[Novalug] Low Internet throughput -- Due to high packet loss?
gmaxwell at gmail.com
Mon Oct 26 18:21:31 EDT 2009
On Mon, Oct 26, 2009 at 6:12 PM, Aaron Porter <atporter at gmail.com> wrote:
> On Mon, Oct 26, 2009 at 3:04 PM, Paul D. Bain <paulbain at pobox.com> wrote:
>> Does this output denote __16%__ packet loss? Is that not very high?
> 16% is insanely high.
That is an intermediate step in the MTR. There doesn't actually
appear to be any loss by the end of that trace.
You need to take middle of the path loss reported by MTR with a grain
of salt: Loss can be falsely reported due to routers rate limiting
their own ICMP responses (to prevent people from causing trouble by
attacking the router) or because there is routing asymmetry and that
particular router reaches back to you via a path which is losing
packets but which neither the traffic from you to the far side or the
far side to you actually takes.
Likewise on latency: High latency at one hop is only indicating a
possible real problem if it's high by the end. Middle high numbers can
be due to throttling ICMP towards the router itself (rather than
through it) or, again, due to inconsequential path asymmetry.
Basically: If the loss isn't showing up at the last displayed hop,
it's not real.
However if you see loss start someplace in the middle and persist to
the end then its a good bet that the loss began around the middle
point where you see it reflected (which is 100% of the use of seeing
mid-path loss numbers).
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