Game Traffic Analysis: An MMORPG Perspective

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Online gaming is one of the most profitable businesses on the Internet. Of all the genres of online games, MMORPGs (Massive Multiplayer Online Role Playing Games) have become the most popular among network gamers, and now attract millions of users who play in an evolving virtual world simultaneously over the Internet. To gain a better understanding of game traffic and contribute to the economic well-being of the Internet, we analyze a 1, 356-million-packet trace from a sizeable MMORPG called ShenZhou Online. This work is, as far as we know, the first formal analysis of MMORPG server traces.

We find that MMORPG and FPS (First-Person Shooting) games are similar in that they both generate small packets and require low bandwidths. In practice, the bandwidth requirement of MMORPGs is the lower of the two due to less real-time game playing. More distinctive features are the strong periodicity, temporal locality, irregularity, and self-similarity observed in MMORPG traffic. The periodicity is due to a common practice in game implementation, where game state updates are accumulated within a fixed time window before transmission. The temporal locality in game traffic is largely due to the game’s nature, whereby one action leads to another. The irregularity, which is unique to MMORPG traffic, is due to the diversity of the game’s design so that the behavior of users can vary drastically, depending on the quest at hand. The self-similarity of the aggregate traffic is due to the heavy-tailed active/idle activities of individual players. Moreover, we show that the arrival of game sessions within one hour can be modelled by a Poisson model, while the duration of game sessions is heavy-tailed.

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Game Traffic Analysis: An MMORPG Perspective

  1. 1. Appeared in ACM NOSSDAV 2005 (15th International Workshop on Network and Operating System Support for Digital Audio and Video) Game Traffic Analysis: An MMORPG Perspective (MMORPG: Massive Multiplayer Online Role Playing Game) Kuan-Ta Chen, Polly Huang, Chun-Ying Huang, Chin-Laung Lei Department of Electrical Engineering National Taiwan University Apr. 29, 2005
  2. 2. Talk Outline Overview network game research current status of MMORPG Trace collection Traffic characterization & their physical explanations Conclusion Future work Game Traffic Analysis: An MMORPG Perspective 2
  3. 3. Network Game Research Traffic analysis and modeling packet size/arrival process connection time/arrival process User behavior analysis and modeling session time, session arrival process session membership The effects of network QoS affect player duration? affect arrival / departure rate? affect overall score or running speed? Game Traffic Analysis: An MMORPG Perspective 3
  4. 4. Network Game Research (cont.) Dead reckoning (client-side prediction) Interest management (preference clustering) Server discovery mechanism (select a best game server) Network infrastructure multicast – group management multi-tier (proxyed) p2p / overlay networks Game Traffic Analysis: An MMORPG Perspective 4
  5. 5. Motivation Network games contribute 3% -- 4% Internet traffic at backbones in 2000 MMORPG the dominate network game genre in Asia exhibit distinct features, such as • no explicit game rounds • no restrict on player number Game Traffic Analysis: An MMORPG Perspective 5
  6. 6. The Increasing Popularity of MMOG Figure curtsey of http://www.mmogchart.com/ Game Traffic Analysis: An MMORPG Perspective 6
  7. 7. Popular Genres in MMORPG Figure curtsey of http://www.mmogchart.com/ Game Traffic Analysis: An MMORPG Perspective 7
  8. 8. Network Games in Taiwan 120 network games in 1st quarter, 2003 market value of 6,800 million NT dollars in 2003 fl 80% share of the whole PC game industry Gamania (Lineage) owns > 4,000 Mbps links R. O. has a record of 370,000 players online, equivalent to 1.5% of the population Game Traffic Analysis: An MMORPG Perspective 8
  9. 9. Online a mid-scale, commercial MMORPG in Taiwan a typical Asia MMORPG --- Microsoft Windows platform (Windows 2000, MS SQL Server) data communication based on TCP (By the way) Issues on network protocols UDP: Ultima Online (EA), Everquest series (SOE) TCP: World of Warcraft (Blizzard) no general agreement on the use of base protocol Game Traffic Analysis: An MMORPG Perspective 9
  10. 10. 神州 Online m e It’s
  11. 11. Trace Collection - Setup Game Traffic Ethernet Gigabit Management a FreeBSD PC interface w/ tcpdump L3 switch Game & Database servers Monitoring interface Port forwarding Traffic Monitor L4 switch L2 switch Game Traffic Analysis: An MMORPG Perspective 11
  12. 12. Trace Collection - Summary Trace Sets Date Time Period Drops N1 3 8/29/04 (Sun.) 15:00 8 hr. 0.003% N2 2 8/30/04 (Mon.) 13:00 12 hr. ? Trace TCP Packets Bytes Conn. (in/out/both) (in/out/both) N1 57,945 342M / 353M / 4.7TB / 27.3TB / 695M 32.0TB N2 54,424 325M / 336M / 4.7TB / 21.7TB / 661M 26.5TB 1,356 million packets in total Game Traffic Analysis: An MMORPG Perspective 12
  13. 13. Term definition Client traffic all traffic sent from clients Client packets all packets sent from clients Client data all packets excluding “pure TCP ack packets packets” (40 bytes) sent from clients The same rules apply to server traffic, server packets, and server data packets Game Traffic Analysis: An MMORPG Perspective 13
  14. 14. Traffic Characterization Tiny packets Low bandwidth requirement Temporal dependency in both within-connection traffic aggregate traffic Periodicity and synchronization Game Traffic Analysis: An MMORPG Perspective 14
  15. 15. Payload size distribution - CDF client packets 98% pkts’ payload ≤ 31 bytes the most two modes occupy 90% fl certain commands are popular server packets avg. payload size 114 bytes contrast to the mean packet size 400 bytes observed in backbones Game Traffic Analysis: An MMORPG Perspective 15
  16. 16. The consequence of tiny packets overhead of protocol in client traffic 73% bytes are headers 30% bytes (38% pkts) are for pure TCP acks The challenge on infrastructures overall avg. pkt size is 84 bytes routers generally assume pkt size within 125 -- 250 bytes when vendors claim 1 Gbps rate, they may indicate 5M pkt/sec for avg. pkt size = 200 bytes Game Traffic Analysis: An MMORPG Perspective 16
  17. 17. Packet load distribution < 5 pkt/sec for server data pkt in most of conn. < 15 pkt/sec for 99% of conn. Game Traffic Analysis: An MMORPG Perspective 17
  18. 18. Bandwidth Usage client traffic < 3 Kbps data < 8 Kbps w/ ack server traffic < 13 Kbps << 40 Kbps for a FPS (First Person Shooting) game, Counter-Strike Similar to Warcraft III, a RTS (Realtime Strategy) Game Game Traffic Analysis: An MMORPG Perspective 18
  19. 19. Cannot Overlook the Traffic of MMOGs R. O. in Taiwan announced a record of 370,000 online players assuming each user use 10 Kbps fl total 3.7 Gbps is required in average for just A game. Game Traffic Analysis: An MMORPG Perspective 19
  20. 20. Packet Interarrivals within a Connection User inputs is not Poisson Temporal dependence exist in both client traffic and server traffic Game Traffic Analysis: An MMORPG Perspective 20
  21. 21. CDF of Packet Interarrival Times deviation from exponential distribution Game Traffic Analysis: An MMORPG Perspective 21
  22. 22. Diversity in User Behaviors active player: close to active player exponential common player idle player: idle player uniform + determinist distr. common player: in-between the two extremes Game Traffic Analysis: An MMORPG Perspective 22
  23. 23. 神州 Online These players are keeping stalls.
  24. 24. CDF of Packet Interarrival Times 50% are around 200 ms fl signature of periodic message dispatch Game Traffic Analysis: An MMORPG Perspective 24
  25. 25. Temporal Locality in Client Traffic ACF: auto-correlation functions clustering nature in player actions active actions: walking, fighting inactive actions: talking, viewing equipments, trading, idle Game Traffic Analysis: An MMORPG Perspective 25
  26. 26. Clustered nature in user actions Client packet inter-arrival times from a player 30 s 100 s 120 s 120 s 150 s 140 s 400 s Game Traffic Analysis: An MMORPG Perspective 26
  27. 27. Temporal Locality in Server Traffic Server pkt primarily convey position updates the rate of position updates depends on the number of nearby characters Game Traffic Analysis: An MMORPG Perspective 27
  28. 28. Spatial Locality in # of Neighbors Pos Neighbor # (3,3) 1 (2,3) 2 … (1,1) 4 (1,2) 5 (1,3) 4 Game Traffic Analysis: An MMORPG Perspective 28
  29. 29. Transformation: Spatial Locality to Temporal Locality The spatial locality shows up in terms of temporal locality in the traffic as the characters move continuously on the map. t Neighbor # 1 1 2 2 3 1 … 10 4 11 5 12 4 Game Traffic Analysis: An MMORPG Perspective 29
  30. 30. Temporal locality in server traffic Server packet rates for a player Game Traffic Analysis: An MMORPG Perspective 30
  31. 31. Aggregate Packet Arrivals the aggregate packet arrival time series count the number of incoming/outgoing packets regardless of connections take samples every 10 ms Patterns identified temporal dependence periodicity Game Traffic Analysis: An MMORPG Perspective 31
  32. 32. ACF of aggregate server pkt arrivals periodity: 200 ms position updates are synchronous to all clients incurring packet bursts Game Traffic Analysis: An MMORPG Perspective 32
  33. 33. ACF of aggregate client pkt arrivals Positive temporal dependence up to three minutes. Game Traffic Analysis: An MMORPG Perspective 33
  34. 34. The “flash crowds” effects ACF for successive 3 minutes Players are active simultaneously at times “global events” lead to flash crowds effects Game Traffic Analysis: An MMORPG Perspective 34
  35. 35. Frequency Components in Server Traffic PSD: power 5 Hz spectral density another proof of the 200 ms round Servers seem to Multiples adapt frequency of 5 Hz by certain metrics, such as number of nearby characters Game Traffic Analysis: An MMORPG Perspective 35
  36. 36. Frequency Components in Client Traffic by auto-walk and 6 Hz auto-attack timers Adjust frequency by level/skill and weapons held Multiples of 6 Hz client timers are synchronized Does the sync. lead to performance problems? Game Traffic Analysis: An MMORPG Perspective 36
  37. 37. Conclusion Traffic characteristics & physical explanations Tiny packets Low bandwidth requirement for individual client Non-poisson user inputs (diversity of user behaviors) Temporal dependency in within-connection traffic (clustering nature in user inputs) Temporal dependency in aggregate traffic (flash crowds effects) Periodicity and synchronization (common implementation practice) Game Traffic Analysis: An MMORPG Perspective 37
  38. 38. Conclusion (cont.) TCP maybe an overkill for MMORPG, e.g., in oveall client traffic 73% bytes used by TCP/IP headers 30% bytes used by pure TCP acks Game Traffic Analysis: An MMORPG Perspective 38
  39. 39. Future Work assessment for impacts of network QoS more traffic characterization Identify abnormal sessions, e.g., bots in Lineage & Ragnarok Online Identify game traffic performance evaluation To provide a better network infrastructure for netgames Game Traffic Analysis: An MMORPG Perspective 39
  40. 40. Questions?
  41. 41. Thank You! kuan@ilife.cx http://kuan.ilife.cx/

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