JP3844221B2 - Design method of optical network - Google Patents

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]
BACKGROUND OF THE INVENTION
The present invention relates to a method for designing an optical network, and in particular, an optical network that does not require a new bypass optical path when a failure occurs and can share a backup optical path between any optical paths that do not cause a failure at the same time. The optical network design method can determine the number of optical paths including backup optical paths to be provided on each route candidate so that the equipment cost is minimized while satisfying the failure recovery rate.
[0002]
[Prior art]
In an optical network configured by connecting a plurality of nodes to each other through an optical path, in order to ensure the reliability, conventionally, when a failure occurs in an optical path, the traffic flowing in the optical path in which the failure has occurred Has been proposed that uses a different optical path.
[0003]
As this method, for example, a method of providing a detouring optical path in a one-to-one correspondence with a working optical path (dedicated protection method), a method of sharing a detouring optical path between a pair of node pairs (shared protection) Methods), methods that share a detouring optical path between any pair of nodes (restoration method), etc. are known. In these methods, including the current optical path and the detouring optical path, the equipment cost is reduced. The deployment of optical paths that minimize is determined.
[0004]
[Problems to be solved by the invention]
However, in the case of the protection method, there is a problem that since an optical path for detouring is provided for each node pair, the number of optical paths increases as a whole, and only an optical network with a high equipment cost can be realized.
[0005]
Further, in the case of the restoration method, there is a problem that only an optical network that cannot perform high-speed failure recovery can be realized because a detour optical path is newly set after a failure occurs.
[0006]
An object of the present invention is to solve the above-described problems of the prior art, so that it is not necessary to newly set a bypass 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. To provide an optical network design method that can determine the number of optical paths including standby optical paths to be deployed on each route candidate so that the equipment cost is minimized 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-described problems, the present invention is configured such that when a plurality of nodes are connected to each other by an optical path and a failure occurs in the optical path, the traffic flowing in the failed optical path is transferred to the plurality of backup optical paths. In an optical network design method in which a spare optical path can be shared between any optical paths that are bypassed and that do not become obstacles at the same time, the route candidates and the number of required optical paths between each pair of nodes that make up the optical network are determined. Linear programming including constraints that can achieve the specified failure recovery rate by diverting the traffic that was flowing in the failed optical path through multiple spare optical paths that are not damaged as input solve law, determine the number of light paths including the backup optical paths to be deployed to facility cost is minimized on each route candidates, the constraints, each route To distinguish the light path number and the number of backup optical paths to be deployed on the complement, it is characterized in including the failure recovery rate Ru der those formulated.
[0008]
According to this feature, it is not necessary to set a new detouring optical path when a failure occurs, so it is possible to quickly recover from a failure, and at the same time, a backup optical path for detouring between any optical paths that do not cause a failure. An optical network that can be shared and requires a small number of optical paths can be realized at a minimum equipment cost while satisfying a failure recovery rate specified in advance.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block 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. Arbitrary label switch routers are connected to a plurality of connecting devices by optical paths via optical fibers.
[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 the input packet to the optical path according to the label inserted therein. To do. The failure recovery of the optical network is performed by diverting the traffic that has been flowing in the failed optical path via a plurality of backup optical paths.
[0011]
For example, as shown in FIG. 1, the traffic flowing in the working optical path 20 of the node A to the optical fiber 10 to the connection device 2D to the optical fiber 13 to the node C, where the node A is the originating node and the node C is the destination node. If a failure occurs in the optical fiber 10, the traffic is divided into two backup optical paths of node A to optical path (backup optical path) 21 to node E to optical path (backup optical path) 22 to node C. Is detoured through an optical path (circulation optical path) 30 constituted by
[0012]
Next, an embodiment of the optical network design method of the present invention will be described. As described above, the present embodiment eliminates the need to newly set a detour optical path when a failure occurs, and at the same time, in an optical network in which a standby optical path can be shared between any optical paths that do not cause a failure. The objective is to determine the number of optical paths including backup optical paths to be deployed on each route candidate so that the equipment cost is minimized 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 the optical path, the traffic flowing in the failed optical path is bypassed via the plurality of backup optical paths, and In an optical network in which a spare optical path can be shared between any optical paths that do not become obstacles at the same time, when a route candidate between each pair of nodes and the number of required optical paths are given, it is specified using linear programming. The deployment of optical paths including standby optical paths that minimize the equipment cost while satisfying the failure recovery rate is required.
[0014]
For this purpose, the route candidate r between the node pair s and d in the optical network and the required number of optical paths Ds and d are input, and the cost of equipment is minimized while satisfying the specified failure recovery rate using linear programming. It is necessary to arrange an optical path including a spare optical path.
[0015]
Constraints in linear programming that can achieve the specified failure recovery rate by diverting traffic that has flowed through the failed optical path via up to two unprotected optical paths The condition is expressed by the following formula.

Here, the meaning of each symbol in the above formula is as follows.
N: node set,
s: originating node,
d: Incoming 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: a set of route candidates from the source node s to the destination node d,
r: route candidate,
F: a set of fault conditions,
f: fault condition,
FRf, s, d: a set of route candidates from the faulty source node s to the destination node d in the fault state f
Rs, d, r: failure recovery rate of optical path on route r from source node s to 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: 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 requested paths from the source node s to the destination node d.
[0016]
Here, only up to two backup optical paths, ie, detour optical paths passing through 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, and t are always considered 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 handled as real numbers while suppressing deterioration in solution accuracy. The solution can be obtained at high speed.
[0017]
The equipment cost Cost to be minimized is represented by the following equation, for example.

Here, the meaning of each symbol in the above formula is as follows.
WPs, d, r, w: the number of optical paths including the standby 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 l
Mn: used switch size at node n,
UWn: number of used switch planes at node n,
PRn: fixed 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 the route r from the originating node s to the terminating 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 originating node s to the terminating node d,
RNn: a 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 satisfying the logical expression
Card {}: number of elements in 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: half the cost required to terminate the optical path,
δ: Failure cost per optical path.
[0018]
Specified by solving the above constraints and the maximum capacity of the optical network as constraints and solving the linear programming with the equipment cost as an objective function to obtain the values of Ps, d, r and SPs, d, r It is possible to determine the optical path deployment including the standby 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 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 A detour protection optical path can be shared between them, and an optical network with a small number of necessary optical paths can be realized with a minimum equipment cost while satisfying a failure recovery rate specified in advance.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of an optical network to which the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10-17 ... Optical fiber, 20 ... Optical path, 21, 22 ... Backup optical path, 30 ... Detour optical path, A-E ... Node, 1A-1E ... Label Switch router, 2A-2E ... Optical cross-connect device

Claims (1)

Multiple nodes are connected to each other via an optical path, and when a failure occurs in the optical path, the traffic that has flowed through the failed optical path is bypassed via the multiple backup optical paths and does not become a failure at the same time. In a design method of an optical network that can share a backup optical path between arbitrary optical paths,
By inputting the route candidate between each pair of nodes constituting the optical network and the number of requested optical paths, and diverting the traffic that was flowing through the failed optical path via multiple unprotected optical paths Solve the linear programming method including constraints that can achieve the specified failure recovery rate, find the number of optical paths including backup optical paths to be deployed on each route candidate so that the equipment cost is minimized , the constraints to distinguish light path number and the number of backup optical paths to be deployed on each route candidate design method of the optical network, characterized in der Rukoto those formulated including failure recovery rate.

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