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

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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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net