Hierarchical Logical Topology in WDM Ring Networks with Limited ADMs

Transcription

1 Hierarchical Lgical Tplgy in WDM Ring Netwrks with Limited ADMs Tmya Kitani, Nbu Funabiki 2, Hirzumi Yamaguchi 3, and Teru Higashin 3 Graduate Schl f Infrmatin Science Nara Institute f Science and Technlgy, Nara, Japan 2 Graduate Schl f Natural Science and Technlgy Okayama University, Okayama, Japan 3 Graduate Schl f Infrmatin Science and Technlgy Osaka University, Osaka, Japan t-kitani@is.naist.jp, funabiki@cne.kayama-u.ac.jp, {h-yamagu,higashin}@ist.saka-u.ac.jp Abstract. This paper presents a methd fr cnstructing lgical tplgy in multi-hp WDM netwrks hierarchically. Our lgical tplgy can be built ver WDM ring netwrks with nly three ADMs (Add-Drp Multiplexers) and transceivers per nde. We aim t realize lw-cst WDMs that can be deplyed fr MANs and LANs. Due t well cnstructed hierarchical tplgy, bth the maximum distance between tw ndes and the number f required wavelengths n each ptical fiber are reduced t the lgarithmic rder f the number f ndes. This cntributes t mitigate traffic csts in WDM netwrks. Furthermre, we prpse a nde labeling scheme t achieve efficient ruting withut ruting table lkup. Frm ur numerical experiments, we have shwn that we culd cnstruct a lgical tplgy cnsisting f, ndes with a very small diameter and 6 wavelengths in a WDM ring netwrk. Keywrds: WDM ring netwrks, lgical tplgy design algrithm, hierarchical tplgy, cmpact ruting algrithm Intrductin Wavelength Divisin Multiplexing (WDM) technlgy enables high-speed and highvlume data transmissin ver fiber-ptic netwrks by multiplexing several ptical carrier signals using different wavelengths. Because f its significance fr very high-speed cmmunicatin infrastructure, the WDM methdlgy and the related issues have been widely investigated s far. In particular, since multi-hp WDM netwrks are required t assign lightpaths amng tw ndes and any data is carried ver thse lightpaths, the quality f lightpath design bviusly has great impact n the netwrk perfrmance such as the vlume f traffic that can be accmmdated withut causing cngestin. Therefre, many algrithms n designing lgical tplgies ver multi-hp WDM netwrks have been cnsidered [, 2].

2 The existing methdlgies n lgical tplgy design ver WDM netwrks have fcused n minimizing the number f required wavelengths [3 6], the number f required ADMs (Add-Drp Multiplexers) and transceivers [5 7], the blcking prbability [8], the number f required paths [9], the ttal amunt f relayed traffic [, ], the number f required wavelength cnverters [3, 2] and s n, fr given traffic matrices. It is well-knwn that the number f prts (ADMs and transceivers) per WDM nde has big impact n hardware csts. Als in rder t save netwrk resurces, minimizing the number f required wavelengths is als desirable. Althugh sme methds try t reduce the ttal number f prts fr cst-efficient design f WDM netwrks [3], it is desirable t cnsider WDM netwrks with a small number f prts per nde since MANs and LANs may emply a large number f lw-cst ndes. Thus, the traffic grming methds t minimize the number f ADMs and wavelengths have been investigated s far. In ur previus wrk [4], we have prpsed a lgical tplgy called Hierarchical Chrdal Ring Netwrk (HCRN). In HCRN, each nde has nly three prts (ADMs and transceivers) and the netwrk diameter and the number f required wavelengths are prprtinal t N (N dentes the number f ndes). Arra et al. have prpsed a methd t cnfigure a lgical tplgy fr WDM ring netwrks such as a prevalent MAN [5]. This tplgy has the netwrk diameter and the number f required wavelengths which are prprtinal t the lgarithmic rder f N by using lightpaths with O(2 N ) lengths (physical hp-cunts). Hwever, this methd may require each nde t use mre prts in the lgical tplgy whereas HCRN uses nly three prts. In this paper, we prpse a methd f designing a lgical tplgy where the netwrk diameter and the number f required wavelengths are the lgarithmic rder f N n the WDM ring netwrks cnstituted by ndes with nly three prts. We als prpse a multi-hp ruting methd ver this lgical netwrk. This tplgy is cnfigured by clustering adjacent ndes in a similar way t HCRN and Arra s methd. This tplgy can admit mst traffic patterns and variance because f its regularity. Althugh lgical tplgies may smetimes be recnfigured accrding t changes f traffic patterns, frequent recnfiguratin cannt be applied in practice due t its verhead. Therefre, it is imprtant t cnstruct a tplgy which is adaptive t mst traffic patterns. Furthermre, expliting regularity and hierarchy f the lgical tplgy, we prpse a nde labeling scheme t achieve effective ruting n the lgical tplgy withut ruting table lkup. Frm the numerical results, we have shwn that we culd cnstruct lgical tplgies f, ndes with a very small diameter and up t 6 wavelengths per fiber-ptic cable, and the methd is dminant t the methd in Ref. [6] that generates dynamic tplgies and Chrdal Ring Netwrk tplgy. 2 Related Wrk Reference [6] is ne f the initial literatures n lgical tplgy design ver ptical netwrks, and prvides several heuristic algrithms such as HLDA (Heuristic Lgical tplgy Design Algrithm) and TILDA (Traffic Independent Lgical tplgy Design Algrithm). Later we will cnduct perfrmance cmparisn with them t see efficiency

3 f ur methd. Reference [6] deals with ptical ring netwrks, and gives the lwer bund analysis f wavelengths and ADMs usage in WDM netwrks. The results indicate t what degree ur achievements have been attained; ur upper bund analysis shws that we culd achieve almst the lwest in mst cases. Reference [5] intrduces several lgical tplgies in dynamic lightpath assignment, minimizing the number f transceivers. References [, ] als assume SONET ring netwrks, minimizing the relay traffic n lgical tplgies by ILP frmulatin. In particular [] cnsiders the upper and lwer bunds f the minimized relay traffic fr cst-efficient design. The recent wrk [7] has presented the imprvement f existing heuristic algrithms by the rllut technique. We have prpsed the lgical tplgy called Hierarchical Chrdal Ring Netwrk (HCRN) [4]. HCRN is inspired frm the Chrdal Ring Netwrk tplgy (CRN) [8], where each nde has nly three prts (ADMs and transceivers). HCRN achieves less netwrk diameter and less number f required wavelengths than the riginal CRN by clustering adjacent ndes and cnfiguring internal / inter-cluster lightpaths. Hwever, in bth CRN and HCRN, the netwrk diameter and the number f required wavelengths are rder f N (N is the number f ndes). Arra et al. have prpsed the methd t cnfigure a lgical tplgy fr WDM ring netwrks [5]. The tplgy achieves that the netwrk diameter and the number f required wavelengths are the lgarithmic rder f N. In the methd, the cncept f cnfiguring lightpaths is similar t the distributed hash table (DHT) algrithm named Chrd fr peer-t-peer netwrks [9]. Bth methds use lightpaths/cnnectins whse lengths (physical hp-cunts) are pwer f tw. Hwever, they may make each nde need mre prts in the lgical tplgy whereas it uses nly three prts in CRN. We nte that recent researches have dealt with wavelength assignment fr highend, brand-new architectures like WDM netwrks with wavelength cnverters [3] and ROADM (Recnfigurable Optical Add-Drp Multiplexer) with mdulatrs [2]. Als sme thers aim at attaining nn-blcking rearrangement [4], achieving fairness in wavelength assignments [2] and s n. Different frm thse researches, we revisit the imprtant tpic; lgical path design and ruting ver WDM netwrks with limited capabilities f equipments. Even several heuristic slutins have been presented ver the last decade, we believe that this prblem has nt been slved cmpletely and ur slutin is quite significant fr efficient usage f lw-cst WDM netwrks. 3 Target WDM netwrk mdel In this sectin, we shw the architecture f WDM netwrks t explain the prblem dealt with in this paper. An ptical netwrk is mdeled as a ring graph G phy = (V, E phy ) where V = {,,, N } is a set f ndes and E phy V V is a set f fiber-ptic cables called physical links r simply links. Each nde is equipped with OADMs (Optical Add-Drp Multiplexers) and fr data transmissin between tw ndes; their transceivers are required t be tuned t a cmmn wavelength in advance. The resulting lgical path is called lightpath, and the tw ndes are called terminal ndes. Since each lightpath needs a prt (transceiver) at its

4 bth terminal ndes, the number f input and utput prts at each nde is greater than that f lightpaths which are terminated at the nde. The number f prts is called degree bund. We shw the architecture f WDM ndes in Fig.. Fr a lightpath, each nnterminal nde n the lightpath acts as an ptical repeater where the ptical signal is passed thrugh frm an ingress prt t the crrespnding egress prt. Meanwhile, ruting is dne by the terminal ndes by the cnversin between ptic signals and electric signals. We assume the same number f ADMs and transceivers fr each nde tw ADMs and three transceivers fr each nde in Fig., and thus the maximum number f wavelengths n each physical link is identical and is dented by W. We als assume that in the similar reasn, the degree bund f all ndes and the capacity f all the lightpaths are identical, and they are dented by D and C, respectively. λ,, λ w λ Optical Add- Drp MUX λ w Optical Add- Drp MUX λ λ w λ,, λ w λ a Transceiver λ b λ c λ e λ d Transceiver Electric Ruter Transceiver λ f Fig.. Architecture f WDM Nde 4 Prpsed Hierarchical Netwrk Tplgy Here, we explain the prpsed hierarchical lgical tplgy. We assume a physical ring netwrk G = (V, E phy ) where V = {,,..., N } and E phy = {(l, l ) l V } is a set f bi-directinal physical links (i j (i + j) md N). 4. Clustering f Ndes In the given physical ring netwrk, a subsequence f ndes in the nde ring is called cluster. First, we start with a whle, single cluster [,..., N ]. As shwn in Fig. 2, fr

5 each cluster we establish a lightpath called chrd lightpath between the bth end ndes f the cluster, and create tw same-sized sub-clusters using the ndes in the cluster except the bth end ndes. Then we establish a lightpath between an end nde f an i-th level cluster and its physically adjacent nde, which is an end nde f the (i + )-th level sub-cluster. Fr each sub-cluster, we repeat the same prcedure until the cluster size is less than r equal t fur. The cnsequent hierarchical netwrk tplgy is called HLT (Hierarchical Lgical Tplgy). As shwn in Fig. 3(a), all ndes n this HLT can be clustered hierarchically. chrd lightpath i -th layer chrd lightpath (i+)-th layer Fig. 2. Clustering f ndes (a) Hierarchical Cnstructin f Chrds Links n the ring Chrd Links (b) Hierarchical Nde Labeling Fig. 3. Nde labeling and ruting in a cluster f HLT Then, fr ruting purpse, we give nde labels accrding t the plicy belw (see Fig. 3(b)). Fr the end ndes in the st-level (the highest level) cluster, we assign the

6 nde labels and t thse ndes. If the end ndes f an i-th level cluster have the nde labels X and X, we assign t the end ndes f the (i + )-th level clusters the nde labels X, X, X and X. Accrding t this labeling plicy, the ndes in the same level s clusters have the nde labels based n Gray cdes where the labels f any tw ndes that are directly cnnected by a lightpath differ in nly ne digit (Fig. 3). Als if a nde p f (i + )-th level cluster is cnnected by a lightpath with a nde f i-th level cluster with nde label Y, the nde label f p is Y. These cdes are called variable length Gray cdes. In this hierarchical lgical tplgy HLT, the netwrk diameter (the maximum distance (hp cunt) between tw ndes in the netwrk) is O(lg N). One may think that this is similar with the Chrdal ring netwrk tplgy [8], hwever its netwrk diameter is O( N). Thus, the prpsed hierarchical tplgy HLT can attain smaller netwrk diameters than Chrdal Ring Netwrk tplgy in large-scale netwrks. As shwn in Fig. 3, all the chrd lightpaths established in the clusters f the same level can use a cmmn wavelength because they never share the physical links. Therefre, as a ttal, we nly need H wavelengths where H is the number f hierarchy levels. Since N 2 H+ 2, the number f required wavelengths is btained as fllws; H = lg 2 (N + 2) lg 2 N () We nte that if we use a physical ring netwrk tplgy, the wavelength fr the st level can be the same as that used fr the secnd level, and this can save ne wavelength. Fr example, in Fig. 3, the wavelength assigned t the chrd lightpath between ndes and can be the same as that used fr the tw chrd lightpaths between and and between and since there is a direct physical link between ndes and. As we have seen abve, the mst significant feature f HLT is that the netwrk diameter and the number f required wavelengths are suppressed t the lgarithmic rder f N. 4.2 Ruting n Prpsed Hierarchical Lgical Tplgy Here, we cnsider a ruting n the prpsed netwrk tplgy. Fr ruting n the hierarchical tplgy HLT, as shwn in Fig. 3(b), the prpsed variable length Gray cdes can be used fr deciding the rute frm a surce nde t its destinatin nde. If ndes and are the surce nde and its destinatin nde respectively, the path,,,,,,,, is ne f the shrtest rutes. Basically, each packet is relayed frm the surce nde t a nde n an upper level, and then it is frwarded frm the nde n the upper level t the destinatin nde. This is the basic ruting plicy. There is an exceptin. If ndes and are the surce nde and its destinatin nde, the path,,,, is the shrtest rute, and the rute thrugh,,, becmes lnger. The lightpath frm t makes the length f the rute shrter. Fr each nde S with nde label s, s 2,, s k, there are fur ruting actins. UP dentes the actin which frwards the received packet t its parent nde S UP = s, s 2,, s k. UP can be used nly fr s k =. DW dentes the actin which frwards the received packet t its child nde S DW = s, s 2,, s k, (s k+ = ). BR dentes the actin which frwards the received packet t its sibling nde S BR = s, s 2,, s k thrugh the chrd lightpath (r nrmal lightpath)

7 between s, s 2,, s k and s, s 2,, s k. Here, nte that x = if x =, and that x = if x =. CO dentes the actin which frwards the received packet t its cusin nde S CO = s, s 2,, s k, s k thrugh the lightpath between s, s 2,, s k and s, s 2,, s k, s k. CO can be used nly fr s k =. Hereafter, Frward(S, U P ), Frward(S, DW ), Frward(S, BR) and Frward(S, CO) dente the frwarded ndes S UP, S DW, S BR and S CO, respectively. Let S = (s,, s i, s i+,, s k ) and D = (s,, s i, d i+,, d h ) dente the variable length Gray cdes fr ndes S and D. Here, we assume that the first i bits f the variable length Gray cdes f ndes S and D are the same (s i+ d i+ ). The fllwing algrithm R-HLT(S,D) calculates the ruting actin f nde S (here, NIL dentes n actin). [Ruting Algrithm R-HLT]: if (S = D) then NIL else if ( (k i > 2) (h = i) ) then if ( s k = ) then UP else BR else if ( k i = 2) then case (s k, s k ) f (, ): if ( k > h ) then UP else BR (, ): if ( d k = ) then BR else CO (, ): if ( d k = ) then CO else BR (, ): if ( k > h ) then UP else BR end else if ( k i = ) then BR else (* k = i *) DW If nde S is a surce nde r relay nde, the abve ruting algrithm R-HLT(S,D) can decide the ruting actin f nde S when S must frward its received packets t nde D. If the surce nde S wants t decide the strict ruting path and its length frm nde S t its destinatin nde D, we can calculates them by repeating R-HLT and calculating the path S = S, S =Frward(S,R-HLT(S, D)), S 2 =Frward(S,R-HLT(S, D)),, S q = D =Frward(S q,r-hlt(s q, D)) until we find nde D as S q. This path dentes the strict ruting path frm S t D and its path length is q. This ruting can be used when we use surce ruting. 5 Perfrmance Evaluatin and Numerical Results 5. Cmparative Mdels Here, we will explain existing lgical tplgies which can be applied fr WDM netwrks with nde degree 3. A Chrdal ring netwrk has a ring tplgy with N ndes (N must be even) whse nde IDs are t N. Fr each nde with nde ID k, ne chrd is cnnected t either nde k +L r k L. Here, L dentes a cnstant number. In Ref. [8], it is shwn that if N +3 N 2 hlds, we can maximize its netwrk diameter when an dd number clsest t N + 3 is specified as the cnstant L. If N + 3 N 2

8 45 HLT CRN t n u25 c p 2 h 5 s t h g n le e v a w f # Netwrk Diameter f HLT Ave. hp cunt f HLT Netwrk Diameter f CRN Ave. hp cunt f CRN # f ndes (a) Netwrk diameter and average hp cunt # f ndes (b) Number f required wavelengths Fig. 4. Cmparisn between HLT and CRN des nt hld, we can assign the maximum dd number which is less than r equal t N 2 as the cnstant L. In this situatin, the netwrk diameter and the number f required wavelengths f CRN are bth prprtinal t the square rt f the number N f ndes. On the ther hand, as we explained abve, the prpsed HLT tplgy nly requires the netwrk diameter and the number f required wavelengths which are prprtinal t the lgarithmic rder f N. Figure 4 dentes the cmparisn abut the netwrk diameter, the average hp cunts and the number f required wavelengths f HLT and CRN netwrks. Nte that, as shwn in Fig. 4(b), CRN needs twice the number f wavelengths in rder t cnstruct itself when N cannt be divided by the chrd length L. There are als sme dynamic tplgy cnstructin methds. Fr example, in Ref. [6], HLDA (Heuristic Lgical tplgy Design Algrithm) and TILDA (Traffic Independent Lgical tplgy Design Algrithm) are prpsed, and they are ften used fr perfrmance cmparisn. In HLDA, in rder t minimize the ttal amunt f traffic, ndes with heavy traffic are given pririty t use usable ptical wavelengths. In HLDA, the fllwing algrithm is used. Algrithm HLDA Step. An ptical link is given between every physically adjacent ndes s that all ndes can cmmunicate each ther. Step. Estimate the traffic amunt P ij fr every link (i, j). Step.2 Find link (i, j) whse P ij is maximum. If there is an usable wavelength n the link (i, j), we assign ne wavelength t link (i, j). Then, we set P ij t. Step.3 If all P ij are, g t Step.4. Otherwise, return t Step.2. Step.4 If we still have usable wavelengths, we assign thse wavelengths t pssible links randmly. We repeat this prcess until we cannt assign new wavelengths. On the ther hand, TILDA des nt cnsider traffic amunts, and gives pririty fr assigning usable wavelengths t physically clser links. In TILDA, the fllwing algrithm is used.

9 Algrithm TILDA Step. An ptical link is given between every physically adjacent ndes s that all ndes can cmmunicate each ther. Step. Set i = 2. Step.2 If a nde has usable ADMs and if there is a usable wavelength n the path frm the nde t anther nde with i hp distance, we assign ne wavelength t all links n the path. If there is n such a path fr tw ndes with i hp distance, we set i = i + and repeat the same prcess. 5.2 Perfrmance Evaluatin We have evaluated the perfrmance f the prpsed HLT, HLDA and TILDA by simulatin. Here, we have used three types f traffic matrices: randm mdel, server-client mdel and small-wrld mdel. In ur analyses, we have changed the number N f ndes frm 5 t, in units f 5 ndes, and tried three numerical analyses fr the abve three types f traffic matrices, respectively. Here, we assume that HLDA can als use the same number f wavelengths as much as that used in the prpsed methd. The unifrm randm numbers between and are given as the traffic matrix f the randm mdel. In the server-client mdel, 5% f ndes are selected as servers, and we have sent times f traffic t thse server ndes. In the small-wrld mdel, first we cnstruct a traffic matrix based n the server-client mdel, and then we make traffic amng neighbring ndes increase times [2]. We als make the traffic between tw ndes decrease in prprtin t the distance between tw ndes. Fr the given traffic matrices, we have evaluated the netwrk diameters, the average number f hps, and verall traffic vlume. The traffic vlume, dented by Q hereafter, is defined as fllws; Q = T uv h uv (2) u v where h uv and T uv dente the number f lightpaths and traffic n the rute frm u t v, respectively. We shw ur numerical results fr the abve three mdels in Fig. 5. Figure 5(a) (c) dentes the netwrk diameters and average numbers f hp cunts. Figure 5(d) dentes the verall traffic vlumes Q where all the traffic vlumes are nrmalized s that the traffic vlume f HLDA is represented as. Fr all the traffic mdels, if the number f ndes exceeds, the prpsed lgical tplgy HLT is better than ther tplgies. The reasn is that if the number f ndes is small, relatively we can use mre wavelengths. On the ther hand, if the number f ndes becmes large, relatively we can use less wavelengths. If HLDA can assign enugh number f lgical links between ndes with heavy traffic, we can assign enugh number f lgical links. Hwever, if the number f ndes becmes large, we might nt be able t assign enugh number f lgical links fr such purpses. Fr the netwrk diameters, in the prpsed hierarchical tplgy HLT, the netwrk diameters are stable independently f traffic fluctuatin and deviatin. On the ther hand, HLDA gives pririty t assigns lgical links fr nde pairs with heavy traffic. This makes the hp cunts fr nde pairs with light traffic increase. The traffic fluctuatin and deviatin als make big influence t the netwrk diameters.

10 2 4 TILDA (Net. dia.) TILDA (Ave. hp) TILDA (Net. dia.) 2 TILDA (Ave. hp) 8 t n u c p h 6 HLDA (Net. dia.) t n u c p h 8 6 HLDA (Net. dia.) 4 HLT (Net. dia.) HLDA (Ave. hp) 4 HLT (Net. dia.) HLDA (Ave. hp) 2 2 HLT (Ave. hp) HLT (Ave. hp) # f ndes # f ndes (a) Net. dia. and ave. hp cunts n Randm mdel (b) Net. dia. and ave. hp cunts n Server-Client mdel 4 TILDA (Net. dia.) 8 t n u c p h TILDA (Ave. hp) HLDA (Net. dia.) HLDA (Ave. hp) HLT (Net. dia.) ) = 7 6 T L 5 ( H Q t n 4 u m a 3 f ic a 2 tr TILDA (Randm) TILDA (S/C) TILDA (Small-wrld) HLDA (Small-wrld) 2 HLT (Ave. hp) HLT = HLDA (Randm) HLDA (S/C) # f ndes # f ndes (c) Net. dia. and ave. hp cunts (d) Rati f netwrk traffic amunts Small-wrld mdel in HLT, HLDA and TILDA (HLT = ) Fig. 5. Netwrk diameter, average hp cunts and traffic amunts in HLT, HLDA and TILDA Next, we fcus n the average hp cunts and ttal traffic vlumes fr the randm mdel and server-client mdel. In HLDA, the average hp cunts are small fr the randm mdel since ptical fiber links are assigned unifrmly. In the server-client mdel, the ttal traffic vlumes relatively becme small since HLDA gives pririty t assign lgical links fr nde pairs with heavy traffic. Since the prpsed tplgy is regular, it ffers almst fixed perfrmance independently f traffic mdels and vlumes. It can als guarantee the upper limit f the netwrk diameters theretically. In general, the randm mdel and server-client mdel have similar tendency fr the average hp cunts. Lastly, we fcus n the average hp cunts and ttal traffic vlumes fr the smallwrld mdel. HLDA assigns many ptical links fr neighbring nde pairs since we assume relatively heavy traffic t neighbring nde pairs. Then, it becmes difficult t assign ptical links fr nde pairs with lng distances. On the ther hand, the prpsed tplgy can assign hierarchical chrds fr nde pairs with lng distances while neighbring nde pair can cmmunicate with each ther using the links n the riginal ring tplgy. Frm the abve reasn, ur prpsed tplgy HLT and HLDA have rather different tendency. In Fig. 5(d), if the number f ndes is mre than 4, the ttal traffic vlumes f the prpsed tplgy HLT is less than 6% f thse fr HLDA.

11 We can bserve that ur tplgy culd save the usage f wavelengths because it culd unifrmly distribute lightpaths ver physical links. As shwn in Fig. 5(d), fr a lgical tplgy with, ndes, an HLT tplgy nly requires 6 wavelengths. Meanwhile, in HLDA and TILDA, it is likely t ccur that sme lightpaths are established ver sme specific physical links first due t degree limitatins. In that case n mre lightpaths were accepted ver the link if n mre wavelength is available, and the ther lightpaths are needed t detur the link. Thus cnsequent tplgies may have lng rutes that require many hps and make the diameters larger. 6 Cnclusin In this paper, we prpse a design methd f hierarchical lgical tplgy in multi-hp WDM netwrks. Our lgical tplgy can be built ver WDM netwrks with limited ADMs. The methd can be applied fr bth ring-type and mesh-type WDM netwrks. The prpsed lgical tplgy has features that bth the maximum distance between tw ndes and the required number f wavelengths n each physical ptical link are prprtinal t the lgarithmic rder f the number N f ndes. Frm theretical and numerical pints f views, we have cmpared the prpsed lgical tplgy with general Chrdal ring netwrk tplgy and HLDA (Heuristic Lgical tplgy Design Algrithm) based netwrk tplgy. The prpsed lgical tplgy has smaller average hp number, netwrk diameter and ttal traffic amunt. If the number N f ndes n a given WDM netwrk becmes large, ur lgical tplgy becmes mre efficient. It is shwn that the prpsed lgical tplgy has enugh scalability fr large scale WDM netwrks. We have als shwn that the netwrk perfrmance can be further imprved by cmbining HLDA ver ur lgical tplgy. T investigate detailed netwrk perfrmance n real WDM netwrks is ne f ur future wrk. References. R. Dutta and G.N. Ruskas: A survey f virtual tplgy design algrithms fr wavelength ruted ptical netwrks, Optical Netwrk Magazine, vl., pp (2). 2. H. Zang, J.P. Jue and B. Mukherjee: A Review f Ruting and Wavelength Assignment Appraches fr Wavelength-Ruted Optical WDM Netwrks, Optical Netwrks Magazine, vl., n., pp (2). 3. L-W. Chen and E. Mdian: Efficient Ruting and Wavelength Assignment fr Recnfigurable WDM Ring Netwrks With Wavelength Cnverters, IEEE/ACM Trans. n Netwrking, vl. 3, n., pp (25). 4. P. Saengudmlert, E.H. Mdian and R.G. Gallager: Dynamic Wavelength Assignment fr WDM All-Optical Tree Netwrks, IEEE/ACM Trans. n Netwrking, vl. 3, n. 4, pp (25). 5. O. Gerstel, R. Ramswami and G.H. Sasaki: Cst-Effective Traffic Grming in WDM Rings, IEEE/ACM Trans. n Netwrking, vl. 8, n. 5, pp , (2). 6. A.R.B. Billah, B. Wang and A.A.S Awwal: Effective Traffic Grming in WDM Rings, Prc. f the 45th IEEE Glbal Telecmm. Cnf.(GLOBECOM 25), vl. 3, pp (22).

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