PARNIAN: A TWO-STAGE NESTED-AUCTION FOR DYNAMIC BANDWIDTH ALLOCATION IN ETHERNET PASSIVE OPTICAL NETWORKS *

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1 IJST, Transactons of Electrcal Engneerng, Vol. 35, No. E1, pp Prnted n The Islamc Republc of Iran, 2011 Shraz Unversty PARNIAN: A TWO-STAGE NESTED-AUCTION FOR DYNAMIC BANDWIDTH ALLOCATION IN ETHERNET PASSIVE OPTICAL NETWORKS * A. R. HEDAYATI 1** AND M. N. FESHARAKI 2 1 Dept. of Computer Engneerng, Scence and Research Branch, Islamc Azad Unversty Hesarak, Poonak Sq., Tehran, I. R. of Iran Emal: ar.hedayat@srbau.ac.r 2 Dept. of Informaton and Communcaton Technology, Malek Ashtar Unversty of Technology Shahd Babae Hghway, Lavzan Ave., Tehran, I. R. of Iran Abstract One of the key challenges n next generaton access networks based on Ethernet Passve Optcal Network (EPON) technology s Dynamc Bandwdth Allocaton (DBA) process. In ths paper we have proposed Parnan, a two-stage nested-aucton for dynamc bandwdth allocaton management n Ethernet Passve Optcal Networks. In the proposed Parnan method, by runnng nested aucton, based on EPON archtecture, the Optcal Network Unts locally optmze the users' bandwdth requests by frst stage aucton and then the Optcal Lne Termnal runs the second stage aucton for allocatng the requested bandwdths dynamcally and effectvely. Smulaton results show that Parnan, n comparson wth the Far Sharng wth Dual Servce Level Agreement (FSD-SLA) and lmted servce Interleaved pollng wth adaptve cycle tme (IPACT) experences more delay, but regardng other qualty of servce parameters such as executon tme, packet loss rato, lne utlzaton, and throughput, t has a better performance. Keywords Dynamc bandwdth allocaton (DBA), ethernet passve optcal network (EPON), aucton theory, qualty of servce (QoS) 1. INTRODUCTION As a result of the sgnfcant ncrease n the number of network users and ther requests for recevng varous types of networkng servces, t s essental to explot the next generaton access networks [1]. One of the major technologes on the wred platform n the development of next generaton networkng s the Ethernet Passve Optcal Network (EPON) technology (Fg. 1) [2]. EPON s a network that conssts of an Optcal Lne Termnal (OLT), as an operatng centre, and several Optcal Network Unts (s), whch are the users whose requests are gong to be dealt wth. In ths network archtecture, the downstream lne from the OLT to the s s a pont to multpont network and the upstream lne from the s to the OLT s a multpont to pont network, where there s a channel shared between the s for sendng the frames based on the MAC layers [1]. The advantages of EPON over the older methods nclude a hgh capacty for confguraton, large scale compatblty, and lower cost of bandwdth allocaton to the users [3]. Therefore, development of EPON technology has been the center of attenton of many researchers as one of the best and most sutable ways for creatng the next generaton access networks [4]. The recognton of bandwdth bottleneck s mportant not only for research relablty, but also for the successful mplementaton of access networks that wll be desgned for the survval of communcatons and keepng the next generaton access network actve on the "last mle" communcaton network areas [5]. Receved by the edtors October 27, 2010; Accepted Aprl 19, Correspondng author

2 46 A. R. Hedayat and M. N. Fesharak Fg. 1. EPON s archtecture The dynamc allocaton of bandwdth and the effcent tme management for sendng the s requested frames are two essental ssues that the EPON technology has developed n order to prevent data nterference and queung up the members at any tme. All the current methods based on the EPON archtecture are desgned as ether dynamc or statc [6]. In ths paper, a new dynamc bandwdth allocaton method s proposed based on two-stage nestedaucton [7] mechansm. Bandwdth auctonng methods have been proposed before n whch bandwdth s assgned to a node/port based on the bds that are submtted by all the nodes/ports n the network. The node that submts the hghest bd s the allocated bandwdth. To ensure the success of such a method, the bddng s done ahead n tme and s also arbtrated through a central authorty. In ths approach, two stages of aucton [8] are conducted between the users and the s separately. The bandwdth allocaton s performed by runnng aucton n two stages, one for the s under the OLT Control and another for the users under the s admnstraton. In the Proposed method Dynamc bandwdth allocaton automatcally occurs n Inter- and Intra- levels of EPON technology. The rest of ths paper s organzed as follows: In secton 2, some mportant DBA methods wll be brefly analysed based on EPON archtecture. Secton 3 covers the Parnan method n detal. Secton 4 presents smulaton results and dscusson. Fnally, the concluson wll be n secton RELATED WORK Currently, varous methods are desgned based on the EPON technology and can be classfed nto statc bandwdth allocaton and dynamc bandwdth allocaton methods [9]. In statc bandwdth allocaton methods each s allocated a tme slot wth a fxed length that requres no bandwdth negotaton and s due to the burstng nature of the network traffc [9]. Ths, however, may result n a stuaton n whch some tmeslots are overflowed even under very lght loads, causng packets to be delayed for several tmeslots, whle other tmeslots are not fully used, even under very heavy traffc, leadng to an under-utlzed upstream bandwdth. Thus, the statc allocaton s not preferred [10]. In dynamc bandwdth allocaton methods used to ncrease the bandwdth utlzaton, the OLT must dynamcally allocate a varable tmeslot to each based on the nstantaneous bandwdth requests of the s. Gven that Qualty of Servce (QoS) s the man concern n EPONs, these methods are classfed nto DBA wthout QoS support and DBA wth QoS support [11]. In order to dynamcally allocate bandwdth wthout QoS support, several algorthms have been developed based on pollng whch are centered around the OLT. One of these algorthms s nterleaved pollng wth adaptve cycle tme (IPACT) whch dynamcally responds to the s requests through the OLT s pollng functon. Three types of servces are offered by the IPACT method ncludng constant servce, gate servce, and lmted servce [10]. Ths method has been extended and mproved wthn the IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011

3 Parnan: A two-stage nested-aucton for dynamc bandwdth 47 followng algorthms: IPACT wth Smallest Avalable Report Frst (SARF) [12], nterleaved pollng wth adaptve cycle tme and grant estmaton (IPACT-GE), and Estmaton-based dynamc bandwdth allocaton [13]. Another DBA wthout QoS support method s the Bandwdth guaranteed pollng (BGP) algorthm whch has been developed to guarantee the bandwdth allocaton n the EPON archtecture [14]. In ths method, all of the s are dvded nto ether s wth a guaranteed bandwdth or s wthout a guaranteed bandwdth. However, OLT s stll responsble for bandwdth allocaton based on the pollng functon, where all of the s are gven a constant pollng tme and are then assgned a constant bandwdth accordng to the servce level agreement [15]. Ths method causes a reducton n the delay, although more guard tme s needed nbetween the allocatons whch wll eventually result n reduced lne utlzaton. Therefore, all the current methods are sutable for the best effort traffc [11]. In the EPON system only some of the receved data traffc types are based on the best effort and the rest are spontaneous types of traffc such as sound, vdeo, etc. whch mght face lmted bandwdth, delay n packet transfer, and delay jtter. Therefore, to tackle these challenges, the DBA approaches wth QoS support are needed. One of the major methods n ths category s Far Sharng wth Dual Servce Level Agreement (FSD-SLA) where all of the s that requre lower bandwdth are gven a hgher prorty and bandwdth allocaton occurs n a tme perod wthn the upstream level. On the other hand, the s wth greater bandwdth requests are gven a lower prorty. Ths method s based on the servce level agreement, although the major ssue n ths approach s starvaton, whch s nevtable durng the second level of the servce level agreement. Thus, to overcome ths ssue Mn-Max algorthm s exploted to allocate the bandwdth n a more justfed manner [15]. Another method under the DBA wth QoS support s Lmted sharng wth traffc predcton (LSTP) whch uses adapted mechansms to allocate the bandwdth n a more effectve way. Ths method can predct the traffc based on the watng perod for recevng a bandwdth, or n other words, the bandwdth allocaton can be calculated based on the prevous tme perods of the traffc. Therefore, the s requests for bandwdth allocaton are comprsed of an estmated queue length whch can then be used by the OLT n order to allocate a share of an upstream bandwdth for data transfer. Consequently, the delay and the packet loss rato wll be reduced [16]. Other algorthms classfed as DBA wth QoS servce nclude Class-of-Servce-orented Packet Schedulng (COPS) [17], Hybrd Grantng Protocol (HGP) [18], Dynamc Bandwdth Allocaton wth Multple servces (DBAM) [19], Two-layer bandwdth allocaton [20], Lmted allocaton wth excess dstrbuton [21], Queue-based dynamc bandwdth allocaton [22], QoS-aware dynamc bandwdth allocaton [23], Intra- bandwdth schedulng [24], Intra- bandwdth allocaton [25], Fne schedulng [26], Prorty-based dynamc bandwdth allocaton for emergency handlng [27], Admsson control for QoS protecton [28], and Far bandwdth allocaton usng effectve multcast traffc share [29]. 3. THE PROPOSED PARNIAN METHOD The Parnan dynamc bandwdth allocaton method (Fg. 2) s based on two-stage nested-aucton under the EPON network. The bandwdth allocaton s performed by runnng aucton n two stages, one for the s under the OLT management and another one for the users under the s control. The proposed method organzes the aucton n two stages by the OLT and the s. Therefore, n order to further descrbe ths method, each stage wll be explaned separately: June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1

4 48 A. R. Hedayat and M. N. Fesharak Fg. 2. Overall desgn of the proposed Parnan method a) Frst stage The frst stage aucton s performed by the s. Overall, the man steps of the frst stage n the Parnan method (Fg. 3) are lsted as follows: Frst step: Announcng the aucton by the s for recevng the bandwdth allocaton requests from the users and submttng the ntal condtons to them. Second step: Analyzng the ntal aucton condtons by the users and announcng the bandwdth requests parameters to s n order to run the frst stage aucton for users. Thrd step: Evaluatng the receved requests from the users, runnng aucton, and selectng the wnners followed by producng a lst of s wth wnner users for the second stage of the nested-aucton. Fourth step: Forwardng the relevant s n the thrd step to the second stage of aucton and generate the users lst whch dd not wn n the frst stage of the aucton. Fg. 3. Overall desgn of nested-aucton s frst stage n the proposed Parnan method In the frst step of the frst stage n nested aucton, s submt the condtons of the aucton to all the users, ncludng the allocated tme slot to each user n order to send ther requests for partcpatng n the frst step of nested-aucton, the maxmum buffer avalable for the, and the tme requred for to respond to users. In the second step of the frst stage n nested-aucton, the users send ther requests, whch are parametrc bd values, to the s after evaluatng the frst step condtons. The bd value s comprsed of three parameters ncludng the user s cost functon, requested bandwdth, and prorty, whch are llustrated n Eq. (1-3). IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011

5 Parnan: A two-stage nested-aucton for dynamc bandwdth 49 Bd Re q ( t) = α( π ( t), BW ( t),pr ( t)) (1) In Eq. (1), π () t s the cost functon that the j th user from announces for the requested bandwdth Req and BW () t s the requested bandwdth of the j th user from at tme t. Eq. (2) shows the value of user π () t, where the Pr ( t ) s the prorty of the j th user from whch has requested a bandwdth through the. Pr ( t) π ( t) = Re q (2) BW ( t) D ( t) In Eq. (2), Re q BW () t shows the requested bandwdth of the j th user from and D s the maxmum delay that can expect to receve the requested servce or, n other words, the tme length that s requred for the j th user from to receve a response. Moreover, n ths method, for a more effectve smulaton, four levels of traffc prorty have been proposed whch are crtcal, hgh, medum, and low. One of the major advantages of ths method s that the ncreased levels of traffc prorty wll not affect the functon of the algorthm and, therefore, dfferent prorty levels can be mantaned. Furthermore, all of the s are gven a smlar level of prorty. Table 1 llustrates these prorty levels. Table 1. s prorty Prorty Crtcal Hgh Medum Low Value Fnally, n Eq. (2) BW Re q () t s equal to: Re q Frame Frame () BW t = m L (3) Frame Where the m shows the number of requested frames of the j th Frame user from and L s the length of the frames sent by the j th user of. In the thrd step of the frst stage n nested aucton, calculates users bds regardng the receved requests, runs the frst stage n nested aucton, and evaluates each user based on the frst-prce aucton theory. Fnally, the users who have the greatest value of not more than the maxmum buffer capacty of the are selected. In the fourth step of the frst stage n nested aucton, to ncrease the success rate for the users who were not successful n ths stage and prevent ther starvaton, a credt-based mechansm s developed to calculate and store ths type of users new cost functon. To acheve ths, the cost functon s calculated for ths type of user and the new receved requests wthn the next tme perod (Eq. (4)). Where λ equals π () t = [1 + λ] π ( t 1) (4) λ = thre [ π ( t 1)] π ( t 1) (5) w w In Eq. (5), thre s the lowest bd of wnner users who have won n the prevous step. The requested bandwdths are not allocated to the users at ths stage and the wnner s requests wll be stored n a separate buffer. However, the bandwdth wll be allocated n the second stage of nested aucton to the wnner users. Fgures 4 and 5 show the pseudo code and overall executon of the frst stage of nested aucton n Parnan. June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1

6 50 A. R. Hedayat and M. N. Fesharak Fg. 4. Pseudo code for frst stage of nested-aucton n Parnan Fg. 5. Overall executon process n the frst stage of nested-aucton IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011

7 Parnan: A two-stage nested-aucton for dynamc bandwdth 51 b) Second stage The second stage n nested-aucton s performed by the OLT. In ths stage, aucton s beng managed by the OLT whch responds to the bandwdth requests of the s relatve to ther prorty and the maxmum tme they can wat to receve the requested bandwdths. Overall, the man steps n the second stage of nested-aucton n the Parnan method (Fg. 6) are lsted as follows: Frst step: Announcng the aucton by the OLT for the allocaton of s requested bandwdths and submttng the second stage aucton condtons to the s. Second step: Analyzng the ntal aucton condtons by s and announcng the bandwdth requests parameters from s to the OLT. These parameters are the maxmum watng tme of an to receve a servce, the requested bandwdth of an, and the s prorty. Thrd step: Evaluatng the receved requests from the s, runnng aucton, and selectng the wnner s followed by producng a sub-lst from wnners of the second stage n the two-level nested-aucton process. Fourth step: Allocaton of the requested bandwdths to the wnner s and montorng the bandwdth under use. Ffth step: Repeat frst stage of nested-aucton. Fg. 6. Overall desgn of the second stage of nested-aucton n the proposed Parnan method The second stage of the algorthm n the proposed Parnan method s dscussed n more detal here. In the frst step of the second stage n nested-aucton, OLT submts the condtons of the aucton to all the s, ncludng the allocated tme slot that each s gven n order to send t s requests, the maxmum bandwdth avalable from the OLT, and the tme requred for the OLT to respond to the receved requests. In the second step of the second stage n nested-aucton, the s send ther requests to the OLT as parametrc bd values after evaluatng the condtons of the aucton. The relatonshp between varous parameters and the fnal bd value s demonstrated n Eq. (6), (7) and (8). Req βπ Bd () t = ( (), t BW ()) t (6) In Eq. 6, π () t s the cost that announces for the requested bandwdth and BW requested bandwdth of at tme t. Req () t s the June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1

8 52 A. R. Hedayat and M. N. Fesharak Pr ( t ) () t Req π = BW () t D () t (7) Equaton (7) shows the value of π () t, where Pr ( t ) s the average prorty of the users who have sent ther bandwdth requests to the. In order to smplfy the calculatons and load reducton, the prorty of users s determned based on the type of ther requested traffc whch provdes a far and equal stuaton. Eq. (8) shows the prorty of Req Pr j= Pr ( t) = 1 (8) k Addtonally, n Eq. (7) BW () t s equal to the maxmum requested bandwdth that has been announced to the s by the users dependent on ther type usage. It has also been assumed that the buffer has a lmted capacty for recevng the submtted requests from the users. Eq. (9) shows the requested bandwdth of. m BW () t = BW () t (9) Req Fnally, n Eq. (7), the D () t value s the maxmum delay that can expect to receve the requested servce or, n other words, the maxmum tme length that the can use to respond to the users requests (Eq. (10)). D ( t) = mn D ( t) (10) IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011 k j = 1 = 1 j Req [ ] user Here, t s necessary to explan the mnmum D () t n Eq. (10), snce the mnmum latency used to receve the requested servce has to employ the maxmum or average servce desperaton tme that exsts between users wll cause users to lower ths lmt. Watng tme has never receved the requested bandwdth and we can see starvaton n ths method. In the thrd step of the second stage n nested-aucton, OLT evaluates the requests receved from the s. Ths evaluaton s medated by ntally confrmng whether at least one submtted a request or not. If the above was confrmed, a lst of all the s who have requested to partcpate n the aucton s generated, wth the assumpton that they are currently dle. Ther bd values are then calculated and ' examned wth the frst prce aucton theory. At ths step, K number of s are selected as the wnners of the second stage n nested-aucton and then, n the fourth step of the second stage n nested-aucton, the bandwdth s allocated wth the only condton that the total requested bandwdth of the wnners should be less than or equal to the maxmum avalable bandwdth offered by the OLT. Ths has been further llustrated n Eq. (11). k W = 1 Req w ABW () t BW () t (11) OLT In Eq. (11), ABWOLT () t s the bandwdth avalable to the OLT and BWw () t s the requested bandwdth of the wnner s. Furthermore, n order to ncrease the effcency of lne utlzaton and robustness n the proposed method, f there was more bandwdth avalable than the total allocated bandwdth to the wnners, there would be another round of aucton between the s who could not wn earler. The remanng bandwdth s then allocated to the second round wnners of the second stage n nested-aucton. However, there could be no wnners. Req

9 Parnan: A two-stage nested-aucton for dynamc bandwdth 53 In the fourth step of the second stage n nested-aucton, OLT also montors the bandwdth under use. Ths part of the fourth step from the second stage s called servce tme level n the Parnan method, where OLT stands by untl a part of the earler allocated bandwdth becomes free and can be offered by the OLT n another round of nested-auctonng. The mnmum level of bandwdth requred for rentatng the nested-aucton s defned as the bandwdth threshold (Eq. (12)). A threshold Allocated TBWOLT ( t 1) 1 ABWOLT ( t) 3 = 0 Otherwse (12) In Eq. (12), A threshold defnes the tme of rentatng the nested-aucton, whch s a Boolean value and Allocated TBWOLT s the total allocated bandwdth to the s n the prevous round of aucton. Fgures 7 and 8 show the pseudo code and the overall executon process for the second stage of nested-aucton n the Parnan method. Fg. 7. Pseudo code for second stage of nested-aucton n Parnan June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1

10 54 A. R. Hedayat and M. N. Fesharak Fg. 8. Overall executon process n the second stage of nested-aucton The assessment of Farness ndex n the Parnan method s most dffcult when most of bandwdth requests are from the users wth the hghest prorty level or when the users watng tme to receve bandwdth s very lmted. 4. SIMULATION RESULTS In order to compare the performance of Parnan wth other dynamc bandwdth allocaton methods, a C++based EPON smulator s desgned. In the smulaton process, a multpont to pont network, based on the EPON archtecture s used. Table 2 shows the smulaton parameters. IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011

11 Parnan: A two-stage nested-aucton for dynamc bandwdth 55 Table 2. Smulaton parameters Parameters Value Number of s 16 Amount of bt rate for ` to OLT` connecton 5 to 57.5 Mbt/s Two-way fber delay 200 µs Packet sze Byte (30 Packets) Ethernet overhead 38 Byte Request message sze 570 Bt Upstream bandwdth 1 GBt/s Maxmum transton wndow 10 Packets Guard tme 5 µs Max cyclng tme 2 ms Buffer capacty 10 Mbyte Traffc type CBR, VBR The proposed Parnan method has been compared to FSD-SLA and "lmted servce" IPACT. The comparson was done based on QoS parameters such as delay, throughput, packet loss rato and lne utlzaton. Besdes, the executon tme of ths method has also been compared wth other methods. The values of the parameters that are set for the smulaton of varous models are the values that are used n the smulatons desgned n recent bandwdth allocaton methods. Furthermore, n order to ncrease the credblty and accuracy of smulatons for the Parnan method, smlar parameters were chosen to those used n IPACT and FSD-SLA methods [9, 10, 15, 30 and 31]. The equatons that were used to calculate the QoS parameters n Parnan model have been compared n Table 3, wth the current bandwdth allocaton methods such as "Lmted Servce" IPACT and FSD- SLA. Table 3. Equatons of QoS parameters QoS parameters Equatons DIPACT = DPoll + DGrant + DQueue D POLL = tme between packet arrval and next request sent by that. On average, ths delay equals onehalf of the cycle tme. D GRANT = tme nterval from an s request for a transmsson wndow untl the begnnng of the tmeslot n whch ths frame s to be transmtted. Ths delay may span multple cycles (.e.,a frame may have to skp several tmeslots before t reaches the head of the queue), dependng on how many frames there were n the queue at the tme of the new arrval. D QUEUE = delay from the begnnng of the tmeslot tll the begnnng of frame transmsson. On average, ths delay s equal to half of a slot tme and s nsgnfcant compared to the prevous two components. Delay D = T + D + D FSD SLA Cycle Tme Grant SLA T Cycle-Tme = Maxmum tme cycle duraton. The scheduler at the OLT may schedule bandwdth for a maxmum duraton of T n one teraton of schedulng D GRANT = tme nterval from an s request for a transmsson wndow untl the begnnng of the tmeslot n whch ths frame s to be transmtted. Ths delay may span multple cycles (.e., a frame may have to skp several tmeslots before t reaches the head of the queue), dependng on how many frames there were n the queue at the tme of the new arrval. D SLA = delay for checkng the Prmary and secondary SLA of Requests. D = D + D + D Parnan Announce Aucton Process Allocaton D Announce = Tme to kck off the aucton and submt the bd D Aucton-Process = tme that aucton process was runnng. (Assess and select wnners) D Allocaton = Tme that bandwdth was allocated to the wnners June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1

12 56 A. R. Hedayat and M. N. Fesharak Table 3. Contnued. Packet loss rato Throughput rate N PL N : Number of lost packets. PR : Number of packets receved successfully. ( N PL ) PLR = ( N + N ) Take To Recv Info Tme-Recv = the useful nformaton that needs to be delvered between end-ponts. PL Info TR = Tme Total Recv PR Tme Take-to-Recv = the tme t takes to delver t. Lne utlzaton N: number of s B: guard tme. R: remander. t C : cycle tme U Lne N ( B + ( R / RN ) = 1 ( t ) c Fgure 9a shows the delay comparson for the methods based on CBR traffc. Over the course of runnng aucton, due to the decrease n the number of requests, less calculaton tme s requred and, thus, the behavor of Parnan s approxmately the same as "lmted servce" IPACT. As the number of requests ncreases, more delay wll be expected. As n FSD-SLA, the SLAs whch request the bandwdth should be checked n each tme of the bandwdth allocaton process, thus t consstently has the largest delay. (a). CBR (b). VBR Fg. 9. Comparson of average delay n FSD-SLA, "lmted servce" IPACT, and Parnan Accordng to the use of VBR traffc n the smulaton, Fg. 9b llustrates the comparson between the delay factors of the above methods. It can be observed that there s a delay n the proposed Parnan method at the begnnng of the nested-aucton. Ths s greater snce the calculaton of the requested amount of bandwdth from all s should be accomplshed based on the frst stage algorthm and optmzng the buffer sze before beng sent as a parametrc bd. On the other hand, over the course of runnng the IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011

13 Parnan: A two-stage nested-aucton for dynamc bandwdth 57 aucton, due to the decrease n the number of requests, less calculaton tme s requred and thus, the behavor of the proposed method s approxmately the same as the behavor of the FSD-SLA method. By the end of the thrd step of the proposed method, as the number of requests ncreases, more delay wll be expected. In ths Step, however, FSD-SLA has the greatest delay consstently, whch s due to the greater tme requred for analyzng the SLAs that are receved from the requestng users. Overall, "lmted servce" IPACT has the mnmum delay durng the smulaton. Based on CBR traffc type Fg. 10a llustrates the comparson of packet loss rato. Parnan has the least packet loss rato because s whch can announce more bds n the aucton can wn t, and, based on ther bd they wll receve bandwdth, therefore, transferrng ther packets, whereas n FSD-SLA, analyzng the SLAs shows that the smaller packets are gven hgher prorty and vce versa. Therefore, the larger packets wth lower prorty would be lost. In "lmted servce" IPACT, accordng to the rules, round robn wll be sent out to the s wthout any lmtaton and only n allocated tme slots. So, due to the buffer overflow, "lmted servce" IPACT has the worst packet loss rato n comparson. Fgure 10b demonstrates the packet loss rato n both the IPACT and FSD-SLA methods compared wth the proposed Parnan method. The Parnan method shows a lower level of packet loss rato snce all the users who submt a greater bd value can wn the aucton and receve a bandwdth relevant to ther Bd values, whch have been optmzed based on the frst and second stage of auctonnng, and transfer ther packets. However, n the FSD-SLA approach, through evaluatng the SLAs the smaller packets are gven hgher prorty and vce versa. Therefore, the VBR packets wth lower prorty would be lost. Moreover, n IPACT, accordng to the rules, round robn wll be sent out to the s wthout any lmtaton and only n ther allocated tme slot. Furthermore, as can be notced n Fg. 10b, the packet loss rato s sgnfcantly hgher n the FSD-SLA method snce n ths method, based on the prmary and secondray of SLA concept, the s are only permtted to send small sze packets at a specfed tme slot. Thus, many packets are lost due to over-rdng the tme lmt of recevng the servce. Fg. 10. Comparson of packet loss rato n FSD-SLA, "lmted servce" IPACT, and Parnan Fgure 11a demonstrates the comparson between the throughput rates of the three methods based on transferrng CBR packets. Just as t s notceable n the graphs, n "lmted servce" IPACT, snce a monotonous, stable and steady perod of tme has been gven to all of the s, the throughput rate wll show smlar behavor aganst ncreasng traffc load. The condton of throughput n FSD-SLA s better than "lmted servce" IPACT, but because the allocaton prorty s defned accordng to SLAs wth a lower volume of traffc, the throughput rate s lower at the begnnng and t wll be mproved by ncreasng the traffc load and usng the mn-max soluton. Parnan has the best throughput rate n ths comparson as the bandwdth s allocated n dfferent stages based on the aucton theory, thus creatng a condton for the s to send ther requests for takng part n the aucton. Fgure 11b shows the throughput rate of the VBR packets n the compared methods. As t can be observed, n IPACT, snce a stable perod of tme s gven to each accordng to ts buffer sze, the throughput rate shows a smlar behavor aganst the ncreased traffc load. Therefore, n IPACT, the throughput rate s lower as a result of lack of varety between the allocated bandwdth to the s. June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1

14 58 A. R. Hedayat and M. N. Fesharak Although the condton of throughput n the FSD-SLA s better n comparson wth IPACT, the allocaton prorty s defned accordng to the SLAs wth a lower sze of traffc load. Therefore, the throughput rate s lower at the begnnng and t wll mprove by ncreasng the traffc load and usng the mn-max soluton. On the contrary, our proposed method demonstrates a better throughput rate because the bandwdth s allocated n a more robust manner based on the frst prce aucton theory where the desgned condtons allow all the users wth requests to partcpate n the seccond stage of nested-aucton whch s comprsed of dfferent steps. Ths observed mprovement n the throughput rate s due to the bandwdth allocaton to all the users through ther s, whch s shown to be a better approach n VBR type of traffc. (a). CBR (b). VBR Fg. 11. Comparson of throughput n FSD-SLA, "lmted servce" IPACT, and Parnan Fgure 12a and b shows the comparson for lne utlzaton. As they clearly show, the best lne utlzaton belongs to Parnan, because all the packets are beng sent n dfferent specfc tmes and therefore the lne s beng used at ts best condton. As "lmted servce" IPACT allocates a specfc perod of unlmted tme alternately to each, and because t s possble that n the mentoned perod s mght not have any packet to send, the lne utlzaton s lower than Parnan. The FSD-SLA allocates a hgher prorty to smaller packets and vce versa, thus, t cannot have approprate lne utlzaton n comparson. (a). CBR (b). VBR Fg. 12. Comparson of lne utlzaton n FSD-SLA, "lmted servce" IPACT, and Parnan Fnally, the comparson of the average executon tme between IPACT, FSD-SLA and Parnan models s shown n Fgure 13. Moreover, the parameters requred for the calculaton of average executon tme for each of the above bandwdth allocaton methods are summarzed n Table 4. Table 4. Executon tme parameters Number of s 4-32 Iteraton As t can be notced (Fg. 13), when the number of s s ether 4 or 8, the "lmted servce" IPACT approach has the lowest executon tme amongst all, whch s due to the short supervson tme n ths approach. However, n the Parnan method the length of executon tme s the longest because of the IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011

15 Parnan: A two-stage nested-aucton for dynamc bandwdth 59 nested aucton process. By ncreasng the number of s and consequently ncreasng the length tme requred for ther requests, the smulaton results show that the average executon tme n the Parnan method s more than the other approaches. The reason for the above observaton s due to the fact that n the Parnan method s assess the bandwdth requests of the users after the frst stage of nested aucton and then send them to the OLT for partcpatng n the second stage nested aucton and, therefore, the tme spent at ths method s consdered when the nested aucton s runnng. It can also be observed that the FSD-SLA method has the longest executon tme of all, whch s a result of both supervsng the s and analyzng the SLAs and the traffc prorty of the s wth a bandwdth request. Thus, ths method has the longer executon tme than the "lmted servce" IPACT. Totally, wth the ncreased number of s, Parnan has the best executon tme amongst all. Fg. 13. Comparson of Executon Tme n FSD-SLA, "lmted servce" IPACT and Parnan 5. CONCLUSION Regardng the mportance of dynamc bandwdth allocaton n next generaton access networks based on EPON technology, n ths paper we have proposed Parnan, an optmal DBA method based on aucton theory. In ths new method, the dynamc bandwdth allocaton s performed by runnng aucton n two stages, one for the s under the OLT management and another one for the users under the s control. Smulaton results show that Parnan, n comparson wth FSD-SLA and "lmted servce" IPACT experences more delay, but regardng other qualty of servce parameters such as packet loss rato, lne utlzaton, and throughput, t has better performance. On the other hand, the average executon tme n Parnan method s better than the "lmted servce" IPACT and FSD-SLA approaches and, as a result, t works faster. The future research potental n the dynamc bandwdth allocaton process n EPON networks wll allow us to go further and open new research horzons by utlzng heurstcs methods such as genetcs algorthm, cellular automata, neural networks, and etc. nstead of runnng aucton n user level. Moreover, t would be possble to apply ths new DBA method n W-F and WMax envronments and evaluate the performance. REFERENCES 1. Hedayat, A. R. et al. (2010). Mobna: A novel DBA method based on second prce aucton n Ethernet Passve Optcal Network. IJCNS Journal, Vol. 5, pp Effenberger, F., Cleary, D., Haran, O., Kramer, G., L, R. D., Oron, M. & Pfeffer, T. (2007). An ntroducton to PON technologes. IEEE Communcatons, Vol. 45, No. 5, pp. S17-S Kramer, G. (2005). Ethernet passve optcal networks. McGraw-Hll Professonal. June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1

16 60 A. R. Hedayat and M. N. Fesharak 4. Kramer, G. et al. (2001). Ethernet PON (EPON): Desgn and analyss of an optcal access network. Journal of Photonc Network Communcatons, Vol. 3, No.3, pp Luo, Y. & Effenberger, F. (2009). Ggabt passve optcal network transmsson convergence extenson for next generaton access. ed: Google Patents. 6. Zheng & Mouftah, H. (2009). A survey of dynamc bandwdth allocaton algorthms for Ethernet passve optcal networks. Optcal Swtchng and Networkng, Vol. 6, pp Krshna, V. (2010). Aucton theory. Elsever Academc Press. 8. Schreber, A. Th. et al. (2000). Knowledge engneerng and management: the CommonKADS methodology. Massachusetts Insttute of Technology. 9. Krammer, G., Mukherjee, B. & Pesavento, G. (2002). IPACT: A dynamc protocol for an Ethernet PON (EPON). IEEE Communcatons Magazne, Vol. 40, Issue 2, pp Kramer, G., Mukherjee, B. & Pesavento, G. (2002). Interleaved pollng wth adaptve cycle tme (IPACT): A dynamc bandwdth dstrbuton scheme n an optcal access network. Photonc Network Communcatons Journal (Sprnger), Vol. 4, No.1, pp Byun, H. J., Nho, J. M. & Lm, J. T. (2003). Dynamc bandwdth allocaton algorthm n Ethernet passve optcal networks. IEEE Electroncs Letter, Vol. 39, Issue 13, pp Bhata, S. & Bartos, R. (2007). IPACT wth smallest avalable report frst: A new DBA algorthm for E.P.O.N. Proc. of IEEE ICC'07, Glasgow, UK, pp Zhu, Y. & Ma, M. (2008). IPACT wth grant estmaton (IPACT-GE) scheme for Ethernet passve optcal networks. IEEE/OSA Journal of Lght wave Technology, Vol. 26, Issue 14, pp Ma, M., Zhu, Y. & Cheng, T. (2003). A bandwdth guaranteed pollng MAC protocol for Ethernet passve optcal networks. Proc. of IEEE INFOCOM'03, Vol. 1, pp Banerjee, Kramer, G. & Mukherjee, B. (2006). Far sharng usng dual servce-level agreements to acheve open access n a passve optcal network. IEEE Journal on Selected Areas n Communcatons, Vol. 24, No.8, pp Luo, Y. & Ansar, N. (2005). Lmted sharng wth traffc predcton for dynamc bandwdth allocaton and QoS provsonng over EPONs. OSA Journal of Optcal Networkng, Vol. 4, No. 9, pp Naser, H. & Mouftah, H. (2006). A jont- nterval-based dynamc schedulng algorthm for Ethernet passve optcal networks. IEEE/ACM Transactons on Networkng, Vol. 14, Issue 4, pp Sham, A., Ba, X., Ass, C. & Ghan, N. (2005). Jtter performance n Ethernet passve optcal networks. IEEE/OSA Journal of Lght Wave Technology, Vol. 23, Issue 4, pp Luo, Y. & Ansar, N. (2005). Bandwdth allocaton for multservce accesses on E.P.O.Ns. IEEE Communcatons Magazne, Vol. 43, Issue 2, pp Xe, J., Jang, S. & Jang, Y. (2004). A dynamc bandwdth allocaton scheme for dfferentated servces n EPONs. IEEE Communcatons Magazne, Vol. 42, Issue 8, pp Ass, C. M., Ye, Y., Dxt, S. & Al, M. A. (2003). Dynamc bandwdth allocaton for qualty-of-servce over Ethernet PONs. IEEE Journal on Selected Areas n Communcatons, Vol. 21, Issue 9, pp Choudhury, P. K. & Saengudomlert, P. (2007). Effcent queue based dynamc bandwdth allocaton scheme for Ethernet PONs. Proc. of IEEE GLOBECOM'07, Washngton DC, pp Myosh, H., Inoue, T. & Yamashta, K. (2004). QoS-aware dynamc bandwdth allocaton scheme n Ggabt- Ethernet passve optcal networks. Proc. of IEEE ICC'04, Pars, France, pp Ghan, N., Sham, A., Ass, C. & Raja, M.Y.A. (2004). Intra- bandwdth schedulng n Ethernet passve optcal networks. IEEE Communcaton Letters, Vol. 8, Issue 11, pp IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1 June 2011

17 Parnan: A two-stage nested-aucton for dynamc bandwdth Chen, J., Chen, B. & He S. (2005). A novel algorthm for ntra- bandwdth allocaton n Ethernet passve optcal networks. IEEE Communcaton Letters, Vol. 9, Issue 9, pp Chen, B., Chen, J. & He, S. (2006). Effcent and fne schedulng algorthm for bandwdth allocaton n Ethernet passve optcal networks. IEEE Journal of Selected Topcs n Quantum Electroncs, Vol. 12, Issue 4, pp Moon, B. (2008). Emergency handlng n Ethernet passve optcal networks usng prorty-based dynamc bandwdth allocaton. Proc. of IEEE INFOCOM'08, Phoenx, AZ, pp Dhan, A. R., Ass, C., Maer, M. & Sham, A. (2008). Per-stream QoS and admsson control n Ethernet passve optcal networks (E.P.O.Ns). IEEE/OSA Journal of Lght Wave Technology, Vol. 25, Issue 7, pp Km, N., Lm, H. S. & Kang, M. (2008). Far bandwdth allocaton usng effectve multcast traffc share n TDM-PONs. IEEE/OSA Journal of Lghtwave Technology, Vol. 26, No. 7, pp Soleyman, S. et al. (2007). A new approach for bddng strategy of gencos usng partcle swarm optmzaton combned wth smulated annealng method. Iranan Journal of Scence & Technology, Transacton B: Engneerng, Vol. 31, No. B3, pp Tabataba vakl, V. & Azmnejad, A. (2004). A new dynamc channel allocaton scheme based on compact pattern concept wth pattern restoraton. Iranan Journal of Scence & Technology, Transacton B: Engneerng, Vol. 28, No. B3, pp June 2011 IJST, Transactons of Electrcal Engneerng, Volume 35, Number E1