Differentiated Service of Streaming Media Playback Technology

Transcription

1 Iteratoal Coferece o Advaced Iformato ad Commucato Techology for Educato (ICAICTE 2013) Dfferetated Servce of Streamg Meda Playback Techology CHENG Z-ao 1 MENG Bo 1 WANG Da-hua 1 ZHAO Yue 1 1 Iformatzato Ceter of Laog Uversty Abstract Wth users crease the persoalzed demad of streamg meda servce, to esure the smooth trasmsso of streamg meda ad a reasoable reducto of resources has become a measure of the qualty of streamg meda servces. Accordg to dstgushg the type of servces ad takg the persoalzed mprovemet to segmeted prefetchg data ad proxy server cache replacemet whch affects the streamg meda techology, ths paper proposes respectvely SPDS algorthm ad CRDS strategy. Smulato results show that these mprovemets ca effectvely reduce the proxy server load, reduce the waste of resources ad etwork badwdth cosumpto, whle provdg a better Qos. Keywords: dfferetated servce; segmeted prefetchg; cache replacemet 1. Itroducto Wth the growth of Mass actve data ad the tegrty of real-tme data, a complete set of the proxy server cache maagemet strateges maly clude two aspects of data prefetch ad cache replacemet. From the aspect of tme, by meas of prefetchg the segmets of streamg meda data, the user termal ca obta streamg meda formato from the earest proxy server; From the aspect of space, a effcet cache replacemet strategy proxy server, ot oly mprove the effectve use of physcal resources, but also allow users to play smoothly streamg meda fle the clet feelg less tha cachg data for watg to playback caused by "remote" server loadg pressure. So, for these two aspects, ths paper takes the persoalzed mprovemet to segmeted prefetchg data ad proxy server cache replacemet whch affects the streamg meda techology, ad proposes respectvely Segmetato Prefetchg based o Dfferetated servce of Streamg Meda (SPDS) ad Cache Replacemet based o Dfferetated servce of Streamg Meda (CRDS) [1]. 2. Prefetchg model of streamg meda At preset, may scholars have phased some models based o the probablty of vstg, data mg, popularty ad segmetato prefetchg, etc. These several prefetchg methods are oly a sgle users request as a separate streamg meda data request. Wth dverse developmet of data servces, Not oly are the streamg data requested by the user operatos dfferet, but also ther operatoal characterstcs are dfferet. Ths paper desgs a cache replacemet based o dfferetated servce of streamg meda SPDS whch s based o the exstg popularty prefetch model ad combes the dfferet characterstcs ad types of the streamg meda servce The authors - Publshed by Atlats Press 214

2 2.1. Streamg meda servce classfcato ad characterstc I order to eable the termal to playg o dfferet servce smoothly ths paper proposes segmetato prefetchg algorthm based o dfferetated servce of streamg meda. Accordg to the playback modes, the curret streamg meda servces that are frequetly-used ca be dvded to three types ad combe the dfferet segmetato strateges, as follow[1-2]: Lve servce segmetato: Because of the requremet of the hgher real-tme, expoetal segmetato prefetchg algorthm (ESPA) s adopted whch has hgh growth. As early as possble data are prefetched ad cached proxy server cache to esure smooth playback by the users. O-demad servce segmetato: The real-tme requremet of o-demad servce s feror to that of lve servce, whch above dowload. To esure a certa umber of data blocks the proxy server cache, so the twce sum of eve umber segmetato prefetchg algorthm (TSENSPA) s adopted. Dowload servce segmetato: The uform segmetato prefetchg algorthm (USPA) s adopted, because ts real-tme s lower, whch of data block s the least umber, each s more complete proxy server cache. Streamg servce processg platform wll geerate call detal records (CDR) [4].By extractg the part of the streamg data formato, the SCDR formato s geerated - Smlar CDR. The source server or the proxy server accordg to the user request to dstgushg streamg meda fle type detfcato, ad the SCDR a fle s detfed(as Idetfcato Number : Type Of Server)that as follows:0 s O-Demad servce;1 s Lve servce;2 s Dowload servce Segmetato algorthm Ths paper adopts frst a segmetato prefetchg algorthm [1] based o the twce sum of eve umber. I accordace wth the respectve characterstcs of streamg meda servces, combg wth USPA ad ESPA.The paper proposed Segmetato Prefetchg based o Dfferetated servce of Streamg Meda- SPDS, whch s better to solve the cotradcto of USPA ad ESPA. The sze of prefetchg segmetato data-l should be combed wth the type of servce uder certa codto of badwdth ad data. The proxy server wll make full use of resources ad mprove the playback of real-tme ad cotuous. B 1 Case 1: Whe Bs> Bt, ad Bt, > 0, ths case, streamg meda fle whch the proxy server receve are smaller tha oe that set to the user termal, ad so user termal playback speed, the proxy server usg the classfcato of streamg meda segmets to prefetchg strategy. Prefetchg posto x should satsfy the followg formula: L x L 1 L 1 (1) Bs Bt L M (2) Whe the proxy server determes the type of streamg meda, we ca assg [α, β, γ] accordg to the detfer of SCDR type. As follows that: O-Demad servce: [α, β, γ] = [1, 0, 0];Lve servce: [α, β, γ] = [0, 1, 0];Dowload servce: [α, β, γ] = [0, 0, 1]. Case 2: whe Bs <Bt, streamg meda fle whch the proxy server receve are larger tha oe that set to the user termal, as well as case 1, f the proxy server cache partal streamg data for a log perod of tme, there s o reasoable updated for streamg data. As there were suffcet cache resources of proxy server, both that ad user termal s 215

3 playback would cause jtter. I order to more fully usg proxy server to cache resources, ths paper wll troduce a ew cache replacemet algorthm to solve ths problem. 3. Dfferetated type of streamg meda servces ad cache replacemet The thkg of tradtoal cache replacemet polcy s by exchages old. Ad the so-called "old" meda objects may be that user perfetch the most cotet, whch s replace the "ew" streamg object to affect the user's playback. I accordace wth the abovedescrbed mprovemet of prefetchg algorthms, ths paper combes the fluetal factor of streamg data playback wth the cache techology of proxy server, to mprove cache replacemet for streamg meda proxy server. Ad that predct data from the popularty of streamg meda data, trasmsso rate ad the jtter of trasmsso rate. By meas of whch, the cache prorty (utlty value sze) of streamg meda data the proxy server wll be reset. Ths paper desgs a cache replacemet strategy based o dfferetated servce of streamg meda-crds [1, 3] Parameter of CRDS strategy At preset, the assessmet model of the fle popularty s maly based o the Zpf dstrbuto. Accordg to the fact that the probablty of -th segmet accessed follows a Zpf dstrbuto (θ=0.271), t s used as a quota of the cached data prorty by popularty as follows: 1 T (3) To usg GM (1, 1) predcto model combg wth hstorcal statstcal data (the average trasfer rate of ut data segmet-r c, that predct the trasfer rate value-r p of the ext perod -th segmet data. The paper desgs a tred factor of trasmsso rate through the comparso of the predcted values ad the sample value-q, order to calculate the mea-μ of the tred factor of trasmsso rate the rage of sample tme, to express the tred chage of the data trasmsso rate for the ext segmet, ad also desg aother oe of the jtter level of trasmsso rate tred the process-σ 2. j R R P k1 Ck EQ Q j (4) 2 D Q E Q E Q 2 (5) 3.2. Utlty fucto of CRDS strategy Each streamg data whch have bee cached or would be cached, t must make detaled statstcal aalyss o the three quotas. See by the utlty fucto, utlty value coferred by each data segmet s proportoal to the popularty ad the trasmsso rate, ad s versely proportoal to the jtter level of the trasmsso rate. The data requested the proxy server are calculated ts utlty value whch stored the lst of proxy server wth the data segmet formato, order to facltate users proxy server storg ad maagg the cached streamg data whe user requests that. So through three quotas, t could be more reasoable assessmet of the prorty level of cached streamg data segmets the proxy server, thereby reasoable usg resources. T 2 (6) Accordg to the characterstc about hgh real-tme, ths paper t s defed 216

4 that the lve servce cache must ow the hghest prorty ad the cache prorty of the o-demad s lower tha the lve oe, but hgher tha the dowload oe. Whe t s drected by proxy server, the segmets wll be cached the hgh cache. After all the lve segmets set out to the ed user termal, the cache space occuped oce would be released. If the cache space of lve servce has bee full whle the proxy server wll cache the ew lve segmets, the part cache of the odemad servce cache wll be occuped ad so o. Whe there are o spaces the proxy server, whch wll use the CRDS strategy for the streamg meda data segmets ad replace the space occuped by the lowest prorty of the dowload servce segmets whch do ot cota the beg accessed oes. After ths, there are stll o eough spaces, the segmets beg lower prorty of the dowload servce segmets wll released ad so o utl there are eough oes cachg the lve servce segmets. Whe the lve servce fshes playg, the spaces are released. The prorty of the o-demad servce s feror to the oe of lve servce. Whe the spaces of the o-demad are full whle the proxy server wll cache the ew o-demad segmets, the oes occupy the cache spaces of the dowload. The basc strategy s smlar to the lve oe. The prorty of the dowload servce s the lowest, so whe there are the ew oes eedg be cached ad o eough spaces, the proxy server oly replaces the lower utlty value to satsfy that. 4. Expermet Table 1. Proxy server testg parameters lst [1-4] Parameter ame Parameter sze The sze rage of 100MB to 500MB streamg fles The umber of streamg meda 1000 fles The average terval 10s tme of request The fle popularty a Zpf dstrbuto (θ=0.271) The etwork delay 100ms of proxy server ad user termal The etwork delay of proxy server ad 200ms source server The legth of ut 6s data block /B The legth of prefx 4B data block The expermet shows that the segmetato prefetchg ad cache replacemet strategy based o dfferetated servce has the advatage of the byte ht rato the sample tme tha the smplex oe. Whe the proxy server cache occuped below 40%, the byte ht rato s bascally cosstet betwee them. Whe above 40%, the SPDS-CRDS algorthm exhbts slghtly advatage. 217

5 gores ad expermeted. But the ew servce are costatly emergg, order to better meet the eeds of the users ad the extesve developmet, t s stll eeded makg the ecessary adjustmets to some parameters mpactg o cache replacemet. I short, I beleve that wth the developmet computer etwork ad the vestmet ad costructo by ISP, these problems wll be solved. 6. Refereces Fgure 1. The byte ht rato ad jtter rato of the three algorthms 5. Coclusos Accordg to the user eedg more streamg meda servce types ad the commo streamg meda playback modes, these are dvded to three cate- [1] Cheg Z-ao. Research ad Desg of Dfferetated Servce of Streamg Meda Play Techology [D], Laog Uversty, [2] DAI Zhog, YANG Ge, LIAO Jax, ZHU Xao-m, ad HUANG Ha. Actve prefetchg algorthm for streamg meda based o atural umber segmetato, Joural o Commucatos [J], vol. 29 No.3 March 2008: [3] YANG Chuadog,YU Zhewe,WANG Xggag,ZHANG Huayua.Proxy Cache Replacemet Algorthm Based o Popularty Predcto of Streamg Meda Fle of Streamg Meda Fle.Computer Egeerg[J].vol.33 No.7Aprl [4] Geeral Techcal Requremets Of Moble Streamg Servce Dgtal Cellular Moble Telecommucato Network, Mstry Of Iformato Idustry Of the People s Republc Of Cha, YD/T