bad books and bad teachers

sometimes my school drives me crazy.
Last night in Operating Systems class we were going over network topology. the book and teacher defined Bus, ring, star as the basics then reviewed the various hybrids such as star bus etc.

anyway, star config was defined as computer cabled into one central location like a hub or switch. Bus defined as a main networking line that computers are hooked into. (like with old coax) The discussion point was what would be the best way to network one floor of a college dorm.

To me the answer is obvious. . . a star config! There's a hub in the hall closet and all computers run CAT5 cable to the hub. She (the instructor) says no BUS is the best. I say but you wouldn't want to use old technology like coax to make this work, you'd use cat5 and you couldn't do a straight bus in this case. She says you can. So I ask how it's even possible to do it this way with CAT5 RJ45 connections. She says you have the cables in the wall and the computers plug into the wall jacks.

This doesn't make any sense because the straight through cables -in the wall or not- still have to go somewhere to make a connection. Like to a patch panel then to a hub which makes it a star config. I explain this and add that the only way I can see using a straight (non-hybrid) bus topology with CAT5 is to have two computers hooked via crossover. Then you have one networking line that both computers are hooked into.

Now the morons in the class who've never set up a network, or made a cable and run it, start jumping in trying to tell me I'm wrong and that you can get the adapters at radio shack to make it work for $1.99. AARRGH!

Finally I just give up and say "fine whatever you say, just let me know what the answer will be in the test so I can get it correct."

I agree with you on the Star topology. Although the Bus just needs the backbone to be terminated at both ends, if there's a break or a disconnection in the cabling everybody loses connectivity.

I know what you mean. I've been putting up with an extrememly poor instructor for the past year. The old instructor who at least had some real world experience moved to Colorado. I don't know where the hell they found this new guy! But if he was the best of the bunch I'm extremely firghtened about the expertise in this area. I constantly correct him in class. At least he takes it well. He's to the point where he admits that he is still learning this stuff too, so he welcomes my input (although my grade seems to slip the more I provide the input). When issues come up in class now, the class takes over the discussion and we toss it around a little until we understand it. Usually by then the instuctor sits back and listens.

I thank God that this is my last quarter.

They say that those who can't do, teach. Considering teacher salaries I can see why. You've got to look at this like a game. Why? Because you're right. But, you don't want to fail. So, you have to humor your teacher.

Or, you can get yourself in a world of dung and tell her that the CCIE at work told you that an 80/20 multilayered switched network (a hierarchial mesh) is best and she should shut her trap if she doesn't know what she's talking about. I'm not a CCIE but she doesn't know that. ;)

RJ45 cannot be used in bus topologie. Just can't. Has for bad teachers, i have a very esentric one.. He hates windows, but is teaching it (this is how you move folders, and no you can't do it that way(in resposne to a question) but you can unser linux!). Also whenever grades are good, it's because he's a good teacher, but if things go bad, it's cause we don't pay attention... Shesh..

[quote]Originally posted by Matridom:
<strong>RJ45 cannot be used in bus topologie</strong><hr></blockquote>
Exactly what I said to her! But she insisted that it could be done.

I'm half tempted to take in 3 old computers with NICs a fair length of cable with loose ends and crimpers. Then slap it all down on the table and say "show me how to cable this 3 computer network as a bus topology with RJ45 connections."

I'm no networking guru and have only set up very simple peer to peer "star" networks but I have some idea of what's going on.

[quote]Originally posted by kato2274:
<strong>
Exactly what I said to her! But she insisted that it could be done.

I'm half tempted to take in 3 old computers with NICs a fair length of cable with loose ends and crimpers. Then slap it all down on the table and say "show me how to cable this 3 computer network as a bus topology with RJ45 connections."

I'm no networking guru and have only set up very simple peer to peer "star" networks but I have some idea of what's going on.</strong><hr></blockquote>

Do it! Or better/easier yet, print this disscussion out and show her and the class. I do this stuff for a living and what she is saying would only be possibel if there was a coax backbone and your CAT5 has converters at the point of hookup to the coax (can't think of the name of the converters, made by hubble tho). This would be the only way, but a very stuupid and slow way.

And if that is not good nuff, tell her to log on to windrivers and ask it herself!!! She would get an arse riping then, eh?

Here are a few comments i found on the Cisco page (if they don't know netowrking, i don't know who does)

"A bus topology uses a single backbone segment (length of
cable) that all the hosts connect to directly.

A ring topology connects one host to the next and the last
host to the first. This creates a physical ring of cable.

A star topology connects all cables to a central point of
concentration. This point is usually a hub or switch, which
will be described later in the chapter.

An extended star topology uses the star topology to be
created. It links individual stars together by linking the
hubs/switches. This, as you will learn later in the chapter,
will extend the length and size of the network.

A hierarchical topology is created similar to an extended
star but instead of linking the hubs/switches together, the
system is linked to a computer that controls the traffic on
the topology.

A mesh topology is used when there can be absolutely no
break in communications, for example the control systems
of a nuclear power plant. "

so has suggested earlier, have her network 3 or more computers using one length of ethernet cable. And has per the above definitions, if she needs to use a hub/switch, she has just created a star topologie (the above definiations are cut/past from Cisco)

what if you put 2 nics in each machine?

Thats about the only way I can even fathom your instructor would think of a bus topolgy with cat5

[quote]Originally posted by Matridom:
<strong>Here are a few comments i found on the Cisco page (if they don't know netowrking, i don't know who does)

"A bus topology uses a single backbone segment (length of
cable) that all the hosts connect to directly.

A ring topology connects one host to the next and the last
host to the first. This creates a physical ring of cable.

A star topology connects all cables to a central point of
concentration. This point is usually a hub or switch, which
will be described later in the chapter.

An extended star topology uses the star topology to be
created. It links individual stars together by linking the
hubs/switches. This, as you will learn later in the chapter,
will extend the length and size of the network.

A hierarchical topology is created similar to an extended
star but instead of linking the hubs/switches together, the
system is linked to a computer that controls the traffic on
the topology.

A mesh topology is used when there can be absolutely no
break in communications, for example the control systems
of a nuclear power plant. "

so has suggested earlier, have her network 3 or more computers using one length of ethernet cable. And has per the above definitions, if she needs to use a hub/switch, she has just created a star topologie (the above definiations are cut/past from Cisco)</strong><hr></blockquote>

Those are all physical topology definitions. If you look at them as logical topologies (how they actually work) a switch is a mesh and a hub is a bus. A logical star topology would be something like a terminal server setup or a mainframe or AS400. I don't know why they call it a bus because only one machine can ride at a time :)

Sounds like you guys are going to ITT on the CNST/IT program.....
I just graduated from the first CNST class our location had. (class mascot: the guinea pig) and I can identify with you. We had some GREAT instructors, but unfortunately the best one became the program chairman and did nothing but administrative functions at the school. Boy did we ever have some lUsers, though. The instrutor in the hardware class is probably trying to make a voodoo doll out of me :p

[quote]Originally posted by Damned Angel:
<strong>what if you put 2 nics in each machine?

Thats about the only way I can even fathom your instructor would think of a bus topolgy with cat5</strong><hr></blockquote>

yeah that's about the best (only) way I could figure. each machine connected to one another via crossover cable

[quote]Originally posted by FatalExceptionOE
<strong>Sounds like you guys are going to ITT on the CNST/IT program.....
I just graduated from the first CNST class our location had. (class mascot: the guinea pig) and I can identify with you. We had some GREAT instructors, but unfortunately the best one became the program chairman and did nothing but administrative functions at the school. Boy did we ever have some lUsers, though. The instrutor in the hardware class is probably trying to make a voodoo doll out of me
</strong><hr></blockquote>

Give that man a peanut!!! I am indeed going to ITT for CNS. Even typing this reply from the visual basic class which is is going way too slowly for me. I expected a lot more from a national educational organization. If I would have known it was going to be like this, I would have picked any five and dime tech school and not paid the 30K+. Hopefully things will get better.

Matridom - can you send the link of the cisco page you cut and pasted from. I think I might like to print that up with the cisco logo and url and take it to class next week.

[quote]Originally posted by iateyourcat:
<strong>

Those are all physical topology definitions. If you look at them as logical topologies (how they actually work) a switch is a mesh and a hub is a bus. A logical star topology would be something like a terminal server setup or a mainframe or AS400. I don't know why they call it a bus because only one machine can ride at a time :) </strong><hr></blockquote>

i beg to differ, switch (layer 2) and hubs(layer1) are used by star topologies, The differnce between a hub and a switch is that a switch acts has a repeater (repeating the information to all ports) where a switch is inteligent and forwards based on mac address, a mesh topologie would be where all major devices are interconnected(i have 5 switch, i have 5 ports in each switch dedicated to connect to each other switch) all topologies are classified has above REGARDLESS of software running on it. You can run a terminal senerio on a bus topologie.

The above argument would be valid ONLY if your trying to map the software to a hardware type. if that's the case, why not compare the mesh topologie to the GPS system? We are talking about architecture here, not software.


Damned Angel, in your senerio, what would happen is that each computer could talk to it's neighbour, but no one else..

For education.. i'm working on CCNA and taking networking full time at school, I also have 3 years experience in a tech shop.

[quote] Matridom - can you send the link of the cisco page you cut and pasted from. I think I might like to print that up with the cisco logo and url and take it to class next week.
<hr></blockquote>

Sorry man, I'll post a pic for ya if you want, just let me know, the URL unfortunatly is password protected.

If the question is "what is the BEST way to set up the network?" Then in my mind that completely negates the fact that you COULD set it up with a Bus topology. Yes it can be done as many intelligent people have pointed out here, but that is not the question.

IMHO~ Star topology with a switch is the way to go.

Under a Bus topology, the signal weakens as more computers are added to the line, there is no management of who can broadcast at any give time and therefore your bandwidth is shot as they all try to talk at the same time. And it is harder to troubleshoot errors, outages and performance loss. Don't even try to add more computers or remodel the building or you're asking for heartache.

Under a Star topology you have centralized management for troubleshooting from the center of the star, (like a managed switch or troubleshooting at the hub) it is more fault tolerant as a single computer outage at any point of the Star does not affect the rest of the nodes on the network.

Your teacher probably never remotely managed a switch or diagnosed network problems from 45 miles away at 3:00 in the morning or had to expand and move computers in an Emergency room without affecting the connectivity. ;)

A good book to pick up on Networking is <a href="http://www.sybex.com/SybexBooks.nsf/booklist/2914" target="_blank">this one</a> from Sybex it's a thick book it's informative and it's cheap.

[quote]<strong>
i beg to differ, switch (layer 2) and hubs(layer1) are used by star topologies, The differnce between a hub and a switch is that a switch acts has a repeater (repeating the information to all ports) where a switch is inteligent and forwards based on mac address, a mesh topologie would be where all major devices are interconnected(i have 5 switch, i have 5 ports in each switch dedicated to connect to each other switch) all topologies are classified has above REGARDLESS of software running on it. You can run a terminal senerio on a bus topologie.</strong><hr></blockquote>

Physical topology defines the cable's actual physical configuration (star, bus, mesh, ring, cellular, hybrid). Logical topology defines the network path that a signal follows. The signal of a device connected to a switch is capable of reaching any other device while at the same time any other device within the switch can also reach any other device directly.

Physically a switch is at the center of a star topology. Logically, there is an entire mesh network within the switch connecting each endpoint to each other endpoint directly. That's why switches are so much more expensive than hubs.

As I said before, an 80/20 multilayered switched network is the way to go. Check it out. The info is in any CCNP design book.