[Standards] XEP-0369 (MIX): Early stages of a clients connection
jonas at wielicki.name
Thu May 18 15:09:41 UTC 2017
Dear Steve and others,
In the xsf@ MUC, we were discussion the interaction of MIX and roster, and the
question what happens with roster versioning and MIX entries came up.
The key scenario which is unclear is the following: Assuming a server and
client both support and use roster versioning, what happens when the client
gains MIX capability in an update? The client connects to the server and posts
its roster version X to the server. How does the server reply? Of course, the
server can "overlay" the addition of MIX (from the point of view of the
client) ontop of the changes accumulated since version X.
I think this should at least be discussed in the MIX XEP.
A somewhat related point brought up by Dave was *how* does the server find out
whether a client supports MIX when asked for the roster? The theory was that
the server would know, because of XEP-0115 Entity Capabilities or similar
mechanisms. However, at the point the roster is requested, the client may
easily not have sent presence yet.
So the server might need to make a disco#info request while letting the client
wait for the roster response. An extra round-trip, which is not even obvious
to the client.
Steve and others on the list, opinions?
P.S.: It also seems underspecified in the MIX XEP whether a client needs to
send available presence to receive MIX messages and whether a client which
sent available presence, but with negative priority, receives MIX messages.
But I think Steve already took note of that in the xsf@ MUC. Only including it
here for completeness.
P.P.S.: None of these issues were found by me (the first was found by Georg,
the second and third by Dave); I am just re-laying those to the list since we
don’t have logs currently and I think those are worth discussing.
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