The argument made by the draft authors is that since multicast
packets already have a UDP header with a checksum, there is no
additional benefit and indeed some cost to nodes to both compute
and
check the UDP checksum of the outer (encapsulating) header.
However,
Consequently, IPv6 should make an exception to the rule that the
UDP
checksum MUST not be 0, and allow tunneling protocols to set the
checksum field of the outer header only to 0 and skip both the
sender
and receiver computation.
It is worse than that for AMT. Since the control packets are
encapsulated
in
an IGMP packet format. There is an IGMP checksum performed as
well, then
on
top of that encapsulated in UDP, with the UDP checksum performed
there
too.
So please note that the burden might be less in the control-
plane, but it
is
less necessary to do UDP checksum as well in this case. I think you
shouldn't deprecate the behavior in the spec, but outline how
double
check-summing is occurring in this case.