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Subject: New issue: Facilities to support optional MakeConnection.underspecified


The spec implies that MakeConnection is required of all implementations.  Since there appear to be preconditions to initiating polling, and these preconditions are outside the scope of the spec, it is entirely possible that a particular implementation can refuse to accept the preconditions that require polling.

 

Such a refusal is reasonable, as polling can be resource intensive (requires a store of messages waiting to be polled).  Buffering messages has inherent limits:

  • The physical machine hosting the buffering service may have less than infinite capacity.  In fact, it may appear to have no capacity to create a new buffer for a particular user.
  • The buffering service may have policies on when an unpolled buffer can be discarded.
  • The buffering service may need to reject or destroy to avoid DoS attacks.

 

Since accepting the preconditions is not mandatory, effective use of a MakeConnection is also effectively optional.  However the negotiation of this scenario is currently outside the scope of the spec, and is likely to suffer a loss of interoperability as a result.  The optional nature should be clarified in the spec, and further infrastructure should be deployed (e.g. a MakeConnectionRefused error, possibly an rm:MakeConnectionEnabled policy assertion) to assist in interoperability in determining at run time, possibly even at design time, whether a MakeConnection attempt has been, or will be, successful.

 

With MakeConnection+SeqID, there is a clear marker that Polling is being "initiated" - a CreateSequence+Offer+WSA-AnonymousEPR indicates that two way reliability with Anon is happening. The server can either fault CreateSeqRefused or can fail to accept the Offered sequence (which is after all the troublemaker).  However, with MakeConnection+RManonURI, the RMAnonURI can be "slipped" in at some earlier point into messages that do not have any relationship to the RM agent, for example as a ReplyTo. The RM agent may not be handling that message, but in this case what does the server do with this message?

 

Jonathan Marsh - http://www.wso2.com - http://auburnmarshes.spaces.live.com

 

 



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