2cb3f144_able_Messaging___Project_Kenai__Description
[Option] Message Delivery Assurance [Description] 
This option tells our Reliable Messaging implementation what type of the message delivery assurance is expected. Currently it can be set to "Exactly Once" and "At Least Once". Exactly Once delivery assurance, as the name suggests, guarantees that each message request from the web service client will be delivered to the web service endpoint once and only once. By default, this delivery assurance strategy is applied. At Least Once delivery assurance guarantees that each message request from the web service client will be delivered to the web service endpoint, however it is possible that duplicate messages may be delivered under some circumstances. In general, this type of delivery assurance may provide better performance.
Chapter 10. Using Reliable Messaging — Project Kenai
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