Nmap Development mailing list archives

Re: Nmap question (timeout versus scan-delay)


From: Martin Mačok <martin.macok () underground cz>
Date: Thu, 5 Oct 2006 17:38:48 +0200

On Thu, Oct 05, 2006 at 11:08:02AM -0400, John P. Wilson wrote:

If scan-delay is zero (which I assume it is by default) then
I suppose multiple probes can be sent to multiple ports at once,
right (parallel probing)?

Yes.

If scan-delay is greater than zero then, as you point out, this
enforces serialization - only dealing with one probe at a time.

Not exactly true because scan_delay could be smaller than timeout and
next probe can be sent out before giving up waiting for reply to
previous probe.

Is there ever a case where multiple probes are sent all at once to
one port?

I don't know of any.

If no reply is received and timeout expires, and if there are still
retries to perform, is the probe sent out immediately, regardless of
what scan-delay is set to?

No, if scan_delay is greater than timeout then the next probe will not
be sent sooner than scan_delay after previous probe was sent.

Also: must scan-delay be greater than timeout?

No.

Martin Mačok
ICT Security Consultant

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