|Thread Links||Date Links|
|Thread Prev||Thread Next||Thread Index||Date Prev||Date Next||Date Index|
On 6/5/09 2:40 AM, Unterdorfer, Pascal wrote:
That would be because it is a requirement of 802.3af that you do not turn power on until the PSE positively identifies (Discovery and Classification) that the device at the other end of the link segment has the probe signature response that is unique to an 802.3 PD.Hello Everybody, I have a question about the PSE Interface, Detection and Safety! In the actual IEEE 802.3af standard, 33.2.9 Power supply allocation, the behaviour of connecting a PSE PI with another PSE PI is not explained.
If you are worried about a cabling topology where a UTP cable is daisy-chained to multiple (i.e. more than two) interfaces then you are out of scope for 802.3 as well as most other applications for Category 5/6/7 cabling. If that is the case, then you are on your own and we can't help you. Note that it talks about a "link." A "link" is a single point-to-pont connection.
No. In the text above a "system" refers only to what is within the scope of 802.3, specifically the 802.3 (and not the higher layer aspects of the same devices) portions that are hooked to a single point-to-point link. For that reason that any connection "in a line" or "in a ring" of Ethernet interfaced devices has to resolve all issues of how to hook multiple Ethernet point-to-point link segments together within whatever higher layer device is used to hook together the multiple Ethernet interfaces. An 802.1D Bridge is the usual device for doing this and allows devices to be hooked in a line quite nicely. If you try to hook 802.1D devices in a ring then it will undo one of the segments in the ring as the topology violates the Spanning Tree protocol.See:33.2.9 Power supply allocation
Neither PSE will try to supply powerWhat happens if I connect two PSE PI's together?
Hopefully, this answers your question.Can anybody help me with this question?
Manny thanks! With best regards, mit freundlichen Grüssen Pascal Unterdorfer Product Manager Industrial Networking Hirschmann Automation and Control GmbH Stuttgarter Str. 45-51 D-72654 Neckartenzlingen * +49 7127 14-1120 v +49 172 9446954 * *+49 7127 14-1561 * Pascal.Unterdorfer@xxxxxxxxxxxxx * http://www.hirschmann.de