From: ccie2be (ccie2be@nyc.rr.com)
Date: Fri Jul 30 2004 - 13:22:14 GMT-3
Oh, OK. Thanks.
I had the impression that it was possible to generate 4 pings starting
simultaneously.
One last question:
Do you know of or can you think of any way to use pings to generate a
specified rate of traffic, for example, 32kbps or 48kbps, etc.?
If there were such a way of doing so, I think that could be very helpful
both for testing dialer load-threshold as well as numerous QoS problems, for
example, FRTS, CAR, GTS, etc.
Thanks again. You've been wonderfully helpful.
Tim
----- Original Message -----
From: "Daniel Ginsburg" <dginsburg@mail.ru>
To: "Group Study" <ccielab@groupstudy.com>
Sent: Friday, July 30, 2004 11:44 AM
Subject: Re: Generating enough pings to make dialer load threshold kick in
> Hi, Tim.
>
> I think you have to take it literally:
> telnet R2
> ping R1 size 1500 repeat 10000
> ctrl-shift-6 x
> telnet R2
> ping R1 size 1500 repeat 10000
> ctrl-shift-6 x
> telnet R2
> ping R1 size 1500 repeat 10000
> ctrl-shift-6 x
> telnet R2
> ping R1 size 1500 repeat 10000
> ctrl-shift-6 x
>
>
> On Fri, Jul 30, 2004 at 11:29:48AM -0400, ccie2be wrote:
> > Hi Daniel,
> >
> > Thanks for that very detailed and insightful explanation. It is truly
very
> > appreciated and helpful.
> >
> > Do you recall seeing a post yesterday from Richard Dumoulin. He
suggested
> > creating 4 telnet sessions and pinging simultaneously from all 4 telnet
> > sessions to generate a greater traffic load.
> >
> > I asked him how exactly to do that but didn't hear back. Have any ideas
> > about how I could do that?
> >
> > Thanks again. Tim
> >
> >
> > ----- Original Message -----
> > From: "Daniel Ginsburg" <dginsburg@mail.ru>
> > To: "Group Study" <ccielab@groupstudy.com>
> > Sent: Friday, July 30, 2004 10:11 AM
> > Subject: Re: Generating enough pings to make dialer load threshold kick
in
> >
> >
> > > As far as I know timeout parameter affects only how long router waits
> > > for reply before printing '.' instead of '!'.
> > >
> > > I ran ping with default timeout, with 0 timeout and with timeout 100.
> > > All three completed in approximately same time. My conclusion is that
> > > rate of packets dictated only by round-trip time.
> > >
> > > Please note that 50% is upper bound. It can be significantly less is
> > > case of LFN (long fat pipe).
> > >
> > >
> > > On Fri, Jul 30, 2004 at 03:56:58PM +0200, Richard Gallagher wrote:
> > > > What about setting the timeout to zero? Then we don't ever hang
around
> > > > and wait for a response. We just send as fast as the router can.
> > > >
> > > > On Fri, 2004-07-30 at 15:29, Daniel Ginsburg wrote:
> > > > > On Thu, Jul 29, 2004 at 10:50:38AM -0400, ccie2be wrote:
> > > > > > Hey Richard,
> > > > > >
> > > > > > I don't dispute or disagree with what you're saying but how do
know
> > that 4
> > > > > > simultaneous pings with a packet size of 1500 will load the
channel
> > to over
> > > > > > 80%? How do you know what load exactly that will put on the
> > channel? If
> > > > > > you don't know exactly what load that puts on the channel, how
do
> > you know
> > > > > > that that is NOT, for example, a 65% load or 75 % load?
> > > > > >
> > > > >
> > > > > Unlike many other ping implementations which send 1 echo request
per
> > > > > interval cisco's one sends next echo request as soon it receives
echo
> > > > > reply or waits for timeout if request or reply is lost. So average
> > > > > bandwidth utilization in one direction with one 'ping a.b.c.d size
X'
> > > > > will never exceed 50%.
> > > > >
> > > > > Let me illustrate this with the diagram
> > > > >
> > > > > ---
> > > > > ^ BW
> > > > > |
> > > > > | (1) (3) (5)
> > > > > |----- ----- -----
> > > > > |
> > > > > | (2) (4)
> > > > > ----------------------------------------->
> > > > > Time
> > > > >
> > > > > (1) router transmits ping request
> > > > > (2) router waits for ping reply
> > > > > (3) router transmits next ping request
> > > > > (4) router waits for next ping reply
> > > > > etc.
> > > > >
> > > > > So router uses the link almost[1] exactly half of the time. Please
> > note
> > > > > that this 50% figure almost[1] doesn't depend on size of echo
> > > > > request/reply.
> > > > >
> > > > > [1] I'm saying almost because router needs to ponder a very short
> > period
> > > > > of time before replying to echo request. This period of time may
be
> > > > > negligible or not depending on speed of the link.
> > > > >
> > > > > Two simultaneous pings will theoreticaly saturate the link. Run
four
> > to
> > > > > make sure ;)
> > > >
> > > >
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