Date: Thu, 04 Jan 2007 18:05:27 -0500 From: Bob McIsaac <bobmc@bobmc.net> To: Doug Hardie <bc979@lafn.org> Cc: questions@freebsd.org Subject: Re: network tuning and performance troubleshooting Message-ID: <459D8837.20502@bobmc.net> In-Reply-To: <68EDC705-4D55-4B69-8F97-D7901A2F5D71@lafn.org> References: <459CA574.4050001@bobmc.net> <68EDC705-4D55-4B69-8F97-D7901A2F5D71@lafn.org>
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Doug Hardie wrote: > > On Jan 3, 2007, at 22:57, Bob McIsaac wrote: > >> Problem: Browser status 'looking up address' for 10 seconds for any >> web page clicked. Slashdot takes almost a minute to load. But FTP >> performance is good and running a shoutcast stream is no problem. >> Sending mail via my ISP is slow. >> >> Investigation: - "sysctl -a | grep net | less" shows a ton of >> variables >> with values assigned. Ping of nameserver assigned by dhcp takes 0.5ms. >> Ping of freebsd.org = 90ms. Nothing obvious in loader.conf or >> rc.conf (defaults). /var/log/messages has only startup info. >> >> Question: - How to solve this thorny performance problem? -Bob- > > You might want to run tcpdump and monitor one of those slow loads. > Include the timestamp in the output and see what it is doing during > that time. I would tend to suspect DNS timeouts. > > tcpdump confirms there is a ten second delay as seen on the browser. 1. there are some UDP packets to/from the nameserver. 2. nothing happens for ten seconds 3. now there is a TCP connection tcpdump: listening on vr0, link-type EN10MB (Ethernet), 17:34:07.537419 proto: UDP (17) 192.168.1.102.53032 > 192.168.1.254.domain: 45959+ A? www.google.ca. (31) 17:34:07.545218 IP proto: UDP (17) 192.168.1.254.domain > 192.168.1.102.53032: 45959 6/7/4 www.google.ca. CNAME[|domain] 17:34:07.545500 IP proto: UDP (17) 192.168.1.102.64463 > 192.168.1.254.domain: 45960+ AAAA? www.google.ca. (31) 17:34:07.868410 IP proto: UDP (17) 192.168.1.102.61375 > 192.168.1.254.domain: 48085+ PTR? 254.1.168.192.in-addr.arpa. (44) 17:34:12.545947 IP proto: UDP (17) 192.168.1.102.54649 > 192.168.1.254.domain: 45960+ AAAA? www.google.ca. (31) 17:34:12.868866 IP proto: UDP (17) 192.168.1.102.55840 > 192.168.1.254.domain: 48085+ PTR? 254.1.168.192.in-addr.arpa. (44) <<<<<<<< nothing happens for 10 seconds?? >>>>>>>>>>>> 17:34:22.546051 (tos 0x0, ttl 64, id 226, offset 0, flags [DF], proto: TCP (6), length: 64) 192.168.1.102.52363 > qb-in-f147.google.com.http: S, cksum 0x3aa5 (correct), 1762925400:1762925400(0) win 65535 <mss 1460, nop,wscale 1, nop,nop,timestamp 1758025 0,sackOK,eol>
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