Network Topology - Balancing A Cable based Tree Network

Various Network Topologies

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Network Topology

The term Network Topology refers to the physical layout of the components of the network. There are a few different methods to lay out a network that are commonly used. They include; A Bus, A Star, A Tree and a Ring.

This article will focus on the Tree Network which is a mix of a star and a bus usually. The reason I am writing this is to clear up an issue I ran into when the cable installer came to troubleshoot the internet service at a new address.

A Bus Topology

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Bus Topology

A Bus network consists of a cable run that has multiple “spurs” coming off of the backbone and feeding the devices on the network. Each spur comes off the backbone by means of a tap. The tap has three terminals two of which are straight through connections with no noticeable loss and a tap which has attenuation built in. Taps come in various attenuation rates.

A Star Topology

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Star Topology

A Star Network consists of a central hub with the devices connected to it like the spokes of a wheel. Each device communicates directly through the hub. Many times the hub will be both a gateway and a router but can be a simple hub feeding each device with no filtering at all as well.

A Tree Topology

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The Tree Topology

The Tree Network is a combination of the Bus and the Star. It is the most common topology used in residential networks especially cable TV and Internet. In a Tree the devices connect to a hub or multiple hubs some of which feed from another hub and or the backbone if one is used. In cable TV/Internet, the drop from the utility pole ending at the point of entry is called the bus. This would include the modem if that is where the cable ends. There would be splitters coming off the bus and distributing the network to the various cable boxes and or modem.

This Case

In this case, the cable was already installed in the residence I moved to, and was quite a mess with old splitters and un-terminated cable. At some point a contractor came out and replaced the splitters and disconnected a long run of cable that was not in use. The network was still complicated, but was functional.

When I moved to this location, I connected the long run of cable that had been left off and replaced the connectors on that cable. I was not able to get a strong enough signal to allow internet service to my modem. A technician came out and determined that a booster was necessary, and installed one at the end of the long run, so that the entire boost was focused in one modem and TV box.

The problem was, that the signal was far too strong for the TV box and needed to be dropped using a tap. My contention is that the booster should have been placed at the point where the drop entered the home thereby boosting the entire network and making the tap unnecessary.

The Proposed Network

This network covers a main home and two remote buildings that are 100 and 180 feet away respectively.

The following two diagrams show the network as it exists and the proposed fix I made. In the first diagram, you can see that the booster was placed in the remote building (Dotted Green Box) right before the tap and the modem/TV Box. This makes the boost apply only to those two devices and is mostly wasted energy.

I proposed that the booster be placed on leg four of the splitter in the main House (Dotted Orange Box) so that the 180 + feet of cable going to the two remote buildings got the boost. The main house has adequate signal and does not require a boost. This is called "Balancing the Network."

Network Drawing 1

As the Technician Installed the network
As the Technician Installed the network | Source

Network Drawing 2

The Proposed Network
The Proposed Network | Source

Let’s assume that the signal coming from the cable supplier is +30DB as it enters the home. It first goes through a female to female connector with a ground tap. This has no appreciable loss. Next it hits a two way splitter and has a loss of -3.5DB on each leg. Then one leg hit another two way splitter at the main home. This means the Home modem is getting 23DB of signal and the TV box is getting 23 DB.

The other leg of the first splitter hits a four way splitter that feeds the other TV boxes in the main home and the remote buildings. At the output of the four way splitter the signal is now 16DB as each leg has a -7DB loss. At 16 DB we are still good for TV and for a modem.

The fourth leg of the four way splitter goes to another two way splitter at the remote building 1 and then to the remote building two. So remote building 1 gets 12.5 DB and remote building 2 gets 9 DB which is too low for reliable use.

Now at building 2, there is a booster at +15 DB and a tap. So after these added devices, the modem gets 24 DB and the TV/box get 20.5 DB. This is fine for building 2 but building one is marginal.

My proposal puts the boost in the main house boosting the run to the remote buildings. In this case, building 1 would get 27.5 DB and building 2 would get 24 DB. This would make the b2 modem receiving 20.5 DB and the TV box 20.5 DB. This way both remote buildings get good strong signal.

This is not rocket science, common cable company installers, get your acts together!

© 2012 Mark G Weller

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Comments 16 comments

Daisy Mariposa profile image

Daisy Mariposa 4 years ago from Orange County (Southern California)

Mark,

You've done a great job of making what can be a complicated topic easy to understand. The illustrations you provided were extremely helpful.


Curiad profile image

Curiad 4 years ago from Lake Charles, LA. Author

Thank you Daisy, It can be complicated but not impossible to work out.


billybuc profile image

billybuc 4 years ago from Olympia, WA

Mark, I gotta tell ya, you are flying way over my head on this one. You have done a great job of laying it all out for someone who even has a clue what the heck this means but man, that ain't me. :) I'm just here to lend you some support and tell you great job as always.


Curiad profile image

Curiad 4 years ago from Lake Charles, LA. Author

Thank you Bill, It was instigated by the sloppy work done by the cable technician that was sent to solve my issue.


Angela Brummer profile image

Angela Brummer 4 years ago from Lincoln, Nebraska

Unbelievable intelligent. Again informative and meticulously put together

This article has been shared on Stumble, Twitter, Reddit, Google+, Facebook, and my hub following.

Via: http://angelabrummer.hubpages.com/hub/Hubber-Alert


Curiad profile image

Curiad 4 years ago from Lake Charles, LA. Author

I am really pleased that you like my writing Angela. It is a boost to my efforts and I appreciate you!


dwachira profile image

dwachira 4 years ago from Nairobi, Kenya

Great hub Curiad, a lot of users expect the network installers to do all the work, i wish we could have a clue of what they are doing like you did rather than depending on their suggestions some of which might be less productive. Thanks for sharing.


phdast7 profile image

phdast7 4 years ago from Atlanta, Georgia

Good Evening Curiad - I am so technologically backward its not even funny, and I don't fully understand what your article is about. But the graphics are terrific and clear and I am sure very useful (to people who know more than me, which is almost everyone). Often, I have stumbled across a hub that uses only words, lots of complicated words, and I am utterly lost.

So thank you for thinking of the rest of us the non-techies. Next time he comes over my IT son and I will sit down and go over your hub and make sure I understand it...but terrific graphics! Hope you have a great week. :)


Curiad profile image

Curiad 4 years ago from Lake Charles, LA. Author

Thank you for visiting phdast! If you ever have questions feel free to message me, I'll be happy to help.


sandrabusby profile image

sandrabusby 4 years ago from Tuscaloosa, Alabama, USA

May not be rocket science to you, but it's Greek to me. Thanks for being one of those who understands.


Curiad profile image

Curiad 4 years ago from Lake Charles, LA. Author

My pleasure Sandra, I am glad you visited.


ChristyWrites profile image

ChristyWrites 4 years ago from British Columbia, Canada

Wow, I know so little on the topic yet your diagrams and explanations help the details make more sense to me. Well explained Curiad and this looks to be a good reference manual.


Curiad profile image

Curiad 4 years ago from Lake Charles, LA. Author

Thank you Christy, I appreciate you!


Wesley Meacham profile image

Wesley Meacham 4 years ago from Wuhan, China

Makes sense to me. Interesting Article. Though I'm not as well versed in networks as you are I'm no stranger to wondering why "professionals" in certain areas do things the way they do instead a way that is well thought out. I think in general they are just looking for the quickest fix possible and don't want to take the time to think through their actions. Voting up and sharing.


Curiad profile image

Curiad 4 years ago from Lake Charles, LA. Author

Thank you Wesley, I agree many technicians simply take the easy way out.


Shruti 24 months ago

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