SYN and ACK bit

Question

If SYN=0 and ACK=1

What actually it indicates about ? Means if they are give some information about data packet or ACK packet?

Comments

@Ashwin

why SYN cannot represent 1st packet?

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I said when SYN =0 it is surely not first packet.

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yes, why?

Answer 1

1) SYN=1 , ACK =0 {First segment or request for connection establishment}

2) SYN=1 ACK =1 {second segment or reply segment}

here ACK= 521 is ack number.

3) SYN=0, ACK=1 {pure ACK}

SYN=0, ACK=1 {piggybacked ACK}

Comments

SYN representing sequence number?