[svlug] Networking questions.

Dave Zarzycki dave at zarzycki.ml.org
Wed Nov 11 22:44:16 PST 1998


On Wed, 11 Nov 1998, Scott Jaderholm wrote:

> This doesnt really pertain to linux but some of you will know the answers
> to some of my questions so here it goes.
> What is the difference between dynamic and static routing?

Static is hard coded and needs a "human" to change update the routing
tables when things change. Dynamic routing uses somewhat intelligent
routing software to determine where to send packets, when to send them, or
what to do when things change.

> What is STP cable?

Shielded Twisted Pair. As opposed to Unshielded Twisted Pair, or UTP. STP
is basically a more noise resistant version of UTP. It's also more
expensive.

> What is FDDI? Is it some kind of a design for a network?

Sort of. FDDI, or Fiber Distributed Data Interface, is a networking
technology similar to Ethernet in some ways, and not in others. Back
before Fast Ethernet came out, FDDI was the way to go for a 100Mbps
throughput. FDDI spoke what was basically large (4.5KB) Ethernet frames
over fiber. FDDI is commonly setup in a "dual" ring which allows for a
ring to be broken and still maintain connectivity. Since FDDI is token
based, it can achieve higher aggregate throughput with lots of nodes
talking. A Ethernet network on the other hand will typically be subject to
collisions, lowering aggregate throughput.

> I heard someone some where talking about CSMA/CD w/ Token Passing or
> something. What is that?

CSMA, or Carrier Sense, Multiple Access / Collision Detect is the way
Ethernet works to detect that somebody else is trying send a packet, and
either not send your own, or that you have collided with someone else and
you should back off and try again.

Token Passing is a technique used in networks that are designed to work as
a ring. Basically, image a token that only one host can have at a time.
Now being in a ring, imagine that the data can only flow one way. The
following scenario unfolds:

if I'm handed a token with data, and it's for me, take it and pass the
[now] empty token on to the next guy.

if the data is not for me, pass the token on to the next host with the
data.

if the token has no data attached to it, and I have some to send, attach
it and send it on it's merry way.

if the token has no data attached to it, and I have none to send, send it
on to the next guy.

Now isn't that spify.

> Ok well those are my questions.  Thanks in advance for any responses.  

No problem. Now you too can be the excitement and life of the party. ;-)

Personally speaking, I think FDDI is cool, but prohitively expensive. It
used to be, and still is in many places, the backbone of choice. I think
the next cool LAN technology will be IP over FireWire. But that is *very*
LANish in the "local" sense of the acronym. But at 400Mbps and with faster
speeds on the way, it's just too cool of a technology to pass up. Now all
we need is Linux drivers (yes I know someone, somewhere is working on it).

davez



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