Sequence Number Synchronization

Hello guys! It took me some time to understand some concepts that why I got delayed with my next post.

Just to note our connection part is not over. I just figured out an important part of connection which is titled as “Sequence Number Synchronization”

I hope all you are aware of the concept of Sequence number else go to the Link.

Consider there are two devices A and B which is trying to establish a connection. We know when they are sending data each data packet would get a packet number/ sequence number. What if both the devices send with the same sequence number. It’s not compatible, right?

To remove that we introduce this new feature. Before A and B sends in data they first make sure that they ¬†exchange the initial sequence number they want to use. It is also called as ISN. But there can also come an issue if segments after the ISN get the same number. For that, we use a counter. ISN is choosen using a clcoked counter that increments every 4 microseconds. The counter is iniatilsed when the TCP is started. A new connection to be estbalish would take in an ISN starting from the last one. Here we won’t have the issue of conflicts as only 4 hours a repition of Sequence numbers can take place and by that time the packets would have been transfered.

Note that both the devices sent to each other their ISN’s.


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