Performance Analysis of Optical Burst Switching for High Speed Networks

Abstract

The field of networking has experienced growth at a tremendous rate over the last decade. The popularity of the Internet is soaring as more people gain an increased awareness of the vast amounts of information available at the click of a button. This growing demand is leading to many new opportunities in networking, as people demand faster and better applications and services, such as World Wide Web browsing, video-on-demand and interactive television. The rapid expansion of the Internet and the ever-increasing demand for multimedia information are severely testing the limits of our current computer and telecommunication networks. There is an immediate need for the development of new high-capacity networks that are capable of supporting these growing bandwidth requirements. We need to be able to scale current networks to support the increasing volumes of information. Optical networks are a logical choice to meet the future communication demands, with optical fiber links offering huge bandwidth.

Thus, optical burst switching (OBS) is considered as a suitable transport methodology for the realization of optical core networks due to the balance it offers between coarse-grained optical circuit switching (OCS) and fine-grained optical packet switching (OPS). OBS avoids the use of optical buffering and optical processing logic unlike in OPS but still achieves switching in optical domain. It improves the utilization of the fiber compared to OCS because of statistical multiplexing of bursts on different wavelengths.

Although, optical burst switching appears to offer advantages over optical circuit switching and optical packet switching, several issues need to be considered before optical burst switching can be deployed in transport networks. In particular, these issues include; network architectures problems in terms of lower blocking probability, reservations techniques for efficient utilization of bandwidth as well as network resources; burst dropping and contention resolution schemes supporting quality of service, which need to be investigated further. Keeping in view the above mentioned aspects, the objectives of the research were formulated which are listed as follows: 1. To study and analyze various optical burst switching architectural alternatives in terms of the burst handling techniques and with the possible use of fiber delay-line for buffering and contention resolution. 2. To study and compare various reservation schemes for efficient network utilization and bandwidth in optical burst switched networks. 3. To analyze and compare the different burst segmentation policies with the standard dropping policies. 4. To investigate, analyze and compare the performance of various contention resolution policies and control schemes for optical burst switched network, in order to reduce packet/burst loss, while supporting quality of service.

An efficient OBS network architecture incorporating small fiber delay line (FDL), adaptive burst assembly as well as dynamic route selection techniques, has been proposed for improving system’s performance, in terms of lower blocking probability and higher throughput. The simple closed-form expressions are derived for the burst loss probability of both classless and prioritized traffic. Also, in order to have reduction in electronic switching processing time, delay associated with FDL usage in the above architecture, another efficient congestion-free OBS network architecture utilizing a short-prior-confirmation-packet and optical label processing with just enough time (JET) signaling, has been presented. The proposed architectures make exemplary use of the advantages of all-optical technology by meticulously delegating switch planning and contention avoidance for control processing. The quality of service (QoS) oriented reservation schemes have been investigated in order to enhance bandwidth and channel utilization in OBS networks. An adaptive reservation scheme based on a multi-service OBS edge node with synchronized bandwidth reservation mechanism has been proposed. The proposed scheme provides a flexible and efficient platform for convergence of packet-based and circuit-based network traffic based on OBS capabilities. In order to have better channel utilization, higher throughput and lower blocking probability, we have investigated an efficient reservation scheme in which data burst are scheduled in batches. To obtain better fairness control and bandwidth utilization, we have presented another efficient reservation scheme in which

each edge router finds a suitable route to the destination edge router autonomously by using feedback and prior information packets. It is shown that by leveraging statistical multiplexing, re-configuration cost is minimized and thus bandwidth utilization is enhanced. To minimize the burst drop rate in OBS network, an efficient burst dropping policy based on even selection of burst (BDPES) has been proposed. Also, suitable burst assembly and congestion control mechanisms have been used in the proposed policy in order to provide differentiated service for supporting the quality of service (QoS) requirements. In order to obtain better results in terms of bandwidth utilization, lower burst loss rate etc, flexible and enhancing bandwidth utilization, burst dropping technique based on packet count number (PCN) has been presented for contention resolution. The results obtained show that the proposed dropping scheme reduces packet loss rate (PLR) and makes bandwidth utilization more efficient and flexible than existing schemes. Contention, which may occur when two or more bursts compete for the same wavelength on the same link, is a critical issue. Thus, we have proposed possible better solutions to reduce blocking probability due to contention. Through hybrid contention resolution techniques such as WConv, delay and deflect; WConv, deflect and delay and Prioritized delay, deflect and delay, it is shown that both contention and the burst loss rate have been minimized. In order to have proportional differentiated services, lower packet loss etc, an efficient scheme based on adaptive wavelength selection and burst assignment, which supports better proportional differentiated services with lower packet loss in the buffer-less OBS networks, has been developed. Further, to have both contention resolution and congestion control for reducing burst loss in OBS network, we have investigated an integrated contention resolution and control scheme. Finally, to achieve improvements in terms of wavelength utilization and wavelength efficiency, an efficient scheme based on resource reservation and adaptive network flow routing has been investigated. It has been observed in the achieved results that the proposed schemes reduces burst loss in the network significantly, provides congestion control, support differentiated services and also improves wavelength utilization and efficiency as compared to the conventional schemes.