10 - IP Telephony Services

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IP Telephony

Services

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Power over Ethernet



PoE is defined in IEEE 802.3af and facilitates the

delivery of regulated power over a standard copper

Ethernet network cable



PoE deployments consist of two primary components:

•PSE provides power

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Power Classification



IEEE 802.3af has an optional power classification

feature that allows a PSE to budget the required

power based on the class of the attached devices,

significantly reducing power capacity requirements

•With power classification: The switch (PSE) identifies power needs and reserves power for PDs based on class

•Without power classification: The switch (PSE) assigns all PDs the default class (Class 0), which budgets a full 15.4 watts per port

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Power Class Definitions

7 watts 2 15.4 watts 3 4 watts 1 Future expansion 4 15.4 watts reserved

(Actual device requirement can be less) 0 (Default)

Maximum Power at Output Port of PSE Class Number

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Power Management



Power management modes include:

•Static: Power is deducted from the total power pool as specified by the user for that interface

• Ensures that the maximum power specified for the interface is always reserved

•Dynamic: Power budgeted from the total power pool for each port matches the actual power consumed

•Class: Power budgeted from the total power pool for each port matches the maximum power for the power class

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Power Pool Usage Guidelines



Three power supply

capacities:

•320 W, 600 W, and 930 W



Any power supply can

be installed in any switch

model



Installing a higher capacity

power supply does not

increase the number of

PoE ports on the switch

410 W (24 PoE ports at 15.4 W each) 190 W 600 W 740 W (48 PoE ports at 15.4 W each) 190 W 930 W 130 W (8 PoE ports at 15.4 W each) 190 W 320 W Power Budget for PoE Pool Switch

Consumption Power Supply

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PoE Telemetries



Switch provides telemetries support to keep history of

power usage for each PD

•Disabled by default; you enable PoE telemetries through configuration and specify duration and interval values

[edit poe interface interface-name telemetries] user@switch# set ?

Possible completions:

+ apply-groups Groups from which to inherit configuration data + apply-groups-except Don't inherit configuration data from these groups disable Disable telemetries

duration Duration to continue recording of data (1...24 hours)

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Configuring PoE

[edit poe]

user@switch# show

interface all | interface { disable;

priority high | low; maximum-power watts; telemetries { disable; interval minutes; duration hours; } }

Determines priority for shutdown of individual ports when there is insufficient power for all PoE ports

Allows per-port PoE consumption tracking Sets maximum amount of power that can be supplied for a port

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user@switch> show chassis hardware Hardware inventory:

Item Version Part number Serial number Description Chassis REV X3 750-021256 BM0207431960 EX4200-24T

FPC 0 REV 02A 711-021264 AK0207431816 EX4200-24T, 8 POE …

Power Supply 0 REV 01 740-020957 AT0507420091 PS 320W AC …



Use the show chassis hardware command to

verify PoE capabilities

•Use the show poe controller command to view PoE

power usage and availability

Monitoring PoE (1 of 2)

user@switch> show poe controller

Controller Maximum Power Guard-band Management Index Power Consumption

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Monitoring PoE (2 of 2)



Use the show poe interface command to verify

the operational status of a PoE interface, as well as

the actual power being consumed by PDs

•Optionally, verify the same details for an individual interface user@switch> show poe interface

Interface Admin-status Oper-status max-power priority power-consumption Class ge-0/0/1 Enabled ON 15.4W Low 3.5W 0 ge-0/0/3 Enabled OFF 12.0W High 0.0W 0 ge-0/0/5 Enabled OFF 15.4W Low 0.0W 0 …

user@switch> show poe interface ge-0/0/3 PoE interface status:

PoE interface : ge-0/0/3 Administrative status : Enabled Operational status : OFF Power limit on the interface : 15.4W Priority : High

Power consumed : 0.0W Class of power device : 0

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Voice VLAN



The voice VLAN feature enables access ports to

accept both untagged (data) and tagged (voice) traffic

and separate that traffic into different VLANs

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Usage Guidelines



When using the voice VLAN feature:

•Recommend to configure CoS before enabling voice VLAN

•Enable voice VLAN for switch access ports with IP phones

•Use LLDP-MED to provide voice VLAN ID and 802.1p values to attached IP phones

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Configuring a Voice VLAN

[edit ethernet-switching-options] user@switch# show

voip {

interface (access-ports | interface-name) { vlan (vlan-name | vid);

forwarding-class class; }

}

Associates VoIP parameters with all access ports

Associates VoIP parameters with specified access port

Referenced VLAN and forwarding class must be defined locally on switch

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Monitoring Voice VLAN



Use the show vlans detail vlan-name

command to verify voice VLAN membership, tag, and

state information

user@switch> show vlans detail voice VLAN: voice, 802.1Q Tag: 500, Admin state: Enabled

Description: Used for Voice Traffic Number of interfaces: 3 (Active = 3)

Tagged interfaces: ge-0/0/0.0*, ge-0/0/1.0*, ge-0/0/10.0*

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Link Layer Discovery Protocol



LLDP, as defined in IEEE 802.1ab, is a Layer 2

neighbor discovery protocol that allows network

devices to advertise their identity and capabilities



LLDP-enabled devices are called LLDP agents

•LLDP agents exchange LLDPDUs

•Information learned from neighbors is stored in a database

• Database entries are refreshed periodically



LLDP frames use TLV tuples

•LLDP defines a set of mandatory and optional TLVs

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LLDPDU Frame Format

LLDP multicast address: 01-80-C2-00-00-0E

Chassis ID TLV M Port ID TLV M Time to Live TLV M Optional TLV Optional TLV End of LLDPDU TLV M …

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LLDP Updates



LLDP update considerations:

•Periodic updates are sent at regular intervals

• Default is 30 seconds; valid range is 5 to 32768 seconds

•Triggered updates are sent when local value changes

• Triggered updates conform to 1 per second limit

•Updates are sent as unsecure, one-way advertisements

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LLDP Transmit Agent



Transmit agent sends periodic and triggered updates

•TTL TLV (txTTL) mechanism determines the length of time information remains valid on the receiver:

• msgTxInterval (default of 30 seconds) x msgTxHold (default of 4 seconds)

• By default, messages are sent with a default TTL value of 120 sec • If information is not refreshed before TTL expires, it is discarded



Transmit agent notifies neighbor of state changes

•Final shutdown LLDPDU is sent with chassis ID, port ID, TTL TLV field set to 0, and end-of-LLDPDU TLV set

•If the transmit agent fails to send shutdown TLV before the interface goes down, LLDP is maintained until TTL age timer expires Chassis ID TLV Port ID TLV Time to Live TLV Optional TLV Optional TLV End of LLDPDU TLV …

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LLDP Receiver Agent



Receiver stores information in a neighbor database

•Neighbor database information is accessible by SNMP

•Database is updated to ensure data accuracy



Receiver maintains statistic counters for each

interface; these statistics include:

•Frames received

•Frames with errors

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What Is LLDP-MED?



LLDP-MED is an extension to LLDP developed by TIA

(ANSI/TIA-1057) to support interoperability and

enhance discovery between VoIP endpoint devices and

other networking devices



LLDP-MED devices are categorized into three classes:

•Class 1: All devices requiring base LLDP discovery service

•Class 2: Any device with IP media capabilities

• Examples include voice and media gateways, and conference bridges

•Class 3: Any device used for end-user IP communications

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LLDP-MED Usage



LLDP-MED can be used for the following:

•Network policy discovery

• Allows a switch to deliver VLAN and CoS settings to an IP phone

•Power negotiation

• Allows a switch and IP phone to negotiate power requirements and offerings

•Inventory management

• Allows a management system to retrieve system information from endpoint devices

•Location discovery

• Identifies the location of IP phones based on the switch port; primary usage is for emergency services

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LLDP and LLDP-MED Interaction



LLDP and LLDP-MED interaction details:

•All mandatory LLDP TLVs are advertised in LLDPDUs as soon as LLDP is enabled

•All optional LLDP and LLDP-MED TLVs are enabled by default

•LLDP-MED TLVs are sent only after detecting a MED device

1. Interface starts

advertising base LLDP TLVs (non-LLDP-MED) 2. LLDP-MED frame

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LLDP-MED and 802.1X



LLDP-MED and 802.1X considerations:

•When 802.1X is enabled, LLDP frames are not transmitted or received until the port is authenticated

•An IP phone and PC connected to the same switch port can be authenticated separately (multiple supplicant mode) and can receive different VLAN assignments and policies for

data and voice

• If only the IP phone or the PC is 802.1X capable, use the single supplicant mode

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LLDP and LLDP-MED Example (3 of 4)

xxxx Switch ge-0/0/3 … … … xxxx IP phone ge-0/0/1 xxxx PC ge-0/0/2 xxxx Gateway ge-0/0/0 Information Device Port xxxx PC/Server ge-0/0/3 … … … xxxx IP phone ge-0/0/1 xxxx PC/Server ge-0/0/2 xxxx Switch ge-0/0/0 Information Device Port

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LLDP and LLDP-MED Example (4 of 4)

xxxx Switch ge-0/0/3 … … … xxxx IP phone ge-0/0/1 xxxx PC ge-0/0/2 xxxx Gateway ge-0/0/0 Information Device Port Management Application xxxx PC/Server ge-0/0/3 … … … xxxx IP phone ge-0/0/1 xxxx PC/Server ge-0/0/2 xxxx Switch ge-0/0/0 Information Device Port SNMP SNMP

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Configuring LLDP and LLDP-MED

[edit protocols] user@switch# show lldp { disable; advertisement-interval seconds; hold-multiplier number;

interface [all | interface-name] { disable;

} }

lldp-med { disable;

interface (all | interface-name){ disable;

} }

}

Determines TTL value sent to neighbor devices

Disables protocol on referenced interface (suggested on untrusted boundaries)

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Monitoring LLDP and LLDP-MED



Use the following key commands to monitor LLDP:

•Verify LLDP status:

user@switch> show lldp detail

•View learned neighbor information:

user@switch> show lldp neighbors •Check local LLDP details:

user@switch> show lldp local-info

•View LLDP statistics and counters:

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