KR100349655B1 - Path setup method for path protection/recovery in MPLS networks and path recovery method using the same - Google Patents

Abstract

The present invention relates to a connection establishment method for connection protection and recovery in MPLS network, a connection failure recovery method using the same, and a recording medium thereof. In the case of LSP connection failure in MPLS network, protection is performed in advance using past connection failure information. To establish a connection and perform a fast recovery using the MPLS failure notification signal (FIS) to provide a connection establishment method that provides efficient use of network resources and fast connection failure recovery, a connection failure recovery method using the same, and a recording medium thereof. In order to receive the request for connection establishment, a first step of sending a request for connection establishment in a switch-only router (PSL) to a router (LSR) of a lower stream; A second step of checking whether a response received from the router of the lower stream includes link information that has experienced a past failure in a link through which a connection passes; And a third step of pre-establishing a protection connection for the connection passing through the link having experienced the failure, when the response to the connection establishment includes the link information having experienced the past failure according to the test result of the second step. It includes.

Description

Path setup method for path protection / recovery in MPLS networks and path recovery method using the same}

According to the present invention, when a Label Switched Path (LSP) connection failure occurs in a Multi Protocol Label Switching Network (MPLS) network, a protection connection is established in advance using past connection failure information, and an MPLS failure notification signal (FIS: Fault). Connection setting method that provides efficient use of network resources and fast connection failure recovery by performing fast recovery using Indication Signal, connection failure recovery method using the same, and a computer readable record that records a program for implementing the above methods. It is about the medium.

MPLS is a transport mechanism designed to provide flexibility and scalability of the Internet Protocol (IP) while providing ATM (Asynchronous Transfer Mode) or Frame Relay (QoS) of QoS. It can provide a virtual private network (VPN), "Voice over IP", "Video over IP", web hosting, e-commerce, and traffic engineering.

The basic idea behind MPLS is to perform label swapping by forwarding different control modules together. The control module can be a basic unicast routing module, a traffic engineering module, a VPN module, or the like. The label switched path (LSP), which is a connection in the MPLS network, is set by the label distribution protocol (LDP), which is a connection establishment protocol of MPLS, and packet delivery in the LSP is efficiently and quickly performed using a short header called a label. The packet can be sent.

As shown in FIG. 1, the components of the MPLS network are located at the boundary with the existing network and attach an IP packet to create an MPLS packet to enter the MPLS network, and to connect the MPLS network to the other existing network. It consists of a Label Edge Router (LER) 12, which serves to terminate the network, and a Label Switched Router (LSR) 13, which serves as a label replacement.

The subscriber may be connected to an end system 11 that performs a routing function and receive MPLS service through the MPLS domain a. Here, in the event of a failure, the set of LSRs for which fast connection recovery is guaranteed is called the protection domain (b), which is a subset of the MPLS domain (a).

As such, when the failure occurs in the MPLS network, the existing methods that can be provided can be classified into the following three ways.

Firstly, after routing information is updated to set a new LSP, IP rerouting method is used to transmit traffic using the new LSP.

Secondly, in case of LSP setup, the protection connection is set up in advance in case of a failure, the failure notification signal is used for the quick delivery of the failure information, and when the failure notification is received after the failure, the PSL switches to the protection connection. to be.

Third, the transfer switch LSR (PSL: Path Merge LSR), which uses the failure notification signal for prompt delivery of the failure information and receives the failure notification information after the failure, is dedicated to traffic aggregation. This is how to switch traffic by setting up a new LSP.

Here, both the second existing method and the third existing method establish a protection connection or perform a transfer using a failure notification signal, and the necessary components and connections are shown in FIG. 2. This includes PSL, which is an LSR that performs connection switching or establishing a protection connection in the event of a failure, and PML, which is an LSR that integrates traffic of an existing connection and a protection connection, and RNT (Reverse Notification), which is path information for passing failure information from PML to PSL. Tree).

Based on these components, the connection recovery method is performed as follows.

When a failure occurs, the upper LSR of the failure link transmits a failure notification signal to the PSL of all connections through the link based on the RNT information. The PSL receiving the failure notification signal redirects traffic to an alternate path.

The difference between the second existing method and the third existing method is that the second existing method establishes a protection connection before failure, and the third existing method establishes a protection connection after failure.

Looking at the problems of these conventional techniques as follows.

Assuming that the link recovery procedure of the IP Rerouting method, which is the first method, has failed in the link between LSR4 and LSR6 in the network of FIG. Since the routing information converges to the entire network after the routing protocol converges, the route calculation is performed again, a new LSP is generated according to the changed routing entry, and traffic is required to be transferred. Therefore, a very long recovery time of several minutes is required. .

Assuming that the link recovery procedure of the second method, Pre_Established, is a failure in the link between LSR4 and LSR6 in the network of FIG. This means that when establishing a basic connection, the PSL that received the notification of failure in case of failure by setting up the protection connection can directly transfer traffic to the protection connection, thereby providing the fastest recovery time. However, setting a protection connection in advance for all connections wastes resources that can be used, which is a problem for efficient resource usage.

Assuming that the link recovery procedure of the last method, Established_on_Demand, is a failure in the link between LSR4 and LSR6 in FIG. When a failure occurs, the failure information is quickly informed to the PSL to perform the transfer based on the RNT, which is the failure notification path information. However, since a new path needs to be set afterwards, a certain amount of failure recovery time is required. However, faster recovery is possible than the first method.

As described above, in the related art, an IP rerouting method in which an MPLS connection is established again after a routing table is reconstructed by reconstructing information related to a connection failure by an IP routing protocol without a special MPLS connection recovery mechanism, and a recovery time in case of connection failure To reduce this, there are Pre_Established method for establishing MPLS connection in advance, and Established_on_Demand method for establishing new protection connection and switching traffic after failure using MPLS connection recovery mechanism.

However, the first method, IP Rerouting, has a problem that fast recovery is impossible because connection recovery time takes several minutes because the MPLS connection is reset after failure information is converged and the routing table is reconfigured. Second method, Pre_Established The method pre-sets the connection for fast recovery in the event of a connection failure, but there is a problem that can cause a waste of network resources by setting up many unused protected connections. Finally, there is a problem that the Established_on_Demand method cannot be recovered faster than the second existing method.

In order to solve the above problems, the present invention, in the case of LSP connection failure in the MPLS network, establishes a protection connection in advance by using the previous connection failure information, and quickly by using the MPLS failure notification signal (FIS) It is an object of the present invention to provide a method for establishing a connection that provides efficient use of network resources and fast connection recovery by performing recovery, and a method for recovering a connection failure using the same, and a computer-readable recording medium recording a program for implementing the methods. .

1 is an explanatory diagram showing a protection domain in which connection recovery is guaranteed with an MPLS domain in a general MPLS network;

2 is an explanatory diagram showing components and connection relationships for a connection recovery method in a general MPLS network;

3 is a flowchart illustrating a process of restoring a connection by a conventional IP rerouting method in a general MPLS network.

4 is a flowchart illustrating a process of restoring a connection by a conventional Pre_Established method in a general MPLS network.

5 is a flowchart illustrating a process of restoring a connection by a conventional Established_on_Demand method in a general MPLS network.

FIG. 6 is a diagram illustrating an embodiment of a label mapping message of an LDP used to notify past failure information in a connection establishment and connection failure recovery method according to the present invention; FIG.

FIG. 7 is an exemplary explanatory diagram showing an additional TLV of an LDP label mapping message to notify past failure information in a connection establishment and connection failure recovery method according to the present invention; FIG.

8 is a flowchart illustrating a process of performing PSL for connection establishment and connection failure recovery according to the present invention.

9 is a flowchart illustrating a process of performing LSR for connection establishment and connection failure recovery according to the present invention.

* Explanation of symbols for the main parts of the drawings

11 End System 12 Label Edge Router (LER)

13: label switch router

In order to achieve the above object, the present invention provides a connection setup method for a connection failure occurrence in an MPLS network, and upon receiving a request for connection establishment, a request for connection establishment in a switching dedicated router (PSL). Transmitting a to a router (LSR) of a lower stream; A second step of checking whether a response received from the router of the lower stream includes link information that has experienced a past failure in a link through which a connection passes; And a third step of pre-establishing a protection connection for the connection passing through the link having experienced the failure, when the response to the connection establishment includes the link information having experienced the past failure according to the test result of the second step. Characterized in that comprises a.

The present invention relates to a method for establishing a connection failure in an MPLS network, wherein when a failure occurs on an own link in an intermediate router (LSR), related failure link information and failure time are stored. A first step of making; A second step of checking whether the connection includes link information that has experienced a past failure when receiving a response to the connection establishment from the lower stream router (LSR); And if the request connection includes link information that has experienced a past failure, the router of the higher stream including link information that has experienced a past failure in a response to the connection establishment according to the check result of the second step. And a third step of transmitting to the LSR to use the determination information of whether to establish a protection connection in advance in the switching dedicated router (PSL).

In addition, the present invention further includes a fourth step of deleting the link information that has experienced the past failure in the case where the failure of re-occurrence does not occur for a predetermined time in the request connection in the intermediate router (LSR). It is characterized by.

The present invention for achieving the above object, in the connection failure recovery method when the connection failure in the MPLS (MPLS) network, upon receiving a request for connection establishment, a request for connection establishment in the switching dedicated router (PSL) Transmitting to a router (LSR) of a lower stream; It checks whether the response for connection establishment received from the router (LSR) of the lower stream includes link information that has experienced a past failure in the link through which the connection passes, and protects the connection through the link that experienced the failure. A second step of presetting; When receiving failure information from the router (LSR) of the lower stream, a protection connection is established if a protection connection is not set in advance, and if the protection connection is set in advance, a traffic transfer is performed through a preset connection. Three steps; And a fourth step of, upon receiving failure recovery information from the lower stream router (LSR), switching traffic to the restored existing connection and leaving the protection connection intact for failure reoccurrence.

In order to achieve the above object, the present invention provides a connection to an MPLS network having a processor for connection establishment in preparation for a connection failure. A first function of sending a request for setting to a router (LSR) of a lower stream; A second function of checking whether a link received through a link is included in a response to a connection establishment received from a router (LSR) of the lower stream; And a third function of presetting a protection connection for a connection passing through a link that has experienced a failure, when the response to the connection establishment includes link information according to a test result of the second function. A computer readable recording medium having recorded thereon a program for realizing the present invention is provided.

In order to achieve the above object, the present invention provides an MPLS network with a processor for connection establishment in preparation for a connection failure, when a failure occurs on its link in an intermediate router (LSR). A first function of storing link information and failure time; A second function of checking whether a connection includes link information that has experienced a past failure when receiving a response to a connection establishment from a router (LSR) of a lower stream; And in response to the connection establishment, if the request connection includes link information that has experienced a past failure, the router of the higher stream including link information that has experienced a past failure in a response to the connection establishment. And a computer readable recording medium having recorded thereon a program for realizing the third function, which is transmitted to the LSR and used as determination information of whether or not to establish a protection connection in advance in a switching dedicated router (PSL).

In addition, the present invention further provides a fourth function for deleting link information that has experienced stored past failures when a failure reoccurrence does not occur for a predetermined time in the request connection in the intermediate router (LSR). A computer readable recording medium having recorded a program is provided.

The present invention for achieving the above object, in order to recover from a connection failure in connection failure, MPLS network with a processor, upon receiving a request for connection establishment, connection establishment in a dedicated switch router (PSL) A first function of sending a request for a to a router (LSR) of a lower stream; It checks whether the response for connection establishment received from the router (LSR) of the lower stream includes link information that has experienced a past failure in the link through which the connection passes, and protects the connection through the link that experienced the failure. A second function of presetting; When receiving failure information from the router (LSR) of the lower stream, a protection connection is established if a protection connection is not set in advance, and if the protection connection is set in advance, a traffic transfer is performed through a preset connection. 3 functions; And a program for realizing a fourth function of, upon receiving failover information from the lower stream router (LSR), switching traffic to the recovered existing connection and leaving the protected connection intact in case of failure again. Provides a record medium that can be.

The present invention is to optimize the protection connection configuration by using the failure information of the past in order to minimize the inefficiency of the fast recovery and resource usage when a failure occurs.

To this end, the present invention stores the specific failure information of each link in each LSR, and forwards this failure information together in the LSP establishment response, and the link that the LSP that has established the connection in the PSL performing the transfer has experienced past failures. Only set the protection connection in advance if it passes. In case of a failure, a failure notification signal is used to immediately notify the PSL of the failure, and the notified PSL performs a switchover immediately if there is a protection connection on the corresponding connection. In addition, even when a fault is recovered, the PSL is quickly delivered to the PSL through a failure recovery notification signal, and the PSL received the signal transfers traffic back to an existing connection and leaves a protection connection in case of a failure again.

According to the present invention, since there is no information about past connection failures after the network is initially configured, the protection connection is established after the failure is generated using On_Demand_Established, but when the failure information is collected, past failures are generated. By establishing a protection connection in advance using the Pre_Established method only for the connection of a specific high-failure link, two advantages can be obtained: fast connection recovery and efficient use of network resources.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As a more preferred embodiment, to explain the MPLS connection recovery method, it is assumed that the MPLS protection domain is the same as FIG. The assumed MPLS protection domain consists of 10 LSRs that perform MPLS label swapping, PSL1 and PSL9 switch between the primary and protection connections in case of double failure, and also the primary connection in case of failure. There is a PML7 that performs data merge between the connection and the protection connection (these are called LSR1, LSR9, LSR7 because these PSL1, PSL9, and PML7 basically perform LSR functions).

The default LSP connection is a 1-2-3-4-6-7 connection (represents a connection that passes sequentially through LSR1, LSR2, LSR3, LSR4, LSR6, LSR7). Each LSR knows the Reverse Notification Tree, which is the reverse of the primary connection. For example, if a failure occurs at L [3,4] (links between LSR3 and LSR4), the failure notification path information is used to notify the failure of LSR2 and LSR9, the upper streams of the two connections affected by the failure.

On the other hand, there are two types of connection failures in the MPLS network. One is PF (Path Failure), which is impossible to transmit when the link connection itself is damaged or a hardware error occurs. Connectivity is not a problem, but the quality of the connection is below a certain level. In this case, the latter PD failure may be a problem on the network line or the physical equipment itself, or may be caused by an excessive amount of traffic. If there is a problem with the physical equipment itself, it will not be possible to improve the quality of the connection without exchanging itself, and in many cases the traffic patterns will change at regular intervals, so traffic engineering may be performed on high-traffic links. Unless you increase the capacity of the link, there is a high probability that the quality will drop to a certain level.

In the present invention, using the characteristics of the failure, the PD of the two types of failure PF and PD that can use the past failure information as the determination information to set the protection connection in advance due to the high failure reoccurrence rate according to the traffic characteristics or link conditions. I use it. In other words, the protection connection is set up only for the connection passing through the link that has experienced the PD in the past to prepare for the recurrence of failure, and the selective setting of the protection connection in advance minimizes the waste of bandwidth.

The PD information is stored at each LSR when a failure occurs, and when the LSP connection response includes a past failure link, the PD information is transmitted to the upper LSR, and the PSL decides whether to establish a protection connection in advance. Use it as judgment information.

At this time, the label mapping message which is an LSP connection response message used is shown in FIG. In the present invention, TLV (Type-Length-Value) as shown in FIG. 7 is defined in order to transmit past response information in the response message, and the defined TLV is attached after the optional parameters of the response message. Will be sent.

As shown in FIG. 7, the TLV is a TLV based on the LDP Vendor-Private TLV, and is filled with 1 in the first and second U bits and F bits. This means that if the corresponding TLV is unknown in the intermediate LSR, the value is ignored and forwarding is performed.

The third item, Type, is a TLV type and can be from 0x3E00 to 0x3EFF in the case of LDP Vendor-Private TLV. One of these values is used, and the fourth item, Length, includes the Vendor ID item. Since it is the item to save the length after that, use 0x0a value.

In addition, the fifth item, Vendor ID, needs to use ID value assigned by IEEE in each company. Subsequent items, LSR ID and Outgoing Interface Number, are used to transmit failure link information. The ID of the LSR located in the upstream and the interface number to the failed link are stored and transmitted to the PSL.

Now, referring to FIG. 8, a process of performing a PSL for performing a switch between a basic connection and a protection connection when a failure occurs in order to perform the connection establishment and connection failure recovery method of the present invention will be described in detail.

First, when receiving information that triggers the failover method (801), it is analyzed whether the received information is the LDP connection establishment request (802).

As a result of the analysis, when a new LSP connection establishment is requested, in order to determine whether to establish a protection connection in advance, an LDP connection establishment is requested and a connection establishment response is waited (803). Subsequently, upon receiving the connection establishment response, it checks (804) whether there is link information that has experienced a past PD failure in the link through which the connection passes, and establishes a protection connection (805).

If the PSL receives the failure notification information (806), it is checked whether a protection connection is established in advance (807). If the protection connection is established in advance, the traffic is transferred to the preset protection connection (809). If not, the switchover is made after establishing the protection connection (808) (809).

On the other hand, when the PSL receives the failure recovery notification information (810), after switching traffic to the existing connection, the used protection connection is left without disconnecting for failure reoccurrence (811).

Now, with reference to Figure 9 will be described in more detail the process performed in the LSR of the protection domain for connection establishment and connection failure recovery of the present invention.

First, when receiving information that triggers the failure recovery method (901), it is analyzed whether the received information is the LSP connection establishment response from the lower stream LSR (902).

When the analysis result shows that the LSP connection establishment response is received from the lower stream LSR, the request LSP checks whether there is link information that has experienced a past PD failure (903), and if the response includes past failure information, the connection establishment is performed. Include this information in the response (904) and send it to the higher stream LSR (905). If not, a connection establishment response that does not include past failure information is sent to the higher stream LSR (905).

In addition, the intermediate LSRs store the corresponding link information and set a timer (907) when a PD failure occurs (906) for connection establishment and connection failure recovery of the present invention. If the PD failure does not occur again until the timer set as described above is timed out (908), the corresponding PD failure information is deleted (909).

The above-described process will be described with the MPLS protection domain of FIG. 2 as follows.

First, assume that the network is initialized so that all LSRs do not have PD failure information.

Subsequently, it is assumed that the LSP connection request is made from LSR1 to LSR7 to determine the optimal path as 1-2-3-4-6-7, and then request LSP basic connection establishment along this path. Then, the response LSR1 has no fault information in the response, so the traffic is sent to the established default connection without establishing a protection connection.

Next, assume that PD failure occurs in LSR3 and LSR4. Then, LSR3, which detects the occurrence of a failure, stores failure information for this link, and sets a timer for the failure information. In addition, the LSR2 is notified using the failure notification path information, and the received LSR2 is also notified to the LSR1 performing the PSL role using the failure notification path information. At this time, the LSR1, which is notified of the failure, checks whether there is a pre-configured protection connection, determines that there is no protection connection, requests a protection connection establishment, establishes a protection connection of 1-5-7, and performs traffic switching to the protection connection. . The PML of this connection, LSR7, aggregates the traffic from the primary and protection connections and sends it to the next LSR.

Next, assume that an LSP connection establishment of 8-9-3-4-6-7 is requested. The LSP connection request is transmitted along this path, and when the response is transmitted in the reverse direction, the LSR3, which stored the fault information, includes this information in the response. The LSR9 in the PSL role, which has received a response containing the fault information, sets up 9-10-7, which is a protective connection to LSR7.

As described above, the present invention uses PD failure information, which has a high failure reoccurrence rate according to traffic characteristics or link conditions, and can use past failure information as decision information for establishing a protection connection in advance. Accordingly, the present invention minimizes the recovery time in the event of a failure by setting up a protection connection in case of a failure including a link in which a PD failure has occurred in the past, and enables fast switching by immediately transmitting a failure notification signal to the PSL in the event of a failure. Done. In addition, this selective connection can be established to minimize the waste of bandwidth due to the protection connection.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

As described above, the present invention can optimize the protection connection setting by using the failure information of the past, thereby reducing the inefficiency of the fast recovery and resource usage when a failure occurs.

Claims (15)

In the connection establishment method for the occurrence of a connection failure in the MPLS network, A first step of, upon receiving a request for establishing a connection, transmitting a request for establishing a connection from a dedicated switch router (PSL) to a router (LSR) of a lower stream; A second step of checking whether a response received from the router of the lower stream includes link information that has experienced a past failure in a link through which a connection passes; And A third step of pre-establishing a protection connection for the connection passing through the link in which the failure has occurred, when the response to the connection establishment includes the link information which has experienced the past failure according to the test result of the second step; Connection setting method in MPS network comprising a. The method of claim 1, The router (LSR), Whenever there is a failure on the link, it stores the link, and if the connection contains a past failure link, it includes this information and forwards it to the switch-only router (PSL). A method of establishing a connection in an MPS network, characterized by using as judgment information of whether or not to set up. In the connection establishment method for the occurrence of a connection failure in the MPLS network, A first step of storing related fault link information and fault occurrence time when a failure occurs on its link in an intermediate router (LSR); A second step of checking whether the connection includes link information that has experienced a past failure when receiving a response to the connection establishment from the lower stream router (LSR); And According to the check result of the second step, if the request connection includes the link information that has experienced the past failure, the router (LSR) of the upper stream including the link information that has experienced the past failure in the response to the connection establishment The third step, so that the transfer dedicated router (PSL) can be used as judgment information on whether to establish a protection connection in advance. Connection setting method in MPS network comprising a. The method of claim 3, wherein A fourth step in which the intermediate router (LSR) deletes the link information that has experienced the past failure if the failure does not occur in the request connection for a predetermined time; Connection setting method in MPS network further comprising a. The method according to any one of claims 1 to 4, In order to transmit in response to the connection establishment including the link information that has experienced a past failure, A method for establishing a connection in an MPS network, comprising using a message in which a failure link information and a corresponding router identification information (LSR ID) are added to a label mapping message that is a connection establishment response message. The method of claim 5, The disorder is Substantially, there is no problem in the connectivity of the link, but the connection establishment method of the MPS network, characterized in that the quality of the connection state of the PD (Path Degrade) disabled below a predetermined level. In the connection failure recovery method at the time of connection failure in MPLS network, A first step of, upon receiving a request for establishing a connection, transmitting a request for establishing a connection from a dedicated switch router (PSL) to a router (LSR) of a lower stream; It checks whether the response for connection establishment received from the router (LSR) of the lower stream includes link information that has experienced a past failure in the link through which the connection passes, and protects the connection through the link that experienced the failure. A second step of presetting; When receiving failure information from the router (LSR) of the lower stream, a protection connection is established if a protection connection is not set in advance, and if the protection connection is set in advance, a traffic transfer is performed through a preset connection. Three steps; And A fourth step of switching traffic to the restored existing connection and leaving the protection connection in case of failure reoccurrence upon receiving failover information from the router (LSR) of the lower stream; Connection failure recovery method in MPS network comprising a. The method of claim 7, wherein The connection establishment process in the router, A fifth step of storing related failure link information and failure time when a failure occurs on its own link in an intermediate router (LSR); A sixth step of checking whether the connection includes link information that has experienced a past failure when receiving a response to the connection establishment from the lower stream router (LSR); And According to the check result of the second step, if the corresponding connection includes the link information that has experienced the past failure, the router (LSR) of the upper stream including the link information that has experienced the past failure in the response to the connection establishment Step 7 so that the switch-only router (PSL) can be used as judgment information on whether to establish a protection connection in advance. Connection failure recovery method in MPS network comprising a. The method of claim 8, An eighth step in which the intermediate router (LSR) deletes the link information that has experienced the past failure when the failure does not occur in the request connection for a predetermined time; Connection failure recovery method in MPS network further comprising a. The method according to any one of claims 7 to 9, In order to transmit in response to the connection establishment including the link information that has experienced a past failure, A method for recovering a connection failure in an MPS network, comprising using a message in which a failure link information and a corresponding router identification information (LSR ID) are added to a label mapping message that is a connection establishment response message. The method of claim 10, The disorder is Substantially, there is no problem in the connectivity of the link, but the connection failure recovery method in MPS network characterized in that the quality of the connection state is below the PD (Path Degrade) disabled. In order to establish a connection in case of a connection failure, the MPLS network with a processor, A first function of, upon receiving a request for establishing a connection, transmitting a request for establishing a connection from a dedicated switch router (PSL) to a router (LSR) of a lower stream; A second function of checking whether a link received through a link is included in a response to a connection establishment received from a router (LSR) of the lower stream; And A third function of pre-establishing a protection connection for a connection passing through a link that has experienced a failure, when the response to the connection establishment includes link information according to a check result of the second function; A computer-readable recording medium having recorded thereon a program for realizing this. In order to establish a connection in case of a connection failure, the MPLS network with a processor, A first function of storing relevant failure link information and failure time when a failure occurs on its link in an intermediate router (LSR); A second function of checking whether a connection includes link information that has experienced a past failure when receiving a response to a connection establishment from a router (LSR) of a lower stream; And According to the check result of the second function, when the request connection includes the link information that has experienced the past failure, the router (LSR) of the higher stream including the link information that has experienced the past failure in the response to the connection establishment A third function that allows the transfer dedicated router (PSL) to use it as judgment information on whether to establish a protection connection in advance. A computer-readable recording medium having recorded thereon a program for realizing this. The method of claim 13, A fourth function of deleting the link information that has experienced the past failure when the intermediate router (LSR) does not generate a failure in the request connection for a predetermined time; A computer-readable recording medium that records a program for further realization. In order to recover from a connection failure in case of a connection failure, the MPLS network with a processor, A first function of, upon receiving a request for establishing a connection, transmitting a request for establishing a connection from a dedicated switch router (PSL) to a router (LSR) of a lower stream; It checks whether the response for connection establishment received from the router (LSR) of the lower stream includes link information that has experienced a past failure in the link through which the connection passes, and protects the connection through the link that experienced the failure. A second function of presetting; When receiving failure information from the router (LSR) of the lower stream, a protection connection is established if a protection connection is not set in advance, and if the protection connection is set in advance, a traffic transfer is performed through a preset connection. 3 functions; And A fourth function of switching traffic to the restored existing connection and leaving the protection connection in case of failure reoccurrence upon receiving failover information from the router (LSR) of the lower stream; A computer-readable recording medium having recorded thereon a program for realizing this.