Takuji Tachibana

Burst-cluster transmission: service differentiation mechanism for immediate reservation in optical burst switching networks

In this article we propose a service differentiated burst transmission called burst-cluster transmission to provide service differentiation in terms of burst loss for optical burst switching networks. The proposed method consists of a burst assembly algorithm and burst transmission scheduling, and it works only at the ingress edge node. A mixed timer/burst-length-based assembly algorithm is considered for burst assembly, and bursts with different service classes are assembled simultaneously according to the algorithm. A burst-cluster is generated so that the bursts in the cluster are arranged in order from lowest priority to highest. Then the burst-cluster is transmitted according to the burst transmission scheduling. We also consider the application of burst-cluster transmission to delay-sensitive traffic. We evaluate by simulation the performance of the burst-cluster transmission for NSFNET. Numerical examples show that burst-cluster transmission succeeds in providing different service grades even though the burst loss probabilities of high-priority service classes are affected by the traffic load of low-priority ones

Performance analysis of timer-based burst assembly with slotted scheduling for optical burst switching networks

In this paper, we analyze the performance of a timer-based burst assembly for optical burst switching (OBS) networks. In our analytical model, an ingress edge node has multiple buffers where IP packets are stored depending on their egress edge nodes, and bursts are assembled at the buffers in round-robin manner. Moreover, bursts are transmitted in accordance with slotted scheduling where each burst transmission starts at the slot boundary. We construct a loss model with two independent arrival streams, and explicitly derive the burst loss probability, burst throughput, and data throughput. In numerical examples, we show the effectiveness of our analysis in comparison with the Erlang loss system. It is shown that our model is quite useful for an OBS network with a large number of input and output links.

Round-robin burst assembly and constant transmission scheduling for optical burst switching networks

In this paper, we propose a round-robin burst assembly and constant burst transmission for optical burst switching (OBS) network. In the proposed method, ingress edge node has multiple buffers where IP packets are stored depending on their egress edge nodes, and bursts are assembled at the buffers in round-robin manner. Moreover, bursts are transmitted at fixed intervals with scheduler. To evaluate the performance of the proposed method, we construct a loss model with deterministic and Poisson arrivals, and explicitly derive burst loss probability, burst throughput, and data throughput. In numerical examples, we show the effectiveness of our analysis and compare the performance of the proposed method with Erlang loss system.

Distributed power adjustment based on control theory for cognitive radio networks

In this paper, we propose two power adjustment methods for cognitive radio networks. In the first algorithm, the transmitter derives the transmission power with PID control in order to satisfy the QoS constraints in secondary networks. The derived transmission power is compared with a constraint condition in order to avoid the interference with primary networks, and then the actual transmission power is decided. Because the constraint condition affects the performance of our proposed method significantly, we propose an effective update algorithm. On the other hand, the second algorithm is based on model predictive control (MPC). In this method, the decision of transmission power is formulated as quadratic programming (QP) problem and the transmission power is derived directly with the constraint condition. We evaluate the performances of our proposed methods with simulation and compare the proposed methods with the distributed power control (DPC) method. In numerical examples, we show that our proposed methods are more effective than the existing method in some situations. We also prove analytically that the interference with primary networks can be avoided with probability one by using our proposed method if each transmitter has the information about every channel gain.

Last-hop preemptive scheme based on the number of hops for optical burst switching networks

We propose a preemptive scheme based on the hop number of a burst for optical burst switching (OBS) networks. In the proposed scheme, when a burst fails in reserving a wavelength at its last hop, the burst can preempt another burst transmission. We consider a tandem network with four OBS nodes and analyze the burst loss probability for the proposed scheme with a continuous-time Markov chain. We also evaluate by simulation the performance of our proposed scheme for a unidirectional ring network. Numerical examples show that our proposed method effectively decreases the loss probability of the burst with a large number of hops.

A preemptive scheme with two-way release message transmission in optical burst switching networks

In this paper, we propose a new preemptive scheme with release message for optical burst switching networks. In the proposed scheme, when a low priority burst is preempted at some intermediate node, two release messages are sent immediately from the intermediate node to both source and destination nodes (two-way transmission), and the release messages release the corresponding wavelengths for the preempted burst. We consider five wavelength selection rules for the preemption and evaluate the performance of the selection rules with simulation. In numerical examples, we show that with our method, the wavelengths are utilized effectively and that our proposed method with the optimal selection rule can decrease the burst loss probability in a large-scale DWDM network.

Dynamic Management of Computing and Network Resources with PID Control in Optical Grid Networks

In this paper, in order to manage both computing and network resources effectively in optical grid networks, we propose a dynamic management method which is implemented in a job manager. The proposed method adjusts the number of tasks which are transmitted to a computing site with PID control so that a resource manager can store a constant number of tasks, resulting in an effective utilization of computing resources. Moreover, lightpaths are established and released dynamically by comparing output signal of PID controller with the maximum number of transmitted tasks, resulting in an effective utilization of network resources. We evaluate the performance of the proposed method, and then we investigate the impact of PID parameters. In numerical examples, we show that the proposed method can manage computing and network resources at the same time more effectively than a conventional method.

Lightpath Establishment Without Wavelength Conversion Based on Aggressive Rank Accounting in Multi-Domain WDM Networks

In multi-domain WDM networks, in order to establish inter-domain lightpaths across multiple domains without wavelength conversion, a lightpath establishment method based on rank accounting has previously been proposed. With the method, the inter-domain lightpaths are established with small blocking probability based on ranking databases for wavelengths; however, the performance of the method deteriorates when the ranking databases are not frequently updated. In this paper, we propose a lightpath establishment method based on aggressive rank accounting so that ranking databases are updated frequently. In the proposed method, border-node information is used in addition to wavelength usage information, and ranking databases for multiple nodes are updated simultaneously every time a lightpath establishment is processed. From the border-node information, accuracies of the wavelength usage information for each node are computed, and then the ranking database for each node is updated with the wavelength usage information and the computed accuracies. With the updated ranking database, each source node establishes an inter-domain lightpath without wavelength conversion to its destination node across multiple domains. We also present two implementations of the proposed method toward its practical use based on RSVP-TE signaling. We evaluate by simulation the performance of the proposed method, and we show that the proposed method provides smaller blocking probability than the conservative, conventional method when inter-domain lightpaths are not frequently established. We also show that the proposed method still provides smaller blocking probability even if routes of the inter-domain lightpaths change. Finally, we show that the performance of the proposed method is insensitive to the two implementations.

Intermediate-Hop Preemption to Improve Fairness in Optical Burst Switching Networks

In optical burst switching (OBS) networks, burst with different numbers of hops experience unfairness in terms of the burst loss probability. In this paper, we propose a preemptive scheme based on the number of transit hops in OBS networks. In our proposed scheme, preemption is performed with two thresholds; one is for the total number of hops of a burst and the other is for the number of transit hops the burst has passed through. We evaluate the performance of the scheme by simulation, and numerical examples show that the proposed scheme improves the fairness among the bursts with different numbers of hops, keeping the overall burst loss probability the same as that for the conventional OBS transmission without preemption.

End-to-End Lightpath Establishment Based on Rank Accounting in Multi-Domain WDM Networks

In this paper, we propose an end-to-end lightpath establishment method in multi-domain WDM networks. In this method, each domain contracts the provision of wavelength-state information and the number of wavelengths provided to neighbor domains. According to the contract, each source node selects the probed wavelengths, which are the candidates for backward wavelength reservation. In order to select wavelengths that are likely to be idle through the multi-domain network, the source node collects wavelength-state information from each destination node and ranks wavelengths for each destination node for giving priority. The source node selects the wavelengths with higher ranks. We propose two rank accounting methods for this purpose. Through simulation experiments, we show that the proposed rank accounting methods with the above contract provide better performance in terms of blocking probability with conventional methods, especially when intra-domain traffic is low. We present the effective number of contract wavelengths. Further, we also extend these rank accounting methods to methods that aggressively collect wavelength-state information from other destination nodes. We show further improvement of performance by the extended rank accounting methods.