TCP/IP Data Transmission Basics [Wireshark Example]

TCP 3-Way Handshake

Let’s take a real life example and illustrate it via wireshark:

First, the TCP 3-Way Handshake will establishes a connection between the client and server:


You can refer to following post:


TCP/IP Data Transmission

Once the connection is established, data can be exchanged reliably using sequence (SEQ) and acknowledgment (ACK) numbers:


  • The example is based on TLS negociation process.
  • First packet was “Client Hello”, len 186:


  • Then, we have Ack from the server, ACK=187 (No data send from server yet):


  • Next, we see the “server Hello” sent with len=1460 (which is the value MSS in this example):


  • Then , more data sent from server (for certificate, key exchange etc) with Len 628.
  • Here, the sequence number for this segement is 1460 (since server already sent 1460 Bytes) and same ACK value representing what received from client and next expected seq from client:

And the client ACK back, ACK=2089 (1460+628 + 1), and seq num=187 based on what server already sent (186 Bytes

Bilel Ameur

Enthusiastic Network Engineer specializing in Cisco ACI, passionate about solving challenges. A lifelong learner who loves gaining and sharing knowledge. Profile: https://www.linkedin.com/in/bilel-ameur-71116b2b5
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