-----Original
Message-----
From: Julio Arruda
[mailto:[EMAIL PROTECTED]]
Sent: Quinta-feira, 25 de Maio de 2000 13:31
To: Lista de Discuss�o Rede Wan
Subject: RE: [redewan] Capacidade real
FastEthernet
Lista de Discuss�o Rede
Wan - http://www.networkdesigners.com.br
Se nao me engano, o maximo teorico
seria:
100Mbps -
"tempos mortos"
Fazendo um cut&paste
descarado de um post recente na comp.dcom.lans.ethernet (note que os
"timings" de giga/fast/ethernet sao iguais em "bit times", e como nao
estamos levando em conta em giga-half-duplex o "quebra-galho" chamado
carrier extension, da para usar o mesmo "conceito).
[], <O-O>
===========================
n article
<[EMAIL PROTECTED]>,
Sam
<[EMAIL PROTECTED]> wrote:
>Hi,
>
>May we expect more than
500 or 600 Mbps on an Ethernet Gigabit
>link ?
You may expect well over 900Mbps in each
direction on a Gigabit Ethernet
link. That is, of course, assuming that you have the
traffic to fill it.
>What is the general rule for Ethernet
saturation and does it
>depend on the medium that is being used (fiber, copper, ...)
?
Ethernet in full duplex mode can be as
saturated as a serial line between
two points. Depending on frame size Upper-layer
protocols will limit the
amount of traffic that can pass in any one conversation
as the protocols
wait for acknowledgements. The one caveat is that there is a
160 bit-time
gap
between packets for historical reasons (96 bit interframe gap, 64
bit
preamble). So, for a 1524 byte frame, Ethernet is only 98.7%
efficient.
For
64 byte frames, Ethernet is only 76% efficient. Average traffic
is
256 bytes,
which is 92.7% efficient.
Ethernet in Half duplex can be saturated to the
same amount, However, the
contention mechanism deployed to determine what happens
when two devices
attempt to communicate at the same time (collisions) will offset
the
efficiency
to some extent. A single collision on a 1524 byte frame
will
knock your
efficiency down to 97.4%, while on a 64 byte frame it will be
61%.
So, on shared 10 megabit ethernet with only 64
bytes frames, and a 100%
collision rate, you should end up with 6.1 Mbps.
With 1500 byte frames
and 100% collision rate, you should end up with 9.74Mbps. Not
too shabby
that...
--
Daniel J
McDonald CCIE # 2495, CNX
[EMAIL PROTECTED]
I support Alan Keyes for
President - <Http://www.keyes2000.org>
Visit my website:
<http://www.io.com/~djmcdona>
(nao entrado em detalhes de cpu para segurar o
rojao).
[],
<O-O>
-----Original Message-----
From: Alessandro R Nobre
[SMTP:[EMAIL PROTECTED]]
Sent:
Tuesday, May 23, 2000 4:26 PM
To:
Lista de Discusso Rede Wan
Subject: [redewan] Capacidade real
FastEthernet
Lista de Discuss�o Rede Wan - <http://www.networkdesigners.com.br>
Pessoal,
Alguem saberia me
dizer qual a capacidade de transmissao de uma rede Fast Ethernet. E se
utilizo Full duplex como ficaria esta capacidade real ?
[]�s
********************************************************
Alessandro
R Nobre
[EMAIL PROTECTED] < <mailto:[EMAIL PROTECTED]>> | ICQ:
70701329
********************************************************
Nobre.vcf >>
