Ki-Hyuk Nam

Software-defined networking (SDN): A reference architecture and open APIs

Recently, Software-defined networking (SDN) is emerging and intensively discussed as one of the most promising technologies to make networks programmable and virtualizable, so that SDN could simplify network operations, reduce cost and accelerate service delivery. Even if openness which gives network customers choice to build best-of-breed their networks is one of main properties of SDN, open architecture, interfaces, APIs, etc. are not fully investigated yet. In this paper, we discuss SDN reference architecture and APIs for open networking environment.

High‐resolution transmission electron microscopy study of solid phase crystallized silicon thin films on SiO2: Crystal growth and defects formation

A high‐resolution transmission electron microscopy study of the solid phase crystallization of amorphous silicon thin films deposited on SiO2 at 520 °C by low pressure chemical vapor deposition and annealed at 550 °C in a dry N2 ambient was carried out so that the grain growth mechanism, various types of defects, and the origins of defect formation could be understood on an atomic level. Silicon crystallites formed at the initial stage of the crystallization had a circular shape and grains had a branched elliptical or a dendritic shape. Many twins, of which {111} coherent boundaries were parallel to the long axis of a grain, were observed in the interior of all the elongated grains. In addition to twins, the following defects were observed in the grain: intrinsic stacking faults, extrinsic stacking faults, perfect dislocations, extended screw dislocations, and Shockley partial dislocations. These defects were formed by the following reasons: errors in the stacking sequence at the amorphous/crystalline int...

Formation mechanism of crystallites in the as-deposited mixed-phase low pressure chemical vapor deposition silicon thin films

Transmission electron microscopy study on the microstructure of silicon thin films, deposited at temperature ranges of 565 °C∼600 °C and at 200 mTorr by low pressure chemical vapor deposition and annealed at 570 °C, was carried out so that the formation mechanism of crystallites observed in as‐deposited mixed‐phase silicon thin films could be proposed. Crystallites were observed only at the Si/SiO2 interface in the as‐deposited silicon thin film deposited at 570 °C for 28 min. Their size was about 20 nm and they had an irregular shape. Areal density of crystallites in the as‐deposited film was about 4 × 1010/cm2, but that in the film deposited as an amorphous phase and annealed at 570 °C for 2 h was about 2×109/cm2. No remarkable crystal growth occurred in the film deposited at 570 °C for 28 min and then annealed at 570 °C for 1 h. Two kinds of crystallites were observed in the film annealed at 570 °C for 3 h. The first, observed only at the Si/SiO2 interface, had an irregular shape, and the second, grown...

Formal Modeling and Verification of SDN-OpenFlow

Software-Defined Networking (SDN) is a network architecture where a controller manages flow control to enable intelligent networking. Currently, a popular specification for creating an SDN is an open standard called OpenFlow. The behavior of the SDN OpenFlow (SDN-OF) is critical to the safety of the network system and its correctness must be proven so as to avoid system failures. In this paper, we report our experience in applying formal techniques for modeling and analysis of SDN-OF. The formal model of SDN-OF is described in detail and its correctness is formalized in logical formulas based on the informal specification. The desired properties are verified over the model using VERSA and UPPAAL. Our work-in-progressinvolves the development of a model translation tool that facilitates automatic conversion of the verified model to Python for modular code synthesis on the application platform

A Method for Distributing Web Applications

Web has influenced the form of software applications. These web applications are generally difficult to distribute by novice users since their usage was restricted to the network based massive servers which has many server modules requiring difficult configurations. However, web applications became widespread and used in daily basis from simple utility programs to PIMS. This paper proposes a web application model and distribution method for portable web applications to adapt to current trends. The most salient features of the method are click & run interface for installing, configuring, and executing web applications, and offline execution by providing a web server, a DBMS on movable disks such as USB memory sticks. The method has been verified by developing a simple application platform and package builder supporting applications written in Ruby and PHP.

Formal specifications for software-defined networking

It is important to understand the correct specification of SDN in order to implement and analyze the SDN in mind. However, natural languages are usually ambiguous and misleading the specification due to the nature of natural language understanding. Hence, it has been required to have formal specifications after natural language documents. We have two formal specifications for a part of SDN, and compare the formalisms, called ACSR and Z.

SDL and MSC description of ETRI software streaming protocol

In this paper, we describe a software streaming protocol for software on-demand service in SDL and MSC. The protocol was developed originally in SOFTonNET Inc. It was adopted and enhanced in the SoD system in ETRI for on-demand service in Korean. We name it as ESSP (ETRI software streaming protocol). We first refine major factors for designing software-streaming protocol, which can affect the performance as well as functionalities. Then, we show a few parts such as architecture and message sequence charts

Design of unified streaming systems

The unified streaming system (USS) is a networked multimedia system which integrates multimedia streaming with software streaming. With the USS, software applications and multimedia contents can be interwoven in a semantic level, so the new kinds of streaming services can be developed. The basic idea of the USS came from the similarity between decoding multimedia contents and executing software applications. It is similar to MPEG-J in that software and multimedia contents can be combined, but the main difference between two technologies is that the USS allows full-fledged applications to be synchronized with multimedia contents. Furthermore, application parts of the USS contents are executed on the ServiceOnNet S/W Streaming Engine, which enables application to be executed on-demand from remote server without installation

Verifying Behavior of L4 Microkernel based Mobile Phone

The embedded mobile phone based on L4 microkernel are known to be difficult to predict their behavioral correctness since L4 microkernel communicates with various components for their execution. That means its correctness is not easy to guarantee by using traditional design and testing methods. In this paper, we propose a formal approach to prove the correctness of L4 based mobile platforms.

Design and Implementation of SoD Engine for Linux

Software-on-demand (SoD) is an emerging technology that enables S/W applications to be executed on-demand without download and installation, so that the applications are available virtually everywhere in the network. ETRI has proved that the software-on-demand is feasible for Windows and Linux desktop systems by making prototypes and testing on www.serviceonnet.net. To enhance the performance and functionality of Linux SoD systems, we implemented a new version of SoD engine for Linux. In this paper, we present improvements on structure and functionality of the SoD engine for Linux, which include engine module minimization, caching, and background downloading. The result of the improvements shows that the average application load time is decreased in comparison to the prototype