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

[Christopher B Ferris <chrisfer@us.ibm.com>]

Charlton wrote:

> It makes the most sense to me to take this approach. Although more 
choice 
> is usually good, it seems onerous to me to require support of AtMostOnce 
 
> semantics on the wire. Unless I see something that proves otherwise, I 
> feel we should say that our protocol is AtLeastOnce.

Actually, more choice typically leads to lower interop:-) However, I 
concur 
with Anish's #1 that we should stick with the way that the *protocol* is 
designed 
(AtLeastOnce)

As for DA, again, that is a function of the contract between the RMD and 
AD (IMO)
and not at all related to the wire protocol.

Cheers,

Christopher Ferris
STSM, Emerging e-business Industry Architecture
email: chrisfer@us.ibm.com
blog: http://webpages.charter.net/chrisfer/blog.html
phone: +1 508 377 9295

Charlton Barreto <cbarreto@adobe.com> wrote on 07/28/2005 04:31:48 PM:

> On Thu, 28 Jul 2005 13:06:50 -0700, Anish Karmarkar 
> <Anish.Karmarkar@oracle.com> wrote:
> 
> > The protocol, as is defined today, is AtLeastOnce (as Chris keeps 
> > reminding us), between the RMS and RMD.
> >
> > It seems to me that using this protocol for AtMostOnce is 
> > wasteful/inappropriate/expensive. I.e., if AtMostOnce semantics is 
> > desired why would one use WS-RM and pay for AtLeastOnce semantics 
(whose 
> > costs can be significantly higher).
> >
> > The two sensible options that I see are either:
> >
> > 1) say that our protocol is AtLeastOnce and we don't say anything 
about 
> > AtMostOnce at all. If someone wants to use AtLeastOnce at the protocol 
 
> > level and implement AtMostOnce at the application level they can 
> > certainly do it. We don't say that 'Unreliable' DA is supported, but 
> > someone can use WS-RM to do unreliable messaging (and pay the higher 
> > cost) -- although I don't know why someone would do that.
> 
> It makes the most sense to me to take this approach. Although more 
choice 
> is usually good, it seems onerous to me to require support of AtMostOnce 
 
> semantics on the wire. Unless I see something that proves otherwise, I 
> feel we should say that our protocol is AtLeastOnce.

Actually, more choice typically leads to lower interop:-) 

> 
> > or
> >
> > 2) say that AtMostOnce semantics are important in the world of 
reliable 
> > messaging and Tom/Gil have cited use cases for it, and change our 
> > protocol on the wire to accommodate this. I.e., the protocol on the 
wire 
> > will not always be AtLeastOnce protocol. This would allow the 
> > sender/receiver to pay the price for the QoS that is desired (and 
> > nothing higher).
> >
> > Comments?
> >
> > -Anish
> > --
> >
> > Dan Leshchiner wrote:
> >> if AS makes RMS aware that AtMostOnce is used by AD/RMD, then RMS can 
 
> >> assume that no retransmissions will be necessary and, consequently, 
> >> does not need to take up its resources to make retransmissions 
> >> available, right?
> >>  Christopher B Ferris wrote:
> >>
> >>> I think you meant AtMostOnce mode. I suppose you could do that, but 
> >>> from the
> >>> perspective of the RMS, it is still retransmitting until it receives 
 
> >>> an ack.
> >>>
> >>> Cheers,
> >>>
> >>> Christopher Ferris
> >>> STSM, Emerging e-business Industry Architecture
> >>> email: chrisfer@us.ibm.com
> >>> blog: http://webpages.charter.net/chrisfer/blog.html
> >>> phone: +1 508 377 9295
> >>>
> >>> Dan Leshchiner <dleshc@tibco.com> wrote on 07/27/2005 06:36:24 PM:
> >>>
> >>>
> >>>> Christopher B Ferris wrote:
> >>>>
> >>>>
> >>>>> However, the protocol as specified would never be able to complete 
a 
> >>>>> sequence
> >>>>> if there are lost messages from the RMD perspective and the RMS is 
 
> >>>>> not
> >>>>> retransmitting them.
> >>>>>
> >>>>>
> >>>>>
> >>>> why so? as RMD, if i see a gap or AckRequested for a sequence 
number 
> >>>> i have not received and i am operating in "at least once" mode with 
 
> >>>> my AD,
> >>>
> >>>
> >>>> why cant i just send an Ack? if i did so, wouldn't that enable us 
to 
> >>>> complete the sequence?
> >>>>
> >>>> thanks,
> >>>> dan
> >>>>
> >>>
> >>>
> 
> 
> 
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