WiFi Peer to Peer (P2P) aka WiFi Direct enables devices to communicate with each other in a peer to peer manner without requiring any Access Point at typical WiFi speed with WPA2 security. With its huge prospect in revolutionizing device to device communication, WiFi P2P can potentially play a much larger role amid the growing interest in M2M communication and Internet of Things. However, unlike a conventional P2P network which operates on mesh topology, WiFi P2P requires one of its group members to act as Group Owner, with whom all the other devices in the group stay associated. The group suffers from a temporary network disruption when the Group Owner suddenly leaves the group without any prior notice. In addition, restoration of the group connectivity consumes much time which is intolerable for most delay sensitive applications. In this paper, we address this issue using our proposed concept of Seamless Group Reformation which helps in maintaining near continuous connectivity and alleviates over dependence of the group on the Group Owner. The concept is seconded by the proposed mechanism of Dormant Backend Links to cut down the total group-disruption time. We implement the mechanism of Dormant Backend Links on a practical WiFi P2P testbed and present an experimental evaluation.

Recently, along with the widespread use of Wi-Fi devices, there has been high expectation for contents sharing in the Wi-Fi networks that consists of large number of nodes. In this paper, we present an efficient one-to-many content distribution method for Wi-Fi networks. In our method, a source node selects a representative node from destination nodes which requested for the same content and then sends the content to the selected representative node by using TCP. At the same time, the rest of destination nodes receive the content by overhearing TCP traffic generated from the source node to the representative node. We also present a technique to enable overhearing in an environment which employs pairwise key and group key based encryption mechanism such as WPA. Finally, we evaluate the effectiveness of our method through simulations using QualNet. Our simulation results show that our method can shorten the content delivery time up to 94% compared with content distribution using FTP in the network consists of 500 nodes.

This paper proposes a routing protocol in a large-scale DTN network. After the 2011 Great East Japan Earthquake, the demand for an infra-less communication system has been rapidly increased. The infra-less communication system can provide an information sharing platform for victims about an evacuation warning of earthquake or Tsunami, personal safety confirmation or safe shelters, all of which were required when the earthquake happened. To realize the infra-less communication system, we propose a scalable DTN routing protocol which can operate even if massive nodes are widely spread with intermittent connectivity among the nodes. Through the simulation results, we show the effectiveness of our proposal in a large-scale DTN network with more than 1000 nodes.

Dynamic replication schemes for cost-effective, scalable content delivery networks (CDNs) are discussed. Based on content replication granularity, current dynamic replication approaches can be classified into entire replication (entire content is replicated) and object replication (individual objects are replicated) schemes. The drawbacks of these schemes are low replication performance and low scalability, respectively. We propose two schemes delivering replication performance close to that of object replication scheme with replication granularity close to that of entire replication scheme. The schemes aggregates objects in the origin server into multiple content groups and then replicate them on per-group granularity. The content groups are either statically created in advance or dynamically created upon replication. Simulation of the proposed scheme showed that the scheme of dynamic group creation can achieve almost the same performance as the optimal scheme of object replication. Even the scheme of static group creation provides much better performance than entire replication under skewed request distribution. The effect of the number of content groups on performance is also investigated.

Adaptive and efficient multiple path pre-computation schemes for QoS routing protocols such as the QoS-enabled open shortest path first (OSPF) protocol are discussed. Conventionally, for QoS routing protocols that pre-compute multiple disjoint paths as candidate paths, both the convergence time for first bootstrapping and the update time of candidate path upon detection of a network failure are quite long, particularly in large-scale networks. We propose two schemes for efficient pre-computation of multiple paths: (i) adaptive pre-computation based on the current CPU load to reduce the convergence time for the first bootstrapping, and (ii) a virtual area partitioning (VAP) algorithm to reduce the update time of the multiple candidate paths. Simulation of the proposed schemes showed that the adaptive pre-computation significantly reduces the convergence time without degrading the optimality of routing entries. It also showed that VAP reduces the processing delay of the multiple path calculation to half that of the conventional k-shortest path (KSP) algorithm.

This paper proposes a hierarchical multilayer QoS routing system with dynamic SLA management for large-scale IP networks. Previously, the promising approach to provide QoS in large-scale IP networks using a mixture of DiffServ-based QoS management and MPLS-based traffic engineering has been actively discussed. However, the introduction of QoS exacerbates the already existing scalability problems of the standard IP routing protocols. In order to address this issue, we propose a new scalable routing framework based on hierarchical QoS-aware path computation. We augment the existing OSPF and CR-LDP protocols to support hierarchical QoS routing, QoS aggregation, and QoS reservation in our MPLS-DiffServ-based hierarchical routing network. In order to provide additional flexibility and cost-efficiency, we augment the network with a policy server which is capable of dynamically handling SLAs between the networks and providing load balancing management within the network. We implement a prototype of the proposed framework and study its performance with a virtual network simulator and specially designed QoS routing algorithm simulator. In our simulations, we evaluate both the implementation complexity and algorithms performance; the results demonstrate the efficiency of the framework and its advantages over the existing proposals.