[Cerowrt-devel] [Babel-users] [Make-wifi-fast] perverse powersave bug with sta/ap mode

Juliusz Chroboczek jch at pps.univ-paris-diderot.fr
Thu Apr 28 09:37:43 EDT 2016

> Multicast is seductive to designers who ignore the realities of
> propagation and channel coding issues, because they think it works one
> way, but the reality is quite different.

Hold on.

Mulsticast is used for two distinct purposes: for broadcast-style
applications (streaming), and for discovery (ARP, ND, mDNS, and of course
the Hello beaconing of routing protocols).

For broadcast-style applications, multicast can be replaced with multiple
unicast streams, as Netflix shows, although this is best done at the
routers rather than at the senders, since this allows building a single
distribution tree without the need for application-layer proxies ("CDNs").

For discovery, multicast is unavoidable -- there's simply no way you're
going to send a unicast to a node that you haven't discovered yet.

-- Juliusz

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