Ensuring someone is listening before telling a joke

  • Alice (speaking to Bob): Bob, I have a good joke to tell, can I call you at 12:00 ?
  • Bob (turns head towards Alice): OK, fine for me, but can we make it at 13:00 ?
  • Alice (nodding): Works for me.
  • At 13:00, Alice starts telling a joke.

Did you recognize the three way TCP handshake ?

Protagonists:

  • Alice: Client
  • Bob: Server

Dialog:

  • I have a good joke to tell: TCP segment with SYN flag
  • 12:00: initial sequence number
  • OK: TCP segment with SYN and ACK flag
  • 13:00: acknowledgment number (initial sequence number + 1)
  • Works for me: TCP segment with ACK flag, acknowledgment of the server acknowledgment

More details on this in https://www.linuxjournal.com/article/6447 and remember tcpdump uses a dot(‘.’) to indicate segments with the ACK flag.

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