Core Packet Research Articles

Adhesion molecule Amigo2 is involved in the fasciculation process of the fasciculus retroflexus.

The fasciculus retroflexus is the prominent efferent pathway from the habenular complex. Medial habenular axons form a core packet whereas lateral habenular axons course in a surrounding shell. Both groups of fibers share the same initial pathway but differ in the final segment of the tract, supposedly regulated by surface molecules. The gene Amigo2 codes for a membrane adhesion molecule with an immunoglobulin-like domain 2 and is selectively expressed in the medial habenula. We present it as a candidate for controlling the fasciculation behavior of medial habenula axons. First, we studied the development of the habenular efferents in an Amigo2 lack of function mouse model. The fasciculus retroflexus showed a variable defasciculation phenotype. Gain of function experiments allowed us to generate a more condensed tract and rescued the Amigo2 knock-out phenotype. Changes in Amigo2 function did not alter the course of habenular fibers. We have demonstrated that Amigo2 plays a subtle role in the fasciculation of the fasciculus retroflexus.

A Novel Approach for the Modeling of Electromagnetic Forces in Air-Gap Shunt Reactors

Shunt reactors are usually used in electrical systems to imbibe reactive powers created by capacitive powers on the lines when the system is operating on low or no loads. Moreover, they are also used to balance reactive powers and maintain the stability of a specified voltage. In general, the air gaps of a magnetic circuit shunt reactor are arranged along the iron core to reduce the influence of fringing and leakage fluxes. Therefore, non-magnetic materials made of ceramics or marbles are often used in air gaps to separate the iron core packets. The direction of the fringing flux is perpendicular to the laminations, so the core packets of the shunt reactor are generally made from radially laminated silicon steels. Due to the alternating electromagnetic field through the core, a periodically altered electromagnetic force is produced between the core packets, tending to compress the ceramic spacers. This electromagnetic force causes vibration and noise in the core. In this research, a finite element approach based on the Maxwell stress tensor was developed to compute the magnetic flux density and the electromagnetic forces appearing in a shunt reactor.

Dynamic Core Allocation and Packet Scheduling in Multicore Network Processors

With ever increasing network traffic rates, multicore architectures for network processors have successfully provided performance improvements through high parallelism. However, naively allocating the network traffic to multiple cores without considering diversified applications and flow locality results in issues such as packet reordering, load imbalance and inefficient cache usage. Consequently, these issues degrade the performance of latency sensitive network processors by dropping packets or delivering packets out of order. In this paper, we propose a packet scheduling scheme that considers the multiple dimensions of locality to improve the throughput of a network processor while minimizing out of order packets. Our scheduling policy tries to maintain packet order my maintaining the flow locality, minimizes the migration of flows from one core to another by identifying the aggressive flows, and partitions the cores among multiple services to gain instruction cache locality. Our light weight hardware implementation shows improvement of 60 percent in the number of packets dropped and 80 percent in the number of out-of-order packet deliveries over previously proposed techniques.

Technique for Differential Timing Transfer Over Packet Networks

Accurate timing transfer and recovery over packet networks (IP, Ethernet, MPLS, etc.) has become an important requirement for delivering many telecommunication services. This requirement stems from the fact that current networks are migrating from time-division multiplexing (TDM) technologies to packet based ones, and also the need to synchronize the many timing-dependent devices like TDM access devices and wireless base stations. Unlike TDM, packet networks are asynchronous by design and do not have embedded timing transfer capabilities. Differential clocking is used when there is a network interface with its own reference source clock (the service clock) and there is the need to transfer this clock over a core packet network (with its own independent reference network clock) to another interface. The network clock serves as a sampling clock for the service clock. Timing transfer and recovery over a packet network is a networked control problem given the difficulty in making the recovered clock at the remote location compliant with strict telecom standards. In this paper, we describe the architecture, servo algorithm, and phase-locked loop (PLL) of a method for implementing differential clock recovery over packet networks. The technique involves a clock source or transmitter sending counter values to a receiver from a counter that is clocked and reset, respectively, by the service clock and network clock. It is general enough to be applied in a wide variety of packet networks such IP, MPLS, Ethernet, etc.

High Performance Ethernet Packet Processor Core for Next Generation Networks

As the demand for high speed Internet significantly increasing to meet the requirement of large data transfers, real-time communication and High Definition ( HD) multimedia transfer over IP, the IP based network products architecture must evolve and change. Application specific processors require high performance, low power and high degree of programmability is the limitation in many general processor based applications. This paper describes the design of Ethernet packet processor for system-on-chip (SoC) which performs all core packet processing functions, including segmentation and reassembly, packetization classification, route and queue management which will speedup switching/routing performance making it more suitable for Next Generation Networks (NGN). Ethernet packet processor design can be configured for use with multiple projects targeted to a FPGA device the system is designed to support 1/10/20/40/100 Gigabit links with a speed and performance advantage. VHDL has been used to implement and simulated the required functions in FPGA.

TCAM-based NFA implementation

Regular expression matching as the core packet inspection engine of network systems has long been striving to be both fast in matching speed (like DFA) and scalable in storage space (like NFA). Recently, ternary content addressable memory (TCAM) has been investigated as a promising way out, by implementing DFA using TCAM for regular express matching. In this paper, we present the first method for implementing NFA using TCAM. Through proper TCAM encoding, our method matches each input byte with one single TCAM lookup --- operating at precisely the same speed as DFA, while using a number of TCAM entries that can be close to NFA size. These properties make our method an important step along a new path --- TCAM-based NFA implementation --- towards the long-standing goal of fast and scalable regular expression matching.

In‐plane eddy current analysis for end and interior stator core packets of turbine generators

PurposeThe purpose of this paper is to investigate the distribution of in‐plane eddy currents in stator core packets of turbine generators, and to reveal the loss reduction effect by the slits in the stator teeth.Design/methodology/approachThe in‐plane eddy currents are calculated by a 3D finite element method that considers lamination of electrical steel sheets. First, this method is applied to a simple model that simulates the stator core of the turbine generators. The calculated losses are compared with the measured losses in order to confirm the validity. Next, the same method is applied to a 250 MVA class turbine generator.FindingsThe validity of the calculation method is confirmed by the measurement of the simple model. By applying this method to the turbine generator, it is clarified that the considerable in‐plane eddy currents are generated not only at the end stator packets, but also at the top of the teeth of the interior packets due to the duct space. It is also clarified that the in‐plane eddy‐current loss decreases as nearly half by the slits of the stator teeth.Originality/valueA reliable calculation method for the in‐plane eddy‐current loss in the turbine generators is developed. The results obtained by this method are valuable for the design of the generator from the viewpoint of heat conduction.

Thermal overload tests on a 400-MVA power transformer with a special 2.5-p.u. Short time loading capability

Comprehensive load /thermal testing was performed on a 400/400/125-MVA transformer representing a new design generation for large power transformers with a short time emergency loadability of 2.5 p.u. This particular overloadability factor required special design features to control the very high leakage flux resulting from such a loading condition and hence ensure that the transformer satisfies existing standards limits on hot-spot. This paper presents these design features along with a description of a full-size transformer which was built for the sake of developing these flux control measures. Hot-spot temperature measurements in the windings and in the outer core packets and structural parts under a number of overloading conditions are presented and discussed. The results confirm the soundness of the design to handle the 2.5-p.u. overloadability while satisfying the hot-spot requirement according to the existing loading guides for 1.5-p.u. overloading. The measurements also show that the hot-spots will rise much faster than what an exponential function based on the time constant of top oil would predict.

End-to-end adaptive QoS provisioning over GPRS wireless mobile network

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users over wireless frequency-division duplex links with time division multiple access, and core packet data networks. This paper presents a dynamic adaptive guaranteed Quality-of-Service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain GPRS QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic with peak bandwidth allocation adapted to the current queue length. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests with higher admission priorities over new calls via a dynamic multiple guard channels scheme, which dynamically adapts the capacity reserved for dealing with handoff requests based on the current traffic conditions in the neighboring radio cells. Integrated services (IntServ) QoS provisioning over the IP/ATM-based GPRS core network is realized over a multi-protocol label switching (MPLS) architecture, and mobility is supported over the core network via a novel mobile label-switching tree (MLST) architecture. End-to-end QoS provisioning over the GPRS wireless mobile network is realized by mapping between the IntServ and GPRS QoS requirements, and by extending the AP-CAC protocol from the wireless medium to the core network to provide a unified end-to-end admission control with dynamic adaptive admission priorities.

Thermal Overload Tests on a 400 MVA Power Transformer with a Special 2.5 P.U. Short-Time Loading Capability

Comprehensie load/ thermal testing was performed on a 400/400/125 MVA transformer representing a new design generation for large power transformers with a short time emergency loadability of 2.5 p.u. This particular overloadability factor required special design features to control the very high leakage flux resulting from such a loading condition and hence ensure that the transformer satisfies existing standards limits on hot spot. This paper presents these design features along with a description of a full size transformer that was built for the sake of developing these flux control measures. Hot-spot temperature measurements in the windings and in the outer core packets and structural parts under a number of overloading conditions are presented and discussed. The results confirm the soundness of the design to handle the 2.5 p.u. overloadability while satisfying the hot-spot requirement according to the existing loading guides for 1.5 p.u. overloading. The measurements also show that the hot spots will rise much faster than what an exponential function based on the time constant of top oil would predict.