ESTABLISHED,RELATED allows packets which are part of an established TCP
connection i.e. the 3-way SYN-SYN/ACK-ACK has completed with no subsequent
RST. It also allows UDP packets from a source IP/port which was a
destination within the past 30s.
The ESTABLISHED state doesn't just apply to packets in an established tcp
connection though, it also allows packets which are part of the initial
connection exchange, the syn-ack packet, otherwise you would also need
rules to allow out these packets.
John
--
Nigel Wade, System Administrator, Space Plasma Physics Group,
University of Leicester, Leicester, LE1 7RH, UK
E-mail : nmw@xxxxxxxxxxxx
Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555
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