Re: Sunday traffic curiosity

[Saku Ytti <saku () ytti fi>]

On Sun, 22 Mar 2020 at 22:43, Alexandre Petrescu
<alexandre.petrescu () gmail com> wrote:

> On another hand, link-local multicast does seem to work ok, at least
> with IPv6.  The problem it solves there is not related to the width of
> the pipe, but more to resistance against 'storms' that were witnessed
> during ARP storms.  I could guess that Ethernet pipes are now so large

This is a case where the cure is far worse than the poison. People do
not run IPv6 ND like this, because you can't scale it. It would be
trivial for anyone in the LAN to exhaust multicast states on the L2
switch. It is entirely uneconomical to build L2 switch which could
support all the mcast groups ND could need. So those do not exist
today, defensive configuration floods the ND frames, just the same as
ARP.

You also cannot scale interdomain multicast (bier is trying to solve
this), because every flow S,G needs to be programmed in HW with list
of egress entries, this is very expensive to store and very expensive
to look, it is flow routing. Today already lookup speeds are not
limited by silicon but by memory access, and the scale of the problem
is much much smaller (and bound) in ucast.

-- 
  ++ytti