JP2004015339A - Method for designing optical network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decide the number of optical paths including a standby optical path on each routing candidate so as to minimize the installation cost while satisfying requirements of a fault recovery rate in an optical network wherein it is not required to newly set a bypassing optical path on the occurrence of a fault and the standby optical path is shared in common. <P>SOLUTION: Traffic communicated through an optical path 20 in which a fault takes place is bypassed through a plurality of the standby optical paths 21, 22 wherein no fault is caused. A linear programming problem including constraint conditions to attain a fault recovery rate designated through bypassing is solved by using a routing candidate and the number of request optical paths between node pairs as an input, thereby obtaining the number of optical paths including standby optical paths to be located on each routing candidate so as to minimize the installation cost. <P>COPYRIGHT: (C)2004,JPO

Description

ここで、上記の式中の各シンボルの意味は、次の通りである。
Ｎ：ノード集合、
ｓ：発信ノード、
ｄ：着信ノード、
ＴＲｓ，ｄ：発信ノードｓから着信ノードｄまでの迂回トラヒックが経由する迂回ノードの集合、
ｔ：迂回ノード、
ＲＴｓ，ｄ：発信ノードｓから着信ノードｄまでのルート候補の集合、
ｒ：ルート候補、
Ｆ：障害状態の集合、
ｆ：障害状態、
ＦＲｆ，ｓ，ｄ：障害状態ｆにおいて、障害となる発信ノードｓから着信ノードｄまでのルート候補の集合、
Ｒｓ，ｄ，ｒ：発信ノードｓから着信ノードｄまでのルートｒ上の光パスの障害回復率、
Ｐｓ，ｄ，ｒ：発信ノードｓから着信ノードｄまでのルートｒ上に設定される光パス数、
ＳＰｓ，ｄ，ｒ：発信ノードｓから着信ノードｄまでのルートｒ上に設定される予備光パス数、
ＡＰｓ，ｄ，ｒ，ｔ：発信ノードｓから着信ノードｄまでのルートｒ上のトラヒックのための迂回ノードｔを経由する迂回用光パス数、
Ｄｓ，ｄ：発信ノードｓから着信ノードｄまでの要求パス数。
【００１６】
ここでは、２本までの予備光パス、すなわち１つまでの迂回ノードを経由する迂回用光パスのみを考える。ｔ＝ｄの時、ＡＰｓ，ｄ，ｒ，ｔは、迂回ノードを経由しない、発信ノードｓと着信ノードｄを直接接続する迂回用光パス数を表す。ｔ＝ｓの時、ＡＰｓ，ｄ，ｒ，ｔは常にゼロであるとみなす。Ｐｓ，ｄ，ｒ、ＳＰｓ，ｄ，ｒおよびＡＰｓ，ｄ，ｒ，ｔは、本来整数であるが、値の範囲が充分広い場合には、実数として扱うことにより、解精度の劣化を抑えつつ、高速に解を求めることができる。
【００１７】
最小とすべき設備コストＣｏｓｔは、例えば以下の式で表される。

ここで、上記の式中の各シンボルの意味は、次の通りである。
ＷＰｓ，ｄ，ｒ，ｗ：発信ノードｓから着信ノードｄまでのルートｒ上の波長ｗを使用する予備光パスも含めた光パス数、
ＵＦｌ：リンクｌにおける使用ファイバー数、
ＵＣｌ：リンクｌにおける使用チャネル数、
Ｍｎ：ノードｎにおける使用スイッチサイズ、
ＵＷｎ：ノードｎにおける使用スイッチプレーン数、
ＰＲｎ：ノードｎにおけるコストの固定分、
ＵＰｎ：ノードｎを端点とする光パス数、
ＲＦｌ：リンクｌの単位距離当たりの故障率、
ＲＦｎ：ノードｎの故障率、
ＬＲｓ，ｄ，ｒ：発信ノードｓから着信ノードｄまでのルートｒに含まれるリンクの集合、
ＲＬｌ：リンクｌを含むルート（ｓ，ｄ，ｒ）の集合、
ＮＲｓ，ｄ，ｒ：発信ノードｓから着信ノードｄまでのルートｒに含まれる中継ノードの集合、
ＲＮｎ：ノードｎを中継ノードとするルート（ｓ，ｄ，ｒ）の集合、
ＭＡＸｗ：波長ｗについての最大値、
｛ｗ｜論理式｝：論理式を満足する波長ｗの集合
Ｃａｒｄ｛　｝：集合｛　｝の要素数、
α１：単位距離当たりのケーブルコスト、
α２：単位距離当たりのファイバーコスト、
α３：ファイバーコストの固定分、
α４：チャネルコスト、
β：ポート当たりのノードコスト、
γ：光パスを終端するために必要なコストの２分の１、
δ：光パス当たりの障害コスト。
【００１８】
上記の制約条件や光ネットワークの最大容量を制約条件とし、設備コストを目的関数とする線形計画法を解いて、Ｐｓ，ｄ，ｒ及びＳＰｓ，ｄ，ｒの値を求めることにより、指定された障害回復率を満足しつつ設備コストを最小化するような予備光パスを含めた光パス配備を決定することができる。
【００１９】
【発明の効果】
以上の説明から明らかなように、本発明によれば、障害発生時に新たに迂回用光パスを設定する必要がないので高速な障害回復が可能であり、しかも同時に障害にならない任意の光パスの間で迂回用の予備光パスを共用することができ、必要な光パス数が少ない光ネットワークを、あらかじめ指定された障害回復率を満足しつつ、最小設備コストで実現することができる。
【図面の簡単な説明】
【図１】本発明が適用される光ネットワークの一例を示す構成図である。
【符号の説明】
１０〜１７・・・光ファイバ、２０・・・光パス、２１、２２・・・予備光パス、３０・・・迂回用光パス、Ａ〜Ｅ・・・ノード、１Ａ〜１Ｅ・・・ラベルスイッチルータ、２Ａ〜２Ｅ・・・光クロス・コネクト装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for designing an optical network, and more particularly to an optical network in which it is not necessary to newly set up a detour optical path when a failure occurs, and at the same time a backup optical path can be shared between any optical paths that do not cause a failure. The present invention relates to a method for designing an optical network capable of determining the number of optical paths including a backup optical path to be deployed on each route candidate so as to minimize the equipment cost while satisfying a failure recovery rate.
[0002]
[Prior art]
In an optical network in which a plurality of nodes are connected to each other by an optical path, in order to ensure the reliability, when a failure occurs in the optical path, the traffic flowing through the failed optical path is conventionally used. Is detoured by using another optical path.
[0003]
As this method, for example, a method in which a detour optical path is provided in one-to-one correspondence with a working optical path (dedicated protection method), and a method in which a detour optical path is shared between a pair of node pairs (shared protection) Method), a method of sharing a detour optical path between arbitrary node pairs (restoration method), and the like. In these methods, the equipment cost including the current optical path and the detour optical path is reduced. The deployment of the optical path to minimize it has been decided.
[0004]
[Problems to be solved by the invention]
However, in the case of the protection method, since a detour optical path is provided for each node pair, the number of optical paths increases as a whole, and there is a problem that only an optical network with a large equipment cost can be realized.
[0005]
In addition, in the case of the restoration method, since a detour optical path is newly set after a failure occurs, there is a problem that only an optical network that cannot perform high-speed failure recovery can be realized.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problem of the related art, so that it is not necessary to newly set up a detour optical path when a failure occurs, and at the same time, a spare optical path can be shared between any optical paths that do not cause a failure. Provided is a method for designing an optical network that can determine the number of optical paths including a backup optical path to be deployed on each route candidate so as to minimize the equipment cost while satisfying the failure recovery rate in a simple optical network. It is in.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, the present invention provides a method in which a plurality of nodes are connected to each other by an optical path, and when a failure occurs in the optical path, the traffic flowing in the failed optical path is transferred to a plurality of backup optical paths. In a method of designing an optical network in which a spare optical path can be shared between arbitrary optical paths that do not cause a failure at the same time as a detour via a route, a route candidate and the number of required optical paths between each pair of nodes constituting the optical network are determined. As input, linear programming including constraints that can achieve the specified failure recovery rate by diverting the traffic flowing through the failed optical path through multiple non-failed backup optical paths The method is characterized in that the number of optical paths including the spare optical path to be deployed on each route candidate is determined so that the equipment cost is minimized by solving the method.
[0008]
According to this feature, it is not necessary to newly set a detour optical path when a fault occurs, so that high-speed fault recovery is possible, and at the same time, a detour spare optical path can be set between any optical paths that do not cause a fault. An optical network that can be shared and requires a small number of optical paths can be realized at a minimum facility cost while satisfying a failure recovery rate specified in advance.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an example of an optical network to which the present invention is applied. This optical network includes label switch routers 1A to 1E and optical cross connect devices (hereinafter, referred to as connect devices) 2A to 2E. The nodes A to E are connected by optical fibers 10 to 17. In addition, an arbitrary label switch router is connected to a plurality of connecting devices by an optical path via an optical fiber.
[0010]
A label (identifier) is inserted in a packet transmitted on the optical network, and each of the label switch routers 1A to 1E selectively transfers an input packet to an optical path according to the label inserted therein. I do. The recovery from the failure of the optical network is performed by diverting the traffic flowing in the failed optical path via a plurality of backup optical paths.
[0011]
For example, as shown in FIG. 1, traffic flowing through the working optical path 20 of the node A, the optical fiber 10, the connecting device 2 D, the optical fiber 13, and the node C, where the node A is the transmitting node and the node C is the receiving node. In the case where a failure occurs in the optical fiber 10, the traffic is transmitted through the two backup optical paths of the node A to the optical path (backup optical path) 21 to the node E to the optical path (backup optical path) 22 to the node C. Are detoured through an optical path (detour optical path) 30 composed of
[0012]
Next, an embodiment of an optical network designing method according to the present invention will be described. As described above, in the present embodiment, it is not necessary to newly set a detour optical path when a failure occurs, and at the same time, in an optical network in which a spare optical path can be shared between any optical paths where no failure occurs, a failure occurs. The goal is to determine the number of optical paths including backup optical paths to be deployed on each route candidate so as to minimize the equipment cost while satisfying the recovery rate.
[0013]
In the present invention, a plurality of nodes are connected to each other by an optical path, and when a failure occurs in an optical path, traffic flowing in the failed optical path is diverted through a plurality of backup optical paths, and In an optical network in which a backup optical path can be shared among arbitrary optical paths that do not simultaneously cause a failure, given a route candidate between each pair of nodes and the required number of optical paths, a designated path is specified using a linear programming method. An optical path including a backup optical path that minimizes the equipment cost while satisfying the failure recovery rate is required.
[0014]
For this purpose, the route candidate r between the node pairs s and d in the optical network and the required number of optical paths Ds and d are input, and the facility cost is minimized using a linear programming method while satisfying the specified failure recovery rate. It is required to provide an optical path including a backup optical path.
[0015]
Constraints in linear programming that can achieve a specified failure recovery rate by diverting traffic flowing through a failed optical path through up to two non-failed backup optical paths The condition is represented by the following equation.

Here, the meaning of each symbol in the above equation is as follows.
N: node set,
s: originating node,
d: destination node,
TRs, d: a set of detour nodes through which detour traffic from the source node s to the destination node d passes;
t: detour node,
RTs, d: set of route candidates from the source node s to the destination node d,
r: route candidate,
F: set of failure states
f: failure state,
FRf, s, d: a set of route candidates from the source node s to the destination node d in the failure state f,
Rs, d, r: failure recovery rate of the optical path on the route r from the source node s to the destination node d,
Ps, d, r: the number of optical paths set on the route r from the source node s to the destination node d,
SPs, d, r: the number of backup optical paths set on the route r from the source node s to the destination node d,
APs, d, r, t: the number of detour optical paths via detour node t for traffic on route r from source node s to destination node d,
Ds, d: number of required paths from the source node s to the destination node d.
[0016]
Here, only up to two spare optical paths, that is, detour optical paths via up to one detour node are considered. When t = d, APs, d, r, and t represent the number of detour optical paths that directly connect the source node s and the destination node d without passing through the detour node. When t = s, APs, d, r, t are always assumed to be zero. Ps, d, r, SPs, d, r and APs, d, r, t are inherently integers, but when the range of values is sufficiently wide, they are treated as real numbers, thereby suppressing degradation of the solution accuracy. The solution can be found at high speed.
[0017]
The equipment cost Cost to be minimized is represented by, for example, the following equation.

Here, the meaning of each symbol in the above equation is as follows.
WPs, d, r, w: the number of optical paths including the backup optical path using the wavelength w on the route r from the source node s to the destination node d,
UFl: Number of fibers used in link l,
UCl: Number of channels used in link 1
Mn: used switch size at node n,
UWn: number of used switch planes at node n,
PRn: fixed amount of cost at node n,
UPn: number of optical paths having node n as an end point
RFl: failure rate per unit distance of link l,
RFn: failure rate of node n,
LRs, d, r: a set of links included in a route r from the source node s to the destination node d,
RLl: set of routes (s, d, r) including link l,
NRs, d, r: a set of relay nodes included in the route r from the source node s to the destination node d,
RNn: set of routes (s, d, r) with node n as a relay node,
MAXw: maximum value for wavelength w,
{W | logical expression}: set of wavelengths w that satisfies the logical expression Card {}: number of elements of set {},
α1: cable cost per unit distance,
α2: fiber cost per unit distance,
α3: fixed fiber cost,
α4: channel cost,
β: node cost per port,
γ: 1/2 of the cost required to terminate the optical path,
δ: failure cost per optical path.
[0018]
The above-mentioned constraints and the maximum capacity of the optical network are used as constraints, and a linear programming method using the facility cost as an objective function is solved to obtain values of Ps, d, r and SPs, d, r. It is possible to determine an optical path arrangement including a backup optical path that minimizes the equipment cost while satisfying the failure recovery rate.
[0019]
【The invention's effect】
As is apparent from the above description, according to the present invention, it is not necessary to newly set up a detour optical path when a failure occurs, so that high-speed failure recovery is possible, and at the same time, any optical path that does not cause a failure can be used. A spare optical path for detour can be shared between the optical networks, and an optical network with a small number of necessary optical paths can be realized at a minimum facility cost while satisfying a failure recovery rate specified in advance.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an example of an optical network to which the present invention is applied.
[Explanation of symbols]
10 to 17: optical fiber, 20: optical path, 21, 22: spare optical path, 30: detour optical path, A to E: node, 1A to 1E: label Switch router, 2A ~ 2E ... Optical cross connect device

Claims (1)

A plurality of nodes are connected to each other by an optical path, and when a failure occurs in an optical path, traffic flowing in the failed optical path is diverted through a plurality of backup optical paths, and the failure does not occur simultaneously. In a method for designing an optical network in which a backup optical path can be shared between arbitrary optical paths,
By inputting the route candidates between each pair of nodes constituting the optical network and the number of required optical paths, the traffic flowing through the failed optical path is bypassed through a plurality of non-failed backup optical paths. Solving a linear programming method that includes constraints that can achieve a specified disaster recovery rate, and finding the number of optical paths, including spare optical paths to be deployed on each route candidate, to minimize equipment costs An optical network design method characterized by the following.

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