-----Original Message-----
From: Julio Arruda
[mailto:[EMAIL PROTECTED]]
Sent: Quinta-feira,
25 de Maio de 2000 13:31
To: Lista de Discussão
Rede Wan
Subject: RE: [redewan]
Capacidade real FastEthernet
Lista de Discussão 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 Discussão 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
********************************************************
_____
<< File: Alessandro R Nobre.vcf >>
