The handoff in Mobile IP networks causes packet sequence disruption during a packet forwarding procedure and may result in performance degradation in higher layer protocols. We investigate the impact of handoff in the Mobile IPv6 networks, where an optimized routing with the smooth handoff is adopted. The impact on the packet sequence is measured by an 'unstable time period (UTP)' and a 'silence time period (STP).' The UTP explains the time duration of out-of-sequence packets while the STP reflects the blackout duration of a mobile node after the initiation of handoff procedure. With the analysis on the UTP and STP, the total transient time period (denoted as handoff time period or HTP) after the handoff initiation can be estimated. In our previous work, focusing on the UTP, the packet flow sequence under the smooth handoff is analyzed for the Mobile IPv4 networks. The proposed queuing-based analysis is extended in this work for the Mobile IPv6 networks. That is, several modifications are made to conform to Mobile IPv6 and at the same time the queuing analysis itself is improved to better model the handoff procedure. The numerical results show that the queuing delay for the handoff packets (affected by background traffic) and the involved link (or route) capacities affect the estimated UTP, STP, and HTP. In addition, two schemes such as priority queuing and buffered packet forwarding are introduced to reduce the transient period and the improvements are analyzed for comparison.

The handoff of in Mobile IP causes packet sequence disruption during packet forwarding procedure, which may result in degradation of network performance in higher layer protocol. In this paper, we investigate the impact of handoff on out-of-sequence packets in Mobile IP with Route-Optimization extension. To evaluate the handoff procedure, we use the unstable time period (UTP) when the packet sequence could be mis-ordered. The results show that the UTP mainly depends on queuing delay of old Foreign Agent (FA) and link capacity between old FA and new FA. Further, we propose that the priority queuing for the astray packets in the old FA can increase Mobile IP performance during handoff procedure by reducing the UTP.

With the rising innovative antigens (such as intruders and viruses) through Internet, reliable security mechanisms are required to perceptively detect and put them down. However, defense techniques of the current host system over Internet may not properly analyze Internet antigens, because trends of attacks are unexpectedly shifted. In this paper, we introduce an Antibody Layer that mediates proper security services based on the biological mechanism to rapidly disclose and remove innovative antigens. The proposed Antibody Layer also employs a new topology called antibody cooperation protocol to support real-time security QoS for one host as well as host alliance.

This paper proposes a new MAC scheme for ATM based Passive Optical Network (APON) which follows the ITU-T recommendation G.983.1. MAC schemes for APON mostly adopt single-side scheduling in which only OLT (Optical Line Termination) schedules upstream access order for ONUs (Optical Network Units) that inform cell arrival information to OLT. In this paper, we propose a MAC scheme called double-side scheduling protocol (DSP) in which both OLT and ONU participate in scheduling process. Through the computer simulation we find out that the CDV (cell delay variation) performance of the real-time service can be improved remarkably using fewer overhead slots than that of the MAC schemes adopting CDV control algorithm. For the proposed MAC scheme, we present grant field format, minislot format, divided slot format, and scheduling algorithm.