Evaluation Of The HyperVerse Avatar Management Scheme Based On The Analysis Of Second Life Traces Markus Esch University of Luxembourg Email: markus.esch@uni.lu Wei Tsang Ooi National University of Singapore Email: ooiwt@comp.nus.edu.sg Ingo Scholtes University of Trier Email: scholtes@syssoft.uni-trier.de Abstract—Massive Multiuser Virtual Environments (MMVEs) and the idea of a global scale 3D Web have grown popular in recent years. While commercial precursors of such environments for the most part rely on centralized client/server architectures, it is commonly accepted that a global scale virtual online world can only be realized in a distributed fashion. Within the HyperVerse project, we have developed and recently presented a two-tier Peer-to-Peer (P2P) architecture that incorporates a loosely structured P2P overlay of user peers and a highly structured overlay of server machines constituting a reliable backbone service. In such a distributed environment, an essential question is how avatars are tracked and interconnected in order to allow mutual rendering and interaction. We have previously proposed a hybrid avatar management scheme that utilizes the backbone service for avatar tracking if necessary, but handles tracking in a P2P fashion when peers can track each other to reduce the backbone load. This paper presents a detailed performance analysis of this algorithm under a realistic scenario, using traces from a large scale MMVE called Second Life. Moreover this paper presents and evaluates an optimization for the hybrid avatar tracking scheme that can be utilized under a weaker condition. Keywords-P2P, MMVE, DVE I. I NTRODUCTION Virtual online environments like Second Life or World Of Warcraft currently attract a lot of attention. Though much research work is done in the field of distributed architectures for such environments, the commercial solutions for the most part still rely on centralized client/server architectures due to advantages in terms of manageability and controllability by the publisher. The drawback of such a centralized solution is the limited scalability. Having global scale scenarios like a 3D Web in mind, it is commonly accepted that distributed Peer-to-Peer (P2P) technologies need to be applied. Within the HyperVerse project, we study the feasibility of P2P tech- nologies for a global scale virtual online environment. We envision the 3D Web to be a combination of virtual globes like Google Earth and avatar-based interaction. Similar to reality, a user can move through a virtual representation of the real world in order to meet friends, undertake a sightseeing tour, shop and so forth. In [1], we have pro- posed a two-tier P2P architecture as basic infrastructure for such a 3D Web scenario. This architecture incorporates a loosely structured P2P overlay of user machines and a highly structured overlay of reliable server machines. The federation of server machines is responsible for the reliable and persistent hosting of the online world while the client overlay is primarily utilized for data distribution. Similar to today’s Web, for the provision of the server machines, we rely on the incentive of being able to publish information in the 3D Web. In centralized client/server systems, the interconnection of peers in virtual proximity is not an issue, since the server typically has a global view and hence is able to make two peers in virtual proximity mutually aware. Due to the absence of a global view, interconnection of peers in virtual proximity becomes an issue in P2P systems. If the graph falls apart into several connected components, avatars in different components will not be able to interact. In [3], we have presented an avatar management scheme for the HyperVerse infrastructure that handles avatar interaction in a hybrid fashion utilizing both the backbone service and the user machines. In opposite to many other P2P-based infras- tructures for virtual environments, in HyperVerse, it would be possible to utilize a centralized solution for the avatar management, since the backbone service is existing. It is obvious that such an approach would not fit the requirements of a global scale environment, since it is likely to overburden the backbone service even if this service is a federation of multiple server machines. Especially in highly populated regions of the world, the server responsible for such a region may become overloaded. Utilizing our hybrid scheme, the server load is reduced in a self-scaling fashion. Though the backbone service is available as a reliable fallback solution, the avatar management is automatically handled in a pure P2P fashion whenever the peer density in a certain region is high enough. This paper presents a detailed analysis and evaluation of HyperVerse’s avatar management scheme using actual avatar traces from Second Life. Additionally, this paper presents and evaluates an optimization for our avatar interaction scheme that can be utilized under weaker conditions than we previously proposed, leading to lower load on the backbone servers, especially in lower density regions. Section II first briefly describes our hybrid avatar manage-