Date: Tue, 8 Jul 2008 21:47:22 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Erik Trulsson <ertr1013@student.uu.se> Cc: FreeBSD Net <freebsd-net@FreeBSD.org>, Andre Oppermann <andre@FreeBSD.org>, Ingo Flaschberger <if@xip.at>, Paul <paul@gtcomm.net> Subject: Re: Freebsd IP Forwarding performance (question, and some info) [7-stable, current, em, smp] Message-ID: <20080708214624.W1168@besplex.bde.org> In-Reply-To: <20080707131550.GA69202@owl.midgard.homeip.net> References: <486D35A0.4000302@gtcomm.net> <alpine.LFD.1.10.0807041106591.19613@filebunker.xip.at> <486DF1A3.9000409@gtcomm.net> <alpine.LFD.1.10.0807041303490.20760@filebunker.xip.at> <486E65E6.3060301@gtcomm.net> <alpine.LFD.1.10.0807052356130.2145@filebunker.xip.at> <4871DB8E.5070903@freebsd.org> <20080707191918.B4703@besplex.bde.org> <4871FB66.1060406@freebsd.org> <20080707213356.G7572@besplex.bde.org> <20080707131550.GA69202@owl.midgard.homeip.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, 7 Jul 2008, Erik Trulsson wrote: > On Mon, Jul 07, 2008 at 10:30:53PM +1000, Bruce Evans wrote: >> On Mon, 7 Jul 2008, Andre Oppermann wrote: >>> The theoretical maximum at 64byte frames is 1,488,100. I've looked >>> up my notes the 1.244Mpps number can be ajusted to 1.488Mpps. >> >> Where is the extra? I still get 1.644736 Mpps (10^9/(8*64+96)). >> 1.488095 is for 64 bits extra (10^9/(8*64+96+64)). > > A standard ethernet frame (on the wire) consists of: > 7 octets preamble > 1 octet Start Frame Delimiter > 6 octets destination address > 6 octets source address > 2 octets length/type > 46-1500 octets data (+padding if needed) > 4 octets Frame Check Sequence > > Followed by (at least) 96 bits interFrameGap, before the next frame starts. > > For minimal packet size this gives a maximum packet rate at 1Gbit/s of > 1e9/((7+1+6+6+2+46+4)*8+96)/ = 1488095 packets/second > > You probably missed the preamble and start frame delimiter in your > calculation. Thanks. Yes, that was it. Bruce
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20080708214624.W1168>