[Standards] Resource conflict handling

Glenn Maynard glenn at zewt.org
Fri Jun 10 17:48:01 UTC 2011

On Fri, Jun 10, 2011 at 8:35 AM, Dave Cridland <dave at cridland.net> wrote:

> What M-Link does is ping the old session on a conflict, with a short
> timeout (of, if I recall, 10 seconds).
> So on a conflict, you get three cases:
> 1) The act of sending the ping causes an error, in which case the old
> session is cleaned up and the new bind succeeds.

> 2) The old client responds, in which case the new bind pauses for one RTT,
> and then generates a new resource. (ie, #3).
> 3) The old client does not respond, in which case it's terminated after the
> timeout, and the new bind succeeds after the timeout.

This won't work properly if the existing client is a paused BOSH session,
which may not unpause the session to reply for arbitrary lengths of time.

The common case is actually #1, however if you simply terminate the old
> session blindly, it's very easy to get into ping-pong loops with multiple
> client instances both asking for the "Home" or "Gajim" resource.

That's why clients should explicitly declare that they want the
disconnection behavior.  It's essentially a declaration by the client that
it's designed to avoid this problem, probably by using a resource that it
knows won't conflict.

Glenn Maynard
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