Nmap Development: Re: Desired improvements in Nmap performance? [SCAN BUDDIES]

[Brandon Enright <bmenrigh () ucsd edu>]

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On Tue, 2 Dec 2008 17:00:08 -0700
David Fifield <david () bamsoftware com> wrote:

> > Now with the --initial-rtt-timeout:
> >
> > $ sudo ./nmap --datadir ./ -p- -T5 -v -d -PN -n
> > --initial-rtt-timeout 50 132.239.7.132 SYN Stealth Scan Timing:
> > About 0.18% done Current sending rates: 33.81 packets / s, 1472.89
> > bytes / s.
> >
> > Of course, the buddy was *much* faster than this.
> I see, it also has to do with the congestion window (number of probes
> allowed to be outstanding at once). Just like with the RTT, hosts with
> no responses can take their congestion window from the global group
> (HostScanStats::getTiming). The scan buddy allows the global
> congestion window to grow. My guess is that combining
> --min-parallelism with --initial-rtt-timeout would give you
> comparable speeds. With -d3 you can get an output of the current
> congestion window size. It looks like
>
> **TIMING STATS** (0.7920s): IP, probes
> active/freshportsleft/retry_stack/outstanding/retranwait/onbench,
> cwnd/ccthresh/delay, timeout/srtt/rttvar/ Groupstats (1/1
> incomplete): 49/*/*/*/*/* 49.75/75/* 154278/66678/21900
>
> Here the congestion window has a size of 49.75.
>
> David Fifield
Bingo.  I ran:

$ time sudo nmap -v -d3 -p- -T5 -PN -n 132.239.7.132,131 --open 2>&1 | egrep -A 1 'TIMING STATS' | tail -n 2

The last stats were:

**TIMING STATS** (25.0050s): IP, probes active/freshportsleft/retry_stack/outstanding/retranwait/onbench, 
cwnd/ccthresh/delay, timeout/srtt/rttvar/
   Groupstats (1/2 incomplete): 0/*/*/*/*/* 300.00/237/* 50000/268/26

I then ran (without the buddy):

$ time sudo nmap -v -d3 -p- -T5 -PN -n 132.239.7.132 --initial-rtt-timeout 50 --min-parallelism 300 --open 2>&1 | egrep 
-A 1 'TIMING STATS' | tail -n 2

The scans finished within a second of each other.

Brandon

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