Re: maximum Ethernet throughput


Charles Hedrick (hedrick@aramis.rutgers.edu)
Wed, 9 Mar 88 13:07:07 EST


We know of no evidence that Suns violate the minimum spacing
requirement. Indeed if they did, things that work for us would fail,
so I don't believe it. However 8Mb transfers would certainly open us
to a whole range of things that have never been tested before. While
Ethernet should in theory tolerate multiple simultaenous high-speed
users, as far as I know it isn't being used that way now. Proper
functioning would depend upon everybody's random backoff working
right. Given the past history in networking, I am not prepared to bet
that untested features work. One could imagine failures everywhere
from Ethernet controller microcode to device drivers to protocols
implementation. It would also let us test whether protocol designs
implicitly assume that an Ethernet can never be congested. Certainly
DECnet deals very differently with Ethernet than with point to point
lines, and to a certainly extent IP does as well. When designers were
thinking of Ethernet, I rather suspect they might not have considered
the possibility that one host could actually use all 10Mb of
bandwidth. It is possible that protocols such as ARP and DECnet hello
would have to be rethought in this context. (For the benefit of the
person asking the original question, let me note that there's no reason
to think that a token ring would help. Indeed it is slower, so one
is in danger of reaching this unknown realm sooner.)



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