On 20-sep-2007, at 16:52, Keith Moore wrote:
6to4 is a crapshoot, it can be
reasonable or it can completely fail, with everything in between. But
it's never going to be better than native IPv4, obviously.
No, not obviously - because if the application has a need to do
address
referral then there are conditions in which the 6to4 address will work
better.
I was talking about performance. I guess even there there are a few
cases where 6to4 can do better than the IPv4 it's carried over, but
that should be rare.
I agree that this is an important issue, but I fail to see how this
relates to applications knowing about addresses, unless applications
are going to do their own performance testing, which I don't
recommend.
p2p applications are doing this already.
Do you mean BitTorrent? Those applications don't really test
performance, but simply use different addresses concurrently. Which
is an excellent way to make the question of which address performs
better moot, by the way.
As I said, a good start would be that API because once applications
use it, people working on better address selection etc have a
place to
insert their stuff and improve performance of real applications
without having to rewrite the application.
I spent a fair amount of time trying to come up with an API that would
let applications push this decision-making to a lower layer while
allowing that lower layer to make those decisions effectively based on
the needs of that particular application. That API ended up looking
fairly complex. There are lots of factors that influence address
selection.
Yes, communicating application needs back and forth would be tricky.
For instance, suppose I have two links: one is 2 Mbps ADSL. This is
not so bad that an application can't run, but if my other link is
1000 Mbps, then the application would probably want to use that link.
But the application doesn't know if that's the case, it could also be
a GPRS link with enormous latency and virtually no bandwidth. So what
does the application say?
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