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\title{System design and implementation for the class using the VNC screen sharing}
\author{School register number:085734D　Name:Yu Taninari　Instructor:Shinji Kono}
\date{}
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\section{First}
When usually performing teaching,In many cases performed using the projector.
but, when performed using the projector It is difficult to be visible at rear side seat.
If participation class students have personal computer that it can  the teacher's screen display.
If it makes students at rear side seat can be seen easily to teachers display.
Using VNC can display the teacher's screen to students display.
However, the screen will no longer keep up with the progress of the class fell and process it may end up connecting to a PC at the same time teacher of students of multiplayer.
This problem happen at same time access to teacher display.

In this study, the client into a tree structure so that you can share the screen in multiplayer
Do the design and implementation of (TreeVNC) system that is sharing the screen in such a way that will sink the data in order from top to be connected.


\section{About VNC}
VNC(Virtual Network Computing) is Remote Desktop software. It is can be remote operation using 'RFB Protocol'.
VNC is divided into the client side and server side, start the server, the client makes a connection to the server.

\section{Rfb Protocol}


\section{Design policy for TreeVNC}
First, problem arises when using VNC multiplayer. Since there is many connection,Processing performance falls. it will go down.
In order to solve this problem .  I developed how the client which received the data of screen drawing pours data to the following client was considered. 
A client to do screen sharing to becomes VNC server itself.
Moreover, I were considered as it is better to connect by a tree structure. 
PC (Top) which is present in the top of a tree performs management of connection of clients, Only Top node is made to connect with a VNC server. \\
This time is created Tree VNC is The above-mentioned method. only screen sharing do(not allow Operation).


\section{Precedence example}
There are Vnc Reflector and VNc Projector in order to reduce the load to a Vnc server.

\subsection{VNC Reflector}
Vnc Reflector is a program which enters between a Vnc server and a client and performs communication with a Vnc server instead.
Because the only client to connect to the  Vnc Reflector. we can  reduce the load on the Vnc server in order to the connection with a Vnc server serves as only Vnc Reflector.

\subsection{Vnc Projector}
Vnc Projector is screen sharing software using by Broadcast.

Since Broadcasting is used, there is little load to a server. 

This software is a charge.
It is possible to correspond to the wireless LAN, because not use Broadcast.

\section{Impliments of TreeVNC}
TreeVNC created based on the java version of TightVNCVirewer.TightVNC is free software for VNC.
VNC servers created by C++ the Windows version and the Java version is published as of August 9, 2011.


\subsection{construction of Tree}
ients connected to a host as tree structure. The following procedures perform composition of a tree. 
　\begin{enumerate}
  \item When a client connects, it connects with the proxy (this proxy will be described to be Top from now on) linked to a host. 
　\item The Top teaches the place which should be connected to a client. (It is taught at this time whether you are parents' number, your and number  together)
　\item A client connects with the node specified from Top. 
　\end{enumerate}


\subsection{reconstruction of Tree}
Since the client is connected in the shape of a tree as for this mounting, if a parent node falls, a child node will also fall together. \\
Therefore, reconstruction of a tree is needed. The procedure which reconstructs Tree is followed as follows. 
\begin{enumerate}
  \item A child reports to root that parents be down state. 
　\item when root is reported. orders to become instead of the parents who fell to largest number node.
　\item The client which received the command from root reconnects with the place where root was specified. 
　\item root updates the list of clients -- new parents' information is taught to the children to whom parents state down. 
　\item The child who doesn't have parents connect to new parents.
　\end{enumerate}
In this way, Tree can be reconstructed.$\\$
When the child to whom the following sauce and parents fell has connected, it is a part of code of the portion which waits for all children's connection. 


\section{Evaluation}
TreeVNC was implemented and comparison with Vnc Reflector was performed. 
Test environment prepares 48 VM(s) on a Blade server, and is TreeVNC and Vnc Reflector besides a Blade server. 
PC was placed and it experimented by making 48 VM(s) access. 

\subsection{Compare VncReflector to TreeVNC}
As for overconcentrated type Vnc Reflector, the throughput fell from 20 mega to five mega. 
On the other hand, it has checked that the direction of TreeVNC saved as [ 20 mega ] for a throughput. 
This is unlike Vnc Reflector 48 units to gain access to a communication band of this is because the client will communicate with each other.

\subsection{The advantage and fault of TreeVNC}

Since clients exchange data, there is little load to a Vnc server. 

Since it is not an overconcentrated type, when using by a lot of people, there is little stress of a display. 

The Top itself can also have a viewer. 

Communication speed of minutes all up, high load to the switch.



\section{Result and Future works}
In this research, the screen shared system was developed using VNC and a tree structure.
A result a throughput without dropping its connection at 48 sets.

Since the test in an actual lesson etc. is omitted, I would like to test whether it can use by actual lesson, although the test on a virtual machine was done this time. 

Since the portion of UI of a client is not made, I would like to enrich UI and to design an easy-to-use system. 


\thispagestyle{fancy}
\begin{thebibliography}{9}

\bibitem{VncReflector}{TightVNC: VNC-Compatible Free Remote Control / Remote Desktop Software}: 
http://vnc-reflector.sourceforge.net/
\bibitem{TightVNC}{TightVNC: VNC-Compatible Free Remote Control / Remote Desktop Software}: 
http://www.tightvnc.com/

\bibitem{VNC}{Tristan Richardson, Quentin Stafford-fraser, Kenneth R. Wood, Kenneth R. Wood, Andy Hopper}:
Virtual Network Computing (1998): Virtual Network Computing (1998)

\bibitem{ZLIB}{P. Deutsch, J-L. Gailly }:
ZLIB Compressed Data Format Specification version 3.3

\end{thebibliography}
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