<Dt> Sequence number (32 bits) </Dt> <Dd> Has a dual role: <Ul> <Li> If the SYN flag is set (1), then this is the initial sequence number . The sequence number of the actual first data byte and the acknowledged number in the corresponding ACK are then this sequence number plus 1 . </Li> <Li> If the SYN flag is clear (0), then this is the accumulated sequence number of the first data byte of this segment for the current session . </Li> </Ul> </Dd> <Ul> <Li> If the SYN flag is set (1), then this is the initial sequence number . The sequence number of the actual first data byte and the acknowledged number in the corresponding ACK are then this sequence number plus 1 . </Li> <Li> If the SYN flag is clear (0), then this is the accumulated sequence number of the first data byte of this segment for the current session . </Li> </Ul> <Li> If the SYN flag is set (1), then this is the initial sequence number . The sequence number of the actual first data byte and the acknowledged number in the corresponding ACK are then this sequence number plus 1 . </Li>

Why are sequence numbers used and are important in the tcp protocol
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