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TalkTalk and DSCP and 19 second latency: Difference between revisions
TalkTalk and DSCP and 19 second latency (view source)
Revision as of 21:25, 7 December 2021
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This page is about in interesting problem that was reported to us, by a customer, in December 2021. We have written this up so that this page can be found if other people are seeing a similar problem.
We've masked the IP we're pinging in this page as it doesn't matter what IP you ping - in our tests though we were mostly pinging the IP of our LNS, as that is the 'next hop' on the customer's route to the internet. the examples below are pings to IPv4 addresses, but the same latency is seen on IPv6.
=TL;DR=
For some reason, TalkTalk's kit is reading IP DSCP marks from IPv4 & IPv6 packets inside PPPoE, and then putting them in a funny queuing setup which results in latency quickly increasing to over 19 seconds:
1408 bytes from x.x.x.x: icmp_seq=986 ttl=63 time='''19084.589 ms'''
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