-----Original Message-----
From: ecrit-bounces at ietf.org [mailto:ecrit-bounces at ietf.org]
On Behalf Of Henning Schulzrinne
Sent: Tuesday, August 02, 2005 11:57 AM
To: Byron Smith
Cc: ecrit at ietf.org
Subject: Re: [Ecrit] Suggestion for "performance and
reliability" section
I don't think I mentioned NENA. My source of the information
was the LAPD PSAP (which I visited during the NENA meeting).
The person in charge said that their goal was 10s in 95% (not
sure about the
percentage) from call to human answer. They apparently
tracked this information. In their case, the concern was
primarily human response time, not routing time. Call setup
time in mobile systems often approaches several seconds.
Beyond these anecdotal numbers, I'm not sure that we'll be
able to rely on existing performance standards and that we
can draw much insight from any number we get, except that
having a gnome looking up the information in an atlas is
likely to be unsatisfactory and that faster is better.
I also suspect that the only protocol that would likely fail
a reasonable lookup time test, except by pure implementor
stupidity, would be one that walked a geo search tree with
widely distributed servers for each query.
Byron Smith wrote:
Henning, where do you get the NENA 2s and 10s numbers? The
only thing
I have found in NENA documents is:
" 9 Call Set-up Time
It is recommended that emergency call set-up time not
exceed the
average call set-up time for any
other type call made by the customers of that
particular serving
office.
It is also strongly recommended that in all circumstances the
caller hear either audible ring tone or a
recording alerting them that their call is being processed."
The above is from NENA 03-501. I have looked for other NENA
recommendations, but have not found them.
I would appreciate a reference if you have one.
Not that this is terribly relevant: But I would make a small wager
that more than 50% of the (rural) wireline 911 systems in
the country
fail to meet the above recommendations. (Probably closer
to 80%) The
observed call setup time for systems that use CAMA trunks
is usually
3-7 seconds dial-to-ring, with 5 seconds being typical.
Most digital
end-office switches make local dial-to-ring setups on the
order of 1 second.
Byron
-----Original Message-----
From: ecrit-bounces at ietf.org
[mailto:ecrit-bounces at ietf.org]On Behalf
Of Henning Schulzrinne
Sent: Tuesday, August 02, 2005 4:08 AM
To: ecrit at ietf.org
Subject: [Ecrit] Suggestion for "performance and
reliability" section
I would think capturing the known external requirements as such is
helpful. For example, the NENA 2s (dial-to-ring)
requirement, which is
part of the 10s dial-to-pick-up I mentioned could just be
captured as
such external guidelines, possibly in a separate "performance and
reliability" section. If early implementations, with reasonable
assumptions on round-trip times and topology, can't satisfy
those, we
know we have a problem.
Henning
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