Calculation of Terminal Reliability for Two Nodes in a Network

This is a tool for calculating the terminal reliability of a network. It takes as input the network topology and the reliability of each link within the network and calculates the the terminal reliability between any two nodes in the network. The nodes themselves are considered to be fault free for the purpose of this calculation. However , we can account for the node failures by changing the
reliability of the associated links accordingly .This tool doesnot have any restriction on the number of nodes or links that the user wants to specify. The computation time would however increase as more and more complex networks are specified. So the user is advised to have a little more patience in those scenarios.

The algorithm that has been used is SYREL : A Symbolic Reliability Algorithm Based on Path and Cutset Methods. This was authored by Salim Hariri and C.S.Raghavendra in IEEE Transactions on Computers , VOL. C-36, NO. 10, OCTOBER 1987. The user is encouraged to read the paper to get an insight into the algorithm that has been implemented if he so desires.

If you are using the tool for the first time it is strongly suggested that you read step by step through the manual presented below . If comfortable go ahead and use the tool.
 Terminal Reliability Calculation Tool

Manual for Using this Tool

The user will be taken through a step by step procedure to clarify how the tool works. An example is considered here which consists of 4 nodes configured as shown in the figure below.
 Adding Nodes
 Adding Unidirectional Link
 Adding Bidirectional Link
 Specifying Source
 Specifying Destination
 Calculating Reliability
 Extra Editing Options
Attaching Java Plug-In


The tool comes up with a Graphical User Interface for specifying the Parameters. The GUI has several buttons and text areas for input and output. Each of those components are explained below.
The snapshot of the initial setting is presented below.


Adding Nodes

This creates the nodes that are in the network. The user has to press the Add Node button everytime he wants to add a node in the network. The nodes are numbered sequentially. Please note that every time the user wants to add a node he has to press the Add Node button and then click on the required position of the drawing canvas.

In the example, the Add Node button has to be clicked four times each time followed by a click in the specific position of the canvas which does the node placements.

Adding Unidirectional Link

This creates the unidirectional links in the network. For example, the input for the link between Node 1 and Node 2 having link reliability of 0.9 is shown below. The link is represented by a red line from the source to the destination and the destination is indicated by a red circle near it's vicinity.


Adding Bidirectional Link

This creates bidirectional link between the source and the destination. This is represented by a black line with circles near both the source and the destination nodes.

Specifying the Source Terminal

 The user has to type the ID of the source node in the textfield position next to the Source.

In our example, we specify the Node 1 as the input.The corresponding Window is shown below.

Specifying the Destination Terminal

The user has to type the ID of the destination node in the text field position next to the Destination.

In our example, we specify the Node 4 as this input. Th corresponding Window is shown below.

Calculating the Reliability

This will calculate the Terminal Reliability between the source and the destination as specified in the windows mentioned before.

Interpreting the Output

Once this user has pressed the option for calculating the reliability he will get some the output in two places . In the textfield near the terminal reliability window the output will show the overall terminal reliability that was calculated for that particular network topology. In addition there is a textarea in the right side . This shows the many different paths that can be there between the source and the destination. The conditional reliability of each path  (given that the previous paths are not functional) is displayed . The final window after calculating reliability is shown below.

Extra Editing Options


This clears all the previous input parameters and the user has to do the entire run right from the scratch.

To run the Example

An example has been already put in place. The user has to press the Load Example window and has to then press the Calculate Reliability button to calculate the reliability .

Attaching Java Plug-In

The tool has been developed as an applet that uses Java Swing package. As a result in order to run this applet properly JRE-1.3 with the Java Plug In needs to be supported in your browser.
In case your browser doesnot support this plug-in currently it is important to load the plug-in. It is easy to do by following the instructions written below. You can also refer to the java website of the SUN to get a indepth procedure of how to load this applet.

Download the  JRE ver 1.3.1

If you are using the Linux OS , it is recommended that you download the RPM script. Follow the  instructions to install the RPM properly.
You need to add the path of the directory that contains the plug-in in the NPX_PLUGIN_PATH.
For example , if you use the bash shell , add the following line
in the bashrc and using netscape 4.x

export NPX_PLUGIN_PATH=<jre>/plugin/i386/ns4

where , <jre> is the path of the top level directory of your Java 2 Runtime Environment installation.

You need to close the netscape and restart it and again close it and restart to embed the plugin properly. Closing and restarting twice is very important to take care of a bug in Netscape

Right, now you are all set to use

Please send any feedback or bug-report to  Diganta