[smokeping-users] Less smoke.

[Tobias Oetiker]

Hi Josh,

so in essence what you are saying is that the first ping is special
and might be worth preserving but it should not be mixed in with
the others ...

So loosing it in the smoke is good but keeping it as a spearate
piece of information might be worth doing ...

cheers
tobi

Today Josh Luthman wrote:

> I want to say thank you very much for publishing this!  This is really
> good information.
>
> I do also want to comment that with the ARP cache populating and all
> that noise on the first ping, I personally would like to have that in
> my data.  This way I can judge if ARP is being way too slow upon new
> connections.  Just personal preference at this point.
>
> I do have to give you my compliments, though.  Great job!
>
> On Fri, May 23, 2008 at 2:29 PM, Tobias Oetiker <tobi at oetiker.ch> wrote:
> > Hi Ged,
> >
> > cool stuff ... thanks for the patch
> >
> > tobi
> > Today G.W. Haywood wrote:
> >
> >> Hi there,
> >>
> >> It's very common for the RTT of the first ping in a series to be much
> >> greater than those subsequent.  This is easily explained because there
> >> may be much more work for the routers etc. along the way to do for the
> >> first packet, they have to populate ARP caches for example.
> >>
> >> However this can give very misleading statistics in some cases.  I've
> >> modified my copy of FPing.pm to send one more ping than requested, and
> >> then to discard the first returned RTT value.
> >>
> >> 8<----------------------------------------------------------------------
> >> *** FPing.pm.original 2008-05-23 15:02:39.000000000 +0100
> >> --- FPing.pm  2008-05-23 15:08:15.000000000 +0100
> >> ***************
> >> *** 32,37 ****
> >> --- 32,40 ----
> >>
> >>   The (optional) B<packetsize> option lets you configure the packetsize for the pings sent.
> >>
> >> + This version of FPing sends one more ping than requested, and discards
> >> + the first RTT value returned as it's likely to be an outlier.
> >> +
> >>   The FPing manpage has the following to say on this topic:
> >>
> >>   Number of bytes of ping data to send.  The minimum size (normally 12) allows
> >> ***************
> >> *** 121,127 ****
> >>
> >>       my @cmd = (
> >>                       $self->binary,
> >> !                     '-C', $self->pings, '-q','-B1','-r1',
> >>                   @params,
> >>                       @{$self->addresses});
> >>       $self->do_debug("Executing @cmd");
> >> --- 124,130 ----
> >>
> >>       my @cmd = (
> >>                       $self->binary,
> >> !                     '-C', ($self->pings)+1, '-q','-B1','-r1',                                               # Add an extra ping
> >>                   @params,
> >>                       @{$self->addresses});
> >>       $self->do_debug("Executing @cmd");
> >> ***************
> >> *** 134,140 ****
> >>           my @times = split /\s+/;
> >>           my $ip = shift @times;
> >>           next unless ':' eq shift @times; #drop the colon
> >> !
> >>           @times = map {sprintf "%.10e", $_ / $self->{pingfactor}} sort {$a <=> $b} grep /^\d/, @times;
> >>           map { $self->{rtts}{$_} = [@times] } @{$self->{addrlookup}{$ip}} ;
> >>       }
> >> --- 137,143 ----
> >>           my @times = split /\s+/;
> >>           my $ip = shift @times;
> >>           next unless ':' eq shift @times; #drop the colon
> >> !         shift @times;                                                                                       # Junk the first result.
> >>           @times = map {sprintf "%.10e", $_ / $self->{pingfactor}} sort {$a <=> $b} grep /^\d/, @times;
> >>           map { $self->{rtts}{$_} = [@times] } @{$self->{addrlookup}{$ip}} ;
> >>       }
> >>
> >> 8<----------------------------------------------------------------------
> >>
> >> In some circumstances, the results can be striking:
> >>
> >> http://www.jubileegroup.co.uk/JOS/misc/less_smoke.png
> >>
> >> --
> >>
> >> 73,
> >> Ged.
> >>
> >> _______________________________________________
> >> smokeping-users mailing list
> >> smokeping-users at lists.oetiker.ch
> >> https://lists.oetiker.ch/cgi-bin/listinfo/smokeping-users
> >>
> >>
> >
> > --
> > Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten
> > http://it.oetiker.ch tobi at oetiker.ch ++41 62 213 9902
> >
> > _______________________________________________
> > smokeping-users mailing list
> > smokeping-users at lists.oetiker.ch
> > https://lists.oetiker.ch/cgi-bin/listinfo/smokeping-users
> >
>
>
>
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten
http://it.oetiker.ch tobi at oetiker.ch ++41 62 213 9902