🚀 go-pugleaf

In article <1991Sep1.195029.16374@aber.ac.uk> pcg@aber.ac.uk (Piercarlo Grandi) writes:
>scogen@xenitec.on.ca (scogen@xenitec.on.ca) writes:
>> Another important detail is that each computer will be talking over a
>> Cisco router with one ethernet card per computer.
>
>Note that you need an Ethernet card per computer anyhow :-).
>
>Probably what you mean is that you will have a separate Ethernet cable per
>computer. This of course means that each machine would have its own 0.8MB/s
>Ethernet dedicated to itself. The problem is that I doubt very much that
>this would buy you anything at all, as I would expect the CISCO router not
>to be able to sustain more than 0.8MB/s aggregate anyhow, as routers are
>normally not designed to sustain the maximum combined bandwidth of all the
>Ethernets they link. Does anybody know for sure what is the maximum thruput
>of a CISCO router?

Ours forwards at about 15000 packets per second, and routes at about
2000 packet/sec. The newer ones are supposed to about double that.

Lessee ---- 15000 * 1500 = 22.5MBytes/sec, a tad faster than Ethernet
will go.  Even routing implies (assuming max size legitimate packets)
3MBytes/sec.  I suspect that the quoted Cisco rates are for minimum (50
byte) or fairly small packets, netting somewhere in the neighborhood of
100KBytes/sec. 

[ Stuff bites dust ]

>
>The bad news are that the TCP/UDP/IP sw on the host, and in particular
>SCO's, will have such huge overheads and misdesigns that in practice you
>will not be able to use more than a fraction of the nominal speed of the
>hardware. Somebody (Van Jacobson and others) have spent some serious effort
>in tuning up certain implementations of TCP/UDP/IP and can boast of being
>able of getting TCP/UDP/IP end-to-end connections that exploit 90-95% of the
>hardware capacity, but figures like 30-50% are far more common. I don't
>remember exactly, but I seem to remember that you'd be lucky to get more than
>300-400KB/s end-to-end on a TCP/UDP/IP connection from SCO's Internet
>protocol stack.

Our SCO box, with WD8003e, 33MHz 80386 and caching ESDI controller
simply is incapable of EVER exceeding 100KB/sec over the network, even
using a simple send the same packet over and over again through a UDP
connection. Average rcp/ftp stuff is about 70KB/sec.

My Dell V.4 box, admittedly running on a '486-25 with SCSI and WD8013,
averages 285KB/sec talking to our HP9000/720, sending 20MB at a whack.


>Piercarlo Grandi                   | ARPA: pcg%uk.ac.aber@nsfnet-relay.ac.uk
>Dept of CS, UCW Aberystwyth        | UUCP: ...!mcsun!ukc!aber-cs!pcg
>Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@aber.ac.uk

Dave
-- 
Dave Remien +*+*+*+*+*+*+*+*+*+*+*+*+*+*+ WINCO Computer Engineering Group 
  dave@pmafire.inel.gov or rzd@inel.gov      "Dave Barry for President"