Transcript Next Generation Power Over Ethernet

Universal Power Over Ethernet
- World’s First Power-Extended Network
Rev 6
UABU Engineering
12/1/2010
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• Power over Ethernet basics
• Universal Power Over Ethernet (UPOE)
• LLDP based UPOE
• Forced 4-pair UPOE
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Power Over Ethernet Basics
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GLOSSARY:
PoE – Power Over Ethernet
DTE – Data Terminal Equipment
PSE – Power Sourcing Equipment (eg: CAt4K Switch)
PD – Powered Devices (end device receiving power)
LLDP – Link Layer Discovery Protocol (Layer 2 protocol)
ALT-A : IEEE Terminology for Signal pair – (1,2) & (3,6) on a RJ45
pinout
ALT-B : IEEE Terminology for Spare pair – (4,5) & (7,8) on a RJ45
pinout
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Power over Ethernet
(PoE) Delivers DC
Power and data over a
Standard Copper
Ethernet Cable(RJ45)
Power Sourcing
Equipment
PSE
Ethernet
Cable
Powered
Device
IP-Phone
PD
Source: Fred Schindler, PoE Nerd lunch presentation
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• PoE/PoE+ is intended for DTE powering – to provide a 10Base-T, 100Base-T or 1000Base-T
device with a single interface to both data it requires and power to process this data.
• PoE : IEEE 802.3af – Delivery of upto 15W of power over ALT A pairs of RJ45
• PoE+ : IEEE 802.3at –Delivery of upto 30W of power over ALT A pairs of RJ45
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• Figure 1 below shows the normal Data transmission between two PHY silicon.
• Figure 2 depicts how power is inserted along with data on ALT-A or ALT-B pairs to provide DTE
powering. A power source introduces a port voltage “V” through the center tap of the Ethernet
transformer. The end device in need of power, connects its load to the center tap of the Ethernet
transformer to draw power from the source voltage “V”. This power does not affect the data since
it is fed as a common-mode voltage.
Fig 1.Ethernet Data Transmission over RJ45
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Fig 2. Overlaying Power with Data
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• Power is coupled from PSE to PD through a
center tap transformer configuration
• Power is extracted on the PD side from center
• The diode bridge is to ensure PD is polarity
PD
chip
tap again and fed to a diode bridge
50-57V
insensitive (see next slide).
• The diode bridge in turn feeds a PD chip which
takes care of implementing the PD features.
• This configuration can provide upto 30W
• To double the power, the unused ALT B pairs
(shown in the picture) are put to use as well.
Simply by duplicating the circuitry shown on
unused pairs upto 60W can be drawn.
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Source: Fred Schindler, PoE Nerd lunch presentation
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AC
+
+
+
AC
+
Source: Fred Schindler, PoE Nerd lunch presentation
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• Detection—is this a true PD device?
• Physical Layer Classification—how much power is required? (PoE - Type I)
• Power-on—provide the requested power (upto 12.95W is available at the PD).
• Data Link Layer Classification (LLDP) —refine the required power(more than
15.4W request and upto 30W – Poe+ - Type II).
Source: Fred Schindler, PoE Nerd lunch presentation
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DETECTION:
• Send Detection voltage pulse, measure
current, Calculate Rdet = (V1-V2)/(I1-I2)
Vport
Detection
Classification
Power-On
• Valid Detection Signature? – Yes
(IEEE802.3af/at define the valid and invalid
ranges)
CLASSIFICATION:
• Send Classification Voltage pulse, measure
current (Physical layer classification)
• Valid Classification signature? – Yes
(IEEE802.3af/at define the valid and invalid
ranges)
Time
POWER ON:
• Turn on power
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•
•
•
•
IEEE 802.3at defines all the parameters related to power on, power monitoring and related timing etc for PoE/PoE+
This is to ensure safety and proper operation for a PoE powered network
The table below shows some key parameters. Ie Inrush control and Power on time
Refer to IEEE802.3at for a detailed list and explanation
Parameter
Unit
Power turn on time
ms
Inrush current(startup
mode)
mA
400
450
Inrush time
ms
50
75
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Min
max
400
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Upper limit due to:
- component limits
- safety
Short Circuit limit
-PSE protection
PD Surge Allowance (~15%)
Lower limit:
- supports the
maximum average
PD demand
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• DC Disconnect
- Decided based on maintain power signature
-If PD current draw is in the range of Imin for greater than TMPDO
-After power removal – PSE goes back to start of state machine (detection state)
Parameter
Symbol
Unit
Min
Max
IDLE state current
Imin
mA
0
5
PD maintain power
signature dropout time
Tmpdo
ms
300
400
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Universal Power Over Ethernet
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PDChip
• Replicate the same ALT-A HW circuitry on the unused
50-57V
ALT B pairs
• Upto 60W delivery using all the 4-pairs on cat5e
• Even under worst case (100m cable) 51W available at
PD
PDChip
• Cisco’s proprietary UPOE defines two power up
mechanisms
 LLDP based (preferred)
 Forced 4-pair
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50-57V
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LLDP based UPOE
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• LLDP – Link Layer Discovery Protocol
LLDP is a layer 2 protocol in Networking. It is vendor-neutral and used for advertising identity, capabilities
and neighbours on a LAN
LLDP uses Type, Length and Value fields(TLV) to convey the information
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• IEEE 802.3at already defines LLDP for power negotiation greater than 15.4W and
upto 30W. UPOE uses the same negotiation method to provide upto 60W contingent
on a successful 4-pair handshake. IEEE802.3at LLDP format is shown below.
• “4-wire Power Via MDI” - is the new subtype for Cisco specific OUI TLV. It is present
in all modes of operation and is used to exchange 4-pair capabilities before enabling
4pair and providing upto 60W.
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TLV type
TLV information
String Length
7 bits
9bits
TLV type-127(organisation specific)
Information string length = 5 (bytes)
Cisco OUI Identifier = 00-01-42
Cisco OUI subtype = 1
Bit
Cisco OUI
Identifier
3 octets
Cisco OUI
subtype
PSE/PD
capabilities
1 octet
Function
Value/Meaning
0
UPOE supported
0=No
1=Yes
1
ALT-B pair
Detection/Classification
Required
0=No
1=Yes
2
PD ALT-B pair desired state
0=No
1=Yes
3
PSE ALT-B pair operational
state
0=Disabled
1=Enabled
4:7
Reserved
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1 octet
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NOTE: This is an example for
independent PD architecture –
Actual handshake will depend
on the PD architecture
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Forced 4-pair UPOE
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• To support already deployed devices which don’t have LLDP capabilities
• Physical layer signature is a must on both ALT-A and ALT-B pairs. This is used in lieu of
LLDP to detect UPOE end device.
• Least Preferred – Doesn’t support the advantages that come with LLDP.
• For instance, In LLDP if a UPOE port drops down in power consumption this extra power can now be
returned to general pool for use by other ports. Forced 4-pair implementation doesn’t support this –
power allocation to a forced 4-pair port is static at 60W
• By Default UPOE switch uses LLDP – to turn on forced 4-pair a CLI command is
provided => “power inline four-pair forced”
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1
2
3
4
5
6
7
8
Diode
Bridge
Vout
Input
50-57V
PD chip(s)
DC-DC
Vout_rtn
RJ45
Diode
Bridge
Data Path
Power Path
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• For Utilizing UPOE the end device should have the following
 A IEEE802.3at compliant Powered Device (PD) circuit
(ALT-A and ALT-B pairs could combine before and feed into a single PD chip if LLDP capabilities are
present; However if forced UPOE is needed then a compliant PD chip would be needed on both ALT-A and
ALT-B pairs)
 LLDP implementation of Cisco 4-pair power via MDI TLV
 LLDP TLV for power negotiation
• NOTE: In absence of LLDP forced 4-pair can be utilized but this method is not the
preferred method of implemention. If LLDP implementation is possible the end device is
advised to take that route.
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Thank you.
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