> Anyhow, two NTP related questions: > 1) What kind of accuracy/precision loss occurs when you run ntpd on > an asymmetrical connection (e.g., DSL).
My understanding is that, provided the asymmetry is the same for all traffic, all it does is produce an unobservable offset. When I say "unobservable", I mean, one that cannot be seen over the network, since the offset is reversed by the same effects that generated it in the first place. Now, _you_ probably have network access that does not get affected by the asymmetry (other machines on a LAN with it). Those machines can see the offset, but they will have trouble noticing it unless they have something more accurate to compare it to. You may not care, since the offset is on the order of the latency difference induced by the asymmetry. > 2) Do any of you use the limit and/or kod options in your config? I believe some people do. I don't. > I've noted some really obnoxious clients (bursts of 20+ queries at a > time, every minute or so) hitting my servers in the past and wondered > if any of the other pool admins take proactive steps against such > clients. I do, but not limit/kod. Instead, I have a process snooping port-123 traffic; if it sees abusive-looking traffic from an IP, that IP gets dropped in my border router's "drop on sight" list. (That list is currently cruising at about 700 entries, and I've seen it jump as high as about 1500 - NTP is not the only kind of traffic that can earn an IP a place on that list.) Just doing a spot-check with tcpdump, though, most of my port-123 traffic at the moment is people sending me packets with RFC1918-private source addresses (which of course I don't reply to - ntpd doesn't even see them, actually, because that's a statically configured drop criterion at my border). > Glad to find a list to communicate with all of you! Welcome to the madhouse. :) /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML [email protected] / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
