BHP flooding vulnerability and countermeasure

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.

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).

On burst assembly in optical burst switching networks—A performance evaluation of just-enough-time

In this paper, we address the problem of data-burst grooming in optical burst-switched (OBS) networks. In OBS networks, IP packets with the same edge-node destination are assembled into larger packets called data bursts. Depending on the core node's switching technology, data bursts are required to have a minimum length. On the other hand, each IP packet in a burst has a time delay constraint, called maximum end-to-end delay, which determines the upper time limit before which the packet must reach its destination. Thus, a data burst cannot wait indefinitely until a sufficient number of IP packets are assembled and the minimum burst length requirement is met. In order to satisfy the packet maximum end-to-end delay requirement, many bursts will be timed out and released before they reach the minimum-length requirement. Under such circumstances, padding overhead must be added to these short bursts, called sub-bursts. Excessive padding results in high overhead and high data-burst blocking probability. One approach to minimize the amount of padding overhead, while maintaining the end-to-end delay requirement of IP packets, is to groom multiple sub-bursts together. That is, sub-bursts with different destinations are aggregated together at the edge node and transmitted as a single burst until they are separated at some downstream node. In this paper, we present an edge-node architecture enabling burst-grooming capability. We also develop two basic grooming approaches, namely No routing overhead (NoRO) and minimum total overhead (MinTO). Through a comprehensive simulation study, we show that, in general, our proposed grooming algorithms can significantly improve the performance compared to the case of no grooming. However, careful considerations must be given to network-loading conditions and the number of sub-bursts allowed to be groomed together. We show that although simple greedy algorithms can reduce network overhead, they may alter the traffic characteristics and increase its burstiness, resulting in high packet blocking probability.

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.

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.

Optical Burst Switching (OBS) is an optical network that is efficient and reliable. However, there are some critical issues in OBS such as burst loss ratio, which occur due to contending bursts as optical buffers are lacked at the core node. Many techniques have been proposed to tackle the problem such as using offset time. Offset time is managed to allow Burst Header Packet (BHP) to reserve the required resources necessary for a successful transmission process. If the added extra time is long, it reserves the resources for a long time. In contrast, setting low offset time results in burst loss. As a consequence, the techniques that manages offset time need to be developed. This paper proposes an Intelligent Offset Time (IOT) algorithm that adapts offset time based on the condition of the network and the traffic. Three parameters are used as IOT’s fuzzy input that are burst size, destination and burst queuing delay. The proposed algorithm is evaluated against the conventional offset time and adaptive offset time algorithms. The results of IOT’s simulation show that it has effectively reduced burst loss ratio and end-to-end delay in comparison with the conventional and adaptive algorithms.

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

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.

Since Transmission Control Protocol (TCP) is the dominant protocol on the Internet and optical burst switching (OBS) networks represent the optical transmission solution that can meet future high bandwidth requirements, TCP and OBS networks represent a possible combination for the next-generation Internet. However, a problem with this combination model is that operations at the OBS layer need to be controlled so that false congestion detection at the TCP layer is minimised. Considering the combination of TCP Vegas and OBS, congestion detection at the TCP layer is based on the round-trip time (RTT), where congestion is detected if the current RTT exceeds a given RTTmax. The extra delay may be due to some actual loss, but it may also be due to the extended execution time caused by some OBS layer operations. Therefore, reducing the time of operations at the OBS layer will reduce false congestion detection at the TCP layer. This paper investigates the impact of reducing the buffering time at the ingress node on the false congestion detection rate at the TCP layer. The reduction of the burst buffering time is accomplished by nesting the offset time in the assembly time. The simulation results and analysis show that the transmission efficiency in TCP Vegas over OBS networks is significantly improved; the throughput remains high, and the delivery success rate is significantly increased compared to the conventional buffering mode.

Many recent studies have convincingly demonstrated that network traffic exhibits a noticeable self-similar nature which has a considerable impact on network performance. Therefore, we present a novel scheme for optical burst switching (OBS) networks, called logical cascaded private subnet. We define the concept of `canoe' relative to `cluster' in self-similar traffic, and introduce a new device named payload segregator at the edge node as a gateway to the core node in OBS networks. According to the changes in the edge node framework, we put forward the concept of cluster private subnet and canoe private subnet in the core node correspondingly. Performance study indicates that, the new scheme is robust under self-similar traffic

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

Dynamic wavelength selection and delayed burst assignment schemes for Optical Burst Switching networks

Optical Burst Switching (OBS) is a promising switching technology for the next generation all-optical networks. An OBS network without wavelength converters and fiber delay lines can be implemented simply and cost-effectively using the existing technology. However, this kind of networks suffers from a relatively high burst loss probability at the OBS core nodes. To overcome this issue and consolidate OBS networks with QoS provisioning capabilities, we propose an absolute QoS differentiation scheme, called Absolute Fair Quality of service Differentiation (AFQD), which is based on a wavelength partitioning scheme, called Optimization Topology-aware Wavelength Partitioning scheme (OTWP). AFQD is the first absolute QoS provisioning scheme that guarantees loss-free transmission for high priority traffic inside the OBS network. Simulation results show that AFQD not only guarantees loss-free transmission for high priority traffic but also substantially decreases the loss probability of best effort traffic to a remarkable level compared to the existing schemes.

There is a growing demand for OBS (optical burst switching) networks, which is based on the concept of providing switching of data bursts without any intermediate switching and O/E/O conversions. The OBS technology is very economical and flexible to create new definitions for networking processes. OBS networks can also help in creating several types of new services which involve more bandwidth usage. The present research paper focuses on the OBS network and its benefits. The major problems of burst contention and congestion control using OBS networks are addressed in this research. In this paper, a possible solution to burst contention and congestion control is presented by the use of an algorithm, called BAT algorithm. The multi-objective optimisation problem is solved using a multi-objective BAT algorithm (MOBA). The proposed algorithm presented effective results to maximise the traffic demand, burst loss ratio minimisation, and reduction in overall burst block probability.