From: Jeroen Massar <jeroen@massar.ch>
To: sam@circlenet.us, nanog@nanog.org
Subject: Re: Help me make sense of these traceroutes please> Hello Nanog community,
> I would like to enlist your help with understanding this latency I'm
> seeing.You are likely seeing the effects of asymmetric routing.
. .. or the effect of passing traffic through NSA infrastructure.
SCNR, #m
...
> You are likely seeing the effects of asymmetric routing.
. .. or the effect of passing traffic through NSA infrastructure.
Ah... NSA. That's probably it.
So much for my theory of a Router virtual chassis straddling the atlantic.
or the extra kinetic energy carried by the overseas-bound packet took
longer for the router to absorb and rebound with an ICMP.
But in all seriousness --- what is probably happening here, is the result
of extra "hops" that don't show up in traceroute.
MPLS tunnels could well fit the bill.
Other things to consider when latency seems sensitive to destination IP ---
are preceding device in the traceroute might also have multiple links to
the same device; with one link congested and some form of IP-based load
sharing, that happens to be the toward-overseas link.
Start at slide 50:
This is documented further by the following Nanog presentation. http://www.nanog.org/meetings/nanog47/presentations/Sunday/RAS_Traceroute_N47_Sun.pdf
-Marcus
Thanks to everyone who responded off list and on.
Sam Moats