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

Thu Dec 22 05:32:20 UTC 2022

Because there is no standard for discarding "old" traffic, only discard is for packets that hop too many times. There is, however, a standard for decrementing TTL by 1 if a packet sits on a device for more than 1000ms, and of course we all know what happens when TTL hits zero. Based on that, your packet could have floated around for another 53 seconds. Having said that, I'm not sure many devices actually do this (but its not likely it would have had a significant impact on this traffic anyway).

-----Original message-----
From:Jason Iannone <jason.iannone at gmail.com>

Sent:Wed 12-21-2022 11:11 am
Subject:Large RTT or Why doesn‘t my ping traffic get discarded?
To:North American Network Operators‘ Group <nanog at nanog.org>; 

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? As I understand it, buffers in SP gear are generally 100ms. According to my math this round trip should have been discarded around the 1 second mark, even in a long path. Maybe I should buy a lottery ticket. I don't get it. What is happening here?
 Jason
 64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=392 ttl=54 time=4834.737 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=393 ttl=54 time=4301.243 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=394 ttl=54 time=3300.328 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=396 ttl=54 time=1289.723 ms
Request timeout for icmp_seq 400
Request timeout for icmp_seq 401
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=398 ttl=54 time=4915.096 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=399 ttl=54 time=4310.575 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=400 ttl=54 time=4196.075 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=401 ttl=54 time=4287.048 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=403 ttl=54 time=2280.466 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=404 ttl=54 time=1279.348 ms
64 bytes from 4.2.2.2 <http://4.2.2.2> : icmp_seq=405 ttl=54 time=276.669 ms

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