Jae-Hwoon Lee

An IPv4-to-IPv6 dual stack transition mechanism supporting transparent connections between IPv6 hosts and IPv4 hosts in integrated IPv6/IPv4 network

IPv6 offers significant advantages over the current IPv4, however it will take long time to replace IPv4 with IPv6. Therefore, these two protocols are expected to coexist during the transition period. A number of transition mechanisms are proposed by IETF Next Generation Transition Working Group. However, most of them provide only the mechanism to initiate sessions from hosts within the IPv6 network to those within the IPv4 network, but do not support the initiation from IPv4 hosts to IPv6 ones. In this paper, we propose the IPv4-to-IPv6 dual stack transition mechanism (4to6 DSTM) which can operate even in the case that hosts in the IPv4 network initiate connections within hosts in the IPv6 network.

An efficient multicast data forwarding scheme for mobile ad hoc networks

In order for multicast data packets to be transmitted efficiently, the multicast data forwarding is required at each router. Within a wired network, a network interface of a node has a one-to-one connection to one of the incoming interfaces of other nodes. If the packet coming into an incoming interface needs to be forwarded, it is delivered to the corresponding outgoing interface. However, in a mobile ad hoc network (MANET), in most cases each node has only one network interface, so the incoming interface is the same as the outgoing one and the wireless network interface of a node has a one-to-many connection to those of neighboring nodes. This difference may cause problems such as routing loops and packet duplication. Therefore, in this paper, we propose a multicast data forwarding scheme which can be used in the multi-hop wireless ad hoc network without causing either routing loops or packet duplication. In the proposed scheme, a table is defined for the prevention of packet duplication that can happen when the tree-based multicast routing protocol is used. We have implemented our proposed scheme by using the netfilter [1] of the Linux OS.

A Flow-based Mobility Support Mechanism in Proxy MIPv6 based Network

Proxy Mobile IPv6 (PMIPv6) is the network-based mobility management protocol that network supports the mobility of mobile node (MN) on behalf of the MN. In PMIPv6, a multi-homed MN can connect to the PMIPv6 domain by using only one interface even though it has multiple interfaces. It would be efficient when such a multi-homed MN connects to the PMIPv6 domain by using all of its interfaces. If such a multi-homed MN utilizes all of its interfaces, flow mobility can be provided that the MN handovers one or more flows from one interface to another without re-establishing session. In this paper, we propose the flow-based mobility management protocol by considering the intention of the user. The Router Advertisement (RA) message is used in order for the PMIPv6 domain to inform that the MN can utilize the flow mobility. The proposed mechanism is evaluated by analyzing signaling overhead and handover latency, and the numerical results show that the performance is affected by mobility speed of the MN and the failure probability of the wireless link.

Adjusting the Cluster Size Based on the Distance from the Sink

One of the most important issues on the sensor network with resource-limited sensor nodes is prolonging the network lifetime by effectively utilizing the limited node energy. The most representative mechanism to achieve a long-lived sensor network is the clustering mechanism which can be further classified into the single-hop mode and the multi-hop mode. The single-hop mode requires that all sensor nodes in a cluster communicate directly with the cluster head (CH) via single hop and, in the multi-hop mode, sensor nodes communicate with the CH with the help of other intermediate nodes. One of the most critical factors that impact on the performance of the existing multi-hop clustering mechanism (in which the cluster size is fixed to some value, so we call this the fixed-size mechanism) is the cluster size and, without the assumption on the uniform node distribution, finding out the best cluster size is intractable. Since sensor nodes in a real sensor network are distributed non-uniformly, the fixed-size mechanism may not work best for real sensor networks. Therefore, in this paper, we propose a new dynamic-size multi-hop clustering mechanism in which the cluster size is determined according to the distance from the sink to relieve the traffic passing through the CHs near the sink. We show that our proposed scheme outperforms the existing fixed-size clustering mechanisms by carrying out numerical analysis and simulations. Keyword: Sensor Network, Clustering, Wireless Network.

Proactive Internet Gateway Discovery Mechanisms for Load-Balanced Internet Connectivity in MANET

The mobile ad hoc network (MANET) is a rapidly configurable multi-hop wireless network without an infrastructure and originally proposed for the military use. In order to make the MANET a more commonly used network in our daily lives, it may be necessary to connect the MANET to the global Internet. A MANET node can communicate with an Internet node via the Internet gateway. To support fault tolerance and increase the bandwidth, multiple Internet gateways can be deployed within a MANET and, in this case, the network performance can be improved by balancing the load among Internet gateways. In this paper, we propose load-balancing Internet gateway discovery mechanisms for the MANET with highly mobile nodes and multiple stationary Internet gateways. Existing mechanisms are analyzed through simulations and, from the simulation results, problems of the existing mechanisms are figured out. Based on the analysis, several enhanced mechanisms are proposed and compared with the existing mechanisms by using the NS-2 simulator.

Load balancing mechanisms in the MANET with multiple internet gateways

A mobile ad hoc network (MANET) is an infrastructureless wireless network that supports multi-hop communication For the MANET nodes wishing to communicate with nodes in the wired Internet, the global Internet connectivity is required and this functionality can be achieved with the help of the Internet gateway For the support of reliability and flexibility, multiple Internet gateways can be provisioned for a MANET In this case, load-balancing becomes one of the important issues since the network performance such as the network throughput can be improved if the loads of the gateways are well-balanced In this paper, we categorize the load-balancing mechanisms and propose a new metric for load-balancing Simulation results show that our proposed mechanism using the hop distance and the number of routing table entries as a load-balancing metric enhances the overall network throughput.

Address Configuration and Route Determination in the MANET Connected to the External Network

In this paper, we propose an address autoconfiguration mechanism and a route establishment mechanism appropriate for the modified MANET architecture which overcomes the multi-link subnet problem. For the delivery of Router Advertisement (RA) messages without causing the duplicate packet reception problem in the multi-hop wireless network environment, the Scope-Extended RA (Scope-Extended Router Advertisement) message is defined. Also, by defining the MANET Prefix option, a MANET node is allowed to send packets destined to a host not in the MANET directly to the gateway. This can prevent the performance degradation caused by broadcasting control messages of the reactive routing protocol for route establishment. The performance of the proposed mechanism is analyzed through NS-2 based simulations and, according to the simulation results, it is shown that the proposed mechanism performs well in terms of the control message overhead.

An Efficient Reactive Routing Protocol based on the Multi-rate Aware MAC for Mobile Ad Hoc Networks

ABSTRACT Mobile ad hoc networks (MANETs) allow mobile nodes to communicate among themselves via wireless multiple hops without the help of the wired infrastructure. Therefore, in the MANET, a route setup mechanism that makes nodes not within each others transmission range communicate is required and, for this, the Ad-hoc On-demand Distance Vector (AODV) was proposed as one of the reactive routing protocols well suited for the characteristics of the MANET. AODV uses the hop count as the routing metric and, as a result, a node selects the farthest neighbor node as its next hop on a route, which results in a problem of deteriorating the overall network throughput because of selecting a relatively low data rate route. In this paper, we propose an efficient reactive routing protocol based on the multi-rate aware MAC. Through the simulations, we analyze the performance of our proposed mechanism and, from the simulation results, we show that our proposed mechanism outperforms the existing mechanism.Key Words:Multi-Rate Aware Mac, Manet, Reactive Routing Protocol

Load Balancing Schemes in the MANET with Multiple Internet Gateways

A mobile ad hoc network (MANET) is an infrastructureless network that supports multi-hop communication. For the MANET nodes wishing to communicate with nodes in the wired Internet, the global Internet connectivity is required and this functionality can be achieved with the help of the Internet gateway. For the support of reliability and flexibility, multiple Internet gateways can be provisioned for a MANET. In this case, load-balancing becomes one of the important issues since the network performance such as the network throughput can be improved if the loads of the gateways are well-balanced. In this paper, we categorize the load-balancing mechanisms and propose a new metric for load-balancing. Simulation results show that our proposed mechanism using the hop distance and the number of routing table entries as a load-balancing metric enhances the overall network throughput.

A Route Optimization Mechanism Using an Extension Header in the IPv6 Multihoming Environment

A multihomed enterprise or AS (Autonomous System) improves reliability and performance by acquiring its Internet connectivity from more than one ISP (Internet Service Provider). When connectivity through one of the ISPs fails, its connectivity to the Internet can be continued by using tunneling mechanism through Non-direct EBGP (Exterior Border Gateway Protocol). However, this mechanism causes the problem that makes the communication route non-optimal. In this paper, we propose a route optimization mechanism by using an extension header in the IPv6 mutihoming environment.