The massively multiplayer online game (MMOG) industry is suffering from huge outgoing traffic from centralized servers. To accommodate this traffic, game companies claim large bandwidth to Internet Data Centers (IDCs), and several months' payment for that bandwidth is likely to even exceed the cost for MMOG servers. In this paper, we propose a MMOG server architecture to reduce outgoing bandwidth consumption from MMOG servers. The proposed architecture distributes some functions of servers to selected clients, and those clients are in charge of event notification to other clients in order to reduce the outgoing traffic from servers. The clients with server functions communicate with each other in peer-to-peer manner. We analyze traffic reduction as a function of cell-daemonable ratio of clients, and the results show that up to 80% of outgoing traffic from servers can be reduced using the proposed architecture when 10% of clients are cell-daemonable.

In this paper, we address how to construct efficient retransmission trees for reliable multicast. Efficiency of retransmission trees mainly depends on locations of repairers, which are in charge of retransmitting lost packets. We propose an algorithm for each receiver to find a repairer for efficient recovery. The resulting tree for retransmission is organized by pairs of a receiver and a repairer which is the host "nearest" to the receiver among the multicast group members "nearer" to the sender. We formally prove that the proposed algorithm realizes reliable multicast with only constant times of a lower bound cost achievable through impractical router support. We also evaluate the algorithm through extensive simulations.

Class-based delay differentiation model has been recently proposed as a part of relative differentiated services frameworks, and it is shown that the model can provide delay differentiation without admission control and end-to-end resource reservation. In this paper, however, we observe that there can be inconsistent delay differentiation caused by different size of packets. We propose packet size-based delay differentiation model and show that packet size-based queueing is effective to achieve equal delay within a class and provide consistent delay differentiation between classes through simulations. Simulation results also show that the proposed model improves jitter characteristics of CBR flows.