🚀 go-pugleaf

In article <PCG.91Sep9183332@aberdb.aber.ac.uk> pcg@aber.ac.uk (Piercarlo Grandi) writes:
] The theoretical maximum is a bit less than 1MB/s, and even that cannot
] in practice be achieved because the Ethernet is a simplex channel, and
] most protocols require ACKs every now and then, and thus in practice you
Actually, if you're Van Jacobson, and have really high-tech equipment
(a pair of Sun 3/60s!) it's possible to achieve 8 Mbits/sec for
large-block file transfers by careful tuning.  The 3/60 had AMD LANCE
Ethernet chips - the 3/280 used Intel chips, and he could only get
about 5-6 Mbits/sec.

My first reaction to the request, however, was "Wow!  What is this
guy trying to accomplish?  Are PCs and Ethernets the right approach?
If he's got money to burn, why isn't he using FDDI?  Is this broadcast
data, or really point-to-point, or does he have one blazing-fast data
source that he's trying to store?  Is this data being stored to disk,
or just displayed on screens?  If it's being stored, how much is there?
Maybe you want one big machine with 100 MB RAM to store it and shove
it out gradually?"

Especially if the real application is broadcast, there's been a lot
of work on broadcast protocols.  Alternatively, as some people have
suggested, there are other networks such as SCSI that are cheap,
fast, and efficient.  How many machines are you trying to connect?

(NASA has some large data-shuffler that's basically a big multi-ported
memory box with a bunch of DMA connections to a bunch of buffers,
which they've used for some high-speed data applications;
I don't remember any details, since it's been about 3 years since I
read about the beast, but it was very hard to emulate with
non-custom approaches.)

Oh - cisco routers DO have a lot of bandwidth, at least in the large models -
I think it's the AGS-PLUS (we paint a Death Star on the front and 
sell it as the AT&T StarWAN 450).  The C-Bus backplane has a 533
Mbits/sec bandwidth, and the high-speed multiport Ethernet cards can
do essentially full bandwidth for (all? 4-6?) each port.
Most routers have traditionally been limited by their
packet-processing rate, but the newer products from cisco, Proteon,
and a few other people have fast enough processors to get beyond that.
The 450's packet-processing rate was something around 50-60kpps for
short packets, and being increased as they tuned the software,
but for this job you'd presumably use large packets so the problem
is bus bandwidth and memory buffers anyway - should be ok.

		Good luck!
-- 
				Pray for peace;      Bill
# Bill Stewart 908-949-0705 erebus.att.com!wcs AT&T Bell Labs 4M-312 Holmdel NJ
# "After all, the 'good of society' is based upon the 'rights of the individual.'
# Not the other way around, IMHO." -- Chris Preston