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Subject: Re: Intermediary support in the 1.1 version of the MSG and CPP/A specs
Chris: I agree with you that there will be use cases where a forwarding intermediary may need to use different transport protocols for inbound and outbound messages. I believe Dale is assuming that a common CPA will be used by the From Party, the To Party, and the intermediary/intermediaries. Maybe that assumption is too restrictive. Even with such an assumption, it is not clear to me how it can be made to work. Consider the one intermediary case, if the intermediary's endpoints are transparently used by the From Party and the To Party as their own endpoints in the CPA (i.e., the transport endpoints in the CPA all contain addresses associated with the intermediary), then where does the intermediary find the real forwarding addresses for the From Party and To Party? Clearly, there is extra configuration information needed by the intermediary that is missing from the CPA. I also tend to agree with Marty that once you take into consideration transport level security or if there are multiple intermediaries, it will be unwieldy to capture all the relevant configuration information in one CPA. Has anyone worked out simple examples where a separate CPA is used between each adjacent pair of MSH nodes? What kind of business processes have to be used to represent the message forwarding activities? What Service and Action elements will be appropriate under the Via element? Is the existing CPP/A element structure sufficient for this purpose? Regards, -Arvola -----Original Message----- From: christopher ferris <chris.ferris@Sun.COM> To: Arvola Chan <arvola@tibco.com> Cc: ebxml-msg@lists.oasis-open.org <ebxml-msg@lists.oasis-open.org>; ebxml-cppa@lists.oasis-open.org <ebxml-cppa@lists.oasis-open.org> Date: Tuesday, September 25, 2001 11:14 AM Subject: Re: Intermediary support in the 1.1 version of the MSG and CPP/A specs >Arvola, > >A couple of comments. > >Cheers, > >Chris > >Arvola Chan wrote: ><snip/> >> =========================================================== >> >> Messaging >> >> Arvola reported a fair amount of list traffic on RM and whether end-to-end >> retransmission should be specified. He asked if version 1.1 will we deal >> with forwarding intermediaries appropriately. Dale distinguished between >> two cases: forwarding intermediaries, where a CPA isn?t needed, and >> multiparty cases, which is in the scope of version 2.0. He opined that the >> approach taken in the proof-of-concept demo is probably sufficient for >> forwarding intermediaries (the intermediary is only involved in the CPA as a >> transport endpoint). Arvola questioned whether that made the Via >> (messaging) element unnecessary. Dale responded that it wasn?t necessary >> for the forwarding case, and would be used at the discretion of the >> originating MSH. Our commitment is to support the endpoint mechanism, and >> exactly what else is needed is unclear. We may recommend that CPA software >> check the coherence of values given for timeouts, retries, etc. According >> to Tim, that assumes the same security and transport on both sides of the >> intermediary. Dale said we?re assuming that the intermediary doesn?t alter > >It isn't a requirement that the same transport protocol be used on either side >of a forwarding intermediary, IMO. e.g. the sending node might use >HTTP between itself and the intermediary and then between the intermediary >and the recipient, the protocol might be SMTP. What may be necessary >is that between the Intermediary and the MSH to which it forwards messages >there be a separate CPA, one that possibly deals only with transport >details (as David B has suggested). Thus, the intermediary might introduce >a Via element to account for that. This isn't completely clear. > >I certainly agree that for forwarding, there is no explicit need (for the >first hop) of a Via element. > >As for security, things start to get a little crazier. I think that the >same level of security needs to be applied, whether it is necessarily the same >set of certificates, etc is less clear. > >> packaging and security - to the extent that the Via element or the >> TraceHeaderList impacts such things, it will be reflected in an agreement. >> Marty asked if the intermediary can pass through transport level security >> info, and if not, he suspects we?re into a multiparty situation. Jamie >> questioned whether the Via element could potentially thwart the policy >> intentions of a party if it resulted in changed messaging settings. Dale >> recalled ?case 1.5? of a forwarding intermediary that restructures or >> re-encapsulates the message/payload in some manner - a CPA may be needed >> then. Tim proposed acknowledging that such cases exist but are not >> supported for 1.1. David stated that the Messaging committee considers >> intermediaries out of scope for their version 1.1. Jamie asked if an >> intermediary is considered to be a pure forwarder bound to respect the CPA >> between two end parties; we then discussed advantages of keeping CPA content >> technical in nature from the standpoint of expediting agreement and >> implementation. Tim asked about how non-repudiation and error propagation >> happen with intermediaries. We discussed that some errors may come from the >> endpoint and others from an intermediary, and David (?) thought that in any >> case they?re just ebXML messages. Arvola asked if an intermediary would >> have to identify itself as the end party if it?s not explicitly identified >> in the CPA. >> >> ---------------------------------------------------------------- >> To subscribe or unsubscribe from this elist use the subscription >> manager: <http://lists.oasis-open.org/ob/adm.pl>
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