At 11:53 25/06/01 +0300, Lyytinen Petteri wrote:
>On Mon, 25 Jun 2001, Reckhard, Tobias wrote:
>
> > How can it be ACK SYN ACK, when there is only one ACK bit in the TCP
> > header?
>
>I first heard the term "ACK SYN ACK" during a lecture on a Networking
>Techniques and Protocols course at the university and I believe it was
>just meant to differentiate the third packet from the second packet (I
>know the lecturer could've used other ways, putting more emphasis on the
>sequence numbers or something such) and, it kinda took in *shrug*.
1. the client sends a first packet with SYN set (and a seq num provided)
2. the server responds with a packet with SYN and ACK set (a seq num is
provided and
an ack num is filled)
3. the client follows with a packet with ACK (no more sins:).
- so the first packet has SYN but not ACK
- the second (server to client) has both SYN and ACK
- the rest have ACK but no SYN
so there is no amibguity here.
>Anyway, this is getting OT so I'll stop here.
not OT for me. understading how this works is necessary to configure
static (and sometimes dynamic) filters.
cheers,
mouss
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