Columbia ISA
Audio – Video




Cable Modems



Cable Modems, Routers and DSL
Home Networking

Hookup to High-Speed Internet at Home
Cable Modems from Cable TV providers

Diagrams : Wiring : Cable Modems : Routers : DSL : Blu-ray Basics

Cable Modems.

After using dial-up internet service from home and experiencing the often slow download times, many people looked for a way to speed up their response times. How could consumers access the internet from home and get faster speeds than dial-up?

Besides the telephone company wires, many homes have the coaxial cable from their cable TV provider connecting them to the "headend" or cable company telecommunications facilities. This link into the home offers an alternative and one that has the potential to be faster. The coaxial cable has greater capacity than the phone company wires.

If your cable TV provider can offer high-speed internet service, often called BROADBAND, they will make more money and be more successful. What is needed is a way to connect the home computer to the cable TV coaxial cable, thru the cable TV "headend" and out to the internet.

Enter the cable modem. The cable modem allows the home computer to hook up to the cable TV coaxial cable. In addition, you can be on the internet all the time without tying up your phone line. It is sometimes called "always on".

How It Works

Cable modem service is offered through a partnership between the ISP (Internet Service Provider) and your local cable company. Typically, you'll be charged for broadband service on your cable bill, rather than paying the ISP directly. Your cable company is responsible for installing the cable modem and maintaining the quality of your service over the local cable network. At the main network office -- commonly referred to as the "headend" -- you're connected to the cable ISP's national backbone. It, in turn, is linked to the Internet.

If your cable modem service runs into a problem, you're best advised to call the cable company. A technican will probably be dispatched to your household if there's a cable network problem. If there's an ISP problem, the cable company will route your call to a technical support center to try to resolve the issue.

If you want to subscribe to cable modem service, your cable company will require you to use Road Runner or another ISP of its choosing. You'll still be able to link up with another ISP, but it may cost extra.

Road Runner was founded by Time Warner Cable -- North America's second-largest cable company -- and Time Inc. to deliver broadband cable modem service. In December 1997, MediaOne Group invested in Road Runner, which gave the service access to more than 28 million homes, or one-quarter of North America's cable households. In June 1998, Microsoft Corp. and Compaq invested in Road Runner, which has since then forged affiliate agreements with several other cable TV companies. Typically, subscribers pay $40 per month for a package that includes unlimited Internet access and cable modem rental. For more information, visit the Road Runner corporate Web site at

Cable Modem Hookup Diagram

Cable Modem Front Panel

1. power indicator - modem device is on

2. data receive

3. data send

4. Cable company connected link

5. User device link (PC or router)

Modem Light Indicators

Power Flashing – Startup diagnostics in progress.
Power On – Cable modem is powered on.

Receive Flashing – Scanning for a downstream channel.
Receive On – Downstream channel is connected.

Send Flashing – Scanning for an upstream channel.
Send On – Upstream channel is connected.

Online Flashing – Scanning for a network connection.
Online On – Startup process complete. Modem aqcuired.

Flashing or On – Transmitting or receiving data.

This light turns on when the standby button is pressed and standby mode is activated. If this light is on, all other lights will be off. Cuts off internet.

Cable Modem vs. DSL Comparison

When evaluating cable and DSL internet services, you should consider:

Speed: Cable boasts faster speed than DSL Internet in theory. However, cable does not always deliver in everyday use.

Popularity: In the U.S., cable Internet enjoys greater popularity than DSL, although DSL has been closing the gap. Outside the U.S., DSL continues to hold the edge.

Customer Satisfaction: In the U.S. cable services generally rate lower than DSL in customer surveys.

Security: Cable and DSL implement different network security. Historically, more concerns have existed with cable security. It's likely both DSL and cable are "secure enough" for most people's needs.

Cable modem Internet services on average promise higher levels of bandwidth than DSL Internet services, and this bandwidth roughly translates to raw speed. However, while cable Internet will theoretically run faster than DSL, several technical and business reasons can reduce or even eliminate this advantage.

In terms of theoretical peak performance, cable modem runs faster than DSL. Cable technology supports approximately 30 Mbps of bandwidth, whereas most forms of DSL cannot reach 10 Mbps. One type of DSL technology, VDSL, can match cable's performance, also supporting 30 Mbps. However, Internet service providers generally do not offer VDSL, but rather the cheaper and slower ADSL or SDSL services.

In practice, cable's speed advantage over DSL is much less than the theoretical numbers suggest. Cable modem services can slow down significantly if many people in your neighborhood access the Internet simultaenously. Both cable modem and DSL performance vary from one minute to the next depending on the pattern of use and traffic congestion on the Internet. DSL and cable Internet providers often implement so-called "speed caps" that limit the bandwidth of their services. Some home networks cannot match the speed of the Internet connection, lowering your performance.

Both cable and DSL service providers commonly employ bandwidth / speed caps for residential customers. Bandwidth caps place an artificial limit on the maximum speed a customer can achieve by monitoring their individual traffic flow and throttling network packets if necessary. Bandwidth caps can reduce a 30 Mbps service down to 3 Mbps or even lower.

Service providers may have several motivations for imposing speed caps including the following:

o 1. Providers concerned about the capacity limits of their network may implement a cap so that they can accomodate more customers.
o 2. Providers may believe that the vast majority of customers do not actually need any more bandwidth than that allowed under the cap.
o 3. Providers may want to create a fair-and-equal distribution of bandwidth of customers. Without a cap, for example, some DSL subscribers would enjoy much higher bandwidth levels than others in the same neighborhood.
o 4. Providers may be want to charge higher or lower rates for greater or lesser bandwidth levels.

DSL - Digital Subscriber Line

ADSL (Asymmetric Digital Subscriber Line) is a form of Digital Subscriber Line (DSL) Internet service. ADSL provides greater bandwidth for downloads at the expense of upload speeds. ADSL is the most common form of DSL used in home networking.

ADSL is designed to support the typical home user who frequently downloads large amounts of data from Web sites but upload relatively less often. ADSL works by allocating a majority of the available phone line frequencies for communication of downstream traffic.

In other respects, ADSL possesses all of the characteristics one associates with DSL, including "high-speed" service, an "always on" combination of voice and data support, and availability and performance that is limited by physical distance. ADSL is technically capable of up to 6 Mbps (roughly 6000 Kbps), but ADSL customers in practice obtain 2 Mbps or lower for downloads and up to 512 Kbps for uploads.


VDSL (Very-high-speed Digital Subscriber Line) was developed to support exceptionally high-bandwidth applications such as High-Definition Television (HDTV). VDSL is not as widely deployed as other forms of DSL service. However, VDSL can achieve data rates up to approximately 51,840 Kbps, making it the fastest available form of DSL.

To perform at this speed, VDSL relies on fiber optic cabling. VDSL is designed to work more as a business service that uses ATM internetworking rather than as a consumer service that utilizes IP. VDSL supports both voice and data communication on the same line, like other forms of DSL.

Also like most DSL technology, the performance of VDSL depends significantly on the physical distance traversed by wires: Shorter distances mean faster networking. The technology was originally named VADSL ('A' for asymmetric), but VDSL has now been improved and can operate in either symmetric and asymmetric modes.


coaxial cable (coax) - A type of wire consisting of a center wire surrounded by insulation and a grounded shield of braided wire. The shield minimizes electrical and radio frequency interference. Home type coaxial cable is identified as RG-59 or RG-6 cable.

DOCSIS - The CableLabs Data-Over-Cable Service Interface Specification defines interface standards for cable modems and supporting equipment.

download - To copy a file from one computer to another. You can use the Internet to download files from a server to your home PC. A DOCSIS cable modem downloads its configuration from a server during start-up.

downstream - In a cable data network, downstream describes the direction of data received by your computer from the Internet.

Ethernet - The most widely used type of local area network (LAN). The most commonly installed Ethernet networks are called 10Base-T. 10Base-T provides transmission speeds up to 10 megabits per second (Mbps), usually over twisted-pair wire. Fast Ethernet (100Base-T) provides transmission speeds up to 100 Mbps.

expansion slot - An opening in a computer where a circuit board can be inserted to add new capabilities.

F-type connector - A connector used to connect coaxial cable to equipment.

IP address - An Internet Protocol address is an identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the destination IP address. Your cable service provider assigns your cable modem an IP address to provide a continuous Internet connection.

MAC address - The Media Access Control Address uniquely identifies each device that can be connected to an Ethernet network. It is permanently written to read-only memory (ROM) at the factory. You need to provide the MAC address to your cable service provider.

MHz Mega Hertz. A measure of radio frequency - millions of cycles per second. One MHz means one million cycles per second.

RJ-45 - The most common type of connector (jack) for Ethernet networks.

splitter - A splitter is a device that divides the signal power from an input cable equally between two or more signals, each carrying a selected frequency range.

TCP/IP - Transmission Control Protocol/Internet Protocol is a set of protocols that provides standards and rules for communication between networks.

Upstream - In a cable data network, upstream describes the direction of data sent from your computer to the Internet.

USB - Universal Serial Bus is a computer interface for add-on devices such as printers, scanners, and cable modems.


The cable modem connects to your computer with an (RJ-45) Ethernet connection (CAT-5 cable) or USB, and the coaxial jack (RF) on the cable modem connects to the cable company's line using a RG-6 type coax cable. You can hookup a router also so you can use multiple computers, even wireless such as a laptop. Your TV can be connected also using a splitter and another coax cable hookup. The cable provider splits the TV signals and the internet data and routes to their destinations.

The cable modem has several lights on the front to indicate status.

DOCSIS 3.0 Data-over-Cable-Service

50 to 60 Mbps Speeds Across the U.S.A.

Comcast is offering its wideband products on two different tiers: the top level tier, Extreme 50, features 50 Mbps downstream speeds; the company's Ultra tier product includes 22 Mbps downstream speeds. Plus Comcast customers can save money by bundling their wideband high-speed Internet service with their cable television and digital voice services.

Charter Communication's Ultra 60 wideband product touts up to 60 Mbps downstream speeds and customers can bundle their Internet connection with other Charter services to save money. Charter's Max tier, a high-speed broadband product featuring downstream speeds up to 22 Mbps is currently available in many of Charter's markets.

DOCSIS 3.0 Technology and Cable Operators

Cable operators across the U.S. provide high-speed Internet access to their customers through a broadband connection via a cable modem. These modems are based on DOCSIS technology, or Data Over Cable Service Interface Specifications. In America today, more than 25 million people access the Internet using DOCSIS-based modems for their cable broadband connections.

DOCSIS has had four successive versions to date, each version providing improved broadband Internet connectivity, security features, quality, reliability, and flexibility. DOCSIS 3.0 makes it possible for cable operators to offer Internet connection speeds at hundreds of megabits and, potentially, hundreds of gigabits per second.

What is the Best Cable Modem?

Cable modem technology has come light years over the past decade. Utilizing DOCSIS 3.0 wideband technology, cable modems offer Internet download speeds of up to 50 to 60 Mbps with significantly faster speeds planned in the next few years. If you’re considering a new cable modem purchase, you’ll want to be sure that you’re purchasing top-of-the-line equipment that will give you access to the fastest connection speeds available.

Cable modems should offer fast and reliable Internet connections. To find out which modem will work best for you, it’s important to research the types of hardware products available and consider professional ratings and reviews for each.

You can find ratings of today’s top modems at, an excellent resource for information about broadband and wideband Internet connections, cable modem and DSL technology, and TCP/IP performance over high speed/latency networks.

Another information website for cable modem research is Here you’ll find technical definitions, relevant articles, and product reviews for every type of cable modem available on the market today.

To ensure that any cable modem you purchase uses DOCSIS 3.0 wideband Internet capabilities, you can find a complete listing of approved manufacturers and devices at Cable Labs is the non-profit industry organization which developed DOCSIS technology. The organization also evaluates and certifies cable modems based on conformity to DOCSIS 3.0 standards. Products are tested based on fairness and verifiable criteria, rather than the opinions of testers or novice cable modem users. To find a complete list of Cable Labs certified products visit

Motorola makes some very good cable modems. Look at them on the Motorola broadband site HERE.

Cable Modems and DOCSIS 3.0 Technology

Beginning in the fall of 2008, cable operators across the U.S. started offering wideband Internet connections with download speeds in the 50 to 60 Mbps range thanks to DOCSIS 3.0. If you’re buying a new cable modem, it’s paramount that your device includes DOCSIS 3.0 specifications to enable you to access the Internet at the fastest speeds currently available, and to be prepared for even faster speeds over the next few years.

How to Configure TCP/IP

In addition to connecting your cable modem and computer, you will need to configure TCP/IP. On a windows PC, the procedure varies somewhat but generally follows the process of going into CONTROL PANEL, clicking on Network, clicking on LAN, selecting PROPERTIES, selecting Internet Protocol TCP/IP, select PROPERTIES and be sure to check the OBTAIN IP ADDRESS AUTOMATICALLY button. Also check OBTAIN DNS server address automatically. Next click OK. This will setup DHCP to get IP addresses automatically.

You can verify by the following process:
Windows computer - click START, then RUN and type in CMD (to enter command prompt mode). hit the enter key. A popup window should appear which allows you to type in IPCONFIG. hit enter key. You should see some results showing IP addresses. You can also type IPCONFIG/RENEW to renew IP address.

Your cable provider should help you configure your cable modem and assist with any problems.

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