Full-duplex Fast Ethernet isn't CSMA/CD either. There are only two stations
that can send and they each have their own private transmit pair and
receive pair. So it's not really multiple access (MA). There's no need to
sense the carrier to see if someone else is sending. There isn't anyone
else. So it's not CS. There's no need to detect collisions since they can't
happen and it's legal to be receiving while sending, so there's no CD either.
Priscilla
At 08:56 PM 1/23/01, Brian Lodwick wrote:
>Well that depends, are you talking about Fast or Gigabit?
>FastEthernet is always using CSMA/CD, but Gigabit has a specification to
>better utilize full-duplex links which doesn't use CSMA/CD. Take a look at
>802.3x. It sounds like you are talking about Fast Ethernet since you are
>talking about copper, unless you are talking about 1000BASE-CX.
>
> >>>Brian
>
>
> >From: "Erik Mintz" <[EMAIL PROTECTED]>
> >Reply-To: "Erik Mintz" <[EMAIL PROTECTED]>
> >To: "Priscilla Oppenheimer" <[EMAIL PROTECTED]>, "Brian Lodwick"
> ><[EMAIL PROTECTED]>, <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]>
> >Subject: RE: EASY ?? FOR MOST OF YOU
> >Date: Tue, 23 Jan 2001 15:27:31 -0500
> >
> >I have a question regarding CSMA/CD vs full duplex. If the problems
> >relating to distance are set due to the limitations of CSMA/CD,
> >what are the limits when using full duplex? I have had several situations
> >where I had to run fiber because of distance, but these
> >where almost invariably full duplex uplinks or trunks. Can I go farther
> >with copper if the link is full-duplex?
> >
> >-Erik
> >
> >-----Original Message-----
> >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> >Priscilla Oppenheimer
> >Sent: Monday, January 22, 2001 7:16 PM
> >To: Brian Lodwick; [EMAIL PROTECTED]; [EMAIL PROTECTED]
> >Subject: Re: EASY ?? FOR MOST OF YOU
> >
> >
> >At 09:20 PM 1/22/01, Brian Lodwick wrote:
> > >BBBBBBBBBBBBBBBBBBBBBBBBBBBBB for
> > >
> > > >>>Brian
> > >My additional question on top of this one is:
> > >
> > >If the maximum legal length was set to 1/10th the size to make regular
> > >(10Mb/sec) increased by a factor of 10, what was done to further increase
> > >100Mb/sec Ethernet by a factor of 10 to get Gigabit Ethernet?
> >
> >I like your plan to turn this into a non-easy question! The only experience
> >I have with Gigabit Ethernet is in a fully-switched network where every
> >port is full duplex, in which case CSMA/CD parameters are not an issue.
> >However, shared, half-duplex Gigabit Ethernet is viable also.
> >
> >With shared 10 and 100-Mbps Ethernet, the minimum frame size is equal to
> >the maximum round-trip propagation delay of the network. In other words,
> >the minimum frame size is equal to the slotTime = 512 bits. Sticking to
> >this rule would haver resulted in impracticably small networks for Gigabit
> >Ethernet, however. The solution was a process called "carrier extension."
> >
> >According to Rich Seifert in his excellent book, "Gigabit Ethernet," "The
> >key change is that the slotTime and the minimum frame are no longer the
> >same. The minimum frame is maintained at 512 bits (64 bytes, as in 10 Mbps
> >and 100 Mbps Ethernets), but the slotTime is set at 4096 bit-times (512
> >bytes).
> >
> >Frames that are shorter than the slotTime are artificially extended by
> >appending a carrier-extension field so that they are exactly one slotTime
> >long. This extends the duration of the time that the station transmits....
> >If a collision occurs during any time from the beginning of the frame to
> >the end of the extension field, the MAC will jam, abort, and backoff."
> >
> >See the book for even more gory details! &;-)
> >
> >Priscilla
> >
> >
> >
> > > >>>Brian
> > >
> > >
> > >attenuation is effected by 3 elements spreading, scattering, and
> >absorption.
> > >
> > > >From: Alvarado Jesus <[EMAIL PROTECTED]>
> > > >Reply-To: Alvarado Jesus <[EMAIL PROTECTED]>
> > > >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]>
> > > >Subject: EASY ?? FOR MOST OF YOU
> > > >Date: Mon, 22 Jan 2001 14:10:43 -0500
> > > >
> > > >The network span of a 100Base-T Network (205) meters is approx. 10
> >times
> > > >smaller than the network span of a 10Base-T network (2500) meters
> >Because
> > > >....
> > > >
> > > >A) , Higher speed data signals attenuate more quickly and so cannot be
> > > >transmitted that far
> > > >
> > > >
> > > >B) . Both Networks have minimum frame sizes of 64 bytes and the
> >network
> > > >spans must be tied directly to the minimum frame transmission time to
> >avoid
> > > >collisions.
> > > >
> > > >_________________________________
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> >
> >________________________
> >
> >Priscilla Oppenheimer
> >http://www.priscilla.com
> >
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