What is Data Over Cable Service Interface Specification (DOCSIS)?

DOCSIS is a standard developed by CableLabs and other companies that allows cable TV providers to send and receive internet data over unused TV channels.

What is a data channel?

A data channel is a set amount of frequency used to upload or download data to and from a cable internet provider’s CMTS. Generally, cable modems support more downstream channels than upstream ones. The more downstream channels a modem supports, the more megabits you can download each second. For example, a modem listing 4×4 means it has an equal number of downstream and upstream channels. A 32×8 modem has 32 downstream channels but just 8 upstream ones. The DOCSIS version also applies in terms of speed. A 32×8 modem based on DOCSIS 3.0 has a maximum download speed of 1,400 Mbps while DOCSIS 3.1 enables 10,000 Mbps. Check out our guide on the best modems for gigabit internet if you want to replace your provider’s unit.

Can you use any modem with your internet connection?

No, you cannot use any modem. As described above, you can’t use a cable modem with a DSL connection, nor a DSL modem with a fiber connection. Your provider typically supplies the correct device for the internet type you have. You can purchase a modem if you want to avoid monthly fees, but it must be authorized by your internet provider. Spectrum, for example, provides a list of compatible modems that work with its three cable internet plans.8 We list the best cable modems for Xfinity, Spectrum, Cox, and more.

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