Scalable Peer-to-Peer Networked Virtual Environment Shun-Yun Hu* & Guan-Ming Liao+ * Dept. of CSIE, Tamkang Univ. + Institute of Physics, Academia Sinica Taiwan 2004/08/30 2004/08/30

The BIG Question How do we create a true cyberspace (Networked Virtual Environment)? “True” means: 3D-based, interactive and persistent Feels realistic and immersive REALLY BIG  Scalability Problem 2004/08/30

Issues for Creating NVE Consistency Performance (Responsiveness) multiplayer Security Scalability Persistency massively multiplayer Reliability (Fault-tolerance) 2004/08/30

The Scalability Problem Many nodes on a 2D plane ( > 1,000,000) Need to interact with those within Area of Interest (AOI) How does each node receive only the necessary messages? 2004/08/30

Scalability Solutions Strategies Increase resource  More servers Decrease consumption  Interest management (message filtering) Architectures: Point-to-point (LAN) tens 10^1 Client-server hundreds 10^2 Server-cluster thousands 10^3 ? millions 10^6 … Peer-to-Peer 2004/08/30

Promise & Challenge of P2P Promises Growing resource, decentralized  Scalable Commodity hardware  Affordable Nobody has done it yet!  Cool  Challenges Topology maintenance  dynamic join/leave Efficient content retrieval  no global knowledge 2004/08/30

Design Goals Observation: desired content is specifically defined (messages from neighbors within AOI)  locality of interest to be exploited Solve the Neighbor Discovery Problem in a fully-distributed, message-efficient manner. Specific goals: Scalability  Limit & minimize message traffics Performance  Direct connection with AOI neighbors 2004/08/30

Voronoi Diagram Plane partitioned into regions by sites, each region contains all the points closest to its site Can be used to find k-nearest neighbor easily Neighbors Region Site 2004/08/30

Design Concepts Use Voronoi to solve Neighbor Discovery Problem Identify enclosing and boundary neighbors Each node constructs a Voronoi of its neighbors Enclosing neighbors are maintain as the minimal set Mutual collaboration in neighbor discovery Circle Area of Interest (AOI) White self Yellow enclosing neighbor L. Blue boundary neighbor Pink enclosing & boundary Green other neighbor D. Blue unknown neighbor 2004/08/30

Procedure (JOIN) Send join request to any existing node Join request forwarded to acceptor region Acceptor region’s node sends back its neighbor list Joining host contacts those neighbors one-by-one 2004/08/30

Procedure (MOVE) Send movement to all neighbors, mark boundary neighbors B. Neighbors check for AOI & enclosing neighbors overlap Connect to new neighbor upon notification (update Voronoi) Disconnect any non-overlapped neighbor 2004/08/30

Procedure (LEAVE, etc.) Leave Other actions (chat, jump, trade) Simply disconnect Others update Voronoi (query new boundary) Other actions (chat, jump, trade) Exchange message with individual or all neighbors 2004/08/30

Problems of Voronoi Approach Performance Circular round-up of nodes Redundant message sending Incomplete neighbor discovery Inconsistent / incorrect neighbor list Fast moving node 2004/08/30

Related Works P2P support for MMP Games (Univ. of Pennsylvania) DHT-based, Pastry + Scribe [Knutsson et al. INFOCOM 2004] P2P Message Exchange Scheme for LS-NVE (Univ. of Tokyo) Constant exchange of neighbor list [Kawahara et al. Telecommunication System 2004] Solipsis (France Telecomm R&D) Mutual collaboration between nodes, maintain within convex hull [Keller and Simon. PDPTA 2003] 2004/08/30

Summary Scalability in P2P is a neighbor discovery problem Desirable properties for Voronoi P2P NVE Efficient message transmission due to direct connection Low overhead P2P topology maintenance Problems with current approach Moving speed limit Lack of recovery mechanism from inconsistency Interesting and promising direction 2004/08/30

Future Works Recovery mechanism from inconsistency Variable-radius AOI Game states persistency (OceanStore) 3D content distribution (3D streaming on P2P) Towards a true cyberspace  2004/08/30

Acknowledgement WISE Lab, Tamkang Univ. Joaquin Keller (France Telecomm R&D) Laboratory of Statistical & Computational Physics, Academia Sinica Anonymous reviewers Dr. Chin-Kun Hu Prof. Wen-Bing Horng Prof. Jiung-Yao Huang 2004/08/30

Q & A Thank You! 2004/08/30