Avaya Power Over Ethernet Page 1 Practical Manual Download

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A Practical Guide to Power Over Ethernet
(PoE) by Avaya

Release

1.1 Avaya

Labs

ABSTRACT

This paper will discuss the highlights in the Power over Ethernet standard (IEEE 802.3af) and the earlier
pre-standard PoE implementations. Common implementation issues are also addressed to help you avoid
unpleasant surprises.

External posting:

www.avaya.com

Application Note

October 2006

COMPAS ID 122875

MJK

Summary of Contents for Power Over Ethernet

Page 1: ...lights in the Power over Ethernet standard IEEE 802 3af and the earlier pre standard PoE implementations Common implementation issues are also addressed to help you avoid unpleasant surprises External posting www avaya com Application Note October 2006 COMPAS ID 122875 MJK Copyright 2006 Avaya Inc All Rights Reserved 1 ...

Page 2: ... Inc All other trademarks are the property of their respective owners NOTICE While reasonable efforts were made to ensure the information in this document was complete and accurate at the time of printing Avaya can assume no responsibility for any errors Changes and corrections to the information contained in this document may be incorporated into future releases Comments or questions may be email...

Page 3: ... addressed to help you avoid unpleasant surprises The first part of this paper describes the basics of the IEEE 802 3af standard that was ratified in June 2003 The second part of this paper describes practical differences in Power over Ethernet PoE implementations of Avaya and Cisco equipment compared to the standard and to each other This paper is not intended to point out shortcomings of any oth...

Page 4: ...idence in Avaya s products knowing that Avaya led the IEEE standards committee with the ultimate solution for Powering devices over the Ethernet cable No one implements Power over Ethernet PoE better than Avaya Avaya can intelligently and dynamically apply the right amount of power to ANY vendor s products that are standards compliant Please see section 5 of this paper for details 2 Definitions Be...

Page 5: ...specifics on invalid and non compliant signatures Capacitance and inductance values are also measured when validating a PD to the IEEE 802 3af standard Table 1 Parameters for a valid PD power signature Valid PD Detection Ramp up Conditions Resistive Signature Range Initial Resistive load for a potential PD 23 75K Ω 26 25K Ω Required resistance during voltage ramp up 2 7V 10 1V 23 75K Ω 26 25K Ω In...

Page 6: ...signature measured in milli Amps The chart below describes the values that a PD presents to a current under a constant voltage The values returned to the PSE then classify that PD into an IEEE power class Table 3 Values used to assign PDs into IEEE 802 3af classes Classification Signature Conditions Values Current for Class 0 14 5V 20 5V 0 4 mA Current for Class 1 14 5V 20 5V 9 12 mA Current for C...

Page 7: ...ew if any PDs require more than 11 watts so the assumption of having to apply 15 4 watts rarely happens Static power allocation results in a brute force application that is wasteful and unintelligent It is easy to calculate and deliver power based on the top of the power class but it results in wasting or stranding power logically from the total power pool The practical results are 9 Incurring low...

Page 8: ...ower from a pool There is no logical pool to consider Each device is given the amount of power it requires The assumption that each port connected to a Class 3 device should be ready to provide 15 4 Watts at any time still doesn t make sense with IP telephones or any other standards compliant device Again very few if any devices operationally vary in power needs more than one Watt A phone taking 8...

Page 9: ...CDP a proprietary discovery protocol to discover Cisco IP telephones After discovering which Cisco phone type is connected to a switch port the exact amount of power for that phone is logically reserved from a total pool of power available If a non Cisco PD is attached to the same switch port the power class from the PD is read and the power limit at the top of the power class range is reserved fr...

Page 10: ...plies no unintelligent static allocation of power and no penalties when using any vendor s standards compliant PD Another benefit of dynamic power allocation is the small number of commands needed to configure and maintain the switch or Mid Span As you will see there are fewer commands and command options using Avaya PSE products All ports can be used on all of Avaya s PSE equipment even with the ...

Page 11: ...24 is an additional 24 button button module that is powered from its associated phone It is not recognized as a standalone PD but still draws power as listed in the table The addition of this module will NOT cause a class 2 phone to become a class 3 phone The Gig E adapter is a module that fits into all 96ss models except the 9610 and 9630G to allow Gigabit Ethernet data flow through the phone The...

Page 12: ...g power means detection has taken place and power is being supplied Searching means a non PoE capable device is attached and the switch keeps searching for a valid PD signature Off means powering that port has been administratively disabled using the set port powerinline command Fault means a problem has been detected and no power is supplied The power allocated class column will always display cl...

Page 13: ...not require or rely on an advertised class of power All ports have power enabled by default Commands are Enable or disable power to a port or group of ports Set port powerinline mod port enable disable Assign a priority in case over subscription requires shutting down port power Set port powerinline priority mod port priority Low Default setting standard priority for standard devices High higher p...

Page 14: ...e commands for one or both OS platforms just the most important commands to control PoE Fixed Switch Configuration Fixed switches like the Catalyst 3560 and 3750 have power sensing enabled on all ports by default This means all ports continually sense for a valid PD and if found will provide power based on class for non Cisco PDs The show power inline command will display the total amount of power...

Page 15: ... in global configuration mode for the entire switch or individual values for each interface port A global setting of 6 watts for every port would be Switch config power inline consumption default 6000 An individual port setting for port 2 at 11 watts would be Switch config interface gigabitethernet 1 0 2 Switch config if power inline consumption default 11000 This command is extremely useful if yo...

Page 16: ...f an existing PoE switch Show system to verify the number of power supplies and their status Show environment power or show power to verify consumed power and reserve power Show module to verify the line model and daughter card sub model Show port inline power to verify power used and allocated per port on a blade These commands start at the system level and go to the port level The power supplies...

Page 17: ...maximum wattage allotted to each port on that line card Use the command show module to check the status of the PoE line card installed and the daughter card if applicable Note the sub model at the bottom of the display shows the inline power daughter card WS F6K GE48 AF installed on the line card model WS X6148 GE TX The status should be OK MJK Copyright 2006 Avaya Inc All Rights Reserved 17 ...

Page 18: ...le power pool To PD is the power level leaving the line card to the PD Device type either IEEE or Cisco phone model number The class of PD connected to each port The third line showing the Total power drawn by module x displays the amount of power consumed by the PDs attached to it and does NOT include the power needed to run the module itself Don t assume that a PoE capable line card can support ...

Page 19: ...llocating power Max milli watts allows you to specify a power ceiling that is lower than the class maximum but higher than the PD requires Valid range is 2000 to 15400 milli watts This option will reduce the amount of logically reserved power and is especially important when using class 3 PDs Never disallows power to a port even if a PD is connected Allocation works much like the max milli watt op...

Page 20: ...ort basis and can be used instead of the previous command that used auto or static This command is not based on the PD s power class This option will reduce the amount of logically reserved power and is especially important when using class 3 PDs Wattage range is 2000 through 15400 milli watts Auto uses IEEE or CDP limits without administrator knowing PD requirements set inlinepower defaultallocat...

Page 21: ...Using the partial command power inline with no arguments defaults to auto mode and 15400 milli watts Cat OS 8 5 or higher set port inlinepower mod port auto static limit max wattage off Set port inline power specifies a power mode for a port or group of ports Auto will sense the class of a non Cisco PD and apply power of the top of the class range Static acts the same as auto except that it pre al...

Page 22: ... commands are stated in this paper because Cisco is the predominant infrastructure of many Avaya customers 8 Future Directions Power over Ethernet is still young and is changing The IEEE 802 3af standard is being supplemented with a newer but not yet ratified IEEE 802 3at standard This newer standard defines double PoE and seeks to raise the limit of 15 4 Watts per port to 30 Watts and possibly ev...

Page 23: ...ower inline consumption default b Never use IOS earlier than 12 2 20 SE1 because power could still flow through a port even after the valid PD was removed This might damage a non PD device Cisco Chassis Switches 4 Verify power supply s status and available power a Use the command show system 5 Verify power statistics at the line card level a Use the command show environment power 6 Verify module s...

Page 24: ...s regardless of the port density 9 Power can be logically conserved by using the command s a 4500 series IOS power inline allocation default xxxx b 4500 series Cat OS set port inlinepower consumption xxxx c 6500 series IOS power inline auto max or power inline static max d 6500 series Cat OS set port inlinepower mod port limit max MJK Copyright 2006 Avaya Inc All Rights Reserved 24 ...

Page 25: ...Both invalid and non compliant signatures mandate removing power almost instantly by the PSE Table B Parameters for an invalid or non compliant power signature Parameter Conditions Range of Values Condition Voltage Ramp up V 10 1V 12K Ω or 45K Ω Invalid Signature Input Capacitance V 10 1V 10 µF Invalid Signature Lower Guard band Start up and Steady State 12K Ω 23 75K Ω Non Compliant Upper Guard ba...

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