[j-nsp] What exactly causes inconsistent RTT seen using ping utility in Junos?

[Saku Ytti]

Also it's now different again. Because Linux KVM running FreeBSD
guest. Lot of things are very slow now due to the Linux=>FreeBSD
limit.

And then again different with Junos Evolved.

But certainly LC_CPU doing something else and needing to send ICMP
towards RE will cause some jitter. Of course many other places could
introduce jitter too.

On Wed, 17 Apr 2019 at 13:33, Raphael Mazelier <raph at futomaki.net> wrote:
>
> >
> > For those of you interested in all the details around how the transit as
> > well as host-inbound and host-outbound traffic is handled on juniper MX3D
> > Trio architecture I'd recommend reading the following FREE book in its
> > entirety.
> > https://www.juniper.net/us/en/training/jnbooks/day-one/networking-technologi
> > es-series/packet-walkthrough-mx-series/
> > It's an excellent book that will answer, among others, all your questions
> > around where the ICMP might be delayed in the system and where and how it is
> > handled.
> >
> > I'd say it's a must read for all NetEng/Arch working with Juniper MX.
> >
> >
>
>
> This is sure a very good resource (from the excellent David Roy). I've
> already read it in the past and forget most of it. So for icmp we are in
> the case of an "exception packet" that are "punted" to the RE. But the
> document did not detail what really happen in the RE. It mention that
> theses packets transit by gigabit ethernet interfaces in the TPP
> proprietary protocol, but nothing after. What daemon is in charge of
> handling TPP flow on the RE side ? rpd ? for icmp is at the end the
> packet go through the freebsd kernel (seems logic but). And what cause
> latency in response ?
>
>
> --
> Raphael Mazelier
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp



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  ++ytti