How TCP Works - Sequence Numbers

TCP is important stuff for network engineers to know.

Why?

Today's problems aren't so cut-and-dry as they used to be. When a problem strikes, we can't just say "it's not the network" and go along with our day. A core understanding of TCP and how it carries and acknowledges data goes a long way in finding the root cause of performance problems today.

One key aspect of TCP that is important to learn is the Sequence and Acknowledgement process. To put it simply, these numbers in the TCP headers indicate how much data has been sent and received. They allow each endpoint to determine if there was packet loss, what needs to be retransmitted, and help to determine how much data is in flight.

For a six-minute crash-course on how TCP Sequence numbers work, check out this video:

Thanks for checking it out and hopefully it helps all packet-heads out there!

Author Profile - Chris Greer is a Network Analyst for Packet Pioneer LLC and a Certified Wireshark Network Analyst. Chris regularly assists companies in tracking down the source of network and application performance problems using a variety of protocol analysis and monitoring tools including Wireshark. Chris also delivers training and develops technical content for several analysis vendors. Got network problems? Let's get in touch.