IPv6 /64 links (was Re: ipv6 book recommendations?)

Tue Jun 12 16:25:21 UTC 2012

Masataka Ohta wrote:
> Karl Auer wrote:
> 
> >> : I've seen links with up to 15k devices where ARP represented
> >> : a significant part of the link usage, but most weren't (yet) IPv6.
> >>
> >> MLD noise around a router is as bad as ARP/ND noise.
> >
> > Possibly true, but that's another discussion.
> 
> Then, you could have simply argued that there is no ARP problem with IPv6,
> because ND, not ARP, were another discussion.
> 
> >> That's how IPv6 along with SLAAC is totally broken.
> >
> > I think we have different ideas of what constitutes "totally" broken.
> 
> It is because you avoid to face the reality of MLD.

MLD != ND
MLD == IGMP
ND ~= ARP

ND is less overhead on end systems than ARP because it is only received by
nodes that are subscribed to a specific multicast group rather than
broadcast reception by all. There is no difference in L2 resolution traffic
at the packet level on the network. There are multicast join messages for
groups specific to ND use, but those should not be frequent, and were a
specific tradeoff in minor additional network load to reduce significant end
system load. There are DAD messages that impact group members, but in IPv4
there are gratuitous ARP broadcasts which impact all nodes, so while the
number of messages for that function is the same, the system-wide impact is
much lower.

Multicast group management is inherently noisy, but a few more bits on the
wire reduces the load on the significantly larger number of end systems. Get
over it ... 

Tony