[c-nsp] Cisco IOS ping utility reports lower RTT than possible

[Aaron]

The initial is most likely due to arp. Depending how long it is between
runs, the arp cache may clear.

On Fri, May 3, 2019 at 10:57 AM Octavio Alvarez <octalcnsp at alvarezp.org>
wrote:

> On 5/3/19 5:14 AM, Martin T wrote:
> > Hi Octavio,
> >
> > instead of a two-card laptop I used the available ports in server
> > named "svr", but in principle I built the setup you described:
> >
> > CISCO1921[Gi0/0] <-> [eno1]test-br[eno2] <-> [eno3]svr
>
> I intended to have an independent measurement tool (including an
> independent clock) but that should be good enough too, as it's highly
> unlikely that you have serious clock drifting issues.
>
> > Success rate is 100 percent (5/5), round-trip min/avg/max = 8/9/12 ms
>
> > As seen above, minimum measurement was 8ms and average was 9ms.
>
> I don't know how far (in ms) is the router from the server but max=12ms
> also looks way off.
>
> > Cisco IOS ping command inserts the timestamp into the payload of the
> > ICMP "echo request" message and at least it seems to increment it, i.e
> > that part seems to be fine.
>
> Does it? If you are referring to the -ttt output than that is done by
> tcpdump.
>
> Good experiment. Sorry to say that I don't know why the measurements are
> so inaccurate. I kow the Cisco ISR 1912 is a very low-end device but I
> don't know if so enough to get into this level of inaccuracy.
>
> Octavio.
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>