Speed limit of Fast Ethernet

Discussions of the Ethernet/IEEE 802.3 protocols.

Speed limit of Fast Ethernet

Postby wslim22 » Tue Nov 22, 2005 12:20 pm

Why is the speed limit of Fast Ethernet limited to 100mbps? Is it
becasue of the packet length?
wslim22
 

Re: Speed limit of Fast Ethernet

Postby Walter Roberson » Tue Nov 22, 2005 12:20 pm

In article <1132673994.911346.74680@g43g2000cwa.googlegroups.com>,
wslim22 <wslim22@gmail.com> wrote:
:Why is the speed limit of Fast Ethernet limited to 100mbps? Is it
:becasue of the packet length?

No, the rate is defined by the carrier frequency and choice of
encoding schemes onto the carrier. It is not just a plain
"1 bit per hertz" though; there are concerns about EMI and
frequency attenuation and negotiation. See, e.g.,
http://www.industrialethernetu.com/courses/103_3.htm
--
I was very young in those days, but I was also rather dim.
-- Christopher Priest
Walter Roberson
 

Re: Speed limit of Fast Ethernet

Postby Walter Roberson » Wed Nov 23, 2005 6:00 pm

In article <1132781868.095455.65150@g47g2000cwa.googlegroups.com>,
DigitalSignal <digitalsignal999@yahoo.com> wrote:
:100 is an odd number.

Yes, in any number system whose base is an odd positive integer (3 upwards)

:I really prefer 120. But these guys just don't listen!

Interestingly, 120 is an odd number in exactly the above set of
number systems that 100 is odd for.

More generally, 1p0 base q is odd if and only if
q is odd (3 upwards) and p is even.
For example, 130 is not odd in any positive integer base (4 upwards).


[Sorry, when you are programming in a symbolic computation language
for days on end, you start thinking about general solutions to statements
that contain assumptions such as "odd"...]
--
Is there any thing whereof it may be said, See, this is new? It hath
been already of old time, which was before us. -- Ecclesiastes
Walter Roberson
 

Re: Speed limit of Fast Ethernet

Postby DigitalSignal » Wed Nov 23, 2005 10:37 pm

100 is an odd number. I really prefer 120. But these guys just don't
listen!
DigitalSignal
 

Re: Speed limit of Fast Ethernet

Postby James Knott » Thu Nov 24, 2005 12:20 pm

DigitalSignal wrote:

100 is an odd number. I really prefer 120. But these guys just don't
listen!

I thought the answer was 42. ;-)
James Knott
 


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