On Wed, 25 May 2011, Philip Homburg wrote:
So you are saying (with a bit exaggeration from my side) that some links
in data centers have so many hosts that a network disruption of a few
seconds will cause a multicast storm big enough to meltdown the network.
With modern CPUs and a Gbit/s network that seems very odd to me.
I have an example from reality:
At AMSIX, there are a few hundred routers on the same L2 network.
Connected to this we have a router from a major well known vendor. This
vendor does not filter IPv6 multicast messages on the linecard, but
instead punts all of it to RP, and AMSIX L2 infrastructure treats all
multicast as broadcast, so all multicast (mainly ND traffic) is sent out
on all ports.
This traffic to the RP was enough to cause IPv6 BGP sessions to go down
because it was continous ND messages coming in all the time (few hundred
PPS).
ND is chatty, and it does cause problems on large networks. One might call
this multiple faults on multiple levels (bad linecard code, bad L2
platform, bad low-performing CPU on the RP), but it does cause problems in
real life regardless.
--
Mikael Abrahamsson email: swm...@swm.pp.se
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