[Standards] Stanza Size Limits (was Re: [jdev] Communicate between two client instances of the same ID)

Pedro Melo melo at simplicidade.org
Wed Sep 3 09:36:10 UTC 2008

On Sep 3, 2008, at 5:47 AM, Peter Saint-Andre wrote:

> Justin Karneges wrote:
>> Dragging this over from jdev:
>>>>> Hmm. XMPP is not optimized for sending around 100k+ messages.
>>>> Would 64KB chunks a reasonable thing to do?
>>> That's probably still too high.  There is currently no specified  
>>> maximum
>>> size for XMPP stanzas, but individual implementations may enforce  
>>> different
>>> values.  The original jabberd 1.0 server had around a 10KB  
>>> maximum.  The
>>> general consensus is that stanzas should be "small", and this is  
>>> largely in
>>> part because large stanzas block transmission of other stanzas  
>>> (you cannot
>>> send many stanzas in parallel over one stream).
>> Right now it's fuzzy as to how small you should chunk your data for  
>> maximum compatibility.  I think we should define the largest stanza  
>> size that must be supported by clients and servers.  We could just  
>> make this value 10000 bytes, from the opening '<' to the final '>'  
>> of the stanza.  The text should go into RFC 3920bis as a SHOULD.
>> This way, stanzas 10000 bytes or smaller are guaranteed to succeed  
>> in transmission.  Stanzas larger than 10000 bytes would still be  
>> transmittable, but without any guarantees that the other side will  
>> accept it (which is not any worse than the situation today).
>> A question: which stanza error are we supposed to use to reject a  
>> stanza that is too large?  Such an error would be very useful to  
>> determine the MTU.
> http://www.xmpp.org/extensions/inbox/stanzalimits.html

Why not make section 3 a stream feature instead?


   <limits xmlns='urn:xmpp:tmp:stanza-limits'>

This would signal the client that the max stanza size is 65355 bytes,  
and the max allowed rate of stanzas per second is 10.

Other limits could be included also (max presence changes per time- 
period?) but at least <size> and <rate> seem important to me.

Best regards,
Pedro Melo
Blog: http://www.simplicidade.org/notes/
XMPP ID: melo at simplicidade.org

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