Hello, Tom,
Tom Yates wrote:
: According to https://www.ntppool.org/a/MadHatter , my server's not
: doing so well, since the afternoon of 18/4. Interesting thing is
: that the graph below is the same server, reached via ipv6. So the
: server's not the problem.
:
: I've asked my ISP if they're doing any kind of anti-DDoS filtering
: that might be blocking ipv4, and so far they say no.
:
: Any ideas where I can look next? I assume everyone's not seeing
: similar issues, or someone would have said so already here.
I see similar problems with my server:
https://www.ntppool.org/a/Yenya
unlike yours, I see only occasional but deeper drops in IPv4 score,
IPv6 is fine. It seems that filtering or rate limiting (or packet loss
in general) happens several ASs upstream. What I usually do is to
look at the score of other pool members near me (in the same AS,
then in the same city in another AS). If I see a similar pattern in their
score graphs, the problem is probably not anywhere near me.
I also tried to catch NTP traffic comming through my router/fw with tcpdump,
and the number of incoming and outgoing NTP packets is about the same.
Which means my server and my router are not the ones who drop them.
Sometimes I see low score only in the NTP Pool Beta monitoring site,
but sometimes only in the production site.
It seems that the times when the Internet was TCP/IP are gone :-),
now anything beyond ICMP, DNS, and HTTP is suspicious...
-Yenya
--
| Jan "Yenya" Kasprzak <kas at {fi.muni.cz - work | yenya.net - private}> |
| http://www.fi.muni.cz/~kas/ GPG: 4096R/A45477D5 |
IORING_OP_NOP ... the benefits of doing nothing asynchronously are minimal,
but sometimes a placeholder is useful. --Jonathan Corbet at LWN
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