Game Theory and Network Multicasting
In computer networking, the traditional routing method is unicast routing. The unicast routing provides a mechanism such that each data packet is transmitted to a single user. For a small number of users, this method of data transmission is proved to be sufficient. However, for a large group of users, especially when real time data transmission such as video/audio streaming is required, unicast routing is not efficient enough to ensure the service delivery. Therefore, multicast is introduced as a way to solve this problem. Different from unicast, multicast uses a one-to-many data transmission mechanism. It delivers information from a single source to a group of users at the same time, through this process, only one copy of the information is sent and the copies are made by other network components such as routers.
Modeling the multicast network from a game theory perspective, there are three kinds of players in the game: ICP( Internet Content Provider), ISP(Internet Server Provider) and the user. As discussed in the paper “A Practical Pricing Model of Inter-Domain Multicasting Based on Game Theory” (Zhao, 2006), a basic model of network is constructed. The network is rooted at some ICP, each ISP is simplified as nodes of the spanning tree of the network and users reside through ISP as end of tree branches. The incentive of this multicasting group to function is that each player, including the ICP, ISPs and users, is to maximize their welfare. The notion of currency is introduced in this network, participants of the network trade information by exchanging packets with “money”. Namely, ICPs want to collect more currency from users and get the most packets with the least possible payment to ISPs. The ISPs tend to obtain the most payment from ICPS and other ISPs. The users want to pay the least amount to ICPS and get as much as information possible. The basic assumption which this game is based on is limited information. Players of the network do not know about the number of players, the information other players are holding and any features of the network structure other then their own actions and the corresponding payoffs.
In the paper, several multicast protocols were introduced. For example, one example provides a model that currency flows in the direction as the following: users,ICPs, ISPs. Another example requires that the ICPs provide service freely, leaving only one process of monetary trade between the ISPs and ICPs.A new ICP-ISPs model is further introduced to optimize the network under certain situations.
In conclusion, multicast is a promising way of real-time data transmission for a large group of users. The fundamental principles of it is based on game theory. By modifying incentives of players or the rules of the game, people can obtain optimized result out of it.
source:
http://delivery.acm.org/10.1145/1240000/1230050/a40-zhao.pdf?
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