RST packets

Rob Sterenborg rob at sterenborg.info
Mon Jul 18 16:12:53 CEST 2005


> Hi,
>
>
> a simple question, though I could not clearly read it from the TCP RFC...
> do RST packets always have ACK set?

It seems that isn't so :

(http://www.knowplace.org/netfilter/ip_overview.html)

Resetting a connection

The four-way handshake is not the only way to tear down an established TCP
connection. Sometimes, if either hosts need to tear down the connection
quickly (timeout, port or host unreachable, etc.), a RST (Reset) packet is
sent. Note that since a RST packet is not necessarily always part of a TCP
connection, it can be sent by itself. RST packets that are part of a TCP
connection is usually accompanied by the ACK flag as well.

Note that RST packets are not acknowledged.



Gr,
Rob





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