"Stateful" firewalls understand the flow of packets in a connection as opposed to inspecting each packet by itself and not in the context of a flow of data.
Think of a gated residential community where the security guard checks each car before letting it into the community but doesn't care about the car ahead of it or behind it. That is un-stateful checking.
Now think of a police officer watching a funeral procession. He sees a car in the middle of a procession that does not have a purple flag (which is used in the US to show a car is part of the procession). He knows that car cut into the line and doesn't belong there, so he stops it. That is stateful inspection. It's a much smarter way of watching the flow of data.
Stateful firewalls look at the entire flow of data to determine if any packets are trying to get through that don't seem to belong there and will block them.
A replay attack occurs when a malicious person (or program) records a stream of data and then resends it for some nefarious purpose. A good firewall can detect this. As an example, think of logging into your bank account using a touch tone telephone and authorizing a transfer to another account. If I tape record your phone call, I can call the bank later and replay the first part of the tones you sent, but change the destination account by putting in the tones corresponding to a different account number. Since I've recorded and replayed your account number and PIN, the fraudulent transfer may go through.
From your logs I cannot tell if these are advisory messages or were actual problems. In any event, unless they keep recurring it probably was a hiccup in the data transmission and can be ignored.
Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.