A QoS Scheme for a Congestion Core Network Based on Dissimilar QoS Structures in Smart-Phone Environments

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1 Sensos 2010, 10, ; do: /s OPEN ACCESS sensos ISSN Atcle A QoS Scheme fo a Congeston Coe Netwok Based on Dssmla QoS Stuctues n Smat-Phone Envonments Sung-Ryong Hong 1, Wonshk Na 1 and Jang-Mook Kang 2, * 1 2 Dept. of Geneal Educaton, Namseoul Unvesty, 21 Maeju-, Seonghwan-eup, Seobuk-gu, Cheonan-cty, Choongnam, , Koea; E-Mals: sh@nsu.ac.k (S.-R.H.); wnne@nsu.ac.k (W.N.) Electonc Commece Reseach Insttute, Dongguk Unvesty, 707 Seokjang-dong, Gyeongju, Gyeongsangbuk-do, , Koea * Autho to whom coespondence should be addessed; E-Mal: mooknc@gmal.com o edsea@dongguk.ac.k. Receved: 25 Septembe 2010; n evsed fom: 20 Octobe 2010 / Accepted: 25 Octobe 2010 / Publshed: 9 Novembe 2010 Abstact: Ths study suggests an appoach to effectve tansmsson of multmeda content n a apdly changng Intenet envonment ncludng smat-phones. Guaanteeng QoS n netwoks s cuently an mpotant eseach topc. When tansmttng Assued Fowadng (AF) packets n a Mult-DffSev netwok envonment, netwok A may assgn poty n an ode AF1, AF2, AF3 and AF4; on the othe hand, netwok B may evese the ode to a poty AF4, AF3, AF2 and AF1. In ths case, the AF1 packets that eceved the best qualty of sevce n netwok A wll eceve the lowest n netwok B, whch may esult n doppng of packets n netwok B and vce vesa. Ths study suggests a way to guaantee QoS between hosts by mnmzng the loss of AF packet class when one netwok tansmts AF class packets to anothe netwok wth dffeng pncples. It s expected that QoS guaantees and the expemental value may be utlzed as pncples whch can be appled to vaous moble-web envonments based on smat-phones. Keywods: smat-phone; taffc classfcaton; Dffsev; QoS; multmeda content

2 Sensos 2010, Intoducton The Intenet envonment has changed and developed dastcally, so few uses now access t va modems, whch wee wdely used a few yeas ago. As a esult, the tadtonal Vtual Temnal (VT) envonment has been eplaced by the Gaphc Use Inteface (GUI), and text based smple HTML (Hypetext Makup Language) sevce has become a multmeda based sevce. At an ealy stage, n an attempt to ensue QoS, the Intenet Engneeng Task Foce (IETF) suggested the IntSev mechansm usng the Resouce ResSevaton Potocol (RSVP) Sgnalng Potocol, but ths led to mllons of esouce esevatons n the Coe Route. The most ctcal poblem s that all of the esouce esevatons must be confgued agan when the topology changes. Ths envonment can seously delay tansmsson of multmeda educatonal content and eques a complcated cost chage system because thee s no lmt to the numbe of classfed sevces demanded by each flow. To solve the above poblem, IETF suggested the Dffsev mechansm now n pactcal use. Dffsev classfes packets nto thee classes: EF (Expedted Fowadng), AF (Assued Fowadng), and DE (Default Fowadng). Ths study suggests a way of tansmttng multmeda contents wth the best qualty, whethe the netwok povdes DffSev o not [1]. To acheve ths goal, the poposed method wll ewte the unused 2 bts of Dffeentated Sevce Code Pont (DSCP) value among the 8 DffSev DSCP value bts. 2. Related Wok The Dffsev sets up DSCP values afte classfyng thee EF, AF and DE sevce classes n edge outes. Then t tansmts values to coe outes that afte ecevng DSCP values, detemne Pe Hop Behavo (PHB). Snce the DffSev dentfes the DSCP values by usng 6 bts out of the 8 bts whch ae Type of Sevce (TOS) bytes n the IT Heade, the netwok can povde dffeentated sevces accodng to the packets [2]. When data comes fom othe netwoks, Mult-DffSev fst checks f t s tansmtted though the pope oute as contacted. Then, t allows packets to go to the coe outes though the Routng Coe and PHB. In ths case, the DSCP values can be econfgued o be tansmtted wthout change. In the same DffSev, popetay DSCP values can be defned AF(Assued Fowadng) Class The DffSev has EF, AF, and DE classes of packets, of whch the AF Class s sepaated dvded nto fou classes (AF1, AF2, AF3, AF4), so n total sx sepaate classes ae povded. Due to the chaactestcs of the DffSev netwok, AF1 gven the hghest poty n the AF class can dop to the lowest poty class when swtchng netwoks. A sngle netwok may apply a unfom polcy, but t s not easy to apply the same polcy n a multnetwok, gven the dffeent chaactestcs of Intenet Sevce Povdes (ISPs) [3,4]. As seen n Fgue 1, f thee ae netwoks A, B and C and packets wll be tansmtted fom A to B and C and netwoks A and C have the same AF packet poty ode, but B smply povdes AF, when a packet depatng netwok A entes netwok B, the packet wth AF1 value wll lose ts value and be povded wth sevce as an AF packet.

3 Sensos 2010, Fgue 1. An Example of Mult DffSev Achtectue. Even though ths packet entes netwok C though netwok B, the packet cannot eceve AF1 level sevce snce t has lost the AF1 value. Even f a packet can dectly ente netwok C, thee can be a poblem, too. If netwok C has an AF packet condtonng pocess opposte to that n netwok A, a packet of the hghest sevce n netwok A wll eceve the lowest sevce n netwok C Reconfguaton of DSCP n AF Class Mult DffSev sevce sets up a blateal Sevce Level Ageement (SLA) wth ts neghbo DffSev netwoks, and contans nfomaton on Sevce Type, Sevce Type Paametes and Sevce Restctons [5]. As seen n Fgue 2, the taffc condtone n edge outes fst checks the data fom othe netwoks. Afte examnng f use taffc sent packets as contacted, the Mult DffSev sends packets ove the outng coe and PHB to the coe outes. The Mult DffSev can econfgue DSCP values o mantan the ognal condtons. The same DffSev can use ts defned popetay DSCP values. Fgue 2. Mechansm of Dffsev Edge Route.

4 Sensos 2010, In an nstance that a netwok eceves an AF1 packet fom a neghbo netwok and the cuent netwok does not defne AF1, the netwok has the popetay DSCP value of the exstng DffSev. Theefoe, t wll encode the DSCP value and send t to the coe outes. Then t wll pefom PHB and succeed n tansmttng the AF packet. 3. Suggested Method and Mathematcal Confmaton Ths pape suggests tansmttng packets afte codng DSCP at TC of edge outes by usng the unused 2 bts. As seen n Fgue 3, f Host A n the Mult DffSev netwok A tansmts AF11 packet to Host B n netwok C, the confgued DSCP value would be and t passes the coe outes n netwok A and eaches the edge outes whch ae n the mddle of netwok A and netwok B. Fgue 3. IP Datagam. Because netwoks A and B have an ageement on a sngle AF, packets fom netwok A ente the edge outes n netwok B and the TC changes ts DSCP value to a sngle AF value. If the sngle AF value s supposed to be , the DSCP value would be and passes ove the coe outes n netwok B to the outes at the edge of netwok C. Due to the SLA between netwoks B and C, the packets wll be tansmtted to netwok C. Then, the TC n netwok C ecognzes the packets as AF, but the last two bts 00 tells that ts dop pefeence s low. These packets wll be andomly coded wth the DSCP value that goes wth AF low and sent to the coe outes. If a low DSCP value s andomly allocated, the fnal value may o may not be the ognal AF11 value. The dop pefeence of AF packets, howeve, s low, and thus t has an advantage that the ognal sevce s guaanteed to a cetan degee, even though the settng of the AF packet s dffeent. Anothe advantage s that AF packets can be exchanged accodng to the class wthout othe confguaton.

5 Sensos 2010, As shown n Fgue 4, thee PTC compostes consst of Token Bucket phase, Pobablty Decson phase and Buffe Management phase. Wth sophstcated algothms, each phase contols taffc comng nto the DffSev netwok by flteng packets fom AS (Assued Sevces) uses n ode sequence. Fgue 4. Stuctue of the Thee Phased Taffc Condtone. At the Token Bucket phase, the token bucket measues taffc, and the packets wll be e-maked fom OUT to IN when an abtay use volates the contacted bandwdth. Equatons 3, 4 and 5 show the Pobablty Decson phase. Pobablty means the oppotunty that packets belongng to an abtay taffc flow can ente the DffSev netwok and s ndcated as WP (p wte). Ths pape assumes that edge outes ensues AS uses DffSev netwok and contacted bandwdth ( ev ). WP s decded by the contacted bandwdth ( ev ) and the amount of the token bucket measued taffc that eaches the edge outes. In ode to calculate WP, t s necessay to defne ate ato ( ev / max ), whch s the ato of the contacted bandwdth of each AS taffc to a oute and s used as a basc pobablty n calculatng WP. max epesents the maxmum value among ev of the vaous AS taffcs. AS taffc that eaches edge outes s accumulated fo a defned tme wndow. WP s calculated fom the accumulated taffc( ev ) and ate ato. Each TCP and UDP have dffeent WP decson fomulas. Fst, the TCP WP decson fomulae ae shown n Equatons 3, 4, and 5. Tems α and β ae obtaned fom the dffeence between aand ev. If as smalle than ev fo one tme wndow, α s decded by the dffeence between the amount of the aval taffc and the contacted bandwdth; f as bgge than ev, β s decded fom the amount of the aval taffc exceedng the contacted bandwdth. On the bass of ths concept and wth the compute smulaton, the fomulae fo α and β ae deduced as follows: ev a ev a ev a ev max 0.5 (1) (2)

6 Amount of Packet Loss (Byte) Sensos 2010, It s a poblem that TC0P taffc of naow contacted bandwdth o small RTT oveuses the netwok esouces so that AS uses who have compaatvely wde bandwdth o lage RTT fal to acheve the contacted sevce level: f ( a f ( a ev ev ), ), p wte p wte ev max ev max (3) (4) ev f ( a ev ) & ( n 2), p wte max ev max n (5) 4. Results and Analyss In ode to test the pefomance of the suggested DffSev method and the exstng IEFT DffSev method, ths study used the ns2 smulato and adopted the topology of a smat-phone envonment. Host A sends packets to Host B and passes ove fou outes. The test envonment fo the study assumes that the DffSev netwok envonment s settled and the suggested DffSev module s on the Host. Constant bt ate (CBR) s used fo Taffc, the packet sze s 1,024 bytes, and Modfed WRR Mode2 (MWRR2) Schedulng Algothms ae used. Fgue 5 dsplays the amount of packets eceved by Host B fom Host A pe unt tme thoough the DffSev netwok o the smat-phone envonment. Fgue 5. Compason of the Amount of Packets Loss pe Unt Tme Dffsev(Suggested) Dffsev(Exstng) TIME As seen n Fgue 5, the advantage of the suggested DffSev s not dscenably emakable fo the fst 100 seconds because both netwoks have eceved almost same amount of packets dung ths peod; howeve, the gaph shows dffeences afte 200 seconds and t s obvous that the suggested DffSev eceved lage packets than the othe afte 400 seconds, whch was the last test pont. Sendng a small amount of packets wll not make a bg dffeence. Theefoe, the suggested method can poduce moe

7 Recved Packets (Byte) Sensos 2010, satsfactoy esults when sendng a lage amount of packets fo a longe peod of tme. Fgue 6 shows the compaatve success ate of ecevng packets between of the suggested DffSev and the exstng DffSev when packet tansmsson s nceased. The gaph ndcates that packets ae tansmtted fom Host A to Host B and shows the amount of packets eceved at Host B. Fgue 6. Compason of the Receved Packets pe Unt Tme Dffsev(Suggested) Dffsev(Exstng) TIME 5. Conclusons When taffc congeston occus n a DffSev netwok, the netwok does not guaantee QoS n ode to decease the taffc. In the nstances of DffSev taffc congeston, t s necessay to tansmt packets moe effectvely [6]. To cope wth the congeston bette than the exstng DffSev netwok does, ths study suggests the followng method: the host detemnes a DSCP value and sends t dectly to the edge outes, so that these do not need to set up the DSCP value but only to make the coe outes dentfy the PHB fo the packets. Consequently, ths method deceases taffc load on the edge outes and the wokload to defne DSCP values. The poblem wth ths suggeston s that t s mpossble fo all the sevce povdes to set the same DffSev pncples, theefoe, EF o DE Class can be povded wth a sngle sevce, but AF Class can be povded wth fou sepaate classes. Ths method can avod the poblem and poduce a moe effcent DffSev netwok achtectue. It s expected that QoS guaantees and the expemental values may be utlzed as a pncple whch can be appled to vaous moble-web envonments based on smat-phones. Acknowledgments Fundng fo ths pape was povded by Namseoul Unvesty.

8 Sensos 2010, Refeences 1. Blake, S.; Black, D.; Calson, M.; Daves, E.; Wang, Z.; Wess, W. An Achtectue fo Dffeentated Sevces; RFC 2475, Decembe 1998; pp Hassanen, H.S.; Chen, H.Q.; Mouftah, H.T. Povdng Packet-Loss Guaantees n DffSev Achtectues. In Poceedngs of Pefomance Computng and Communcatons Confeence, Plymouth, UK, July 16 18, 2002; pp El Hachm, M.; Abouassa, A.; Loenz, P.; Sathya, R. Contol Algothm fo QoS Based Multcast n Dffsev Doman. In Poceedngs of IEEE Communcaton Technology Poceedngs, ICCT 2003; Pas, Fance, Apl 9 11, 2003; pp Pak, S. Dffsev Qualty of Sevce Suppot fo Multmeda Applcatons n Boadband Access Netwoks. In Poceedngs of 2006 Intenatonal Confeence on Hybd Infomaton Technology (ICHIT'06), Cheju Island, Koea, Novembe 09 11, 2006; pp Lopes, N.V.; Ncolau, M.J.; Santos, A. Effcency of PRI and WRR DffSev Schedulng Mechansms fo Real-Tme Sevces on UMTS Envonment. In Poceedngs of New Technologes, Moblty and Secuty, NTMS '08, Tange, VA, USA, Novembe 5 7, 2008; pp Y, P.; Hu, H.C.; Wang, B.Q.; L, H. PMUF: A Hgh-Pefomance Schedulng Algothm fo DffSev Classes. In Poceedngs of 2009 Intenatonal Jont Confeence on Computatonal Scences and Optmzaton CSO 2009, Sanya, Hanan, Chna, Apl 24 26, 2009; pp by the authos; lcensee MDPI, Basel, Swtzeland. Ths atcle s an open access atcle dstbuted unde the tems and condtons of the Ceatve Commons Attbuton lcense (