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Subject: Re: [ws-rx] NEW ISSUE: semantics of "at most once" delivery assurance

Tom Rutt wrote:

> *Title*: Semantics of  "At most once" Delivery assurance.
> *Description*:
> The semantics of the "at most once" delivery assurance are not clear.

I just came up with another interpretation:

Given that any use of ws-reliabile messaging protocol implies an 
obligation that the rm-destination will return acknowledgments
for all messages sent in a sequence, the obligation of the rm-source to 
retransmit unacknowledged messages is what distinguishes
exactly once from at most once delivery assurance levels.

It is interesting that this implies an overlap of semantics with base 
retransimssion interval, in that a value of infinity would imple that 
the sender
will never retransmit. 

> One interpretation is that at most once implies that the sender is not 
> required to retransmit mesages which are not acked.
> *Justification*:
> It is important to clarify whether the sender must retransmit 
> unacknowledged messages when the "at most once" delivery assurance is 
> in use.
> *Target*: (core | soap | wsdl | policy | schema | all)
> all
> *Type: *(design | editorial)
> design
> *Proposal*:
> Clarify the semantics.  There are at least three possible semantics 
> associated with "at most once"
> proposal 1) at most once means that the sender will never retransmit a 
> message, regardless of whether it is acknolweged by the destination.
> Proposal 2) The sender may retransmis messages, but is not required to 
> to so,  however the destination will not deliver duplicates
> Proposal 3) the sender must retransmit messages, however the 
> destination may drop messages in times of resource saturation, but 
> will never deliver a duplicate.
> *Related issues*:
> Issue 9

Tom Rutt	email: tom@coastin.com; trutt@us.fujitsu.com
Tel: +1 732 801 5744          Fax: +1 732 774 5133

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