Re: Issues with "prefer IPv6" [Re: Variable length internet addresses in TCP/IP: history]

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Mark Andrews wrote:

>>> Brian already covered "unconditional prefer-IPv6 was a painful lesson
>>> learned," and I'm not saying that those older systems did it right.

You learned a wrong lesson, then.

The essential problem is that there is half hearted support
for handling multiple addresses.

It is not an operational problem but a fundamental defects
of protocols.

> I contend that OS are IPv6 ready to exactly the same extent as they
> are IPv4 ready.  This isn't a IPv6 readiness issue.  It is a
> *application* multi-homing readiness issue.  The applications do
> not handle unreachable addresses, irrespective of their type, well.

In part, it is an application problem. However, it is also an
IP layer problem.

> The address selection rules just made this blinding obvious when
> you are on a badly configured network.

The half hearted address selection rules will keep causing
this kind of problems, until IPv6 specification is
fundamentally fixed.

> No one expect a disconnected IPv4 network to work well when the
> applications are getting unreachable addresses.  Why do they expect
> a IPv6 network to work well under those conditions?

With proper IP layer support, which is lacking, which means
IPv6 specification is not ready to handle multiple addresses,
which means hosts are not IPv6 ready to handle multiple
addresses, we can expect applications work well if one of
an address among many works and rest of the addresses are
unreachable.

						Masataka Ohta

PS

IPv4, of course, is not ready to handle multiple addresses
properly, which causes some problems for multihomed hosts.

But it is not a serious problem because IPv4 hosts do not
have to have IPv6 addresses.
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