Data Packets

Data packets are considered as basic unit for functioning of internet.When two system communicate data are sent in form of packets.

                                     Structure of data packet

Data packet contains sender's IP means it contains sender's ID it also contains IP address of system where it has to reach.The actual data or w can say message that we want to send.A single message may break into several data packets.

                                     Journey of packets

As we can see that transfer of data packet is a complex process during its journey it travels through various of system.

Example:

While connecting to google.com we send a data packet to google.com so we will trace the route of data packets through tracret command in CMD.

Android user can download terminal emulator from play-store and use trace-route command

We can see that we are getting various IP at right side of IP by IP lookup method we can find detail of these IP and get information about the journey of data packet that we have sent to Google.com

                         TTL  value 

Every data packet contains a special value known as ttl value it tells routers when to discard a certain data packets every time a data packet reaches a router ttl value decreases by 1 when this ttl value become 0 the data packets is discarded an a message is send to sender a special feature of data packet is that different OS have different ttl value.

So if we want to know OS of any server or a victim system that you want to hack on you can know the OS the victim is using ttl value

First we have to know the IP address of a victim's system learn how to find victim's IP address at https://goo.gl/F8KX3N

After that we have to open CMD and command ping <ip address>

in this case i am using my own system IP address

Process of finding OS

First open CMD and command ping <IP address>
           -------note the ttl value
Then command tracert <IP address>
           -------note the number of hops
Add ttl value and no of hops(ttl+hops)
            ------we will get initial ttl value of victim's system.
            ------and we know that different OS have different initial ttl.

In the case shown above ttl is 60 and no of hops is 3 so initial ttl is 63

here  is chart of OS and different OS we can see that ttl for the above shown case is 63 and ttl of android is 64. So we have find the OS of victim system.

**There can be difference b/w exact ttl and obtained ttl due to packet loss.