DOCSIS 3.0 and Multicast

Phil Bedard bedard.phil at
Fri Nov 29 15:34:29 UTC 2013

I would take a look at the presentation in the other post, there are
multitude of ways it can be accomplished and some of those are spelled out
in the DOCSIS 3.0 specs.

Like the other poster said, HFC architectures are very centralized and
controlled at the head-end and the components in the field such as the
fiber node and even the CM are not active in making decisions about where
traffic goes, they just receive what has been sent to them and pass it
along.  Ultimately any multicast streams will go to a set-top box (or some
other video device) and in the case of dynamic multicast it would be the
STB generating the IGMP joins.

But to answer your question, the answer is yes, the same stream can be
sent to two different receivers in the same service group.  By the time it
gets to the fiber node, it's just RF and if the CM is tuned to the right
frequencies, either a specific one for video, or a shared one, it can be

Most providers aren't doing IP video over DOCSIS, they are still using QAM
based delivery via dedicated video spectrum.


On 11/29/13, 9:32 AM, "mr. s" <sigasecure at> wrote:

>To Those Who Do DOCSIS3.0,
>I can't seem to find a simple answer to this, possibly because it is self
>evident to those actually using Multicast over DOCSIS. Which we are not
>Multicast over DOCSIS 3.0, to 3.0 CM, can the CM share the same media
>stream on their node?
>In example, 2 Cable Modems in the same node (no splitting, same US/DS
>channels/ports, CMTS..), each have a customer watching ESPN.
>Is there one or two media streams worth of content on the plant, channels,
>We now how this operates in other worlds, GPON, xDSL and AE. Just haven't
>seen it specifically mentioned out right in DOCSIS literature.
>Thanks for any direction you have.

More information about the NANOG mailing list