Date: Tue, 1 Jun 1999 11:03:04 -0700 (PDT) From: "Jonathan M. Bresler" <jmb@hub.freebsd.org> To: dennis@etinc.com Cc: thorpej@nas.nasa.gov, hackers@freebsd.org Subject: Re: xl driver for 3Com Message-ID: <19990601180304.A259715024@hub.freebsd.org> In-Reply-To: <199906011650.MAA24039@etinc.com> (message from Dennis on Tue, 01 Jun 1999 11:46:22 -0400)
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> > If your nic driver chains packets (such that there is no time in between) > you will see good throughput from the box but your overall network > performance will suffer. A PCI card with continueous traffic can completely > hog your lan (particularly at 10Mb/s)...which can cause a lot more > collisions on your network as other devices will not have access until the > hog is finished sending. For "Fairness" gaps in between frames are better > as you approach capacity of your wire. > > Dennis the interframce gap will allow other hosts to contend for the wire. the ethernet capture effect decreases as the number of hosts on the segment increases. the interpacket gap is 9.6uS (or 96 bit times). an ethernet card listens to the wire before transmitting a card that is not able to transmit because the wire is busy will begin transmitting as soon as the wire goes quiet. the max length of an ethernet is 46 bit times. so a waiting card will alaways get first crack at the wire. capture effect is due to stations colliding in trying to access the wire. those that dont collide, are immune to the capture effect and get the wire first. http://wwwhost.ots.utexas.edu/ethernet/papers.html jmb To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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