From: Richard Gallagher (rgallagh@cisco.com)
Date: Fri Jul 30 2004 - 10:56:58 GMT-3
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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