Date: Sun, 08 Jun 2008 07:01:55 -0400 From: Jon Radel <jon@radel.com> To: "Gelsema, P \(Patrick\) - FreeBSD" <freebsd@superhero.nl>, freebsd questions <freebsd-questions@freebsd.org> Subject: Re: NFE setting manually to 1000baseT and half duplex Message-ID: <484BBC23.90505@radel.com> In-Reply-To: <56297.82.95.198.17.1212870050.squirrel@webmail.superhero.nl> References: <56297.82.95.198.17.1212870050.squirrel@webmail.superhero.nl>
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[-- Attachment #1 --] Gelsema, P (Patrick) - FreeBSD wrote: > Hi List, > > I am using the nfe driver on Freebsd 7.0R and I am unable to change > the NIC driver manually to 1000baseT with half-duplex. I believe I am > not getting the max out of my network connection and want to see if > changing the duplex will help. Even if you do have hardware that supports half-duplex gigabit ethernet on both ends, the need to do carrier extension for any frame shorter than 512 bytes so that CSMA/CD actually works on a reasonable sized cable, does horrible things to your throughput if you've got lots of small frames. (In other words, at gigabit speeds, frames smaller than 512 bytes zip down the wire so quickly that you can no longer reliably detect collisions, so the frames all get padded.) I'm having trouble wrapping my head around any circumstances other than horribly, horribly broken hardware or software where half-duplex would increase your performance over full-duplex. That said, most (an imprecise way saying "every time I've looked this has been the case, but I generally no longer bother looking") gigabit ethernet hardware I've ever touched has been incapable of doing half-duplex when it's being used at gigabit speeds. The specs for doing it exist more for theoretical completeness than out of practical utility. See, for example http://www.intel.com/network/connectivity/resources/doc_library/white_papers/solutions/copper_guide/gig_over_copper.htm for a discussion on this and related topics. My suggestion would be to let both sides auto-detect if they're both capable of gigabit ethernet. --Jon Radel [-- Attachment #2 --] 0 *H 01 0 + 0 *H 100\mtv0 *H 0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA0 080324165921Z 090324165921Z0^10 URadel10U* Jon Thomas10UJon Thomas Radel1 0 *H jon@radel.com0"0 *H 0 t,P p# ٬q_2=L-^m >z3ʟV![([ AoE}ϛ3/6?cWx(/)'$6sTl<*i'=uox Mbt rdtnxud1R6T>zU0FZ,vN9NP{>qE`^P; *Wg/jN*OVՠQMB(=: *0(0U 0 jon@radel.com0 U 0 0 *H h!oܨ[А!fN#[Z b$3?x&$~Ħ9}`MX[It}/bXZajgxɥ' 2NrtWAr sFި'^@mDVw\)00\mtv0 *H 0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA0 080324165921Z 090324165921Z0^10 URadel10U* Jon Thomas10UJon Thomas Radel1 0 *H jon@radel.com0"0 *H 0 t,P p# ٬q_2=L-^m >z3ʟV![([ AoE}ϛ3/6?cWx(/)'$6sTl<*i'=uox Mbt rdtnxud1R6T>zU0FZ,vN9NP{>qE`^P; *Wg/jN*OVՠQMB(=: *0(0U 0 jon@radel.com0 U 0 0 *H h!oܨ[А!fN#[Z b$3?x&$~Ħ9}`MX[It}/bXZajgxɥ' 2NrtWAr sFި'^@mDVw\)0?0 0 *H 01 0 UZA10U Western Cape10U Cape Town10U Thawte Consulting1(0&U Certification Services Division1$0"UThawte Personal Freemail CA1+0) *H personal-freemail@thawte.com0 030717000000Z 130716235959Z0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA00 *H 0 Ħ<UsUNʙZ hup [v :aQP 0cZ,p+Z?qV˯< 6$*+w=+>@dקe*TH<a@ dr` 00U 0 0CU <0:08642http://crl.thawte.com/ThawtePersonalFreemailCA.crl0 U 0)U "0 0 10UPrivateLabel2-1380 *H HP . fgCL!6 -6/ P p<ab:~ t%Pb'qW%ݩ9 Oe_N4[5MwV!x!5$ F]_eO1d0`0v0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CAmtv0 + 0 *H 1 *H 0 *H 1 080608110155Z0# *H 1%QWm:L10R *H 1E0C0 *H 0*H 0 *H @0+0 *H (0 +71x0v0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CAmtv0 *H 1xv0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CAmtv0 *H 4+ Y{W`7yV$TOwPciѐB炫eTsq帞K :7*ٲ[A r2W"<ϓ?4 ]2!G=l ߶{+z H+#Ύ[Vq̣EdSk<9^<thr{h-Z-jj>s# L4.ڗf u"swK^OQubr!?IԿzw^iyA [help
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