On Sep 13, 2007, at 23:42 , Keith Moore wrote:
Disconnect current session, reconnect.
Uh, not unless your application has some sort of retry or
checkpoint-restart capability. SMTP is pretty resilient in the
face of
connection breakage, and for some interactive applications you just
hit
"retry" or the equivalent, which has caused some people to think that
somehow it's okay if the network changes a host's IP addresses out
from
under it. But it doesn't work in general.
I think the way IPv6 handles this by deprecating the current address
but keeping it alive for some time is entirely reasonable. So if
you're doing a large file transfer or something like that, you can
finish it, then disconnect and reconnect using the new address.
Assuming that you can keep a session alive for weeks or months
without the ability to recover from disconnects is not a smart idea,
to say the least.
This falls under the heading of "nobody is stopping us from doing
this
and it works today so now it's a feature and it can never be taken
away".
No, it just means that people shouldn't assume that existing DNS names
(i.e. the ones we're already using to identify hosts and services)
will
work as endpoint identifiers for the purpose of connection restart.
Huh?
What ARE DNS names good for, if not that?
Obviously if people put a bunch of hosts in the DNS under a common
service name, the idea is that all of the hosts provide the service
in question.
I also don't feel responsible for keeping the host/service
distinction. If a certain protocol needs to talk to individual hosts
and not services, then the people creating DNS names for use with
that protocol should take that into account and not whine.
People are using DNS names to name things that aren't hosts (e.g.
services or groups of hosts) for valid reasons and any solution that
destroyed this functionality would be a non-starter.
Like I said, EVERYTHING is a non-starter today so we don't start
anything anymore. The assumption that everything that works today
will continue to work forever is broken.
That's the least of the problems with renumbering. A few years ago I
was involved in renumbering of a class B IPv4 network. DHCP and DNS
doesn't even begin to cover it.
You have to design to be renumberable.
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