Date: Wed, 18 Sep 1996 23:07:02 -0700 From: David Greenman <dg@root.com> To: Julian Elischer <julian@current1.whistle.com> Cc: questions@freebsd.org Subject: Re: Giant Sized Ethernet Packets Message-ID: <199609190607.XAA01531@root.com> In-Reply-To: Your message of "Wed, 18 Sep 1996 22:47:11 PDT." <Pine.BSF.3.95.960918224427.3098C-100000@current1.whistle.com>
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> > >On Wed, 18 Sep 1996, David Greenman wrote: > >> >I was wondering if it is possible to send giant sized ethernet packets (>1500 >> >bytes say 1550) using the current 'de' driver for the SMC 10/100 DEC 21140 >> >cards. >> >> No. >Bzzzzt! >Sorry, but thanks for playing.. >don't forget to collect your tie-pin on the way out.. >The chip it trivially programeed to do this.. we do it all teh time with Again, read the question and what I replied. The current de driver does NOT support this! >15500 byte packets.. (10 x normal) > >It's to support legacy systems that date from the dawn of ethernet when >the >packet size was not so 'fixed' as it is now.. Are you sure that this works in 100BASE-TX mode? The question was about the DC21140... >> >If not, would somebody know if this is possible with the above h/w >> >at all? >> >> The answer to this is complicated, but it basically ends up being "no". >> I just spent about 15 minutes looking over the DC21140 hardware reference >> manual. It appears that the chip can except larger frames, but it signals >> an error condition when this occurs, so I don't think you could do this >> as a normal mode of operation. It also appears that it is possible to >> generate larger than 1500 byte packets, but the frames wouldn't be ethernet >> (the type/length field would not be IEEE 802.3) and you'd have to invent your >> own encapsulation. ...that's how I read it, anyway. Perhaps Matt Thomas will >> correct me on this. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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