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Huawei Sx700 Series Switches
UPOE+ Technology White Paper
Issue
01
Date
2016-02-27
HUAWEI TECHNOLOGIES CO., LTD.
Copyright © Huawei Technologies Co., Ltd. 2016. All rights reserved.
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Huawei Technologies Co., Ltd.
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Contents
Contents
1 Overview......................................................................................................................................... 1
2 Implementation ............................................................................................................................. 3
2.1 PoE Power Supply Modes ............................................................................................................................................ 3
2.2 PD Power-on Process.................................................................................................................................................... 6
2.3 Product Capability ........................................................................................................................................................ 7
3 Typical Networking ...................................................................................................................... 8
A Abbreviations ............................................................................................................................... 9
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1 Overview
1
Overview
Power over Ethernet (PoE) is a technology that provides power on the 10BASE-T,
100BASE-TX, 1000BASE-T, 2.5GBASE-T, or 10GBASE-T Ethernet at a distance of up to
100 m. It can be used to effectively provide centralized power for terminals such as IP phones,
WLAN Access Points (APs), chargers of portable devices, POS machines, cameras, and data
collection devices. This eliminates the need for separate cabling for power supply and powers
on these devices when they connect to the network.
A PoE system consists of power sourcing equipment (PSE) and powered devices (PDs). A
PSE provides power, and a PD receives power from a PSE. As shown in Figure 1-1, the PoE
switch functions as a PSE, and terminals such as IP phones, WLAN APs, and cameras are
PDs.
Figure 1-1 Diagram of a PoE system
PoE Switch
PSE
PD
IP phone
WLAN AP
IP camera
PC
TV
PoE technology facilitates installation and management, and ensures security and stability. It
is widely used in scenarios such as home applications, WLAN construction, security
protection, retail, and entertainment.
The PoE function complying with IEEE 802.3af provides a maximum of 15.4 W power. The
PoE+ function complying with IEEE 802.3at provides a maximum of 30 W power. Emerging
service types and new terminals require higher input power. To meet this requirement, Huawei
developed the next-generation Universal Power Over Ethernet Plus (UPOE+) switch in
compliance with IEEE 802.3bt. The UPOE+ function provides up to 90 W output power,
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1 Overview
meeting more terminals' power requirements. The following table describes detailed
performance parameters of PoE, PoE+, and UPOE+ functions.
Category
PoE
PoE+
UPOE+
Standard
IEEE 802.3af
IEEE 802.3at
IEEE 802.3bt
(draft)
Power supply distance
100 m
100 m
100 m
Classification
0-3
0-4
0-4
Maximum current
350 mA
720 mA
960 mA
PSE output voltage
44-57 V DC
50-57 V DC
50-57 V DC
PSE output power
<=15.4 W
<=30 W
<=90 W
PD input voltage
36-57 V DC
42.5-57 V DC
42.5-57 V DC
Maximum power of PD
12.95 W
25.5 W
81.6 W
Cable requirement
Unstructured
CAT-5 or better
CAT-5 or better
Number of power line pairs
2
2
4
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2 Implementation
2
Implementation
2.1 PoE Power Supply Modes
A PoE power supply system consists of PSE and PDs. PoE standards define two methods of
transporting direct current (DC) power to PoE devices over Ethernet cables: midspan and
endpoint.

Midspan
The PoE module is installed outside a switch, and is deployed between a common switch
and network terminals. The PoE module provides power for the terminals over network
cables. A midspan PSE is a dedicated power management device and is usually deployed
together with the switch. Each port on a midspan PSE has two RJ45 jacks. One is
connected to the switch using a short cable, and the other is connected to a remote
device.

Endpoint
The PoE module is integrated into a switch, which saves dedicated cables and devices
deployed for independent power transmission.
Huawei switches support built-in PoE modules and are endpoint PSEs. The following
introduces the endpoint mode of power supply.
Standard category 5 or higher category cables have four twisted pairs. IEEE80 2.3af defines
the power interface (PI), which is used by PSEs and PDs to connect to network cables. PI
supports two power supply modes: Alternative A (line pairs 1/2 and 3/6) and Alternative B
(line pairs 4/5 and 7/8). PSE supports only one power supply mode. However, PDs must be
able to adapt to the two power supply modes simultaneously.
On 10BASE-T and 100BASE-T ports, two line pairs are used to transport data. That is, line
pairs 1/2 and 3/6 are signal cables, and line pairs 4/5 and 7/8 are idle cables. Huawei switches
support only the Alternative A mode. That is, these switches support only power supply over
signal cables. As shown in Figure 2-1, signal cables (line pairs 1/2 and 3/6) are used to
transport data and power simultaneously. When signal cables are used to supply power, DC
power supply can be connected to the midpoint of the transformer. Line pair 1/2 then connects
to the positive (or negative) polarity, and line pair 3/6 then connects to the negative (positive)
polarity. Data and DC power are transmitted over a single pair of lines. DC power and data
frequency are independent; therefore, the transmission of DC power does not affect data
transmission.
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Figure 2-1 Line pair connection on 10BASE-T/100BASE-TX ports
On 1000BASE-T and 10GBASE-T ports, all the four line pairs are used to transport data.
Both Alternative A and Alternative B modes transmit power on data transmission line pairs.
Huawei switches support only the Alternative A mode, in which signal line pairs 1/2 and 3/6
transmit both data and power, as shown in Figure 2-2.
Figure 2-2 Line pair connection on 1000BASE-T/10GBASE-T ports
In PoE and PoE+ modes, a PSE uses two line pairs to provide 15.4 W and 30 W output power,
respectively. In the UPOE+ mode, four line pairs on a single port are all used to transport PoE
power. The connections of line pairs 1/2 and 3/6 in the UPOE+ mode are the same as that in
PoE and PoE+ modes. Line pairs 4/5 and 7/8 are also used to transport power. Line pair 4/5
connects to the negative polarity, and line pair 7/8 connects to the positive polarity. Each two
line pairs (1/2 and 3/6, or 4/5 and 7/8) provide 45 W power. Therefore, a PSE can provide a
total of 90 W power.
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Figure 2-3 shows power line connections on 10BASE-T or 100BASE-T ports in the UPOE+
mode. Signal pairs 1/2 and 3/6 provide 45 W power, and idle pairs 4/5 and 7/8 also provide 45
W power. The PD receives power from these four line pairs.
Figure 2-3 Line pair connection on 10BASE-T/100BASE-TX ports
Figure 2-4 shows power line connections on1000BASE-T or 10GBASE-T ports in the
UPOE+ mode. Line pairs 1/2 and 3/6 provide 45 W power, and line pairs 4/5 and 7/8 also
provide 45 W power. The PD receives power from these four line pairs.
Figure 2-4 Line pair connection on 1000BASE-T/10GBASE-T ports
A 2.5G electrical port on Huawei UPOE+ switches supports UPOE+ and provides 90 W
output power. Line pairs 1/2 and 3/6 provide 45 W power, and line pairs 4/5 and 7/8 also
provide 45 W power. Figure 2-5 shows the output power of PoE/PoE+ and UPOE+.
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Figure 2-5 PoE/PoE+/UPOE+ power output diagram
2.2 PD Power-on Process
Figure 2-6 shows how a PD obtains power supply when connecting to a PSE system.
Figure 2-6 PD power-on process
Detection
Classification
Power-on
Operation
(PM/RTP)
Disconnection
The power-on process is divided into the following phases:
1.
Detection: The PSE checks whether a PD exists.
The PSE checks whether a PD is connected by transmitting a low voltage to detect the
capacitive resistance between power output line pairs. In detection phase, the output
voltage ranges from 2.8 V to 10 V, and the voltage direction is the same as -48 V voltage
output. The PSE proceeds to the next stage only when a PD is detected.
The following situations indicate presence of a PD:
2.
−
The DC resistance ranges from 19 kohm to 26.5 kohm.
−
The capacitance is less than or equal to 150 nF.
(Optional) Classification: The PSE determines the power consumption of the PD.
The PSE obtains the power level of the PD according to the output current. In
classification phase, the output voltage on a port ranges from 15.5 V to 20.5 V. The
voltage direction is the same as -48 V voltage output.
3.
Power-on: The PSE provides power for the PD.
When the downstream device connected to the port is a valid PD and the PD is classified
into a category (optional), the PSE delivers -48 V voltage to the PD.
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4.
RTP & PM (real-time performance, power management)
5.
Disconnection: The PSE detects whether the PD is disconnected.
The PSE detects whether the PD is disconnected. If the PD is disconnected, the PSE
shuts down the port to stop providing power. The port enters the detection state.
Figure 2-7 shows the ideal output voltage waveform for the PSE power supply system.
Figure 2-7 Waveform for PoE output voltage
2.3 Product Capability
The S5720-14X-PWH-SI-AC switch supports UPOE+. It provides the following ports:

Eight GE electrical ports. These ports support PoE+ and provide 30 W output power.

Four 2.5GE electrical ports, which can be used as 1000M/100M ports. These ports
support UPOE+ and provide 90 W output power.

Two 10GE SFP+ optical ports, which are used on uplinks.
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3 Typical Networking
3
Typical Networking
As shown in Figure 3-1, UPOE+ switches are deployed at the access layer to provide power
for various terminals. Since a UPOE+ switch provides 90 W output power per port, it allows
more types of high-power terminals.
Figure 3-1 Typical network deployment
DC
Egress router
Radius DHCP server
Firewall
CSS
S12700/S9700/S7700
Core layer
L3 routing
L2 switching
UPOE+ switch
S5720-14X-PWH-SI-A C
Access
layer
IP phone
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WLAN AP
IP camera
Printer
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A Abbreviations
A
Abbreviations
Full Name
PoE
Power over Ethernet
PoE+
Power over Ethernet Plus
UPOE+
Universal Power Over Ethernet Plus
PSE
Power Sourcing Equipment
PD
Powered Device
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Abbreviations
9