This is referred to as a "three way handshake." The "SYN" flags are requests by the TCP stack at one end of a socket to synchronize themselves to the sequence numbering for this new sessions. The ACK flags acknowlege earlier packets in this session. Obviously only the initial packet has no ACK flag, since there are no previous packets to acknowlege. Only the second packet (the first response from a server to a client) has both the SYN and the ACK bits set.
des is von
da
und gefunden hat das
www.google.com
anscheinend verwenden viele DoS attacken genau das und wenn man dann in protokoll sieht das da der wert ansteigt kann man so syn packete verbieten... soweit ich das verstanden habe hehe