Zhenrong Zhang

Drop policies and multiple edge thresholds to enhance the performance of TCP over OBS networks with retransmission

Due to the bufferless nature of OBS networks, contention will unavoidably occur in core nodes. When the retransmission scheme is introduced into OBS networks, the bursts in the contention will be dropped selectively according to the drop policy adopted in core nodes, and retransmitted by edge nodes. In this paper, we proposed a drop policy based on Hop Number, in which the bursts with the larger total hop number will be given the higher priority in the contention. Taking the retransmission cost into account, we proposed another novel drop policy based on Hop Number Factor. Meanwhile, in edge nodes, multiple thresholds are also proposed to limit the unnecessary retransmission, and ease the deteriorated network performance. Both theoretical analyses and simulation results show that the proposed mechanisms can reduce the burst loss rate and the round trip time effectively, and improve the throughput significantly in TCP over OBS networks with retransmission.

Dynamically survivable WDM network design with shared-cycles-based PWCE

The concept of a protected working capacity envelope (PWCE) is very attractive for designing a dynamically survivable WDM network. In this paper, we consider a shared-cycles-based PWCE approach for designing survivable WDM networks where the traffic demand is dynamically changing. We develop an integer linear programming formulation to determine the protected working capacity envelope and use simulations to evaluate the blocking performance.

TCP performance analysis of grid over OBS networks

TCP performance is analyzed in Grid over OBS network with the high Bandwidth-Delay Product scenario. The impacts of the influential factors of both the TCP layer and the OBS layer are analyzed all-roundly.

Server vision: a new perspective for next generation optical networks

Under the current and foreseeable limitations of optical technology, performance of the next generation optical network is mainly hampered at the network node by resource contention. Existing work addresses contention resolution mostly in the wavelength domain (as wavelength conversion, WC), the time domain (buffering by using fiber delay lines, FDLs, the space domain (as deflection routing), and the burst domain (as segmentation). In this paper, a new architecture of optical networks-the server view based on optical networks is proposed. From the point of this new architecture, the network can be modeled as a server system with three type servers-the access server, the node server and the link server. The network performances such as cost, energy consume and network capacity can be affected by the capability of these three type servers. Unlike existing research activities that are focused on the node server design, we present the Dual fiber link (the link server solution) and IP calking (the access server solution) to ease the resource contention. To evaluate the performance of the proposed methods, computer simulations are conducted. The simulation results show these solutions can reduce the contention effectively with existing commercial devices.

p-cycle-based strategy for adaptive PWCE design

Future WDM optical networks are foreseen to be more dynamic and sensitive to failures. Therefore, dynamic service provisioning with network survivability becomes a critical requirement for network planning and management. The concept of protected working capacity envelope (PWCE) is attractive because it does not need protection resources to be dynamically configured thereby simplifying network management and reducing processing overheads. In this paper, we consider a p-Cycle-based Strategy for adaptive PWCE (protected working capacity envelope) design where PWCE can adaptively change with dynamically changing traffic. The blocking performance of this new strategy is compared to that of p-Cycle-based PWCE under a dynamic and non-uniform traffic model. The results show that the new strategy can adapt well to dynamic traffic demands that are non-uniform among the network nodes.

Research on Control and Management Mechanism of an Optical Network Testbed Based on Flow Switching

Optical flow switching is a promising technology for future optical network data transport. This paper presents the research on control and management mechanism of an optical network testbed based on flow switching. A control and management system of this testbed is designed and implemented to perform routing and network resource scheduling. The functional modules of the control and management plane in the testbed and related critical design issues are presented. In addition, the network performance of the testbed is experimentally tested and compared with the simulation results. Furthermore, we analyze the key factor influencing the network performance based on the control and management mechanism.

Network Capacity Analysis for Survivable WDM Optical Networks

In this paper, a new architecture of optical networks-the server view based on optical networks is considered. New ILP formulations are proposed to analyze the network capacity with Network survivablity under the two types of node servers. Computer simulations are conducted to evaluate the effectiveness of these new formulations. The study has shown that the network can achieve the same throughput under the two types of node servers and the network throughput increases when the maximum allowed variation increases.

Data transmission model based on multi-channel unidirectional ring network

Based on a multi-channel unidirectional ring network test bed, a data transmission model is established and tested. The settings and the implementation of the model are introduced in detail. Finally, the model is tested based on the test bed. The results from both the sending and the receiving transmission platforms show the data transmission model can work effectively.

Optimizing TCP window for Grid over OBS networks

In TCP over OBS networks, the parameters from both of TCP and OBS layers will affect the network performance when supporting the upper layer applications, such as Grid application. According to our previous work, we found that TCP window is the key limitation for such a network to support Grid application. The embedded AIMD model of TCP is too conservative. Especially in the network with high bandwidth-delay product scenario, it will take TCP a long time to increase the TCP window according to the slow start and the congestion avoidance rules. In this paper, according to the established analytical model, the TCP window size is optimized in Grid over OBS network. The analytical results show that the optimization of TCP window can improve the TCP throughput significantly.