Satellite optical networks combined with multi-beam technologies can be referred to as multi-beam satellite optical networks (MB-SONs). These networks are expected to play a crucial role in satellite Internet, potentially achieving Gigabit/s inter-satellite (IS) communication in the future. However, the growing demand for the satellite-to-mobile communications bring a challenge for making use of hybrid IS and satellite-to-ground (SG) transmission resources, which is worthy of studying. Given the different characteristics of IS links and SG links in terms of time windows and transmission capacities, existing solutions can hardly provide a suitable option for the optimal utilization of transmission capacity in MB-SONs. In this paper, we focus on the joint scheduling of optical wavelengths in IS and multiple beams in SG for the services sent from one ground station to the other ground station (which are referred to as end-to-end services). In response to the above-mentioned different characteristics of IS and SG links, we find that at least two constraints need to be followed in the joint scheduling. Also, the length of common time window will not exceed the minimum time window of IS and SG links on the path. The second one is that the volume of transmission capacity of a path depends on the length of CTW and the minimum bandwidth of IS and SG links, which should meet the service requirements. Considering these two constraints related to the length of CTW and the volume of transmission capacity, the main contributions of this paper can be concluded: i) defining the joint time slot allocation (JTSA) problem for multiple beams and wavelengths with different transmission capacities, ii) proposing an integer linear programming (ILP) model with object to minimize the number of time slots occupied by services, iii) designing the common time window for time slot assignment (CTW-TSA) algorithm as an option in practical implementations. The proposed ILP and CTW-TSA algorithm are evaluated by comparing the simulation results with the scheme using. The simulation of the CTW-TSA algorithm was compared to separate resource scheduling (SRS) without the store-and-forward function. The results showed a reduction of almost 0.201 in service blocking probability and an increase in average bandwidth utilization of about 0.159 for IS links and 0.164 for SG uplinks/downlinks.

We propose a novel high performance computing (HPC) network architecture$\mathrm {HFOS}_{L}$based on$L$parallel levels distributed low radix fast optical switches (FOS). We provide a detailed description of the blade, FOS and the operation of the$\mathrm {HFOS}_{L}$network. The$\mathrm {HFOS}_{L}$HPC network is highly scalable, and HFOS4 architecture can support an extremely large HPC network of 65,536 blades under distributed FOS with the same radix of 16 in each level. In principle, the$\mathrm {HFOS}_{L}$HPC network can be built by FOSes with different radices at each level. To find out the best configuration of FOS at each level and solve the energy and cost optimization problem in$\mathrm {HFOS}_{L}$network, we break down all the components in the FOS and develop the energy and cost models for the FOS. We verify that the energy and cost per radix functions of FOS are convex functions. Given this foundation, the theoretical investigation of the energy and cost optimization problem shows that the$\mathrm {HFOS}_{L}$network could achieve the minimum energy and cost only when the FOS radices of all levels in$\mathrm {HFOS}_{L}$network are the same. Besides, the cost and power consumption of$\mathrm {HFOS}_{L}$networks are compared with a widely used Leaf-Spine network.

In elastic optical inter-datacenter networks, multiple software-defined networking (SDN) controllers have been used to improve scalability and reliability. The static controller deployment faces the problem of controller load imbalance under dynamic changes in network traffic. In response to this problem, existing research works proposed to use dynamic switch migration to achieve the controller load balancing. However, the efficiency of the existing switch migration is low, because the load balancing performance of controllers does not improve significantly after the switch migration and the migration activities can also cause additional migration costs. Thus the efficiency of switch migration has not yet been well resolved. In this work, we propose a highly-efficient switch migration (HESM) for controller load balancing. The proposed HESM method defines multiple load metrics to measure the load of controllers, and selects the optimal target controller with the largest remaining resource, which improves the load balancing performance. HESM selects switches based on minimizing migration costs, reducing additional migration costs. In addition, HESM can handle the load of multiple controllers in parallel during a switch migration activity, which improves the efficiency of migration. The simulation results show that HESM significantly improves load balancing performance of controllers and reduces the migration cost compared to existing solutions.

Software defined networking (SDN) can bring considerable flexibility to the management of inter-DC elastic optical networks. However, in the large-scale network, unreasonable placement of multiple SDN controllers may cause the unbalanced distribution of controller loads. To address this issue, we propose a two-sided matching method (TSMM) and design its corresponding algorithm to implement the optimal multi-controller placement. We solve the controller placement problem as the two-sided matching problem and consider optimizing multiple metrics which affect the controller placement. Different from previous research ideas, TSMM implements placement choice from the bilateral perspective of switch and controller. Additionally, TSMM algorithm can achieve the optimal controller placement by maximizing mutual satisfaction between controller and switch. The simulation results show that TSMM can achieve the optimal multi-controller placement and the balanced distribution of controller loads when compared with the existing schemes.