1. Traffic Analysis of Avatars in Second Life James Kinicki and Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA http://www.cs.wpi.edu/~claypool/papers/second-life/

2. May 2008 NOSSDAV, Braunschweig, Germany2 Introduction – Online Virtual Worlds Users interact with world and other users via avatar For both business and leisure –Walt Disney to Wells Fargo creating new virtual worlds Second Life most well-known virtual world today –Over 12 million users –Over 950 thousand having logged in in the past month Online Games Forms of interaction are limited to gameplay interactions Static, preexisting environments Low bitrate requirements (small, frequent packets) Virtual Worlds Flexible forms of interaction with emergent user behavior Dynamic environments - users add objects, media… Significantly higher bitrates What is the turbulence for virtual worlds?

3. May 2008 NOSSDAV, Braunschweig, Germany3 Research Questions Are results from previous experiments (Fernandes et al., NOSSDAV 2007 [6]) reproducible? Does turbulence of Second Life vary with number of objects and avatars in zone? What is turbulence for teleportation? How does turbulence of Second Life compare with online games?

4. May 2008 NOSSDAV, Braunschweig, Germany4 Outline Introduction(done) Methodology(next) Analysis Conclusions

5. May 2008 NOSSDAV, Braunschweig, Germany5 Methodology Determine avatar actions to study Select Second Life zones to visit Setup measurement environment Gather data Analyze results

6. May 2008 NOSSDAV, Braunschweig, Germany6 Methodology - Avatar Actions Teleporting - user selects new zone on map and teleports avatar, standing after arrival Standing - avatar remains still (no movement of mouse or keyboard) Walking - avatar moves in straight line across single zone at constant speed Flying - avatar flies in circle around the edge of single zone at constant speed

7. May 2008 NOSSDAV, Braunschweig, Germany7 Methodology - Zones Hypothesis is that both objects and avatars affect the Second Life network traffic  find four zones –sparse and deserted –dense and deserted –dense and crowded –sparse and crowded (but this one tough)

8. May 2008 NOSSDAV, Braunschweig, Germany8 Methodology - Measurement Environment PC w/Windows XP pro on a 2.8 GHz P4 with 1 GB of RAM Second Life v 1.18.2 Residential broadband connection –Based on [6], not a bottleneck –Cable modem (4.5 Mb/s down, 1 Mb/s up) Wireshark –Capture all traffic to/from Second Life servers

9. May 2008 NOSSDAV, Braunschweig, Germany9 Methodology - Data Gathering Since single server handles one zone, not actually leave zone as avatar moves –Flying goes in a circle –Walking goes in a line, can cross zone in about 30 seconds –Teleport waits until all objects rendered Deserted have no other avatars Dense, crowded between 90 and 100 people Streaming media was turned off

10. May 2008 NOSSDAV, Braunschweig, Germany10 Outline Introduction(done) Methodology(done) Analysis (next) Conclusions

11. May 2008 NOSSDAV, Braunschweig, Germany11 Analysis - Bandwidth Action Walking, flying require more (8x) than standing Flying requires only slightly more than walking Teleportation requires similar to flying Zone Dense, crowded requires more than sparse and deserted zones Upstream/Downstream Up 10x less than down Fewer correlations (zone, action) (down for rest of analysis)

12. May 2008 NOSSDAV, Braunschweig, Germany12 dense, crowdeddense, deserted sparse, deserted Zone Dense and crowded both larger Sparse and deserted small Action Standing smallest Walking and flying larger Teleport always moderately large Analysis – Packet Size

13. May 2008 NOSSDAV, Braunschweig, Germany13 dense, crowdeddense, desertedsparse, deserted Analysis – Inter Packet Time Frequent packets, regardless of zone or action Half the packets arrive back-to-back. Highest rate for teleporting

14. May 2008 NOSSDAV, Braunschweig, Germany14 Comparison to Online Games Second Life turbulence far greater than online games –Bandwidth use10x-100x –Packet sizes15x-20x –Packets sent3x-20x Large turbulence suggests meeting QoS over wide range of networks could be a challenge

15. May 2008 NOSSDAV, Braunschweig, Germany15 Conclusions 1.Previous results (Ferdandes et al. [6]) somewhat reproducible –Yes, zone and avatar affect Second Life turbulence –No, magnitude of bandwidth different  Suggests further study needed before models 2.Turbulence impacted by objects and avatars –Dense, crowded 10x bwidth and psize of sparse, deserted –Dense, deserted 2x bwidth and psize of sparse, deserted  Suggests avatars plays larger role than objects 3.Teleport most turbulence for all zones 4.Second Life more turbulence than online games (10x) Bandwidth results –Help users in broadband selection choices –Help ISP’s and virtual world server hosting w/capacity planning Packet results –Used for classification and simulation

16. May 2008 NOSSDAV, Braunschweig, Germany16 Future Work Private zone w/full control over access –Control exact number of objects and avatars Caching, in conjunction with motion Quality of Service requirements –May be similar to third-person online games (or not)

17. Worcester, Massachusetts, USA October 21-22, 2008 http://netgames2008.cs.wpi.edu/ Game related topics in Networks and Systems (Like a NOSSDAV for games!) Papers due June 15th!

18. Traffic Analysis of Avatars in Second Life James Kinicki and Mark Claypool Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA http://www.cs.wpi.edu/~claypool/papers/second-life/