Performance Bounds for P2P Streaming System with Transcoding

Transcription

1 Appl. Math. Inf. Sc. 7, No. 6, Appled Mathematc & Informaton Scence An Internatonal Journal Performance Bound for P2P Streamng Sytem wth Trancodng Shua Zeng 1,, Lemn L 1 and Dan Lao 2 1 School of Communcaton and Informaton Engneerng, Unverty of Electronc Scence and Technology of Chna, Chengdu, Chna 2 Inttute of Electronc and Informaton Engneerng n Dongguan, UESTC, Chengdu, Chna Receved: 6 Apr. 2013, Reved: 10 Aug. 2013, Accepted: 11 Aug Publhed onlne: 1 Nov Abtract: In th paper, we develop a flud model that ee to expoe the fundamental charactertc and mathematcal theory of peerto-peer treamng ytem wth trancodng. We fnd out and prove that, to provde peer recevng data above ome flow rate, there a lower bound of erver upload bandwdth n th nd of ytem. We gve a flow rate ocaton algorthm to acheve the mnmal erver upload bandwdth n the proof. We compare th lower bound wth the mnmal demand of erver upload bandwdth of no trancodng ytem. And, we prove that, the demand of erver upload bandwdth n trancodng peer-to-peer treamng ytem ung the propoed algorthm the neceary not uffcent condton for the no trancodng one. At lat, we gve the mulaton experment to how the dfference of erver load n trancodng and no trancodng ytem. Keyword: Peer-to-peer Networ, Networ Optmzaton, Flow Rate Allocaton, Streamng Sytem. 1 Introducton Wth the popular of peer-to-peer P2P treamng, peer become more and more complex. Thee clent, uch a PC, TV, tablet, PDA, cellphone, and o on, have varou creen ze, color depth and multmeda qualte. Specy, they may have dfferent multmeda codng algorthm wth heterogeneou hardware and oftware, and they may have dfferent bandwdth wth heterogeneou networ [1, 2]. In tradtonal P2P multmeda treamng ytem, one ngle overlay networ or erver cannot upport of thee clent. However more networ and erver may need more reource. In recent year, there are ome lterature whch tude on trancodng or named peer-ated trancodng [4] technque utlzed n P2P treamng ytem. [3] propoe a multmeda treamng archtecture n whch trancodng ervce coordnate to tranform the treamng data nto dfferent format n P2P ytem. [4] propoe a ytem named PAT Peer-Ated Trancodng to enable effectve onlne trancodng and ee to reduce the bandwdth conumpton and computng overhead n P2P networ. In [5], the trancodng technque ued n ome total new networ envronment. The paper dcue ue that are relevant to enablng P2P treamng n networed conumer electronc, NAT/frew traveral, and codec nflexblty. [6, 9] alo dcue the vdeo trancodng n P2P networ of IPTV ytem. [7] propoe a P2P trancodng method for heterogenety moble treamng. The paper ee to ncreae the flexblty of codng data, whch bae on dvere dplay ze, computng power, memory, and meda capablte n devce. [8] degn a trancodng ytem for P2P treamng baed on farmng computng archtecture. [2] ummarze and categorze the P2P treamng ytem wth trancodng by dfferent networ envronment and trancodng ervce place. [10] preent a P2P treamng ytem named CloudStream, whch a cloud-baed vdeo proxy that can delver treamng vdeo by trancodng the orgnal vdeo n real tme to a calable codec. And [11] propoe a collaboratve trategy that leverage the peerng archtecture of P2P networ and mae the computatonal reource of peer harable and collaboratve. Thee reearche announce that, compared wth tradtonal degn, P2P treamng ytem wth trancodng have better performance n ome tuaton, uch a heterogeneou drver, varou multmeda codng, peer churn, and o on. Neverthele, extent tude jut focu on networ protocol degn and Correpondng author e-mal: mallnger@gmal.com

2 2478 S. Zeng et al: Performance Bound for P2P Streamng... multmeda codng algorthm, whch lac of mathematcy nvetgate and deeply undertand ther ytem n networ flud theory. Even more mportantly, there ext no relatve reearch that focue on what condton the trancodng ut and how much beneft exactly n quantty the new technque taen to the ytem. In th paper, we are ntereted n the bac flud theory for P2P treamng ytem wth trancodng. We develop a flud model that ee to expoe ome fundamental charactertc and lmtaton of P2P treamng ytem wth trancodng. There are ome lterature that dcue and analyze the ue of P2P treamng ytem upload bandwdth by mathematc flud model n varou tuaton. [12] develop a bac tochatc model and flud theory for the typcal P2P treamng ytem. [13] derve and prove the performance bound for mnmum erver load and maxmum treamng rate n P2P treamng ytem. [14, 15, 16] dcue the ue of achevable treamng rate n P2P treamng ytem wth multple multmeda channel. [17] provde a taxonomy of P2P treamng ytem, dependng on whether the gven topology a full meh graph or an arbtrary graph, whether the number of peer a node can have bounded or not, and o on. In thee dfferent tuaton, the paper dcue the maxmum rate achevable by recever repectvely. And n [18], the author develop a flud model for P2P treamng ytem wth networ codng and mathematcy analyze the performance of th nd of ytem. In th paper, our analy and reult are baed on both prevou reearch and the feature of P2P treamng ytem wth trancodng. Furthermore, we compare P2P treamng ytem wth trancodng wth no trancodng ytem both n mathematcal analy and mulaton experment. The remander of the paper organzed a follow. Secton 2 decrbe and nt the bac model of P2P treamng ytem wth trancodng. In Secton 3, we compute and prove the mnmal bandwdth demand of erver for gven flow rate of peer, and we gve an algorthm to acheve th mnmal load n the proof. We alo compare th mnmal value wth the one n no trancodng tuaton n th ecton. And we gve our mulaton reult n Secton 4. Fny, we conclude th paper and dcu future wor n Secton 5. 2 Model and Algortm P2P treamng ytem wth trancodng can upport multple multmeda codng rate n one overlay networ. For brevty, ue TRANSCODING to mean P2P treamng ytem wth trancodng n the remander of th paper. A hown Fgure 1, n a TRANSCODING, ytem dvded nto everal regon. In the ame regon, peer receve the ame multmeda codng data. Th mean every regon ha a certan codng rate. We c a TRANSCODING an m-regon ytem when there are m regon lvng n the ytem. By the order of regon 1 regon 2 regon 3 Fg. 1: Example of P2P treamng ytem wth trancodng. multmeda qualty, we denote by r = 1,...,m for the codng rate of the regon, and we c a regon rego, when ther codng rate r. A peer n regon can play multmeda program moothly whet receve freh data bt from ytem at leat at rate r. Defnton 1. In an m-regon TRANSCODING, partcpatng peer receve the multmeda data at leat at rate r = 1,...,m of ther own regon, we ay that the ytem provde general unveral treamng GUS or the ytem run on GUS. A we now, the eental purpoe of P2P treamng ytem to enure QoE, whch peer recevng multmeda data from the ytem above multmeda codng rate, and, at the ame tme, mnmze the erver bandwdth conumpton. Denote by for the mnmal demand of erver upload bandwdth guaranteeng the ytem provdng GUS. Notce the defnton of unveral treamng US n [12]. That an m-regon TRANSCODING can provde GUS mean that every ubytem of regon r = 1,2,...,m can provde US. Compared wth the tradtonal P2P treamng ytem, whch commtted to mnmze the demand of erver for provdng US, th paper ee to fnd u mn. Before gvng u mn next ubecton, we contnue to ntroduce ome relatve notaton and expreon of the ytem model. In our ytem, there one erver and total n peer n m regon. Let P be the et of peer. Let be the number of peer n rego and P be the et of peer n rego. Denote by for the erver and p for the jth peer n rego. We have P= { p }, f or,...,m; j= 1,...,n P = { p }, f or j= 1,...,n n= P = m, = P Denote by R for the et of codng rate n the ytem, whch R = {r 1,...,r m }. A the aumpton mentoned n prevou ecton, we have that the r = 1,...,m 1

3 Appl. Math. Inf. Sc. 7, No. 6, / codng data can be trancoded to r R : > codng data by the peer n rego. Denote by u for the upload bandwdth of and u for the upload bandwdth of p. Let u be the functon of upload capacty ummaton. For example, up = u = m P u. Let u be the average upload bandwdth of peer and u be the average upload bandwdth of peer n rego. We have u= up P = u = up P m u = n u Other notaton ntroduced n the ytem model are ummarzed n Table 1. We gve the proof of u mn th ubecton. We dvde the proof nto two part. We gve a bound for u mn part one and prove GUS can be upported wth th bound n part two. Notce that part two alo a flow rate ocaton algorthm to acheve the mnmal erver load the mnmal demand of erver upload bandwdth of TRANSCODING. Theorem 1. Let u mn denote mnmal bandwdth demand of erver for a m-regon TRANSCODING provdng GUS, then u mn = max n r u n 0 = r 0 = u 0 = r m+1 = 0,,...,m+1 Proof: Part one: Notce that for the whole ytem P = m, 1 obvouly u mn r 1. And for the ubytem P, t u mn +n 1 u 1 r 1 r 2, where regon 1 at leat cot n 1 r 1 u 1 bandwdth. By analogy, for the ubytem m P =2,...,m, u mn + n u r r.. And for = the whole ytem, we have u mn + m u r 0. Therefore u mn r 1 u mn n r u, f or =2,...,m 2 u mn m r u For convenence, let n 0 = r 0 = u 0 = r m+1 = 0. Then, combnng thee three nequalte gve u mn max n r u n 0 = r 0 = u 0 = r m+1 = 0,,...,m+1 m =2 P,, 3 It reman to how that f u = max n r u n 0 = r 0 = u 0 = r m+1 = 0,,...,m+1, 4 then GUS can be upported. Part two: Let P0 ={}. Conder the ubytem P0 P1 frtly. When r 1 n 1 r 1 u 1,.e. r 1 n 1 u 1 n 1 1. Conder a multmeda tream of rate r 1. Dvde th multmeda tream nto n 1 ubtream, wth the jth ubtream havng rate o 1 j = u 1 j r 1 up1 = u 1 j r 1 n 1 u 1, f or j= 1,...,n 1 Notce that n 1 o 1 j = r 1 u. So the erver can copy the jth ubtream to the p 1 j repectvely. Furthermore, becaue n 1 1 o 1 j = n 1 1u 1 j n 1 u 1 r 1 n 1 1u 1 j n 1 u 1 n 1 u 1 n 1 1 = u 1 j, p 1 j can copy t tream to each of the other n 1 1 peer n regon 1. Thu each peer n regon 1 receve a ubtream from the erver and alo receve n 1 1 addtonal ubtream from the other n 1 1 peer n the ame regon. The total rate at whch p 1 j receve n 1 tr 1 j = o 1 j + o 1 = : j o 1 j = r 1 Hence the rate r 1 can be upported n regon 1, whch mean, n th tuaton, the ytem can provde US for regon 1. When r 1 < n 1 r 1 u 1. In th tuaton, dvde the multmeda tream nto n 1 +1 ubtream, wth th ubtream havng rate { o 1 j = u 1 j n 1 1, f or j= 1,...,n 1 o 1n 1 +1 = r 1 up1 n 1 1 = r 1 n 1 u 1 n 1 1 And the erver copy two ubtream to each peer n regon 1: the jth ubtream o 1 j and the ubtream o 1n The erver can do th becaue n 1 o 1 j + n 1 o 1n 1 +1 = n 1 u 1 n n 1 Furthermore, becaue n 1 1 o 1 j =n 1 1 = n 1 r 1 u 1 u r 1 n 1 u 1 n 1 1 u 1 j n 1 1 = u 1 j, f or j= 1,...,n 1 p 1 j can copy t tream o 1 j to each of the other n 1 1 peer n regon 1. Thu each peer n regon 1 receve two

4 2480 S. Zeng et al: Performance Bound for P2P Streamng... ubtream from the erver and alo receve n 1 1 addtonal ubtream from the other n 1 1 peer n the ame regon. The total rate at whch p 1 j receve n 1 tr 1 j = o 1n o 1 j + o 1 = o 1n : j o 1 j = r 1 Hence the rate can be upported n regon 1, whch mean, when r 1 < n 1 r 1 u 1, the ytem can provde US for regon 1 alo. Then, whether r 1 n 1 r 1 u 1 or r 1 < n 1 r 1 u 1, the 1-regon ubytem P0 P1 can run on GUS, and the total ret of avalable upload bandwdth u = u + n 1 u 1h = u +n 1 u 1 r 1 r 2 Next, we conder the ubytem P, f or = 2,..., m. Notce that, the total ret of avalable upload bandwdth of P = + =u + n u r And a 4, we have r. When r r u,.e. r u 1. Conder a multmeda tream of rate r, whch can be trancoded from the tream of rate r, f or,...,. Dvde th multmeda tream nto ubtream, wth the jth ubtream havng rate o = u up u r = u u u + n u r r, f or j= 1,..., And dvde th multmeda tream nto ubtream, wth the jth ubtream havng rate = u Notce that up o = r = u u u up u u + n u r r = r, f or j= 1,..., r. A r, we have o u. So the erver can copy o to the p j= 1,..., repectvely. And, a = u up u r = r p g = 1,...,;h = 1,..., can copy to p j = 1,..., repectvely. So p j= 1,..., get o + = u Furthermore, becaue 1 o + up u = u r up n u u u r up = n u up p j = 1,..., can copy o + n u 1 = u r = n u u r to each of the other 1 peer n rego. Thu each peer n rego receve a ubtream from each peer or the erver n the et P and alo receve 1 addtonal ubtream from the other 1 peer n the ame regon. The total rate at whch p receve tr = o + = u up r = r Hence the rater an be upported n the rego, whch mean, n th tuaton, the ytem can provde US for the rego. When r < r u. Conder a multmeda tream of rate r whch can be trancoded from the tream of rate r, f or,...,. Dvde th multmeda tream nto +1 ubtream, wth the jth ubtream havng rate o = u 1 u + n u r o +1 r = u 1, f or j= 1,..., u + n u r

5 Appl. Math. Inf. Sc. 7, No. 6, / And dvde th multmeda tream nto +1 ubtream, wth the jth ubtream havng rate = u 1 u + n u r +1 = r u 1, f or j= 1,..., u + n u r ubytem 1 regon 1 ubytem 2 regon 2 ubytem 3 regon 3 Notce that o + o +1 = r u u u + n u r Fg. 2: Example of no trancodng P2P treamng ytem. A 4, we have u n r u,...,m,.e. So u + n u r r u o + o +1 u, whch mean the erver can copy o +o +1 to the p,..., repectvely. And, a + +1 = r u u + n u r p g = 1,...,;h = 1,..., can copy + +1 to p j= 1,..., repectvely. So p j= 1,..., get flow rate o + Furthermore, becaue 1 + o + o +1+ p j = 1,..., can copy o + = u +1 to each of the other 1 peer n rego. Thu each peer n rego receve two ubtream from each peer or the erver n the et P and alo receve 1 addtonal ubtream from the other 1 peer n the ame regon. The total rate at whch p receve tr = o + + o = r. Hence the rate r can be upported n rego, whch mean, n th tuaton, the ytem can provde US for rego alo. To um up, when u atfy 4, baed on the flow rate ocaton algorthm n part two, the TRANSCODING can provde US for of the regon, whch mean the whole ytem can run on GUS. Conderng 3, we have u mn = max n r u n 0 = r 0 = u 0 = r m+1 = 0,,...,m+1. 3 Comparon No trancodng P2P treamng ytem, a hown Fg. 2, compoed of multple ndependent ubytem. The overlay networ of thee ubytem have ther own multmeda codng rate r = 1,...,m repectvely, and no communcaton among them. For brevty, we alo c the et of peer, whoe codng rate r, rego n no trancodng degn. And other notaton mean the ame a TRANSCODING. Let mn,...,m be the mnmal bandwdth demand of erver for ubytem P = 1,..., m runnng on US n no trancodng degn. And let mn be the mnmal bandwdth demand of erver for every ubytem runnng on US, whch equvalent to GUS n TRASCODING. Bae on [12,13], for the ubytem P1, for the ubytem P2 mn1 = maxr 1, n 1 r 1 u 1 mn2 = maxr 2, n 2 r 2 u 2 and for the ubytem Pm mnm = maxr m, n m r m u m,

6 2482 S. Zeng et al: Performance Bound for P2P Streamng... A the feature of no trancodng P2P treamng ytem, we have m mn = mn = r r u r < r u r u 5 5 a ueful equaton to fgure mn but not a clear way expreng the eence between no trancodng degn and TRASCODING ung the propoed algorthm. Let u turn bac to the ubytem P. Conder the tuaton of ubytem P runnng on US. Frt, mn need to be bgger than multmeda codng rate n rego. Second, the total upload bandwdth of ubytem P hould be able to atfy the total download conumpton of P. So we have the neceary condton for ubytem P runnng on US, whch { u NT mn r mn +n 6 u r Furthermore, f we need ubytem n no trancodng degn runnng on US, whch equvalent to GUS n TRANSCODING, the condton 6 mut be atfed for,...,m at the ame tme, whch { u NT mn r mn + u r, f or,...,m. Notce that we have m mn =unt mn and m r r 1, a mn r, mn r 1 7 And a mn + u r, f or,...,m, we have mn + u In 8, when =m, we have r, f or,...,m 8 mn m r u 9 Noctce mn+1 r +1, f or,...,m 1. So addng mn+1 r +1 to 8, we have +1.e. mn + +1 u mn r +1+ A mn = m we have mn r +1+ mn +1 r +1, f or,...,m 1 r u, f or,...,m 1 mn, f or = 1,...,m 1, r u, f or,...,m 1 10 We rewrte 10 a mn r + n r u, f or =2,...,m 11 Notce that 7, 9 and 11 come from neceary condton for whole no trancodng degn runnng on US. Compared wth 1 and 2 of TRNSCODING ung the propoed algorthm, we conclude that, n the ame tuaton, the condton that provde regon n no trancodng degn runnng on US are the uffcent condton for TRNSCODING ung the propoed algorthm runnng on GUS, whch mean the bandwdth demand of erver for whole no trancodng degn runnng on US alway able to atfy TRNSCODING ung the propoed algorthm runnng on GUS. So we have our econd theorem. Theorem 2. Let mn be the mnmal demand of upload bandwdth for peer n no trancodng P2P treamng ytem recevng data above ther multmeda codng rate. Let u T mn be the mnmal demand of upload bandwdth for peer n TRASCODING ung the propoed algorthm recevng data above ther multmeda codng rate. In the ame tuaton, we alway have where mn = :r r u u T mn = max 4 Smulaton mn ut mn :r < r u r u n r u In our mulaton experment, we mplement the algorthm of P2P treamng ytem wth trancodng and no trancodng decrbed n the Secton 2 and 3. Our tet networ are generated by the Georga Tech topology generator [19]. To conduct rgorou quanttatve analy of the ytem under wde range of worng condton, we mplement our experment to emulate the charactertc of realtc ytem wth dfferent parameter and a large number of tet tme. The parameter are choen randomly. We et m,, r and u randomly, whch chooe m from 2 to 10, from 5 to 100, r from 100bp to 1500bp, and u from 20bp to 1000bp. We tet the erver load of trancodng and no trancodng degn 500 tme repectvely n the ame condton, and urvey the dfference D = mn ut mn. The reult hown Fg. 3. We can ee that the D value range from about 100bp to about 10Mbp, that to ay, the erver load n trancodng ytem ung the propoed algorthm le than no trancodng degn, whch meet the mathematcal analy.

7 Appl. Math. Inf. Sc. 7, No. 6, / than the no trancodng degn. And the reult of mulaton experment alo how the ame concluon. Acnowledgement Fg. 3: Dfference of erver load n trancodng and no trancodng degn. Table 1: Notaton ued n th paper. Symbol Illutraton n Total number of peer n the ytem. Total number of peer n rego. m Total number of regon n the ytem. Server. p The jth peer n the rego. P Set of peer. P Set of peer n rego. r Multmeda codng rate n rego. R Set of codng rate n the ytem. u Upload bandwdth of erver. u Upload bandwdth of p. u Functon of upload bandwdth Summaton. u Average upload bandwdth of peer. u Average upload bandwdth of peer n rego. u mn Mnmal erver load to provde GUS. u Ret of upload bandwdth below the rego. u Ret of p upload bandwdth below rego. u Total ret of upload bandwdth below rego. o The rate of multmeda ubtream from to p. The rate of multmeda ubtream from p to p. tr The total rate of p receved from the ytem. 5 Concluon In th paper, we have mathematcy tuded the performance of P2P treamng ytem wth trancodng. We have derved the performance bound of erver load for the extence of a flud dtrbuton cheme that acheve GUS n P2P treamng ytem wth trancodng, and gven an algorthm to acheve the mnmal load n the proof. We have compared the mnmal erver load wth typcal tradtonal P2P treamng ytem wth no trancodng. The reult have hown that, n the ame tuaton, the mnmal erver load of trancodng P2P treamng ytem ung the propoed algorthm le Th wor party upported by The Natonal Natural Scence Foundaton of Chna NSFC NO and and Fundamental Reearch Fund for the Central Unverte ZYGX2010X001. The author grateful to the anonymou referee for a careful checng of the detal and for helpful comment that mproved th paper. Reference [1] M.-T. Lu, J.-C. Wu, K.-J. Peng, P. Huang, J. J. Yao, and H. H. Chen, Degn and evaluaton of a P2P IPTV ytem for heterogeneou networ, IEEE Tran. Multmeda, 9, [2] T. Wolf, In-networ ervce for cutomzaton next generaton networ, IEEE Networ, 24, [3] F. Chen, T. Repant, and V. Kalogera, Coordnated meda treamng and trancodng n peer-to-peer ytem, n Proc. IEEE Int. Parel Dtrbuted Proce. Symp., 56b [4] D. Lu, E. Setton, B. Shen, and S. Chen, PAT: Peer-ated trancodng for overlay treamng to heterogeneou devce, n Proc. Int. Worhop Netw. Oper. Syt. Support Dg. Audo Vdeo, [5] S. R. Narayanan, D. Braun, J. Buford, R. S. Fh, A. D. Gelman, A. Kaplan, R. Khandelwal, E. Shm, and H. Yu, Peer-to-peer treamng for networed conumer electronc, IEEE Commun. Mag., 45, [6] Guntur Ravndra, Sumt Kumar, Sureh Chntada, Dtrbuted meda trancodng ung a P2P networ of et top boxe, Proceedng of the 6th IEEE Conference on Conumer Communcaton and Networng Conference,La Vega, NV, USA, [7] J. Noh, M. Maar, and B. Grod, Streamng to moble uer n a peer-to-peer networ, In Internatonal Moble Multmeda Communcaton Conference, London, England, [8] Can Yang, Yuanqong Chen, Ylong Shen, The Reearch on a P2P Trancodng Sytem Baed on Dtrbuted Farmng Computng Archtecture, n Proc. of KESE 09, Pacfc- Aa Conference on Knowledge Engneerng and Software Engneerng, [9] Atena M, Canova A, Garca M, Lloret J, IPTV trancodng to avod networ congeton, The Sxth Internatonal Conference on Networng and Servce, ICNS, Cancun, Mxco, 2010, [10] Zxa Huang, Chao Me, L Erran L and Thoma Woo, CloudStream: delverng h-qualty treamng vdeo throu a cloud-baed H.264/SVC proxy, In Proceedng of IEEE Internatonal Conference on Computer Communcaton INFOCOM mnconference, [11] J.-C. Wu, P. Huang, J. J. Yao, and H. H. Chen, A collaboratve trancodng trategy for lve broadcatng over peer-to-peer IPTV networ, IEEE Tran. Crcut Syt. Vdeo Technol., 21,

8 2484 S. Zeng et al: Performance Bound for P2P Streamng... [12] R. Kumar, Y. Lu, and K. W. Ro, Stochatc Flud Theory for P2P Streamng Sytem, n Proc. of IEEE INFOCOM, [13] S. Lu, R. Z. Shen, W. Jang, J. Rexford, and M. Chang, Performance Bound for Peer-Ated Lve Streamng, n Proc. of ACM SIGMETRICS, [14] D. Wu, C. Lang, Y. Lu, and K. Ro, Vew-upload decouplng: A redegn of mult-channel p2p vdeo ytem, n IEEE INFOCOM, [15] D.Wu, Y. Lu, and K. Ro, Queung networ model for mult-channel p2p lve treamng ytem, n IEEE INFOCOM, [16] C. Zhao, X. Ln, and C Wu, The treamng capacty of parely-connected P2P ytem wth dtrbuted control, n Proc. of IEEE INFOCOM, [17] S. Sengupta, S. Lu, M. Chen, M. Chang, J. L, and P.A. Chou, Peer-to-Peer Streamng Capacty, IEEE Tranacton on Informaton Theory, 57, [18] C. Feng and B. L, On large-cale peer-to-peer treamng ytem wth networ codng, n Proc. of the 16th ACM nternatonal conference on Multmeda, Vancouver, Brth Columba, Canada, [19] E. W. Zegura, K. L. Calvert, and S. Bhattacharjee, How to model anternetwor, n Proc. of IEEE INFOCOM, Shua Zeng wa born He receved the B.S. and M.S. degree from the Chongqng Unverty of Pot and Telecommuncaton CQUPT, Chongqng, n 2003 and 2007, both n communcaton and nformaton engneerng. He currently purung the Ph.D. degree wth the School of Communcaton and Informaton Engneerng, UESTC. H current reearch nteret nclude networ optmzaton, P2P networ and wrele networ. Lemn L receved the BS degree n electrcal engneerng from Shana Jaotong Unverty, Chna n From 1952 to 1956, he wa wth the Department of Electrcal Communcaton at Shana Jaotong Unverty. Snce 1956 he ha been wth the Unverty of Electronc Scence and Technology of Chna UESTC. From to , he wa a Vtng Scholar n the Department of Electrcal Engneerng and Computer Scence at the Unverty of Calforna at San Dego, USA. He currently a Profeor of the School of Communcaton and Informaton Engneerng, UESTC. He a member of the Chnee Academy of Engneerng. H preent reearch nteret are n the area of communcaton networ. Dan Lao receved the Ph.D. degree from Unverty of Electronc Scence and Technology of Chna n He ha been an aocate profeor at UESTC nce H current reearch nteret nclude P2P networ, wrele networ and cloud computng.