Jun-ichiro itojun Hagino wrote:
that I personally use? I'm guessing about a half-dozen, though I don't
use them all everyday. some other apps work across NAT but with
degraded functionality.
okay. if you could name them we can try to convince people who are
responsible.
the people responsible for polluting the network with NATs? it's too
late to punish them, I fear :)
no, the people who have implemented your applications that are written
in
IPv4-only and NAT-unfriendly, to be IPv4/v6 bilingual. i do not care
about NAT (un)friendliness, i just need it to support IPv6.
you have it backwards. It is the NATs that are unfriendly to apps, not
the other way around.
it's easy to write a distributed app that can handle the case where all
nodes are IPv4, or the case where all nodes are IPv6. it is much more
difficult to write such an app that can handle the case where some nodes
are IPv4, some are IPv6, some are both, and there is a need to
communicate between arbitrary pairs of nodes within the app and to allow
some nodes to do referrals to other nodes. DNS names are not a good way
to solve this problem for reasons of performance and reliability and
because a DNS name does not, in practice, uniquely bind to a particular
host.
we kame are guilty for almost every application IPv6 support, including
Python, Apache, Ruby, Postfix (wietse rewrote the whole thing), all
tools
on *BSD, BSD libc, whatever. honestly noone can beat us on this
topic:-P
and the rest of us are very appreciative! of course, not all of the
applications that people use are those that are shipped with *BSD. and
while it's quite helpful if programming languages support IPv6, that
doesn't mean that the programs written in those languages will
automatically work with IPv6.
well, that depends on what kind of programming language you will be
using. Python uses a model where you explicitly need to invoke bind(2)
and getaddrinfo(3), so the programmer has to be knowledgeable enough
to handle IPv4/v6 stuff. iirc Ruby TCPSocket class embeds all the
details about getaddrinfo(3) loop within the class/instance method,
so you do not have to care about which IP version is in use.
it is not reasonable to assume that for all apps the correct model is to
do a DNS lookup and then try the resulting IP addresses one at a time
until a connection succeeds for one of them.
that, and getaddrinfo() is broken in a great many ways: it isn't tied to
DNS (so if your app is defined to use DNS then you can't trust
getaddrinfo() to do what your app needs); even if the implementation
does use DNS, getaddrinfo() can only do A and AAAA queries, it's not
asynchronous, and the whole idea that a host stack can select a
source/destination address pair by trial-and-error and get good results
within a reasonable time is, quite frankly, a joke.
so, which is your real-world protocol which has the above problem? or
is it a theoretical debate? "code then spec".
no, it's not a theoretical debate. I worked with a number of distributed
systems: PVM, some MPI implementations, and one of my own design that
didn't become so popular. There are a lot of applications layered on top
of one or the other of these. But unless you're into high-performance
computing you probably aren't aware of them.
may i talk with you/designer of PVM/MPI code so that they can implement
them in IPv6-friendly manner? privately.
I don't work there any more, and none of the people whom I knew that
worked on those codes work there any more either.
one way is to have a session-layer protocol (finally!).
or, you can switch from TCP to SCTP.
for several reasons, SCTP is not a drop-in replacement for TCP. (but I'd
love to see further development and standardization of multipath TCP -
that seems like a very promising avenue)
there were tons of multipath TCP drafts, but there's no real
authentication so all of them failed badly. so i see some future in
ssh.
ssh is not a bad protocol, but it doesn't solve the
multiple-addresses-per-host problem, even if you change it to allow
peers to re-connect (which would be a nice feature).
please tell me, your apps are totally multicast or broadcast?
if not, we need to solve 2-nodes communication first, then you can
solve communication among n (n could be very big) nodes.
this isn't a multicast or broadcast problem I'm speaking of. I'm
speaking of the need for the network to provide complete connectivity
between arbitrary pairs of nodes in a distributed system.
you have to. you cannot be that lazy.
our goal in IETF should be to allow programmers to be that lazy.
separation of function between the host and the network is a Good Thing.
let the hosts exchange packets and the network route them.
the goal is certainly not to keep increasing complexity of the network
and to keep making programmers' jobs more difficult.
then use vendor libraries that are URL-based.
my, you have a simplistic view of the application world!
Keith
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