Hideki Sakauchi

Bio: Hideki Sakauchi is an academic researcher from NEC. The author has contributed to research in topics: Node (networking) & Network packet. The author has an hindex of 4, co-authored 8 publications receiving 553 citations.

Packet-switched network having alternate virtual paths

Abstract: In a broadband ISDN system where each switching node is connected to each adjacent node by a transmission line having communication links and a service link, the switching node comprises a self-routing network for routing a cell from an input to an output of the network according to a virtual path identifier it contains. Static connections are established between communication links and the routing network by a digital cross-connect system. A virtual path memory stores data indicating link-to-link connections associated with normal virtual paths and link-to-link connections associated with alternate virtual paths. A fault detector is coupled to the communication links to detect a link failure. If a link failure occurs, a fault message is transmitted to adjacent switching nodes through service links, and data corresponding to the faulty link is retrieved from the memory in response to a fault message that is received from the fault detector or from an adjacent node. The cross-connect system is controlled in accordance with the retrieved data so that the route of the cells is switched from a normal virtual path to an alternate virtual path.

A self-healing network with an economical spare-channel assignment

Abstract: With the advent of networking technologies intelligent network elements, such as the digital cross-connect system (DCS), will make it possible to dynamically reconfigure a network for restoration purposes. Both restoration control of DCSs and spare-channel design issues are presented, and how they work together so that a fast and economical SONET self-healing network is obtained. In order to achieve fast restoration, a distributed control mechanism that is applicable to both line and path restoration is proposed. The proposed method allows the shared use of spare channels for various failure scenarios, including multiple failure cases, so that the efficient use of spare channels can be achieved. A linear-programming-based scheme is proposed to obtain spare-channel assignment, where a network-flow technique is used. Through a simulation study, a fast and economical self-healing network is verified. >

Self-healing network with distributed failure restoration capabilities

Abstract: In the event of a failure on a transmission line, a sender, or a terminal node of the failed line, broadcasts CONTROL packets to each of all adjacent tandem nodes, containing a hop count and node trace data. In response to a CONTROL packet, each tandem node increments the hop count of the packet, updates its node trace data, makes a record of all arriving CONTROL packets, and broadcasts copies of each arriving CONTROL packet to adjacent nodes if the hop count is smaller than a prescribed value. A chooser, which is the other terminal node of the failed line, responds to CONTROL packets from a given node for sending back to the given node as many RETURN packets as there are failed channels. Each tandem node makes a record of all arriving RETURN packets, checks the node trace data of each RETURN packet against that of the CONTROL packets in the record to detect if there is a spare channel to an adjacent node on a route to the sender with a least hop count, transmits each RETURN packet to it if a spare channel is detected, or causes retransmission of a RETURN packet from the chooser to another tandem node if no spare channel is detected. The sender responds to each RETURN packet by switching a link from a failed channel to a spare channel indicated by the packet. An END packet is sent back from the sender to each tandem node along which the RETURN packet travelled between the chooser to the sender. On reaching the chooser, the END packet is used to switch a link from a failed channel to a spare channel indicated by the received END packet.

Design and control issues of integrated self-healing networks in SONET

Abstract: An integrated self-healing network is discussed, where RD (route diversity), SSR (shared self-healing ring), and DSH (dynamic self-healing algorithms) together perform the whole network restoration. In order to achieve a higher degree of network survivability, a joint use of SSR and DSH techniques is one of the solutions. The authors specifically propose the shared use of protection routes between SSR and DSH, which can reduce the total amount of spare capacity. The proposed integrated self-healing can be applied to a practical SONET (synchronous optical network) environment in which a variety of network elements are placed. Various survivability requirements are given. >

Concurrent network management system using distributed processing techniques

Abstract: This paper proposes a concurrent network management system which can integrate various management applications in an efficient way. The proposed system provides both techniques and tools to attain concurrent execution of management applications in a distributed processing environment. For instance, each concurrently executed management application has its own communication module, named the virtual object, that interacts with other applications. The virtual object as a much enhanced version of the well-known RPC stub is capable of managing application connections and communicated data structures, or handling communication errors. The efficiency of integration is further enhanced through the use of a virtual object generator, which automatically generates the virtual object program codes. The effectiveness of the proposed system has been tested and confirmed in a newly developed experimental system that integrates our management applications such as network design, control, and diagnosis. >

Routing, Flow, And Capacity Design In Communication And Computer Networks

Abstract: In network design, the gap between theory and practice is woefully broad. This book narrows it, comprehensively and critically examining current network design models and methods. You will learn where mathematical modeling and algorithmic optimization have been under-utilized. At the opposite extreme, you will learn where they tend to fail to contribute to the twin goals of network efficiency and cost-savings. Most of all, you will learn precisely how to tailor theoretical models to make them as useful as possible in practice. Throughout, the authors focus on the traffic demands encountered in the real world of network design. Their generic approach, however, allows problem formulations and solutions to be applied across the board to virtually any type of backbone communication or computer network. For beginners, this book is an excellent introduction. For seasoned professionals, it provides immediate solutions and a strong foundation for further advances in the use of mathematical modeling for network design. (Less)

Survivable WDM mesh networks

Abstract: In a wavelength-division-multiplexing (WDM) optical network, the failure of network elements (e.g., fiber links and cross connects) may cause the failure of several optical channels, thereby leading to large data losses. This study examines different approaches to protect a mesh-based WDM optical network from such failures. These approaches are based on two survivability paradigms: 1) path protection/restoration and 2) link protection/restoration. The study examines the wavelength capacity requirements, and routing and wavelength assignment of primary and backup paths for path and link protection and proposes distributed protocols for path and link restoration. The study also examines the protection-switching time and the restoration time for each of these schemes, and the susceptibility of these schemes to multiple link failures. The numerical results obtained for a representative network topology with random traffic demands demonstrate that there is a tradeoff between the capacity utilization and the susceptibility to multiple link failures. We find that, on one hand, path protection provides significant capacity savings over link protection, and shared protection provides significant savings over dedicated protection; while on the other hand, path protection is more susceptible to multiple link failures than link protection, and shared protection is more susceptible to multiple link failures than dedicated protection. We formulate a model of protection-switching times for the different protection schemes based on a fully distributed control network. We propose distributed control protocols for path and link restoration. Numerical results obtained by simulating these protocols indicate that, for a representative network topology, path restoration has a better restoration efficiency than link restoration, and link restoration has a faster restoration time compared with path restoration.

Survivable WDM mesh networks. Part I-Protection

Abstract: This investigation considers optical networks which employ wavelength cross-connects that enable the establishment of wavelength-division-multiplexed (WDM) channels, between node-pairs. In such and other networks, the failure of a network element (e.g., fiber link, cross-connect, etc.) may cause the failure of several optical channels, thereby leading to large data losses. This study examines different approaches to protect mesh based WDM optical networks from single-link failures. These approaches are based on two basic survivability paradigms: (a) path protection/restoration, and (b) link protection/restoration. In path- and link-protection schemes, backup paths and wavelengths are reserved in advance at the time of call setup. Path- and link-restoration schemes are dynamic schemes in which backup paths are discovered (from the spare capacity in the network) upon the occurrence of a failure. In part 1 of this study presented in this paper, we formulated integer linear programs to determine the capacity requirements for the above protection schemes for a static traffic demand.

Redundant trees for preplanned recovery in arbitrary vertex-redundant or edge-redundant graphs

Abstract: We present a new algorithm which creates redundant trees on arbitrary node-redundant or link-redundant networks. These trees are such that any node is connected to the common root of the trees by at least one of the trees in case of node or link failure. Our scheme provides rapid preplanned recovery of communications with great flexibility in the topology design. Unlike previous algorithms, our algorithm can establish two redundant trees in the case of a node failing in the network. In the case of failure of a communications link, our algorithm provides a superset of the previously known trees.

Method and apparatus for coupling an antenna to a device

Abstract: Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.