It's not uncommon for data to arrive out of order,
and when this does occur,
we need a method that can allow us to reliably
recover from this type of an event.
Let's take a closer look at reassembly.
Reassembly relies on an order of operations to sequence sessions
that arrive out of order. To organize data into the correct order,
it actually uses the sequence number.
Let's take a moment to view a diagram to make this less abstract.
Using our prior diagram,
we can see that the data is out of order as sessions 3 and 4 have been swapped.
The sequencing, though, is smart enough to know this so that the data will be
re‑sequenced into the proper order using the sequence number.
With the sequencing complete,
the robot picture will finally arrive intact by the time it arrives at the layer 7 application layer.