Re: The IPv6 Transitional Preference Problem

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In message <20100620195212.4BD395413@xxxxxxxxxxxxxxxxxxx>, Geert Jan de Groot writes:
> > I would argue the opposite; people won't turn it on otherwise, 
> > due to lack of knowledge or negligence. What I would also argue is 
> > that the API that opens a session should try all available 
> > address pairs in relatively short order - on the order of 
> > tens of milliseconds between new attempts 
> 
> Internet protocols historically have had good scaling properties
> on widely varying bandwiths and RTT times.
> Short probe intervals will cause difficulty if RTT isn't also
> in the order of tens of milliseconds.
> 
> There's places (I was in one only 2 weeks ago) where RTT to USA
> was 400 ms, unless we were on backup vsat, in which case it was
> 2-4 seconds, with congestion and packet loss.
> And they pay a lot more for bytes transferred than we're used to.
> 
> Not all the world has low latency and high bandwith.
> Adding a dependency on this in IPv6 will not help acceptance.
> 
> IMHO, there's 2 issues:
> 1. Global IPv6 connectivity doesn't exist - at best, it's a tunnel mess
>    with bits and pieces continuously falling off, then getting reconnected
>    again, and nobody seems to care - there's no effort to make connectivity
>    more stable

And many of the tunnels are not a issue even if it would be better if they
were turned into native connections.

> 2. A new client query type - AAAAA - (that's 5 A's, meaning "give me IPv6
>    unless it doesn't exist, in which case return me IPv4),
>    with this result cached, would be helpful in high-latency
>    situations

It would do *nothing* to help.  The client or the libraries it calls
can already do this if they want.  Making two lookups is not a real
issue.  You would need to upgrade both clients and libraries to
make this change without breaking existing application.  Just add
a new flag to getaddrinfo() and upgrade the clients to set it.

While you are upgrading getaddrinfo() change the sorting order of
of the addresses you return and you have addressed most of the tunnel
issues as well.

Mark

> Geert Jan
> 
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka@xxxxxxx
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