KR20030025433A - Traffic grooming and light-path routing method in wdm ring networks with hop-count constraint - Google Patents

Abstract

PURPOSE: A method for integrating demands and setting an optical path having restricted hop counts in an optical wavelength division multiplexing ring communication network is provided to integrate demands with a replaced path in consideration of the number of photoelectric conversion times during demand integrating process used to minimize the number of optical wavelengths, thereby solving transmission delay. CONSTITUTION: A demand integration process(100-160) is performed as follows. When assigning optical wavelengths to process optical transmission demands given between nodes configuring a communication network, amounts of optical transmission demands for optical wavelengths showing a minimum using rate are integrated to optical wavelengths of other replacing path. The demands are integrated until the number of photoelectric conversion times satisfies a hop count range set in each commodity. An optical wavelength path setting process is performed as follows. After arranging all optical path demands to have the same direction for each commodity between determined nodes, the number of maximum optical wavelengths assigned in a clockwise direction is compared with the number of maximum optical wavelengths assigned in a counter-clockwise direction on the basis of start nodes of the commodities. Amounts of the demands are rearranged to have load balance.

Description

TRAFFIC GROOMING AND LIGHT-PATH ROUTING METHOD IN WDM RING NETWORKS WITH HOP-COUNT CONSTRAINT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a WAVELENGTH DIVISION MULTIPLEXING (WDM) ring communication network, and more particularly to a method for integrating demand within a limited hop count range and setting an optical path accordingly to limit the number of photoelectric conversions.

The development of information communication technology and the emergence of various information communication services requiring broadband are accelerating the speed of the communication network. The high speed of the communication network may be possible due to the development of optical transmission technology, and one of the most recent high speed optical transmission technologies is an optical transmission method using Wavelength Division Multiplexing (WDM) technology. That is, by multiplexing multiple optical wavelengths on the same optical cable to dramatically increase the transmission speed to effectively provide a broadband service, many telecommunications companies are trying to invest in the construction of a WDM optical transmission network.

In the WDM network, when the transmission demand to be transmitted between nodes is given, a path for transmitting the transmission demand should be set, and an optical wavelength for transmitting an optical signal should be allocated. Since the installation cost of the WDM network is dependent on the number of optical wavelengths, it is urgently required to reduce the number of optical wavelengths used in the network.

A diagram illustrating a typical demand aggregation and optical path setting method is illustrated in FIG. 1, and Table 1 below shows transmission demand between nodes. In Table 1 below, k indicates a demand for transmission between two nodes. The tee (commodity) is shown, and each of o (k) and d (k) represents the starting point and destination of the commerciality k. And Is the transfer demand to be transferred between o (k) and d (k), Represents the transmission capacity of each light wavelength, and it is assumed that they are all at OC-48 level.

k o (k) d (k) One A B 15 OC-1 2 A C 10 OC-1 3 A D 20 OC-1 4 B C 5 OC-1 5 B D 20 OC-1 6 C D 30 OC-1 Light wavelength transmission capacity = OC-48

Referring to FIG. 1, first, it is assumed that (a) shows a demand for optical transmission between nodes A, B, C, and D, and the demands shown in Table 1 are given between these nodes. (B) of FIG. 1 is a case of allocating optical wavelengths to all the optical transmission demands (6) shown in Table 1 above. , , ), The optical wavelength is required. An example of the wavelength path setting in this case is shown in (c), and six light wavelength installation sections are required.

On the other hand, in Figure 2 (a) up to two ( , ) 'S optical wavelength to handle all demands. In addition, four light wavelength installation sections are required. In other words, node A and node B demand Transmits to node C using WP, and multiplexes with other transmission demands from node C to node B. Passes up to node B using the wavelength of. Demand between node A and node D is connected in the same way via the light wavelength between AC and the light wavelength between CD.

As described above, in comparison with FIGS. 1B and 2A, the number of optical wavelengths required for processing transmission demands among all nodes shown in Table 1 is relatively small in FIG. 2A. Also, it can be seen that the light wavelength installation section is also smaller than that of FIG. 2 (b) of FIG.

This result can be implemented by "Demand aggregation and optical wavelength routing method in optical wavelength division multiplexed ring communication network" filed in 2001 by the applicant of the Korean Intellectual Property Office.

Briefly describing the "demand aggregation and optical wavelength routing method in an optical wavelength division multiplexing ring network", the method allocates an optical wavelength for processing each optical transmission demand given between nodes constituting the communication network, while maintaining a minimum utilization rate. By allocating the optical transmission demand for the indicated optical wavelength to other optical wavelengths, the demand is first integrated so that the number of optical wavelengths installed between the nodes constituting the ring is minimized.

After that, all of the optical path demands are arranged in the same direction with respect to each of the commutation nodes determined in the demand aggregation process, and then the maximum number of optical wavelengths allocated to the clockwise link around the starting node of the corresponding commodity and It is a method of minimizing the total number of optical wavelengths consumed on a ring by comparing the maximum number of optical wavelengths allocated to the counterclockwise link and rearranging the demand to balance the load.

However, the method involves frequent photoelectric conversion because there may be multiple paths back to the destination node via several nodes to minimize the number of light wavelengths. Such frequent photoelectric conversions cause transmission delays and loss of data throughput, resulting in a deterioration in the quality of transmission services.

Accordingly, an object of the present invention is to provide a demand aggregation and optical path setting method having a limited hop count that can guarantee the quality of a transmission service by limiting the number of photoelectric conversions in a transmission demand integration process of a WDM communication network.

1 is a diagram illustrating a configuration of a WDM ring communication network and optical wavelength routing between switching nodes when demand aggregation according to an embodiment of the present invention is not considered.

2 is a diagram illustrating a configuration of a WDM ring communication network and optical wavelength routing between switching nodes when demand aggregation is considered according to an embodiment of the present invention.

3 is a flowchart illustrating a demand aggregation process according to an embodiment of the present invention.

4 is a flowchart illustrating an optical wavelength path setting process according to an embodiment of the present invention.

Figure 5 is an exemplary view of the optical path change for explaining the optical wavelength path setting process according to an embodiment of the present invention.

Method according to an embodiment of the present invention for achieving the above object,

Allocate optical wavelengths to handle optical transmission demands between nodes constituting the communication network, and integrating optical transmission demands for optical wavelengths representing minimum utilization among the allocated optical wavelengths into optical wavelengths of other alternative paths, the number of photoelectric conversions to the destination A demand aggregation process of accumulating demand to satisfy the hop count range set in the community;

The maximum number of optical wavelengths allocated to the clockwise link centered on the departure node of the corresponding commodity after arranging all the optical path demands in the same direction for each of the commodities between nodes determined in the demand gathering process. The optical wavelength routing process minimizes the total number of optical wavelengths required on the ring by rearranging the demand to balance the load by comparing the maximum number of optical wavelengths allocated to the clockwise link.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

First, the demand aggregation and light path setting method having a limited hop count to achieve the object of the present invention can be classified into a demand aggregation process and a light path setting process.

3 is a flowchart illustrating a demand aggregation process according to an embodiment of the present invention. Fig. 3 shows that the hop count is limited in integrating demand within a range of optical transmission capacities that can be transmitted in one optical wavelength for all the commercialities.

The demand aggregation process starts with allocating different optical wavelengths (step 100) to a given transmission demand between nodes as shown in FIG. At this time, when the optical transmission demand between the two nodes exceeds the optical wavelength transmission capacity, the optical wavelength is installed between the two nodes as long as the optical transmission demand can be accommodated. To do this, we consider a network with arcs for each wavelength of light allocated between nodes. We will mark this network as G = (N, E). N is defined as a set of nodes constituting the WDM communication network, E is a set of arcs representing the optical wavelength. If multiple wavelengths have to be allocated between two nodes, multiple arcs between the two nodes can be solved and included in E.

In the embodiment of the present invention, each demand is initially allocated to different optical wavelengths as shown in FIG. Therefore, since the light wavelength is required as many as the number of commercials, the set L of the light wavelengths can be replaced by the set K of the commercials. Also, in G, where each light wavelength is represented by an arc, the arc set E can be replaced with L. This is defined as a variable initialization step (step 110) in FIG.

Meanwhile Denotes the quantity allocated to the light wavelength l, which can be expressed as the quantity allocated to the arc l on the G phase. Therefore, a set of commercials using K (l) as light path l, It can be calculated as shown in Equation 1 by defining as the utilization of the optical path l.

Therefore, the optical path having the minimum utilization rate for the set L of optical paths (which can be interpreted in the same sense as arc) Select (step 120), select the selected arc Set of commercials using ) Demand Check whether it can be replaced with other arcs (step 130) to select the replacement path.

The alternative route selection is as follows. That is, K ( In G for each commercial k in and Till The path using other arcs is selected, and only the arcs having less than 1 arc utilization are selected as alternative paths. In this case, the arc set of the selected path is called PA (k), and the maximum free capacity considering the margin on this path Is calculated by the following equation (2).

If PA (k) sets exist In order to prevent the transmission delay and service loss by limiting the number of photoelectric conversions, it is necessary to convert the demand amount of the k k into the alternative paths by checking the number of photoelectric conversions within the hop count range. By selecting, the quantity of the corresponding k is accumulated. That is, if the value of the photoelectric conversion number is set in advance for each k, the photoelectric conversion number generated when the demand k of the k is integrated into the alternate path and transferred to the destination node in the demand aggregation process. If the value exceeds the preset hop count value for the community, the currently selected path is not used as an alternative path. If the value is within the preset hop count value, the current path is set as an alternative path to accumulate demand. . If there are multiple paths in the PA set to replace the demand for the commodity, it is necessary to first select the path with the least margin in the set and check whether it can be used as an alternative. It is preferable. If the number of photoelectric conversions that can occur when selecting a path with a small margin and transmitting the demand to the destination has a value within a predetermined hop count range, the path may be removed from the set of alternative paths. This is because the process time for this can be reduced gradually.

On the other hand, if there is no PA (k) set, Any other arc indicates that it cannot be used, making it an essential arc. therefore Since it is no longer necessary to apply the alternative path selection process, proceed to step 160 after removing from the set L of optical wavelengths.

If K ( Reconciliation results for all commodities in Ramen Is removed from L. This adjustment process can be repeated until there is no further arc removal to determine the light wavelength installation section required for the acceptance accumulation (step 160).

As described above, in the demand aggregation process according to the embodiment of the present invention, in selecting an arc having the minimum utilization rate and assigning it to the alternative path, the alternative path is selected within the range of limiting the photoelectric conversion frequency in consideration of the hop count. Therefore, transmission delay and service loss due to photoelectric conversion can be minimized.

The above-described demand accumulation process is summarized as follows.

First step (initialization);

Defined as G = (N, E), L = K, E = L, T (Light-wavelength demand set) = L from WDM ring and demand.

(when k = l) ( , Where ;

K (l) = k (when k = l), K (l) = 0 ( ), Where ;

▶ second stage (selection of demand adjustment arc);

1) calculation of utilization of each optical path; ,

2) Selection :

▶ Stage 3 (Alternate Path Selection and Demand Adjustment)

One) To select PA (k).

2) If PA (k) = 0, Removed from L.

3) If PA (k) ≠ 0, Calculation.

Ⅰ) If,

when , when Of the arc belonging to PA (k) adjustment.

Ii) If,

when , when l Of the arc belonging to PA (k) adjustment.

4) If, Remove from L and T

▶ 4th Step (End)

If L = 0, it ends. If L ≠ 0, repeat from step 2.

Hereinafter, an optical wavelength path setting process according to an embodiment of the present invention will be described.

First, when the wavelength range of installation is determined in the demand aggregation process, only G, the necessary arc set T, remains among the arcs representing the light wavelength. One arc is assigned to this arc and used to convey the demand for each commodity. In this process, the demand connected by one arc corresponds to the optical wavelength transmitted in the same wavelength without photo / electric conversion in the middle, and the demand through two or more arcs undergoes photo / electric conversion in the middle as many as the number of arcs.

The optical wavelength path setting process according to the embodiment of the present invention is a process for minimizing the total number of optical wavelengths required in the ring by appropriately disposing the optical wavelength determined in the demand aggregation process on the ring.

First, when the wavelength range of installation is determined in the demand aggregation process, the set of these wavelength demands is defined as T, and each wavelength demand is defined as the commercial k. Also Is the demand quantity of the light wavelength demand k determined in the demand aggregation process, and is defined as 1 for each commercial property of T. The optical wavelength demand can be set to a transmission path by being assigned to either the right path or the left path on the ring for one reference node, and the path should be set so that the total number of optical wavelengths required on the ring is minimized.

In the embodiment of the present invention, Y.S. Myung, H.G. Kim and D.W. Tcha, "Optimal load balancing in SONET bidirectional rings," Operations Research, Vol. By modifying and applying the balanced load solution described in 45, 1997, 148-152, it is possible to allocate the wavelength demand on the ring and to assign different wavelengths accordingly. Myung et al. Proposed an optimal solution to find the optimal solution within the polynomial calculation time for the load balancing problem in case of dividing demand in SDH / SONET ring network.

However, when the division of demand is given in integer units, the optimal solution cannot be guaranteed, so the solutions proposed in these studies have been modified and applied in the embodiments of the present invention. In more detail,

first Assume that light wavelength demand k (i.e., k) is the demand for selecting the clockwise path on the ring during the t th iteration. It is assumed that denotes the arc set of the clockwise path and the arc set of the counterclockwise path, respectively, for the light wavelength demand k. Under these assumptions, if all the wavelength demands (ie, optical path demands) are initially placed clockwise for the establishment of the optical wavelength path, the total number of optical wavelengths decreases when allocating the optical wavelength demands counterclockwise. Examine and apply the method of improvement one by one.

After the initial demand allocation, we define a set of demands using each link on the ring. That is, a demand set that includes arc l as the optical wavelength transmission path or If the set of demands routed in the clockwise direction and the set of demands routed in the counterclockwise direction, respectively, Only exist, Will be the empty set. For each arc l, if the sum of all light wavelength demands passing through l is g (x, l), it is calculated as in Equation 3 below.

Therefore, for the demand k, the maximum value of the quantity allocated to the clockwise arc and the maximum quantity of the quantity allocated to the counterclockwise arc are respectively calculated, and the value is allocated to the entire ring by adjusting the quantity of demand k in the smaller direction. Balance the demand for light wavelengths. This process can be repeated for all demands until the bidirectional demand balance no longer improves.

The above-described optical wavelength path setting process will be described in detail with reference to FIG. 4 as follows.

4 is a flowchart illustrating an optical wavelength path setting process according to an exemplary embodiment of the present invention.

Referring to FIG. 4, first, in step 200, a variable ( ) And place all light wavelength demands clockwise. In operation 210, the maximum number of optical wavelengths allocated to the clockwise link between the source node and the destination node with respect to the source k based on the source node ( ) And the maximum number of optical wavelengths assigned to the counterclockwise link ( ) Are calculated by the following equations (4) and (5), respectively.

In step 220, the maximum number of optical wavelengths allocated to the clockwise link between the source node and the destination node based on the source node ( ) And the maximum number of optical wavelengths assigned to the counterclockwise link ( ) And branches to the optical wavelength rearrangement step of step 230 to 240. This step 220 can be expressed as a load balancing step.

If the maximum number of light wavelengths allocated to the clockwise link in the load balancing step (step 220) is greater than the maximum number of light wavelengths allocated to the counterclockwise direction, the arrangement of the light wavelengths assigned to the clockwise direction in the counterclockwise direction is the wavelength on the ring. Reduce demand Accordingly, the number of wavelengths to be rearranged may be rearranged counterclockwise by a smaller value between a maximum integer not exceeding half of the maximum number of wavelengths allocated in the clockwise direction and a number of wavelengths assigned in the clockwise direction among the k commodities. In this case, only the demand for k commutation in the clockwise link Decrease by The demand for other commodities remains unchanged.

On the other hand, step 240, which is another light wavelength rearrangement step, if the maximum number of light wavelengths assigned to the counterclockwise link to the k commerce is greater than the maximum number of light wavelengths assigned to the clockwise direction, the equation described in step 230 ( On the contrary, it is possible to reduce the wavelength demand on the ring by arranging optical wavelengths assigned in the counterclockwise direction. Therefore, the number of wavelengths to be rearranged can be rearranged clockwise by the smallest value of the maximum integer not exceeding half of the maximum number of wavelengths allocated in the counterclockwise direction and the number of wavelengths assigned in the counterclockwise direction among k commercialities. . In this case, only the demand for k commutation in the clockwise link Decrease by The demand for other commodities remains unchanged.

Thereafter, in step 250, it is checked whether the current commerciality k exceeds the optical wavelength demand set T, and if it does not exceed, k is increased (260), and the above-described load balance confirmation step and optical wavelength relocation step are repeated.

Summarizing the above-described optical wavelength path setting process,

First, in the initialization step (step 200), all the initial demands of all the commodities are placed in the clockwise direction, and then the load balance states of the rings are checked by selecting one by one from the commodities 1 to T (steps 210 and 220). That is, taking the k commerce as an example, the maximum wavelength in the clockwise direction and the maximum wavelength in the counterclockwise direction are calculated based on the starting node of the k commerce and the magnitudes thereof are compared. Thereafter, the wavelength rearrangement steps 230 and 240 are performed. If the demands allocated in the clockwise and counterclockwise directions are not balanced with respect to the k commerce, then the half of the excess wavelength demand (the maximum integer) or the clock of the k commerce is exceeded. Directional (or counter-clockwise) load balance is achieved by relocating as little as the smaller of the allocated demand. This step reduces the number of optical wavelengths needed on the ring. When the load balance check and the light wavelength rearrangement of clockwise / counterclockwise directions are completed for all commercialities, the light wavelength routing process is finished.

Hereinafter, one example is provided to help understanding the above-described optical wavelength routing.

First, it is assumed that the optical path demand between nodes is determined through the demand aggregation process in the four node rings, and the optical wavelength routing process for this is explained.

-Commerce (k) 1, Departure Node A, Destination Node B, 2 Light Path OC-48s

-Commerce (k) 2, Departure Node A, Destination Node D, 1 Light Path OC-48

-Commerce (k) 3, Departure Node B, Destination Node C, 2 Light Paths OC-48

-Commerce (k) 4, Departure Node B, Destination Node D, 1 light path OC-48. (Light wavelength is assigned to OC-48 1 one)

First, in the initializing step, all the light path demands are allocated to the clockwise link, but each commodity can be arranged as shown in (a) of FIG. 5. As can be seen in (a) of FIG. 5, in the initialization step, the optical path demand in the clockwise direction with respect to community 1 ( ) Is 2, and the demand for light paths in clockwise direction for commodity 2 is 1, and the demand for light paths in clockwise direction for commodities 3 and 4 is 2 and 1.

Then check the load balance for the commercial k = 1 (Link 1), (Link 2) = 0. That is, no light wavelength rearrangement step is performed. Thus, the initially assigned lightpath remains unchanged even after relocation to commerce 1 ( = 2, = 1, = 2, = 1).

On the other hand, if you check the load balance for commercial k = 2, , Because of to be. Therefore, the light wavelength rearrangement step yields the same result as (b) ( = 2, = 0, = 2, = 1). That is, the light path is rearranged in the counterclockwise direction with respect to the commerciality 2.

And if you check the load balance for commercial k = 3 (Link 2), (Link 1) to be. Therefore, performing the wavelength relocation step yields the same result as (c) ( = 2, = 0, = 1, = 1).

And if you check the load balance for k = 4 (Link 3), (Link 1) to be. Therefore, no wavelength relocation step is performed. Therefore, the result of wavelength assignment remains unchanged. = 2, = 0, = 1, = 1).

Since k = 4, the optical wavelength path setting process ends.

Therefore, the number of optical wavelengths used in the WDM ring communication network is minimized by the above-described optical wavelength path setting, and the number of photoelectric conversions is limited during the demand aggregation process, thereby preventing the degradation of service quality due to transmission delay.

As described above, the present invention may occur due to the selection of an alternative path unconditionally because the demand is integrated into the alternative path in consideration of the number of photoelectric conversions in the demand accumulation process used to minimize the number of optical wavelengths used in the WDM communication network. There is an advantage that can solve the problem of transmission delay.

Claims (4)

In an optical wavelength division multiplexing network, Allocate optical wavelengths to handle optical transmission demands between nodes constituting the communication network, and integrating optical transmission demands for optical wavelengths representing minimum utilization among the allocated optical wavelengths into optical wavelengths of other alternative paths, the number of photoelectric conversions to the destination A demand aggregation process of accumulating demand to satisfy the hop count range set in the community; The maximum number of optical wavelengths allocated to the clockwise link centered on the departure node of the corresponding commodity after arranging all the optical path demands in the same direction for each of the commodities between nodes determined in the demand gathering process. Demand routing with a limited hop count, characterized in that it consists of an optical wavelength routing process that minimizes the total number of optical wavelengths consumed on the ring by rearranging the demand to balance the load by comparing the maximum number of optical wavelengths assigned to the clockwise links. How to set up integration and light path. The method of claim 1, wherein the demand aggregation process; A first step of allocating a given optical transmission demand between nodes constituting the communication network to different optical wavelengths; A second step of replacing a set of allocated light wavelengths with a set of commodities and replacing the set of arcs representing the light wavelengths with the set of light wavelengths to initialize the allocated light wavelengths into a network having an arc; A third step of selecting an arc representing a minimum utilization rate by calculating a utilization rate of each arc in the set of arcs; A fourth step of checking whether the demand amount of the commerce set using the selected arc can be replaced with other arcs; A fifth step of determining, for each of the replaceable arcs, whether the number of photoelectric conversions to the destination has a value within a hop count range set in the commerce to be integrated; And a sixth step of integrating the demand amount in the arc having a value within the hop count range set in the corresponding result as a result of the determination. 3. The limited hop count of claim 2, wherein an arc having the least margin among the replaceable arcs is selected first to determine whether to accumulate demand. Demand aggregation and light path establishment method. The method of claim 2, wherein the optical wavelength path setting process; An initialization step of arranging all of the optical path demands to have a path in the same direction with respect to each of the commerce between nodes determined in the demand aggregation process; For each of the commercialities, calculating a maximum number of optical wavelengths allocated to the clockwise link and a maximum number of optical wavelengths allocated to the counterclockwise link with respect to the starting node of the corresponding commercialities, and comparing the load balance states; When the load is not balanced as a result of the comparison, the direction exceeding the smallest value between the integer number of half of the maximum light wavelength in the exceeding direction for the corresponding k and the number of wavelengths allocated in the exceeding direction among the corresponding k Repositioning in the opposite direction of; characterized in that it comprises a demand aggregation and light path setting method having a limited hop count.