Switch Priority Class; Line Loss - HP ProCurve zl Series Planning And Implementation Manual

Switch Priority Class

Port priority classification can be used by the switch to allocate power to
ports. It is a prioritization scheme by which the user can assign a low (default),
high, or critical priority to any given port. This assignment is done through
the command line interface (see the Management and Configuration Guide
which is on the ProCurve Web site,
the switch and alters the hardware port-number priority for power allocation.
■ Low (default) - This priority class receives power only if all other priority
classes are receiving power. If there is enough power to provision PDs on
only some of the ports with a low priority, then power is allocated to the
ports in ascending order, beginning with the lowest-numbered port in the
class until all available power is in use.
■ High - This priority class receives power only if all PDs on ports assigned
with a critical priority are receiving full power. If there is not enough
power to provision PDs on ports assigned with a high priority, then no
power goes to the low priority ports. If there is enough power to provision
PDs on only some of the high priority ports, then power is allocated to the
high priority ports in ascending order, beginning with lowest-numbered
high priority port, until all available power is in use.
■ Critical - This priority class is the first to be allocated power. If there is
not enough power to provision PDs on all of the ports configured for this
class, then no power goes to "High or Low" priority ports. If there is
enough power to provision PDs on only some of the critical ports, then
power is allocated to the critical ports in ascending order, beginning with
the lowest-numbered port in the class.

Line Loss

A certain amount of power is consumed by the resistance of the wire in the
LAN cable connected from the switch to the powered device (typically less
than 16% loss), which can be influenced by cable length, quality, and other
factors. The IEEE 802.3af specification has addressed loss of power by
providing more power than a powered device requires. As well, depending
upon the classification (Class 0-3) of the device, the switch will provide more
or less power to address the specific power needs of that end device.
Provisioning Power for PoE
(See
www.procurve.com
Operating Rules
page 1-4.)), of
2-5