In-Yong Hwang

Impact of burst control packet congestion on burst loss rate in optical burst switched networks

In the Optical Burst Switching (OBS) research area, the burst control packet (BCP) queuing delay problem has not been addressed because it is believed to be quite small However, with a realistic OBS simulator, we have investigated this issue and clarified its impact on performance degradation from the point-of-view of data burst loss rate We know that the BCP load to the control channel is not negligible Thus, the burst loss rate due to the queueing delay of BCP on the control channel is very serious compared to the existing well-known burst contention We propose a Dynamic Offset-Time Update scheme to avoid serious data burst loss due to BCP queueing delay, and a Priority BCP queue to guarantee the minimum offset-time for high class bursts Our simulation results show that the Dynamic Offset-Time Update scheme can completely avoid data burst loss due to BCP congestion while guaranteeing a certain level of minimum offset-time.

The influence of burst length in optical burst switching system with completely isolated classes

In optical burst switching (OBS) networks, class differentiation is achieved by assigning an adequately long offset time between a burst control packet (BCP) and a data burst (DB). Blocking probability is one of the main performance measures in OBS networks. Though the effects of length distribution of low-class burst and the ratio of arrival rates of low-class and high-class on high-class blocking probability have been studied, there has been no examination of the effects of the length of low-class on burst blocking probability. In this paper, we analyze loss performance of OBS network by examining the burst size of low-class bursts. When we vary the burst size of low-class burst from large to small, the evaluation results show that while the high-class blocking probability remains same, the low-class blocking probability decreases significantly. These results imply that it is important for OBS network designers to take into account the burst size of low-class to improve system performance in OBS networks

A new burst scheduling algorithm for edge/core node combined optical burst switched networks

The burst contention problem in Optical Burst Switching network is an intrinsically serious problem. Many researches have tried to solve this problem, however it have been known that avoiding the burst loss is very difficult issues in the current OBS network. To improve burst blocking rate, we consider the edge/core combined OBS network where the core node performs the edge node function as well. Through this architecture, available amount of data burst that the node generates can be expected with respect to offset-time of transit data bursts. Any researches for this area has not been performed, thus we propose a new data scheduling algorithm for the edge/core combined OBS network where data bursts that the node generates do not interrupt transit data bursts from previous nodes. We analyzed the data burst loss rate and the throughput in relation with the offset-time of transit data bursts. Results show that the loss rate of the data bursts is drastically reduced and the throughput improves when the offset-time of transit data bursts increases.

A New Paradigm of Optical Burst Switching System for Lossless Transmission

In this paper, we evaluate the performance of JET based OBS protocol in mesh networks, especially in NSFNET, extract drawbacks of this protocol and propose a new lossless burst transmission scheme in OBS networks. Because it is unavoidable to reduce blocking probability without breakthrough optical buffer technologies in JET-based OBS protocol, the high blocking rate makes it hard to commercialize the OBS network in Internet domains. Optical Internet with JET-based OBS can not achieve reasonable throughput in TCP layer because the size of the contention window for each TCP sessions will be decreased even though there is only one burst loss in the OBS network. To achieve a lossless optical transmission system, the large mesh networks are hierarchically arranged from the source node and the number of hops for source and destination pairs is virtually limited with 2 hops. The bursts are transmitted by sharing time within transmission cycle. By using the proposed network structure, the OBS will be commercialized in Internet domains.

A new size-based burst assembly scheme for OBS switches

We propose a new size-based burst classification algorithm which assembles arriving packets with different burst size according to classes in OBS ingress switches. In JET-based OBS scheme, because the high priority class bursts are likely to occupy channels in advance, the low priority class bursts should find void intervals between high-class bursts to avoid burst blocking. The research results show that there was close relation between blocking rate of low-class bursts and size of its bursts. By limiting the maximum length of low-class bursts, loss, throughput and assembly delay performances are improved when proposed scheme is compared to conventional scheme.

A new fairness guaranteeing scheme in optical burst switched networks

Optical burst switching (OBS) paradigm has been proposed to achieve the packet switching level throughput in the all optical domains. To meet the recent OBS commercialization requirement, we study the edge/core node combined (ECNC) OBS networks where the core node performs the edge node function as well. In this type of networks, the fairness problem occurs because the remaining offset-time decides the priority under the JET-based OBS. To solve this problem, we propose a fairness guaranteeing scheme by grouping bursts based on the destination and the remaining offset-time and assigning them to each wavelength group. Also, we propose a new burst generating and scheduling scheme for the ingress node and analyze the networks throughput.

Offset-Time compensation algorithm – qos provisioning for the control channel of the optical burst switching network

Optical Burst Switching (OBS) has intrinsically time-sensitive nature with the separation of the header and the payload. Thus, minute care for offset-time is definitely required, which has not been a highlighted issue in an existing OBS research. In this paper, we focus on the relatively early arrival of the data burst due to the excessive queueing delay of the burst control packet (BCP) under a heavily loaded network. We propose a new scheduling algorithm for the OBS control channel, the Offset-Time Compensation (OTC) algorithm to solve the early arrival problem incurring the data burst drop. In the OTC algorithm, the offset-time is determined by the existing static offset-time scheme and the proposed dynamic offset-time reflecting the offered load of the OBS network. scheme varying with the network condition. By scheduling the BCP, the OTC can reduce the data burst loss rate due to early arrival. With the dynamic offset-time scheme, the data burst loss rate decreases significantly and maintains regular rate regardless of the offered load. We also expend the OTC, QoS-Aware (QA) OTC to provides controllable QoS differentiation in terms of data burst loss rate due to early arrival. The service objective of higher class is satisfied even in a heavily loaded situation.

A study on Offset Time Based Burst Generation Scheme for Optical Burst Switching Networks

Even though the optical burst switching scheme is simple and cuts through data bursts without opto-electro-optic (O/E/O) conversion in core nodes, burst loss due to contention and the fairness problem in the mesh network have become intrinsically serious problems. To solve these problems, we proposed a new burst generation and fairness guaranteeing scheme in edge/core node combined mesh networks in previous researches. We showed that fairness was guaranteed among the same priority by grouping bursts according to offset times and using separate wavelength groups for each priority burst. In this paper, we propose a new scheme to improve the performance of the optical burst switching system by assigning higher priority to long traveled bursts over bursts just generated by previous nodes. We use a mathematical method to compare the proposed and conventional schemes. Our analysis results show that the proposed scheme has less blocking probability than the conventional scheme.

BcN Architecture based on Optical Burst Switched Networks

We propose a new broadband convergence network (BcN) architecture based on ITU-Ts NGN architecture with optical burst switching (OBS) technology. With the centralized resource manager, we can improve QoS in terms of burst loss rate.

A new application identification method using the hybrid mapping for Broadband Convergence Network (BcN)

We identify applications using hybrid mapping with signature mapping and protocol mapping. Basically, mapping needs much time. Thus, we make a set and check the limited number of packets to reduce the mapping time.