Welcome back.
In this section, I'd like to show you the Cisco IP phone start up process.
And by doing that, explain the infrastructure requirements for Cisco IP phones to function.
We need to talk about power, VLANs, IP addressing configurations, firmware and so forth, which are
all required for Cisco IP phones to function before getting double tone on a Cisco IP phone.
A sequence of events has to take place.
An infrastructure needs to be provided for the phone to function.
In this section, I'd like to explain phone Start-Up in more detail.
I'd also like to give you more detail on Skinny Client Control Protocol, or CCP, commonly known as
Skinny and Session Initiation Protocol or CIP.
So this section assumes that you've been through the introductory sections and you understand what a
codec is.
You have an understanding of the history of voice technologies and a basic foundation to voice.
Now this is an important overview of the phone's start up process, and I would remember these steps
both for troubleshooting in the real world and for study purposes.
I'm going to mention the process in brief now and then in the following slides.
We're going to dive into each of these topics in a lot of detail.
The first thing the phone requires is power.
So the phone will obtain power from the switch or from wall power, or by using mid span power.
So the phone will obtain power from a switch.
For example, the phone, once it has obtained power, will load its locally stored image.
This can cause a lot of confusion.
The phone will boot up with the image files stored locally and the configuration that it had previously.
So if a phone has a configuration already, it will use that configuration when it boots up.
The switch will then provide VLAN information to the phone using either CDP or LDPE.
Once again, I'll discuss those in more detail in the upcoming slides.
Once the phone has its VLAN, it will require an IP address and will for instance get an IP address
from a DHCP server.
DHCP uses a very special option option 150 to point the phone to a FTP server.
The phone will then download its firmware and configuration from a TFTP server.
If the locally stored image file or firmware is a different version to the version that it's meant to
use when connecting to a system, for example, the phone will upgrade its firmware.
It will also download its configuration from the TFTP server.
It will then register using either skinny or sip to the SIU sim and then in skinny case it will download
its soft key template.
The SIU sim essentially sends the soft key template to the phone using skinny messages.
So that's an overview of the phone startup process.
Let's dive into the details.
Now once again, what is a phone require to function?
And the first thing is power.
There are multiple ways to provide power to an IP phone.
The first method is to use a power cube where a local power adapter is used to provide power to the
phone.
This would typically be used where power of Ethernet or power is not available.
I've just put the pot code for one of the adapters here.
Please check the specifications of the individual handset so that the right power cube is ordered for
a specific handset.
Typically, a phone is connected directly to a switch.
And a PC is connected to the back of the phone.
The phone requires power to operate, and this is the first method to provide power to the phone and
one of the most simple methods.
However, it does have multiple disadvantages if power is lost to the building.
Phones will no longer be able to make and receive calls.
So UPS would be required on each individual power cube.
That doesn't scale well.
So these days this is one of the least used methods.
A second option would be to use a power injector where mid span power is provided to the phone.
This would be typically used where a switch does not support power over Ethernet.
So the switch is physically connected to a power injector and the power injectors physically connected
to the phone with the power injector providing power to the handset.
So notice here on the back of the power injector, there are two ports, one to connect back to the
switch and one to connect to the phone.
The power injector would be physically powered from a wall socket.
The advantage of this method is that you do not have to upgrade switches and the power injector would
typically reside in a wiring closet where there may be UPS power.
In the real world, this is typically used when you have a single or a small number of phones connected
to a switch, and it's less costly to purchase power injectors than it is to replace the entire switch.
The preferred and recommended way to provide power to IP phones and other devices is to use power over
Ethernet.
Historically, power of Ethernet was used for two main applications.
IP telephony and ADA 2.11 wireless networking.
IP phones like standard PBX phones require 48 volts of power.
Switches and other devices providing power are known as power source equipment or PC devices, and the
phones are known as powered devices.
Power of the Ethernet is provided on pins one, two, three and six.
So the same pins used to transmit data.
That is different to the mid span power that we discussed previously, which uses pins four, five,
seven and eight.
There are three main types of power over Ethernet.
The first one is the original power of Ethernet or POA, developed by Cisco many years ago.
This provided 6.3 watts of power to IP phones.
Older models of phones that you may encounter like the 79, 60 and 7940.
Use Cisco's Poe and require 6.3 watts of power.
The Industry Standard 82.3 AF was ratified to provide interoperability between multiple vendors, phones
and network equipment.
So you can connect a Nortel phone to a Cisco switch or a Cisco phone to an HP switch.
There are different classes of devices.
In ADA 2.3, RF IP phones fall into what is called Class three, which provides power at 15.4 watts.
Since the completion and ratification of the I triple E to 2.3 AF standard, the required power consumption
for these devices has begun to extend beyond the level specified in the standard.
Specifically with the introduction of Triple E A2 2.11 N wireless technology, there is now a requirement
to provide power above the maximum of 15.4 watts available in the 2.3 standard.
Cisco also has an extension to 802.3 AF, providing up to 20 watts of power known as Power over Ethernet
plus Poe Plus was developed because Cisco did not want to wait for the ratification of 802. 3at here
WI plus allowed for the immediate implementation of technologies requiring power greater than 15.4 watts.
The introduction of network devices that require more than 15.4 watts has forced the Triple E to develop
a new Poe standard that can deliver even more power than what was defined in the triple E 82.3 AF standard.
The new standard 82 point 3at, also known as Poe Plus, is designed to deliver up to 30 watts of power
per port.
The two that we're going to concentrate on in this course are power of Ethernet or Poe and ADA 2.3 AF,
which also goes by the name Poe.
Just note the names.
Poe is often used to refer to ADA 2.3 AF, but in all the documentation it refers to Cisco's proprietary
implementation of power of Ethernet.
So just read carefully between the lines to know which power is actually being referenced.
Another advantage of power of Ethernet is that the switch can dynamically and automatically discover
whether an IP phone is plugged into a port or whether a PC or other device is plugged into that port.
In Cisco's original implementation, a first link pulse or FLP was sent down the wire to detect whether
a phone was connected or not, so the switch would send an FLP down the wire and in its unpowered state
the phone would loop back the FLP to the switch.
If LPs are normally used for speed and duplex negotiation so the switch wouldn't normally expect to
see its own FLP returned to it.
But in this case, the phone does and the switch therefore knows that an IP phone is connected to it
and can provide power down to the handset.
The Industry Standard 8.3 RF uses a different method to detect the presence of an IP phone.
In error.
Two or three have the power sourcing equipment or switch in this case applies a small current limited
voltage to the cable, so a DC voltage is applied to the cable.
We obviously want to make sure that no damage is possible to the equipment that may be present in an
Ethernet system.
So the switch is going to look for a device that complies with the ADA two or three AF specification
and thus applies a DC voltage between the transmit and receive pairs on the Ethernet cable and then
measures the received current in amps or voltage received.
The switch expects to receive a 25 k ohm resistance between the pairs for the device attached to be
considered a valid powered device.
In other words, the switch is looking for this resistance from the phone or other type of device to
ensure that it's a valid powered device.
If the switch or PC does not detect a valid resistance, power is not applied to the port.
But if a power device is discovered, power is applied, and optionally a power device classification
can be done.
The PFC can then detect what are called 82.3 AF clauses by default Cisco switches, assigned phones
or other power devices to class zero.
Now an editor or three AIF we have clauses zero one, two and three.
Clause zero has a maximum power of 15.4 watts, which is the default clause allocated to a powered device.
The switch in the phone can negotiate the amount of power required.
So for example.
A 7941, 79, 61 phone is deemed to be a class two device and through CDP can negotiate down to 6.3
watts of power at 79.
65, for example, is deemed to be a class three device, thus using 15.4 watts of maximum power, but
through CDP can negotiate down to only use 12 watts of power at 7971.
Also, a Class three device will negotiate down to 14.9 watts of power.
Now, the amount of power required by different phone varies.
Firstly, on the phone model, as you can see in this example and also the state of the phone as an
example, a 7971 phone in the idle state only requires 9.17 watts of power and a maximum power consumption
of 12.28 watts.
Phone model and features and user preferences can increase the power consumption on a phone, for instance,
if it's a colour screen versus scale, the gigabit Ethernet line speed, the ring and speakerphone volume
and the illuminated keys such as message weighting, light and line buttons.
For this course.
You don't need to know this amount of detail, but I just want you to be aware.
In the real world, different phones require different amounts of power, and thus you need to be careful
when specifying your switches in a real world environment.
Now certain phones in the 8900 series and 9900 series are deemed to be close for eight of 2.3 AF devices.
In other words, they are 802.38 devices.
In certain cases, they require more power, especially with the use of external add on devices like
a video camera.
Now the power requirements for individual handsets vary.
We're not going to go through a comprehensive list of mentioned some examples already.
Please refer to the data sheets and other information for details of the power requirements for individual
phones and individual power over Ethernet devices such as access points.
However, close for devices may require more than 15.4 watts of power.
For example, a Cisco Internet 1250 Series access point requires 18.5 watts of power, thus exceeding
the 15.4 watts in 82.3 if this is required to support 82.11 n.
We're not going to go through it in this course.
But there's a calculator on Cisco's website called The Power Calculator, which allows you to work out
how much power is required in a specific switch or PC to power a certain number of phones or wireless
access points.