2026-06-11

TCP Retransmission

networkTCPWiresharkpacket analysis

When a client sends a packet (i.e. an initial "Client Hello") but never gets a response back, it starts a countdown onto itself, and when the retransmission countdown expires it re-transmits the data.

A Wireshark capture showing the client's initial hello and the retransmission that follows when no reply arrives

Here the client had sent the initial client hello.

For practice and visualization, use this pcap file.

Retransmission recall2 blanks

When a client sends an initial Client Hello and gets no reply, it starts a and re-sends the data when it expires — a .

try it before revealing

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