RE: Every time ..., was Re: General formula

[Alan Lloyd <Alan.Lloyd@xxxxxxxxxxxxxxxxxxxx>]

Gosh Andy - all you ever do is spend is two bob - which represents AU$
0.50. :-)
 For my three bobs worth, the fundamental issue is that a complex
problem like the lifetime of a lump of data cannot be solved by a simple
(or lightweight) solution or formula eg. good old LDAP did not and will
not solve directory SYSTEM issues - just server - access issues.

Cert validity / lifetimes should be modelled in terms of operational
usage with the reliability requirements of the service.. ie from a
requirements perspective  in the context of a system design - not a
predictive perspective  based on theory or massive assumptions about the
data.

The process of ILS, LCC, error mode and criticality analysis and service
availablity prediction processes work for me in this regard - as it
takes into account the system components, their architecture and their
usage, etc.. 

Perhaps a discusion on ILS and LCC might be useful eh!

regards alan 

> -----Original Message-----
> From:	Andrew Probert 
> Sent:	Friday, June 04, 1999 10:57 AM
> To:	PKIX
> Subject:	RE: Every time ..., was Re: General formula
> 
> Two bobs worth ..
> 
> Erlang calculations have been tablulated to give people an easy lookup
> for
> telephony calculations.  Given a presented load in seconds, and a
> number of
> lines, what is the percentage of calls that will get a busy signal?
> 
> It works, given 3 factors you can lookup any way you like.
> 
> However for this, or any capacity planning exercise, real-world data
> and
> assumptions are input to the model.  
> 
> Erlang tables require the user to input their assumptions on presented
> load
> (an average) and number of lines avaliable to derive busy.
> Alternatively
> how much busy time they can tolerate, for a given load to derive a
> minimum
> number of lines.
> 
> I'm all for a model, please send me the Excel spreadsheet
> implementation
> when its complete.  
> 
> However, I think the real world of certs is too complex.
> 
> 
> Andew Probert
> Rotek Consulting   http://www.rotek.com.au
> a Division of Secure Network Solutions
> Tel  +61 3 9690 8877
> Fax +61 3 9690 8171
> 
> 
> 
	snip