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That's exactly how the multicast works. It's not broadcast, it's multicast. Your local set tells the next closest router the streams it's interested in. If i
by ismarc 16y ago
That's exactly how the multicast works. It's not broadcast, it's multicast. Your local set tells the next closest router the streams it's interested in. If it's already receiving them, the packets are forwarded to your on-site router. If it's not, it calls to it's next hop router and does the same registration. A multicast stream is a "limited broadcast" in that it only goes to the nodes that wish to participate and is managed by a tree structure in the network so that any given link only has as much travelling over it as the child nodes are requesting.
- pdonis 16y agoYes, but what about the "if it's already receiving them" part? I don't know exactly how the cable providers provision their networks, but I'd be very surprised if my local set's registration had to go more than one or maybe two hops up the router chain to find one that was already receiving all 150 channels. Otherwise it's hard for me to believe that changing channels would be as fast as it is (effectively instantaneous). (Note, I'm not saying this is a necessary feature of any multicast setup, just that it seems like it would have to be set up that way for the cable providers because of user expectations.)
- ismarc 16y agoCable distribution of channels is completely different from the U-Verse example. Cable uses a certain band of frequencies for channels, each HD channel requiring a larger band. The Internet access they provide is delivered the same way, but with a smaller band for upstream. The bands for Internet service are shared by all customers on the segment, with rate limiting at the maximum rate you're paying for. For cable carriers, there is no "profiling" ability to prefer one over the other, they each have separate channels. U-Verse and similar services (like the Verizon fiber solution) use a multi-homed router on your premise with one network for TV, one for VoIP and one for Internet. They are all 3 IP based networks and travel over the same copper, meaning they share the same bandwidth, but only one of them is actually connected to the Internet. For those services, you only receive the channels over the copper that your local router has requested the multicast streams for, allowing for a much more efficient use of the bandwidth but providing the possibility for services to interfere with each other.
- pdonis 16y agoThanks, the technical background makes things clearer (I wasn't familiar with the details of how the different services get distributed).