Enterasys S-Series S8 Chassis Hardware Installation Guide B-1
B
About PoE (Power over Ethernet)
This
appendix
provides
an
overview
of
Power
over
Ethernet
technology
and
how
it
is
implemented
in
relation
to
the
S
‐
Series
devices.
Overview
Power
over
Ethernet
(PoE)
refers
to
the
ability
to
provide
operational
power
through
the
same
Ethernet
cabling
to
a
PD
(powered
device)
connected
to
a
data
network.
Modern
Ethernet
implementations
employ
differential
signals
over
twisted
pair
cables.
This
requires
a
minimum
of
two
twisted
pairs
for
a
single
physical
link.
Both
ends
of
the
cable
are
isolated
with
transformers
blocking
any
DC
or
common
mode
voltage
on
the
signal
pair.
PoE
exploits
this
fact
by
using
two
twisted
pairs
as
the
two
conductors
to
supply
a
direct
current.
One
pair
carries
the
power
supply
current
and
the
other
pair
provides
a
path
for
the
return
current.
While
several
proprietary
legacy
implementations
of
PoE
have
been
deployed
by
LAN
equipment
vendors,
in
2003
the
IEEE
published
the
IEEE
802.3af
‐
2003
specification,
which
is
part
of
the
802.3
suite
of
standards.
The
S
‐
Series
chassis
that
support
PoE
are
fully
compliant
with
the
IEEE
802.3af
and
802.3at
standards.
They
support
the
standard
resistor
‐
based
detection
method,
as
well
as
AC
disconnect
capability.
Each
PD
has
a
PDC
(Powered
Device
Classification)
that
is
transmitted
to
the
S
‐
Series
chassis
for
power
management
purposes.
lists
the
classifications
and
the
associated
power
ranges
based
on
the
802.3af
standard.
This
table
will
be
updated
with
802.3at
class
information
when
the
802.3at
draft
is
ratified.
Proprietary PD Detection
S
‐
Series
devices
support
a
subset
of
the
currently
deployed
proprietary
PoE
methods.
This
includes
support
for
Cisco
PDs,
including
a
proprietary
capacitor
based
detection
scheme.
Table B-1 Powered Device Classifications
Class
Usage
PD Maximum Power Range Usage
0
Default
0.44 to 12.95 Watts
1
Optional
0.44 to 3.84 Watts
2
Optional
3.84 to 6.49 Watts
3
Optional
6.49 to 12.95 Watts
4
Not Allowed
Reserved for Future Use
Summary of Contents for S4-Chassis
Page 2: ......
Page 12: ...x...
Page 16: ...xiv...
Page 20: ...Getting Help xviii About This Guide...
Page 28: ...Features 1 8 Introduction...
Page 62: ...Completing the Installation 3 32 Chassis Setup...
