Re: [Atoca] Requirement D2: "Large Audience"

<mark.wood@engineer.com> Mon, 17 January 2011 11:00 UTC

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Date: Mon, 17 Jan 2011 11:03:21 -0000
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Subject: Re: [Atoca] Requirement D2: "Large Audience"
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Hello chaps,

Yes, it's only possible to have any kind of delivery reports regarding
specific terminals on a one-to-one kind of unicast delivery. The Australians
were not considering Cell Broadcast or any other kind of multicast
technology as they have selected a SMS based delivery system, so this is
probably what they had in mind. I noticed that atoca language about this is
reserved mostly for the 'subscription push' kind of distribution.  We need
to take care not to make it look like a mandated requirement for
broadcast/multicast bearers. 

IMHO, the other special problems with multicast,  mean that it needs
different and special requirements and cannot be generalized with other
'push' or 'pull'  technologies quite so easily, tempting though that is. I
think this problem happens because most IT professionals are familiar with
TCP and UDP but rarely use multicast so are unfamiliar with its very
different attributes.

Many vendors offer systems which do have a positive indication of who got
what,  and this is a good thing for applications of up to about 10,000
receivers. Netherlands studies showed that by the time you scale up to
millions,  the mass scale of all this becomes a problem, so large scale
systems will have to reluctantly abandon the notion of  individual
confirmation.

Besides, the police authority of a large city don't have the time, during an
emergency, to check out millions of replies nor take any action if someone
does not reply (they are too busy). On the other hand a smaller community
may value such a facility, so it seems that they authority will need to
choose whatever is appropriate for the circumstances at their discretion.
There is no 'one size fits all' solution so we will have to blend many
bearers in any real situation.  For example the Norwegians take the opposite
view.

However, it is possible to confirm that the multicast was transmitted, as a
network of feedback receivers is envisaged in conjunction with an outer loop
reporter system, which would report of the message was transmitted on air.
If it did not, then an alarm would be generated by the originating
aggregator for the log file. So the positive indication of the fact of the
transmission over the air is satisfied even though individual delivery is
not. 

In summary, IMHO,  Broadcast/multicast bearers will need special treatment
as they don't neatly conform to the classic notions of 'push' or 'pull'. 

Warm regards, Mark  Wood.