Re: OT Why Ethernet cannot still cross the 10m barrier ?

That's a good point. If we're running full duplex and collision detection
is disabled, does that eliminate the 100m restriction since the limiting
timing factor no longer applies?

On Fri, Jun 14, 2013 at 3:51 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar>wrote:

> I beg your pardon ?
> I have not seen any implementation of multiaccess 1G ethernet,
> and it's ages since I last saw a 100 Mb hub.
>
> What's the point of half duplex and colission detection nowadays ?
>
> -Carlos
>
> John Neiberger @ 14/06/2013 16:03 -0300 dixit:
> > Exactly what I was thinking. The 100m limit is there because longer
> cables
> > mess with synchronization and timing. Here's a snippet I found that
> > explains it for the OP:
> >
> > On 10-Mbps Ethernet one bit at the MAC layer requires 100 nanoseconds
> (ns)
> > to transmit. At 100 Mbps that same bit requires 10 ns to transmit and at
> > 1000 Mbps only takes 1 ns. As a rough estimate, 20.3 cm (8 in) per
> > nanosecond is often used for calculating propagation delay down a UTP
> > cable. For 100 meters of UTP, this means that it takes just under 5
> > bit-times for a 10BASE-T signal to travel the length the cable.
> >
> > For CSMA/CD Ethernet to operate, the sending station must become aware
> of a
> > collision before it has completed transmission of a minimum-sized frame.
> At
> > 100 Mbps the system timing is barely able to accommodate 100 meter
> cables.
> > At 1000 Mbps special adjustments are required as nearly an entire
> > minimum-sized frame would be transmitted before the first bit reached the
> > end of the first 100 meters of UTP cable. For this reason half duplex is
> > not permitted in 10-Gigabit Ethernet.
> >
> > http://ethernettiming.blogspot.com/
> >
> >
> >
> >
> > On Fri, Jun 14, 2013 at 11:58 AM, Joe Sanchez <marco207p_at_gmail.com>
> wrote:
> >
> >> Preamble , Preamble
> >>
> >> Regards,
> >> Joe Sanchez
> >>
> >> ( please excuse the brevity of this email as it was sent via a mobile
> >> device. Please excuse misspelled words or sentence structure.)
> >>
> >> On Jun 14, 2013, at 4:23 AM, marc edwards <renorider_at_gmail.com> wrote:
> >>
> >>> This isn't distance limitation of Ethernet. Instead this is physical
> >>> limitation of Ethernet over copper cabling.
> >>> Law's of Physic's . The signal degrades over length and also you have
> >> issue
> >>> with the time the signal takes to both ends. You can push ethernet pass
> >>> 100m, i have personally seen 160m for a connection between console
> server
> >>> and device but i would not advise it.
> >>>
> >>>
> >>> On Wed, Jun 12, 2013 at 11:32 PM, Ahmed <ahmedsalim_at_gmail.com> wrote:
> >>>
> >>>> Is there a history for this 100m barrier ? Even with the modern
> >> switches ,
> >>>> cannot this be overcome ?
> >>>>
> >>>>
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> >>>>
> >>>>
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> >
> >
>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina

Blogs and organic groups at http://www.ccie.net
Received on Fri Jun 14 2013 - 16:01:48 ART