# Reliable User Datagram Protocol as a Solution to Latencies in Network Games
## 1 Introduction  
One of the major problems to be solved for network games is latency, which is usually referred to as 'lagging,' and affects the customer's satisfaction level greatly. Latency mainly results from an insufficient hardware specification or the internet speed of the user. As online games become larger in scale, a faster internet connection or better hardware specification is required, but it is quite difficult for users to upgrade their systems or change internet service providers. Therefore, it is better and more effective if game companies offer a better communication algorithm for their games. The reliable user datagram protocol (RUDP)-based communication system could be a good alternative in this respect, so a prospective model has been designed and implemented in this paper. The seriousness of the latency problem felt by game users is different depending on the games they play. That is, the players of real-time strategy (RTS) or turn-based games do not encounter this problem frequently because of the slower process of these games, but those who play games that require much faster reactions like twitchy or shooting games are affected by even a slight delay in their actions and therefore demand a faster communication system. The first thing to consider in regard to the latency problem is the communication distance. The longer the distance, the slower the communication speed. Gamers cancheck the communication response time by pinging a certain internet protocol (IP) address and the result obtained represents the communication environment as far as the speed is concerned. In a local area network (LAN) environment, this response can be obtained within a time range of between one and two milliseconds, whereas it will take a few to hundreds of milliseconds with an ordinary internet connection.  
The second factor affecting game performance is the bandwidth used. Bandwidth indicates how much data can be transmitted in a fixed time, as well as the internet speed. For a LAN a speed range from 100 Mbps to 1 Gbps is usually available, while an average of 50 Mbps is guaranteed for common optical connections in the Republic of Korea (ROK). Figure 1 shows examples of the communication configuration for network games.  
Finally, packet loss is another important factor determining game performance that should be dealt with. The volume of lost packets or undelivered packets is considered when evaluating the stability of the network communication. An increased number of packet loss incidents would mean that the network is unstable and that its quality is degrading.  
There are several causes of packet loss but it mostly occurs due to overloads in the server, especially during gaming where many commands have to be processed simultaneously and instantly. When this happens, a user's PC screen may freeze or the communication with the remote game server could be interrupted. These phenomena are a little different from the slower movements in the massive multi-user online role-playing game (MMORPG) games caused by lower bandwidth.  
The role of a user datagram protocol (UDP) in the network games is quite important for the reason that it shows a reaction speed close the physical network latency. In many cases, however, it is used restrictively due to its low data reliability. Nevertheless, if it is possible to improve reliability by approaching the problems in terms of supplementing its demerits, it will effectively replace part of the functional weak points of transmission control protocol (TCP). In this regard, many attempts have been made to implement reliable UDP (RUDP) for the well-known overseas games or network engines. It is expected that such a method will form a significant technological basis coupled with the activation of MMORPG.  
Figure 1: An example of the communication configuration for network games.