Design and protection algorithms for path level aggregation of traffic in WDM metro optical networks

Wavelength Division Multiplexing (WDM) promises to offer a cost effective and scalable solution to meet the emerging demands of the Internet. WDM splits the tremendous bandwidth latent in a fiber into multiple non-overlapping wavelength channels, each of which can be operated at the peak electronic rate. Commercial systems with 128 wavelengths and transmission rates of up to 40 Gbps per wavelength have been made possible using state of the art optical technologies to deal with physical impairments. Systems with higher capacities are likely to evolve in the future. The end user requirements for bandwidth, on the other hand, have been ranging from 155 Mbps to 2.5 Gbps. Dedicating a wavelength for each end user will lead to severe underutilization of WDM channels. This brings to forefront the requirement for sharing of bandwidth in a wavelength among multiple end users.;The concept of wavelength sharing among multiple clients is called grooming. Grooming can be done purely at the optical layer (optical grooming) or it can be done with support from the client layer (electronic grooming). The advantage of all optical grooming is the ease of scalability due to its transparency as opposed to electronic grooming which is constrained by electronic bottlenecks. Efforts towards enhancing optical grooming is pursued through increasing optical switching speeds. However, technologies to make optical switches with high speeds, large port counts and low insertion losses have been elusive and may continue to remain so in the near future.;Recently, there have been some research into designing new architectures and protocols focused on optical grooming without resorting to fast optical switching. Typically, this is achieved in three steps: (1) configure the circuit in the form of a path or a tree; (2) use optical devices like couplers or splitters to allow multiple transmitters and/or receivers to share the same circuit; and (3) provide an arbitration mechanism to avoid contention among end users of the circuit. This transparent sharing of the wavelength channel utilizes the network resources better than the conventional low-speed circuit switched approaches. Consequently, it becomes important to quantify the improvement in achieved performance and evaluate if the reaped benefits justify the cost of the required additional hardware and software.;The contribution of this thesis is two fold: (1) developing a new architecture called light-trails as an IP based solution for next generation WDM optical networks, and (2) designing a unified framework to model Path Level Aggregation of Traffic in metrO Optical Networks (PLATOONs). The algorithms suggested here have three features: (1) accounts for four different path level aggregation strategies---namely, point to point (for example, lightpaths), point to multi-point (for example, source based light-trails), multi-point to point (for example, destination based light-trails) and multi-point to multi-point (for example, light-trails); (2) incorporates heterogenous switching architectures; and (3) accommodates multi-rate traffic. Algorithms for network design and survivability are developed for PLATOONs in the presence of both static and dynamic traffic. Connection level dedicated/shared, segregated/mixed protection schemes are formulated for single link failures in the presence of static and dynamic traffic. A simple medium access control protocol that avoids collisions when the channel is shared by multiple clients is also proposed.;Based on extensive simulations, we conclude that, for the studied scenarios, (1) when client layer has no electronic grooming capabilities, light-trails (employing multi-point to multi-point aggregation strategy) perform several orders of magnitude better than lightpaths and (2) when client layer has full electronic grooming capabilities, source based light-trails (employing point to multi-point aggregation strategy) perform the best in wavelength limited scenarios and lightpaths perform the best in transceiver limited scenarios.;The algorithms that are developed here will be helpful in designing optical networks that deploy path level aggregation strategies. The proposed ideas will impact the design of transparent, high-speed all-optical networks.</p

Network design for IP-centric light-trail networks

We explore network design principles for next-generation all-optical wide-area networks, employing light-trail technology. Light-trail is a light-wave circuit that allows multiple nodes to share the optical bandwidth through the inclusion of simple but flexible hardware overlaid with a lightweight control protocol. We develop light-trails as a novel and amenable control and management solution to address IP-centric communication problems at the optical layer. We propose optical switch architectures that allow seamless integration of lightpath and light-trail networks, and assess their costs and capabilities. We formulate the static light-trail RWA problem as an integer linear program. Since this programming problem is computationally intractable, we split it into two subproblems: (a) trail routing, for which we provide three heuristics, (b) wavelength assignment, for which we use the largest first heuristic available in literature. The objective of our design is to minimize the optical layer and electronic layer costs in terms of the number of wavelengths and communication equipment required. We illustrate our approach by comparing the performance of our trail design heuristics on some test networks

On Traffic Grooming Choices for IP over WDM networks

Traffic grooming continues to be a rich area of research in the context of WDM optical networks. We provide an overview of the optical and electronic grooming techniques available with focus on IP as the client layer. We discuss the various architectural alternatives available: peer, over-lay and augmented models. We first provide a survey on the research work in the area of traffic grooming in opti-cal circuit switched networks. We then identify problems with electronic grooming in terms of high speed router de-sign and bring out the merits of optical grooming. Next, we describe the shared wavelength optical network tech-nology called light-trails and compare its performance with electronic grooming networks for both the peer and over-lay models. Based on our simulations on random graphs of various diameters, we identify the threshold router speeds at which light-trails can compete with the electronic grooming solution for a given network scenario. We conclude that since the present router capacities are below the thresh-old speed or such routers are likely to remain expensive for some time, light-trails is an appealing candidate solution.

Traffic Grooming in Statistically Shared Optical Networks

We investigate the characteristics and performance of architectures that allow statistical sharing of wavelengths in the optical layer. The bandwidth of a light-wave circuit can be shared in the optical layer by multiple nodes that are along a linear path in a network through the inclusion of simple but flexible hardware overlaid with control software. We consider three types of architectures- lightpath (LP), light-trail (LT) and source based light-trail (SLT) networks. The three differ in their level of optical sharing, in their hardware and software requirements and in their performance. We study the interplay between statistical sharing at the optical layer and circuit switched sharing at the electronic layer. We develop a generic auxiliary graph model for traffic grooming in heterogeneous WDM mesh networks that can accommodate constraints related to transceivers, wavelengths, and groomers for architectures with different levels of statistical sharing and for both static and dynamic scenarios. We conclude based on our simulation results that sharing wavelength in the optical domain is beneficial and can lead to reduced blocking

On Traffic Grooming Choices for IP over WDM networks

Traffic grooming continues to be a rich area of research in the context of WDM optical networks. We provide an overview of the optical and electronic grooming techniques available with focus on IP as the client layer. We discuss the various architectural alternatives available: peer, overlay and augmented models. We first provide a survey on the research work in the area of traffic grooming in optical circuit switched networks. We then identify problems with electronic grooming in terms of high speed router design and bring out the merits of optical grooming. Next, we describe the shared wavelength optical network technology called light-trails and compare its performance with electronic grooming networks for both the peer and overlay models. Based on our simulations on random graphs of various diameters, we identify the threshold router speeds at which light-trails can compete with the electronic grooming solution for a given network scenario. We conclude that since the present router capacities are below the threshold speed or such routers are likely to remain expensive for some time, light-trails is an appealing candidate solution.This is a manuscript of a proceeding published as Balasubramanian, Srivatsan, and Arun K. Somani. "On traffic grooming choices for IP over WDM networks." In 2006 3rd International Conference on Broadband Communications, Networks and Systems, (2006). DOI: 10.1109/BROADNETS.2006.4374410. Posted with permission.</p

Network design for IP-centric light-trail networks

We explore network design principles for next-generation all-optical wide-area networks, employing light-trail technology. Light-trail is a light-wave circuit that allows multiple nodes to share the optical bandwidth through the inclusion of simple but flexible hardware overlaid with a lightweight control protocol. We develop light-trails as a novel and amenable control and management solution to address IP-centric communication problems at the optical layer. We propose optical switch architectures that allow seamless integration of lightpath and light-trail networks, and assess their costs and capabilities. We formulate the static light-trail RWA problem as an integer linear program. Since this programming problem is computationally intractable, we split it into two subproblems: (a) trail routing, for which we provide three heuristics, (b) wavelength assignment, for which we use the largest first heuristic available in literature. The objective of our design is to minimize the optical layer and electronic layer costs in terms of the number of wavelengths and communication equipment required. We illustrate our approach by comparing the performance of our trail design heuristics on some test networks.This is a manuscript of a proceeding published as Balasubramanian, Srivatsan, Ahmed E. Kamal, and Arun K. Somani. "Network design for IP-centric light-trail networks." In 2nd International Conference on Broadband Networks, 2005., pp. 41-50. IEEE, 2005. DOI: 10.1109/ICBN.2005.1589599. Posted with permission.</p