IPv6 "bloat"

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Tue Mar 22 14:04:09 UTC 2022

Owen DeLong wrote:

>> IPv6 optional header chain, even after it was widely recognized 
>> that IPv4 options are useless/harmful and were deprecated is an 
>> example of IPv6 bloat.
>> Extensive use of link multicast for nothing is another example of
>> IPv6 bloat. Note that IPv4 works without any multicast.
> Yes, but IPv6 works without any broadcast. At the time IPv6 was being
> developed, broadcasts were rather inconvenient and it was believed
> that ethernet switches (which were just beginning to be a thing then)
> would facilitate more efficient capabilities by making extensive use
> of link multicast instead of broadcast.

No, the history around it is that there was some presentation
in IPng WG by ATM people stating that ATM, or NBMA (Non-Broadcast
Multiple Access)in general, is multicast capable though not
broadcast capable, which was blindly believed by most, if not
all excluding *me*, people there.

It should be noted that IPv6 was less bloat because
ND abandoned its initial goal to support IP over NBMA.

 > Turns
 > out multicast was arguably a wrong guess, but all indications
 > available at the time were that it was a good bet.

See above.

 > There is still a valid argument to be made that in a switched
 > ethernet world, multicast could offer efficiencies if networks were
 > better tuned to accommodate it vs. broadcast.

That is against the CATENET model that each datalink only
contain small number of hosts where broadcast is not a
problem at all. Though, in CERN, single Ethernet with
thousands of hosts was operated, of course poorly, it
was abandoned to be inoperational a lot before IPv6,
which is partly why IPv6 is inoperational.

						Masataka Ohta

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