The vMatrix: Equi-Ping Game Server Placement For Pre-Arranged First-Person-Shooter Multiplayer Matches IEEE/ACS AICCSA’2006 Amr A. Awadallah Mendel Rosenblum Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006

Lag Sensitivity of Online Games: First Person Shooter (Halo, Battlefield2, Doom, CounterStrike) Extremely Lag sensitive (on the order of 50ms) MMORPG (World of Warcraft, Everquest, Lineage) Moderate sensitivity to lag (on the order of 500ms) Real Time Strategy (Warcraft, Generals, Dawn of War) Moderate sensitivity to lag (on the order of 500ms) Turn Based Strategy (Civilization 4, Risk, Chess, Pool) Not sensitive to lag (on the order of seconds)

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 The Problem: Unfair Lag Clan A Clan B 130ms 30ms Game Server

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 The Solution: Equi-Ping Server Clan A Clan B 80ms Real Machine 80ms VMM Virtual Game Server in VM

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 Virtual Machine Monitors Virtual Machine Monitor Real Machine (CPU, Memory, Disks, Network) Virtual Machine 1: vCPU, vMem, vDisk, vNet OS1: Windows 2000 Virtual Machine 2: vCPU, vMem, vDisk, vNet OS2: Linux MySQL, Apache Oracle, IIS

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 Screenshot from Halo PC:

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 Live Demo of VMware player:

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 What is The vMatrix?

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 The vMatrix! A network for delivering virtual machines (VMs) between real machines (RMs) running the virtual machine monitor (VMM) software.

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 Advantages: Equi-ping placement of game servers to minimize round-trip-time difference between participants Backward compatibility leading to zero cost for converting existing Economies of scale: this network can be shared among many games

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 Equi-ping placement problem Red dots are servers, green dots are players, we need to pick the Red dot that is equi-distant from all players.

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 S = set of m servers available to host the match. P = set of n players participating in this match. RTT s,p = round-trip-time (ping) from server s to player p The Algorithm has 3 main steps: 1.Disregard all servers that have any RTT s,p larger than 180ms 2.For each server s we compute a closeness factor C s representing the average differential ping between the players if server s is picked: 3.Pick the server with smallest C s The order of complexity of this algorithm is O(n 2 m) ≈ O(m) since m » n Equi-ping placement Algorithm

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 Experience: Halo PC server placement Real Machine (PIII-550MHz, 640MB RAM, 9GB hard disk) VMware ESX VMM Server (consumes 184MB RAM, 3.5GB hard disk and 5% CPU) Virtual Machine exposes a PIII-550MHz with 512MB RAM and 5.5GB hard disk. Operating System: Windows XP (1.8GB) Halo PC Game Server (278MB)

Stanford University – Computer Systems Lab – IEEE/ACS AICCSA’2006 Conclusion Equi-ping server placement is very important for fairness of online FPS games. The vMatrix is a practical backward-compatible solution for solving this problem today.