What is DOCSIS?

What is DOCSIS?
What is DOCSIS?
2018-11-07 22:08:41

What is Docsis?

 

DOCSIS stands for:  Data Over Cable Service Interface Specification.  This is the international industry standard for devices suppling Internet over Cable service providers or Cable ISPs.  There have been several revisions over the years as technology and speed requirements have increased.  All cable modems and Gateway (router/modem combo devices) adhere to this standard.  The first version of the DOCSIS standard was released in 1997 with the most recent revision coming in 2017.

 

Speed in a DOCSIS equipped modem is dependent on the ammount of Downstream and Upstream channels the device has.  The chart below will give you the average maximum speed each channel configuration for a DOCSIS 3.0 modem will obtain.

Downstream Channel

Upstream Channel

Downstream Speed

Upstream Speed

4

4

150 Mbps

108 Mbps

8

4

304Mbps

108Mbps

16

4

608Mbps

108Mbps

24

8

912Mbps

216Mbps

32

8

1216Mbps

216Mbps

*Speeds are averaged out but may be different based on a customer’s Cable ISP

Cable service providers can limit a modem’s function for instance the maximum theoretical speed a 16x4 modem like the TC-7620 can achieve is 680Mbps down.  However, most Cable ISPs limit this modem to 300Mbps.  Some ISPs may not even allow certain modem/gateways to work with their service.  Before buying a modem or gateway it is always a good idea to check their official approve modem/gateway list.  Most ISPs have this list published on their website.

 

DOCSIS standards do come with some limitations.  First, on DOCSIS gateways you are not in control of the software (firmware).  Firmware updates are pushed via the Coaxial cable and ISPs must review and approve an update before it is pushed to customers.  This process and subsequent delays can leave customers without essential improvements or bug fixes.  Also, at times certain basic features may not be available, such as changing your DHCP pool or LAN IP subnet.  While the manufacture would love to be able to include all of the feature a customer would want or need, when it comes to DOCSIS devices, sometimes our hands are tied. 

 

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