Intelligent Offset Time Algorithm for Optical Burst Switching Networks

Optical burst switching (OBS) is a switching technology that can efficiently operate in the optical core network using WDM technology and can also develop the future optical internet. The OBS switching technology presents a trade-off between the two switching technologies: optical circuit switching (OCS) and optical packet switching (OPS). This switching approach increases resource utilization compared with OCS technology and avoids the technological barriers of OPS networks. In OBS networks, many packets are assembled into one data burst at the edge node and a burst header packet (BHP) is sent before the burst transmission by an offset time in order to reserve the required resources in core nodes. This can cause security issues in the network and more specifically denial of service attacks that can occur if a source node is compromised. In this paper, we study a specific denial of service attack which we refer to as "BHP flooding attack", which prevents legitimate traffics from reserving the required resources at intermediate core nodes. We also propose the design of a reconfigurable BHP flooding countermeasure module that allows to counter against this type of attacks in an OBS network.

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.

We propose and evaluate fast reservation (FR) protocols for optical burst switched (OBS) networks. The proposed reservation schemes aim at reducing the end-to-end delay of a data burst, by sending the burst header packet (BHP) in the core network before the burst assembly is completed at the ingress node. We use linear prediction filters to estimate the expected length of the burst and the time needed for the burstification process to complete. A BHP packet carrying these estimates is sent before burst completion, in order to reserve bandwidth at each intermediate node for the time interval the burst is expected to pass from that node. Reducing the total time needed for a packet to be transported over an OBS network is important, especially for real-time applications. Reserving bandwidth only for the time interval it is actual going to be used by a burst is important for network utilization efficiency. In the simulations conducted we evaluate the proposed extensions and prove their usefulness.

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.

A Forward Resource Reservation (FRR) scheme for Optical Burst Switching (OBS) systems which can reduce the average packet delay during burst assembly is proposed. Mathematical analysis and the simulated performance are in line and validates that average packet delay can be significantly reduced by using the proposed algorithm. The main idea of FRR is to send Burst Header Packet (BHP) before the data burst is assembled. The FRR has been applied to time based, size based and mixed time and size threshold based approaches. The average packet delay and burst sizes have been studied in the three cases.

In optical burst switched (OBS) networks contention is the main source of burst loss. Burst cloning scheme is a proactive loss recovery mechanism that attempts to prevent burst loss at core nodes. However, at high load, burst cloning scheme leads to a significant burst loss at edge nodes due to burst queue saturation. In this paper, we adopt the burst cloning scheme with star topology, and we propose an enhancement for burst cloning scheme, called opportunistic burst cloning scheme, which aims to control the extra load of burst cloning through a simple technique to disable/enable burst cloning mechanism. We analytically analyze conventional OBS, basic burst cloning scheme and opportunistic burst cloning scheme over star networks. The results obtained from simulation confirm that our analytical model exhibits a good accuracy. The both analytical and simulation results confirm that opportunistic burst cloning scheme achieves better overall network performance than the other approaches.

Next-generation high-speed Internet backbone networks will be required to support a broad range of emerging applications which may not only require significant bandwidth, but may also have strict quality of service (QoS) requirements. Furthermore, the traffic from such applications are expected to be highly bursty in nature. For such traffic, the allocation of static fixed-bandwidth circuits may lead to the over-provisioning of bandwidth resources in order to meet QoS requirements. Optical burst switching (OBS) is a promising new technique which attempts to address the problem of efficiently allocating resources for bursty traffic. In OBS, incoming data is assembled into bursts at the edges of the network, and when the burst is ready to be sent, resources in the network are reserved only for the duration of the burst. The reservation of resources is typically made by an out-of-band one-way control message which precedes the burst by some offset time. By reserving resources only for the duration of the burst, a greater degree of utilization may be achieved in the network. This book provides an overview of optical burst switching. Design and research issues involved in the development of OBS networks are discussed, and approaches to providing QoS in OBS networks are presented. Topics include: - Optical burst switching node and network architectures - Burst assembly - Signaling protocols - Contention resolution - Burst scheduling - Quality of service in OBS networks

In optical switching paradigm, there are three approaches; optical circuit switching, optical packet switching, and optical burst switching (OBS). OBS is a technology that takes the best features of packet switching and circuit switching by providing a flexible infrastructure for carrying IP traffic and at the same time ensuring efficient utilization of the fiber link. In this paper we propose an effective contention resolution scheme to achieve minimum burst loss at core nodes. Algorithm of zero burst loss for bimodal burst switching is extended from single node star network topology to two node star topology. Scheduling at the core node, typically an optical cross connect (OXC), is performed in two modes i.e., Mode 0 & Mode 1. Mode 0 is for burst transmission between all directly connected edge nodes whereas Mode 1 is for burst transmission through remote core node to a particular destination edge node. Synchronization of the reservation request between the core nodes is a critical task in such a topology. In order to achieve minimum burst loss, using a small length of fiber delay line in recirculation mode results in an effective strategy.

In an all optical networks we made a study on two important variants of TCP like TCP-Reno and TCP-Vegas. In an OBS network the bursts are aggregated at the edge nodes and they travel cutting through all optical network. A data burst is preceded by a control packet with an offset time. There is an amount of hop-delay for the data burst between the core nodes in the OBS network. There is also a limit on the number of packets for each burst which we call as burst size. At the ingress node burstification takes place and packets are assembled into bursts which forms a maximum flow queue. In our simulation we have taken the hop delay, maximum flow queue and burst size as parameters and analyzed the performance of TCP-Reno and TCP-Vegas using NS-2 simulator.

The current edge assembly granularity preserved beforehand in optical burst switched (OBS) networks lacks flexibility to actual network traffic and increases assembly overhead and delay. Offset time generating mechanism after traffic shaping increase network delay and cut down its robustness. Consequently, it is significant to present an effective dynamic burstification scheme to process real-time traffic, reduce assembly delay and provide QoS guarantee for different priority traffic at edge node. This paper focuses on dynamic burst assembly at edge node in optical burst switching networks, which can be implemented to improve the performance of the whole network. Based on traffic prediction, a new dynamic adaptive assembly mechanism on load estimate, termed Dynamic Adaptive Assembly (DAA), is proposed to reduce assembly delay, estimate real-time network traffic character and dynamically adjust Burst Assembly Time (BAT) at edge node. The dynamic range of BAT for four traffic classes is introduced to make compare among current and previous prediction with different prediction time under QoS based offset time. We investigate the influence of current and previous offered load with different prediction time and offset time. Simulation studies are carried out for various traffic classes. The results show that DAA can achieve little delay and provide adaptivity, flexibility and delay fairness for burst assembly.

The most important design goal in Optical Burst Switching (OBS) networks is to reduce burst loss resulting from resource contention. Especially, the higher the congestion degree in the network is, the higher the burst loss rate becomes. The burst loss performance can be improved by employing an appropriate congestion control. In this paper, to actively avoid contentions, we propose a dynamic load-aware congestion control scheme that operates based on the highest (called ‘peak load’) of the loads of all links over the path between each pair of ingress and egress nodes in an OBS network. We also propose an algorithm that dynamically determines a load threshold for adjusting burst sending rate, according to the traffic load in a network. Further, a simple signalling method is developed for our proposed congestion control scheme. The proposed scheme aims to (1) reduce the burst loss rate in OBS networks and (2) maintain reasonable throughput and fairness. Simulation results show that the proposed scheme reduces the burst loss rate significantly, compared to existing OBS protocols (with and without congestion control), while maintaining reasonable throughput and fairness. Simulation results also show that our scheme keeps signalling overhead due to congestion control at a low level.

The single-hop star-based network is proposed as a feasible topology to fit the rapidly-increasing bandwidth requirement in the AAPN research project. This paper investigates the node architecture to implement all-optical operations in such a network using available technologies. Based on the node placement in the network, two architectures are designed, one is placed in the edge and another one is used in the core. The edge node is a multi-stage electronic/optic switch, which aggregates legacy traffics and transmits them to the core node, or accepts optical messages from the core node and sends them to legacy networks. Each stage uses either electronic or optical components to implement signal storage, conversion or transmission. The core node is an all-optical switch which switches optical signals in different wavelength planes, while the controlling part works in electronic domain. A separate control plane is designed to manipulate the operation of different component devices. This system provides a common platform for the overlaid-star network. By introducing synchronization or not, we can employ reservation-based optical time-division-multiplexing (OTDM) or contention-based optical burst switching (OBS) in the designed architecture. No wavelength conversion or optical buffering is necessary by agilely scheduling the messages in both mechanisms. Our research is an efficient and feasible solution which satisfies the transmission requirement by taking into account of technological availability. Our design is supported by the performance evaluation of OTDM and OBS methods, and their comparisons under different scenarios.

Parallel Optical Burst Switching (POBS) is a variant of Optical Burst Switching (OBS) which is proposed as a new optical switching strategy for Ultra-Dense Wavelength Division Multiplexing (U-DWDM) to support the enormous bandwidth demand of the next generation Internet. As opposed to OBS, POBS transmits bursts in two dimensions: the wavelength dimension and the time dimension. POBS network uses an one-way resource reservation mechanism to set up the resources for each data burst transmission. The use of this mechanism may cause bursts to contend for the same resources at the same time at core (intermediate) nodes of the network. Therefore, the performance of POBS networks depends on the contention resolution policies to reach acceptable levels for bandwidth usage. These policies may increase both the cost and complexities of the core nodes in POBS networks. Most literatures on OBS networks apply contention resolution at the core nodes based on reactive strategies that are activated after contention takes place in core nodes. This study proposes the use of a proactive contention resolution technique at ingress nodes of POBS network as well as reactive contention resolution technique at core nodes for reducing the probability of burst drop in the network in order to increase the performance of the network. The simulation results show that the use of POBS network with the proposed Reactive Odd/Even Node ID Wavelength Assignment Technique (POBS-ROENIDWAT) shows a better performance in terms of reduced data loss rate and increased throughput compared to the performances of both POBS network with Sequential Wavelength Assignment Technique (POBS-SWAT) and OBS network with Burst Segmentation (OBS-BS).

Enhanced packet routing queuing model in optical burst switching network using queue-based dynamic optical route scheduling

A crucial issue in optical burst switching (OBS) networks is burst loss caused by resource contention. As a result, many methods are currently being proposed to reduce burst loss rate. These methods can be summed up into two categories: burst scheduling algorithms and contention resolutions. Both categories of methods can reduce burst loss rate to a certain degree. However, to make OBS to become a viable solution, the burst loss rate needs to be further reduced. Furthermore, almost all methods ignore the fact that an unfortunately scheduled, locally generated single-hop burst could block a number of future incoming transit bursts, though the burst just travels to its next downstream node. This phenomenon becomes more evident when links are heavily loaded in mesh OBS networks. To eliminate contention caused by single-hop traffic completely, this paper proposes a novel transfer mode called packet calking by differentiating between single-hop traffic from multihop traffic for OBS networks. An analysis model is developed to evaluate the performance of packet calking. Theoretical results are validated through extensive simulations in both ring and mesh networks. These results show that packet calking outperforms the transfer mode without packet calking in terms of burst loss rate and link utilization.