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Comcast's last mile network in Seattle has been struggling in some areas from the morning until around 4 to 5 PM. It's not massive loss, but enough to disrupt video conference. Run a mtr towards an Internet dest and you'll see loss at the first hop and everything behind it.



Mtr isn’t a reliable measure of packet loss. Routers drop “extra” packets like ping before they drop “paying” packets.


Yes I'm well aware of routers policing TTL=1 packets, but if you see consistent loss all the way down it's usually a sign. This compared to seeing individual spikes on intermediate routers which are usually control plane policing.


mtr uses UDP data packets, as far as I am aware.

Yes, the ICMP response packets could still be skewed, and the effect you mention is definitely real, but on a good connection, usually there should not be much to drop at all, neither TCP/UDP traffic nor ICMP packets.


>mtr uses UDP data packets, as far as I am aware.

Doesn't matter what it uses (though by default MTR does use regular old ICMP Echo - you have to specify -u or -t to get it in UDP or TCP mode). When TTL expires it still requires an ICMP TTL Exceeded be sent, regardless of whether or not you were sending ICMP through it.

Traceroute implementations in general are probably telling most everyone in this thread a lot less than they think, even without icmp deprioritization being taken into account.

https://archive.nanog.org/meetings/nanog47/presentations/Sun... is worth a read for most anyone that's ever attempted to use traceroute to troubleshoot networking, because they're almost certainly doing it wrong.




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