title: sequence number in TCP
body: <p>Why do we need the sequence number and the next sequence number field in the TCP header? </p>
  
  <p>Below is a TCP header from a packet captured using wireshark.</p>
  
  <p><a href="https://i.stack.imgur.com/Mw09y.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Mw09y.png" alt="TCP Header from a packet captured using wireshark"></a></p>