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Subject: Re: T2, Proposed solution for ... Re: SyncReply andReliableMessagingMethod in QualityOfServiceInfo
Date: Fri, 17 Aug 2001 09:04:29 -0500 From: David Fischer <david@drummondgroup.com> Intermediate duplicate detection precludes retries by the From Party MSH. If we deal with the whole issue of intermediaries by using a layered approach, we would not have this problem. Consider the analogy with the Internet protocol stack. TCP (at layer 4) is defined to be once-and-only-once. It's built on IP, which is built on link-level (layer 2) protocols. The link-level protocols do not promise (in their contract to the higher layers) any kind of retransmission of data, but some of them do retransmission anyway (going beyond what they promised to do), because they are in a good position to retransmit efficiently and the net effect is to reduce the amount of retransmission that the higher layers have to do, thus increasing net performance. Analogously, In the layering of ebXML MS that I and others have been suggesting, we should have end-to-end reliable messaging, with the IM's not *promising* to be reliable; an IM could drop a message or duplicate a message, without breaking its contract. An IM might do duplicate elimination anyway (going beyond what it promised to do) for the sake of improving overall performance, but that would be entirely invisible to the higher-layer ebXML MS protocol. And so, intermediate duplication detection would *not* preclude retries by the From Party MSH. -- Dan
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