Subject: Re: [eman] Terminology: power states - battery state - power supplystate

From: "John Parello (jparello)" <[email-masked]>
Date: Thu, 15 Sep 2011 13:49:35 -0700

Hi,

For states I put the terms Power State and Power Series to reflect what
we discussed at the last two meetings.

I don't see a distinction between the state as they refer to a battery
or a simple device. As we discussed at IETF81 (I think Juergen S brought
it up) why not keep the same information for the battery.

I kept it simple in the definition and if there's new terms from this
thread please do let me know.

Jp

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Juergen Quittek
Sent: Saturday, August 13, 2011 5:32 PM
To: eman mailing list
Subject: [eman] Terminology: power states - battery state - power
supplystate

Dear all,

Here are some thoughts on what a power state is and how it relates to
the battery state and the power supply state of a device.

So far, there is no document where we clearly define what a power state
is and what it is not. Please find a list of definitions that I
collected from other documents further below.  This email mainly serves
for sharing some thoughts on this issue in order to jointly work on a
more clear definition of a power state.

My main question is: What is characteristic for a power state?
1. the operational state (Is the device not/fully/partially
operational)?
2. the power consumption in a power state? (min/max/average
power/demand)?
3. the power supply state (running on mains/battery/self-generated
power)?
4. the total power balance (consuming/providing power)?

As we have discussed it in the eman WG and as other standards bodies
including DMTF, ACPI, PWG see it, it is just 1. with some implications
on 2. Here is another try on a definition of a power state:

   "A power state represents one or multiple operational states of a
device.
   A power state indicates specific properties of a device concerning
its the energy 
   consumption when being in this state."

Of course this one cries for definitions of an operational state.

Operational state:
   "An operational state defines the availability of services provided
by a device."

We certainly need some more text elaborating on power states beyond the
plain definition, maybe in the framework document.  There is one note
that I would definitely like to add there:

   "Energy consumption of a device is not the only state to be
considered 
   when managing the power supply of a device. If the device contains
batteries
   or facilities for energy harvesting/generation, also the battery
charging state 
   and the power supply state of a device need to be considered. For
example,
   a device in a non-operational state such as "off" or "sleep" may
still draw 
   a considerable power for charging its batteries. Or it may be in
state "on" and 
   not draw any mains power at all, because it runs on battery or
supplies itself
   with a built-in generator."

This leads us to the definition of battery state and power supply state:

Battery state:
The battery state indicates the flow of energy into or out of a battery.

Power supply state:
The power supply state indicates which power supply is in use at a
device.
Examples are: mains power, secondary mains power, battery, built-in
generator

We definitely need the battery state for the battery MIB (see object
batteryChargingState in draft-ietf-eman-battery-mib-03). I think we also
need something like the power supply state. But my ideas on it are much
less clear than on the battery state that we have been discussing for
some months already.

Here are the definitions of power state that we have tried so far:

1. draft-ietf-eman-framework-02 and draft-parello-eman-definitions-0
   A Power State is a way to classify a Power setting on an Energy 
   Managed Object (e.g., on, off, or sleep).  A Power State can be 
   viewed as a method for Energy Control 

Comments: 
  - Yes, a power state may be used to classify power setting.
     But this is a way to use it, not a way define it. 
  - No, a power state is definitely not a method.

2. draft-ietf-eman-requirements-03
   Power state of an entity is defined as a specific settings of an
   entity that influences its power.  Examples of power states of an
   entity are on, off, hibernate, and sleep.

Comment: 
  - This is correct, but it neglects the relationship to operational
states

3. draft-quittek-power-mib-02
   A power state defines a limitations of services provided by a device
   and implicitly limits energy consumption.  Examples for commonly
   implemented power states include 'on', 'full power', 'low power',
   'sleep', 'stand-by', and 'off'.  There is no commonly agreed
   convention for power states naming and semantics.  Therefore power
   states with the same names may have different semantics and different
   names may be in use for the same power state.
   But the actual energy consumption of a device depends on more than
   just its power state.  Also the current load, the kind of load, and
   many other factors influence energy consumption.

Comments: 
  - first line is OK. It explains a power state as an operational state
     without using the term "operational state" (which might be
desirable).
  - second line does not seem to be correct. A power state may have 
    power limitations. But this is not a necessary property of it.
  - rest seems correct, but examples are not a definition and the
following
    text does not belong into the definition.

4. draft-ietf-eman-energy-monitoring-mib-00   
   A Power State is defined as a specific power setting for a 
   Power Monitor (e.g., shut, hibernate, sleep, high). Within the 
   context of a Power State  Set, the Power State of a device is 
   one of the power saving modes in that Power State Set. 

Comments: 
  - First sentence correct, but it neglects the relationship to
operational states
  - The second sentence does not belong to the definition.
  - Second sentence explains power state as power saving mode.
     What is a power saving mode? Is "full power" a power saving mode?

Thanks,

    Juergen
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