[EAS] Duplicate CAP alert criteria

[Ed Czarnecki]

Dave - I meant to also point out also point out that the criteria used to
decode duplicate SAME EAS alerts are the same as those used to de-dupe CAP
alerts.

The EAS manufacturers standardized around he ECIG Implementation Guide
(adopted by both FEMA and FCC).
- ORG code is contained in a CAP element with the value name "EAS-ORG"
- Event code (EEE) is contained to a CAP element called <eventCode> and
subelement <valueName> of "SAME" 
- Location (PSSCCC) correlates to a CAP element called <location> also with
a subelement <valueName> of "SAME" - the FIPS code
- Time (JJJHHMM) correlates with the CAP element <sent>
- Duration (TTTT) is actually calculated as the difference between the CAP
<sent> time value and the CAP <expires> time value.  TTTT = <expires> -
<sent>

If you look at the time parameter, it may be feasible that an alert
originator rapid-fired an exactly identical alert, because they CAP messages
were so closely spaced in seconds that the JJJHHMM value remains the same.
So alerts "machine gunned" out (for example) 09:45:50 and 09:45:59 and then
09:46:05 present a challenge.  The first two are identical values as far as
translation to EAS. Both "round" to a JJJHHMM value of 09:45.  

If all the other filter parameters are also the same, then this example
shows how two the messages were treated as a duplicate, but the third (with
a time value that crossed the minute mark) was not a duplicate because the
JJHHMM value was different.

This was a subject of discussion within ECIG - because the time value in CAP
can be calculated in seconds, but the time value in EAS is in minutes.

This is one of many reasons we'd like to see the EAS protocol revisited, to
add support for a message ID (the same one in a corresponding CAP message),
and a better time usage.

This itself is a "rapid fire" summary of a fairly complex challenge
coordinating EAS and CAP.  (But, as someone reminded me just yesterday,
technology is not the complex part ... people are the complex part...).

Ed

Ed Czarnecki
Senior Director – Strategy and Government Affairs.
Monroe Electronics Inc / Digital Alert Systems
Reston VA | Lyndonville NY
www.digitalalertsystems.com 

-----Original Message-----
From: EAS [mailto:eas-bounces at radiolists.net] On Behalf Of Dave Turnmire

I have long been familiar with the criteria used by decoders to identify
"duplicate" S.A.M.E. alerts.  But... a recent event caused me to wonder
about what the criteria is for recognizing duplicate CAP alerts.

Last week a bug in the software used in our state caused the user to be told
"message not sent" after they pressed the Send button. So... they tried