TCP Flow

Study notes from reviewing TCP and the basic components.

Segments are chunks of data that come into the TCP buffer.  A segment on the wire includes the data and headers.

Sequence numbers start with a random value (ISN) and are unidirectional.  The sequence number tracks the data flow and is used to track down what chuck of the flow is lost.

ACK's are the sequence number plus 1.

Windows size is a collection of sequence numbers and is used to track how much of the buffer the receiver can consume.  It slides is a scaling factor number (grows and the connection is stable and shrinks when drops occur).

Selective ACK's can group a range of packets to identify what was lost (this speeds up the flow of TCP).

TCP is also full-duplex, so the same steam is used for both directions, unlink IPSec SA's.