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Network Topology
Author: JonnyGURU
Date Posted: October 1st, 2001
URL: http://www.slcentral.com/agurusworld/23

Network Topology

A topology is the general structure of a network. This term should not be confused with topography, which is the surveying of the surface features of a place.

In actuality, the two terms are relatively similar in spelling and nature. Maybe that's why I always get the two confused!

I received a goody box from Intel the other day. Where I work we carry Intel NICs and CAT5 cable in custom cut lengths, so I suppose they thought it was a good idea to introduce us to their PRO/Wireless 2011.

Intel had sent us two 11 Mbps PCMCIA cards... Oops. I forgot that we're calling them "PC Cards" now days. They sent a PCI carrier for one of the PC Cards, and one of the 2011 LAN Access Points, which looks like a cross between rabbit ears for a television set and Poo-Chi, the robotic dog.

Now before some of you nerds start to assume that this is some sort of a review of a wireless network kit, I'll have you know that I have no inclination in writing a review.

You want a review? Here's my review: Plug it in, turn it on, and if all of the PCs have a PRO/Wireless 2011 card in it, then everyone is online without any CAT5 or Coax. Imagine how easily LAN get togethers would be if everyone had one of these cards and the host of the party had an Access Point? Sweet, eh?

What I thought was funny is that I was the only one that volunteered to take the gizmo home. At home, I already have several networking gizmos and bringing home this little guy was sort of the icing on the cake... and thus, this week's edition of AGW. My own network topology appeared so grossly ridiculous to me, that inspired me to type up this quick little crash course on networks.

Most topologies look like this:

I'll take the time to break this down for you. The Internet comes into the house via a MODEM, Cable MODEM (which is more of a "reverse-MODEM" rather than your typical modem for dial up), DSL, ISDN or what have you. Now, if there is more than one computer on a network that needs to be attached to this single Internet connection, then a router is required. Essentially, a router is a bridge from one network to another and in my example; it's bridging an internal network to the Internet. A LAN to a WAN. Simple.

Despite the word "bridge" being used in the above paragraph, a router is different then a bridge. A bridge connects two LANs together using the same protocol. This example topology doesn't use a bridge, but we'll get back to bridges in a little bit.

Hubs and switches are very similar. The serve the same function, but do their jobs in different ways. A hub allows a central connection point for several computers. Hubs are fairly dumb pieces of equipment. All they do, in a sense, is take a data signal and split it up into multiple ports.

Now a switch is a bit smarter than a hub. A switch still allows several computers to connect to a common connection, but a switch direct network packets to only the ports those packets were intended for. This speeds up the network by not feeding all data to all ports.

And now for the topology in my house. Feel free to laugh. I did too once I put it to paper...

Actually, this is what it would look like if you were to put it on paper, but it's really not as bad as it looks.

The Internet enters the house via a cable modem. The cable modem is hooked up to a router. I use an SMC Barricade, so my router, switch and print server are actually all built into one.

I'm using all four ports on my Barricade's built in switch. One port for each PC in the living room, one port to a Netgear Home PNA bridge, which is a bridge because it bridges a CAT5 media based network with a Home PNA phone line based network, and one port plugged into the Intel 2011 Access Point, which is technically another bridge since it bridges the CAT5 media with a wireless network.

I have the Netgear Home PNA bridge because I live in an old house with high ceilings and a low roof leaving me with virtually no attic. Add to this that most of the walls are concrete and the floors are Terrazzo (I have run under carpet before). I wasn't about ready to drop cable in this place. Taking this and the cost of materials (cables, ends, wall plates, etc) and it was easy for me to conclude that my time was worth more than a $125 bridge.

The Intel 2011 Access Point is actually just a toy. But I can see it having its uses.

The photo above is a shot of the floor underneath my wife's desk. The cable modem is on the desk so we can make sure we have connectivity and a cable drops down to the SMC Barricade, which then goes of to the Netgear Home PNA switch, a printer, two PCs and the Intel 2011

Using the Intel 2011 system is ludicrous for someone that simply doesn't want to drop cable, such as my self. Although I'm impressed with the 11 Mbps access speeds over a wireless connection, the cost of components is a bit out there. Each PC Card is over $100 and the PCI adapter for use with desktop PCs is another $75! And the price of the Access Point? It costs over $650!

But where the Intel 2011 really shined, and was actually quite fun, was in using it in a laptop. One could be in the bedroom, in the living room, in the kitchen or in the can, and as long as you battery held up or there was an electrical outlet near by, you could be online.

On the other end of the house there is a second Netgear Home PNA bridge. Why did I spring for a second bridge rather than a cheap little $20 Home PNA network card? Well, I do a lot of work at home in the center bedroom, so to install a Home PNA NIC in every machine I bring into the house is not practical. I have the second bridge hooked up to an 8-port hub and since most PCs have NICs in them, connecting to the network is very easy.

Another reason for the second bridge is cross platform compatibility. To my knowledge, Home PNA does not have drivers or software for anything but Windows. If I bring in a Linux box, I'm screwed as far as I know in trying to get a Home PNA adapter to work.

Also, because the bedroom that this second bridge is in is for me to work on PCs without getting in my wife's way (I manage to do this anyway), there is a D-Link powered KVM switch installed on the desk as well as the aforementioned 8 port hub, so several PCs can be networked and running making take home jobs much easier.

Now just when you thought the limit of the gizmos in my house were limited to just networking goodies, the icing on the cake is the X10 Entertainment Anywhere transmitter and receiver in the living room. Sure, it's not a network device and doesn't really go anywhere in a text book topology, but if you have gotten the jist of how much of a jungle of CAT5 and AC Adapters my place is, then you can understand why this gizmo needs to be mentioned.

The computer has a DVD player in it and more music in the form of MP3 files, than I have music on CD. Watching a DVD on a 17" monitor isn't that great and listening to music on a pair of Sony SRS-170s isn't exactly room filling.

The Entertainment Anywhere system allows me to broadcast these movies and music, without wires, to the entertainment center on the other side of the living room. All of the pieces fit (I know because I watched them fall away).

Now if I only had a larger television set to watch those DVDs on. :(

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