The machines are connected via a Netgear DS108 dual speed hub.  I think I
understand what you are saying except for one thing.  Does the speed get
negotiated for every packet?  If so, isn't there a lot of overhead?  If not,
how does a packet from a machine connected at 100mb get switched/routed to a
machine connected at 10mb?  Does it go through a "transformer"?

It might help my understanding if I knew what was different about 10mb and
100mb ethernet other than the maximum throughput.  For example, does 100mb
use a greater frequency bandwidth, does it send more pulses per unit time,
or what?

I measured the throughput using ftp from a 1.0Gz PIII to a 400Mhz K6-3 and
to a 750Mhz PIII.

Mike

> -----Original Message-----
> From: tclug-list-admin at mn-linux.org
> [mailto:tclug-list-admin at mn-linux.org]On Behalf Of Troy.A Johnson
> Sent: Monday, November 19, 2001 8:58 AM
> To: tclug-list at mn-linux.org
> Subject: Re: [TCLUG] Co-living 100mb and 10mb ethernet
>
>
> Mike,
>
> Here are my (not necessarily correct) answers:
>
> >>> mbresnah at visi.com 11/18/01 04:15PM >>>
> >Could someone explain to me in a nutshell how 10mb and 100mb co-exist
> >happily on the same ethernet?
>
> Technically, as stated before, they cannot. If your local
> network is connected by a HUB, they are all on the
> same ETHERNET SEGMENT. If your local network
> is connected by a SWITCH, the switch provides a
> separate a ethernet segment for each connection and
> connects those with a BACKPLANE (which runs at
> least as fast as the fastest network segment). Steve
> explained dual speed hubs, but basically they provide
> two ethernet segments: one 10Mb, one 100Mb; via an
> internal two port switch.
>
> >For example, I have 3PCs and a DSL modem on
> >my local network.  1 PC and the modem have 10mb cards and 2 of
> the PCs have
> >100mb cards.  When I transfer a file from one of the 100mb
> machines it takes
> >about 5 times less time than when I transfer to the 10mb machine, so it
> >certainly appears that the network is capable of both speeds.
> Evidently the
> >10mb is able to detect and handle collisions with the 100mb and
> vice versa.
> >Perhaps it's because they both use the same carrier frequency;
> if they use
> >such a thing?  Also, is a 5x speed difference what I should expect?  Not
> >10x?
>
> The speeds are differentiated by a factor of 10 only
> for the theoretical maximum throughput for each
> medium. It may be difficult for your PCs to push a
> 100Mb connection close to it's max. It may be that
> the 10Mb connection is full duplex (actually 20Mb
> max) while the 100Mb connection is half duplex.
> A factor of 5 is not an unusual speed difference,
> but it may depend on the service used (those with
> less overhead (like FTP) will probably be faster).
>
> >Take pity on me.  I'm a software guy.
> I do pity you, Mike, and I pity me too. ;-)
>
> Troy
>
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