On 29-mrt-2006, at 16:43, Keith Moore wrote:
it would be okay if the only apps you needed to run were two-
party apps. in other words, it's not just users and hosts that
need addresses to be the same from everywhere in the network -
apps need stable addressing so that a process on host A can say
to a process on host B, "contact this process on host C at
address X and port Y"
Isn't this the kind of stuff the DNS was invented for?
not really. and even to the extent DNS was invented for this, it
doesn't work well in practice.
Since when is that any kind of argument? The real questions are
whether it CAN work well for this and whether there's something else
that can do it better/easier.
- DNS is often out of sync with reality
Dynamic DNS updates are your friend.
- DNS is slow and unreliable.
It doesn't have to be, running a decent DNS service isn't rocket
science.
- many networks use other ways of doing name to address mapping for
local hosts.
Not sure what you mean here.
- there's no good way for hosts to know their own DNS names
Again, dynamic DNS updates. When IPv6 materializes where it's
impossible to pre-populate the reverse tree and systems generate
their own addresses, traditional DNS management will be out the
window anyway.
- more generally, there's no good way for a host or an app to know
what a DNS name means.
This one can be problematic but it's not a fundamental problem but
rather a local management problem: apps should be able to obtain the
local hostname that they can use for referral purposes. This isn't
necessarily the same hostname that you'd get from a reverse lookup.
IMHO, DNS is best used as a sort of bootstrapping mechanism - a way
for an app to get an initial contact point for some service. After
that initial contact is made, DNS is contraindicated.
I wouldn't have a problem with that except that people somehow think
that IP addresses DO fulfill all the requirements for being stable
references. In traditional IPv4 they did to a large degree, but then
NAT came along. With IPv6 a single host routinely has multiple
addresses (of more than one scope), and with MIP and shim those
addresses change from time to time. IP addresses are what get the
packets from point A to point B. That's hard enough. Stable identity
needs to happen at a higher level, and rejecting DNS names for this
because of a few simple operational difficulties is a bad idea.
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