Acknowledgement number of an RST packet

Question

This question states that the acknowledgement number of an RST packet should be 0, but I have found it to be other than 0 when I captured some HTTP packets using Wireshark.

So when does the acknowledgement number of an RST packet contains a value other than 0?

Answer 1

The acknowledgement number is completed when the packet is an acknowledgement to a previous packet. In this case, the ACK bit is set.

You can have an ACK packet, that is also an RST packet. It both ACKnowledges a previous packet, and signals that the TCP session should be reset.

This is called an RST/ACK packet (simply because the ACK and RST bits are set).