At 01:54 PM 10/11/00, Kevin L. Kultgen wrote:
>I'm looking at some of the study notes for CNX from www.optimized.com and I
>can answer most situations but there are two that confuse me:
>
>a) Significantly more than 8 bytes of "55" or "AA" hexadecimal data
>appended to the end.
If it's more than 8 bytes of 55s and AAs, there's something more seriously
wrong than a collision, such as a jabbering transceiver, (which is rare
these days). When a collision occurs, the protocol analyzer captures some
bits from the closest transmitter and then some preamble bits from the
collider. If I remember correctly, you won't see the jam or the added bits
that a repeater adds to fragments.
None of this is particularly relevant to a Cisco study list since Cisco
recommends microsegmenting so that there are only a few devices sharing a
collision domain. Cisco would like it best if you bought only switches, in
which case each collision domain has only two participants: the switch port
and the connected device. Full-duplex means there's no collision domain
whatsoever.
Also, keep in mind that a lot of the CNX material is written from the point
of view of a protocol analyzer sitting on a shared coax piece of wire. Not
really relevant to what we do today.
Could you send these questions to a CNX list?? Check this site to see if
there is such a thing: http://www.optimized.com/cnx/
Good luck!
Priscilla
>Four bytes get appended by the initial host (for local collisions) and 4
>more by the repeater (for remote echoing). Would this be the second machine
>noticing the collision (later) and appending it's four bytes too? And how
>about the repeater coming back (for a total of 16 bytes)?
>
>B) Streaming "00" or "FF" patterns of hexadecimal data appended to the end.
>
>I have no clue. The closest I could come up with was that one book stated
>that the the jam signal was not defined as a AAAA/5555 sequence and could be
>any sequence ie FFFF or 0000.
>
>I've read two Ethernet books and they tend to skim over top collisions and
>don't go into any depth.
>
>Thanx
>--
>Kevin L. Kultgen
________________________
Priscilla Oppenheimer
http://www.priscilla.com
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