Date: Sat, 18 Dec 1999 09:08:08 +1300 From: "Juha Saarinen" <juha@saarinen.org> To: "daniel B" <danielb@pacex.net> Cc: <freebsd-questions@freebsd.org> Subject: RE: Not such good networking performance with FreeBSD Message-ID: <LNBBIBDBFFCDPLBLLLHFMEGNGGAA.juha@saarinen.org> In-Reply-To: <Pine.BSF.4.10.9912170933560.2761-100000@almazs.pacex.net>
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Hi Daniel, I can only give you some general advice based on my experience with RADSL (rate-adaptive DSL), and not anything terribly useful for FreeBSD... My telco runs ATM over DSL over which a PPP connection to my ISP is encapsulated, so to speak. To start with, the telco had some problems with its DSLAMs that caused long pauses and sometimes routing timeouts, making interactive apps like ssh unusable. The telco said this was partly due to ATM cells being lost which is disastrous for the larger IP packets, as it causes lots of retransmissions... not so sure about that, but anyway, it shows the complexity of squeezing that amount of bandwidth through plain old copper wires, I guess. Even though the router says I've got 5.7Mbps (bits per second) to the exchange, the telco appears to have capped each TCP session at 2Mbps max (grrr...). That's still pretty good, but what complicates things for me is the high latencies I see as soon as I connect to servers outside New Zealand: traceroute to pacex.net (204.1.219.156), 30 hops max, 40 byte packets 1 m10 (192.168.1.254) 1.075 ms 0.993 ms 0.913 ms 2 203-79-82-254.adsl-wns.paradise.net.nz (203.79.82.254) 86.952 ms 85.922 ms 66.505 ms 3 192.168.253.225 (192.168.253.225) 45.744 ms 45.747 ms 45.314 ms 4 kelly.ipnet.paradise.net.nz (203.96.153.138) 46.478 ms 45.642 ms 46.252 ms 5 cassandra.paradise.net.nz (203.96.152.3) 46.431 ms 45.809 ms 46.426 ms 6 a4-0-0-5.akbr1.netgate.net.nz (202.37.246.77) 55.911 ms 56.173 ms 56.100 ms 7 a0-0-0-2.tkbr1.netgate.net.nz (202.37.246.121) 57.310 ms 56.517 ms 59.378 ms Leaving NZ, going to LA: 8 s1-1-4.labr1.netgate.net.nz (202.37.245.166) 238.127 ms 181.145 ms 181.776 ms 9 s5-0-0.lsanca1-cr1.bbnplanet.net (4.24.24.17) 180.932 ms 185.284 ms 181.803 ms 10 p2-1.lsanca1-ba1.bbnplanet.net (4.24.4.5) 184.113 ms 180.490 ms 181.832 ms 11 p7-0.lsanca1-br1.bbnplanet.net (4.24.4.2) 236.089 ms 237.078 ms 236.339 ms <snip> 22 dsl1.irvnca01.us.ra.verio.net (192.215.247.103) 218.263 ms 218.406 ms 215.212 ms 23 compappcon-dw.customer.ni.net (204.1.216.14) 216.128 ms 217.187 ms 218.471 ms 24 almazs.pacex.net (204.1.219.156) 272.606 ms 273.758 ms 272.252 ms These are quite good roundtrip times for me actually. Sometimes they go well into the 300-400ms range, which really makes applications that depend on opening lots of connections and getting small files (like Web browsing) suck, despite my multi-Mbps connection. Anyway, what I've found to help on all operating systems apart from FreeBSD is to enable and tune the TCP High Performance extensions settings (RFC 1323). It's less than obvious how you do this on FreeBSD, unfortunately. This is what I've dug up so far... correct me if I'm wrong by all means. Put: tcp_extensions="YES" into /etc/rc.conf Then, it looks like you have to use the sysctl command to check and tune some of the TCP settings: sysctl -w net.inet.tcp.sendspace=65536 && sysctl -w net.inet.tcp.recvspace=65536 should give you 65KB TCP windows -- for some reason, FreeBSD defaults to 16KB which is quite small. There are two more settings which I can't find documented anywhere, but which I suspect affect things as well: net.inet.tcp.mssdflt: 512 (is this the default Maximum Segment Size? shouldn't it be 1460 bytes?) net.inet.raw.recvspace: 65536 (I've bumped it up as an experiment -- think the default is 8192). sysctl -a | less shows you all the settings. Other than that, having an MTU/MRU of 1500 seems to work the best, and you might want to check that you're not using e.g. PPP compression settings that aren't compatible with with your ISP's peer. I have no idea how well stuff like PPP address field and header compression works with high bitrate connections, but I suspect that enabling them would add latency. Hope the above is of some use to you... Cheers, -- Juha > -----Original Message----- > From: daniel B [mailto:danielb@pacex.net] > Sent: Saturday, 18 December 1999 06:41 > To: Juha Saarinen > Cc: freebsd-questions@freebsd.org > Subject: RE: Not such good networking performance with FreeBSD > > > Sorry to intrude on this thread; but I am kinda having the same problem. > My DSL speed was kinda OK when I wwas running 2.2.8 but ever since I > upgraded to 3.x releases I just get poor performance and sometimes ssh > kinda hungs up when accessing lan via ppp. > Are there tricks and ways to get better networking performance on FreeBSD? > this may soung very trival but I have realy noticed performance drop on > this FreeBSD boxens. > > Dan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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