Performance Evaluation of Multicast Video Streaming via P2P Networking

Transcription

1 Secal Issue of Internatonal Journal of Comuter Alcatons ( ) on Electroncs, Informaton and Communcaton Engneerng - ICEICE o.4, Dec 20 erformance Evaluaton of Multcast Vdeo Streamng va 2 etworkng Rajesh Bhadada Brendra Ra Deartment of Electroncs& Communcaton Engneerng, M.B.M. Engneerng College, J..V.Unversty, Jodhur ABSTRACT In the ast few years, the multcast vdeo streamng va 2 networkng has become a very successful and ncreasngly oular n dstrbutng multmeda content by encouragng an mortant number of users to act as both clents and servers. Vdeo on demand (VoD) streamng one such servce where vdeos are delvered to asynchronous users wth mnmum delay and free nterconnectvty. The VoD s costly due to the lmted uload caacty of the vdeo server and tradtonal centralzed clent/server archtecture. eer-to-eer streamng technques are an aroach to allevate server load through eer-asssted sharng. roxy cachng s a key technque to reduce transmsson cost for on-demand multmeda streamng. Ths nnovatve aroach combnes the advantages of both roxy cachng and eer-to-eer clent communcatons. In ths aer, frstly we rovde a better understandng of the basc concet of multcast vdeo streamng, meda delvery structure, streamng meda storage sze, bandwdth requrement, vdeo streamng archtecture and then resent a novel aroach for the erformance evaluaton of multcast vdeo streamng va 2 networkng usng servers and roxy servers stuated between local area networks (LAs). The results demonstrate the benefts of multcast vdeo streamng on the server-roxy aths. descrbes the overvew of the system and ts model. Secton 4 resents otmal roxy cache allocaton technque. The erformance evaluatons are resented n Secton 5, n whch the effect of roxy cachng on the transmsson cost and benefts of usng multcast from server to roxy are beng observed. Fnally Secton 6 summarses conclusons. 2. MEDIA DELIVERY The meda delvery structure s dected n Fgure. Meda data can be stored and delvered to a clent ether from the local fle system or from a remote server across the network by usng streamng technques [2,3]. Data from lve contnuous meda such as lve web cams are also streamed from server to clent. A clent may be a ersonal comuter or a smaller devce such as a handheld comuter, ersonal dgtal assstant (DA) or cellular telehone. Keywords eer-to-eer (2) networkng, roxy cachng, Vdeo Streamng, Local Area etwork (LA), Multcast, Vdeo on demand (VoD). ITRODUCTIO The multcast vdeo streamng va eer-to-eer (2) networkng archtectures have radly gan the oularty, where clents store the meda data after the streamng servce, and act as sulyng eers by streamng the meda data to other requestng clents (eers) n the near future[,2,4,6]. 2 networks overcome the setback of bottleneck around centralzed server due to ts dstrbuted desgn and archtecture. The man am of ths aer s to understand the concet of multcast vdeo streamng and study the benefts of usng multcast nstead of uncast on the serverroxy aths. roxy cachng s an mortant technque to reduce transmsson cost for multmeda streamng. A technque to determne the otmal cache allocaton at each roxy server among dfferent vdeos, and an effcent roxy-asssted transmsson scheme when server-clent aths are multcast caable are beng studed through ths aer [9, 0]. The rest of ths aer s organzed as follows. Secton 2 exlans the meda delvery structure, the requrement of streamng bandwdth and storage sace n uncast/multcast and lve streamng envronments and exlanaton of 2 network archtecture for sngle/multle source models. Secton 3 Fg.. Meda Delvery Structure Dagram In ths aer, we consder stored vdeo streamng and ts realtme transmsson. On-demand delvery of vdeo (stored) n the real-tme transmsson s the rme art of multmeda. There are two technques for transmsson of stored vdeo namely the rogressve download technque and real tme streamng technque va 2 networkng. () rogressve download technque: In ths technque a meda fle contanng audo or vdeo s down loaded and stored on the clents local fle system. As the fle beng downloaded, the clent can lay back the meda fle wthout wat for the fle to be down loaded comletely n ts entrety. Ths technque s more useful for relatvely small meda fles such as short vdeo cls. () Real tme streamng: When the meda fle s streamed to the clent but s only layed and not stored by the clent, t s called 32

2 Secal Issue of Internatonal Journal of Comuter Alcatons ( ) on Electroncs, Informaton and Communcaton Engneerng - ICEICE o.4, Dec 20 real tme streamng. As the meda fle s not stored on the clent system, real tme streamng s referred over the rogressve download for large meda fles. It elmnates need for storage on the user system, lke full vdeo Internet rado and TV broadcasts. 2. Streamng bandwdth and storage sace The storage sace for streamng meda s calculated from the streamng bandwdth and length (n seconds) of the meda by usng the formula as gven: umber of MBytes transferred = Length n seconds Bt rate n bt / seconds Examle: hour of vdeo encoded at 500 Kbt/s requres 3, ,000.e. aroxmately 25MBytes of storage If the fle s stored on a server for on-demand streamng and ths stream s vewed by 200 eole at the same tme, then the bandwdth requrement by usng uncast, multcast and lve streamng envronments wll be determned as follows: () Uncast Streamng: It requres multle connectons from the same streamng server even when t streams the same content as dected n Fgure 2. Uncast rotocols send a searate coy of the meda stream from the server to each recent [, 8]. Uncast s the norm for most nternet connectons, but does not scale well when many users want to vew the same rogram concurrently usng a uncast rotocol, the bandwdth requrement s: 500 Kbt/s 200 = 00,000 Kbt/s = 00 Mbt/s of bandwdth. Ths s equvalent to around 45 GByte/ hour. Fg.2. Uncast Streamng () Multcast Streamng: Multcastng broadcasts the same coy of the multmeda over the entre network to a grou of clents as dected n Fgure 3. Usng a multcast rotocol the server sends out only a sngle stream that s common to all users. Hence, such a stream would only use 500 Kbt/s of servng bandwdth. Multcast rotocols are develoed to reduce the data relcaton (and consequent server/network loads) that occurs when many recents receve uncast content streams ndeendently. These rotocols send a sngle stream from the source to a grou of recents Fg.3. Multcast Streamng () Lve streamng: The calculaton for lve streamng s smlar. Let us assume that the seed of the encoder be 000 Kbt/s. If the show duraton last for 3 hours, wth 200 vewers then the bandwdth requrement s calculated as follows : Encoder seed n Kbs o. of seconds o. of vewers Kbs hours 200 o. of vewers = 264 GBytes aroxmately. 2.2 eer-to-eer (2) systems: A eer s consdered to be a rovder and a consumer of resources along wth servng caacty nto the system. These systems sgnfcantly reduce the load n the server. Unlke centralzed server- clent based schemes, 2 systems are dstrbuted systems consstng of eers nterconnected wth each other, able to self organze nto network toologes n order to share resources lke content, bandwdth, CU cycles and storage. The 2 network streamng archtecture refers to the manner used for multmeda content transfer and the enttes whch are nvolved durng the streamng mechansm [8,5]. A gven eer can lay three dfferent roles n the ersectve of 2 streamng: Source: eer contanng the meda contents and ntended to share wth other eers. eer can store whole or a art of a gven content Intermedate: An ntermedate eer, receve a gven content and then transmt t to the next ntermedate eer. Intermedate eer serves as a transort node to facltate the streamng mechansm Destnaton: It s the clent who requests for the content. Clent eer can obtaned meda contents from one or more sender eers deendng on the archtecture. We defne two knds of network archtectures namely sngle source and multle source () Sngle source: In ths case, the multmeda content s stored nto only one source eer n the network [8]. The content eer starts transmttng the content to all clent eers requestng for t and the ntermedate nodes can lay a more mortant role. Fgure 4 gves an examle of sngle source streamng towards two eer clents 33

3 Secal Issue of Internatonal Journal of Comuter Alcatons ( ) on Electroncs, Informaton and Communcaton Engneerng - ICEICE o.4, Dec 20 entrety at the roxy server, then makes the contact wth the remotely located server for the suffx of the stream. The server multcasts the requred suffx to the roxy servers, and the roxy servers multcasts the ncomng data to the clents that request the vdeo. System Model: To rovde a formal model of the system, Table ntroduces the notatons and the man concets that wll be used n ths aer. Suerscrt and subscrt have been used to reresent the ndex of the roxy and the vdeo [5,7,9,0,]. TABLE : otatons used Fg.4. Sngle-Source 2 streamng model () Multle sources: In ths case each clent eer receves ackets of a multmeda content from multle sender eers whle each sender eer can send ackets to one or multle clent eers. Fg.5. Mult-Source 2 streamng model The contents can be retreved from several eers nto the network smultaneously as dected n Fgure 5. The role of ntermedate eer s lmted to the transfer of the receved acket towards the destnaton eer. 3. OVERVIEW OF THE SYSTEM Archtecture of streamng vdeo n the nternet as shown n fgure 6 has been consdered, where a server and a set of roxes are connected [9, 3, 4, 5]. arameter V n b c c β A s v S v C ( v ) Defnton umber of vdeos Length of vdeo (unts) umber of roxes Cachng gran (smallest unt of cache allocaton) Sace of vdeo (unts) Mean bandwdth of vdeo (bts er sec.) Transmsson cost from server to roxy (er bt) Transmsson cost from roxy to ts clent (er bt) The multcast scalng factor Access robablty of vdeo at roxy Request rate for vdeo at roxy Aggregate request arrval rate for vdeos at roxy Aggregate request arrval rate for vdeo at all roxes The cache sace (unts) of roxy Length (sec) of cached refx for vdeo at roxy Storage vector of vdeos,,, v ) v =( v, v, Transmsson cost er unt tme for vdeo when the storage vector for vdeo s 2 v 3 v Fg.6: Streamng vdeo n the Internet The each roxy server s held resonsble for multle clents and they are closely located wth relatvely low communcatons costs. The server s located n remote from clents, and the communcatons among them ncur much hgher costs. We consder multcast s avalable from server to roxy and vce versa. We assume that clents always request layback from the begnnng of a vdeo. The roxy server ntercets the clents request and, f a refx of the vdeo s resent locally, streams the refx drectly to the clents. If the vdeo s not stored n ts A server wth a reostory of Constant-Bt-Rate (CBR) vdeos and roxes has been consdered. Let A be the access robablty and be the access rate of vdeo at roxy resectvely. It s assumed that the access robablty of all vdeo and the aggregate access ratet to the vdeo reostory are known a ror. Hence A and let be the aggregate request arrval rate for vdeo at all the roxy server, then. Let be the aggregate access rate to the vdeo reostory at roxy then = A. It s also assumed that 34

4 Secal Issue of Internatonal Journal of Comuter Alcatons ( ) on Electroncs, Informaton and Communcaton Engneerng - ICEICE o.4, Dec 20 cachng gran of sze u to be the smallest unt of cache allocaton and all allocatons are n multles of ths unt. The cachng gran can be one bt or one mnute of data, etc. We exress the sace of vdeo and the cache sace at each roxy server n multles as the cachng gran. Vdeo has layback bandwdth b bs, length V seconds, and sace n unts, u n = b V. roxy can store S unts where S The storage vector n. v =( v, v, v,, 2 3 v ) secfes that a refx of length v seconds for each vdeo s cached at roxy, I =,2,3,.,. It may be noted that the vdeos cached at the roxy server cannot exceed the storage lmtaton of the roxy server, that s b v S. For smlcty of exoston, etwork roagaton latency s gnored by us. On recevng a clent request for a vdeo, the roxy server determnes a transmsson schedule that deends on the transmsson scheme n use. Ths transmsson schedule secfes, for each vdeo frame, when and on what transmsson channel (uncast or multcast connecton) t wll be transmtted by the roxy server. The roxy server also determnes and requests the suffx from the server. A receton schedule s transmtted from the roxy server to the clent. It secfes, for each frame n the vdeo, when and from whch transmsson channel the clent should receve that frame. ote that a clent may need to receve data from multle transmsson channels smultaneously. Frames receved ahead of ther layback tmes are stored n a clent-sde work ahead buffer. For smlcty, we shall assume the clent has suffcent buffer sace to accommodate an entre vdeo cl. Let c s and c be the cost assocated wth transmttng one bt of vdeo data from server to roxy server and roxy server to ts clent resectvely usng uncast. To mnmze the mean transmsson cost er unt tme s aggregated over all vdeos n the reostory,.e. where C ( v C (v ) ) s the transmsson cost er unt tme for vdeo when a refx of length v of the vdeo s cached at the roxy server. When a roxy server and ts clents are located n a local area network (LA) envronment, the bandwdth requred to send one bt from the roxy to multle clents usng multcast s stll one bt. Therefore, the transmsson cost to send one bt from the roxy to multle clents s stll from server to roxy server aths, we assume the cost to transmt a bt of data from the server to m roxes usng multcast s mc s where (, ) and s m referred to as the multcast scalng factor. The mnmum value for β s n whch case the cost of transmttng a bt of data m from the server to m roxes s c s same as n a LA envronment. The cost when usng multcast n a wde area network deends on a varety of factors ncludng the multcast tree toology and the sze of the multcast grou. We make t a note that when c = 0 and mc s = the transmsson cost reduces to be the server bandwdth usage. When c = and c s = 0, the transmsson cost reduces to be the amount of outgong traffc at the roxy server. 4. OTIMAL ROXY CACHE ALLOCATIO A general technque to determne the otmal roxy refx cache allocaton for any gven roxy asssted transmsson scheme has been roosed. Let A = m {0 m refxes for vdeo, where n } denotes the set of ossble m unts s the sace and m b seconds s the length of a ossble refx of vdeo. For a gven transmsson scheme, the average transmsson cost er unt of tme for vdeo, at the roxy, 0 C ( v v ( m ), where m = ( ) s a functon of the refx V cached V. We defne savng m, m, m, m ), to be the savng n 2 the transmsson cost when storng m unts of refx of vdeo at roxy server over the cost when vdeo s not stored at the roxy server, =, 2, 3... Our man am s to maxmze the aggregate savngs and, hence, mnmze the aggregate transmsson cost over all the vdeo. The otmzaton roblem can therefore be formulated as maxmze: s.t. ( ) S, m m 3 A, ( },. savng( m ) Let B be a two-dmensonal matrx, where entry B(, j j, and ), where =( j, j 2,., j ) reresents the maxmum savng n the transmsson cost when usng vdeos and j unts of storage are allocated at roxy server, (0 ) and j (0 j S ) unts of the roxy cache. 0, = 0 B (, j ) = Max {B (-, j ), B (, j )}, > 0 Where, B, ) j ) = max {B(-, j - m ) + savng ( m )}.Ths matrx s flled n row-order startng from B (0, j = 0;, S The value B(, S ) ), j s the maxmum savng n 35

5 Secal Issue of Internatonal Journal of Comuter Alcatons ( ) on Electroncs, Informaton and Communcaton Engneerng - ICEICE o.4, Dec 20 transmsson cost when all vdeos have been used. The mnmum transmsson cost s C (0) B( S ) Snce the savng s relatve to storng nothng at the roxy. The otmal cache allocaton can now be comuted as follows. For each entry, we store a onter to an entry from whch ths current entry s comuted. By tracng back the onters from the entry B(, S ) the otmal allocaton s obtaned. 5. ERFORMACE EVALUATIO The erformance of multcast vdeo Streamng va 2 etworkng s evaluated n ths secton. The man ont s ncurred transmsson cost reducton by ntroducng roxes and clent s co-oeraton, under assumtons as follows. The vdeo storage sace n the server contans =00 CBR (constant Bt Rate) vdeos cls each of 52 Kbs rate. Ther lengths are unformly dstrbuted n between 00 and 40 mnutes; the mean (20 mnutes) s a tycal length of a move. We assume the access robabltes of the vdeos follow a Zf dstrbuton wth skew factor θ = The cache gran (unt) s set to the sze of one mnute vdeo data. All the cache saces dscussed n ths secton are normalzed by the total sace of the vdeo reostory, and the transmsson costs are normalzed by the corresondng cost of a system wth no cache. The transmsson cost s normalzed by both the vdeo bandwdth and the value of cs. That s, the normalzed transmsson cost C s (v ) / (c b ) Let ĉ = c /c s. In ths secton, we assume ĉ (0, ). It s observed that ĉ =0 corresonds to c =0 and ĉ = corresonds c = c s.we reresent the roxy cache sace as a ercentage r, reresents sace of the vdeo reostory. Fg.7. Relatve reducton of transmsson cost over no refx Cachng Furthermore, the reducton s more mressve for ĉ = 0 and ĉ = 0.3.Ths s because, for lower values of the savngs from transmttng drectly from the roxy cache to the clents s more mressve. Fnally, we observe smlar characterstcs for other request arrval rates. ()Benefts of usng multcast from server to roxy server ath: Fgure 8 dects the transmsson cost when usng multcast and uncast on the server to roxy server aths as a functon of the roxy server cache sace for =50/mnute and β = 0.4. Usng multcast on the server to roxy server aths leads to a sgnfcant savng of transmsson cost for small and medum roxy server cache sace only. We observe that by usng multcast the transmsson cost reduces by 32% and 9% over that usng uncast for ĉ = 0 and ĉ = 0.3 resectvely and uncast archtecture, when usng β= 0.4 & =50/mnute Homogeneous roxy servers have been consdered that s, the confguratons for all the roxy servers are the same, ncludng roxy cache sace, vdeo access robabltes, aggregate arrval rate,67 c s and c, etc. We assume that the aggregate arrval rate ranges from 0 to 500 requests er mnute. The total number of roxes = 0 or 00. The multcast scalng factor ranges n (, ). The erformance trends under =0 and =00 are smlar, hence n ths aer =00 has been assumed. () The effect of roxy cachng on the transmsson cost: We observe that the roxy server cachng leads to lower network transmsson cost n all the settngs. Ths s exected snce data from the server ass the roxy server and hence transmttng a stream drectly from a roxy ncurs less cost than from the server. We defne the relatve reducton under otmal roxy cache allocaton over no roxy cachng to be the dfference n the costs under these two settngs dvded by the cost wthout roxy cachng. Fgure 7 lots the relatve reducton thus defned when the aggregate arrval rate to a roxy s 50 er mnute and β ranges from 0.2 to 0.8. It s observed that a relatvely small roxy cache (%-0% of the vdeo reostory) s suffcent to realze substantal savngs n transmsson cost and the roxy cache sze has a dmnshng effect on the cost savngs. Fg.8. Comarson of the transmsson cost between multcast As the roxy cache ncreases, more contents are transmtted from the roxy servers cache drectly and the cost on the server-roxy aths becomes less domnant n the total cost. That exlans why transmsson costs usng multcast and uncast on the server to roxy server aths become close for large roxy cache saces. We observe that the cost savngs from usng multcast on serverroxy aths are more sgnfcant for small values of ĉ. Ths s because, n that case, the cost on the server to roxy server aths s more domnant n the total cost and the benefts of usng multcast are more obvous. 36

6 Secal Issue of Internatonal Journal of Comuter Alcatons ( ) on Electroncs, Informaton and Communcaton Engneerng - ICEICE o.4, Dec COCLUSIO Revew of the basc concet of meda delvery structure, storage sace and bandwdth requrement of uncast/multcast/lve streamng envronment, 2 streamng model as sngle source and multle source and roxy server-clent catchng system that combnes the best features of roxy cachng and eer-to-eer networkng has been carred. Technques for dstrbutng vdeo streamng among the roxy server and clent are surveyed. The erformance has been evaluated under varous system confguratons. The man fndngs can be summarzed as follows () roxy server based archtecture sgnfcantly reduces the transmsson cost for on demand vdeo streamng () for the same roxy sze, use of refx cachng for a set of vdeos result n sgnfcantly lower transmsson costs comared to entre-object cachng olces () under otmal refx cachng, a relatvely small roxy cache (%-0% of the vdeo reostory) s suffcent to realze substantal savngs n transmsson cost (v)the allocaton under otmal refx cachng s senstve to the transmsson scheme, the aggregate arrval rate and the value of ĉ. The benefts of usng multcast from server to roxy server ath have been consdered. Fnally t can be seen that the combnaton of these technques and 2 networkng for multcast vdeo streamng has otental to fulfll future meda nternet challenges. Future nternet ntatves should be taken to take nto consderatons these technques whle desgnng new archtectures and rotocols to enable future ersonalzed alcatons and servces, oeratng under hgh heterogeneous and dynamc envronments for maxmzng the QoS of the users. 7. REFERECES [] Jagadeesh M. Dyaber, Karthk Kannan, and Vjay S. a, Storage Otmzaton for a eer-to-eer Vdeo-on-Demand etwork, MMSys 0, February 22 23, 200, [2] Yfeng He, Ivan Lee and Lng Guan, Dstrbuted Throughut Maxmzaton n 2 VoD Alcatons IEEE TRASACTIOS O MULTIMEDIA, VOL., O.3, ARIL 2009 [3] Brendra Ra and Rajesh Bhadada, Futurstc Scoe of Automated Vdeo on demand System: Vson and Desgn Internatonal Conference on Emergng & Futurstc System and Technology, at LIET, Alwar (Raj.), Arl 2009 [4] Alvaro Chalar Zúñga, Deartamento Arqutectura decomutadoresy Sstemas Oeratvos, Unversdad Autónoma de Barcelona, System Analyss of a eer-to-eer Vdeo-on- Demand Archtecture Kangaroo, 2008 [5] Weqang Sun, Kan Ln and Yang Guan, erformance Analyss of a Fnte Duraton Multchannel Delvery Metho n ITV IEEE TRASACTIOS O BROADCASTIG, VOL. 54, O. 3, SETEMBER 2008 [6] Bn Cheng, Xu zheng Lu, Zheng Zhang, Ha Jn,Lex Sten, Xaofe Lao, Evaluaton and otmzaton of a eer- to-eer vdeo-on-demand system, Journal of Systems Archtecture 54 (2008) , December 2007 [7] Thoun F. and Coates M., Vdeo-on-Demand etworks: Desgn Aroaches and Future Challenges, n IEEE etwork, Volume 2, Issue 2, ages 42-48, March Arl [8] D. Meddour, M. Mushtaqm, and T. Ahmed. Oen Issues n 2 Multmeda Streamng. MULTICOMM. Istambul. Jun [9] B. Wang, S. Sen, M. Adlerand D. Towsley, Usng Multcast for streamng vdeos across wde area networks, Tech. Re , Deartment of Comuter Scence, Unversty of Massachusetts, Amherst, 2003 [0] B.Wang, S. Sen, M. Adler and D. Towsley, Otmal roxy Cache allocaton for effcent streamng meda dstrbuton, n ro. IEEE IFOCOM, [] J. C. I. Chuang and M.A. Srb, rcng Multcast Communcaton: Acost-based aroach, Telecommuncaton Systems, vol. 7, no.3, , 200. [2] Daeng Wu, Ywe Thomas Hou, Wenwu Zhu, Ya-Qn Zhang, and Jon M. eha, Streamng Vdeo over the Internet: Aroaches and Drectons IEEE Transactons on Crcuts and Systems for Vdeo Technology, Vol., o. 3, , March 200 [3] D. Wu,Y. T. Hou,and Y.-Q.Zhang, Transortng Real- Tme Vdeo over the Internet: Challenges and Aroaches, roceedngs of the IEEE, vol. 88, no. 2, Dec [4] L. Gao and D. Towsley, Threshold-based multcast for Contnuous meda delvery, IEEE Transactons on Multmeda, vol. 3, , December 200. [5] Bruce A.Mah, Srnvasan Seshan, Kmberly Keeton, Randy H. Katz, Domenco Ferrar, rovdng etwork Vdeo Servce to Moble Clents, Aeared n roceedngs of the Fourth Worksho on Workstaton Oeratng Systems, aa, CA, October