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International Journal of Computer Games Technology
Volume 2014 (2014), Article ID 602403, 17 pages
http://dx.doi.org/10.1155/2014/602403
Research Article

Analyzing the Effect of TCP and Server Population on Massively Multiplayer Games

1Faculty of Electrical Engineering and Computing, University of Zagreb, Unska 3, 10000 Zagreb, Croatia
2Communication Technologies Group (GTC), Aragon Institute of Engineering Research (I3A), EINA, University of Zaragoza, 50018 Zaragoza Ada Byron Building, Spain

Received 30 May 2013; Revised 18 November 2013; Accepted 4 December 2013; Published 20 January 2014

Academic Editor: Alexander Pasko

Copyright © 2014 Mirko Suznjevic et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Many Massively Multiplayer Online Role-Playing Games (MMORPGs) use TCP flows for communication between the server and the game clients. The utilization of TCP, which was not initially designed for (soft) real-time services, has many implications for the competing traffic flows. In this paper we present a series of studies which explore the competition between MMORPG and other traffic flows. For that aim, we first extend a source-based traffic model, based on player’s activities during the day, to also incorporate the impact of the number of players sharing a server (server population) on network traffic. Based on real traffic traces, we statistically model the influence of the variation of the server’s player population on the network traffic, depending on the action categories (i.e., types of in-game player behaviour). Using the developed traffic model we prove that while server population only modifies specific action categories, this effect is significant enough to be observed on the overall traffic. We find that TCP Vegas is a good option for competing flows in order not to throttle the MMORPG flows and that TCP SACK is more respectful with game flows than other TCP variants, namely, Tahoe, Reno, and New Reno. Other tests show that MMORPG flows do not significantly reduce their sending window size when competing against UDP flows. Additionally, we study the effect of RTT unfairness between MMORPG flows, showing that it is less important than in the case of network-limited TCP flows.