Subject: Re: [Ieprep] draft-ietf-ieprep-requirements-01.txt

From: Rex Buddenberg <[email-masked]>
Date: 01 Nov 2002 08:51:16 -0800

On Thu, 2002-10-31 at 12:29, RJ Atkinson wrote:

> Section 1,
> meta:		It is unclear whether the author intends only VoIP applications
> 			when the phrase "Emergency Telecommunications Service" is used
> 			xor means other things in addition (e.g. email, web).  This needs
> 			to be made more clear at a minimum.  If only the voice applications
> 			are intended, that scoping needs to be a whole lot more clear than
> 			it is at present.
> 

and

> Section 1.2,
> page ?:		I think it is possible that the PSTN is migrating to VoIP, as  
> this
> 			claims, but I do not think that it is certain to be the case.  The
> 			PSTN architecture is very much tailored for voice services and the
> 			Internet architecture is quite deliberately general (not tailored
> 			for voice services).  So it isn't really universally accepted that
> 			"convergence" is happening or guaranteed to happen.

Went through a rather lengthy discussion on this topic with a couple of
thesis students who just graduated.  Let me replay some of it; at least
partly germane.

As an economic analysis, the students did some life cycle costing
against three choices. If you need to replace your PBX then:
	- buy a new PBX?
	- buy a VOIP capability instead?  (Assumption is that you have a data
network)
	- some hybrid between?
The analysis clearly said buy whole hog into VOIP; don't buy a new PBX
(the month following, our campus bought a new PBX...)

What was not covered in this analysis was the economies of 'collapsed
bandwidth'.  Right now, the typical naval ship has several radios, each
with a 3kHz voice equivalent bandwidth (ignoring digitization and ssb
stuff).  And the commstas have the ability to splice radio calls into
the PSTN (phone patch).  Yeah, all these radios are mutually interfering
emitters.  But a large (and proportionally growing) portion of the radio
comms is data.  If you push all of that into a fewer number of larger
sized pipes (keeping overall bandwidth constant) the number of emitters
goes down (less self-interference).  There are a whole bunch of
economies here to avoiding having to maintain voice channels, video
channels and data channels and just having IP channels.  All of this
argument reinforces the economy conclusion the students did find.

Why is this important to ieprep?  Many (most?) emergency services
providers have mobile platforms and need the radios to reach to them. 
Further, the radio links are often impressed as altroutes to cover
damaged fiber/copper links between fixed sites.  It makes a whole lot
more sense in the longer term for all of these emergency services
outfits to each maintain a single flavor of radio-WAN plumbing.  

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From: RJ Atkinson <[email-masked]>
Date: Sat, 2 Nov 2002 07:06:44 -0500

> (the month following, our campus bought a new PBX...)

Extreme did that analysis within the last ~year and reached the 
conclusion
that a PBX had lower life-cycle and business costs.  So we have a PBX
at the office I work in.  Not sure what was in your students' analysis,
but maybe their model had different assumptions than a business might 
use.

> argument reinforces the economy conclusion the students did find.

And the USN has been trying to merge its stovepipe comm systems for at
least 10 years (that I personally recall) with near zero success.  One
of the problems has been getting different groups of people responsible
for different (sub)systems to agree on how a shared bandwidth comm 
system
would allocate its bandwidth.  Another problem is that the RF 
characteristics
of those systems vary significantly (consider HF Radio and the sunspot 
cycle
with SHF SATCOM and rain fade; similar issues in theory but very 
different
in operational practice).  In the early 90s, this activity was sometimes
called "Copernicus" by some parts of the USN.

Ran
[email-masked]