A transmission control protocol (TCP) using an additive increase multiplicative decrease (AIMD) algorithm for congestion control plays a leading role in advanced Internet services. However, the AIMD method shows only low link utilization in lossy networks with long delay such as satellite networks. This is because the cwnd dynamics of TCP are reduced by long propagation delay, and TCP uses an inadequate congestion control algorithm, which does not distinguish packet loss from wireless errors from that due to congestion of the wireless networks. To overcome these problems, we propose an exponential recovery (ER) TCP that uses the exponential recovery function for rapidly occupying available bandwidth during a congestion avoidance period, and an adaptive congestion window decrease scheme using timestamp base available bandwidth estimation (TABE) to cope with wireless channel errors. We simulate the proposed ER-TCP under various test scenarios using the ns-2 network simulator to verify its performance enhancement. Simulation results show that the proposal is a more suitable TCP than the several TCP variants under long delay and heavy loss probability environments of satellite networks.

Automatic discovery of physical topology plays a crucial role in enhancing the manageability of modern large Ethernet mesh networks. Despite the importance of the problem, earlier research and commercial network management tools have typically concentrated on either discovering active topology, or proprietary solutions targeting specific product families. Recent works [1]-[3] have demonstrated that physical topology can be determined using standard SNMP MIB, but these algorithms depend on Filtering Database and rely on the so-called spanning tree protocol (IEEE 802.1d) in order to break cycles, thereby avoiding the possibility of infinitely circulating packets and deadlocks. A previous work [1] requires that Filtering Database entries are completed; however it is a very critical assumption in a realistic Ethernet mesh network. In this paper, we have proposed a new topology discovery algorithm which works without the complete knowledge of Filtering Database. Our algorithm can discover complete physical topology including inactive interfaces eliminated by the spanning tree protocol in LEMNs. The effectiveness of the algorithm is demonstrated by an implementation.

In this paper, we examine the Interleaved Polling with Adaptive Cycle Time (IPACT) that was proposed to control upstream traffic for Gigabit Ethernet-PONs, a promising technology for the Fiber To The Home (FTTH). We analyzed the performance for the gated service and the limited service mathematically. To do this, the IPACT protocol was modeled as a polling system and analyzed by using mean-value analysis technique. The traffic arrival rate λ was divided into three regions, and each region was analyzed separately and merged appropriately by using an interpolation method. The average packet delay, average queue size, and average cycle time of both the gated service and the limited service were obtained through the analysis. In order to evaluate the accuracy of the mathematical analysis, discrete event simulation was performed for the IPACT protocol. Simulation results show the accuracy of the mathematical analysis. The analysis results can be widely used in the design of the FTTH system based on EPON, as the performance results in the present study can be obtained in a rather short time. We can design an appropriate system depending on various traffic conditions by adjusting system parameters, such as the number of users N, the maximum transfer window WMAX, and so on.