Re: Switchless TCP/IP networking?

jimhicks@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (Jim Hicks) writes:

Matthew Clark wrote:
What if I used thinnet as the connection medium? Could I?

1) Adapt the blades' TP ports to a BNC connector?
2) String them together via thinnet?

Is this feasable? Also, I've read that "100Base2" doesn't
exist. Are they simply referring to a lack of hardware NICs,
or a limitation of the coaxial medium itself?

Matt

coaxial wire has two conductors, (1 pair), 100mbit ethernet adapters
have four wires, two twisted pairs of wires.
Coax has an impedence of 75ohms, or 92ohms. Twisted pair has a
different
impedence, but I forget what for now.

Twisted pair wires are commonly available/used with the following
impedances:
- 100 ohms (nodern sructured cabling, CAT5/CAT6 cables)
- 110 ohms (used on some automation applications and digital audio)
- 120 ohms (seen on telecom infrastruture)
- 150 ohms (used on old IBM data cabling)

Nowadays the trand is to use 100 ohms cable.
The normal 100mbit ethernet adapters are designed to work with
100 ohms twisted pair wiring.

Twisted pair requires the transmit pair from one adapter to connect to

the receive pair on the other adapter, and vice versa. This allows an
adapter to transmit and receive simultaneously.
Coax has a tranceiver that is either transmitting, or receiving. This
limits the speed of the conversation, and is referred to as half
duplex.
Aside from the data losses due to mismatched impedence, you would have

to invent a tranceiver for this to work. In addition it would require
a
firmware patch on the card to implement the collision avoidance and
collision detection that is not required on switched links.
You are doing this to avoid buying a $30 switch????


--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
.

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