[Standards] XEP-0301 Session handling

Gunnar Hellström gunnar.hellstrom at omnitor.se
Tue Feb 28 23:07:22 UTC 2012

Sometimes it is very helpful with a clear beginning and a clear end of 
an XMPP text session.

For example if you are gatewaying to a SIP call, and want to cause a 
hangup on the SIP side, or get an indication to the XMPP side when the 
SIP side has closed the session.
I wonder if there is a session start - session end indication that has 
dominating support among XMPP text messaging implementations that can be 
used as the default mechanism for XEP-0301 real-time text session control.

Right now in XEP-0301, there is an "start" event and a "cancel" event 
defined in section 4.2.3 with indications that they MAY be used to 
indicate session start and end.
See http://xmpp.org/extensions/xep-0301.html

I have found some other mechanisms, and I wonder if the "start" and 
"cancel" events should be deleted from XEP-0301, and instead some 
already existing mechanism used, in order to not increase the number of 
optional ways to handle session start and end.

It seems to me that there is a basic mechanism for session control 
defined in RFC 6121 section 5.1
Initiation of a session should begin with a message with type=chat,
Both parties shall set their presence <show/> to "chat"
End of session should be signaled by indicating directed presence 
A change of <show/> to anything else than chat should also be taken as 
indication of end of session.
An example is presented in section 7 of RFC 6121.

I assume that there are a multitude of exceptions when this sequence 
does not occur, but it seems to me to be a good basic sequence to support.

On top of that, there seems to be a range of more comprehensive session 
control options:
-XEP-0166 Jingle session establishment.
-XEP-0155 Session establishment
-XEP-0045 Multi-User Chat  ( that also uses directed "unavailable" 
presence for closing the session as the main method above.)

So, for XEP-0301, I want to check if it would be wise to delete the 
"start" and "cancel" events from chapter  4.2.3 and instead insert a new 
subsection in chapter 6 saying:

"6.4 Session control
Session control is essentially out of scope for this media related 
A recommendation is though to follow the basic principles described in 
RFC 6121 section 5.1.
Any further session handling such as Jingle, MUC or the Session 
establishment extension may be added as found suitable for each specific 
application of this extension."

Gunnar Hellström
gunnar.hellstrom at omnitor.se

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