Search

How to select proper relay nodes to ensure the successful delivery of messages is still a hot topic in delay tolerant networks (DTN). In this paper, we propose a probabilistic Spray-and-Wait routing algorithm based on node interest preference (called NIP-PSW). Firstly, considering the influence of the social attributes of nodes, we define a metric called node interest preference (NIP) to measure the probability of nodes becoming friends. Secondly, in view of the influence of node quality and connection time between nodes on message forwarding, we define the delivery probability (DP). Finally, according to the historical information of nodes, the node interest similarity (NIS) is proposed. In spray phase, NIP and DP are used to select the relay node and allocate the number of message copies adaptively. In wait phase, it is judged whether to forward the message to the encountering nodes again according to the NIS and the DP. In addition, the concept of message storage value (MSV) and the acknowledgment (ACK) mechanism are introduced to manage the buffer of nodes. The simulation results show that the NIP-PSW not only can significantly improve the delivery rate and reduce the average delay but also shows good performance in network overhead and average number of hops.

In this paper, we propose a novel ant colony optimization algorithm based on improved brainstorm optimization (IBSO-ACO) to solve the vehicle routing problem with soft time windows. Compared with the traditional ant colony algorithm, the proposed IBSO-ACO can better address the local optimum problem, since we have carefully designed an improved brainstorming optimization algorithm to update the solutions obtained by the ant colony algorithm, which enhance the solution diversity and the global search ability. Furthermore, we use the classification method to accelerate the convergence of the proposed algorithm. The extensive experimental results have confirmed that the proposed IBSO-ACO algorithm can achieve a lower routing cost at a high convergence rate than the traditional ant colony algorithm and the simulated annealing ant colony algorithm.

At present, P2P streaming media live systems widely adopt application-layer multicast technology. In order to apply the high performance application-layer model to the live streaming media systems, this paper does research on a scalable and decentralized application-layer multicast infrastructure— Scribe, and then designs a distributed, robust and low-latency streaming media live system based on it. This system is built upon Pastry, a generic, scalable and efficient P2P system, and makes full use of Pastry’s properties to form a decentralized, robust and self-organizing overlay network in the Internet. Besides, this paper takes QoS requirements into account in the process of group member joining to make it more suitable for live streaming media fields.

Topology-aware application layer multicast takes the real underlying physical network connections into consideration while constructing multicast tree. The aim is to shorten end-to-end data forwarding delay, but it may lead to some end systems with high bandwidth close to the source node need to provide data forwarding service for many sub-nodes, and finally become the bottleneck of the multicast tree. To balance the requirement mentioned above, we propose a more comprehensive problem model MDDLRB (Minimum Delay, Degree-Limited Residual-Balanced) to construct application layer multicast spanning tree. Furthermore, to solve the MDDLRB problem, we present a heuristic algorithm based on delay increment and equilibrium optimization strategy. The simulation results show that the algorithm can get a better system performance.

The fault detection mechanism of existing topology-aware ALM protocol is very simple which greatly weakens its performance. So it needs a more efficient mechanism to ensure the robustness and QoS of ALM. We propose a novel fault detection mechanism named REW (Reverse-inhibition Early Warning) which can send warning message before the buffer data are consumed away to avoid the termination of service. It can reduce the number of repetitive and wrong warning through reverse-inhibition strategy at the same time. The simulation results show that REW fault detection mechanism can reduce disconnection delay caused by multicast members' fault with low maintain and control overhead.

Recently, application-layer multicast (ALM) has emerged as a means to solve most of the problems of IP-based multicast. Topology-aware approach of ALM is more attractive because it exploits underlying network topology data to construct multicast overlay networks. In this paper, a novel overlay network construction mechanism called balanced multi-domain topology-aware grouping (BMTAG) is introduced. BMTAG adopts a special node (domain monitor) to be the parent of all other nodes in the same domain. The mechanism can not only save the time used to discover the topology and execute the path matching algorithm but also lower the depth of the multicast tree. Building a multicast tree with balanced traffic to avoid the bottleneck is another purpose of BMTAG. Simulation results show that BMTAG can get higher performance than TAG especially when the group size is large or the percentage of domain nodes is high.