Qihan Zhang

Failure recovery solutions using cognitive mechanisms based on software-defined optical network platform

Abstract. Fault tolerance is one of the most desirable properties in the optical network since a large amount of data will be lost if the failure recovery cannot be well achieved. The software-defined network is an innovative paradigm—which decouples the control module from the underlying data forwarding plane—to make fast decisions on detecting and restoring link failures. Therefore, we focus on failure recovery solutions based on software-defined optical networks. The out-of-band control mechanism is utilized for the communication between the controller and the data forwarding elements. We demonstrate the performance of the proposed solutions—including a failure detection scheme, a dynamic all pairs shortest paths algorithm, and a failure recovery application—based on our software-defined optical network platform. Experimental demonstration and numerical evaluation both show its overall feasibility and efficiency.

Experimental demonstration of an intelligent control plane with proactive spectrum defragmentation in SD-EONs

The cooperation of software-defined networking and flexible grid optical transport technology allows operators to elastically control the network using software running on a network operating system within a centralized way. However, existing approaches dealing with spectrum fragmentation are mostly the reactive strategy, which reconfigures network resources to overcome spectrum fragmentation when the controller detects the fragmentation. In this paper, we focus on how to improve the control plane intelligence of software-defined elastic optical networks (SD-EONs) by using a proactive strategy. More specifically, we design a novel routing, modulation level and spectrum allocation algorithm (RMLSA) based on spectral efficiency and connectivity (SEC) i.e., SEC-RMLSA, in order to improve the utilization efficiency of network resources. Meanwhile, we develop a routing application and an extended OpenFlow protocol to achieve a seamless operation between the controller and the optical data plane. Moreover, all the proposed methodologies are implemented and demonstrated in an SD-EON testbed that has both OpenFlow-based control plane and data plane. Finally, the proposed framework, experimental demonstration, and numerical evaluation are reported for different optical flows. The results show the systems overall feasibility and efficiency.

Optical-wireless hybrid virtual network embedding based on location recommendations

Location data reflects user preferences and even interdependency among users. Owing to this interdependency, the advertiser can push the corresponding products to users through location recommendations, i.e., advertisement targeting. To maximize the profitability of advertisement targeting, a novel design framework of optical-wireless hybrid virtual network embedding is proposed by us. This framework determines the interdependency (similar recommended Point of Interest (POI) trajectories) among user groups so that we can embed virtual networks of user groups with a high interdependency into the same part of the substrate optical-wireless hybrid infrastructure. The simulation results show that our framework has the higher profitability of advertisement targeting compared to the benchmark and has an effective bound analysis.

Joint resource allocation and software- based reconfiguration for energy- efficient OFDMA-PONs

The widely deployed passive optical network (PON) is a cost-effective way to create a front/backhaul carrier for ubiquitous wireless access connectivity. To hide the difference of frame formats and multiplexing methods, an orthogonal frequency division multiplexing access PON (OFDMA-PON) was proposed. In upstream transmission, multiple optical network units (ONUs) from the same segment or residential area can transmit data through a shared group of orthogonal low-bitrate subcarriers (SCs) during different time slots (TSs) within the entire transmitting period. In downstream transmission, the optical line terminal can send control signaling of reconfiguring ONUs’ parameters so that SCs can be reallocated among segments, thus sleeping segments with empty data load while ensuring service continuity. Though energy savings can be ensured for upstream data transmission by using existing solutions, only frequency and time domains are involved. It is meaningful for us to make the flexible and energy- efficient configuration of transmitting power and modulation level assigned for ONUs in terms of improving energy efficiency. In this paper, we investigate joint resource allocation for energy-efficient upstream data transmission in OFDMA-PONs, with the help of software-based ONU reconfiguration. We formulate the problem, and the upper bound of energy saving is also derived. To solve the problem in a short span of time, we propose a novel heuristic algorithm whose effectiveness has been demonstrated by extensive simulations.

Joint Optimization of Latency Monitoring and Traffic Scheduling in Software Defined Heterogeneous Networks

Since the current Internet is only able to provide best-effort services, the quality of service (QoS) for many emerging businesses cannot be well guaranteed. Meanwhile, due to the privatization of networks management, multi-vendor heterogeneous networks are difficult to provide end-to-end QoS assurance on demand. Therefore, heterogeneous devices from different vendors also bring new challenges to the flexible control of network equipment. Software defined network (SDN) is an emerging paradigm which separates the network’s control logic from the underlying routers and switches. In this paper, we design a monitoring loop of link latency by using both LLDP and Echo probing modules. Then, a dynamic routing algorithm is proposed to select optimized transmission path based on the information of link latency. In addition, we develop a routing application assorted with the monitoring mechanism by extending the RYU controller. We implement our solution in a semi-practical SDN testbed. Finally, the overall feasibility and efficiency of the proposed solution are experimentally verified and evaluated.

Software-Reconfigurable System Supporting Point-to-Point Data Communication Between Vehicle Social Networks and Marketers

Social users can be flexibly covered by a vehicle traveling along a certain trajectory in a city. This scenario provides opportunities for marketers to utilize vehicles as recommenders targeting potential customers. As a result, the vehicle social network (VSN) concept emerges. Since a marketer usually operates from a remote central office (CO), an effective communication system is urgently required to support data transmission between VSNs and COs. Orthogonal frequency division multiplexing (OFDM) is a modulation technique characterized by high spectral efficiency and dispersion resistance, and intensity modulation and direct detection (IM/DD) is an effective solution for optical OFDM (OOFDM) data transmission. Performing discrete Fourier transform (DFT) and discrete Hartley transform (DHT) operations can enable the satisfaction of various transmission requirements between a VSN and a CO. In this paper, we support the above claims through theoretical and simulation-based analyses. Moreover, a software-reconfigurable platform is established to achieve flexibility between DFT and DHT functionalities. Thus, diverse transmission requirements can be satisfied by modifying individual modules deployed in a single smart system instead of using multiple rigid network architectures. Simulated and experimental results both demonstrate the feasibility and effectiveness of our solutions.

Maintenance and bandwidth scheduling for cloud rendering in optical data center networks

Animation rendering aims to transform a digital design into a vivid cartoon. To achieve a high-quality animation in the short term, the cloud rendering was presented through consolidating Data Center (DC) resources. Since DCs are far away from each other due to the space limitation, the cloud rendering will run over the Optical Data Center Network (ODCN) where DCs are interconnected by high-speed optical links. This high-speed interconnection well supports the fast data migration for the DC maintenance, which is a preventive measure for safeguarding the uptime of cloud rendering. In this paper, to achieve the least batch maintenance scheduling, multiple DCs are maintained simultaneously through one batch, which makes Rendering Processes (RPs) migrated among DCs via high-speed optical links, and brings the extra costs such as the link-bandwidth consumption. Thus, after performing the least batch maintenance using the heuristic, we determine the bandwidth provisioning for the optical links along a migration trajectory. Simulation results demonstrate the effectiveness of our method.