Re: Suggested Objectives, DTE Pwr via MDI Study Group from TIA TR-41.3.4
To: Phil Holland, Chair, TR-41.3.4
From: Geoff Thompson, WG Chair, Steve Carlson SG Chair, IEEE 802.3 DTE
Power via MDI SG
Thank you for your letter which was received during the course of our
meeting and for the time that you took during your meeting to consider our
work. The Study Group took a careful look at your input. The results of
that consideration are mixed in with your text below as appropriate
At 12:01 AM 11/9/99 -0800, Phil Holland wrote:
>As agreed during the meeting in York, the DTE Power Via MDI Study Group's
>five Criteria and proposed Objectives were presented at our meeting on the
>eighth of November. In attendance were 35 Telecommunications Industry
>Association members representing a wide cross section of the telecom
>industry. All present expressed support for the project that Study Group
>has proposed and will provide input where applicable.
>Due to and intense interest in the Study Group's objectives, about half of
>the one day meeting was devoted to their discussion and review. This
>resulted in the three suggestions that are attached. We hope that they can
>be considered and included in the final objectives of the Study Group.
> Phil Holland
>Suggestions from TR-41.3.4: Performance and Interoperability Requirements
>for Voice-over-IP Telephone Terminals
>A. Common Powering for 10/100/1000BASE T Networks
>The TR-41.3.4 working group supports and would like to have additional
>emphasis placed on the DTE Power via the MDI Study Groups first two
>objectives. To clarify the emphasis that the working group felt should be
>placed on the first objective, the following revised wording was suggested.
> 1. Economically provide power to 10BASE- T and 100BASE- TX
>devices, and not preclude powering 1000BASE-T devices.
> 2. Select one power distribution technique for world-wide use
>Today, 10/100BASE-TX networks are common. These will move to 100/1000BASE-T
>in the near future. A power methodology that supports 10/100/1000BASE-T
>networks is therefore HIGHLY DESIRABLE. For this reason, any powering
>methodology selected must not preclude 1000BASE-T products in the future.
>We recognize the 1000BASE-T networks could be difficult to support. While
>it may not be possible to include 1000BASE-T in the initial version of an
>IEEE 802.3 DTE Power via the MDI, future technologies may make this possible
>as long as the wiring scheme does not preclude it. Leaving this option open
The group chose not to change the current wording of the objective. This
was done with considerable discussion and, in particular, after
presentations from magnetics vendors on the impact on the magnetics of
providing power over signal pairs. It was felt that to go any further would
have a much larger negative impact on the incremental cost than the
positive impact would be from adding 1000BASE-T. There was also discussion
that a future system for 1000BASE-T could probably be implemented that
would go through a 2 step operation. This was felt to be acceptable in the
face of the already considerable constraints to the solution space as all
1000BASE-T PHYs in development are expected to support multiple speeds. The
magnetics people have indicated that 300mA is the effective limit for
current through the transformers. Given their power consumption, the
present 1000BASE-T PHYs could not be powered, much less the rest of a system.
We firmly agree that our standard should apply uniformly and equally on a
>B. Powering of Intermediate Devices
>An additional objective should be to recognize that intermediate devices may
>need to be powered via the MDI and in turn pass power on to an endpoint.
>These intermediate devices will be required to facilitate the economic mass
>deployment of VoIP telephones.
>For example, consider a small router placed in an office to connect a VoIP
>Telephone, a PC and other devices that require powered or un-powered
>connections. Passing power through such devices is important to provide an
>economic means of supplying backup power. Telephones and their related
>network infrastructure must remain operational during a power failure.
The scope for our group as chartered from 802.3 is to develop power for a
DTE from the cabling infrastructure or a sublayer below the PHY at a
far-end device. To do this we must set limits on the power to be supplied
and consumed. To supply standardized power beyond a single device would be
to take on an open-ended problem. The result would be a significantly
longer development time and a significantly lower quality solution. The
group declined to make this part of the effort. I feel personally confident
that there will be implementations that will provide this capability to
>C. Safety Standards
>Any powering methodology defined by the Study Group should be compatible
>with existing, internationally recognized safety standards.
The DTE Power SG is in complete agreement with this objective and would
request that TR41.3.4 provide with information and specifics on any safety
standards they believe to be relevant.
We hope that you had a productive meeting in Sparks as we did in Kauai. It
is our understanding that your next meeting is on Maui sometime in
February. We would appreciate schedule and venue details as quickly as
Geoff Thompson, Chair, IEEE 802.3
Steve Carlson, Chair, DTE Power via MDI Study Group
Steven B. Carlson
Co-Chair, ESTA Control Protocols Working Group
Chair, ESTA ACN Task Group
Chair, IEEE 802.3 DTE Power via MDI Study Group
High Speed Design, Inc.
11929 NW Old Quarry Road
Portland, OR 97229
| Geoffrey O. Thompson |
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