At 09:20 PM 1/22/01, Brian Lodwick wrote:
>BBBBBBBBBBBBBBBBBBBBBBBBBBBBB for
>
> >>>Brian
>My additional question on top of this one is:
>
>If the maximum legal length was set to 1/10th the size to make regular
>(10Mb/sec) increased by a factor of 10, what was done to further increase
>100Mb/sec Ethernet by a factor of 10 to get Gigabit Ethernet?
I like your plan to turn this into a non-easy question! The only experience
I have with Gigabit Ethernet is in a fully-switched network where every
port is full duplex, in which case CSMA/CD parameters are not an issue.
However, shared, half-duplex Gigabit Ethernet is viable also.
With shared 10 and 100-Mbps Ethernet, the minimum frame size is equal to
the maximum round-trip propagation delay of the network. In other words,
the minimum frame size is equal to the slotTime = 512 bits. Sticking to
this rule would haver resulted in impracticably small networks for Gigabit
Ethernet, however. The solution was a process called "carrier extension."
According to Rich Seifert in his excellent book, "Gigabit Ethernet," "The
key change is that the slotTime and the minimum frame are no longer the
same. The minimum frame is maintained at 512 bits (64 bytes, as in 10 Mbps
and 100 Mbps Ethernets), but the slotTime is set at 4096 bit-times (512 bytes).
Frames that are shorter than the slotTime are artificially extended by
appending a carrier-extension field so that they are exactly one slotTime
long. This extends the duration of the time that the station transmits....
If a collision occurs during any time from the beginning of the frame to
the end of the extension field, the MAC will jam, abort, and backoff."
See the book for even more gory details! &;-)
Priscilla
> >>>Brian
>
>
>attenuation is effected by 3 elements spreading, scattering, and absorption.
>
> >From: Alvarado Jesus <[EMAIL PROTECTED]>
> >Reply-To: Alvarado Jesus <[EMAIL PROTECTED]>
> >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]>
> >Subject: EASY ?? FOR MOST OF YOU
> >Date: Mon, 22 Jan 2001 14:10:43 -0500
> >
> >The network span of a 100Base-T Network (205) meters is approx. 10 times
> >smaller than the network span of a 10Base-T network (2500) meters Because
> >....
> >
> >A) , Higher speed data signals attenuate more quickly and so cannot be
> >transmitted that far
> >
> >
> >B) . Both Networks have minimum frame sizes of 64 bytes and the network
> >spans must be tied directly to the minimum frame transmission time to avoid
> >collisions.
> >
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________________________
Priscilla Oppenheimer
http://www.priscilla.com
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