Mahesh Sivakumar

Bio: Mahesh Sivakumar is an academic researcher from University of Maryland, Baltimore County. The author has contributed to research in topics: Node (networking) & Mesh networking. The author has an hindex of 6, co-authored 12 publications receiving 125 citations. Previous affiliations of Mahesh Sivakumar include University of Baltimore.

On partial protection in groomed optical WDM mesh networks

Abstract: In this paper, we consider the problem of survivable network design in traffic groomed optical WDM mesh networks with sub-wavelength capacity connections. In typical survivable network designs, individual sessions are provided either full protection or no protection. We consider a quality of protection (QoP) framework where a connection is provided partial protection, i.e. when a link failure occurs on the primary path, the protection bandwidth provided on the backup path is less than or equal to the primary bandwidth. Each connection request specifies the primary bandwidth and a minimum backup bandwidth required. The network will guarantee at least the minimum backup bandwidth and, if capacity is available, higher backup bandwidth up to the primary path's bandwidth. The advantage of such a model is that it can reduce backup capacity requirements based on connection needs leading to lower blocking probability and lower network costs. We consider two scenarios: (i) a network with static traffic and formulate the problem of providing partial protection in groomed networks as an integer linear program (ILP); and (ii) a network with dynamic traffic that is analyzed using discrete-event simulation models. The results quantify the gain in blocking probability for different partial protection scenarios.

A hybrid protection-restoration mechanism for enhancing dual-failure restorability in optical mesh-restorable networks

Abstract: In this paper, we investigate the problem of enhancing dual-failure restorability in path-protected mesh-restorable optical wavelength division multiplexed (WDM) networks. A key finding of recent studies that have demonstrated the need to survive simultaneous dual-link failures is that designs providing complete (i.e. 100%) protection from all dual-failures may need almost thrice the spare capacity compared to a system that protects against all single-link failures. However, it has also been shown that systems designed for 100% single-link failure protection can provide reasonable protection from dual-link failures. Thus, the motivation of this work is to develop a hybrid mechanism that provides maximum (close to 100%) dual-failure restorability with minimum additional spare capacity. The system architecture considered is a circuit-switched WDM network with dynamic arrival of sessions requests. We also consider sparse wavelength conversion, where only some nodes have converters. We propose an adaptive mechanism, which we term active protection, that builds upon a pro-active path protection to provide complete single-failure restorability and adds dynamic segment-based restoration. The objective is to optimize network survivability (and minimize spare capacity needs) with ragard to dual-link failures while maintaining complete single-failure restorability. The basic premise of the algorithm is to identify scenarios in the dual-link failure model that necessitate additional spare capacity and provide protection for those scenarios only. Our findings indicate that the proposed scheme achieves close to complete (100%) dual-failure restorability with only maximum of 3% wavelength-links needing two backups even at high loads. Moreover, at moderate to high loads, our scheme attains close to 16% improvement over the base model that provides complete single-failure restorability.

Performance evaluation of time switching in TDM wavelength routing networks

Abstract: Advances in optical WDM technology have paved the way for high-capacity wavelength channels capable of carrying information at Gb/s rates. However, with current traffic streams requiring only a fraction of a wavelength's bandwidth, it becomes necessary to groom these independent low rate traffic streams on to higher capacity wavelength channels. An all-optical approach to grooming is to allow many connections to time-share a wavelength. Accordingly, in a TDM wavelength routing network, the establishment of a connection requires the assignment of time slots in addition to routing and wavelength assignment. One of the primary challenges in such networks is the need for quick reconfiguration at the routing nodes. In this paper, we investigate the effects of switch reconfigurability, wavelength conversion and time slot interchangers (TSIs) on the blocking performance of connections with multiple rates. Heuristics for time slot assignment that consider constraints imposed by six different node architectures are proposed, and the blocking performance of the TDM wavelength routing network is evaluated through simulations. Results indicate that limited reconfigurability at the nodes is sufficient to attain the performance obtained with full reconfigurability, especially when connections occupy only a small fraction of the wavelength capacity. Furthermore, the blocking performance is not seen to benefit significantly with the introduction of wavelength converters and TSIs, thus signifying that the improvement in blocking is largely dependent on the switch reconfigurability at the nodes.

A Survey of Survivability Techniques for Optical WDM Networks

Abstract: In an optical wavelength division multiplexed (WDM) network, link or node failures may result in huge amounts of lost data, due to the enormous fiber throughput. This requires that optical WDM network be designed to be resilient to failures. Thus, survivability can be defined as the ability to respond gracefully to such failures. This chapter presents a comprehensive survey of various mechanisms proposed to achieve survivability. The survey considers different topologies, different failure models, implementation issues, signaling issues and quality-of-protection issues.

Design of Disaster-Resilient Optical Datacenter Networks

Abstract: Survivability against disasters-both natural and deliberate attacks, and spanning large geographical areas-is becoming a major challenge in communication networks. Cloud services delivered by datacenter networks yield new opportunities to provide protection against disasters. Cloud services require a network substrate with high capacity, low latency, high availability, and low cost, which can be delivered by optical networks. In such networks, path protection against network failures is generally ensured by providing a backup path to the same destination (i.e., a datacenter), which is link-disjoint to the primary path. This protection fails to protect against disasters covering an area which disrupts both primary and backup paths. Also, protection against destination (datacenter) node failure is not ensured by a generic protection scheme. Moreover, content/service protection is a fundamental problem in a datacenter network, as the failure of a datacenter should not cause the disappearance of a specific content/service from the network. So content placement, routing, and protection of paths and content should be addressed together. In this work, we propose an integrated Integer Linear Program (ILP) to design an optical datacenter network, which solves the above-mentioned problems simultaneously. We show that our disaster protection scheme exploiting anycasting provides more protection, but uses less capacity than dedicated single-link failure protection. We show that a reasonable number of datacenters and selective content replicas with intelligent network design can provide survivability to disasters while supporting user demands. We also propose ILP relaxations and heuristics to solve the problem for large networks.

A new approach to optical networks security: attack-aware routing and wavelength assignment

Abstract: Security issues and attack management in transparent wavelength division multiplexing (WDM) optical networks have become of prime importance to network operators due to the high data rates involved and the vulnerabilities associated with transparency. Deliberate physical-layer attacks, such as high-powered jamming, can seriously degrade network performance and must be dealt with efficiently. While most approaches are focused on the developing fast detection and reaction mechanisms triggered in case of an attack, we propose a novel approach to help deal with these issues in the network planning and provisioning process as a prevention mechanism. Namely, we propose to route lightpaths in such a way as to minimize the potential damage caused by various physical-layer attacks. We present a new objective criterion for the routing and wavelength assignment (RWA) problem, which we call the maximum Lightpath Attack Radius (maxLAR), and formulate the routing subproblem as an integer linear program (ILP). We test it on small networks to get an insight into its complexity and compare it to a formulation that minimizes congestion. Results indicate that our formulation achieves significantly better results for the maxLAR while obtaining near-optimal or optimal congestion in all cases. For larger networks, we propose a tabu search algorithm for attack-aware lightpath routing, in combination with an existing graph-coloring algorithm for wavelength assignment. Testing and comparing with existing approaches from literature indicate its superiority with respect to the maxLAR and average lightpath load, albeit at the expense of somewhat higher congestion. However, this is justified with the obtained improvement in network security.

Network Design and Architectures for Highly Dynamic Next-Generation IP-Over-Optical Long Distance Networks

Abstract: The DARPA CORONET project seeks to develop the target network architectures and technologies needed to build next-generation long-distance IP-over-Optical-Layer (IP/OL) networks. These next-generation networks are expected to scale 10-100 times larger than today's largest commercial IP/OL network. Furthermore, DARPA has established advanced objectives for very rapid provisioning of new IP or private line connections, very rapid restoration against up to three simultaneous network failures, and future dynamic ldquowavelengthrdquo services ranging from speeds of 40-800 Gigabits per second. Besides these ambitious goals, the CORONET project seeks to establish a commercially-viable network architecture that supports both commercial and government services. In this paper, we describe the CORONET program requirements, and present our initial architectures and analysis of the early phases of this long-term project. We propose a novel 2-Phase Fast Reroute restoration method that achieves 50-100 ms restoration in the IP-Layer in a cost-effective manner, and a commercially viable OL restoration method that can meet the rapid CORONET requirements. We also estimate the magnitude of the extra capacity needed to provide dynamic wavelength services compared to that of static services, and show that the extra capacity to restore a small percentage of high priority traffic against multiple failures requires a small amount of extra capacity compared to that of single failures.

Network design and architectures for highly dynamic next-generation IP-over-optical long distance networks

Abstract: We present initial network architectures and capacity-efficient design for an IP/Optical network with highly dynamic IP and wavelength services, restoration against up to 3 failures, and aggregate traffic levels that represent a 10-fold increase over today's network traffic.