Choosing Your Hardware
One of the first things to do when setting up Asterisk is to figure out your hardware needs. Hardware is a bit
of a catch-all term and refers to the server, the phones, and the connections between them.There is no
standard ratio for Asterisk that dictates “To support A calls over a B period of time, you need a server with
X megabytes of RAM, a processor faster than Y, and a hard drive bigger than Z” or that “If you are in a
call-center environment, X brand phones is the best choice.”To figure out what is the correct fit for your
situation, research is required.
Picking the Right Server
Picking the right server is a key decision when running Asterisk.The last thing a company wants to hear is
that their phone system is down. Asterisk can run on obsolete hardware, but you will get what you pay for.
Reliable, capable equipment is the foundation for any reliable, capable PBX system.
Processor Speed
Processor speed is the most important feature when looking at a server to run Asterisk.The more processing
power, the more responsive the system will be when it is placed under heavy call loads. Asterisk runs well
on any modern processor, handling moderate call loads without any issue. However, this does depend on
how the system is configured to handle calls.
Transcoding and Protocol Translation
Transcoding is when the server is handling a conversation that is coming in with one codec and coverts it on-
the-fly to another.This happens a lot more than thought, as most VoIP telephones transmit in μ-Law, which
is the standard codec for telephone conversations. If the server is using the GSM codec for outbound calls,
it needs to “transcode” the conversation and convert it from μ-Law to GSM.This, by itself, is pretty simple;
however, when the server starts having to transcode multiple conversations simultaneously, more processing
time is required. If a performance bottleneck develops, the conversations will start to exhibit delays in the
conversation, more commonly referred to as “lag.” Protocol translation is the same problem as transcoding,
except instead of converting the audio codec, it needs to translate the protocol used.This is also common
with VoIP providers who only offer access to their networks via specific protocols.
RAM
RAM usage on Asterisk is pretty low. Asterisk can easily fit within a 64MB footprint even on a fairly large
install. Since Asterisk is modular, trimming RAM consumption is as easy as removing modules from the
startup sequence.A bare bones Asterisk startup can fit within a memory footprint of fewer than 30MB.
Storage Space
Storage space is probably one of the least important choices when choosing a server for Asterisk. Hard
drives keep getting larger and cheaper with each passing month, allowing even a low-end computer to have
massive amounts of space. Asterisk, by itself, hardly takes up any room; however, when voice prompts for
Interactive Voice Response (IVR) menus and voice mail start being added to the system, Asterisk’s
footprint starts growing. Hard drive size needs to be determined by the amount of users on the system and
the amount of voice mail expected.
While this may not seem like a lot at first, consider that a person can average about five voice mails a day in
a busy office. If each of those messages is about a minute each, and there are 100 people in the office, that’s
500MB of storage per day! When you calculate the math per year, we’re talking almost 13GB! Plus, other
factors exist as well. Let’s say a team leader sends a five-minute group message to his or her team of ten
people.That 5MB message just copied across the system into ten separate mailboxes consumes 50MB.
Also, don’t forget to factor in saved messages, people on extended absences, and group mailboxes that
may be accessed by the public. Asterisk, like any high-demand server application, benefits from Redundant
Arrays of Independent Disks (RAIDs). RAIDs are very important in any kind of high-availability environment.
Picking the Right Phones
Phones are arguably the most important part of a PBX setup.This is how most users interface with the PBX
system. Picking the proper phone is key to a successful PBX deployment.There have been instances where
users were ready to give up on Asterisk solely because they hated their phones.Thankfully, changing phones
is easy and these users quickly changed their opinions once new phones were installed.
Soft Phones
The easiest phone to set up with Asterisk is a soft phone.A soft phone is a computer program that emulates
a phone on your PC. Soft phones are easy to set up and can be configured in a matter of minutes.They’re
usually very easy to use, often displaying a telephone-like interface on the screen. Soft phones utilize the
computer’s sound card for transmitting and receiving audio, or optionally a “USB phone,” which is a phone
like device that plugs into the computer’s USB port. Soft phones are inexpensive (often free) and USB
phones generally cost less than $50.USB phones sometimes can help, but they usually aren’t geared for a
business environment. In addition, these users are tethered to a PC. If the PC crashes, no phone calls.
Hard Phones
The alternatives to soft phones are hard phones—the phones we’ve used the past 125+ years: a physical
device that sends and receives telephone calls. Hard phones are on the opposite side of the spectrum from
soft phones: they’re expensive and often harder to set up than their software counterparts. However, most
users prefer a hard phone; it’s what they’re accustomed to. The most common hard phones include IP
phones: analog phones connected to an Analog Terminal Adapter (ATA) and analog phones connected via
interface cards.
IP Phones
IP phones are one of the most common solutions you’ll see for VoIP in a business environment.They plug in
to an Ethernet connection and emulate a regular analog phone.They’re made by numerous companies,
including Cisco Systems, Polycom, Aastra, and Siemens, just to name a few.The price and quality of these
phones run the gamut, but the general rule of “you get what you pay for” applies here. In today’s market, a
good IP phone will cost you at least $150 per unit, like the Cisco 7960 IP Phone
Analog Telephone Adapters
ATAs are the bridge between the world of analog telephones and the world of VoIP. They are small
devices, usually in the form of a small plastic cube, with a power port, one or more telephone jacks, and an
Ethernet port. An analog phone connected through an ATA can participate in phone calls on a VoIP
network. ATAs are cheaper then IP phones, mainly because they are slightly simpler.ATAs are often
offered by the same companies that make IP phones and range in price from $50 to $100 depending on
the protocols they support, the number of ports, and, of course, the number of features. Some ATAs have
both a port for a phone and a port for an outside phone line, allowing a quick and easy way to interface
Asterisk with both your phone and the public switched telephone network. ATAs work with most phones,
the exceptions being proprietary phones from digital PBXs and older rotary dial phones. Digital phones are
nearly impossible to support due to their complexity and the differences between one manufacturer and
another. Rotary phones aren’t supported by most ATAs because most developers consider, somewhat
correctly, that pulse dialing is an obsolete protocol.
One of the first things to do when setting up Asterisk is to figure out your hardware needs. Hardware is a bit
of a catch-all term and refers to the server, the phones, and the connections between them.There is no
standard ratio for Asterisk that dictates “To support A calls over a B period of time, you need a server with
X megabytes of RAM, a processor faster than Y, and a hard drive bigger than Z” or that “If you are in a
call-center environment, X brand phones is the best choice.”To figure out what is the correct fit for your
situation, research is required.
Picking the Right Server
Picking the right server is a key decision when running Asterisk.The last thing a company wants to hear is
that their phone system is down. Asterisk can run on obsolete hardware, but you will get what you pay for.
Reliable, capable equipment is the foundation for any reliable, capable PBX system.
Processor Speed
Processor speed is the most important feature when looking at a server to run Asterisk.The more processing
power, the more responsive the system will be when it is placed under heavy call loads. Asterisk runs well
on any modern processor, handling moderate call loads without any issue. However, this does depend on
how the system is configured to handle calls.
Transcoding and Protocol Translation
Transcoding is when the server is handling a conversation that is coming in with one codec and coverts it on-
the-fly to another.This happens a lot more than thought, as most VoIP telephones transmit in μ-Law, which
is the standard codec for telephone conversations. If the server is using the GSM codec for outbound calls,
it needs to “transcode” the conversation and convert it from μ-Law to GSM.This, by itself, is pretty simple;
however, when the server starts having to transcode multiple conversations simultaneously, more processing
time is required. If a performance bottleneck develops, the conversations will start to exhibit delays in the
conversation, more commonly referred to as “lag.” Protocol translation is the same problem as transcoding,
except instead of converting the audio codec, it needs to translate the protocol used.This is also common
with VoIP providers who only offer access to their networks via specific protocols.
RAM
RAM usage on Asterisk is pretty low. Asterisk can easily fit within a 64MB footprint even on a fairly large
install. Since Asterisk is modular, trimming RAM consumption is as easy as removing modules from the
startup sequence.A bare bones Asterisk startup can fit within a memory footprint of fewer than 30MB.
Storage Space
Storage space is probably one of the least important choices when choosing a server for Asterisk. Hard
drives keep getting larger and cheaper with each passing month, allowing even a low-end computer to have
massive amounts of space. Asterisk, by itself, hardly takes up any room; however, when voice prompts for
Interactive Voice Response (IVR) menus and voice mail start being added to the system, Asterisk’s
footprint starts growing. Hard drive size needs to be determined by the amount of users on the system and
the amount of voice mail expected.
While this may not seem like a lot at first, consider that a person can average about five voice mails a day in
a busy office. If each of those messages is about a minute each, and there are 100 people in the office, that’s
500MB of storage per day! When you calculate the math per year, we’re talking almost 13GB! Plus, other
factors exist as well. Let’s say a team leader sends a five-minute group message to his or her team of ten
people.That 5MB message just copied across the system into ten separate mailboxes consumes 50MB.
Also, don’t forget to factor in saved messages, people on extended absences, and group mailboxes that
may be accessed by the public. Asterisk, like any high-demand server application, benefits from Redundant
Arrays of Independent Disks (RAIDs). RAIDs are very important in any kind of high-availability environment.
Picking the Right Phones
Phones are arguably the most important part of a PBX setup.This is how most users interface with the PBX
system. Picking the proper phone is key to a successful PBX deployment.There have been instances where
users were ready to give up on Asterisk solely because they hated their phones.Thankfully, changing phones
is easy and these users quickly changed their opinions once new phones were installed.
Soft Phones
The easiest phone to set up with Asterisk is a soft phone.A soft phone is a computer program that emulates
a phone on your PC. Soft phones are easy to set up and can be configured in a matter of minutes.They’re
usually very easy to use, often displaying a telephone-like interface on the screen. Soft phones utilize the
computer’s sound card for transmitting and receiving audio, or optionally a “USB phone,” which is a phone
like device that plugs into the computer’s USB port. Soft phones are inexpensive (often free) and USB
phones generally cost less than $50.USB phones sometimes can help, but they usually aren’t geared for a
business environment. In addition, these users are tethered to a PC. If the PC crashes, no phone calls.
Hard Phones
The alternatives to soft phones are hard phones—the phones we’ve used the past 125+ years: a physical
device that sends and receives telephone calls. Hard phones are on the opposite side of the spectrum from
soft phones: they’re expensive and often harder to set up than their software counterparts. However, most
users prefer a hard phone; it’s what they’re accustomed to. The most common hard phones include IP
phones: analog phones connected to an Analog Terminal Adapter (ATA) and analog phones connected via
interface cards.
IP Phones
IP phones are one of the most common solutions you’ll see for VoIP in a business environment.They plug in
to an Ethernet connection and emulate a regular analog phone.They’re made by numerous companies,
including Cisco Systems, Polycom, Aastra, and Siemens, just to name a few.The price and quality of these
phones run the gamut, but the general rule of “you get what you pay for” applies here. In today’s market, a
good IP phone will cost you at least $150 per unit, like the Cisco 7960 IP Phone
Analog Telephone Adapters
ATAs are the bridge between the world of analog telephones and the world of VoIP. They are small
devices, usually in the form of a small plastic cube, with a power port, one or more telephone jacks, and an
Ethernet port. An analog phone connected through an ATA can participate in phone calls on a VoIP
network. ATAs are cheaper then IP phones, mainly because they are slightly simpler.ATAs are often
offered by the same companies that make IP phones and range in price from $50 to $100 depending on
the protocols they support, the number of ports, and, of course, the number of features. Some ATAs have
both a port for a phone and a port for an outside phone line, allowing a quick and easy way to interface
Asterisk with both your phone and the public switched telephone network. ATAs work with most phones,
the exceptions being proprietary phones from digital PBXs and older rotary dial phones. Digital phones are
nearly impossible to support due to their complexity and the differences between one manufacturer and
another. Rotary phones aren’t supported by most ATAs because most developers consider, somewhat
correctly, that pulse dialing is an obsolete protocol.
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