What Is DOCSIS and What Is It Used For?
DOCSIS makes it possible for an internet cable modem to be used with a cable TV system.
Data Over Cable Service Interface Specification (DOCSIS) is the international data transfer standard for existing cable television systems (CATV).
DOCSIS Versions - Speed and Feature Comparison
| DOCSIS Version | Max Download | Max Upload | Features |
|---|---|---|---|
| 1.0 | 40 Mb/s | 10 Mb/s |
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| 1.1 | 40 Mb/s | 10 Mb/s |
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| 2.0 | 40 Mb/s | 30 Mb/s |
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| 3.0 | 1 Gb/s | 200 Mb/s |
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| 3.1 | 10 Gb/s | 1-2 Gb/s |
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| 4.0 | 10 Gb/s | 6 Gb/s |
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Learn more about how internet speed can be affected by which cable modem you use in my article, Does a Modem Affect Internet Speed? .
What Upload and Download Speed Does My Cable Modem Support?
Your upload and download speeds depend on the DOCSIS version of your modem and the speed tier you purchased from your internet service provider. Refer to the DOCSIS Versions - Speed and Feature Comparison table for maximum supported speeds.
How Is DOCSIS 4.0 Better Than DOCSIS 3.1?
DOCSIS 4.0 now supports faster upload speeds, allowing for upload speeds of 6 Gb/s and download speeds of up to 10 Gb/s. DOCSIS 3.1 only supports upload speeds of 1-2 Gb/s.
What Is the Latest Version of DOCSIS?
DOCSIS 4.0 is the latest DOCSIS standard. Its specification was first issued in 2019. DOCSIS 4.0 is not yet used in any released products, but will be more widely adopted in the future.
DOCSIS 4.0 was previously branded as DOCSIS 3.1 Full-Duplex before being rebranded.
Are DOCSIS 3.1 Cable Modems Backward/Forward Compatible?
A modem and internet service provider (ISP) must support the same DOCSIS version to achieve the listed speeds for each version. For example, a DOCSIS 3.0 modem with an ISP providing DOCSIS 4.0 will only reach a download speed of 1 Gb/s and upload speed of 200 Mb/s.
If your ISP supports a higher version of DOCSIS than your modem, your modem may still work but only allow for the speeds of the earlier version. If your ISP uses DOCSIS 4.0, but your modem only supports DOCSIS 3.0, you will be receiving the lower speeds of DOCSIS 3.0.
It's recommended to have the latest DOCSIS cable modem version for future-proofing and stability.
Does a DOCSIS Cable Modem Work With Fiber Internet (FTTH/FTTP)?
You can't use a DOCSIS cable modem with Fiber Internet because they use fundamentally different technologies.
Cable internet uses a coaxial cable, while Fiber internet uses a fiber-optic cable. Fiber-optic and coaxial cables can NOT be used interchangeably with each other's modems/cables.
Fiber speeds are still possible with hybrid fiber-coaxial. Hybrid fiber-coaxial is when fiber lines are run to local communities and then translated into radio frequencies for transmission over coax cables.
Is DOCSIS/Cable Better Than Fiber Internet (FTTH/FTTP)?
Fiber internet is far superior to cable internet. Fiber-optic cables, used for fiber internet, have around 10 thousand times more bandwidth than a typical coaxial cable used for cable internet.
The increased bandwidth allows fiber internet to reach higher speeds to customers.
Do I Need DOCSIS 4.0 and Is It Worth Upgrading?
DOCSIS 4.0 is a recent technology and isn't implemented for customers yet. When it is implemented, most people won't need to upgrade unless their internet service provider allows for it and if you're paying for the highest speed plan.
Does DOCSIS 4.0 Require a Different Cable, and Is It Interchangeable?
DOCSIS 4.0 operates at frequencies up to 1.8 GHz. Most coax can operate at these speeds, but RG-6 coax (typical home coax thickness) loses power at 8.97 dB /100 ft at 1.8 GHz frequencies, so you'd either need to not run the coax very far, or use an amplifier, which would also increase noise.
Splitters and other components may need to be upgraded to support these frequency ranges.
Does Having a DOCSIS 4.0 Modem Affect or Increase My Internet Speed?
Having a DOCSIS 4.0 modem will increase your internet upload speeds if you're paying for those speeds from your internet service provider.
DOCSIS 4.0 modems will also receive newer modem firmware which will future proof your modem further and improve stability.
Does Having a DOCSIS 3.0 Modem Affect or Decrease My Internet Speed?
DOCSIS 3.0 is an older technology. Having a DOCSIS 3.0 modem has lower internet speeds, fewer security features, and more packet loss when compared to DOCSIS 3.1 and above.
Most internet service providers, like Xfinity, no longer support DOCSIS 3.0 or below.
If your ISP does support DOCSIS 3.0 and if you're paying for higher speeds than 1 Gb/s download and 200 Mb/s upload, a DOCSIS 3.0 modem won't be able to reach those higher speeds.
Best DOCSIS 3.1 Modem
Motorola MB8611
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6 Gbps max speed.
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2.5 Gbps Ethernet port.
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Lightning and power surge protection.
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Active queue management, which can reduce internet latency.
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Backwards compatible to DOCSIS 3.0.
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Works with Comcast Xfinity, Comcast Business, Cox Communications, and Charter Spectrum.
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Some downsides are that it won't support future DOCSIS 4.0 service when available.
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It does not have a built-in wireless router.
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It does not have telephone call capability.
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What DOCSIS Versions Does Comcast XFINITY Support?
Xfinity currently fully supports DOCSIS 3.1 and is currently preparing its network for DOCSIS 4.0 service, but DOCSIS 4.0 support is currently unavailable.
What DOCSIS Versions Does COX Communications Support?
Cox currently fully supports and highly recommends using DOCSIS 3.1. Cox is presently preparing its network for DOCSIS 4.0 service, but DOCSIS 4.0 support is currently unavailable.