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Comment by chatmasta | Hacker News Reader

Actually, I didn't realize that broadcast was done with IP multicast. I was thinking it used a separate, older technology. So does that mean that generally speaking, modern ISP's that bundle Internet + Cable push the cable content over the IP transport using multicast in the layer 2 DOCSIS network?

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I used to have a fiber + TV package. It was definitely multicast. I found that when I swapped their router for my own I had to make sure IGMP was handled in order for TV and on-demand to work.

Yes, I did the IGMPProxy dance too!

I was amazed that a bit of software that is basically in all home routers is so old, unloved and misunderstood.

Multicast is a funny thing. For years people thought it was the future until they realised 1) it requires the WAN end to support it and 2) people to watch stuff at the same time.

It's not the only way, but yes, there are absolutely cable companies that transmit via IP multicast. There'll still be other filtering going that bundles a couple channels together into the radio/DOCSIS version of a channel so that the end devices don't have to digitally filter all of the firehose of data, but then it's IP multicast on top of that.

I know that AT&T pushes TV over IP but I no longer use a TV provider. Also when I had slower AT&T services over twisted pair they would only send the signal of the TV channel your we’re watching from the DSLAM to your house. It would take a noticeable second to switch channels.

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