A surgical cutting and fastening instrument. The instrument comprises an end effector and a shaft connected to the end effector. The shaft comprises a drive train for powering the end effector. The instrument also comprises an electric, DC motor connected to the drive train for powering the drive train. The instrument also comprises a torque-limiting device connected between to an output pole of the motor and an input pole of the drive train.

Motorized surgical cutting and fastening instrument having a magnetic drive train torque limiting device

To support bursty traffic on the Internet (and especially WWW) efficiently, optical burst switching (OBS) is proposed as a way to streamline both protocols and hardware in building the future gener...

Optical burst switching (OBS) - a new paradigm for an optical Internet

In this paper we review studies of the growth of the Internet and technologies that are useful for information search and retrieval on the Web. We present data on the Internet from several different sources, e.g., current as well as projected number of users, hosts, and Web sites. Although numerical figures vary, overall trends cited by the sources are consistent and point to exponential growth in the past and in the coming decade. Hence it is not surprising that about 85% of Internet users surveyed claim using search engines and search services to find specific information. The same surveys show, however, that users are not satisfied with the performance of the current generation of search engines; the slow retrieval speed, communication delays, and poor quality of retrieved results (e.g., noise and broken links) are commonly cited problems. We discuss the development of new techniques targeted to resolve some of the problems associated with Web-based information retrieval and speculate on future trends.

Information retrieval on the web

The switching speeds of electronics cannot keep up with the transmission capacity offered by optics. All-optical switch fabrics play a central role in the effort to migrate the switching functions to the optical layer. Optical packet switching provides an almost arbitrary fine granularity but faces significant challenges in the processing and buffering of bits at high speeds. Generalized multiprotocol label switching seeks to eliminate the asynchronous transfer mode and synchronous optical network layers, thus implementing Internet protocol over wavelength-division multiplexing. Optical burst switching attempts to minimize the need for processing and buffering by aggregating flows of data packets into bursts. In this paper, we present an extensive overview of the current technologies and techniques concerning optical switching.

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Optical switching: switch fabrics, techniques, and architectures

Flexgrid technology is now considered to be a promising solution for future high-speed network design. In this context, we need a tutorial that covers the key aspects of elastic optical networks. This tutorial paper starts with a brief introduction of the elastic optical network and its unique characteristics. The paper then moves to the architecture of the elastic optical network and its operation principle. To complete the discussion of network architecture, this paper focuses on the different node architectures, and compares their performance in terms of scalability and flexibility. Thereafter, this paper reviews and classifies routing and spectrum allocation (RSA) approaches including their pros and cons. Furthermore, various aspects, namely, fragmentation, modulation, quality-of-transmission, traffic grooming, survivability, energy saving, and networking cost related to RSA, are presented. Finally, the paper explores the experimental demonstrations that have tested the functionality of the elastic optical network, and follows that with the research challenges and open issues posed by flexible networks.

Routing and Spectrum Allocation in Elastic Optical Networks: A Tutorial

A new extended signaling and traffic engineering method for the GMPLS-based photonic and electrical multilayer router (Hikari router) is proposed. The method allows dynamic optical network management and photonic signal recovery, such as regeneration, reshaping, etc., to be realized adaptively. Wavelength conversion is also adaptive, which reduces network cost. Multilayer traffic engineering, which yields the dynamic cooperation of IP and photonic layers, is described to provide IP services cost effectively. To realize multilayer traffic engineering, we propose the OSPF extension, which advertises both the number of total wavelengths and the number of unused wavelengths, and the RSVP-TE extension, which minimizes the number of wavelength conversions needed. In addition, this paper proposes a heuristics-based multilayer topology design scheme that uses IP traffic measurements in a generalized multi-protocol label switch (GMPLS). The proposed scheme yields the optical label switch path (OLSP) network topology, that is, OLSP placement, that minimizes network cost, in response to fluctuations in IP traffic demand. In other words, the OLSP network topology is dynamically reconfigured to match IP traffic demand. Networks are reconfigured by the proposed scheme so as to utilize network resources in the most cost effective manner.

GMPLS-based photonic multilayer router (Hikari router) architecture: an overview of traffic engineering and signaling technology

This article presents two dynamic multilayer routing policies implemented in the photonic MPLS router developed by NTT for IP+optical generalized MPLS networks. According to IP traffic requests, wavelength paths called lambda label switched paths are set up and released in a distributed manner based on GMPLS routing and signaling protocols. Both dynamic routing policies first try to allocate a newly requested electrical path to an existing optical path that directly connects the source and destination nodes. If such a path is not available, the two policies employ different procedures. Policy 1 tries to find available existing optical paths with two or more hops that connect the source and destination nodes. Policy 2 tries to establish a new one-hop optical path between source and destination nodes. The performances of the two routing policies are evaluated. Simulation results suggest that policy 2 outperforms policy 1 if p is large, where p is the number of packet-switching-capable ports; the reverse is true only if p is small. We observe that p is the key factor in choosing the most appropriate routing policy. We also describe items that need to be standardized in the IETF to effectively achieve multilayer traffic engineering.

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Dynamic multilayer routing schemes in GMPLS-based IP+optical networks

The rapid development of Asynchronous Transfer Mode technology in the last 10-15 years has stimulated renewed interest in the design and analysis of switching systems, leading to new ideas for system designs and new insights into the performance and evaluation of such systems. As ATM moves closer to realizing the vision of ubiquitous broadband ISDN services, the design of switching systems takes on growing importance. This paper seeks to clarify the key architectural issues for ATM switching system design and provides a survey of the current state-of-the-art.

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Architectural choices in large scale ATM switches

This letter proposes a disjoint path selection scheme for generalized multi-protocol label switching (GMPLS) networks with shared risk link group (SRLG) constraints. It is called the weighted-SRLG (WSRLG) scheme. It treats the number of SRLG members related to a link as part of the link cost when the k-shortest path algorithm is executed. In WSRLG, a link that has many SRLG members is rarely selected as the shortest path. Simulation results show that WSRLG finds more disjoint paths than the conventional k-shortest path algorithm.

A disjoint path selection scheme with shared risk link groups in GMPLS networks

When bandwidth in an ATM network is controlled so as to increase in accordance with a user request, there is a considerable delay from the occurrence of the request until the bandwidth is actually changed; and there is therefore a need to control the traffic flowing in ATM network transmission paths faster and more flexibly. There is also a need to decrease the probability of overbooking occurring when deciding whether or not to accept a bandwidth change request. Route information that includes information relating to residual bandwidth is therefore collected in advance by subscriber switches that serve terminals. In response to a request from a user, a subscriber switch alone replies rapidly. During this process, the fact that there are a plurality of bandwidth change requests within the same residual bandwidth measurement period, is considered and a portion of the measured residual bandwidth is held for other bandwidth change requests. This enables the delay to be shortened. In addition, it is sufficient if the functions corresponding to the plurality of protocols employed by users are provided at and only at the subscriber switches which directly serve those users, whereby the hardware configuration of the transit switches etc. can be simplified. In addition, bandwidth can be allocated with high precision.

Naoaki Yamanaka

Papers

GMPLS-based photonic multilayer router (Hikari router) architecture: an overview of traffic engineering and signaling technology

Dynamic multilayer routing schemes in GMPLS-based IP+optical networks

Architectural choices in large scale ATM switches

A disjoint path selection scheme with shared risk link groups in GMPLS networks

Variable-bandwidth network