On Fri, Nov 17, 2017 at 7:48 PM, Baldur Norddahl <baldur.norddahl@gmail.com> wrote:
Does multicast have any future?
Multicast is a fine replacement for local-lan (i.e. direct connected interface) broadcast. For video distribution, multilevel caching simply works better. It's no deep mystery why. Wide scale multicasting requires ISPs to allow the most critical inline resource (the routers) to accept fine-tuned instructions from any third party that wants to be a content head-end. For ordinary routing we don't allow anything more fine tuned that a /24 and we've been reluctant to allow that. We're somehow going to beef up the routers to allow non-paying third parties to fine-tune down to the video stream? Not happening. Multilevel caching consumes upwards of an order of magnitude more data transfer than an optimal multicast system, but it does it to the side, out of the critical path. If a node breaks, it doesn't take down the network with it. And you can slap a cheap server in place And of course caching supports time-shifting which multicast does not. Given how people consume video today, that's an important distinction. Peering in to my crystal ball, I see an abstracted caching system which isn't tied to any particular vendor. Fetch decryption keys directly from the video vendor, then find the nearest cache via a solicitation to a protocol-standard anycast IP address. The cache fetches from the next cache up. ISP deploys as many caches as it finds convenient and cost effective. Paid megacache at the top of the hierarchy located at the carrier neutral data center that's cheaper than transit for both the eyeball networks and the content providers. Data cached in chunks of arbitrary data that only mean anything to the producer and consumer but are identified in such a way that multiple consumers for the same data request the same chunk ID. And small enough chunks that real-time feeds are delayed by few enough seconds to make them practical. Unicast with a little bit of anycast. No multicast on that road map. Regards, Bill Herrin -- William Herrin ................ herrin@dirtside.com bill@herrin.us Dirtside Systems ......... Web: <http://www.dirtside.com/>