[Standards] Whiteboard XEP, Gajim and GSoC2008

Dave Cridland dave at cridland.net
Fri Mar 7 09:23:19 UTC 2008


On Fri Mar  7 03:58:37 2008, Joonas Govenius wrote:
> 
>> On 3/3/08 6:23 PM, "Joonas Govenius" <joonas.govenius at gmail.com>  
>> wrote:
>> 
>>     >  What I don't like of the current SXE definition is the  
>> inability of
>>     >  sending the whole document or chunks it, instead of being  
>> obliged of
>>     >  sending all the necessary events for recreating the  
>> document.
>> 
>>     If the extra bandwidth really is such a problem we could  
>> define an
>>     implicit way of creating the objects out of a chunk of XML as  
>> I've
>>     mentioned but it doesn't seem worthwhile to me at this point.
>> 
> Boyd Fletcher wrote:
>> sending the entire document is a big show stopper for large group  
>> collaboration (especially if you are using a large number of  
>> whiteboard pages) and if your are using satellite/cellular  
>> communications (like is very common in military or 3rd world  
>> countries).
>> 
>> we dealt with the problem by using sequence numbers and the client  
>> can request which numbers it wants to receive.
> 
> You and Fabio are referring to slightly different issues here:
> 
> 1. Fabio is concerned about the bandwidth used for sending the  
> state to a client when it first joins the session. It would be  
> higher by some significant constant factor so this is probably a  
> legitimate concern but could be solved as I mentioned above; I just  
> think it would be a little premature at this point.
> 
> 
Boyd's also mentioned this. Note that his design is used quite  
heavily for presentation, where there's effectively an existing  
"whiteboard" - a collection of SVG pages - unknown to the audience  
prior to the event.


> 2. You are concerned about optimizing reconnects by taking  
> advantage of the state that the client already has. I gave this  
> some thought and there's actually no reason why SXE couldn't do  
> basically the same thing as your protocol:
> 
> 
Of course, Boyd's mentioned this, too, as well as the related case  
where a presentation using whiteboarding spans a day or two, and the  
next morning, the presenter has updated the document.

This is a particular case of resynchronization, because the  
assumption here is that there's a significant chunk of events that  
may need shipping.

SXE appears, to my eyes anyway, to be particularly inefficient at  
transmitting large changes, and I suspect that this may be at the  
core of Boyd and Fabio's concerns.

Dave.
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