Application Layer Packet Processing Using PISA Switches

This paper investigates and proposes a solution for Protocol Independent Switch Architecture (PISA) to process application layer data, enabling the inspection of application content. PISA is a novel approach in networking where the switch does not run any embedded binary code but rather an interpreted code written in a domain-specific language. The main motivation behind this approach is that telecommunication operators do not want to be locked in by a vendor for any type of networking equipment, develop their own networking code in a hardware environment that is not governed by a single equipment manufacturer. This approach also eases the modeling of equipment in a simulation environment as all of the components of a hardware switch run the same compatible code in a software modeled switch. The novel techniques in this paper exploit the main functions of a programmable switch and combine the streaming data processor to create the desired effect from a telecommunication operator perspective to lower the costs and govern the network in a comprehensive manner. The results indicate that the proposed solution using PISA switches enables application visibility in an outstanding performance. This ability helps the operators to remove a fundamental gap between flexibility and scalability by making the best use of limited compute resources in application identification and the response to them. The experimental study indicates that, without any optimization, the proposed solution increases the performance of application identification systems 5.5 to 47.0 times. This study promises that DPI, NGFW (Next-Generation Firewall), and such application layer systems which have quite high costs per unit traffic volume and could not scale to a Tbps level, can be combined with PISA to overcome the cost and scalability issues.

The method for constructing fault-tolerant photonic switches for high-performance computing systems

In this paper the new type of fault-tolerant non-blocking photonic switch is presented for the first time. The proposed switch architecture is based on quasi-complete graph topology which use provides non-blocking and fault-tolerant switching process. The new two-stage switch architecture uses the stage of dual photonic switches and pairs of photonic demultiplexers and multiplexers which have been described in detail by authors in their previous works. Depending on the number of different backup connections, the two types of fault-tolerant pho-tonic switches are considered in this paper: single-channel fault-tolerant photonic switch and dual-channel fault-tolerant photonic switch. The mathematical expressions for calculating the switching and fiber complexities of these two types of fault-tolerant photonic switches are also presented here for the first time. The numerical calculations shown that the increasing the reliability of the fault-tolerant photonic switches twice leads to an increasing their switching complexity in 1.4 times and fiber complexity in 1.8 times.

An eight-state molecular sequential switch featuring a dual single-bond rotation photoreaction

Typical photowitches interconvert between two different states by simple isomerization reactions, which represents a fundamental limit for applications. To expand the switching capacity usually different photoswitches have to be linked together leading to strong increase in molecular weight, diminished switching function, and less precision and selectivity of switching events. Herein we present an approach for solving this essential problem with a different photoswitching concept. A basic molecular switch architecture provides precision photoswitching between eight different states via controlled rotations around three adjacent covalent bonds. All eight states can be populated one after another in an eight-step cycle by alternating between photochemical Hula-Twist isomerizations and thermal single bond rotations. By simply changing solvent and temperature the same switch can also undergo a different cycle instead interconverting just five isomers in a selective sequence. This behavior is enabled through the discovery of an unprecedented photoreaction, a one photon dual single bond rotation.

Molecular switch architecture determines response properties of signaling pathways

Many intracellular signaling pathways are composed of molecular switches, proteins that transition between two states—onandoff. Typically, signaling is initiated when an external stimulus activates its cognate receptor that, in turn, causes downstream switches to transition fromofftoonusing one of the following mechanisms: activation, in which the transition rate from theoffstate to theonstate increases; derepression, in which the transition rate from theonstate to theoffstate decreases; and concerted, in which activation and derepression operate simultaneously. We use mathematical modeling to compare these signaling mechanisms in terms of their dose–response curves, response times, and abilities to process upstream fluctuations. Our analysis elucidates several operating principles for molecular switches. First, activation increases the sensitivity of the pathway, whereas derepression decreases sensitivity. Second, activation generates response times that decrease with signal strength, whereas derepression causes response times to increase with signal strength. These opposing features allow the concerted mechanism to not only show dose–response alignment, but also to decouple the response time from stimulus strength. However, these potentially beneficial properties come at the expense of increased susceptibility to upstream fluctuations. We demonstrate that these operating principles also hold when the models are extended to include additional features, such as receptor removal, kinetic proofreading, and cascades of switches. In total, we show how the architecture of molecular switches govern their response properties. We also discuss the biological implications of our findings.