This paper proposes fast repairing methods that uses hierarchical software defined network controllers for recovering from massive failure in a large-scale IP over a wavelength-division multiplexing network. The network consists of multiple domains, and slave controllers are deployed in each domain. While each slave controller configures transport paths in its domain, the master controller manages end-to-end paths, which are established across multiple domains. For fast repair of intra-domain paths by the slave controllers, we define the optimization problem of path configuration order and propose a heuristic method, which minimizes the repair time to move from a disrupted state to a suboptimal state. For fast repair of end-to-end path through multiple domains, we also propose a network abstraction method, which efficiently manages the entire network. Evaluation results suggest that fast repair within a few minutes can be achieved by applying the proposed methods to the repairing scenario, where multiple links and nodes fail, in a 10,000-node network.

Multi-tenant datacenter networking, with which multiple customer networks (tenants) are virtualized and consolidated in a single shared physical infrastructure, has recently become a promising approach to reduce device cost, thanks to advances of virtualization technologies for various networking devices (e.g., switches, firewalls, load balancers). Since network devices are configured with low-level commands (no context of tenants), network engineers need to manually manage the context of tenants in different stores such as spreadsheet and/or configuration management database (CMDB). The use of CMDB is also effective in increasing the ‘visibility’ of tenant configurations (e.g., information sharing among various teams); However, different from the ideal use, only limited portion of network configuration are stored in CMDB in order to reduce the amount of ‘double configuration management’ between device settings (running information) and CMDB (stored information). In this present work, we aim to bridge the gap between CDMB and device status. Our basic approach is to automatically analyze per-device configuration settings to recover per-tenant network-wide configuration (running information) based on a graph-traversal technique applied over abstracted graph representation of device settings (to handle various types of vendor-specific devices); The recovered running information of per-tenant network configurations is automatically uploaded to CMDB. An implementation of this methodology is applied to a datacenter environment that management of about 100 tenants involves approximately 5,000 CMDB records, and our practical experiences are that this methodology enables to double the amount of CMDB records. We also discuss possible use cases enabled with this methodology.

Clustering technology is very important in ad hoc networks and sensor networks from the view point of reducing the traffic load and energy consumption. In this paper, we propose a new structure formation mechanism as a tool for clustering. It meets the key clustering requirements including the use of an autonomous decentralized algorithm and a consideration of the situation of individual nodes. The proposed mechanism follows the framework of autonomous decentralized control based on local interaction, in which the behavior of the whole system is indirectly controlled by appropriately designing the autonomous actions of the subsystems. As an application example, we demonstrate autonomous decentralized clustering for a two-dimensional lattice network model, and the characteristics and adaptability of the proposed method are shown. In particular, the clusters produced can reflect the environmental situation of each node given by the initial condition.

We consider the problem of designing a physically diverse network that can support any two simultaneous node-to-node traffic flow requirements as called for by special events such as communication link failures or surges in network traffic. The design objective is to obtain a network with the minimum level of network capacity, yet robust enough to handle any two simultaneous traffic flow requirements between any nodes. To arrive at the minimum necessary network capacity,we introduce the concept of nodal requirement. Based on nodal requirements, we can build what may be called uniform protection subnetworks for equal nodal requirements. Successive uniform protection subnetworks can be built for incremental nodal requirements. This direct approach supersedes the extant work on building fully connected networks or loops from maximum spanning trees that can cope with only one traffic flow requirement. Our nodal requirements approach generalizes well to multiple simultaneous traffic flow requirements. Hub subnetworks are introduced to provide protection for networks with a unique node that has the largest nodal requirement. Further, a heuristic is considered and analyzed that assigns edge capacities of the protection network directly based on the largest two traffic flow requirements incident on the end nodes of an edge. The heuristic is attractive in being simple to implement.

The Asynchronous Transfer Mode (ATM) is expected to be the basic transmission technology for B-ISDN. Before this happens, however, it will be necessary to predict the impact of fully-deployed ATM-based networks quantitatively. This paper compares the cost-efficiency of an ATM-based network with that of an STM-based network and clarifies the applicable areas of ATM network configurations, in terms of required facilities and considering the effect of statistical multiplexing. It shows cost-effective network configurations based on different service classes and a network configuration suited to ATM. It also discusses the effect of a Synchronous Digital Hierarchy architecture for Virtual Path dimensioning.