Re: Discovery process
Here are my personal opinions:
First of all, I think that I mostly agree with you, Gérard.
The DTE power should be sent over the UTP cable based solely on the presence of proper identification and verification that the wiring is proper, i.e. a proper and successful discovery process. The discovery process should be independent of whether the end device is already powered. This would allow for the use of redundant power sources, as you mentioned, and make the particular sequencing of local vs. DTE power unimportant.
Also, DTE power should be applied without the need for any network management, for example in the case of a low end switch or hub. Network management would, of course, be an add on for larger systems that require power management and provisioning.
Here is the control sequence that I favor:
1) DTE power is not on
2) the discovery process keeps repeating until successful, then:
3) DTE power is turned on
4) a small minimum load is maintained at the terminal (load) end
5) if the load current falls below the minimum load, the DTE power is turned off
return to step 1.
As far as the discovery process goes, we need to select one that is robust, low cost, and easy to implement.
- Rick
At 11:10 AM 04/19/2000 +0200, you wrote:
>
>Hi guys,
>
>I am thinking about the different proposals done, concerning
>the discovery process, that in case where the terminal is
>locally powered then the power via MDI is not sent.
>Unfortunately, this case will be unavoidable since very often
>the terminal is installed by the end user who is not awared
>about the properties of the network infrastructure.
>Moreover the network is able to provide a safe power
>distribution (power with battery-back-up) and therefore
>it will be better to provide such a power to any terminals.
>
>What are you thinking about this problem?
>
>Our solution is to analyse the impedance under alternative
>voltage and this analyse stays efficient even the terminal
>is locally powered and therefore this allows providing a
>safe power to terminal whatever its state and in case of mains
>breaking holding the current communication with this terminal.
>
>Gérard
>
>
>