On Tue, 03 Aug 2004 20:14:25 -0400, Ben Vitale <bsvitale@xxxxxxxxxxx> wrote: > Jack Bowling wrote: > > >On Mon, Aug 02, 2004 at 08:53:58PM -0400, Ben Vitale wrote: > > > > > >>Hi, > >> Yes, I realize this is an often asked question, and for that I > >>apologize. I have the two lines.. > >> > >>alias net-pf-10 off > >>alias ipv6 off > >> > >> ..in my /etc/modprobe.conf, and I have restarted several times since > >>they were put in place. They have had no effect, and I don't think IPv6 > >>is the culprit anyway.. my ifconfig shows all regular IP addresses. > >> I checked the ping times of my nameservers, and the one at the top > >>of /etc/resolv.conf has the best times - on average, 8.5ms. I would > >>assume this is just a Comcast provider problem, but this was not an > >>issue until I upgraded to FC2. > >> > >> > > > >Ben - I wonder if it is a problem with ECN on the nameserver or somewhere > >on the route? First check to see if you have ECN turned on in your kernel: > > > >cat /proc/sys/net/ipv4/tcp_ecn > > > >If you get a 1 back, it is turned on. As a test, turn it off by: > > > >echo 0 > /proc/sys/net/ipv4/tcp_ecn > > > >and see if the slow ping still happens. > > > >BTW, Ian Gulliver wrote a useful program called ecncheck which tests ECN > >along a route. There is also a companion program called ecnmx which > >compiles from the same tarball that does the same for mailservers. Look for > >it on freshmeat.net > > > > > > > > > Without any changes to kernel 2.6.6-1.435.2.3, > > [bvitale@vandelay ~]$ cat /proc/sys/net/ipv4/tcp_ecn > 0 > [bvitale@vandelay ~]$ > > [bvitale@vandelay ~/ecncheck]$ ecncheck 68.48.0.6 53 > With ECN: Connection accepted by ns02.rtchrd01.md.comcast.net > [68.48.0.6] at hop #7 > Without ECN: Connection accepted by ns02.rtchrd01.md.comcast.net > [68.48.0.6] at hop #7 > WARNING: Host doesn't support ECN but fails gracefully > [bvitale@vandelay ~/ecncheck]$ > > Not sure how to interpret that? > > Also, do you think 8.5ms is "slow" for a DNS server ping? > > Ben > > > Hi What's the dns query return time? what if you do a dig @ns02.rtchrd01.md.comcast.net comcast.net. also, have you tried to use a different dns server and see what the performance is? if it's under around 100 ms, then it's not the DNS server. I would use a different server if it's above 500 ms. You will get performance problems with DNS server of your ISPs from time to time. Yang
