Re: T2 Retry with Delivery Receipt

[Dan Weinreb <dlw@exceloncorp.com>]

   Date: Thu, 13 Sep 2001 10:59:00 -0500
   From: "David Fischer" <david@drummondgroup.com>

   Confirmation of non-delivery is not really possible (Logic 101 -- you can never
   prove a negative).  TTL may come into play here and help resolve this but TTL is
   likely to be too long for time-sensitive issues.

I believe that the only way you can confirm non-delivery, i.e. confirm
that the message has not been delivered and never *will* be delivered,
is to wait for the TTL to expire and then confirm that the message
isn't in the To MSH's persistent store (and never was).

It's important that the From application should have some way to
remove doubt about whether a message was delivered.  TTL is, as far as
I can tell, essential for this.

I'm not sure why TTL needs to be too long for time-sensitive issues.
Suppose that time-sensitive means that we need to know after one
day.  Either:

(a) The network very, very rarely delivers messages after a delay
of more than one day.  Then just set TTL to one day.

(b) The network delivers messages after a delay of more than one day
relatively often.  In that case, why are you using that network for
time-sensitive business interaction anyway??