Date: Tue, 10 Jul 2001 17:08:59 -0400 (EDT) From: bicknell@ufp.org To: FreeBSD-gnats-submit@freebsd.org Subject: conf/28882: Network defaults are absurdly low. Message-ID: <200107102108.f6AL8xF03740@ussenterprise.ufp.org>
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>Number: 28882 >Category: conf >Synopsis: Network defaults are absurdly low. >Confidential: no >Severity: non-critical >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: change-request >Submitter-Id: current-users >Arrival-Date: Tue Jul 10 14:10:00 PDT 2001 >Closed-Date: >Last-Modified: >Originator: Leo Bicknell >Release: FreeBSD 4.2-RELEASE i386 >Organization: United Federation of Planets >Environment: FreeBSD 4.x based systems, they all seem to be the same for this particular problem. >Description: The following sysctl variables show FreeBSD defaults: kern.ipc.maxsockbuf: 262144 net.inet.tcp.sendspace: 16384 net.inet.tcp.recvspace: 16384 These are absurd. The tcp.sendspace/recvspace limit the window size of a TCP connection, which in turn limit throughput. On a 50ms coast to coast path, it imposes a limit of 16384 Byes * 1000ms/sec / 50ms = 327 KBytes/sec. This is a third of what a 10Mbps/sec cable modem should be able to deliver, say nothing of a 100Meg FE connected host (eg server) at an ISP. Go further, 155ms to Japan from the east coast of the US and you're down to under 100 KBytes/sec, all due to a poor software limit. >How-To-Repeat: Do some FTP's from a well connected host to a far away well connected host with these values. You can see the probelms first hand. >Fix: To allow a 100Mbps FE host to get 100Mbps to Japan, I put the following values in /etc/sysctl.conf: kern.ipc.maxsockbuf=16777216 net.inet.tcp.sendspace=4194304 net.inet.tcp.recvspace=4194304 I suspect the FreeBSD authors will want tobe more conservative to allow lower memory machines to operate properly, so I suggest the following system defaults: kern.ipc.maxsockbuf=1048576 net.inet.tcp.sendspace=524288 net.inet.tcp.recvspace=524288 I believe it is important to make these defaults as few users know to enable them. I also believe that: tcp_extensions="YES" should be the default, as they are highly unlikey to break anything in this day and age, and are necessary to use windows over 64K. An interesting compromise would be to only set the settings I suggest if tcp_extensions is turned on. >Release-Note: >Audit-Trail: >Unformatted: To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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