[Standards] UPDATED: XEP-0199 (XMPP Ping)
justin-keyword-jabber.093179 at affinix.com
Thu May 10 17:36:08 UTC 2007
On Thursday 10 May 2007 5:28 am, Mridul wrote:
> Justin Karneges wrote:
> > On Wednesday 09 May 2007 11:46 am, Mridul Muralidharan wrote:
> >> probe is a mechanism for servers to discover presence - I dont see how
> >> it makes sense for directed presence case.
> > You're right. However, lately we've been talking about using probes even
> > when the presence is already known, as a way to resolve s2s problems. In
> > that case, it would be ideal if probing worked for both kinds of
> > presence.
> Yes, but this was to solve a particular problem - and the generic
> solution for that is not probe. probe would be a hack which would need
> to work until we fix retransmissions between servers properly.
> I am not sure if we need to introduce workarounds into the rfc.
> If required, why not have an informational xep for this probe behavior
> which would get deprecated later on when 198 becomes mandatory to
> implement in client/server (hopefully, in the not so distant future).
> This way, the rfc's remain agnostic to the implementation details.
I don't know if XEP-198 solves ghosted presence very well, or at least not on
its own. With 198, it is possible for a sender to know if a stanza delivery
has failed, so that it can be redelivered or bounced. In the case of
presence, we'd never want to bounce, because then that could cause a
ghosting. So the server would want to attempt redelivery forever.
What happens if the sending server goes down and cannot redeliver? We would
have a presence ghost until the server comes back online. What if the server
closed its business for good? :)
Now, XEP-198 might work if we also had a presence TTL value of some sort.
This way, if the sending server of presence does not resend new presence
within the TTL, then the receiving server can expire presences.
I think a proper solution here is going to either require TTL values in
presence packets (burden on sender to resend presence), or presence probing
(burden on receiver to monitor presence validity).
More information about the Standards