Won-Ho So

Offset Time Decision (OTD) Algorithm for Guaranteeing the Requested QoS of High Priority Traffic in OBS Networks

In this paper, we propose the Offset Time Decision (OTD) algorithm for supporting the QoS in optical networks based on Optical Burst Switching (OBS), which is the new switching paradigm, and evaluate the performance of the OTD algorithm. The proposed algorithm can decide a reasonable offset time to guarantee the Burst Loss Rate (BLR) of high priority traffic by considering traffic load of network and the number of wavelengths. In order to design this effective OTD algorithm, firstly we illustrate the new burst loss formula, which includes the effect of offset time of high priority class. As the decision of offset time corresponding to the requested BLR, however, should use the reversed formula of new one, we are not able to use it without any changes. Thus, we define the Heuristic Loss Formula (HLF) that is based on the new burst loss formula and the proportional equation considering its characteristics. Finally we show the OTD algorithm to decide the reasonable offset time by using HLF. The simulation result shows that the requested BLR of high priority traffic is guaranteed under various traffic load.

Design and Performance Evaluation of Traffic Grooming Algorithms in WDM Multi-Ring Networks

In this paper, we propose novel traffic grooming algorithms to reduce the cost of the entire system in WDM multi-ring networks. In order to achieve this goal, it is important to construct a virtual topology and groom the traffic in these networks. We consider four kinds of virtual topologies of WDM multi-ring networks according to the way in which traffic is transmitted among rings. Accordingly, we design four kinds of traffic grooming (TG) algorithms depending on the considered virtual topologies: mixed (MTG), partially mixed (PMTG), separate (STG), and independent (ITG) traffic grooming algorithms. Each algorithm consists of a separation, a connection-ring construction, and a grooming procedure. In the separation procedure, all traffic connections are classified into intra and inter-connections. The connection-ring construction procedure makes full connection-rings from traffic connections. The grooming procedure groups connection-rings onto a wavelength in order to reduce the number of SONET add/drop multiplexers (SADMs) and wavelengths and to improve the utilization of network resources. To analyze the performance of each algorithm, a circular multi-ring architecture with uniform traffic is considered. The simulation results show that ITG and PMTG are more efficient in terms of wavelengths. STG and PMTG require a smaller number of SADMs.

Study on Adaptive Intrusion Detection Engine Based on Gene Expression Programming Rules

High false alarm rate and time-space cost of rule extraction and detection limit the application of machine learning in real intrusion detection system (IDS), and IDS cannot satisfy most system performance requirements simultaneously. In this paper, a Constraint-based gene expression programming rule extraction algorithm (CGREA) is proposed which guarantees the validity of rules and reduces the evolution time through grammar constraint and probability restriction. Additionally, an adaptive intrusion detection engine (AIDE) is applied to automatically renew the detected order of rules according to the performance metric. The KDD CUPpsila99 DATA is used for evaluation and results show that the rules, which are extracted by the CGREA algorithm within a few evolution generations, can not only achieve high detection rate but also detect unknown attacks. Moreover, the AIDE based on CGREA increases the attack detection rate, and adapts itself to different performance requirements with different sequences of rule detection.

QoS Supporting Algorithms for Optical Internet Based on Optical Burst Switching

In this paper, we propose a protocol architecture and quality of service (QoS) supporting algorithms for optical Internet based on optical burst switching (OBS) technology. Firstly, the function of each layer of the protocol architecture and the formats of control packets are defined in order to adopt GMPLS to the control plane of OBS. Then, the offset time decision (OTD) algorithm to cooperate with the proposed protocol architecture is designed for optical Internet. A new burst loss formula taking into account the effect of offset time is introduced to design the OTD algorithm. This algorithm can decide on the appropriate “priority-offset” time according to the required QoS by using the reversed equation of the so-called heuristic loss formula (HLF) which is approximated as a proportional equation of our new loss formula. Finally, we propose a CAC algorithm based on the OTD algorithm for the purpose of increasing the availability of wavelength resources and supporting the QoS of established connections in optical Internet. The performance of the proposed algorithms is evaluated in terms of burst loss rate and the number of connections through simulation.

Fair MAC protocol for optical ring network of wavelength-shared access nodes

In this paper, a WDM optical ring consisting of access nodes with fixed transmitter-n fixed receivers (FT—FRn) is considered. As access nodes share a wavelength channel there is trade-off between node throughput and fairness among them. In order to abbreviate the transmission unfairness and to increase the throughput, we propose p-persistent medium access control (MAC) protocol. Each node uses the carrier sense multiple access with collision avoidance (CSMA/CA) protocol to transmit packets, and decides whether to use a local empty slot with probability p when a transferred packet based on source-stripping is dropped and emptied. Numerical prediction for the proposed MAC protocol is introduced to compute the maximum node throughput under uniform traffic condition. For more detail results, we use network simulation with self-similar traffic and introduce various results. The proposed MAC protocol gives better node throughput than non-persistent protocol and shows an improved fairness factor than 1-persistent protocol. Through simulation, we also find the reasonable probability of p-persistent protocol for a given architecture.

A Hybrid Restoration Scheme Based on Threshold Reaction Time in Optical Burst-Switched Networks

Optical Burst-Switched (OBS) networks usually employ one-way reservation by sending a burst control packet (BCP) with a specific offset time, before transmitting each data burst frame (BDF). Therefore, a fiber link failure may lead to loss of several BDFs as the ingress nodes sending these BDFs remain unaware of the failed link till they receive the failure indication signal (FIS). In this paper, we propose a hybrid restoration scheme, wherein we employ a novel combination of sub-path as well as path restoration schemes. In particular, the upstream node preceding the failed link employs sub-path restoration as soon as it detects the failure. Thereafter, when the source ingress node receives the FIS message, it (source ingress node) takes over the responsibility and employs path restoration. However, sub-path restoration is exercised by the upstream node only if the remaining time intervals left for the yet-to-arrive BDFs (for which BCPs have already left the upstream node) are less than a minimum time interval (called as threshold reaction time). Performance of the proposed scheme is evaluated through extensive computer simulation using OPNET. Our results indicate that the proposed restoration scheme significantly reduces burst losses due to link failure and, thus, outperforms the existing restoration schemes.

Analysis of AWG based Elementary Switches for Multistage WDM Optical Switches

This paper is a precedent study to design AWG based elementary switch for constructing large-scale optical switch with multistage architectures. To decide the appropriate size and architecture of AWG based elementary switches, burst drop rate and throughput are evaluated in terms of the number of input/output ports and wavelengths by numerical analysis and simulation is also executed to verify the results of numerical analysis. AWG based switches with slow-light buffer are also considered as a candidate for the elementary switch. Performance is evaluated by Markov state transition diagram, for the equivalent virtual buffer model, and is compared with OPNET simulation results. Finally, we provide insight into the design of multistage WDM optical switches by investigating the effect of various parameters.

A novel approach for similarity measure schemes based on multiple moving objects in video databases

The general aim of this paper is to study the spatio-temporal modeling techniques which can efficiently represent multiple moving objects’ in video databases. The traditional schemes only consider direction property, time interval property, and spatial relationship property for modeling moving objects’ trajectories. But, our scheme also takes into account on distance property, conceptual location information, and related object information so that we may improve a retrieval accuracy to measure a similarity between two moving objects as well as them. As its application, we implement the Content- and Semantic-based Soccer Video Retrieval (CS2VR) system by using MS Visual C++ and DirectX for indexing and searching on soccer video data. The CS2VR helps users to easily extract the trajectory information of soccer ball form soccer video data semi-automatically as well as to conveniently retrieve the results acquired by sketching query trajectory with mouse button.

Cooperative Scenario based Centralized Defense Mechanisms for Low-Rate TCP Attacks

The low-rate TCP attack has been reported recently. That is essentially a periodic short burst which exploits the homogeneity of the minimum retransmission timeout (RTO) of TCP flows. It is difficult to identify this sort of attack in BcN (broadband convergence network) due to no cooperative defense mechanisms among different networks. In this paper, NCP (network control platform) based centralized defense mechanisms are proposed. Firstly, low-rate TCP attack and the previous defense mechanisms are reviewed. It helps us to find and select reasonable features of them for supporting the proposed mechanism. Secondly, we propose a cooperative defending scenario between NCP as centralized controller and MDRs (monitoring and defending routers). Without adopting defense mechanism to all routers in network, it is possible to effectively protect network resource from low-rate TCP. That is because the attack flows can be filtered at both victim-side and attack side MDRs with cooperative scenario. The performance id evaluated by using ns-2 simulator