about WSA ReplyTo

["Durand, Jacques R." <JDurand@us.fujitsu.com>]

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