[Standards] UPDATED: XEP-0199 (XMPP Ping)

Justin Karneges 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).

-Justin



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