At 09:24 PM 7/12/00, Francisco Muniz wrote:
>Ethernet (as well as token ring) use a physical star topology. There's a
>center (the hub, switch, or MAU) and a series of spokes attached to it. I
>think a physical implementation of a ring would be like an old style
>ethernet ("bus style" - 10base5 I think) where the last computer connects
>to the first, wouldn't it? What do you think?
Yikes. Connecting an old-style Ethernet as a ring was an infamously bad
thing you could do to completely break it. 10Base-2 and 10Base-5 were
physically cabled as a bus that had to be terminated on each end. If by
mistake you connected the tail to the end, the signal would wrap around
forever looking like continual traffic and collisions.
These days Ethernet is cabled in a physical star with a hub at the center.
It can still be thought of as a long bus cable that goes in and out of each
port, (though that's kind of stretching it.) Logically you should still
think of shared Ethernet as a bus. When a station transmits, the frame
radiates out to every device on the collision domain, much as it would if
the devices were all connected to one long cable.
Token Ring has always been a physical star. Logically it's a ring because
instead of each station hearing the radiated signal from every other
station as in Ethernet, each station takes in bits from the upstream
neighbor and transmits them to the downstream neighbor. The sending station
sees the frame come back and strips the bits. If the sending station should
fail to do this (because of a crash or something), that's OK because the
active monitor strips any frame that has already been around once. The
active monitor sets a bit in the frame. If a frame comes back with that bit
set, the active monitor strips the frame.
Unfortunately, this is all stuff you need to know for the Cisco tests, even
the old bus Ethernet stuff! ;-)
Priscilla
>
>Francisco Muniz.
>>"Oscar Rau" <<mailto:[EMAIL PROTECTED]>[EMAIL PROTECTED]>
>>escribió en el mensaje de noticias
>><000901bfec6d$475cd5c0$[EMAIL PROTECTED]">mailto:000901bfec6d$475cd5c0$[EMAIL PROTECTED]>000901bfec6d$475cd5c0$[EMAIL PROTECTED]
>>I was reading about network topology and they say that an example of bus
>>topology is Ethernet network. Wouldn't ethernet network be a ring
>>topology due to
>>hub/switch environment?
>>
>>Please correct me where I am wrong.
>>
>>Thank you in advance.
>>
>>Oscar Rau
>><mailto:[EMAIL PROTECTED]>[EMAIL PROTECTED]
>>
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Priscilla Oppenheimer
http://www.priscilla.com
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