The Effect of TCP Variants on the Coexistence of MMORPG and Best-Effort Traffic

TL;DR

This study investigates how different TCP variants affect the coexistence of MMORPG traffic with other TCP applications like FTP in ADSL networks, focusing on queuing delays and buffer size impacts.

Contribution

It compares TCP SACK, TCP New Reno, and TCP Vegas in a realistic network scenario, highlighting TCP Vegas's advantage in maintaining stable game traffic performance.

Findings

TCP Vegas maintains constant game traffic rate

TCP SACK and New Reno increase sender window size

Smaller buffers reduce delays for MMORPGs

Abstract

We study TCP flows coexistence between Massive Multiplayer Online Role Playing Games (MMORPGs) and other TCP applications, by taking World of Warcraft (WoW) and a file transfer application based on File Transfer Protocol (FTP) as an example. Our focus is on the effects of the sender buffer size and FTP cross-traffic on the queuing delay experienced by the (MMORPG) game traffic. A network scenario corresponding to a real life situation in an ADSL access network has been simulated by using NS2. Three TCP variants, namely TCP SACK, TCP New Reno, and TCP Vegas, have been considered for cross-traffic. The results show that TCP Vegas is able to maintain a constant rate while competing with the game traffic, since it prevents packet loss and high queuing delays by not increasing the sender window size. TCP SACK and TCP New Reno, on the other hand, tend to continuously increase the sender window size, thus potentially allowing higher packet loss and causing undesired delays for the game traffic. In terms of buffer size, we have established that smaller buffers are better for MMORPG applications, while larger buffers contribute to a higher overall delay.