I think she answers in her book, in a roundabout way, that in FULL-DUPLEX
mode, collisions are non-existant, since two stations can transmit at the
same time on the wire (a switch and the PC or device on it's port,
transmitting and receiving at the same time)
Marc
"Steve Brokaw" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Well, I have a different question that kinda goes along here. If you are
in a switched environment, i.e. dedicated bandwidth per port, how can you
have a collision at all? To me it seems (and Radia Perlmann touches on this
in her book but doesn't give any explanation) that if there is no chance for
a collision (switched environment) then why a distance limitation? I'm sure
there are some other physics factors that would limit distance but would
they be the same as the distance required to detect a collision?
>
>
> Steve
>
>
> ------Original Message------
> From: "Randy Witt" <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Sent: July 27, 2000 1:53:55 PM GMT
> Subject: CCDA question-512 bit times
>
>
> I have a question regarding the round-trip propagation delay on an
Ethernet network.
>
> Page 123 of the Cisco Press "Designing Cisco Networks" book states:
>
> "The most significant design rule for Ethernet is that the round-trip
propagation delay in one collision domain must not exceed 512 bit times,
which is a requirement for collision detection to work correctly."
>
> With 100Mbps Ethernet, the maximum round-trip delay would be 5.12 seconds,
resulting in a distance limitation of 205 meters.
>
> I currently oversee a large flat network covering several miles in
diameter. All of the links between buildings are single-mode fiber links.
No routing is involved, everything is switched - one large broadcast domain.
>
> How does the 512 bit time rule apply to fiber optic cabling? I see on
page 127 of the same book that the Round trip delay in bit times per meter
for Cat5 cable is 1.112, whereas Fiber-optic cable it's 1.0.
>
> I guess I'm having difficulty understanding how fiber can overcome the 512
bit-time rule and can have a much longer distance.
>
> I do realize that this is not exactly a Cisco question, though covered on
the DCN/CCDA material. If someone could kindly refer me to any material
that covers this topic, I'd appreciate it.
>
> ___________________________________
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> Steve Brokaw, MCSE CCNA
> Sprint Enterprise Network Services
> [EMAIL PROTECTED]
> [EMAIL PROTECTED] (pager)
>
>
>
****************************************************************************
***
>
> Never mistake motion for action.
>
> -- Ernest Hemingway
>
****************************************************************************
***
>
>
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