At 01:26 AM 12/26/00, Bowen, Shawn wrote:
>Very well said Priscilla, more or less what I was trying to say from
>memory. Also included in this is that when a collision is detected a jam
>is sent on the wire and the back off mechanism comes into play, should
>another collision occur, then another back off of a longer period takes
>place, and so on. After 4
16
>(If I remember correctly) back offs the packet is dropped and left to a
>higher layer protocol to retransmit. You are correct that a late
>collision indicates a collision that is past the preamble and should never
>happen in a properly designed and specified Ethernet segment, however when
>they do occur it is most likely a cable that is beyond length in spec.
A late collision is one that happens after the preamble AND the first 64
bytes of the frame. I agree with everything else you said. Thanks.
Priscilla
> While we are on the topic I am often asked what a runt is, simply
> put it is the fragments that result in collisions on an Ethernet segment,
> a somewhat normal condition. With Store and Forward switching runts will
> be eliminated from the wire while with cut-through switching they can be
> propagated. This being said, even though Cut-Through can be faster on a
> lightly loaded network store and forward can provide for higher
> throughput on a more saturated network due to this fact.
>
>
> Also I am asked what giants are. They are the result of an
> Ethernet frame being larger than the IEEE limit of 1524 (Or 1518
> depending on who your talking to) Bytes. This can be from a few things,
> the most important being VLAN tagging. Other sources are mis-configured
> stations on the wire or NIC's that are spewing garbage on the wire.
>
> For anyone really interested in a GREAT sight covering these
> items the original writer of the CNX certification has an excellent web
> site with all these goodies on it. It is www.optimized.com go there and
> check out the Technical Compendium link.
>
>Merry Christmas to all,
> Shawn
>
>-----Original Message-----
>From: [EMAIL PROTECTED]
>[<mailto:[EMAIL PROTECTED]>mailto:[EMAIL PROTECTED]]On Behalf Of
>Priscilla Oppenheimer
>Sent: Monday, December 25, 2000 7:47 PM
>To: Bowen, Shawn; Li Song; [EMAIL PROTECTED]
>Subject: RE: is this statement true ??
>
>At 01:07 PM 12/25/00, Bowen, Shawn wrote:
> >According to IEEE NO, 100 Meters is the max cable distance for Half or Full
> >100MB Ethernet over TP. In reality, Yes it will extend the range, The
> >reason why is that at full duplex you can not have collisions, and
> >collisions are the main reason for the distance limitation (Cross Talk
> comes
> >into play as well). The reason behind this is that in the original IEEE
> >spec the distance limitation was set so that a single 64Byte packet (the
> >smallest) could be transmitted down the line and would collide with another
> >packet before the 64Byte packet header had been completely transmitted,
> when
>
>Minor correction: The distance limitation is defined so that if a station
>is transmitting a minimum-size frame (64 bytes) and a collision occurs at
>the other end of the network, the collision will reflect back to the sender
>while the sender is still sending. If this didn't happen, the sender would
>have stopped monitoring for a collision with its transmission, and would
>not automatically retry. An upper layer would have to retransmit, which
>takes a lot longer.
>
> >this does not happen properly you see late collisions, these indicate a
> >collision past the preamble header of the packet and indicate a cable
> length
> >that is to long.
>
>A late collision is one that happens past the preamble and past the first
>64 bytes of the frame. A collision within the first 64 bytes is legal,
>normal, and not late.
>
>Priscilla
>
> >If you need to even go close to the 100 Meter mark you
> >should consider 100BaseFX or similar.
> >
> >Shawn
> >
> >-----Original Message-----
> >From: [EMAIL PROTECTED]
> [<mailto:[EMAIL PROTECTED]>mailto:[EMAIL PROTECTED]]On Behalf Of Li
> >Song
> >Sent: Monday, December 25, 2000 4:33 AM
> >To: [EMAIL PROTECTED]
> >Subject: is this statement true ??
> >
> >"full-duplex can be used over longer distance than
> >half-duplex" ??
> >what 's your opinion ??
> >
> >
> >_________________________________
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>________________________
>
>Priscilla Oppenheimer
><http://www.priscilla.com>http://www.priscilla.com
>
>_________________________________
>FAQ, list archives, and subscription info:
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>
>Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
________________________
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http://www.priscilla.com
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