### Specifying Source and Destination of Messages

One of the frequently asked questions in the community is how to specify which particular nodes would act as source(s) and destination(s) of the messages created in the ONE simulator. The simulator, in fact, provides a pair of settings (shown below in bold face) aimed for this particular purpose.

Let us consider that there are $n + 1$ nodes in an OMN.  Further, let the nodes with addresses from $x$ to $y$, both inclusive, would create messages. The nodes in the range $w$ to $z$, both inclusive, would be the destinations of those messages, where $0 \le x \le y \le n$, and $0 \le w \le z \le n$. Then, the corresponding simulation scenario can be configured as follows.

## Message creation parameters

# How many event generators
Events.nrof = 1
# Class of the first event generator
Events1.class = MessageEventGenerator
# (Following settings are specific for the MessageEventGenerator class)
# Creation interval in seconds (one new message every 25 to 35 seconds)
Events1.interval = 25,35
# Message sizes (500kB - 1MB)
Events1.size = 500k,1M
# The source nodes -- nodes that create the messages
# Lower bound is inclusive; upper bound is exclusive
Events1.hosts = x, y+1
# The destinations of the messages created
# Lower bound is inclusive; upper bound is exclusive
Events1.tohosts = w, z+1
# Message ID prefix
Events1.prefix = M

Note that the expressions $y + 1$ and $z+ 1$ should be replaced with their actual values. For example, if nodes $10$ to $20$ would create messages (both inclusive), and node $25$ is their destination, then the settings would like the following.

Events1.hosts = 10, 21
Events1.tohosts = 25, 26

Update: An alternative approach toward message creation is discussed in Juliano's blog.

1. Excellent post Barun, this helped me :D! I tested yesterday, it was nice seeing the simulation nodes, through the GUI, and I saw only the two nodes I wanted "stacking up green and blue message blocks", this must mean it worked haha.

2. thanks Barun, it's really flawless post.
I have a question after doing this how do we know that message successfully send from source to destination ? please

1. Hi,

Not sure what you are asking. Are you talking about delivery of a message to its destination?

yes, I want to know, does the message transfer from source to destination successfully or not
for example :
Events1.host = 10
Events1.tohost = 25
how can I be sure that the message created by node 10 deliver to node 25?
Thanks again

3. It is hard to provide a guarantee that a given message would be delivered. Its delivery depends on several factors such as, routing protocol used, TTL, contacts, and others. Depending on your simulation parameters, in most scenarios, you would not get 100% delivery ratio.

On the other hand, if your intention is that a source node should know of the delivered messages, you can use some form of acknowledgements. Alternatively, at each node maintain (and exchange) a list of messages received as destination. A source node would gather that knowledge at some later point of time.

4. Thank you so much Sir, as usual, you explained very well.

5. Hi,
We can get this info by overiding the delivered message report.

3. Thanks a lot for this tutorial. In this particular scenario,message is moving from 10 to 25, How could we get information which hop/nodes it is using as a relay node.

1. Hi Rashmi,

The routing protocol would dictate which all nodes should be used as relays. E.g., in PRoPHET, a node with better delivery predictability can become a relay node.

However, if you want to know which nodes have helped in replicating a copy of a message till now, you can use the getHops() method of the Message class.

2. Sir can i get the implimentaion of routing algorithms in C language

4. Thanks Barun, it helped!

5. Sir I need some help in imlimenting these dtn algorithms majorly epedimics in c language.Please can you help me in this

6. Hello, I would like to appreciate your work. It’s a great platform got to learn a lot. Your data is really worthy. Thank you so much. Keep it up!

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### Text Highlighting in Latex

While preparing a manuscript with Latex, it is often useful to highlight the changes made in the current revision with a different color. This can be achieved using the\textcolor command provided by Latex. For example,\textcolor{red}{Hello World}would display the string "Hello World" in red color.

However, the final/published copy of the manuscript does not contain any highlighted text. Therefore, if a large volume of changes were made, it becomes tiresome at the end to find and remove all the individual portions of highlighted text.

This can be circumvented by defining a utility command to switch highlighting on and off as desired. In the following, we define a new Latex command, highlighttext, for this purpose. The command takes only a single argument -- the text that it should highlight.

\usepackage{color}

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