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New Visitor
dviglione02
Posts: 3
Registered: ‎06-23-2012

how is possible to have internet without cable tv setup

I'm currently using comcast high speed internet but I don't have cable (we at least not cable tv). My understanding is my cable modem allows my computer to connect to the Internet through a cable TV wire, instead of a telephone line. Yet I don't have cable tv so how is this connection happening? This question is more or less just understanding how the digital data from my computer is transmitted to analog signals via radio frequency with the absence of cable tv. 

Connection Expert
EG
Posts: 43,220
Registered: ‎12-24-2003

Re: how is possible to have internet without cable tv setup

The internet service and the T.V. service operate on separate dedicated frequencies / channels independent of each other.

 

Basically, the modem ("mo" "dem") is a "mod"ulator / "de"modulator media converter device that converts digital ethernet signals to analog RF signals and vice versa.

New Visitor
dviglione02
Posts: 3
Registered: ‎06-23-2012

Re: how is possible to have internet without cable tv setup

So you are saying that there are separate hybrid fiber coax channels for internet and tv? So the HFC that transmits analog radio signals my modem to the CMTS is independent of the cable tv wire?

Connection Expert
EG
Posts: 43,220
Registered: ‎12-24-2003

Re: how is possible to have internet without cable tv setup


dviglione02 wrote:

So you are saying that there are separate hybrid fiber coax channels for internet and tv?

 

Yes.

 

So the HFC that transmits analog radio signals my modem to the CMTS is independent of the cable tv wire?

 

No. It's all done on the same wire.


 

New Visitor
dviglione02
Posts: 3
Registered: ‎06-23-2012

Re: how is possible to have internet without cable tv setup

Thanks for response. They say that CMTS equipment has an ethernet interface that connects it to the internet. I don't fully understand what they mean by this. I thought ethernet was used for building a local area network in a person's home so that multiple computers in the same house can share the internet using separate private ip addresses. In other words, IP packets use ethernet to transmit the right data to the right computer. But CMTS is a piece of equipment that from my understanding sends data to thousands of homes in a service area via a public facing ip address. So how does the CMTS ethernet interface work then?

Recognized Contributor
bnaughty
Posts: 256
Registered: ‎06-16-2012

Re: how is possible to have internet without cable tv setup

The CMTS provides service to many customers, but it's not by means of one IP address....  Each customer is assigned one IP address that dynamicaly changes, from time to time...  Your router uses that one IP address, and splits it into many, comprising your home network...  each device you own has an IP assigned by the router, not comcast...  all traffic is still routed through the one IP address comcast assigned your modem...

 

As far as the inner workings of a CMTS, I only have a basic understanding of it...  perhaps there are some technical details online somewhere, but nothing so specific that it jeopardizes the company...  it all starts with headend....  several nodes are connected from the headend, and multiple taps from each node...  you are connected to one of the taps....  It works similar to how a home network would, but MUCH more complex....

 

I'm sorry I don't have your exact answer....

Connection Expert
EG
Posts: 43,220
Registered: ‎12-24-2003

Re: how is possible to have internet without cable tv setup

[ Edited ]

bnaughty wrote:

The CMTS provides service to many customers, but it's not by means of one IP address....  Each customer is assigned one IP address that dynamicaly changes, from time to time...  Your router uses that one IP address, and splits it into many, comprising your home network...  each device you own has an IP assigned by the router, not comcast...  all traffic is still routed through the one IP address comcast assigned your modem...

 

FWIW, The WAN (public) IP addy that their (CC's) DHCP server assigns is actually forwarded by the modem to whatever device is directly connected to the LAN side of it (be it a router or a computer) and not to the modem device itself. The modem acts as a layer 2 bridge however it does get assigned an internally used IP of its own with which the ISP uses for managerial purposes via SNMP.

 


 

Recognized Contributor
bnaughty
Posts: 256
Registered: ‎06-16-2012

Re: how is possible to have internet without cable tv setup

I appreciate the clarification...