Toerless Eckert wrote:
Not sure why rfc1981 PMTUD was never fixed.
Because IPv6 people believe multicast PMTUD MUST work.
RFC1981 even states:
The local
representation of the "path" to a multicast destination must in fact
represent a potentially large set of paths.
that they actively bless multicast PMTUD to cause implosions.
We did manage to get section 11.1 into rfc 3542 though. It's a little
bit long due to committee design, but i was hoping it was sufficient to avoid
the problem by default.
It is not a protection against malicious attempts nor decided
attempts by PMTUD believers-in, which means cautious operators
must still filter ICMPv6.
Considering that destination address fields of inner packets
in ICMPv6 are located at the 73th to 88th bytes (ignoring MAC
header), which may not be filtered by hardware, it is likely
ICMPv6 packet too big against unicast packets will also be
filtered.
If folks see IPv6 multicast> 1280 as a
real problem in deployments,
It is merely that IPv6, as is, is not operational and
operators MUST violate RFC2463 not to generate ICMPv6
packet too big and filter ICMPv6 packet too big.
It, of course, is a real problem against PMTUD, including
unicast ones.
Masataka Ohta
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