[josm-dev] IPv6 problems

Dirk Stöcker openstreetmap at dstoecker.de
Fri Jan 1 13:03:57 UTC 2016

On Fri, 1 Jan 2016, Florian Lohoff wrote:

> Currently josm tries to be clever and either does v6 or v4 and tries
> to detect whether the host is v6 enabled. This is broken by design.
> You cant detect whether you will be able to issue v6 connections
> until you try. There are v6 blackholes in the internet, there is
> intermittet connectivity, there are ULA prefixes which is just an v6
> island whathever. Its the INTERNET - Everything is built on a "best
> effort" base. It may work - it may also not. IPv6 put the responsibility

That's nonsense. If you extend the meaning of "best effort" to "it may 
work or not" then it's ok when a provider only delivers data to half of 
the world? Well, why pay money for devlivery the other half?

A network access which has permanent connectivity issues is broken!

If you go into the future you will have IPv6 only. No IPv4 fallback. And 
it has to work. Yes - we currently have a chance to try again with IPv4 
and JOSM doesn't use that chance. Well, JOSM doesn't do many other things 
as well.

But telling me that it's JOSM's fault that providers are incapable to do 
their work properly is nonsense.

> for the user experience in the hands of application writers by making
> strong recommendations on how to write your applications. If it fails
> because the application is broken people turn off ipv6 and will never
> ever turn it back on because of bad reputation. This will hurt
> IPv6 adoption and in the end will hurt us all.

As said. If it does not work, then it's a providers fault. I see that 
someone coming from an ISP doesn't want to hear that, but providing a 
broken connectivity is not an application issue.

> There are even more broken assumptions in josm. I live in the rural
> outback and i have 348kbit/s - Sometimes on josm startup it fails to
> fetch the motd or mappaint styles or whetever it tries to do on startup.
> Some requests on startup timeout because my line is congested. This
> causes josm to refuse to do ANY network interaction afterwards. You cant
> download data etc etc. Sometimes i need to start josm 3-4 times until it
> actually is willing to play with me. This never happens on a VDSL
> 50MBit/s connection etc.

I don't remember a report about such behaviour. Please tell me the ticket 

I also don't believe that's a JOSM issue, as JOSM does not remember any 
states between connections. Maybe your connection is simply to slow and 
you need to increase the timeouts so it works for your system. JOSM uses 
reasonable timeouts for modern connections of half a minute. That should 
be enough also for a 348kbit/s connection.

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