star bus - is it physically a bus at all - hubs in series?

is the star bus network physical star and logical bus. or is it a
physical hybrid, i.e. physical bus too. I find that differnt sites say
different things.
Mike Meyers book says it's physical star logical bus. But 2 other
sites say it's a physical hybrid.


http://web10.eppg.com/betabooks/nov01/meyers/ch04.html
"Star bus networks use a physical star design that provides improved
stability and a logical bus that maintains compatibility with existing
Ethernet standards"

so that says that a star bus is a physical star, but a logical bus.

http://web10.eppg.com/betabooks/nov01/meyers/ch04.html
"In a network, physical topology describes the layout of the wires,
while logical topology describes the behavior of the electronics"

so it appears that a star bus is physically just a star, - not a bus at
all.

Yet these sites appear to state it differently

http://distancelearning.ksi.edu/demo/370/ch01d.htm
"The star bus is a combination of the bus and star topologies. In a
star-bus topology, several star topology networks are linked together
with linear bus trunks. Figure 1.28 shows a typical star-bus topology.
"

so that site appears to imply that a star bus topology is physically a
star and physically a bus. It's a 'physical hybrid topology'(my
expression).

http://www.enlightenment.co.uk/frame...c/w-netwrk.htm
"Daisy chain topology
This topology is also sometimes called a star-bus. Hubs (which could
contain star network segments) are linked in series. "


thanks in advance

jameshanle...@yahoo.co.uk wrote:
> is the star bus network physical star and logical bus. or is it a
> physical hybrid, i.e. physical bus too. I find that differnt sites
say
> different things.
> Mike Meyers book says it's physical star logical bus. But 2 other
> sites say it's a physical hybrid.
>
>
> http://web10.eppg.com/betabooks/nov01/meyers/ch04.html
> "Star bus networks use a physical star design that provides improved
> stability and a logical bus that maintains compatibility with
existing
> Ethernet standards"
>
> so that says that a star bus is a physical star, but a logical bus.
>
> http://web10.eppg.com/betabooks/nov01/meyers/ch04.html
> "In a network, physical topology describes the layout of the wires,
> while logical topology describes the behavior of the electronics"
>
> so it appears that a star bus is physically just a star, - not a bus
at
> all.
>
> Yet these sites appear to state it differently
>
> http://distancelearning.ksi.edu/demo/370/ch01d.htm
> "The star bus is a combination of the bus and star topologies. In a
> star-bus topology, several star topology networks are linked together
> with linear bus trunks. Figure 1.28 shows a typical star-bus
topology.
> "
>
> so that site appears to imply that a star bus topology is physically
a
> star and physically a bus. It's a 'physical hybrid topology'(my
> expression).
>
> http://www.enlightenment.co.uk/frame...c/w-netwrk.htm
> "Daisy chain topology
> This topology is also sometimes called a star-bus. Hubs (which could
> contain star network segments) are linked in series. "

Get used to seeing networking terms used differently in different
contexts.

Read the pages carefully and you should see the similarity _and_ the
differences in their use of the term "star bus". They are _not_ using
the term in precisely the same way -- nor are they addressing the
network problems in quite the same way. The first reference is more
tied to the notion of a _physical_ bus arranged in a star configuration
(thus overcoming a cable fault with a "straight/linear" bus) while the
second is more a notion of multiple stars connected via a (chaining)
"bus" (using hubs).

In any case, buses (ie., the physical equivalent of
coax/thicknet/thinnet) are seldom encountered today and these
discussions are mostly of historical/test interest (IMO). Eg., note
how little is said about switches rather than hubs. It is good to be
familiar with these designs in case you encounter the occassional "old"
net segment and more important to understand _why_ these designs were
seen as solutions to problems of the day. The basic ideas remain
today, though the solutions are different.

Hubs were quite an advance over coax and made _making_ star (aka, hub
and spoke) topologies much easier. Switches were an equally notable
advance over hubs. If you understand the basic differences between
hubs and switches, you will also get a clearer picture of why
_physical_ topology (and wiring) was much more significant re: network
design than it is today (again, IMO).

Then once you understand what switches bring to the mix (physically
_and_ logically) you can tackle VLANs which are becoming much more
common as a means of segmenting networks into different traffic
flows/patterns.

I would suggest you augment these "hardware" level discussions of
networking with something a bit broader, more "logical" like IP routing
and the OSI reference stack model to better understand the interplay of
physical devices/wiring and toplogy designs/managing packet flows. It
is daunting at first, but the light _will_ go off and you will
"suddenly" understand the sense of it all (at least if your lucky
Then a review of the hardware discussions will be clearer.

Have a look:
http://www.cisco.com/univercd/cc/td/..._doc/index.htm
http://www.cisco.com/univercd/cc/td/...idg4/index.htm
http://www.cisco.com/univercd/cc/td/...ntwk/index.htm

I'm not a Cisco snob -- they just happen to a have a good one-stop
place to get some docs. Worth a look.

hth,
prg

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> is the star bus network physical star and logical bus. or is it a
> physical hybrid, i.e. physical bus too. I find that differnt sites say
> different things.
> Mike Meyers book says it's physical star logical bus. But 2 other
> sites say it's a physical hybrid.

I think you might be confusing physical topologies with logical topologies.
A physical toplogy merely refers to how the network devices (workstations,
hubs, switches, routers, etc.) are arranged. A logical toplogy refers to
how the electronic data is trasnmitted/arranged on the network. To answer
your question, I believe a "star bus network" refers to a network that has a
*physical* star toplogy, and a *logical* bus toplogy.

It's a physical star because the devices all connect to a central location.
For instance, take the set up you see inside most people's houses these
days. In my house, we have 4 desktop computers and 2 laptops that all
connect to a central linksys router/switch, which then connects to our cable
modem and goes out to the internet. This is a physical "star" because all
the computers/laptops are connected to *one* central location (the
router/switch).

As for the logical part, think of it this way....the router/switch
essentially has a "bus line" inside that all the computers/laptops are
connected into. So, even though the network devices are arranged in a star
toplogy, they still kind of have a "data bus" inside the switch. I probably
skimmed over a couple technicalities here (maybe a hub would be a better
example of a logical bus device than a switch), but hopefully I cleared it
up for you somewhat.

It's easy to see why you got confused. It's almost like anything these days
in IT - the verbiage/lingo is very ambiguous and often doesn't lend itself
to being explained very clearly. Most of the time, it's not really relevant
to understanding the material either.

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com

> is the star bus network physical star and logical bus. or is it a
> physical hybrid, i.e. physical bus too. I find that differnt sites
> say different things.
> Mike Meyers book says it's physical star logical bus. But 2 other
> sites say it's a physical hybrid.

When you eventually become comfortable with the idea of network
"topologies", you'll begin to understand the ideas presented in various
papers.

--
use hotmail for email replies

(E-Mail Removed) wrote:
> is the star bus network physical star and logical bus. or is it a
> physical hybrid, i.e. physical bus too. I find that differnt sites say
> different things.
> Mike Meyers book says it's physical star logical bus. But 2 other
> sites say it's a physical hybrid.
>
>
> http://web10.eppg.com/betabooks/nov01/meyers/ch04.html
> "Star bus networks use a physical star design that provides improved
> stability and a logical bus that maintains compatibility with existing
> Ethernet standards"
>
> so that says that a star bus is a physical star, but a logical bus.
>
> http://web10.eppg.com/betabooks/nov01/meyers/ch04.html
> "In a network, physical topology describes the layout of the wires,
> while logical topology describes the behavior of the electronics"
>
> so it appears that a star bus is physically just a star, - not a bus at
> all.
>
> Yet these sites appear to state it differently
>
> http://distancelearning.ksi.edu/demo/370/ch01d.htm
> "The star bus is a combination of the bus and star topologies. In a
> star-bus topology, several star topology networks are linked together
> with linear bus trunks. Figure 1.28 shows a typical star-bus topology.
> "
>
> so that site appears to imply that a star bus topology is physically a
> star and physically a bus. It's a 'physical hybrid topology'(my
> expression).
>
> http://www.enlightenment.co.uk/frame...c/w-netwrk.htm
> "Daisy chain topology
> This topology is also sometimes called a star-bus. Hubs (which could
> contain star network segments) are linked in series. "
>
>
> thanks in advance
>
>
I buy the Mike Meyers definition. It is physically a star, but the
logical bus circuitry is in the hub.