Tripp Lite VoIP and Internet Telephony Applications Mode d’emploi

Practical Power Guidelines for VoIP and

Internet Telephony Applications

www.tripplite.com

WHITE

PAPER

95-2914

by David Slotten

Cisco, Cisco Systems, the Cisco Systems logo, and the Cisco Square Bridge logo

are registered trademarks or trademarks of Cisco Systems, Inc. and/or its affiliates

in the U.S. and certain other countries.

SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE.

ALL TRADEMARKS ARE THE PROPERTY OF THEIR RESPECTIVE OWNERS.

Integrate Backup Power into VoIP Networks

Voice over IP (VoIP) is exploding in popularity as an application for business

data networks. VoIP promises to consolidate a company's data and

telecommunications infrastructure as well as its support resources. As a

result, a company can lower its hardware and service costs while raising

productivity through the use of more elaborate and customizable telephony

applications.

Unfortunately, there are serious limitations inherent to the data networks

that are increasingly called upon to support VoIP. The primary limitation is

power availability. Before moving voice traffic from traditional circuit-

switched public phone systems to private data network connections, one

must consider a public phone system's unique attribute—battery support. In

order to deliver extremely high availability for such vital services as

emergency 911 support in the event of extended power outages, public

phone systems are connected to massive battery arrays.

While most data networks have some type of backup support during power

outages (provided by UPS Systems and/or generators), the backup runtime

is generally much less than the 4 to 8 hours of backup that is typically

provided for public phone systems. Because of this shortcoming, VoIP

applications generally require an increase in the UPS System-supported

power capacity (e.g. more or larger UPS Systems). Increased UPS System

capacity provides power for network-dependent phones and increases

overall backup runtime to ensure that normal telephone operation (including

911 service) remains available in the event of an extended power outage.

Reflecting on important lessons learned during its own transition to IP

telephony, Cisco provides several best-practice recommendations. One of

the most important recommendations is installing a UPS System to

guarantee availability:

“Plan Your Power: When an IP network carries voice,

reliability is essential. In case of an emergency,

people need to summon assistance by dialing 911.

When using inline power to switches and routers, make

sure they are connected to an uninterruptible power

supply [UPS System] to guarantee dial tone if the

power should go out.”

Source: Cisco Systems white paper “The Transition to IP Telephony at Cisco Systems”.

http://www.cisco.com/en/US/tech/tk652/tk701/technologies_white_paper09186a00800cb7fd.shtml

SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE.

ALL TRADEMARKS ARE THE PROPERTY OF THEIR RESPECTIVE OWNERS.

Consider the Diverse Needs of VoIP Network Equipment

Before selecting a UPS System to ensure 100% availability of IP telephony

systems, it's important to consider the unique requirements of VoIP network

equipment. Network designs hosting VoIP applications will vary widely from

business to business due to a number of variables, including the scale of

the network and the variety of legacy equipment involved. However, three

devices are common to all networks:

Client Devices (phones, PC-based soft phones, etc.)

During the transition to IP telephony, these devices will either (a) derive

their power from the network cable via a Power over Ethernet (PoE)

connection scheme, or (b) plug into a local AC source.

If they plug into a local AC source, they must be protected by a UPS

System. Often a desktop UPS not only safeguards phone service, but also

guarantees file integrity for associated PC users.

Networking Devices (switches, routers, etc.)

During the transition to IP telephony, port capacity on the network and in

wiring closets will increase to accommodate additional devices (phones)

connected to the network. Increased port capacity will increase the power

requirements placed on your UPS System, either reducing runtime or

overloading the UPS. Note that if a networking device also supplies Power

over Ethernet, the aggregate load of all client devices will also be borne by

the networking device's UPS System.

Generally, an existing UPS will be inadequate to (a) power the increased

load [watts] and (b) power the load for an acceptable length of time. Five to

fifteen minutes of runtime provided to gracefully shut down the typical data

network is inadequate for IP telephony users who expect phone service to

continue for HOURS, not minutes.

Call Processing Devices (servers and related storage systems)

During the transition to IP telephony, dedicated servers are typically added

to drive voice and messaging applications, while storage systems are

required for voicemail and other messaging applications. Similar to the

increased burden placed on networking devices, call processing devices will

experience increased loads and will require increased runtime.

Typical VoIP

Network Design

Source: Cisco Systems white paper

“Power and Cooling for VoIP and IP

Telephony Applications”.

http://www.cisco.com/application/pdf/en/

us/guest/netsol/ns412/c654/cdccont_

0900aecd801a2c5f.pdf

SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE.

ALL TRADEMARKS ARE THE PROPERTY OF THEIR RESPECTIVE OWNERS.

Select a UPS System which Provides the Highest Availability, Resiliency

and Manageability

When selecting a UPS System, the most obvious criterion to consider is

whether a UPS System has enough capacity (VA/watts) to power equipment

while having enough battery capacity to operate during a power outage for

your required duration. Specific Tripp Lite UPS System recommendations are

listed at the end of this document. Often overlooked during the selection

process, however, are more subtle, yet critical, criteria that should be

considered, including availability, resiliency to power anomalies and

manageability.

1. Availability

Availability hinges on three considerations: the VoIP equipment's power

supply configuration, the UPS System's battery configuration and the UPS

System's power electronics topology.

A. VoIP Equipment Power Supply Configuration

Many switches and routers are equipped with redundant power supply

capability. If one power supply fails, a second power supply steps in

and powers the device. Redundant power supply configurations are

strongly recommended to ensure continuous system availability.

Whether one or two power supplies are deployed, the equipment can

draw power from one of three sources: directly from facility power alone

(for simplicity's sake we will use the term “wall” to describe this

source), from a single UPS System or from multiple UPS Systems.

The following tables detail a switch's operational status, from a power

perspective, in both redundant and combined (non-redundant) modes.

The tables detail switch status under a variety of operational scenarios,

including power supply failure, utility failure and UPS System failure.

Note: Larger switches often have the capability to be alternatively configured to operate in

a combined (non-redundant) configuration. In combined mode, two power supplies'

capacities will be summed. A true doubling is not generally achieved. A factor of 1.67x is

typical. In combined mode, there is no redundancy. Should a power supply fail, the

available power is generally reduced to the capacity of a single power supply.

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Single Power Supply, or Multiple Power Supplies Operating in Redundant Mode

Configuration 1 2 3 4 5

Power Supply PS1 PS1 PS2 PS1 PS2 PS1 & PS2 PS1 PS2

Power Source Wall Wall Wall UPS1 Wall UPS1 UPS1 UPS2

PS1 Status Utility Status UPS Status System Status System Status System Status System Status System Status

OK OK OK OK OK OK OK OK

Failure OK OK Crash OK OK Crash OK

OK Blackout OK Crash Crash OK OK OK

OK Blackout UPS1 Battery Crash Crash Crash Crash OK

Fails

OK Blackout UPS1 Internal Crash Crash Crash Crash OK

Fault

OK OK UPS1 Battery — — OK OK OK

Fails Hot swap battery Hot swap battery Hot swap battery

OK OK UPS1 Internal — — OK Crash OK

Fault Replace UPS. Replace UPS. Replace UPS.

System on PS2/Wall. System on PS2/UPS2.

Vulnerable to outage Services OK during

during UPS UPS replacement

replacement

OK OK OK

UPS on bypass, UPS on bypass. UPS on bypass,

System on PS2/Wall. System on Wall. System on PS2/UPS2.

Replace UPS1. Services down* Replace UPS1.

Vulnerable to while replacing Services OK during

outage during UPS UPS1 UPS replacement

replacement

*SmartOnline Hot-Swappable Modular 5-16KVA UPS system hardware can be hot swapped without service outage.

Line-Interactive UPS Systems

On-Line UPS Systems

STEP 1: Determine Configuration

STEP 2: Consider Failure Scenarios STEP 3: Consider System Status

Multiple Power Supplies Operating in Dual (Combined, Non-Redundant) Mode

Configuration 1 2 3

Power Supply PS1 PS2 PS1 PS2 PS1 PS2

Power Source Wall Wall UPS1 UPS1 UPS2

PS1 Status Utility Status UPS Status System Status System Status System Status

OK OK OK OK OK OK

Failure OK OK Reduced Output OK OK

OK Blackout OK Crash OK OK

OK Blackout UPS1 Battery Crash Crash Reduced Output

Fails Replace UPS1. Replace UPS1.

Output reduced during UPS Output reduced during UPS

replacement replacement

OK Blackout UPS1 Internal — Crash Reduced Output

Fault Replace UPS1 Replace UPS1. Output reduced

until UPS1 replacement

OK OK UPS1 Battery — OK OK

Fails Hot swap battery Hot swap battery

OK OK UPS1 Internal — Crash Reduced Output

Fault Replace UPS. Plug into wall until Replace UPS1. Plug PS1 into wall

UPS replacement to restore full power until UPS1

replacement. Output reduced

until UPS1 replacement

OK OK

Replace UPS1. Replace UPS1.

Both PS on UPS Bypass. PS1 on UPS1 Bypass circuit,

Services down* while replacing vulnerable to outage. Reduced

UPS1 power during UPS1 replacement

*SmartOnline Hot-Swappable Modular 5-16KVA UPS system hardware can be hot swapped without service outage.

STEP 1: Determine Configuration

Line-Interactive UPS Systems

On-Line UPS Systems

SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE.

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B. UPS System Battery Configuration

UPS System availability, and therefore VoIP system availability, is most

critically dependent upon the capacity of the UPS System's battery

configuration. The number of UPS System batteries, both internal and

external, determines the amount of runtime that is provided during a

power outage. As mentioned previously, the runtime must fit the

application. Most existing data networks are unlikely to provide reserve

runtime power comparable to the public switched phone network. One

has to determine a runtime estimate of what is adequate or desirable

specifically for a VoIP application. Most users conclude that hours, not

minutes, of backup runtime are required to maintain voice operations.

Like any estimate, a runtime estimate will be imperfect and will also be

impacted by future capacity requirements (such as the addition of more

phones). Therefore, it is critical that the selected UPS System can

accommodate external battery packs to increase runtime as needs

increase, or maintain runtime in a growing phone environment.

Runtime scalability with external battery packs also yields the ability to

hot swap battery packs at the end of their useful life without a service

interruption. Similar hot swap battery replacement is also the norm for

the UPS System's internal batteries.

C. UPS System Power Electronics

If a UPS System's power electronics fail during a utility power outage,

the supported IP telephony system will obviously crash. If the UPS

System failure occurs while utility power is present, however, different

UPS power electronics topologies can impact IP telephony system

availability in different ways.

On-Line UPS System with Internal Bypass

With power present, an internal power electronics fault in an on-line

UPS System will result in the load automatically being powered by a

bypass path inside the UPS. As long as utility power remains present,

the UPS will continue to power the connected IP telephony system

without interruption and will continue to condition the power against

basic power anomalies. In the event of a power outage, the system

will crash.

Upon development of a bypass condition, a service interruption needs

to be planned to replace the UPS System.

SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE.

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With power present, a battery system failure will not cause a system

interruption. As long as utility power remains present, the UPS

System will continue to power the connected IP telephony system

without interruption and will continue to condition the power against

most power anomalies. In the event of a power outage, the system

will crash.

In the event of a battery system failure, the internal batteries of the

UPS System and/or the external battery packs can be replaced

without a service interruption.

On-Line UPS System with Internal Bypass and External

Maintenance Bypass

With power present, an internal power electronics fault will result in

the load automatically being powered by a bypass path inside the

UPS. As long as utility power remains present, the UPS will continue

to power the connected VoIP system without interruption and will

continue to condition the power against basic power anomalies. In

the event of a power outage, the system will crash.

In the event of a bypass condition, the power electronics module of

the UPS should be replaced. This can be performed while the system

remains in service, as the input and output power connections are

physically and electrically separated from the power module itself.

This functionality is available presently in Tripp Lite's 5-16KVA

SmartOnline™ Hot-Swappable Modular UPS Systems.

With power present, a battery system failure will not cause a system

interruption. As long as utility power remains present, the UPS

System will continue to power the connected IP telephony system

without interruption and will continue to condition the power against

most power anomalies. In the event of a power outage, the system

will crash.

In the event of a battery system failure, the internal batteries of the

UPS System and/or the external battery packs can be replaced

without a service interruption.

Line-Interactive UPS System

With power present, an internal power electronics fault can result in

the load crashing. As the operational requirements of a line-interactive

UPS System are very simple when power is present, this is extremely

rare. Line-interactive power electronics failures are normally only

detected when the power fails and the UPS attempts to power the load

from its battery-driven inverter.

SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE.

ALL TRADEMARKS ARE THE PROPERTY OF THEIR RESPECTIVE OWNERS.

In the event of a power electronics failure, a service interruption

needs to be planned to replace the UPS System.

With power present, a battery system failure will not cause a system

interruption. As long as utility power remains present, the UPS

System will continue to power the connected IP telephony system

without interruption and will continue to condition the power against

many power anomalies. In the event of a power outage, the system

will crash.

In the event of a battery system failure, the internal batteries of the

UPS System and/or the external battery packs can be replaced

without a service interruption.

2. Resiliency to Power Anomalies

The fundamental outcome one hopes for in adding UPS System support to

a network is to enhance system availability. But an additional concept—

resiliency—is very important as well. UPS System resiliency reflects the

ability to respond positively to a number of operating variables.

A. Voltage Variation

Currently, one of the most popular UPS System topologies for VoIP is

provided by on-line UPS Systems. An on-line UPS System can deliver

perfect power even if it encounters a very wide range of input voltages.

The on-line UPS does this without relying on its battery reserves, leaving it

well prepared to respond to a power outage. Because of its continuous

AC-DC-AC conversion process, during an outage an on-line UPS System

will also exhibit zero transfer time between power failure detection and

power delivery to your equipment. On-line UPS Systems are widely

acknowledged to be compatible with all types of VoIP devices.

In many networks with distributed UPS Systems, line-interactive UPS

Systems are widely deployed. If input voltage levels are below the line-

interactive UPS System's automatic correction capability, the UPS will

switch to battery to maintain acceptable output voltage. In areas with

chronic extreme brownouts, this frequent switching to battery can reduce

reserve power as well as shorten battery service life—putting critical

systems at risk in an outage.

While the transfer time of a line-interactive UPS System (several

milliseconds) is extremely fast, this short delay has been theorized as the

cause of packet losses, or even system shutdown in some applications.

Depending on your power environment and the sensitivity of your IP

telephony components, a line-interactive UPS System may or may not be

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adequate. Generally, line-interactive UPS Systems do not pose a problem.

This is the subject of some debate and is generally presented as a major

issue by vendors biased towards selling online UPS Systems.

Line-interactive UPS Systems do tend to cost less than on-line UPS

Systems and operate with higher efficiency, reducing electrical costs.

In theory, an on-line UPS System battery should be used less frequently

due to input voltage variation, and will therefore last longer. This advantage

will manifest itself more as the frequency of input voltage variation

increases.

B. Harmonic Distortion

Only an on-line UPS System will address input harmonic distortion.

Because an on-line UPS System deconstructs and reconstructs the input

power, it can deliver distortion-free power. A line-interactive UPS System

will pass through input waveform distortions. Harmonic distortion tends to

be an elusive “gremlin” issue when it affects connected loads.

C. Transient Spikes (or “Surges”)

Both line-interactive and on-line UPS Systems address sudden increases in

voltage.

D. Electromagnetic Interference

While both line-interactive and on-line UPS Systems address these

phenomena, an on-line UPS typically offers far superior filtering capability.

3. Manageability

VoIP system availability is closely tied to UPS System manageability. To

ensure continuous availability, UPS Systems must be incorporated as an

integral part of a sound hardware management scheme. UPS Systems are

extremely manageable and responsive, communicating their status

automatically and triggering application shutdowns prior to battery

exhaustion in the event of a power outage or extreme voltage variation.

There are various methods to communicate with UPS systems, including

SNMP, Web, network software and direct connection. While most users

choose SNMP/Web accessory cards installed inside UPS Systems for

communication, the most essential requirement is to deploy and use some

method of communication. Without a management application running for

your UPS Systems, the day will come when the UPS batteries fail and your

system fails as your power fails. Simple management steps taken at

installation can save significant problems later.

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Alerts available from most UPS Systems and network cards include:

• Voltage levels

• Current levels

• Temperature levels

• Humidity levels

• Dry contacts for fire, water, security, etc.

• Battery capacity

• Battery failure

Commands from the administrator to most UPS Systems include:

• Reboot system

• Reboot outlet(s)

• Shut down system

• Shut down outlet(s)

• Run inverter/battery test

Tripp Lite presents a uniquely simple management scheme for VoIP

UPS System hardware. Whether management is through an IP-addressed

SNMP/Web accessory card or PowerAlert Software, Tripp Lite provides

administrators with a single JAVA-based user interface. The commonality

within this design approach makes it ideal for managing VoIP applications

of all scales across multiple OS platforms.

During a power failure, Tripp Lite's PowerAlert Software ensures a smooth

and customizable shutdown of call processing and voice messaging

applications as well as the underlying operating system.

As a unique feature, Tripp Lite's PowerAlert Software and network accessory

card (SNMPWEBCARD) are designed to accommodate multiple power

supply and UPS System hardware deployments. With a single IP address

assigned to the SNMPWEBCARD (or a single PC/Server running PowerAlert)

users can manage multiple redundant UPS Systems working in tandem to

provide optimal power to the IP telephony system's single or multiple power

supplies.

Alternative UPS System manufacturers require each UPS to be managed

individually. With these UPS Systems, there is no easy way to manage their

redundant operation without expensive and space-consuming external

power-switching accessories.

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