On Fri, 13 Nov 2020, 14:33 Alex Samad, <a...@samad.com.au> wrote: > Hi > > Quick question is it normal or acceptable to finish a TCP session or I > should say start to finish session with a fin ack packet. When I google TCP > state I get it's just a fin packet not fin/ack >
Yes. The Ack is acknowledging the Fin. A full close involves two pairs of FINs and matching ACKs in both directions. It's actually possible therefore to have a half closed TCP connection, where only one end has sent the FIN and it's been ACK'd, but that hasn't happened in the other direction, and doesn't have to immediately - and data can still be sent in the still half opened direction. (Although I'd guess firewalls or NATs might stop that working these days.) The book "TCP/IP Illustrated", Volume 1 (2nd Edition now) is great for explaining, and of course illustrating, this stuff. Regards, Mark. > > Alex > _______________________________________________ > AusNOG mailing list > AusNOG@lists.ausnog.net > http://lists.ausnog.net/mailman/listinfo/ausnog >
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