Date: Tue, 18 Apr 1995 18:20:19 +0000 From: Matt Thomas <matt@lkg.dec.com> To: asami@cs.berkeley.edu Cc: hackers@FreeBSD.org Subject: Re: Case for FreeBSD presentation docs? Message-ID: <199504181820.SAA02020@whydos.lkg.dec.com> In-Reply-To: Your message of "Tue, 18 Apr 1995 13:47:50 MST." <199504182047.NAA04963@silvia.HIP.Berkeley.EDU>
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> Also, if people are aware of high-end network components supported by > FreeBSD, it will be great. I've found something about the DEC 21140 > based chip in the mail archive, is the driver fully functional now? > How much does it cost? (Those kinds of questions.) Same goes to the > FDDI driver. Mr. High Speed Networking here. :-) The DC21140 (Fast Ethernet; 100baseT) seems to be fairly stable. Adapters will run from about $200 to $250. However, Fast Ethernet isn't as well established as FDDI which means that choices for switches and hubs are limited. I've also found that Fast Ethernet is an improvement over normal 10Mb/s Ethernet, it still isn't as fast or robust as FDDI. The DEC FDDI adapters have 1MB of buffering on them whereas the DC21140 has around 4KB. Therefore the FDDI adapters are really good at absorbing bursts of traffic while the Fast Ethernet may not be. Long 10Mb/s Ethernet packets take about 1.2ms to transmit and 70us is about the minimum between small back-to-back packets. For Fast Ethernet, that drops to 120us and 7us respectively and when coupled with a smaller MTU (1500 < 4500) gives a considerably higher interrupt load. If you want rock-solid high speed networking right now, go with FDDI. Otherwise, wait out the Fast Ethernet teething problems and go with that. One thing to be noted as well, Fast Ethernet is "easier" to push data than FDDI since with FDDI you need to get the large window scale option to come into play to get optimum performance (a socket buffer size of 240KB is real nice). Fast Ethernet can use the standard socket buffer size. Does that help? Matt Thomas Internet: matt@lkg.dec.com U*X Networking WWW URL: http://ftp.dec.com/%7Ethomas/ Digital Equipment Corporation Disclaimer: This message reflects my Littleton, MA own warped views, etc.
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