In this letter, we show that some stream authentication schemes using hash chaining are highly vulnerable to denial of service (DoS) attacks. An adversary can disrupt all receivers of group by making use of modifying a few packets in those schemes.

Proxy Mobile IPv6 (PMIPv6) has been proposed in order to overcome the limitations of host-based mobility management in IPv6 networks. However, packet losses during doing handover are still a problem. To solve this issue, several schemes have been developed, and can be classified into two approaches: predictive and reactive handover. Both approaches commonly use bi-directional tunnel between mobile access gateways (MAGs). In predictive schemes especially, mobility support for a mobile node (MN) is triggered by simplified link signal strength. Thereafter, the MN sends handover notification to its serving MAG, and is then able to initiate packet forwarding. Therefore, if the MN moves toward an unexpected MAG that does not have any pre-established tunnel with the serving MAG, it may lead to packet losses. In this paper, we define this problem as Early Packet Forwarding (EPF). As a solution, we propose an enhanced PMIPv6 scheme using two-phase tunnel control based on the IEEE 802.21 Media Independent Handover (MIH).

This letter proposes an integrated authentication model for NGN to access the wired/wireless infrastructure. The existing authentication model based on port-based access control is not best suited for integrated network environments. The main focus of this paper is on developing a feasible authentication model using the authenticator positioned in the control function in the NGN.

Proxy Mobile IPv6 (PMIPv6) is designed not only to avoid tunneling overhead over the air but also to manage the mobility of hosts that are not equipped with any mobility management software. However, PMIPv6 leads to increasing signaling cost as mobile nodes move frequently because the protocol is based on the global mobility management protocol. In this letter we propose Localized PMIPv6 with Route Optimization (LPMIPv6-RO). Our numerical analysis shows that the proposed scheme outperforms previously proposed mobility protocols in terms of both signaling and packet delivery cost.

Multicast is an efficient transport mechanism for group-based community communications and mobile ad-hoc networks (MANET) is recently regarded as a promising solution for supporting ubiquitous computing as an underlying network technology. However, it is challenging to deploy the multicast mechanism used in a wired network directly into MANET owing to scarce resources in wireless networks and unpredictable changes in network topology. Several multicast mechanisms have been proposed in the literature to overcome these limitations. In MANET, especially, overlay multicasting schemes present several advantages over network-based multicasting schemes. However we have observed a common limitation of previously proposed overlay multicasting schemes. They introduce redundant data transmissions that waste network bandwidth and the battery of relay nodes. The observation motivated us to propose an efficient way to create and maintain a "semi-overlay structure" that utilizes a few nonmember nodes selected as branch nodes. The proposed scheme, called "SOMRP (Semi-overlay multicast routing protocol)," has been evaluated by using extensive network simulation in two different scenarios, comparing the performance of SOMRP with two previously proposed schemes. Simulation results show that SOMRP outperforms the two schemes in terms of the packet delivery ratio, transmission cost and end-to-end delay.

Packet delivery in Proxy Mobile IPv6 (PMIPv6) relies on an anchor node called LMA. All packets sent by a source node reach a receiver node via LMA, even though the two nodes attach to the same MAG. In some scenarios, PMIPv6 results in high delivery latency and processing costs due to this unnecessary detour. To address this issue, several PMIPv6 route optimization schemes have been proposed. However, high signaling costs and excessive delays remain when handover is performed. For this reason, we propose an enhanced PMIPv6 route optimization (EPRO) scheme. In addition, we analyze the performance of the EPRO. Analytical results indicate that the EPRO outperforms previous schemes in terms of signaling overhead and handover latency.