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

"Peter Sanders" <peter.sanders@one2many.eu> Mon, 17 January 2011 16:01 UTC

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From: "Peter Sanders" <peter.sanders@one2many.eu>
To: "'Brian Rosen'" <br@brianrosen.net>, "'mark.wood@engineer.commark.wood@engineer.com'"@core3.amsl.com
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Date: Mon, 17 Jan 2011 17:04:28 +0100
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Subject: Re: [Atoca] Requirement D2: "Large Audience"
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Hi Brian and Mark,

Brian, you state in your email the following:
"It's VERY valuable to know that every entity that should get the alert got
it"

The authorities may not know who in particular needs to receive the alert
message. They wish that everyone in a specific area receives it. However,
the authorities may have no idea who is in the target area at that moment,
so they can't ask for confirmation; they can, but they don't know if they
miss a few acks.

Finding out who is in a specific area is technically possible, but may
generate far more network traffic than the acks you expect from a few
million people, and it takes time too. 

I just wanted to add these remarks to the discussion.

Best regards,
Peter


-----Original Message-----
From: earlywarning-bounces@ietf.org [mailto:earlywarning-bounces@ietf.org]
On Behalf Of Brian Rosen
Sent: maandag 17 januari 2011 15:44
To: mark.wood@engineer.commark.wood@engineer.com
Cc: earlywarning@ietf.org
Subject: Re: [Atoca] Requirement D2: "Large Audience"

It may be, but I'd like to explore this a bit anyway.

Millions of messages (acknowledgements) is a scale we can deal with today.
Hundreds of millions is probably beyond what we can deal with in a response
to a very large alert.

Most systems consist of several smaller subsystems.  The purpose of an
acknowledgement is to make sure everyone got the message.  If the subsystem
can determine that every one of its clients got it, it can report that up
the line.  It can save missed acks for later analysis, or if there are few
enough of them, report them up.

This means messages national scale which have small effectivity times can't
reasonably ask for message acknowledgement.  Anything smaller than that
probably can.

Since most alerts really don't involve hundreds of millions of
notifications, most alerts probably can ask for them.

If your delivery mechanism is multicast, the multicast mechanism itself
doesn't track who gets the alert in any way we can use.  That implies
something else is tracking who gets the alert, a complication that could
loom large.  Some systems do know who gets the alert (sometimes because it
knows who it is connected to, and all of them get the alert).  Certainly,
anything with a subscription has the characteristic that the sender knows
who all the recipients are.  

It's VERY valuable to know that every entity that should get the alert got
it.  The only other mechanism we have is some repeating of the sending in
the hopes that everyone got it.  In some cases you may have more than one
"path" to the same recipient.  That might be multiple devices, multiple
services, or multiple logical or physical connections.  You may try one
first, and if that doesn't get an ack, try another.  Although we often think
of this mechanism as needing no more than seconds to deploy, in fact many
alerts would be fine with a few minutes, and trying some things sequentially
may make sense.

So, yes, probably a Tsunami alert to all of East Asia can't ask for
acknowledgements.  An "Amber Alert" (possible abducted child) to a county
might very well.  Certainly, a snow emergency closing to the parents of an
elementary school could.

Brian


On Jan 17, 2011, at 6:03 AM, <mark.wood@engineer.com>;
<mark.wood@engineer.com>; wrote:

> 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.
> 
> 
> 
> 
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