netwk 320 week 7 i lab
NETW320 – Converged Networks with Lab
Lab #7 Title: CODEC Selection for a WAN
Introduction
A codec is a device capable of performing encoding and decoding on a digital signal. Each codec provides a different level of speech quality. The reason for this is that codecs use different types of compression techniques in order to require less bandwidth. The more the compression, the less bandwidth you will require. However, this will ultimately be at the cost of sound quality, as high-compression/low-bandwidth algorithms will not have the same voice quality as low-compression/high-bandwidth algorithms.
The following table shows three standard codec types along with their corresponding Coder Type, Bit Rate, Frame Size Delay, and Look Ahead Delay. These particular three were chosen because these are the ones we will use in this lab, but there are others.
ITU Recommended Delay Values/G.114
Compression Method
Coder Type
Bit Rate
Frame Size Delay (milliseconds)
Look Ahead Delay (milliseconds)
G.711
PCM
64 kbps
0.125
0
G.729
CS-ACELP
8 kbps
10
5
G.723.1
ACELP
5.3 kbps
30
7.5
A common scale used to determine the quality of sound produced by various codecs is the mean opinion score (MOS). This standard is based on a scale from 1 to 5, where 1 is very poor and 5 is excellent. Here is a common table used to rate values of MOS.
MOS
Listening Quality
Listening Effort
5
Excellent
Complete Relaxation
4
Good
Attention Necessary
3
Fair
Moderate Effort
2
Poor
Considerable Effort
1
Bad
No Meaning Understood
Objective
In this lab, you will build a wide-area network that will consist of several LANs spread across the country and connected via the Internet with two types of traffic: data and voice. You will configure three scenarios where the data and voice traffic generated will be held constant. The only parameter that you will alter will be the type of codec used. In the first scenario, the
Lab #7 Title: CODEC Selection for a WAN
Introduction
A codec is a device capable of performing encoding and decoding on a digital signal. Each codec provides a different level of speech quality. The reason for this is that codecs use different types of compression techniques in order to require less bandwidth. The more the compression, the less bandwidth you will require. However, this will ultimately be at the cost of sound quality, as high-compression/low-bandwidth algorithms will not have the same voice quality as low-compression/high-bandwidth algorithms.
The following table shows three standard codec types along with their corresponding Coder Type, Bit Rate, Frame Size Delay, and Look Ahead Delay. These particular three were chosen because these are the ones we will use in this lab, but there are others.
ITU Recommended Delay Values/G.114
Compression Method
Coder Type
Bit Rate
Frame Size Delay (milliseconds)
Look Ahead Delay (milliseconds)
G.711
PCM
64 kbps
0.125
0
G.729
CS-ACELP
8 kbps
10
5
G.723.1
ACELP
5.3 kbps
30
7.5
A common scale used to determine the quality of sound produced by various codecs is the mean opinion score (MOS). This standard is based on a scale from 1 to 5, where 1 is very poor and 5 is excellent. Here is a common table used to rate values of MOS.
MOS
Listening Quality
Listening Effort
5
Excellent
Complete Relaxation
4
Good
Attention Necessary
3
Fair
Moderate Effort
2
Poor
Considerable Effort
1
Bad
No Meaning Understood
Objective
In this lab, you will build a wide-area network that will consist of several LANs spread across the country and connected via the Internet with two types of traffic: data and voice. You will configure three scenarios where the data and voice traffic generated will be held constant. The only parameter that you will alter will be the type of codec used. In the first scenario, the