Hi, Priscilla,
I think the best way to find this out is to just get yourself a network
tester to connect between the transmitting host on port 1 and the CISCO box.
( like a FLUKE ) You will be able to see ( or not ) the JAMS on port 1. When
you connect the host in that segment only and there's a jam during a
collision on port 2 you know enough...
In my humble opinion you are right, but that's male intuition ;-)
Barry
Priscilla Oppenheimer <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Hi Group Study,
>
> I got into a discussion with a knowledgeable Sniffer instructor recently.
> When he teaches cut-through-switching theory, he warns his students that a
> cut-through switch does not really isolate collision domains. Consider
this
> example:
>
> * The switch is receiving a frame from port 1 destined for a station out
> port 2.
> * The switch recognizes the destination address and starts forwarding the
> frame to port 2 ASAP.
> * There is a collision on port 2. (It's a shared and/or half-duplex
Ethernet.)
>
> According to the instructor, the Switch sends a jam signal back to port 1
> to let the initial sender know that the frame experienced a collision.
This
> allows the sender to retransmit.
>
> If you read some of the books on switching, you would think that this is
> true. The books make it sound like the frame is passing through the switch
> and disappearing out the destination port as soon as the destination
> address is recognized.
>
> I don't think the Sniffer instructor's conclusion is true, however. I
> believe that a Cisco cut-through switch buffers the frame and hence has
the
> ability to retransmit. There is no requirement to send a jam to the
> original sender because port 2 in our example retransmits after sensing
the
> collision.
>
> I believe that Cisco switches store frames, even when doing cut-through,
> whereas the instructor assumed that the frame has passed through and out
> the port and is no longer available for retransmission by the switch.
>
> Cisco positions cut-through as reducing delay, not reducing the need for
> buffering, so I'm contending that I'm right.
>
> Who do you think is right? Can you point me to any white papers that would
> prove who is right?
>
> Thanks
>
> Priscilla
>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
>
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