[Standards] s2s and gracelessly broken streams

[Philipp Hancke]

Hi Matthias,

Matthias Wimmer wrote:
[...]
> Due to my experience servers that went down is only the cause for a very 
> small fraction of wrong presences. Our main problem still seems to be, 
> that even the user's server has a wrong impression of this user's 
> presence (i.e. servers that do not detect that a user is not online 
> anymore). We now have XEP-0199 that allows a server to probe if a client 
> is still online. We should first see how much the problem of stale 
> presences is improved if servers XEP-0199-pinging idle clients get more 
> widely deployed, before we start tweaking less important factors.

I would suspect temporary s2s hiccups and 'lost' unavailable stanzas to
be another cause.
Whereas those stanzas are 'lost' in a situation like the following:
the user goes offline, the server does the unavailable presence 
broadcast and something (*) goes wrong during s2s. The server will see a

<presence type='error' from='...' to='...'><error .../></presence>

and the information that this was an unavailable presence is lost,
hence there is no chance to resend it.

Philipp

(*) for example your dns server refuses to work - the kind of bugs you
     can hardly ever reproduce