KR20020096754A - Method for determining traffic paths for Protection Switching in MPLS based data telecommunication network - Google Patents

Abstract

PURPOSE: A traffic path setting method for a protection switching in an MPLS(Multi-Protocol Label Switching) data communication network is provided to determine two primary LSPs(Label Switched Paths) and one backup path in one ingress-to-egress, decrease a bandwidth assigned in the one backup path, and effectively treat a network fault. CONSTITUTION: Links in which a current margin capacity capable of traffic transmission is less than the entire traffic quantity to be transmitted are removed from an object among the entire link between nodes of a communication network(S401). The first distance information value about each residual object link is calculated on the basis of information about a currently used traffic quantity and the entire traffic quantity to be transmitted(S402). The first ingress-to-egress traffic path is set up on the basis of the calculated first distance information value(S403). Links in which a current margin capacity capable of traffic transmission is less than the entire traffic quantity to be transmitted and links composed in the first ingress-to egress traffic path are removed from the object among the entire link of the nodes of the communication network(S404). The second distance information value about each residual object link is calculated on the basis of information about the currently used traffic quantity and the entire traffic quantity to be transmitted(S405). The second ingress-to-egress traffic path is set up on the basis of the calculated second distance information value(S406). An assignment quantity is calculated for assigning the entire traffic quantity on the first ingress-to-egress traffic path and the second ingress-to-egress traffic path(S407). Links in which the current margin capacity capable of traffic transmission is less than one value selected among the assignment quantity and links composed in the first and second ingress-to-egress traffic paths are removed from the object among the entire link of the nodes of the communication network(S408). The third distance information value about each residual link is calculated on the basis of information about the currently used traffic quantity and the selected one value(S409). The third ingress-to-egress traffic path is set up on the basis of the calculated third distance information value(S410). The first and second ingress-to-egress traffic paths are determined as primary LSPs to assign the entire traffic, and the third ingress-to-egress traffic path is used as a backup path(S411).

Description

Method for determining traffic paths for Protection Switching in MPLS based data telecommunication network}

The present invention relates to a traffic path setting method for protection switching in a data communication network to which a multi-protocol label switching scheme is applied, and more particularly, to a multi-protocol label switching (MPLS) traffic engineering environment. In a data communication network, a primary label switched path as a primary path for the traffic in order to prepare for a network failure when a high quality of service (QoS) is required for the transmitted data traffic. In addition, a separate spare path for protection switching in case of failure of the primary label switch path is separately set. The present invention relates to a method for efficiently setting such a primary label switch path and a backup path.

MPLS provides quality of service (QoS) for transport traffic in a variety of networks, including Internet Protocol (IP-based) networks, including Internet Protocol-based (IP-based) networks, and IP over DWDM networks over DWDM. It is a technology that has been in the spotlight recently as a traffic engineering method for guaranteeing the reliability and efficiently utilizing network resources.

MPLS traffic engineering establishes traffic paths, or Label Switched Paths (LSPs), in a variety of ways to better accommodate the various QoS requirements of users' IP packets.

At this time, reroute, protection switching, and fast reroute are discussed in the Internet Engineering Task Force (IETF) as a method for preparing for a network failure. In particular, the protection switching and fast reroute methods attempt to cope with a network failure by setting a backup path (or a spare path) for a primary LSP.

However, the setting of the spare path is reserved for the bandwidth of the spare path and thus cannot be used for other purposes. On the other hand, in normal network operation, a method of using the reserved bandwidth for the reserved path for the transmission of traffic having a low QoS and in the case of a failure, for the traffic of the primary LSP has been proposed.

However, there is a need for a method capable of effectively coping with network failures while reducing the bandwidth allocated to the spare path as much as possible. In addition, since the link or node costs considered in the existing routing methods do not consider the traffic flow required for the current transmission, only the flow rate in a given state is considered, and thus, optimal routing is difficult from the overall network perspective. Traffic engineering efficiency is inferior.

The present invention was created to solve the existing problems in the technical background as described above, and its purpose is to provide reliable ingress-to-egress transmission of traffic requiring a high degree of quality of service (QoS). For this purpose, two primary LSPs and one spare path for one end-to-end should be determined according to the new method, while reducing the bandwidth allocated to the spare path as much as possible while effectively coping with network failures. To provide a traffic routing method for protection switching in a data communication network to which a multi-protocol label switching scheme is applied.

In addition, the cost is calculated by considering the amount of traffic to be transmitted when calculating the link cost or node cost of the network required for determining the routes for the primary LSP and backup path, and the generated costs By considering the nonlinear cost function like the delay function for the traffic flow volume, the desired traffic path is optimized and set.

1 is a diagram illustrating an example of a data communication network to which a multi-protocol label switching (MPLS) scheme is applied;

FIG. 2 shows two primary LSP1 and primary LSP2 and one spare path for one end-to-end traffic for protection switching in a data communication network to which multi-protocol label switching (MPLS) is applied according to the present invention. Is a diagram showing a network set up,

FIG. 3 is a schematic block diagram of setting a label switching path LSP and a backup path in the label edge router LER of FIGS. 1 and 2;

4 is a flowchart illustrating a traffic path setting method for protection switching in a data communication network to which an MPLS scheme is applied according to an embodiment of the present invention.

※ Explanation of code for main part of drawing

100: Data communication network with multi-protocol label switching

110210: Ingress Label Edge Router 120220: Egress Label Edge Router

130-133,231-235,241,242: Label Switch Router

In order to achieve the above object, a traffic path setting method for protection switching in a data communication network to which the multi-protocol label switching method is applied includes protection switching in a data communication network to which the multi-protocol label switching method is applied and // Alternatively, a traffic routing method for fast reroute may include a label switch router (LSR) as one or more intermediate nodes from a label edge router (LER) as an ingress in a data communication network to which multi-protocol label switching (MPLS) is applied. A method of establishing an ingress-to-egress traffic path (LSP) to a label edge router (LER) as an egress through a network, wherein: Eliminate links at the destination whose current free capacity to send traffic is less than the total amount of traffic to be transmitted. A first step of; A second step of calculating a first distance information value for each target link remaining as a result of the removal of the first step, based on the information on the amount of traffic currently used on the link and the total amount of traffic to be transmitted; A third step of establishing a first end-to-end traffic path based on the calculated first distance information value; A fourth step of removing from the object of the link between the node and the node of the communication network the link which constitutes the first end-to-end traffic path and the link whose current capacity for transmitting traffic is less than the total amount of traffic to be transmitted; A fifth step of calculating a second distance information value for each target link remaining as a result of the removal of the fourth step, based on the information on the amount of traffic currently used on the link and the total amount of traffic to be transmitted; A sixth step of setting a second end-to-end traffic path based on the calculated second distance information value; And a seventh step of calculating an allocation amount for each distributed allocation of the total amount of traffic to be transmitted on the established first end-to-end traffic path and second end-to-end traffic path; Links that make up the first and second end-to-end traffic paths with a link having a spare capacity that is capable of transmitting current traffic out of a total link between nodes of the communication network and less than a selected one of the quotas (preferably a large value). An eighth step of removing them from the subject; A ninth step of calculating a third distance information value for each target link remaining as a result of the removal of the eighth step, based on the information on the amount of traffic currently used on the corresponding link and the larger value of the quota; A tenth step of establishing a third end-to-end traffic path based on the calculated third distance information value; And determining the configured first and second end-to-end traffic paths as a primary label switching path to allocate all traffic to be transmitted, and using the set third end-to-end traffic path as a spare path. It comprises an eleventh step.

The second step, the fifth step, or the ninth step may be based on information on the amount of traffic currently being used on the link and the total amount of traffic to be transmitted, or information on a larger value of the allocation amount. The derivative values of the second and third delay function values are calculated, and the derivative values of the first, second and third delay function values are used as the first, second and third distance information values, respectively. .

In the third, sixth, and tenth steps, when the first, second, or third end-to-end traffic paths are plural, the traffic paths having relatively small calculated distance information values are routed. It characterized in that it is set to.

Hereinafter, a traffic route setting method for protection switching in a data communication network to which a multi-protocol label switching scheme is applied according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an example of a data communication network to which the MPLS scheme is applied. The network 100 includes a plurality of routers, and serves as an inlet of the network 100 to any data traffic among the plurality of routers. The router is called an Ingress Label Edge Router (LER) 110, and the router serving as an exit is called an Egress Label Edge Router 120. One or more routers serving as nodes of an intermediate path between the ingress LER 110 and the egress LER 120 are referred to as a label switching router (LSR) 130 and the ingress LER 110 The traffic path established from the LSR 130 to the egress LER 120 is called a Label Switch Path (LSP) (LSP1, LSP2). The LSP is an ingress LER 110. Set for incoming traffic , In the figure, for example LSP1 is to say the path set as 110 → 132 → 133 → 120, LSP2 refers to a path set as 110 → 131 → 120.

Figure 2 shows two primary LSP1 and Fry for one Ingress-to-Egress traffic for protection switching in a data network to which the multi-protocol label switching (MPLS) scheme according to the present invention is applied. The primary LSP1 is Ingress → LSR2 → LSR5 → Egress, the primary LSP2 is Ingress → LSR3 → LSR6 → Egress, and the spare path is Ingress → LSR1. → LSR4 → LSR7 → Egress, the reserved spare path is used as a bypass path in case of failure of two primary LSPs. Traffic demand is appropriately divided and allocated to the configured two primary LSPs, and the bandwidth allocated to the spare path is such that a larger bandwidth among the amount of traffic allocated to the two primary LSPs.

FIG. 3 is a schematic block diagram for setting up an LSP and a spare path in an ingress LER, and includes an input / output interface 301 serving as a data communication interface with an external device, a physical switching structure 302, and a routing table. A memory 303 for storing the data, a routing table stored in the memory 303, and controlling the switching structure 302 according to the created and stored routing table to control the traffic through the input / output interface 301. The controller 304 is configured to control input / output, and the LSP and the spare path are also set when the routing table stored in the memory 303 is created under the control of the controller 304. Therefore, the present invention described below is applied to the control unit 304 and implemented.

4 is a traffic path setting method for protection switching in a data communication network to which the MPLS scheme is applied according to an embodiment of the present invention, and shows a flowchart illustrating a method of setting a primary label switching path (LSP) and a spare path. , The physical topology of the network, the cost function (e.g., the delay function), the initial and spare capacity of the network link, and the traffic demand for the traffic requiring the current LSP (i.e. the total amount of traffic to be transmitted) And other information are already known to the ingress LER to which the present invention is applied, and routers (LSRs) on the MPLS network are also aware of the information.

In addition, the following symbols and definitions used in the description of the present invention, network G = (m, n), m is the number of links, n is the number of nodes, yi is the network G at the moment to set the LSP for new traffic Is the amount of flow per link i (i = 1,2, ..., m) for existing traffic transmission, d is the total amount of traffic that needs to be transmitted, and fi (xi) is the amount of flow for link i. Incurred cost (i = 1,2, ..., m), fi '(xi) is the increase cost per unit flow (i = 1,2, ..., m) when the flow rate of link i is xi ), dist (i) is the distance of link i, k th path (k = 1,2) for pk primary LSP.

First, the current capacity of the current traffic transmission in the entire link consisting of nodes and nodes (for example, between 110 and 131, between 132 and 133, etc.) of the communication network 100 configured as shown in FIG. ) Currently removes the links that are less than the total amount of traffic d to be transmitted (S401). In the figure, G (d) of step S401 indicates a network from which a link having a free capacity less than d in the current network G (m, n) is removed. m represents the number of links, n represents the number of nodes.

Next, the first distance information value dist (i) is obtained based on the current traffic amount y _i for each link i of the network satisfying the G (d) and the information on the total traffic amount d to be transmitted. When the yi and d information is used as a variable of the delay function f _i (x _i ) as an example of the cost function for each link, the first distance information value dist (i) is calculated based on Equation 1 below. delay function f _i (y _i + d), so defined by the result of the differentiation the function f _i '(y _i + d) for, using the following equation (1), and y _i and d value information, obtain the distance information value (S402).

In Equation 1, i denotes a corresponding link (i = 1, ..., m) (m = total number of links), dist (i) is a distance information value of the link i, tc _i is the link i The initial capacity, y _i is the amount of traffic currently being used on link i, ci is the current spare capacity of link i, and a relationship of "c _i = tc _i -y _i " is established. In addition, if the delay function representing the delay at each link i is f _i (x _i ), the expression "f _i (x _i ) = x _i / (tc _i -x _i )" is established, where xi is the link i. The amount of traffic passing through. If the delay function is f _i (x _i ), the derivative of f _i '(x _i ) is "f _i ' (x _i ) = c _i / (tc _i -x _i ) ² ". do. Thus, the equation (1) represents the resulting expression into a cleanup for y _i + d in the variables x _i in place of the delay function f _i a function derivative of _{(x i) f i '(} x i).

That is, f _i (x _i ) is an incurring cost function when the flow rate of link i is xi. In this embodiment, a delay function is used as an example of the cost function as described above, and f _i '(x _i ) is link i. the flow amount in the x _i be when increased flow per unit cost function in this case shows a differential function of the delay function.

For reference, although the delay function is used as an example, the cost function is not limited thereto. The cost function may be a function for obtaining distance information on a link based on information about yi and d.

Next, the first end-to-end traffic path (hereinafter referred to as LSP1) is established based on the first distance information value calculated for each link i as described above. Only one LSP is set based on the principle of setting a link having a relatively small value of the calculated first delay function value, that is, the first distance information value, as a traffic path (S403).

Next, when one LSP1 is set in step S403, the link and the first end-to-end of the surplus capacity ci that can transmit current traffic among all the links between the nodes of the communication network 100 is less than the total amount of traffic d to be transmitted. However, the G (d, p1) network is generated by removing the links forming the traffic path LSP1 from the target. That is, the G (d, p1) network indicates a network from which the link forming the LSP1 is removed from the G (d) (S404).

Then, the second distance information value dist (i) on the basis of the information on the current traffic amount y _i and the total traffic amount d to be transmitted for each link i of the network satisfying the G (d, p1). When the yi and d information is used as a variable of the delay function f _i (x _i ) as an example of the cost function for each link, the second distance information value dist (i) is Since the delay function f _i (y _i + d) is defined as the result of the derivative function f _i '(y _i + d), the distance information value is calculated using the following equation (2) and y _i and d value information. To obtain (S405).

In Equation 2, each symbol and definition is the same as in Equation 1, except that the target network is G (d) in Equation 1 and G (d, p1) in Equation 2.

Next, a second end-to-end traffic path (hereinafter referred to as LSP2) is set based on the calculated second distance information value. If LSP2 is found in plural numbers, the calculated second distance information value Based on the principle of setting this relatively small link as a traffic path, only one LSP2 is set (S406).

Subsequently, each of the total traffic amount d to be transmitted d is allocated on the set LSP1 and LSP2, and more specifically, the ratio of q1 and q2 is calculated based on Equation 3, Equation 4, and Equation 5 below. Xi is calculated while varying at a predetermined ratio, and the obtained xi value is substituted into Equation 6 below, and according to the ratio of q1 to q2 when the resultant value of Equation 6 becomes minimum, the LSP1 and LSP2 phases are obtained. the transmission balancing the total traffic amount d each assigned to the need, and sets the quota, q1 and q2 as a value of q _b (S407).

, i = 1, ..., P _km (k = 1or2)]

Where q1 and q2 are traffic amounts to be allocated to the first and second end-to-end traffic paths, d is the total amount of traffic to be transmitted, and δ _i ¹ is the first end-to-end traffic path. Is 1 if it is past link i and 0, δ _i ² is 1 if the second end-to-end traffic path is beyond link i and 0, P _km is the first end-to-end traffic path ( k = 1) or the number of links of the second end-to-end traffic path (k = 2), ci, represents the current redundant capacity of link i.

Next, among the nodes of the communication network 100 and all the links between the nodes, the current traffic transmission margin ci is greater than the quota q1, q2, that is, a link having a larger value, that is, q _b and links forming the LSP1 and the LSP2. To generate a G (d, p1, p2) network. That is, the G (d, p1, p2) network indicates a network from which the link forming the LSP2 is removed from the G (d.p1) (S408).

Next, the third distance information value based on the information on the G (d, p1, p2) the greater of the traffic that is currently in use for each link i of the network to meet the amount y _i and the allocation q1, q2 value q _b dist (i) is obtained, but when the yi and d information is used as a variable of the delay function f _i (x _i ) as an example of the cost function for each link, the third distance information value dist (i) is Since the delay function f _i (y _i + q _b ) is defined as the result of the derivative function f _i '(y _i + q _b ) based on Equation 7, Equation 1 and y _i and q _b value information To obtain the corresponding distance information value (S409).

In Equation 7, each symbol and definition is the same as in Equation 1 and 2, but the target network is G (d) in Equation 1, G (d, p1) in Equation 2, and G in Equation 7. (d, p1, p2) is different from each other.

Subsequently, a third end-to-end traffic path (hereinafter referred to as LSP3) is set based on the calculated third distance information value. When LSP2 is found in plural numbers, the calculated third distance information value is determined. Based on the principle of setting this relatively small link as a traffic path, only one LSP3 is set (S410).

Finally, the set first end-to-end traffic path LSP1 and the second end-to-end traffic path LSP2 are determined as a primary label switching path (primary LSP) to allocate the total traffic d to be transmitted, and The set third end-to-end traffic path LSP3 is used as a backup path (S411).

As described in detail above, the traffic path setting method for protection switching in a data communication network to which the multi-protocol label switching (MPLS) method according to the present invention is applied can transmit traffic by two primary LSPs, thereby reducing the overall incurred cost. Not only can it be greatly reduced, but it can effectively cope with network failures, and the survivability against failures can be improved by maintaining disjoint characteristics between two LSPs and backup paths. In addition, by setting up a backup path by two primary LSPs, the consumption of network resources by the spare path is effectively reduced. In addition, when calculating the link or node cost required for path determination, the traffic flow and the nonlinear cost function are considered to enable optimal path setting. In conclusion, the method of the present invention not only effectively utilizes network resources, but also greatly reduces the transmission cost or delay of traffic transmission caused by traffic transmission.

Claims (6)

A traffic routing method for protection switching and / or fast reroute in a data network to which multi-protocol label switching is applied is a label as an ingress in a data network to which multi-protocol label switching (MPLS) is applied. Ingress-to-Egress traffic path (LSP) from the edge router (LER) to the label edge router (LER) as an egress through the label switch router (LSR) as one or more intermediate nodes. In the setting method, A first step of removing links from nodes and nodes in the communication network, in which the capacity of the current traffic transmission capacity is less than the total amount of traffic to be transmitted, from the target; A second step of calculating a first distance information value for each target link remaining as a result of the removal of the first step, based on the information on the amount of traffic currently used on the link and the total amount of traffic to be transmitted; A third step of establishing a first end-to-end traffic path based on the calculated first distance information value; A fourth step of removing from the object of the link between the node and the node of the communication network the link which constitutes the first end-to-end traffic path and the link whose current capacity for transmitting traffic is less than the total amount of traffic to be transmitted; A fifth step of calculating a second distance information value for each target link remaining as a result of the removal of the fourth step, based on the information on the amount of traffic currently used on the link and the total amount of traffic to be transmitted; A sixth step of setting a second end-to-end traffic path based on the calculated second distance information value; And Calculating a quota for each distributed allocation of the total amount of traffic to be transmitted on the established first end-to-end traffic path and second end-to-end traffic path; An eighth that removes from the target a link of a node of the communication network and a link forming the first and second end-to-end traffic paths and the link whose current capacity of the traffic to be transmitted is less than a selected one of the quotas; step; A ninth step of calculating a third distance information value for each target link remaining as a result of the removal of the eighth step, based on the information on the amount of traffic currently used on the corresponding link and the selected one of the quota values; A tenth step of establishing a third end-to-end traffic path based on the calculated third distance information value; And Determining the configured first and second end-to-end traffic paths as a primary label switching path to allocate all traffic to be transmitted, and using the set third end-to-end traffic path as a spare path. 11. A method of establishing a traffic route for protection switching in a data communication network to which a multi-protocol label switching scheme is applied, comprising the 11 steps. The method of claim 1, The second step, the fifth step, or the ninth step may be performed based on information on the amount of traffic currently being used on the link and the total amount of traffic to be transmitted, or information on a selected value of the quota. The derivative value of the first, second, and third delay functions is obtained, and the derivative values of the first, second, and third delay functions are used as the first, second, and third distance information values, respectively. A traffic routing method for protection switching in a data communication network using multi-protocol label switching. The method of claim 2, The first and second distance information value, The third distance information value is calculated based on the equation Where i denotes the corresponding link (i = 1, ...., m) (m = total links), and dist (i) is the distance information of link i, tc _i Is the initial capacity of link i, y _i is the amount of traffic currently in use on link i, ci is the current spare capacity of link i, and a relationship of "c _i = t _ci -y _i " is established, and d is the total to be transmitted. The traffic amount, q _b represents a value of the selected one of the quota, traffic routing method for protection switching in a data communication network to which the multi-protocol label switching scheme is applied. The method of claim 3, wherein In the third, sixth, and tenth steps, when the first, second, or third end-to-end traffic paths are plural, the traffic paths having relatively small calculated distance information values are routed. A method of establishing a traffic route for protection switching in a data communication network to which a multi-protocol label switching scheme is applied, characterized in that set to. The method of claim 1, In the seventh step, xi is calculated while varying the ratio of p1 and p2 to a predetermined ratio based on Equation (1), Equation (2) and Equation (3) below. ) And on the first end-to-end traffic path and the second end-to-end traffic path, depending on the ratio of p1 to p2 when the result of equation (4) becomes the minimum. Characterized in that each of the total amount of traffic to be transmitted is distributed and transmitted, wherein p1 and p2 are the amount of traffic to be allocated to the first and second end-to-end traffic paths respectively, and d is the total amount to be transmitted. The amount of traffic, δ _i ¹ is ^{1 if} the first end-to-end traffic path crosses link i and 0 otherwise, δ _i ² is 1 if the second end-to-end traffic path crosses link i and Otherwise 0, P _km is the number of links of the first end-to-end traffic path (k = 1) or the second end-to-end traffic path (k = 2). ci is a current redundant capacity of link i, traffic routing method for protection switching in a data communication network to which multi-protocol label switching is applied. --- Equation (1) , i = 1, ..., P _km (k = 1or2) --- Equation (2) --- Equation (3) --- Equation (4) The method of claim 1, The selected one of the quotas in the eighth step is a relatively large value traffic traffic setting method for protection switching in a data communication network to which the multi-protocol label switching scheme is applied.