UDP type packet on the MPLS network according to the kind of desired SLA parameter having a time stamp.

If the path of the LSP to which the MCSPF algorithm is applied is determined from PE (A) to PE (B), the Round Trip Time (RTT), One-Way Delay, and Jitter are expressed by the following equations Can be calculated as follows.

RTT = TS4 - TS1

One-Way Delay = TS3 - TS2

Delay Jitter = Largest Delay - Smallest Delay

In order to measure One-Way Delay, it is possible to measure when each PE is synchronized with NTP (Network Time Protocol). If it is not synchronized, RTT / 2 is used to measure approximate value can do.

In the case of MPLS, if the LSP is set between the PE (A) and the PE (B) as a policy in the case of setting the LSP considering the TE policy, since the PATH of the bidirectional LSP is set equally, The value of the one-way delay is roughly equivalent.

One of the important factors in quality of real-time multimedia service, especially VoIP (Voice over IP) service is delay jitter or jitter. When jitter increases, echo And the service quality of the user is lowered.

In order to measure the jitter value, the probe packet is transmitted N times and the value is measured using the probe packet. To obtain a jitter value, the number N of times the probe packet is transmitted can be set to a desired value to obtain a statistically meaningful value by the network manager.

If the SLA parameter thus obtained satisfies the given LSP protocol per LSP, the MPLS LSP setup is completed and the packet transmission starts normally. If the SLP parameter does not satisfy the LSP protocol and the alternative path exists, the MPLS LSP notification is notified to the MPLS signaling protocol Then, the MCSPF algorithm is reapplied to break the existing LSP and calculate a new LSP.

MPLS signaling protocols such as RSVP-TE and CR-LDP define a new error code corresponding to this case and release the LSP by sending a message, and the fact that the LSP is released (switched) It informs.

The above procedure is performed again with the newly calculated ER information, and an LSP satisfying the above-mentioned SLA is set.

9 is a diagram illustrating a process of releasing an LSP that does not satisfy the SLA protocol and setting an LSP in a new path by applying an active monitoring method according to an embodiment of the present invention.

Referring to FIG. 9, if the LSP newly configured by applying the MCSPF does not satisfy the SLA protocol and the alternative path can not be set any more, the SLA parameter renegotiation process is performed. Renegotiation of SLA parameters can be automatically renegotiated and manually set according to the policies of the network administrator. After renegotiation, a new path is established.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

1 is a block diagram of a wired / wireless communication network using an MPLS network as a core network,

FIG. 2 is a flowchart illustrating an operation of an MCSPF according to an exemplary embodiment of the present invention. FIG.

FIG. 3 is a block diagram illustrating an overall architecture for driving a MCSPF (Multimedia Constraint Shortest First) algorithm according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating an algorithm for obtaining an ER according to an embodiment of the present invention. FIG.

5 is a graph illustrating a CSPF graph considering an available bandwidth according to an embodiment of the present invention,

FIG. 6 is a graph illustrating a CSPF graph considering a delay time according to an embodiment of the present invention,

7 is a graph illustrating the final MCSPF according to an embodiment of the present invention,

FIG. 8 is a diagram illustrating a process of confirming a given SLA in an LSP through active monitoring on an established LSP according to an embodiment of the present invention, and FIG.

9 is a diagram illustrating a process of releasing an LSP that does not satisfy an SLA protocol and setting an LSP in a new path by applying an active monitoring method according to an embodiment of the present invention.

Claims (14)

A method of a network entity for establishing a routing path list, Identifying at least one link that does not satisfy at least one of a required maximum delay time and an available bandwidth among a plurality of links; Selecting a plurality of routing paths by Constraint Shortest Path First (CSPF) based on the remaining links excluding the identified link; Generating a routing path list including at least one routing path based on a sum of delay times of respective links constituting the corresponding routing path for each of the plurality of selected routing paths; Selecting one of the routing paths included in the routing path list as an LSP (Label Switched Path) Setting an SLA (Service Level Agreement) parameter for the LSP; And transmitting the probe packet through the LSP to determine whether the SLA parameter for the LSP is satisfied, thereby completing the LSP setup. An apparatus of a network entity for establishing a routing path list, Identifying at least one link that does not satisfy at least one of a maximum delay time and an available bandwidth among a plurality of links, and determining, based on the remaining links other than the identified link, a plurality of routing paths by CSPF (Constraint Shortest Path First) Generates a routing list including at least one routing path based on a sum of delay times of respective links constituting the routing path for the selected plurality of routing paths, Selects a routing path as an LSP (Label Switched Path) from among the included routing paths, sets a SLA (Service Level Agreement) parameter for the LSP, transmits a probe packet through the LSP, And a controller for completing the LSP setting by determining whether the parameter is satisfied Wherein the. delete delete The method according to claim 1, Wherein the step of generating the list including the routing path comprises: Determining a sum of delay times of the links constituting the routing path for the selected plurality of routing paths, Identifying remaining routing paths other than the routing path whose sum of the determined delay times exceeds the required maximum delay time among the plurality of selected routing paths; And generating the list in which the identified routing paths are sorted based on a sum of the determined delay times. delete The method according to claim 1, Determining whether an alternative path exists in the routing path list if the SLA parameter for the LSP is not satisfied; And resetting the SLA parameter if the alternative path does not exist in the routing path list, and re-determining whether the reset SLA parameter is satisfied for the LSP. The method according to claim 1, And if the alternative path exists in the routing path list, re-determining whether the SLA parameter is satisfied by setting another routing path among the routing paths included in the routing path list to the LSP Lt; / RTI &gt; The method according to claim 1, Transmitting a probe packet through the LSP to determine whether an SLA parameter for the LSP is satisfied, Measuring at least one of a Round Trip Time (RTT), a One-Way Delay, and a Jitter by transmitting a probe packet through the LSP; And determining whether an SLA parameter for the LSP is satisfied using the measurement result. 3. The method of claim 2, Wherein the control unit determines a sum of delay times of respective links constituting the corresponding routing path for the selected plurality of routing paths and determines whether the sum of the determined delay times among the plurality of selected routing paths is a maximum delay Identify the remaining routing paths other than the routing path exceeding the time, and generate the list in which the identified routing paths are sorted based on the sum of the determined delay times. delete 3. The method of claim 2, Wherein the control unit determines whether or not an alternative path exists in the routing path list when the SLA parameter for the LSP is not satisfied, and resets the SLA parameter if the alternative path does not exist in the routing path list , And re-determines whether the reset SLA parameter is satisfied for the LSP. 3. The method of claim 2, Wherein the control unit sets another routing path among the routing paths included in the routing path list to an LSP and re-determines whether the SLA parameter is satisfied when the alternative path exists in the routing path list . 3. The method of claim 2, The control unit transmits at least one of a Round Trip Time (RTT), a One-Way Delay, and a Jitter by transmitting a probe packet through the LSP, and transmits the measurement result to the LSP Gt; SLA &lt; / RTI &gt; parameter is satisfied.

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