A Novel Scheme to Reduce Burst-Loss and Provide QoS in Optical Burst Switching Networks

Transcription

1 A Novel Scheme o Reuce Bur-Lo an Provie QoS in Opical Bur Swiching Nework Ahok K. Turuk an Rajeev Kumar Deparmen of Compuer Science an Engineering, Inian Iniue of Technology Kharagpur, Kharagpur, WB , Inia {akuruk, rkumar}@ce.iikgp.erne.in Abrac. Bur lo ue o conenion i a major iue in opical bur wiching nework. In hi paper, we propoe a conenion reoluion cheme ha ue a offe ime ifferen from ha of convenional opical bur wiching (OBS) o reuce bur lo an o provie QoS in opical bur wiching nework. The propoe cheme can be une o boh prioriize raffic an elay conrain raffic by changing he offe ime. For elecing a aa-channel, we propoe hree channel elecion algorihm, namely Lea Recenly Ue (LRU), Fir Fi (FF), an Prioriy Se (PS) algorihm. We imulae an compare propoe cheme wih he preempive prioriy ju-enough-ime (PPJET) conenion reoluion cheme. We conier bury raffic in our imulaion. I i foun ha our cheme ouperform PPJET in bur-lo. Inroucion There ha been a phenomenal increae in he number of Inerne uer an he variey of Inerne applicaion in recen year. Thi ha reule in exponenial growh of Inerne raffic, emaning a huge banwih a he backbone nework. To mee hi growing eman for banwih, wavelengh iviion muliplexing (WDM) nework ha become he e-faco choice for he backbone nework. IP over WDM nework have rawn much aenion among reearcher, an many inegraion cheme beween IP an WDM layer have been propoe []. To carry IP raffic over WDM nework hree wiching echnologie have been uie: opical circui wiching, packe wiching an bur wiching. Opical circui wiching an packe wiching have heir own limiaion when applie o WDM nework. Circui wiching i no banwih efficien unle he uraion of ranmiion i greaer han he circui eablihmen perio. I i hown ha eablihmen of circui (lighpah) in opical nework i an NP-har problem [2]. Many heuriic an approximaion algorihm exi for eablihing lighpah in opical nework e.g., ee [3] an he reference herein. Packe wiching i hop-by-hop ore an forwar cheme an, nee buffering an proceing a each inermeiae noe. I i flexible an banwih efficien. However, echnology for buffering an proceing in opical omain i ye o maure for hi cheme o commercialize. Fiber elay line propoe in lieraure provie limie buffer capabiliy an are uiable for elay of fixe uraion only. L. Bougé an V.K. Praanna (E.): HiPC 2004, LNCS 3296, pp , c Springer-Verlag Berlin Heielberg 2004

2 30 A.K. Turuk an R. Kumar In hi conex opical bur wiching (OBS) i emerging a he new wiching paraigm for he nex generaion opical nework [4, 5]. I combine feaure of boh circui an packe wiching. A uch here exi no formal efiniion of OBS, he feaure efine by Yoo an Qiao [4] for OBS have become e-faco anar. The bur-ize granulariy (which lie beween circui an packe wiching), eparaion of conrol an aa bur, one-way (for mo cae) or wo-way reervaion cheme, an no opical buffering are imporan characeriic of he OBS paraigm. Some major iue in opical bur wiching nework are: (i) conenion reoluion, (ii) bur aembly, an (iii) qualiy-of-ervice (QoS) uppor. In a buffer-le OBS nework conening bur i lo. Therefore, bur-lo houl be minimize in OBS nework, i he key eign parameer. A few approache o conenion reoluion ue in OBS are: buffering [6], eflecion rouing [7], bur egmenaion [8, 9] an winow bae echnique [0]. Bur aembly i he proce of aggregaing an aembling IP packe ino bur[]. Wih increae in variey of Inerne applicaion, ifferen applicaion uch a voice-over-ip (VoIP), vieo-on-eman, vieo conferencing ec. eman ifferen QoS requiremen. To mee he QoS requiremen of ifferen applicaion, IETF propoe InServ an DiffServ cheme. However, uch convenional prioriy cheme are efine for elecronic omain which rivially manae he ue of buffer a inermeiae noe. Such cheme canno be ue irecly o uppor QoS in buffer-le OBS nework. Thu, any cheme o uppor ifferenial QoS requiremen in OBS nework houl no manae he ue of buffer a inermeiae noe. Many cheme, in recen year, have been uggee o uppor prioriy bae QoS in OBS nework. All he propoe cheme have rie o reuce he bur lo. I i no he bur-lo only bu alo he number of packe-lo ha maer. For example, conier hree bur b, b 2 an b 3 of ize 0, 20 an 50 number of packe each. A lo of any of he bur inicae 33% of he bur lo. However, if we conier lo in erm of packe, he packe-lo come ou o be 4%, 28% an 64% repecively. Therefore, i i eirable ha a conenion reoluion cheme houl ake care of he loe calculae in erm of packe. Conier Fig. (a) an aume boh reque r an r 2 have he ame prioriy an arrive a a noe a he ame ime. In OBS, he bur b 2 i alway roppe. However, if he bur-ize i aken ino accoun he larger bur b 2 coul have ucceee an he maller bur b i roppe. Thi will reul ino larger number of packe ranmie an higher reource uilizaion. Nex, conier Fig. (b) having wo bur of he ame prioriy. In OBS, boh he bur are roppe. However, aking he bur-ize or he number of hop ravere ino conenion reoluion cheme one of he bur uccee. Thi give rie o lower bur lo an larger number of packe ranmie. Thu, if we conier wo more parameer bur-ize an number of hop ravere in reolving conenion, hi will guaranee ha a lea one of he bur uccee an larger number of bi ranmie. En-o-en elay i anoher key parameer for QoS proviioning. All elay eniive applicaion eman ha en-o-en elay i boune by he elay conrain impoe by he repecive applicaion. Conenion houl be reolve by coniering he elay facor oo. In hi paper, we preen a flexible algorihm for conenion reoluion o uppor a larger e of QoS parameer in OBS nework. We conier packe lo an number of

3 A Novel Scheme o Reuce Bur-Lo an Provie QoS in OBS Nework 3 b r r b 2 b2 r2 2 r 2 b 2 (a) (b) Fig.. Illuraion for Conenion Reoluion : (a) wo reque are parially overlappe for a perio, (b) wo reque have he ame reervaion inance hop ravere, in aiion o prioriy, for reolving conenion. Our cheme i generic an can eaily be aape o aify elay-conrain. The aim i o reuce blocking probabiliy of he bur ariing ue o reource conenion a inermeiae noe a well a o mee he elay conrain of he elay eniive raffic. The propoe cheme guaranee ha a lea one of he bur uccee when conenion occur; he conenion houl be reolve in accorance wih aifacion of QoS parameer. To elec aachannel, we propoe hree channel elecion algorihm (i) Lea Recenly Ue (LRU), (ii) Fir Fi (FF), an (iii) Prioriy Se (PS). Channel elecion algorihm run a he ingre rouer o elec a aa-channel for reervaion an for ubequen ranmiion. We evaluae he propoe cheme wih he above channel elecion algorihm. The re of he paper i organize a follow. Secion 2 explain he conenion reoluion echnique; few aumpion an noaion ue are ecribe in Sub-ecion 2.. Channel elecion algorihm are explaine in Secion 3. Simulaion reul are preene in Secion 4 an compare wih PPJET. Finally, ome concluion are rawn in Secion 5. 2 Propoe Conenion Reoluion Scheme 2. Aumpion an Noaion We moel an opical nework by mean of a unirece graph G(V,E) where V i he e of verice (noe) an E repreen he e of link/ege in he nework. Two ype of noe (here afer, we ue he erm noe an rouer inerchangeably) are ienifie: ege rouer an core rouer. Every ege rouer ha (n e ) P elecronic buffer where n e i he number of ege rouer, P i he number of prioriy clae uppore in he yem. Each buffer belong o a pecific pair of prioriy cla an an egre rouer. The core rouer ha no buffer; hi i a eirable feaure of he opical bur wiching nework. A core rouer ac a a rani rouer for aa-raffic. Thu, he aa-raffic remain in opical omain from ingre o egre rouer. Propagaion elay, p, beween every pair of ajacen verice in graph G i aume o be he ame. Proceing elay of he conrol packe a each rouer i aume o be. We ue he following noaion in re of he paper: (r): Number of hop for he reque r beween ource - einaion pair (, ), (r): Remaining number of hop for he reque r beween ource - einaion pair (, ) a noe i. H Hi

4 32 A.K. Turuk an R. Kumar Original bur: A bur for which reource are alreay reerve a he core rouer, Conening bur: A bur whoe reervaion reque ha reule in reource conenion a he core rouer. We efine he following hree iuaion ha can occur when an inermeiae rouer receive a reervaion reque: No conenion (NC): When no conenion for reource occur a he inermeiae core rouer. Conenion reolve (CR): When a conenion occur a an inermeiae core rouer i an for a lea one of he reque Hi (r) >H (r)/2. Conenion-no-reolve (CNR): When conenion occur a inermeiae core rouer() an for none of he reque Hi (r) >H (r)/ Propoe Scheme OBS i bae on eiher one way or wo way reervaion proocol. The minimum laency in one way reervaion proocol i P + H where he minimum laency in wo way reervaion proocol i 2P + H. Our propoe cheme i a one way reervaion proocol however i iffer from oher OBS cheme in wo apec - one, he offe ime, an econ, he meho aope for conenion reoluion. In oher OBS cheme, he offe ime i H where i he proceing elay of conrol packe a each noe an, H i he number of hop beween ource-einaion pair. In our cheme, we ake he offe ime o be P + H where P i he propagaion elay beween ource-einaion pair. The nee for he aiional P uni of ime i explaine ubequenly. The minimum laency of bur in oher OBS cheme, i P + H which i ame if a bur i en along wih conrol packe in opical packe wiching. The minimum laency in opical circui wiching i 3P + H. In he propoe cheme, he minimum laency of a bur i 2P + H. Thu, we can ay he minimum laency in our cheme i ienical o OBS wih wo way reervaion proocol. However, he propoe cheme i a one way reervaion proocol where each bur experience an aiional elay of P uni. The cheme i alo unable o elay eniive raffic. For elay eniive raffic he offe ime in he propoe cheme i aken o be H which i he ame a ha in OBS. However, hi offe can be mae aapive o he applicaion nee. In he cheme, if a conenion occur an he iuaion i a CR one a menione in Secion 2. hen a bur i furher elaye for he conenion perio. However, hi elaying echnique of our cheme i no applicable in cae of elay eniive raffic. For elay eniive raffic if he require reource are no available wihin ha amoun of ime, he bur i roppe. Seconly, he propoe cheme iffer from OBS in he meho aope for conenion reoluion. In OBS, he reource conflic i reolve on he bai of reque prioriy an he ime inance for which reque i mae. In aiion o he above wo parameer, we ake bur-ize an he number of hop ravere o reolve conenion. A higher prioriy reque i given a prioriy. However, for he ame prioriy reque, he one ha ha ravere he maximum number of hop, i accepe for beer reource uilizaion. The reque ha ha ravere he maximum number of hop have more reource reerve on he pah. Acceping hi reque will give rie o higher reource uilizaion. For ame prioriy an he equal number of hop ravere he bur ha ha

5 A Novel Scheme o Reuce Bur-Lo an Provie QoS in OBS Nework 33 larger bur-ize i accepe. For ame prioriy, equal number of hop ravere an he ame bur-ize heir inance of reervaion i aken for reolving he conflic. Thu, he ie in conenion reoluion i reolve in orer of prioriy, number of hop ravere, bur-ize an elay. Nex, we explain he bai of having P aiional uni of elay in offe ime wih he help of iming iagram illurae in Figure 2 an 3. The oal elay encounere by a conrol packe for ource-einaion pair (, ) i no greaer han = H (r). The offe-ime, T, in OBS i aken o be a lea. In Fig. 2 he number of hop beween ource - einaion pair (, ) i 4. Therefore, he offe-ime T in OBS i 4. In OBS, if a conenion occur ay a noe A or a noe C hen he bur i roppe a A or a B a hown in Figure 2(b) an 2(c) repecively. Wih hi offe ime a conening bur canno be furher elaye. T A B C T A B C T A B C (a) (b) (c) Fig. 2. Timing Diagram of bur wiching nework: (a) no conenion occur a inermeiae noe, (b) conenion occur a noe A an (c) conenion occur a noe C T T A B C T A B C 0 0 (a) (b) Fig. 3. Timing Diagram for he propoe cheme: (a) conenion a noe A i reolve, an (b) conenion a noe C bu he bur i roppe a noe B In our propoe cheme, he offe, T, beween ource-einaion pair (, ) i aken o be ( + )H (r). For he above example he offe ime beween ource-einaion pair (, ) i 4( + ). Le u conier Fig. 2(b) where conenion ha occurre a noe A an, be he uraion of he conenion perio. The conrol packe ha aken one

6 34 A.K. Turuk an R. Kumar hop o reach he noe A from he ource. If a meage i en from noe A o he ource o elay he ranmiion of bur for he conenion perio i will reach a T =2( + ) afer he ource ha en he conrol packe (Fig. 3(a)). The offe-ime T>T i.e., ource will receive he meage o elay he ranmiion before he expiry of offe-ime. Hence, he ranmiion of he bur i elaye an i no roppe a noe A a hown in Fig. 3(a). Le u conier Fig. 2(c) where conenion ha occurre a noe C an, be he uraion of he conenion perio. If a meage i en from noe C o he ource o elay he ranmiion of bur for he conenion perio i will reach a T =6( + ). The offe-ime T<T, i.e., ource will receive he elay meage afer i ha ranmie he bur an he bur i roppe a noe C. Therefore, inea of ening a elay meage if a reource-releae meage i en from noe C, he meage will releae he reource reerve a noe B before he bur arrive a noe B an i roppe a noe B raher han a noe C. Thi give rie o beer uilizaion of he reource on link BC which wa earlier occupie by he reque. Thu, in he propoe cheme, a conenion occur a noe i an Hi (r) >H (r)/2 (hi i he CR iuaion a ecribe in Secion 2.), a meage i en o elay he ranmiion of he bur for uraion of he conenion perio. For Hi (r) <= H (r)/2 (hi i he CNR iuaion a ecribe in Secion 2.), a meage i en o releae he reerve reource. We illurae below poible cae of conenion an he way conenion i reolve in he cheme. For all he cae we refer o Fig. (a). In Fig. (a), he value of an 2 inicae he ime of arrival of reque r an r 2 repecively, a a core rouer i. Bur-ize of he reque r an r 2 i inicae by b an b 2 repecively. Below, we give inerpreaion for Cae ; he re of he cae are inerpree in he ame way. In Cae he conenion ha occurre ue o he arrival of reque r an r 2 a he core rouer i a he ame ime ( = 2 ). The remaining number of hop o be ravere for reque r i Hi (r ) >H (r )/2 an, for r 2 i Hi mn (r 2 ) >H mn (r 2 )/2. Wehave aume ha he conenion ha occurre a he core rouer i. Cae : = 2, Hi (r ) >H (r )/2, Hi mn (r 2 ) >H mn (r 2 )/2. Accep he high prioriy reque an en a meage o he ingre rouer of low prioriy reque o elay he ranmiion for he conenion perio. For ame prioriy of boh he reque, accep he reque ha ha ravere he maximum number of hop an en a meage o he ingre rouer of he oher reque o elay he ranmiion for he conenion perio. For ame prioriy an he equal number of hop ravere, accep he reque ha ha larger bur-ize an en a meage o he ingre rouer of oher reque o elay he ranmiion for he conenion perio. Cae 2: = 2, Hi (r ) H (r )/2, Hi mn (r 2 ) >H mn (r 2 )/2. Accep he high prioriy reque. If he low prioriy reque i r hen i i roppe ele a meage i en o he ingre rouer of r 2 o elay he ranmiion for he conenion perio. For ame prioriy of boh he reque, accep he one ha ha ravere he maximum number of hop. Oher reque i procee a explaine. For ame prioriy

7 A Novel Scheme o Reuce Bur-Lo an Provie QoS in OBS Nework 35 an equal number of hop ravere, accep he one wih higher bur-ize. Oher reque i procee a explaine earlier. Cae 3: = 2, Hi (r ) >H (r )/2, Hi mn (r 2 ) H mn (r 2 )/2. Reque are procee a explaine in Cae 2. Here, he reque ha i o be roppe i r 2. Cae 4: = 2, Hi (r ) H (r )/2, Hi mn (r 2 ) H mn (r 2 )/2. Reque are procee a in Cae. Here he reque ha i no accepe i roppe. Cae 5: < 2, Hi mn (r 2 ) >H mn (r 2 )/2. In hi cae he reque r ha arrive before r 2 an reource are alreay reerve for he reque r. For reque r 2 a meage i en o he ingre rouer o furher elay he ranmiion of bur for he conenion perio. Cae 6: < 2, Hi mn (r 2 ) H mn (r 2 )/2. A in Cae 5 reource are alreay reerve for he reque r. Reque r 2 i roppe. Cae 7: > 2, Hi mn (r 2 ) >H mn (r 2 )/2. In hi cae reque r ha arrive a a laer poin of ime han r 2 an i conening wih reque r 2. Reque are procee imilar o Cae 5. Cae 8: > 2, Hi (r ) H (r )/2. A in Cae 7, reque r ha arrive a a laer poin of ime han r 2 an i conening wih reque r 2. Reque are procee imilar o Cae 6. In he above cae, cae 4, 6 an 8 are CNR iuaion an he re are CR iuaion a efine in Secion Channel Selecion Algorihm In hi ecion, we ecribe hree channel elecion algorihm calle (i) Lea Recenly Ue (LRU), (ii) Fir Fi (FF), an (iii) Prioriy Se (PS) algorihm ue in channel elecion for our propoe conenion reoluion cheme (Secion 2.2). The channel elecion algorihm are run only a he ege rouer o fin he aa-channel for which reervaion reque i o be mae an ubequenly ranmi he aa-bur. In LRU, a aa-channel which i ile for he maximum uraion i elece. In FF, aa-channel are earche from he lowe inex an he one ha i available fir, i elece. For example, conier Fig. 4, LRU channel elecion algorihm elec he aa-channel 2 a i i ile for he maximum uraion where a FF channel elecion algorihm elec he aa-channel 0. In PS approach, we ecompoe he e of aa-channel, S, ino P ub-e, S i,of aa-channel. P i he number of prioriy clae uppore. S = S 0 S S P. A prioriy cla i elec he aa-channel from he e S i. If no aa-channel i available in he e S i hen i elec from he e S i an if no available hen from he e S i 2. Thi proce i ierae ill he lowe prioriy e S 0 i earche. If no aa-channel i available in he e S 0 hen he bur i roppe a he ingre rouer. The number of aa channel in he e S i i in proporion o he raffic of prioriy cla i.

8 36 A.K. Turuk an R. Kumar For he prioriy cla 0, if no aa-channel i available in he e S 0 hen he bur i roppe a he ingre rouer. To illurae he working of Prioriy Se approach, we conier wo prioriy clae 0 an ; cla ha higher prioriy han cla 0. We ivie he available aa-channel a hown in Fig. 5 in wo e S 0 = {0, } an S = {2, 3}. Le a bur of cla arrive a a an i i o be ranmie a afer he bae-offe ime offe. Since all he aa-channel in he e S are buy a, channel 0 from he e S 0 i elece a offe Fig. 4 Illuraion for elecion of aa-channel in LRU an FF algorihm a offe Fig. 5 Illuraion for elecion of aa-channel in PS algorihm 4 Simulaion Reul We aume he following ime-uni for ifferen ak o carry ou he imulaion. The propagaion elay, p, beween any wo ajacen noe in he bur wiching nework i aume o be m. The proceing ime of conrol packe a he rouer i aume o be 2µ. We aume here i no wavelengh converion an here exi no opical buffer in he wich. For impliciy an wihou lo of generaliy, we conier wo clae of raffic: cla 0 (low prioriy) an cla (high prioriy). We generae high prioriy raffic wih a probabiliy of 0.4. Traffic i generae only a he ege rouer an, he loa i meaure in Erlang.

9 A Novel Scheme o Reuce Bur-Lo an Provie QoS in OBS Nework 37 We compare he imulaion reul of our propoe cheme wih PPJET [2]. We conier bur blocking probabiliy a he performance meric for comparion. We have aken number of wavelengh available on each link o be even. Traffic in he Inerne i repore o be bury in naure [3]. We conier bury raffic wih Pareo (α =.) iribue bur lengh an Pareo (α =.) iribue iner-arrival ime. We inclue he overall bur lo for he propoe cheme wih hree channel elecion algorihm, in Fig. 6 an compare wih PPJET. I i oberve from Fig. 6 ha he overall bur lo in our cheme i lower han ha in PPJET. Of he propoe channel elecion algorihm, LRU algorihm give lower overall bur lo, an PS give higher. The higher overall bur lo in PS i ue o he higher low prioriy bur lo. We generae many more reul hrough imulaion by varying variou parameer; he eaile reul will be preene uring he conference LRU FF PS PPJET bur blocking probabiliy loa (Erlang) Fig. 6. Overall bur lo in he propoe cheme wih ifferen channel elecion algorihm an PPJET. Pareo iribue bur-ize an Pareo iribue iner-arrival of bur i coniere 5 Concluion In hi paper, we propoe a conenion reoluion cheme for OBS nework. The cheme ake he following hree parameer prioriy, number of hop ravere an bur-ize - ino accoun o reolve conenion. The propoe cheme i aapable o boh prioriize an elay conrain raffic. We alo propoe hree channel elecion algorihm calle, LRU, FF an PS algorihm o elec aa-channel a he ingre rouer for he propoe cheme. We imulae our cheme wih each of he channel elecion algorihm an compare he reul wih PPJET. We conier bury raffic in our imulaion. Simulaion were carrie ou for prioriize raffic. We oberve ha LRU channel elecion algorihm give lower overall bur lo. In aiion, Prioriy Se channel elecion algorihm give he lowe high prioriy bur lo. We compare our cheme wih anoher conenion reoluion cheme calle PPJET. We foun lower overall blocking probabiliy in our propoe cheme uing LRU han

10 38 A.K. Turuk an R. Kumar PPJET for all loa. The propoe cheme uing PS channel elecion algorihm give he lower blocking for high prioriy raffic han PPJET. Thu we can conclue ha if a lower overall bur lo i require hen our cheme wih LRU elecion algorihm can be ue. If a low blocking of high prioriy raffic i eire hen he propoe cheme wih PS algorihm may be he choice. The lower blocking in our cheme come wih an aiional elay. In PPJET an incoming bur i elaye for an amoun of ime which i equal o he oal proceing ime of he conrol oken a each noe. However, in our cheme an aiional elay which i equal o he propagaion ime beween ource o einaion, i involve. Reference. Yao, S., Yoo, S.B., Mukherjee, B., Dixi, S.: All-Opical Packe Swiching for Meropolian Area Nework: Opporuniie an Challenge. IEEE Communicaion Magazine 39 (200) Chlamac, I., Ganz, A., Karmi, G.: Lighpah Communicaion: An Approach o High Banwih Opical WAN. IEEE Tranacion on Communicaion 40 (992) Dua, R., Rouka, G.: A Survey of Virual Topology Deign Algorihm for Wavelengh Roue Opical Nework. Opical Nework Magazine (2000) Yoo, M., Qiao, C.: Opical Bur Swiching (OBS) - A New Paraigm for an Opical Inerne. Journal of High Spee Nework 8 (999) Qiao, C., Yoo, M.: Choice, Feaure an Iue in Opical Bur Swiching. Opical Nework Magazine (2000) Yoo, M., Qiao, C., Dixi, S.: QoS Performance in IP over WDM Nework. IEEE Journal on Selece Area in Communicaion, Special Iue on Proocol for Nex Generaion Opical Inerne 8 (2000) Kim, H., Lee, S., Song, J.: Opical Bur Swiching wih Limie Deflecion Rouing Rule. IEICE Tran. Commun. E86-B (2003) 8. Vokkarane, V.M., Zhang, Q., Jue, J.P., Chen, B.: Generalize Bur Aembly an Scheuling Technique for QoS Suppor in Opical Bur-Swiche Nework. In: Global Telecommunicaion Conference, 2002, GlOBECOM 02. Volume 3. (2002) Zhang, Q., Vokkarane, V.M., Chen, B., Jue, J.P.: Early Drop Scheme for Proviing Abolue QoS Differeniaion in Opical Bur-Swiche Nework. In: Workhop on High Performance Swiching an Rouing, 2003, HPSR. (2003) Farahman, F., Jue, J.P.: Look-ahea Winow Conenion Reoluion in Opical Bur Swiche Nework. In: Workhop on High Performance Swiching an Rouing, 2003, HPSR. (2003) Düer, M., Bayvel, P.: Analyi of a Dynamically Wavelengh-Roue Opical Bur Swiche Nework. Journal of LighWave Technology 20 (2002) Kaheel, A., Alnuweiri, H.: A Sric Prioriy Scheme for Qualiy-of-Service Proviioning in Opical Bur Swiching Nework. In: Proceeing of he Eigh IEEE Inernaional Sympoium on Compuer an Communicaion (ISCC 03). (2003) Paxon, V., Floy, S.: Wie Area Traffic: The Failure of Poion Moeling. IEEE/ACM Tranacion on Neworking 3 (995)