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3 i Second Life DVE S/C DVE Peer-to-peer P2P DVE P2P DVE peer peer peer DVE DVE S/C P2P 2 Lockstep Non-Lockstep DVE Lockstep S/C Non-Lockstep S/C Lockstep P2P Non-Lockstep P2P 4 Lockstep DVE 2 Non-Lockstep DVE DVE Non-Lockstep P2P Local Remote

4 ii DVE peer Non-Lockstep S/C Web Ajax Asynchronous JavaScript + XML Web Web Web Non-Lockstep DVE Ajax Web DVE DVE Non-Lockstep DVE DVE DVE

5 iii Abstract In general, a server-client (S/C hereafter) type of network topology may be employed in the Distributed Virtual Environment (DVE hereafter) such as Second Life. Although this type of DVE that offers the advantage of consistent states of objects in a virtual space, its drawbacks are well known; e.g., server overload and reduction of system throughputs. On the other hand, various peer-to-peer (P2P hereafter) network topologies are available for designing DVEs. P2P-type DVE can decentralize computing load of a server and decrease latency of turnarounds since each peer communicates directly with all of the other nodes. However, synchronization between nodes is not easy because such a network has no server for synchronization management. This issue is the so-called consistency-throughput trade-offs. In this thesis, the author studied the most effective design strategy for real-time type DVE that maintains high quality of consistency and throughput. The topology of DVE is divided into S/C type and P2P type. Moreover, these DVE models are classified by existence of synchronizer of virtual space considering role of each terminal. In this research, the model where virtual space synchronizer exists is called Lockstep type. The other type is called Non-Lockstep type. Consequently, DVE models are classified to Lockstep type S/C, Non-Lockstep type S/C, Lockstep type P2P, and Non-Lockstep type P2P. Then, update interval depends on network latency and communication frequency in two kind of Lockstep type. Therefore, Lockstep type is difficult to be employed in real-time type DVE. In this thesis, the author studied feasibility for real-time type DVE from a perspective of consistency and throughput. First, Non-Lockstep type P2P was discussed. In this model, while the information about a local avatar (virtual player in the DVE) can be quickly available at a local host, a remote avatar s information cannot be simultaneously displayed because of latency. Consequently, shared objects cannot be controlled jointly by all the users because of the temporal difference between the local and the remote avatars in terms of their status in reference to each other. Thus, the author proposed a way to improve consistency to maintain the shared object without sacrificing

6 iv throughput. Concretely, a priority field to control shared object is allocated to each avatar. Moreover, the author proposed the method to avoid absolutely inconsistent phenomena about shared object between peers. As an example of the application, a real-time networked doubles air-hockey was implemented for evaluation of validity of proposed method. Secondly, as an example of the representative of Non-Lockstep type S/C, the author focused on the current Web Ajax (Asynchronous JavaScript + XML) system, the most widely used infrastructure of this type, and proposed a strategy for designing real-time Web games. When a game is actualized on the Web, users can easily play it through a browser, and this tends to lead to growth in the number of users. On the other hand, if HTTP is used to transmit the data, the transmission will not be limited by a firewall. Here, client side prediction by using Ajax can be used in real-time Web games to overcome the limitations of HTTP communication. As a result, proposed concept can be extended to various types of real-time Web interactive application. Finally, this thesis studied feasibility for real-time type DVE from a perspective of consistency and throughput. As a result, in Non-Lockstep type DVE, the author proposed real-time exclusive control about shared object for the first time in the world. Moreover, it was confirmed that feasibility for real-time type DVE and its topology were irrelevant. Therefore, this research will contribute to the method of designing real-time type DVE in the future.

7 v DVE DVE DVE DVE Non-Lockstep P2P AtoZ (Allocated Topographical Zone) Dead Zone Count Down Protocol

8 vi Non-Lockstep S/C Web Web Web Web Dead Reckoning Protocol

9 vii 3.1 MVC Lockstep S/C Time chart Non-Lockstep S/C Time chart Lockstep P2P Time chart Non-Lockstep P2P Time chart AtoZ Count Down Protocol Dead Zone Critical Case Dead Zone Phantom Case Dead Zone MVC DR DR JSON Web pixel MVC 50ms Hz MVC 100ms Hz

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11 ix MVC 50ms DR MVC 100ms DR Web MVC 50ms DR Web MVC 100ms DR MVC 50ms DR MVC 100ms DR

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13 DVE ,266 6, % [106] World Wide Web Web [20] livedoor Blog [53] mixi [58] MySpace [85] Social Networking Service SNS ) Wikipedia [74].com [88] YouTube [82] [94] Flickr [76] Distributed Virtual Environment DVE DVE [6], [18], [19], [33], [46], [48], [52], [78], [79], [95] [97], [99], [100], [108] [35] [38] [54], [103], [105], [110] [61], [80], [81] [104], [114] [54] DVE Multi-player Online Game MOG 3 (1) First-person shooters FPS (2) Real-time Strategy games RTS (3) Role-Playing Game RPG

14 2 1 FPS Counter-Strike [72] Quake 4 [40] Half-Life 2 [73] Unreal Tournament 3 [27] RTS RTS Command & Conquer [26] StarCraft II [10] Age of Empires III [56] RPG RPG [32] Diablo II [9] Ultima Online [25] Everquest II [71] II [60] RPG DQ [90] FF [92] DQ IX [93] 2009 FF XI [91] RPG MORPG Multi-player Online Role-Playing Game MMORPG Massively Multi-player Online Role-Playing Game Wikipedia [75] DQ IX MORPG FF XI MMOPRG Windows Online [84] Wii X [87] Second Life [51] meet-me [89] 3D Second Life [51] DELL PC DVE 1.2 DVE DVE DVE a b c d 4

15 1.2. DVE 3 [69] a - c d DVE DVE 6 [69] 1. DVE [Hz] 1 2. DVE CPU 3. DVE 4. DVE CPU 5. DVE

16 DVE 1 CPU 1 3 d 4 c a - d FTTH ADSL Rich Internet Application RIA RIA Web Web Ajax Asynchronous JavaScript + XML [63] Adobe Flash [1] Microsoft Silverlight [57] DVE

17 DVE DVE S/C Peer-to-peer P2P 2 S/C consistency throughput P2P peer peer peer [69] Lockstep Non-Lockstep DVE Lockstep S/C Non-Lockstep S/C Lockstep P2P Non-Lockstep P2P 4 Lockstep DVE 2 Non-Lockstep DVE DVE 4 Non-Lockstep P2P Local Remote [109], [110] 3 peer 2 5 Non-Lockstep S/C Web Ajax Web Web Web Web

18 6 1 HTTP 1 HTTP Web 6 DVE DVE DVE 1.5 S/C DVE 1 S/C Peer-to-peer P2P DVE 1 P2P peer peer peer Lockstep DVE DVE MVC Non-Lockstep DVE DVE MVC MVC Modeling-View-Control Modeling View

19 Control MVC DVE DVE DVE DVE Allocated Topographical Zone AtoZ DVE Allocated Topographical Zone AtoZ Critical Case peer AtoZ peer Phantom Case Local peer peer Phantom Case

20 8 1 Dead Zone AtoZ Dead Zone DVE AtoZ Dead Zone Count Down Protocol CDP Critical Case Dead Zone peer peer Phantom Case Dead Reckoning DR DR Web Web 3 Information Extraction Layer

21 DR DR 1 [Hz] [Hz] [ms] [ms] S/C DVE

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23 11 2 DVE FPS 10[ms] 100[ms] [7] 1.1 RTS RPG 100[ms] 500[ms] [8]

24 12 2 [102] 2.2 DVE DVE DVE [22], [23] DVE (1) (2) (3) Lockstep Synchronization Lockstep Synchronization [29] DVE DVE Delayed Global Consisntency Delayed Global Consisntency Qin [67]

25 2.2. DVE 13 Time Warp Time Warp [44] Jefferson DVE [50] Dead Reckoning Dead Reckoning DR [68] [111] DR [68] [86] [5] [13] Relevance Filter DVE DVE [4], [12], [70] Area of Interest AOI AOI AOI [3] [69]

26 14 2 IP Internet Protocol 1 [39] S/C P2P S/C NPSNET [54] VLNET [65] RING [28] VELVET [21] [21], [54] DVE [77] [21], [54] Xcast explicit Multi-Unicast [11] DVE P2P DIVE [14] ANGEL [101] MiMaze [24] [101] P2P P2P peer P2P DVE DVE DIS Distributed Interactive Simulation [41] QoS Quality of Service RSVP Resource ReSerVationProtocol [83] DIS

27 DVE ID DR NPSNET [54] RSVP IP UDP User Datagram Protocol 2 CPU QoS 2.3 DVE Lockstep Synchronization Delayed Global Consisntency Dead Reckoning 1.4

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29 17 3 DVE DVE DVE DVE 3.1 DVE S/C P2P 2 Lockstep Non-Lockstep DVE Lockstep S/C Non-Lockstep S/C Lockstep P2P Non-Lockstep P2P 4 MVC Modeling-View- Control [107] 3.1 Modeling View Control Lockstep Non- Lockstep MVC Time chart Lockstep S/C Time chart A B t 3.3 Non-Lockstep S/C Time chart A B MVC

30 18 3 DVE t0 Terminal Modeling t1 Control View Modeling View t2 Control Modeling Control View 3.1: MVC ClientA t0 Control View t1 Control View Viewt2 Control Server ClientB t0 Control View Modeling t1 Control View Modeling t2 Control View 3.2: Lockstep S/C Time chart

31 3.1. ClientA ClientB 19 ta0 Server Modeling tb0 Control View Modeling Control View Modeling ta1 View tb1 Control Modeling Control View Modeling ta2 View tb2 Control Modeling Control View 3.3: Non-Lockstep S/C Time chart t 3.4 Lockstep P2P Time chart Peer A B MVC peer peer peer peer peer 3.5 Non-Lockstep P2P Time chart 3.4 peera B MVC peer peer peer Non-Lockstep S/C peer DVE

32 20 3 DVE PeerA t0 PeerB Modeling t0 Control View Modeling Control View Modeling t1 t1 Control View Modeling Control View Modeling t2 t2 Control View Modeling Control View 3.4: PeerA Lockstep P2P PeerB Time chart Modeling ta0 tb0 Control View Modeling Control View Modeling ta1 tb1 Control View Modeling Control View Modeling ta2 tb2 Control View Modeling Control View 3.5: Non-Lockstep P2P Time chart

33 : Lockstep S/C + O(n) Xcast O(n) Non-Lockstep S/C O(n) Xcast O(n) Lockstep P2P N/A O(n 2 ) Xcast O(n) Non-Lockstep P2P N/A O(n 2 ) Xcast O(n) S/C P2P peer Lockstep S/C Non-Lockstep S/C P2P 2 n S/C O(n) P2P O(n 2 ) Xcast O(n) 3.2 Lockstep DVE Non- Lockstep DVE 3.3 Lockstep DVE 2

34 22 3 DVE 3.2: Lockstep S/C Non-Lockstep S/C Lockstep P2P Non-Lockstep P2P Non-Lockstep DVE DVE 4 Non-Lockstep P2P 5 Non-Lockstep S/C

35 23 4 Non-Lockstep P2P Non-Lockstep P2P Local Remote [109], [110] DVE DVE Shared Soccer [52] [52] P2P peer Non-Lockstep P2P Non-Lockstep P2P peer (1) peer peer (2)

36 24 4 Non-Lockstep P2P (3) peer (4) (1) (3) 4 AtoZ Dead Zone 3 [98] AtoZ Dead Zone [98], [78], [47] Critical Case AtoZ (Allocated Topographical Zone) peer 1 2 peer Local peer peer (1) (2) peer DVE Allocated Topographical Zone AtoZ T t i i i p i P=p 1,p 2, p j,,p n N=1 2 n p i AtoZ AtoZ(p i ) = {x xϵz, Access(x, p i ) = min jϵn (Access(x, p j))} (4.1) AtoZ(p i ) p i AtoZ x Z Access(x, p i ) p i x

37 T=ti AtoZ of A A AtoZ of C C AtoZ of B B O AtoZ of D D T=ti+1 AtoZ of A A C AtoZ of C O B AtoZ of B AtoZ of D D 4.1: AtoZ p i AtoZ p i x Access [98] peer AtoZ O AtoZ (1) (2) peer AtoZ (3) AtoZ peer (3) peer peer peer Non-Lockstep P2P AtoZ Step 1. peer peer peer Step 2. peer Step 1 AtoZ Step 3. Step 2 O AtoZ Step 3-1 Step 3-2

38 26 4 Non-Lockstep P2P Step 3-1. Local peer O O peer Step 3-2. O peer O Step 1 Step 3-2 peer Step 1 3 (4) [98] Dead Zone Critical Case Phantom Case AtoZ AtoZ peer AtoZ Critical Case peer peer Critical Case Critical Case Critical Case peer causality Critical Case Phantom Case Local peer Phantom Case Phantom Case peer Phantom Case

39 Phantom Case Phantom Case Dead Zone Critical Case/Phantom Case AtoZ AtoZ Dead Zone Dead Zone DZ(p i, p j ) = {x xϵz, Access(x, p i) Access(x, p j ) t <([d/ t] + 1) (4.2) [ ] DZ(p i p j ) p i p j Dead Zone d[ms] t[ms] ([d/ t] + 1) 4.1 d[ms] ping Dead Zone Remote peer peer Critical Case AtoZ AtoZ Dead Zone AtoZ Dead Zone Count Down Protocol Critical Case Phantom Case AtoZ Critical Case Phantom Case Dead Zone Dead Zone

40 28 4 Non-Lockstep P2P Count Down Protocol Count Down Protocol CDP Dead Zone CDP Dead Zone AtoZ 2 peer Local peer peer CD Count Down Protocol Step 1. peer CD CD Step 2. peer CD CD 0 Step 3-1 peer Step 3-2 peer CD CD 1 Step 3-1. Step 3-2. CD 1 CD CD peer 2 peer CDP 4.2 peer A B p peer 4.2 peer A B CD t i p i peer B A CD peer CD

41 (Remote avatar) (Local avatar) B BA(ti-p)-p p B BB(ti) O A AA(ti) (Local avatar) peer A O A AB(ti-p)-p (Remote avatar) peer B (peer A CD ) (peer B CD ) 4.2: Count Down Protocol A A (t i ), B A (t i p ) p (4.3) A B (t i p ) p, B B (t i ) (4.4) CD CD peer CDP peer CD Dead Zone peer peer CD CDP Dead Zone Critical Case 2 1. peer CD 1 2. peer CD peer peer peer Critical Case peer 0 CD 4.2 B A (t i p ) p 0 A B (t i p ) p 0 (4.5)

42 30 4 Non-Lockstep P2P Phantom Case Phantom Case Step 3-2 peer peer peer peer Phantom Case Phantom Case 2 CD CDP CD Local peer Remote peer peer peer priority method Step 1. peer peer CD Step 2. peer Step 3-1 Step 3-2 Step 3-1. peer

43 Step 3-2. Step 4. peer 0 CDP Critical Case Phantom Case Phantom Case peer peer CDP peer peer O(n) n 4.3 CDP Tuning Method AtoZ AtoZ AtoZ Dead Zone Dead Zone AtoZ AtoZ Dead Zone Critical Case Phantom Case Critical Case

44 32 4 Non-Lockstep P2P peer Phantom Case peer peer NTP (i) (ii) : 2.89 [m], 1.48 [m] : : 4.1 [cm] : 8.5 [cm] : 3.0 [m/s] : 1.0 [m/s] : 0.8 : 0.8 : TCP : UDP : 25 [ms] x 2 x

45 : P(ti) P(ti+x) M(ti) 4.4: 3 x 4.4 M(t i ) P (t i ) P (t i+x ) t i t i t i+x (i) peer

46 34 4 Non-Lockstep P2P (ii) Critical Case (iii) Phantom Case (iv) Dead Zone (i) (ii) (iii) Dead Zone Critical Case/Phantom Case Critical Case/Phantom Case Dead Zone (iv) peer CDP Critical Case Phantom Case [15] NistNet pareto 3 LAN 57[ms] 28[ms] 57[ms] ping peer [ms] 4.0 [ms] 57.0 [ms] 8.1 [ms] CDP CDP ,000 peer 25, Critical Case Critical Case CDP

47 Dead Zone local avatar if local(t i ) O(t i ) + th(t i ) < remote j (t i ) O(t i ) j, remote avatar otherwise. (4.6) local(t i ) remote j (t i ) O(t i ) t i local avatar j remote avatar th(t i ) t i th(t i ) Critical Case/Phantom Case th(t i ) 0. 4cm 1. th(t i ) = th(t i 1 ) + (4 Competition repeats) :40cm 2. th(t i ) = th(t i 1 ) + (4 Concession repeats) :4cm 3. th(t i ) = th(t i 1 ) Competition repeats Concession repeats Critical Case 57[ms] CDP Critical Case/Phantom Case Critical Case Phantom Case Dead Zone Critical Case Phantom Case 4.8 Dead Zone peer CDP

48 36 4 Non-Lockstep P2P Ownership consistency [%] ms 28 ms 57 ms 0 ms 28 ms 57 ms 0 ms 28 ms 57 ms Tuning Mehotd Count Down Protocol (without priority method) Count Down Protocol Competition Concession Consitency 4.5: 4.5 peer peer peer th(t i ) peer th(t i ) CDP peer Dead Zone Critical Case 90% CDP Critical Case Critical Case Dead Zone Critical Case Critical Case Phantom Case th(t i ) Critical Case Critical Case

49 Critical cases in dead zone [%] Latency [ms] Tuning Method Count Down Protocol (without priority method) Count Down Protocol 4.6: Dead Zone Critical Case CDP Critical Case Critical Case CDP Phantom Case Phantom Case peer Phantom Case Phantom Case Critical Case CDP Critical Case Phantom Case Critical Case/ Phantom Case 4.8 peer Dead Zone peer

50 38 4 Non-Lockstep P2P Phantom cases in dead zone [%] Latency [ms] Tuning Method Count Down Protocol (without priority method) Count Down Protocol 4.7: Dead Zone Phantom Case Critical Case Phantom Case 0.83% CDP 4.4 Non-Lockstep P2P peer Critical Case CDP CDP Critical Case Non-Lockstep DVE Phantom Case 2 peer Critical Case

51 Ownership obtainment in dead zone [%] High Low High Low High Low priority priority priority 0 ms latency 28 ms latency 57 ms latency CDP priority method 4.8: Dead Zone

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53 41 5 Non-Lockstep S/C Non-Lockstep S/C Web Web Web Web DVE Web Web 5.1 Web Web 1.1 Web Web Web Web Web [59] [59] Java MMORPG RuneScape [42] [62] Web Shockwave Tank Ball 2 [55] [69].

54 42 5 Non-Lockstep S/C Web Web Web Web Web Web Web 2 Web 3 (1) (2) (3) Web HTTP 3 (1) Web PC Web (2) (3) HTTP HTTP Web (2) Web

55 5.1. Web 43 (3) 100[ms] [102] [7] 100[ms] Web Web Non-Lockstep Web Ajax [63] Flash [1] Ajax JavaScript HTTP Web Web Web Goole Maps [31] Gmail [30] Google Web Flash ActionScript ActionScript Ajax XML Flash Comet [16] Comet HTTP Web Ajax Comet Ajax Flash Ajaxian.com [2] prototype.js [66] jqury [45] OpenLaszlo [49]

56 44 5 Non-Lockstep S/C Ajax Comet Web Ajax [63] JavaScript Ajax Web MVC (3) DR HTTP Information Extraction Layer

57 : 1 DR GUI Handler Modeler Viewer Dead Reckoning Provider DRP Network Handler 5 MVC Ajax MVC MVC

58 46 5 Non-Lockstep S/C Web Server 5.2: Web [43] XML JavaScript Object Notation JSON [17] Web HTTP GUI Handler GUI Handler DRP DRP Modeler

59 Modeler 5.3: MVC Modeler DRP Viewer Viewer Viewer Modeler Viewer Web Dead Reckoning Provider Network Handler DRP DR Modeler MVC Network Handler Network Handler DR [68] DRP Modeler Web Network Handler Ajax Web

60 48 5 Non-Lockstep S/C 5.3 Dead Reckoning Protocol DVE Web DVE DR [34] PHBDR Position History Based Dead Reckoning [68] DR DR DR HTTP Web DR DR 5.4 DRP GUI Handler Modeler A(t i ) A (t i ) t i A A(t i+1 ) t i+1 A 5.4 DR 3 (1) 5.4 A ε 5.5a (2) u 5.4 B 5.5b t i A A(t i ) A(t i ε ) ε (5.1)

61 : DR (3) ε ε u Web DR Web Web

62 50 5 Non-Lockstep S/C 5.5: DR JSON MVC Web 32 32[pixel] 64[pixel/s] Web HTTP Web

63 ClientA virtual Reconstruction Modeling space Viewby DR of Server ClientB Display to user Data BA virtual Reconstruction Modeling space Operation Control Viewby DR of Data of Data Aavatar input Apache Web Server Operation Display Control to of user avatar Network Tomcat Communication server by Ajaxwith HTTP Data Data Network Binput HTTP Communication server by Ajaxwith Firefox : Web HTTP DR Web MVC (1) (2) MVC (3) Web (4)

64 52 5 Non-Lockstep S/C (5) Web (6) 5.7: Web (1) MVC A A (t i ) A B (t i ) + B A (t i ) B B (t i ) 32 (5.2) pixel A B A B 32[pixel] (1) (2) MVC MVC (3) (4) (5) (6)

65 Web 1 1 DR DR MVC [ms] [ms] 100[ms] DR Web DR DR 300[ms] 1 20[pixel] 5.2 DR [pixel] 5.2 Web Web DR MVC Web JacaScript Firefox JavaScript setinterval MVC Web

66 54 [pixel] 5 Non-Lockstep S/C アバタ 位 置 情 報 の 差 異 DRなし, 200通 信 間 300 隔 [ms] DRなし, DRあり, MVC:50ms DRあり, MVC:100ms 5.8: pixel 5.1: MVC 50ms DR [ms] [ms] [ms] setinterval Web JavaScript JavaScript 5.2: MVC 100ms DR [ms] [ms] [ms]

67 : Web MVC 50ms DR [ms] [ms] [ms] : Web MVC 100ms DR [ms] [ms] [ms] DR Web MVC 50[ms] 100[ms] MVC 100[ms] MVC MVC DR DR DR DR DR 5.10 DR 100[ms] 200[ms] Web 200[ms] Ajax Web MVC Web DR Web

68 56 5 Non-Lockstep S/C アバタの 更 新 頻 度 [Hz] 相 手 DRなし 通 信 間 300 隔 [ms] DRあり : MVC 50ms Hz 68.8[ms] 21.3[ms] Web 2 HTTP O(n) n O(n) JSON O(n) Web O(n 2 ) HTTP Web Web 100[ms] MVC 50[ms]

69 アバタの 更 新 頻 度 [Hz] 相 手 DRなし 通 信 間 300 隔 [ms] DRあり : MVC 100ms Hz 5.5: MVC 50ms DR [ms] [ms] [ms] DR 5.5 Non-Lockstep S/C Web Web DR HTTP Ajax MVC MVC

70 58 5 Non-Lockstep S/C 5.6: MVC 100ms DR [ms] [ms] [ms] DR Web DR Web 2 Web

71 DVE DVE DVE DVE 4 Non-Lockstep DVE 2 Non-Lockstep P2P Non-Lockstep DVE Non-Lockstep S/C Web Web Web DVE Ajax DR DVE DVE 6.2 DVE

72 60 6 AtoZ Web DR HTTP DVE [64], [112], [113]

73 61 6

74

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