nanog mailing list archives

Re: Large RTT or Why doesn't my ping traffic get discarded?


From: Dave Taht <dave.taht () gmail com>
Date: Wed, 21 Dec 2022 13:19:54 -0800

There's this thing called bufferbloat...

On Wed, Dec 21, 2022 at 11:58 AM William Herrin <bill () herrin us> wrote:

On Wed, Dec 21, 2022 at 9:10 AM Jason Iannone <jason.iannone () gmail com> wrote:
Here's a question I haven't bothered to ask until now. Can someone please help me understand why I receive a ping 
reply after almost 5 seconds?

64 bytes from 4.2.2.2: icmp_seq=398 ttl=54 time=4915.096 ms
64 bytes from 4.2.2.2: icmp_seq=399 ttl=54 time=4310.575 ms
64 bytes from 4.2.2.2: icmp_seq=400 ttl=54 time=4196.075 ms
64 bytes from 4.2.2.2: icmp_seq=401 ttl=54 time=4287.048 ms
64 bytes from 4.2.2.2: icmp_seq=403 ttl=54 time=2280.466 ms
64 bytes from 4.2.2.2: icmp_seq=404 ttl=54 time=1279.348 ms
64 bytes from 4.2.2.2: icmp_seq=405 ttl=54 time=276.669 ms

Hi Jason,

This usually means a problem on the Linux machine originating the
packet. It has lost the ARP for the next hop or something similar so
the outbound ICMP packet is queued. The glitch repairs itself,
briefly, releasing the queued packets. Then it comes right back.

Regards,
Bill Herrin


--
For hire. https://bill.herrin.us/resume/



-- 
This song goes out to all the folk that thought Stadia would work:
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Dave Täht CEO, TekLibre, LLC


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