RESEARCH TOPICS

My research topic is related to network virtualization on optical networks.
To deal with short-term changes in network environments (e.g., traffic fluctuations), I am investigating virtual network reconfiguration frameworks with a smaller amount of information.
My approaches are particularly inspired by behavior of living organisms or human's recognition.

Virtual Network Reconfiguration based on Attractor Selection Model

Given the limited number of resources (i.e., frequency slots and transponders at optical switches) in elastic optical networks, one approach to accommodating traffic demand is for the network operator to offer a certain number of leased lightpaths in response to requests from service providers, while configuring a virtual network (VN) that accommodates the traffic demand of other consumers. It is essential to reconfigure the VN according to changes in traffic while setting aside resources for leased lightpaths and accommodating increased traffic demand on the VN. Our research group has proposed a VN reconfiguration method for traditional wavelength division multiplexing networks based on attractor selection, which is a model of the behavior by which living organisms adapt to unknown changes in their surrounding environment. However, simply adopting this method cannot make the best use of elastic optical networks since it assigns all wavelengths to accommodate current traffic demand, which leads to a lack of resources for accommodating future traffic demand. We therefore propose a method for reconfiguring a VN over an elastic optical network. To set aside resources for future traffic demand, we newly define the potential bandwidth as a metric that reflects the bandwidth that can be additionally offered. Our method reconfigures a VN based on attractor selection using information about the service quality on the VN and the potential bandwidth, and also adjusts the bandwidth of all lightpaths that form the VN. Evaluation results show that our method can reconfigure a VN so that the service quality on the VN is improved while keeping some resources unused.
‹Related Paper›
  • Toshihiko Ohba, Shin'ichi Arakawa, and Masayuki Murata, "Virtual network reconfiguration in elastic optical path networks for future bandwidth allocation," IEEE/OSA Journal of Optical Communications and Networking, vol. 8, issue 9, pp. 633-644, Sept. 2016.

Network Virtualizatio on Optical Network
VN Reconfiguration by Attractor Selection

Hierarchical Design of Attractors in VN Reconfiguation based on Attractor Selection

Guided by attractors, our VN reconfiguration method searches for a solution: a VN that can accommodate traffic. Attractors are a subset of the equilibrium points in the solution space and correspond to VN candidates. It is crucial to design the attractors properly since they define the attractive states in the VN reconfiguration. If the VN candidates are not designed properly, it takes a long time for the method to find a solution. We therefore propose a method for designing VN candidates. Our basic approach is to prepare VN candidates in which the bottleneck links (lightpaths) are different from each other. Furthermore, we propose a method that hierarchically contracts a network topology to enable application of our algorithm to large-scale networks. Evaluation results show that the VN reconfiguration method using attractors obtained by our method achieves shorter convergence times.
‹Related Paper›
  • Toshihiko Ohba, Shin'ichi Arakawa, Yuki Koizumi, and Masayuki Murata, "Hierarchical design of an attractor structure for VNT control based on attractor selection," in Proceedings of the 12th Annual IEEE Consumer Communications and Networking Conference (CCNC 2015), pp. 330-336, Jan. 2015.
  • Toshihiko Ohba, Shin'ichi Arakawa, Yuki Koizumi, and Masayuki Murata, "Scalable design method of attractors in noise-induced virtual network topology control," IEEE/OSA Journal of Optical Communications and Networking, vol. 7, issue 9, pp. 851-863, Sept. 2015.

Approach to designing attractors

A Bayesian-based Virtual Network Reconfiguration

Coming soon...