A close up of the Technicolor E31T2V1 modem from Spectrum Internet
Corbin Davenport / How-To Geek
DOCSIS is the cable modem communication standard. DOCSIS 3.0 modems are sufficient for most people, but if you subscribe to your ISP's gigabit or multi-gigabit packages, you'll need a DOCSIS 3.1 modem.

Whether you’re shopping for a modem to avoid ISP fees or just curious about the modem your ISP gave you, here’s what you need to know about DOCSIS and its impact on your internet speed and performance.


Data Over Cable Service Interface Specification (DOCSIS) is a telecommunications standard developed in the 1990s by the non-profit cable research consortium CableLabs to facilitate high-speed data transfer over existing coaxial cable infrastructure (CATV).

The development and standardization of DOCSIS made it possible for cable TV providers to expand from simple one-way delivery of scheduled and on-demand programming into major players in the Internet Service Provider (ISP) space. Before DOCSIS, the efforts of cable companies to provide internet access were fragmented and based on non-interoperable communication standards which was problematic for both the companies and consumers alike.

Just like the rise of dial-up modems and, later, DSL modems served as a method to build out internet delivery over existing infrastructure, the arrival of cable modems in the mid-1990s and the DOCSIS standard to unify them did the same for cable networks, effectively turning vast cable infrastructure into giant high-speed Ethernet-like networks.

If you’re one of the millions of people who get broadband internet through their local cable company, you’re using DOCSIS whether you realize it or not. It’s no hyperbole to say that DOCSIS is the heart of the modern cable broadband experience.

What’s the Difference Between DOCSIS Versions?

Like other communications standards such as Wi-Fi and cellular technology, DOCSIS has gone through multiple versions over the years. Here’s a quick overview of the progression from DOCSIS 1.0 to the present.

What Is DOCSIS 1.0/1.1?

Released in 1997, the first iteration of DOCSIS pulled the best features of the current but non-interoperable propriety cable modems under one umbrella and standardized them. DOCSIS 1.0 supported a theoretical maximum download speed of 40 Mbps, and an upload speed of 10 Mbps.

Two years later, in 1999, DOCSIS 1.1 was released as a relatively minor update to DOCSIS 1.0. Download and upload speeds remained the same, but the standard was updated to cement the outlined by not implemented Quality of Service (QoS) rules from DOCSIS 1.0.

Both DOCSIS 1.0 and 1.1 modems were single-channel setups—your entire connection used a single “lane” of available local cable network for downloads and one for uploads.

What Is DOCSIS 2.0?

DOCSIS 2.0, released in 2001, was a significant upgrade over the two prior iterations. While the maximum download rate stayed at 40 Mbps, the upload rate was boosted to 30 Mbps. This allowed for applications that benefited from symmetric connections like VoIP telephony.

While DOCSIS 2.0 offered improved upload speeds, it still retained the single-channel architecture of DOCSIS 1.0.

What Is DOCSIS 3.0?

Five years later, in 2006, CableLabs released the DOCSIS 3.0 standard with a radically higher potential download and upload capacity. DOCSIS 3.0 theoretical maximum download is 1 Gbps with a 200 Mbps upload capacity.

The speed improvement was due largely to the introduction of channel bonding, which allowed for modems that used multiple up and downstream channels per subscriber account. Instead of a single channel for each transmission direction, the modem could negotiate multiple channels to ensure a stable high-speed experience for concurrent network activities.

DOCSIS 3.0 certified modems are required to support a minimum of 4 channels for downstream and 4 channels for upstream communication but can support up to 32 channels for downstream and 8 for upstream. The number of channels a particular modem supports is commonly designated in a downstream x upstream format, such as 16×4 or 24×8.

DOCSIS 3.0 also included 128-bit AES encryption, a significant step up from the insecure 56-bit encryption found in older versions.

What Is DOCSIS 3.1?

Introduced in 2013, DOCSIS 3.1 continued to build on the improvements of the prior DOCSIS iterations. The update included improved power management and algorithms that reduce latency and connection jitter.

The minimum number channels is 32 for downstream connections and 8 for upstream (32×8), which, among other improvements like the overall restructuring of the channel system, gives DOCSIS 3.1 a theoretical maximum downstream bandwidth of 10 Gbps and upstream bandwidth of 1.5 Gbps.

What Is DOCSIS 4.0?

Originally branded as “DOCSIS 3.1 Full Duplex,” DOCSIS 4.0 was released in 2017. Just like the jump from DOCSIS 1.0 to 2.0 delivered a significant upgrade in terms of download/upload symmetry, DOCSIS 4.0 offers the same relative to 3.0.

DOCSIS 4.0 retains the maximum downstream bandwidth of 10 Gbps but boosts the upstream bandwidth to a theoretical maximum of 6 Gbps, paving the way for future bandwidth-intensive activities.

As of early 2023, DOCSIS 4.0 still isn’t in consumer deployment, though Comcast (in the United States) and Rogers (in Canada) are conducting trials and preparing small high-density markets for a DOCSIS 4.0 rollout.

What DOCSIS Version Do I Need?

Most people will be fine with a DOCSIS 3.0 modem, but DOCSIS 3.1 is required for gigabit cable packages.

Let’s go into more detail: So where does that leave you, the consumer shopping for a new cable modem or wondering if they should bug their ISP for an upgrade?

The DOCSIS 1.0/1.1 and DOCSIS 2.0 modems from our version list above are historical footnotes. Cable internet providers no longer use or support them, and unless you’re propmaster buying one off eBay for maximum set design authenticity, we can skip right over them.

DOCSIS 3.0 Is Still Fine for Most People

Most people will be well served now (and likely for years to come) by a DOCSIS 3.0 modem. Whether you have a 30 Mbps down/3 Mbps up or a 500 Mbps down/50 Mbps up connection, DOCSIS 3.0 can handle it. The only major consideration is whether or not the DOCSIS 3.0 modem has enough channels to handle the maximum speed of the cable internet tier your pay for.

Each channel has a maximum bandwidth capacity, so if the number of channels, in total, can’t handle the full capacity of your internet plan, you’ll be paying for bandwidth you never get to utilize fully.

If you pay for a 500/50 package, for example, a budget cable modem with the minimum 4×4 channel configuration, the maximum upstream and downstream speed is limited to 172 Mbps. That’s enough to cover all your upload speed but only around a third of your download speed. To ensure you had sufficient bonded channels for your 500/50 connection, you’d want at least a 16×4 modem which would allow for up to 686 Mbps down/172 Mbps up.

ARRIS SURFboard SB6190 DOCSIS 3.0 32 x 8

This dependable and popular option from the Arris Surfboard lineup is perfect for cable internet subscribers with any subscription tier at or below 800 Mbps, which is the majority of cable broadband users in the United States.

If you have the other package we mentioned, however, the more modest 30/3 tier, that DOCSIS 3.0 4×4 modem would serve you just fine, potentially with room to bump up to the next tier or two without requiring a modem upgrade.

That said, given that the difference between a 16×4 3.0 modem and a 32×8 modem is usually only $30-50, it doesn’t make a whole lot of sense to buy the cheapest (and least future option) when you can pick up something like the popular Arris Surfboard SB6190 32×8 cable modem for under $100 (and frequently on sale for $60-70).

DOCSIS 3.1 Is Necessary for Gigabit Cable Packages

While, technically, the DOCSIS 3.0 standard can be pushed to support near-gigabit speeds, practically cable internet providers require you to use DOCSIS 3.1 for their top-tier packages.

For anyone in the lower speed tier, options like 100/10, 500/50, or similar offerings, spending twice as much or more on a DOCSIS 3.1 modem doesn’t make sense. For folks with internet packages in the 800+ Mbps range, however, a DOCSIS 3.1 modem is a necessity.

Motorola MB8611 DOCSIS 3.1 Multi-Gig Cable Modem

Perfect for a gigabit cable package today, and an upgrade to a multi-gigabit package next year.

If you want gigabit speeds and to skip your ISP’s modem rental fee, you’ll need a pricier modem like the Arris Surfboard S33 or the Motorola MB8611.

While there are DOCSIS 3.1 modems that fit right into that gap between 800 Mbps and cable provider’s 940-1000 Mbps gigabit plans, we don’t necessarily recommend them. The prices of the just-good-enough-for-gigabit modems aren’t far off from the multi-gig-capable modems. Spending a little extra now makes sense rather than buying an entirely new modem when your cable provider rolls out multi-gig offerings.

And finally, with that cable modem buying advice out of the way, don’t forget to consider the role your Wi-Fi router plays in your home internet experience. Pairing a shiny new DOCSIS 3.1 modem and an expensive gigabit cable package with a router you should have replaced years ago is a recipe for disaster. If your Wi-Fi router is over three years old, it’s time for a replacement.

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Profile Photo for Jason Fitzpatrick Jason Fitzpatrick
Jason Fitzpatrick is the Senior Smart Home Editor at How-To Geek. He has over a decade of experience in publishing and has authored thousands of articles at How-To Geek, Review Geek, LifeSavvy, and Lifehacker. Jason served as Lifehacker's Weekend Editor before he joined How-To Geek.
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