I migrated this question from cryptography - as the acceptance or rejection of packages has usually little to do with cryptography.

Now I can imagine that it gets closed here, but the reason given is that it operates on a layer higher than OSI layer 4. According to any documentation I can find is that it operates (primarily) on the network layer (IP), which is OSI layer 3.

I explicitly looked at the help center and decided to migrate because I was pretty sure that it was not above layer 4 of the OSI model. So where did I reason incorrectly? Or is the mod giving the wrong reason?


IPSec uses TCP as its transport (layer-4) protocol, so IPSec is the payload (next higher layer) of the transport protocol, and it never sees the TCP segment headers or gets involved with TCP decisions. The question itself really doesn't make sense because of that.

I would think a better place for the question would be Information Security, but you should check with the moderators there before migrating it.

  • OK, so though IPSec transports layer 3 it operates on layer 5? Fine. This is not about security either, so it seems IPSec users are out of luck. Maybe Superuser could be used instead, because I'm out of options otherwise. – Maarten Bodewes Sep 5 '19 at 21:03
  • And yeah, TCP should provide a reliable transport layer so I don't see how the question is valid either, if you look at it like that. Maybe the implementation offers a low level packet layer, but even then would you expect that reissued packets would be handled internally. – Maarten Bodewes Sep 5 '19 at 21:06
  • The reason I suggested Information Security was because of the way the question was worded about a malicious replay attack. I think that type of thing is on-topic there. – Ron Maupin Sep 5 '19 at 21:49
  • Could you send it over? I asked at the TL and they are willing to accept it at IT security. – Maarten Bodewes Sep 5 '19 at 23:07
  • It will not let me do that. I even undeleted it, but it doesn't give me the option to say it belongs on a different site, I can only close it as off-topic (so I did). It is still on Cryptography, so you may be able to undelete it and sent it to Information Security. – Ron Maupin Sep 6 '19 at 0:51

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