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Fat AP and Cloud AP V200R008C00 CLI-based Configuration Guide

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Principles

Principles

Introduction to PoE

PoE involves the following devices:
  • Power-sourcing equipment (PSE): The PSE provides power for powered devices (PDs) on the Ethernet, and supports detection, analysis, and intelligent power management.
  • PD: PDs are provided with power, such as wireless APs, portable device chargers, POS machines, and cameras. According to whether a PD conforms to an IEEE standard, PDs are classified into standard and non-standard PDs.
  • PoE power supply: The PoE power supply provides power for the PoE system. The number of PDs connected to the PSE is limited by power of the PoE power supply. According to whether a PoE power supply is swappable, PoE power supplies are classified into built-in and external power supplies.

Working Process of PoE Power Supply

Table 5-20  PoE working process
Procedure Item Description
1 PD detection The PSE provides a low voltage on a port to detect PDs. If specified resistance is detected, PDs that support IEEE 802.3af or IEEE 802.3at on the cable and are connected to the terminal of the cable. The resistance is 19 kΩ to 26.5 kΩ. The voltage is 2.7 V to 10.1 V. The detection period is 2 seconds.
2 Power supply capability negotiation The PSE classifies PDs and supports power supply capability negotiation. Power supply capability negotiation is classified into two modes: analysis of detected resistance and LLDP Power Capability Negotiation.
3 Power-on starting In a period shorter than 15 μs, the PSE provides low voltage for PDs, and then the voltage is increased to 48 V.
4 Power-on The PSE provides 48 V DC power supply for PDs and the power consumption of the PDs is smaller than 37 W.
5 Power-off During the power supply process, the PSE detects the input current of the PD continuously. The PSE cuts off the power supply and repeats detection when the current of the PD is reduced to the minimum value or increased sharply in any of the following situations:
  • The PD is removed.
  • The power consumption of the PD is overloaded or short-circuited.
  • The power consumption of the PD exceeds the power supply load.

PoE Power Management Mode

When PDs connected to the PSE increase, the PoE power supply cannot provide power for all PDs. Therefore, the PSE should manage the power supply. Power management is classified into two modes: automatic and manual.

  • Automatic mode: The PSE automatically powers on or powers off PDs based on power priorities. You can configure a power priority of each port as Critical, High, or Low based on the importance of the PD connected to each port. When providing power nearly at full capacity, the PSE provides power first for the PD connected to the port of Critical priority and then provides power for the PD connected to the port of High priority. If multiple PoE ports have the same priority, the system first supply power to the PDs connected to the ports with smaller port numbers.

  • Manual mode: You can manually power on or power off ports. In manual mode, the PSE provides power for a port without considering the priority. Powering on or powering off a single port does not affect the power supply status. When providing power nearly at full capacity, the PSE cannot continue to power on a new PD.

Power Supply Mode of PSEs

As defined in IEEE standard, PSEs provide power for PDs and are classified into MidSpan (the PoE module is installed out of the device) and Endpoint (the PoE module is integrated to device) PSEs. Huawei's PoE modules are Endpoint PSEs. The Endpoint PSE is compatible with 2.5GE Base-T, 1000Base-T, 100Base-TX, and 10Base-T ports. The Endpoint PSE is more widely used than the Midspan PSE.

Endpoint PSEs can work in Alternative A (line pair 1/2 and line pair 3/6) and Alternative B (Line pair 4/5 and line pair 7/8) power supply modes according to different copper line pairs.
  • Alternative A mode: Power is transmitted over pairs of lines that transmit data.

    The PSE provides power for the PD over copper line pairs connected to pins 1 and 2 and pins 3 and 6. Pins 1 and 2 use the positive voltage and pins 3 and 6 use the negative voltage.

    10Base-T and 100Base-TX ports use copper line pairs connected to pins 1 and 2 and pins 3 and 6 to transmit data, and 1000Base-T ports use four line pairs to transmit data. DC power and data frequency are independent. Therefore, the power and data can be transmitted in one pair of lines.

  • Alternative B mode: Power is transmitted over idle pairs of lines.

    The PSE provides power for the PD over copper line pairs connected to pins 4 and 5 and pins 7 and 8. Pins 4 and 5 use the positive voltage and pins 7 and 8 use the negative voltage.

Generally, a standard PD supports the two modes, whereas the PSE only needs to support one mode. Huawei PSE supports only Alternative A.

LLDP Power Capability Negotiation

Originally, a device analyzes the current that is transmitted between the PSE and PD to classify PDs. Besides current analysis, the device supports Link Layer Discovery Protocol (LLDP) power capability negotiation. IEEE 802.1ab defines the optional TLV: Power via MDI TLV. The Power via MDI TLV is encapsulated in LLDP packets, and is used for discovery and advertisement of MDI power capabilities, and network management.

When the PSE detects a PD, the PSE and PD periodically send LLDP packets with the defined TLV to each other. The peer end records the information in LLDPDIs for information exchange.

The Power via MDI TLV is composed of 2-byte packet header and 12-byte TLV information field, as shown in Figure 5-20.

Figure 5-20  TLV packet

The fields of TLV packets are described as follows:

  • MDI power support

    Bit

    Function

    Description

    0

    Port type.

    1: PSE-side port

    0: PD-side port

    1

    Whether the PSE supports MDI power supply.

    1: indicates that the PSE supports MDI power supply.

    0: indicates that the PSE does not support MDI power supply.

    2

    MDI power support status of the PSE.

    1: enabled

    0: disabled

    3

    Whether the PSE can control the line pair.

    1: indicates that the PSE can control the line pair.

    0: indicates that the PSE cannot control the line pair.

    4-7

    Reserved.

    -

  • PSE power pair:
    • 1: Alternative A: The Endpoint PSE use line pairs connected to pins 1 and 2 and pins 3 and 6 for power supply.
    • 2: Alternative A: The Endpoint PSE use line pairs connected to pins 4 and 5 and pins 7 and 8 for power supply.
  • power class

    Class

    Current (Unit: mA)

    Reference Power (Unit: W)

    Description

    0

    0 to 4

    15.4

    The default class is used when no class can be specified for a PD.

    1

    9 to 12

    4

    Very low power

    2

    17 to 20

    7

    Low power

    3

    26 to 30

    15.4

    Medium power

    4

    36 to 44

    30

    High power, which is supported by 802.3at
  • Type/source/priority

    Field

    Functions

    Description

    Power Priority

    Power supply priority of a port.

    11: indicates the lowest priority.

    10: indicates the secondary highest priority.

    01: indicates the highest priority.

    NOTE:

    This field contains four bits. The two left-most bits are reserved for the system.

    Power Source

    Power supply source.

    PD:
    • 11: indicates the PSE and local source.
    • 10: reserved.
    • 01: indicates the PSE.
    PSE:
    • 11: reserved.
    • 10: indicates the backup power supply.
    • 01: indicates the primary power supply.

    Power Type

    Power supply type.

    11: indicates the PD that does not support IEEE 802.3at.

    10: indicates the PSE that does not support IEEE 802.3at.

    01: indicates the PD that supports IEEE 802.3at.

    00: indicates the PSE that supports IEEE 802.3at.

  • Power value: contains PD requested power value and PSE allocated power value. When the PoE power is sufficient, the two values are the same. The value is an integer that ranges from 1 to 255. Exchange power = 0.1 x Hexadecimal value of the field. For example, if the value of the field is 255, the exchange power is 25.5 W.

PoE Technical Specifications

PoE technical specifications vary depending on PoE technologies. You can select the required PoE technology to power on PDs according to PD requirements.

Table 5-21  PoE technical specifications

Power supply technology

PoE

PoE+

PoE++

Power supply distance

100 m

100 m

100 m

Power class

0-3

0-4

0-8

Maximum current

350 mA

600 mA

1730 mA

PSE output voltage

44 V DC-57 V DC

50 V DC-57 V DC

50 V DC-57 V DC

PSE output power

≤ 15400 mW

≤ 30000 mW

≤ 90000 mW

PD input voltage

36 V DC-57 V DC

42.5 V DC-57 V DC

42.5 V DC-57 V DC

Maximum PD power

12950 mW

25500 mW

81600 mW

Cable requirements

Unstructured

CAT-5e or better

CAT-5e or better

Power supply cable pairs

2

2

4

  • PoE technology complies with IEEE 802.3af.
  • PoE+ technology complies with IEEE 802.3at.
  • PoE++ technology complies with IEEE 802.3bt.
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Updated: 2019-01-11

Document ID: EDOC1000176006

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