about WSA ReplyTo

After internal 
discussion it appears to us that the following way to handle WS-Addressing 
ReplyTo in a multi-hop env is the most appropriate (which means the current 
drafts would need some update but not much) :

 

wsa:ReplyTo 
anonymous (which is the default when no ReplyTo ) should - even when used in a 
multihop context - always indicate that a response will be obtained on the HTTP 
response (backchannel) both on Sender and Receiver sides.

This best ensures 
compliance with current behavior of most SOAP stacks.

 

This means that at 
least on two hops (the edge hops), connection must be kept open for 
communicating response on the backchannel of the request.

 

Consequently, the 
proposal is the following:

 

1- when the sending 
Endpoint adds ReplyTo anonymous (or none at all) this means that it expects a 
Response on the backchannel, whenever a response is expected. This would affect 
the binding of Two-way MEPs (the "reply" message) as well as One-way that need 
an eb:Receipt. Both "reply" and Receipt are expected to be received by sending 
Endpoint on the HTTP backchannel.

Same behavior on the 
receiving Endpoint (final destination).

In-between (I-Cloud) 
the behavior could be more flexible and the binding decided by routing function. 
But the default behavior is here that all intermediaries would keep their 
connections open until they get the response.

 

2- when the sending 
Endpoint adds ReplyTo set to an EPR containing  the "icloud" URI (see the 
most recents drafts), then that means to the Intermediaries that the routing 
function will rely on the ref parameters of this EPR, for routing the 
response.

On the receiving 
Endpoint MSH, this means that the support for WSA is profiled to recognize this 
"icloud" URI, and map it to a predefined (configured) URL, namely the address of 
the first Intermediary the response should go through.

This is easily 
configurable on the endpoint MSH, as part of its expected WSA support, according 
to our engineers.

 

3- when the sending Endpoint adds ReplyTo set to an EPR 
containing  another  URI different from (1) and (2) above (and 
different from "none" wsa URI), then the Receiving Endpoint must send back the 
response directly to this URL. This URL could be the final destination of the 
response. This is a special case where no routing is needed for the response. 
Or it could be the URL of the last Intermediary before the destination MSH. 
This is a special case where no routing is necessary either, except for the last 
hop.

 

So this means that the use of ReplyTo anonymous will be 
quite restricted and implies channel bindings that are rather constraining (keep 
conenctions open). Because the absence of ReplyTo is to be interpreted as same 
as ReplyTo anonymous , the most common usage of ReplyTo in multihop context is 
expected to be (2) above.

 

- Jacques