VoIP over cable broadband: Does it mean business?

Is VoIP over cable reliable enough for business use? A few years ago, most experts would have said no—but things have been changing over the last few years. Deb Shinder examines where cable Internet service and VoIP over cable broadband are today.

By its very nature, VoIP telephony requires an IP network, but not just any IP network will do. To get adequate performance and reliability, you need a high-speed network with excellent uptime.

Once upon a time, businesses relied on dedicated leased lines for high-speed connections to the Internet. But broadband technologies have advanced to the point where cable and DSL connections are available for hundreds of dollars less than a T-1 line—while sporting several times as much bandwidth.

Many businesses already have cable TV service at their sites, making it physically easy to bring in cable Internet service. But businesses depend on their telephone service; an outage can mean a big hit to the bottom line.

Is VoIP over cable reliable enough for business use? A few years ago, most experts would have said no—but things have been changing over the last few years. Let's take a look at where cable Internet service and VoIP over cable broadband are today.

The slow maturation of the cable industry

Telcos were first out of the gate with broadband Internet technologies. That made sense, as they already had a huge infrastructure in place and both consumers and businesses were familiar with using their lines—either regular POTS lines for dial-up connections, or ISDN or T-carrier lines for high-speed digital connections—to connect to the Internet.

The cable TV companies also had existing infrastructures that ran to many homes and offices, but many of them were slower to implement Internet service on a widespread basis. Whereas telephone companies had to upgrade the equipment at the central office (CO) to provide DSL service, some cable operators not only had to add centralized equipment but also upgrade the lines themselves.

The problem was that older cable TV services used simplex, or one-way, communications. The cable company delivered cable TV signals to the end user, but the end user didn't need to send any signals back.

To provide Internet service (including VoIP), the cable lines and equipment had to support two-way communication. Whether accessing a Web site or participating in a phone conversation, the end user must be able to both send and receive data.

That's the reason the earliest implementations of cable Internet service still required users to send data upstream via a phone line while receiving downstream data over the cable link. Today, most cable companies have infrastructures that support two-way communications, used not only for IP services but also for cable TV services such as on-demand and pay-per-view.

Cable companies now compete fiercely with DSL providers and new technologies such as Verizon FiOS for Internet accounts. While many still think of cable Internet as a consumer-only technology, some cable companies are getting wise and starting to target small and midsize businesses.

Consumer plans vs. business plans

In the past, there was a problem with using cable for your company's Internet service, even if your business was small. Most cable companies had only one or a small handful of service plans, all of them designed with home users in mind (usually varying only as to downstream bandwidth).

Although these plans included high-speed downstream service—up to 6 Mbps or more—the upstream bandwidth was often throttled at 128 to 256 Kbps. That works fine for surfing the Web or sending e-mail, but it wasn't so great for business uses such as hosting your own Web server.

In addition, companies usually assigned customers a dynamic IP address, which made hosting servers more difficult. And even if you could live with the slow performance and work around the dynamic IP by using a dynamic DNS service such as TZO, the cable companies' terms of service (TOS) agreements generally prohibited running servers on the connection.

Another problem with using a consumer broadband account for business—and one that would definitely affect VoIP service—was the reliability issue. Cable companies took the position that their services were for "entertainment," not essential services, so they didn't guarantee uptime or try very hard to prevent occasional outages.

However, savvy cable companies are now offering cable Internet plans geared especially for businesses. They include the ability to have static IP addresses and blocks of multiple IPs, higher bandwidth on the upstream, a TOS that allows you to host servers, and better reliability with 24/7 tech support. For examples of such business plans, see Cox Communications' Business Internet PDF datasheet or the Time Warner Cable Business Class Web site.

How to implement VoIP over cable

There are two ways for a small business or consumer to implement VoIP over cable. The first option is to subscribe to an Internet service plan through a cable provider, then subscribe to a VoIP service such as Vonage, Lingo, or Packet8, and connect the VoIP provider's ATA box to the cable router. The second option is to subscribe to VoIP service directly from the cable provider along with your Internet service.

There are advantages and disadvantages both ways. Cable companies' VoIP plans often cost more than those of dedicated VoIP providers, or they charge extra for domestic long-distance calls whereas dedicated VoIP providers offer unlimited service. For example, in comparing Cox, Vonage, and SunRocket VoIP services, the monthly fee for the Cox VoIP is quite a bit lower, but you have to pay 5 cents per minute for long distance. That can add up quickly in a business environment.

On the other hand, using a single provider for both Internet and VoIP reduces compatibility problems and "passing the buck" behavior when troubleshooting problems. In addition, some cable companies prohibit using other VoIP services on their network. It's important to always read the TOS carefully before you sign up for anything.


Is cable a viable option for business VoIP? As with so many questions in IT, it depends. Before signing on with a cable provider, be sure to scrutinize the contract carefully and ask questions.

If your cable provider also offers VoIP services, don't assume it will allow you to use another VoIP provider over its network. And if you need absolute reliability and guaranteed uptime, you're probably still better off with a dedicated leased line, despite the higher cost.

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Deb Shinder is a technology consultant, trainer, and writer who has authored a number of books on computer operating systems, networking, and security. She currently specializes in security issues and Microsoft products, and she has received Microsoft's Most Valuable Professional (MVP) status in Windows Server Security.