In some mail from Nick Simicich, sie said:
> On Fri, 11 Aug 1995, Carsten Schafer wrote:
> > I have recently been getting lots of packets with the SYN bit set
> > and a combination of PUSH, URG and RST. Our packet filter seems
> > to throw away anything with a SYN bit set. I guess I'm wondering
> > which packets are considered connection requests by TCP when the packet
> > contains a SYN bit. Are packets containing the SYN flag and no others
> > considered connection requests? Most of the packets with the other flags
> > set seem to be in response to HTTP requests.
> The initial request for a TCP connection has the SYN bit set, but not the
> ACK bit. Every other TCP packet in a connection has the ACK bit set,
> including the response to the initial SYN, which also has the SYN bit
FIN can be set alone - or at least that is what all the FSM diagrams
describing it seem to suggest, only that more often than not, the FIN
is sent with an ACK for data.