A TCP connection begins by exchanging starting sequence numbers before data. This lesson previews the ordered SYN, SYN-ACK, ACK flow and the exact numbers each side learns.
highlighted = computed this step
Why a connection starts with agreement
Before data can be ordered, each endpoint has to reveal its starting sequence number. The timeline shows the client and server exchanging those starting points.
client ISN=1000
Preview the segments
The client starts at 1000, the server starts at 3000, and the flow uses 3 ordered segments.
1000→3000segments=3
Why sequence numbers appear first
The numbers are not payload bytes yet. They are the initial positions that later byte streams will count from.
sequence numbers before payload
Summary
A handshake exposes both starting sequence numbers before data transfer. Connection setup ordering and exact sequence numbers only; timing, retransmission, and round-trip time are not modeled here.