Zilong Ye

Survivable virtual infrastructure mapping with dedicated protection in transport software-defined networks [Invited]

Efficiently mapping multiple virtual infrastructures (VIs) onto the same physical substrate with survivability is one of the fundamental challenges related to network virtualization in transport software-defined networks (T-SDNs). In this paper, we study the survivable VI mapping problem in T-SDNs with the objective of minimizing the VI request blocking probability. In particular, we address the subproblems of modulation selection and spectrum allocation in the process of provisioning optical channels to support virtual links, taking into consideration the optical layer constraints such as the transmission reach constraint and the spectral continuity constraint. We propose an auxiliary-graph-based algorithm, namely, parallel VI mapping (PAR), to offer dedicated protection against any single physical node or link failure. More specifically, the PAR algorithm can jointly optimize the assignments of mapping the primary and backup VIs by adopting the modified Suurballe algorithm to find the shortest pair of node-disjoint paths for each virtual link. Through extensive simulations, we demonstrate that the PAR algorithm can significantly reduce the VI request blocking probability and improve the traffic-carrying capacity of the networks, compared to the baseline sequential VI mapping approaches.

Joint topology design and mapping of service function chains for efficient, scalable, and reliable network functions virtualization

NFV is promising to lower the network operators capital expenditure and operational expenditure by replacing proprietary hardware-based network equipment with software-based VNFs that can be consolidated into telecom clouds. In particular, NFV provides an efficient way to deploy network services using SFCs that consist of a set of VNFs interconnected by virtual links. A practical but theoretically challenging problem related to NFV management and orchestration is how to jointly optimize the topology design and mapping of multiple SFCs such that the TBC is minimized, which is called the JTDM problem. In this article, we propose a novel heuristic algorithm, Closed-Loop with Critical Mapping Feedback, to efficiently address the JTDM problem. While minimizing the TBC, we also propose scalable and reliable JTDM strategies that can significantly reduce the network reconfigurations and enhance the service reliability, respectively.

GREP: Guaranteeing Reliability with Enhanced Protection in NFV

Network Function Virtualization (NFV) is a promising technique to greatly improve the effectiveness and flexibility of network management through a process called Service Function Chain (SFC) mapping, which can efficiently provision network services over a virtualized and shared middlebox platform. However, such an evolution towards software-defined middlebox introduces new challenges to network services which require high reliability. Sufficient redundancy can protect the network services when physical failures occur, but in doing so, the efficiency of physical resources may be greatly decreased. This paper presents GREP, a novel online algorithm that can minimize the physical resources consumption while guaranteeing the required high reliability with a polynomial time complexity. Simulation results show that our proposed algorithm can significantly improve the request acceptance ratio and reduce resource consumption.

Virtual infrastructure embedding over software-defined flex-grid optical networks

Software-Defined Networking (SDN) enables efficient and scalable network virtualization. Infrastructure resources, such as computing and networking resources, can be abstracted and outsourced as a service using virtualization technology. These SDN features can be extended to the optical transport networks to enable high capacity, low cost, and long reach transport networks. In this paper, we introduce an architecture for Software-Defined Optical Network (SDON), and study the virtual infrastructure embedding (VIE) problem over SDON with the objective of minimizing the blocking probability of VIE requests. We propose two novel heuristic algorithms, namely Compute followed by Network Load Balance (CNLB) and Network followed by Compute Load Balance (NCLB). Specifically, NCLB is the first ever attempt to solve the VIE problem by allocating the networking resource first followed by provisioning the computing resource. We compare these two algorithms with the Shortest-Path Based Embedding (SPBE) algorithm. The simulation results show that both CNLB and NCLB outperform SPBE in terms of minimizing the request blocking probability, and NCLB achieves the best performance.

Virtual network embedding and reconfiguration in elastic optical networks

Recent innovations in Network Virtualization and Elastic Optical Networks (EONs) enable flexible deployment of optical networks as a service. However, one open challenge is how to embed Virtual Optical Network (VON) requests onto the physical substrate network to maximize the sharing of physical resources, which is the so called Virtual Network Embedding (VNE) problem. EONs are prone to the fragmentation of spectral resources during the process of routing and spectrum allocation. The fragmentation of spectral resources in the substrate fiber links may lead to the blocking of incoming virtual network requests. This degrades the utilization of the physical resources of the Infrastructure Providers and also, decreases the revenue of the Service Providers. In this paper, we propose a novel virtual network embedding algorithm called Alignment and Consecutiveness-aware Virtual Network Embedding (ACT-VNE), which takes into account the spectrum alignment and relative loss in spectrum consecutiveness when mapping virtual nodes/links onto the physical substrate nodes/links. We also propose a min-max reconfiguration scheme called Relative Consecutiveness Loss-aware and Misalignment-aware Virtual Network Reconfiguration (RCLM-VNR) that minimizes relative consecutiveness loss and maximizes alignment with adjacent links when reconfiguring the virtual network. Simulation results show that ACT-VNE and RCLM-VNR yield a lower blocking probability and a higher link utilization ratio, which leads to better utilization of the physical resources and increased revenue.

Virtual network mapping for multicast services with max-min fairness of reliability

Network function virtualization (NFV) provides an effective way to reduce the network providers cost by allowing multiple virtual networks (VNs) to share the underlying physical infrastructure. In the NFV environment, especially when supporting multicast services over the VNs, reliability is a critical requirement since the failure of one virtual node can cause the malfunction of multiple nodes that receive multicasting data from it. In this paper, we study for the first time to the best of our knowledge how to efficiently map VNs for multicast services over both general IP networks and orthogonal frequency division multiplexing (OFDM)-based elastic optical networks (EONs) while taking into consideration the max-min fairness in terms of reliability among distinct VNs. For general IP networks, we propose a mixed integer linear programming (MILP) model to determine the upper bound on the reliability with max-min fairness. In addition, an efficient heuristic, namely a reliability-aware genetic (RAG) algorithm, is developed to address reliable multicast VN mapping with a low computational complexity. By encoding multicast tree construction and link mapping into the process of path selection, taking into consideration the reliability with max-min fairness, and the networking reliability factors during mutation, RAG can globally optimize the reliability and fairness of all the multicast VN requests. For OFDM-based EONs, we extend the MILP (RAG) to optical-MILP [(O-MILP) optical RAG (O-RAG)] by considering the most efficient modulation format selection strategy, spectrum continuity, and conflict constraints. Through extensive simulations, we demonstrate that RAG (O-RAG) achieves close to the optimal reliability fairness with a much lower time complexity than the MILP (O-MILP) model. In particular, the path reliability-based mutation strategy in RAG (O-RAG) yields a significant performance improvement over other heuristic solutions in terms of reliability fairness, bandwidth (spectrum) consumption, and transmission delay.

Multicast service-oriented Virtual Network mapping over Elastic Optical Networks

Network Function Virtualization (NFV) allows multiple Virtual Networks (VNs) to share the underlying physical infrastructure via VN mapping, thus improving the utilization of physical resources. In this paper, for the first time, we study the multicast service-oriented VN mapping that can support big data applications over Elastic Optical Networks (EONs). Since the problem of minimizing the spectrum consumption in multicast service-oriented VN mapping is NP-hard, we propose an efficient heuristic algorithm, called Integrated Genetic and Simulated Annealing (IGSA) algorithm to address the problem with low computational complexity. By encoding node mapping, multicast tree construction, link mapping and spectrum requirements in the same gene and auto-adjusted evolution, and utilizing simulated annealing to find the fittest multicast requests mapping order, IGSA can perform joint optimization for all the multicast requests in a global way. Through extensive simulations, we demonstrate that IGSA outperforms the other heuristic solutions in terms of spectrum consumption, blocking probability and normalized throughput, while achieving close to minimum spectrum consumption with a much lower time complexity than MILP.

Survivable virtual infrastructure mapping over Transport Software-Defined Networks (T-SDN)

An algorithm is proposed to map virtual infrastructures with survivability over T-SDN for the first time. The algorithm improves the traffic-carrying capacity of networks by provisioning at least 13% more demands than the baseline algorithms.

A predictive and incremental grooming scheme for time-varying traffic in WDM networks

Traffic grooming can effectively utilize the transmission capacity of WDM networks by properly multiplexing low-speed traffic flows onto high-capacity wavelength channels. In order to maximize the wavelength resource and cut down network costs associated with, e.g. OEO conversion for time-varying yet predictable traffic, we propose a novel predictive and incremental (PI) traffic grooming scheme, named PI-grooming. A conventional traffic grooming approach for fluctuated traffic is to run an algorithm that (re)assigns the traffic flows to as a few wavelengths as possible based only on the current traffic demands of these flows. This however will lead to a lot of OEO traffic. The proposed PI-grooming considers the existing flow assignment, the current traffic demands, and the expected traffic demands in the near future. We show that, compared with the conventional approach, PI-grooming can effectively minimize the amount of OEO traffic while still using a very small number of wavelengths.

Spectrum allocation in spectrum-sliced elastic optical path networks using traffic prediction

Spectrum-sliced elastic optical path (SLICE) networks distribute data on a number of sub-carriers overlapped in frequency domain to provide efficient sub-wavelength and super-wavelength traffic accommodation. In SLICE networks, a routing and spectrum allocation algorithm assigns a spectrum path (SP) to any demand with just enough contiguous sub-carriers while following the spectrum continuity and the sub-carrier consecutiveness constraints. In this paper, we propose efficient sub-carrier allocation algorithms to assign sub-carriers to SPs whose spectrum demands could fluctuate with time. An integer linear programming model is developed to minimize the network reconfiguration and spectrum usage. Based on the historic traffic profile, an interference graph technique is proposed to facilitate the sub-carrier assignment. Simulation results show that the proposed schemes can effectively accommodate the dynamic time-varying traffic while minimizing the network reconfiguration cost in SLICE networks.