Comments inserted.
----- Original Message -----
From: Jay Hennigan <[EMAIL PROTECTED]>
Newsgroups: groupstudy.cisco
To: <[EMAIL PROTECTED]>
Sent: Saturday, October 07, 2000 9:14 AM
Subject: Re: Ethernet Trivia
> On 7 Oct 2000 01:20:43 -0400, whatshakin <[EMAIL PROTECTED]> wrote:
>
> :This makes it sound like there is actually something tangible being put
on
> :the wire. Bits are merely ones and zeros which are signaled by different
> :voltages etc in the line encoding.
> :
> :Bits do not occupy line space.
>
> Sure they do. Ever see the terms "wavelength" or "short wave" on a radio?
>
> Inversely proportional to the frequency, wave length is the physical
length
> of a signal, based on the distance in free space for one cycle at a given
> frequency. As the speed of light is slower in media such as twisted pair
> copper and fiber, the length of a bit at a given frequency is shorter than
> it would be in free space.
The physical length of a signal is not inversely proportional to its
frequency. It differs depending on the line encoding. Again, a bit is the
term applied to the signal state. Signal
states occupy line space.
>
> The ones and zeros obviously travel along the wire from the sending to
> the receiving end. If you could freeze time and take a snapshot, you
> would see a length of wire with a positive voltage, followed by one of
> negative charge, the lengths corresponding to bits.
>
This is quite a good hypothetical scenario, and is indeed correct.
> :Measurements of how fast data can be moved over a wire are the time it
takes
> :for a signal at one end to be heard at the other. The amount of data
> :(signals) which can be moved across a wire is ascertained by the line
> :encoding method, and how many signals the encoding system can be made to
> :produce in a second. Minus the delay factors between point A and B of
> :course.
>
> And those delay factors are the speed-of-light propagation delay of the
> medium, the delay proportional to the length. Distance (length on the
wire)
> equals velocity (speed of light in the medium) divided by time (length of
> a bit in fractions of a second).
>
Your formula is correct, however, it does not apply very well to finding
delay propogation over a wire because of the numerous other factors which
need to be applied additionally. IE: The properties of the wire medium,
EMF, block coding, IFG, protocol overhead...
> :BTW, my calculations for the speed of light resulted in 299,793,100 m/s
>
> Which method did you use? Laser and a spinning mirror? :-)
Very observant! ;-)
>
> --
> Jay Hennigan - Network Administration - [EMAIL PROTECTED]
> NetLojix Communications, Inc. NASDAQ: NETX - http://www.netlojix.com/
> WestNet: Connecting you to the planet. 805 884-6323
>
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